Spare Parts

The rocker arm of a vertical mill is mostly made of cast steel or forged metal, including components such as the upper and lower rocker arms and trunnions, which are connected by shafts, tapered sleeves, etc. Its main functions are to support the grinding roller, allows that the grinding roller maintains an appropriate gap and angle with the grinding table. It bears and transmits the pressure and impact force generated when the grinding roller grinds the material. It can also adjust the position and pressure of the grinding roller with the help of a hydraulic system and other devices, and buffer vibrations and impacts. During operation, the motor drives the grinding table to rotate, and the material enters and moves towards the edge under the action of centrifugal force. The grinding roller, supported by the rocker arm, contacts and crushes the material, and the rocker arm adjusts the pressure and position of the grinding roller in real time according to the grinding condition of the material, contributing to the efficient operation of the vertical roller mill.

1. Strict flaw detection, quality assurance
The rocker arm of the vertical mill implements the second-level flaw detection standard, which is at a relatively high level in the industry. The flaw detection process uses advanced ultrasonic flaw detection technology, radiographic flaw detection technology, etc. to conduct a full-scale inspection of the inside of the rocker arm. During ultrasonic flaw detection, professional flaw detectors precisely debug the flaw detector to emit ultrasonic pulses into the inside of the rocker arm. When the sound wave encounters internal defects such as pores, cracks, inclusions, etc., a reflection wave will be generated. The flaw detector can accurately capture these reflected wave signals and convert them into intuitive images and data. The flaw detectors rely on their rich experience to judge the location, size and nature of the defects based on the signal characteristics. Radiographic flaw detection uses X-rays or γ-rays to penetrate the rocker arm. Different density areas have different degrees of absorption of rays, forming different grayscale images on the film, and the flaw detectors identify internal defects based on this. This high-standard flaw detection can timely discover minor hidden dangers and avoid sudden failures of the rocker arm during operation due to internal defects, greatly improving the reliability and service life of the rocker arm and ensuring the long-term stable operation of the vertical mill.

2. Advanced surface treatment, both inside and outside
Arc planing process to remove defects: The vertical mill rocker arm is processed by arc planing. During arc planing, the oxide scale, defect layer and excess metal on the rocker arm surface are quickly melted and blown away by a special arc planing equipment using a high-temperature arc. When processing the rocker arm surface with complex shapes, the operator can flexibly adjust the angle and power of the arc planing equipment to accurately remove impurities in specific areas to ensure that the surface is flat and free of residual defects. Compared with traditional mechanical grinding methods, arc planing is more efficient and can deeply process some corners that are difficult for mechanical tools to reach, laying a good foundation for subsequent shot blasting.2.
Shot blasting reinforcement to improve appearance: Shot blasting is closely followed by arc planing. In the shot blasting equipment, the high-speed rotating shot blaster throws projectiles such as steel shots and iron shots at extremely high speeds onto the rocker arm surface. The projectiles continuously hit the rocker arm, which, on the one hand, removes the fine oxide layer, oil and other impurities on the surface, making the rocker arm surface present a uniform and clean metallic luster; on the other hand, the impact of the projectile forms a dense cold-work hardening layer on the surface of the rocker arm, which improves the surface hardness and wear resistance. The rocker arm treated with shot blasting is not only beautiful in appearance, but also has stronger corrosion resistance, and can maintain a good condition for a long time in harsh industrial environments.

3. High-quality material selection, excellent performance
The vertical mill rocker arm uses high-quality steel such as ZG270-500 and ZG30SiMnMo, laying a solid foundation for its performance. ZG270-500 has good comprehensive mechanical properties, with a yield strength of 270MPa and a tensile strength of 500MPa, and can withstand the large tensile stress and compressive stress generated during the operation of the vertical mill. When the rocker arm is frequently subjected to roller pressure and material impact, it is not easy to deform. ZG30SiMnMo has excellent wear resistance and fracture resistance due to its high carbon content and alloy elements such as silicon, manganese and molybdenum. Under the condition of long-term friction with materials and alternating stress, the rocker arm surface wear rate is low, which effectively extends the replacement cycle; at the same time, in the face of sudden impact loads, it can also rely on its own good toughness to avoid fracture accidents, ensure the continuous and stable operation of the vertical mill, and reduce the equipment maintenance cost.

4. Multiple rounds of inspection, worry-free quality
Professional non-destructive testing, guarding the safety of the force-bearing surface: Professional inspectors conduct multiple non-destructive inspections on the rocker arm force-bearing surface, using magnetic particle flaw detection, penetrant flaw detection and other technologies. Magnetic particle flaw detection is suitable for detecting defects on the surface and near the surface of the rocker arm. During the inspection, magnetic powder is first applied to the surface of the rocker arm. When there is a defect in the rocker arm, a leakage magnetic field will be generated at the defect, and the magnetic powder will gather at the defective part to form an obvious magnetic mark. The inspector can intuitively judge the defect. Penetrant flaw detection is to apply a penetrant containing a color dye or a fluorescent agent on the surface of the rocker arm to penetrate into the defect, then remove the excess penetrant on the surface, and then apply a developer. The penetrant in the defect will be adsorbed and show traces, so as to accurately locate the defect. This focused inspection of the force-bearing surface ensures that there are no quality risks in the key parts of the rocker arm and ensures safe operation.

5. Full-process quality control, from raw materials to finished products: TONGLI rocker arm production strictly controls quality throughout the entire process. Standard wooden molds are used, and special coatings are applied to the surface of the core. The special coating has good high temperature resistance and shrinkage resistance, which can effectively prevent the wooden mold from deforming and cracking due to high temperature during the casting process, ensuring the dimensional accuracy and surface flatness of the casting. In the raw material link, high-quality waste raw materials and accessories are selected, but before putting into production, the ingredients are strictly tested using advanced spectrometers, metallographic microscopes and other equipment to ensure that the chemical composition and impurity content meet the standards. During smelting, samples are taken three times before the furnace, in the cast state, and after the furnace, and the spectrometer imported from Germany is used for detection to monitor the changes in the composition of the molten metal in real time to ensure the accurate proportion of each element and stable performance of the casting. As a key component of the rocker arm, the trunnion is made of special materials. Its trunnion seat, oil tank flange, bracket, pointed ear and other parts are all tested by flaw detectors. No quality risk point is missed, and the high quality of the vertical mill rocker arm is guaranteed from all links.

The production of Tongli vertical mill rocker arm is a precision manufacturing chain that integrates cutting-edge technology and fine craftsmanship. Every step carries the ultimate pursuit of product quality:

The production of Tongli vertical mill rocker arm is a precision manufacturing chain that integrates cutting-edge technology and fine craftsmanship. Every step carries the ultimate pursuit of product quality:

1. Magma casting software runner simulation: Tongli's technical team first imports the precise 3D model of the rocker arm into Magma casting software. The software uses complex algorithms to simulate the flow trajectory of liquid metal in the preset runner and cavity. In the simulation, it can intuitively show whether the metal liquid is filled evenly, whether there is turbulence, air holding and other conditions. The technicians repeatedly adjust the runner layout and size to ensure that the metal liquid can quickly and smoothly fill the cavity during casting, reduce the probability of defects such as shrinkage holes and pores, and lay a solid foundation for high-quality rocker arm castings.

2. Wood mold production: Experienced craftsmen select high-quality wood to create wooden molds based on optimized drawings. They use high-precision woodworking equipment to carefully carve every detail, from the main contour of the rocker arm to the subtle grooves and holes, all strictly matching the design dimensions. To prevent the wooden mold from being deformed by moisture in the subsequent process, multiple layers of special moisture-proof paint will be applied on the surface to enhance durability. After the production is completed, it is measured by multiple rounds of precision measuring tools to ensure that the size error of the wooden mold is controlled within a very small range, providing an accurate blueprint for the production of sand molds.

3. Making sand molds: With the wooden mold as the core, it is firmly placed in the sand box, and special molding sand with high temperature resistance, high strength and good air permeability is selected and filled in layers. For the complex structure inside the rocker arm, a special core box will be used to make the sand core to ensure the molding accuracy of the internal cavities and special-shaped parts. During the sand filling process, the compactness of the molding sand is uniform through vibration, compaction and other means. After the sand filling is completed, carefully remove the wooden mold, carefully check the sand model cavity, remove the loose sand particles, ensure that the sand mold surface is smooth and the outline is clear, and prepare a high-quality mold for the pouring of molten steel.

4. Steelmaking: According to the specific material standards of the Tongli vertical mill rocker arm, such as the commonly used high-strength cast steel, the selected scrap steel, pig iron and various alloy raw materials are put into the advanced arc furnace or induction furnace in precise proportions. During the high-temperature smelting stage, the temperature and smelting time in the furnace are closely monitored to ensure that the metal is fully melted and evenly mixed. At the same time, slag refining, air blowing and stirring are used to effectively remove impurities and harmful gases in the molten steel, improve the purity of the molten steel, and lay a solid material foundation for casting high-quality rocker arms.

5. Spectrometer composition test: After the molten steel is smelted to the standard, the sample is quickly extracted from it and placed in an advanced spectrometer. The spectrometer emits a beam of light of a specific wavelength to excite the atoms in the sample to produce a characteristic spectrum. The instrument accurately analyzes the content of basic elements and alloy elements such as carbon, silicon, manganese, phosphorus, and sulfur in the molten steel. Compare the test results with the established material standards. Once a component deviation is found, the amount of alloy added is immediately fine-tuned to ensure that the composition of the molten steel meets the stringent performance requirements of the rocker arm.

6. Casting: When the composition and temperature of the molten steel reach the optimal state, a professional casting worker operates the ladle to inject the molten steel into the sand model cavity at a uniform and stable speed. The casting process strictly controls the flow rate and flow rate to prevent the molten steel from impacting the sand mold and ensure that all parts of the cavity are fully and evenly filled with molten steel. After the molten steel cools and solidifies, the rocker arm blank is initially formed. At this time, the blank has the basic shape of the rocker arm, but the internal structure and performance still need to be optimized in subsequent processes.

7. Sand cleaning: After the casting is cooled, first use the vibration equipment to shake off most of the attached molding sand, and then use high-pressure water guns, wind shovels and other tools to carefully clean the residual sand on the surface of the rocker arm and in the internal cavities and gaps. During the sand cleaning process, workers need to operate carefully to avoid damaging the surface of the casting, ensure that the surface of the rocker arm is clean and free of sand, and prepare for the subsequent heat treatment process.

8. Heat treatment: The rocker arm blank after sand cleaning is sent to the heat treatment furnace, and a dedicated heating, insulation and cooling curve is formulated according to the material characteristics and performance requirements. In the heating stage, the rocker arm is evenly heated to a suitable temperature and kept warm for a period of time to promote the full transformation of the internal structure. Subsequently, by controlling the cooling rate, the metallographic structure of the rocker arm is adjusted to improve its comprehensive mechanical properties such as strength, toughness, and hardness to meet the use requirements of the vertical mill under complex working conditions.

9. Shot blasting: The heat-treated rocker arm enters the shot blasting equipment, and the high-speed rotating shot blaster throws a large number of projectiles such as steel shot and iron shot at high speed onto the surface of the rocker arm. The continuous impact of the projectile not only removes the surface oxide scale and impurities, but also forms a dense cold-work hardening layer on the surface, which improves the surface hardness and wear resistance. The surface of the rocker arm after shot blasting presents a uniform metallic luster, providing a good foundation for subsequent machining.

10. Machining: On high-precision machine tools, the rocker arm is finely cut, drilled, ground and processed according to the design drawings. From the key mounting surface, shaft hole to the connection part, the dimensional accuracy and surface roughness of each part are strictly controlled. Advanced CNC machining technology is used to ensure that the geometric tolerances of each processing part meet the standards, ensure the assembly accuracy of the rocker arm and other parts of the vertical mill, and improve the overall equipment operation stability.

11. NDT inspection: Non-destructive testing (NDT) methods such as ultrasonic flaw detection, magnetic particle flaw detection, and penetrant flaw detection are used to conduct a comprehensive inspection of the rocker arm. Ultrasonic flaw detection is used to detect internal defects, magnetic particle flaw detection detects surface and near-surface cracks, and penetrant flaw detection targets tiny opening defects. With professional skills and rich experience, the inspectors carefully identify the detection signals and images to ensure that the rocker arm has no defects that affect the performance and guarantee product quality and safety.

12. Packaging: The rocker arm that has passed the inspection is first cleaned and rust-proofed, coated with anti-rust oil, and wrapped with anti-rust paper. Then, a special packaging wooden box is customized according to the size and shape of the rocker arm, and the internal cushioning materials such as foam board and pearl cotton are filled to fix the rocker arm firmly in the wooden box. After packaging, the product model, specifications, production batch and other information are marked on the outer box to ensure that the rocker arm is not damaged during transportation and is safely delivered to the customer.

1. LOESCHE – LM Series
LOESCHE is a pioneer in VRM technology, and its LM series is widely used in the cement industry. The LM series mills are designed for high throughput, low energy consumption, and efficient grinding of raw materials, clinker, and slag.

2. FLSmidth – OK™ Mill
The OK™ Mill is one of the most popular VRMs for cement grinding, known for its reliability and energy efficiency. It features a modular design that allows easy maintenance and operation flexibility for different types of cement and raw materials.

3. Gebr. Pfeiffer – MVR Series
Gebr. Pfeiffer’s MVR series vertical roller mills are known for their MultiDrive® system, which enhances redundancy and operational reliability. These mills are highly efficient in grinding cement, raw materials, and granulated blast-furnace slag.

4. KHD Humboldt Wedag – RP Series
KHD’s RP series vertical roller mills are designed for efficient cement grinding with optimized energy consumption. They incorporate advanced roller technology to ensure consistent and high-quality output.

5. Polysius (Thyssenkrupp) – Quadropol Series
The Quadropol series by Polysius features a compact design with high grinding efficiency and low power consumption. It is used for grinding cement raw materials, clinker, and slag.

6. Ube Machinery – UM Series
Ube’s UM series VRMs are recognized for their robust construction and ability to grind cement raw materials and clinker efficiently. They offer low maintenance requirements and high operational stability.

7. CITIC Heavy Industries – LGMC Series
CITIC’s LGMC series VRMs are designed for large-scale cement and mining applications. They feature a high grinding capacity, low energy consumption, and advanced process control for optimized performance.

8. Kawasaki Heavy Industries – CK Mill Series
Kawasaki’s CK Mill series is a high-performance vertical roller mill used for cement and slag grinding. It features low energy consumption, stable operation, and reduced maintenance requirements.

9. Zhejiang Tongli Heavy Machinery – ZJTL Series
Zhejiang Tongli's TL series vertical roller mills are widely used in cement plants for grinding raw materials, clinker, and slag. These mills are designed for high grinding efficiency, stable operation.Tongli Heavy Machinery has a strong reputation in the Chinese market and internationally, offering various industrial grinding solutions.

10. Sinoma – HRM Series
Sinoma’s HRM series vertical roller mills are widely used in large-scale cement plants in China and globally. They are known for high grinding efficiency, low power consumption, and stable operation.

11. Dal Teknik Makina – DTRM Series
Dal Teknik Makina’s DTRM series VRMs are used for cement and raw material grinding. They offer a high degree of automation and reliable performance for modern cement plants.

12. AMCL Machinery Limited – BM Series
AMCL, an Indian manufacturer, produces the BM series VRMs for cement and raw material grinding. They are designed for energy efficiency and long-lasting performance.

13. Hefei Zhongya Building Material Equipment – MLS Series
The MLS series vertical roller mills from Hefei Zhongya are widely used in Chinese cement plants. They provide high efficiency, durability, and low maintenance costs.

14. Tianjin Cement Industry Design & Research Institute (TCDRI) – TRM Series
TRM series mills from TCDRI are designed for cement, slag, and coal grinding, offering high efficiency, durability, and energy savings.

15. NHI (Northern Heavy Industries) – MPS Series
NHI’s MPS series vertical mills are designed for grinding cement, coal, and slag. They offer high throughput, low power consumption, and durability in harsh operating conditions.

16. CHAENG (Xinxiang Great Wall) – GRM Series
The GRM series vertical mills from CHAENG are widely used for cement, slag, and coal grinding. They are designed with high efficiency, low noise, and easy maintenance, making them a cost-effective solution for cement plants.

17. Tangshan Jidong Machinery – TRM Series
Jidong’s TRM series VRMs are developed for cement and raw material grinding, with advanced technology ensuring high efficiency and stable performance.

18. Jiangsu Pengfei – PRM Series
The PRM series VRMs from Jiangsu Pengfei are widely used in cement and metallurgy industries. They are known for their simple structure, high efficiency, and reliable operation.

19. Shibang Industry & Technology Group (SBM) – LM Series
SBM’s LM series vertical mills are known for their advanced design and energy-efficient performance. These mills are commonly used in cement, metallurgy, and power plant desulfurization projects.

20. Henan Liming Heavy Industry – LM Series
Liming’s LM series VRMs are widely used in cement, metallurgy, and power plant desulfurization, providing advanced grinding technology and energy savings.

21. HAIJIAN – HJ Series
Haijian’s HJ series VRMs are widely used in cement plants for grinding raw materials, clinker, and slag, featuring high efficiency and low power consumption.

22. Chenzhou Metallurgical Machinery – ZGM Series
ZGM series mills are used for cement, coal, and mineral grinding. They provide efficient grinding and long service life in various industrial applications.

23. Chaoyang Heavy Machinery – CYM Series
The CYM series VRMs are developed for cement, coal, and slag grinding, known for high efficiency and cost-effectiveness.

24. CBMI Construction Co., Ltd. – CBM Series
CBMI’s CBM series VRMs are widely applied in cement and industrial grinding applications, ensuring high reliability and efficiency.

25. Anshan Heavy Duty Mining Machinery – AH Series
AH series VRMs are engineered for cement and mining grinding applications, delivering superior grinding performance and durability.

26. Zhongde Heavy Industries – ZD Series
Zhongde’s ZD series VRMs are designed for cement and raw material grinding, featuring a robust structure and low energy consumption.

27. Wuxi Orient – WX Series
WX series vertical roller mills are used for cement, slag, and mineral grinding, ensuring consistent output and operational efficiency.

28. Yancheng Jida Machinery Manufacture – JLM Series
JLM series VRMs are engineered for cement and industrial grinding, offering high throughput and low operational costs.

29. China National Heavy Machinery Corporation (CHMC) – CHM Series
CHMC’s CHM series VRMs are developed for cement and industrial applications, providing energy-efficient solutions for modern plants.

30. Weifang Jinghua Powder Engineering Equipment – JHP Series
JHP series VRMs are known for their precision grinding, used in cement and powder processing industries.

1. Cast steel: ZG230-450: It has certain strength and toughness, good casting and welding performance, and relatively low cost. It is suitable for some vertical mill rocker arms that do not require particularly high strength and can withstand certain impact and wear.

For the rocker arm of ZG230-450 cast steel, it has certain strength and toughness and can withstand moderate impact and pressure. Due to its good casting and welding properties, it is easy to process into complex shapes and later assembly. However, its strength, hardness and wear resistance are relatively weak. This material is suitable for scenes with mild working conditions such as small cement plants and grinding stations. When the hardness of the processed materials is low and the grinding pressure requirements are not high, it can not only meet production needs but also control costs.

2. ZG270-500: It has higher strength and hardness than ZG230-450, has better wear resistance and fatigue resistance, can work stably under more complex working conditions, and is one of the commonly used materials for vertical mill rocker arms.

The rocker arm made of ZG270-500 cast steel has better strength and hardness than ZG230-450, and has better wear resistance and fatigue resistance. It can remain stable under high grinding pressure and frequent impact, and is not easy to deform or break. It can be used for vertical mills in most conventional working conditions, such as general-sized cement production enterprises and ore grinding plants. In these places, the vertical mill needs to operate stably for a long time and process materials of a certain hardness. The rocker arm made of ZG270-500 material can guarantee performance and a long service life, and is a more common choice.

3. ZG30SiMnMo: It belongs to alloy cast steel. In addition to having high strength and hardness, it also has good toughness and impact resistance. It can adapt to high-load and high-wear working environments. It is often used in large vertical mills or occasions with high requirements for rocker arm performance.

The rocker arm made of ZG30SiMnMo alloy cast steel not only has high strength and hardness, but also has good toughness and impact resistance. The alloy elements make its structure dense and can effectively resist wear and corrosion. Even in harsh environments such as high temperature and high humidity, it can maintain stable performance. It is often used in large vertical mills or places with strict requirements on rocker arm performance, such as large cement production bases and mineral powder processing in large mines. In these places, the vertical mill handles a large amount of high-hardness materials, with high working pressure and complex environment. The rocker arm made of ZG30SiMnMo can better adapt to ensure the normal operation of the equipment and production efficiency.

4. Alloy steel: Some high-end vertical mill rocker arms may use special alloy steel materials, such as alloy steel with added alloy elements such as chromium (Cr), nickel (Ni), and molybdenum (Mo). These alloy elements can further improve the material's strength, hardness, wear resistance and corrosion resistance, allowing the rocker arm to maintain good performance under harsh working conditions.

The rocker arm of the vertical mill made of special alloy steel will have unique properties due to the addition of different alloy elements. For example, after adding elements such as chromium, nickel, and molybdenum, the strength, hardness, wear resistance, and corrosion resistance of the material can be greatly improved, and it may even enhance the high temperature resistance and oxidation resistance. It is suitable for special industrial fields and extreme working conditions such as the chemical industry to handle corrosive materials, or grinding operations under high temperature environments, and can ensure the safe and stable operation of the vertical mill under special conditions.

The life time of the rocker arm may vary from 3 years to 8 years. Factors affecting the life time are as follows:

1. Material and manufacturing process: The rocker arm made of high-strength, wear-resistant high-quality cast steel such as ZG30SiMnMo alloy cast steel and with exquisite manufacturing process has better structural stability and wear resistance, and usually has a longer service life. Under normal maintenance and suitable working conditions, it can be used for 8-15 years or even longer. However, the rocker arm made of ordinary cast steel, such as ZG230-450, and with defects in the manufacturing process may only have a service life of 3-8 years.

2. Working load and working conditions: If the vertical mill is in an overloaded operation state for a long time, or the processed material is of high hardness and high grinding pressure, the rocker arm will be subjected to greater stress and wear, and its life will be significantly shortened. For example, in some mineral powder processing plants that process high-hardness ores, the rocker arm may need to be replaced every 3-5 years. On the contrary, in cement plants that process soft materials and have moderate operating loads, the service life of the rocker arm may reach about 10 years.

3. Maintenance: Regular lubrication, inspection and maintenance of the rocker arm, and timely handling of wear, looseness and other problems can effectively extend its service life. For example, check the connection parts of the rocker arm at regular intervals to ensure that the bolts are tightened, and take preventive measures on the parts prone to wear. On the contrary, if the maintenance is not in place, the rocker arm may be seriously damaged within 2-5 years.

4. Equipment operating environment: The rocker arm of the vertical mill in harsh environments such as high temperature, humidity, and dust is prone to accelerated damage due to corrosion, rust and other problems. For example, in cement plants in some humid areas in the south, if protective measures are not in place, the service life of the rocker arm may be shortened by 2-3 years compared to dry areas.

Improving the wear resistance of vertical mill rocker arms can be done from aspects such as material selection, surface treatment, structural design and daily maintenance:

1. Choose suitable wear-resistant materials: Use high-quality alloy steel: When conditions permit, select alloy steel with added alloy elements such as chromium (Cr), molybdenum (Mo), and vanadium (V). These elements can enhance the hardness, strength and wear resistance of the material. For example, in some vertical mill rocker arms with extremely high wear resistance requirements, alloy steel containing a high proportion of chromium and molybdenum is used, which can significantly improve the wear resistance of the rocker arm.

2 Optimize the surface treatment process quenching and tempering treatment: Quenching and tempering the rocker arm can obtain a fine martensitic structure on the surface of the material, improve the surface hardness and wear resistance. For example, after the appropriate quenching and tempering process, the surface hardness of the 45 steel rocker arm can be greatly improved, and the wear resistance is also enhanced.

3. Surface shot peening: Through shot peening, a compressive stress layer is formed on the surface of the rocker arm, which can effectively improve the surface hardness, refine the grains, and improve the fatigue resistance and wear resistance of the material.

4. Thermal spraying wear-resistant coating: Thermal spraying ceramic coating, metal ceramic coating and other wear-resistant coatings on the surface of the rocker arm. These coatings have high hardness, good wear resistance and high temperature resistance, and can play an effective protective role when the rocker arm contacts the material.

5. Chemical plating treatment: A uniform and dense nickel plating layer is formed on the surface of the rocker arm by using processes such as chemical nickel plating. The nickel plating layer has good corrosion resistance and wear resistance, and can effectively prevent the rocker arm surface from being worn and corroded.

6. Improve the structural design and add wear-resistant lining: Install a replaceable wear-resistant lining at the part where the rocker arm is in direct contact with the material. When the lining is worn to a certain extent, only the lining needs to be replaced without replacing the entire rocker arm, which not only improves the wear resistance but also reduces the maintenance cost.

7. Optimize the shape of the rocker arm: By optimizing the shape of the rocker arm, the impact force and friction force of the material when it contacts the rocker arm can be distributed more evenly, reducing local wear. For example, a streamlined design or an increased transition radius can reduce stress concentration and improve the overall wear resistance of the rocker arm.

8. Timely cleaning and protection: Clean the dust and material residue on the surface of the rocker arm in time to prevent them from accumulating on the surface and causing wear and corrosion to the rocker arm. At the same time, in harsh working environments, effective protective measures such as coating protective paint can be taken to protect the surface of the rocker arm from erosion by the external environment.

9. Accurate installation and debugging: When installing the vertical mill rocker arm, ensure the installation accuracy so that the rocker arm is evenly stressed during operation to avoid aggravated local wear caused by installation deviation.

The rocker arm of the vertical mill needs heat treatment for many reasons. The rocker arm bears complex loads during operation. Heat treatment can change the metal structure through quenching and tempering, improve strength and hardness, improve toughness through tempering, prevent deformation and fracture, and withstand impact. During processing, forging residual stress affects precision and quality. Annealing can eliminate stress, make the structure uniform, and refine the grains for processing. At the same time, heat treatment such as surface quenching can form a wear-resistant phase on the surface of the rocker arm, improve wear resistance, and improve the surface state, forming a stable oxide film or passivation layer, enhancing corrosion resistance, ensuring that the performance and strength of the rocker arm are not damaged in harsh environments, and extending service life.

The heat treatment process of vertical mill rocker arm usually includes quenching, tempering and other main processes. The following is a detailed introduction of the vertical mill rocker arm made of common ZG270-500 cast steel and 42CrMo alloy steel:

1. For ZG270-500 cast steel vertical mill rocker arm, the heating temperature during quenching is generally 840-860℃. Within this temperature range, the structure of ZG270-500 cast steel can be fully austenitized, laying the foundation for subsequent quenching to obtain a good martensitic structure. The insulation time should be determined according to the size and thickness of the rocker arm. Generally, the insulation time is about 1 hour for every 25mm thickness. For example, for a rocker arm with a thickness of 50mm, the insulation time is about 2 hours, which can ensure that the temperature inside and outside the workpiece is uniform and the structure transformation is sufficient. The cooling medium is usually water or a water-soluble quenching medium for cooling. Water has a faster cooling rate, which can make steel parts have higher hardness and strength, but it may produce greater internal stress, which is easy to cause deformation or even cracking; the cooling rate of water-soluble quenching medium is relatively slow, which can reduce the risk of internal stress and deformation cracking to a certain extent.

2. In terms of tempering, the tempering temperature is generally 550-650℃. The tempering temperature is mainly determined by the performance required by the rocker arm. Tempering in this temperature range can effectively eliminate quenching internal stress, stabilize the organization, improve toughness, and maintain a certain strength and hardness. The holding time is generally 2-3 hours. Sufficient holding time can make the tempering process fully proceed, allowing the carbides in the organization to fully precipitate and aggregate, so as to achieve the purpose of improving performance. Air cooling is usually used for cooling after tempering, that is, letting the workpiece cool naturally in the air. This cooling method can avoid the generation of large internal stress again after tempering, and ensure the dimensional stability and performance uniformity of the rocker arm.

3. For 42CrMo alloy steel vertical mill rocker arm, the heating temperature of quenching is 850-870℃. 42CrMo alloy steel contains alloy elements such as chromium and molybdenum, which improve the hardenability and tempering stability of the steel. It needs a higher temperature to fully dissolve the alloy elements in austenite to play its strengthening role. The holding time is also determined according to the size and thickness of the rocker arm. Generally, it is kept warm for 1 hour for every 20mm thickness. For example, for a rocker arm with a thickness of 40mm, the holding time is about 2 hours to ensure that the alloy elements are fully homogenized and create conditions for obtaining good quenching structure and performance in the subsequent process. The cooling medium often uses oil cooling. Since 42CrMo alloy steel has good hardenability, the cooling speed of oil cooling can not only ensure the martensitic structure, but also effectively reduce the quenching internal stress and reduce the tendency of deformation and cracking.

4. During the tempering process, the tempering temperature is 600-680℃. Tempering within this temperature range can decompose the martensite in 42CrMo steel and disperse and precipitate carbides, thereby obtaining good comprehensive mechanical properties and improving the strength, toughness and wear resistance of the rocker arm. The holding time is 2.5 - 3.5 hours. A longer holding time is conducive to the full precipitation and growth of carbides, making the organization more stable and further improving the performance of the rocker arm. The cooling method generally adopts air cooling to cool the workpiece slowly, avoid the generation of new internal stress, and ensure the dimensional accuracy and performance stability of the rocker arm.

The NDT (non-destructive testing) process of the vertical mill rocker arm is an important part of TONGLI to ensure its quality and safety. The following is an introduction to Tongli's inspection process, including the general NDT process of raw material testing using a spectrometer and subsequent magnetic particle testing.

1. The first is raw material testing. The purchased raw materials are tested with a spectrometer. The chemical composition of the raw materials is determined by measuring the characteristic spectrum emitted by the material after being excited to ensure that it meets the design requirements and prevent performance from failing to meet the standards due to chemical composition deviation. For example, for common alloy steel materials, it is necessary to test whether the content of elements such as carbon, chromium, molybdenum, and nickel is within the specified range. At the same time, the surface of the raw materials is visually inspected to see if there are obvious cracks, sand holes, pores, inclusions and other defects. These surface defects may cause problems during subsequent processing and use. It is also necessary to use measuring tools such as calipers and micrometers to measure the key dimensions of the raw materials to ensure that their dimensional accuracy meets the processing requirements and avoid assembly problems or affect the performance of the rocker arm due to dimensional deviation.

2. Inspection is also required during the processing process. After rough machining, ultrasonic testing is performed on the rocker arm. Using the propagation characteristics of ultrasonic waves in the material, when encountering internal defects, ultrasonic waves will be reflected, refracted and scattered. By analyzing the signal of the reflected wave, it is judged whether there are cracks, pores, looseness and other defects inside. The detection depth can reach a deeper position inside the material, which can effectively find internal defects that cannot be detected by the naked eye. If the rocker arm material is ferromagnetic, magnetic particle inspection can be performed after semi-finishing. First, the rocker arm is magnetized to generate leakage magnetic fields at the defects on the surface and near the surface, and then magnetic powder is sprinkled on the surface. The magnetic powder will gather at the leakage magnetic field to form magnetic marks. The location, shape and severity of the defects are judged by observing the shape, size and distribution of the magnetic marks. It is mainly used to detect surface and near-surface cracks and other defects.

3. It is the finished product inspection stage. At the finished product stage, magnetic particle inspection should be performed again to conduct a comprehensive inspection of the entire rocker arm surface to ensure that no new surface or near-surface cracks and other defects are generated during the processing process. At the same time, radiographic detection technology, such as X-rays or γ-rays, is used to irradiate the rocker arm. When the rays pass through the rocker arm, different grayscale images will be formed on the radiographic film due to the different absorption and attenuation of the rays by the defects and the matrix material. By observing the images on the film, it is possible to analyze whether there are defects such as pores, slag inclusions, and incomplete penetration inside, which can intuitively display the internal structure and have a good effect on volumetric defect detection. It is also necessary to use a hardness tester to test the hardness of the key parts of the rocker arm to check whether the hardness meets the design requirements.

4. The hardness value can reflect the strength and wear resistance of the material to a certain extent, ensuring that the rocker arm has good performance. Finally, a final visual inspection of the appearance of the rocker arm is carried out to ensure that there are no defects such as bumps, scratches, and oxide scales on the surface. At the same time, the key dimensions are measured again to ensure that the dimensional accuracy meets the product standards and assembly requirements.
In the entire NDT process of the vertical mill rocker arm, each detection method has its unique role and scope of application. The use of each other can comprehensively and accurately detect various defects in the rocker arm to ensure its quality and reliability.

Common fracture, wear and deformation faults of vertical mill rocker arms have different causes and corresponding solutions. The specific analysis is as follows:

1 Fracture: From the material level, if the material used to make the rocker arm has defects such as internal cracks and inclusions, these defects will gradually expand under long-term alternating load conditions, eventually causing the rocker arm to break. Fatigue damage is also an important reason for equipment operation. When the vertical mill is running, the rocker arm continues to bear periodic bending and torsion stresses. Long-term cyclic loading will cause fatigue cracks in the rocker arm material. The cracks continue to expand, and the effective bearing area of ​​the rocker arm gradually decreases. When the stress exceeds the material strength limit, it will cause fracture. Overload operation is also prone to fracture. When the vertical mill processes too much material, the material hardness exceeds the design range, or encounters foreign matter, the load on the rocker arm increases significantly, exceeding its design bearing capacity, leading to fracture. If there are problems in the installation process, such as installation accuracy not meeting the standard, uneven tightening torque of connecting bolts, and inappropriate clearance between rocker arm and other components, additional stress concentration will be generated during the operation of rocker arm, accelerating damage and even causing fracture.

1.1 A series of solutions can be taken to solve the problem of rocker arm fracture. In terms of material control, quality inspection should be strengthened when purchasing rocker arm materials, and ultrasonic testing, metallographic analysis and other means should be used to ensure that the materials have no internal defects. In terms of operating parameters, according to the design specifications and material characteristics of the vertical mill, the feed amount and material particle size should be reasonably controlled to avoid overload operation. At the same time, an overload protection device should be installed to automatically shut down when the load exceeds the set value. The installation operation must be standardized, and the rocker arm should be installed strictly in accordance with the installation instructions. With the help of precise measuring tools and torque wrenches, the installation accuracy and connection tightness should be guaranteed. After the installation is completed, a comprehensive inspection and debugging should be carried out. In daily maintenance, a regular inspection plan should be formulated, and non-destructive testing technologies such as magnetic particle testing and radiographic testing should be used to comprehensively inspect the rocker arm to promptly detect potential cracks and other defects. For rocker arms with slight cracks, welding repair technology can be used, but the welding quality and process must meet the requirements; for rocker arms with severe cracks or broken, they need to be replaced in time.

2 Wear: The wear of vertical mill rocker arms mainly comes from the following aspects. Abrasive wear is more common. When the vertical mill grinds the material, the hard particles in the material contact the surface of the rocker arm with the movement of the grinding roller, and continuously cut and scrape the surface of the rocker arm. Especially when the material contains high-hardness components such as quartz sand, the wear is more serious. Poor lubrication is also a key factor. The rotating parts and connecting parts of the rocker arm need to be well lubricated to reduce friction. If the lubrication system fails, such as insufficient supply of lubricating oil, deterioration, and uneven application, the friction pair of the rocker arm will be in direct contact, aggravating wear, and dust is easy to enter the rocker arm connection and rotating parts when the seal fails, forming abrasives between the friction pairs, accelerating wear, and contaminating the lubricating oil, reducing the lubrication effect. The working environment of the vertical mill is harsh. High temperature, high humidity, and high dust will accelerate the oxidation and corrosion of the rocker arm surface, reduce the surface performance of the material, and make it more prone to wear.

2.1 To solve the problem of rocker arm wear, a variety of methods can be adopted. In terms of surface protection, the surface of the rocker arm is hardened, such as carburizing, quenching, hard chrome plating and other processes to improve the surface hardness and wear resistance. Wear-resistant coatings such as ceramic coatings and metal ceramic coatings can also be sprayed to effectively resist abrasive wear. Lubrication conditions should be improved, and a complete lubrication management system should be established. Lubricating oil should be checked and replaced regularly to ensure quality and supply. Suitable lubricants and lubrication methods should be selected according to the working conditions of the rocker arm, and automatic lubrication systems should be used to ensure timely and uniform lubrication. Sealing measures need to be strengthened, high-quality seals should be selected and regularly checked and replaced, the sealing structure should be optimized, and multiple sealing methods such as labyrinth seals and rubber seals should be used to prevent dust from entering. At the same time, the working environment should be optimized, ventilation and dust removal should be strengthened, dust concentration should be reduced, and cooling measures should be taken for high-temperature environments, such as installing cooling fans or water cooling systems to reduce the working temperature of the rocker arm.

3 Deformation: The reasons for the deformation of the vertical mill rocker arm are complex. Long-term uneven stress is one of the main reasons. Improper adjustment of the gap between the grinding roller and the grinding disc and uneven material distribution will cause the rocker arm to bear uneven load during operation, resulting in local excessive stress and deformation. The influence of thermal stress should not be ignored. During the operation of the vertical mill, the rocker arm will experience temperature changes due to frictional heat and high material temperature. If the temperature distribution of each part is uneven, thermal stress will be generated, and the rocker arm may deform under long-term action. In addition, if the foundation of the vertical mill settles unevenly, the installation position of the rocker arm will be changed, causing it to bear additional bending moment and torque, which will cause deformation. In terms of material, if the rocker arm material has insufficient strength and rigidity, or poor thermal stability, it is easy to deform when subjected to a certain load and temperature changes.

3.1 To solve the problem of rocker arm deformation, we can start from many aspects. In terms of operating parameter adjustment, regularly check and debug the gap between the grinding roller and the grinding disc to ensure uniformity, optimize the feeding device, make the material evenly distributed on the grinding disc, and avoid local overload. Thermal balance needs to be controlled, and effective cooling measures should be taken to control the operating temperature of the rocker arm and reduce fluctuations. For example, a cooling channel should be set up inside the rocker arm, and cooling medium should be introduced. After shutdown, the machine should be cooled slowly according to the regulations to prevent sudden cooling and heating. Foundation reinforcement is as important as monitoring. Regularly check the foundation of the vertical mill and monitor the settlement. If problems are found, they should be reinforced in time. Foundation grouting and additional foundation support can be used to ensure the stability of the foundation. For rocker arms that are deformed due to material, consider replacing them with materials with higher strength, greater rigidity, and better thermal stability. Optimize the rocker arm structure during the design phase, add reinforcing ribs, and reasonably distribute materials to improve the ability to resist deformation.

1. Vibration monitoring is a common means of vertical mill fault detection. When the vertical mill is operating normally, the vibration of the rocker arm shows a specific pattern and amplitude range. Once a fault occurs, conditions such as bearing damage, loose connection, imbalance, etc. will cause the vibration frequency and amplitude to change. Install acceleration or displacement sensors at key parts of the rocker arm, such as bearing seats and connection points, convert vibration signals into electrical signals and transmit them to the data acquisition system. Use special vibration analysis software to perform spectrum and time domain analysis to determine the type and severity of the fault. You can also set an alarm threshold. When the vibration amplitude exceeds the limit, the system automatically alarms to remind the operator to check and deal with it. Vibration monitoring can monitor the operation of the rocker arm in real time and continuously, and is sensitive to early faults. The technology is mature, and the equipment and maintenance costs are low.

2 In the production process, ultrasonic testing uses the propagation characteristics of ultrasonic waves in materials. When ultrasonic waves encounter defects such as cracks and pores inside the material, reflection, refraction and scattering will occur. Through the ultrasonic detector, the ultrasonic probe is tightly coupled with the rocker arm surface, and the reflected wave signal is emitted and received. The presence or absence of defects is determined based on the characteristics of the reflected wave waveform, amplitude, etc. During operation, the different parts of the rocker arm need to be fully scanned. It has high sensitivity, fast speed and is harmless to the human body for detecting internal defects, but it is difficult to detect rockers with complex shapes and uneven surfaces, and the qualitative and quantitative analysis of defects is relatively complex.

Magnetic particle testing is suitable for rockers made of ferromagnetic materials. After magnetization, magnetic powder is sprinkled on the surface. Due to the distortion of magnetic lines of force at the defect, the magnetic powder will be adsorbed to form magnetic traces, and the defect situation can be judged by observing the magnetic traces. This method can quickly and intuitively detect surface and near-surface cracks, is easy to operate and low in cost, but it is only applicable to ferromagnetic materials, may misjudge rockers with rough surfaces, and can only detect surface and near-surface defects. Radiographic testing uses X-rays and γ-rays to penetrate the rocker arm material. Due to the different degrees of absorption and attenuation of rays by defects and normal materials, different grayscale images are formed on the radiographic film or imaging equipment to judge the defects. Film or digital imaging technology can be used. Digital imaging is more convenient for rapid acquisition, processing, storage and analysis of images.

X-ray detection can clearly present the internal structure and defects of the rocker arm, and the qualitative and quantitative analysis is relatively accurate. The results can be recorded with intuitive images for long-term preservation. However, the radiation has radiation hazards and requires strict protection. The detection cost is high and the speed is slow. Increasing the radiation dose for thicker rocker arms will bring greater risks.

3. Temperature monitoring: During normal operation, the rocker arm generates heat due to friction, load, etc., and the temperature is in a stable range. Once faults such as bearing damage and poor lubrication occur, the local temperature will rise. Temperature sensors such as thermocouples and thermal resistors are installed at key parts of the rocker arm, such as bearings and connection points, and the temperature signals are converted into electrical signals and transmitted to the temperature monitoring system. The system displays the temperature in real time and sets the alarm threshold, and alarms when the limit is exceeded. Temperature monitoring can intuitively reflect the working status of the rocker arm, and quickly discover faults caused by overheating. The sensor is easy to install, low cost, and the system runs stably. It can only reflect temperature changes, and it is difficult to detect non-temperature-related faults. In addition, changes in ambient temperature will affect the monitoring results and need to be compensated and corrected.

4. Oil analysis: The oil in the rocker arm lubrication system carries a lot of operating status information. By analyzing the oil composition, physical and chemical properties, wear particles, etc., the rocker arm wear, lubrication status and potential fault hazards can be understood. For example, the content and type of metal particles in the oil can reflect the degree and location of component wear, and indicators such as oil viscosity and water content can determine deterioration and lubrication performance. Collect oil samples from the lubrication system regularly and send them to professional laboratories for testing. The test items include spectral analysis, iron spectrum analysis, viscosity detection, moisture detection, etc. Comprehensive analysis of the test results to determine the operating status of the rocker arm. Oil analysis can deeply understand the internal wear and lubrication conditions without disassembling the rocker arm. It is of great significance for the diagnosis of early wear and potential faults, and can provide a basis for preventive maintenance. However, it requires professional laboratory equipment and technicians, a long detection cycle, and the results are easily affected by factors such as sampling methods and oil contamination.

1. Loesche: The rocker arm structure of Loesche vertical mill is exquisitely designed. The roller sleeve and the wheel hub are connected by a conical surface structure, and the roller shaft and the rocker arm are connected by an expansion sleeve structure. This connection method greatly facilitates the disassembly and assembly work. In terms of overall layout, Loesche vertical mills are commonly four-roller hydraulic type, equipped with flat grinding discs and conical grinding rollers with wear-resistant linings, and a lightweight hydraulic device for turning out the grinding rollers is thoughtfully set. In terms of functional characteristics, when the Loesche vertical mill is started under load, the grinding rollers will automatically lift off the grinding disc, effectively reducing the starting torque, reducing energy consumption and mechanical wear when the equipment is started. Each grinding roller is independently equipped with a hydraulic pressure device, and each hydraulic cylinder is equipped with sufficient accumulators to ensure that the roller pressure fluctuations during the operation of the mill are minimal, ensuring the smooth operation of the mill and laying a solid foundation for efficient grinding operations.

2. Pfeiffer: The structure of the rocker arm of the Pfeiffer vertical mill (MPS type vertical mill) is relatively complex. The rocker arm device consists of many components such as the upper rocker arm, the lower rocker arm, the rocker arm shaft and bearings, the thrust structure, and the upper and lower rocker arm connecting pins. The lower rocker arm is fork-shaped and cleverly inserted into the two sides of the upper rocker arm. The two are connected by a taper pin and a taper sleeve, and are tightly connected with four bolts to achieve a stable assembly. The upper and lower rocker arms rely on a rocker shaft combination and are supported on two bearing seats with the help of bearings. In terms of functional realization, the Pfeiffer vertical mill transmits the tensioning force through three hydraulic tensioning rods, and transmits the force to the three grinding rollers through the pressure frame in turn, and finally acts on the material layer between the grinding roller and the grinding disc, accurately controlling the grinding pressure to meet the grinding needs of different materials.

3. FL Smidth: The rocker arm of the Atox vertical mill shows unique advantages in structure and function. It adopts a three-roller integrated grinding roller system, which is unique in connection with the rocker arm and hydraulic system. Through the double-acting hydraulic tie rod connection, this design can not only efficiently apply grinding pressure, but also easily lift the grinding roller before starting, without the need for additional auxiliary transmission, simplifying the equipment configuration. The overall structure is simple, and with the column roller and flat disc design, the grinding pressure and reaction force are mainly concentrated in the vertical direction. The rocker arm mainly bears vertical force during work, and the force situation is relatively simple. In terms of functional characteristics, the three-roller integrated grinding roller system gives the Atox vertical mill rocker arm the characteristics of light weight and small inertia. The equipment runs smoothly. Under the same working conditions, the vibration and impact are significantly less than some similar equipment, which reduces the damage to the rocker arm and extends the service life of the rocker arm. At the same time, the double-acting hydraulic tie rod design greatly improves the convenience of equipment operation and maintenance. The lifting and lowering operations of the grinding roller become easy and efficient, saving a lot of time and labor costs for daily inspection and maintenance of the equipment, and significantly improving the operability and maintenance efficiency of the equipment.

The main connection methods between the rocker arm and the grinding roller are rigid connection, flexible connection and semi-flexible connection. The following is the impact of these connection methods on the movement of the grinding roller and the grinding effect, as well as the analysis of their respective advantages and disadvantages:

1. Rigid connection: Rigid connection makes there is almost no relative displacement between the rocker arm and the grinding roller, and the movement of the grinding roller completely follows the rocker arm. During the grinding process, this connection method can ensure that the grinding roller acts on the material on the grinding disc with a stable trajectory and pressure, which is conducive to uniform grinding, and can make the material particle size distribution relatively concentrated, and the product fineness is relatively stable. Its advantages are simple structure and easy installation and maintenance. It can accurately transmit the movement and force of the rocker arm to ensure the accuracy and stability of the grinding roller movement. When processing materials with higher hardness and larger particle size, rigid connection can effectively transmit greater grinding force and higher grinding efficiency. However, rigid connection has extremely high requirements for installation accuracy. Slight installation deviation may cause uneven force on the grinding roller and accelerate the wear of the grinding roller and grinding disc. Moreover, it lacks buffering capacity. When encountering hard blocks in the material or uneven feeding, it is easy to generate large impact loads, which may damage the rocker arm, grinding roller and other components, and affect the service life of the equipment.

2. Flexible connection: Flexible connection allows a certain relative displacement and angle change between the rocker arm and the grinding roller. The grinding roller can automatically adjust its position and angle according to the distribution and characteristics of the material during the grinding process, better adapt to the unevenness of the material, and reduce the vibration and impact caused by material changes. This helps to improve the efficiency and quality of grinding, so that the material is ground more fully, the particle size distribution of the product is more uniform, and the fine powder content is relatively high. The advantage of flexible connection is that it has good buffering and shock absorption performance, can effectively absorb the impact load during the grinding process, and protect equipment components. It has strong adaptability to materials, can compensate for the impact of uneven feeding and other problems on the grinding effect to a certain extent, and can also reduce the noise and vibration of the equipment during operation, and improve the stability and reliability of the equipment. However, flexible connection also has some disadvantages. Its structure is relatively complex and the cost is high. Due to the existence of a certain degree of flexibility, there may be a certain amount of energy loss in the process of transmitting force, which affects the grinding efficiency. After long-term use, flexible parts may experience aging, wear and other problems, and need to be replaced regularly, with high maintenance costs.

3. Semi-flexible connection: Semi-flexible connection has some characteristics of both rigid connection and flexible connection. While ensuring the basic motion stability of the grinding roller, it can also adapt to the changes in materials and the slight displacement of the grinding roller within a certain range. During the grinding process, the semi-flexible connection can not only maintain a relatively stable grinding pressure and trajectory, but also provide a certain buffering and adjustment ability when encountering special circumstances, so that the grinding effect is relatively ideal and the product quality is relatively stable. The advantage of the semi-flexible connection is that it combines some of the advantages of rigid connection and flexible connection, with good stability and force transmission efficiency, as well as a certain buffering and shock absorption ability and adaptability to materials. Compared with flexible connection, its structure is simpler and the cost is lower; compared with rigid connection, it has slightly lower requirements for installation accuracy and less maintenance difficulty. However, semi-flexible connection also has its shortcomings. Under some extreme working conditions, it may not provide sufficient stability like pure rigid connection, nor can it provide sufficient buffering and adjustment ability like pure flexible connection. Its performance depends to a certain extent on specific working conditions and design parameters, and needs to be optimized according to actual conditions.