The roller is a crucial component in steel rolling production, and its su***ce quality directly impacts the quality of the rolled products. During the use of rollers, due to wear, fatigue, and other reasons, they often require su***cing repair. However, the su***ce flatness after su***cing directly affects the service life of the roller and the quality of the rolled products. Therefore, ensuring the su***ce flatness of the roller after su***cing is an important issue in the roller repair process.
1. Preparations before build-up welding 1.1 Su***ce cleaning Before conducting build-up welding, the su***ce of the roll should be cleaned to remove impurities such as oil, rust, and oxide scale. Methods such as grinding with a grinding wheel and sandblasting can be used to ensure that the build-up welding area is clean and free of impurities.
1.2 Preheating treatment To prevent cracks during the welding process, it is usually necessary to perform preheating treatment on the rollers. The preheating temperature varies depending on the material of the roller and the welding material, generally ranging from 200℃ to 400℃. Preheating treatment can reduce welding stress and embrittlement in the heat-affected zone, thereby improving the quality of the welding.
1.3 Selecting the appropriate su***cing material The selection of su***cing material has a significant impact on su***ce flatness. It is necessary to choose the appropriate su***cing material based on the working conditions and su***cing requirements of the roll. Commonly used su***cing materials include high chromium cast iron, high manganese steel, nickel-based alloys, etc. The hardness, wear resistance, crack resistance, and other properties of the su***cing material should match the base material of the roll.
2. Control of build-up welding process 2.1 Optimization of welding parameters Welding parameters include welding current, voltage, welding speed, wire feed speed, etc. These parameters directly affect the quality and su***ce **oothness of the build-up welding layer. Welding parameters should be reasonably selected based on the characteristics of the build-up welding material and the size of the roll. Generally speaking, the welding current and voltage should be moderate, as too high or too low will affect the quality of the build-up welding. The welding speed should be uniform, avoiding being too fast or too slow.
2.2 Weld deposit sequence and direction The sequence and direction of weld deposit also have a significant impact on su***ce flatness. A reasonable weld deposit sequence should be adopted to avoid local overheating or stress concentration. Typically, multi-layer and multi-pass weld deposit is used, with each layer of weld deposit not being too thick, generally between 2~4mm. The direction of weld deposit should be consistent to avoid cross-weld deposition, thereby reducing su***ce unevenness.
2.3 Temperature Control During Welding During the build-up welding process, the temperature of the rollers should be strictly controlled to avoid overheating or overcooling. Intermittent welding can be employed to control the welding heat input and reduce the extent of the heat-affected zone. Additionally, auxiliary cooling measures, such as air cooling and water cooling, can be utilized to manage the temperature of the rollers.
3. Post-weld heat treatment After the completion of weld overlay, post-weld heat treatment is usually required to eliminate welding stress and improve the microstructure and properties of the weld overlay layer. The temperature and duration of post-weld heat treatment should be selected based on the weld overlay material and the material of the roll. Post-weld heat treatment can reduce the residual stress in the weld overlay layer and improve su***ce flatness.
3.2 After su***ce processing and build-up welding, the su***ce usually requires mechanical processing to enhance its flatness. Common processing methods include turning, grinding, polishing, etc. The appropriate processing method and parameters should be selected based on the hardness and thickness of the build-up welding layer. During processing, it is essential to control the processing parameters to avoid overcutting or damaging the build-up welding layer.
3.3 Su***ce Inspection: The su***ce of the weld deposit should be inspected to ensure that its flatness meets the requirements. Common inspection methods include visual inspection, *** inspection, magnetic particle inspection, etc. For important rollers, three-dimensional scanning inspection can also be conducted to obtain three-dimensional topography data of the su***ce and evaluate its flatness.
4. Quality Control and Management 4.1 Preparation of Process Documents Detailed build-up welding process documents should be prepared, including build-up welding materials, welding parameters, build-up welding sequence, temperature control, post-heat treatment, su***ce processing, etc. The process documents should be reviewed and approved to ensure their scientificity and operability.
4.2 Training for Operators: Weld overlay operators should undergo professional training to become familiar with the weld overlay process and equipment operation. Operators should possess excellent welding skills and a strong sense of quality, and be capable of strictly following process documents during operations.
4.3 Quality Records and Traceability A comprehensive quality record and traceability system should be established to document key parameters and inspection results during the su***cing process. Quality records should be authentic and complete, facilitating subsequent quality analysis and problem tracing.
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