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Roller online surfacing repair technology

  1. Roller press repair technology

  The extrusion roll on the roller press is a key component in the production line. The wear layer on the surface of the extrusion roll is usually only 10mm thick, and the metal exposed after wear of the wear layer will be worn away in a very short time, resulting in deep wear of the extrusion roll (see figure 1).

  Therefore, after the roller press works for a period of time, it needs to carry out surfacing welding repair for its surface wear layer. According to the working condition, it can be divided into repair without removing the extrusion roll (online repair for short) and repair with removing the extrusion roll (offline repair for short).

  Among them, due to the advantages of short online repair cycle and small impact on production, most of the extrusion rolls are repaired in this way, but there are the following difficulties in the field construction:

  (1) short construction period is required. The shorter the online surfacing repair period, the better, to meet the requirement of starting up the cement production line as soon as possible after maintenance.

  (2) the large diameter of the roller causes the risk of quality problems after surfacing welding. The diameter of the large extrusion roller is usually 1000~1800mm, and the width of the roller surface is also 450~1400mm.

  This kind of solid roller with large diameter and thickness will produce great welding stress and welding residual stress.

  The welding stress can easily cause the spalling of the high hardness wear-resisting material for surfacing welding on the roller surface, or the overlaying of the welding residual stress with the working load can cause the spalling of the wear-resisting layer for surfacing welding and damage the extrusion roll (see figure 2).

  (3) for surfacing welding of extrusion roll, which involves a large amount of welding work and requires strict welding process formulation, except that the first part of the work is planing, the rest is welding work.

  For surfacing welding of a roller press, the welding wire ranges from 2000 to 4500kg depending on the type. For a single roller, the welding wire ranges from 400 to 600kg per day.

  Due to the particularity of hardfacing welding, different welding materials and processes such as transition layer, repair layer and wear-resisting layer should be adopted during welding.

  2. Implement surfacing welding of roller press

  In view of the above roller press online repair of several major difficulties, key points, in the maintenance and construction must be developed before a reasonable construction plan, welding process guidance and other measures, the construction process must be strictly monitored to ensure the quality of various construction processes.

  (1) organize and implement specific project leaders, safety and quality supervisors, day shift, middle shift and night shift leaders, as well as specific construction personnel.

  The specific construction nodes should be reasonably formulated and completed on time according to the process nodes of preparation, preheating, planing, rounding, surfacing welding transition layer, repairing layer, wear-resisting layer, decorative pattern layer and trimming to meet the short construction period.

  (2) tools and welding materials required for construction before construction, sufficient welding equipment, hoisting tools, grinding tools, cutting tools, cables and other machines and tools shall be prepared according to the site conditions of the project, and consumables shall be matched.

  Prepare different types of welding wire according to welding process and make budget for surfacing welding.

  The welding process is developed after the technical communication with the manufacturer before the construction to understand the material of the extrusion roll. For different roll body materials, different types of transition layer welding materials should be used. Specific welding current, arc voltage, welding speed and other parameters are given for different welding positions.

  Automatic planing and welding are adopted as far as possible to ensure the quality of large workpiece such as extrusion roller and reduce the labor intensity of workers.

  After the welding material and welding parameters are defined, the appropriate preheating and welding interlayer temperature are selected.

  Preheating and heat preservation is to avoid large welding stress and residual stress caused by too large temperature difference between the welding area and other areas.

  Each welding personnel on site shall have a welding process instruction to avoid quality problems in the welding process.

  (4) detailed construction implementation rules should be formulated to enable everyone to guide the work within each node to improve efficiency.

  For example, the following construction steps are as follows: complete the construction procedures remove the slant board remove the side baffle remove the roll surface fatigue layer fully weld the roll surface install the slant board install the side baffle clear the site test machine.

  The implementation of the above plans ensures the progress and quality of our company in the repair site of several rollers. Through the inspection of practice, the construction plan and welding process developed by our company are reasonable.

  I hope I can keep optimizing in the future work to achieve higher efficiency and better quality.

  3. Conclusion

  The welding process of roller press online surfacing repair technology is complex and requires strict requirements, which requires close cooperation and cross penetration of basic science and engineering science, and continuous innovation and development according to the engineering reality.

  With the continuous development of technology, roller online surfacing repair technology will also continue to upgrade, a comprehensive grasp of roller online surfacing repair technology, for the prosperity of China's cement industry and efforts.

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