ã€Abstractã€‘Analysis of the problem of low welding rate of welding wire during the repair process of grinding roller surfacing and welding, and proposed solutions and methods. And the detailed operation rules have been formulated. By cooperating with the refined management production mode, the welding rate of the welding wire in actual production is effectively improved, which provides the necessary guarantee for the enterprise to save production cost and increase production profit.
The coal mill is one of the important auxiliary equipments of the boiler system of the thermal power plant. The grinding roller and the disc lining of the coal mill are the key components of the coal mill, and the rotary rolling effect of the coal roller on the lining of the disc will be The coal between the grinding roller and the grinding disc is pulverized into pulverized coal that meets the burning requirements. After the grinding roller and the grinding disc lining are operated for a certain period of time, the pulverized coal particle size after coal crushing does not meet the burning requirements due to different degrees of wear, which affects the efficiency of the coal pulverizer. Therefore, major power plants will arrange maintenance intervals during the production process to replace worn-out grinding rolls and disc liners. In order to save production costs, the replaced grinding rolls and disc linings can be repaired by surfacing, usually by surfacing high chromium metal materials on the surface and returning to the design size and continuing to use. The use of such a surfacing repair method not only reduces the production cost, but also improves the wear resistance of the surfacing metal material, prolongs the service life, reduces the frequency of inspection and improves the production efficiency.
2. Current problems in production
In the production process of roll surfacing repair, the biggest production cost is the welding wire. According to the industry regulations, the standard welding wire deposition rate should be â‰¥ 85%, but in the actual use process, companies engaged in grinding roller (disk) surfacing repair can not meet this standard. The prevailing situation is: when the loss is minimal, the welding rate of the wire can reach 80%; when the loss is maximum, the welding rate of the wire can only reach 70%; for some enterprises with poor management, the welding rate of the wire is even less than 70%. . The average welding wire deposition rate we have in the specific production is 80%, and there is also the welding rate of the welding wire used by different operators after the grinding roller (disk) surfacing repair under certain welding parameters. A phenomenon that is quite different. It is calculated that if the welding wire price is 40 yuan/kg, the wire loss can be reduced by 0.4 yuan/kg for every one percentage point increase in wire welding rate. If the annual consumption of 40t welding wire, the deposition rate increases by one percentage point, can save wire loss of 16,000 yuan. It can be seen that increasing the welding rate of the wire plays an important role in reducing the production cost.
To this end, we take the fine management concept as the leading factor, start from the details, design a fine management plan, and adopt a series of innovative measures in the management system and specific technical methods, which not only makes the deposition rate of surfacing wire greatly The increase, and the high deposition rate value are very stable in the production of each batch, achieving the purpose of reducing consumption and increasing efficiency.
3. Solution ideas and content
Through the study of the concept of â€œfine management, lean productionâ€, we realized that â€œmanagement starts from the refinement of the production lineâ€ and solves this problem from the details of production.
The specific management ideas and contents are as follows:
(1) Contact the welding wire manufacturer, and the on-site surfacing operation of the professional sent by the manufacturer to verify the specific value of the welding wire deposition rate of the manufacturer.
Inviting the manufacturer of the welding wire to send a special person to our unit grinding roller surfacing repair production line for welding demonstration and on-site guidance. It is estimated that the surfacing welding personnel sent by the manufacturer completes the surfacing repair grinding roller, and the welding wire deposition rate used is 85.78%. According to this, we clarify the welding wire deposition rate reference value after each grinding roller surfacing repair is completed. Set to 85%.
(2) Formulate detailed and detailed instructions for the surfacing repair process, refine the welding parameters, operation steps, operation modes, etc., and finally realize the operation according to the work instructions. The shape and appearance of the grinding roller bead of each operator's surfacing repair are uniform, and the welding wire deposition rate value is â‰¤1%.
The key refinement points are as follows:
First, refine the underlying welding parameters. Since the wear degree of each grinding roller is different, the surface of the roller body after initial repairing is still uneven. On the basis of ensuring the bonding strength, we use low current, high voltage and zero lap to reduce the roller body. Wire spatter loss caused by uneven surface.
Second, refine the number of times the surfacing layer is rolled. On the basis of the welding parameters of the surfacing layer, the original process specification only gives the condition that the grinding roller needs to be turned over. â€œKeep the position of the welding gun perpendicular to the radial horizontal line of the grinding roller (disc)â€. This condition is relatively rough and difficult to master. People often fail to overturn the grinding roller due to the difficulty in flipping the angle, or arbitrarily reduce the number of times the roller is turned over due to the inability to flip the roller in time. No matter how many times the number of inversions is too small or too small, the welding wire and the roller body will not be perpendicular to the horizontal plane of the radial direction, and a large amount of splash will be generated. This splash will not only make the appearance of the roller body unsightly, but also greatly increase the welding rate of the welding wire. decline.
After repeated actual calculations, it is found that in the case of a single pass weld bead width and a lap joint ratio, the total width of the bead of the grinding roll surfacing layer is 15 cm, and the total width of the bead of the grinding wheel surfacing layer is adjusted. Turning the disc angle to 20c m can significantly reduce the welding wire splash, not only improve the welding rate of the welding wire, but also make the surface of the grinding roller after the surfacing repair very small, and the appearance is very flat. Specifically, as shown in the attached drawings.
(3) The work instruction book is equipped with the corresponding flow chart, the operation process is clear at a glance, the technical requirements are simple and clear, and it is convenient for the operator to master the study.
Grinding disc flipping
(4) Formulate the reward and punishment system for the welding rate control of the surfacing welding wire, and classify the operators by the welding rate of the welding wire, and reflect the reward and punishment measures on the distribution of the welding wire.
With the welding wire deposition rate of 85% as the standard, after each batch of grinding rolls is completed, the welding rate of the wire used for the repair of the batch is calculated. According to the welding record, the welding rate of the wire is decomposed to each operator. . If the deposition rate is â‰¥85%, it is rated as Grade 1; the deposition rate is 82%~85%, which is rated as Grade 2; the deposition rate is 80%~82%, which is rated as Grade 3; For 80%, the corresponding penalty is imposed.
4. Application effects and economic benefits
(1) Application effect The statistical results of the project management innovation measures after one month show that the average welding wire deposition rate reaches 87. 2%, and the welding rate of individual operators can reach 90%. After the subsequent actual operation assessment, it was found that with this series of fine management measures, not only the welding wire deposition rate was stable at 87%, but also the grinding roller bead after the surfacing repair was regular, and the entire surface was almost free of visible splashes. Obtain the unanimous approval of customers. The operators also formed a special study technology, learning style that is better than learning, and the first-level operators alternately replaced, and the welding rate of welding wire has reached new highs.
The innovation of the project in the management concept and management system is simple and clear, and the operation is strong. The specific technical methods can be found in the key production processes that affect the production cost and product quality with the refined concept. The key point, therefore the project can be widely promoted in enterprise production management.
(2) Foreseeable economic benefits Through the implementation of refined management methods, we have increased the welding rate of welding wire from 80% to 87%. As mentioned above, the wire welding rate can be saved by one percentage point. 16,000 yuan. The welding wire deposition rate is increased by seven percentage points, and the wire loss is saved by 112,000 yuan.
With the expansion of production scale, when the consumption of wire is 100t, the deposition rate can be saved by 40% for each percentage point, and the wire loss can be saved by 280,000 yuan. Obviously, the larger the scale of production, the lower the production cost and the greater the profit.
Detailed operating procedures are formulated in production, and by implementing refined management methods, the welding rate of the welding wire can be significantly improved, and a strong guarantee for saving production costs and increasing corporate profits is provided. (Author Source: China Armed Industry No. 5 Institute)
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