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The repair work of equipment parts has been paid attention to and developed continuously. For example, since the Sixth Five-Year Plan, the brush plating technology and thermal spraying technology promoted by the State Economic Commission have played a big role in mechanical maintenance. Many equipments have been brought back to life, saving a lot of money for enterprises. However, these techniques have limited repair effects on equipment wear, corrosion and fatigue damage, and are even more ineffective for some serious damage. For example, the herringbone gear of the rolling mill, some of which weigh more than 50 tons left, the hardness of the tooth surface is HB=207～288, and the tooth surface width is about 750mm. After long-term use, the tooth surface wear depth can reach 5~50mm, and most of them are Pitting flaking and broken teeth, etc., such damage is generally difficult to regenerate and use. The maintenance technology that has been promoted on the one hand is that the site is not well operated. Even if it is repaired on site, it is easy to fall off and break after repair. Delamination. In addition, various advanced repair technologies have great limitations on the thickness of the repair coating.
Based on years of practical experience and painstaking research, the author has developed a new material named “FGM-KMâ€, a new material that diffuses and strengthens the composite metal gradient function. This new material is combined with the corresponding treatment and repair process. Complete repair can be realized. The repaired part can not only fuse well with the original matrix, but also its strength, hardness and toughness can be compared with the original matrix or even better than the performance of the original spare parts. Times. This material and fusible can be repaired to a thickness of 1-100mm.
I. Gear Status In 2006, Hebei Wu'an Wenfeng Iron and Steel Plant applied this project to repair the 650 rolling mill herringbone gear shaft and achieved good results.
The basic parameters of the gear shank of the 650 rolling mill gear of Wenfeng Steel Plant, the normal modulus Mn=25, the number of teeth=26, the normal pressure angle 20°, the helix angle 29°55'35'. The gear carrier transmits a torque of 55 MN.m, which is the main equipment for the rolling line. In February 2006, there were 2 teeth broken teeth of the herringbone gear shaft, the length of the broken teeth was 300mm, and the other teeth had different crack lengths and were discontinued for repair. Wenfeng Factory invited the company to review the site and jointly research and determine the use of "FGM-KM" new materials and their deposition process to repair the broken teeth. After Wenfeng Factory requires repair, it must be able to adapt to the working conditions of Wenfeng Factory 650 gear seat to ensure that the repaired folding teeth and the existing gear teeth have the same geometric parameters and good meshing. The operation should be stable and there must be no extra impact. Repair the broken teeth and the existing teeth have the same life.
Second, the repair principle and process 1, "FGM-KM" new material composition and working principle "FGM-KG" new material is a group of special alloy powder series, it has fusibility, easy to fuse with the substrate, and both Comprehensive physical properties such as abrasion resistance, impact resistance, heat resistance and corrosion resistance. The alloy formed by the fusion of the powder on the surface of the substrate has a metallographic structure mainly composed of pearlite, martensite, austenite and biaxial wear-resistant alloy. When the deposited powder is converted from a solid state to a liquid state and then converted into a solid state, the surface metal oxide of the substrate is deoxidized, and a low-melting borosilicate-based slag is formed to form a protective film, so that the molten alloy and the treated solid base are formed. The metal material reaches the metallurgical bond. During this process, the surface metal of the substrate penetrates into the molten metal and diffuses into each other, eventually forming a metallurgically infiltrated alloy layer. During the construction process, according to different substrate materials and different layer requirements such as bonding layer, transition layer, working layer and processing layer, the matching powder is selected for welding, and the above welding process is repeated to obtain the tissue. The dense metal cladding layer with excellent hardness, strength and toughness gives the workpiece working surface a special strengthening treatment effect of wear-resistant and corrosion-resistant two-phase modification.
2, "FGM-KM" new material deposition process authors repeated trial and research, the ordinary arc welding machine through frequency conversion, expansion of power and other special transformation measures, using arc welding for melting, that is, side and side melting process The alloy can be penetrated to metallurgically bond with the substrate. This welding process not only reduces the equipment requirements for repair, but also simplifies the repair process and greatly reduces the cost of repair. The thickness of the deposited layer can be up to about 100 mm.
3, the design of the fragile layer of the herringbone gear and broken tooth "FGM-KM" alloy.
The design of the "FGM-KM" gold-containing cladding layer is critical. As mentioned above, the layers must be designed differently depending on the operating conditions and the material of the substrate. Wenfeng Steel Plant m=25, z=26 tooth profile, should be considered according to the working conditions of steel rolling and the base material 42CrMo. Considering the actuality of Wenfeng, we designed the section of the gear "FGM-KM" welding layer. No weld quality defects are allowed when welding the layers.
4. Repair process of broken teeth: According to the actual situation, we plan the repair process of broken teeth: cleaning and flaw detection→purification and coarsening→preheating→welding “FGM-KM†alloy layer according to layer design→making tooth shape template→coarse grinding tooth Profile → flaw detection and grinding.
Third, the repair effect in accordance with the normal steps after a few days of work day and night, finally repaired the gear shaft successfully a test run, the normal operation is good, has produced 900,000 tons of various types of steel. After parking, the condition of the gear shaft teeth was checked, the tooth surface was well meshed, and no abnormality was found. The repair was well received by the staff of Wenfeng Factory, which saved the Wenfeng plant costs, improved the equipment operation rate, and achieved good economic benefits.
Conclusion It is feasible to use a specially modified silicon rectifying welder to weld the "FGM-KM" alloy material and process by arc welding to repair the broken teeth of the mill's herringbone gear shaft. Through process improvement and exploration, we have applied the “FGM-KM†repair process to repair large parts such as large parts and rotary kiln belts. Practice has proved to be very successful. This method is used to repair workpieces with a thickness of more than 100mm. It has unique effects that cannot be achieved. This technology is widely used in various industries across the country, and it is bound to achieve better economic and social benefits.