The latest repair technology for rolling mill archway wear is different from traditional laser cladding methods

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[Abstract] Use new polymer composite materials to perform on-site repairs on the wear problems of the matching surface of the 1500 hot continuous rolling (rough rolling) mill arch and balance cylinder and the 1580 rough rolling mill arch at the lower support roller.； Compare with traditional laser cladding and other methods [Keywords] rolling mill archway wear, polymer composite materials, laser cladding: TG333.13 Document identification code: B1. Introduction In the strip rolling process, the plate shape control technology has the greatest impact on the strip yield. In the continuous rolling line, the rough rolling is an important equipment in the rough rolling area of ​​the rolling line. Once the rolling mill arch has wear problems, it will inevitably make it difficult to control the operating status of the rolling mill, resulting in a decrease in product rolling quality, affecting rolling accuracy and equipment service life. 2. Traditional maintenance methods for rolling mill archways. Traditional maintenance methods for rolling mill archway wear mainly include the following.: 1. Mechanical removal method. That is, the damaged layer on the surface of the arch is removed by machining online to process the mating surface, and the required accuracy is achieved by increasing the thickness of the lining plate of the balance cylinder or adding gaskets. After being repaired using this method, wear will appear after a period of use, and it will need to be machined again. Repeated machining will have an adverse effect on the strength and stiffness of the arch, and this method cannot fundamentally repair the wear. 2. It needs to be machined on site after repair welding to process the joint surface. Large area surfacing can easily cause the arch to deform and bend due to thermal stress. And after repair, the joint surface and lining plate will wear again due to impact and corrosion. It cannot fundamentally solve the wear and tear, and the construction period is long. It consumes a lot of manpower, material and financial resources of the enterprise. 3. Laser cladding. Compared with traditional surfacing, spraying, and electroplating, laser cladding has the characteristics of small dilution, dense structure, good combination of coating and substrate, many suitable cladding materials, and large changes in particle size and content. Therefore, the application prospects of laser cladding technology are very broad. However, the repair is often unable to be completed in a short time due to reasons such as high cost and long construction period. The comprehensive costs such as maintenance labor costs, equipment transportation and machining costs required for traditional maintenance are higher than those for on-site repairs, and they are also subject to greater on-site space limitations. 3. On-site repair of polymer composite materials On-site repair is a maintenance mode that has emerged in recent years. Its principle is to use polymer composite repair technology to repair on-site without machining. The chemical bond connection force formed after the repair polymer composite material is cured enables it to form excellent adhesion with the repaired metal parts, which meets the requirements of the equipment to withstand various composite forces during operation. On-site repair accuracy is guaranteed through several links: Rely on processing templates to repair worn parts to ensure the flatness and smoothness of the repaired parts ； Rely on the template to position the top screw to ensure the thickness of the material and the spacing between the arch frames. ； Relying on the properties of the material itself such as pressure resistance, corrosion resistance, ductility, and temperature resistance to ensure good use of the material. 4. Application case 4.1. Wear of the mating surface of the transmission side exit arch and balance cylinder of the 1500 rough rolling mill. The mating surface of the transmission side exit arch and balance cylinder of the 1500 rough rolling mill is worn. After the balance cylinder is disassembled, it is judged based on the matching parts of the balance cylinder oil groove and the arch and used as a benchmark to measure the wear size of other parts. The wear amount is about 3-5mm. In view of the wear problem of the matching surface between the balance cylinder and the rolling mill archway, we proposed a repair plan based on the on-site equipment conditions to restore the size of the rolling mill archway to the original design size to meet the installation and use requirements (provided that the thickness, size and flatness of the balance cylinder are not damaged, that is, the size of the balance cylinder after it is assembled with the liner will be the standard size). On-site repair construction technology 1. Process the template with a thickness of about 30-40mm according to the length and width of the balance cylinder and reserve fastening and positioning screw holes ； 2. The surface of the rack is first treated with oil, then the oxide layer is polished, and then the surface is sandblasted. ； 3. Clean the surface of the template, apply release agent to the reserved fastening and positioning screw holes of the template, and install the top screw in place. 4. Install the template. During the installation process, use a micrometer to measure with the symmetrical lining plate as the reference plane. During the measurement process, take at least six measurements to ensure the flatness and verticality after installation and meet the installation tolerance. After the size is adjusted, remove the template and keep the jack screw in place (see Figure 1) ； 5. Calculate the amount of material and mix and apply polymer composite material 2211F ； 6. Install the fastening template and measure the installation dimensions to ensure that the installation error is within the design tolerance. ； 7. After the material is cured, remove the template, polish the surface with sandpaper, remove the smooth layer on the surface of the material, and clean up excess material. ； 8. Apply release agent to the mating surfaces of the balance cylinder and rolling mill arch. ； 9. Mix the material again and apply a thin layer to the surface of the archway to be repaired to achieve a 100% surface fit. ； 10. Assemble the balancing cylinder, assemble it in place, and wait for the material to solidify. ； 11. After the material is cured, tighten the bolts appropriately again, verify the dimensions, and complete the repair. The on-site repair process is as follows: 4.2. 1580 hot continuous rolling rough rolling mill archway wear. The four lining plates at the lower support roller of the 1580 rough rolling mill archway have wear problems on the joint surface with the archway. The wear amount is 3-5mm. The repair was completed using polymer composite materials, and the repair was continued for half a year. The results were good, proving that the archway repaired by Fushilan products has good pressure resistance and corrosion resistance. On-site repair construction process 1) First weld the positioning strip on the lining plate, and after the welding is completed, assemble the positioning jack wire ； 2) Loosen the lining plate bolts, tighten the top screw, measure the crotch size of the arch, and adjust while measuring until the size is appropriate. ； 3) After the adjustment is completed, tighten the top screw cap and remove the lining plate ； 4) The surface of the archway is polished, baked, and sandblasted to make the surface reach Sa2.5 level or above. ； 5) Mix 2211F material and apply it on the repair surface ； 6) Apply release agent on the inner surface of the liner ； 7) Assemble the liner and measure the dimensions to ensure that the repaired dimensions meet the original design tolerances ； 8) Wait for the material to solidify (using heating curing method, 80℃/4h), and the repair is completed. Repair icon: 5. Summary Since we pioneered the polymer composite on-site repair process for impact wear of rolling mill arches in 2006, we have successfully implemented online repairs for the 450-F6 four-high rolling mill, 850 roughing mill, 650 roughing mill, 550 roughing mill, and 650 finishing mill. In 2016, the online repair of the impact wear on the mating surfaces of the eight bending fixing blocks and the rolling mill arch of the 1700mm hot continuous rolling F1-F6 finishing mill was successfully completed. In 2017, the online repair of the wear problem of the matching surface of the 1500 hot continuous roughing mill's archway and balance cylinder was an effective improvement of this technology in on-site equipment maintenance. Compared with traditional maintenance, Fushilan polymer composite on-site repair technology not only saves maintenance time, but also ensures that the equipment operates without abnormality after repair and meets the requirements of traditional repair processes. It is an important technical means for on-site equipment repair and maintenance worth promoting.