First, the market background of laser remanufacturing technology
Remanufacturing engineering is a project practice guided by the product's life cycle theory. The full cost of equipment demonstration, design, manufacture, use, maintenance, and recovery is called life-cycle cost. Traditionally, it only pays attention to the “first half of life†of the equipment (this period only accounts for 20 to 40% of the cost), and often ignores it. The "later half", the cost of use, maintenance and scrapping.
The remanufacturing of equipment is based on the "second half of life" of equipment to improve utilization, save resources, protect the environment, and adhere to sustainable development. The development of remanufacturing technology must be integrated into high technology, and the old parts and equipment must be regained high-quality, high-value-added products. Therefore, the remanufacturing industry is an important technology that achieves leapfrog development and is fully in line with national policies. The U.S. remanufacturing industry has an output value of 53 billion U.S. dollars and employs 480,000 people. They claim that "remanufacturing is a potential giant." The Chinese government attaches great importance to the development of the remanufacturing industry. In 2005, the State Council issued a number of opinions on accelerating the development of circular economy and a notice of the key tasks for the construction of a conservation-minded society. It explicitly stated that it must actively support the remanufacturing of used and used mechanical and electronic products.
However, on the whole, China's remanufacturing industry is developing slowly and is still in the initial stage of exploration. There is still a big gap compared with developed countries. The main problems in the development of China's remanufacturing industry are as follows: First, as a new concept, remanufacturing has not yet been widely recognized, and the importance of all parties in the development of the remanufacturing industry lacks sufficient understanding. Second, remanufacturing has not yet formed an industry. The foundation, technology and management level are still relatively low. Third, the current regulations and policies restrict the development of the parts remanufacturing industry in certain aspects.
The iron and steel metallurgy industry is the basic industry of the country. It also belongs to the country's heavy industry, and its equipment is complex, with many types and heavy tonnage. Due to friction, wear and other reasons, to maintain the normal operation of the equipment, a large number of spare parts will be consumed each year. According to statistics, in 2003 Jinan Iron and Steel Co., Ltd. reached an annual output of 3.34 million tons of steel, and the company's annual spare parts for equipment repair costs as much as 120 million yuan, the spare parts repaired old waste amounted to more than 150t, an economy The benefit is about 20 million yuan. Therefore, reducing the consumption of spare parts and the remanufacturing and remanufacturing of used equipment have a positive role in promoting the reduction of production costs and improving the economic efficiency of enterprises, and there is great room for cost reduction. Among them, laser remanufacturing technology has a very practical significance for the energy conservation and consumption reduction of enterprises in order to repair and repair spare parts.
Second, the feasibility of laser remanufacturing technology
(A) The main features of laser remanufacturing technology â— Laser processing is non-contact processing, there is no direct impact on the workpiece, so no mechanical deformation;
â— No "tool" wear during laser processing, no "cutting force" acts on the workpiece;
â— During the laser processing, the laser beam has a high energy density, a high processing speed, and a local processing, and has no or minimal influence on the non-laser irradiation portion. Therefore, the area affected by heat is small, and the thermal deformation of the workpiece is small and the subsequent processing is minimal.
â— Because the laser beam is easy to guide, focus, and realize the direction change, it is easy to cooperate with the CNC system and process complex workpieces, so it is an extremely flexible processing method;
â— High production efficiency, stable and reliable processing quality, good economic and social benefits;
(B) The advantages of laser processing The laser's valuable properties determine the laser's advantages in the processing field:
1 Because it is non-contact processing, and the energy of high-energy laser beam and its moving speed are adjustable, it can achieve a variety of processing purposes.
2 It can process a variety of metals, non-metals, especially materials that can handle high hardness, high brittleness, and high melting point.
3 There is no "tool" wear during laser processing and no "cutting force" acts on the workpiece.
4 During the laser processing, the laser beam has a high energy density, a high processing speed, and a local processing, and has no effect on the non-laser irradiation site or minimal impact. Therefore, the heat affected zone is small, the workpiece thermal deformation is small, and the subsequent processing volume is small.
5 It can perform various processing on the workpiece in a closed container through a transparent medium.
6Because the laser beam is easy to guide and gather, it can be changed in all directions. It is easy to cooperate with CNC system and process complex workpieces, so it is an extremely flexible processing method.
7 The use of laser processing has high production efficiency, reliable quality and good economic benefits.
Third, the main types of laser remanufacturing technology
1 laser quenching and texturing laser quenching technology is the use of focused laser beam incident on the surface of the steel material, so that the temperature rapidly rise above the phase transition point, when the laser is removed, because the material is still at a low temperature of the inner layer of fast The heat conduction effect quickly cools the heated surface layer to below the martensitic transformation point, thereby realizing surface hardening of the workpiece. For example, the maximum hardened layer depth of laser melting and quenching on the surface of large rolls can reach 2 mm or more.
2 Laser Cladding and Alloying Laser cladding technology is a process that uses a laser beam to cover a specific layer of material on the surface of a selected workpiece to improve the surface performance of the workpiece. For the metallurgical industry, a large number of wearing parts such as rollers, guides, conveyor rollers, pinch rollers, and shear blades, the biggest benefit of the laser cladding and alloying technology is to turn the alloying of the rolls into surface alloying or cladding. , While the service life of consumables such as rolls is greatly increased, the increase in production costs is limited. Obviously, whether the design, selection and use of alloy powders are correct is the key to the success of this technology.
Figure 1 Axial head laser welding repair
3 Laser welding Laser welding is one of the important aspects of the application of laser material processing technology. The principle is to irradiate high-strength laser to the metal surface. Through the interaction of laser and metal, the metal is melted to form a weld. Due to its unique advantages, it has been successfully applied to the precision welding of micro and small parts. For example, the typical cold-rolling process routes currently taking the lead in China's steel industry are: converter smelting - off-furnace refining - bloom-opening - hot continuous rolling - pickling - cold rolling - annealing - smoothing - galvanization (tin) - products . In this typical cold rolling process, strip welding equipment is indispensable. In the course of operation, the first steel strip and the following steel strip must be welded in order to ensure the continuous operation of the production line. When the silicon steel strip is operated online, it needs to undergo many “Sâ€-type bending deformations and withstand a certain amount of running tension, which has high requirements on the performance and quality of the weld seam.
IV. Application of Laser Remanufacturing Technology in Iron and Steel Metallurgy Industry
1. Repair and Strengthening of Rolls Most of the production equipment of the metallurgical industry works in harsh environments with high (alternating) stress and high thermal stress, such as continuous casting rolls, straightening rolls, grooved rolls, semi-steel rolls, cast tube molds. , hot (cold) rolling work rolls, blast furnace chutes, material bells and so on. Among these devices, various rolls are undoubtedly the most critical equipment parts. Their large consumption, high price, and long life span are not only closely related to product cost, but also directly determine the quality of steel products, especially surface quality and plate type. Laser-surfacing welding is used to repair various rolls, which are better at small rolls and local repairs. Performance as new. As shown in Fig.1, in actual use, the first use period of the roller after the surfacing repair has reached more than 1 year, which is more than 3 times higher than the average service period of the non-surfacing 60SiMnMo forged steel roller (3 months). After use, if the substrate is damaged (for flaw detection), resurfacing can be performed again. Most cases are repaired 3-4 times.
Laser hardening technology can surface-enhance all kinds of guide rails, large gears, journals, cylinder walls, molds, shock absorbers, friction wheels, rollers, and roller parts.
Because of the high glossiness of the reflected image after laser painting, the laser texturized automotive board is called “mirror plate†in foreign countries. It is a high-quality plate for the production of high-grade cars. Therefore, laser texturing cold rolled sheet (belt) is an important raw material for automotive, home appliances, electronics and light industry production needs. Figure 2 shows the state of the laser hardening work of the plate roller.
Figure 2 Laser thickening of plate rollers
2. Repair of various shaft parts such as wear, hold, and cracks After welding, the shaft parts have no thick casting structure, and the overlaying layer and interface structure are fine, grain refinement, and no holes. , Blisters, inclusions, cracks and other defects, performance as new.
Figure 3 Laser repair of shaft wear
3. All kinds of high value-added large, medium and small gear parts in the metallurgical industry can be repaired and strengthened by laser welding technology, which can restore the performance of various high-value-added large, medium and small gear parts. Acceptance criteria are still based on original manufacturing standards.
Figure 4 Shenyang Golden Cup door joints laser surface enhancement
4. The repair blades of the high-pressure high-speed fan blades are very harsh because of their poor working environment. The impeller blades are vulnerable to severe corrosion and wear at the air inlet. Generally, the blades are scrapped due to corrosion and wear of the impeller blades after 3 000 to 4 000 h. The use of laser welding technology can make the repair layer metallurgically combined with the original substrate, hardness reaches HRC55 or so. Service performance is like new items.
5. The tailor-welded steel plate for laser welding of automobile plates is to weld several pieces of steel with different materials, different thicknesses and different coatings into one integral plate, so as to meet the different performance requirements of different parts of the parts. Laser Tailored Blanket Technology is a modern processing technology developed based on mature laser welding technology. Using tailor-made blanks can bring huge economic benefits to the automotive industry. For example, a large number of spot welds in the body assembly, the two welding heads are clamped on the edge of the workpiece for welding, the flange width needs to be 16mm, and the laser tailored plate Without lap welding, spot welding can be replaced by laser welding to save steel. The amount of savings depends on the number of tailor-welded plates; two 0.8mm steel stampings are welded with conventional spot welding, with an average of 20 points per minute. The soldering distance is 25mm, and the speed is 0.5m/min. This will take a considerable time. The time needed after replacing the spot welding process with a tailor-made blank can obtain a large amount of savings, and the welding quality can be qualitatively improved. At present, the technology is developed in Baosteel, Wuhan Iron and Steel and Anshan Iron and Steel with the introduction of foreign technologies. The investment is huge. The localization of this equipment and the localization of technology still require the full cooperation of steel production plants, laser manufacturers, universities and research institutes to change the current situation. There is a huge demand in the domestic market for fully automated laser tailor-welded complete sets of equipment. Now the country has invested a lot of funds and support for laser welding technology equipment, and strives to make the complete set of laser tailor-made welding equipment with independent intellectual property rights available on the market as soon as possible. The application of the board contributes its own strength. Figure 5 shows the results of the repair experiment of the laser welding resurfacing size of a metallurgical roll shaft head of a company. FIG. 6 is a schematic diagram of components that can be welded using a laser in a car. As can be seen from the figure, the potential for automotive tailor-welded panels is very large.
Figure 5 Metallurgical Roller Shaft Head Laser Resurfacing Restoration Size Repair
Fig. 6 Schematic diagram of laser welding parts of automobile clutch
V. Cost Analysis and Prospect of Laser Remanufacturing Technology
The biggest cost of laser processing is that the disposable investment of the equipment is relatively expensive. Once the equipment is put into operation, the operating cost is relatively low without considering the input cost of the equipment. Since the rolls, shaft parts, blades, and gears in ferrous metallurgical equipment are high value-added parts, the cost of laser processing is below 25% of the original value. And the short cycle time of laser processing can greatly save the time of maintenance, thus ensuring timely production and performance as new.
With the rapid development of laser processing equipment and processing technology and unprecedented improvement in people's remanufacturing awareness, the depth and breadth of application of laser remanufacturing technology will become more and more in-depth and extensive, bringing unprecedented benefits and development, and saving for construction. Economic society makes application contributions.
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