The mold material technology research and development field faces**

With the development of China's mold industry, higher and newer requirements have been put forward for the quantity, quality, variety and performance of mold materials, and the mold material market has also been rapidly developed. According to Luo Baihui, Managing Director of the International Tool & Die & Plastics Industry Suppliers Association, the range of materials used for moulds is very wide, from general carbon structural steel, alloy structural steel, carbon tool steel, alloy tool steel, high speed tool steel, stainless steel, Maraging steel to hard alloys, refractory alloys, high-temperature alloys, non-ferrous metals, etc. can be used, among which are die steels belonging to alloy tool steels. At present, the output of China's alloy tool steel is among the highest in the world, with about 100,000 tons of alloy die steel. The annual consumption of mold materials by the Chinese mold industry totals 300,000-400,000 tons, of which the alloy mold steel ranges from 130,000 to 150,000 tons.

According to Li Guangchao, an expert consultant of the Steel Professional Committee of the International Die & Metals and Plastics Industry Suppliers Association, the quality of the domestically produced mould steel is relatively low. A considerable portion of the required die steel needs to undergo vacuum refining and electroslag remelting in order to ensure high steel quality. Cleanliness, high density, and high tropism, while the share of die steel remelted by electroslag is small. About 80% of the die steel market is black bar. After users get the material, they have to change their own forging system. The material utilization rate is low and the production cycle is long. It can not meet the needs of the modern mold manufacturing industry.

Traditional steel alternative technology Shenzhen Castro Special Steel Co., Ltd. developed a new type of high-efficiency TS4 mold copper alloy material, hardness up to HRC38-45 degrees, no heat treatment, easy production and processing, low friction coefficient, and add resistance in the alloy Grinding the element makes the wear resistance of the originally wear-resistant copper alloy further improved, and is particularly suitable for the need of a drawing die. In the cost of mold manufacturing, the material cost only accounts for about 20% of the cost of the mold. However, the competition in the mold industry is a competition for the efficiency of the mold, rather than the low price of the mold material, so the long life is required. Molds often require excellence in the selection of mold materials. For example, the use of Cr12MoV steel with 5-6 grades of carbide to produce tensile dies, the service life is often less than 10,000; and the use of TS4 copper alloy molds to produce tensile dies, the service life of up to 70,000 or more . This is because the TS4 copper alloy mold has good thermal conductivity, which can ensure that the temperature distribution of the mold in the work is even, and the mold will not be cracked due to local high temperature, and the surface of the drawn product will not show cold welding off marks and wrinkles. This will not only shorten the mold opening time, increase the life of the mold, but also increase the production efficiency and product quality. Now TS4 copper alloy molds have been successfully applied to stainless steel sheet tensile dies, aluminum alloy die casting dies, plastic injection dies, copper alloy gravity casting and low pressure casting dies, and glass bottle manufacturing dies, which are about to replace traditional die steel and cast iron. It is a revolution in the field of mold materials.

The laser surface enhancement technology for metallic materials can be used for surface strengthening of metallic materials, solving the contradictions that are difficult to overcome by integral strengthening and other surface enhancement methods; it can also be used for surface modification of metallic materials to obtain high-performance surface layers of low-grade materials. The replacement technology of mold materials caused by laser surface strengthening technology opens up new ways to reduce the cost of mold manufacturing.

1. Material Replacement Techniques for Cold Work Dies Cold work die materials require strength, toughness, wear resistance, fatigue resistance, and bite resistance properties. The cold working mold adopts medium-high carbon carbon steel, low alloy steel or cast iron and is replaced with high-grade material of traditional technology after laser phase transformation strengthening, and there is a wide range of technical applications. Although the high alloy steels widely used in cold work molds have the unique wear resistance effect of alloy carbides, laser phase transformation intensification is due to its dispersion strengthening, distortion strengthening, processing process and heat treatment process without oxidation without decarburization and having a strong working layer. It can make up for the wear resistance of the alloy carbides of high alloy steels. Therefore, the advantages of laser-enhanced process flexibility can be more widely used in the field of material substitution technology. When the working temperature of the plastic mold is below 350°C, it has the same material replacement technology space as the cold mold.

2. Material Replacement Techniques for Hot Work Dies In addition to the requirements for strength, toughness, wear resistance, fatigue resistance and occlusal resistance, hot work die materials have special requirements for red hardness and anti-tempering performance. Therefore, the use of low-grade laser transformation hardening can not replace the high-temperature steel with high-temperature properties. Die remanufacturing technology and laser cladding can make carbon steel, low alloy steel or cast iron have high temperature resistance. When the operating temperature of the plastic mold is above 400°C, the same material replacement technology can be used for the hot mold.

3, cast iron mold cast iron mold reinforcement potential depends on whether the matrix is ​​pearlite. If the matrix has too much ferrite, the hardenability of the material will be reduced, so the material substitution of cast iron molds aims to increase the potential for reinforcement. Based on national standards, ductile iron needs to be selected from QT600 or above, vermicular cast iron should be selected above RT380, and gray cast iron should be selected from HT200 or above. At present, a large number of HT150 molds exist in the market, and such molds have poor effect of phase transformation hardening.

4. The remanufacturing technology of gears and molds applies a laser cladding process on the damaged or defective parts of gears or molds to clad specific alloy materials to form a good metallurgical bond with the base metal material. This repair process is not just for gears or Repairing the topography of the mold and improving the performance of the repair site is an enhanced repair. The laser surface cladding that has been used for gear and mold repair is currently referred to as the gear or mold remanufacturing technology.

Before the launch of the third-generation automobile steel industrialization application, Academician Xu Kuangdi, Honorary President of the Chinese Academy of Engineering, witnessed the unveiling of the Advanced Automobile Steel Joint Laboratory of the China FAW Technology Center and the China Iron and Steel Research Institute Iron and Steel Research Institute at the Chinese Academy of Engineering. This marriage between the domestic automakers and the steel research national team officially opened the curtain for the third-generation automotive steel industrialization application that was pioneered by China in the world.

According to the introduction of Gan Yong, the vice president of the Chinese Academy of Engineering and the chairman of the China National Steel Research Institute, among the car's weight, steel materials account for about 70%. Therefore, the development and application of high-performance, low-cost, high-precision, easy-to-process, and green advanced automotive steel materials are critical to the safety, light weight, and energy conservation and emission reduction of automobiles. He disclosed that the Steel Research Institute has taken the lead in successfully developing the third generation of automotive steel technology in the world, forming a leading material R&D advantage in this field; and the Steel Research Institute and the FAW Technology Center during the period from the 8th to the 11th five-year period. There have been numerous cooperations in material technology R&D projects, and a large number of successful applications have been achieved in advanced non-quenched and tempered steel, gear steel, spring steel and stainless steel. The establishment of a joint laboratories between the two parties will enable the strengthening of cooperation in automotive new materials such as hot-formed steel and die steel and related process technologies to form a complete world-class advanced automotive steel R&D and application technology system.

Li Jun, Deputy Chief Engineer and Director of Technical Center of FAW, introduced that in the 12th Five-Year Plan period, FAW’s third-generation high-mobility tactical military vehicles, the liberation of the seventh-generation commercial vehicles, a new generation of lightweight cars, new energy vehicles and other products, as well as automotive lightweight Design, automotive safety design, SCR (Selective Catalytic Reduction System) post-processing of key metal materials, etc., will be the main battlefield for the third generation of automotive steel.