WBM , a professional provider of bearing cold heading dies, taper rollers, grinding tools and detection equipment and comprehensive service of consultation/trading in supply chain in bearing industry will be your best excellent supplier choice.http://www.w-bm.com/products/Tooling/416.html
In the 1950s, all of China's mold steels were attacked by foreign steel grades. In the 1960s, in order to save raw materials and improve the accuracy of blanks, there was a rapid development of less cutting technology and precision forming technology. In order to improve production efficiency, many high-efficiency pressure processing equipments were used, and forging hammers were gradually replaced by presses. The performance of the original mold steel often fails to meet the high performance requirements of the service conditions, affecting the service life of the mold and the promotion and application of new equipment and equipment for pressure processing.
At the end of the 1970s, the use of precision and large-scale engineering plastic products became increasingly widespread. The demand for steel for plastic molds increased sharply, and new requirements were placed on the performance of plastic mold steels. Since the 1960s, with the support of relevant state ministries and commissions, Chinese scientists and technicians have developed a number of new mold steels based on national conditions. Some of the new steel grades with excellent performance and good process performance are subject to mold manufacturing and use units. welcome. During this period, some foreign-used steel grades were also introduced, some of which passed the production trial and achieved good results. For some cold-working die steels and hot-working die steels with better effect, the relevant departments have separately organized performance comparison experiments and put forward suggestions for selection and application.
In order to meet the needs of high wear-resisting and long-life molds, in the late 1950s, China's cemented carbides developed rapidly, and a variety of steel-bonded cemented carbides were also developed, which were used as molds to achieve good results. This paper is divided into six parts: cold work die steel, hot work die steel, plastic die steel, hard alloy and steel bond carbide, mold heat treatment, prospects and recommendations. Cold work die steel At present, the cold work die steel commonly used in China is still the old steel grade of low alloy tool steel CrWMn and high carbon high chromium tool steel Cr12MoV and Cr12. CrWMn steel has proper hardenability and wear resistance, and the heat treatment deformation is small. However, the CrWMn steel needs to be strictly controlled to control the cooling rate after forging, and the appropriate heat treatment is used to make the carbides uniformly and finely granular and distributed on the substrate. Otherwise, it is easy to form a network of carbides, resulting in chipping and cracking of the mold during use. High-carbon high-chromium tool steel has high wear resistance, but its carbide segregation is more serious, leading to a decrease in the direction and strength of deformation.
The degree of segregation can be improved to some extent by repeated dialing. In 1981, China introduced the international high-carbon high-chromium tool steel D2 (Cr12Mo1V1). Compared with Cr12MoV steel, the carbide segregation of D2 steel is slightly improved compared with Cr12MoV, and the strength and toughness are slightly improved. The service life of D2 steel mold has different degrees of service life. High-speed steel (mainly W6Mo5Cr4V2 and W18Cr4V) has higher wear resistance and strength, and is often used to make molds, but its toughness cannot meet the needs of complex large and impact-intensive molds. In order to improve the toughness of this kind of steel, some new cold work die steels have been developed in China, such as: 1 Low alloy cold work die steel The main features of this steel are good manufacturability, low quenching temperature, small heat treatment deformation, and toughness. Good and have proper wear resistance. Such as GD (6CrMnNiMoVSi), 7CrSiMnMoV (abbreviated as CH), DS steel and the like. GD steel has a high service life for making cold-punching molds that are easy to chip and break. The composition of CH steel is the same as that of Japan's SX105V steel. It is a kind of flame hardened steel.
It is often used to make mold parts for automobile and other production lines. When flame quenching, it heats the cut surface of the mold edge and has a high toughness under the hardened layer. The base is padded to give the mold a higher service life. DS steel is a kind of impact cold work die steel, and its impact toughness is significantly better than the commonly used high toughness blade tool steel 6CrW2Si. 2 Base steel Base steel generally refers to steel whose composition is the same as that of the high-speed steel quenched structure. In the United States and Japan, the base steels of the grades Vasco MA, Vasco Matrix I and MOD2 were studied in the early 1970s, which are equivalent to the bases of M2 and M36 high speed steels, but have not been widely used. China has developed some base steels, such as 65Cr4W3Mo2VNb (referred to as 65Nb), 65W8Cr4VTi (referred to as LM1) 65Cr5Mo3W2VSiTi (referred to as LM2) steel.
The main characteristic of these base steels is that their carbon content is slightly higher than the carbon content of the matrix to increase the amount of primary carbides and improve the wear resistance.
A small amount of strong carbides are added to form the element bismuth or titanium to form a relatively stable carbonization. The material prevents the growth of crystal grains during quenching heating and improves the process performance of the steel. Such base steels have been widely used in the production of cold extrusion, thick plate cold stamping, cold heading and other molds, especially for large and complex molds for difficult-to-deform materials, and can also be used as a hot extrusion mold for ferrous metals. 3 High-resistance wear-resistant cold work die steel In order to improve the carbide segregation of Cr12 cold work die steel, improve its toughness, and further increase the wear resistance of steel, China has done a lot of research work and developed many new ones. Steel grades such as LD, ER5 and GM steel. Among these steels, the chromium content is appropriately lowered to improve carbide segregation, and the contents of tungsten, molybdenum, and vanadium are increased to increase secondary hardening ability and to improve wear resistance. Compared with Cr12 cold work die steel, this type of steel has improved carbide segregation and higher toughness.
This type of steel has better wear resistance than Cr12 cold work die steel, so the mold has a higher life, and is more suitable for high-speed punching and multi-station punching. Hot work die steel The hot work die steel commonly used in China is 5CrMnMo, 5CrNiMo and 3Cr2W8V steel. 5CrNiMo steel is mainly used as a large and medium forging die. However, its hardenability is not high enough, and the tempering stability is not high, and its performance cannot meet the performance requirements of large-section forging dies. 3Cr2W8V steel is widely used as a hot extrusion die for black and non-ferrous metals and a die-casting mold for Cu and Al alloys. This steel has high thermal stability and a service temperature of 650 ° C, but the tungsten-based hot work die steel has low thermal conductivity and poor thermal fatigue resistance.
In the early 1980s, China introduced the foreign common chromium hot work die steel H13 (4Cr5MoSiV1). H13 steel has good cold and heat fatigue. When the use temperature does not exceed 600 °C, instead of 3Cr2W8V steel, the die life is greatly improved. Therefore, H13 steel has been rapidly promoted and applied, and its output has exceeded 3Cr2W8V steel. In order to adapt to the new requirements of pressure processing new technology and new equipment for mold steel in terms of toughness and thermal stability, China has developed a number of new hot work die steels, mainly including: 1 hot forging die steel domestic in the 1980s The hardenability of 5CrNiMo steel can not meet the needs of large-section hammer forging die and the use temperature does not exceed 500 °C. A large number of analysis and comparisons have been made on steel at home and abroad. The research shows that the content of Cr, Ni and Mo in foreign similar steel 5CrNiMoV is higher than that of domestic 5CrNiMo steel, and contains a small amount of V, so its hardenability and tempering stability are higher than domestic 5CrNiMo steel, and it is recommended to use 5CrNiMoV. Steel for the manufacture of large, complex heavy-duty hammer forging dies. Large-section hot forging die steels 5Cr2NiMoVSi and 45Cr2NiMoVSi steel have also been developed in China, and have been widely used. Compared to 5CrNiMo steel, these steels have a slightly lower carbon content, which increases the Cr and Mo contents and adds appropriate V and Si, resulting in high hardenability and thermal stability. The carbon and silicon in 45Cr2NiMoVSi steel are slightly lower than that of 5Cr2NiMoVSi steel, which is more suitable for hammer forging.
This kind of steel is used to manufacture forging die of mechanical press above 4000t and forging die of more than 3t, and its service life is increased by 0.5~1.5 times compared with 5CrNiMo and 5CrNiMoV. 3Cr2MoWVNi steel is also a kind of hot forging die steel developed in China with high service life. 2 Hot-pressing die steel H13 is a hot-working die steel widely used at home and abroad. It has good hot and cold fatigue performance when used at temperatures not exceeding 600 °C. It is used as hot extrusion die and aluminum alloy die-casting die. Has a relatively high service life. However, H13 steel has a large size effect, and foreign processes such as scouring outside the furnace, high-temperature diffusion annealing, and isotropic forging are used to improve the size effect and reduce the segregation of components of Cr and Mo. The electroslag remelting process is often used in China. . China has developed a number of hot work die steels for hot extrusion with good toughness and high thermal stability. Some steels are developed on the basis of foreign molybdenum-based 3Cr3Mo3V steel and chromium-based H13 steel, and have certain characteristics in alloying, such as HMI (3Cr3Mo3W2V), TM (4Cr3Mo2WMnVNb), Y4 (4Cr3Mo2MnVB), Y10 (4Cr5Mo2SiV1), Steel such as HD2 (4Cr3Mo2VNiNbB) and 012Al (5Cr4Mo3SiMnVAl). These steels have high thermal stability under the condition of maintaining good toughness, and are used for making hot extrusion die, precision forging die, non-ferrous metal die-casting die, etc., and have good use effect. The relevant departments of our country have organized some research units and users, and selected 27 domestic and foreign applications and newly developed hot work die steels, tested and compared their basic mechanical properties, process performance and performance, and proposed various types. Guidelines for the selection of hot work dies.
Plastic mold steel The output value of plastic forming mold has occupied the first place in the total output value of the mold industry. China did not have any special plastic mold steel in the past. In recent years, while introducing foreign steel for plastic molds, some new plastic mold steels have been developed and developed. 1 Pre-hardened plastic mold steel This kind of steel is made into a module after being fully forged in the steel mill. It is preheated to the required hardness (generally pre-hardened to 30~35RHC), and then used for unit molding. P20 (ie 3Cr2Mo) is the most widely used pre-hardened plastic mold steel in foreign countries. It has been included in China's alloy tool steel standard. It has been widely used in some factories in China since the 1980s. 718 is a modified P20 steel produced in Sweden. It has higher hardenability than P20. It can maintain uniform hardness in large cross-section after quenching and tempering. It is also widely used in China. 2 Free-cutting pre-hardened steel In order to improve the cutting performance of pre-hardened plastic mold steel, free-cutting elements can be added. Some free-cutting pre-hardened steels have been developed in the United States, Japan, and Germany. Foreign free-cutting pre-hardened steel is mainly S-series, and also has S-Se system and Ca system. But Se is more expensive.
The anisotropy of the S-series free-cutting steel is large, and the segregation of sulfide is more serious when the cross-section is increased. China has developed some sulfur-containing easy-cutting pre-hardened plastic mold steels, such as 8Cr2MnWMoVS (8Cr2S) and S-Ca composite free-cutting plastic mold steel 5CrNiMnMoVSCa (5NiSCa). 5NiSCa steel adopts S-Ca composite free cutting system and spray metallurgy technology to improve the morphology and distribution of sulfide and the anisotropy of steel. The distribution of sulfide in the large section is still relatively uniform. 5NiSCa steel has high hardenability and mirror polishing. When the hardness of the mold is 35~45HRC, various processing can be carried out smoothly. 3 Non-tempered plastic mold steel This steel can be processed without pre-hardening after forging and rolling, which is conducive to saving energy, reducing cost and shortening production cycle.
The steels developed in China are: medium carbon manganese boron air-cooled bainite steel, which can be used to make plastic molds and rubber molds; non-tempered plastic mold steel 2Mn2CrVTiSCaRe(FT), S, Ca, Re are added to steel as easy Cutting elements have better cutting performance than S-Ca composite free-cutting steel; low-carbon MnMoVB is non-tempered bainite large-section plastic mold steel (B30), S and Ca are added to steel as free-cutting elements, industrial The trial production shows that the 400mm thick slab is air-cooled after hot rolling, and the hardness is evenly distributed along the cross section. 4 Age hardening steel China has developed several kinds of low-nickel age hardening steels. These steels are mechanically processed after quenching and tempering, and then aged by precipitation, the hardness is improved by precipitation of intermetallic compounds, and the deformation after heat treatment is small.
Age hardened steel is suitable for making high-precision plastic molds, transparent plastic molds, and the like. Such steels are steels such as 25CrNi3MoAl, 10Ni3Mn2AlCu (PMS) and 06Ni6CrMoVTiAl. After quenching and tempering, these steels have a hardness of 20~30HRC, which can be machined and then aged to a hardness of 38~42HRC. 5 Corrosion-resistant plastic mold steel When plastic products are made of chemically corroded plastics, the molds must have anti-corrosion properties. Generally, corrosion-resistant steel is used to make molds. At this time, better wear resistance is required. Commonly used steel grades are 4Cr13 (420), 9Cr18, and 17-4PH. PCR (0Cr16Ni4Cu3Nb) is a kind of corrosion-resistant plastic mold steel developed in China, which has good comprehensive corrosion resistance. Cemented Carbide and Steel Bonded Cemented Carbide Cemented carbide is a type of composite material manufactured by powder metallurgy.
Cemented carbide has high hardness, good wear resistance, high modulus of elasticity and high operating temperature. Used to make certain molds, the service life of the mold can be increased several times and dozens of times. However, cemented carbide is brittle, has poor flexural strength and toughness, and cannot be machined. As a mold material, cemented carbide is mainly used for drawing die, cold extrusion and cold die which are not affected by impact. At present, China has been able to produce various grades of cemented carbide, which can basically meet the needs of the domestic market. In order to meet the needs of manufacturing micro drills for drilling integrated circuit boards, dot matrix printing needles for computers, precision tooling, etc., in recent years, some microcrystals (WC grains less than 1 micron) and ultrafine crystals have been developed in various countries. Granular cemented carbide (WC grains less than 0.6 microns), in conventional cemented carbides, WC grain size is 1.3 to 1.5 microns.
Ultra-fine grained cemented carbides make up for many of the shortcomings of conventional cemented carbides, expand their application range, and achieve good results in the manufacture of wear-resistant and impact-resistant molds. Some research units and cemented carbide plants in China have developed various grades of microcrystalline cemented carbide and ultra-fine grained cemented carbide. The development of high-performance ultra-fine grained cemented carbide is still a hot spot in hard alloy research. Steel-bonded cemented carbide is a composite material in which carbide is a hard phase and steel is used as a bonding phase. Steel-bonded cemented carbide has good wear resistance, its strength and toughness are generally higher than that of cemented carbide, and it has some process properties such as heat treatability, machinability, forgeability and weldability.
The mold is the main application area of steel-bonded cemented carbide. China began to develop this material in the 1960s. It has been developed into a variety of grades of steel-bonded hard alloys, which are used as steel-bonded hard alloys for molds. TiC and WC are mainly used for hard phases, and low-alloy chromium is mainly used for steel substrates. Molybdenum steel, medium and high alloy tool steel or high speed steel, such as TiC series GT35, R5, D1, T1 and WC series TLMW50, GW50, GJW50. Steel-bonded cemented carbide has been used in the production of cold heading die, extrusion die, drawing die, punching die, wire drawing die, hot die. The development of powder metallurgy technology and the application of hot isostatic pressing led to the production and use of non-segregation powder high-speed steel in the 1970s. Its main features are superior toughness, grindability, isotropic and heat treatment process. High speed steel with a relatively high service life.
Contact Us
Henan Weichuang Bearing Precision Technology Co., Ltd
Address:No. 369, Licheng Road, Luolong District, Luoyang City, Henan Province, China
Tel: +8615937969996
Email:info@w-bm.com