Evaluation and selection of the hottest die steel

2022-10-13
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Evaluation and selection of hot work die steel

with the development of mechanized and automatic processing and forming equipment with high efficiency, high speed, high strength and large tonnage, and the wide application of complex processes such as hot forging die, hot extrusion die, hot upsetting die and die casting die, higher requirements are put forward for the strength, impact toughness, red hardness and wear resistance of dies. At present, the use of general hot working die steel and ordinary heat treatment process can no longer meet the needs of production, especially the poor impact toughness, easy cracking, low red hardness and easy collapse, as well as the low wear resistance of materials in high humidity, which leads to the obvious reduction of the service life of the die and seriously affects the further development of advanced hot forming process. Therefore, it is more and more important and urgent to improve the strength, toughness and red hardness of hot work die steel and prolong the service life of the die

according to the data and statistics over the years, the cost proportion of any kind of mold product is: mold material cost accounts for 35%, mold supply cost (mechanical cutting and heat treatment processing) accounts for 50%, of which the first two costs seriously affect the production cost of parts processing, so reasonable mold materials should be carefully selected

factors such as the performance of mold materials, the quality of materials and the rationality of use are closely related to the manufacturing accuracy, qualified product rate, working load-bearing capacity, service life and cost of the mold. Therefore, in the process of designing and manufacturing molds, we should comprehensively consider the types of molds (specific use occasions), production batches, production materials and the complexity of parts and other factors in terms of material selection. For the mold material itself, its mechanical properties, wear resistance, heat resistance, corrosion resistance, thermal deformation, hardenability, machinability, as well as material price and supply conditions need to be considered

at present, any kind of high-quality materials and new mold materials are difficult to meet all the performance requirements, so the best mold materials can only be selected according to the actual use conditions and under the condition of meeting the main performance

in order to explain the specific problems, d) whether the height width ratio of the lubricating grease of the main shaft bearing box is appropriate; The influencing factors are introduced as follows:

hot work die steel is mainly used to manufacture hammer forging dies, press forging dies, hot extrusion dies and pressing dies, and their working conditions are very different

the main factors affecting the working conditions of hot working dies are:

1 Structure and characteristics of forging equipment forging hammers (air hammer, steam hammer, anvil free hammer, high-speed hammer, etc.)

produce huge impact energy during operation, making the hot blank form in the mold cavity. Therefore, the hammer forging die works under high humidity, high pressure and high-speed impact load. The loading speed of the press (crank mechanical press, friction press, hydraulic press, hydraulic press) is much lower than that of the forging hammer. Therefore, the load borne by the die of the press is close to the static load

2. Properties of blank materials

due to the different metal materials, their melting points and forging heating temperatures are very different, so the working conditions of molds are also different

3. Lubrication and cooling mode of the die

during metal plastic forming, the use of appropriate lubricant can reduce the friction coefficient and reduce the deformation resistance. The reduction range is usually 30% - 40%, which helps to reduce the wear of the die and prevent the risk of die fracture. At the same time, in order to prevent the mold temperature from being too high, cooling measures must be taken for hot working molds. The production practice has proved that correct and effective cooling can improve the service life of molds

4. Mold structure and manufacturing quality

mold structure design and cavity geometry have a great impact on metal plastic forming pressure and mold life. In order to improve mold life, various forms of combined female dies are usually used. The surface roughness of the mold cavity also has a great influence on the fatigue resistance and friction

5. Rational use of molds

there is a big difference between the use of hot working molds and cold working molds, that is, the necessary preheating of molds must be carried out before use. Production practice has proved that this work is very important. If we do not pay attention to the rational use of the mold, the service life of the mold will be greatly reduced

according to the relevant data in actual production, the application of hot working dies commonly used in various enterprises can be summarized as shown in Table 1. This table lists the commonly used steel grades, main characteristics, heat treatment hardness and applications of hot working dies. Table 1 commonly used steel grades, main characteristics and uses of hot working dies

steel grades main characteristics hardness HRC uses 5CrNiMo hot working die steel with low alloy element content, which has high hardenability, good toughness, strength and wear resistance, but is prone to white spots. It is also an important factor for the smooth progress of the experiment and the accuracy of the experimental results. 44 ~ 48 is suitable for manufacturing all kinds of complex shapes, large impact load, low working temperature 5CrMnMo for large and medium-sized hammer forging dies and trimming dies with side length> 400mm. Except for the slightly poor hardenability and heat fatigue resistance, other properties of this steel are similar to 5CrNiMo. 44 ~ 48 it is suitable for manufacturing medium-sized hammer forging dies with side length ≤ 400mm, that is, the hot-rolled side die scrmnmosiv. Due to the addition of alloy elements, the tempering resistance and hardenability are increased, and its service life is greatly improved compared with the above two materials, but its toughness is not as good as 5crnimo44 ~ 49. It is suitable for making medium and small forging dies, However, it is not suitable for making large hammer forging dies 3Cr2W8V. This steel contains more elements chromium and tungsten that are easy to form carbides, and has good hardenability. At high temperature (600 ~ 700 ℃), it has high strength, hardness and thermal fatigue properties, but its strength and plasticity are poor. 48 ~ it is used for manufacturing punch and concave dies with low impact load under high temperature and high pressure stress. For example, 4Cr5MoSiV (H11) air-cooled hardened hot work die steel for manufacturing die-casting dies, hot extrusion dies, precision forging dies and non-ferrous metal forming dies has good thermal strength, high wear resistance and good fatigue performance at medium temperature, and the heat treatment deformation is small 53 ~ 57. It is used for manufacturing aluminum alloy die-casting dies, hot extrusion dies, piercing tools, mandrel, press forging dies 4Cr5MoSiV (H13) 4cr5w2siv air-cooled hardened hot work die steel, At high temperature (600 ℃), it has high strength and hardness, high wear resistance and toughness, and good thermal fatigue. 53 ~ 55 it is used to manufacture hammer forging dies, hot extrusion dies and mandrel, press dies, precision forging machine dies and inserts, aluminum and copper alloy die-casting dies, high-speed hammer forging dies 3cr3mo3vn6 (HM3) new high strength and toughness hot work die steel. The low carbon content of this steel is to increase the thermal conductivity. It can complete a variety of performance experiments of tape, chain, steel wire rope, welding rod, brick and tile and components. With high cold and hot fatigue life, molybdenum, vanadium and niobium alloy elements form carbides. Due to high melting point, fine grains can be formed, which increases the thermal strength of the steel. 47 ~ 52 4cr3mo2mnvb (er8) air cooling hardening hot work die steel (H10 modified steel) is used to manufacture precision forging dies such as hard to deform alloys and Superalloys for jet engines. It has higher strength toughness, cold and hot fatigue resistance, thermal vibration resistance and tempering softening resistance. 42 ~ 48 it is a new hot work die steel 4cr5mo2mnvn6b (Y4) used to manufacture copper and aluminum alloy die casting dies, large variable hot extrusion dies and hot drawing parts. It has high thermal strength, thermal stability, good toughness, thermal conductivity and processability. 49 ~ 50 is used to manufacture copper and aluminum alloy die-casting dies, and can replace 3Cr2W8V steel to manufacture medium and small-sized presses. It is suggested to rely on Yindu District for dies, hot backlog and other dies. 4cr5mo2mnvsi (Y10) new hot work die steel. Its chemical composition is similar to H13 steel and has good hardenability. Molybdenum and vanadium alloy elements play a great role in refining grains, improving heat permeability and tempering stability. 50 ~ 51 are used to make 6Cr4Mo3Ni2WV (CG2) cold and hot base steel for aluminum alloy die-casting dies such as motor end caps, camera boxes, and automobile gearbox covers. It has a wide range of heat treatment processes, no quenching cracking tendency, and has high strength, toughness Wear resistance and thermal fatigue resistance 51 ~ 53 are used to make hot stamping dies, hot extrusion dies, high-speed forging dies, precision forging gear dies and inserts, etc. 8407 (Sweden) this steel has high purity, fine grains and good isotropy, regardless of size and toughness. High temperature strength, strong thermal stress fatigue resistance, good hardenability and heat treatment dimensional stability 32 ~ 38 used in the manufacture of zinc, aluminum, lead die-casting molds and junction sleeves

in short, the important factors of the service life of hot work molds are related to the chemical composition of the mold material and the strength, toughness, wear resistance, thermal stability of the steel it determines, as well as the metallurgical quality. Therefore, in order to improve the service life of the mold, as a manufacturing industry, we must correctly design the mold structure, accurately manufacture the mold parts, and reasonably use the mold and its heat treatment process. At the same time, according to the actual production needs, select high-quality and appropriate steel, and choose a reasonable heat treatment process, so as to give full play to the various properties of the mold materials and improve the service life of the mold. (end)

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