Evaluation and selection of hot work die steel
Table 1 Steel grades, main characteristics and uses commonly used in hot work molds Performance advantages: VTM Tube,Tube VTM,VTM Tube Price,VTM Test,VTM Test Tube,Lab Test Tube,Small Test Tube,VTM Sampling Tube Yong Yue Medical Technology(Kunshan) Co.,Ltd , https://www.yongyuepcrtube.com
According to statistics from many years, the cost ratio of any kind of mold products is: mold material cost accounts for 35%, mold plus supply fee (mechanical cutting and heat treatment) accounts for 50%, of which the first two expenses are Seriously affect the production cost of parts processing, so we should carefully select reasonable mold materials.
The performance of the mold material, the quality of the material, the reasonableness of the use, etc., have a close relationship with the manufacturing precision, the qualified product rate, the load carrying capacity, the service life and the cost of the mold. Therefore, in the process of designing and manufacturing the mold, factors such as the type of the mold (the specific use occasion), the production batch, the material and the complexity of the workpiece should be comprehensively considered for the material selection. For the mold material itself, it is necessary to consider its mechanical properties, wear resistance, heat resistance, corrosion resistance, thermal deformation, hardenability, mechanical processing, as well as material prices and availability.
At present, any high-quality materials and new mold materials are difficult to meet all performance requirements, so the best mold materials can only be selected according to the actual conditions of use and meet the main performance conditions.
In order to explain the specific problems, the factors affecting the life of the mold are as follows:
Hot work die steel is mainly used in the manufacture of hammer forging dies, press forging dies, hot extrusion dies and pressing dies, and their working conditions are quite different.
The main factors affecting the working conditions of hot work die are:
1. Structure and characteristics of forging equipment Forging hammer (air hammer, steam hammer, without anvil hammer, high speed hammer, etc.)
When working, it generates a huge impact energy, so that the hot blank is formed in the mold cavity. Therefore, the hammer forging die works under high-humidity, high-pressure, 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 on the press die is close to the static load.
2. Properties of the blank material
Due to the different metal materials, their melting point and forging heating temperature are very different, so the working conditions of the mold are also different.
3. Mould lubrication and cooling method
In the plastic forming of metal, the use of a suitable lubricant can reduce the coefficient of friction and reduce the deformation resistance, which is usually 30% to 40%, which helps to reduce the wear of the mold and prevent the risk of mold breakage. At the same time, in order to prevent the mold temperature from being too high, the hot working mold must adopt cooling measures, and the production practice proves that correct and effective cooling improves the service life of the mold.
4. Mold structure and manufacturing quality
The structural design of the mold and the geometry of the cavity have a great influence on the metal forming pressure and the life of the mold. In order to improve the life of the mold, various forms of combined concave molds are usually used. The surface roughness of the mold cavity also has a great influence on fatigue resistance and friction.
5. Reasonable use of the mold
The use of hot work dies is quite different from cold work dies, where necessary preheating of the mold is necessary before use. Production practice proves that this work is very important. If you do not pay attention to the reasonable use of the mold, it will greatly reduce the service life of the mold.
According to the relevant data in actual production, the application of hot work dies is commonly used in various enterprises, which can be summarized as shown in Table 1. This table lists the steel grades, main characteristics, heat treatment hardness and uses commonly used in hot work molds.
In short, the important factor of the service life of the hot mold is related to the chemical composition of the mold material and the strength, toughness, wear resistance and thermal stability of the steel, and also has a great relationship with the metallurgical quality. Therefore, in order to improve the service life of the mold, as a manufacturing industry, it is necessary to correctly design the mold structure, accurately manufacture the mold parts, rationally use the mold and its heat treatment process, and at the same time select high-quality suitable steel according to actual production needs, and By selecting a reasonable heat treatment process, the various properties of the mold material can be fully utilized and the service life of the mold can be improved. Steel number Main characteristics Hardness HRC use 5CrNiMo Hot work die steel with low alloying element content, high hardenability and good toughness, strength and wear resistance, but easy to appear white spots 44~48 Suitable for manufacturing various shapes and shapes, large impact load, low working temperature, side length >400mm large and medium hammer forging die and trimming die 5CrMnMo The steel has similar properties to 5CrNiMo except for hardenability and thermal fatigue resistance. 44~48 Suitable for manufacturing medium-cut hammer forging ≤400mm, ie hot-cutting die SCrMnMoSiV Due to the addition of alloying elements, the tempering resistance and hardenability are increased, and the service life is much higher than the above two materials, but the toughness is not as good as 5CrNiMo. 44～49 Suitable for making medium and small forging dies, but not suitable for making large hammer forging dies 3Cr2W8V The steel contains more elements of carbide and tungsten which are easy to form carbides, and has good hardenability. It has high strength, hardness and thermal fatigue properties at high temperatures (600-700 ° C), but its strength and plasticity. Poor 48~ It is used to manufacture punches and dies under high temperature and high pressure stress without impact load. Such as manufacturing die-casting molds, hot extrusion dies, precision forging dies and non-ferrous metal forming dies, etc. 4Cr5MoSiV (H11) Air-cooling type hot work die steel has good heat strength, high wear resistance and good fatigue performance at medium temperature, and heat treatment deformation is small 53～57 Used in the manufacture of aluminum alloy die-casting molds, hot extrusion die, perforating tools, mandrel, press forging die 4Cr5MoSiV(H13)4Cr5W2SiV Air-cooled hard working die steel with high strength and hardness, high wear resistance and toughness, and good thermal fatigue resistance at higher temperature (600 ° C) 53～55 Used to manufacture hammer forging die, hot extrusion die and heart bar, press die, precision forging die and insert, aluminum, copper alloy die-casting die, high speed hammer forging die 3Cr3Mo3VN6 (HM3) New high strength and toughness hot work die steel. The steel has a low carbon content in order to increase the thermal conductivity and improve the thermal fatigue life. The molybdenum, vanadium and niobium alloy elements form carbides. Due to the high melting point, the fine crystal grains can be made, and the thermal strength of the steel is increased. 47～52 Used in the manufacture of precision forging dies such as difficult-to-deform alloys and high-temperature alloys for aviation jet engines 4Cr3Mo2MnVB (ER8) Air-cooled hard working die steel (H10 modified steel) with higher toughness, resistance to cold and heat fatigue, thermal shock resistance and temper softening resistance 42~48 For the manufacture of copper, aluminum alloy die-casting molds, large-volume hot extrusion die, hot drawn parts punch 4Cr5Mo2MnVN6B (Y4) New hot work die steel. High thermal strength, thermal stability, good toughness, thermal conductivity and processability 49~50 Used in the manufacture of copper and aluminum alloy die-casting molds, and can replace medium and small press molds, heat back pressure and other molds instead of 3Cr2W8V steel. 4Cr5Mo2MnVSi (Y10) New hot work die steel. Its chemical composition is similar to that of H13 steel, and it has good hardenability. Molybdenum and vanadium alloy elements have a great effect on refining grains, improving heat permeability and tempering stability. 50~51 Used in the manufacture of motor end caps, camera cases, automotive gearbox covers, etc. 6Cr4Mo3Ni2WV (CG2) The base steel for both cold and heat has a wide heat treatment process range, no quenching tendency, and has high strength, toughness, wear resistance and thermal fatigue resistance at higher temperatures. 51～53 Used in the production of hot stamping die, hot extrusion die, high speed forging die, precision forging gear die and inserts, etc. 8407 (Sweden) The steel has high purity, fine grain and good isotropy, regardless of size and toughness. High temperature strength, thermal stress fatigue resistance, good hardenability and dimensional stability of heat treatment 32~38 Used in the manufacture of zinc, aluminum, lead die-casting molds and mouthpieces
1.Strong water absorption capacity
2.Increase the collection and release of samples
3.Good abrasion resistance
4.Do not scratch the wiped device
5.No chip drop
6.100% sterilization and disinfection
Operating Steps:
1 Touch the swab to the surface where it is aimed to obtain the sample.
2 Remove the tube cap and put the swab into the transport medium.
3 Break the shaft of the swab so that it will fit in the tube.
4 Close the cap securely.Write on the tube the necessary information about the patient and sample.