How to eliminate the stress of 1.2344 steel parts

     After rough machining, sensitive or large processing capacity of 1.2344 steel parts, also must carry on stress-relief annealing processing, to eliminate processing stress and straightening stress. Because the stress can cause not to allow change in size, deformation and cracks in quenching process.
     Eliminate stress slowly heating in the low temperature (about 100~150K/h), highest do not exceed 300 degrees C. It is best to use the electric heating furnace with program control and circulating air. After heating, the furnace can also control slow cooling, does not require special protective measures to prevent annealing 1.2344 steel oxide skin or surface damage occurs.

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What are the characteristics of mould steel AISI P20

     P20 steel is suitable for making the plastic mold and die casting mould of low melting point metal.
     The physical properties of mould steel AISI P20 with uniform hardness, good polishing performance and light etching performance. And excellent processing properties of P20 die steel. Therefore it is suitable for TV former shell, telephone, water dispenser, vacuum cleaners and other plastic mould.
     The P20 die steel with high purity by vacuum degassing refining  treatment, more suited to the requirements of polish or etch processing of plastic mold. Such as: TV cabinet, refrigerator inner shell etc..
     P20 die steel pre hardened 285-330HB (30-36HRC), no need of heat treatment can be directly used for molding processing, greatly shortens the construction period, saving its operating costs. And P20 steel has the characteristics of good size stability, pre hardened steel can meet the general use of demand, the service life of the die is 50W mode. Applicable to thermoplastic plastic injection mold, extrusion mold.
     P20 die steel microstructure is compact after the rolling process. You can found P20 mould steel without small hole defects by ultrasonic inspection. So it can be used to make good sealing mould, such as washing machines, buckets, and so on.

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The mechanical properties of 4130 material

     The 4130 is a kind of chrome molybdenum steel, the content of Cr and Mo is relatively high. The 4130 material is relatively hard, the tensile strength and yield strength is two times that of 20# steel, is 1.5 times that of 45# steel. Because the proportion of carbon is moderate, especially suitable for welding.
     Early chromium molybdenum materials scarce, 4130 mostly used in aircraft landing gear. Later, some professional bicycle frame also began to use this material, which is a big selling point, now largely been replaced by a high-strength aluminum alloy and carbon fiber materials. But for the rollcage and steel frame structure of off-road racing, the 4130 steel is still the best choice, in ensuring equal or even greater strength under the premise, the 4130 frame can do more light.
     But note that the 4130 material strength is high, after hot rolling if not temper or normalizing treatment, the tensile strength is more than 1000MPa, the yield strength is very high, the elongation of less than 10%, the result is unable to bend, pipe will break in the pipe, and the steel plate in bending of less than 90 degrees to start cracking. Correctly handle the processing after appearing in the process of stress will be basically eliminated, and has obtained the good toughness at the same time ensure strength, when the impact of the stress point will have instant deformation, but will soon recover, even if there is no permanent deformation in cracking the case, ensure the safety of the car.
     After the correct treatment, stress generated in the processing process will be basically eliminated, not only guarantee the strength, meanwhile, made a very good toughness, When subjected to violent impact , stress points have instant deformation, but will soon recover, even if its permanent deformation, also cannot appear the dehiscence the situation, ensure the safety of the racing car.

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How to heat treatment of DIN 1.2738 die steel

1. Annealing:
     Annealing temperature: 710 ~ 740 °C, holding time is decided by the thickness of the DIN 1.2738 die steel, one hour per 25mm. Colding in furnace after thermal insulation.
2. Destressing:
     Heating temperature: 600 °C (annealed condition), 550 °C (quenching and tempering state), holding time is decided by the thickness of the 1.2738 steel, one hour per 50mm. Colding in furnace after thermal insulation.
3. Quenching and tempering:
     Preheating temperature 500 ~ 600 °C, quenching temperature 840 ~ 880 °C, holding 30min (the mold have to quenching in the protective gas to prevent oxidation and decarbonization). Oil cooling, cooling to 50 ~ 70 °C, immediately tempered.
     Tempering holding time is decided by the thickness of the 1.2738 steel mould, one hour per 25mm, at least 2h. Tempering temperature: 180 °C / 200 °C / 300 °C / 400 °C / 500 °C / 600 °C, the hardness: 52HRC / 51HRC / 48 HRC / 46HRC / 42HRC / 34HRC.
4. Induction hardening:
     The DIN 1.2738 die steel may be treated by flame or induction hardening to increase the surface hardness to 50HRC. Colding in air after hardening. Small mould can use common quenching medium, immediately tempered after hardened, tempering temperature 180 ~ 200 °C.
5. Nitriding:
     Nitriding temperature + nitriding time: 525 ° C + 20h, the nitride layer thickness 0.30mm; 525 °C + 30h, the nitride layer thickness 0.35mm; 525 °C + 50h, the nitride layer thickness 0.50mm.
6. Nitrocarburizing:
     570 °C to maintain nitrocarburizing 2h, the mold surface hardness is about 700HV, nitrided layer depth is about 0.1mm.

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What are the uses of SAE 4340 steel

     The SAE 4340 steel is a kind of special alloy steel, and it contains the main alloy elements are: molybdenum, nickel and chromium. Uses this steel manufacture the product to have the higher tensile strength, and the thermal stability and toughness are higher. That is why this steel is used to manufacture aircraft, automotive and other general engineering components. Molybdenum can reduce the temper brittleness.
     At present, the steel is also used in the manufacture of gear shaft, transmission shaft and car parts and gear lever. Tensile strength of the steel is higher than the 4140 steel, so can be get more strength. The last two digits of the carbon content of steel. This means that, when it is 4340 it contains carbon 40%, and when it is 4130 steel contains carbon 30%.

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How to heat treatment for H13 mould steel

     1. Preheat treatment. The market of H13 mould steel are after annealing heat treatment in steel mill, to ensure that it has a good metallurgical structure, appropriate hardness, good processability, don't need annealing once more. But after forging in the processing factory, the original microstructure and properties were destroyed, an increase of forging stress, must be re annealing.
Isothermal spheroidizing annealing process: 860 ~ 890 °C heating insulation 2h, cooled to 740 to 760 °C isothermal 4h, furnace cooling to 500 DEG baked.
     2. Quenching and tempering. The mould quenching process specification (requirements good toughness):the heating temperature is 1020 ~ 1050 °C, oil cooling or air cooling, hardness of 54 ~ 58HRC. If the requirements of the H13 steel good hot hardness, the quenching process specification is: the heating temperature is 1050 ~ 1080 °C, oil cooling, hardness of 56 ~ 58HRC. Recommendation tempering temperature: 530 ~ 560 °C, hardness of 48 ~ 52HRC; tempering temperature 560 ~ 580 °C, hardness of 47 ~ 49HRC. Tempering should be performed twice. Tempering at 500 °C, the peak of tempering hardening occurs, the tempering hardness is highest, hardness about 55HRC, but the toughness is worst. Therefore, the tempering process should avoid 500 °C advisable. According to the mold use need, tempering at 540 ~ 620 °C is  better. Quenching should be performed preheated twice (600 ~ 650 °C, 800 ~ 850 °C), to reduce the thermal stress in the heating process.
     3. Chemical heat treatment. H13 mould steel if the gas nitriding or nitrocarburizing can make the mould is further strengthened, but the nitriding temperature should not be higher than the tempering temperature, to ensure that the core strength is not reduced, thereby improving the service life of the mould.

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The performance of AISI D2 tool steel

     The wear resistance of AISI D2 tool steel is high, small deformation, the carbon content as high as 1.5%, chromium content up to 11.5%. After heat treatment, the hardness of D2 steel is up to 60HRC, but its ductility, toughness, resistance to rust ability are relatively weak, steel surface to mirror polished is not easy.
     Along with the cold stamping products to the development of high precision and high efficiency, multi species, requirement of die steel has good abrasion resistance and toughness. Compared with Cr12MoV steel, the D2 steel has increased by Mo and V in chemical composition, changing the cast structure of steel, improve the morphology of ledeburite, its strength and toughness and wear resistance is better than that of Cr12MoV steel, improve the service life of mould.
     The yield point and plastic deformation resistance of AISI D2 tool steel is higher than Cr12MoV steel, so the forging properties and thermal plastic forming is slightly worse than Cr12MoV. Cr12MolV, American D2, Japan SKD11, three although the same chemical composition, but the performance difference is very big. After heat treatment, Cr12MolV color slightly orange red, deformation is very large, prone to fatigue fracture at actual use; D2 steel is cold white color, hardness higher than SKD11, the toughness is lower than SKD11, high stress is easy to appear the tiny gap; SKD11 bright luster and the best overall performance.

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