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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The advantages and disadvantages of DIN 1.2080 steel

    The 1.2080 steel is a kind of cold work die steel of high carbon and high chromium. The  content of C and Cr is very high, respectively C 2.00%~2.30% and Cr 11.00%~13.00% (mass fraction). DIN 1.2080 steel belongs to the ledeburite steel, so it has a very high hardenability, hardened and wear resistance, quenching deformation of small. But when the carbide heterogeneity, Its deformation are multi direction and irregular, its main drawback is poor organization. Uneven carbide is difficult to improve by heat treatment method, unless use powder metallurgy to manufacturing. Impact toughness is poor, thermal conductivity and high temperature plasticity is poor, when thermal processing should pay attention to heating and forging process.
    The 1.2080 steel is one of the international common cold work die steel, but in recent years has gradually been better steel replaced, such as Cr12MoV, Cr12Mo1V1 or matrix steel. The same type of foreign steel is 210Cr12 (ISO), Japan SKD1 (JIS), America D3 (AlSI/SAE) etc..
    1.2080 steel mainly for High wear resistance and impact load is smaller cold punching mould parts (the convex and concave mold, cold extrusion concave mold etc.), because of its obvious advantages and disadvantages, the use of limited.

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Can 40Cr replace the P20 mould steel

     P20 steel is a kind of plastic mold steel. P20 steel is mainly used in plastic mold and die casting mold material of low melting point metal. The purity of P20 mould steel is high, with good machinability and mirror grinding performance, made of high precision mold, never deformation, high tenacity.
     40Cr is a commonly used alloy structural steel, the tensile strength, yield strength and hardenability is higher than 1040 steel, but its welding is limited, may crack formation.  It can be made of quenched and tempered parts. After surface quenching, 40Cr can be made a part of load and wear resistance are high and impact force is small, such as gears, sleeves, shafts, crankshafts, etc..
     40Cr also belongs to the nitrided steel, it contains beneficial elements to nitriding. After nitrogen treatment, surface hardness of 40Cr is high, the highest reached 72 ~ 78HRA (43 ~ 55HRC).
     If the P20 mould steel nitriding treatment, its surface microstructure is high hardness. After nitriding surface hardness reaches 650-700HV (57-60HRC), the service life of the die can reach more than one million times, the characteristics of the nitride layer has dense structure, smooth, mold release properties and the anti wet air and salty liquid corrosion performance can be improved.
     Previously, most of the APG die is used 40Cr, and then gradually being replaced by P20 steel. From the processing performance for P20 steel processing performance is better than the 40Cr. From the service life of the die, the frequency of use of P20 steel is 5~10 million times, and the frequency of use of 40Cr is 50000 times.

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Hot work die steel H13 component and nature

     H13 steel containing chromium, molybdenum, vanadium, silicon, manganese. The effect of alloy elements are as follows:
     Chromium: chromium can form chromium carbides in the steel, can improve the high temperature strength and wear resistance of the steel, the C curve shifts to the right, to improve the hardenability and tempering stability of hot work die steel H13. Chromium and other carbide forming elements give steel has high hardenability and resistance to softening ability, so H13 steel can be hardened in condition of air cooling. In the 6barN2 gas vacuum processing conditions can harden diameter is 160mm. But add chromium, carbides will increase the inhomogeneity, the steel will appear in the metastable eutectic carbide. Chromium content increased to improve thermal strength of the material, but the toughness of adverse.
     Mo: can improve the high temperature hardness and the hardenability of the steel. In addition, molybdenum can hinder the austenite grain growth, thereby to refine the crystal grain, reduce the temper brittleness.
     Vanadium: Vanadium to form carbides is easier than the chromium and molybdenum, dissolved in solid solution of iron is extremely small. Vanadium carbides so that the steel has good hot hardness, and refine the grain, improve the wear resistance of hot work die steel H13.
     Si: Silicon has strengthening effect is very good for ferritic solid solution replacement, second only to the phosphorus, but also to some extent reduce the steel toughness and plastic. The general will be restricted in the range of steel deoxidation need. If the Si as alloy elements added to steel, the amount is generally not less than 0.4%. Silicon can also improve the tempering resistance. Si can reduce the diffusion rate of carbon in ferrite,  the precipitation of carbides is not easy to aggregation when tempering, the increase of tempering stability. In addition, silicon is easy to make the steel presents zonal organization, makes the lateral performance of the steel than the longitudinal performance is poor,  also increased the brittle transition temperature of steel. Si also increased decarburization sensitivity of steel, but the Si is beneficial to improve the high temperature oxidation resistance of the mold steel H13 steel.
     Mn: Manganese can change the nature and shape of oxide when during solidification of hot work die steel H13. At the same time it has a greater affinity with S, can prevent formation of low melting point sulfides "FeS" at the grain boundaries, and formation of a certain plastic MnS, thereby eliminating the harmful effects of sulfur, improve hot workability of the steel. Mn has a solid solution strengthening effect, thereby enhancing the ferrite and austenite strength and hardness. Although the solid solution strengthening effect is lower than carbon, silicon and phosphorus, but the ductility of the steel is almost not affected. In the "ferrite - pearlite" type steels, only Mn can increase the yield strength and the cold-brittle transition temperature changes to a minimum.

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What are the methods of DIN 1.2379 steel heat treatment

    Thermal processing of DIN 1.2379 steel:
Start temperature 1050 ℃, end temperature 850 ℃, furnace cooling.
    Softening annealing treatment:
In the protection of gas, heating to 800~850 ℃, then by 10 ℃ /h speed cooling to 600 ℃, then the air cooling, the hardness is less than or equal to 250HBw.
    To eliminate stress treatment:
If want to eliminate the residual stress generated after rough machining, mold should be heated to 650 ℃, heat 2h, and then with the furnace cooling to 500 ℃, then followed by air cooling.
    DIN 1.2379 steel quenching and tempering:
The first preheating temperature 550 ~ 600 ℃, maintained at about 30min per 25mm; the second preheating temperature 800 ~ 850 ℃, maintained at about 30min per 25mm; austenitizing temperature 975 ~ 1040 ℃, maintained at about 30min per 25mm , oil cooling (40 ~ 70 ℃) or gas cooling, cooled to 50 ~ 70mm immediately tempered.
1) low-temperature tempering: tempering temperature 150 ~ 200 ℃, each 25mm for about 60min above, air cooling, hardness ≥61HRC. Tempering should choose a lower austenitizing temperature 975 ~ 1025 ℃.
2) high-temperature tempering: tempering temperature 480 ~ 540 ℃, each 25mm for about 60min or more, air cooling, more than twice tempered, hardness ≥58HRC. Tempering should use a higher austenitizing temperature 1000 ~ 1040 ℃.
    Cryogenic treatment of 1.2379 steel:
After hardening, the workpiece is immediately cooled to between -80℃~ -70℃, maintaining 3 ~ 4h, then tempering. Cryogenic treatment can improve the hardness 1 ~ 3HRC.
    The aging treatment:
Temperature of 110 ~ 140 ℃, thermal insulation 25 ~ 100h, in order to ensure that the workpiece size and stability during use.

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The performance of the 1.2738 mould steel

    The 1.2738 mould steel is manufactured in accordance with German DIN standard, with relatively superior mechanical properties in similar grades of steel, and good processability, mainly used for the production of hot work die processing, where the most common of plastic mold. In addition, special pre the steel hard treatment make it in the factory when has better hardness, can remove the mold production and processing in the heat treatment of links, improve economic benefits.
    The main performance of the 1.2738 mould steel: Material uniform hardness; excellent polishing performance; excellent machining performance; pre-hardened plastic mold steel; may be subjected to nitriding; suitable surface treatment, such as: plated Cr.
    The physical properties of the 1.2738 steel (Sample Hardness: 340HBW, at room temperature and high temperature conditions):
1) Temperature: 20℃ / 200℃ / 400℃, a density 7.8g/cm, 7.75g/cm, 7.7g/cm.
2) Temperature: 20 ~ 200℃ / 20 ~ 400℃, linear expansion coefficient 12.6×10K / 13.5×10K.
3) Temperature: 20℃ / 200℃ / 400℃, the thermal conductivity 29W·(m·K) / 29.5W·(m·K) / 31W·(m·K).
4) Temperature: 20℃ / 200℃ / 400℃, the elastic modulus 205000MPa / 200000MPa / 185000MPa.
    The mechanical properties of the 1.2738 mould steel (sample hardness 340HBW):
1) Temperature: 20℃ / 200℃ / 400℃, tensile strength 1100MPa / 1050MP8 / 850MPa.
2) Temperature: 20℃ / 200℃ / 400℃, conditions yield strength 980MPa / 925MPa / 770MPa.
3) Temperature: 20℃ / 200℃ / 400℃, section shrinkage rate 49% / 51% / 52%.
4) Temperature: 20℃ / 200℃ / 400℃, an elongation 13% / 14% / 16%.
5) Temperature: 20℃ / 200℃ / 400℃, impact toughness (≥) 20J/cm, 32J/cm, 42J/cm.

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The introduction of the mold steel 1.2080 steel

     The mold steel 1.2080 steel is the German D1N standard material number, which corresponds to the Chinese GB standard grade CR12, Japanese JIS standard grade SKD1, U.S. AlSI / SAE standard grade D3. Mold steel 1.2080 steel is a kind of ledeburite steel with high carbon and chromium. It has a high abrasion resistance, hardenability, hardenability, toughness, thermal stability, compressive strength, micro-deformation and excellent overall performance, has good machining and thermal oxidation resistance, wide adaptability. Has a high abrasion resistance, is 3 to 4 times of the general low alloy tool steel. The small deformation hardening.
     Mold steel 1.2080 steel isothermal spheroidizing annealing specification: (850 ~ 870) ℃ × (3 ~ 4) h, with the furnace cooling, (740 ~ 760) ℃ × (4 ~ 5) h isothermal, cooled baked, hardness temperature ≤241HBS, eutectic carbides ≤3 level.
     Ordinary quenching specification: Temperature 950 ~ 1150 ℃, oil quenching, quenching hardness ≥60HRC.
     The 1.2080 steel can be used to make cold working mold of complex shape and working conditions complex. Such as Die punch, thread rolling dies, drawing dies, die cutting, powder metallurgy die, woodworking cutting tools, cold cutting scissors drill sleeve and gauge tool.

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