AISI 4340 steel heat treatment guide

     Performance: the AISI 4340 steel is a high hardenability steel, AISI 4340 steel heat treatment hardenability than any kind of steel in the AISI standard of the higher. When the elements are concentrated, hardenability is within the allowable range, the upper curve of hardenability essentially become a straight line, this indicates that the AISI 4340 steel need air quenching in thinner area. In accordance with the precise carbon content, when hardening, Rockwell hardness in the 54-59 range. Due to high hardenability, AISI 4340 steel using traditional welding methods are not suitable, although it can use this old methods, such as electron beam welding. AISI 4340 steel can be forged effortlessly, although its thermal performance than carbon or low-alloy steel is higher, the need to use high power forging machine. The mechanical processing is not very good.
     Forging: heated to 1230℃. After the temperature dropped to 900℃ to stop forging. Cool slowly to prevent cracks.
     Recommended AISI 4340 steel heat treatment operations:
     Normalizing: heating to 870℃. Cooling in air to 565 degrees; or heated to 830 degrees, rapidly cooled to 650 ℃, and hold 8 hours. In order to get the ball structure and heated to 750℃, rapidly cooled to 705℃, and then at a rate of not more than 3℃ per hour was cooled to 650℃, and hold 12 hours. Ball organizational structure is usually easy machining and heat treatment.
     Quenching: 845 degrees at the time, the steel organization becomes austenitic, then oil quenched. In the casting the thin area can be air quenching.
     Tempering: with all high hardenability steel the same, alloy steel 4340 will produce quenching cracks. In the casting to ambient temperature before (38-50℃), they should be placed in tempering furnace. Tempering temperature depends on the desired hardness or comprehensive mechanical properties.
     Nitriding: through nitriding to produce high surface hardness and enhance the anti fatigue performance.

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Mold steel H13 steel performance introduction

    H13 steel is hot work die steel, it is the steel of adding alloying elements on the basis of carbon tool steel. Mold steel H13 steel is the most widely used and most representative of hot work die steel, its main features are as follows:
    Has high hardenability and high toughness;
    Excellent thermal shock resistance, in the workplace can be water cooled;
    H13 steel with moderate abrasion resistance can also be used carburizing or nitriding process to improve the surface hardness, but the thermal shock resistance will be slightly reduced;
    Because of its low carbon content, tempering the secondary hardening ability is poor;
    Mold steel H13 steel has a softening resistance at a relatively high temperature, but the use of temperatures above 540 ℃ (1000 ℉) hardness decreased rapidly. Therefore, the operating temperature of the H13 steel should not exceed 540 ℃;
    The heat treatment deformation is small;
    Medium and high machinability;
    Moderate resistance to decarbonization capacity.
    The comprehensive properties of H13 steel is good in the mesotherm, high hardenability (in the air that can harden), heat treatment distortion probability is lower, the performance and service life is better than 1.2581 steel. Can be used for die forging hammer forging die, aluminum alloy die-casting die, hot extrusion die, high speed precision forging die and forging press mould. It also can be used for the production of an important component of aviation industry.

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D2 steel heat treatment process

    D2 steel heat treatment methods:
    Stress relief annealing: the workpiece after rough machining, heating to 600~650 ℃, thermal insulation for 2 hours, with the furnace cooling to 500 ℃, followed by air cooling.
    Quenching: for the first time preheating, slowly warming the workpiece to 600 ℃, heat 20 minutes. After temperature uniformity, the second time preheating temperature was raised to 850 ℃, incubated for 30 minutes. Finally heated to 1020 ~ 1040 ℃, heat 25 to 40 minutes, followed by air cooling.
    Tempering: immediately tempering after quenching, and tempering at least twice, each holding time is not less than 2 hours.
    D2 steel heat treatment matters needing attention:
    After quenching, should be timely tempering, prevent cracking, and to prevent surface decarburization, for the manufacture of high precision die and gauge of D2 steel should be cryogenic treatment (-70 ℃), and the use of high-temperature tempering, To reduce the workpiece deformation, high temperature tempering temperature 500 ~ 560 ℃, hardness greater than 58HRC.

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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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The properties of the structural alloy steel 4140 steel

     Structural alloy steel 4140 steel has good workability, machining deformation small, anti-fatigue performance is quite good, is a medium hardenability steel. After the 4140 heat treatment has good strength and excellent mechanical properties, good technology, finished product rate. Maximum use temperature of 427 degrees Celsius. 4140 steel with high strength and hardenability, good toughness, quenching small deformation, high creep strength and lasting strength at high temperatures. 4140 steel can be used for manufacture forgings of higher strength and greater cross-section, such as a locomotive traction gear, turbocharger transmission gear, rear axle,  the connecting rod and the spring clips of great load, can also be used in less than 2000m deep oil drill pipe joints and fishing tools, and can be used for bending machine die etc..

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Introduction of mold steel 1.2379 steel

     The mold steel 1.2379 steel is a high-carbon and high-chromium alloy tool steel, has high hardness and wear resistance after heat treatment, and has a strong hardenability, good dimensional stability. The 1.2379 mold steel is suitable to make high precision and long life of cold work die and thermosetting molding plastic mold.
     The characteristics of mold steel 1.2379 steel are: pure steel vacuum degassing refining process. Ball annealing softening treatment, good cutting performance. Add strengthening elements vanadium, molybdenum, extremely excellent abrasion resistance.
     The 1.2379 steel uses: Sheet thickness no greater than 2MM, efficient blanking die, punch die and pressure die carrier. Scissors, inserts, woodworking blades. Thread rolling die and wear slider. Cold heading die, thermosetting resin molding die. Deep drawing molding die, cold extrusion dies.
     Quenched and tempered to a hardness of 63HRC. Its physical properties at room temperature and high temperature:
1) Temperature 20℃, the density 7700g/cm, the thermal conductivity of 20.0W/(m-K), the elastic modulus 210000MPa.
2) When the temperature of 200℃, the density 7650g/cm, linear expansion coefficient (20℃) 12.2×10K, thermal conductivity: 21.0W/(m-K), elastic moduli 200000MPa.
3) Temperature 400℃, the density 7600g/cm, the thermal conductivity of 23.0W/(m-K), the elastic modulus 180000MPa.

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Introduction of mold steel 1.2344 steel

    The characteristics of the mold steel 1.2344 steel: material uniformity, excellent machinability and polishing. High toughness and high ductility. Excellent overall hardening. Good high temperature strength and thermal fatigue resistance. Deformation of heat treatment is very low. Compared to the conventional steel, the 1.2344 steel have better isotropic, each direction has excellent toughness and ductility. The 1.2344 steel is the pressure hot work mold steel. The steel by electroslag remelting, material uniformity, hardenability good, with excellent machining properties and polishing properties, high toughness and plasticity. It has good abrasion resistance and anti high temperature fatigue and heat resistance at high temperature and low temperature.
    Chemical composition of mold steel 1.2344 steel: C 0.38-0.42; Si 0.8-1.2; Mn 0.30-0.50; P≤0.015; S≤0.002; Cr 4.80-5.50; Mo 1.2-1.5; V 0.90-1.10.
    The mold steel 1.2344 steel is mainly used in die casting mould, extrusion die, hot pressing mould. For high wear-resistant plastic mold, such as car tires alloy rings, engine, fishing line wheel.

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