About mold steel P20 steel

     P20 steel is a type of plastic mold steel, P20 is the United States grades, which corresponds to Chinese brands: 3Cr2Mo; Germany Grade: 1.2311. Steel types: pre-hardened plastic mold steel. Mold steel P20 steel is suitable for the production of plastic mold and die casting mold material of low melting point metal. This steel has good machinability and mirror-polished performance.
     Mold steel P20 steel chemical composition: Carbon: 0.38; Manganese: 1.30; Chromium: 1.85; Mo: 0.40; sulfur: 0.008.
     P20 steel hardness uniform, with good polished performance and photoetching performance, excellent processing performance. Pure steel vacuum degassing refining process, the requirements for polishing or etch processing plastic mold. Pre hardening treatment, without the heat treatment, can be directly used in mold processing, shorten the construction period. After forging rolling processing, compact structure, 100% ultrasonic inspection, no air hole and needle eye.

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Introduction of structural steel 4130 steel

     The structural steel 4130 steel with high strength and toughness, high hardenability. In the oil, the critical quenching diameter 15 ~ 70mm. The structural steel 4130 steel hot strength is also good, at below 500 ℃ with a sufficiently high temperature strength, But the strength was significantly decreased at 550 ℃. When the lower limit of the content of alloying elements, the welding is quite good, but the content of alloying elements is close to the upper limit, the welding performance medium.  And the need to preheat to 175 ℃ above before welding. Good machinability of the 4130 steel, cold deformation plasticity medium. When the heat treatment, has a first temper brittleness in the range of 300 ~ 350 ℃, may form white spots.
     The structural steel 4130 steel is typically used in quenched and tempered condition. In medium-sized machinery manufacturing industry mainly for the manufacture of large cross-section, parts working under high stress conditions, such as shafts, spindles and steering wheel to withstand high loads, bolts, studs, and other gear. In the chemical industry for the manufacture of welded parts, welded structure consisting of plates and pipes. For the manufacture high-pressure pipe at containing nitrogen and hydrogen media work and the temperature does not exceed 250 ℃. Fasteners used in steam turbines, boilers manufactured manufacturing work below 450 ℃, below 500 ℃ under high pressure flange and flange cover.

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Introduced the features of 1.2738 steel

    The 1.2738 steel using advanced die steel refining technology, is a vacuum melting Cr-Ni-Mo alloy steel. The features of 1.2738 steel: The steel has excellent polishing and photo-etching performance; excellent machinability; good wear resistance; large mold hardness is uniform, dense tissue; no quenching crack and deformation of heat treatment of risk, without heat treatment, shorten the molding cycle; surface nitriding performance can be good; flame surface hardening treatment, to improve the surface hardness and wear resistance of the die. Die before quenching, must be fully softening annealing. Should be timely tempering after quenching, slow heating.
    In the late precision electrical discharge machining, shall be conducted in small current, high frequency, so as not to damage the mould. After discharge the mold surface should be removed "electric spark grinding white layer", followed by a second tempering at 500 ℃, to remove stress.
    For grinding machining of the mold after tempering, in order to prevent softening of surface, grinding crack, should be noted: sufficient cooling; suitable grinding pressure; reasonable processing technology.
    The 1.2738 steel has good polishing performance, usually by alumina or gypsum polishing. The first is the rough polishing, and then polished with fine abrasive, every change once abrasives, polishing the direction you want to change, and ultimately a polishing time not too long, otherwise it will affect the roughness of the surface of the mold.
    Nitriding can increase the mould surface hardness, improve the wear resistance and corrosion resistance. Although the steel has been pre-hardening treatment, but still can enhance the hardness by heat treatment.

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Introduction of AISI 4340 steel properties

     AISI 4340 steel is one of the alloy structural steel , also known as alloy steel. It is based on high quality carbon structure steel, properly adding one or several kinds of alloy elements (the total content of not more than 5%) steel made. The AISI 4340 steel properties with high strength, high toughness and excellent hardenability and anti overheating stability, but white has high sensitivity, temper brittleness. Poor weldability, prior to welding need to high temperature preheating, after soldering need to eliminate stress, after adjustment use.
     Mechanical properties of AISI 4340 steel is as follows:
     Tensile strength σb (MPa): ≥980 (100)
     Yield strength σs (MPa): ≥835 (85)
     Elongation δ5 (%): ≥12
     Reduction of area ψ (%): ≥55
     Impact energy Akv (J): ≥78
     Impact toughness αkv (J / cm & sup2;): ≥98 (10)
     Sample size: Sample size is 25mm rough
     Heat treatment: (Quenching temperature: 850 degrees; coolant: oil; tempering temperature: 600 degrees; Coolant: water, oil);
     Steel annealing or tempering condition Brinell hardness GBW≤269
     According to AISI 4340 steel properties, which can be used to make good toughness, high strength, as well as an important regulator of large-size parts, such as heavy machinery and high load shaft. The size of machine shaft large than 250mm in diameter. Helicopter rotor shaft. Turbojet turbine shafts, blades, high load transmission parts. Crankshaft fasteners. And other gear. Can also be used to operate the temperature exceeds 400 ℃ rotor shaft and blades; AISI 4340 steel can also be nitriding treatment, used to manufacture special performance requirements of the important parts, such as shafts, gears, and other fasteners. After quenching or after isothermal tempering can be used for ultra-high-strength steel.

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