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Strong and tough, good impact resistance: The nickel molybdenum ratio brings high impact toughness, resistant to repeated heavy forging hammer strikes, and not easy to crack or collapse.
Excellent hardenability, uniform large section: 300-400mm large section has uniform hardness after oil quenching, and the core is not soft, suitable for large and medium-sized hammer forging dies.
High temperature stability, strong resistance to thermal fatigue: maintaining high hardness and strength at 500-600 ℃, resistant to cyclic cracking, and with a longer lifespan than traditional steel grades.
Good wear resistance and tempering stability: Chromium molybdenum carbide is wear-resistant, molybdenum inhibits tempering brittleness, and the microstructure is stable after heat treatment.
Moderate cost, easy to process and repair: Low alloy design has high cost-effectiveness, good cutting and welding performance, and easy welding repair.
GB | JIS | ASTM | UNS | DIN | W-Nr. | ГOCT | SS |
5CrNiMo | SKT4 | L6 | T61206 | 55NiCrMoV6 | 1.2713 | 5XHM | ～2550 |
element | C | Si | Mn | Cr | Ni | Mo | S,P |
scope | 0.5~0.6 | ≤0.40 | 0.5~0.8 | 0.5-0.8 | 1.4~1.8 | 0.15~0.3 | ≤0.03 |
Tensile strength Rm (MPa) | Yield strength ReL (MPa) | Elongation A (%) | Reduction of area Z (%) | Impact toughness Akv (V-shaped notch J/cm² ) | Hardness H RC |
1250-1450 | 1100-1300 | ≥ 10 | ≥ 35 | 40-60 | 48-52 |
Heating specifications
Heating temperature: 1100-1150 ℃ (fully burned to avoid overheating)
Initial forging temperature: 1050-1100 ℃
Final forging temperature: 800-850 ℃ (≥ 800 ℃ for crack prevention)
Forging operation
Deformation method: alternate upsetting and elongation, ≥ 2-3 times, crushing the as cast structure, uniform grain size, and improving carbide segregation.
Deformation amount: single pass compression amount ≥ 20%, total forging ratio ≥ 3.
Board surface control: The last step is to lightly press and level to ensure flatness and uniform size.
Cooling after forging
Slow cooling (sand cooling/pit cooling/furnace cooling) is necessary to prevent white spots and cracking.
Large forgings: Slowly cool to 150-200 ℃ after entering the furnace at 600 ℃, and then air cool.
Process: Keep at 820-840 ℃ for 2-4 hours, cool in the furnace to 500 ℃ and air cool (fully annealed).
Hardness: HB 197-241, improves machinability and eliminates forging stress.
Quenching
Preheating: 600-650 ℃ (anti deformation and cracking)
Heating: 830-860 ℃ (upper limit for large sizes, lower limit for small sizes)
Cooling: Oil quenching (150-180 ℃ oil out, immediately tempered)
Tempering (according to mold size)
Small forging die: 490-510 ℃, 44-47 HRC
Medium forging die: 520-540 ℃, 38-42 HRC
Large forging die: 560-580 ℃, 34-37 HRC
Swallowtail area: 620-660 ℃ Tempering to enhance toughness and prevent cracking.
Large and medium-sized hammer forging dies (the most mainstream)
Automobile: forging dies for crankshafts, connecting rods, front beams, gear blanks, etc.
Heavy Industry: Hammer forging dies for large gears, bearing rings, valve bodies, etc. (side length>400mm).
Features: Can withstand high impact and high temperature (≈ 800-1000 ℃), has good toughness, and is not easy to crack.
Hot cutting edge/punching/precision forging die
Used for edge cutting, punching, and precision forging after forging, it is resistant to heat fatigue and wear.
Aluminum/copper alloy die-casting molds
The gearbox housing, engine cylinder block, etc. are resistant to metal liquid flushing and thermal cycling.
Hot extrusion die
Hot extrusion of bars, pipes, and profiles, with a working temperature of ≤ 500 ℃ and stable high-temperature strength.
Other
Hot scissor blades, high-temperature fixtures, large plastic molds (high toughness requirements).
