JIS SKT4 is a Japanese Hot work tool steel. it is similar to AISI/SAE L6 Tool Steel | Din 1.2714/55NiCrMoV7 | JIS SKT4. it has good hot hardness and toughness. High purity, good resistance to impact abrasion resistance. Can be used for hot forging die, extrusion die, manufacturing is greater than 350 mm thickness, complex cavity and bearing load larger zhong large forging die and hot die forging press.
Characteristics and Scope of Application
SKT4 steel has good toughness, strength, and high wear resistance. Its mechanical properties are almost the same at room temperature and 500-600 ℃. When heated to 500 ℃, it can still maintain a hardness of around HB300. Mainly used for large and medium-sized hammer forging dies and trimming dies.
Due to the presence of molybdenum in steel, it is not sensitive to temper brittleness. After slowly cooling down from 600 ℃, the impact toughness only slightly decreased.
SKT4 steel has good hardenability. After oil quenching at 820 ℃ and tempering at 560 ℃, the hardness of each part of the section of the 300mm × 400mm × 300mm large steel material is almost the same.
This type of steel is used to manufacture various large and medium-sized forging dies.
However, SKT4 steel is prone to white spots and requires strict control over the smelting process and cooling system after forging and rolling.
Main technical parameters of JIS SKT4 STEEL
| After quenching: |
58 HRc
|
| Quenching temperature ℃: |
830～860
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Delivery Status：
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Annealing：HB≤241
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coolant ：
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Oil
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Chemical composition and equivalent grade
| Grade Number | Standard | C | Si | Mn | P | S | Cr | V | Mo |
| SKT4 | JIS G4404 | 0.50～0.60 | 0.10～0.40 | 0.15-0.35 | 0.030 Max | 0.20 Max | 0.80～1.20 | 0.05～0.15 | 0.35～0.55 |
Corresponding Chinese brand: 5CrNiMo
Corresponding German brand: Din 55NiCrMoV6 (1.2713)
Corresponding US brand: 6F2/ AISI ASTM L6
Corresponding French brand: 338155NCDV7
JIS SKT4 steel mechanical property
Hardness: annealed, 241-197HB, indentation diameter 3.9-4.3mm
Heat treatment specifications and metallographic structure:
Heat treatment specification: Quenching, oil cooling at 830-860 ℃.
Delivery status: Steel is delivered in annealed state.
Tempering process of SKT4 Steel
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Quenching temperature/℃
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cooling
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Hardness（HRC）
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–
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medium
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Medium temperature/℃
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continue
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||
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830～860
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Oil
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20～30
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Temper immediately after reaching 150-180 ℃
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53～58
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2 . In order to avoid large stress and strain during quenching of the hammer forging die, it is heated from 830-860 ℃, pre cooled in air to 750-780 ℃, then oil cooled to around 150-180 ℃, removed and immediately tempered;
3. For large molds, they should be preheated in a heating furnace at 600-650 ℃, and the furnace temperature should be increased after heat penetration; For better heating, the mold should be placed on a cushion plate that is 60-100mm high for heating.