4140 alloy steel flat bar is a good material for industry: the properties, chemical composition, heat treatment, and more below.
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4140 flat steel bar belongs to structural alloy steel. According to the quality requirements of steel grades and steels, the smelting of structural alloy steel can adopt oxygen top-blown converter, open-hearth furnace, and electric arc furnace; or add electro slag remelting and vacuum degassing. The ingot can be continuous casting or die casting. The steel ingot should be cooled slowly or hot forged and rolled. When the steel ingot is heated, it is necessary to seek a uniform temperature and sufficient holding time to improve the segregation defects and avoid uneven deformation during forging and rolling; the steel after forging and rolling has a small size, especially carburization with a carbon content of about 0.2% Steel should be cooled quickly at temperatures above 600°C to avoid aggravating the band structure. Forgings with large cross-sections, measures should be taken to eliminate internal stress and white spots. The quenched and tempered steel should be quenched into a martensite structure as much as possible and then hardened into a sorbate structure; during the carburizing process of carburizing steel, the concentration gradient of the carburized layer should not be too large to avoid a continuous network on the grain boundaries of the carburized layer Carbide; nitrided steel must first be heat-treated to obtain the required properties, and then finally nitrided after finishing. There is no further processing after nitriding, except for grinding and removing the brittle and thin "white layer," no further processing.
4140 flat steel bar is used electric arc furnaces and oxygen top-blown converters for smelting. In addition, out-of-furnace refining, electro slag remelting or vacuum treatment, vacuum induction furnace smelting or double vacuum smelting, and appropriate heat treatment are generally required.
The content of alloy elements in this type of steel is relatively high, mainly including corrosion-resistant steel, heat-resistant steel, wear-resistant steel, magnetic steel, and special steel with other unique physical and chemical properties. As a result, 4140 flat steel bar is widely used in ships, vehicles, aircraft, missiles, weapons, railways, bridges, pressure vessels, machine tools, and other structures.4140 flat steel bar has better mechanical properties than carbon steel, especially excellent heat treatment performance.
4140 flat steel bar has high strength, hardenability, good toughness, small deformation during quenching, high creep strength, and endurance strength at high temperatures. It is used to manufacture forgings that require higher power and larger quenched and tempered sections than 35CrMo steel, such as giant gears for locomotive traction, supercharger transmission gears, rear axles, highly loaded connecting rods, and spring clips—drill pipe joints and salvage tools for oil wells below 2000m.
AISI ASTM SAE 4140 steel flat bar has good workability, processing deformation is small, fatigue resistance is quite good, it is medium-hardenability hardenable steel, 4140 flat steel bar has good strength and good comprehensive mechanical properties after heat treatment, good manufacturability, yield rate High. The maximum operating temperature is 427 degrees Celsius. 4140 steel flat bar strength, high hardenability, good toughness, small deformation during quenching, high creep strength, and long-term strength at high temperature. It is used to manufacture forgings that require higher power and larger quenched and tempered sections than 35CrMo steel, such as giant gears for locomotive traction, supercharger transmission gears, rear axles, highly loaded connecting rods, and spring clips. Drilling pipe joints and salvage tools for deep oil wells below 2000m in length can be used for bending machine molds, etc.
4140 steel flat bar chemical composition[edit | edit source]
- Carbon (C) 0.38%～0.45%,
- Silicon (Si) 0.17%～0.37%,
- Manganese (Mn) 0.50%～0.80%
- Phosphorus (P) ≤0.035%,
- Sulfur (S) ≤0.035%,
- Chromium (Cr) 0.9%～1.20%,
- Nickel (Ni)≤0.30%
- Molybdenum (Mo) 0.15%～0.25%,
- Copper (Cu) ≤ 0.30%
4140 steel flat bar mechanical properties[edit | edit source]
- Tensile strength σb (MPa): ≥1080(110),
- Yield strength σs (MPa): ≥930(95)
- Elongation δ5 (%): ≥12,
- Section shrinkage ψ (%): ≥45,
- Impact energy Akv (J): ≥63
- Impact toughness value αkv (J/cm2): ≥78(8),
- Hardness: ≤217HB
4140 steel flat bar heat treatment process[edit | edit source]
- Annealing No.1 "760±10℃ annealing, furnace cooling to 400℃ air cooling. HB220-230
- Normalizing No.4 860±10℃ normalizing, air cooling.
- Quenching+tempering No.5 840±10℃ quenching water or oil (depending on the complexity of product shape), 680-700 degrees tempering. HB<217
- Quenching+tempering No.6 840±10℃ quenching oil, then tempered at 470 degrees. HRC41-45
- Quenching+tempering No.7 840±10℃ quenching oil, and then 480 degrees tempering treatment. HRC35-45
- Quenching + tempering No. 8 850 ℃ quenching oil, and then 510 degrees tempering treatment. HRC38-42
- Quenching+tempering No.9 850℃ quenching oil, and then tempered at 500 degrees. HRC40-43
- Quenching + tempering No.10 quenching oil at 850℃, then tempering at 510℃. HRC36-42
- Quenching + tempering No.11 quenching oil at 850℃, and then tempering at 560℃. HRC32-36
- Quenching + tempering No.12 860 ℃ quenching oil, and then tempered at 390 degrees. HRC48-52
4140 steel flat bar’s corresponding international standard organization grade: 42CrMo4
- Corresponding Japanese brand: SCM440
- Corresponding to the German brand: 42CrMo4
- Approximately corresponds to the US grade: 4140
- Corresponding to British BS 708M40/708A42/709M40
- Corresponding to French NF 40CD4/42CD4
- Corresponding to Chinese GB 42CrMo
- Corresponding to Russia ГOCT 38XM