4140 alloy steel flat bar is a good material for industry: the properties, chemical composition, heat treatment, and more below.
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扁钢强度高，淬透性好，韧性好，淬火变形小，高温下有较高的蠕变强度和持久强度，用于制造要求比35CrMo钢功率大，调质断面较大的锻件，如机车牵引用的巨型齿轮、增压器传动齿轮、后桥、高负荷连杆、弹簧卡子--2000m以下油井的钻杆接头、打捞工具等。
AISI ASTM SAE 4140钢扁钢具有良好的可加工性，加工变形小，抗疲劳性能相当好，是中等淬硬性可淬硬钢，4140钢扁钢经热处理后具有良好的强度和良好的综合力学性能，工艺性好，成品率高。最高使用温度为427摄氏度。4140钢扁钢强度高，淬硬性高，韧性好，淬火时变形小，蠕变强度高，高温下具有长期强度。用于制造比35CrMo钢要求功率大，调质断面大的锻件，如机车牵引用巨型齿轮、增压器传动齿轮、后桥、高负荷连杆、弹簧夹等。长度2000m以下深油井钻杆接头、打捞工具，可用于折弯机模具等。
4140钢扁钢化学成分
- 碳（C）0.38%～0.45%，
- 硅（Si）0.17%～0.37%，
- 锰（Mn） 0.50%～0.80%
- 磷（P）≤0.035%，
- 硫（S）≤0.035%，
- 铬（Cr）0.9%～1.20%，
- 镍（Ni）≤0.30%
- 钼（Mo）0.15%～0.25%，
- 铜（Cu）≤0.30%
4140钢扁钢机械性能
- 拉伸强度σb（MPa）：≥1080（110），
- 屈服强度σs（MPa）：≥930（95）
- 伸长率δ5（%）：≥12，
- 断面收缩率ψ（%）：≥45，
- 冲击功Akv(J)：≥63
- 冲击韧性值αkv（J/cm2）：≥78（8），
- 硬度：≤217HB
4140钢扁钢热处理工艺
- 退火1号》760±10℃退火，炉冷至400℃空冷。HB220-230
- 正火4号 860±10℃正火，空冷。
- 淬火+回火No.5 840±10℃淬火水或油（视产品形状复杂程度而定），680-700度回火。HB<217
- 淬火+回火No.6 840±10℃淬火油，470度回火 HRC41-45
- 淬火+回火No.7 840±10℃淬火油，480度回火处理 HRC35-45
- 淬火+回火8号850℃淬火油，再510度回火处理。HRC38-42
- 淬火+回火No.9 850℃淬火油，500度回火 HRC40-43
- 淬火+回火10号淬火油850℃，510℃回火HRC36-42
- 淬火+回火11号淬火油850℃，560℃回火HRC32-36
- 淬火+回火No.12 860℃淬火油，再390度回火。HRC48-52
4140钢扁钢对应国际标准组织牌号：42CrMo4
- 对应日本品牌：SCM440
- 对应德国牌号：42CrMo4
- 大约相当于美国等级：4140
- 对应英国BS 708M40/708A42/709M40
- 对应法国NF 40CD4/42CD4
- 对应中国国标42CrMo
- 对应俄罗斯ГOCT 38XM
