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研究了回火温度对一种低温压力容器用低合金高强度(HSLA)贝氏体钢组织和性能的影响。结果表明,经过910℃淬火后组织为粒状贝氏体,贝氏体板条界面及板条上分布有条状或块状M-A岛。回火温度在350~550℃区间升温时,M-A岛分解析出渗碳体;回火温度为635℃时,M-A岛完全分解为细小弥散的渗碳体颗粒;回火温度升至700℃时,贝氏体铁素体组织发生再结晶,板条结构消失,成为块状铁素体结构,渗碳体明显粗化。随着回火温度的升高,抗拉强度降低,伸长率和-50℃冲击功增加,屈服强度先升高后降低,冲击断口由脆性解理断口向韧性纤维断口变化。经过910℃淬火+635℃回火后达到最佳的强韧匹配度,抗拉强度为606 MPa,-50℃冲击功达到279 J。
The effect of tempering temperature on microstructure and properties of low alloy high strength (HSLA) bainitic steels for low temperature pressure vessels was investigated. The results show that the microstructure is granular bainite after quenching at 910 ℃, and strip-like or massive M-A islands are distributed at the bainite slab interface and slab. When the tempering temperature was raised from 350 ℃ to 550 ℃, MA island decomposes into cementite. When the tempering temperature is 635 ℃, MA island completely decomposes into fine and dispersed cementite particles. When the tempering temperature rises to 700 ℃ , Bainitic ferrite recrystallization occurs, the slab structure disappears, becoming a massive ferrite structure, cementite significantly coarsening. With the increase of tempering temperature, the tensile strength decreased, the elongation and the impact energy increased at -50 ℃, the yield strength first increased and then decreased, and the impact fracture changed from the brittle cleavage fracture to the fracture toughness fiber. After the quenching of 910 ℃ + 635 ℃ tempering to achieve the best tough match, the tensile strength of 606 MPa, -50 ℃ impact energy to 279 J.