热处理工艺对XG630DR钢板组织与力学性能的影响

Effects of Heat Treatment Process on Microstructure and Mechanical Properties of XG630DR Steel Plate

采取光学显微镜、扫描电镜研究了热处理工艺对XG630DR钢板组织与力学性能的影响。结果表明:热轧钢板经过正火处理后,带状组织由3.5级降到3.0级,晶粒度由10.35提高到11.79,抗拉强度降低120 MPa左右,伸长率提高,低温冲击韧性改善;正火钢板经过模拟焊后热处理,带状组织减轻,晶粒度达到12.52,珠光体、贝氏体部分分解,铁素体含量增加,屈服强度增加,抗拉强度降低40 MPa左右,冲击韧性进一步改善。钢板正火状态下,随着正火温度的提高,屈服强度增加,抗拉强度略有增加;随着正火时间的延长,强度先降低后增加,冲击韧性先增加后降低。钢板正火+模拟焊后热处理状态下,随着正火温度的提高,强度提高,冲击韧性先降低后增加;随着保温时间的延长,强度变化不大,冲击性能改善。试验钢经过870℃保温50 min正火处理后,模拟焊后热处理钢板具有良好强韧性;与P460NL2标准要求相比,力学性能更优。

The effects of heat treatment on the microstructure and mechanical properties of XG630DR steel were studied by optical microscope and scanning electron microscope.The results show that for hot-rolled steel plate after normalizing treatment,the ribbon microstructure reduces from 3.5 grade to 3.0 grade,the grain size is from 10.35 to 11.79,the tensile strength decreases by about 120 MPa,the elongation increases,the low temperature impact toughness improves.For normalized steel plate after simulated post-welding heat treat ment,the ribbon microstructure reduces,the grain size reaches 12.52,the pearlite,bainite partially decomposition,the ferrite content increases,the yield strength increases,the tensile strength decreases by about 40 MPa,the impact toughness further improves.When the steel plate is in the normalized state,with the increase of the normalizing temperature,the yield strength increases and the tensile strength increases slightly,with the normalizing time increasing,the stength decreases first and then increases,and the impact toughness increases first and then decreases.When the normalized steel plate is in simulated post-weld heat treatment state,with the increase of the normalizing temperature,the strength increases,and the impact toughness decreases first and then increases,with the the holding time prolonging,the strength changes little and the impact performance improves.When the test steel is normalized at870℃for 50 minutes,the steel plate after simulated post weld heat treatment has good strength and toughness,and it has better mechanical properties compared with P460 NL2 standard requirements.