热处理工艺对EH690级特厚钢板心部组织及性能的影响

Effects of Heat Treatment Process on Central Microstructures and Properties of EH690 Grade Extra-heavy Steel Plate

针对不同热处理工艺对EH690级特厚钢板心部组织和性能的影响展开研究,结果表明:经过在线淬火+回火处理,钢板心部的强度能够满足性能要求,但冲击韧性极差,显微组织为粗大粒状贝氏体和珠光体的混合组织;一次淬火+回火处理后,强度下降明显,冲击性能有所改善,但是不能满足-40℃低温冲击吸收功≥69 J的要求,存在混晶,组织为粒状贝氏体+少量马氏体;二次淬火+回火处理后,强度整体偏高,冲击功均值满足标准要求,强韧性匹配程度一般,晶粒细化明显,马氏体含量占比增多。通过调整回火温度,最终获得晶粒细小均匀、以高密度位错回火索氏体为主的组织,钢板心部强韧性匹配较好。

The effects of different heat treatment processes on the microstructure and mechanical properties at the center of EH690 grade extra-heavy steel plate are studied.The results show that the strength at the center of steel plate meets the properties requirement after on-line quenching and tempering,but possesses poor impact toughness,the steel plate is of mixed microstructure including coarse granular bainite and pearlite.The strength obviously decreases with improved impact properties after primary quenching and tempering,but the requirement of low temperature impact absorbed energy value greater than or equal to 69 J at-40 ℃ is not satisfied,mixed crystal exists with the microstructure of granular bainite and litle martensite.The strength is generally higher,the impact absorbed energy values meet the standards requirements,the strength and toughness are generally matching,the grain refines significantly with higher percentage of martensite content after secondary quenching and tempering.By adjusting the tempering temperature,the tempered sorbite with uniform refined grain and high density dislocation is obtained as the major constituent,good matching of strength and toughness at the center of steel plate is achieved.