26CrMoVNbRE钢高效热处理调质工艺边界探索

研究了不同淬火温度、淬火保温时间、回火温度及回火保温时间对26CrMoVNbRE钢组织与性能的影响,结果表明,试验钢870~900 ℃淬火后高温回火,显微组织为回火索氏体,原始奥氏体晶粒细小均匀。870 ℃保温40 min淬火,与900 ℃保温30 min淬火屈服强度相近,前者有良好的综合力学性能,后者更有利于现场高效热处理。900 ℃保温30 min淬火,再经720 ℃回火60 min调质处理,BT110TS钢级油套管各项力学性能满足技术要求。采用SEM结合EDAS对不同回火温度条件下的析出物进行观察,结果表明,试验钢第二相析出物为M₂C型碳化钼以及M₃C型碳化铬形成的复合相,随着回火温度的降低,分布在晶界上的析出物增多,不利于低温冲击性能与耐应力腐蚀。

Study on boundary of efficient quenching and tempering process of 26 CrMoVNbRE steel

Effect of different quenching temperature,and holding time,tempering temperature and tempering time on the microstructure of 26CrMoVNbRE steel was studied.The results show that the microstructure is mainly composed of tempered sorbite after quenched at 870-900℃and tempered at high temperatures,and the primary austenite grains are fine and uniform.The yield strength of the specimens quenched at 870℃for 40 min is similar to that of quenched at 900℃for 30 min.The former has good comprehensive mechanical properties,and the latter is more favorable to field high efficiency heat treatment.Mechanical properties of the BT110 TS oil casing tubes made of the steel can meet technical requirements when quenched at 900℃for 30 min and tempered at 720℃for 60 min.The precipitates were observed by means of SEM and EDAS under different tempering temperatures.The results show that the second phase precipitates in the experimental steel are composite phases formed by M₂C type molybdenum carbide and M3C type chromium carbide.With the decrease of tempering temperature,the precipitates distributed on the grain boundary increase,which is not conducive to low temperature impact properties and stress corrosion resistance.