Abstract: The chemical composition of X70QS seamless steel tube was designed according to the API 5L standard. CCT curve of test steel was measured using thermal expansion instrument, the results show pearlite disappeared and bainite content was more when the cooling rate reached 20 龙/s, the appropriate cooling rate of quenching is more than 20 °C/s. Mass production of X70QS seamless steel tube was carried out using the process of “ 100 t EAF—LF + VD—CCM― ACCU- ROLL machine-quenching and tempering". In the production process, controlled S content, non-metallic inclusion, casting billet segregation. Also solved the problem of sticking steel in piercing. The results show the microstructure of X70QS seamless steel tube is ferrite and tempering bainite, grain size is not smaller than 8. 5, the total grade of all kinds of inclusion is not bigger than 2 ； the mechanical performance and H₂S resistance performance meet with the requirement of API 5L standard ； the ductile-brittle transition temperature is below -60 ℃ .

摘要： 根据API5L标准要求设计了X70QS无缝钢管的化学成分,采用热膨胀相变仪测定了试样钢种的CCT曲线,结果表明,当冷速达到20℃/s时,组织中珠光体消失,贝氏体含量较多,合适的淬火冷却速度应选择20℃/s以上。采用"100 t EAF→LF+VD精炼→圆坯连铸→精密斜轧机组轧制→调质热处理"工艺流程对X70QS无缝钢管进行生产。生产过程中有效控制了S含量、非金属夹杂物、铸坯偏析,解决了穿轧粘钢的问题。结果表明,X70QS无缝钢管的金相组织主要为铁素体+回火贝氏体,晶粒度在8.5级以上,各类夹杂物的总和≤2级;力学性能和抗硫化氢腐蚀性能完全满足API 5L的标准要求;-60℃时未达到材料韧脆转变温度。