Due to the development and application of ultra-deep well and directional well drilling technologies, high grade steel drill pipes, such as G105 and S135, are used widely. The drill pipe failure incidents occur frequently. The fatigue crack length of high grade steel drill pipe is about 60-80 mm at steady developing stage. The impact energy formula of " leak before break" failure mode was proposed, and stress strength coefficient was introduced for the first time. The results show that the impact energy value increases with the increase of critical crack length, stress strength coefficient square, and steel grade. The impact energy values of high grade steel drill pipe and anti-sulfur drill pipe are not less than 80 J and 110 J respectively to ensure drill pipe under "leak before break" failure mode.%随着超深井、定向井等先进钻井技术的应用,高钢级钻杆G105和S135大量使用,钻杆疲劳失效事故频频发生.高钢级钻杆在失效过程中疲劳裂纹稳定扩展长度为60～80 mm.推导出钻杆发生“先刺后断”失效模式的材料韧性指标——冲击功的计算公式,并首次提出应力强度比系数的表示方法.计算结果表明:钻杆材料的冲击功要求值随钻杆临界裂纹长度、应力强度比系数平方和钻杆钢级的增加而增加；为了保证高钢级钻杆发生“先刺后断”的失效模式,冲击功要求值应不低于80 J,抗硫钻杆的冲击功要求值应不低于110 J.
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