为找到S135钻杆焊缝冲击韧性低、不符合要求的原因，对焊缝进行了冲击试验、力学性能试验、金相检验、化学成分分析、非金属夹杂物检验等，并对冲击试样断口进行了宏观及微观分析。结果表明：钻杆接头材料硫元素含量高，A类非金属夹杂物级别高、含量多，造成摩擦焊焊接时焊缝区形成较多A类非金属夹杂物，影响了组织的连续性，受到冲击力时，缺陷的弱结合面处先产生裂纹，裂纹快速扩展最终断裂，导致焊缝试样冲击韧性低、不合格。

In order to find out the reason why the impact toughness of S135 drill pipe welding seam is low and does not meet the requirements, the impact test, mechanical property test, metallographic examination, chemical composition analysis and non-metallic inclusion examination were carried out on the welding seam, and the macro and micro analysis were carried out on the fracture of impact sample. The results show that the high content of sulfur element in drill pipe joint material and the high level and high content of class A non-metallic inclusions result in the formation of more class A non-metallic inclusions in the welding seam zone during friction welding, which affects the continuity of microstructure. Under the impact force, cracks first appear at the weak joint surface of defects, the cracks expand rapidly and finally fracture, resulting in the low impact toughness and disqualification of welding seam sample.