通过化学成分分析、硬度测试、楔载荷、保证载荷和紧固轴力检验,对某批规格为M20 mm×80 mm的10.9S扭剪型高强螺栓连接副紧固轴力偏低的原因进行了分析。结果表明：该批高强螺栓连接副质量合格，但在包装和运输过程中受干燥环境影响，导致其表面磷化膜风化，润滑性下降，轴向摩擦力增大，因而紧固轴力下降。

The reason of low tight axle strergth of the M20 mm×80 mm 10.9S sets of torshear type high strength bolt used for the steel structure was analyzed by means of test for chemical composition,hardness,wedge load,assured load and tlght axle strength. The results showed that the quality of the sets of bolt was eligible,but under the effect of dry circumstance,the phosphide film on the blot and nut was airslaked,the lnbricative capability was reduced and the friction in axes direction was increased that led to the low tight axle strength.