X70钢管道采用铜衬垫根焊的焊接接头疲劳性能

Fatigue property of X70 steel pipeline girth welding joint with copper back-up shoes root welding

利用成组法,在应力比r=0.1的情况下分别对采用铜衬垫与陶瓷衬垫进行根焊的X70钢管道焊接接头进行了高频疲劳试验,并在一定的疲劳载荷及循环次数下,对比两种试样焊趾处疲劳裂纹的启裂情况.结果表明,X70钢管道根焊采用铜衬垫焊接过程中,其背部的渗铜对构件疲劳强度基本没有影响,两种试样的S-N曲线基本一致,疲劳裂纹均起始于根焊背部焊趾处.在相同的应力及循环条件下,焊趾处裂纹萌生情况无明显区别.在此基础上,采用SEM方法进一步对疲劳断口进行了分析.

By using group method,high frequency fatigue test was conducted on X70 steel pipeline girth welding joint with a copper backing and ceramic backing respectively when the stress ratio was 0. 1( r = 0. 1),and the crack initiation of the two kinds of samples were compared in certain fatigue load and cycle times. The results indicated that the copper infiltration in X70 steel pipeline girth welding with copper backing had little influence on fatigue strength and that the S-N curves of the two samples were almost the same. Another finding was that,under the same fatigue load and cycle condition,the crack initiation had no significant difference with the fatigue crack starting at the back weld toe. Furthermore,the fatigue fracture was analyzed by SEM.