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我厂设计的压力为1.2MPa的容器釜,其封头材质为20g,快开门外连接圈材质为中碳钢(φ2000mm)。 我厂过去采用J507碱性低氢型焊条焊接。工艺如下:焊前将焊缝坡口附近清理干净;将工件坡口150～200mm左右处匀速加热到150～250℃;焊条使用前烘干1～2h,温度为300～350℃;焊第一层时,速度放慢,以免焊缝太薄,易拉裂,采用小电流,以减小母材的熔深;沿圆周分成几段,跳焊;焊后加热,并缓慢冷却。 焊后经探伤检测未发现裂纹、气孔及夹渣等缺陷。但进行水压试验过程中,当压力升到1.2MPa时,在离焊趾5～10mm处的中碳钢上,圆周局部出现几处微小裂纹,并有水珠渗出(图1)。
The pressure of our factory is 1.2MPa. The material of the head is 20g. The material of the quick-opening connecting ring is carbon steel (φ2000mm). I used the factory J507 alkaline low hydrogen type electrode welding. The process is as follows: the welding seam before cleaning the groove near the groove; 150 ~ 200mm around the workpiece bevel uniform heating to 150 ~ 250 ℃; electrode drying before use 1 ~ 2h, the temperature is 300 ~ 350 ℃; welding first Layer, the speed slowed down, so as not to weld too thin, easy to crack, the use of small current, in order to reduce the base metal penetration; along the circumference is divided into several sections, jump welding; heating after welding, and slow cooling. After welding, no cracks, pores and slag inclusions were detected by flaw detection. However, during the hydrostatic test, when the pressure rises to 1.2 MPa, several tiny cracks appear on the circumference of medium carbon steel 5 to 10 mm away from the weld toe and water droplets are seeped out (Figure 1).