喷焊层对焊缝组织性能的影响规律

为解决油田管线焊接接头防护问题 ,利用金相显微镜对焊缝组织形貌进行了观察。得到了镍基喷焊层元素熔入量对奥氏体焊缝显微组织及裂纹敏感性的影响规律。结果表明 ,镍基合金喷焊层的合金元素对奥氏体焊缝显微组织有明显影响 ,随着喷焊层元素熔入量的增加 ,焊缝柱状晶变得粗大 ,且方向性变得更明显。在一定范围内 ,增加喷焊层元素熔入量 ,焊缝的热裂纹敏感性将增大 ,但当熔入量再继续增加时 ,由于过量的喷焊层形成的大量低熔共晶物对焊缝冷却过程中的微裂纹起到了“愈合作用” ,使焊缝裂纹敏感性有所降低。同时 ,熔入过量喷焊层元素使得焊缝的薄弱位置发生了变化 ,热裂纹产生的位置由等轴晶区转移到柱状晶区。为了降低焊缝的热裂纹敏感性 ,应该在保证喷焊层耐蚀性的前提下 ,尽量降低喷焊层的厚度

Affecting laws of spraying layer on structure and property of weld

In order to protect weld joint on oil pipeline, the structure morphology of weld was observed by using optical microscopy. The influencing rules of the content of alloy elements in nickel-base spraying layer on the microstructure of austenite weld and the crack sensitivity were found. The composition of the nickel-base alloy-spraying layer has obvious effects on the microstructure of austenite weld. As the composition of the spraying layer increases,the columnar grains in the weld become coarse and the crystal orientation is obvious. As increasing content of alloy elements in the spraying layer to a certain extent, the hot crack sensitivity of the weld will increase. When the content of some elements welded into the spraying layer increases,the crack sensitivity of the weld will decrease. At the same time,much more elements of the spraying layer melted into the weld will change the weak area of weld. The cracking location of hot crack changes from equal-axes grain zone to columnar grain zone. If possible, the thickness of spring layer should be reduced in order to decrease the hot crack sensitivity of weld prior to protection of corrosion resistance of spraying layer.