Cause Analysis of Spot Defects on Surface of Welded Pipe
The IF ( Interstitial Free) steel plate is welded into steel pipe for manufacturing condenser pipe of house-hold appliances by a user. There are local spot defects on the surface of steel pipe when it is subjected to conventional hydrostatic test. Such tests on chemical compositions,microstructure of defect and non-metallic inclusions of spot defects as well as mechanical properties and metallographic microstructure of the steel plate with base metal are carried out with such means as metalloscope and scanning electron microscope. The results showed that there were abnormal microstructures at the spot defects. The abnormal microstructures contain such alloying elements as Cr and Ni,which are different from the chemical compositions of matrix. When foreign matter is pressed into welded pipe,its local stress is concentrated. During hydrostatic test,the leak points of pressuring are at the foreign matter which is weakly combined with matrix. In order to a-void such surface defects,it is necessary to strengthen quality monitoring during the whole production and processing processes of welded pipe to prevent foreign matters from pressing into matrix to destroy its continuity so that the steel quality is reduced.
万方数据
维普
