In-situ Observation of Solidification Cracking of Laser Dissimilar Welded Joints

Abstract

This study is purposed to develop an evaluation method of solidification cracking susceptibility for laser DWJ of different dilution ratios. By using U-type hot cracking test with in-situ observation, the critical strain for the initiation of solidification cracking was measured locally near the crack rather than the macro strain measured in most other hot cracking tests. Meanwhile, the temperature history during laser welding at the trailing region of the molten pool was measured experimentally. The high temperature ductility curve was achieved based on the above test results of the critical strain and the temperature history. The critical strain rate of temperature drop (CST) was used to evaluate the solidification cracking susceptibility. Moreover, the residual liquid metal at the solidification front during laser welding was observed directly by using in-situ observation with an optical microscope lens. Consequently, all the results showed that solidification cracking susceptibility is the highest when the ratio of Inconel600 takes up roughly 40% in the weld bead among the used Inconel600/SUS347 laser DWJ.