When ultra-high strength steel with tensile strength more than 1 600 MPa and BS700 high-strength steel with tensile strength more than 760 MPa are joined together by metal active gas welding, weld cracks are prone to occur in the seam of joint. To solve this problem, comparative welding tests were performed by using ER70-G or ER307Mo welding wire with diameter of 1.0 mm, respectively, with initial welding current of 160-180 A, voltage of 21-24 V, and final welding current of 190-210 A, voltage of 23-26 V. The comparison of process and weldability show that welding with ER307Mo can lead to the sample with bending property obviously better than that by welding with ER70-G. The sample after welding with ER70-G can be found to have micro-cracks not going through the whole cross section of welding seam, with cracking rate on the cross section of seam reaching 35.29%, but no cracks are found on the section of welding seam by using ER307Mo. It is concluded that the ER307Mo welding wire is more suitable for welding ultra-high strength steel and BS700 high strength steel. The study has solved the cracking problem in the joint of ultra-high strength steel and BS700 high strength steel, which can provide a solution for the welding of dissimilar high-strength steel with larger difference in tensile strength.

welding  /  ultra-high strength steel  /  high strength steel  /  welding joint  /  crack  /  welding materials  /  rigid constraint  /  metal active gas (MAG) welding  /  dissimilar steel welding  /  lightweight