| Impact value of the weld metal is one of the most important factors to reflect the quality of the joint, while the inclusion is one of the most important factors to influence the impact value In the forming process of weld metal, the inclusion will supply nucleus to promote the forming of aciculae ferrite (AF) so that the impact toughness of weld metal will be increased. When the pool is becoming cooling, the inclusion will act as the nucleus of the cracking to accelerate crazing so that the impact toughness will be decreased.Aiming at the problem that the impact capabilities of the charpy V-notch specimens welded by submerged arc welding were low, a serious of tests were conducted in the first part of this paper, such as analyzing the composition of weld, fracture analysis and metallographic examinations. It was found that the inclusion with big dimension in the weld was the primary reason for low impact values. Then a new plan was raised to solve this problem and the satisfying result was got after welding in the spot.Then, the contrastive impact specimens were made by welding on 16MnR steel using SJ101 flux and HJ431 flux. After doing some tests it was found that the specimens with high impact value had a high content of AF. So this paper raised a new point that the SJ101 flux can increase the impact value of weld because it can supply more suitable inclusions for the forming of AF. Using a lot of advanced measures such as SEM and TEM to analyse the specimens, the new point above was improved. On the base of tests results this paper raised a more suitable Transformation Kinetics of AF surrounding the inclusion. |
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