Analysis of Bend Test Cracking Problems for the 9Ni Steel Welded Joint
Bend test cracking problems of welded joints are often encountered in welding of 9Ni steel,and the quality of welds does not meet the requirements of LNG tank products,so that the design and implementation of welding procedure need to be improved.By serial welding tests,the causes of cracking were found and the corresponding countermeasures were proposed.The optimized welding procedure was used for the testing pieces'welding,and the mechanical properties of the welded joints ful-filled the specification,the additional side bend specimens did not appear any open defects after bending.The new welding pro-cedure was applied to the welding of type-C cargo tank of 9 500 m3 LNG carrier.The results of all bending tests with 10 mm thick lateral bending specimens met the requirements.The welding quality of 9Ni steel had been recognized both by society and owner.The length of the testing pieces could be half reduced from the longitudinal ones,which effectively enhances the testing efficiency and saves testing materials.
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