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Formation mechanism of transverse crack in repair welding for thick plate of Q345 high strength steel

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China welding 2012年第2期21卷 73-77页

作者：张华军黄红雨蔡春波沈大明陈善本 Shanghai Zhenhua Heavy Industries(Group)Co. Ltd.Shanghai200125 Chen Shanben School of Material Science and TechnologyShanghai Jiao Tong UniversityShanghai200240

Transverse cracks occur usually in repair welding for thick plate of high strength steel. It needs multiple times of repair welding. The quality of production and deliver deadline will be influenced. Therefore, it is very significant to investigate the cause and control of transverse crack in repair welding. In this paper, both ends restraint crack experiment is developed to produce delay transverse crack for high strength steel. Metallographic results show that four types of cracks are found in repair welding metal zone and heat affected zone. Large chevron transverse cracks are found in repair welding zone. Lots of micro transverse cracks are found in inter-layer repair welding metal zone, root HAZ and two ends of repair welding individually. The distribution character and formation mechanism of the transverse crack are further analyzed through hardness testing and residual stress measurement.

关键词： repair welding transverse crack high strength steel thick plate chevron transverse crack

Microstructure and mechanical properties of repair welds of low-pressure sand-cast Mg?Y?RE?Zr alloy by tungsten inert gas welding

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Journal of Magnesium and Alloys 2022年第1期10卷 195-209页

作者： Xin Tong Guohua Wu Liang Zhang Yingxin Wang Wencai Liu Wenjiang Ding National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composites School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China

The sand castings of Mg-Y-RE-Zr series alloys are widely utilized in the large scales and complex shapes in the aerospace industry,as a result of which there are always some cast defects in the products. In this study, the feasibility of repair welding of sand-cast Mg-4 Y-3 RE-0.5 Zr alloy by tungsten inert gas(TIG) welding was scrutinized with different welding currents from 150 to 210 A. The results indicated that defect-free repaired joints with good appearance could be acquired at 170 and 190 A. Interestingly, the grain size of the fusion zone(FZ) was refined initially and then increased with the linear increment of welding current. Because at the higher heat inputs, although the cooling rate of the molten pool was reduced, substantial constitutional supercooling for the grain refinement was attained after the Zr particles were transformed into Zr solutes. The tensile strength of the repaired joint at 170 A was 195 MPa with the maximum joint efficiency of 87.8%, and the elongation reached to 124.4% of the sand-cast base material(BM). However, serious grain coarsening and continuous eutectic structures generated in heat-affected zone(HAZ) above 190 A resulted in the weakening of the joint due to the brittle intergranular fracture.

关键词： Sand-cast Mg-Y-RE-Zr alloy repair welding Microstructure Tensile properties Fracture behavior

Laser Cladding of Cold-Work Tool Steel by Pulse Shaping

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Journal of Materials Science & Technology 2011年第8期27卷 707-713页

作者： Matej Pleterski Janez Tuek Tadej Muhic Ladislav Kosec Faculty of Mechanical Engineering University of Ljubljana Akereva cesta 6 TKC D.O.O. Trnovska Ulica 8 Faculty of Natural Sciences and Engineering University of Ljubljana Akereva Cesta 12

repair welding of cold-work tool steels in cold is very risky and almost impossible by conventional processes. The application of pulse shaping in laser cladding with wire to avoid the solidification problems in relevant steel is demonstrated. The results show that sound remelting and/or cladding can be achieved by the right selection of laser parameters and pulse shape, i.e. long pulse duration, moderate pulse peak powers and ramped-down pulse shape. Despite the defects and softening in the cladding due to the formation of retained austenite, the cladding shows better wear resistance at lower loads compared to the heat-treated base material.

关键词： Laser cladding repair welding Tool steel Wear test

Weldability of steel used in an aged bridge

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China welding 2024年第3期33卷 33-38页

作者： Hirohata Mikihito Department of Civil Engineering Graduate School of EngineeringOsaka UniversitySuita 565-0871Japan

A series of experiments was performed to investigate the weldability of steel used in an aged bridge.A steel material used in an aged railway bridge constructed in 1912 was extracted for this *** chemical compositions of this steel were suitable for ***,the aged steel contained much *** welded joints were fabricated with this aged *** defects or cracks were not observed in the *** Vickers hardness test on the welded part did not confirm extreme hardening or *** yielding by the static tensile test,the cruciform joints were fractured at the welded *** of the specimens was fractured in the middle of the thickness of the aged *** Sulfur contained in the aged steel might cause this type of *** results show that there may be a risk of brittle fracture not only from the welded part but also from the base *** chemical compositions of aged steel must be analyzed when repair welding is applied to the steel.

关键词： aged steel bridge repair welding chemical compositions weld defect brittle fracture