Prevention of the liquid metal embrittlement in Weldment.

The effect of hardness and grain size of steels and their welds on fracture stress and sensitivityof Liquid Metal Embrittlement Cracking in molten Zinc (L MEC) was investigated. The experiment wasconducted using commercial weldable structual steels and Sustained Load Test (SLT) conducted inmolten Zinc with heating range of 430 - c - 470c . the liquid metal embrittlement cracking of heataffected zone (HAZ) of steel in hot dip galvanizing was investigated. The experiment was conductedusing synthetic HAZ of JIS G 3444 STK55 and Sustained Load Test at 370 - C-470 - C heating range inliquid (molten) and solid Zinc. the LMEC behavior of steels and welds in molten Zinc is of thermalactivated process,fractures are intergranular (IG) type witch corresponds to actual LMEC in hot dip galvanising.fracture stress of steels and welds in molten Zinc is obtained by measuring Vicker'shardness and grain size，这些估计值是有correspond with test results. LMEC的敏感性是受影响的hardness of steels and welds.LMEC behavior is of thermal active process and LMEC sensitivity isHAZ. affected by hardness of HAZ. The coarse grain region in HAZ showned The highest LMEC sensitivity.The interfacial enegy of steel is redused by The exsistence of Zinc. The反应速率过程LMEC of steel is controlled by grain boundery diffusion of Zinc. The nucleation and The propagationLMEC in steel are likely to have a close relation to the reduction of interfacial energy due tothe grain boundery diffusion of Zinc。

The effect of hardness and grain size of steels and their welds on fracture stress and sensitivity of Liquid Metal Embrittlement Cracking in molten Zinc (L MEC) was investigated. The experiment was conducted using commercial weldable structual steels and Sustained Load Test (SLT) was conducted in molten Zinc with heating range of 430゜C-470゜C.The liquid metal embrittlement cracking of heat affected zone (HAZ) of steel in hot dip galvanizing was investigated. The experiment was conducted using synthetic HAZ of JIS G 3444 STK55 and Sustained Load Test at 370゜C-470゜C heating range in liquid (molten) and solid Zinc.The LMEC behavior of steels and welds in molten Zinc is of thermal activated process, and fractures are intergranular (IG) type witch corresponds to actual LMEC in hot dip galvanising. Estimation of fracture stress of steels and welds in molten Zinc is obtained by measuring Vicker's hardness and grain size, and these estimation values are correspond with test results. The sensitivity of LMEC is affected by hardness of steels and welds.LMEC behavior is of thermal activated process and LMEC sensitivity is affected by hardness of HAZ. The coarse grain region in HAZ showned the highest LMEC sensitivity. The interfacial enegy of steel is redused by the exsistence of Zinc. The reaction rate process of LMEC of steel is controlled by grain boundery diffusion of Zinc. The nucleation and the propagation of LMEC in steel are likely to have a close relation to the reduction of interfacial energy due to the grain boundery diffusion of Zinc.