Abstract
It is well known that thermal stresses occur in steel structural members by rapid heat transfer from molten zinc, when they are hot dip zinc galvanized, and the residual deformation remains in them. If they have notches, the stress concentration can be induced.On the other hand, it was previously reported by the author that steel was markedly embrittled when coated with molten zinc and then deformed in tension.In this study, from the point of view of fracture mechanics, fracture toughness tests were carried out in molten zinc and the nominal fracture toughness Ki of SM50A steel was obtained using the notched 3 point bend specimens. By analyzing the nominal stress intensity factor at the slit tip of the notched rectangular SM50A steel plate immersed in molten zinc, the immersing speed of crack initiation was obtained. The result of the immersion tests on the notched rectangular plate coincided well with the above analysis.The results obtained are as follows:(1) The nominal fracture toughness Ki in molten zinc of 16mm thick SM50A steel plate with 0.3mm notch width was 100kgf/mm3/2.(2) Even if there exists the stress just below the crack initiating level in molten zinc, the delayed fracture hardly occurred within 10min.(3) The maximum nominal stress intensity factor at the slit tip of the notched rectangular steel plate decreased with increasing immersing speed.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
