Effect of Cooling Condition on Crack Nucleation in Hot-Dip Galvanizing Bolts

Abstract

Cracks sometimes occur at the underhead fillet of a bolt in the hot dip galvanizing process. In the preceeding paper, the effect of Hot-dip galvanizing condition in this process on crack nucleation was investigated experimentally. As a result, it was found that crack nucleation easily occurs in the cooling process.
In this study, to investigated the effect of cooling condition on crack nucleation in the hot dip galvanizing process, some experiments were performed.
The main results obtained are as follows.
(1) In the cases of water cooling method and time water cooling method, cracks occurred at the underhead fillet of a bolt. But, in the cases of shower cooling method and air cooling method, no crack occurred.
(2) In the case of air cooling method, the whole plating layer became Fe-Zn layer and the plating surface became very rough.