PURPOSE: To prevent the cracking of a structural steel material due to hot- dipping at its weld heat-affected zone when the steel material is galvanized after welding so as to prevent corrosion, by adding a specified element to the steel material.
CONSTITUTION: A structural steel material having ≥50kg/mm2 tensile strength and a composition consisting of <0.05% C, <0.3% Si, 1.0W2.0% Mn, <0.03% Ti and the balance Fe is welded and galvanized so as to improve the corrosion resistance. At this time, the weld heat-affected zone causes cracking at grain boundary due to embrittlement of molten Zn, that is, a liq. metal. To prevent the cracking the Pcm value of the steel material is regulated to ≤0.15% by adding at least one among 0.02W0.10% Nb and/or V, ≤1% at least one among Cu, Ni and Mo, and 0.0005W0.0020% B to the steel material or by further adding 0.04W 0.08% sol. Al and <0.0040% N. The resistance to cracking due to hot-dipping at its weld heat-affected zone is improved.
AKAO KAZUTAKA
TAIRA TADAAKI
ICHINOSE HIROYUKI
| JPS486008A | ||||
| JPS4937814A | 1974-04-08 | |||
| JPS54110915A | 1979-08-30 |