US 5,634,988 A · High tensile steel having excellent fatigue strength at its weld and weldability and process for producing the same

Abstract

The present invention relates to a high tensile welded steel plate consisting essentially of, by weight, C: 0.03 to 0.20%, Si: 0.6 to 2.0%, Mn: 0.6 to 2.0%, Al: 0.01 to 0.08%, B: not more than 0.0020%, and N: 0.002 to 0.008% and optionally at least one element selected from Cu, Mo, Ni, Cr, Nb, V, Ti, Ca, and REM with the balance consisting of Fe and unavoidable impurities, and a process for producing a high tensile welded steel plate, usually comprising the steps of: subjecting a slab comprising the above chemical compositions to hot rolling or alternatively hot rolling followed by controlled rolling. The present invention enables fatigue cracking of the as-welded steel, in its heat-affected zone, to be prevented and, at the same time, the propagation of the crack to be prevented or inhibited.

Claims15

Dependent claims

A high tensile welded steel plate having excellent fatigue strength at its weld, and good weldability, consisting essentially of, by weight, C:

0.03 to 0.20%, Si:
0.6 to 2.0%, Mn:
0.6 to 2.0%, Al:
0.01 to 0.08%, N:
0.002 to 0.008%, and B:
not more than 0.0020% with the balance consisting of Fe and unavoidable impurities, wherein said weld in its heat-affected zone has a bainite microstructure fraction of not less than 80 vol. %.

3 more elements

A process for producing a high tensile steel plate having excellent fatigue strength at its weld when welded, and good weldability, comprising the steps of:

heating a slab consisting essentially of, by weight, C:
0.03 to 0.20%, Si:
0.6 to 2.0%, Mn:
0.6 to 2.0%, Al:
0.01 to 0.08%, N:
0.002 to 0.008%, and B:
not more than 0.0020% with the balance consisting of Fe and unavoidable impurities to a temperature in the range from the Ac.sub.3 point to 1250.degree. C., hot-rolling the heated slab in a recrystallization temperature region to provide a hot-rolled plate, subsequently hot rolling said plate in an unrecrystallization temperature region with a cumulative reduction ratio of 40 to 90%, and then air cooling the plate.

4 more elements

Dependencies are inferred from the claim text.

High tensile steel having excellent fatigue strength at its weld and weldability and process for producing the same

Life of this patent

High tensile steel having excellent fatigue strength at its weld and weldability and process for producing the same

Life of this patent

Abstract

Claims15