PURPOSE: To manufacture a steel for electric resistance welded tube combining toughness at low temp. with high strength without adding alloying elements, by subjecting a steel in which respective contents of C, Si, Mn, etc., are specified to hot rolling at a specific temp. and also controlling cooling velocity and winding temp.
CONSTITUTION: The hot rolling of a steel which has a composition containing, as principal components, 0.01W0.07%, by weight, C, ≤0.5% Si, and 0.5W2.0% Mn, further containing one or more kinds among ≤0.060% Nb, ≤0.10% V, and ≤0.050% Ti, and having the balance Fe with inevitable impurities is completed at Ar3 or above point. Subsequently, cooling is applied to the hot-rolled plate from a temp. of the Ar3 point or above at ≤20°C/sec cooling rate to form fine bainite and island martensite, followed by winding at ≤250°C. By using this steel, the high-strength seam welded tube excellent in toughness at low temp. can be manufactured while obviating the necessity of heat treatment over the whole tube.
MURAYAMA HIROSHI
KOYUBA MOTOFUMI
| JPS5947323A | 1984-03-17 | |||
| JPS6289815A | 1987-04-24 |
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