| 摘要 |
PROBLEM TO BE SOLVED: To produce an inexpensive electric resistance welded pipe exhibiting excellent hydroforming workability without newly providing special stages such as heat treatment. SOLUTION: As for the method for producing a high workability carbon steel pipe for hydroforming, a hot rolled steel strip having a composition containing, by mass, <0.06% C, 0.05 to 2.0% Si, 0.75 to 2.50% Mn, <=2.0% Cu, <=2.0% Ni, <=2.0% Cr, <=2.0% Mo, <=0.5% V, <=0.5% Nb, <=0.5% Ti and <=0.2% Al, and the balance Fe with inevitable impurities, satisfying the following inequalities (1) and (2), in which the content of P as impurities is controlled to <=0.2%, S to <=0.03% and N to <=0.01%, and moreover, the ratio of a ferritic phase in the structure exceeds 95% is used, and heating conditions for both edge parts of an open pipe subjected to continuous forming are controlled: Cu(%)+Ni(%)+Cr(%)+Mo(%)<=5.0%...(1), and Nb(%)+V(%)+Ti(%)<=1.0%...(2).
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