| 摘要 |
PROBLEM TO BE SOLVED: To proivde a stock for a thin WALL vessel producible with high productivity and also at a low cost and uniform in the material in a coil without requiring the conventional strict temperature control and special equipment investment. SOLUTION: By steel containing, by weight, 0.0040 to 0.0300% N and 0.005 to 0.080% Al, and in which the content of C is controlled to <=0.0400% at need under the conditions free from any special control of the uniformity of hot rolling temperature in a coil, i.e., under the conditions that hot rolling finishing temperature is <=930 deg.C, the temperature difference between the width central part and the width edge parts is >=20 deg.C, coiling temperature is >=200 deg.C, the temperature difference between the width central part and the width edge parts is >=30 deg.C, and the temperature difference between the longitudinal central position and the longitudinal tip or terminal position is >=30 deg.C, a steel sheet in which the variation of the material (standard deviation) between the width position and the longitudinal position is 20 MPa by 0.2% proof stress, is <=20 MPa by the maximum load, and <=2% by an earing ratio is produced. In particular, N may be contained to <=0.0300% by executing nitriding treatment in a continuous annealing furnace.
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