| 摘要 |
PURPOSE:To improve the formability of a steel sheet and the toughness after the shaping welding and heat treatment of the steel pipe by applying the three- stage heat treatment consisting of quenching, intermediate heating and cooling heat treatment, and tempering for improving the low-temp. toughness of a 9% Ni steel sheet to the production of the title steel pipe. CONSTITUTION:The hot-rolled 9% Ni steel sheet is water-cooled or air-cooled from the complete austenite region temp., then reheated to 600-700 deg.C, and subjected to the water-cooling or air-cooling intermediate heat treatment. The steel sheet is then shaped into a pipe, and the seam is welded to obtain a steel pipe. The steel pipe is then rapidly heated from room temp. to the complete austenite region temp. in 15min, then water-cooled, and then tempered. By this method, the yield strength of the steel sheet is decreased, the formability of the steel sheet can be improved, and the toughness of the base material of the steel pipe after the quenching and tempering can be improved.
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