| 摘要 |
PURPOSE:To efficiently manufacture the steel pipe having the end part shape excellent in its accuracy by forming a wall thickness part and outer upset tapered part by an outer upsetting at the pipe end and performing the forming of the inner upsetting by pressing. CONSTITUTION:An outer upsetting is executed at the end part of a steel pipe 1 by using a die 2A and punch 3 to thicken the end part of the steel pipe 1 and the part becoming an inner upset tapered part is formed as the outer upset tapered part. The inner upset tapered part 5 is then formed by pressing it with the upper and lower dies 2B. The inner face shape is finished by using the punch 3 in the state of closely fitting the die 2B. After executing an outer upsetting by using the die 2B notching a grooved die K and a punch 3B the end part of the steel pipe 1 is subjected to a pressing by moving it in the counter punch direction. With this method, the working of the upset part of the steel pipe 1 end part can be performed with good accuracy.
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