Screw joint for steel piping

摘要

This screw joint is configured from a pin (10) and a box (20). The pin (10) is provided with, in the following order from the tip-end side, a shoulder surface (11), a nose part (12), a first seal surface (13), a first male screw part (14), an annular part (15a), a second seal surface (16), and a second male screw part (17). The box (20) is provided with a shoulder surface (21), a concave part (22), a first seal surface (23), a first female screw part (24), an annular part (25a), a second seal surface (26), and a second female screw part (27). When the screw joint is in a fastened state, the shoulder surfaces (11, 21) are in contact with each other, the first seal surfaces (13, 23) are in contact with each other, the second seal surfaces (16, 26) are in contact with each other, a gap is formed between the nose part (12) and the concave part (22), a gap is formed between the annular parts (15a, 25a), the first male screw part (14) and the first female screw part (24) fit together, and the second male screw part (17) and the second female screw part (27) fit together.