PURPOSE: To improve productivity of a steel pipe and to perform its cost down, by specifically selecting hardness and an edge point angle of a V-shaped parting tool, which cuts the steel pipe by placing the tool in a gap obtained by splitting one part of a cylinder tool, so that the steel pipe of large thickness in its manufacturing process is smoothly cut.
CONSTITUTION: A steel pipe is cut by a V-shaped parting tool, which is placed in a gap obtained by splitting one part of a cylinder tool along the periphery of the steel pipe, and the parting tool sets its hardness to HRC60W65 and edge point angle to 90W120°. Here the hardness influences a crack in the edge point, and the tool decreases its toughness, if the hardness exceeds HRC65, while collapses the edge point being unable to cut the steel pipe if the hardness is less than HRC60. While the edge point angle influences seizure in an edge point side and its crack, and the tool provides a cutting chip to be internally wound in an intermediate cutting process easily generating the seizure with large resistance for the edge point side, if the edge point angle is set too small, while increases shearing force sometimes generating a crack if the edge point angle is set large. Accordingly, this constitution enables the steel pipe of large thickness is its manufacturing process to be smoothly cut while the productivity to be improved and the cost down to be performed.
YADOHISA HAKOBU
TAKEUCHI MASAAKI
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