ROUND BILLET FOR SEAMLESS METAL TUBE AND METHOD FOR PRODUCING SEAMLESS METAL TUBE
Provided is a round billet capable of reducing damage on a piercing plug in a method of producing a seamless metal tube with a Mannesmann process. The round billet ( 5 ), for use in a seamless metal tube, to be produced into a seamless metal tube with a Mannesmann process includes a body having a hole ( 6 ) formed in an axial direction of the body. The hole ( 6 ) includes an aperture ( 6 a ) opening at least at one end face of the round billet ( 5 ), and a tapered portion ( 61 ) continued to the aperture ( 6 a ) and having a diameter gradually increasing toward the aperture ( 6 a ).
1 . A round billet, for use in a seamless metal tube, to be produced into a seamless metal tube with a Mannesmann process,
the round billet comprising:
a body having a hole formed in an axial direction of the body,
wherein
the hole including:
an aperture opening at least at one end face of the round billet; and
a tapered portion continued to the aperture and having a diameter gradually increasing toward the aperture.
2 . The round billet according to claim 1 , wherein
the tapered portion has a length in the axial direction less than a length of a rolling portion of a piercing plug for use in the Mannesmann process.
3 . The round billet according to claim 1 , wherein
the tapered portion has a taper angle greater than a taper angle of a piercing plug for use in the Mannesmann process.
4 . The round billet according to claim 1 , wherein
a region adjacent to the aperture among the tapered portion is chamfered.
5 . A method for producing a seamless metal tube comprising:
a step of preparing the round billet according to claim 1 ; and
a step of piercing-rolling the round billet with the tapered portion of the round billet opposite to the piercing plug.
6 . The round billet according to claim 2 , wherein
the tapered portion has a taper angle greater than a taper angle of a piercing plug for use in the Mannesmann process.
7 . A method for producing a seamless metal tube comprising:
a step of preparing the round billet according to claim 2 ; and
a step of piercing-rolling the round billet with the tapered portion of the round billet opposite to the piercing plug.
8 . A method for producing a seamless metal tube comprising:
a step of preparing the round billet according to claim 3 ; and
a step of piercing-rolling the round billet with the tapered portion of the round billet opposite to the piercing plug.
9 . A method for producing a seamless metal tube comprising:
a step of preparing the round billet according to claim 4 ; and
a step of piercing-rolling the round billet with the tapered portion of the round billet opposite to the piercing plug.
10 . A method for producing a seamless metal tube comprising:
a step of preparing the round billet according to claim 6 ; and
a step of piercing-rolling the round billet with the tapered portion of the round billet opposite to the piercing plug.