Sumitomo Metal Industries, Inc.

Nippon Steel Sumitomo Metal Corporation

Hajime Osako

Kunio Kondo

Hideki Takabe

Takeshi Maekawa

Takahiro Kushida

Nobuyuki Hisamune

Nobutoshi Murao

It is a problem of the present invention to provide a method of manufacturing the seamless pipes having better mechanical properties, by means of a pipe manufacturing method with large energy-saving effect to continuously carry out processes from pierce-rolling to heat treatment. A method of manufacturing a seamless pipe comprising the steps of a pierce-rolling process, elongation rolling process, sizing process, reheating process, quenching process and tempering process, wherein the sizing process is completed with a temperature of the seamless pipe not less than 600&#xb0; C. but less than 800&#xb0; C., the seamless pipe is charged into a reheating furnace with a temperature not less than 400&#xb0; C. and is reheated with a temperature not less than Actransformation temperature but not greater than 1000&#xb0; C. in the reheating process.

Method of manufacturing seamless pipe and tube

There is provided a foreign pipe or tube determining method capable of accurately determining a foreign pipe or tube. The foreign pipe or tube determining method in accordance with the present invention includes a step for determining the presence of a foreign pipe or tube by comparing the length of each pipe or tube in a size measuring step with the length of each pipe or tube measured in an actual weighing and length measuring step, which is associated with each pipe or tube in the size measuring step, a step for determining the presence of a foreign pipe or tube by comparing the weight of each pipe or tube calculated in a weight calculating step with the weight of each pipe or tube measured in the actual weighing and length measuring step, which is associated with each pipe or tube in a weight calculating step, and a step for determining the presence of a foreign pipe or tube based on the material of each pipe or tube determined in a material determining step.

Foreign pipe or tube determining method

In straightening a duplex stainless steel pipe on a multi-roll pipe straightener, the value of A defined by the formula (1) is set to not more than 2.0% when it is not necessary to improve the mechanical strength of the pipe, and the value of A is set to more than 2.0% but not more than 3% when it is necessary to improve the mechanical strength of the pipe. Thereby, the mechanical strength of the duplex stainless steel pipe is regulated,=()/&#x2003;&#x2003;(1)

Method for producing duplex stainless steel pipe, method for straightening, method for regulating strength, and method for operating straightener

A high strength seamless steel pipe having mgh yield stress and excellent hydrogen-induced cracking resistance, comprises by mass %, C:-%, Si:-%, Mn:-%, p:% or less, S:% or less, Ti:-%, Al:-%, Cr:-%, Mo:-%, V:-%, Ca-%, N:% or less and O (Oxygen):% or less, the balance Fe and impurities. The steel microstructure is bainite and/or martensite and ferrite is precipitated at grain boundaries. The seamless steel pipe can contain at least one of Cu:-% and Ni:-%. To produce the pipe, it is desirable to limit a starting temperature of quenching after rolling, a cooling rate and a tempering temperature.

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Wakayama, Japan

Hajime Osako