Nippon Steel Corporation

Hitachi Zosen Corporation

Yukio Noguchi

Tatsuro Ochi

Koe Nakajima

Mitsuru Nakamura

Yoshiro Koyasu

Matsuo Ataka

Koshiro Aoyagi

Toshihiro Ishibashi

Ichizo Taguchi

Jun-ichi Tsumura

Yutaka Toda

A steel comprising 0.1 to 1.5% of C and 0.25 to 2.0% of Mn is heated to 900.degree. to 1250.degree. C., and the heated steel is hot-rolled at a temperature in the range of from Ar.sub.3 to (Ar.sub.3 +200).degree. C. or Arcm to (Arcm+200).degree. C. with a total reduction of area of 30% or more. The hot-rolled material is cooled to complete a ferrite/pearlite transformation or a pro-eutectoid cementite/pearlite transformation. The transformed material is subjected to finish hot rolling at a temperature in the range of from (Ac.sub.1 -400) to Ac.sub.1 .degree. C. with a total reduction ratio of 10 to 70%. If necessary, the material after the finish hot rolling is cooled to 300.degree. C. at an average cooling rate of 1.degree. C./sec or less. A spheroidization annealing of the steel bar wire rod produced according to the process of the present invention enables a good spheroidized texture to be formed.

Process for producing steel bar wire rod for cold working

The invention is directed to provide a rolling method which enables an enlarged range of reduction ratio in sizing-rolling in the common drive system. The invention provides that when tension applied to rolled material between the upstream and downstream-placed mills is made higher than a value that tension/average resistance to deformation of rolled material is 0.2, the upstream-placed mill is caused to perform force rolling, and when compressive force of the rolled material is made higher than a value that compressive force/average resistance to deformation of rolled material is 0.1, the downstream-placed mill together with the upstream-placed mill are caused to perform tensile rolling in the common drive system. The rolling methods provides a stable rolling in a larger sizing range without decrease of diameter or buckling of rolled material.

Rolling mill driving mechanism

Bars and wire rods are rolled from billets or blooms in the disclosed process which includes a primary rolling step resulting in an intermediate material, a secondary rolling step and a heat treatment. The primary (first) rolling step includes rolling the billet or bloom steel material into an intermediate material at a mass flow rate to enable it to be maintained during the primary rolling within a temperature range corresponding to a predetermined deformation resistance level of the steel material. This predetermined deformation resistance level is selected so as to take advantage of an opportunity to save energy. The intermediate material resulting from primary rolling is coiled and its temperature is adjusted so as to maintain the intermediate material at a desired starting temperature for the secondary rolling step. The desired starting temperature for secondary rolling is related to a desired starting temperature for the heat treatment following the secondary rolling enabling heat treatment to be carried out in line.

Reduced energy consumption method for rolling bars or wire rods

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Futtsu, Japan

Yukio Noguchi