Cold roll forming method for reducing a diameter of a metal pipe, and a metal pipe product having its diameter reduced by such method

Abstract

A cold roll forming method for reducing a diameter of a metal pipe and a metal pipe product having a diameter reduced by such a method are disclosed, wherein the method includes: passing a raw metal pipe through a set of pre-forming rolls so that it can be pre-formed into an intermediate metal pipe having an elliptical, elongated circular or rectangular cross-sectional shape; and then passing the intermediate metal pipe through a set of diameter-reducing rolls disposed on a downstream side of the set of pre-forming rolls so that it can have its outer circumferential length reduced to be smaller than an outer peripheral length of the raw metal pipe, while at the same time being re-formed into a circular cross-sectional shape or any other cross-sectional shape different from the cross-sectional shape of the intermediate metal pipe.

Description

[0001] This application is a continuation of U.S. application Ser. No. 10 / 381,341, filed Mar. 25, 2003, which was the National Stage of International Application No. PCT / JP01 / 08310, filed Sep. 25, 2001.BACKGROUND [0002] 1. Technical Field [0003] The present invention relates to a cold roll forming method for reducing a diameter of a metal pipe, and a metal pipe product having its diameter reduced by such method. More particularly, the present invention relates to a metal pipe so formed that its diameter can be reduced by the cold roll forming process. [0004] 2. Prior Art [0005] There are a number of conventional cold roll forming methods, more specifically, cold diameter-reducing methods, whereby a diameter of a metal pipe may be reduced. These methods are briefly described below. [0006] One method is provided for cold-reducing a steel pipe by using a 3-roll reducer (Japanese patent application as published under No. H7 (1995)-51707). This method is specifically designed to eliminat...

AI Technical Summary

Benefits of technology

[0010] It is therefore one object of the present invention to provide a cold-working method, more specifically, a cold roll forming method, that provides an easy and reliable manner for cold roll forming raw metal pipes by using sets of diameter-reducing rolls, without having to increase a number of roll stands used, wherein the method may be used to roll a raw metal pipe so that it can have a reduction in terms of its diameter, or to roll the raw metal pipe so that it can have a pattern of alternating grooves and ridges on inner and / or outer circumferential surface(s) thereof while at the same time having reduction in terms of its diameter, or to roll a double pipe including an outer pipe and an inner pipe so that it can have a reduction in terms of its diameter.

Problems solved by technology

The above mentioned methods may serve their respective cold-working or cold-roll-forming purposes, but any of the methods has problems in that a machine that is used to implement this method is designed for particular applications, there are restrictions on size (angle) of a steel pipe that can be cold-worked or rolled, a number of roll stands must be increased, and the like.

Images