Method of forming cold diametrally reducing roll for metal pipe and metal pipe formed by the method

Abstract

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

What is claimed is:  
     
         1 . A cold roll forming method for reducing the diameter of a raw metal pipe, including: 
 a pre-forming step for pre-forming the raw metal pipe into an intermediate metal pipe having any of the elliptic, elongated circular, rectangular, and polygonal cross-sectional shapes by passing the raw metal pipe through a set of pre-forming rolls; and    a diameter-reducing step for reducing the diameter of said pre-formed intermediate metal pipe having said any cross-sectional shape by passing said pre-formed intermediate metal pipe through a set of diameter-reducing rolls disposed on the downstream side of said set of pre-forming rolls, so that said pre-formed intermediate metal pipe can have its outer circumferential length reduced to a smaller length than the outer circumferential length of the raw metal pipe while at the same time it can be re-formed into a circular cross-sectional shape or any other cross-sectional shape different from said any cross-sectional shapes of said pre-formed intermediate metal pipe.    
     
     
         2 . A cold roll forming method for reducing the diameter of a raw metal pipe, including: 
 a pre-forming step for pre-forming the raw metal pipe into an intermediate metal pipe having any of the elliptic, elongated circular, rectangular, and polygonal cross-sectional shapes by passing the raw metal pipe through a set of pre-forming rolls; and    a diameter-reducing step for reducing the diameter of said pre-formed intermediate metal pipe having said any cross-sectional shape by passing said pre-formed intermediate metal pipe through a set of diameter-reducing rolls disposed on the downstream side of said set of pre-forming rolls, so that said pre-formed intermediate metal pipe can have its outer circumferential length reduced to a smaller length than the outer circumferential length of the raw metal pipe while at the same time it can be re-formed into a circular cross-sectional shape or any other cross-sectional shape different from any of said cross-sectional shapes of said pre-formed intermediate metal pipe, wherein the sequence of said pre-forming step followed by said diameter-reducing step is repeated several times.    
     
     
         3 . A cold roll forming method for reducing the diameter of a raw metal pipe, including: 
 a pre-forming step for pre-forming the raw metal pipe into an intermediate metal pipe having any of the elliptic, elongated circular, rectangular, and polygonal cross-sectional shapes by passing the raw metal pipe through a set of pre-forming rolls, wherein said pre-forming step occurs one or more times; and    a diameter-reducing step for reducing the diameter of said pre-formed intermediate metal pipe having any of said cross-sectional shape by passing said pre-formed intermediate metal pipe through a set of diameter-reducing rolls disposed on the downstream side of said set of pre-forming rolls, so that said pre-formed intermediate metal pipe can have its outer circumferential length reduced to a smaller length than the outer circumferential length of the raw metal pipe while at the same time it can be re-formed into a circular cross-sectional shape or any other cross-sectional shape different from said any cross-sectional shapes of said pre-formed intermediate metal pipe, wherein said diameter-reducing step occurs one or more times.    
     
     
         4 . The cold roll forming method for reducing the diameter of a raw metal pipe, as defined in any one of claims  1  through  3 , wherein said set of pre-forming rolls includes several sets of pre-forming rolls, and said set of diameter-reducing rolls includes several sets of diameter-reducing rolls, and wherein some or all of the rolls in each set of pre-forming rolls and some or all of the rolls in each set of diameter-reducing rolls are rotatably linked with each other, in order to permit the raw metal pipe to be moved through each set of pre-forming rolls and each set of diameter-reducing rolls.  
     
     
         5 . The cold roll forming method for reducing the diameter of a raw metal pipe, as defined in any one of claims  1  through  3 , wherein said set of pre-forming rolls includes several sets of pre-forming rolls and said set of diameter-reducing rolls includes several sets of diameter-reducing rolls, and wherein some or all of the rolls in each set of pre-forming rolls and some or all of the rolls in each set of diameter-reducing rolls are idler rolls that are free from the external driving force, in order to permit the raw metal pipe to be moved through each set of pre-forming rolls and each set of diameter-reducing rolls by pushing the raw metal pipe from the upstream side into the bore formed by the rolls in each set of pre-forming rolls and into the bore formed by the rolls in each set of diameter-reducing rolls, by drawing the raw metal pipe through the bore formed by the rolls in each set of pre-forming rolls and through the bore formed by the rolls in each set of diameter-reducing rolls toward the downstream side, or by pushing the raw metal pipe from the upstream side into the bore formed by the rolls in each set of pre-forming rolls and into the bore formed by the rolls in each set of diameter-reducing rolls together with by drawing the raw metal pipe through the bore formed by the rolls in each set of pre-forming rolls and through the bore formed by the rolls in each set of diameter-reducing rolls toward the downstream side.  
     
     
         6 . The cold roll forming method for reducing the diameter of a raw metal pipe, as defined in any one of claims  1  through  5 , wherein each of the rolls in the set of diameter-reducing rolls has a pattern of ridges and grooves formed on its surface, and wherein after the raw metal pipe has been pre-formed into an intermediate metal pipe having a particular cross-sectional shape, the intermediate metal pipe is passed through the following set of diameter-reducing rolls so that it can have its diameter reduced while at the same time it can have the pattern of ridges and grooves formed on the surface thereof.  
     
     
         7 . The cold roll forming method for reducing the diameter of a raw metal pipe, as defined in any one of claims  1  through  6 , wherein a pattern molding die is disposed in the bore formed by the rolls in the set of diameter-reducing rolls so that the pattern molding die can be inserted into the raw metal pipe when the raw metal pipe is passed through the bore formed by the rolls in the set of diameter-reducing rolls, the pattern molding die having a pattern of ridges and grooves formed on the outer circumferential surface thereof, whereby the raw metal pipe can have the pattern of ridges and grooves formed on the inner circumferential surface thereof while at the same time it can have its diameter reduced, when the raw metal pipe is passed through the bore formed by the rolls in the set of diameter-reducing rolls.  
     
     
         8 . The cold roll forming method for reducing the diameter of a raw metal pipe, as defined in any one of claims  1  through  7 , wherein when the raw metal pipe is passed through the set of pre-forming rolls and then through the set of diameter-reducing rolls disposed on the downstream side of the set of pre-forming rolls, the raw metal pipe has its diameter reduced at the diameter reduction rate of 3% or more.  
     
     
         9 . A cold roll forming method for reducing the diameter of a raw pipe, wherein the raw pipe includes a double pipe comprising an outer metal pipe having a greater diameter and an inner pipe having a smaller diameter and inserted into the outer metal pipe, the method including: 
 a pre-forming step for pre-forming the outer metal pipe into an intermediate outer metal pipe having any of the elliptic, elongated circular, rectangular and polygonal cross-sectional shapes by passing the raw pipe through a set of pre-forming rolls; and    a diameter reducing step for re-forming the interm diate outer metal pipe into a circular cross-sectional shape or any other cross-sectional shape different from the cross-sectional shape of the intermediate outer metal pipe while at the same time reducing at least the outer circumferential length of the intermediate outer metal pipe to a smaller length than that of the original outer metal pipe, by passing the raw pipe through a set of diameter-reducing rolls disposed on the downstream side of the set of pre-forming rolls, whereby the double pipe is finished by causing the inner circumferential surface of the outer metal pipe tightly to engage some or all of the outer circumferential surface of the inner pipe.    
     
     
         10 . A cold roll forming method for reducing the diameter of a raw pipe, wherein the raw pipe includes a double pipe comprising an outer metal pipe having a greater diameter and an inner pipe having a smaller diameter and inserted into the outer metal pipe, the method including: 
 a pre-forming step for pre-forming the outer metal pipe into an intermediate outer metal pipe having any of the elliptic, elongated circular, rectangular and polygonal cross-sectional shapes by passing the raw pipe through a set of pre-forming rolls; and    a diameter reducing step for re-forming the intermediate outer metal pipe into a circular cross-sectional shape or any other cross-sectional shape different from the cross-sectional shape of the intermediate outer metal pipe while at the same time reducing at least the outer circumferential length of the intermediate outer metal pipe to a smaller length than that of the original outer metal pipe, by passing the raw pipe through a set of diameter-reducing rolls disposed on the downstream side of the set of pre-forming rolls, wherein the pre-forming step and the diameter-reducing step are repeated several times, whereby the double pipe is finished by causing the inner circumferential surface of the outer metal pipe tightly to engage some or all of the outer circumferential surface of the inner pipe.    
     
     
         11 . A cold roll forming method for reducing the diameter of a raw pipe, wherein the raw pipe includes a double pipe comprising an outer metal pipe having a greater diameter and an inner pipe having a smaller diameter and inserted into the outer metal pipe, the method including: 
 a pre-forming step for pre-forming the outer metal pipe into an intermediate outer metal pipe having any of the elliptic, elongated circular, rectangular and polygonal cross-sectional shapes by passing the raw pipe through a set of pre-forming rolls, wherein the pre-forming step is repeated one or more times; and    a diameter reducing step for re-forming the intermediate outer metal pipe into a circular cross-sectional shape or any other cross-sectional shape different from the cross-sectional shape of the intermediate outer metal pipe while at the same time reducing at least the outer circumferential length of the intermediate outer metal pipe to a smaller length than that of the original outer metal pipe, by passing the raw pipe through a set of diameter-reducing rolls disposed on the downstream side of the set of pre-forming rolls, wherein the diameter-reducing step is repeated one or more times, whereby the double pipe is finished by causing the inner circumferential surface of the outer metal pipe tightly to engage some or all of the outer circumferential surface of the inner pipe.    
     
     
         12 . The cold roll forming method for reducing the diameter of a raw pipe, as defined in any one of claims  9  through  11 , wherein the inner pipe is inserted into the outer metal pipe so that the inner pipe and the outer metal pipe overlap each other along some or all of the total length of the outer metal pipe.  
     
     
         13 . The cold roll forming method for reducing the diameter of a raw pipe, as defined in claims  9  through  12 , wherein said set of pre-forming rolls includes several sets of pre-forming rolls, and said set of diameter-reducing rolls includes several sets of diameter-reducing rolls, and wherein some or all of the rolls in each set of pre-forming rolls and some or all of the rolls in each set of diameter-reducing rolls are rotatably linked with each other, in order to permit the raw pipe to be moved through each set of pre-forming rolls and each set of diameter-reducing rolls.  
     
     
         14 . The cold roll forming method for reducing the diameter of a raw pipe, as defined in any one of claims  9  through  12 , wherein said set of pre-forming rolls includes several sets of pre-forming rolls and said set of diameter-reducing rolls includes several sets of diameter-reducing rolls, and wherein some or all of the rolls in each set of pre-forming rolls and some or all of the rolls in each set of diameter-reducing rolls are idler rolls that are free from the external driving force, in order to permit the raw pipe to be moved through each set of pre-forming rolls and each set of diameter-reducing rolls by pushing the raw pipe from the upstream side into the bore formed by each set of pre-forming rolls and into the bore formed by each set of diameter-reducing rolls, by drawing the raw pipe through the bore formed by the rolls in each set of pre-forming rolls and through the bore formed by the rolls in each set of diameter-reducing rolls toward the downstream side, or by pushing the raw pipe from the upstream side into the bore formed by the rolls in each set of pre-forming rolls and into the bore formed by the rolls in each set of diameter-reducing rolls together with by drawing the raw pipe through the bore formed by the rolls in each set of pre-forming rolls and through the bore formed by the rolls in each set of diameter-reducing rolls toward the downstream side.  
     
     
         15 . The cold roll forming method for reducing the diameter of a raw pipe, as defined in any one of claims  9  through  14 , wherein each of the rolls in the set of diameter-reducing rolls has a pattern of ridges and grooves formed on its surface, and wherein after the raw pipe has been pre-formed into an intermediate raw pipe having a particular cross-sectional shape, the intermediate raw pipe is passed through the following set of diameter-reducing rolls so that its outer metal pipe can have its diameter reduced while at the same time it can have the pattern of ridges and grooves formed on the surface of the outer metal pipe.  
     
     
         16 . The cold roll forming method for reducing the diameter of a raw pipe, as defined in any one of claims  9  through  15 , wherein when the raw pipe is passed through the set of pre-forming rolls and then through the set of diameter-reducing rolls disposed on the downstream side of the set of pre-forming rolls, its outer metal pipe has its diameter reduced at the diameter reduction rate of 3% or more.  
     
     
         17 . A metal pipe product obtained by the cold roll forming method as defined in any one of claims  1  through  16 .