Roll for roll forming and method therefor

Abstract

Provided are a roll for roll forming and a roll forming method therefor, by which a strip of sheet material is continuously fed and passed between roll stands that are arranged continuously, and is sequentially formed so that the sectional shape of the sheet material becomes circular, and by welding both ends of the sheet material, a pipe is finally produced. In the method, pressure parts and non-pressure parts are selectively disposed on a convex roll or a concave roll and the frequency of pressuring by the convex roll and the concave roll is reduced or adjusted such that the work hardening of the roll formed material or produced pipe is lowered or made to be uniform. Accordingly, the material characteristic and reprocessing characteristic of the roll formed material or pipe are greatly improved.

What is claimed is:  
     
         1 . A roll for roll forming, which has an axis coupling part for coupling with a rotation axis, and a circular sectional shape, and pressures and deforms a sheet of material passing between two rolls for roll forming, the roll comprising: 
 a plurality of pressure parts which are formed along the circumference of the circumference surface of the roll, are disposed with intervals in the width direction, and divide and pressure the sheet material passing by; and    a non-pressure part which is disposed between the pressure parts and is to not pressure partially the sheet material passing by, wherein the pressure parts and non-pressure part are disposed symmetrically on the left side and right side.    
     
     
         2 . The roll of  claim 1 , wherein the non-pressure part is formed in the form of a groove, the non-contact length of the roll and the sheet material is less than 60% of the effective length of the roll, and equal to or more than 10% of the width of the sheet material.  
     
     
         3 . The roll of  claim 1 , wherein the pressure part and the non-pressure part are formed alternately in the width direction.  
     
     
         4 . A roll forming method by which while sheet material is sequentially passed between a plurality of convex rolls and a plurality of concave rolls, the sheet material is pressured so that the sectional shape of the sheet material is formed as desired, wherein the plurality of convex rolls are arranged with intervals, and have convex circumference surfaces, and the curvatures of the convex rolls are sequentially diminishing, and the plurality of concave rolls are arranged neighboring the convex rolls to make respective roll pairs with corresponding convex rolls, and have concave circumference surfaces corresponding to the circumference surface of the convex rolls, respectively, the roll forming method comprising: 
 dividing and disposing a pressure part for pressuring the sheet material passing by, and a groove-shaped non-pressure part for not pressuring the sheet material passing by, on the circumference surface of the convex roll or the concave roll, so that the frequency of pressure applied to at least one part of the sheet material, which passes through the roll pairs, by the roll pairs is reduced in order to reduce work hardening of the at least one part of the sheet material.    
     
     
         5 . The roll forming method of  claim 4 , wherein the pressure part formed on one roll pair is disposed so that the pressure part does not overlap the pressure part of another roll pair equal to or more than (the number of roll pairs —2) times and by doing so, the frequency of pressure applied to each part of the sheet material passed through is less than the number of the roll pairs.  
     
     
         6 . The roll forming method of  claim 4 , wherein the pressure part formed on one roll pair except the parts corresponding to both ends of the sheet material is disposed so that the pressure part overlaps the pressure part of another roll pair at a roughly identical frequency, and by doing so, the frequency of pressure applied to each part of the sheet material except both ends of the sheet material has a roughly identical distribution in the width direction of the sheet material.  
     
     
         7 . A roll forming method by which while sheet material is sequentially passed between a plurality of convex rolls and a plurality of concave rolls, the sheet material is pressured so that the sectional shape of the sheet material is formed to a circle and parts of the sheet material facing each other are welded to produce a pipe, wherein the plurality of convex rolls are arranged with intervals, and have convex circumference surfaces, and the curvatures of the convex rolls are sequentially diminishing, and the plurality of concave rolls are arranged neighboring the convex rolls to make respective roll pairs with corresponding convex rolls, and have concave circumference surfaces corresponding to the circumference surface of the convex rolls, respectively, the roll forming method comprising: 
 dividing and disposing a pressure part for pressuring the sheet material passing by, and a groove-shaped non-pressure part for not pressuring the sheet material passing by, on the circumference surface of the convex roll or the concave roll, and by adjusting the frequency of pressure applied to each part of the sheet material by roll pairs formed with the convex rolls and the concave rolls, adjusting the degree of work hardening of each part of a finished pipe.    
     
     
         8 . The roll forming method of  claim 7 , wherein the pressure part formed on one roll pair is disposed so that the pressure part does not overlap the pressure part of another roll pair equal to or more than (the number of roll pairs —2) times and by doing so, the frequency of pressure applied to each part of the sheet material passed through is less than the number of the roll pairs.  
     
     
         9 . The roll forming method of  claim 7 , wherein the pressure part formed on one roll pair except the parts corresponding to both ends of the sheet material is disposed so that the pressure part overlaps the pressure part of another roll pair at a roughly identical frequency, and by doing so, the frequency of pressure applied to each part of the sheet material except both ends of the sheet material has a roughly identical distribution in the width direction of the sheet material.