Patent ID: 11945020
Assignee: JFE STEEL CORPORATION
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 1:
2. The method for manufacturing a metal pipe according to claim 1, wherein, in the pipe-end-portion expansion step:
expansion tools are inserted into the mother pipe in the pipe axial direction from the pipe extreme ends of the mother pipe having an average outer diameter D0 (mm) and an average wall thickness t0 (mm), and
the pipe end portions are expanded by a compressive force of the expansion tools while outer circumferential surfaces of columnar portions each of which is included in one of the expansion tools and each of which has an outer diameter D1 (mm) defined by Formula (3):, D
          1
        
        =
        
          
            
              (
              
                1
                +
                
                  a
                  /
                  100
                
              
              )
            
            ×
            
              D
              0
            
          
          -
          
            2
            ×
            
              (
              
                1
                -
                
                  a
                  /
                  200
                
              
              )
            
            ×
            
              t
              0
            
          
        
      
    
    
      
        (
        3
        ), and an inner circumferential surface of the mother pipe are in contact with each other, and in the internal pressure application step:
axial compression is performed on the pipe extreme ends by using the expansion tools with the axial compression amount s (mm), and
the mother pipe is expanded by applying the internal pressure, p, to the entire interior of the mother pipe placed in a metal die until the outer circumferential surface of the mother pipe is brought into contact with an inner wall surface of a cylindrical containing portion that is formed in the metal die and in which the mother pipe is contained, the containing portion having a cross-sectional shape with an inner diameter D2 (mm) defined by Formula (4):, D
          2
        
        =
        
          
            (
            
              1
              +
              
                
                  a
                  /
                  1
                
                ⁢
                0
                ⁢
                0
              
            
            )
          
          ×
          
            
              D
              0
            
            .
          
        
      
    
    
      
        (
        4
        )