Patent ID: 11926002
Assignee: TIANJIN UNIVERSITY
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 0:
1. A cold metal transfer (CMT) automatic overlaying method for opening holes in a side wall of a bimetallic composite pipe, comprising:
S1. establishing a mathematical model of an opening in a side wall of a composite pipe to be welded, and keeping an axis of the opening in the side wall of the composite pipe parallel to a horizontal plane; wherein an expression of the mathematical model is a parameter equation of a saddle line weld at any point in a wall thickness direction of the opening in the side wall of the composite pipe:, {
  
   
    
     
      x
      =
      
       
        
         
          R
          t
          2
         
         -
         
          
           r
           2
          
          ⁢
          
           sin
           2
          
          ⁢
          t
         
        
       
       -
       
        R
        1
       
      
     
    
   
   
    
     
      y
      =
      
       r
       ⁢
       sin
       ⁢
       t
      
     
    
   
   
    
     
      z
      =
      
       r
       -
       
        r
        ⁢
        cos
        ⁢
        t
       
      
     
    
   
  
 

in the mathematical model, r is a radius of the opening in the side wall, R1 is a radius of an inner wall of the composite pipe, Rt is a radius at any point in the wall thickness direction, and Rt∈(R1,R2), R2 is a radius of an outer wall of the composite pipe, t∈[0,2π];
S2. based on the mathematical model, illustrating a projection pattern of the opening in the side wall of the composite pipe, and determining a trajectory of a saddle line during overlaying based on the projection pattern:
a degree of curvature of a saddle line on the inner wall of the composite pipe and a saddle line on the outer wall of the composite pipe are compared based on the projection pattern:
if a difference between the degree of curvature L1 of the saddle line on the opening in the inner wall of the composite pipe to be welded and the degree of curvature L2 of the saddle line on the opening in the outer wall is less than a preset value, a trajectory of the saddle line on the opening in the outer wall of the composite pipe is used as trajectories of all saddle lines on the openings in the side wall of the composite pipe during overlaying;
if the difference between the degree of curvature L1 of the saddle line on the opening in the inner wall of the composite pipe to be welded and the degree of curvature L2 of the saddle line on the opening in the outer wall of the composite pipe is not less than the preset value, then a trajectory of a saddle line at the middle position of the opening in the side wall of the composite pipe is replaced with the trajectory of the saddle line on the opening in the outer wall of the composite pipe during overlaying;
S3. dividing the trajectory of the saddle line into several welding runs, all of which adopt a downslope welding process, and planning an overlaying sequence of the welding runs, the overlaying sequence comprising: dividing the trajectory of the saddle line on the opening into an upper half and a lower half with a horizontal midline of the trajectory of the saddle line on the opening as a boundary, and the lower half of the welding runs is below the horizontal midline; when welding, all the welding runs on the lower half are welded sequentially by downslope welding, then the opening in the side wall of the composite pipe is turned 180° around the axis, and then all the welding runs on the lower half are welded sequentially by downslope welding until all the welding runs are welded;
S4. establishing a three-dimensional model of the opening in the side wall of the composite pipe to be welded and a CMT overlaying system simulation model;
S5. based on the overlaying sequence, planning an overlaying path of the CMT overlaying system simulation model to the three-dimensional model, and generating an overlaying offline instruction based on the overlaying path, specific steps comprising:
S501. obtaining a pipe intersecting characteristic curve after the side wall of the composite pipe is opened based on the three-dimensional model;
S502. extracting downslope welding path trajectory characteristics of each section of the welding runs from the pipe intersecting characteristic curve, and setting welding gun posture information corresponding to each section of the welding runs in the CMT overlaying system simulation model based on the downslope welding path trajectory characteristics;
S503. generating the overlaying offline instruction based on the welding gun posture information;
S6. based on the overlaying offline instruction, performing CMT overlaying on the opening in the side wall of the composite pipe to be welded according to the overlaying sequence, so as to obtain a weld overlay.