The basic process of carbon steel elbow pipe forming technology is: first welding a polygonal polygonal polygonal ring shell or closed at both ends of the polygonal fan shell, the internal pressure is filled with pressure medium, the internal pressure under the action of the cross section from polygon gradually become round, and then become a circular ring shell.  According to the need of a circular ring shell can be cut into four 90 ° elbow pipe fittings or six 60 ° elbow pipe fittings and other specifications of the carbon steel elbow pipe fittings, the technology is suitable for manufacturing elbow pipes diameter with carbon steel elbow pipe diameter ratio greater than 1.5 large elbow pipe fittings of any specifications, is the ideal method of manufacturing large pressure on the elbow pipe.  

 
The advantages are mainly shown in the following aspects:  
 
(1) Without tube blank as raw material, the cost of tube making equipment and mould can be saved, and the carbon steel elbow pipe with arbitrary large diameter and relatively thin wall thickness can be obtained.  
 
(2) The blank is flat or developable surface, so the feeding is simple, the accuracy is easy to ensure, and the assembly and welding are convenient.  
 

(3) Due to the above two reasons, the manufacturing cycle can be shortened and the production cost greatly reduced.  Because no special equipment is required, it is especially suitable for on-site processing of large elbow pipe fittings.