Causes Analysis on Flanging Cracking of Fuel-adding Pipes

The cracking reasons of fuel-adding pipes made from St12 high frequency welding pipes during flanging were analyzed by means of chemical compositions analysis, metallographic examination and SEM analysis. The results show that the high frequency welding quality and chemical compositions of the St12 steel cold-rolling sheet all conformed standard requirements, and the cracks mainly located at a distance of 2 - 3 mm of the removed burrs area of the weld. The thinning of the material was evident in the cracking area by strain of flanging. Numerical simulation by the Dynaform software system showed that a higher r value of deep drawing cold-rolling steel sheet rather than St12 should be choose to make the fuel-adding pipes which could stand large deformation during flange.