Causes and solutions for lateral cracking of 304 stainless steel product sidewalls
304 stainless steel products often have various cracking phenomena during the deep drawing process. Among them, lateral or point cracks on the sidewall are common processing failure forms of 304 stainless steel products with relatively large deep drawing. Especially in recent years, the cost-reduction work of stainless steel products processing procedures has continued to advance. The number of drawing passes has been reduced from 5 times to 3 times commonly used at present, and the number of intermediate annealing has been changed to one annealing or no annealing after stamping. The formability of the material puts forward higher requirements. The lateral or point-like cracking defects on the sidewall of stainless steel products may be caused by material inclusions, delta ferrite and other material intergranular defects, or may be caused by factors such as the drawing process and drawing oil during the processing of stainless steel products.
The lateral or point cracking of the side wall of 304 stainless steel pipe is mainly caused by inclusions or delta ferrite in the material matrix. Therefore, the following points should be controlled during the production of stainless steel:
(1) Improve the purity of the material and reduce the content of inclusions in the stainless steel material.
(2) Improve the composition design and hot rolling and cold rolling annealing process to reduce the content of δ ferrite in the stainless steel material matrix.
However, because stainless steel pipe materials inevitably have these two manufacturing defects during the production process, appropriate process measures can also be taken during the processing of stainless steel products to reduce or avoid cracks caused by inclusions or delta ferrite defects. phenomenon:
(1) Change the forming method from reducing wall thickness drawing to equal thickness drawing.
(2) Increase the number of deep drawing passes, increase the radius of the die fillet, and reduce the difficulty of material deformation.
(3) Appropriately increase the viscosity of the drawing oil to promote uniform deformation of the material and avoid excessive stress concentration.
