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Blanking&Punching→Punching partial expansion and bending→Blank Edge bending
Expansion ratio: S=(d-d0)/d0
Cracking material SUS304
0.67 0.4~0.5
Causes of cracking:
The state of the cut surface in the borehole is relatively good, and it can be judged that the expansion ratio exceeds the limit of the expansion ratio of the ordinary 304 steel 0.4 to 0.5, and cracking occurs.
Precaution:
- Post-Blanking heat treatment: annealing of work-hardened parts;
- Use of excellent formability materials, conversion of steel: SUS304J1, SUS305;
-Improve lubrication condition and Die surface condition Although there is no direct cause of cracking, but by improving lubrication conditions and die surface conditions, the occurrence of cracking can be reduced.
Cracks in openings, eg: solar water heaters, heat exchangers
Expansion pipe cracking
Material cracking causes and countermeasures
1 Processing that exceeds the forming limit of the material remains within the forming limits
2 Material cleanliness is not enough to improve the cleanliness of the material
3 material elongation is not enough annealing
Cracking causes and countermeasures for welding sites:
No. Cause of occurrence Prevent measures
1 Bad welding, resulting in setting the proper welding conditions on the unwelded
2 Bad welding at the welding site, which leads to poor cutting at the welding site.
3 Welding site contamination (oil, moisture, dust removal set welding speed after appropriate welding speed
4 Rapid welding results
5 No attention was paid to the protection and use of combustion-supporting gases, which resulted in oxidation of the welded parts, resulting in protection and careful management of the gas.
6 Excessive pipe work exceeding the processing limit of the welding area
7 Expanding tube speed to adjust tube expansion speed
8 Bad material cleanliness improves material cleanliness
9 material elongation is not enough annealing
Prevention and countermeasures for expansion and cracking of stainless steel
I. Expansion cracking and prevention