Fabricating stainless is fabricating with three extra constraints: it work hardens as it is formed, it springs back further than mild steel, and it must not be contaminated by carbon steel at any point in the process or it will rust in service despite being stainless. Shops that do it well keep it physically separate from everything else.
Forming behaviour
Stainless work hardens as it deforms, so a bend region becomes harder and stronger than the surrounding sheet and reworking it risks cracking. It also springs back further than mild steel, so more overbend is needed and the compensation values differ by grade and temper. Press brake tonnage requirements are higher for the same thickness.
Contamination is the thing that catches people
Free iron transferred from carbon steel tooling, brushes, grinding wheels or even a shared workbench embeds in the surface and rusts, which looks exactly like the stainless having failed. Serious shops keep dedicated tooling, dedicated abrasives and a separate area for stainless. Where contamination is possible, passivation afterwards removes free iron and restores the passive layer.
Grades and finishes
The common austenitic grades cover most fabrication, with the molybdenum bearing grades used where chloride corrosion matters. Sheet is supplied in standard mill finishes from dull to bright, and a brushed or grained finish is applied for appearance. Because the finish is directional, panels in an assembly should have their grain running the same way, which has to be specified.
Welding and what it does
Welding stainless puts heat into a material with poor thermal conductivity and high expansion, so distortion is worse than in mild steel and heat tint forms along the weld. That tint is a chromium depleted layer and is a corrosion site, so it is removed by pickling, passivation or mechanical cleaning. Back purging with inert gas prevents it forming on the reverse side.
Questions people ask about stainless steel sheet metal fabrication
Why does my stainless part have rust spots?
Almost always free iron contamination from carbon steel tooling, abrasives or work surfaces. Passivation removes it and dedicated tooling prevents it.
Does stainless spring back more than mild steel?
Yes, appreciably, and it work hardens as it forms. Overbend compensation differs by grade and temper and press tonnage is higher.
What is heat tint and why does it matter?
The coloured oxide along a weld, which is chromium depleted and corrodes. It is removed by pickling, passivation or mechanical cleaning, and prevented on the back by purging.
Does grain direction matter on stainless panels?
On any brushed or grained finish, yes. Panels in one assembly should have the grain running the same way, and that must be specified on the drawing.