A food processing equipment fabricator in Wisconsin needed to verify their per-inch cost on 304 stainless TIG welds. At $4.20 per linear inch, the cost breakdown revealed that the shielding gas premium (tri-mix argon/helium/CO2 versus standard 75/25) added $0.65/in versus carbon steel equivalents. The shop also carried a higher overhead allocation for stainless — dedicated tooling, segregated storage, and passivation verification time. IronKit's Weld Cost Calculator isolated each cost component, helping the shop justify a 3× premium over carbon steel welding rates on their food-grade bids.
Frequently Asked Questions
Why does 304 stainless cost $4.20/inch vs. $0.85/in for carbon steel?
Five factors: (1) TIG process is 3× slower than MIG; (2) tri-mix gas costs 4× more than 75/25; (3) more pre-weld cleaning required; (4) dedicated SS tooling adds overhead; (5) passivation is required for food-grade applications. Each factor compounds.
Why use tri-mix gas instead of pure argon for stainless?
Tri-mix (Ar/He/CO2) improves arc stability and penetration versus pure argon on stainless. The helium increases heat input, which helps on thicker material. The 2.5% CO2 stabilizes the arc. Pure argon is acceptable but produces a colder, less stable arc on material above 1/4".
Is passivation required on every stainless weld?
For food-grade, pharmaceutical, and sanitary applications — yes, passivation per ASTM A967 is typically specified. It removes surface iron contamination from tooling, grinding, and welding heat that would otherwise rust on 304/316 stainless. Cost is typically $0.15–$0.25/in for shop passivation.
Can IronKit calculate stainless weld cost with back purge?
Yes. Add a back purge requirement in the calculator and IronKit adds the argon purge gas cost (typically 15–25 CFH, $0.012/cu ft per minute) as a separate line item. Back purge cost is usually $0.30–$0.60 per foot of root bead, which is significant on stainless tube and pipe.