Automotive

Stainless steel in vehicles falls into two categories: heat-resistant (exhaust) and decorative. The grade systems and acceptance standards differ between them, and mixing the two costs you either money or failure.

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Typical Parts and Material Selection

Part	Grade	Surface / Size	Watch Out For
Exhaust Manifold / Exhaust Pipe	409 / 441	2B / 1D, 1.2–2.0 mm	High-temperature oxidation, thermal stress
Muffler / Exhaust Pipe	409 / 436L	8–1.5 mm	Condensate corrosion
Trim / Polished Molding	304 / 430	BA / 8K, 0.3–0.8 mm	Surface class, cracking during bending
Fuel Tank / Bracket	304 / 441	0–2.0 mm	Formability, spot weldability
Seat Frame	301 / 304	High-strength sheet 0.5–1.2 mm	Yield ratio, stress

These are the usual configurations.Actual selection depends on the medium, temperature, and welding method— the same part may move from 304 to 316L or 2205. Describing the service conditions is more useful than naming a grade.

Three Real Constraints in This Industry

Exhaust Is Not "the More Expensive, the Better"

409 is titanium-stabilized, inexpensive, and adequate; 441 adds Nb+Ti for higher heat. Both mistakes are common: 304 in the exhaust cracks at welds due to thermal expansion, and 409 in a hot section scales.

Deep Drawing Depends on the r Value, Not Hardness

Finishing parts need high r and low Δr. The same grade from different rolling schedules behaves very differently — always run a trial draw before the batch, don't just read the mill certificate.

Electrode Life Determines Tack Time

Stainless steel has high resistance and low conductivity, so spot welding electrodes wear quickly. Plan electrode changes by weld count, and control incoming oil film and roughness.