Automotive Sector

Stainless steel in vehicles falls into two families: heat-resistant (exhaust) and decorative. Their grade systems and acceptance criteria differ, and mixing them costs money or causes failure.

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Typical Parts and Material Selection

Part	Grade	Surface / Size	Watch Out For
Exhaust manifold / downpipe	409 / 441	2B / 1D, 1.2–2.0 mm	High-temperature oxidation resistance, thermal fatigue
Muffler / exhaust pipe	409 / 436L	0.8–1.5 mm	Condensate corrosion
Trim / bright profiling	304 / 430	BA / 8K, 0.3–0.8 mm	Surface class, no cracking on bending
Fuel tank / bracket	304 / 441	1.0–2.0 mm	Formability, spot weldability
Seat frame	301 / 304	High-strength sheet 0.5–1.2 mm	Yield ratio, fatigue

These are the usual configurations.The actual choice depends on the vehicle, temperature and welding method— the same component can move from 304 to 316L or 2205. Describing the operating conditions is more useful than naming a grade.

Three Real Constraints in This Sector

Exhaust Is Not "the More Expensive the Better"

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

Deep Drawing Depends on the r Value, Not Hardness

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

Electrode Life Determines Takt Time

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