Automotive

Stainless steel in automotive splits into two families: heat-resistant (exhaust systems) and decorative. Their grade systems and acceptance criteria differ, and mixing them up costs you either money or a failed part.

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Typical Parts and Material Selection

Part	Grade	Surface / Size	What to Watch For
Exhaust manifold / downpipe	409 / 441	2B / 1D, 1.2–2.0 mm	High-temperature oxidation, thermal fatigue
Muffler / exhaust pipe	409 / 436L	0.8–1.5 mm	Condensate corrosion
Trim / bright forming	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 common configurations.Actual selection depends on environment, 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-World Constraints in This Industry

Exhaust Systems: Not a Case of "the More Expensive, the Better"

409 is titanium-stabilized, inexpensive and sufficient; 441 adds Nb+Ti for higher heat resistance. Both mistakes are common: 304 in an exhaust system cracks along weld seams due to thermal expansion, while 409 in the hot zone is prone to scaling.

Deep Drawing Depends on r-Value, Not Hardness

Decorative parts require high r and low Δr. The same grade behaves very differently under different rolling schedules — always run a trial draw before production, never rely on the mill certificate alone.

Electrode Life Determines Cycle Time

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