Drawing No. EH–MT–024 // Engineering Materials
Stainless Steel Properties
Reviewed September 2026
Type 304 is the familiar 18Cr-8Ni austenitic stainless steel and is used here as the stainless-steel reference. It combines corrosion resistance and ductility with lower thermal conductivity and higher thermal expansion than carbon steel.
Representative properties
Switch units without changing the underlying material reference.
What changes these properties?
Engineering variability
- The stated strength values represent minimum/typical annealed 304-type data; cold-worked material can be much stronger.
- Thermal conductivity rises with temperature while elastic modulus generally falls.
- 304 has no single fixed ‘melting point’; alloy melting occurs over a solidus–liquidus interval.
- Corrosion resistance depends on environment, surface condition, fabrication and exact chemistry.
Selection note
A strong general-purpose choice for corrosion-resistant sheet, plate, vessels, piping and fabricated equipment, but not a substitute for alloy-specific corrosion selection.
Do not combine strength from one grade/condition with modulus, thermal data or temperature limits from another without checking compatibility. Where the overview shows a range, it is intended to expose variability—not establish allowable bounds.
Stainless steel in practice
A family, not a material — and the differences between its branches matter more than the word they share.
Where it is specified
Austenitic grades (304, 316) dominate: food and pharmaceutical process equipment, chemical plant, architectural work, cryogenic vessels, and anywhere cleanability matters. 316 adds 2–3% molybdenum, which is what buys resistance to chloride pitting and is why it is specified for marine and coastal work.
Duplex grades (2205, 2507) serve chloride duty needing strength — seawater piping, desalination, offshore. Martensitic grades (410, 420, 17-4 PH) are used for valve trim, pump shafts and cutlery, where hardness matters more than corrosion resistance. Ferritic grades (430, 444) appear in exhausts and appliances, where the absence of nickel keeps cost stable.
Chosen over what
Against coated carbon steel: three to five times the price, but it removes maintenance painting and the risk of coating breakdown in inaccessible places. Over a 25-year life the comparison is often closer than purchase price suggests.
Against 316 specifically: do not specify 316 reflexively. In clean non-chloride service 304 performs identically for less money; in seawater, 316 will still pit and a duplex or 6% Mo superaustenitic grade is required. The molybdenum buys chloride resistance, not general superiority.
How it fails
Chloride pitting and crevice corrosion. The passive film breaks down locally and attack is deep, narrow and hard to detect. Crevices under gaskets, deposits and partial-penetration welds are the usual sites. Pitting resistance is ranked by PREN = %Cr + 3.3×%Mo + 16×%N — roughly 18 for 304, 24 for 316, 35 for 2205.
Chloride stress-corrosion cracking of austenitic grades above about 60 °C: branching transgranular cracks, often through a vessel wall, with no general wastage to warn of it. Duplex and ferritic grades resist it far better.
Sensitisation — chromium carbide precipitation at grain boundaries between 450 and 850 °C, depleting adjacent chromium and causing intergranular attack. Hence L grades (304L, 316L) with restricted carbon, or stabilised grades (321, 347), for welded assemblies.
Galling on threaded connections. Austenitic stainless seizes against itself readily; anti-seize compound or dissimilar grade pairing is standard practice.
Fabrication notes
Machinability is poor, around 45% of B1112 for 304. It work-hardens rapidly, so tooling must take a positive cut and never dwell or rub. Rigid setups, sharp tools and generous feed are the rule; light or interrupted cuts are what produce work-hardened surfaces and sudden tool failure.
Weldability is good for austenitic grades, but heat input must be controlled to limit sensitisation and distortion. Thermal expansion is about 50% higher than carbon steel while conductivity is a third, so distortion is markedly worse. Ferrite number in weld metal is controlled to avoid hot cracking, and pipework needs argon back-purging to prevent root oxidation.
Post-weld cleaning matters. Heat tint is chromium-depleted and corrodes preferentially; pickling and passivation to ASTM A380/A967 restores the passive film. Iron contamination from carbon steel tooling or grinding media will rust on the surface, so tools must be segregated.
Specifications and standards
ASTM A240 for plate and sheet, A312 for pipe, A276 for bar; EN 10088 for the European designation system; ASTM A380/A967 for cleaning and passivation; NACE MR0175/ISO 15156 for sour service; ASME BPVC Section II Part D for allowable stresses.
References
ASM Specialty Handbook, Stainless Steels; Sedriks, Corrosion of Stainless Steels; Outokumpu and Sandvik technical handbooks for grade-specific corrosion data.
Property interpretation
Stiffness vs strength
Young’s modulus controls elastic deformation. Yield or fracture strength controls how far the material can be stressed. These are separate material characteristics.
Thermal response
Thermal conductivity controls temperature gradients, specific heat contributes to thermal inertia, and expansion controls thermally induced strain when movement is restrained.
Temperature transition
The final property card is deliberately labeled “melting / transition.” Metals often have a solidus–liquidus range; amorphous polymers and glass use softening or glass-transition concepts; concrete and wood decompose instead of exhibiting one clean melt point.
Technical sources
Source hierarchy favors manufacturers, industry associations, standards bodies and government engineering references. Strength data must still be reconciled with the exact procurement specification.