1. Stainless Steel
Stainless steel is an alloy steel containing at least 10.5% chromium (Cr) , which provides excellent corrosion resistance mainly through the formation of a chromium oxide passive film. According to its microstructure and application, stainless steel can be classified into the following major types.
2. Overview of Stainless Steel Types
Type
Microstructure
Characteristics
Common Applications
Austenitic
Non-magnetic (FCC)
Good corrosion resistance, high toughness, good weldability
Food, medical, chemical, construction
Ferritic
Magnetic (BCC)
Low cost, moderate corrosion resistance, poor chloride stress corrosion resistance
Home appliance casing, automotive exhaust systems
Martensitic
Magnetic (BCT)
Heat treatable, high hardness, wear resistance
Cutting tools, instruments, valves, turbines
Duplex
Austenitic + Ferritic
High strength, excellent pitting resistance, chloride corrosion resistance
Seawater systems, oil & gas equipment
Precipitation Hardening (PH)
Heat strengthened
High strength, precise dimensional control
Aerospace, military, precision machinery
3. Common Stainless Steel Grade Comparison Table
AISI (US)
JIS (Japan)
UNS Number
Type
Main Composition
Characteristics & Applications
304
SUS304
S30400
Austenitic
18Cr-8Ni
Most common, good corrosion resistance, food & construction
304L
SUS304L
S30403
Austenitic
Low Carbon
Intergranular corrosion resistance, welding parts
316
SUS316
S31600
Austenitic
18Cr-10Ni-2Mo
Chloride corrosion resistance, seawater & chemical industry
316L
SUS316L
S31603
Austenitic
Low Carbon with Mo
Less corrosion after welding, chemical equipment
310S
SUS310S
S31008
Austenitic
High Cr, Ni
High temperature oxidation resistance, furnace materials
430
SUS430
S43000
Ferritic
17Cr
Low cost, general corrosion resistance, decorative home appliances
410
SUS410
S41000
Martensitic
13Cr
Heat treatable, high hardness, suitable for cutting tools
420J2
SUS420J2
S42000
Martensitic
High C-13Cr
Cutting tools, scissors, medical instruments
440C
—
S44004
Martensitic
High C-17Cr
High hardness and wear resistance, bearings, precision parts
2205
—
S32205
Duplex
22Cr-5Ni-3Mo
High strength, chloride pitting resistance
2507
—
S32750
Super Duplex
25Cr-7Ni-4Mo
Ultra-high corrosion resistance, seawater/saltwater facilities
17-4PH
—
S17400
PH
Cr-Ni-Cu + Nb
High strength and corrosion resistance, aerospace and precision machinery
4. Quick Material Selection Recommendations
Usage Condition
Recommended Stainless Steel
Food grade / sinks, cookware
304 / 304L
Coastal / saltwater environment
316 / 316L / 2205
High-temperature furnace / heat treatment equipment
310S
Cost consideration / decorative use
430 (magnetic)
Cutting tools / medical knives
420J2 / 440C
High strength precision parts
17-4PH (precipitation hardened)
5. Summary Comparison Table
Type
Magnetic?
Corrosion Resistance
Strength
Cost
Austenitic (304, 316)
No
✅✅✅
Medium
Medium-High
Ferritic (430)
Yes
✅
Average
✅ Low
Martensitic (410, 420, 440C)
Yes
Average
✅✅✅ High
Medium
Duplex (2205, 2507)
Yes
✅✅✅✅
✅✅✅ High
High
PH (17-4PH)
Yes
✅✅
✅✅✅✅
High
