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X12CrNi25-21 (310S)

310S — high Cr-Ni austenitic stainless for high temperature service to 1100 C. For furnace parts, annealing boxes, heat treatment equipment and burner nozzles.

Stainless Steels Austenitic Stainless Steel ENX12CrNi25-21 / 1.4845 AISI/SAE310S ASTMA240 / A276 Type 310S UNSS31008 +4
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Description

X12CrNi25-21 (EN 1.4845 / AISI 310S) per EN 10088. 25%Cr + 21%Ni gives the best oxidation resistance of standard austenitic stainless grades. Maximum continuous service temperature 1050 C (oxidising), 1100 C (intermittent). Low carbon (<0.08%) for improved intergranular corrosion resistance. Standard for heat treatment furnace components, radiant tubes and annealing equipment.

Key Properties — Solution Annealed
Rm (Tensile Strength)
515
MPa
Re / Rp0.2 (Yield)
205
MPa
A₅ (Elongation)
≥ 30.0
%
Hardness
— – 217
HB
E (Young's Modulus)
200
GPa
Density
7.98
g/cm³
Main Designations (8)
Standard BodyDesignationCountry / RegionNote
EN X12CrNi25-21 / 1.4845 EU
AISI/SAE 310S USA
ASTM A240 / A276 Type 310S USA
UNS S31008 USA (UNS)
JIS SUS310S Japan
GOST 20H23N18 (20Kh23N18) Russia
BS EN 310S31 UK
JUS C.4592 Yugoslavia High-temp austenitic stainless; JUS C.B2.040
Standards (8)
#Standard BodyDesignationCountry / RegionNote
1 EN X12CrNi25-21 / 1.4845 EU —
2 AISI/SAE 310S USA —
3 ASTM A240 / A276 Type 310S USA —
4 UNS S31008 USA (UNS) —
5 JIS SUS310S Japan —
6 GOST 20H23N18 (20Kh23N18) Russia —
7 BS EN 310S31 UK —
8 JUS C.4592 Yugoslavia High-temp austenitic stainless; JUS C.B2.040
All values in wt.%
C
Carbon
≤ 0.0800
Si
Silicon
≤ 1.5000
Mn
Manganese
≤ 2.0000
Cr
Chromium
24.0000 – 26.0000
Ni
Nickel
19.0000 – 22.0000
ElementSymbolMin %Max %Typical %
Carbon C — 0.0800 0.0400
Silicon Si — 1.5000 0.7000
Manganese Mn — 2.0000 1.2000
Chromium Cr 24.0000 26.0000 25.0000
Nickel Ni 19.0000 22.0000 21.0000
Mechanical Properties
ConditionCode Rm min
MPa		Rm max
MPa		 Re min
MPa		Re max
MPa		 A₅ min
%		 Z
%		 KV
J		 HB minHB max HRC minHRC max E
GPa
Solution Annealed +AT 515 — 205 — 30.0 — — — 217 — — 200.0
Physical Properties
Density
7.980
g/cm³
Melting Point
1380–1420
°C
Young's Modulus
200.0
GPa
Poisson's Ratio
0.290
—
Thermal Conductivity
14.2
W/m·K
Thermal Expansion
15.90
×10⁻⁶ /K
Specific Heat
500
J/kg·K
Electrical Resistivity
0.7800
µΩ·m
Magnetic
No
 
Heat Treatment
Solution Annealing
Temperature:1040°C – 1150°C
Medium:Water quench
Duration:Sufficient
Cooling:Rapid
Hardness After:<=HB 217
For maximum high-temperature corrosion resistance.
Machinability
Machinability Rating
relative to AISI B1112 = 100%
38.0%
Very Difficult
Turning Speed (HSS)
16
m/min
Turning Speed (Carbide)
82
m/min
Feed Rate (Turning)
0.100
mm/rev
Drilling Speed (HSS)
9
m/min
Milling Speed (Carbide)
85
m/min
CoolantHigh-pressure flood coolant mandatory
Chip FormationLong stringy chips; severe work-hardening
Tool MaterialTiAlN carbide; positive rake
Surface FinishRa 0.4-1.6 um
Similar machining to 316L but higher cutting forces. Work-hardening extreme.
Applications
Heat Treatment Equipment
Furnace retorts, annealing boxes, radiant tubes, muffle furnaces and conveyor belts.
Petrochemical
Ethylene cracker tubes, reformer furnace components and high-temperature reactors.
Power Generation
Superheater supports and components in coal-fired power stations.
Technical Notes
✅
vs 309S
310S: 25%Cr+21%Ni — highest oxidation resistance of standard grades; service to 1100 C. 309S: 23%Cr+13%Ni — lower cost, service to 980 C. Use 310S when temperature exceeds 980 C or sulphur-bearing atmospheres.
⚠️
Sigma Phase
Prolonged exposure at 600-900 C causes brittle sigma phase. Parts must not be impact loaded after high-temperature service without reconditioning.