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28NiCrMoV8-5 (Large Turbine Rotor Forging Steel)

28NiCrMoV8-5 -- Ni-Cr-Mo-V rotor forging steel for steam turbine and generator rotors. Rm 780-930 MPa with guaranteed through-thickness properties in forgings exceeding 1000 mm diameter. For steam turbine rotors, generator rotor shafts and other massive forged components.

Alloy Steels Ultra-Large Forging Steel EN 1026928NiCrMoV8-5 / 1.6932 DIN W.Nr1.6932 ASTM (nearest)A470 Class 8 (nearest rotor steel) JISSNCM439 (nearest, smaller scale) +1
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Description

28NiCrMoV8-5 (EN 1.6932) per EN 10269/VdTUV specifications. High Ni (1.8-2.3%) + Cr + Mo + V gives excellent hardenability enabling uniform mechanical properties through the enormous cross-sections of steam turbine and generator rotor forgings -- often 800-1200+ mm diameter, where achieving consistent properties from surface to core is the defining metallurgical challenge. Standard for fossil and nuclear steam turbine rotors, large generator rotor shafts, and other massive power-generation forgings.

Key Properties — Q+T (large rotor forging, core)
Rm (Tensile Strength)
780 – 930
MPa
Re / Rp0.2 (Yield)
590 – 780
MPa
A₅ (Elongation)
≥ 15.0
%
Hardness
235 – 280
HB
E (Young's Modulus)
206
GPa
Density
7.85
g/cm³
Main Designations (5)
Standard BodyDesignationCountry / RegionNote
EN 10269 28NiCrMoV8-5 / 1.6932 EU
DIN W.Nr 1.6932 Germany
ASTM (nearest) A470 Class 8 (nearest rotor steel) USA
JIS SNCM439 (nearest, smaller scale) Japan
JUS Nema direktnog; rotorski celik za turbine Yugoslavia/BiH 28NiCrMoV8-5 za turbinske rotore
Standards (5)
#Standard BodyDesignationCountry / RegionNote
1 EN 10269 28NiCrMoV8-5 / 1.6932 EU —
2 DIN W.Nr 1.6932 Germany —
3 ASTM (nearest) A470 Class 8 (nearest rotor steel) USA —
4 JIS SNCM439 (nearest, smaller scale) Japan —
5 JUS Nema direktnog; rotorski celik za turbine Yugoslavia/BiH 28NiCrMoV8-5 za turbinske rotore
All values in wt.%
C
Carbon
0.2300 – 0.3000
Ni
Nickel
1.8000 – 2.3000
Cr
Chromium
1.5000 – 2.0000
Mo
Molybdenum
0.3000 – 0.5000
V
Vanadium
0.0500 – 0.1500
ElementSymbolMin %Max %Typical %
Carbon C 0.2300 0.3000 0.2650
Nickel Ni 1.8000 2.3000 2.0500
Chromium Cr 1.5000 2.0000 1.7500
Molybdenum Mo 0.3000 0.5000 0.4000
Vanadium V 0.0500 0.1500 0.1000
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
Q+T (large rotor forging, core) +QT 780 930 590 780 15.0 45.0 60.0 235 280 — — 206.0
Physical Properties
Density
7.850
g/cm³
Melting Point
1415–1450
°C
Young's Modulus
206.0
GPa
Poisson's Ratio
0.290
—
Thermal Conductivity
32.0
W/m·K
Thermal Expansion
12.30
×10⁻⁶ /K
Specific Heat
475
J/kg·K
Electrical Resistivity
0.2600
µΩ·m
Magnetic
Yes
 
Heat Treatment
Homogenising / Diffusion Anneal
Temperature:1200°C – 1250°C
Medium:Furnace
Duration:20-40 h (section dependent)
Cooling:Slow cool
Hardness After:Reduces ingot segregation
Essential first step for very large forging ingots before forging.
Normalizing
Temperature:870°C – 910°C
Medium:Air
Duration:-
Cooling:Air cool
Hardness After:Grain refinement
Standard intermediate step in the large-forging heat treatment sequence.
Austenitizing (very large section)
Temperature:830°C – 870°C
Medium:Water or oil quench (specialised large-forging quench systems)
Duration:Many hours (section dependent)
Cooling:Slow, controlled quench through massive section
Hardness After:HRC 40-48
Achieving through-section hardening in 1000+ mm sections requires purpose-built quenching facilities.
Tempering (very long duration)
Temperature:600°C – 660°C
Medium:Furnace
Duration:24-72+ h (section dependent)
Cooling:Very slow furnace cool
Hardness After:Rm 780-930 MPa with guaranteed core toughness
Tempering time scales dramatically with section size to ensure through-thickness uniformity.
Machinability
Machinability Rating
relative to AISI B1112 = 100%
35.0%
Very Difficult
Turning Speed (HSS)
18
m/min
Turning Speed (Carbide)
98
m/min
Feed Rate (Turning)
0.100
mm/rev
Drilling Speed (HSS)
12
m/min
Milling Speed (Carbide)
96
m/min
CoolantSoluble oil 5-8%
Chip FormationMedium chips
Tool MaterialCarbide P20 TiAlN
Surface FinishRa 0.8-1.6 um
Good machinability, though production involves extremely large, specialised machine tools given component scale.
Applications
Steam Turbine Rotors
Fossil and nuclear power plant steam turbine rotor forgings.
Generator Rotors
Large generator rotor shaft forgings.
Massive Power Forgings
Other very large forged components in power generation equipment.
Technical Notes
💡
The Metallurgical Challenge of Scale
Large turbine rotor forgings present a unique metallurgical challenge: a 1000+ mm diameter, many-tonne forging cools and hardens far more slowly at its centre than at its surface during quenching, risking a soft, coarse-grained core if hardenability is insufficient. 28NiCrMoV8-5 high Ni content specifically addresses this -- giving deep hardenability so that even the slowly-cooling core achieves adequate strength and toughness, which is verified by mandatory core-sample testing on every rotor forging before turbine assembly.