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38Si7

Silicon spring steel with good toughness. For general spring applications and flat springs not requiring elevated temperature resistance.

Spring Steels Spring Steel EN / ISO38Si7 DIN38Si7 / 1.5023 AISI/SAE9255 (nearest) BS EN251H60 (nearest) +11
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Description

38Si7 per EN 10089. Lower carbon than 60SiCr7 gives better toughness at the cost of elastic limit. Q+T achieves Rm 1300-1550 MPa with improved ductility (A>=10%). Standard for flat springs, blade springs, agricultural springs and mining machinery springs.

Key Properties — Soft Annealed
Rm (Tensile Strength)
750 – 950
MPa
Re / Rp0.2 (Yield)
550 – 750
MPa
A₅ (Elongation)
≥ 13.0
%
Hardness
223 – 280
HB
E (Young's Modulus)
210
GPa
Density
7.82
g/cm³
Main Designations (15)
Standard BodyDesignationCountry / RegionNote
EN / ISO 38Si7 EU / International
DIN 38Si7 / 1.5023 Germany
AISI/SAE 9255 (nearest) USA
BS EN 251H60 (nearest) UK
JIS SUP6 (nearest) Japan
GOST 55S2 (55S2) Russia / CIS
UNI 38Si7 Italy
NF 38S7 France
SS 2085 (nearest) Sweden
PN 55S2 Poland
CSN 13255 (nearest) Czech Republic
UNS G92550 (nearest) USA (UNS)
GB 60Si2Mn China
JUS C.5223 Yugoslavia / Serbia Si spring steel; JUS B.B3.200
ONORM 38Si7 Austria
Standards (15)
#Standard BodyDesignationCountry / RegionNote
1 EN / ISO 38Si7 EU / International —
2 DIN 38Si7 / 1.5023 Germany —
3 AISI/SAE 9255 (nearest) USA —
4 BS EN 251H60 (nearest) UK —
5 JIS SUP6 (nearest) Japan —
6 GOST 55S2 (55S2) Russia / CIS —
7 UNI 38Si7 Italy —
8 NF 38S7 France —
9 SS 2085 (nearest) Sweden —
10 PN 55S2 Poland —
11 CSN 13255 (nearest) Czech Republic —
12 UNS G92550 (nearest) USA (UNS) —
13 GB 60Si2Mn China —
14 JUS C.5223 Yugoslavia / Serbia Si spring steel; JUS B.B3.200
15 ONORM 38Si7 Austria —
All values in wt.%
C
Carbon
0.3500 – 0.4200
Si
Silicon
1.5000 – 1.8000
Mn
Manganese
0.6000 – 0.9000
ElementSymbolMin %Max %Typical %
Carbon C 0.3500 0.4200 0.3800
Silicon Si 1.5000 1.8000 1.6500
Manganese Mn 0.6000 0.9000 0.7500
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
Soft Annealed +A 750 950 550 750 13.0 40.0 — 223 280 — — 210.0
Q+T (spring) +QT 1,300 1,550 1,150 — 8.0 28.0 — 390 460 — — 210.0
Physical Properties
Density
7.820
g/cm³
Melting Point
1400–1450
°C
Young's Modulus
208.0
GPa
Poisson's Ratio
0.285
—
Thermal Conductivity
38.0
W/m·K
Thermal Expansion
12.00
×10⁻⁶ /K
Specific Heat
480
J/kg·K
Electrical Resistivity
0.2350
µΩ·m
Magnetic
Yes
 
Heat Treatment
Spheroidising Anneal
Temperature:680°C – 720°C
Medium:Furnace
Duration:3-5 h
Cooling:<=20 C/h
Hardness After:<=HB 255
Before machining.
Austenitizing
Temperature:860°C – 900°C
Medium:Oil
Duration:15-20 min
Cooling:Oil quench
Hardness After:HRC 52-58
Lower Si than 60SiCr7 — lower austenitising temp.
Tempering (spring)
Temperature:400°C – 480°C
Medium:Oil bath or air
Duration:45-90 min
Cooling:Air cool
Hardness After:HRC 42-48
Standard spring temper.
Machinability
Machinability Rating
relative to AISI B1112 = 100%
50.0%
Difficult
Turning Speed (HSS)
30
m/min
Turning Speed (Carbide)
145
m/min
Feed Rate (Turning)
0.170
mm/rev
Drilling Speed (HSS)
22
m/min
Milling Speed (Carbide)
148
m/min
CoolantSoluble oil 8-12%
Chip FormationMedium chips
Tool MaterialCarbide P30
Surface FinishRa 0.8-1.6 um
Machine in spheroidised condition.
Applications
Flat Springs
Leaf springs for railway stock, trucks and agricultural machinery.
Mining
Heavy-duty mining equipment springs and shock absorber components.
Agricultural
Plough spring assemblies and cultivator spring tines.
Technical Notes
✅
vs 60SiCr7
38Si7 has better toughness (A>=8-10%) vs 60SiCr7 (A>=5-6%) — use where resistance to impact or vibration loading is important alongside spring function.