4340 Alloy Steel Available Now at NeoNickel

Characteristics of 4340 Alloy Steel

4340 Alloy Steel can be heat treated to achieve high strength whilst maintaining good toughness, wear resistance and fatigue strength levels, combined with strength up to 315 ºC.

UNS Number: G43400
AMS: 6409
Other: 6415, 2304

Product availability

We stock 4340 Alloy Steel in round bar form, available in a wide range of sizes to suit different aerospace, automotive and high-strength engineering applications. To view available sizes and submit an inquiry, use the dropdown selector below.

To view available sizes and submit an enquiry, use the dropdown selectors below.

Round Bar

26 Products

Chemical analysis

%	Fe	Ni	Cr	Mn	C	Mo	Si	S	P
Min	95.195	1.65	0.70	0.60	0.37	0.20	0.15	-	-
Max	96.33	2	0.90	0.80	0.43	0.30	0.30	0.04	0.035

Key Properties

Density: 7.85 g/cm^3
Melting Range: 1340-1380°C
Specific Heat Capacity: 448 J/kg*K
Electrical Resistivity: 1.09 µΩ.m
Coefficient of Thermal Expansion from -18-93°C : 11.3 µm/mm/°C
Coefficient of Thermal Expansion from -18-649°C : 14.6 µm/mm/°C

About 4340 Alloy Steel

4340 Alloy Steel is an iron-based alloy containing nickel, chromium and molybdenum. The relatively high carbon content provides this alloy with superior strength in applications where severe service conditions exist.

4340 Alloy Steel has high strength, superior toughness and good ductility. In addition, the alloy is immune to embrittlement.

To learn more about 4340 Alloy Steel contact us today, or fill in our online quote form and we’ll get right back to you!

Mechanical & Physical Properties

Mechanical & Physical Properties	21.1°C	100°C	204.4°C	315.6°C	400°C	537.8°C	648.9°C	700°C	760°C	815°C	870°C	982°C
Ultimate Tensile Strength /MPa	792	-	-	-	-	726	473	-	286	-	139	66
	407	-	-	-	-	363	275	-	152	-	68	31
	-	-	-	-	-	-	-	-	-	-	-	-
	31	-	-	-	-	27	32	-	75	-	90	91
	-	-	-	-	-	-	83	47	26	15	8.3	-
	-	11	12.7	13.4	13.9	14.3	15	15.4	-	16.5	17.1	18.2
	10.06	-	-	-	-	-	-	-	-	-	-	-
	221	216	210	203	197	190	181	173	-	165	153	140

Room Temperature Mechanical & Physical Properties at Various Tempering Temperature (Normalised at 899-927 °C/Austenitised at 816-829°C/Oil Quenched)

Room Temperature Mechanical & Physical Properties at Various Tempering Temperature (Normalised at 899-927 °C/Austenitised at 816-829°C/Oil Quenched)	204°C	260°C	316°C	427°C	538°C	593°C	649°C
Ultimate Tensile Strength /MPa	1905	1830				1140
0.2% Yield Strength /MPa	1530	1530				1035
Reduction of area %	35	25				60
Elongation %	11	8				18
Room Temperature Hardness/ Rockwell C at Various Tempering Temperature (Austenitised at 843°C/Oil Quenched/Tempered Twice for 2+2 Hours)	52		47	41	35		25

Hardness/ Rockwell C at Various Testing Temperature

Hardness/ Rockwell C at Various Testing Temperature	21 °C	93°C	204°C	316°C	427°C	538°C
Condition A: Normalised at 899 °C for 1 hour + air cool/ Austenitised at 816 °C for 0.5 hour + oil quench/ Tempered at 246 °C for 2+2 hours +air cool	49	48.5	48	45.5	35	18
Condition B: Normalised at 899 °C for 1 hour + air cool/ Austenitised at 816 °C for 0.5 hour + oil quench/ Tempered at 482 °C for 2+2 hours +air cool	40.5	38	36.5	34	31.5	18
Condition C: Normalised at 899 °C for 1 hour + air cool/ Austenitised at 802 °C for 0.5 hour + oil quench/ Tempered at 593 °C for 2 hours +air cool	34	32.5	30	27.5	24	13

Applications of 4340 Alloy Steel

Commercial and military aircraft
Automotive systems
Forged hydraulic systems

Resources (3)

Understanding the Different Types of Alloy Steels

Optimising Automotive Drive Shafts for Speed, Reliability and Safety

Aircraft Landing Gear

All technical resources

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