5120 Alloy Steel-ASTM A29 | SCr420

5120 steel is a low carbon alloy structural steel containing 0.7-0.9% chromium as per American standard ASTM A29.

Due to its good toughness, forgeability and weldability, 5120 steel can meet the manufacturing needs of various shapes and sizes. This alloy steel responds well to heat treatment processes, and its hardness and strength can be adjusted through heat treatment.

After carburization, 5120 alloy steel has high hardness and wear resistance. It not only withstands high loads and impact loads, but also resists friction and wear, extending the service life of the material. Therefore, it is widely used in the manufacturing of automotive parts, such as transmissions,gears, crankshafts, piston pins, etc.

5120 STEEL CHEMICAL COMPOSITION

Grade	C	Si	Mn	P	S	Cr
5120	0.17-0.22	0.15-0.35	0.7-0.9	≤0.035	≤0.04	0.7-0.9

5120 STEEL RELATED STANDARD & EQUIVALENT GRADE

CHINA:20Cr

JAPAN:SCr420

EN/DIN:20Cr4/1.7027

5120 STEEL PHYSICAL PROPERTY

Density, g/cm3	7.83
Melting point,℃	1430
Specific heat capacity，(0~100℃),J/(kg.k)	477
Linear expansion coefficient,10^-6/k	13.56
Poisson’s ratio	0.3
Elastic Modulus,Mpa	210100
Shear modulus,Mpa	82400
Thermal conductivity,W/(m.K)	50.66(20℃)

5120 STEEL FORGING

Initial Forging Temperature：1200℃
Final Forging Temperature：>800℃
Forging Ratio：above 4:1
Cooling Method After Forged:As low carbon alloy steel,5120 steel is generally treated by slow cooling in sands after forging.

5120 STEEL HEAT TREATMENT

Critical Temperature for Heat Treatment of 5120 Steel

Ac1:766℃
Ac3:838℃
Ar1:702℃
Ar3:799℃

Temperature Selection for Different Types of Heat treatment for 5120 steel

Normalizing: 870 – 900°C,Cooling in air,hardness below 207HBW
Annealing:860 – 890°C,Cooling in furnace,hardness below 179HBW
Carburizing:900-940°C
Core-hardening:850-870°C
Case-hardening:780-820°C
Tempering:180-200°C,Surface hardness：58-62HRC,Core hardness20-32HRC.

5120 Steel Mechanical Property with Quenched and Tempered Condition

First Quenching Temperature,ºC	Second Quenching Temperature,ºC	Tempering Temperature,ºC	Tensile Strength Mpa	Yield Strength Mpa	Elongation %	Reduction of Area %	Impact Charpy-V J
880ºC W/O Quench	800ºC W/O Quench	200ºC	≥850	≥550	≥10	≥40	≥60