Alloy Steel 5120

Chemical Analysis
C% Carbon
0.17 – 0.22
Mn% Manganese
0.70 – 0.90 max
P% Phosphorus
0.040 max
S% Sulfur
0.040 max
Si% Silicon
0.20 – 0.35
Cr% Chromium
0.70 – 0.90

General characteristics of Alloy Steel 5120

This is a low-carbon chromium-bearing, case-hardening alloy steel used where good wear resistance and toughness are required.


This alloy is used for highly stressed parts with medium cross sections for automotive and general engineering applications, such as forged camshafts and gears, gear shafts, bushings and connecting rods.


This alloy would be forged between 2200 and 1700ºF (1200 and 925ºC.)

Heat treatment

Annealing: This alloy is seldom annealed. Structures of better machinability are developed by normalizing or by isothermal transformation after forging.

Normalizing: 1650-1700ºF (900-930ºC.)

Carburizing: 1650-1740ºF (900-950ºC) and oil quench.

Hardening: Core: 1560-1620ºF (850-880ºC) and oil quench. Case: 1490-1540ºF (810-840ºC) and oil quench

Tempering: 340-410ºF (170-210ºC.)

Machinability: The alloy is best machined in the normalized condition prior to case hardening.

Weldability: The alloy is easily welded, but should be welded prior to case hardening.

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