Alloy Steel AISI 8720

General Characteristics of Alloy Steel AISI 8720

Alloy steel 8720 is a case-hardening low-alloy steel  containing nickel, chromium and molybdenum as alloying elements.

 Chemical Analysis

C% Mn% P% S% Si% Ni% Cr% Mo%
 0.18/0.23 0.70/0.90 0.040 max 0.040 max 0.20/0.35 0.40/0.70  0.40/0.60 0.20/0.30

This alloy may be used in the production of medium-strength parts such as forged camshafts, fasteners and gears.

This alloy is forged at a start temperature of around 2250ºF (1230ºC) and could be forged down to approximately 1700ºF(925ºC.) The alloy is air cooled after forging.

Heat Treatment
Annealing: For optimum machinabilty, an as-forged structure is normally sufficient for this grade of alloy steel. If this proves not to be the case then an iso-anneal from around 1650ºF (900ºC) to 1225ºF (660ºC) will improve machinability.

Normalizing: 1700ºF (925ºC) and air cool. This is another method of improving machinability in this grade; normalizing might also be used prior to case hardening.


Hardening: The alloy will be austenitized at around 1550ºF (840ºC) and oil or water quenched depending upon section size and intricacy.

 Tempering : to desired hardness, using temperatures based on past experience, following water or oil quench.

Machinability: This grade of alloy is readily machined following suitable heat treatment.

Weldability: This steel may be welded by normal fusion methods, but prior to any heat treatment that will modify the steel’s properties.