8620 Carburizing Steel
8620 is a low-carbon alloy steel designed to be carburized, giving a hard, wear-resistant surface over a tough, relatively soft core.
- Family /
- Alloy Steels
- Machinability /
- ~78%
- Condition /
- Supplied soft, carburized after machining
- Also called /
- eighty six twenty
8620 is a low-carbon alloy steel designed to be carburized, giving a hard, wear-resistant surface over a tough, relatively soft core.
Machinability is approximate and rated against free-machining 1212 steel at 100%. Higher is easier to cut.
What it is
Its low carbon content means it cannot be through-hardened to high hardness, which is the point. Carbon is diffused into the surface during carburizing, then the part is hardened — producing a hard case over a core that stays tough and absorbs shock.
How it cuts
In the as-supplied condition it machines easily, closer to a mild steel than to 4140. Almost all machining is done before carburizing, while the material is still soft.
What catches people out
The hardened case is thin — often measured in a few hundredths of an inch. Machining or grinding a carburized surface afterwards can cut straight through the case and expose soft core material, so any post-treatment stock removal has to be planned into the case depth from the start.
8620 Carburizing Steel — Common Questions
Can 8620 be hardened all the way through?
- No, and it is not meant to be. Its low carbon content limits through-hardness; the hardness comes from carburizing the surface. If you need a through-hardened part, 4140 or 4340 is the right family.
Other alloy steels
Got a part for 8620 Carburizing Steel?
Send the drawing or the sample. We will tell you straight what it will take to make.