HRS vs. CRS

[Thrud]

JCHannum:
That is a good point about the free machining stuff being unsuitable for high stress parts - but CRS and HRS should not be used for that either.

[JCHannum]

Definitely not. However, there are some leaded and free cutting alloys, 41L40, for example which should also not be used.

Any alloy which has L in it is leaded, I do not know what denotes sulphur, but it should also be avoided.

[Herb W]

<font face="Verdana, Arial" size="2">Originally posted by Thrud:
I picked up some Starrett #498 Low Carbon Killed steel off eBay -
</font>

What is "killed" steel?

[snorman]

From metalmart.com:

The term “killed†indicates that the steel has been sufficiently deoxidized to quiet the molten
metal when poured into the ingot mold. The general practice is to use aluminum ferrosilicon or
manganese as deoxidizing agents. A properly killed steel is more uniform as to analysis and is
comparatively free from aging. However, for the same carbon and manganese content Killed
Steel is harder than Rimmed Steel. In general all steels above 0.25% carbon are killed, also all
forging grades, structural steels from 0.15% to 0.25% carbon and some special steels in the low
carbon range. Most steels below 0.15% carbon are rimmed steel.

[Thrud]

The term "killed" as I used it refers to its physical properties - that being very malleable, annealed, and stabilized. For instance, a killed cold rolled sheet is usually used in deep drawing operations such as oil filter cans. If they did no use these "killed" metals in this operation the result is an uneven wall thickness and tearing of the metal from overworking it. The drawing operation (cold working) greatly increases the items strength.

The term used in the context of the metals composition is as Snorman has stated.

JCH,

Starrett's label on the plastic wrapper says it is a .17% Carbon Fine Grained Killed Steel with Sulphur of forging quality roughly equivelant to an AISI 1117S. Starrett claims it to be 37% better machinability than free machining AISI 1018. It can be carburized to 1/32" deep if held in carburizing salts for 3 hours @ 1700*F or can be case hardened.