4140 steel designation

[Vernonv]

Does anyone have a reference to the letter that is sometimes used after the steel number i.e. 4140T or 4140G.

I think the T standards for hardened and tempered, however I don't know what the G stands for.

[Ashore]

If I remember correctly the T is for high Tensile and the G is for ground , what we use to call bright shaft :rolleyes:

[Vernonv]

Thanks Ashore.

Could you have HT bright bar? Would that be 4140TG?

[pipeclay]

As far as I know all Centreless Ground bar is H/T.

[.RC.]

This booklet here may be handy..

http://www.martensite.com.au/Martensite%20Australia%20Technical%20Handbook%20Issue%201%202009.pdf

[60,000psi]

It refers to the heat-treated condition, 'T' being the commonly stocked version of 4140.

Lots of specific info on heat treating it here...
4140 High Tensile Steel - Interlloy (http://www.interlloy.com.au/data_sheets/high_tensile_steels/4140.html)