Acheiving least deformation after heat treating?

A

asid61

Plastic

Joined

Sep 19, 2014

Location

Bay Area, California, USA

• Dec 6, 2014

• #1

What is a tool steel that deforms the least after heat treating? I know A2 would be fine, but that's about it.
I don't have a grinder that can fit the contour I'm grinding (gear tooth shape) so I need a tool steel that won't deform too much. Tolerances on the gear are not really important (maybe grade 7 or 8) but it does need to be made of some kind of hardened tool steel. I need to make these on demand for a local high school robotics team so I can't really outsource it. They're lenient on the material though.

 

V

Vancbiker

Diamond

Joined

Jan 5, 2014

Location

Vancouver, WA. USA

• Dec 6, 2014

• #2

Gears are commonly made of 8620 then carburized. Very stable. Able to achieve 60+Rc and retain a tough core. Machines better than most tool steels too.

 

D

Dan from Oakland

Titanium

Joined

Sep 15, 2005

Location

Oakland, CA

• Dec 7, 2014

• #3

You don't say how hard you need these- but if distortion is your main concern- consider making them from 17-4. Buy it in the annealed condition, machine your parts and then heat treat them to the H900 condition. This is a low temperature heat treatment at 900 deg f with air quench and the parts will be about 42 Rc with almost no growth or distortion.

 

Last edited: Dec 7, 2014

A

asid61

Plastic

Joined

Sep 19, 2014

Location

Bay Area, California, USA

• Dec 7, 2014

• #4

I need them to be at least hardenable to 40 Rc apparently. I'll try out 8620 and 17-4.
Thanks!

 

gbent

Diamond

Joined

Mar 14, 2005

Location

Kansas

• Dec 7, 2014

• #5

The 8620 will have to be carburized before hardening. Not what I'd consider suitable for short run, low budget activities. I'd be another vote for 17-4. But has someone actually ran the numbers to know hardened gears are needed, or did they just think they sounded better?

 

1

18my

Cast Iron

Joined

Oct 11, 2014

Location

Melbourne

• Dec 7, 2014

• #6

In australia I get m238 (trademark name I think) from a local supplier and get it vacuum hardened. Distortion is minimal. Can't remember exact hardness off the top of my head.

 

M

Mark Rand

Diamond

Joined

Jul 9, 2007

Location

UK Rugby Warwickshire

• Dec 7, 2014

• #7

I made a complete set of replacement apron gears for my Hardinge HLV out of 4340. Any distortion after hardening has not caused any problems with them.

 

Zahnrad Kopf

Diamond

Joined

Apr 5, 2010

Location

Tropic of Milwaukee

• Dec 7, 2014

• #8

Dan from Oakland said:

You don't say how hard you need these- but if distortion is your main concern- consider making them from 17-4. Buy it in the annealed condition, machine your parts and then heat treat them to the H900 condition. This is a low temperature heat treatment at 900 deg f with air quench and the parts will be about 42 Rc with almost no growth or distortion.

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This. Dan's on the money.

 

D

David_M

Hot Rolled

Joined

Sep 30, 2014

Location

Midway, GA, USA

• Dec 7, 2014

• #9

Another approach is nitriding using Nitralloy 135M. 1025-degree process without a sudden quench; leaves teeth straight with a super-hard wearing surface. One more is nitrocarburizing (not carbonitriding or carburizing). It can be used with 8620, 9310, 41*0 and 43*0 steels. …just mentioning these (I like the one above for simplicity).

--david

 

A

asid61

Plastic

Joined

Sep 19, 2014

Location

Bay Area, California, USA

• Dec 7, 2014

• #10

gbent said:

The 8620 will have to be carburized before hardening. Not what I'd consider suitable for short run, low budget activities. I'd be another vote for 17-4. But has someone actually ran the numbers to know hardened gears are needed, or did they just think they sounded better?

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I know it will need to be carburized, so I'm leaning towards 17-4 right now.
They apparently ran the numbers and decided they needed really, really hard gears. 17-4 will be all right according to them.

@18my I'll give 4340 a go.

 

Zahnrad Kopf

Diamond

Joined

Apr 5, 2010

Location

Tropic of Milwaukee

• Dec 7, 2014

• #11

asid61 - I've got a little experience with Robotics Teams and making Gears for them. Given the fact that the tolerances are not that high and they're fine with 42HRC I'd be inclined to believe that they really don't need much at all. You might want to dig a little deeper and them - and yourself - some time, effort, and cost. Even the College projects don't really need that much, usually. Just a suggestion.

 

V

Vancbiker

Diamond

Joined

Jan 5, 2014

Location

Vancouver, WA. USA

• Dec 7, 2014

• #12

gbent said:

The 8620 will have to be carburized before hardening. Not what I'd consider suitable for short run, low budget activities.

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For the type of job the OP describes, I think that, regardless of material, he'll pay only whatever the heat treaters minimum charge is.