Choosing a Steel Alloy for Parts - A36, 1045, or 4140

Rick Finsta · Nov 2, 2020

I've got parts that are... well google "torque plate" and you'll see. I have a customer looking for a steel plate (I only usually make these for diesel applications or some oddball stuff where it is really necessary) and need to figure out what alloy to use in the long run as well.

Last time I cut them out of 1045 HR plate. It cleaned up fine and held flatness (I try for <0.0005" flatness and parallelism over a 20" length) but the surface finish was very dull gray, I could not get it to look "pretty."

I don't think I want to use A36, and it is only a $50 difference (about 10% increase in my final product price) to go with the 4140 "as rolled" material.

Thoughts? Otherwise I'll give the customer the 1045 price with a $50 upgrade option. I imagine the 4140 will be more wear resistant over time, but maybe not in as-rolled condition?

Garwood · Nov 2, 2020

In functionality I'm not sure it matters much. If you're going to make it hard and grind it then pick whatever material makes the most sense for your process. If no heat treat then I would not use an expensive material.

When I'm making something from plate and need way better than A36 I look at HSLA steels- A514 (T1)

T1 is cheap, every supplier has it on the shelf and tough as hell, but machines nicely.

Bobw · Nov 2, 2020

Your squeezing it, not pulling on it, so it doesn't have to be strong.

All steels, even if heat treated, should take the same amount of force to
twist and bend them. You're only going to be moving a thou or 2 anyways,
so that's kind of moot.

You aren't sliding it around, so wear shouldn't be a huge consideration.

The only real considerations it seems would be how dinged up will it get
when its sitting on the floor in the corner, and how good(shiny) does
it look.

You can make almost any steel shiny by machining it hard and fast. A36
is completely unpredictable and can be somewhat like ferrous bubble gum,
so I'd probably skip that. Obviously you want a hot rolled material so it
doesn't warp up on you.

1020, 1045, 8620, 4140, 4340.. I don't think its going to make all that much
difference, they all machine pretty similar when they are annealed.

6 of one, half dozen of another, I don't think it much matters. My personal
deciding factor would be cost.

Hardplates · Nov 2, 2020

I find when facing mild steel I need to run in excess of 1000 sfm dry to get a mirror finish when taking a light cut.

Garwood · Nov 2, 2020

You guys are forgetting he makes automotive stuff.

Sometimes the secret sauce to automotive stuff is using a fancy material.

You always have those "best of the best" guys that want better than anyone else. You make their part out of 7075 and type 3 ano it or you use T1 and do something different like black zinc and they think you're a fucking god.

Rick Finsta · Nov 2, 2020

LOL you're not wrong. I've got a part I'm making for a customer where we limited the stepover so instead of being smooth it has a bunch of visible scallops (larger cusp height) to make it look MOAR BILLET!

I had luck with the 1045 last time other than the surface finish... maybe I'll just double my SFM and go from there.

Thanks!

TDegenhart · Nov 2, 2020

I would say that the most important requirement is hot rolled or fixture plate. You don't want it twisting after its cut. After that I would say its just cosmetics.

Tom

Richard Winn · Nov 2, 2020

if they are doing hot honeing needs to be out of the same material as the block

ali or castiron

DouglasJRizzo · Nov 2, 2020

I've always had great results in 4140. Good surface finish and a good material for the customer. I usually rough it in the lathe at 400 SFM, then finish at 600 and it looks great.

Rick Finsta · Nov 2, 2020

Richard Winn said:
if they are doing hot honeing needs to be out of the same material as the block

ali or castiron

I don't cut any cast iron (yuck); 99% of my plates are 6061-T6511 and then I'll do steel only on special request. Generally that is for diesel and certain dirt track applications. I've got Pro Stock and NASCAR shops for customers - they use aluminum plates with a special setup procedure (they don't just torque them down to spec.). The only reason this customer is asking is they are a very large volume rebuilding outfit and they just want to make sure it will hold up to the handling wear better than aluminum. They are ordering aluminum for their lower volume marine applications.

One of these days I do want to make a test fixture and actually measure some of this stuff on my CMM, but for now I'm going to assume that if the top levels of motorsports are doing it, I'm not one to argue.

EmGo · Nov 2, 2020

Rick Finsta said:
The only reason this customer is asking is they are a very large volume rebuilding outfit and they just want to make sure it will hold up to the handling wear better than aluminum.

If it's going to be steel anyhow and the purpose is wear resistance, I'd do 8620 and carbo-nitride it. Then grind. Yeah, I know, buncha work but if they want special, you can get 63 Rc for wear resistance easy and if you want flat after carburizing may as well plan on grind.

They'd be special

Another way to go is 4130, quench and temper to about 40, finish machine, then nitride. You get a very hard case that way for wear resistance but it's thin, only a few thou. No grinding though. If you just nitride over a soft core it's not going to hold up as well.

They have some other *really* hard coatings but now we're talkin' expensive.

Grinding would be better for flatness anyhow, what the heck, may as well give them something to brag about.

btw, on your aluminum ones, if you make them out of 7075 and hard anodize (real hard anodize, it's not the same) then you get a VERY wear-resistant surface, really really hard. Ugly color tho, and you can't get it in any of the normal dyes, won't take. I've made sprockets this way and they are killer.

memphisjed · Nov 3, 2020

Ar plate is cheaper than t1, and it does not wear (like the name implies -abrasion resistant). Astm 75, like a36 only more better for sales in your case, fractional more than a36/a50 cost wise.

Rick Finsta · Nov 3, 2020

Well to be clear it is better for my sales if they need replacement more often LMAO.

I just prefer to not waste my customers' money!

Hardplates · Nov 3, 2020

I've made a fair amount of torque plates in the past and still do some custom stuff for local engine builders.

Whenever wear from high use was a concern and or cost was no object I simply and bored pressed in hardened bushings for the nuts/washers/bolts to run against.

Rick Finsta · Nov 3, 2020

All my plates have hardened insert washers including my steel plates!

EmGo · Nov 3, 2020

Rick Finsta said:
All my plates have hardened insert washers including my steel plates!

Well, see, if you did carbo-nitrided 8620 you wouldn't have to do that

I had a Norton vertical spindle grinder that would be perfectg for that ... like a Blanchard with a reciprocating table. Those things are around and usually cheap, they aren't very good for general-purpose work. Ground faces might be a good wackoff marketing point, almost like making your parts out of military grade aircraft aluminum billet.

Of course none of us machinist-types would talk to you anymore, but who cares ? You'd be rolling in dough

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Choosing a Steel Alloy for Parts - A36, 1045, or 4140

Rick Finsta

Stainless

Garwood

Diamond

Bobw

Diamond

Hardplates

Stainless

Garwood

Diamond

Rick Finsta

Stainless

TDegenhart

Diamond

Richard Winn

Aluminum

DouglasJRizzo

Titanium

Rick Finsta

Stainless

EmGo

Diamond

memphisjed

Titanium

Rick Finsta

Stainless

Hardplates

Stainless

Rick Finsta

Stainless

EmGo

Diamond

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