Materials question- Can thin Carburized 1018 act like hard 1095?

Garwood · Feb 26, 2020

I'm designing a thin clamp that needs some spring in the assembly (allows the clamped part to self align). Essentially, there will be a flat spring in the assembly that does not move except during assembly.

Currently this assembly is 2 pieces- One larger formed part of 1018 that gets carburized for wear resistance then a small formed part made from 1095 pre-hard spring steel. I can't make the entire thing from 1095. It's just too expensive. But I am very curious if I made this assembly all one piece and the "springy part" (about 2" by .600" of 16 gauge) was just carburized 1018 would it work the same?

I know it's a difficult question to answer without seeing the actual use, but what I'm really curious about is whether carburized 1018 sheetmetal is ever used as a cheaper substitute to spring steel?

guest · Feb 26, 2020

What's you case depth and hardness?

I'm thinking you'd need .030" to get close to the mechanicals of 1095 Q&T using 16 ga. 1018.

Just a gut impression- nothing really to back it up...

johnoder · Feb 26, 2020

And that means high carbon just about all the way thru

guest · Feb 26, 2020

johnoder said:
And that means high carbon just about all the way thru

Yep. Basically turning the 1018 into a high carbon steel.

Normally I'd say not worth the trouble- but the part is already being carburized, so it might just mean a longer soak...

Mtndew · Feb 26, 2020

Garwood said:
One larger formed part of 1018 that gets carburized for wear resistance

Would 8620 be a better option? Or if it's just for wear resistance, why not cast iron (if you're bolting the 2 pcs together)

EDIT: nevermind, I didn't see that you are using sheet metal.

Garwood · Feb 26, 2020

guest said:
What's you case depth and hardness?

I'm thinking you'd need .030" to get close to the mechanicals of 1095 Q&T using 16 ga. 1018.

Just a gut impression- nothing really to back it up...

I just need a minimum RC50. No problem for heat treater to do .030 depth.

Everyone I've talked to says the same thing.... "No that won't work, but wait, maybe it would? It's basically making 1095 out of 1018 right?"

cyanidekid · Feb 26, 2020

Garwood said:
I just need a minimum RC50. No problem for heat treater to do .030 depth.

Everyone I've talked to says the same thing.... "No that won't work, but wait, maybe it would? It's basically making 1095 out of 1018 right?"

carbon content isn't the only thing that makes a reliable spring. once you have the hardness, all kinds of flaws become stress risers and can lead to cracking. how much of a move the "spring" makes, how many cycles the part has to last for, and what happens when it fails?

Fal Grunt · Feb 26, 2020

One of my products is essentially a spring. Originals were a low carbon steel case hardened. Since some of the cross sections are so thin, they are thru hardened.

I wanted 4340, but couldn’t find any in the size I needed. So I made them from 4140. HT, quench in oil, draw to 48-50RC. They won’t crack, and can still deform if need be. Thinnest cross section is. . . Don’t remember, pretty damn thin.

I can buy several 12ft bars of 4140 Ann for what a little block of 1095 costs. Wear resistance and over all quality is better in my opinion.

DavidScott · Feb 26, 2020

How much do you need it to deflect over what length? I have tried this with a few cheaper steels and mine failed because I am deflecting too much. So yes I do have a little direct experience, not 1018 exactly but steels on either side of it, 50 and 58 HRC but the hardness didn't make much difference. I say it may work if you're deflecting very little.

To be clear I carbonitrided.

TDegenhart · Feb 26, 2020

A few thoughts. In pure bending the stress is highest at the surface and zero along the center line. The carbon distribution of a carburized steel is highest on the surface and lowest in the center, if carburized on both sides. That would make a carburized low carbon functionally equal to the high carbon steel. However, a steel like 8620 will carburize better than just low carb.

It sounds like in your two piece assembly that the thicker piece does not flex and depends on the thinner piece for the spring action. Making the assembly into one will essentially make a very strong spring, probably well stronger than what you want. Without the thickness of the spring I can't calculate the change in spring constant, but be it said that for the given geometry and deflection, the force varies as the cube of the thickness.

Tom

Rickyb · Feb 26, 2020

Garwood said:
I just need a minimum RC50. No problem for heat treater to do .030 depth.

Everyone I've talked to says the same thing.... "No that won't work, but wait, maybe it would? It's basically making 1095 out of 1018 right?"

Yes, in fact you are making 1018 into 10100. Carbon level will be a full 1%. Since your part is thin you may encounter quench cracking at quench and/or warping. Should work if these two problems don't bite you.

EmGo · Feb 26, 2020

Rickyb said:
Yes, in fact you are making 1018 into 10100. Carbon level will be a full 1%. Since your part is thin you may encounter quench cracking at quench and/or warping. Should work if these two problems don't bite you.

There's more than that to it ... thickness comes into play, too. With carburized 8620 you get a soft core - about 34-ish usually - with the hard case and a boundary layer between the two. So depending on the thickness of the part and the thickness of the case, you're going to have a more complex situation than just hardness of materials.

The only realworld (tm) experience I can offer is some parts that had a flange that another part slid up against, then a fastener clamped it all together. 8620, flange was about an eighth thick, case was .050" (on each side tho, which I didn't pick up on looking at the print, so cased alnost all the way thru). Mating part slid on a spline nicely, up against the shoulder, spin the nut on, tighten it down a little, SNAP ! off went the flange. Not even really tight.

Based on that I probably would not do what you suggest

Garwood · Feb 26, 2020

Thanks for the replies. Luckily, after starting this thread, I had an aha moment and redesigned the whole mess to use less parts and an off the shelf 20 cent spring.

I think the 1018 may have worked here. The deflection's minimal and it just moves once at install then never moves again.

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Materials question- Can thin Carburized 1018 act like hard 1095?

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