CR4 Steel - Enough Carbon for Springy Application..?

Hello all,

I've been having a mess with pressing some sheet steel into shape. It's one of those jobs that might turn into a few-off batch, but for now remains a series of tests to satisfy my curiosity.

The steel I've been using isn't known - rescued from a skip, quite ductile - I've been cutting it on my router and pressing it between a couple of formers made from 6082.

So, if this were to turn into a 'job', would CR4 form as readily as what I have here and would it respond well to heat treatment to harden and temper it to a springy condition?

It will form well, but is a mild steel and contains very little carbon. So it can't be hardened and tempered.

Andrew

Edited By Andrew Johnston on 28/03/2023 00:36:44

Thanks Andrew,

Just had a dig around and EN8 with a carbon content around 0.4% looks like it could do the job...

Might be hard finding EN8 in anything much thinner than 6mm plate.

Something like annealed CS70 comes in thinner sheet, might need to adjust the formers as it may well have a bit more spring back even in annealed state

Edited By JasonB on 28/03/2023 07:32:55

Thanks Jason.

Yeah, the EN8 in sheet seems a little hard to come by. My usual supplier (Smiths) does have it listed in sheet form, so I'll ask 'em what's the thinnest they'll go.

In the interests of keeping things complete, some further findings:

I got chatting to a sheet metal worker local to me the other day and he suggested I look at gauge plate/shim-stock and save myself the hassle of heat treatment. I have a bit of old 0.5mm shim-stock in my drawer and it certainly 'feels' like it'll do the job. I traced the purchase back and it turns out it's 304 stainless. So, provided I can buy it in small quantities, cut it and form it, this may be the way to go.

Gauge plate is not available in thin sheets. In general shim stock is not heat treatable. I have made "spring" clips from shim, but it needed annealing first. Otherwise it fractured when bent.

It would be sensible to decide what properties are needed and then pick a material to suit, rather than pick materials at random and ask if they will be ok.

Andrew

Understood and agreed, Andrew. Jason's original CS70 suggestion is pretty much THE way to go for this sort of thing (I've since discovered from a spring clip manufacturer). I'm just struggling to find it in a thickness of 0.5-0.7mm in quantities that don't involve buying entire rolls. This is all freebie work, so I'm splashing about a bit here with very little latitude for buying in the most appropriate material at personal expense. The 304 shim stock 'felt' like it would work, but I'll bow to your better judgement/expertise.

M-machine list 0.7mm sheet cut to size but check if it is annealed, other ME suppliers like Reeves do the annealed but as the main use is for model leaf springs they don't go vey wide

I suppose a lot will depend on how much "spring" you need and will it be flexed or over flexed often? The natural springback in various metals may be enough depending on application.

Edited By JasonB on 30/03/2023 16:51:20

Thanks for the link, Jason. Very helpful - I'll give 'em a call.

Well, I couldn't help myself - I found a larger piece of 0.4mm 304 shim-stock and morbid curiosity got the better of me.

Not entirely bad, but as predicted - didn't form quite as well: a bit more spring-back and evidence of some tension across the bottom of the bowl, but no tearing. In terms of give and shape retention 304 has what I'm after - even at 0.4mm there appears to be enough stiffness to hold a stop-watch but with enough give for easy removal - it's a very light-duty application.

But yep, next I'll go with Jason's original suggestion of annealed CS70. It's been an adventure. 😄