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Doubt about steel
5

Doubt about steel

Doubt about steel

(OP)

Good Morning,
I have a piece of a machine, which is a sheet of steel 0.3 mm thick.

On this sheet are mounted some rollers that press a notebook that passes through a conveyor belt. The function of the sheet is to act as a spring. (After bending, he returns to his initial position)

I have seen that there is a type of steel according to German standards, I think it is CK75. Would it be suitable for manufacturing that sheet? What other types of steel are there that are valid to manufacture this 0.3 mm thick sheet? Is there any other equivalent designation other than the German one?

Greetings

RE: Doubt about steel

I guess it depends on your region. Here in the USA, AISI 1075 would be the equivalent. Heat treatment is going to be the most important factor to consider.

RE: Doubt about steel

(OP)
Thanks, Spain. I don't know if there is a similar steel.

RE: Doubt about steel


Ck75 means it is a cold rolled spring steel.
Could you verify your part being made of that material? Else, imo you need to contact a good supplier to make an assessment of your application / the material used.

Roland Heilmann

RE: Doubt about steel

(OP)
The function of this 0.3 mm thick sheet in the machine is that some rollers mounted on it put pressure on a notebook and once it passes, it recovers its shape.

I see that it is a more suitable type of steel for this and that it is supplied in sheets. I assume there is another but I don't know.

Spoiler:

RE: Doubt about steel

RolMec's posted picture identifies a 9 equivalents.

If that is not enough, there are more here https://equivalentmaterials.com/materials/aisi-107...

One of them is an EN identifier. C75S.

You're in Spain. Spain is in the EU.

These are spring steels. You are describing something with a spring's function.

Might work. Might not. You haven't given enough details to let anyone tell you more.

RE: Doubt about steel

(OP)
What details are necessary? Dimensions? Forces?

RE: Doubt about steel

Quote (Galvano)

What details are necessary? Dimensions? Forces?

Yes, those would be a good start.

RE: Doubt about steel

And maybe a hardness?
At least that you give you an approximation of what properties to look for.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Doubt about steel

(OP)
Dimensions

Width 30mm length 86mm thickness 0.3mm

Surface hardness is not important, the important thing is that it acts like a spring.

The bending force at its longitudinal ends is minimal, it has to be deformed allowing the passage of a notebook transported by a conveyor belt.

RE: Doubt about steel

For your case I suggest gravity, together with a hinge.

RE: Doubt about steel

(OP)
No, this part is necessary

RE: Doubt about steel

If the piece is fixed at one end and flexes, then strength is super important.
The strength has nothing to do with the force that it takes to flex, but it does determine how far it can flex before it becomes bent.
So to preserve the shape and springiness you need this to be heat treated correctly so that it is strong enough.
And in most steels the hardness correlates fairly well with strength.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Doubt about steel

(OP)
I've seen 40-50 HRC in some pages.also say that the original strap seems stainless (same surface appearance)

RE: Doubt about steel

From what I see here so far I think that you will not be able to properly quantify your requirements, select the right material and successfully design a spring-based device to press down on notebooks passing by on a conveyor.

I am assuming that gravity is in a useful direction for you.

So, instead of a rollers on a spring use rollers on a hinged flap. Have a simple way to add weight to the flap.

This way the users can tune the machine as needed by simply adding or removing weight.

RE: Doubt about steel

It seems to me that you've jumped automatically to a conclusion that ANY springy steel would be adequate, but you seemingly ignored the forces involved/required; a spring is modeled by F=-k*x, so what k do you need and how will that relate to the material selection?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Doubt about steel

(OP)
I don't know the strap constant. Being a sheet I don't know how it would be calculated.

What I know is that I have seen coiled leaf springs that have this steel. But I doubt if the C75S is supplied hardened or if it needs to be tempered to serve as a strip.

RE: Doubt about steel

Well, you ostensibly know, or can calculate, what force is applied, and you know, or can calculate, how much deflection occurs. But, that might be getting too far into the weeds, and might just be easier to get the plate assayed, which would allow you to figure which alloy(s) is might be and have someone fabricate another copy with the putative alloy

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Doubt about steel

We're talking s few dollars worth of material here. Maybe just grab a piece of hardened 1075 and give it a shot. Even give 1095 a run. It's more wear resistant and may perform better.

RE: Doubt about steel

(OP)
Exactly. It is a simple sheet with 6 holes. My question is whether I should put hardened C75S or simply C75S in the manufacturing drawing (I don't know if the C75S is supplied already hardened or should I say so)

I would also like to know if this steel is stainless or should it be coated. The original that is in the machine has the appearance of stainless.

RE: Doubt about steel

I didn't realize you had holes. You've added significant cost now. For already hardened material, C45-50 are pushing the limits of basic tools to drill. A water jet or laser would be best for mass production but the tool up costs will be several hundreds of dollars US minimum. You could probably make a single piece by sandwiching it between to sacrificial plates and drilling with a carbide tipped drill by hand.

Buying annealed and heat treating adds tool up costs again. Heat treatment isn't particularly expensive, a run usually costs a few hundred dollars but that costs is the same whether you're making one or a thousand.

RE: Doubt about steel

(OP)
Yes, but my question is... Should I indicate hardened C75S on the drawing? Because the C75S steel is supplied without heat treatment I suppose... Yes, the hardness is 40 to 50 HRC I think.

RE: Doubt about steel

You need to specify what you want. If your sending the material to a vendor to get punched, you will want to specify soft in the drawing. If you're sending it for water jet or laser you're going to want to specify spring temper. The part may have different drawings depending on what stage of production it is in.

RE: Doubt about steel

(OP)
I will make a manufacturing plan and the company's workshop left it to an external company that has laser cutting, etc.

That is, the plan must contain all the necessary annotations for its manufacture from the beginning.

I have also seen that if you bend the sheet a lot, it does not return to its original shape.

That is, it only recovers its shape if the deformation is small. If you exert a lot of force, it stays curved.

RE: Doubt about steel

(OP)
AISI 301 is stainless and I read that it would also work. Certain? This would be better because it is stainless. And as I said before, I think we should ask him to hold on to serve as a spring.

RE: Doubt about steel

301 stainless is not heat treatable and can only be work hardened to 41 HRC which is less than 1075. If you need more corrosion resistance than 1075, 420 stainless steel may be a good option.

RE: Doubt about steel

You can buy a lot of different SS alloy sheet to ASTM A666 and have it cold rolled to 3/4 or full hard for descent spring properties.
You will still need to waterjet or laser cut the holes.
Just see which SS you can get that hard.
It might be 301, or 304, or even a 201.
They will all have similar corrosion resistance.
The 200 alloys should cost less.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Doubt about steel

"I have also seen that if you bend the sheet a lot, it does not return to its original shape.
That is, it only recovers its shape if the deformation is small. If you exert a lot of force, it stays curved."

So you //almost// have some real, useful empirical clues about the loading the part must endure.

Like others said, from practically the first reply, understanding all of that stuff is necessary to make a good material choice.
Unless you have some parts that perform OK, and then you have the material analyzed, including yield strength, which cannot be directly derived from hardness.

RE: Doubt about steel

(OP)
I have verified that the foil is somewhat magnetic (I think the 301 can be magnetic when heat treated)

On the other hand, I attach a photo of the sheet. When I hold it in the center and apply a force of about 1kg, it later recovers its shape. Dimensions are 86mm long, 30mm wide and 0.3mm thick.

RE: Doubt about steel

300 series stainless steel can become magnetic after cold working. There is no heat treatment.

RE: Doubt about steel

Thanks TBE.
Yes, most autenitic SS grades will become magnetic when cold worked.
Some will become very magnetic.
The only HT for SS is solution anneal (Unless it is a PH or martensitic grade).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Doubt about steel

(OP)


I have seen the drawing of a sheet with the same spring function.

The flat steel says that it is the equivalent to 304 but I suppose that it will also have to be treated later so that it can serve as a spring in that flat spring.
I definitely think that the 301 4/4 or also called full hard will be valid.

I see that 304 can also be hardened and that both obtain the same hardness but for laser cutting 304 is better and resists oxidation more.

RE: Doubt about steel

(OP)
AISI 301 4/4 ┬┐Yes?

RE: Doubt about steel

You continue to randomly stab at different materials; THIS is not the way to do design. You need to come up with actual and numerical requirements, and then select the materials that fit the requirements.

And again, a material assay should be performed on the existing component.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Doubt about steel

(OP)
I don't know how to do those calculations, I only know the dimensions and the approximate strength (I put it before)

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