Cheap, Ferrous Spring Steel?

[Cam06]

I'm a Mechanical Engineer but I figured I'd get a quicker answer here..

I'm designing something where the spring steel will serve as the paddle on a pressure switch, and it will trigger an inductive sensor. For the sensor to work, the target material must be ferrous metal.

what is a cheap, highly ferrous spring steel?

 

[ornerynorsk]

Any corrosion resistance or other properties that would eliminate certain choices? Many plain carbon steels can be made into springs easily and cheaply.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[Cam06]

I suppose resistance to acid would be good...but not necessary if it drives up the cost too much.

>Many plain carbon steels can be made into springs easily and cheaply.

I am keeping this as a flat piece of steel riveted to a frame, a substance will move a diaphragm that will push in on the spring steel paddle, thus moving into range of the sensor. Sensor will shut off a motor, substance will deplete allowing the spring steel to spring back away from sensor and allow the motor to stay on.

So I'm not actually creating a coil spring. Not sure if that's what you were implying by that sentence or not, but I thought I'd clarify.

 

[SwinnyGG]

If you can find non-ferrous spring steel I'll be impressed

All jokes aside, this doesn't sound like a very demanding application. Go to McMaster or whatever MRO you typically use, and order some spring steel. Unless you're going to deep dive into your actual design in this thread, including fatigue life, there's not much more detailed information any of us can provide.

 

[WKTaylor]

Take a look at...

ASTM A682 Standard Specification for Steel, Strip, High-Carbon, Cold-Rolled, Spring Quality, General Requirements for
------------
NOW, just to be clear...

WHY, explicitly, does the spring have to be ferrous within an electrical component...? Need magnetic properties for a 'non-contact proximity sensor'?

Are You intending to 'blank/stamp-out' the part from 'thin strip' material?

A thin/small carbon-steel leaf-spring will have-to-have a very high quality mechanical finish on all surfaces and edges [radius/polish edges to eliminate shear-blanking burrs] to avoid cracking if a high-# of open-close cycles are expected.

With rare exceptions You will have to apply a finish to the steel spring to mitigate corrosion... which could induce premature cracking... even if it is just 'blackened/oiled' or flash-plated.

There ARE magnetic CRES and [non-magnetic] nonferrous spring materials which are more commonly used within EE-assys... they won't work because...?

Regards, Wil Taylor

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[Tmoose]

https://contentinfo.autozone.com/znetcs/product-info/en/US/grn/25341/image/3/

3 US bux.
A variety of thicknesses, since you have not said what spring rate, maximum force and maximum deflection you require.
Trim-able with good quality snips.

When you determine the thickness you need, the leafs/blades are avalable individually.
If the stress at max deflection is not too high, mild steel would work too.