Shotpeen residue removal 3

[vipereyes]

Hello all,

We manufacture springs and a couple of our jobs require shotpeening. The parts are made from Oil Tempered Chrome Silicon wire. We send the parts through a spray wash cabinet followed by a heated air dry after shotpeening but some shot residue remains and is causing us to fail sediment testing for both particle size and total weight.

Does anyone have any experience with post shotpeen cleaning to remove residue that hides in pockets and crevices?

Thanks in advance for any help you can provide,

Kim

 

[cloa]

You should detail the troublesome springs and treatment programme to get a good answer.

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[swall]

You didn't say how big the springs are, but I have used ultrasonic cleaning on master cylinder springs to remove the shot peen debris.

 

[vipereyes]

Hi swall,

They are fairly big as springs go. Approximately 7" long by 2.5" diameter.

We were wondering if an ultrasonic would loosen and remove the residue. Now we know it should. We are looking to order a small unit to try it out. If we use one for our production requirements I think it might be cost prohibitive? We have never priced a large system before.

 

[EdStainless]

How about a vibratory (bowl) unit, there is very gentle media available and you can run them wet to rinse and flush away residue.

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P.E. Metallurgy, Plymouth Tube

 

[TVP]

What type of shot peening media are you using? Cast shot or cut wire? If it is cast shot, switch to cut wire. Ultrasonic cleaning will definitely remove surface contamination.

 

[vipereyes]

Thanks all.

EdStainless, we use vib bowls for many other applications here but for this application we need an inline system, not a batch type system. The cleaning station is incorporated into the manufacturing cell and we would need more than one large vibs to keep up with the production requirements.

TVP - we use cast shot and I will have to ask about the possibility of using cut wire. The shot is used to remove residual stress of the steel and the type of shot may be a customer requirement.

 

[AidanMc]

The shot is used to remove residual stress

I'm obviously unfamiliar with your process but I don't believe I've ever seen shotpeening used to remove stress. As it has shot impacting the surface you are typically attempting to impart a compressive residual stress. This compressive stress is beneficial in terms of fatigue life as it will help to keep cracks from forming on the surface.

Aidan McAllister
Metallurgical Engineer

 

[berkshire]

If this is a continuous line operation , can you add a CO2 pellet operation behind the shot blast to remove the remaining residue.
One of the beauties of dry Ice pellet blasting is that there is no cleanup required after the fact.
B.E.

You are judged not by what you know, but by what you can do.

 

[vipereyes]

Aidan,

You are correct about the shotpeen process. I did not describe it correctly. Thanks.

Berkshire, dry ice blasting is something we have discussed for many different applications here. For this particular job it was dismissed due to footprint constraints but I would love to see what it could do for some of our other cleaning projects.

 

[WKTaylor]

Guys... note...

Springs are generally formed from material tempered to a very high hardness, IE: 'spring-temper' which includes heat treatment followed by high-strain hardening. Peening should both induce compressive stresses in the surface and 'wash-out' minor surface imperfections that could be embedded stress-risers.

Due to the high hardness spring temper material, cast-steel or steel balls or cut-wire steel shot MUST have high surface hardness, 55-to-62 HRc[example: AMS2431/2, /5, /8]... not regular hardness 45-to-52 HRc. High hardness shot 'should' make it easier to minimize or eliminate surface residue/contamination on high-hardness parts.

NOTE.
For even deeper peening effects with minimal residues, laser-shock peening [example: AMS2546] is beginning to make in-roads in aerospace.

Regards, Wil Taylor

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