Using vibration to control stress during martempering 6

[Greenleader]

We know you can use sub to low sonic waves to relive stresses in carbon, alloy steel cased by machining, welding etc.

When martempering, (marquenching), carbon alloy steels, is it possible to use the same vibrational frequencies that reduce stress, to reduce the built in stresses caused by the transformation of austenite to martensite? Could vibration be used to reduce retained austenite during martempering?
Metastable austenite is very plastic. It seems you could take advantage of this state and manipulate crystal formation with sound waves.
Any studies out there? I can not seem to find any myself. Thanks

 

[Greenleader]

You need to understand that you don't understand. I am not in a position to explain our process in any detail that would satisfy. It was discovered as a "byproduct" of a process that has nothing to do with VSR. The machine was custom made for a certain part.One of a kind that produced one of a kind conditions. We had a rather large batch of forgings that the vendor took a shortcut on. After years of producing good parts, suddenly my department was accused of damaging high cost machined forgings. Process A. Process B had similar warping show up after processing in their shop.Process B produces no vibrations. I had an idea for a test and since heat lots and dimensions are carefully recorded as the norm, it was easy to accurately control an experiment. I had everything CMM'd before and after. I had been masking part of the component in question. I unmasked it and processed normally.

Long story short, the vendor was putting unnecessary strain in the forgings and showing up consistently in process A and B. Especially A. Tons of testing later they concluded that, no my process has no negative effect on parts and the unique conditions somehow relived certain strains. There is a low amount of heat involved, but very low.

MR&D did lots of testing, flying to this country and that country etc. They came up with their own conclusions. They gathered enough to write a future spec to relieve stress or strain what ever you wish to call it, using very low intensity/frequency vibrations in conjunction with process B.

In the meantime, I kind of took your comments personally. We do not build faulty products. We really don't care about the debate about VSR. We often times take off the shelf processes and "make them our own" so to speak. It's a tradition we are proud of.

In a few days, I will celebrate 20 years with the company. I am considered a newcomer, in the shop anyway. You can see why I got a little hot. Especially when my original question really had nothing to do with VSR. I admit I was naive about VSR and had no idea of the debate going on outside.
What I really wanted, was to know if ultra sound, low freq. sound, any kind of sound waves could help austenite crystals "slip" into martensite crystals when carbon alloy steel is in metastable austenite during marquench. They use sound waves to refine grain in solidifying aluminum, and wondered if something similar could work for steel.

http://www.tms.org/pubs/journals/JOM/9802/Vives/

If you don't mind, I would like to bow out of anymore discussion about VSR, as I am not a metallurgist, and am bound by non disclosure. Hopefully I haven't got my tit in the wringer already.

 

[unclesyd]

Understand been there and done that. No problem.

Again no reflection on the information in your post, in fact it was intriguing and something that I was going to look into as I’ve seen a little information on warming a material prior to forming. As for a low level of heat affecting a part we have a large SS rotating element that if allowed to be heated by the sun and rolled 180° and heated again it achieves a degree of RT stability, measured by TIR, that we had never seen before. This was a serendipitous discovery as I understand yours is. Serendipitous discoveries are usually made by a very observant person with a practical and analytic mentality. The old “How Come?”.

Having worked with a large complex legacy process and the let's do it like grandpa did, don't rock the boat, put it back to OEM conditions attitude, I hope you achieve your Eureka moment as they are few and far between these days.

If you get to complete your investigations and are able to publish anything please let the Forum
know. As if you have probably noticed there is always a question on the stability of metals in one form or the other.

We tried VSR several times in it’s infancy and got absolutely no verifiable results on some pretty controlled tests. The current project that I’m involved with could use such a procedure if there convincing proof it would work.

 

[nematic]

A couple years ago it was found that VSR effects were dramatically increased with applied heat. This approach was subsequently patented and a company formed. See

http://www.acceledyne.com/

for some limited information.

 

[bklauba]

To help clarify some of the issues, I have posted the paper published by the ASM on the web:

http://www.msnusers.com/VSRUsersResearch

then click on Documents, and open the ASM 04-2005.pdf.

Much of the research cited by mtnengr is also cited in this paper, especially note the work of Dawson & Moffat. The most distinctive aspect of their work was their success in relieving 90% of the residual stresses in numerous samples of three different alloys.

What we consider to be an extension/continuation of this work is that of Walker, Waddell and Johnston (also cited in the paper), in which they showed that stress relieving by vibration can be achieved at load levels significantly lower than previously thought. They offer this as a likely explanation of the failure (at least thus far) to find real-life examples of workpieces that have suffered fatigue damage from vibratory stress relief. In our efforts to find some (the survey of users of vibratory stress is summarized at the end of the paper), we only were able find users who reported reduced incidents of cracking, which they attribute to using vibratory stress relieving. One user of the method does so for purely to minimize fatigue damage that otherwise occurs to their products (vibratory screening systems) during use.

We also continue to get feedback from users who have switched to using vibratory stress relief, due to quality improvement, i.e., specifically, tighter achieved dimensional accuracy, on their stream of precision production components. This is true not only of 300 series stainless steel fabs (which respond marginally to PWHT, due to their robust high-temperature strength), or lo-C, high-strength steels, which manufacturers are reluctant to PWHT, but mild steel fabrications. Much of this improvement might well be due to the ease of performing a vibration treatment both before and after rough machining.

As nematic's posting shows, vibratory stress relief appears to fall into the catergory of "working in practice, but not in theory". A number of us are busy crafting new theory, to help explain the practice.

bklauba

 

[IdealME]

Gentlemen,
I've been researching VSR for use in MFG. We currently own a unit that we've been using for 15 years. We use it during welding and with reasonable results. We are trying to use it for VSR of machining shaft stresses. Is there any suggests on how we can be successful with this method?

 

[bklauba]

You should start a new thread on this subject, rather than "piggyback" on this one, both for your benefit in getting answers directed at your specific questions, and sharing the discussion with the community.

When you start your thread, perhaps you can supply details, such as materials, sizes and tolerances.

BK