Vibrations to relieve welding stress 1

[koeskoes]

Happy new year,

Have you heard of a process that uses a vibrator to vibrate the workpiece while it is being welded to relieve the welding stress to reduce/prevent warping?

Does it work? What are the equipments needed? How do you set it up? What are the limitations?

I am welding a 3/8" thick x 4" diameter tube (coupling) onto a 12" x 12" x 1/8" plate.

I want to reduce/eliminate the warping of the plate.


Thank you

Koes2

 

[bklauba]

We are a builder of vibratory stress relief systems, which we recommend be used as a post-weld or mid-term machining means of rendering precision components dimensionally stable. This equipment (and also that made by our competitors, who are great aspousers of vibration during welding) is also used by our customers to minimize welding distortion. It is most commonly used in situations where very high shrink occurs, such as with stainless, aluminum, or other metals that tend to distort more than mild steel during welding. We also have heard from shops that perform weld repairs, esp. on castings, which are quite tricky to weld-repair, that they see benefits from this method. Let's make a distinction between vibratory stress relief (VSR), which is the post-weld method of enhancing dimensional stability, and vibration during welding (VDW), which is what your question is about.

We have NOT found welding during vibration to be either a very predictable or repeatable process, based on feedback from both our customers and those of our competitors. We do not believe that a parameter or group of parameters have been identified which allow adjustment of aspects of the vibration, such as vibrator speed, vibrator unbalance, etc. One frequent comment/complaint we do get from those who do biz with our competitors is the disappointing results they obtained from efforts to use VDW. Thus, we do not recommend VDW, and we do not raise the subject in our lit or support material.

That being said, I have seen some interesting demonstrations that would indicate that there might be some positive effect from VDW. If have seen a plasma cutter used to cut a 24 inch wide, 8 foot long, 1" thick mild steel plate down the middle, lengthwise, resulting in two pieces slightly less than 12" wide. The cut widens and separates, due to shrinkage of the material, as the cutting head moves down the length of the plate.

If the plate is vibrated gently (a vibrator with adjustable unbalance up to 3 in-lbs, adjusted to 20%, and turning at 2500 RPM, with the AOR [axis of rotation] aligned with the length of the plate), the separation, which one could liken, or consider analogous, to some degree with welding distortion, was reduced by more than 75%.

To perform mere VDW, a full blown vibratory stress relief system is NOT needed. Indeed, a better choice from an equipment reliability standpoint, rather than using an electric vibrator, might well be a pneumatic vibrator, condsidering the heat the vibrator might be subjected to. Speed control can be done with control of the air supply.

What material are you welding, how much distortion are you suffering, and what target distortion level do you hope to achieve?? There might well be other means, or a combination of methods available, such as pre-heat (I do not claim to be a welding expert) that would solve your problem.

BK

 

[swall]

koeskoes--do a site search. There have been a number of threads on this topic.

 

[BTIGUY]

Hi Koes2,

I work for a company that specializes in using sub-harmonic vibrations during welding. We have been doing this since early 1970's on various metals including most steel alloys, stainless steels, aluminums and exotic metals too. My father actually was the one who developed the process. According to NASA and General Motors this "sub-harmonic" vsr process is very reliable. That's why both NASA and GM use it regularly on such things as the nose cones to the space shuttles, space station life boat mounts, shuttle landing gears, and engine cradles. Add to this the JBD's for the Navy (jet blast deflectors) and the howitzer bases for the Army, all using this sub-harmonic process during welding, and you get a clear picture. This is a very reliable process. The violent resonant vsr can't be used during welding. It would be counterproductive on weld quality.

For 36 other examples of using this sub-harmonic process "during welding" on many metals I suggest checking out

http://www.meta-lax.com.

Then go to the Photo Gallery section - pages 2, 7 and 10.

As far as for your application, it sounds mainline to me. So I expect that you will prevent at least 50% of your normal weld distortion from occurring, perhaps more. If that kind of distortion control is to your liking how about contacting me through the website mentioned above. Oh yes, to maximize weld distortion control you will need to alter the welding parameters a bit. We'll talk about that later.

BTIGuy