Friction welding

[artist334]

Hi

I did some testing to figure out if friction welding stainless steel valve stems
would be possible at home. First I tried to do this with some scrap materials on lathe but I could not get a good joints. Also the tailstock was not really up to the task. For the next try I bough some 4mm stainless steel rod. (not sure which alloy) I set up the pieces on a milling machine as shown in the picture.

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This proved to be a quit easy and quick method. It would take maybe 5 seconds to heat the joint to glowing orange, aligning was easy and the pressure needed to heat the material was not excessive, maybe something similar to used with 10-12mm twist drills on steel.

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It took three tries to get a good weld. At least I am not able to break the one shown in picture without tools. With every try I heated and pushed the pieces to each other a bit more.

I still need to do some more destructive testing to see if I can get the process to be repeatable and to figure out how much strain these welds will take.

Henri

 

[artist334]

First complete valve made with this technique. Again it took three trys to get a holding joint. The other ones would weld but they cracked while bending. This one could take some visible bending of the stem but I am not sure how much it could take. The steel build up around the weld was easy to machine away but it felt that the steel had hardened to some degree. This may well be the reason for brittle welds as well.

The head diameter is 24mm and overall length is around 62mm (If this was to be used I would cut the stem to length after welding and machine a grove for retainer ring.

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It sure would be nice to get this technique to work well as the method is very quick and accurate compared to machining from billet.

Henri

 

[stevehuckss396]

I am interested to see if the valve holds up. I would love to make valves this way if you can perfect the method.

 

[Entropy455]

You need to shield the weld with an inert gas. You cannot weld stainless without some sort of shielding, or you'll get black and very brittle oxidation.

You might try placing a can around the work-piece, and flooding it with argon during the friction-weld.

 

[artist334]

I will try that if I make further experiments I was led to doing this how I do by some videos on friction welding where I didnt see anything related to inert gas. Do you know if inert gas is needed on mild steel while friction welding?

Also I believe that some of that brittleness was caused due to the rotated part not stopping quick enough. For the complete valve shown in picture I used a slower RPM so that there would be less rotating while cooling.

Henri

 

[Entropy455]

Do you know if inert gas is needed on mild steel while friction welding?

Mild steel will also imbrittle and crack if welded without shielding from the atmosphere. The effects are not nearly as pronounced as with stainless steel. That being said - you “might” be able to get away with no shielding on the mild steel – but I wouldn’t try it.

I recommend getting a low-cost TIG welder (DC only machine). You can easily weld a 300 series stainless steel valve stem & head together, using 100% argon shielding gas – resulting in a clean weld with no oxidation.

 

[artist334]

Ok thanks. So pretty much everything involved with any normal welding method seem to count in this also. I am fond to this method as it is so accurate, but I guess TIG will be just as accurate if a good fixture is made.