Heat Treating Torsen Splines

[Glenn]

We just got our torsen ouput splines. They are made of 4340!? We are planning on welding them to mild steel cv couplings and are not sure what type of filler rods to use? Has anyone done anything similar.

Also, when it comes to heat treating, how do you do this? Does it not soften the splined end?

[Glenn]

We just got our torsen ouput splines. They are made of 4340!? We are planning on welding them to mild steel cv couplings and are not sure what type of filler rods to use? Has anyone done anything similar.

Also, when it comes to heat treating, how do you do this? Does it not soften the splined end?

[Garbo]

We have tried similar things in the pat and would counsel against it. I'm not 100% on the rod but I think it was the same filler we used on the 4130 frame. The axles broke, the stub shafts welded in the same manner didn't.

This year, our stub shafts are machined and hardened 4340. I think some other people have tried welding these prts with mixed success.

G

[Denny Trimble]

We do this. I can't remember what filler rod we use, but it's also important to "v-out" the weld area as deeply as you can, to allow for a full penetration weld, and to pre-heat the parts to about 400F before welding.

[Kirk Feldkamp]

We do that and there hasn't been any problems. Everyone I talked to suggested that we use 308 filler because we didn't know exactly what the cast CV flange was made out of (some sort of cast steel flange). The stainless filler is a good mate between two dissimilar metals because it can flex a little without cracking. This is especially important as the weld is cooling. I also agree with Denny that you should "V" the joint so you can get full penetration, and build up the joint if needed. Another thing I tend to do when there is a shaft like that is to crossdrill the outer piece (2 or 4 holes) so you can get some weld into the side of the inner piece. If there is a lot of metal in the area acting as a heat sink, I also don't tend to shy away from the heat. Get it hot so the weld can penetrate. Oh yeah, preheat too!!! Any annealing can be reversed with the heat treatment. The only reason we go with this method is that, at the time, we didn't have the time or money to machine up the whole thing.

With the heat treatment I was worried the whole assembly would twist or crack. It didn't happen to us, but it's really up to how you plan on attaching the axle to the flange. We ended up pressing the axle into the flange and then welding that.

-Kirk
UC Berkeley

[alfordda]

We have done this for a few years, with only a few problems. One time we had the wrong material for the splines and another time we had weld penetration issues. We also had some alignment issues. Our process went something like this.

V-out the area to be welded, assemble parts in fixture, pre-heat to something like 400F, use lots of heat with ER70S-2 filler. If you've got the room the rosette welds that turbotwig suggests would be good too. For heat treating, we have tried oil and water quenching, both have worked when done properly. I want to say that we heat the part to 1500F and then swirl the part around in the quenching liquid. You don't want the liquid near the part to boil and essentially change your quenching fluid to air. We have caught the oil on fire a couple of times, so you may want to have a fire extinguisher handy.

[Garbo]

Definately vee out the weld area as deep as possible... we got a good vee on the art that didn't fail... not so good on the part that did fail.

We also tried the rosette (I call them plug) welds on the part that failed (no room for a big vee)> I got into a fight with the guys doing it because they refused to pre-heat. On the part that failed, I think that the crack initiated at a stress raiser in the weld. Also, because of the lack of pre heat, the fusion to the inner piece was poor on the plug welds.

If I had to do it again, I would be sure to pre-heat and not use the plug welds. We have been running without the plug welds on that car (remade the axles) for two years without further problems.

Incidentally, how do people who make the splines do it? Ours were about 3 days start to finish from 4340. The splines were cut using a butchered threading tool adapted to the mill and ground to the correct angle. There is good contact and no backlash in the joints.

Cheers
g

[alfordda]

http://www.eng.uc.edu/studorg/sae/fsae/pictures02-03/030302.jpg

Thats not a great picture, but that is how we do it. It takes 8 full hours after you get the tool ground properly to cut one axle. What you cant see off to the right is an indexing type of thing that rotates the axle. I'll see if I can find a better picture.

[Frank]

its interesting how "unstraight" a spline gets when you weld near it, or heat treat it