Advise needed for welding the axle pin to the stub axle please

[eagle1903]

Dear Friends,

I would like to weld the pin to the stub axle once the pin is interference fitted to the stub axle.

Pin goes into the bore with 0.045 mm interference. I can freeze the pin in liquid nitrogen and oven heat the stub axle to 150 Celcius and it drops in. But the pin has to be welded at the back side as I tried to show the area which it will be mig welded.

The pin is 4340 ( EN24 ) and the stub is forged 4140.

I would be grateful if you could advise the voltage, parameters and the required mig wire for this weld please.

Also, would it be a logical way of checking the penetration in the test part. I can cut couple of samples but I am not sure if it will reveal the penetration that we are looking for.

As some of you might recognize the part, it is an Escort front stub axle and this is a typical modification in order to have a stronger axle pin in the rallying field.

Regards

kerem

 

[hotponyshoes]

What's the upright made from?
Looks like it might be cast?

 

[brightspark]

What's the upright made from?
Looks like it might be cast?

be cast steel . we used to shorten the steering arms on the stockcar and weld them back together

 

[eagle1903]

What's the upright made from?
Looks like it might be cast?

It is 4140 stell forged into its form with a heavy forging press. Finished part is originally like this but when the pin gets tired we machine off the pin and install a new pin.

 

[eagle1903]

be cast steel . we used to shorten the steering arms on the stockcar and weld them back together

It is hot forged into its final form then machined. In a way same as the steering arms but steer arms use different steel, 36Mn5.

 

[hotponyshoes]

That should weld up fine then.
If it was a trailer stub axel or something on a lorry I would be running a 4mm stick around it at about 180a.

If you want to test for penetration properly cut one in half and etch it. Or less destructive, grind an area of the weld flat then drill in that area over the join and see how deep you go before you hit the line.
Countersink the drill hole and back fill it if you want to use the test part.

 

[tigdlo]

What is the heat treatment of both parts? how will the heat of welding affect the heat treat?

Maybe make new stub axles with a flange and machine a counterbore in the rear of the upright, loctite and press it in from the rear?

 

[eagle1903]

What is the heat treatment of both parts? how will the heat of welding affect the heat treat?

Maybe make new stub axles with a flange and machine a counterbore in the rear of the upright, loctite and press it in from the rear?

View attachment 338205

I do not know the heat treatment process but once the upright hot forged it goes to heat treatment then it gets machined. The upright and the stub axle as a single part as you may see in the below photos. It is manufactured in a factory which forges and machines for defence industry and supplied to motorsport market since 20 years. It is a well proven part as a complete unit. But in its life time it gets tired and the stub axle part cut, the upright bored to accept a new stub axle. The replacement stub axle that I got made in Finland and it is 4043 ( I think that is En24 ) and I believe it doesn’t get an additional heat treatment.
This stub axle replacement procedure is a common practice for tired upright/stub axle ( as they are originally one piece ) the way I am planning to do but I do not know the correct mig wire ( although I think it is SG2 or SG3 ) and I also do not know welding parameters.
Regarding the welding, the tube ( st44 or st52 ) which the Blistein insert works in also welded to the upright as well to make a complete the complete McPherson strut.

 

[Melvyn Best]

As already suggested , a stub axle with a flange would eliminate any need for welding . Peugeot/Citroen rear stub axles are pressed in and never cause any problems

 

[eagle1903]

As already suggested , a stub axle with a flange would eliminate any need for welding . Peugeot/Citroen rear stub axles are pressed in and never cause any problems

After the advise I understood it can be a good solution although I haven’t seen on Escort before. But the reason I haven’t seen is because %90 the strut tubes already in place and people just want to replace the stub axle. But since I already have an access to the blanks, this may be good idea. The only problem is I already have 5 sets of stubs already bought

if I try to get the stub axle done locally, do you think that EN24 will be good enough as it comes heat treated afaik.

Regarding the pressing interference fit, do you think that my 0.045 mm is good ?

But, if I opt for the welding for already tubed struts, my original post regarding the welding parameters still valid.