Welding castings

[johnna]

Hi folks, I am exploring the notion of welding two cut down gear box bellhousings to one another in order to change the engine in a classic car.

I'd look to use my big meaty arc welder. I've searched for info upon cast welding and NI rods are recommended, but so is preheating with dissimilar rods...

Can castings be welded for high torque/ anti-shear applications? Which route is the best route?

What are dissimilar rods?

Thanks in advance.

 

[Drains]

309's are dissimilar rods, usually for m/s to s/s. High nickel. Nicrex is one type, made by Murex. Also 307's 308's 312's

You can get various rods for cast, including machinable/ cold welding etc etc. Allsorts in fact. Any recommended should work if you do it right. Re heating, whatever you're using, take the edge off the cold. Minimum 20 degrees on a cold rod, and whatever's recommended for a pre heat rod.

You will need to weld short lengths (20-25mm) and leave to cool. Do this leaving gaps, then fill in the gaps. You'll spread the heat evenly over the job that way.You may also need to pein the weld after welding, to remove stresses.

More info will come, maybe from Snowcat and Technic Al

 

[Woody.v8]

I would not like to put you off nor underestimate your abilities but this sort of job is susceptible to quite a lot of torque and stress so would be a shame to ruin a project through the "learning curve"
May be some one local could weld it if you did the prep??

 

[matt1978]

I have to admit Castings is not something I have had much experience of.

All of what Simon said (Insert own joke there) is correct, there is also a method of Buttering the faces of the castings to be joined, you use a certain rod (High Nickel content I think) and weld over the faces and then use another rod to make the actual join.

Hopefully some of the other guys who have more experience of this will comment

 

[johnna]

Thanks chaps, all of that makes sense to me. I have plenty bits of casting to practise upon prior to having a go at the actual piece.

So in essence, I should mate up the faces, butter them with a high nickel content rod, then weld short sections with, no more than an inch at a time then tickkle them with a few hammer taps.

I know I have simplified it horribly, but are those the basic principles?

Also, do I assume correctly that there will be different flow or pool characteristics to the weld?

 

[johnna]

I would not like to put you off nor underestimate your abilities but this sort of job is susceptible to quite a lot of torque and stress so would be a shame to ruin a project through the "learning curve"
May be some one local could weld it if you did the prep??

Whilst I'd rather not farm the jobs out, if the price is right I will do!

 

[Woody.v8]

OK then v prep both sides of joint and a slight preheat will help penetration and stop haz cracks, weld hit and miss like simon said id use a hi NI rod like a dissimilar rod (i use casolin eutectic myself) but the chose is up to you and allow to cool slowly

 

[johnna]

Excellent advice, cheers fella!

 

[snowcat]

That is a hell of a job to undertake, A machinable solution with dowels or a LCMS adapter plate would be my much preferred method, Vibration and fluctuations in temperature and possible oil ingress on the original castings are not going help....

Now I'm assuming its a Grey cast welding????

There are many true Cast rods on the market which have an iron content along with the Nickel, and copper alloys which help with the high carbon content, (All of these specialist rods are animals to use and require much adjustment of seatings technique etc etc to get to work)

OK if I was going to do the job, Id V prep out to a decent grove, pre heat to around 300 degrees, invest in some temperature sticks, 314 dissimilar to butter the first joint small rooting rod, peen and DE-slag, go in with 2 passes larger specialist cast rod, Nickel-Iron.....

Once hot keep it hot work the job quickly then once done, try and keep it warm, even if its just left in front of a space heater or something to allow it to cool slowly.......

again preheat slow, cool slow, but work fast.....

This is a very specialist weld, and Id really recommend an alternative method, especially if this is the first experience of cast work.......but if you do have a go good luck...

Anything to add TA???

 

[snowcat]

Oh and just to add, IMHO I wouldn't work in short bursts I find with MMA its far better to hit the job and keep it running (once Upto temp of course) The cracking is most likely to occur of the initial stages of heating or welding not once every things hot....

Also theres a way of running stringers in instead of preheating, never done it myself, but someone out there might of and knows if it works........

You also want to keep the weld pool to a minimum, It will simply dilute the parent material and cause cracking.

 

[runnach]

Big problem with cast is the cooling down, ideally a slow post cooling process be put in place if possible, what Simon stated is correct, called "cold welding" with the peening to boot, can be a very difficult job without the proper post heat. can be more miss than hit, dont mean to burst your bubble, you state you have plenty of practice pieces at hand, go for this first and, good luck.

Cheers........

 

[snowcat]

Big problem with cast is the cooling down, ideally a slow post cooling process be put in place if possible, what Simon stated is correct, called "cold welding" with the peening to boot, can be a very difficult job without the proper post heat. can be more miss than hit, dont mean to burst your bubble, you state you have plenty of practice pieces at hand, go for this first and, good luck.

Cheers........

Agree 100%, Its faily easy to control the preheating and welding tempretures but the cooling process????, blankets etc all very hit and miss...

 

[piman]

Hello Johnna,

if you are doing what I think you are doing, the feasibility of a sound weld is the least of your problems. I'm assuming that you are trying to adapt a gearbox to fit an engine that it was not originally fitted to? If so the alignment will be extremely difficult to get anywhere near true. The usual way to adapt a non standard gearbox is to make a special back plate for the engine.

Alec

 

[johnna]

Thanks Piman, that is another option.
Please bear with me whilst I meander off topic...

I have been gifted a 1969 MGBGT and I have a 2 litre Zetec engine to fit. I'm not a fan of the Ford type 9 gearbox, so am contemplating using the original MG gearbox. An Mt 75 or even a type 3 four speed would be a different matter.

The B series engine that I shall be removing has a detachable back plate that I should be able to drill to suit the ford engine and even to cant it to allow clearance for the inlet manifold and oil filter within the engine bay.

The MG box has an integral bell housing, whereas a lot of ford boxes have detachable bell housings. I have a spare bell housing from a type nine.

So, effectively I am covering all bases in depth before committing to a course of action.

Thanks to all for their feedback!

 

[mart]

Have a look here Johnna-it looks like Paul Daniels has helped out-brilliant stuff-a lot of patience.

http://www.mig-welding.co.uk/cast-iron.htm

 

[aametalmaster]

This is the rod i use.
http://www.crownalloys.com/page10.pdf
Preheating is not required for cast with this rod and it has a soft arc and will weld steel to cast iron. The rod is fully machinable and the weld has no hard spots in it. Here is a tractor part i fixed a few weeks ago that had a 1/4" inch gouge gut in to it. The part had to be watertight after welding because it was the radiator base. No probems welding or now with it. Don't just grab any SS rod because thats the way to do it on cast iron look at all your options. I see lots of failed welds and parts because everyone wants to lay down some SS...Bob

 

[snowcat]

Bob,

Its a fine repair, BUT, Like all cast repairs I do,it is not a major structural part, like the part Johnna is intending to weld , a 314 is fine to butter with (a dissimilar rather than a straight S/S rod) an iron nickel rod then to fill........I have welded cast cold and peened, BUT this is such a major part, that a full procedure should be followed if undertaken.....preheating surely a must to avoid stress cracking........followed by slow cooling

Personally I would not weld this casting, having a gearbox housing brake away a 70mph does not bear thinking about, I hope you can appreciate why I have pushed the poster away from the job, and been such a stickler for correct welding disaplins.....

 

[malcolm]

I'd not weld a cast bellhousing structure. Most people use adapter plates, maybe modify the input shaft to suit the length. Failing that occasionally I've seen development bellhousings fabricated very accurately from mild steel. Much more predictable than cast.

Even more definately wouldn't braze it together either.

 

[aametalmaster]

Bob,

Its a fine repair, BUT, Like all cast repairs I do,it is not a major structural part, like the part Johnna is intending to weld , a 314 is fine to butter with (a dissimilar rather than a straight S/S rod) an iron nickel rod then to fill........I have welded cast cold and peened, BUT this is such a major part, that a full procedure should be followed if undertaken.....preheating surely a must to avoid stress cracking........followed by slow cooling

Personally I would not weld this casting, having a gearbox housing brake away a 70mph does not bear thinking about, I hope you can appreciate why I have pushed the poster away from the job, and been such a stickler for correct welding disaplins.....

Agreed, an adaptor for the trans would be much better...Bob

 

[johnna]

Thanks to all who have contributed.
Upon reflection the job will be beyond me, as I can't say that I can control the cooling sufficiently to protect against stress weaknesses after the weld cools.
As I stated earlier, this is one of a few approaches I was considering.