Thread: Welding Question

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I cut the AIR tubes off of a pair of '81 Corvette stock shorty headers and need to close up the holes. The tubes protrude inside the header tubes about 1/2" and I didn't remove that part yet. I'll leave it until I get the holes welded shut. These header tubes are cast stainless and the AIR tubes are also stainless. They are going on my '69 truck.

What's the best way to weld them up?

Mig with stainless wire? How thick?

Stick welder with a small diameter rod?

Take them to a pro and write a check?

Thanks for the help.

Tom

Cast iron is a most common metal in industry because of its simplicity of manufacture. It can be cast with only a gas furnace whereas steel, having a higher melting point, requires an electric furnace for casting. Cast iron can be machined easier and at higher speeds than steel. This metal alloy is readily and economically manufactured into useful machinery because of its low melting point, fluidity, and simplicity of melting.
Cast iron is manufactured from an endless number of formulae. A great deal of scrap iron of unknown analysis is used in manufacturing cast iron. Most cast iron contains in addition to iron and carbon, silicon, manganese, sulphur, and phosphorous.

The main difference between steel and cast iron is its carbon content. Mild steel contains less than 0.30% carbon, and most high carbon steel contain less than 1.0% carbon. The maximum carbon that can be put into steel is 1.7% as this is the maximum carbon that can be absorbed in solution with iron. When larger amounts of carbon are combined with iron, the carbon not absorbed by the iron is present in the form of small flakes of graphite. Grey iron contains up to 4.5% carbon, usually between 3.0% and 4.0%.

When cast iron is heated, at a temperature near its melting point, practically all of the carbon goes into solution with the iron in a combined form of iron carbide. If the cast iron is allowed to cool very slowly nearly all of the carbon will pass out of the combined state and segregate as free flakes of graphite. If the iron is cooled rapidly a large portion of the carbon will remain combined with the iron as iron carbide.

It is this high carbon content that makes cast iron so different from steel. If we could remove the graphite flakes from cast iron and squeeze what is left together, we would have steel.

The factor of the two forms in which the carbon can exist in cast iron requires major attention in welding. If the cast iron (or parts of it) is melted and then cools slowly, the weld and the base metal will be soft and machinable. If cast iron is melted during welding and cooled rapidly, the cast iron, or at least areas of it, will be hard and difficult if not impossible to machine. This is what causes the condition of "hard-spots" in cast iron welds.

Because cast iron has the flake-graphite structure which prevents it from bending and causes it to have no elongation, it breaks readily. It is a common event in factories, construction companies, farms, and all other industries for cast iron machinery to fracture. Often a costly casting breaks simply from vibration. Costly downtime from mishap with cast iron machinery is common in industry. Also, because cast iron is soft, it often wears. For example in threaded holes, the threads wear or strip easily. No one can estimate the loss to industry by breakage of automobile and truck motor blocks, exhaust manifolds, transmission housings, and in factories of such indispensable machines such as pump housings, punch presses, electric motor housings and the myriad of other cast iron machinery components.

When a cast iron part breaks, the cost is enormous to almost any industry. It is impossible for an industry to carry spare castings in their store room. Often the machinery is old and obsolete and the manufacturer cannot provide a spare. To make a new casting usually involves making a pattern first. This can take up to four weeks just to make a pattern and often the pattern can cost thousands of dollars.

It is for these reasons that industry must be well prepared with Magna Maintenance Welding Electrodes and Alloys, to enable quick restoration of the broken machinery to useful service.

Many engineers who have encountered repeated failures in attempts to repair cast iron with ordinary cast iron production welding rods.

Some engineers state that they have been able to weld cast iron, in some cases using brazing rods or gas welding rods, which require a long complicated procedure. Usually brazing or gas welding cast iron involves: Dismantling; building a fireplace around the casting; preheating, often for as much as 24 hours; gas welding; burying the casting in lime or other insulating material; and slow cooling for up to one week.

The answer to successful welding of cast iron is the development of Magna 770 which has brought industry a practical solution.

Maintenance-designed cast iron electrode

There are a number of companies that market production welding cast iron electrodes. They usually offer from 3 to 7 different cast iron electrodes, since they readily admit that each electrode has only a limited range of applications on which it can be used on.

Obviously welding electrode manufacturers that offer several different electrodes for cast iron are not capable of serving the needs of maintenance. Such a variety of cast iron electrodes, each with a limited scope of usage, is generally all right for production welding where only a limited number of applications exist. A production factory manufacturing, for example, pumps and has only one analysis and one thickness of cast iron to weld under perhaps only one condition, can select one of these production cast iron electrodes for the one application.

In maintenance the conditions are completely different. In maintenance they never know what type of cast iron will break, what thickness it will be or whether or not the weld will have to be machined or not. Generally they do not know what the analysis of the casting that may break will be.

MAGNA has solved this old industrial problem of cast iron failures with Magna 770, which welds all types of cast iron, thick or thin, including grey, malleable, meehanite and nodular iron. It welds in all positions, including overhead or vertical. It makes porosity-free welds without undercut. The welds are fully machinable and crack-free. Magna 770 even welds cast iron to steel.

Magna 770 is the one practical solution that can help you prevent costly downtime and loss of profit due to cast iron failure.
A Great Metallurgical Breakthrough! For the First Time, You Can Now Weld Cast Iron Positively Crack-Free!

Without dismantling... totally without preheat... even on oil-saturated, dirty cast iron... this cuts your machinery downtime and enables you to save motor blocks, gears, housings and machinery parts you' ve always had to scrap before.
Magna 770 has all these advantages:

Machinable through and through without hard spots
All position welding characteristics
Highest elongation ever built into a cast iron electrode positively prevents cracking
Gives perfect welds on all kinds of cast iron including malleable iron, grey iron, ductile iron, meehanite, and steel to cast iron
Highest tensile strength ever achieved
Low viscosity slag enables you to weld pass-on-pass without removing slag between passes
Non-cracking feature enables continuous welding without stopping between passes

http://www.breckocorp.com/


Tensile Strength up to p.s.i. (kg/mm2)
Typical Hardness Brinell
Electrode Current
Sizes

58,500 (41)
160
AC-DC RP hope this help you...
4.8mm-3/16"
4.0mm-5/32"
3.2mm-1/8"
2.4mm-3/32"

I did the same thing to the set on my 33. I didn't give it too much thought and just TiG welded them with stainless filler rod. I ground the welds down and wad the headers Jet Hot coated. I have 22,000 miles on them with no problems.
Jerry...

Wasn't the question about cast stainless - not cast iron?

Are you sure it is cast stainless? We have done the exact same thing to three sets that were of the 1985 or so vintage and they were made from welded stainless tube....you coud still see the seam on the tubes. These exhaust manifolds are a cheap way to get block hugger headers.....they sell on EBay for sometimes $30 a set. You take the ugly sheetmetal covers off.

One note, of the six manifolds that we welded using MIG, one warped slightly and we had to tweak it back. If we had thought of it, we would have bolted it to a junk head while welding.

mike in tucson

Originally posted by 39Deluxe
I cut the AIR tubes off of a pair of '81 Corvette stock shorty headers and need to close up the holes. The tubes protrude inside the header tubes about 1/2" and I didn't remove that part yet. I'll leave it until I get the holes welded shut. These header tubes are cast stainless and the AIR tubes are also stainless. They are going on my '69 truck.

What's the best way to weld them up?

Mig with stainless wire? How thick?

Stick welder with a small diameter rod?

Take them to a pro and write a check?

Thanks for the help.

Tom

You could TIG weld them Same as welding mild steel or 4130. For best weld you should fill the header tubes with argon so the weld doesn't get contaminated from the back side. There are other ways to weld stainless, but that's how I would do it.

MIG welding will work as well. I did that before and it worked good with a MIG welder. The Argon thing like Pro said would work too, I never did that but just clean the surface real good and dont sit there and put the bead on there real huge and get the pipe too hot or nothing. If it messes up then the worse thing that can happen is that the hole will just come back from the bead falling out.

We put a chamfer on both sides of the hole. The insides of these manifolds arent the smoothest anyway, especially down where the four tubes join......looks like a beginning welder. We ground the outside smooth but didnt try to do too much to the inside since we were removing the tube and improving things anyway. Then, the manifolds were jet hot coated and you couldnt tell where the weld was.

By the way, the flange studs on ours were metric thread. Was real confusing to the muffler shop guy. We finally used stainless
socket head bolts that work fine from the underside.

mike in tucson

Forgot to add....make sure you check the port match on these
manifolds.....we used those Earl's gasket sets with the inserts and they havent leaked in over two years. However, we did find
that the manifolds missed matching by about 0.100 inches in the vertical direction on a set of aluminum fast burn heads. We have a set of the Corvette manifolds to mount on a set of Vortec heads but we havent tested the port match yet.

Also, the tubes around the mounting holes are a pain but they do move the bolt head out and make it easier to wrench. Manifold studs are too short if you leave the bolt tubes on.

mike in tucson

I was lookiing at the flash in the seams inside the tubes and thought they might be cast stainless. I'm sure your're right that it is stainless tubing. I still need to check the port match. The beads around the inside of the flanges are huge and I'm sure I can smooth off some of that without any problems. Thanks for the replies. I'll post pics of the complete headers.

So how did you guys get them clean enough down in the tight areas to coat

Tom

For ours, we glass beaded them. Since they were not going on
a show car, we left the factory welds intact. The new JetHot coating is more chrome-like than the older color.....our only coating problem is discoloration from grease getting on a tailpipe and making a dark stain.

www.locknstitch.com Buy a few of these that will fit in the hole or a slightly enlarged hole, break the top off, and grind it flush. You'll never know there was ever a hole there.

It's a 1/16 wall tube......awfully thin for threaded fixes!

The exhaust mnifolds you have flow very well. Lingerfelder(sp?) used these.'
As far as welding either MIG or TIg will work