<VV> Cast Iron Repair, No Corvair

[Garth Stapon]

Keith:

Clean the material with acetone before you begin. The cleaner it is the
better off you are.Grinding helps, but remember, what you remove generally
has to be replaced.

You said you had a Tig welder so here goes.

Use 100% argon shielding @ a gas flow rate 15 cfh. Weld on a bench in the
flat position if possible.

Use DCSP (electrode negative)

3/32 tungsten - 2% thoraited works best (safety note -  wear breathing
protection such as a 3M dust mask while grinding thorium alloyed tungsten
because it is slightly radioactive and you want to keep grinding dust out
of your lungs). Consult the msds on the tungsten electrode manufacturer for
more information - few people read that stuff right.

Set the panel on the machine at 40 amps maximum. Use a foot control or
remote hand control to limit amperage if possible. Sit down if possible as
you want to be comfortable. An auto darkening helmet is definitely
recommended (especially when removing a stud). This type of helmet allows
you to see until you strike an arc and will darken immediately upon arc
initiation. Everyone that buys one loves it (cost - $ 200 on up)

Buy 99% pure nickel Tig electrode - 1/16 diameter works best. Some like 55%
nickel, but I prefer 99% as it is easier to grind or machine.

You have to be patient on cast iron as I belive the best way to weld it is
to keep it as cold as possible with a skip welding technique.

(Different people have different opinions, some belive brazing is the best
way to go). I am not going to debate this. As I have said in the past, in
welding there is more than one way to skin a cat. My technique has been
well proven over many applications so if you have some alternate idea on
how to do this differently be my guest and share your success with the
group.

Use a vice grip with a copper plate laid directly on the surface next to
the area that you are doing the repair. (Cut and flatten some 3/4" plumbing
pipe from Home Depot.)

Open circuit voltage is 70-80 Volts on most Tig /  Stick machines so
striking an arc directly on the cast iron base metal will cause a hard spot
and increase base metal dilution. Once you strike the arc on the copper
plate, hop off onto the cast iron without extinguishing the arc. Welding
voltage is 15 -18 volts so heat input is much lower.


The first step is to butter the surface with nickel. DO NOT PREHEAT! (this
is also an area of contention when welding cast iron)

Using less amperage is better as it will minimize base metal dilution.

Apply the nickle material very SLOWLY.  While applying the butter pass the
arc time should no more than 3 seconds per weld and once you deposit some
nickel on the cast iron surface STOP welding to let the base material cool
back down to room temperature. (For metal replacement on cast iron, a
complete job could take up to three hours or more - do not rapid cool the
casting - some apply an air blast after welding. This will cause additional
stress and typically results in a crack).  If you see a crack starting to
form, use a 1/16 " drill bit to drill a hole at the end of the crack. This
will stop it from propagating.

You should be able to put your bare hand on the casting without discomfort
before you add additional passes. The key here is to minimize heat input.
If you see weld metal porosity, remove it with a dremel tool or grinder.
This will likely be the case for the first and second pass as the manifold
may have residual oil present. Once you have been successful in applying a
butter layer of nickel to the cast iron, you can weld steel to the casting
but continue to use the nickel rod and go slowly to limit heat input. 99%
nickel is very machineable, so removal of porosity should be relatively
easy. GO SLOW (third time I have said this do you think this matters?) and
let the casting cool and never exceed 5 seconds of arc time.

Use a skip weld technique. In other words, if you have a large area to
repair, do not focus the welding in the same area. Move around if possible
to limit the expansion stresses in the casting.

For those that only have a stick welder use the same technique, if you have
a DC machine set your electrode to DCSP (electrode negative) and use the
99% nickle electrode with the striker plate. 3/32 "diameter electrode is
best and limit arc current to 60 amps. AC welders also work. Remember to
limit arc time and use a striker plate. Higher nickel content in the
electrode works better as it is more ductile.

I hope this helps.

Regards, Garth
stapon1 at earthlink.net
Late Power Glide Sedans Rule

> [Original Message]
> From: Keith Hammett <khammett at stainlessfab.com>
> To: <stapon1 at earthlink.net>
> Date: 8/25/2005 9:56:15 AM
> Subject: RE: <VV> Exhaust Manifold Stud Removal Technique
>
> Yes.  The ear must have been cracked and when I went to tighten down the
> donut it would not snug up.  The problem appeared when the ear fell off.
> There is half the hole left.
>
> Keith
>
> -----Original Message-----
> From: Garth Stapon [mailto:stapon1 at earthlink.net]
> Sent: Thursday, August 25, 2005 8:48 AM
> To: Keith Hammett
> Subject: RE: <VV> Exhaust Manifold Stud Removal Technique
>
>
> Keith:
>
> Am I correct in assuming that the manifold is made of cast iron?
>
> Regards, Garth
>
>
> > [Original Message]
> > From: Keith Hammett <khammett at stainlessfab.com>
> > To: <stapon1 at earthlink.net>
> > Date: 8/25/2005 8:31:47 AM
> > Subject: RE: <VV> Exhaust Manifold Stud Removal Technique
> >
> > Thanks Garth,
> >
> > Now if I could just get the ear back on and a stud stuck in it. ggg  Any
> > technique to weld a nut to the exhaust manifold to replace the ear?
> >
> > Keith Hammett
> >
> > -----Original Message-----
> > Garth Stapon wrote:
> >
> > Keith:
> >
> > Buy a box of 1/16 or 3/32 " diameter grade 309 stainless steel stick
> > electrode (flux coated). Grade 312 stainless is also an effective
> > substitute. The smaller diameter electrode is better.
> >
> > Set your stick welder at 40-50 amps for 1/16", 60-70 amps for 3/32".
> Ground
> > the welder directly to the manifold as this will improve arc starting.
> >
> > Put a mild steel nut that has the same inside diameter as the stud
located
> > as close to the middle of the hole directly above the broken stud.
> >
> > Put the electrode inside the middle of the nut and strike an arc on the
> > stud (that is recessed in the hole) for one second.
> >
> > (no longer)
> >
> > Let it cool for three seconds.
> >
> > Re strike the arc.repeat as many times as is necessary. If you run the
arc
> > for too long, you will weld the stud to the manifold, so one second of
arc
> > time per strike works best.
> >
> > Try (if you can) to remove some of the flux between arc strikes, but if
> the
> > stud is recessed,  it will be difficult.
> >
> > After 10-12 strikes you should have enough material built up (above the
> > surface) to weld the stacked tack welds directly to the nut. The flux
will
> > protect the threads in the manifold.
> >
> > The heat input from the arc will help to free up the stud, but let it
cool
> > to close to room temperature before removal.(Hot metal expands)
> >
> > Use a wrench on the nut to remove the stud.
> >
> > When I have showed this technique to mechanics, they have always bought
me
> > a coffee the next time they saw me.
> >
> > Regards, Garth
> > stapon1 at earthlink.net
> > Late Power Glide Sedans Rule!
> >
> >
>
>
>