Hi, I'm Joe Kolasa. I'm the
welding instructor at the Lincoln Electric welding school. We are here in Cleveland
Ohio at the Lincoln Electric corporate headquarters,
and I'm here to help you with some welding tips on cast iron. Most of the
problems that we have with cast iron is due to its high carbon content.
That creates cracking problems,
which creates a lot of thermal
control versus mild steel welding. In mild steel, you have very low carbon.
Generally, they're classified as a 1015 or a 1020 carbon steel.
What that means is that their carbon content is around .20
In cast irons, cast irons have around two-to-four percent carbon with a lot of silicon.
The more carbon content you add to your metals,
the harder the steel gets,
and the more carbon content you add to your metals, the stronger your steel gets.
But also it's very crack sensitive,
so when we're working on anything of a cast iron with a very high carbon content,
we have to start really following rules of welding and not just striking
an arc on the material.
I have an oxy-propane setup here with Harris products.
Then over here I'm going to be using an AC/DC 125/225 welder
and it's going to be sent on DC positive and I'm going to be running about 85 amps
and I'm going to be using a 1/8 nickel 55 Softweld electrode.
Most of the time there's several different ways you can repair castings.
One of the ways is stick welding, and they make several different types
of consumables.
We make a Ferroweld, we make a nickel 55 Softweld, and we also make a
nickel 99 Softweld.
The difference between them is that the Ferroweld is basically a steel electrode
designed to weld castings but it will not be machinable
so if you have to do any machining
you have to not make sure you use Ferroweld
The nickel 55 has a lower end nickel, which actually gives it more
strength in thicker sections.
And then the nickel 99 has almost 100 percent nickel
and the reason for that is that it is a non-ferrous alloy, which does
not absorb any carbon into the weld so it is very good for single pass welds, also
for castings that need to be machined.
So make certain that you're very
aware of the selection of the material you were going to use to weld your casting.
On this casting
i have an area that is ground out.
This crack is in the casting
but it's not all the way through the casting.
So first of all, I have to take a grinder or a carbide drill,
anything of that nature that can take and remove the material,
and I'm going to V it out into around a 30 degree bevel
and I want to remove all of the crack.
Once I get that done, I'll take and clean the material
and then I will have to take and add preheat to the casting.
What that does is that the preheating in the casting will allow the casting not
to cool very fast.
Therefore, we're going to limit
or hopefully
not have any cracking problems.
If I would just weld on this casting without any preheat,
it would cool too fast. You would actually hear a slight pinging sound, which
means it's cracking again.
You have to control the preheating in the casting, so what we have here is a
temple stick.
And the temple stick, they are marked with celsius and fahrenheit.
They are various degrees that they melt at.
So I am going to take and preheat this up and when I touch the temple stick to the casting,
when this melts means that that's when I come weld on the casting.
It has enough heat into a to keep it from cracking.
I'm also going to limit myself in a parameter of thermal.
I will take a 300 degree temple stick, 500 degree temple stick,
and maybe have an 8 or 900 degree temple stick
and I can stay within that range of temperature
to keep the casting as is where it doesn't get a lot of stresses.
Therefore, when I'm done with the casting I can take and slow cool.
Either wrap the casting in a
fireproof blanket
and/or put the casting in an oven and drop it down 50 degrees an hour.
Generally, that will allow the casting to stress relieve itself.
However, we don't have all the options of doing that at home, so the best thing is
you can bury it in sand if you have to. All we need to do is control the
slow cooling of the casting.
So one of things that I do is I
put charcoal in a grill,
let it burn out. When I'm working on a casting, after the charcoal has burned out
I'll throw more charcoal in it.
I'm done with the casting welding on it for two hours, I throw the casting in a
charcoal grill and let it come down for two days and it's still warm when I get done.
That's more or less something that we can do to control thermal care when
we're trying to repair things at home.
So what I'm going to be right now is show you the preheating
technique that we do and how I actually use the temple sticks.
And then I'm going to show you some of the techniques we do welding.
First thing I'm going to do is I'm going to light the oxy-propane
torch system.
And what I'm going to do is take and then preheat the casting.
And while preheating the casting I'm going to take this temple stick
and I'm going to start scraping it along the casting then when it melts,
that's when I can start doing my welds on the actual casting.
So let's go ahead and light the torch here.
As you noticed
that I kept checking on the casting in different areas to make sure that the heat is localized.
I want to make sure that everything is going into the casting at an even rate.
I have my welder set to go at 85 amps, I'm on DC positive.
I am running as I said before the 1/8
nickel 55 Softweld.
And before you proceed with your welding, you've got make certain of a few things.
You want to make certain you have the right safety gear on. The safety gear
that I'm wearing here are big heavy gloves. Make sure you have a correct
helmet on. Make sure you cover your head because of the sparks.
You want to protect yourself from getting burned.
Most importantly, you want to make certain you have some way of eliminating the fume exposure.
Right here I have a portable
fume extractor that I'm going to turn on before I weld.
And it actually takes away the fumes out of your breathing zone.
So make certain that you follow these instructions and also make certain
you have your safety glasses on under the hood.
Sparks can fly everywhere.
What I'm going to be doing is I'm going to start my beads
in the casting. I'm going to weld approximately about one inch of weld.
Then I'm going to stop welding, take my chipping hammer,
clean the slag off, but at the same time I'm actually doing what they call peening the weld.
It's basically a mechanical type of stress leaving.
What you can do is also use a very small ball-peen hammer to do the same thing.
But you want to make certain that you don't over-peen the weld because you can
re-harden it.
All we're doing is trying to relieve the stresses out of the weld.
And then after I do that I'm going to skip around on the casting itself
and repeat the same procedure.
If you noticed that when I was welding, I kept skip welding,
and take the chipping hammer
and clean the slag off but at the same time I'm basically peening the weld.
You want to stagger and stop your starts as to localize the heating.
so you're going to put a little bit of heat here, a little bit of heat hear, a little bit here,
you're going to move it around so we don't get one area of localized heating.
So therefore you have a uniform bead, you're going to make very small beads.
and you follow that sequence all the way out through welding to make sure
until your casting is actually completed.
Following these rules, you should have quite a bit of success in your castings.
If you like to learn anything more about the products that we used today, you can
visit our website at www.lincolnelectric.com