Learn how to weld cast iron with a MIG welder. A few years back, I had the challenge of creating some piping for a welding project at work, but the measurements were all very awkward, and I needed it to be made of cast iron.
Now while there are probably a variety of options to creating this sort of pipe which you could use, including special custom machinery or just fabricating it yourself out of sheet metal, neither was an option due to time and budget constraints.
Cast iron is not the most common metal to weld. It requires a special type of MIG welding, called pulse MIG, which keeps your welder’s power and heat consistent through the material for a nice smooth bead. You can also use pulse MIG to weld stainless steel.
Why is it Difficult to Weld Cast Iron?
Welding cast iron is a process that involves melting the metal, adding filler material, and forming it into another piece.
The problem with welding cast iron is that it’s hard to control. It’s difficult to get it to melt consistently and evenly enough for the metal to come together in a way that will allow it to be used as part of a functional piece of machinery.
Cast iron also has a high thermal conductivity, which means that it absorbs heat quickly and evenly across its surface.
This makes it difficult for you to control how much heat is being applied at one time; if you don’t apply just enough heat, you’ll end up with something brittle; if you apply too much heat, you’ll end up with something soft enough that it can’t be used as part of any kind of machine at all.
But dont worry, I will discuss the whole process of welding cast iron through a MIG welder in this article, so keep reading!
Which Wire is Best For Cast Iron during MIG Welding?
Cast iron is a popular choice for MIG welding, and with good reason. It’s strong, durable, and relatively inexpensive. However, it can be difficult to work with if you’re new to using MIG welders.
I have put together this guide to help you identify the best wire for cast iron during MIG welding so that you can get started on your next project with confidence!
1. Nickel-based Wire for Cast Iron
Cast iron is usually 50% silicon, which makes it brittle and prone to cracking. This means that it’s important to use a high-silicon filler metal when welding cast iron. The most common filler metal used for this purpose is ERNiFe-CI (or ERNi55).
This alloy has a high nickel content as well as other elements like chromium, molybdenum, and cobalt, all of which help strengthen your welds against cracking in this kind of material.
You can then use a stronger but more expensive Erni-CI (or ERNi99) wire. The main element of the ERNiFe-CI wire is iron, and it’s also 55% nickel, which makes it an excellent choice for welding cast iron.
The other elements are very small and have little influence on the properties of the weld metal.
If you want all the benefits of 100% nickel, but don’t want to sacrifice the strength of steel, then try Erni-CI. It’s an outstanding wire for a variety of materials and applications, including cast irons.
But the most commonly used wire for welding cast iron is ERNiCu. This is a wire that has increased nickel content and consequently decreased copper content; it has excellent ductility and toughness.
But this doesn’t mean that you should always use it. While this combination works well for most applications, using a lower-copper alloy can be really helpful when welding thin sections or in applications where more fluidity is needed to penetrate through tight places.
Nickel welding wire is the best for cast iron, it’s more expensive than steel wire, but it produces the highest quality welds. To increase the efficiency of welding, I recommend you use a 75%/25% mixture of argon and helium shielding gas.
2. Mild Steel Wire for Cast Iron
Cast Iron is a very tough material to weld, and it requires a special type of wire for the job. The most common kind of mild steel wire is ER70S-6, which is a very good choice for welding other metals like stainless steel and carbon steel.
However, if you want to weld cast iron with this type of wire, it isn’t recommended for any kind of critical weld. You should only use it if you are working on something that will not be subjected to much stress or strain after the weld has been completed.
The gas mixture of 75% argon and 25% CO2 (or C25) is recommended for cutting stainless steel because it provides a reduced level of penetration.
3. Flux-cored Wire for Cast Iron
The welding of cast iron can be done with a MIG welder using Ni-55FC wire when the same results are desired as those produced with ERNiFe-CI.
You can weld cast iron with a flux-core wire, but be aware that it is not as easy to work with as gas shielded wires (GMAW) or inert metal gas (MIG) electrodes.
Once I worked on my welding project, and it was difficult for me to work with gas-shielded wires and MIG electrodes.
This means you won’t have the best results, and you may not even be able to use your welder without making some changes. It’s not impossible, though!
The E71T-11 self-shielded steel wire shares some of the same limitations as ER70S-6, but it cannot be used to weld thin castings.
The Most Popular Ways to Weld Cast Iron
There are many ways to weld cast iron, but each type of welding has its own unique requirements. Here is a guide to the different techniques and methods for welding cast iron.
1. MIG Welding
MIG welding, or metal inert gas welding, is one of the most common methods for welding cast iron. MIG stands for “inert metal gas,” which is what you use to protect the weld from contamination by oxygen.
The process uses a constant flow of shielding gas at high temperatures (around 2,000°F) to protect the molten metal from oxygen in the atmosphere.
To MIG weld cast iron, you’ll need a MIG welder and some rods made for the purpose. You can even use carbon steel wire if you have it on hand. Just make sure it’s not galvanized steel wire!
You’ll also need to connect your machine to an electrical supply with at least 115 volts of power and a ground clamp that connects the workpiece (or “wire”) to the earth.
In order to get started with MIG welding cast iron, first ensure that your welder has been properly grounded before beginning work by using a multimeter or other device that measures electrical resistance.
Then set your machine up according to its instructions and begin feeding in material as needed through its nozzle while pressing down on its trigger until your desired shape or thickness has been achieved.
2. TIG Welding
TIG welding is very similar to MIG welding, but it uses a tungsten electrode and a shielding gas. The difference between TIG and MIG is that with TIG, you’re actually welding with an arc that’s created by the amperage on your welding machine.
This is different from MIG in that it allows you to control the heat of the arc more easily than with MIG.
The other thing that’s different about TIG welding is that you have to use a filler metal or rod with it because there’s no shielding gas involved in this process. You can’t use flux-cored wire as you can with MIG because there’s no shielding gas involved in this process.
So if you want to weld cast iron, then this is probably not going to be your best bet for doing so without having some issues arise during its completion due to these factors being at play here when trying out certain techniques/methods like this one for example so make sure that you take note of these things before making any decisions about what type of material will work best for your needs when doing.
3. Gas Welding
Gas welding is a process in which two materials are joined together by means of an electric arc created by a gas flame. In this process, the filler rod melts and flows into the joint between the base metal and weld metal.
This method is commonly used when welding cast iron with carbon steel, stainless steel, or aluminum. The arc itself produces heat that melts both metals, so there’s no need for filler material like fluxes or shielding gases like argon or helium.
It’s also common practice to use gas-shielded electrodes because they’re less likely than solid electrodes to leave porosity in the weld area (which can lead to cracking).
4. Arc/Stick Welding
This is the most common type of welding. Arc welding is done by striking an arc between a wire electrode and the metal being welded. Stick welding uses a rod electrode that is fed into the work area. The arc is struck between the tip of the rod and the workpiece, and then it is fed into the area to be welded.
The advantages of stick welding are that it can be used to weld any size or shape of metal, including thin sheets and pipes; it does not require a lot of power; it can be used with both AC and DC current; its arc is easily controlled.
It produces less spatter than other types of welding; it works well on dirty or rusty surfaces; it works well with low-carbon steel, and it can be used in tight spaces where other types of welding would not fit.
The disadvantages are that this type of welding produces fumes that can be dangerous if used improperly (it should always be done in a well-ventilated area), requires the use of an electrode holder (which must be well maintained), and requires more training than some other types of welding, produces a lot more spatter than some other types.
How to weld cast iron with a MIG welder: Step by Step
Welding cast iron with a MIG welder is no different from welding any other metal. The only thing you need to remember is that cast iron is brittle, so you have to take precautions to avoid cracking it. Welding cast iron is a complicated and highly specialized process. It requires extensive knowledge, experience, and equipment to execute properly.
1. Recognize the Alloy of Cast Iron
If your cast iron is painted or has a coating on it, the first thing you should do is clean off the coating before you start welding. You can use any good solvent to do this. Just be sure to wear gloves and eye protection when working with solvents.
The second thing you need to know about welding cast iron is that there are four different kinds of cast iron: gray, white, ductile, and malleable.
- Grey Cast Iron
This type of cast iron contains roughly 0.75% carbon and 4% silicon. It has a low melting point (1120°C), low tensile strength, and poor weldability compared to other alloys in the family.
Grey cast irons are used for structural applications where low strength is acceptable, as well as wear applications such as gears or other parts requiring high abrasion resistance.
- White Cast Iron
White cast irons are made from pure elemental iron with no alloying elements added during production, so they have high tensile strength and good weldability when compared to grey cast irons, but they have poor wear resistance.
- Ductile (Nodular) Iron
Ductile (nodular) iron is used in the automotive industry, as well as the construction industry. It has a higher tensile strength than malleable cast iron, so it can be used in engine blocks, cylinder heads, transmission cases, and other components that require high strength. The tensile strength of ductile cast iron is between 36 and 52 MPa (5,000-7,500 psi).
- Malleable Iron
Malleable cast iron is used to make machine parts because it can be machined into complex shapes easily. Its tensile strength ranges from 24 to 35 MPa (3,000-4,000 psi).
2. The Right Welding Technique
Welding cast iron can be a challenge for the beginner welder. The difficulty lies in the fact that cast iron has a high carbon content, which makes it difficult to weld. The best way to overcome this challenge is by using the right welding technique.
The first step in any welding project is to choose the right type of welding rod and wire. Cast iron requires a hard wire such as E6013 or E7024, which provides enough penetration without damaging the underlying material.
It is also important to use a shielding gas such as argon or helium so that you don’t damage the surface of your workpiece by exposing it to oxygen during heating.
It’s best to use an arc setting between 25 and 40 amps, depending on how thick your material is.
For example, if you’re welding something that’s 1/4″ thick, then you’ll want to set your arc at around 30 amps.
However, if you’re working on something that’s 1″ thick, then set it at around 40 amps instead because there will be more resistance due to greater heat loss through conduction, plus there will be more surface area which means more heat loss through convection.
If you do not use the right welding technique, then you might have to face some issues during welding, as I always preferred the suitable welding technique for my own welding project.
3. The Suitable Welding Rod
To weld cast iron, you need to use a MIG welder. The material is highly resistant to heat and requires special welding rods.
When choosing your rod, consider the thickness of the metal you are welding. A thicker rod will be more suitable for welding thicker pieces of cast iron.
Thin rods will not be able to penetrate through the metal as easily and may break while you are working with them.
If you are planning on using a thin rod, make sure that it has a high enough carbon content so that it can withstand high temperatures without breaking or melting away during welding operations.
- Steel Rods
These rods are used for all-purpose welding and are appropriate for mild steel, stainless steel, and cast iron.
- 99% Nickel Rods
99% Nickel is most commonly used for low carbon steels and low alloy steels. It’s also great for when you’re welding stainless steel pipe or tubing.
- 55% Nickel Rods
55% Nickel is used for high-strength alloys such as chrome-moly, Inconel, and Hastelloy. As a general rule of thumb, the higher percentage of nickel in a wire rod, the more efficient it will be at transferring heat from your torch tip to your workpiece while maintaining good arc stability over long periods of time (which means less spatter).
4. Surface Cleaning
The surface of the metal must be free of any dirt or corrosion. You should also remove any paint from the area that will not be welded. If there is rust on your piece of cast iron, you may need to grind it off with an angle grinder first.
Next, apply flux to the joint and then use a wire brush to remove any excess dirt or other foreign materials from inside the joint.
You should only use a wire brush if you have access to an electric arc welder because using a handheld one could cause sparks which could ignite fumes in your work area and cause an explosion!
You should also protect yourself from fumes while cleaning by wearing respiratory protection (such as a dust mask) as well as eye protection (such as goggles).
Another option is to preheat the cast to 750 °F, equivalent to 400 °Cfor 20 to 30 minutes, but it’s expensive.
5. Detach Broken/Cracks from Casting
For the best results when repairing a cast iron joint, I suggest you use the chisel and hammer method. This should be done before you weld the part.
First, use a die grinder with carbide burrs to remove any material between the crack and its edges on both sides of the casting.
Then use an angle grinder with a sanding disc to polish up surfaces so they will be clean and smooth after welding them. This can also be done by hand if necessary because neither process requires much power or finesse.
- Criteria of Detaching Cracks
You want to make sure that your casting is free of cracks. Otherwise, you’ll end up with a big old crack. Never weld on a crack or damaged area. If there is any doubt, heat up the metal with a grinder until it glows, then inspect to see if it is clean.
To avoid cracking issues, I highlight some of the steps to follow in the form of the table:
| Steps | Description |
| Step 1 | Drill the holes to remove any stress and make sure the crack doesn’t widen. |
| Step 2 | Lay out a 2-inch long groove, then stop welding at around 1/9 inch (3.5 mm) to allow room for grinding and other operations. |
| Step 3 | You may want to make sure you have good ground clearance by covering everything in wax paper or cardboard. |
- Criteria of Detaching Broken Parts from the Casting
Firstly, you need to determine the size of the welding cast iron. The weld seam must overlap the edge of the break or crack by 40 mm max.
When you’re ready to start, tack weld the broken part back together, then create a groove in the iron around where the crack was by welding back and forth over the groove.
6. To Avoid Fast Expansion, Preheat Casting
Preheat casting before you begin welding it. The general rule of thumb is that you need to preheat cast iron by 100 degrees Celsius for every 1/8 inch (3 mm) of thickness, so that means if you have an 8-inch (203 mm) thick piece of cast iron, you’ll want to preheat it by 800 degrees Celsius.
It’s important to note that some people will heat their castings before they start welding and then let them cool down once the weld is complete.
But I recommend using a flame torch or other source of direct heat instead of relying solely on your welding machine’s heat source because it can be difficult to get an even distribution of heat from just one source.
7. Avoid Long Beads for Stable Temperature
When you weld cast iron, you should weld short, 1-inch to ¼ -inch beads at the most. The more heat you put into the cast iron, the more brittle it will become. Make sure you clean and grind any porosity in your cast iron before welding it.
This tip will help you weld cast iron with a MIG welder. It works for all cast iron thicknesses from 1/4″ to 1/2″. The size of the bead can vary depending on your preference, but a general rule is that it should be no more than 1/3rd of the casting thickness and ideally about 1/8th of the casting thickness.
8. Rescue the Welding Surface from Shrinking
The heat of the weld will cause the metal to shrink, which can cause cracks in the weld. Peening involves striking the surface of the metal with a hammer immediately after each bead is laid down by your welder; this helps prevent cracks from forming by keeping them from spreading too far.
To peen your cast-iron weld, use an angle grinder with a wire wheel attachment to grind off the top of your weld bead. Then, use a hammer and punch to hammer down the edges of your weld bead until it is flush with the surface of the base metal.
This will relieve the stress from contraction during cooling, which will help prevent cracking or popping out of place during cooling.
9. Reheat if Needed
Post heat your welds to fix temperature differences and reheat if needed. If you don’t do this, your weld may crack or break off later. Next, remove any rust or oil from the surface of the metal with a wire brush or other abrasive tool.
10. It’s Time to Cool Down the Surface with Care
Finally, remember that cast iron has high thermal conductivity, so it needs to be cooled down slowly after welding so as not to crack under stress from thermal fatigue or cold cracking over time.
To cool a casting, preheat an oven to 200 degrees Fahrenheit. Once the oven is preheated, place the casting in it and leave it for 15 minutes. If not, then you have to cover some things.
How to Weld Cast Iron with a MIG Welder: Without Preheating
Welding cast iron without preheating is possible, but I do recommend it because I tried this.
Welding cast iron can be done without preheating, but this is generally only done in the following certain situations:
- If you’re working with a small piece of cast iron that’s going to be moved and set down in a new location, it’s impractical to preheat the whole piece because it will have to be reheated before moving again.
- If you are trying to repair an existing piece of cast iron while it’s already installed in place, preheating may not be practical or even possible.
- However, if you’re planning on welding cast iron as part of a larger project and want to avoid heating up the entire piece every time you need to weld something together, you should use some form of liquid metal transfer system that allows for rapid cooling during welding operations.
MIG welding cast iron without preheating is not for the faint of heart! You must use nickel tungsten (ERNi99 and ERNi55), go for short beads, and constantly be peening the weld puddle. The goal is to avoid a fillet bead, as this will create reflow/excess carbon.
You should have to follow some of the things for welding cast iron without preheating, as discussed in the following table:
| No. | Subtitle | Description |
| 1 | Arc Length | Your arc length must be at least 3/8″ long. You can adjust this using the width knob on your welder (the one that controls how wide your arc is). |
| 2 | Voltage Settings | You’ll want a higher voltage setting than usual, around 110V for an AC/DC machine or around 220V for an inverter machine. |
| 3 | Ampere Settings | You’ll also want a lower amperage setting than usual, around 35 amps for an AC/DC machine or around 60 amps for an inverter machine. |
| 4 | Good Connection | You’ll need to make sure that you have good contact between your electrode and the piece of metal being welded. |
Cast Iron Applications
Cast iron is an all-around awesome material. It’s durable, it lasts forever (or at least longer than you will), and it can be used for just about anything.
But how do you know what to use it for? That’s where we come in! I am going to tell you about some of the many different ways you can make use of cast iron and why they’re so great.
Cast iron pans are great for cooking because they retain heat very well, which means you don’t have to keep heating up the pan when you want to switch from one thing to another. This saves time and energy, both of which are valuable commodities in any kitchen!
Cast iron skillets are also great for frying things up quickly. If you have a cast iron skillet, you’ll never have to worry about going out to get fast food again. All you need is some oil and whatever ingredients you want to be cooked up!
Cast iron pots are perfect for slow-cooked meals like stews or soups because they retain heat well over long periods of time, so your meal will stay warm even if it takes a little longer than usual before everyone gets their fill!
Final Words!
Do many people think about how to weld cast iron with a MIG welder? And it is technically true. Cast iron does not melt in a normal arc welding situation.
But it can be welded quite easily with the right processes on certain cast irons and electrodes.
Welding cast iron requires a few special considerations, but the general process is surprisingly simple when you break it down. Read the above article with proper concentration because I shared valuable information as an expert.
FAQs:
Can you MIG weld to cast iron?
Mig welding to cast iron is possible, but certain precautions must be taken. Cast Iron is carbon steel and much harder than other materials that we typically work with. Don’t look to your flux core or argon to save you here! This extra hard material requires different welding parameters, including lower heat input and voltage, as well as more shielding gas than you would use on mild steel.
Which welding is best for cast iron?
Shielded metal arc welding (SMAW) is the best option that provides you with greater control over your final product’s strength and appearance. The weld quality generally depends on the techniques used by the welder and the type of equipment they use in order to make their precise welds. Shielded metal arc welding is also called manual metal arc welding (MMAW).
Do you have to preheat cast iron before welding?
Preheat each piece you intend to weld with cast iron or copper electrodes to a minimum temperature of 250°F. Electrodes that are used without preheating are known as nickel electrodes.
