How to Weld Cast Iron: Do It Like a Pro, Hassle-Free!

If you’re looking for a durable, long-lasting piece of metal to drive your machine operation, cast iron is the way to go.

Replacement costs for cast iron parts could go through the roof and exceed your budget. That’s why some operators prefer cheaper metal fittings instead.

But what’s the need to go on the cheap when you can learn how to weld cast iron?

Using cast iron fittings provides an excellent level of durability for your machine operation.

If a cast iron machine or fitting gets damaged, it could be a heart-wrenching experience for many. But not anymore! There’re now efficient ways to weld cast iron without experiencing too much difficulty.

Read on with your attention fixed, and you’d certainly be grateful at the end.

What Kind of Cast Iron Do You Have?

Just as you’d expect, cast iron comes in different builds. These builds have distinct properties relating to their ore residue and alloy content.

I don’t want you to freak out, that’s why you should know there’s some cast-iron you can’t weld.

But with luck and the right tools, you’re likely to have a cast iron that can be welded. Here’re the types available;

  • Pliable cast iron
  • Ashen iron
  • White iron
  • Flexible iron

Among these cast iron types, pliable cast iron is the easiest to weld. It has more agreeable properties which make welding possible. But don’t be in a hurry to get a welder on as great detail is needed to get the perfect join.

It’s possible to weld ashen iron even if there’s a lot you’ve got to get right beforehand.

White iron can be welded but after great effort. But flexible iron can’t be welded with any process. The properties of flexible iron expose it too easy disintegration from a welding arc process.

Easiest Ways to Find out Your Cast Iron Type

The maker

If you’re lost on the kind of cast iron you’ve got on your hands, contacting the maker is an excellent choice. Makers of this product can easily offer you essential details on what type of cast iron you have or whether it can be welded or not.

Physical assessment

If you don’t have your cast iron maker’s info, getting a firsthand look at the metal should help you easily identify it.

But if you’re not an expert in assessing the differences among cast-iron types, enlist the help of a seasoned metalworker.

An experienced metalworker can easily determine if you stand any chance of perfectly joining cast iron perfectly.

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Getting Started

Choose a Welding Technique

Unlike mig welding thin aluminum, which could be easily achieved with almost any material, cast iron is different.

Here’re the possible methods to guarantee a seamless cast iron weld;

Stick Welding

Using stick welding is so common anyone can manage a perfect join with a first try. On the flip side, getting the perfect kind of electrode is what makes the difference in a cast iron weld.

Select among the top two electrodes when it comes to making a perfect cast iron join. There’re nickel alloy electrodes which guarantee a better result than other electrodes for cast iron welding.

Also, you can make a choice for copper electrodes. Copper alloy electrodes are ideal for cast iron based on their high cohesiveness with a vast range of metals.


An old-fashioned, but efficient means of getting your cast iron welded is brazing.

All you need to do is get a filler rod with high cohesive properties. Get the base metals heated up and fuse the filler into the cast iron opening.

Based on the filler rod’s low melting point, it remains solid through the welding process and joins tightly to both base metals.

Oxy-Acetylene Welding

This kind of welding makes use of electric arc current which forms when an oxy torch and electrode come in contact.

But you’ve got to have an extra focus for this method to reap any benefits. Oxidizing base metals results in easy filler disintegration. This affects the weld’s strength and overall outlook.

MIG Welding

With a MIG welder and the right wire, you can get cast iron metals welded. But just as other methods, you’ve got to take note of some stuff before starting up the weld.

Ensure you make use of the right filler wire for starters. And make sure your preferred shielding gas has the right properties.

Since MIG welding promotes shielding temperatures around the arc for a tight join, it’s ideal for thick cast iron.

Note: Detailed info on the appropriate filler wire is provided in the next section

Select a Filler Wire

You could opt for stick welding with an electrode that possesses the right makeup to weld cast iron. But if you’re going for MIG welding, pay close attention when selecting a filler wire.

What Your Filler Wire/Electrodes Should Possess for a Perfect Cast Iron Join

Your chosen filler wire should have high nickel content since nickel creates a tight join on cast iron. Your filler wire should have a 55 – 90% nickel content to weld cast iron seamlessly.

If you’re on a budget and need something that will work, steel electrodes can still get the job done with excellent results.

Tips to Get the Perfect Weld

Cleaning Surfaces

A flush surface is needed when you’re keen on perfectly welding cast iron.

If the base metals’ surface has chips or debris of any kind, it could allow pores to develop underneath your weld. Weld pores weaken its overall strength and are dangerous when you’re working in a high-pressure environment.

Making both base metal ends smoothened encourages a perfect join, limiting the chances of a leaky weld.

Should You Go for Hot or Cold Welding?

The right temperature

Striking the right balance before getting your cast iron joined is so essential to a successful weld. In most types of cast iron, sudden temperature drops or increases could easily total your operation.

What you need is to ensure your cast iron remains within 265°C – 600°C. Preheating to this temperature range keeps the iron malleable enough to support a seamless join with another part.

Why pre-heating cast iron is the best for your metal

Pre-heating cast iron is regarded as the ideal step by a lot of expert welders. And there’s good reason to it.

Pre-heated cast iron retains greater flexibility which supports an easy join. If your base metals are too cold, there’s a high chance of no cohesion taking place at all, wasting your time as a result.

Why cool welding isn’t so cool for cast iron

When you’re working with a mig welder for 1/2 steel, quick cooling of the base metal is a great idea. But in welding cast iron, it’s a step you shouldn’t take.

Cooling surfaces around the intended join point limits your cast iron cohesive nature. Using the right temperature (stated above) is vital to making cast-iron surfaces agreeable to welding.

How to Cool Your Welded Cast Iron

There’re two main methods to cool off your welded cast iron. One is letting it out to dry in the open air. The other is to let it blow off steam in a sand oven.

Cast iron responds better to slow cooling. So ensure you get the slowest cooling method you can find. Don’t ever use compressed air and cold water in accelerating the cast iron’s cooling time.

Peening while cooling

If you just finished welding cast iron and don’t like the way it looks, there’s still a chance to do something. Peening the join gradually during cooling will improve your cast iron’s shape.


What’s the Best Rod When Welding Cast Iron?

The best kinds of welding rods to use for cast iron should have a greater nickel percentage or be pure steel.

How Long Does It Take Cast Iron to Cool After Welding?

Depending on your cooling method, it could range from a few hours to 3 days.

Open air drying is faster but less efficient than an oven cool. Placing it in an oven will let the heat dissipate evenly with no rapid bursts, creating a stronger join in the process.

Why Does Cast Iron Crack During Welding?

During and after welding, you’ve got to monitor the cast iron’s temperature drop. If there’s any sudden shift in temperature, the cast iron could crack easily under stress.

Can Cast Iron be glued?

It’s not advised to glue cast iron regardless of how thick or thin it is. Get a welder to handle joining the metal back together if you’re not much of a DIY guy.

Can I Join Cast Iron to Steel?

Yes. It’s very possible to join cast iron with steel. But be sure the cast iron you intend to weld allows welding.

Final Word

I’m keen to ensure you save more money, and that’s why these steps will lead you right to the cost-effective cast iron welding methods available. Knowing how to weld cast iron is more natural than ever!

Make a choice based on your equipment and budget. It’s certain you’d join up cast iron like a pro!