Informational Guide

Mig Welding Cast Iron

With the Bureau of Labor Statistics stating that there are 21 welding accidents for every 100,000 workers in the United States, it’s vital that you use the appropriate machine for the material you are working with. If you are thinking of Mig welding cast iron, we recommend reading this guide first to ensure your safety.  

Can you weld cast iron with a Mig welder? Welding cast iron with a Mig welder is possible, but it's often not recommended. The job is quite tricky, and you might find more cracks in the completed project than you started with. Overall, you can anticipate a success rate of about 50%.  

Can I weld cast iron with a Mig welder? Yes, the task isn't impossible. However, cast iron has a much higher carbon content than other materials. Therefore, during welding, it becomes difficult to deal with the brittle and hard nature of cast iron.  

You might find just as many issues using a TIG welder. Most technicians prefer using manual metal arc welding instead of learning how to weld cast iron with a Mig welder. This would be the go-to way to handle the welding of cast iron.  

Let’s look closer at a few scenarios. 

Mig Welding Cast Iron Steel 

Learning the steps to welding cast iron to steel with a Mig welder isn’t impossible, but it will cause some headaches. Instead, we recommend manual metal arc welding for a high-quality finish.  

MIG weld cast iron

Mig Welding Cast Iron Engine Block 

Mig welding a cast iron block can be done if you use flux-cored electrode wires. However, the welded joint won’t be nearly as strong as if you use MMA arc welding.  

Mig Welding Cast Iron Exhaust Manifold 

Welding cast iron with Mig flux core is possible. If you want to work with the exhaust manifold, take your time to create a solid joint. The slower you go, the more chance you have of success.  

Mig Welding Cast Iron With Flux Core 

It’s imperative that you use flux core if you want to Mig weld cast iron. This dual shield welding technique offers a better chance of success.  

Mig Welding Cast Iron With Stainless Wire 

There’s very little flexibility with this application. Even if you do everything right, you could end up with cracks in the finished piece.  

Mig Welding Cast Iron With Silicon Bronze  

While it’s possible to use silicon bronze with Mig welding cast iron, you will need a special machine. Not every welder is compatible with silicon bronze wire. 

Mig Welding Cast Iron Cylinder Head 

If you are going to weld the cylinder head, make sure you properly preheat it first. This vital step helps to avoid cracks.  

MIG weld cast iron cylinder head

How To MIG Weld Cast Iron (Complete Step-By-Step Guide) 

You can follow some basic steps if you want to know how to weld cast iron to steel with a Mig welder. We cover the simplest guidelines that help you achieve welding success.  

  1. 1
    Preheat for better results. Use your blowtorch to heat up the material. Most cast iron pieces should be heated to 500-1200 degrees Fahrenheit. Don’t take the temperature over 1400 degrees Fahrenheit or the material could become overheated.  
  2. 2
    Weld low and slow. It's imperative that you move slowly and keep a low current. We recommend welding an inch at one time, and it helps to weld in different spots.  
  3. 3
    Pause between segments. Give yourself 45 seconds to avoid build-up and overheating the piece.  
  4. 4
    Inspect the work. Once you’ve accomplished the weld, look for slag holes or cracks.  
  5. 5
    Remove slag. Use your slag brush to grind down the excess. Work on it until it reaches a smooth surface.
  6. 6
    Post-heat the material. Wrap your piece in insulated material so it cools down slowly. This ending step helps reduce cracking as the temperature changes.  

While you are welding, you want to remain safe. So please, follow all of these safety guidelines.  

  • Keep your area clean.  
  • Work in a well-ventilated, well-lit area. 
  • Inspect the Mig welder before using it. If you notice any defects, don’t use the machine. 
  • Wear the appropriate safety equipment, including eye protection, boots, gloves, and a long-sleeve shirt. You also want a welder helmet and apron or leather jacket. 
  • Keep a first aid kit within reach. 
  • Have a fire extinguisher handy for emergencies.  

Can I Mig weld cast iron at home? If you have enough experience and the appropriate equipment, there's no reason to pay a professional for the work. Just don't bite off more than you can chew, and you might save yourself some money.  

how to MIG weld cast iron

Frequently Asked Cast Iron Welding Questions 

Why is cast iron difficult to weld?  

Cast iron has a higher carbon content than other materials, making it more prone to cracking. As a result, most professionals prefer to use manual metal arc welding to avoid cracking on these jobs.  

How can you tell the difference between cast iron and cast steel? 

A spark test will help you identify the materials. Steel creates bright yellow sparks when hit with the wheel, while the iron is going to create orange or red sparks instead.  

Which type of cast iron is the most widely used? 

In automotive applications, grey iron is the most popular. It’s named because of the fracture color when the iron is broken or cracked. Grey iron is made from 2.5-4% carbon, combined with 1-3% silicon. 

How long does it take to MIG weld cast iron? 

Mig welding cast iron is going to take longer than most other applications. Not only do you need to pre- and post-heat the material, but you must move extremely slow at a low current to ensure the material doesn’t crack.  


It might be more difficult Mig welding cast iron with steel wire, but you can do it with a bit of finesse. Follow our step-by-step guide to ensure a solid weld that lasts.