Successfully Welding Cast Iron Requires Experience, Skill and Knowledge

Nov 16, 2021

The seemingly fragile nature of cast iron often makes people wonder whether it can be welded effectively. Its near-steel hardness lends confidence to the notion it can be mended and joined. But the fact that cast iron often fails to handle hard impacts gives welders pause. If you are considering welding cast iron, the following information could prove valuable.

Can You Weld Cast Iron?

Although possible, welding cast iron poses a significant challenge. It possesses upwards of 10 times the volume of carbon typically encountered in other metals. With a content that reaches upwards of 4 percent, carbon tends to migrate into the heat-affected zone. This usually results in heightened brittleness and post-weld cracking.

Another challenge associated with welding cast iron involves knowing the specific grade. Cast iron materials can widely differ in terms of carbon content, impurities, and additives. These differences can present added complexity when making decisions about welding cast iron.

Common Types of Cast Iron

This highly versatile metal has been used since the 5th Century B.C. to fashion products such as agricultural tools. These days, consumer products that encounter heat, such as cookware and automotive parts rank among the prevalent uses. But when welding cast iron, knowing the differences between the following grades is helpful.

  • Gray Cast Iron: Considered the most common type, gray cast iron includes a graphite microstructure that creates the color. Although this grade does not absorb hard impacts as well as steel, it does offer significant strength.
  • White Cast Iron: This type earns its name from the light coloration driven by cementite below the surface. Like others in its class, white cast iron possesses adequate strength and resists abrasions.
  • Ductile Cast Iron: This soft grade of cast iron usually includes a high carbon content. It employs traces of magnesium and cerium to impede the hardening process and was developed during the 1940s.
  • Malleable Cast Iron: Also called “workable” cast iron, it’s typically created by applying a heat treatment to white cast iron materials over two days. When processed, malleable cast iron can be bent and manipulated.

Understanding the type of cast iron you are working with helps welders make informed decisions about the process. Welding cast iron can test one’s skills, but knowledge and experience make wonderful teachers.

Which Type of Welding is Best for Cast Iron?

It’s important to understand that welding cast iron involves differing degrees of difficulty. Malleable cast iron undergoes composition changes during the welding process. Although an experienced welder can join malleable cast iron, it will likely lose its flexibility. Ductile cast iron requires an extensive and slowing welding process reserved for people with advanced skills, and white cast iron is virtually unmanageable.

Those are reasons why welding cast iron is largely reserved for gray grades. When working with gray materials, welding cast iron typically entails a few methods which may include MMA Arc welding, MAG or even TIG welding (which may require more skill to complete). Of these processes, MMA Arc welding would be one of the best processes for welding cast iron as long as the appropriate rods are employed.

Tips for Welding Cast Iron

If not diligently performed, welding cast iron can produce uneven results, cracking, and brittle material. It’s not uncommon for unsuccessful welds to snap apart easily. However, an experienced welder who hones their skills can effectively navigate the process, and the following tips may be helpful.

  • Preparation: Cast iron quickly accumulates rust and requires significant cleaning and prepping.
  • Preheat: Using a torch to preheat the cast iron can improve weld success when feasible.
  • Weld Beads: It’s crucial to avoid beginning down a bead where the previous one ended. This increases the chances of buildup and cracking. Consider using an L-shaped motion during your sweeping motion.
  • Peen: Make sure you thoroughly peen each weld to reduce unnecessary stress and minimize cracking.

It’s also essential to firmly clamp materials in place to eliminate movement during the welding process. Trying to weld a moving target rarely pans out.

What are Applications for Welding with Cast Iron?

Possessing the skills to join and mend cast iron provide professionals and casual welders wide-reaching opportunities. Cast iron has emerged as a go-to metal resource, and new applications continue to emerge. These include the following.

  • Agricultural Equipment
  • Pipe Fittings
  • Machine Tools
  • Automobile Engine Blocks
  • Automobile Cylinder Heads
  • Wood Stoves

Enjoying the ability to weld cast iron opens the door to making repairs instead of ordering new parts and equipment. Developing cast iron welding skills can also lead to lucrative work.

Contact Arizona’s Leader in Welding Supplies

The professionals at Vern Lewis Welding Supply in Arizona hope this cast iron welding information proves valuable. We maintain a complete inventory of welding supplies, PPE and offer a wide range of services, as well as educational resources. If you are considering welding cast iron and have any questions, contact one of our eight locations.

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