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Can You Weld Cast Iron With Mild Steel MIG Wire?

Can You Weld Cast Iron With Mild Steel MIG Wire

Welding cast iron with mild steel MIG wire is a common welding practice, but many welders don’t know the proper technique for doing so. It can be a tricky process, as cast iron has different properties than mild steel. Understanding the process and its challenges are essential for the successful welding of cast iron with mild steel MIG wire. Let’s take a look at what you need to know.

Process of Welding Cast Iron With Mild Steel MIG Wire

Welding cast iron with mild steel MIG wire requires that you preheat the casting before welding. Preheating helps to reduce thermal shock and prevent cracking from occurring in the casting during or after welding. Generally, preheating should be done at temperatures between 350°F and 550°F (177°C and 288°C). It is also important to note that preheating will not only reduce thermal shock but will also help to reduce spatter resulting from the difference in coefficients of thermal expansion between the two materials.

When selecting a wire for your weld, make sure that you select a mild steel wire specifically designed for welding cast iron. These wires have been designed to provide excellent weldability when used on cast iron components and are available in both solid and flux-cored options. When using solid wire, it is important to use an appropriate shielding gas mixture such as 75% Ar/25% CO2 or 95% Ar/5% O2, as these gases will help protect the weld puddle from oxidation while reducing spatter levels compared to other mixtures such as 100% CO2.

The finishing touches are just as important as your technique when welding cast iron with mild steel MIG wire. After completing your welds, it is important to perform a post-weld stress relief treatment on your casting by heating it up at temperatures between 400°F and 600°F (204°C and 316°C). This final step will help ensure that any residual stresses caused by the heat input during welding are relieved before putting your component into service.


Welding cast iron with mild steel MIG wire may seem like an intimidating task, but if done correctly, it doesn’t have to be complicated! By following the proper procedures outlined above, you can ensure success each time you perform this type of weld job. Preheating your casting prior to welding, selecting an appropriate wire type for your application, ensuring proper shielding gas coverage when using solid wires, and performing post-weld stress relief treatments all go hand in hand with achieving successful welds when working with these materials! If you are still unsure about how best to approach this process, then consider consulting an experienced welder who can guide you through each step of the way!

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