Steel Iron Fabrication in Delhi NCR

Which metal is used in iron welding?

When you “weld iron,” you’re typically referring to cast iron due to its widespread use in industrial and historical applications. Welding cast iron (especially to itself, or to steel) requires specific filler metals due to its unique properties.1

The primary metals used in filler rods or electrodes for welding cast iron are:

  1. Nickel-based alloys: These are the most common and generally preferred choice.
    • 99% Nickel (ENi-CI / Ni-99): This type of electrode produces a very soft and highly machinable weld deposit.2 It’s excellent for repairs where the welded area needs to be drilled, tapped, or otherwise shaped after welding.3 It minimizes cracking and provides a clean weld. It’s often used for thinner sections or when excellent machinability is paramount.4
    • Nickel-Iron (ENiFe-CI / Ni-55): This electrode typically contains around 55% nickel and 45% iron. It produces a stronger weld than pure nickel electrodes and has a lower coefficient of thermal expansion, which helps reduce residual stresses and cracking, particularly important when welding dissimilar metals like cast iron to steel.5 It’s also machinable, though usually not as easily as pure nickel. This is often the go-to for general-purpose cast iron repairs and for joining cast iron to steel.
  2. Steel-based electrodes: While less common for general cast iron repair due to their higher susceptibility to cracking (because steel doesn’t accommodate the high carbon content and brittleness of cast iron as well as nickel), they can be used for very specific applications where high strength is prioritized and machinability is not a concern, and where cracking can be managed through extensive preheating and slow cooling. These welds are generally harder and less ductile.
  3. Copper-based alloys (Brazing rods): While technically not “welding” in the sense of melting the base metal, brazing is a highly effective and common method for joining cast iron, and often for joining cast iron to steel. Brazing rods use a filler metal (like silicon bronze or brass) with a lower melting point than the base metals.6 The filler metal flows into the joint by capillary action and creates a strong bond without melting the cast iron itself, significantly reducing the risk of cracking.

In summary, for welding cast iron:

  • Nickel-based alloys (especially Ni-99 and Ni-55) are the most frequently used and recommended filler metals for arc welding processes (like Stick or TIG).
  • Copper-based alloys are widely used for brazing cast iron, which is often a more forgiving method.7

The specific choice of filler metal depends on the type of cast iron, the welding process, the desired mechanical properties of the weld (strength, machinability), and whether it’s being joined to another piece of cast iron or to steel.8

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