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Cast Iron Welding Electrodes

Cast iron is welded mainly with nickel and nickel-iron electrodes, with careful heat control to avoid cracking. This sheet covers the AWS A5.15 electrode families, when to use each and the general techniques used on cast iron repairs.

Ref WG-0111AWS A5.15

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Cast iron has high carbon and little ductility, so it cracks easily when heated and cooled unevenly. Nickel-based fillers are used because nickel does not form hard, brittle structures with the carbon from the base metal, and the weld stays softer and machinable. Electrodes and rods for cast iron are classified in AWS A5.15. The common stick electrodes are ENi-CI (nearly pure nickel) and ENiFe-CI (nickel-iron). Other classes include ENiCu types (nickel-copper) and ESt (steel), plus bare rods and wires for oxyfuel and gas shielded welding.

How to identify

Read the class on the box and the imprint on the electrode coating. Nickel electrodes are often sold in small packages because they are costly. Identify the casting before choosing. Gray iron is the most common. Ductile (nodular) iron and malleable iron behave differently. See identifying base metals in the field. A spark test and a file test help separate cast iron from steel.

Electrode families

Class	Nominal chemistry	Best for	Notes
ENi-CI	High nickel	Thin castings, repairs needing machining	Most machinable deposit; lower strength
ENiFe-CI	Nickel-iron	Thicker sections, ductile iron, cast iron to steel	Stronger; often more crack resistant on heavy sections
ENiFeMn-CI	Nickel-iron-manganese	Ductile iron, higher strength repairs	Less widely stocked
ENiCu types	Nickel-copper	Some machinable repairs	Check maker guidance
ESt	Steel	Non-machined repairs, low-cost fixes	Hard deposit near the fusion line; not machinable
RCI and RCI-A rods	Cast iron rods	Oxyfuel welding with preheat	Close color and property match
ERNiFeMn-CI and similar wires	Nickel-iron wire	Gas shielded production repairs	Machine process

General technique

Clean thoroughly. Oil-soaked castings may need heat to burn out oil before welding.
Drill a small hole at each end of a crack to stop it from running.
Groove the crack to sound metal.
Use preheat suited to the casting and filler, or a cold-weld method with short beads, per the filler maker.
Weld short stringer beads, alternating location to spread heat.
Peen each bead lightly while hot to relieve stress, if the procedure calls for it.
Cool slowly. Cover the part or bury it in insulating material.

Key points

Preheat temperatures and interpass limits depend on casting size, shape and filler. Get them from the filler maker or a qualified procedure.
Even preheat matters. Local heating can crack a casting.
Keep amperage low, within the electrode's range.
Some castings, such as exhaust manifolds, move with heat in service. Repairs may still crack.

Common mistakes

Running long, hot beads on cold cast iron.
Using a steel electrode where the repair must be machined.
Skipping crack-stop holes.
Quenching or cooling the casting quickly.

Governing standards: AWS A5.15 (welding electrodes and rods for cast iron). Filler maker data sheets for preheat and technique.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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