Material guide
Welding Cast Iron: Preheat, Nickel Rods and Patience
Cast iron repairs fail from haste, not technique: heat it fast, cool it fast, and the weld cracks beside the bead. The fix is a ritual — preheat, short beads, peen, bury it.
Process and filler selection
Default process: stick with nickel (ENiFe) rods, low and slow with preheat. Filler: ENiFe-CI (nickel-iron) rods; plain steel rods crack.
Preparation
Grind the casting skin off, drill small stopper holes at crack ends. Fit-up matters more than settings: gaps eat filler and heat control at exactly the wrong moment.
Heat management
Preheat 100–250°c, short staggered beads, peen each pass, cool slowly under a blanket — rushing it cracks the job
The method
- Drill small stopper holes at the ends of cracks before you groove them out
- Grind a V through the defect to sound metal
- Preheat 100–250°C (temperature crayon or IR thermometer)
- ENiFe nickel-iron rods, low amps, short 20–30 mm beads
- Peen each bead as it cools; let the area cool between beads
- Bury the whole part in sand or a fire blanket overnight — slow cooling is the whole trick
Frequently asked questions
Can you weld aluminium with a MIG welder?
Yes, with two conditions: the machine supports a spool gun or has an aluminium-capable drive, and you use 100% argon with aluminium wire (ER4043 or ER5356). Soft aluminium wire jams in long conventional MIG torch liners — that's what the spool gun solves. Thickness under ~1.6 mm belongs on TIG.
How to weld mild steel
To weld mild steel: use MIG or stick, gasless flux-core outdoors, filler matched to the parent metal (ER70S-6 MIG wire, E48xx stick rods, ER70S-2 TIG rod), and prepare properly — grind back to bright metal at least 20 mm each side of the joint. The key adjustment vs mild steel: baseline (40 A/mm MIG rule).
What filler wire or rod for mild steel?
For mild steel use ER70S-6 MIG wire, E48xx stick rods, ER70S-2 TIG rod. Matching filler to the parent grade is the rule — mismatched filler either cracks, corrodes or underperforms the base metal.
Best welding process for mild steel?
The best process for mild steel is MIG or stick, gasless flux-core outdoors — chosen for how the metal conducts heat and what contamination costs you.
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