Cast iron welding: cracks, broken lugs and old parts

What the price depends on

The rate is hourly. The time depends on the length of the crack, the thickness of the part, the method and the prep: the part has to be cleaned to bare metal, and oil-soaked cast iron also has to be burnt out. On-site work, on a gate for instance, usually takes longer than a part that’s been removed. Rates are in the table.

Rods or filler, gas and consumables are paid separately, and nickel rods cost noticeably more than ordinary ones. If the part has to be removed, brought in or machined after welding, that’s extra too.

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Methods and what can be welded

Cold welding uses nickel or nickel-iron rods in short runs of a few centimetres. Each run is peened with a hammer straight away to relieve stress, and the part is left to cool before the next one. Most on-site repairs are done this way.

Hot welding means heating the whole part to several hundred degrees, welding it and cooling it slowly. The weld behaves more like the cast iron itself, but you need a furnace or serious preheating, so it’s workshop work.

Brazing with a brass rod runs at a lower temperature: the parent metal doesn’t melt, so there’s less risk of cracking. It suits unloaded parts and decorative castings.

Not everything is worth welding. A cracked cast iron soil pipe is usually replaced with a section of plastic. A leaking section of an old radiator is more often swapped out. Parts under gas or steam pressure, boiler bodies and gas fittings aren’t welded by a general handyman: they need replacing or a specialist service.

Safety first

Welding gives off UV light, spatter and fumes, and fumes from nickel rods are bad for the lungs. The space needs ventilation and nothing flammable nearby: paint, solvent, dry grass, paper. If the welding happens in a garage or basement, clear out what you can and keep an extinguisher to hand. Nobody looks at the arc without a mask, and children and pets stay well away.

How the job goes

1. Assessment from photos: what the part is, where the crack is, what load it carries.
2. Cleaning to bare metal and degreasing, burning out oil if needed.
3. The ends of the crack are drilled so it can’t run further, and the crack is ground into a groove.
4. Welding by the chosen method, in short runs, with peening.
5. Slow cooling: the part is covered and never cooled with water or a draught.
6. The weld is cleaned up and, if needed, leak-tested or fitted in place.

Common mistakes

• Welding with an ordinary steel rod, and a new crack appears beside the weld.
• Crack ends left undrilled, so the crack keeps creeping.
• Pouring water on the hot part to cool it faster.
• Welding over oil and dirt, which leaves a porous weld that won’t hold.
• One long bead instead of short runs.

What to prepare

• Photos of the whole part and a close-up of the crack, with a tape measure next to it.
• If the part can come off, take it off: workshop conditions make the job easier.
• A few words on what the part is and what load it takes.
• For on-site work, clear access and nothing flammable around.
• A socket nearby, since the welder needs power.

Frequently asked questions

How to order

Describe the part in the app: what it is, where the crack is, whether it can be removed, and add photos. Tradespeople near you will send offers with their own price and timing. Pick one by reviews; only that person sees your address.

You pay the handyman directly and they issue the invoice. They stand behind their own weld and will redo it if it’s porous or lacks penetration. New cracks in the old metal next to the weld, fatigue in the part and hidden casting flaws are not on them.

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