Structural cast-iron repair with Dillon
Ordinary high-pressure gas welding is extremely difficult on cast iron — turbulent flame, hard to control heat and melt. Dillon's 0.5 bar torch with its soft concentrated flame is what makes structural cast-iron repair practically workable.
Cast iron needs gradual preheating and controlled heat – Dillon's soft 0.5 bar flame and the nozzles in the kit give you that control.
Why both MIG and ordinary gas welding are hard
MIG puts in too much heat too fast — the cast iron cools unevenly, the joint cracks and becomes hard and brittle. Ordinary oxy-acetylene at high pressure is nearly as difficult: turbulent flame, poor heat control, and uneven melt that still cracks. Cast iron needs gradual heating and controlled cooling — something that demands full control of the flame.
Dillon's soft 0.5 bar flame — why it works
Dillon's mixing chamber produces a soft, concentrated 0.5 bar flame without turbulence. You get full control of heat input: preheat the casting gradually, use matching grey-iron rod and cast-iron flux, let the melt flow out gently, and let the structure cool slowly. The result is a homogeneous joint that behaves like the parent material.
What you need to weld cast iron
Cast iron flux
Protects the melt from oxidation and lets the cast-iron rod flow out.
Buy cast iron fluxCast iron rod
Grey-iron rod that matches the parent material's structure — gives homogeneous results.
Buy cast iron rodWire + flux pack
Complete pack with cast-iron rod and flux — everything you need to get started.
Buy packSee the repair in the workshop
Tips for best results
Preheat the casting
Warm up the cast iron gradually before you start welding. This reduces stresses and prevents new cracks.
Always use cast-iron flux
Flux protects the melt and gives a clean, tight joint. Without flux the joint oxidizes and won't hold.
Let it cool slowly
Cover the casting with insulation or sand after welding. Slow cooling prevents cracking.
Cast iron welding FAQ
Can you weld cast iron with gas welding?
Yes. With Dillon you weld cast iron using grey-iron cast iron rod and cast iron flux. The soft 0.5 bar flame gives you control of the heat, so you can preheat, weld and let the part cool slowly with the same torch.
Why does cast iron crack when welded?
Cast iron is hard but brittle and cannot handle rapid temperature changes. MIG puts in too much heat too fast, so the part cools unevenly and the joint cracks. Ordinary high-pressure gas welding gives a turbulent flame that is hard to control.
How hot should cast iron be preheated?
Heat the whole part evenly until it turns dark red, around 500–600 °C. On larger castings a bigger welding nozzle makes this easier.
Which rod and flux do I need?
Grey-iron cast iron rod (4 or 6 mm) and cast iron flux – or the wire + flux pack. Ordinary steel rod does not work on cast iron, and without flux the joint oxidises and does not hold.
How should cast iron cool after welding?
Very slowly. Bed the part in dry sand or vermiculite straight after welding and let it cool for several hours. Water or a fan causes new cracks.
Can I braze cast iron instead of welding it?
Yes. Brazing with brass rod (welding bronze) and bronze flux needs a lower working temperature and further reduces the risk of stress.
Is the Standard Kit enough for cast iron?
For most engine blocks, manifolds and castings in a hobby or home workshop, the Standard Kit is enough. Besides the kit you need oxygen and acetylene, regulators rated 0–1 bar and hose. If you already own a Dillon, you only need rod and flux.
You need a Dillon torch
If you already have an ordinary high-pressure gas welder, it won't work for structural cast-iron repair — you need Dillon's soft 0.5 bar flame. Standard Kit or Pro Kit includes torch, tips and accessories. You just need cylinders, regulators and hose. If you already have Dillon, just buy flux and rod above.
Learn more
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