Cast Iron

Stick electrodes for welding and repairing cast iron - engine blocks, housings, machine bases, pump bodies and the awkward repairs nobody wants to quote on.

Cast iron is not steel, and it does not forgive

Grey cast iron contains 2 to 4 percent carbon as graphite flakes. Those flakes are why it machines beautifully, damps vibration and resists wear - and why it cracks when you weld it carelessly. Heat the casting unevenly and the stresses go straight into a brittle matrix that has almost no ductility to absorb them.

Most cast iron repairs fail not at the weld but in the heat-affected zone beside it, days later.

Choosing the electrode

• E40 - dirty cast iron. For castings contaminated with oil, grease or years of service absorption. Engine and gearbox castings soak up oil through their whole section and it cannot be fully cleaned out. E40 tolerates what is left.
• E41 - cast iron to steel. For joining a casting to a steel section, and for build-up where machinability afterwards matters.

Technique decides the outcome

Short stringer beads, never long runs. Peen each bead while it is still hot to relieve the contraction stress before it locks in. Let the work cool to hand-warm between passes - if you cannot rest your palm on it, stop.

On a large or intricate casting, preheat slowly and evenly and cool slower still, wrapped or buried. A casting that cools in a draught will crack regardless of the electrode.

Find the end of the crack first

Drill a stop hole at each end of the crack before you weld. Weld a crack without arresting it and it simply continues past your repair under the next thermal cycle.

If you are not sure what the casting is

Grey, ductile, malleable and white cast irons behave differently, and a mis-identified casting is where most failed repairs start. Call us and describe the part - identifying the casting first beats a guess.

Related stick electrodes: all stick electrodes, dissimilar metals and hardfacing.

Counter pickup in North York.