Your Guide To Welding Cast Iron
Cast iron is made up of alloys of iron, carbon and silicon. Welding cast iron has many uses like repairing casting defects in a foundry. Here they salvage worn or broken castings. They are also useful in fabrication of welded assemblies.
As the whole procedure is quite tricky, it is necessary to do it with care.
How Do You Use Welding Cast Iron?
First the cast iron that is being welded has to be cleaned properly. This is done with a degreaser. Any accessory parts to the material should be removed. If you are welding a small crack, you have to determine the beginning and ending points of the crack. You should then drill a 1/8 inch hole, also called the ‘stop hole’ at each end of the crack. You can use sand paper for grinding and also look through a magnifying glass to se the hole. A ‘V’ shaped has to be ground down the length of the crack. You should take care not to go all the way through the cast iron.
Pre- heating of the whole cast iron material to be welded to 500 degrees C is very essential. This helps in prevention of any damage that may be caused due to heat from the welding process. The right welding rods should be used and welding should be done on low heat at each end with short tacks. While welding, you should do it in the same direction each time. Where ever the crack is too long, short welds should be made. While welding cast iron, short cool down time should be allowed between welds so that heat is kept to a minimum.
It is very essential to let it cool down slowly to an ambient temperature. It should be placed in a hot oven. The temperature should be kept at 50 to 60 degrees per hour until air temperature is reached. The material can be wrapped in a fireproof blanket or dry sand can be used, in case a hot oven is not available.
While welding cast iron, you must get the rods of the right size. For this purpose, you can check with the manufacturer.
When ever there is a crack or where two pieces of cast iron have to be welded, you should follow the same method.
It is very important while welding cast iron to have the material pre-heat and cool down slowly, as otherwise, the material cool very quickly if left in open air.
Where Do You Use Welding Cast Iron?
Welding of cast iron is used in
- Making Enclosures
- Machine Forms and Bases
- Pipe Fittings
- Clutch Plates
- Brake Drums
- Counter Weights
Why Do You Use Welding Cast Iron?
The reason for selecting cast iron for welding purposes is that is generally economical, has good casting ability even in complex forms. It dampens vibrations, and resists heat checking or heat shock.
Cast iron cannot be as welded as easily welded as carbon steel as it has much more carbon and silicon. It is brittle and tends to crack. Hence it is necessary to choose a ductile material as filler. Cast iron electrodes specially formulated for this purpose is also available.
The manufacturer’s recommendations that are given by the suppliers should be followed for welding cast iron.
So, it is necessary for the welder to have the appropriate welding equipment and should be able to follow all the rules for welding cast iron to get a good weld that will not crack and will last long.