Welding a cast iron can be difficult but it’s not impossible as you just need to use the right tools and methods for it. Most of the cast iron welding works surround the repairs of issues with it.
If you use effectively in house welding for the cast iron then it might save a lot of time and money for you. It might cause troubles for you but if you want to save money then its definitely worth the trouble.
If you make any mistake during the welding then it might cause cracking in the product. It is always wise to seek the help of a professional welder for the work to ensure everything is perfect.
How to weld cast iron
The first thing you need to determine before using cast iron is to find out which type of iron-carbon alloys is it. Most of the cast iron retains its hardness and they are also ductile but less malleable than iron or steel.
Due to the heat involved in the welding, the metal will expand and contract which can cause tensile stress. The cast iron does not stretch or deform which means that it can crack easily and making the welding much more difficult process.
These are the cast irons which are easier to weld than the others.
- Grey Cast Iron
- White Cast Iron
Remove dust and perfectly clean the casting
In order to learn how to weld cast iron, you need to first take care of the cleaning. No matter which type of alloy you are dealing with, you need to first take care of the cleaning.
The first thing you need to do is remove the grease, oil, paint and other materials from the zone where you need to weld. The first thing you need to take care of during the welding to apply the heat slowly.
You can use weld pass on the metal which you are going to weld which will be porous if there are any impurities on it. If it is not cleaned then you need to do it again until the surface it properly ready.
Pre-Heat to prevent cracking
For learning how to weld cast iron you need to learn about their cracking under the stress. As already mentioned above that cast iron are vulnerable to cracking and cannot sustain high temperatures.
That is why here are some of the steps you need to follow in order to weld a cast iron.
- Low Heat supply
- Cooling it slowly
The heat control is due to the thermal expansion as the metal warms it expands. The heating needs to be done properly such that it does not heat up all the items around it.
Not only that you need to also take care of cooling pressure for cast iron as the stress reduce instantly then it can also cause cracks in it.
You can learn how to pre-heat the cast iron by searching for the whole process online. Make sure to follow all the safety precautions to ensure there are no accidents.
Which welding technique you want to use?
There are various welding methods you can use for the cast iron and in order to learn how to weld cast iron you can read the following points.
- Braze welding – The first step to learn how to weld cast iron is braze welding. It is a common method which can be used for the joining of cast iron parts. In this process, a welding rod can be used for welding which will be used on the iron surface. The melting point of the filler will be quite lower than the cast iron, it does not dilute with the cast iron meaning it will remain on the surface. Before the start of the process, you need to take special care of the cleaning and make sure there is no foreign object on it. You need to use flux during the welding in order to prevent the formation of oxides on the surface.
- Oxyacetylene welding – Oxy acetylene welding use electrodes for the welding in which an Oxy acetylene torch is used for the process. Cast iron and copper-zinc electrodes are the best choices for Oxyacetylene welding of cast iron. Such a process needs to be done by the experts as it needs a lot of precision which comes only after a lot of practice. For the Oxyacetylene welding, a lot of care needs to be taken in order to prevent the oxidizing of the cast iron. During the process, the cast iron might face silicon loss which will form white iron in the weld. To reduce the temperature gradient in the welding process the welding rod needs to be melted inside the weld pool.
- Stick welding – If you want to know how to weld cast iron then this process is very important for that. The shield welding is also called metal arc welding, as it uses a consumable electrode which is surrounded by a flux. For this process, different types of electrodes can be used to match the color. You need to handle a lot of work when you use this method to weld cast iron. Nickel alloy electrodes are the popular choice for welding the cast iron. As you know that nickel-iron weld is quite stronger and it is also quite efficient in thermal expansion meaning you do not have to worry about cracking issues.
The final parts of the welding
For the last part of learning how to weld cast iron, you need to focus on the thermal contraction. Well, cooling down the iron cast needs to be done slowly because if the stress is reached at a certain point then it will surely crack.
So you need to ensure that you reduce the chances of cracking. A professional welder can use various techniques for welding to ensure there are no problems.
By using methods like peening in which you can use a ball-peen hammer to deform the bead till its soft. The peening will reduce the risk of cracking of iron cast significantly.