Cast iron is cheap, thorn, and brittle in fresh condition to fix them. However, it is one of the most common materials used everywhere, from the kitchen to workshops. It is definitely the biggest nightmare for cast iron machine owners to break or crack the cast component. This also means that either they have to spend hundreds on hiring a welding specialist or thousands of dollars for the replacement parts.
When it is about welding, cast iron is probably the toughest material. Any wrong move can ruin the broken parts and make them worse. So, you must know the perfect technique to make the welding proper when the cast iron is internally weak.
Therefore putting in an informed effort is more beneficial than any other thing. When you follow guidelines on how to weld the cast iron, you will surely make sure that there is no crack on the welds. Additionally, its internal strength is also enough to withstand the purpose.
How To Properly Weld Cast Iron?
When you follow a proper in-house technique for welding cast iron parts, it can save you money and time. However, you must be aware of the challenges. Remember that in case of welding failure, it can also result in damage or cracking. In case it involves critical parts, it will be a wise decision to seek help from experienced welders from the welding facility to ensure a good result.
Following are some of the significant steps that can be helpful to improve the results.
1. Find The Cast Iron Type
Cast iron belongs to the family of iron-carbon alloys. They contain a huge amount of carbon that provides some specific characteristics to cast iron. The hardness of this material is one of the major characteristics. However, it also depends on the ductility. Compared to wrought iron or steel, these are less malleable. Its cooling and heating cycle is wholly based on welding as Metal goes through contraction and expansion.
However, you must know that cast iron does not deform or stretch when it is under pressure or heat. Rather, they start cracking, which makes them extremely hard to weld. However, when you start adding alloys, the characteristics can be improved. So, the very first step is to find out the type of cast iron. You can find a range of types, and you must understand their ability to weld.
- Gray iron: Grey iron is a common type of cast iron. During the manufacturing process, carbon generally starts precipitating out into graphite, either into ferrite or pearlite microstructure. It is considered more nimble and ductile compared to white cast iron. But, there are still some challenges to the welders as graphite flakes can cause metal embrittlement.
- White iron: White iron is another type that generally retains carbon in the form of iron carbide minus the precipitation. It is brittle and hard because of the crystalline cementite. This is why white iron is mostly considered unweldable.
- Ductile iron: Since there are microstructural differences, these kinds of iron are less brittle. However, the process is very slow and extensive. These are considered weldable iron but are rare in nature.
- Malleable iron: In the welding process, it can change the property of metals. Therefore, malleable iron type is generally considered not weldable and useless.
One of the finest ways to understand which cast iron type requires welding is by consulting with the manual or getting in touch with the manufacturer if you do not find the detail of the material. Even though there are minute differences in fresh cracks available in such materials, unless you have experience in working with welding cast iron, it is always a wiser decision to consult the manufacturer.
As mentioned above, one of the most common types of welded cast iron is Grey cast iron. Hence, it must be the only attempt unless you have experience in welding or casting iron. Someone having knowledge can assist you in finding a great alternative.
2. Select A Welding Process
Now that you’re sure about the Grey cast iron, the next essential step is selecting the welding process you’re going to use. There are many processed weld cast iron, but you need to use the correct filler material along with a suitable welding procedure. It is definitely dependent on your personal preferences but considering some factors while welding cast iron can ease the process.
TIG weld can be a great option if you are welding the machine surface. Stick welding or MIG is not recommendable, as it might cause some unnecessary damage to the machine surface and not be welded properly. With TIG welding, you will not face spattering issues.
Another common process that is also used for cast iron welding is oxy-acetylene. This can be a great choice for minimizing extreme cooling and heating of the electric welding process. It is far easier to maintain the temperature of the components.
Brazing is another option, but it is not welding. It does not really fuse metals as welding does. However, this can be a great option if you find it troubling to weld cast iron. However, you have to make sure that the braising surfaces are properly clean and it will not stick to rusty or dusty iron.
MIG and stick welding can be great choices when you choose the correct consumables. However, it can go wrong and can cause cracking if you choose the wrong filler metal. So it is always a mandatory thing to choose a proper cast iron before welding.
3. Select A Good Filler Wire Or Electrode
You can find only a limited number of electrodes or filler wires that work suitably with the cast iron welding process. Most of them you find are not properly designed, especially for cast iron, and can result in stress cracking or not fusing appropriately with cast iron.
Wire consumables and electrodes:
- High nickel content: It is probably a great kind of wire or electrode because of its machinable and soft nature. It looks similar to cast iron and does not cool quickly. However, because of the characteristics, these are really expensive and are definitely not a great choice for welding the ticker sections.
- 45% iron max, 55% nickel: It can be considered an affordable option, and it has similar looks to that of cast iron after welding. It is a good choice for machinable welding even when it is harder compared to 99% of nickel welds. These materials have lower shrinkage chances compared to most iron rods; hence these can minimize the chances of cracking.
- Stainless steel: When cast iron is fused with stainless steel, there is no change in properties, and it does not get hard with iron consumables. This material would not contract or expand while cooling or heating in the welding process. So it might become challenging to use. However, this is mostly used for welding cast iron and produces a proper machinable surface.
- Iron: Iron is another type that is generally inexpensive and can produce a range of color welds compared to cast iron. However, the process is challenging because of the shrinkage properties. These materials have higher shrinkage properties. Additionally, it is not machinable because it starts getting hard during the process.
- Brazing bronze: You can use rods or oxyacetylene braze with the TIG welder. This is one of the best ways to get a stronghold in the cracks or between components that requires joining. Apart from this, it will also not crack or change the properties of cast iron.
4. Peening And Cleaning The Welding Surfaces
Just like any other welding process, cleaner surfaces are always a better choice for welding. Many times you will find material that is highly expensive, and it will be very challenging to weld. So, there are many things that you must know before welding cast iron.
When you start using welding consumables that are designed to contaminate cast iron, like MG289 welding alloy rods, it is one of the finest ways to make sure of a sufficient weld.
The peening process is tapping the soft weld with the ball peen hammer when it cools to reduce the chances of cracking. However, you must take much caution and perform when welding can deform. However, this is not always mandatory, as the primary reason for cracking is rapid heating or irregular heating or cooling of the component. So the preheating and slow cooling process is very crucial.
5. Cold-Weld / Preheat?
You might find several options and opinions about whether you should choose too cold or hot weld. Most people will agree to the fact that preheating can be a great choice, but some people will also suggest welding by using minimum heat.
When you have to make a decision about how to weld cast iron, you must take a critical approach, as you should know that, cast iron is considered brittle. Heating will always have some deforming effect on the metals. When one section of metal cools or heats faster than the other section, it generally results in cracking or stressing on the cast iron.
So, preheating is mostly recommended as it has the ability to minimize the chances of cracking and stress by changing the surrounding area of the metal to the nearer welding temperature. Therefore, it makes the entire component change in a uniform manner. Changes in cast iron are made above 1400°F, so it is a must for you not to put too much heat on the component.
You can also choose to weld cast iron in the way without preheating. By making use of minimum heat, you can reduce the temperature. It can be advantageous as it does not produce visible cracks and offers stronger welding than hot welding. However, some kind of internal stress is still there, which might show in the later part of the life of the component. With this process, weld quality will be weaker compared to choosing preheating before welding.
When you choose experienced welders of cast iron who generally work for manufacturing or repairing products, they mostly choose to preheat. It is one of the finest ways to make sure about strong internal welding without any visible cracks.
6. Cool Slowly
The cooling procedure is a vital aspect of the cast iron welding process. It is always suggested not to quench with cold compressed air or cold water. Rather than that, when you choose a slower approach to cooling, it can provide a better result.
So, to your question about how to weld cast iron, hopefully, you have got the answer. Following these few steps can be helpful for you to get beneficial and stronger results.
What Are The Many Applications Of Cast Iron?
Cast iron is one of the most common materials that is chosen for a range of purposes. While there are many, the following are some of the most common applications of cast iron.
- Agricultural equipment
- On machine tools like bases, brackets covers
- Cast iron pipe
- Fittings of pipe
- Automotive engine hands, manifolds, and blocks
- Water preps
Apart from this, there are several other applications which include making construction machinery and other sections where you require a solid product to bear weight.
What Are The Benefits Of Welding Metal?
Irrespective of the sector, welding metal has a lot of demand. The characteristics that it holds are one of the biggest reasons why welding metal is considered a great choice. Following are some of the major benefits of welding cast iron.
- It is a low-cost material.
- It has desirable properties like rigidity, robustness, humidifying capacity, and thermal conductivity.
- It can be easily given a shape with the use of sand casting.
- It is a better fluid than steel metal.
- It has a lower melting point compared to steel.
Why Can It Be Problematic To Weld Cast Iron?
You must comprehend the challenges in performing the job before starting with the process of welding cast iron. There is only a 50% chance of proper welding of cast iron. Since welding cast iron generally results in damaging or cracking the piece, it is always recommended to choose the correct process.
But what can be the most common reason for the problem? Well, the answer is that as different materials have different proportions, problems might arise. It is not possible for the person to actually evaluate the accurate strength of the metal that they are working with. Besides, it is also challenging to understand how much heat the metal requires so that it can withstand the pressure without cracking. When cast iron has more carbon content, it results in cracking.
When you start welding, the carbon content can transfer to the welded metal or to the section next to the metal which has been heated. This causes improved hardness and brittleness that leads to cracks post-welding.
Conclusion
There is no denying that welding cast iron is extremely hard and challenging. It needs a lot of preparation and care during the entire process of welding and cooling. However, there will be nothing like metal that will have strength and last a lifetime.
So, it is always recommended to choose the proper steps for welding cast iron. And this is why we have included how to weld cast iron, its application, and its benefits. Hopefully, it will be helpful for you to understand the benefits, the preparations, and the procedure. Remember not to take shortcuts as it might result in cracking or making the metal internally weak.
