Cast iron is hard, brittle, expensive, cheap material and a thorn in the flesh; however, it is used in every area from workshops to kitchens. It’s a disaster to discover a crack in cast iron parts. It could result in a significant financial loss when replacing the damaged part or hiring experienced casting iron welding experts to join the crack. Consider it an opportunity to study the art of welding cast iron which will be a new technique for many beginner welders.

The challenge of knowing the best way to weld cast iron isn’t easy since a mistake can ruin your broken piece more. Be sure to follow the instructions strictly to ensure that the casting iron welding you are doing has no cracks and the strength that is internal enough to stand up to the demands of the part. The goal you have set is knowing how to weld cast iron components can help you save money and time. Also, know about the welding career, whether is welding a great career and what kind of welding has a great career ahead.

Cast Iron Welding Processes

Welding can be used to salvage castings made of iron for repair, fix castings that have failed during service, and join castings or steel parts used in manufacturing processes. The choice of welding procedure and welding filler metals is based on the kind of desired weld properties as well as the planned service timeframe. For instance, in the case of our shielded metal-arc welding method, there are various kinds of filler metals that may be employed. Also, read what is arc welding.

Filler metals will impact the color matching of the weld compared to the base metal. The color match could be an important factor in the repair or salvage of castings where the color difference will not be acceptable. Certain preparation steps should be followed in whichever welding technique is chosen. The techniques are vital to follow if you want to get a great result with cast iron welding.

Cast Iron Welding Preparation

When preparing the casting for welding, it is important to remove any surface material to cleanse the casting within the area where the weld will be. This involves removing grease, paint oil, and unwanted materials from the weld area. Moreover, the best way to weld cast iron must be valued in order to carry out the preparations. 

It is recommended to heat the weld area for a brief period to eliminate gas trapped within the weld zone of base metal. The high silicon or skin layer should be removed in addition to the weld region on both faces and the root side. The edges of the joint need to be chipped away or ground into 60deg angles or slopes.

When grooves are needed in the design, a V groove with a 60-90deg included angle is recommended. The V should be approximately 1/8 inch. (3.2 millimetres) from the base part of the crack. A small hole must be made at the end of the crack to prevent it from expanding.

Complete penetration welding should be the only method to be used since cracks or defects that are not fully removed could reappear under the conditions of service. Also, read what is Arc Blow in welding.

Why Welding Cast Iron Can be Problematic

The question which arises after how to weld cast iron is how difficult it is to perform. Moreover, it is important to comprehend the difficulties of completing the task before finding ways to join cast iron. This is because the chance rate of correctly welding cast iron is only 50%. There is an increased chance that the cast-iron item you’ve welded may crack or be damaged after you’ve finished welding it.

What is the reason for this issue? Because a variety of different materials in various proportions form cast iron. Assessing the durability of the metal you’re working on can be challenging. It is also difficult to figure out the amount of heat a cast iron can withstand before it begins to break. The high carbon content in this iron piece is the reason for all of these issues.

When you weld, the carbon may transfer to the metal that you welding or the area adjacent to the metal being welded that is being heated. This can lead to more brittleness and hardness, which can cause post-weld cracks. A welder should also be familiar with what is flashback in welding.

The Different Techniques/Methods for Welding Cast Iron

There are many methods of welding but here we specifically discuss how to weld cast iron. We’ll only be able to talk about the most commonly used methods to weld cast iron. The methods are gas welding, arc/stick welding, MIG, and TIG welding. Here is a brief description of each. These are the best methods of welding cast iron. 

Gas Welding

Compared to the Arc-based techniques that use cast iron for welding, the heating process is much slower when using gas welding. Furthermore, the flame is lower in temperature than an arc utilized for this method. 

The benefit of this is that carbon migration is usually not a concern when casting iron is welded with the gas welding technique. It is, however, essential to use a specialized gas welding rod for the procedure. 

The main issue with this method is that it needs an enormous amount of heat when large parts are being used to weld. Gas welding is also slower than other methods of casting iron welding.

Arc/Stick Welding

A shielded metal-arc welding method is suitable for the welding of cast iron. There are four different types of filler metals that can be employed. There are many reasons for using every one of the distinct electrodes. These are the machinability of the electrode, the color matching of the deposit, the durability of the deposit, and the flexibility of the final weld.

When arc welding using casting iron electrodes (ECI), prepare between 250 to 800degF (121 to 425degC) according to the casting’s dimension and nature and the requirement to machine the area around the deposit. The greater the degree of heating, the greater the ease of working world deposits. In general, it’s ideal to use small-sized electrodes with a 1-oh current set. An arc of medium length is recommended, and, if feasible, welding must be performed in a flat position.

How to Weld Cast Iron With a MIG Welder

While cast iron is welded using the MIG process and specially designed flux-cored electrode wires welding joint, the results will not be as robust as one made with MMA Arc welding. In the past, MMA sticks were suggested as the best way to weld cast iron. Here we discuss how to weld cast iron by TIG welding.

TIG Welding Cast Iron

It is true that TIG welding can provide a clean weld on cast iron. However, it is not generally preferred due to the highly localized heating characteristics that result from this process. In general, the quality of the finished weld will largely be determined by the skill with which the welder performs the process of TIG welding. Therefore, you must choose a professional welder for the welding of cast iron with a TIG welder.

Choosing the Proper Electrode & Wire Consumables

The selection of electrodes and filler wires on how to weld cast iron is incredibly limited. The products available are not designed to be used with casting iron alone. They are prone to cool quickly, cause stress cracks, and are not joined properly. Below are a few choices available in the market.

Rich in nickel content: This is the most popular electrode on the market since it is machinable and soft. The appearance is like cast iron, but it doesn’t cool rapidly also. The drawback of this electrode is that it’s expensive and unsuitable for welding large sections.

Mix Nickel 55%, Iron 45%: Iron is the same appearance as cast iron once welded, but it is quite cost-effective. The weld it makes can be machined, but it is harder than nickel’s weld. The shrinkage is less than most iron rods used for the electrode to ensure the least chance of cracking.

Iron: The welding of this rod creates a distinctive hue not found in cast iron. The property of shrinking is apparent, and it is a difficult material to the welding of cast iron. It becomes hard during welding. However, it isn’t machinable. It’s an economical choice and can easily be ground.

Cast iron: Stainless steel, when joined with stainless steel, doesn’t change the properties, or it will not harden like iron consumables. It doesn’t expand or shrink significantly during the cooling and heating of the melting process and presents an issue when it comes to using it. It produces a machine-able process following welding.

Bronze brazing: There is an option to braze using oxy-acetylene or a Tig welder. It is possible to create a sturdy patch to fill in cracks or between two parts that want to join. Brazing can join the two surfaces without altering the fundamental characteristics that cast iron has.

The Key Steps in Welding Cast Iron

The answer to the question of how to weld cast iron involves some steps. If you are welding cast iron yourself, You must be aware of the crucial steps to efficiently welding cast iron. Four steps are in DIY casting iron welding. If you follow each step in the order listed below, you’ll be able to create an extremely long-lasting cast iron welding.

1. Identify the Alloy

Cast irons belong to the iron-carbon alloy family, and an abundance of carbon characterizes them, where they obtain their characteristic of hardness. Although cast iron is extremely hard, it comes at the cost of flexibility. When compared to wrought iron, or steel, it is more brittle.

2. Clean the Casting

All castings must be prepared properly before beginning to weld, regardless of the casting alloy you’ve selected for welding. The other important thing to remember when welding is to clean the surface of all materials to make the casting ready to be welded. This ensures that the casting within the weld zone is free of dirt.

After that, the next step will be removing grease, oil paint, and obstructions to the weld’s area. One of the most crucial aspects to be aware of is that the heat will be transferred slowly and with care to the weld area for a limited time. 

This can help remove any gas that is trapped within the weld zone of the base metal. One technique you could utilize to check the preparation of the cast-iron surface is placing a weld passage over the iron. If there are impurities on the metal, it is porous. To ensure that the porosity has been eliminated, run the procedure several times before grinding away the process.

3. Preheat

If they are stressed, the cast irons will be vulnerable to slipping. The primary factor in avoiding cracked cast irons is to control the welding heat. The three stages when the process of welding cast iron. 

The three steps include the re-heating process, the low-heat input, and slow cooling.

The main reason for thermal expansion is managing heat when welding. Metal tends to expand once it’s warmed. 

But, heating and expanding a complete cast iron item at the same time can help reduce stress on the metal. However, heating the localized area in the zone affected by heat can create stress within the iron.

The issue with localized heat is that it may cause limited expansion. In this case, the metal cooler around the zone of heat is responsible for controlling the HZ. Furthermore, the thermal variation between the body of the cast and the zone that is affected by heat determines the amount of stress.

4. Choose a Welding Technique

We’ve covered the four principal methods used to weld cast iron. According to the data we’ve provided above, you must choose a method of welding that is most suitable for your work. You must select the best way to weld cast iron according to the dimensions of the metal and the alloy to be welded.

5. Finishing

Once you’ve chosen and employed the appropriate welding method for the casting iron you are planning to weld, the next step will be completing the weld. As the weld gets cooler and expands, tensile stress can be incorporated into the casting iron that is being welded.

So, the thermal contracting stage is when the cast metal is more likely to experience cracks. Welds will certainly start cracking when the stress has reached the point of no return. However, there is a method to decrease the risk of the weld forming cracks. It involves applying compressive stress during cooling to counter tension stress.

Read More: What is Overlap in Welding?

How to Fix Cast Iron Without Welding

Before looking at how to weld cast iron, another question of absolute importance is talking about no welding for fixing it. Fixing a loose cast-iron piece is feasible. If you’re not planning to join the cast iron piece, you can handle it in a manner to prevent it from becoming loose once more. The best method of fixing loose cast iron pieces is to apply the epoxy primer. 

Epoxies are commonly used in concrete to make it stronger and last longer. They also serve as a popular method of fixing pieces of cast iron that have fallen off.

Epoxies are available in a variety of colors at the majority of hardware stores. You can apply the epoxy primer on your cast iron item as you would for any other concrete project. Instead of using an epoxy primer, you can apply hot glue to repair the cast iron piece. 

This will stop it from falling loose and slipping away. But, it isn’t the ideal solution as hot glue is not particularly durable and may eventually come loose and break.

Frequently Asked Questions (FAQs)

Are steel and cast iron more durable? 

The debate is over which is more durable, whether cast iron or steel. It is believed that cast iron has greater compressive strength, whereas steel has more tensile strength. Steel is both hard and soft to cast. It can be difficult to determine which one is more durable.

Can a magnet adhere to iron?

Magnets can attach only to the alloy or metal, with powerful metals such as cobalt and iron as their basic constituents. In their original states, metals like brass, silver, copper, or gold don’t attract magnets.

How do you braze weld cast iron?

It requires someone with expertise to braze a cast iron. It is possible to practice using a grinding wheel 1/16 to 1/8th of an inch into the alloy. The brazing tip is bright red at 600 degrees and continues to warm and fill the gap without altering that base material.

What is the most effective cement for cast iron?

Liquid weld is a term used to describe resin and steel epoxy available. They require mixing before use. However, epoxy hardens more quicker than resin. The epoxy can be set within 5-30 minutes, while resin can take more than 8 to 10 hours to cure.

Read More: What is cold welding?


Of course, you can weld cast iron. There are a handful of points to take into consideration. Preheating is generally recommended in particular for preheating methods. Using this method, the metal must be heated before welding. This goal is to stop the iron casting from being welded from stretching. While welding cast iron never undermines safety so always wear the best welding pants while any kind of welding operation.

Additionally, it is essential not to be unable to remember what to do if cracks are present on the casting iron that needs welding. In this case, the direction of welding must always be from the outside toward the inside. Attention should be given to handling the temperature and heat produced when welding. This should be taken into consideration when casting is welded. If you follow these guidelines, you’ll be competent in welding cast iron.

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