The Best Methods To Weld Cast Iron To Steel

Yes, cast iron and steel may be welded together. However, when welding cast iron to steel, a few factors must be kept in mind.

There are several reasons someone might wish to fuse cast iron to steel. There are methods to make these two metals cling together, whether the final application is structural, ornamental, or somewhere between.

Depending on your application, I’ll go through several methods you can pull off effectively in this article. I’m not saying that my ways are the greatest; they’re simply what has worked for myself and others.

Method To Weld Cast Iron To Steel

If you’re inquiring about welding cast iron to steel, you’re probably conducting a repair or a retrofit, so double-check the pieces for stress fractures or other evidence of damage.

If there is damage to the casting, it may be best to fabricate a replacement rather than cutting it off and replacing it afterwards.

Next, think to yourself, “Am I sure this is cast iron?” The metallurgy of cast iron, cast carbon steel, and many forms of iron castings may appear identical, yet they are not. Cast iron isn’t all the same, though. Gray iron and ductile iron have distinct properties.

Regardless, you should be able to weld any of them with steel, but you don’t want a poor weld because you mistook cast iron for something that melts at a higher temperature.

Furthermore, remember that cast iron has a lower melting temperature than steel. Because of the lower melting temperature, you must modify your welder’s settings correctly and be cautious while working with thinner cast iron parts.

Fourth, if the casting is small enough, preheating helps prevent fractures around the weld from developing. Before welding, heat the casting to a temperature of 500-1100 degrees Fahrenheit (do not exceed 1100 degrees Fahrenheit). If you can’t get the complete component to 100 degrees, contact the weld region to that temperature.

Lastly, you should only weld around 1” at a time to avoid cracking. You can needle-weld your component first, then fill up the gaps later.

Relevant Post: Methods to Fix Cast Iron Without Welding

Is Welding Cast Iron Difficult?

Because of its unique composition, cast iron might be tough to weld, but it is not impossible if you apply the proper welding method to avoid weld fractures. This entails careful heating and cooling, including preheating, selecting suitable welding rods, and allowing the component to cool gradually.

Welding Types You Can Use To Weld Cast Iron:

Any popular arc welding techniques, such as manual metal arc welding, flux-cored arc welding, metal active gas welding, submerged arc welding, and so on, can theoretically be utilized; however, a process that allows for gradual heating and cooling is often preferable.

  1. Manual Metal Arc Welding(MMA)
  2. Metal Active Gas(MAG) Welding
  3. Oxy-Acetylene Welding

Manual Metal Arc Welding:
This form of welding, also known as shielded metal arc welding (SMAW), is often the best overall method for cast iron welding — as long as suitable welding rods are employed.

The application will determine the electrode to use, the required colour match, and the post-weld machining amount. Iron-based and nickel-based electrodes are the two most common types used in manual metal arc welding.

Because iron-based electrodes generate weld metal with a high carbon martensite content, they are typically used for minor casting repairs and colour matching.

The most popular electrodes are nickel alloy, which provides a more malleable weld metal. By producing a lower strength weld metal, nickel electrodes can also assist in minimizing preheating and HAZ cracking.

Metal Active Gas Welding:
A nickel consumable is typically used in MAG welding. A gas mixture of 79% argon and 21% carbon dioxide will be enough for most purposes. Although brazing wire can be used, it is not advised since braze metal is much weaker than the casting.

Oxy-Acetylene Welding:
An electrode is used in oxy acetylene welding; however, the heat is generated by the oxy-acetylene torch instead of an arc created by an electrical current. The procedure’ low heat intensity and gradual heating will produce a big HAZ, but the slow heating will help prevent high carbon martensite production in the HAZ.

repairing cast iron bath tub using oxy acetylene welding
Alex Repairing Cast Iron Bathtub Using Oxy Acetylene Welding

To make welding possible, the low heat intensity of the operation will necessitate preheating to a higher temperature, generally in the range of 600°C. Welding is done using a neutral or slightly decreasing flame.

Welding Rods You Can Use:

The type of welding rod is critical when welding cast iron; however, most experts recommend nickel rods.

55% Nickel Rods:
These are less costly than 99% rods, machinable, and commonly used for thick section repairs. Because the expansion coefficient is more minor, these rods create fewer fusion line fractures than 99% of rods. For welding cast iron to steel, these ferrous-nickel rods are excellent.

99% Nickel Rods:
These electrodes are more costly than other alternatives but deliver the most effective outcomes. 99% of nickel rods provide machineable welds and are best used on low or medium phosphorous castings. The weld deposit created by these pure nickel rods is soft and pliable.

Steel Rods:
Steel rods are the most affordable of the three and are ideal for minor repairs and fills. Steel electrodes create harsh welds that are difficult to process and require further grinding to complete. Despite these disadvantages, steel rods give better colour matching and can withstand less-than-perfect castings than nickel rods.

Final Words

Welding cast iron to steel is a complex procedure that needs to be performed under certain working parameters. So I don’t recommend using it for joining critical metals if you aren’t an experienced welder.

However, if you have decided to do so, the most preferred filler metal is NiFe-CI.Furthermore, preheating the metal being welded increases the success rate, and make sure not to cool down the metal immediately using external sources. Instead, let it cool down slowly on its own.

Braze welding is another great option to consider to join metals together. However, it does not offer the same strength as welding.

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About Dave Walker

Dave Walker, a professional welder who has been welding from an early age. Now aims to help others by making them learning skills and finding them new opportunities. He has written for many welding blogs and helped many pursue their welding goals by helping them in choosing the best welding tools of the time.