Many people confuse cast steel and cast iron. The two metals look almost alike. Most of the castings are made from steel instead of iron because steel has better flexibility and high shock resistance, which cast iron does not pose. You can differentiate cast steel from cast iron by the look of the surface color. Steel is grey. Also, the metals can be distinguished by their melting temperature through the torch flame. When cast steel melts, it appears to be white-hot, while cast iron melts when it is red heat.
The majority of cast steel is almost similar to medium-carbon and low-carbon in structure, making it easily weldable. When you want to weld cast iron, you need to be more careful as it is prone to cracking and leaves locked-in stresses. You do not need experience in welding cast steel. What you need to care about in cast steel welding is a distortion because steel usually stretches and becomes elongated. Distortion can also damage casting utility.
Types of Cast Steel
There are different types of cast steel, as discussed below:
- Alloyed cast steel – this is classified as low-alloy steel or high-alloy steel. Low-alloy steel has the same properties as standard carbon steel, but its hardness level is higher. High-alloy steel is characterized by wear resistance, heat resistance, and corrosion resistance. Stainless steel, together with Hadfield’s manganese steel, is an example of high-alloy steel.
- Carbon cast steel – this type of cast steel is categorized based on carbon content. Low carbon steel is moderately soft and not ideal for heat treatment. On the other hand, medium carbon steel is generally harder and is heat treatable. You can use high carbon cast steel when you need optimal wear resistance and hardness.
Necessary steps for cast steel welding
The following are pre-welding steps for cast steel:
Identify the alloy: steel has better ductility than iron; hence it does not crack when exposed to heat or cooled. It would help if you had a better understanding of the alloy type you want to work with. High-alloy steel is resistant to heat, wear, and corrosion, while low-alloy steel has normal carbon elements.
Clean the cast: this is an essential step. Ensure you thoroughly clean the cast steel before you commence welding. It involves removing any dirt like oil, grease, and paint on the surface metal. It is advisable to wipe the cleaned surface using mineral spirits to eliminate any graphite before welding.
Choose the right preheat temperature – unlike cast iron, cast steel is not prone to cracking. But you should be more careful to avoid distortion. It is essential to select the best preheat temperature together with the best welding technique so that you can get impressive results. Steel is known to relieve stress through stretching. Preheating helps to minimize residual stresses that come as a result of welding. It is recommended that you preheat and cool slowly, depending on carbon content.
How to weld cast steel using manual metal arc welding (MMAW)
This method is also called shielded metal arc welding (SMAW). It is the most preferred technique to weld cast steel. Manual metal arc welding will give you impressive results if you use the right welding rods. However, the type of electrode to use mainly depends on the application. Nickel-based and steel-based are the significant types of electrodes used in shielded metal arc welding. The most commonly used rods are nickel alloy electrodes since they provide a more malleable weld metal. Temperatures in metal arc welding get very high, up to 6500-degree Fahrenheit. The technique is mostly used in steel erection, pipeline welding, heavy equipment repair, and other construction projects.
Advantages of using metal arc welding
- Arc welding equipment is less expensive
- It works well on dirty metal
- The technique can be used anywhere provided there is the power supply
Disadvantages of metal arc welding
- The method produces more waste than other types of welding
- It needs trained professionals. Non-professionals will do unpleasant work
- Metal arc welding is more challenging when using thin metals
Cast steel with TIG Welding
The technique gives a clean weld on cast steel. However, many people do not like this method since it generates a lot of heat. It is essential to note that the quality of TIG welding depends on the welder’s expertise.
Advantages of using TIG Welding
- TIG welding is suitable for welding thin metals
- It welds different alloys
- The method produces less heat compared to other types of welding
- It offers clean and neat welds
Disadvantages of TIG Welding
- It requires more cleaning; hence uses a lot of time
Cast steel with MIG Welding
MIG welding uses nickel consumables. Many applications make use of 20% carbon dioxide gas, and 80% argon mix works best. However, brazing metal can be used, but it is weaker than casting.
Advantages of using MIG Welding
- The technique is ideal for welding various alloys
- It does not generate flux during welding
- MIG welding is much fast and quick than other welding types
Disadvantages of MIG Welding
- The technique is not used in windy conditions
- You must have an external shielding gas tank; hence more demanding
Cast steel with Braze Welding
The technique is used to weld cast steel though it has less effect on the base metal. When using this method, clean the surface to allow the filler to run over the base metal. You can use flux to prevent the formation of oxides and promote wetting.
The welding rods to use in cast steel weld
The following are the best welding rods to use:
Steel rods – these rods are cheap compared to other rod types. They are ideal for minor filling and repair. Steel electrodes are known to create complex welds and need additional grinding to finish. These rods are not machineable but offer the best color.
99% Nickel rods – the rods will give you excellent results, but they are more expensive. They can create machined welds and are ideal for casting low and medium alloys. 99% of nickel rods make a soft, malleable weld deposit.
55% nickel rods – the rods are less expensive compared to 99% nickel rods. The rods are machinable and are suitable for thick section repairs.
Difference between Cast Iron and Cast Steel
Cast steel contains less than 2% of carbon. It comprises alloy steel and carbon steel, making it ideal for design. You can easily manipulate cast steel to create different shapes and hollow pieces. When steel metal is welded, it changes its chemical composition. It is perfect to use in heavy loads and humid environments.
Cast steel also boasts uniformity in various directions. You can create specific and accurate finished products. Most people prefer cast steel because of its affordability and takes less time to manufacture. the faults of steel lie in the wear resistance and mobility
Cast iron contains 2% carbon which has ductile, gray iron, and malleable. When cast iron is welded, its durability is increased, and vibration decreased. The metal can be used to make oil pans, hammers, wheels, and flywheels.
Ductile iron is common in agricultural and engineering industries and pressure pipes, while grey cast iron prevents rusting. Cast iron can handle heavy loads. Besides, malleable and ductile iron is known for its flexibility and heat-resistant features. The metal is ideal for manufacturing processes despite it being expensive and complicated.
Welding cast steel is very much possible, provided you use the proper techniques. Cast steel is highly flexible, allowing you to form hollow cross-section parts and complex shapes with a lot of ease. The strongest variability provides better weld-ability and functionality. When used in any project, cast steel guarantees extended durability and reliability.