What steps should you take for stick welding cast iron?
This article will discuss that. The two sections of the discussion are understanding cast iron and how to weld cast iron. Let’s start!
Understanding Cast Iron
Cast iron is a combination of iron (Fe) and carbon (C), but with a carbon content greater than 2%.
Cast iron also contains the element silicon (Si) which functions as a graphite booster, meaning it encourages graphite to form in cast iron.
Graphite is free carbon which has a material that does not bond with other elements to form compounds, so it is relatively soft.
It has an important role in determining the mechanical properties of cast iron.
Types of cast iron include gray cast iron, nodular cast iron, malleable cast iron, white cast iron.
Steps to Weld Cast Iron
It’s crucial to learn the processes involved in creating the component that will be successfully welded if welding is being done at home.
Before beginning, there are four essential steps to take:
- Determine the alloy.
- Thoroughly clean the casting.
- Decide on the preheating temperature.
- Pick a suitable welding technique, in this case, stick welding cast iron.
Determine the Alloy
When heated or squeezed, cast iron does not stretch or flex; instead, it fractures, making welding highly challenging.
This feature can be enhanced by the addition of other alloys.
Checking the original specs is the most effective approach to identify if you have a white or gray iron.
These requirements can be obtained through spectrochemical examination after the fact.
There are various ways to check in store if this exact procedure is not feasible.
Gray iron’s microstructure contains graphite, which causes gray to show along the fracture points.
Due to the cementite, white iron is paler near the fault.
Sadly, the fracture test is only effective if the welder is aware of the color of the material—gray or white. This is the more ancient and conventional type of cast iron.
Moreover, they are more prevalent in some categories of commodities.
A more recent material, ductile iron, is significantly more weldable and also fairly white along the fault.
Thoroughly Clean the Casting
Clean the weld zone of paint, oil, and other unwanted substances.
To release trapped gasses from the base metal weld zone, it is advisable to gently and slowly apply heat to the weld area for brief periods of time.
Placing a weld track on cast iron is a quick method of determining whether the surface is ready to be repaired.
Dirt will cause metal to be porous. Repeat this technique again and over until the porosity is gone.
Decide on the Preheating Temperature
Under stress, all cast iron is prone to breaking. The most crucial element in preventing cracks is controlling heat.
For high temperature welding procedures, a higher temperature preheat is typically required.
When proper preheating cannot be accomplished, reducing heat input is the best course of action.
Cast Iron Stick Welding
This stick welding, also known as MMA, uses a consumable electrode that has been flux-coated.
Depending on the application, the level of needed color matching, and the degree of post-weld machining, many types of electrodes can be employed.
For cast iron stick welding, there are three primary categories of fillers that are effective:
- Electrodes coated with cast iron.
- Electrode made of copper alloy.
- Electrode made of nickel alloy.
For welding cast iron, Electrodes made of nickel alloy are most prevalent.
According to New Hampshire Materials Laboratory Inc., nickel-iron welds have a lower coefficient of thermal expansion, making them stronger and reducing weld stress and increasing crack resistance.
Metal is melted and fused by an electric arc that forms between the electrode and the welding region.
To reduce dilution, the arc should be pointed at the weld pool rather than the base metal.
To reduce heat stress, I advise utilizing the lowest current setting permitted by the manufacturer.
When using cast iron or copper electrodes for welding, preheat the component to at least 250°F. It is possible to use nickel electrodes without preheating.
Make sure you follow steps for cast iron to make the best welding quality.