Welding is a manufacturing process in which two or more parts are fused by heat, pressure, or both to form a joint when the parts cool. Today we will discuss how to weld cast iron, a group of iron-carbon alloys with a carbon content of over 2%. Welding cast iron is possible, although it can be problematic due to its high carbon content. This carbon content is often about 2-4%, which is about 10 times that of most steels. The welding process transfers this carbon to the weld metal and / or heat-affected zone, increasing brittleness / hardness. This can cause cracks after welding.
Let’s take a look at how to weld cast iron, the process, its benefits, and the different techniques for welding cast iron.
Cast Iron Welding
Cast iron is composed of iron and carbon in varying proportions with additional elements such as manganese, silicon, chromium, nickel, copper, molybdenum, etc. to enhance certain properties. In addition, there may be significantly higher levels of sulfur and phosphorus. Since the inconsistencies make it difficult to weld without cracks.
1. Pre-Welding Steps for Cast Iron
Following are the steps that you should take into consideration for effective cast iron welding:
· Detecting the Alloy
· Scrubbing the Cast
· Choosing the Accurate Pre-Heat Temperature
· Choosing the Right Welding Technique
Detecting the Alloy
Cast iron has low ductility and can crack due to thermal stress when heated or cooled rapidly. The susceptibility to cracking depends on the type / category of cast iron. This means that you need to understand the type of alloy you are using.
Grey Cast Iron
· White Cast Iron
· Ductile (Nodular) Iron
· Malleable Iron
The simplest way is a Chemical and metallographic analysis which can also help in identifying the category of the cast iron that you exactly require for your working.
2. Scrubbing the Cast
It is important to clean the cast iron before welding by removing all surface materials such as paint, grease and oil, paying particular attention to the welding area. It is important that the surface is cleaned with mineral spirits to remove surface graphite before welding.
3. Choosing the Accurate Pre-Heat Temperature
If you want to minimize the residual stresses build-up during the heating and cooling process than you must avoid stress cracking in cast iron is heating/cooling control.
4. Choosing the Right Welding Technique
In general, there are many techniques for cast iron welding. It is generally preferred that you just need to focus on that process, which facilitates slow heating and cooling.
· Manual Welding
· Flux Cored Arc welding
· Metal active gas welding
· Submerged arc welding
· Tungsten arc welding
· Brief Description of major welding Techniques
Manual Welding
This type of welding, also known as shielded arc welding (SMAV), is generally believed to be the best overall cast iron welding process – provided the correct welding rods are used. The choice of electrode will depend on the application, the required color matching and the amount of processing after welding.
Flux Cored Arc welding
Flux-coated arc welding is a semi-automatic or automated arc welding process. FCAW requires continuously fed continuous tubular electricity with constant flux and voltage or, more often, a conventional-constant welding power supply. The pool is protected by a flux contained inside the tubular electrode with an extra shield from gas emitted from the outside.
Metal Active Gas Welding
MAG (Metal Active Gas) welding is an arc welding process in which an electric arc is created between the consumable wire electrode and the material to be joined. MAG welding uses active shielding gases, primarily for welding steels. These gases include carbon dioxide, argon and oxygen.
Submerged Arc Welding
Submerged arc welding (SAW) is a process of welding that mainly involves the formation of an arc between a continuously fed electric and the workpiece. A blanket of powdered flux generates a protective gas shield and slag (and can also be used to add alloying elements to the welding tank) that protects the welding belt.
Tungsten Arc Welding
Gas tungsten arc welding (GTAW), which is also regarded as inert tungsten gas welding (TIG), it is an arc welding process that uses a non-consumable tungsten electrode in order to produce welding. The welding area and the electrode are protected from oxidation or other atmospheric contamination by an inert shielding gas (argon or helium).
Key Benefits Of Cast Iron As A Weld Metal
Many desirable properties include strength, toughness, thermal conductivity, and moisture capacity.
· Ability to shape by throwing sand
· Low cost material
· Lower melting point than steel
· Wet more than steel
Conclusion
It is possible to weld cast iron, but you need to follow the correct technique and be careful not to crack. Most welding methods require surface cleaning of the material, while cast iron requires pre- and post-weld heating and thorough cooling.
All this ensures a good finish and efficient welding of the cast iron. You know how to weld cast iron. Many thanks!
