Welding Cast Iron to Steel

Welding is a method of fabrication used by joining metals or thermoplastics, with the help of coalescence. In involves the melting of workpieces and addition of a filler material to form a pool of molten material. This weld pool cools to become a strong joint, in order to produce the weld. Cast iron is a term which generally refers to Gray iron, however, it is also identified with a large group of ferrous alloys. Besides ferrous, which constitutes around 95% of the alloy material, the other elements present in it are carbon (C) and silicon (Si). Carbon constitutes around 2.1 to 4 wt%, whereas silicon constitutes normally about 1 to 3 wt% in the alloy. The melting temperature of cast iron lies between 1150^oC to 1200^oC, which is about 300^oC lower than the melting point of pure iron. Cast iron also shows good fluidity, excellent machinability, resistance to deformation, resistance to oxidation (rust), and castability. Nowadays cast irons have a wide range of applications in the engineering field, including car parts, pipes, etc.

Steel is also an alloy of iron, with variant carbon content. The carbon content in steel lies between 0.2% and 2.1% by weight, and it is the most cost-effective alloying material for iron. Besides carbon, other alloying materials, like manganese, chromium, vanadium, and tungsten are also used in the production of steel. Invention of the Bessemer process in the mid-19th century, made steel a relatively inexpensive material. Steel is one of the most common materials today and finds place in many applications like in infrastructure, tools, ships, machines and appliances. Cast iron welding is useful for various engineering and structural purposes. For these purposes, shielded metal arc welding (SMAW), which is also known as manual metal arc welding (MMA), is used.

Welding Process

Following are the steps for welding cast iron to steel:

1. The first step involves proper cleaning of the metal surfaces. It helps in the removal of dust which can adversely affect the durability of the weld. An air brush can be used for the process of cleaning.
2. Put a liberal amount of flux on the electrode. While welding, basically the electric current strikes an arc between the base material and electrode rod, which is made of steel and is covered with a flux. The flux protects the weld area from oxidation and contamination by the production of carbon dioxide gas during the welding process.
3. Perform the initial checkup of the electricity connection by testing the connection with a small tap of the welding stick.
4. Put the welding stick on the surface to be welded along with the flux. Try to make use of small and short overlapping beads. One should be prudent while holding the welding stick on the surface, as it produce too much heat.
5. A ball peen hammer should be used for tapping the weld while it is hot. It avoids the formation of cracks in the weld during the cooling period. The cooling process can be easily accomplished by wrapping a towel around the weld.

The process of welding cast iron to steel is versatile and can be performed easily with the help of inexpensive equipment. This makes it well suited to shop jobs as well as field work. The same special electrodes can be used for the welding of nickel, aluminum, copper and other metals.