Welding Cast Iron to Steel

Welding cast iron to steel is an important part of many engineering processes. The following article provides information about how this process is carried out.
Welding is a method of fabrication used to join metals or thermoplastics, with the help of coalescence. In involves melting of the work pieces and addition of a filler material to form a pool of molten material. This weld pool then 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. 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 1150oC to 1200oC, which is about 300oC 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 iron has a wide range of application in the engineering field, including car parts, pipes, etc.

Steel is also an alloy of iron, with variable carbon content. The carbon content in steel lies between 0.2% to 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 various 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 may adversely affect the durability of the weld. An air brush can be used for this purpose.
  2. Put a liberal amount of flux on the electrode before starting the process. While welding, basically the electric current strikes an arc between the base material and the 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 carbon dioxide gas which is produced 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 careful while holding the welding stick on the surface, as it produce a lot of 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 wet towel around the weld.
The process of welding is versatile and can be performed easily with the help of inexpensive equipment. This makes it well suited for shop jobs as well as field work. The same special electrodes can be used for the welding of nickel, aluminum, copper, and other metals also.