Cast Iron Welding Procedures: How to Weld Cast Iron

What is Cast Iron?
Cast iron is one of the alloys of iron that has a significant content of carbon in it. The content of carbon varies from about 2% to 4%. This carbon content is about 10 times greater than it is found in other alloys like wrought iron or steel. The cast iron manufacturing process is simple as a result of its simple combination. The process of casting, or molding of cast iron, is relatively easy and it goes as follows.

• Initially, normal iron that has been purified in the blast furnace, is poured out into casts and a good amount of carbon is mixed-in as it starts cooling down.
• This process of mixing takes place when the iron is in a semi-molten form. The temperature of the molten metal is about 1450 degrees Fahrenheit. This prevents the carbon from burning and helps it blend with the molten matter.
• The iron which has now become cast iron is let to cool down gradually and properly.
• This process of cooling down makes the surface of the cast iron smooth and prevents it from cracking. A disturbance in the cooling down process produces cracks or uneven cervices in the surface. The carbon that is present in the molten iron, forms flakes of graphite throughout the alloy that gives it the characteristic of brittleness.

Though cast iron has many uses, it's characteristic of being brittle becomes a headache, when it comes to repairing objects made up of cast iron. The following are some of the processes that prove to be useful while repairing and welding cast iron.

How to Weld Cast Iron?
Before welding and repairing cast iron, it is always advisable to make the surface, that is to be welded, smooth and clean. The clean surface ensures a very good quality in welding and also prevents it from cracking. Cast iron welding procedure can be carried out in four ways, which are as follows.

• Cast iron welding procedures with the help of preheat.
• Cast iron welding procedures without preheat.
• Sealing cracks with the help of cast iron welding procedures.
• Studding method

Cast Iron Welding Procedures with the help of Preheat
The cast iron welding procedure that is carried out by applying preheat is usually used in heavy industries. The concept of application of preheat makes the process a bit complicated as appropriate heating equipment is also required. Most of the times the whole object that is to be welded, is heated up till a temperature that ranges between 500 to 1200 degrees Fahrenheit. However one must avoid heating more than 1400 degrees as the metal starts turning into a molten stage. After the metal reaches the high temperature, start welding it using a low current. The low current should be used so to minimize admixture and the residual stress. Sometimes it also becomes necessary to restrict the width of the welds. Ideally the welds must be minimized to about an inch long segment. An excessive weld can also lead to cracking of the surface. The cooling process is extremely critical in the preheated welding process. The object must not be disturbed and must be allowed to cool down gradually. For gradual cooling the object can be buried in sand or can even be covered with an insulation blanket.

Cast Iron Welding Procedures without Preheat
Preheated welding can be easily carried out at the domestic levels for small and manageable objects. While welding the cast iron without preheating, it is extremely essential to have a good control over the welding gun and have the welds as small as possible. The best option is to make the welds about 1 inch thick. It is also very important to let the welds cool down gradually. After the cooling process is complete, it is important to peen the extra welds that are deposited on the surface.

Sealing Cracks
Cracks in the surface of cast iron tend to be very troublesome. It is hence advisable to use the preheated technique to seal cracks. One can also use the peening action in order to make the welded crack smooth and even.

Studding Method
The studding process is an extremely complex process due to the fact that one requires a lot of skill for this method. The first step is to drill and tap holes on the surface that has beveled. The next step is to put in steel studs and weld them into the surface. The steel studs will help in covering the entire surface into the location where the surface has cracked. The welded deposit can be further used to make a reinforcement over the crack.

It is recommended that one resorts to the non-preheating cast iron welding procedure for domestic purposes. While welding cast iron to steel the preheating procedure proves to be highly effective.