Material Composition

It has something to do with the method of casting and cooling. What you mentioned actually fits ductile iron, low carbon but have considerable strength and weldability than grey iron. Try to read basic material science, regarding void, dislocation, grain etc. Forgive me, i took material science about 10 years ago. I am poor with terminology nowadays. What carbon does, are filling the voids thus making your metal tough, hard and brittle. What casting and cooling methods do is making the shape of grains in your metal. Irregularly shape or coarse grains results a brittle and hard metal, regularly shape and fine grains results malleability and ductility of metal. This is as far as my memory could go. I suggest you go open a book or google material science basic.

Dear Dhinesh,

The reason for reducing the carbon content and alloying elements for increasing weldability is like this. You must be aware that as carbon content in steel increases it becomes difficult to weld (weldability) due to the formation of more volume of carbides (cementite). Almost all alloying elements form carbides which decrese weldability. Weldability in steel is calculated by calculating carbon equivalent (CE) due to all alloying elements added. That is exactly why carbon is reduced in alloy steels where you need better weldability. For example if you consider 304 class of stainless steel people prefer to use 304L, which means carbon content is reduced in chemistry, for better weldability.

I hope the explanation given above satisfies your requirement.

Frankly, I don't know whether this particular information is correct or not. But if you are relying on Wikipedia as a source for critical material properties information you are making a big mistake and compromising the quality of your work. There are much better sources of information on metallurgy and welding on-line. Use them, not Wikipedia.

thank you all for your suggestions. frankly says, i'm new to these metallurgic field. so can you suggest me any links or books to learn it in depth.i'm very interested to learn this in detail. but i haven't have any materials in my hand. kindly do the needful. thank you.

This links serves for carbon steels and weldability

http://en.wikipedia.org/wiki/Equivalent_carbon_content