Cast irons are a family of iron-carbon alloys. Their high carbon content (usually 2–4%) gives cast iron its characteristic hardness. However, that hardness comes at the expense of ductility. It is less malleable in comparison to steel or wrought iron. The heating and cooling cycles during welding cause expansion and contraction in the metal, inducing tensile stress. Cast irons do not stretch or deform when heated or stressed—instead, they crack—making them extremely difficult to weld. This characteristic can be improved by adding different alloys.
Some cast iron alloys are easier to weld than others:
Grey cast iron
Grey cast iron is the most common form of cast iron. Carbon precipitates out into graphite flakes during manufacturing into either a pearlite or ferrite crystalline microstructure. It is more ductile and weldable than white cast iron. However, it still poses a challenge to prospective welders as the graphite flakes within grey cast iron can enter the weld pool to cause weld metal embrittlement.
White cast iron
White cast iron retains the carbon as iron carbide without precipitating it out as graphite. The cementite crystalline microstructure is very hard and brittle. White cast iron is generally considered unweldable.
Ductile, nodular, or malleable iron
These cast irons are all less brittle due to microstructural differences due to manufacture. All three have spheroidal carbon microstructures created by their unique manufacturing processes.
ABOUT KEVA
Keva Casting is a professional casting company that focuses on Construction, Machinery, Automobile, Hardware, Pipeline and many other industries.
We provide top quality products with the best service based on our complete production chain including our own mold design, advanced production techniques, and full management of the supply chain. Keva Casting has two factories located in Zhucheng, China's Shandong province.
We use "shell molding", which is a new technique that has been developed in recent years.This new technique has simplified production procedures and reduced air pollution compared with traditional sand casting and investment casting. Shell making and core making are faster to ensure production in enormous quantities. The dimensions and surface finishing are satisfactory for all kinds of industrial requirements. Besides supplying our own formwork & scaffolding systems, our casting products also supply OEM services in various industries.