To successfully weld cast iron it is necessary to consider which type of cast iron you are dealing with and the welding technique required for that particular type. Some types of CI are not weldable such as white aka chilled iron. cast iron. It is also necessary to investigate the reason for the damage and to take into account the requirements of the finished piece.
Types of Cast Iron
Gray cast iron,the most common of cast iron types, is usually identified according to its tensile strength. 30 grade cast iron has a tensile strength of 30,000 psi; 40 grade cast iron has a tensile strength of 40,000 psi; and 60 grade cast iron has a tensile strength of 60,000 psi. The most common grades of cast irons are the 20 and 40 grades. Gray cast iron is a ferrous material containing more than 1.75% of carbon, the greater part of which is present in the structure in the form of graphite. This graphite gives to the fracture a color varying from light to dark gray. Compared with steel, gray cast iron has low malleability or ductility caused by the separation of the major portion of the elementary carbon in the form of graphite, which form a network throughout the metallic matrix and separate from it.
The chemical composition of a common machine casting is as follows:
Carbon 3.0% to 4.2% any higher than this as a carbon content and it get real hard to weld.
Silicon 1.5% to 2.5%
Manganese 0.6% to 1.2%
Phosphorus 0.4% to 0.6%
Sulphur 0.05% to 0.18%
Basically, cast iron is steel with a lot more carbon. Steel contains carbon up to 1.75%. If steel has more than 1.75% carbon, it is called cast iron. Steel can dissolve up to 1.75% carbon. If more carbon is added, it won&#;t dissolve and remains a free carbon. When you look at cast iron under a microscope the free carbon appears as black flakes, hence the name &#;gray cast iron.&#; With the use of proper techniques and the correct filler alloy, most gray cast irons can be successfully welded.Be aware that there is another type of cast iron, called &#;white&#; or &#;chilled&#; cast iron. It is generally considered not weldable. White cast iron does not have the distinctive gray color of most cast iron and is generally found in equipment where extreme hardness is needed (e.g. rock crushers, steel mill rollers, etc.).
Generally id is usually by its application .It its off a machined part you can usually say its grey cast iron,though the exception is nodular cast iron found in cranks and camshafts. Even preheating is called for especially in castings with thin to thick sections .Braze welding is the easiest, followed by cast iron filler rods with oxy and lastly arc welding with nickel based electrodes. Cast iron does tend to absorb materials that interfere with a sound welding process. Some exhaust manifolds can be difficult to weld as the carbon in the exhaust material mixes with the carbon in compound and raises the overall carbon content too high to do a reasonable job.Diesel oil (a hydracarbon) soaked into a crack ain't a whole lot of fun either.
The Lincoln Electric book "Metals and how to weld them" gives some pretty good info on the types and process .
Personally I like to weld with Oxy acetylene and cast iron filler with borax based flux.Its possible to float the contaminants out on top of the molten weld puddle. Its time consuming but gives the best results ,but the process takes time to learn and is hot and uncomfortable for non welders.
Thats the quick and dirty on it.
Oz
The company is the world’s best oem the gray cast iron has supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
There are primarily 4 different types of cast iron. Different processing techniques can be used to produce the desired type, which include:
Cast Iron is an iron-carbon alloy that typically contains greater than 2% carbon. The iron and carbon are mixed in the desired quantities and smelted together before being cast into a mould.
Grey Cast iron refers to a type of cast iron that has been processed to produce free graphite (carbon) molecules in the metal. The size and structure of the graphite can be controlled by moderating the cooling rate of the iron and by adding silicon to stabilize the graphite. When Grey Cast Iron fractures, it fractures along the graphite flakes and has a grey appearance at the fracture site.
Grey Cast Iron is not as ductile as other cast irons, however it has an excellent thermal conductivity and the best damping capacity of all cast irons. It is also hard wearing making it a popular material to work with.
The high wear resistance, high thermal conductivity, and the excellent damping capacity of Grey Cast Iron makes it ideal for engine blocks, fly wheels, manifolds, and cookware.
If you want to learn more, please visit our website oem iron casting manufacturer.
White Cast Iron is named based on the appearance of fractures. By tightly controlling the carbon content, reducing the silicon content, and controlling the cooling rate of iron, it is possible to consume all carbon in the iron in the generation of iron carbide. This ensures there are no free graphite molecules and creates an iron that is hard, brittle, extremely wear resistant and has a high compressive strength. As there are no free graphite molecules, any fracture site appears white, giving White Cast Iron its name.
White Cast Iron is used primarily for its wear resistant properties in pump housings, mill linings and rods, crushers and brake shoes.
Ductile Cast Iron is produced by adding a small amount of magnesium, approximately 0.2%, which makes the graphite form spherical inclusions that give a more ductile cast iron. It can also withstand thermal cycling better than other cast iron products.
Ductile Cast Iron is predominantly used for its relative ductility and can be found extensively in water and sewerage infrastructure. The thermal cycling resistance also makes it a popular choice for crankshafts, gears, heavy duty suspensions and brakes.
Malleable Cast Iron is a type of cast iron that is manufactured by heat treating White Cast Iron to break down the iron carbide back into free graphite. This produces a malleable and ductile product that has good fracture toughness at low temperatures.
Malleable Cast Iron is used for electrical fittings, mining equipment and machine parts.
For more Reducer Housinginformation, please contact us. We will provide professional answers.