Product Description and Process
wear resistance of chromium cast iron sand castings foundry
Production process: green sand molding, lost foam process
Surface treatment process: paint coating
Product Material and Uses
Normally produce with ASTM A532 class IA, class IB, class IC, class ID, class IIA, class IIB, class IID, class III A, etc.
The wear resistant cast iron casting products are widely used for mining machinery components, ball crusher parts, crusher hammerhead parts, mud pumps components, etc.
Ni Hard Cast Iron Casting & Wear Resistance
Wear resistance can be achieved in cast iron in two basic ways. Firstly a normal grey iron can have small additions of copper, molybdenum, vanadium or chrome added. These are usually up to 1% and can increase the hardness from a base of about 150 Brinell up to 200 to 300 Brinell by promoting the formation of pearlite in the casting, particularly if the carbon and silicon levels are controlled to the lower end of the desired range. If these hardness’s are sufficient, this method has the advantage that the resultant alloy is still machineable.
The second method involves the use of chrome and nickel in much higher quantities, the chrome content being as high as 28% to create a structure that includes a high proportion of primary carbides. Although a lot of chrome iron castings are supplied in the as cast state, these alloys are heat treatable, which promotes the growth of secondary carbides, and can attain hardness’s as high as 700 Brinell.
Tempering can be used to increase the toughness. This second method is, unfortunately, only machineable using special techniques and cutting processes which usually results in castings that are cast to size. Where fixings are required it is possible to cast in threaded bars or blocks of steel that can be drilled and tapped after the casting is made to give fixing and location points.
Wear Resistant Ni Hard Cast Iron Castings Methods
There are a number of ways of describing this highly alloyed type of iron – Chrome Iron, Wear Resistant Iron, Ni Hard or 28% Chrome being the more common ones, along with a range of national and international standards. This can cause some confusion and at Durham Foundry we are happy to advice on a suitable grade that will give the wear resistance required. One side effect of the levels of chrome and nickel used in these grades is that they can have good corrosion resistance which can lead to alternative applications.
Also, given the inherently higher melting point of chrome compared to cast iron, they can be used for heat resistant castings, particularly if the carbon content is controlled to the lower end of the permissible range in some of the 28% chrome grades. These heat resistant versions have applications in castings such as fire bars and grate assemblies in stoves.