High chromium cast iron

High chromium cast iron is the third generation of white cast iron developed from ordinary white cast iron and hard nickel cast iron. The chromium content of high chromium white cast iron is more than 11%, and the ratio of chromium to carbon is between 4~8. Under these conditions, M7C3 type carbides with high hardness almost completely replace M3C type carbides. The M7C3 type carbides basically exist in an isolated hollow hexagonal shape. Compared with the M3C type carbides, the matrix continuity is greatly enhanced, so the toughness of the whole material is significantly improved. At present, high chromium cast iron is widely used in mining, cement, electric power, road construction machinery and refractory materials.

Better wear resistance of high chromium cast iron mainly depends on its matrix structure and the type and distribution of carbides.
High chromium cast iron is a multi-component alloy with Fe, Cr and C as the basic components. The matrix in the high-chromium cast iron that has just solidified is extant, which is stable when heated to a higher temperature, and is saturated with elements such as C and Cr. When the temperature is lowered, the austenite will transform. Under normal conditions, high-chromium cast iron presents a multiphase structure dominated by estimate. The cast iron of this structure can better exert the potential of the material itself when used at high temperatures.
High-chromium cast iron is a chromium-based white cast iron with a chromium content between 12% and 28%. Due to the large amount of chromium added, the M3C-type carbide in the white iron becomes M7C3-type carbide. This alloy carbide is very hard and imparts good wear resistance to high chromium cast iron. On the other hand, during the solidification process, the M7C3 carbides are isolated and distributed in rod shape, which improves the toughness of high chromium cast iron to a certain extent.

Grade and chemical composition of high chromium cast iron (%)

Grade	C	Mn	Si	Ni	Cr	Mo	Cu	P	S
KmTBCr12	2.0-3.3	≤2.0	≤1.5	≤2.5	11.0-14.0	≤3.0	≤1.2	≤0.10	≤0.06
KmTBCr15Mo	2.0-3.3	≤2.0	≤1.2	≤2.5	11.0-18.0	≤3.0	≤1.2	≤0.10	≤0.06
KmTBCr20Mo	2.0-3.3	≤2.0	≤1.2	≤2.5	18.0-23.0	≤3.0	≤1.2	≤0.10	≤0.06
KmTBCr26	2.0-3.3	≤2.0	≤1.2	≤2.5	23.0-30.0	≤3.0	≤1.2	≤0.10	≤0.06

High chromium cast iron (containing 12% chromium >) is an excellent wear resistant material.In the research of high chromium cast iron, generally focus on high chromium cast iron such as Cr15, Cr20.With the increase of Cr content and the addition of various alloying elements, the influence on the change properties of the structure was studied.

Hardness of high chromium cast iron

Grade	As-cast or stress relieved		Hardened state or hardened state stress relief treatment		Soft Annealed
	HRC	HBW	HRC	HBW	HRC	HBW
KmTBCr12	≥46	≥450	≥56	≥600	≤41	≤400
KmTBCr15Mo	≥46	≥450	≥58	≥650	≤41	≤400
KmTBCr20Mo	≥46	≥450	≥58	≥650	≤41	≤400
KmTBCr26	≥46	≥450	≥56	≥600	≤41	≤400

The high temperature strength and high temperature hardness of high chromium cast iron are high, especially in the atmosphere containing chemical components such as SO2 oxidation resistance is very good.Therefore, it is widely used in heat resisting parts of blast furnace, coke oven, sintering furnace and other industrial furnaces.Especially at high temperature, high chromium cast iron also has better physical wear resistance, which is better than high aluminum cast iron.

High chromium cast iron application

High chromium cast iron as high wear-resistant material, has been effectively used in crushing, grinding, conveying and other mechanical and metallurgical equipment, particularly in the abrasive wear and impact wear of parts (such as crusher roller, bin liners, bell and hopper, blast furnace coal worse lining plate, coal mill roller cover, rolling stick, slurry pump flow components, etc.) is more widely applied.