Abrasion-Resistant White Cast Iron 5
- B. High chromium white cast iron
The eutectic structure of high chromium cast iron (Cr > 13%) is different from that of ordinary pearlite white cast iron. And its eutectic carbide is M7C3 type of hexagonal system. The hardness of the carbide is up to HV1600 ~ 2100. At the same time the carburizing hardness of common white cast iron is HV1100. When Cr/ C is greater than 4 it forms M7C3 eutectic carbide. With the increase of Cr / C the solidification characteristics of the cast iron also change greatly.
When common white cast iron solidified eutectic carbide M3 C type is continuous. Meanwhile A body express isolated phase. On the contrary, the eutectic carbide M7C3 formed by the high chromium white cast iron express isolated. And the A body is a continuous phase. Which greatly reduces the separation or embrittlement of the high hardened abrasion-resistant relative to the matrix.
After heat treatment the matrix appears as martensite with high hardness. So that the cast iron shows good comprehensive properties. Grinding ball in cement industry we use Cr13% high chromium cast iron. And in the production of ball mill liners in cement industry we use high chromium steel with Cr1.0% to 1.5%.
In 1958,L.Limex molybdenum company T.E.Norman invented Cr15 – Mo3 (Cr15 % ~ 18 %). Which was recognized by its good anti-wear and comprehensive mechanical properties.There are two types of the cast iron. One is medium carbon (below 2.8%) and the other is high carbon (C2.8% to 3.6%). Due to the high cost of Mo the applications are limited. So by replacing part Mo with Ni, Cu and Mn developed many 15Cr type Abrasion-Resistant White Cast Iron. For example, type 15-2 – 1 and so on. In the following-up articles we’ll list the typical brands and related properties of high chromium white cast iron.