As a wear-resistant material, white cast iron has experienced three stages: ordinary white cast iron, nickel hard white cast iron and high chromium white cast iron. The bucket teeth made of them have good wear resistance, but poor toughness. They are suitable for working conditions with small impact and low material hardness.
An isothermal quenched ordinary white cast iron is introduced. Its chemical composition is 2.21% ~ 2.40% C, 0.28% ~ 0.30% Si, 0.69% ~ 0.71% Mn, 0.03% ~ 0.04% P, s content is less than 0.08%, impact toughness is 2.1 ~ 2.54j/cm2 (sample size is 15mm) × 15 mm × 55mm), with a hardness of 55 ~ 59HRC. It is used on the bucket teeth of wu400 / 700 bucket wheel excavator and tested in Maoming open pit mine, Guangdong. Under normal conditions, its service life is three times that of high manganese steel. The chromium content of high chromium cast iron is generally greater than 15%, and w (CR) / w (c) is greater than 4. The carbide becomes isolated rod or strip, which improves the toughness, and the hardness of carbide is also increased to 1200 ~ 1600hv, which ensures good wear resistance. It is mostly used for cast-in-place bucket teeth and bucket tooth ends of bucket wheel excavators.
C | Si | Mn | Cr | Mo | Ni | Cu | S | P |
2.0~3.6 | ≤1.2 | ≤2.0 | 14.0~18.0 | ≤3.0 | ≤2.5 | ≤1.2 | ≤0.06 | ≤0.10 |
In the same brand of high chromium cast iron, low carbon cast iron has good impact toughness but low hardness, which is suitable for high impact load conditions; High carbon cast iron has good wear resistance and is suitable for occasions with small impact load. The chemical composition (mass fraction,%) of Cr15 cast iron is shown in Table 1, and the corresponding metallographic structure and mechanical properties are shown in Table 2.
Status | Metallographic structure | HRC | αk/(J/cm2) |
Air quenching + Tempering | Martensite + M7C3 + secondary carbide + retained austenite | ≥58 | ≥3 |