Abrasion wear resistance is most required for hot rolling mill rolls, and cast iron with high carbon content, which has hard carbides, is widely used to the rolls. In the rolling operation, the roll surface is heated by contact with high-temperature rolled steels and with friction heat by rolling load in the roll-bite. This causes the roll to wears under the high temperature. Until now the effect factors were evaluated based on the microstructure and hardness at room temperature because of convenience. In this study the effect of high temperature hardness and the microstructure were investigated for the multi-component white cast iron which has widespread in recent years. And Ni that increases the hardenability and the high temperature property was added. As a result, the wear resistance has strong correlation with carbides amount and micro-hardness in matrix structure. The correlation with hardness at high temperature hardness was the same as room temperature hardness. Hot wear was small for white cast alloys containing 1.5mass%C-Ni-free and 3mass%C-7.5mass%Ni. The former is thought to due to the high hardness martensite matrix and the latter due to the reinforcement of the matrix structure by adding Ni and the large amount of high hardness carbide in the multi-component white cast iron.
Multi-component white cast iron containing Cr, Mo, W, V has excellent abrasive wear resistance due to the MC carbide with high hardness. In the centrifugal casting, since the MC carbide formed by V has a lower specific gravity than that of molten metal, there is a tendency to segregate itself toward the inside because of the centrifugal force. As a measure to solve this problem, it has been proposed to add Nb which forms the same type of MC carbide with a high specific gravity and to suppress the segregation by making the composite M (V, Nb) C carbide crystallize. In this research, the effect of Nb content on the degree of segregation was investigated. In the hyper-eutectic region, Nb with a higher specific gravity was enriched outward by the centrifugal force. In the hypo-eutectic region, a simultaneous enrichment of Nb and V was observed near the inner surface. Although the effective range of Nb content must be limited, the possibility to reduce the segregation by Nb-addition was confirmed.
The wettability behavior of molten Al-Si alloy and carbon fibers (CF) was evaluated by the dipping coverage method. This study focused on the effects of silicon content in Al-Si alloy melts on the wettability at 1000℃, and identified the interfacial products around the CF hot-dipped in the Al-Si alloy melts. Depending on the Si content, the interfacial product changed from Al4C3 to SiC. The product at the Al alloy/CF interface was Al4C3 when the amount of Si in the molten Al was 0 to 10 mol%. When the amount of Si was 20 mol%, it was a mixture of SiC and Al4C3, which is different from the prediction based on the calculated phase diagram. This was due to a partial decrease in the concentration of silicon in the Al-Si alloy during SiC formation. The change trend of the wetting rate with Si content was almost consistent with that of the driving force for carbide formation. This suggests that the change in wetting rate with Si content may be due to the difference in the formation rate of interfacial products.