Study on microstructure and properties of chromium series wear-resistant Cast Iron Grinding Ball
Based on the effect of Cr in Cr-based WEAR-RESISTANT CAST IRON, three kinds of wear-resistant cast iron grinding balls with diameter of 110mm and different Cr content were designed by means of metallographic technique, electron microscope technique, TEM technique and X-ray diffraction technique, the macro hardness, microhardness, impact toughness and wear properties of the material were compared and analyzed.
The effect of different chromium content on the properties of high chromium wear resistant cast iron was discussed, and two different heat treatment methods were used to improve the structure and properties of high chromium wear resistant cast iron. And the influence of two different heat treatment processes on the material is discussed and summarized. The results show that the EUTECTIC structures of the three cr-based cast irons are all Ledeburite, the eutectic structures of the low and middle cr-based cast irons are coarser, and the eutectic structures of the high cr-based cast irons are smaller.
With the increase of chromium content, the carbides of three chromium series cast irons changed from M3c to M7C3. The low chromium type of carbides was mainly M3c, and the carbides were distributed as honeycomb and network The carbides in medium chromium cast iron are a mixture of M3C and M7C3. The amount of carbides in medium chromium cast iron is more than that in low chromium cast iron. The type of carbides of high chromium cast iron is M7C3, which is a kind of high hardness carbides. The microhardness of the material is higher than that of medium chromium type M7C3 carbides are distributed in the Matrix in the form of hexagonal rods and slats, and the degree of continuity is greatly reduced.
The hardness of as-cast high chromium cast iron is higher than that of low and medium chromium cast iron, and the surface hardness is up to 53HRC, and the impact toughness of the three chromium series cast iron is lower than 4.73 j / cm2. On this basis, two heat treatment schemes were designed to study the effect of heat treatment process on the microstructure of high chromium cast iron. The results show that when the high chromium cast iron with about 15% chromium content is treated by conventional heat treatment, when the quenching temperature is 850 °c and the tempering temperature is 350 °c, the microstructure and properties of high chromium cast iron are the best, and the Matrix with Martensite is obtained The main type of carbides is M7C3, and the content of carbides is high, and the carbides are distributed as broken block and strip. The surface hardness can reach 60HRC and the impact toughness can reach 6.3 j / cm2. The Matrix structure of Martensite and needle-like lower bainite can be obtained by ISOTHERMAL quenching Heat Treatment. The hardness of Lower Bainite is close to Martensite, and the toughness is better than that of Martensite, so the high chromium cast iron has better impact toughness. The optimum matrix structure can be obtained by isothermal quenching at 320 °C for 1.5 H. The hardness is up to 63HRC and the impact toughness is up to 8.4 j / CM2.
The results show that the ISOTHERMAL quenching process can improve the microstructure and properties of the material effectively, and obtain a better impact toughness of the material. The results show that the fracture of high chromium cast iron is brittle fracture and the wear mechanism is mainly abrasive wear. The wear resistance of high chromium cast iron after austempering is better than that of conventional heat treatment.
Our heat treatment machine has two types, one is the electrical type, another type is the gas type. For each type have the same effect during the heat treatment process, including oil/air quenching, tempering, annealing.