Semi-solid High Chromium Cast Iron Microstructure And Properties

Semi-solid metal forming is a new forming technology on the rise of the 70s.In recent years, it had a deep understanding and shaping the law of the Semi-solid forming. Semi-solid forming had got a good commercial applications in the low melting point alloy and the light metal, but in the high melting point semi-solid forming of steel materials, the process is still in the initial stage. In this paper, the high chromium cast iron with high melting point was chosen for the study, semi-solid billets of the high chromium cast iron were papered by electromagnetic stirring. Compared the performance of high chromium cast iron in different electromagnetic stirring process with the conventional high chromium cast iron, we hope that we can obtain the optimal process of high-chromium iron billets. And the optimal processing to prepare the semi-solid ingot of high-chromium cast iron has been explored, providing the basis for the further study on the semi-solid forming technology of high-chromium cast iron. The commercial application of Semi-solid forming technology can be speeded up in the high melting point material.In this experiment, we take the voltage of the main factors affecting the magnetic induction and the mixing time as a high-chromium cast iron melt variable process parameters, using comparative methods to study the process parameters on high-chromium cast iron performance. We set the input voltage at 160v,180v,200v,stirring time at 75s,90s,120s, The results showed that:the use of electromagnetic stirring semi-solid preparation of high chromium cast iron billet organization is effective and feasible; Primary austenite of the high-chromium alloy cast iron morphology changed from the traditional large-cast into a petal-shaped dendrite and agglomerate; The average equivalent diameter of primary austenite significant decline, the average equivalent diameter is 49.9μm, the largest average diameter of primary austenite decreased by 67.6%, Primary austenite become smaller and the distribution is more uniform; The shape factor of primary austenite was improved significant, the average shape factor is 0.709, the maximum increase rate of 83.2%. The primary austenite tends to elliptical and nearly spherical. In the same input voltage, the primary austenite grain equivalent diameter increases with the mixing time continuously decreased, the shape factor on the rise. When the mixing time to reach a certain value, its equivalent diameter and shape factor stabilized; in different input voltage, Increased with the input voltage intensity, the primary austenite equivalent diameter will be decreased firstly and then increased slightly, the shape factor will be decreased after upgrading continuously, which show that the input voltage is not as high as possible. The performance of semi-solid cast iron mechanical samples has also been greatly improved, When it reaches a certain value after the change of high chromium cast iron stabilized electromagnetic stirring on the influence of high chromium cast iron drop; Under the same magnetic flux density, hardness of semi-solid high-chromium cast iron will increase and the decrease with the adding mixing time, toughness changed little; under the same stirring time, the semi-solid high-chromium cast iron has the similar trend; There are two aspects on the solidification curve of the high-chromium cast iron in the magnetic field(heating,cooling), the dominant position of two aspects will be different with the different input voltage, and then we will get the different curves of solidification.This paper also studied the performance and structure of the high chromium cast iron under the same heat treatment. The results showed that the organization of the samples retained austenite and martensite is more obvious after the same heat treatment, in which martensite was relatively small, dispersed distribution of secondary carbides. Performance of the materials had a significant improvement. Performance of semi-solid without heat treatment will be better than both of the conventional high chromium cast iron sample and the sample with heat treatment. So, achieved the same performance of high chromium cast iron, prepared by semi-solid forming method eliminates the need for heat treatment process, which can reduce industrial production processes and production costs, It will have great commercial value.In my experiment, we get the best processing of the high chromium cast iron prepared by the semi-solid method of electromagnetic stirring (input voltage at 180v,stirring time at 90s),laying the foundation for the development of the semi-solid forming technology of high chromium cast iron.