The Research Of The Vermicularizing Treating Process And The Mechanism Of The Rare-earth Compacted Graphite Cast Iron

In this paper, under laboratory conditions, it use the small medium frequency induction furnace to melt and handle vermicular cast iron and at the same time use a rotating magnetic field device to affect and control the injection vermicularizing process. To study the influence law of the different kinds of vermicularizing alloy, addition amount, injection vermicularizing treatment, inoculation and injection vermicularizing process and applying rotating magnetic field in the process of solidification of the creep rate and vermicular cast iron graphite morphology, matrix organization and performance. Especially for the problem of the narrow scope of vermicularizing alloy addition amount and the difficulty control with the injection vermicularizing treatment, it do a detailed study of the effects of various factors on injection vermicularizing treatment and the range of vermicularizing alloy and strive to expand the addition amount of vermicularizing alloy and reduce the difficult to control the production process. The experimental results show that:(1) The different vermicular agents have the different amount of vermicular agents to get the high vermiculizer. The graphite morphology will become the vermicular graphite from flake graphite and eventually became spherical graphite with the change of the amount of the vermicular agents.The matrix organization will be also different and occur the transformation from ferrite to pearlite. To get the same vermiculizer, the matrix organization will be different with the different vermicular agents. The castings have the more ferrite with the re-ferrosilicon alloy and the castings have the more pearlite transformation with the rare earth magnesium alloy and the pearlite is most important in the castings with the rare earth magnesium calcium alloy. Tensile strength and hardness of the cast iron in general are increased with the increase of the addition amount of vermicularizing alloy.(2) Due to the addition of inoculation,the castings have the ferrite and pearlite. Inoculation can not only eliminate the white tissue, but also increase the amount of graphite. The fixed time of the creep and the incubation can get stable high vermicular graphite rate and good tensile strength and hardness and the more number of effective vermicular. The slower cooling rate can easier get vermicular graphite and the faster cooling rate can easier get spherulitic graphite.(3) The mixture vermicularizing alloy with the titanium and calcium have the better injection vermicularizing effect and the more wide of the addition amount range. To get the similar injection vermicularizing effect with the two kinds of hybrid vermicularizing alloy, vermicularizing alloy containing titanium have big chilling tendency and it is easier to obtain pearlite of as-cast structure and vermicularizing alloy with calcium have the fewer ferrite and the less pearlite of the matrix organization.(4) Magnetic field is applied to promote injection vermicularizing process and make the creep rate increased and increase the addition amount range of vermicularizing alloy and reduce the difficulty of the control of the production process of the vermicular cast iron. With the residual plenty of creep element, the electromagnetic stirring can make the process or mechanism of the graphite growth change and promote the formation of vermicular graphite and make the creep rate increase. The electromagnetic field has little effect on the matrix organization and the value of the tensile strength and hardness decreased only slightly.