Abstract: The present disclosure relates to the field of tungsten smelting, and in particular to a leaching method of scheelite, and provides a new technology that scheelite is leached in low temperature with a mixture acid of sulfuric acid and hydrochloric acid or nitric acid and hydrochloric acid, calcium is precipitated incompletely, and then the acid leaching solution is regenerated and closed-circuit recycled is provided. The new technology is able to leach scheelite sufficiently in low temperature so as to improve the recovery rate of tungstate and decrease the requirement of equipment. As well, the inner wall of the reaction kettle, the heating pipe and the temperature measuring device are made of steel lined tetrafluoro material which has high acid corrosion resistance and is able to deal with scheelite with high fluorine, resists the corrosion of HF.

Abstract: The invention belongs to the technical field of metal ceramics, in particular to a metal ceramic and a preparation method thereof. The hard phase is formed by at least four kinds of crystal grains with different compositions and shapes; and in the scanning electron microscope photograph of the metal ceramic, it can be observed the first hard phase comprising black titanium nitrocarbide, a thin ring and a thick ring wherein the core phase is pure black; the second hard phase in the form of a dark gray core-ring structure particles; the third hard phase in the form of a high-brightness white core-gray ring; and the fourth hard phase in the form of a homogenous gray phase and off-white core-gray ring structure particles. In addition, a white binder phase can also be observed, and the binder phase is at least one of cobalt and nickel.