Method for preparing high-melting-point metal powder through multi-stage deep reduction

A method for preparing a high-melting-point metal powder through a multi-stage deep reduction, comprising the following steps:

• step 1, performing a self-propagating reaction:
• drying a high-melting-point metal oxide powder to obtain a dried high-melting-point metal oxide powder, mixing the dried high-melting-point metal oxide powder with magnesium (Mg) powder to obtain mixed materials, adding the mixed materials into a self-propagating reaction furnace to perform the self-propagating reaction, and performing cooling to obtain an intermediate product in which a low-valence oxide MexO of a high-melting-point metal (Me) is dispersed in an MgO matrix,
• wherein the intermediate product in which the low-valence oxide MexO of the high-melting-point metal is dispersed in the MgO matrix is a mixture of low-valence high-melting-point metal oxides with a non-stoichiometric ratio,
• x is 0.2-1,
• the high-melting-point metal specifically comprises one or more of W, Mo, Ta, Nb, V, Zr, Hf and Re,
• the high-melting-point metal oxide is one or a mixture of several kinds of WO3, MoO3, Ta2O5, Nb2O5, V2O5, ZrO2, HfO2 and Re2O7, and
• when the high-melting-point metal oxide is WO3, a mixing proportion in molar ratio of WO3 to Mg is 1 to (0.8-1.2), when the high-melting-point metal oxide is MoO3, a mixing proportion in molar ratio of MoO3 to Mg is 1 to (0.8-1.2), when the high-melting-point metal oxide is Ta2O5, a mixing proportion in molar ratio of Ta2O5 to Mg is 1 to (2.7-3.3), when the high-melting-point metal oxide is Nb2O5, a mixing proportion in molar ratio of Nb2O5 to Mg is 1 to (2.7-3.3), when the high-melting-point metal oxide is V2O5, a mixing proportion in molar ratio of V2O5 to Mg is 1 to (2.7-3.3), when the high-melting-point metal oxide is ZrO2, a mixing proportion in molar ratio of ZrO2 to Mg is 1 to (0.8-1.2), when the high-melting-point metal oxide is HfO2, a mixing proportion in molar ratio of HfO2 to Mg is 1 to (0.8-1.2), and when the high-melting-point metal oxide is Re2O7, a mixing proportion in molar ratio of Re2O7 to Mg is 1 to (2.7-3.3);
• step 2, performing a primary leaching:
• placing the intermediate product in which the low-valence oxide MexO of the high-melting-point metal is dispersed in the MgO matrix into a closed reaction kettle, leaching the intermediate product with hydrochloric acid as a leaching solution to obtain a leaching solution and a leaching product, removing the leaching solution, washing the leaching product, and performing vacuum drying on the washed leaching product to obtain a low-valence oxide MexO precursor of the low-valence high-melting-point metal, wherein a molar concentration of hydrochloric acid is 1-6 mol/L;
• step 3, performing the multi-stage deep reduction:
• uniformly mixing the low-valence oxide MexO precursor of the low-valence high-melting-point metal with calcium (Ca) powder, performing pressing at 2-20 MPa to obtain a block blank, placing the block blank in a vacuum reduction furnace, performing heating to 700-1,200° C., performing a secondary deep reduction for 1-6 h, obtaining a block billet after the secondary deep reduction, and cooling the block billet along with the vacuum reduction furnace to obtain a deep reduction product, wherein a molar ratio is described as follows:
• MexO:Ca=1:(1.5-3);
• and
• step 4, performing a secondary leaching:
• placing the deep reduction product in the closed reaction kettle, leaching the deep reduction product with hydrochloric acid as a leaching solution to obtain a filtrate and filter residues, removing the filtrate, washing the filter residues and performing vacuum drying to obtain a low-oxygen high-melting-point metal powder,
• wherein a molar concentration of hydrochloric acid is 1-6 mol/L,
• the low-oxygen high-melting-point metal powder comprises the following ingredients by percentage by mass of equal to or smaller than 0.8% of O, greater than or equal to 99% of the high-melting-point metal and a balance of inevitable impurities, and
• a particle size of the low-oxygen high-melting-point metal powder is 5-60 μm.