Abstract: A process is provided for producing a fine tungsten carbide powder, which comprises the steps of drying a slurry, which is obtained by mixing an aqueous ammonium tungstate solution with a carbon powder, at low temperature, to form a precursor, mixing a reduction and carburization product, which is obtained by reducing and oxidizing the precursor in an inert gas, with a carbon powder in a proportion required to substantially carburize the entire tungsten component into tungsten carbide (WC), and carburizing the mixture; and a high-performance fine tungsten carbide powder produced by the process, which has an average particle size of 0.8 ?m or less and is free of a coarse power having a particle size of more than 1 ?m, and which also contains less metal impurities and contains oxygen and nitrogen in a predetermined amount.

Abstract: A process is provided for producing a fine tungsten carbide powder, which comprises the steps of drying a slurry, which is obtained by mixing an aqueous ammonium tungstate solution with a carbon powder, at low temperature, to form a precursor, mixing a reduction and carburization product, which is obtained by reducing and oxidizing the precursor in an inert gas, with a carbon powder in a proportion required to substantially carburize the entire tungsten component into tungsten carbide (WC), and carburizing the mixture; and a high-performance fine tungsten carbide powder produced by the process, which has an average particle size of 0.8 ?m or less and is free of a coarse power having a particle size of more than 1 ?m, and which also contains less metal impurities and contains oxygen and nitrogen in a predetermined amount.

Abstract: A process is provided for producing a fine tungsten carbide powder, which comprises the steps of drying a slurry, which is obtained by mixing an aqueous ammonium tungstate solution with a carbon powder, at low temperature, to form a precursor, mixing a reduction and carburization product, which is obtained by reducing and oxidizing the precursor in an inert gas, with a carbon powder in a proportion required to substantially carburize the entire tungsten component into tungsten carbide (WC), and carburizing the mixture; and a high-performance fine tungsten carbide powder produced by the process, which has an average particle size of 0.8 ?m or less and is free of a coarse power having a particle size of more than 1 ?m, and which also contains less metal impurities and contains oxygen and nitrogen in a predetermined amount.

Abstract: A process is provided for producing a fine tungsten carbide powder, which comprises the steps of drying a slurry, which is obtained by mixing an aqueous ammonium tungstate solution with a carbon powder, at low temperature, to form a precursor, mixing a reduction and carburization product, which is obtained by reducing and oxidizing the precursor in an inert gas, with a carbon powder in a proportion required to substantially carburize the entire tungsten component into tungsten carbide (WC), and carburizing the mixture; and a high-performance fine tungsten carbide powder produced by the process, which has an average particle size of 0.8 &mgr;m or less and is free of a coarse power having a particle size of more than 1 &mgr;m, and which also contains less metal impurities and contains oxygen and nitrogen in a predetermined amount.

Abstract: The invention provides hot-rolled steel strips which, after having been acid-pickled, can be directly used. The strips have no Cr-decreasing layer and no shot blasted marks on their surface and have good corrosion resistance. The invention also provides a technique of efficiently producing the hot-rolled steel strips. A steel slab having a Cr content of from 6.0 to 25.0 wt. % is hot-rolled, then coiled at a temperature not higher than 700° C., then optionally quenched in water immediately after the coiling, then annealing in a reducing atmosphere, and thereafter acid-pickled in a solution of nitric acid/hydrochloric acid.

Abstract: A process for preparing a semipermeable membrane, which comprises contacting a thin polyamine film applied to a liquid-permeable microporous substrate with a polyalicyclic diisocyanate or polyalicyclic dicarbonyl halide capable of reacting with the amino or imino groups in the polyamine, thereby to crosslink the polyamine at the surface portion of the thin film.

Abstract: A process for preparing a colorless, odorless and transparent polymer oil having a low number average molecular weight, iodine value and viscosity and a high flash point, characterized by copolymerizing a mixture of n-pentene-1 and at least one other chain pentene in specific quantitative ratios in a Friedel-Crafts type catalyst and then hydrogenating the thus obtained liquid copolymer to a certain extent, and the polymer oil prepared thereby.

Abstract: Liquid polymers made predominantly of 1,3-pentadiene and 1,3-butadiene, which have a number average molecular weight of 300 - 10,000 and an iodine number of at least 250 and are capable of forming hydrocarbon solvent-insoluble coatings thereof; a process for preparing the liquid polymers; and paint compositions comprising the liquid polymer as the vehicle.