WEAR-RESISTING PIECES CONSISTING OF CEMENTED HARD METALLIC COMPOSITIONS-NAMELY, INSERTS TO BE USED IN DIES AND TOOLS FOR WORKING, CUTTING OR SHAPING METAL AND OTHER MATERIALS, IN LATHE-CENTERS, IN BEARING-SURFACE AND WEARING-SURFACE PARTS, IN PUMP-VALVES AND PARTS THEREOF, AND FOR DIES, CUTTING TOOLS, LATHE-CENTERS, BEARING-SURFACE AND WEARING SURFACE PARTS, PUMP-VALVES WHICH EMBODY SUCH WEAR-RESISTING PIECES