| 摘要 |
The invention relates to tools with inserts of composite materials with functional material gradient of WC-Ni type, to a centrifugal casting plant and to a process for manufacturing the said tools which are meant to be employed for fitting out equipments using rotating tools, such as scarifying bolts, asphalt and concrete milling tools or tools for drilling foundations in variable-hardness ground. According to the invention, the tools have an insert made by compacting the two WC-Ni powders in equal ratios, 90.18 ... 9.82% and 87 ... 13%, sintered for one hour at a temperature of 1470°C and coated by galvanization with several successive layers of Ni sulphate, Ni chloride and boric acid, resulting in a final outer layer with a thickness of 25 ... 35 μ m. The claimed plant comprises a sealed multi-post chamber (1) with six casting moulds, a central vertical axle (2) including also a component for absorbing the air from the casting chamber, the framework (3) of the entire equipment, an electric motor (4) for driving the centrifugation equipment, a box (5) with the electrical equipment, a set (6) for vacuuming the moulding cavities and the housing (7) for protecting the entire equipment. The claimed process has the following stages: making the casting moulds with the casting cavities inclined at an angle Ψ =8 ... 15° in relation to the feed direction of the molten mass, fixing the inserts by wetting with a refractory paint comprising 70 ... 82% zirconium silicate, 8 ... 12% alcohol and 6 ... 22% dextrine, smelting, in an induction furnace, a steel of the following chemical composition: C=36%, Mn=2.11%, Si=1.42%, Cr=1.2%, Ni=1.15%, Mo=0.31% and Fe=90.91%, at a melting point ranging between 1510 ... 1610°C, coating the cavities with a 1.5 ... 2.5 mm-thick layer of refractory paint, for adherence control, centrifuging at a rotary speed of 250 rpm to obtain the vacuum, casting the molten mass which is solidified in 12 min after which the moulds are removed. |
