Forming method for graphite ceramic composite pipe

Abstract

The invention discloses a forming method for a graphite ceramic composite pipe. The forming method mainly comprises the following process steps: mechanically and uniformly mixing natural flake graphite powder, thermosetting phenolic resin powder, silicon powder and silicon dioxide powder in a certain proportion; adding the mixed powder to a preheated metal mold provided with an annular cavity in batches, performing prepressing once for each time of filling, and repeating the step many times to obtain a graphite ceramic composite pipe blank; treating the graphite ceramic composite pipe blank athigh temperature under the protection of vacuum atmosphere to obtain a graphite ceramic composite pipe preform; finally, impregnating the preform in silica sol under vacuum pressure, and obtaining the high-strength graphite ceramic composite pipe after drying. The prepared graphite ceramic composite pipe has good compressive strength and lower resistivity, can be used as a heating element to replace a traditional graphite pipe or metal pipe in production of polycrystalline diamond composite sheets, and is helpful for establishment of a reasonable and stable temperature field in the reaction chamber, and accordingly, product quality is improved and the production cost is reduced.

Description

technical field [0001] The invention provides a graphite ceramic composite tube forming method, which belongs to the technical field of inorganic non-material forming and engineering application. Background technique [0002] Polycrystalline Diamond Compact (PDC) is a new type of functional material that combines diamond powder on a cemented carbide substrate under ultra-high pressure and high temperature conditions (generally 1300°C~1600°C, 5~6Gpa). It not only has the high hardness, high wear resistance and thermal conductivity of diamond, but also has the strength and impact toughness of cemented carbide. It has become an ideal material for manufacturing high-performance cutting tools, drilling bits and other wear-resistant tools. [0003] Polycrystalline diamond compacts are usually synthesized in the ultra-high pressure and high temperature reaction chamber of the six-sided top press. There are both pressure field and temperature field in the ultra-high pressure and hig...

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Problems solved by technology

In addition, the combination of PDC reaction chambers ( figure 1 It is a schematic diagram of a common PDC reaction chamber assembly) It will also have a significant impact on the temperature field and the wear resistance and hardness of PDC

[0004] Graphite tubes are generally cut and processed from artificially synthesized graphite round rods. When graphite tubes are selected as heating elements in the reaction chamber, there are several problems: First, due to their low compressive strength, the graphite The tube is very easy to break, resulting in changes in the resistance value, which affects the actual heating effect and the stability of the temperature field of the PDC reaction chamber, and serious gas leakage occurs, leading to accidents; secondly, it is restricted by the existing artificial synthetic graphite production technology level , the randomness of the internal tissue composition and pore distribution of the graphite tube will also affect the stability of the resistivity, and it is necessary to make dynamic adjustments to the high-temperature synthesis PDC process parameters, which increases the difficulty of the high-temperature synthesis of PDC; the graphite tube is a thin-walled structure Parts (the wall thickness of which is generally less than 2mm), in addition to low material utilization, low yield, and high cost, mechanical cutting is difficult, and dust pollution needs to be controlled; Reaction chamber assembly poses certain difficulties

[0005] When choosing a metal tube as the heating element of the PDC reaction chamber, the metal tube is not easily damaged, and the production, assembly and transportation are more convenient; however, the resistivity of the metal tube is very small, only one percent of that of the graphite tube. According to the heat calculation formula Q 热 =0.24I 2 r 内 , in order to generate equal heat and obtain the same heating effect, it is necessary to increase the current value of the six-sided top press by more than ten times, and the resulting adverse effects are: increased energy consumption, in addition, under the impact of high current , the upper and lower electrode pressure heads are easy to burn out, which increases the cost of production and maintenance

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