The method of obtaining products of chrome carbide
(57) Abstract:Usage: the invention relates to the production of carbide materials. The inventive method consists in that the synthesis of chromium carbide is carried out directly in the harvest of the future details. Implementation of the proposed method in comparison with the prototype ensures carbide not just in powder form, but also in the form of products of a certain form. Furthermore, the method allows to obtain products of different composition (type of carbide, carbide-carbon) and different porosity (within certain limits). 3 C.p. f-crystals, 1 table. The invention relates to the production of carbide materials.The main methods of obtaining refractory carbides are the synthesis of the elements or the recovery of oxides of carbon, for example,
< / BR>However, the high temperature synthesis 1500 1550oC, as a rule, do not contribute to the formation of carbides dispersed in the form.The chromium carbide in powder form and at a lower temperature synthesis can be obtained by using the carbon component is formed by the decomposition of natural gas or other hydrocarbons. As a prototype of the selected method, consisting in on what abotu carried out at 800 to 1200oC in the reactor with a fluidized bed of metal oxide, through which serves hydrocarbon. The oxide of the metal begins to actively naglergasse. When this oxide particles begin to evenly covered with pyrolytic carbon (PU). The speed of accumulation of hydrocarbon oxide depends on the temperature and gas flow. The degree of carbonization depends on the duration of the process. Incorporated PU has a fine structure, high reactivity, spectral purity.The disadvantages of the prototype method is that this method is only preparation of the oxides of rare metals to carbidization; synthesized in the future from this material carbide can only be obtained in powder form.The task of the invention to provide chromium carbide in the form of finished products.This goal is achieved due to the fact that the carbide synthesis takes place directly in the harvest of the future details.The invention consists in the following.From a powder of chromium oxide (III) a temporary binder to form the workpiece, as close in shape to the desired items. The obtained porous preform, the porosity of which can WA is the mass change of the workpiece 20 34% from the initial one. While in the pores of the workpiece on the surface of the particulate source of chromium oxide proceeds in a heterogeneous chemical reaction of formation of the carbon layer. The formed layer is a strongly connected with the base (the surface of the particles) graphite-like carbon.Obtained at this stage, the semi-finished product is a reactive system with uniform distribution of components, which, in addition, is provided in direct contact with a highly developed surface section, which facilitates the further course of the reaction of their chemical interaction.The semi-finished product has the same shape and size as the workpiece. He has more strength and can be subjected to machining (e.g. drilling) for the formation of surfaces that cannot be obtained by shaping the workpiece. Synthesis of carbide is carried out at 1150 1250oC by high-temperature processing of semi-finished product in a vacuum or inert gas environment.The porosity of the preform is set depending on the requirements posed details:
composition (type carbide);
the porosity of the part.To mould the workpiece with an initial on the Sabbath. To mould the workpiece with an initial porosity of more than 65% does not make sense, because even in the formation of carbide porosity details will be more than 75% and the item will have very low strength.The increase in the mass of the workpiece by more than 34% is not always advisable, because after a reaction time of carbidopazapomnit in the pores of the items will remain the excess carbon that is often undesirable. The increase in the mass of the workpiece is less than 20% does not provide the possibility of obtaining from it the final details.The mutual combination of the initial porosity of the workpiece and the amount of typing in her carbon allows to obtain details with different porosities.Example 1. From a powder of chromium oxide (III) is formed into a billet parts, for example, ROM. The item is placed in the reactor, served there natural gas and maintained at a temperature of its decomposition. Then the reactor is cooled. The resulting intermediate product is placed in a vacuum furnace, heated to 1200oC and incubated for 20 minutes After the furnace is cooled and the part is removed. The thus obtained disk of porous chromium carbide.Examples 2 and 3. Carried out analogously to example 1 (see table).Thus, implementation of the proposed JV is a certain form. Furthermore, the method allows to obtain products of different composition (type of carbide, carbide-carbon) and different porosity (within certain limits).Literature
1. Kosolapov So Ya Carbides. M. Metallurgy, 1968. 299 S.2. "The method of preparation oxides of rare metals to carbidization" (Listov A. I. Galitsky N.In. Live N.A. /Description of the invention to the author's testimony. Bulletin No. 15, published 26.04.1968. 1. The method of obtaining products of chrome carbide, synthesized from oxide chromium (III) and pyrolytic carbon, including heat treatment of chromium oxide in an environment of gaseous hydrocarbons or their mixtures at a temperature above the temperature of decomposition, wherein the pre from a powder of chromium oxide is formed into a billet products, after which it thermoablative to increase the weight by 20 34% from the initial and synthesis of carbide is carried out directly in the volume of the workpiece by heat treatment.2. The method according to p. 1, characterized in that the carbide synthesis is carried out at 1150 1250oC.3. The method according to PP.1 and 2, characterized in that the carbide synthesis is carried out in a vacuum.4. The method according to PP.1 to 3, characterized in that sintech carbide carry out
FIELD: powder metallurgy, in particular ceramic material composition.
SUBSTANCE: claimed composition contains (mass %) boron nitride 10-20; silicium carbide 73.5-82; titanium 3-7; silicium 0.1-1. Composition is obtained by blending and subsequent plasticizing with organic binder. Composition is useful as refractory materials for high temperature furnaces and chemical reactors. Articles from composition of invention are produced by hot pressing and have heat capacity of 577-601 J/kg0C at 250C, thermal conductance of 6.4-8.0 W/m.K at 4000C, thermal-shock resistance of 25-29 heating cycles up to 14000C followed by cooling with water at 200C.
EFFECT: materials with improved bending strength and hardness.
FIELD: construction element for microwave muffle furnace.
SUBSTANCE: claimed construction element is made from radiation absorbing environment friendly ceramic material, which makes it possible to achieve high temperature for short period and doesn't release destructive gaseous compounds during heating. Heater for microwave furnace is obtained by mixing of silicium carbide or modified silicium carbide with grade fineness of 200-500 mum or 80-100 mum, respectively, and leucoxene concentrate with grade fineness of 80-250 in ratio 14-19:1-6, wherein said leucoxene concentrate is reprocessing product of titaniferous oil-bearing ore with organic binder, followed by compaction and two-step thermal treatment in oxidative atmosphere.
EFFECT: increased maximum working temperature achieved within short period.
2 ex, 2 dwg
FIELD: refractory industry; manufacture of monolithic linings.
SUBSTANCE: proposed silicon-carbide concrete contains the following components, mass-%: plasticizing agent, 0.3-0.5; microsilica, 2.0-5.0; high-alumina cement, 7.0-10.0; the remainder being silicon carbide. Concrete may additionally contain high-alumina component at content of Al2O3 no less than 95 mass-% in the amount of 5-15 mass-%, for example in form of synthetic corundum of fraction lesser than 50 mcm or dust from electric filters of calcination furnaces in alumina production process.
EFFECT: enhanced strength of concrete at 600-1000°C; enhanced resistance to oxidation.
4 cl, 2 tbl
SUBSTANCE: present invention concerns blend compositions, which can be applied in manufacturing thermocouple tips for furnace temperature measurement. The blend includes the following components, in mass %: aluminum oxide 5.0-15.0; silicon carbide 15.0-20.0; tantalum carbide 70.0-75.0. The thermocouple tips made of the blend withstand open-hearth temperature for approximately 3 hours.
EFFECT: prolonged work life of thermocouple tips.
SUBSTANCE: present invention pertains to making carbon based composite materials and products made from the material, intended for use in conditions of complex static and dynamic loads at temperatures up to 2000°C in an oxidising medium and high-speed streams of end products of fuel combustion (aerospace engineering, high-temperature electrothermal equipment etc.). The method involves stacking coal-fibre filler in form of packets of work pieces with a bulk structure, saturation with a carbon forming binding substance, moulding, carbonisation, compression and ceramising. Saturation of the filler with coal-fibre is done before putting the packet into a complex binding substance, containing an oligomeric non-coking resin in form of a 40-80 wt % solution of oligomeric unsaturated polyester resin in a monomer of unsaturated ester and oligomeric carbon forming resin in form of 45-55 wt % alcoholic solution of oligomeric phenol-formaldehyde resol resin. The ratio of non-coking to carbon forming oligomeric resin is (30-40):(60-70) wt %. Content of complex binding substance in the filler saturated with coal-fibre is 30-50 wt %. Polymerisation of non-coking resin after saturation is done using ionising radiation, and the carbon forming resin is polymerised at 130-190°C temperature in the process of moulding carbon-fibre reinforced plastic work pieces.
EFFECT: obtaining material with good physical and mechanical and operating characteristics.
6 cl, 3 tbl, 1 dwg
FIELD: construction industry; chemistry.
SUBSTANCE: ceramic coating is applied on carbon-bearing material for product protection from oxidation in the air at high operation temperatures. Protection method of carbon-bearing materials by silicon carbide includes preparation of mixture from carbon-bearing compound in organic solvent with soluble silicon-bearing compound treated by hydrolysis catalyst, hydrolysis. Then this mixture heated up to 40÷90°C is used for soaking carbon-bearing materials with the application of ultrasonic influence till gel formation. Soaked material is dried first at 60÷80°C within 10÷24 hours, then at 100÷140°C within 4÷12 hours, after that there performed is thermal treat first at 450÷1000°C and depression 1·10-2÷1·10-1 kPa within 1÷4 hours, then the temperature is increased up to 1100÷1400°C and soaked material is held within 4÷20 hours at depression 10-5÷10-2 kPa.
EFFECT: exclusion of carbon-bearing materials degradation, and increase of oxidation resistance.
4 cl, 2 tbl, 12 ex
SUBSTANCE: invention refers to the compounds and compositions for preparation of sialon-containing materials. The latter includes the following phases (wt %): β-sialon Si3Al3O3N5 25-55%, α-sialon SiAl4O2N4 10-35%, cubic silicon carbide in nanodimensional state 3C-SiC 10-20% , hexagonal silicon carbide 6H-SiC 20-40% with particle size 5-50 mcm and yttrium aluminate Y3AI5O12 7-15%. The specified material is obtained from the following composition (wt %): sialon-containing powder with particle size not more than 150 nm 50-75, 6H-SiC (particle size 5-50 μ) 20-40, Y2O3 5-10, where the sialon-containing powder contains the following phases (wt %): Si3Al3O3N5 35-70, SiAl4O2N4 15-35, 3C-SiC 10-20, Al2O3 5-10. The invention allows to obtain without hot-pressing the material with compressive resistance 620-1030 MPa, thermal conductivity at 100°C 40-88 W/(m·K) and total porosity 5-15%.
EFFECT: invention provides the material with enhanced fastness and thermal conductivity which can be used in high-temperature equipment eg in the design of heat-exchangers.
2 cl, 15 ex, 1 tbl
SUBSTANCE: invention relates to production of structural components based on carbon or graphite, particularly silicicated graphite. The composition contains carbon in form of powdered graphite with particle size of not more than 200 mcm in amount of 10-80 wt %, silicon carbide in amount of 10-60 wt % and binder - the rest. Carbon and silicon carbide are in inverse proportion and their total content in the composition is in the range 60-95 wt %. Density of the obtained material is 2.92-3.08 g/cm3, and ultimate compression strength is 4550-4970 kgf/cm2.
EFFECT: increased corrosion resistance.
2 cl, 2 tbl
SUBSTANCE: invention relates to monolithic refractories, and more specifically to mixtures used for closing tap-holes of blast-furnaces after tapping cast iron and slag. The tap-hole mix contains a refractory component, consisting of oxide and carbon-bearing materials and silicon carbide, and a binding component, consisting of refractory clay and a plasticiser. The refractory component also contains a composite material based on silicon nitride with ferrosilicide binding material, containing iron silicide, silicon and/or iron, in the following ratio of components in wt %: silicon nitride - 60.0 to 95.0; iron silicide - 0.1 to 38.0; silicon - 0.1 to 23.0; iron - 0.1 to 8.0; components of the tap-hole mix are in the following ratio, wt %: refractory component - 50 to 80; binding component - 20 to 50.
EFFECT: increased strength of tap-hole mix.
2 cl, 1 ex, 1 tbl
SUBSTANCE: invention relates to production of porous permeable ceramic materials for making ceramic filters and membranes for purifying gases and liquids from suspended particles, porous ceramic moulds, used in casting and moulding ceramic objects. The mixture for making porous permeable ceramic material contains monofraction silicon carbide, alumina, bentonite and clay, where the said alumina is in form of hydraulically hardening aluminous component Alphabond 300, with the following ratio of components of the mixture, wt %: silicon carbide 88 to 92, Alphabond 300 2 to 5, bentonite 1 to 2, clay 4 to 6.
EFFECT: increased heat resistance and strength of porous material.
2 tbl, 1 ex