摘要:
Substantially all residual oxidizing gas in a treating atmosphere which is inert or reducing, is eliminated by injecting into the atmosphere a gaseous silicon hydride at a temperature between 50 and 1,600.degree. C. and in amount such that the ratio R of the content of hydride to the content of oxidizing gas to be eliminated is within the range of 1.5 to 20. The rapid action of the trace amounts of hydride injected enables one to control with precision heat treatment processes by maintaining the residual oxidizing gas contents below predetermined very low thresholds.
摘要:
The thermal treatment atmosphere is obtained by catalytic reaction of an impure mixture of nitrogen, advantageously obtained by permeation or adsorption, and hydrocarbon, the catalytic reaction being carried out at a temperature between 400.degree. and 900.degree. C., typically between 500.degree. and 800.degree. C., with a noble metal base catalyst, typically platinum or palladium on alumina support. The reaction may be carried out in a reactor placed inside or outside the furnace.
摘要:
The invention concerns glass-metal sealing comprising effecting on a metallic piece, in particular an alloy based on iron and nickel or iron, nickel and cobalt, first of all a decarburization under an atmosphere, at a temperature of between 950.degree. C. and 1,150.degree. C., formed by hydrogen (10 to 99%), water vapor (1 to 8%), with a ratio hydrogen/water vapor higher than five, the possible remainder being nitrogen, then an oxidation under an atmosphere formed by an inert vector gas such as nitrogen, either at a temperature of 600.degree. C. to 800.degree. C. and with a water vapor content of 8% to 2%; or at a temperature of 900.degree. C. to 1,100.degree. C. and with a water vapor content of 4% to 0.5%; then establishing the connection. The gas mixture for a treatment atmosphere is obtained by mixing nitrogen and hydrogen conducted through pipes (13, 14), to which oxygen is added through a pipe (15) upstream of a catalytic chamber (11) permitting the elimination of the oxygen and the production of a content of water vapor.
摘要:
Provided are novel gas permeable bricks of a refractory material suitable for use in a hot grid of a regenerative heat exchanger. In accordance with one aspect of the invention, the brick has an inner face and an outer face on opposite sides of the brick. One or more cavities extend from the inner face partially into the brick. A plurality of channels for each of the cavities extend from the outer face to the cavities. The cavities and channels allow a gas to pass through the brick. Also provided is a hot grid suitable for use in a regenerative heat exchanger formed from a plurality of the bricks.
摘要:
Process for heat treating articles by hardening them in a recirculating gas medium which is in contact with the treated articles, the hardening gas being cooled by means of a heat exchanger, of the type in which helium is used as hardening gas, and is stored under holding pressure in a buffer container, wherein at the end of a hardening operation, a helium load is extracted from the treatment enclosure, in final phase by means of pump until a primary vacuum is obtained, the extracted helium is brought to purifying pressure by means of a compressor associated to a mechanical filter, and the helium under purifying pressure is sent to a purifier in which impurities are removed, after which it is transferred, if desired, after recompression in the buffer container.
摘要:
The invention concerns the production of ceramic-metal multilayer components comrising effecting, after making up in the crude state, in particular by metallization and stacking of pre-cut raw ceramic bands, a simultaneous firing operation, termed cofiring, on the components under an atmosphere based on hydrogen or nitrogen or a mixture of hydrogen and nitrogen, having a regulated water vapor content at a temperature of first of all between 800.degree. C. and 1800.degree. C., and more precisely either at a moderately high temperature plateau between 800.degree. C. and 1300.degree. C. for certain ceramic materials such as codierite and metallic materials such as copper and nickel, or at a temperature plateau between about 1400.degree. C. and 1800.degree. C. for refractory materials such as tungsten, molybdenum, alumina, according to which the atmosphere having a water vapor content is obtained by addition to a vector gas at (13) and (14) of a quantity of additional oxygen (15), and a quantity of additional hydrogen at (14) sufficient to obtain by hydrogen-oxidation reaction the predetermined water vapor content, and determining these quantities of addition of oxygen and the contingent addition of hydrogen so that said water vapor content is, in the course of the cofiring, that which is the most appropriate for the different stages of said cofiring.
摘要:
Metallization of ceramics of the type comprising depositing a metallic paste based on molybdenum and/or tungsten and manganese on a ceramic substrate and effecting the sintering of the paste in an atmosphere having a predetermiend oxido-reduction potential, with a rise in and a maintenance of a temperature between 1300.degree. C. and 1600.degree. C., then cooling to ambient temperature, with production of an atmosphere by the addition to a pure neutral gas of a quantity of additional oxygen and a quantity of hydrogen at least sufficient to subsequently obtain by catalytic reaction the desired content of water vapour and contingently the excess content of hydrogen.
摘要:
The method of carburizing steel workpieces comprises loading workpieces to be carburized in a furnace and maintaining them in a carbon enriching atmosphere comprising carbon monoxide, hydrogen and nitrogen. The treatment comprises a first phase carried out at a temperature from 850.degree. C. to 1050.degree. C. followed by a second phase carried out at a temperature from 700.degree. C. to 950.degree. C. During the first phase an atmosphere is used having a carbon potential from about 1.1% to about 1.6% by weight and during the second phase the amount of nitrogen in the atmosphere is increased from two to thirty times so that the carbon potential for the second phase is at least about 0.5% by weight less than the carbon potential for the first phase.
摘要:
Provided is a novel regenerative heat exchanger and a method for heating a gas in the heat exchanger. The regenerative heat exchanger features a chamber separated into a plurality of annular concentric spaces, including: a first, inner annular space defining a hot collection chamber; a second, outer annular space concentric to and around the first space defining a cold collection chamber; and a third annular space defining a heat exchange zone concentric to and between the first and second spaces. The heat exchange zone contains a particulate heat transfer material. The third space is supported on the inside by a concentrically disposed hot grid, and the external diameter of the third annular space is less than about double the internal diameter of the third annular space. The invention has particular applicability to the feeding of hot blast to a blast furnace in the iron making industry.
摘要:
Liquid waste material, particularly material containing sulfuric acid, may be combusted using an oxygen-rich material by a process in which:(i) a primary oxidant and fuel issuing from a burner are combusted in a furnace, the proportion of primary oxidant to fuel being such that there is insufficient oxygen to combust the fuel completely;(ii) introducing into the furnace the liquid waste material in atomized form around the burner;(iii) introducing into the furnace spaced from the burner a secondary oxidant which contains sufficient oxygen to combust completely the fuel not combusted by the primary oxidant the direction in which each of the primary oxidant, fuel and liquid waste material is introduced being such that the substances flow in substantially the same direction, the rate at which the primary oxidant, fuel, liquid waste material and secondary oxidant are introduced being such that a plug flow of substances through the furnace is created.