SE192178C1 - - Google Patents

Description

CLASS INTERNATIONAL SWEDISH C 03b80 b: 8/16 PATENT AND REGISTRATION AGENCY Ans. 3991/1957 received on 26/4 1957 issued on 24/2 1964 SG KRAPF, BEVERLY HILLS, CAL., USA Worn to hot-press refractory shaped bodies during exothermic reaction and apparatus for carrying out the set Priority begtird freuz on 30 April 1956 (USA) The invention relates to a set for the production of refractory moldings, in which a uniform mixture of finely divided particles, composed of a relatively inert, first component with a high melting temperature, such as oxide, carhide, nitride and carbon, a second component in the form of metal, is compressed in a mold chamber. , such as Mg, Al or Zr, and a third component in the form of metal compound, such as CrO3, WO3, M003, Cr (CO) 6, Mo (CO) G, CA (CN) N1 (CN) 2, Fe (Fe (Fe) CN) 6); or B 2 O 3, which component is reactable with the other component at elevated temperature in a self-sustaining exothermic reaction to form a ceramic refractory body, such as oxide, carbide or nitride, and the method is characterized in that electric current is passed through the mixture while Compressed, for heating the mixture to the temperature at which the exothermic reaction takes place, that the mixture is then heated or maintained at this temperature by means of further current passage, the heating and the reaction being carried out without interruption and with continuous application of pressure and continuous supply. of electrical strain.

The invention also relates to an apparatus for carrying out the method according to the above, which apparatus comprises a mold chamber, which is delimited by two spaced apart electrically conductive portions, which are connectable to an electrical power source, and a third portion, which forms a The first two portions are slidably receiving, electrically insulating sheath, the apparatus having a pressure applying means arranged to relatively move the portions defining the mold chamber for changing the volume of the chamber, and the apparatus being characterized in that the third portion has rock sections which are mantle-forming layer.

At 1000-2000 ° C refractory materials have hitherto been pressed and sintered materials or metal or metal compound with a high melting point together with a metal preform with a lower melting point, which binder has been incorporated into the metal or metal compound. In this case, prepared refractory materials do not breathe satisfactorily up to 2000 ° C. Even at temperatures just below 1800 ° C Or their useful life short. It has been joked that it is possible to convert all parts or components of the thermoformed masses of the materials into shapes or chemical compositions which are not narrow or soft at 2000 ° C.

In the process of the invention, the second and third components unite during the reaction and together with the first component form a refractory body with a homogeneous structure, which body differs significantly from the above-mentioned, hitherto known, mechanically bonded, refractory materials. The refractory compositions prepared according to the invention are physically stable and usable at temperatures up to 2700 ° C. By means of the apparatus according to the invention, the produced body has a smooth surface and can be used directly for the intended purpose without slip-flaking and other finishing. The reactions associated with the invention take place under both chemical and electrical influences, and precisely these reactions are caused to occur due to the electrically generated and induced state of charge of one or more of the reacting substances and to give bodies which have desired properties and which differ from products, sour would arise from chemical reactions Dupl. at 40 b: 3/20; 40 b: 17; 80 b: 8/01; 80 b: 8/03; 80 b: 80/11; 80 b: 8/12; 80 b: 8/13; 80 b: 8/18 2— - without the addition of electrical influence. This ratio is illustrated below with formulas. The homogeneous structure and smooth surface of the body are thus removed by continuously mixing the mixture under pressure during the treatment and igniting throughout the mass substantially simultaneously due to the electrical influence.

In the process of the invention, a thermally stable product is prepared by pressing in a mold under high pressure a mixture comprising three types of components: the first component, which is relatively inert chemically and of the nature of a thermally stable filler with a higher melting temperature. 2000 ° C; the second component, which is a reducing metal and which is preferably selected from those metals whose headings, carbides and nitrides have moderate melting temperatures, at least some of which exceed 2000 ° C; and the third component, which is a metal compound or B 2 O 3 and which has been subjected to reduction by exothermic reaction with the metal component, any or some of the oxygen, carbon, nitrogen or a metal or compounds thereof becoming available for reaction with the metal component. According to the invention, a product with improved tightness is obtained if the pressing takes place during the supply of electric shorn.

The process kit comprises heating a compressed mass of the uniformly mixed starting components with a grain size of 20-400 .mu.m. This mixture is pressed at 250-2000 kp / cm 2 or more in the mold, whereby electric current is passed through the mixture so that the reactions in question are carried out and electrically actuated. Conductivity and uniformity in current strength and heat generation throughout the compressed mixture are promoted by small size and even distribution of the conductive metal particles. The metal particles in the mixture serve as electrical conductors and have a grain size of about 45 tons, so that the particles can be arranged around the larger particles of the first and third components and touch each other to provide continuous electrical current paths through the mixture. During the first heating stage, the current flow through the mixture raises its temperature to the level at which the described reduction of the third component takes place or begins to take place. Although the temperature rise is subjected to variation, depending on the various compounds and the metal or metals in the mixture, at this initial heating stage due to the electrical energy supply it will usually be in the range of about from room temperature to 1200 ° C. The electrical resistance of the mixture is a function of the applied pressure, and therefore the amount of pressure used in any particular operation can be selected in connection with other variables which will be described and which also affect the resistance of the mixture, thus heating the mixture. by means of electrical means can be achieved in a short time interval to the temperature at which exothermic reaction begins. After initiating exothermic reduction of the third component by electric heat supply to about 1200 ° C, the mixture is further heated to about 1800 ° C by the additional chemical exothermic heating. The formation of metal carbide, oxide or nitride takes place by electric heating to 1800-2300 ° C, preferably 2000 ° C. Due to the limited high temperature resistance or resilience of most practically usable mold materials, it is advisable to keep the heating short, for a total of about 25 seconds. The product is quickly removed from the mold for controlled slow cooling. The inert component consists of any heist or mixtures of different oxides, carbides or nitrides, preferably those having higher melting temperatures above 2000 ° C. The oxides include TiO, ZrO 2, ThO 2, MgO, BeO, CeO, Al 2 O 3 and CaO; the carbides include TiC, Zre, ThC2, B4C, WC, W2C and VC; and the nitrides include TiN, ZrN and BN. It may even in some cases be inconvenient to include carbon as a component of the first component. In addition, it is possible to include therein one or more metals with high melting temperature, which may remain as such in the final product with relatively little chemical change, such as chromium, molybdenum, tungsten, titanium and zirconium. When such metals are used in the first or filler component, they can also serve as electrical conductors.

The second component comprises metals or mixtures thereof, which are reactive with the third (reducible) component to form oxide, carbide or nitride such as magnesium, aluminum and zirconium.

The reducible third component may be selected from any or mixtures of such anhydrides as CrO 3, WO 3, MoO 3, B 2 O 3, carbonyls, including Cr (CO) 6, Mo (CO) 6, and metal cyanides, including Ca (CN) 2, Ni (CN) 2 and Fe (Fe (CN) 6).

The relative proportions Ono are 20-70% by weight of the first component, 10-40% by weight of the second metal component and 20-40% by weight of the third component. The components should leave sufficient with oxygen, carbon or nitrogen by reduction of the third component to convert substantially all of the metallic second component to light melting oxide, carbide or nitride or mixtures thereof.

The proportion of the first component is chosen so that the resulting mixture has an electrical resistance which allows heating of the mixture by means of electrical means in a short time interval to the temperature at which the exothermic reaction begins.

A particularly important and distinguishing aspect of the invention is that the reactions which have been described above are affected both chemically and electrically. This relationship is explained as follows. For example, chromium oxide and magnesium could normally react according to 2 CrO 3 + 3Mg- Cr 2 O 3 + MgO.

Under the influence of high temperatures alone, the reaction can be brought to be 2 CrO 2 + 3Mg Cr 2 O 3 • 3Mg0.

Under the reaction conditions contemplated by the invention, the electric state of charge of the reacting substances produced by the current flowing through the mass causes the reaction to proceed on another salt and leads to the formation of a chromium-magnesium oxide, which is superior in its resistance to extreme high temperatures, i.e. 2 CrO 3 + 3111g-Cr 2 Mg 2 O 6.

The following can be given as typical examples of various components which, when subjected to heating and reaction in an electrical fait in the manner explained later, lead to the formation of bodies which are usable at extremely high temperatures. As previously stated, the nature and end products of the reactions are determined by both chemical and electrical particle charge effects and conditions. In these examples, the grain size of each component is small enough to pass through a 0.250 mm sieve orifice, and in each case the components are mixed and heated evenly while compressing about 700 kp / cm 2.

Example I. A mixture consisting of Mo, Mg, Mo (CO) 6, TiO and carbon mainly in the proportions indicated by the left side of the reaction equation below is heated at the beginning of alternating current (60 periods) passing therethrough. to about 1200 ° C, at which temperature exothermic reduction of the carbonyl takes place and gives a temperature rise to about 1700 ° C-1800 ° C, after which continued current flow in the pulp raises its temperature to about 2200 ° C. of a product the size of ordinary refractory bricks, the entire heating can skc ph about 25 seconds. The reaction is assumed to be essentially: Mo + 6 Mg + Mo (CO) 6 + TiO + C = = 6 MoC + 6 Mg0 + TiO + C.

Example II. A mixture of Mo, Mg, Mo (CO) 6, TiC and C mainly: in the proportions indicated by the left side of the reaction equation below, is heated substantially as in Example I so that the carbonyl reduction, oxidation and product formation are effected in according to the following reaction: Mo + 6 Mg + Mo (CO) 6 + T1C + C = = 5 Mo + 6 MoC + 6Mg0 + TiC + C Example III. A mixture of Ni (CN) 2, B, Zr and TiN mainly in the proportions indicated by the left side of the reaction equation below is heated as before to produce a metal nitride and carbide complex according to the equation: Ni (CN) 2 + 2 B + 2 Zr + TiN = = Ni + 2 BN + TiN + 2 ZrC.

As far as the temperature is concerned, the point of heating at which an exothermic reaction occurs can, of course, vary somewhat according to the particular reacting substances, which none. In all cases, however, it will be introduced what can be considered as three heating stages, of which in the first stage the temperature is raised by current passage and resistance heating inside the mixture, in the second stage exothermic reaction takes place and continues by a further temperature rise usually of several hundred degrees, and in the third heating stage, continued power supply is maintained and preferably the temperature rises to the range of 2,000 ° C and beyond. Alternating current or direct current can be used, and the voltage and current are selected in relation to the desired heating for the size and the electrical resistance of the particular mixture being heated. In the examples given above with 0.5 kg of mixture under heating, 50 volts alternating current is used at 60 p / s and 800 amperes. When mixtures are used which leave some metal components in the final product, the printed tension must usually be increased during the third heating stage due to the considerable increase in resistance of the material. Even when no metals are present, it becomes a power line, because oxides and similar compounds become semiconductors at elevated temperatures.

In Tart and one of the examples, the final product is for controlled slow cooling.

A suitable apparatus for practicing the invention is shown in the following description of the accompanying drawing. Fig. 1 shows an illustrative example of a mold or mold assembly in a vertical section. Fig. 2 is a horizontal projection of Fig. 1.

The mold assembly comprises a chamber 10, within which the previously discussed, evenly mixed, finely divided components are subjected to heating under compression to form a product, the shape of which corresponds to the contour shape of the chamber. The mold chamber 10 is defined by side rocks 11, 12, 13 and 14, which rest on a bottom part 14a and a removable plug or piston 15 at the bottom. These parts can be made of chrome-nickel steel. The bottom piston 15 should be electrically conductive and may be made of limiting the current flow through the material in the chamber 10 between the piston 15 and the piston described later, the side cradles being lined with an electrically insulating ceramic material 16.

The mixed components are subjected to high pressure by a steel piston 17, the piston rod 18 of which can be actuated by a force source (not shown), which is capable of subjecting the material in the chamber 10 to the above-mentioned high compression pressures. Conductors 19 and 20 from a suitable electric cold source are connected to the piston 17 or the piston rod 18 respectively. with the bottom piston 15. A lamp rheostat or other control device 21 dr inserted in the electrical circuit said that the current flow through the mass, which is heated, can be varied as desired to 20-50 volts and 800-1200 amperes.

Due to the extremely high temperatures which develop inside the mixture in the chamber 10, it is difficult to ensure the absorption of heat from the chamber cradles and preferably also from the piston 17. For this purpose, proper heat absorption or cooling elements are arranged, preferably in in the form of conductive metal blocks or cradle sections 22, 23, 24 and 25, which can abut flat against the surface of the side cradles 11-14. Each block is provided with a suitable arrangement of channels 26, through which water or other cooling liquid is circulated by means of connecting lines 27. The piston 17 can be subjected to cooling by being provided with internal channels 28, through which cooling rollers are circulated via connecting lines 29. The bottom flask 15 can be cooled in a similar way. The side cooling elements or blocks 22-25 can be mechanically retractable from abutment against the chamber cradles on which it was conveniently set as a lift, e.g. by casting the blocks for reciprocating movement in bottom guides 30 and by connecting the blocks of rods 31 to double-acting pistons, which are schematically indicated at 32.

In carrying out the dyeing kit described above, an even mixture of the three components is applied to the chamber 10 and subjected to high compression, 250-2000 kp / cm 2, with the cooling elements abutting the chamber cradles and the cooling water circulation initiated thereby also through the pistons 15, 17. during the entire heating through the stream, which is passed through the compressed mixture. Due to the extremely high temperature to which the material has been heated, the body united to a cohesive belt is rapidly removed from the mold at the end of the heating, e.g. by pulling out the piston 15, and the mass is allowed to cool slowly, let saga Over a period of from 1 to 4 hours.

Claims (10)

Patent claim: Salt for the production of refractory moldings, in which a mold is compressed in a mold chamber. even mixture of finely divided particles, composed of a. relatively inert,. first component with high melting temperature such as oxide, carbide, nitride and carbon, a second component in the form of metal, such as Mg, Al or Zr, and a third component in the form of metal compound, such as CrOs, WO3, MoO3,. Cr (CO) 6, Mo (CO) 6, Ca (CN) 2, Ni (CN) 2, Fe (Fe (CN) 6); or B20s, which component Or is reactable with the other component at elevated temperature in a self-sustaining exothermic reaction to form a ceramic refractory body, such as oxide, carbide or nitride, characterized in that electric groin is passed through the mixture, while this Or is compressed, for heating the mixture to the temperature at which the exothermic reaction takes place, that the mixture is then further heated by means of further stronation, or at least maintained at this temperature, the heating and reaction being carried out without interruption and with continuous application of pressure and continuous electric current. 2. A kit according to claim 1, characterized in that a flour with a high melting temperature was allowed to the first component. 3. A kit according to claim 1, characterized in that the first component has a higher melting temperature of 2000 ° C. 4. according to claims 1-3, characterized in that the mixture contains 20-70% by weight of the first component, 40% by weight of the second component and 20-40% by weight of the third component. 5. Set according to claims 1-4, characterized in that after the exothermic reaction the mixture is heated to a maximum temperature above the temperature obtained by the exothermic heating. 6. Set according to patent claims 1-5, characterized in that the grain size of the mixed starting components Or 20-400 m. 7. 7. Set according to patent claim 6, characterized in that the grain size of the second component Or 45 pan. 8. According to one of the preceding patent claims, it can be claimed that the heating time of the mixture is at most 25 seconds. 9. Set according to patent claims 1-8, characterized in that the mixture is maintained under heating between 250-2000 kp / cm 2 during heating. An apparatus for carrying out the kit according to any of the preceding claims, which has a mold chamber (10) defined by two electrically conductive portions (15, 17) spaced apart from each other, which are connectable to an electric power source, and a third portion (11-14, 22-25), which forms an electrically insulating jacket slidably receiving the two first-mentioned portions, the apparatus having a pressure-applying means, arranged to relatively move the portions defining the mold chamber for changing the volume of the chamber, , aft the third part has cradle sections (22-25), which aro isarforbara from a mantle-forming layer. Request publications: Patentskrifter! Ran Sverige 59 930, 151 513; United Kingdom 228,599; Germany 950 988; USA 788 132, 2,149,596, 2,372,605, 2,670,301.