DE1072541B - Metallothermal process for the production of highly heat-resistant and chemically resistant ceramic and semi-metallic products - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

kl. 80 b 8/18

■ INTERNAT. KL. C 04 b

PATENT OFFICE ^ f ty

EDITORIAL 1072

W 16991 IVc / 80 b

REGISTRATION DATE: JUNE 3, 1955 5 "

NOTICE THE REGISTRATION AND ISSUE OF THE EDITORIAL. DECEMBER 31, 1959

It has been proposed to use highly refractory products by producing that powdery mixtures of metals and capable of exothermic reactions Metal oxides are brought to agglomeration by initial ignition. It is also known by Initial ignition caused reaction by adding substances that do not take part in the reaction, to delay. However, the experimental review of the work instructions did not result in any technically perfect results. The material agglomerated insufficiently, none formed mechanically solid body. In order to overcome these difficulties, it has been proposed to supplement the reaction mixture to press after the ignition has taken place. Now an agglomeration also found itself in the choice of different ones Metals and metal oxides instead.

As the word "agglomerate" implies, the inventor wanted to create agglomerations. In the interior of the respective materials, however, there were tensions that led to breakage of the agglomerated parts or workpieces. In the course of the further development of the process, the A subsequent annealing was introduced to relieve the stresses. With this proposal, workpieces were made achieved, which held better than the previous ones, but they were also technically not usable.

If you want to manufacture materials that are technically flawless, solid and usable even over long periods of time remain, one must proceed according to the new invention of powder mixtures that are adjusted so that there is a chemical equilibrium crystal structure in the end product formed by thermal diffusion.

This can be achieved according to the invention by taking part in the metallothermal reaction Substances are measured in terms of quantity in such a way that they contain any additives that may have become known in the troubled waters Patents also with "tax rate", "delay material", "insulation material" or "brake mixture" have been designated to communicate so much of their released energy that they are able to fully to diffuse into the first-mentioned substances, and that on the basis of the set between the two types of substances stoichiometric quantity ratio is a uniform material that is in chemical equilibrium arises. In other words: both the reaction components and, if appropriate, the additives of the process are coordinated in terms of weight and energy so that one and / cder several distinct types of crystals form, which can be mixed with each other up to the temperature of use of the product Stand balance. In this way it is possible to use materials with a statu nascendi Making crystal bond because of the increased metallothermal process

for the production of highly heat-resistant

and more chemically resistant

ceramic and semi-metallic

Products

Applicant:
Dr. phil. nat. Gustl Strunk-Lichtenberg,

born stalk,
Bonn, Heerstr. 55

Dr. phil. nat. Gustl Strunk-Lichtenberg, née Strunk,

Bonn,
has been named as the inventor

Diffusion of the components into one another have particularly favorable properties.

The practical implementation of the process is done in such a way that a stoichiometrically measured and energetic Calculated amount of a mixture either in powder form, loosely poured into a mold, ignited therein and \ during or shortly after the reaction is pressed or dry - or with easily evaporating Binders bound - preformed, dried, then placed in the final shape, ignited in it and hot-pressing is also carried out in a known manner during or shortly after the reaction.

Through the pressing process, the reaction skins that have formed around the individual particles are pierced and still reactive particles are brought so close together that an afterglow of the pressed parts is necessary in order to compensate for the differences in concentration and the mechanical stresses arising during the rapid process. This is best done in an oxidizing atmosphere at 1500 ^° C. for 1 to 2 hours with subsequent slow cooling.

In the manner described, for example, spinels, mixed crystal spinels, spinels with silicates or Spinels are formed with a metal phase ..

example 1

The following mixture is used to form a chrome spinel product:

1.2 CrO ₃ + 1.8 Mg + (1.7 Cr ₂ O ₃ + 0.5 MgO)
- »- 0.6 Cr ₂ O ₃ + 1.8 MgO + 1.7 Cr ₂ O ₃ + 0.5 MgO
- * - 2.3 MgCr ₂ O ₄

909 7U7 / 297

Claims (6)

3 4 The resulting product is in the homogeneous Al ions are exchanged. The fire resistance of such Equilibrium, because the reaction rate of this process increases inevitably, since the pure products 1,2gmolCrO ₃ andl, 8gmolMg chromium spinel has a melting point of 2,000 ⁰ C ^6th . (S. Holgersson, Ztschr. Anorg. General Chem., 192 sets 259.6 kcal in freedom, which the molecules of 5 [1930], p. 127), while known as a semi-precious stone Additive "MgAl ₂ O ₄ spinel only melts at 2135 ± 2O ^{0 C.} 1.7 gmol Cr ₂ O _{3 and} 0.5 gmol MgO Example 2 Supply so much kinetic energy that it is completely 2.2 CrO ₃ + 2.2 Al + (0.5 Cr ₂ O ₃ + 2.7 MGO) incinandcrdiffundicrcn and so a uniform work- io, <· ■ nr,, η c r λ, ο- * * _λ ^ Form material from chrome spincll. + ¹ ^ ^Cr * ° 3 + U ^M * ° * + ° · ^{5 Cr} ₂ ° 3 + 2.7 MgO In order to master the reactions well, it is useful- -> - 1.6 Cr ₂ O ₃ + 1.1 Al ₂ O ₃ + 2.7 MgO moderate to choose such an additive which - »- 2 7 Mg (Cr AU O is capable of producing mixed crystals' ^ol '' ^{a 4} to build. α-Α1 ₂ 0 ₃ with the corundum structure can also not be brought into solution by stoichiometric Be-Spinclllittcr, while calculating the substances newly formed from the reaction and 3 / -Al ₂ O ₈ crystallize and even in the spin type with this the additives, which not only form mixed crystals from the end components. the metallothermal reaction should exist, a It is also possible to select the type of reaction to form the second type of crystal, which is intimately mixed partner and the Ziisätzc in such a way that they are mixed with the first, for example spinels with Crystalline spinllc form, some of the chromium ions against silicates. Example 3 2.4 CrO ₃ + 3.6 Mg + (1.0 Cr ₂ O ₃ + 3.0 MgO + 2.2 SiO ₂ )
-> - 1.2 Cr ₂ O ₃ + 3.6 MgO + 1.0 Cr ₂ O ₃ + 3.0 MgO + 2.2 SiO ₂
■ + 2.2 (Cr ₂ O ₃ MgO) + 2.2 (2 MgO SiO ₂ )
-> - 2.2 MgCr ₂ O ₄ + 2.2 Mg ₂ SiO ₄ The newly emerging amount of MgO together with the also those bodies which in the final state next to one If the amount of inert substance added exceeds the amount of oxidic substance, it may contain a metallic phase Cr ₈ O ₃ , which is present from the reaction and additive. This is an improvement according to the guidelines given here MgO excess is experienced with the additive attached, by saturating the amount of SiO ₂ by carrying out the corresponding reaction, which is caused by the released 35 both on mixed crystal formations and alloys Heat of reaction was enabled to diffuse. Metals evolve as if certain and with is in . Intimate mixing of both a spinel and the metals in chemical equilibrium like the magnesium orthosilicate forsterite. oxide crystal species is targeted. Example 4 1.5 FeCr ₂ O ₄ + 3.0 Al + 1.5 Mg + (0.5 MgO + 0.5 Al ₂ O ₃ )
-y 1.5 Al ₂ O ₃ + 1.5 MgO + 3.0 Cr + 1.5 Fe + 0.5 MgO + 0.5 Al ₂ O ₃
. - + ■ 2.0 Al ₂ O ₃ + 2.0 MgO + 3.0 Cr + 1.5 Fe
-> - 2.0 MgAl ₂ O ₄ + (66.6 mol percent Cr + 33.3 mol percent Fe) An alloy forms between chromium and iron. and should take about 1 to 2 hours. Through this For the technical implementation of the thermal reaction, the grain association of the product is strengthened and see method according to the facial 50 set out above, the shrinkage is reduced. At points, it is advisable to adhere to the following rules: 5. It is advisable to use raw materials that are as pure as possible 1. Choose the calculation of the offset for production, as this will cause any change of place inconsistencies The body itself has to a minimum, taking into account the regions in the products Important factors as well as the released warmth are reduced and thereby the physical effort to be done, d. That is, a loss of heat in terms of chemical and chemical properties is an improvement Environment must also be taken into account. experience. 2. The substances must be intimately connected with each other before the reaction. According to the new process, it is possible to go through can be mixed and, if necessary, selection and coordination of the starting materials too completely be preformed. to arrive at novel end products that are 3. The substances must be pressed after ignition, 60 are superior to the products known up to now because the pressing after the reaction brings the are. Particles of the additive or control substance which may be patent claims the reaction itself does not lead to diffusion could be brought back into a reactive 1. metallothermal process for production capable state, since the 65 enveloping these particles are more heat-resistant and chemically resistant Rcaktionshäutc are pierced and so capable ceramic and semi-metallic products to become diffusive again. using easily oxidizable metallic 4. The products must then be tempered, powders on the one hand and metal oxides on the other. This subsequent tempering must be done on the side and under certain circumstances with the addition of a Bremsschlcunigung the diffusion at about 1500 ⁰ C 70 mixture, characterized in that the metallic see powder with oxides and a braking mixture consisting of the end products of the metallothermal Reaction or from the end products and other oxides which form a type of crystal with them can be mixed and made to react by initial ignition, the amounts of the to mixing substances are calculated stoichiometrically in such a way that the heat released during the reaction is sufficient for the complete conversion of the reaction products and those added as a brake mixture To bring about substances in the desired uniform crystal form. 2. Metallothermal process according to claim 1, characterized in that metallic powders such as Al, Si, Mg ₁ Zr ₁ Ca, Be, and metal oxides such as CrO ₃ , WO ₃ , MoO ₃ , TiO ₂ , B ₂ O _3, among others, which in the metallothermal process in a lower oxidation stage or the metal components pass alone and then particularly highly heat-resistant and / or corrosion-resistant Have properties, find use. 3. Metallothermal process according to claim 1 and 2, characterized in that the reaction mixture is pressed after ignition and the products are then ^{tempered at about 150O 0} C for 1 to 2 hours and slowly cooled. Considered publications:
German Patent Nos. 144 913, 504 484, 853 069, 557, 915 390, 915 391; Remy, Textbook of Inorganic Chemistry, 1st Volume 1954, pp. 127 and 136; Archiv für das Eisenhüttenwesen, 24 (1953), issue 7/8, pp. 285 to 306.