SE204116C1

SE204116C1 -

Info

Publication number: SE204116C1
Authority: SE
Publication date: 1965-01-01

Description

Uppfinnare: N G Sehrewelius Foreliggande uppfinning haul& sig till eft salt ail framstalla :av pulver pressade .sintrade kroppar sksom elektriska upphettningselement .och dylikt, huvudsakligen bestaende av MoSi2 och en mindre del oxidmaterial, banehallande A120, och S2, vilka kroppar fardigsintras. i oxiderande atmosfar. Uppfinningen har sar skill till andamal att astadkomma en I sinterkroppen likformigt fordelad glasartad mum.. Inventors: N G Sehrewelius The present invention relates to the production of salt: powder-pressed sintered bodies such as electric heating elements and the like, consisting mainly of MoSi2 and a small amount of oxide material, containing A120 and S2, which bodies are sintered. in oxidizing atmospheres. The invention differs from the object of achieving a glassy mum uniformly distributed in the sintered body.

Uppfinningen utnyttjar harvid den i och for sig kanda metoden, att yid sintringen av silicider anvanda vissa ,svallbara leror, som innehalla mineralet bentonit, eller andra sadana leror av montmorillonitgruppen, :sasom heidellit och saponit. The invention makes use of the per se known method, which in the sintering of silicides uses certain, swellable clays which contain the mineral bentonite, or other such clays of the montmorillonite group, such as heidellite and saponite.

Ealigt uppfirmingen blandas pulverformig finmalen molybdendlicid med Masa finfOrdelat plastiskt lermaterial av montmorillonitgruppen, auvenderat i en polar vatska, sisom vatten, varpa blandningen formas -och pa i och for sig kant satt forsintras i vatgas och den darvid erhallna porosa fOrsintrade formkroppen fardigsintraai luft yid temperaturer c:a 1600° C, varvid det darvid ,smalta lerrnaterialet och den -av .siliciden. eventuellt bit-dad kiseldioxid tillsammans utfylla formkroppens parer och forhindra silicidens komtillvaxt vid hoga temperaturer. Harigenom har det for forsta gangen blivit mOjligt att pa enkelt silt framstalla porfria upphettningselement och liknande ,sinterkroppar med tillfredsstallande och varaktig hallbarhet. . According to the invention, powdered finely ground molybdenum liquid is mixed with Masa finely divided plastic clay material of the montmorillonite group, applied in a polar liquid, sisom water, the mixture is formed and on its own edge pre-sintered in hydrogen gas at 1600 ° C, whereby the molten clay material and the silica. possibly bit-dad silica together fill the mold body pairs and prevent the growth of the silicide at high temperatures. This has for the first time made it possible to easily produce pore-free heating elements and the like, sintered bodies with satisfactory and durable durability. .

DO ,det i 'foljande beskrivning talas em ben,- -tonit, inbegripas harunder awn ovannamnda andra svailhara leror ur montmorillonitgruppen. Bentonit i torrt tillstand fordigger i form av ytterst tunna kriStallblad. DO button:it blan- - das med vatten ,eller andra vatskor- aged hog dielektricitetskonstant ,intranga vatskemolet kyler Indian bladen .och skilla dem at, varigenom bentoniten svaller. Data medfor en mye-_ ket hog plastisk formharhet hos materialeti Den keramiska industrien ancvander .sig sedan, lange av derma pastiska formbarhet for att framstalla formkroppar .av magra keramiska material, ,sasom kiselkarbid, kvarto osv. DO, which in the following description is referred to as bone, - -tonite, is included among the above-mentioned other svailhara clays from the montmorillonite group. Bentonite in the dry state defends in the form of extremely thin crystalline leaves. DO button: it is mixed with water, or other vatskor- aged hog dielectric constant, the intrusive vatskemolet cools the Indian leaves .and separates them at, whereby the bentonite swells. Data The ceramic industry has since become very high in plastic mold hardness to produce molded bodies from lean ceramic materials, such as silicon carbide, quarto, etc.

Det har tidigare foreslagilts, -att utfora --for7 sintring i :dissocierad NH3 och slutsintrin0 oxiderande atmosfar. Foretagna prov ha emeI7 lertid visat, att en forsintring i en. sadan u.ttn.oafar joke Or liiirnplig i f5religgande fall, enar NH3 fOrorsakar ruitridbildning och:.sonderfall hos den sintrade MoSirkroppen. I sjalva ver, ket Or del vid kombinationen arv bentonittill7 satsen, forsintringen i vatgasoch fordigs-int-. ring i luft vid c :a 1800° G som MoSirproduk: ten med hOg oxiclationsbestandighet och -me7 kanisk hallfasthet kunna ,erhailas-. It has previously been proposed to perform sintering in dissociated NH3 and final sintering oxidizing atmospheres. Tests taken have emeI7 however shown, that a sintering in a. so u.ttn.oafar joke Or liiirnplig in the present case, enar NH3 fOrorsakar ruitridbildning och: .sonderfall hos den sintrade MoSirkroppen. In fact, Or del in the combination inherited bentonite to7 the batch, the pre-sintering in vatgas and fordigs-int-. ring in air at about 1800 ° G as the MoSir product with high oxiclation resistance and -me7 mechanical resistance can be obtained.

I detta -sammanhang hanvisas aven trill I. ex. den syeaiska patentskriften 155 836, varav framgar, :att diet_ Or kint att vid tillverluring av formade -och shitrade MoSirkroppar till-Waft SiO2-material och att harvid sintra I en skycldsatmosfar, vantigen H2,- argon - eller - va- kiium, och sedan tillfOra en oxiderande gas,. In this context, reference is also made to trill I. ex. U.S. Pat. No. 155,836, which states that in the production of shaped and sheathed MoSir bodies to Waft SiO2 material and that it sinks in a shielding atmosphere, containing H2, argon or vacuum, and then supplying an oxidizing gas,.

Vid uppfiamingens praktiska utforande Man:- -das ett finfordelat pulver av molybdensilicid med: en ringa mangd svalld- hentonit. Den sit; Junda erhalina produkten kan formas genom vanliga pulvermetallurgiska eller keramiska fOrfaran_den, sasom t. ex. strangpressning, pressning eller sprutgjutning, yarpa de erhallna formkropparna sintras. i -tva. steg enligt vad evan framhallits, Sintringen bör ske *id en temp.eratur, som ar hogre an b-entoni- Dupl. kl. 21 c: 55/01; 21 h: 1; 80 b: 8/16; 80 b: 8/22; 80 c: 17/ 2 tens smaltpunkt ,och som fardras for att man skall ,erhalla en mycket tat produkt. In the practical implementation of the invention, a finely divided powder of molybdenum silicide is present with: a small amount of swallowed hentonite. It sits; Junda erhalina product can be formed by conventional powder metallurgical or ceramic procedures, such as e.g. extrusion, pressing or injection molding, yarpa the obtained shaped bodies are sintered. i -tva. step according to what evan highlighted, The sintering should take place * id a temp.eratur, which is higher than b-entoni- Dupl. at 21 c: 55/01; 21 h: 1; 80 b: 8/16; 80 b: 8/22; 80 c: 17/2 melting point, and which is required to obtain a very dense product.

Det liar visat sig vara fOrdelaktigt att an-vanda ett I mojligaste man finfordelat utAangsmaterial, lampligen med kornstorlekar, som endasf foga oversluida 1 mikron. Bentonitmingden bor valjas, storre, ju mindre molybdensilicidens kornstorlekar aro. It has been found to be advantageous to use a finely divided starting material as far as possible, preferably with grain sizes which can only exceed 1 micron. The bentonite mixture should be chosen, the larger the smaller the grain sizes of the molybdenum silicide.

Sintring av eu blandning av till 5 mikron finmalen molybdensilicid (MoS12) med c :a 5 vikt- % svald bentonit yid 16000 resulterar en mycket vardefull, varmebestandig och oxidationshestandig produkt. Denna uppvisar i farhallande till rem MoSi2 flera fordelaktiga egenskaper, sasom battre plasticitet vid h8ga temperaturer, mycket ringa korntillvaxt samt god svetsbarhet. Den mekaniska hallfastheten hos ett enligt uppfinningen av MoS12 och bentonit framstallt sintrat material ar ungefar dubbelt sa hag sam den yid ett av ren molybdendisilicid framstallt material. Alltefter man.gden bentonit och kornstorleken kan yid ovannaninda exempel en hallfasthet vid rem MoSi2nv 20 kp/mm2 h&j as till 60 kp/mm2. Sintering of a mixture of up to 5 microns of finely ground molybdenum silicide (MoS12) with about 5% by weight of cooled bentonite yid 16000 results in a very valuable, heat-resistant and oxidation-resistant product. This exhibits several advantageous properties in relation to the MoSi2 belt, such as better plasticity at high temperatures, very low grain growth and good weldability. The mechanical strength of a sintered material made according to the invention of MoS12 and bentonite is about twice as good as that of a material made of pure molybdenum disilicide. Depending on the size of the bentonite and the grain size, the above-mentioned strength at a belt MoSi2nv of 20 kp / mm2 can be increased to 60 kp / mm2.

Raknad p5. torrvikt Sr blandningens bentoMithalt mellan. 0,2 ach 20 %, varvid procenttalet ar beroende av kornstorleken has MoSi2 och narrnare bestamt omvant proportionellt mot denim. Shaved p5. dry weight Sr mixture bentoMithal between. 0.2 and 20%, the percentage depending on the grain size has MoSi2 and narrower determined inversely proportional to denim.

Formkroppar, vilka innehalia fuktig lera och torkas ha redan i detta tHistand en avseyard mekanisk hallfasthet, vilket Sr av betyformkroppar. delse, .sarskilt vid framstallning av stoma - Vid genomforandet av forfarandet enligt upprinningen liar det visat sig att MoSi2 vid sintring i tuft eller en. annan, syrgas innehallande atmosfar oxideras delvis sa att en tuna kiseldioxidfilm bildas, silken. reagerar med den tilsatta bentoniten under bildning av ett som liar en lagre smaltpunkt an kisel- dioxiden och bildar ett karntillvaxten hindrande gr.ansskikt. Molds which contain moist clay and are dried already have a certain mechanical strength in this condition, which means of moldings. especially in the production of the stoma - In carrying out the process according to the origin, it has been found that MoSi2 when sintered in tuft or a. another, oxygen-containing atmosphere is partially oxidized to form a thin film of silica, silk. reacts with the added bentonite to form a layer which has a lower melting point of the silica and forms a core growth-impeding growth layer.

Utforingsexempel Molybdendisilicid (MoSi2), som framstaHts gamma reaktion mellan molybdenpulver och kiselpuilver i en. vatgasatmosfar krossas och males darefter under 120 timmar i kulkvarnar pied kulor av hardmetall. Varje kvam beskickas med 4,5 kg silicid. Del bildade silicidpulvret torkas under vaku.um. Pulvrets kornstorleksfordelning är foljande: 100 % finale An 10 mikron och 50 % Rua-re an. 3 mikron. En typisk analys ar 63,0 % Mo, 36,6 % Si och 0,4 % Fe. Embodiments Molybdenum disilicide (MoSi2), which produces the gamma reaction between molybdenum powder and silicon powder in a. water gas atmosphere is then crushed and ground for 120 hours in hard metal ball mills. Each kvam is loaded with 4.5 kg of silicide. Part of the silicide powder formed is dried under vacuum. The grain size distribution of the powder is as follows: 100% final An 10 microns and 50% Rua-re an. 3 microns. A typical analysis is 63.0% Mo, 36.6% Si and 0.4% Fe.

Av detta MoSi2-pulver blandas 100 delar med 5 delar wyaming-bentonit och forsattes med vatten till dess att blandningen Fitt kan bearbetas. Denna bentanit hair fOljande ge nomsnittliga sammansattning, namligen 60 % S2, 20 % A1203, 15 % H20 och 5 % frammande amen, sham' Fe208, CaO, MgO och Na2O. Den plastiska blandningen knadas i vakuum under 48 timmar i en. knadmaskin, under vilken behandling fuktighetshalten nedgar tit 8 vikt-%. I en strangpress utmutas sta.var av onskade langder och med en diameter av 7 eller 14 ram. Stavarna torkas och fOrsintras 1 rem vatgas (hOgst 0,5 volym- % 02) vid 1000° C och skjutas sedan genom en ugn vid 1200 till 1400° C. Efter derma behanclling, viiken likasa utfores i rem vatgas, besitta stayarnn en si stor hallfasthet att de utan svarighet kunna handhas. Stavarnas, porositet uppgar nu till 15-20 volym- %. En typisk analys dr fOljande: 59,7 % Mo, 36,0 % Si, 0,7 Al, 0,7 Fe och 0,2 fOroreningar, varvid resten eller 2,2 % bestar av ,syre. Den mineralogiska samman.sattningen ar 91 volym-% MoSi2 och 9 volym- % glas, som i huvudsak utgares av smalt bentonit. Of this MoSi2 powder, 100 parts are mixed with 5 parts of wyaming bentonite and continued with water until the mixture Fitt can be processed. This bentanite hair following give average composition, namely 60% S2, 20% Al2 O3, 15% H2 O and 5% promoting amen, sham 'Fe2 O8, CaO, MgO and Na2O. The plastic mixture is kneaded in vacuo for 48 hours in one. kneading machine, during which treatment the moisture content decreases to 8% by weight. In an extruder, rods of desired lengths and with a diameter of 7 or 14 frames are excavated. The rods are dried and pre-sintered in 1 g of hydrogen (at most 0.5% by volume of O 2) at 1000 ° C and then pushed through an oven at 1200 to 1400 ° C. After this treatment, which is also carried out in a stream of water, firmness that they can be handled without responsibility. The porosity of the rods now amounts to 15-20% by volume. A typical analysis is as follows: 59.7% Mo, 36.0% Si, 0.7 Al, 0.7 Fe and 0.2 compounds, with the remainder or 2.2% consisting of oxygen. The mineralogical composition is 91% by volume of MoSi2 and 9% by volume of glass, which is mainly composed of narrow bentonite.

En. elektrisk strom bringas, att passera genom tie forsintrade ,stavarna for att Mom . ett fatal minuter hetta upp clessa I luft till 1600° G och harigenom fardigsintra ostavarna. Produkten ham da en parositet av mellan 0 och 5 % motsvarande en tathet av 5,6 g/cm3. Bojningshallfastheten yid Tumstemperatur ar 50 kp/mm2 gentemot -ungefor 20 kp/mm2 vid rein MoSi2. En typisk analyst ar foljande 57,7 % Mo, 34,9 % Si, 0,7 % Al, 0,7 % Fe och 0,2 % faroreningar, varvid resten pa 5,8 % utgores av syre. Den meneralagiska sammansattningen Sr 82 valym-% MoS12 och 18 volyan-% gins. Glasfasen ar en reaktionsprodukt av smalt bentonit och Si02 som bildats genom oxidation av siteider. Denna keramiska bestanclsdel ar mycket viktig, enar den forebygger siliciclens koratillvaxt vid hoga tempera-hirer. Vid 1600° C kunna de nyframstallda, luetsintrade stavarna underkastas varje godtycklig farming. Efter nagra timmars upphettning ager ,emellertid en reaktion ruin i materialet, vilken kan innebara en hardning av glasfasen genom att alkali bortgar under sintringen, varav den. praktiska foljden. Mir att fortmkrappen sedan icke kan utsattas for flagon ytterligare deformation utan bibehatler sin ,erhallna form. One. electric current is brought, to pass through tie pre-sintered, the rods to Mom. a fatal minutes heat up the clessa in air to 1600 ° G and thereby finish the cheese sticks. The product then has a parosity of between 0 and 5% corresponding to a density of 5.6 g / cm 3. The bending strength yid Inch temperature is 50 kp / mm2 compared to -ungefor 20 kp / mm2 in pure MoSi2. A typical analyzer is the following 57.7% Mo, 34.9% Si, 0.7% Al, 0.7% Fe and 0.2% hazardous impurities, the remainder of 5.8% being oxygen. The meningeal composition Sr 82 valym-% MoS12 and 18 volyan-% gins. The glass phase is a reaction product of narrow bentonite and SiO2 formed by oxidation of siteides. This ceramic component is very important, as it prevents the growth of silicon at high temperatures. At 1600 ° C, the newly produced, lute-sintered rods can be subjected to any arbitrary farming. After a few hours of heating, however, a reaction ruins in the material, which may involve a hardening of the glass phase by removing alkali during sintering, of which it. practical consequence. Mir that the forearm can then not be subjected to flake further deformation without maintaining its, obtained shape.

Claims

Patent claim:

Salt for the production of powder-pressed sintered bodies such as electric heating elements and the like, consisting mainly of MoSi2 and a major proportion of oxide materials containing Al2 O3 and SiO2, which bodies are sintered in an oxidizing atmosphere, which may be characterized by mixed with similarly finely divided plastic clay material of the montmorillonite group, suspended in a polar liquid, such as water, to form the mixture and pre-sintered in water per se. and that the resulting porous pre-sintered shaped body is then fully sintered in air at temperatures of. about 1600 ° C, whereby the molten clay material and the silica, possibly formed by the silicide, together fill in the pores of the mold body and prevent the grain growth of the silide at high temperatures.

SW according to patent claim 1, characterized in that the grain size of the molybdenum silicide fOga exceeds 1 micron.

3. Set according to patent claim 1 or 2, characterized in that bentonite is used as the clay material. Request publications: Patentskrifter iron Sverige 112 974, 155836; France 809 961, 827 501, 997 160; Switzerland 205,098; Great Britain 725 577; USA 2 118 789.