SE181100C1

SE181100C1 -

Info

Publication number: SE181100C1
Authority: SE
Publication date: 1962-01-01

Description

Uppfinnare: 0 Krifka Prioritet begard fran den 22 fuli 1955 (osterrike) strukturen i strangar av legerade byggnadsstal eller konstruktionsstal, vilka framstains enligt stranggjutningsmetoden, har vatesprickor (aven benamnda »flakeW kunnat konstateras, ehuru de genom statisk gjutning (standgjutning) framstallda goten av samma smalta voro fria fran vdtesprickor. Orsaken hartill ansags fOrst uteslutande Tara den vid stranggjutning nodvandiga snabbare avkylningen av gjutstrangarna. Emellertid voro vissa delar av gjutstrangen fria fran vd- tespriekor, varf5r aven andra orsaker mhste vara forhanden. Inventor: 0 Krifka Priority requested from 22 fuli 1955 (Austria) the structure in strands of alloyed building or structural steel, which are produced according to the continuous casting method, can have crack cracks (also called »flakeW, although they are produced by static casting). The reason for this was considered solely to be the faster cooling of the casting tubes required for continuous casting. However, certain parts of the casting strand were free from wet cracks, for which other reasons must also be present.

Det ãr kant, att vatesprickor fOrekommer I strukturen hos legerade stal, speciellt legerade byggnadsstM eller konstruktionsstal, am vatehalten i stalet overstiger ett bestamt varde. Den grans for vatehalten i stalet, vid vilken dylik sprickbildning annu icke upptrader, har i allmanhet antagits vara ungefar 5 cm3 per 100 g stal. It is not uncommon for cracks in the steel to occur in the structure of alloy steels, especially alloyed structural or structural steels, if the water content of the steel exceeds a certain value. The limit for the water content in the steel, at which such cracking does not yet occur, has generally been assumed to be approximately 5 cm 3 per 100 g of steel.

Vid stranggjutning passerar gjutstrangen, sedan den lamnat den kylda kokillen, vanligen en efterkylstracka, i vilken strangen kyles ytterligare genom pasprutning med vatten. Darvid gar man till 'raga pa det sattet, att den i ytskiktet stelnande gjutstrangen pasprutas med duschar eller dimmunstycken fran en eller flera ringformiga ledningar. Ndr vattenpartiklarna traff a den glodande strangytan, forangas kylmedlet och stiger den bildade vattenangan uppat med mycket stark lyftkraft pa grand av sin hoga temperatur relativt den omgivande atmosfaren. Denna snabbt uppstigande anga framkommer till den ur behallaren uttradande stralen av smalt stal och kommer i intim beroring med den heta metallen. Harigenom uppkommer vate genom termisk dissociation under kemisk bindning av syre, vilket vate upptages av smaltan under genomstromningen i sh stor grad, att bildning av vatesprickor intrader. Det är vanligt att tacka over efterkylstrackan, ear den bildade angan forsvarar sikten vid gjutningen. Darvid anordnades pla.tar omkring gjutstrangen efter sprutmunstyckena. Den storsta delen av den bildade vattenangan kondenserar pa dessa platar. Ehuru dylika skyddscylindrar aro oppna uppat och nedat, forbattras andock siktforhallandena genom desamma i sa betydande grad, att nagon anga icke kan observeras vid kokillen. Vid efterforskning av orsakerna till bildningen av vatesprickorna konstaterades emellertid, att vattenanga steg upp genom spalterna i gjutbryggan och att denna vattenanga var orsaken till bildningen av vatesprickor i gjutstrangen. In continuous casting, the casting strand, after leaving the cooled mold, usually passes a post-cooling stack, in which the strand is further cooled by injection spraying with water. This is done by spraying the solidifying casting strand in the surface layer with showers or mist nozzles from one or more annular pipes. When the water particles hit the glowing strand surface, the coolant evaporates and the formed water vapor rises upwards with a very strong lifting force due to its high temperature relative to the surrounding atmosphere. This rapidly rising anga emerges from the jet of narrow steel emerging from the container and comes into intimate contact with the hot metal. As a result, vate arises through thermal dissociation during chemical bonding of oxygen, which vate is taken up by the melt during the flow to such an extent that the formation of vase cracks occurs. It is common to grate over the post-cooling stack, before the formed steam defends the view during casting. In this case, plates were arranged around the casting strand after the spray nozzles. Most of the water vapor formed condenses on these plates. Although such protective cylinders are open upwards and downwards, the visibility conditions are improved by them to such an extent that no indication can be observed at the mold. However, when investigating the causes of the formation of the water cracks, it was found that water vapor rose through the gaps in the casting bridge and that this water vapor was the cause of the formation of water cracks in the casting strand.

Uppfinningen avser en forbattrad anordning for undvikande av vatesprickor i strukturen hos stalstrangar vid gjutning i stranggjutningsanlaggningar, yid vilka kylning sker genom att strangen i en efterkylstracka underkastas pasprutning eller annan liknande behandling med vatten, och det f8r uppfinningen utmarkande dr att ledytor aro sa anordnade ovanfOr efterkylstrackan, att de undantranga den frau efterkylstrackan uppstigande vattenangan i riktning bort fran smaltans fria yta. The invention relates to an improved device for avoiding hydrogen cracks in the structure of steel strands when casting in continuous casting plants, in which cooling takes place by the string in a post-cooling stack being subjected to pass spraying or other similar treatment with water, and the object of the invention , that they displace the water vapor ascending from the post-cooling stage in the direction away from the free surface of the melt.

For att de bildade vattenangorna skola hallas undan fran smaltan, är det i vissa fall tillrackligt att over efterkylstrackan, exempelvis i fOrbindelse med den undre kokillkanten, anordna ledplatar pa sadant satt, att angorna bortstromma eller bortsugas i sidled med avseende pa den ur en behallare till en ranna eller kokill flytande stralen. Eventuellt kan emellertid aven sjalva gjutstralen vara omgiven av tackplatar eller andra tackytor. In order for the formed water vapors to be kept away from the melt, it is in some cases sufficient to arrange baffles on the cooling floor, for example in connection with the lower mold edge, in such a way that the vapors drain away or are sucked out laterally with respect to it from a container to a gutter or mold liquid jet. Possibly, however, the casting jet itself may also be surrounded by roofing sheets or other roofing surfaces.

Det ar visserligen forat kant att gjutstralen kan tillforas smaltytan inuti ett ror eller 1 ett munstycke, men denna atgard är anvandbar endast vid sadana gjutmetoder, vid vilka kopparlegeringar gjutas, och den har till uppgift 2— — att trygga en virvelfri instromning av stralen i kokillen. Gjutning av svarsmaltbara metaller genom ett munstycke, som nar fram till smaltytan eller till dennas niva, är joke möjhg pa grund av den. hOga temperaturen hos smaltan och pa grund av risken f Sr att material fastnar pa munstyckskanten i form av grader, 2.skagp eller dylikt. It is true that the casting jet can be fed to the narrowing surface inside a tube or in a nozzle, but this method can only be used in such casting methods in which copper alloys are cast, and it has the task of ensuring a vortex-free inflow of the jet into the mold. . Casting of molten metals through a nozzle that reaches the melting surface or its level is a joke because of it. high temperature of the melt and due to the risk of material sticking to the nozzle edge in the form of burrs, 2.skagp or the like.

En utforingsform av anordningen enligt uppfinningen är sasom exempel schematiskt askadliggjord p5. bifogade ritning, pa vilken en stranggjutningsanlaggning med anordningen enIigt uppfinningen âr visad i frontvy i fig. 1 och i sido-vy i fig. 2. An embodiment of the device according to the invention is, as an example, schematically damaged p5. attached drawing, in which a continuous casting plant with the device according to the invention is shown in front view in Fig. 1 and in side view in Fig. 2.

Smaltan gjutes fran gjutskanken 1 ned i gjutrannan 2, i vilken den fordelas till de bada kokillerna 3 i den for tva strangar avsedda anlaggningen. Smaltytan i kokillerna Jigger fritt, for att slaggpartiklar skola kunna avlagsnas. Sedan gjutstrangarna 5 stelnat pa. ytan matas de ut ur kokillen med hj alp av nedsfinkningsvalsarna 6. For att gjutstrangens karna shall stelna hastigare är en efterkylstracka 4 anordnad for vardera gjutstrangen efter dennas uttrade ur kokillen. Inuti efterkylstrackan kyles gjutstrangen effektivt genom pasprutning av vatska medelst duschar. Genom att kylvatskan traffar de glodande gjutstrangarna bildas ett mom n av anga. Da delar av detta a.ngmoln kommer i beroring med den flytande smaltan, foretradesvis i kokillerna ovanfor dessa, utskiljes vate och orsakas den forut omnamnda sprickbildningen. The melt is cast from the casting shank 1 down into the casting gutter 2, in which it is distributed to the two molds 3 in the plant intended for two strands. The narrow surface of the molds Jigger freely, so that slag particles can be removed. Then the casting strands 5 solidified on. the surface, they are fed out of the mold with the aid of the countersink rollers 6. In order for the tubes of the casting strand to solidify more rapidly, a post-cooling rack 4 is arranged for each casting strand after it has left the mold. Inside the post-cooling rack, the casting tubes are cooled efficiently by spraying liquid with showers. As the cooling fluid hits the glowing casting strands, a mom n is formed. As parts of this cloud of contact come into contact with the liquid melt, preferably in the molds above them, cotton wool is precipitated and the aforementioned cracking is caused.

For att angan skall hindras fran att kom ma i beroring med den flytande smaltan ar en tackplal 7 fast pa kokillerna 3 och aro tackplatar 8, 9 anordnade pa. sidorna om och framfor utrymmet omkring efterkylstrackorna 4. Tackplattoma aro forsedda med sugstutsar 10 for bortsugning av angan. Enar till och med ytterst smâ mangder anga kunna orsaka vatesprickor, är dot nodvandigt att fogarna mellan platarna aro angtata. En dylik angtat forbindelse kan astadkommas genom s. k. angsarger 11, dvs. vatskefyllda rannor, i vilka kanterna pa tackplaten 7 inskjuta. In order to prevent the contact from coming into contact with the liquid melt, a filling plate 7 is fixed to the molds 3 and filling plates 8, 9 are arranged on it. the sides about and in front of the space around the post-cooling stairs 4. The roof plates are provided with suction nozzles 10 for suction of the steam. Although even extremely small amounts can cause water cracks, it is necessary for the joints between the plates to be tight. Such an assumed connection can be effected by so-called anxiety joints 11, i.e. water-filled gutters, into which the edges of the roof plate 7 protrude.

Claims

1. Patent claim: Device for avoiding hydrogen cracks in the structure of steel strands when casting in extruded casting plants, in which cooling takes place by the string in a post-cooling section being subjected to pass spraying or other similar treatment with water, characterized in that joint surfaces are arranged above the post-cooling section. that they displace the water vapor rising from the post-cooling stage in the direction away from the free surface of the melt. Request publications: Patents treat Germany 753985, 871501; USA 2 705 353., 4ndra Publikatiorter: Steel 1940: 8 april, p. 49. Stockholm 1962. Kungl. Boktr. P. A. Norstedt & Sorter. 620089