DK151776B

DK151776B - PROCEDURE FOR THE PREPARATION OF FROZEN CASTLE OR CORE

Info

Publication number: DK151776B
Application number: DK267580AA
Authority: DK
Inventors: Emil Jespersen; Bakshi Brijindra Singh
Original assignee: Dansk Ind Syndikat
Priority date: 1980-06-23
Filing date: 1980-06-23
Publication date: 1988-01-04
Also published as: ES503284A0; JPH0144424B2; IT8122460A0; EP0054061A1; PL130506B1; IT1136695B; WO1982000015A1; DD159531A5; BE889350A; DK151776C; ES8301130A1; JPS57500819A; EP0054061B1; CA1183320A; ZA814230B; SU1366043A3; DK267580A; CS257755B2; PL231819A1

Description

PK 151776BPK 151776B

Opfindelsen angår en fremgangsmåde til fremstilling af frosne støbeforme eller kerner af kornformigt materiale og et bindemiddel i et apparat omfattende et formkammer eller en kernekase, ved hvilken der anvendes et bindemiddel, som ved 5 positive temperaturer regnet i °C er luft- eller væskeformigt.The invention relates to a process for producing frozen molds or cores of granular material and a binder in an apparatus comprising a molding chamber or core, using a binder which is gaseous or liquid at 5 positive temperatures calculated in ° C.

Fra beskrivelsen til US-A-4.150.704 kendes en sådan fremgangsmåde, ved hvilken formsandet tilsættes en afmålt mængde vand, som efter formningen fryses til is i en vis dybde fra den overflade, der kommer i kontakt med smeltet metal, 10 f.eks. ved, at der anbringes et lag kulsyresne eller sprøjtes flydende nitrogen på denne overflade. Derved fås en meget stærk formoverflade, som bevarer sin styrke og form, indtil overfladen af metallet er størknet. Efterhånden som metallet afgiver sin varme, smelter og fordamper vandet, så 15 formen begynder at falde sammen uden brug af mekaniske mid ler. Der udvikles praktisk taget ingen røg under støbeprocessen, og formsandet kan uden videre bruges igen.From the specification of US-A-4,150,704, there is known such a method in which the molded sand is added a metered amount of water which after molding is frozen to ice at a certain depth from the surface which comes into contact with molten metal, e.g. . by applying a layer of carbon dioxide or spraying liquid nitrogen on this surface. This gives a very strong mold surface which retains its strength and shape until the surface of the metal is solidified. As the metal releases its heat, the water melts and evaporates, so that the mold begins to collapse without the use of mechanical agents. Practically no smoke develops during the casting process and the mold sand can be used again.

I en artikel i det russiske tidsskrift Liteinoe Proizvodsto 1975, nr. 5, side 21-22, er beskrevet frysning af en sand-20 form indeholdende 3-7% vand ved hjælp af et kølemiddel, der cirkulerer gennem fordamperen i et køleanlæg og gennem formen.In an article in the Russian journal Liteinoe Proizvodsto 1975, no. 5, pages 21-22, describes the freezing of a sand-20 form containing 3-7% water by means of a refrigerant circulating through the evaporator in a refrigeration plant and through shape.

Den omstændighed, at frysningen af det tilsatte vand ifølge sin natur er en temmelig langsom proces, og at der følgelig går forholdsvis lang tid fra det øjeblik, da formeprocessen 25 er afsluttet, til formen er frosset dybt nok til at kunne modstå virkningen af smeltet metal i tilstrækkelig lang tid, bevirker, at den samlede formfremstilling bliver betydelig mere tidskrævende end de konventionelle formfremstillingsprocesser.The fact that the freezing of the added water is, by its nature, a rather slow process and that consequently a relatively long time goes from the moment the molding process 25 is completed until the mold is frozen deep enough to withstand the effect of molten metal. for a sufficiently long time, causes the overall mold making to be considerably more time-consuming than the conventional mold-making processes.

o 30 I SU-D-428.843 er det foreslået at formindske procestiden ved anvendelse af en hul model, hvis hulrum kontinuerligt får tilført et kølemiddel. Et andet forslag fremsat i PL-P-218 .-611 går ud på at fryse væske i sandforme eller -kerner ved, at den pågældende model eller kernekasse, som 2o 30 In SU-D-428,843 it is proposed to reduce the process time using a hollow model whose cavity is continuously supplied with a refrigerant. Another suggestion made in PL-P-218.-611 is to freeze liquid in sand molds or cores by using the particular model or core box as 2

DK 151776BDK 151776B

sandet kommer i kontakt med, nedkøles i forvejen. I PL-P-224.193 er beskrevet anvendelse af en éngangsmodel af et gennemtrængeligt materiale, som nedbrydes, når det udsættes for smeltet metal, og hvorigennem der føres gas i væskeform 5 til formsandet. Endvidere er det i SU-D-718.215 foreslået at blande formsandet med kulsyresne, inden sandet påføres modellen, hvilken kulsyresne tjener til at afkøle sandet, som indeholder ca. 4% vand. AT-B-359.223 viser en formfremstillingsproces, ved hvilken to strømme af sand føres til et 10 blandeapparat. I den ene strøm tilsættes der vand til sandet, medens den anden strøm udsættes for påvirkning af et kølemiddel, såsom væskeformig nitrogen. Pra blandeapparatet føres blandingen af fugtet og afkølet sand til formkassen.the sand comes into contact with, cooled in advance. PL-P-224,193 discloses the use of a disposable model of a permeable material which decomposes when exposed to molten metal and through which liquid gas 5 is fed to the mold sand. Furthermore, in SU-D-718,215 it is proposed to mix the mold sand with the carbonic acid before applying the sand, which carbonic acid serves to cool the sand, which contains approx. 4% water. AT-B-359,223 shows a mold making process in which two streams of sand are fed to a mixer. In one stream, water is added to the sand while the other stream is subjected to the influence of a refrigerant such as liquid nitrogen. From the mixer, the mixture of moistened and cooled sand is fed to the mold box.

Ifølge opfindelsen kan der opnås en yderligere reduktion af 15 den tid, der kræves til fremstilling af frosne støbeforme eller kerner derved, at bindemidlet fryses inden det blandes med det kornformige materiale. Derved reduceres fremstillingstiden i det væsentlige til den tid, det tager at fylde formkassen eller kernekassen med blandingen af sand og binde-20 middel og at komprimere blandingen tilstrækkeligt omkring modellen eller ved de vægge, der begrænser kernekassens formhulrum, til at bindemidlet kan bringes til at kitte sandkornene sammen.According to the invention, a further reduction of the time required to prepare frozen molds or cores can be obtained by freezing the binder before mixing it with the granular material. Thereby, the manufacturing time is substantially reduced to the time it takes to fill the mold box or core box with the mixture of sand and binder and to compress the mixture sufficiently around the model or at the walls that restrict the mold cavity of the core box to allow the binder to be putt the grains of sand together.

Det anvendte bindemiddel kan som angivet i krav 2 fryses til 25 fine, dendritiske partikler, f.eks. sne, inden det blandes med det kornformige materiale, og en kompression under formeprocessen kan medføre, at bindemidlet opnår en del af eller hele sin bindeevne afhængigt af temperaturforholdene på formfremstillingstidspunktet.The binder used can be frozen as claimed in claim 2 to 25 fine dendritic particles, e.g. snow before mixing with the granular material, and a compression during the molding process may cause the binder to achieve part or all of its bonding ability, depending on the temperature conditions at the time of molding.

30 Det anvendte bindemiddel kan også som angivet i krav 3 fryses til findelt pulvermateriale, f.eks is, i formmaterialet, inden det blandes med det kornformige materiale, og en kompression under formeprocessen kan medføre, at bindemidlet opnår en del af eller hele sin bindeevne afhængigt af tem-35 peraturforholdene på formf remstillingstidspunktet.The binder used can also be frozen, as defined in claim 3, into finely divided powder material, for example ice, in the molding material before mixing with the granular material, and a compression during the molding process can cause the binder to achieve part or all of its bonding ability. depending on the temperature conditions at the time of shaping.

33

jf DK 1517768 ; .Scf. DK 1517768; .S

Ved kompression af en passende blanding af kornformigt materiale og sne eller knust is i en formkasse bringes sneen eller isen til at kitte materialekornene sammen, således at formen eller kernen får tilstrækkelig sammenhængskraft til 5 at kunne modstå påvirkningen fra flydende metal, der hældes ned i den færdige form med eller uden kerner. En tilsvarende virkning kan opnås ved indsprøjtning af en af de nævnte formmaterialeblandinger i en kernekasse med tilstrækkelig stor kraft og hastighed.By compressing a suitable mixture of granular material and snow or crushed ice in a mold box, the snow or ice is brought together to seal the material grains so that the mold or core has sufficient cohesiveness to withstand the influence of liquid metal poured into it. finished form with or without cores. A similar effect can be obtained by injecting one of the aforementioned mold material mixtures into a core box of sufficiently high force and velocity.

10 Det frosne bindemiddel i form af pulveriseret materiale kan også som angivet i krav 4 blandes med flydende gas, inden det blandes med det kornformige materiale. Derved kan formmaterialet bringes ned på en meget lav temperatur forud for og under formeprocessen samt under den umiddelbart efter-15 følgende støbeproces. Blandingen skal være homogen og let strømmende.The frozen binder in the form of powdered material can also, as stated in claim 4, be mixed with liquid gas before being mixed with the granular material. Thereby, the molding material can be brought down to a very low temperature prior to and during the molding process and during the immediately following molding process. The mixture should be homogeneous and slightly flowing.

Der er i og for sig heller intet i vejen for at anvende konventionelle hærdebindonidler, der kan bringes til at foreligge på frossen form. Således kan der f.eks. til dannelse af det frosne bindemiddel anvendes 20 vandglas og flydende kuldioxid, som angivet i krav 5. Det frosne binde-middel kan desuden dannes ved en blanding af polyisocyanat og phenol-harpiks, son er tilsat forud kølet, flydende dimethylethylamin eller triethylamin, son angivet i krav 6L Den forud kølede, flydende dimethylethylamin eller triethylamin aktiverer blandingen af polyisocyanat og 25 phenolharpiks. Derved opnås mulighed for nedsat forbrug af miljøskadeligt bindemiddel.In itself, there is also nothing in the way of using conventional hardener binders which can be made available in frozen form. Thus, e.g. to form the frozen binder, 20 water glasses and liquid carbon dioxide are used, as set forth in claim 5. The frozen binder can further be formed by a mixture of polyisocyanate and phenol resin added pre-cooled, liquid dimethylethylamine or triethylamine, as indicated. in claim 6L The pre-cooled liquid dimethylethylamine or triethylamine activates the blend of polyisocyanate and phenolic resin. This gives the possibility of reduced consumption of environmentally harmful binder.

For at opnå en større modstandsdygtighed mod varmepåvirkningen fra det smeltede metal og dermed en forsinkelse af formens eller kernens opvarmning under støbeprocessen, kan det 30 kornformige materiale, der anvendes til dannelse af formen eller kernen, være forud dybkølet på i og for sig kendt måde.In order to obtain greater resistance to the heat stress of the molten metal and thus to delay the heating of the mold or core during the molding process, the granular material used to form the mold or core may be pre-cooled in a manner known per se.

Der kan også forud være foretaget dybkøling af blandingens bestanddele ved hjælp af et tilsat frysemiddel, som f.eks. flydende gas. Ved anvendelse af en inert gas undgås enhver J ζ riaiVfl •fnr' Irsmi elro anrrroh nå ή af- -Ml rirnroccon anuenrife π ri — 4Also, deep cooling of the constituents of the mixture may be carried out by means of an added freezing agent, such as e.g. liquid gas. Using an inert gas avoids any J ζ riaiVfl • fnr 'Irsmi elro anrrroh reaching ή of- -Ml rirnroccon anuenrife π ri - 4

DK 151776BDK 151776B

Den nødvendige afkøling kan også foregå eller understøttes ved, at de apparatdele, hvormed formmaterialet kommer i kontakt under formeprocessen, er dybkølede. Ved fremstilling af støbeforme kan således specielt modelbrættet, der kommer j 5 i kontakt med den samme formoverflade som senere det smeltede metal, være forud dybkølet, og ved fremstilling af kerner kan der anvendes en forud dybkølet kernekasse. Der kan også foretages afkøling af kernekassen med kerne eller kerner samtidigt og yderligere, f.eks. med flydende gas.The necessary cooling can also be carried out or supported by the fact that the apparatus parts with which the molding material comes into contact during the molding process are deep chilled. Thus, in the manufacture of molds, especially the model board which comes into contact with the same mold surface as later the molten metal can be pre-cooled, and in the preparation of cores a pre-cooled core box may be used. It is also possible to cool the core box with cores or cores simultaneously and further, e.g. with liquefied gas.

10 Ved en særlig udførelsesform for fremgangsmåden ifølge opfindelsen ved fremstilling af støbeforme anvendes der dybfrosne éngangsmodeller af et materiale, der fordamper ved opvarmning, som angivet i krav 7, og dette materiale kan hensigtsmæssigt være dybfrosset og opskummet som angivet i 15 krav 8. Sådanne modeller kan fremstilles løbende i en særlig todelt modelformkasse svarende til en konventionel kernekasse og anbringes i et lukket rum, hvorefter mellemrummet mellem modellen og rummets vægge fyldes med formmateriale, der afkøles af modellen og yderligere kan være afkølet i 20 forvejen som ovenfor nævnt. Efter formeprocessens afslutning fordamper modellen hurtigt på grund af den modtagne varme. Herved undgås den generende gasudvikling, som ellers finder sted ved formning med éngangsmodeller.In a particular embodiment of the process according to the invention in the manufacture of molds, disposable frozen disposable models of a material evaporating by heating as set forth in claim 7 are used, and this material may conveniently be deep frozen and foamed as set forth in claim 8. Such models can be made continuously in a special two-part model mold box similar to a conventional core box and placed in a closed compartment, whereupon the space between the model and the room walls is filled with mold material cooled by the model and may be further cooled in advance as mentioned above. After the molding process is completed, the model evaporates rapidly due to the heat received. This avoids the annoying gas evolution that otherwise occurs when forming with disposable models.

Ved denne udførelse af fremgangsmåden fås særlig nøjagtigt 25 støbegods, fordi de unøjagtigheder, der ved den konventionelle f omf remstillingsmetode forårsages af slitage på modelbrættet hidrørende fra sandskuddene, undgås. Desuden kræves der ingen todeling af fomkassen, når der anvendes let fordampelige modeller.In this embodiment of the method, particularly accurate castings are obtained, because the inaccuracies caused by the conventional method of fitting are caused by wear on the model board resulting from the sand blasting. Furthermore, no two-partition of the fume box is required when easily evaporative models are used.

30 Ved en særlig udførelsesform for fremgangsmåden ifølge opfindelsen anbringes apparatet . eller dele deraf i et kølerum forud for nedfrysning af bindemidlet, hvorved de fornødne temperaturforhold uden videre kan opretholdes hele tiden, så der ikke går værdifuld produktionstid tabt med at vente på 35 afkøling.In a particular embodiment of the method according to the invention, the apparatus is placed. or parts thereof in a cold room prior to freezing of the binder, whereby the required temperature conditions can be maintained at all times, so that valuable production time is not lost while waiting for 35 to cool.

Claims

A process for producing frozen molds or cores of granular material and a binder in an apparatus comprising a molding chamber or core box using a binder which is gaseous or liquid at positive temperatures calculated in ° C. by freezing the binder before mixing it with the granular material.

Process according to claim 1, characterized in that the binder is frozen to fine dendritic particles, e.g. snow before mixing it with the granular material.

Process according to claim 1, characterized in that the binder is frozen into finely divided powder material, e.g. ice, in the molding material before mixing it with the granular material.

Process according to claim 3, characterized in that the frozen binder in the form of powdered material is mixed with liquid gas before it is mixed with the granular material.

Process according to claim 1, characterized in that water glass and liquid carbon dioxide are used to form the frozen binder.

Process according to claim 1, characterized in that a mixture of polyisocyanate and phenolic resin added with pre-cooled liquid dimethylethylamine or triethylamine is used to form the frozen binder.

Process according to any one of claims 1-6 in the manufacture of molds, characterized in that 30 frozen single-use models of a material which evaporate on heating are used. t DK 151776 B T t

Method according to claim 7, characterized in that disposable models made of deep frozen, resuspended material are used.

Method according to one of the preceding claims, characterized in that the apparatus or parts thereof are placed in a cold room prior to the freezing of the binder.