SE506027C2

SE506027C2 - Magnesium process for producing a treated melt with less than 100g / t non-metallic inclusions and apparatus for carrying out the process

Info

Publication number: SE506027C2
Application number: SE9003756A
Authority: SE
Inventors: Ivo Henych
Original assignee: Fischer Ag Georg
Priority date: 1989-11-28
Filing date: 1990-11-26
Publication date: 1997-11-03
Also published as: DK173273B1; ES2028563A6; DK276890A; DK276890D0; SE506027C3; RU2127320C1; SE9003756L; ZA909520B; SE9003756D0

Abstract

Procedure for treating a molten metal mass, especially iron, with magnesium. It involves controlling the reaction of treatment with magnesium at a depth of at least 200 mm below the surface of molten mass in such a way that the amount of magnesium evaporated generates a mixture energy of at least 1,000 W/m3, with a non- oxidating atmosphere being provided in the treatment vessel, above the surface of the molten mass. The invention is useful for producing a molten metal mass treated with magnesium which contains less than 100 grams of non-metal inclusions per ton of molten mass.

Description

506 027 L = fiotationshojd i mm D = partikelstorlek i pm are - specifik vikt för järn i kg/m3 (vooo) óslagg = specifik vikt för slaggen i kg/m3 (3000) t = flotationstiden i sekunder p = dynamisk viskositet (0,007) De praktiska mätningarna har visat att vid de konventionella behandlingsmetoderna ligger mängderna av svävande partiklar mellan 200 och 600 g/t behandlat järn, vilka därefter med gjutstràlen ingjutes i den form som skall fyllas. Undersökning- arna visade likaledes att dessa inneslutningar, som kvarstannar i gjutstycket, kan väsentligt försämra gjutstyckets egenskaper. 506 027 L = fiotation height in mm D = particle size in pm are - specific gravity for iron in kg / m3 (vooo) non-slag = specific gravity for the slag in kg / m3 (3000) t = flotation time in seconds p = dynamic viscosity (0.007) The practical measurements have shown that in the conventional treatment methods the amounts of suspended particles are between 200 and 600 g / t of treated iron, which are then cast with the casting jet into the mold to be filled. The investigations also showed that these inclusions, which remain in the casting, can significantly impair the properties of the casting.

För att möjliggöra flotation av reaktionsprodukterna maste smältan vara kvar under längre tid i skänken. Detta har emel- lertid till följd avsevärda, i regel oacceptabla temperaturför- luster (6-lït/minut).To enable flotation of the reaction products, the melt must remain in the ladle for a longer time. However, this results in significant, generally unacceptable temperature losses (6 liters / minute).

Användningen av det fràn stàltillverkningen kända förfarandet med spolning av smältan med inertgas (N, Ar, etc.) förorsakar en ökad oxidation av magnesium, som leder till bildning av ytterligare, nya inneslutningar, varför det eftersträvade målet icke uppnås med detta förfarande.The use of the process known from steelmaking to flush the melt with inert gas (N, Ar, etc.) causes an increased oxidation of magnesium, which leads to the formation of additional, new inclusions, so that the desired goal is not achieved with this process.

Föreliggande uppfinning har till uppgift att föreslå ett förfarande och en anordning, med vilkas hjälp behandlings- reaktionen kan styras på sådant sätt, att de icke-metalliska inneslutningarna i den behandlade smältan reduceras till ett minimum.The object of the present invention is to propose a method and an apparatus by means of which the treatment reaction can be controlled in such a way that the non-metallic inclusions in the treated melt are reduced to a minimum.

Denna uppgift löses enligt den kännetecknande delen av patent- kraven 1 och 9.This object is solved according to the characterizing part of claims 1 and 9.

Ytterligare fördelaktiga utföringsformer av förfarandet enligt uppfinningen framgår av de beroende patentkraven. 506 027 3 A _ Genom den reglerade spolningen av smältan i en reducerande atmosfär över ytan av järnsmältan redan under magnesiumbehand- lingen koaguleras de vid behandlingen bildade reaktionspro- dukterna och transporteras med de uppàtstigande magnesiumång- blàsorna såsom slagg till ytan av smältan. Koaguleringen av reaktionsprodukterna àstadkommes genom de bildade ángmängderna och genom blandningsenergin. Erfarenheterna visar att intensi- teten av koaguleringen genom sammanstötning av de icke-metal- liska partiklarna förstärkas väsentligt vid tidpunkten för dessas bildning, dvs. på reaktionsstället. Blandningsenergin kan bestämmas med följande ekvation: 6,2 x 10 x Q x T (1-273/T) x ln p/pO E' = blandningsenergi i W/m3 gasmängd i N1/minut O I T - temperatur i.°K p0 - tryck på småltans yta 1 at. p - p0 + ferrostatiskt tryck 1 at.Further advantageous embodiments of the method according to the invention appear from the dependent claims. 506 027 3 A - By the controlled flushing of the melt in a reducing atmosphere over the surface of the iron melt already during the magnesium treatment, the reaction products formed during the treatment are coagulated and transported with the ascending magnesium vapor bubbles as slag to the surface of the melt. The coagulation of the reaction products is accomplished by the amounts of vapor formed and by the mixing energy. Experience shows that the intensity of the coagulation by collision of the non-metallic particles is significantly enhanced at the time of their formation, ie. at the reaction site. The mixing energy can be determined by the following equation: 6.2 x 10 x Q x T (1-273 / T) x ln p / pO E '= mixing energy in W / m3 gas quantity in N1 / minute OIT - temperature in. ° K p0 - press on the surface of the smolt 1 at. p - p0 + ferrostatic pressure 1 at.

V - smältans volym i m3 De praktiska försöken visade att mängderna av icke-metalliska inneslutningar i småltan kan reduceras till värden under 100 g/t, när blandningsenergin år större än 1000 W/ma, magne- siumàngorna bildas på ett djup av minst 200 mm under ytan av smaltan och atmosfären över smältan är övermättad med magne- siumánga.V - melt volume in m3 The practical experiments showed that the amounts of non-metallic inclusions in the melt can be reduced to values below 100 g / h, when the mixing energy is greater than 1000 W / ma, the magnesium vapors are formed at a depth of at least 200 mm below the surface of the melt and the atmosphere above the melt is supersaturated with magnesium vapor.

Detta beskrives i det följande med ett exempel: Exempel: Av en järnsmålta med legeringssammansättningen 506 027 4 C = 3,72 % Si = 2,3 % Mu = 0,27 % S - 0,08 % P = 0,05 % uttogs efter en behandling med renmagnesium i ett slutet behandlingskärl med en öppning av 30 cmz, där fyra reaktions- öppningar, vilka förenar reaktionsrummet med smältan, uppvisar en total tvärsnittsyta av 1.250 mmz, efter en reaktionstid av 60 sekunder. Analysen visade 3 ppm syre och 50 ppm svavel. Man räknade en mängd av 20 g/t av icke-metalliska inneslutningar.This is described in the following with an example: Example: Of an iron painted with the alloy composition 506 027 4 C = 3.72% Si = 2.3% Mu = 0.27% S - 0.08% P = 0.05% was taken after a treatment with pure magnesium in a closed treatment vessel with an opening of 30 cm 2, where four reaction openings, which connect the reaction space with the melt, have a total cross-sectional area of 1,250 mm 2, after a reaction time of 60 seconds. The analysis showed 3 ppm oxygen and 50 ppm sulfur. An amount of 20 g / h of non-metallic inclusions was calculated.

Den kvantitativa metallografiska analysen visade en mängd av icke-metalliska inneslutningar av 23 g/t.The quantitative metallographic analysis showed an amount of non-metallic inclusions of 23 g / h.

Claims

506 G27 5. PATENT REQUIREMENTS

Magnesium treatment process for the production of a treated melt with less than 100 g / t non-metallic inclusions, characterized in that the treatment reaction is controlled in such a way with the magnesium at a depth of at least 200 mm below the surface of the melt, that the amount of the vaporized magnesium produces a mixing energy of at least 1000 W / m 3, maintaining a non-oxidizing atmosphere over the surface of the melt in the treatment vessel.

2. A method according to claim 1, characterized in that piece-shaped pure magnesium is used as treatment agent. '

3. ~ 3. Process according to Claim 1, characterized in that magnesium granules are used as treatment agents.

4. A method according to claim 1, characterized in that a mixture of pure magnesium granules with a reaction-neutral material, for example iron shavings, etc. with at least 40% by weight of magnesium, is used as treatment agent.

5. A method according to any one of claims 1 to 4, characterized in that the magnesium utilization is not higher than at 75%.

Process according to one of Claims 1 to 5, characterized in that the starting melt has a sulfur content of between 0.001 and 0.30% by weight.

Process according to one of Claims 1 to 6, characterized in that the treatment temperature is set between 1,400 and 1,530 l.

A method according to any one of claims 1 to 7, 506 027, characterized in that the basicity of the treatment slag is higher than 1.

Apparatus for carrying out the process according to any one of claims 1 to 8, characterized in that it comprises a reaction vessel having a reaction space divided by the melt, which is provided with at least two openings, with which the connection between the reaction space and the melt can achieved.

Device according to claim 9, characterized in that the openings have a total cross section of at least 500 mm 2.

11. ll. Device according to claim 9, characterized in that the uppermost opening is arranged at least 200 mm below the surface of the melt.

12. Device according to claim 9, characterized in that the reaction vessel is provided at its upper part with an opening which provides a connection to the surrounding atmosphere and that an overpressure of magnesium vapor of at least 0 is ensured over the surface of the melt. 01 bar.