CA1282220C

CA1282220C - Procedure and apparatus for continuously casting a metal strip

Info

Publication number: CA1282220C
Application number: CA000518615A
Authority: CA
Inventors: Wolfgang A. Schneider; Kurt Kramer
Original assignee: Vereinigte Aluminium Werke AG
Current assignee: Maerz Gautschi Industrieofenanlagen GmbH Germany
Priority date: 1985-09-20
Filing date: 1986-09-19
Publication date: 1991-04-02
Anticipated expiration: 2008-04-02
Also published as: DE3666549D1; AU6294686A; JPH06104267B2; EP0218855B1; NO863097D0; NO863097L; ATE47544T1; NO167443C; EP0218855A1; JPS6268657A; NO167443B; DE3533517A1; AU588369B2

Abstract

ABSTRACT OF THE DISCLOSURE

The invention relates to a process and device to produce billets with a smooth and clean surface by continuous casting. A chill equipped with a super-structure is employed. Air, nitrogen, or inert gas introduced at the junction of the chill and the superstructure. Separating and/or lubricating agents have been added to the gas prior to its introduction.
The running surface of the chill is kept absolutely smooth, and the incoming metal prevented from contact with the chill wall, by creating in a gap between the chill and the starter block, A vacuum which is due to the suction effected by the coolant streaming out at the exit of the chill.

Description

1~82220 METHOD AND A~PARATUS FOR ~ONTINUOUS CASTING

F~ld of the In~ren~lon 1 Ihe pre~ent lnvention relate6 tO contlnuou- assting.
More pArtlcularly, the lnventio~ relate~ to contlnuou~
ca~tlng with 4 ch~ll.
Background of th- lnven~ on In contlnou~ CB~tlng proces~e~, molten met~l is poured at a 8teady rate lnto a cooled mold. Typlcally, a shel~ forms by solidlficatlon of the metal on the mcld wall. The ca~tlng 1~ withdrswn from the bottom of the mold. The molten metal 1~ contalned ln~lde the solldifled shell. The cast~ng emer-~lng from ~he bottom of the mold i8 sprayed to cool and 601i-dlfy the metal further.
A chlll CAn be u~ed to lncrea~e the rate of cool~ng of the ca~ting. A chlll ls typlcally a metal or graphlte ln~ert, placed in A mold to rapldly cool and solldlfy the casting, thu~ produclng a ~ard ~urface, One type of contlnuou~ castlng mold wlth ~ chlll has an upper ~uperstructure po~lt~oned abo~e the chlll. The lnn-r wall ~faclng the molten metal) of the super~tructu~e project~ closer to the molten metal thAn the lnner wall of the chill to form an overhang over the chlll where the chlll meet~ the super~tr~cture. In u~e, the lnner wall of the chill i6 cool-d and lubrlcatod, and a ga~ under pre~sure ~- lntrodu~-d ln th- mold ¢avity at the point whcro the uper~tructur- m--ta the chlll.
~he method and apparatu- ae wrlbed above 1~ dls-clo~-d ln DE-OS 27 34 388, to Showa. The method descrlbed ln the 8howa reference load~ to falrly smooth blllet ur-f~oe~ only und-r avorabl- conditlon-. When ~tarting to oa~t, for xumplo, monltorlng and regulating th- pressure of the ga~ and lubrlcatlng oll flow iB neco~ary. In ~ddltlon, contlnuous temporature mea~urement~ mu~t be m~de to ~d~u~ the ca~tlnq parameter-. In CA~t hou~e practlce, th- n-ed ~or contin~s monltorlng and adju~tment often le~da to dlffloulti-~ ln produclng ~atlsfactory oa~tlngs.

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, ~82220 These problems are compounded by fluctuations of the metal level and changes of the metallostatic pressure in the running casting process.
Further it has been found that with the method according to DE - OS 27 34 388 lead-containing alloys containing up to 2.5% lead cannot be cast satisfactorily. These alloys are of special importance in the manufacture of continuous casting products to be machined by chipping.
Experiments with gaseous lubricants like acetylene, butadiene, propane and trichloroethylene have shown that, under the conditions (pressure and temperature) pre~ailing in the chill, it is not possible to obtain a perfect lubrication making use of the decomposition of the gaseous lubricants. When conventional lubricants without gas are used by introduction parallel to the chill axis, lubricant combustion will occur in the starting phase and subsequent underdosing of lubricant will occur along the running surface of the chill. It is therefore, not possible to establish optimal lubrication by lubricant dosing only.
Ob~ects of the Invention It is an object of the present invention to avoid the disadvantages of the process described above, and to develop a method and an apparatus for continuous casting whereby smooth and neat billet surface can be obtained independently of the respective casting conditions. The high surface quality entails the prevention of sticking areas and reduction of surface .
~ '' ' ' ~z~o 2a 23828-48 liquation. A casting with a high surface quality is advantageous because further processing is possible without having to turn the ingot on a lathe.
According to one aspect of the present invention there is provided a process for continuous casting employing a chill equipped with a superstructure, the inner wall of which projects over the inner wall of the mold, wherein said inner wall is cooled and lubricated and compressed gas is introduced into the mold at the junction between the superstructure and the mold cavity, said process comprising mixing the separating and/or lubricating agent with the gas in a volumetric ratio of 1 to 4 : 1000 prior to the introduction into the mold cavity, wherein the mixture issues from the overhang of the superstructure and blows out in the direction of the draw-off parallel and over the running surface of the mold.
According to another aspect of the present invention there is provided a device to perform the above defined process comprising a superstructure placed on a chill wherein superstructure is provided with a channel-like aperture extending in parallel and alongside a meniscus cavity in the direction of billet draw-off.
Summarv of the Invention In the method according to the present invention, it has been unexpectedly discovered that it is important that the chill running surface (below the overhang) be absolutely smooth and free of holes, steps and grooves.

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1 The ~mooth surface i- nQaded to allow a lamlnar ~low to be est~bll~h~d ~nd ~lnt~ln~d ~t l~ partlcul~rly lmportant ~t the ~t~rt of cA~tlng, to mAlnta~n a l~mina~low p~rallel to th- chlll runnlng ur~o~ o th~t ~he lnflow~ng m t~l ~oes not make contact wlth tho c~lll w~ll Thl~ e~fect l~ lnten-slfled dur~ng the ~t~rtlng phase ln th~t a mlnlmu~ d~tance of 2 to 5 mm l~ provided betwe~n ~tartlng block and chlll runnlng ~urface, ~nd ln that an un~erpre~sure is generated ln thi~ lnter~pwe between the chlll And the cA~tlng, prefer-ably by the effeet of the coolan~ ~et blown out at the chill diwharge end (water ~et pumping effe~t) Brlef De~crlptlon of the Drawlng~
Other feature~ ~nd advantage~ of the present inventlon oan be moro fully under~tood from the followlng detalled descrlptlon wlth referenoe to the accomp~nylng drawlng~ ln whlch FIG 1 1B ~ longltudlnal ~ectlon vlew of a flr~t embodlment o~ thc present lnventlon;
ZO FIG. 2 1~ a longltudlnal ~ection vlew of a ~cond embodlment of the present lnventlon;
FIG 3 l~ a longltudinal ~ectlon vlew of a thlrd embodlmont of th- pre-ent lnventlon;
FIG. 4 ~8 a longltudlnal -ctlon vlew of a fourth embodlment of the pr-~ent lnventlon~ and FIG 5 l~ a longltudln-l ~ectlon vlew o~ a flfth embod~m nt of th pre-ent lnv-ntlon D-talled Do~orl~tlon of the Pre~errod Embodiments 3~ In ~ flr-t ~mbodlmont of the lnvent~on lllu~-tr~ted in FIG 1, refor-nce numeral 1 ropre~ents ~ cbill, t~k-n through ~ tr~nsver~o ~eotion Molt up-r-tructur- 2 1- po~ltloned above chlll 1 ~h~ ~up-r-tructure 2, l~clude6 ~ hot h-~d 2 ~nd ~ y~- conductlon blOCk 3 A g~- ohann-l 13 run- through gas conduotlon bloak 3 Hot head 2 ~nd gas conductlon block 3 ~r- -aled to each other by g~-k-t~
Chlll 1 oontain- ~ bor- 4 lor ~upplyinq ~eparatlng ~ent ~nd/or lubrlcant A ch~nnel 5 l~ provlded 1 .~B ~220 1 ln chlll 1 for the wator coollng sy~tem chlll 1 ~nd g conductlon bloak 3 ar- ~ecured to e~ah oth~r such that th- lnn-r ~C~9 of both chill 1 and g~ conductlon block 3 ar~ ~ub~tantl~lly p~rall~l Th- lnn-r face oS ohill 1 con~tltut-~ the runnlng ~ur~ace 7, Not hoAd 2 l~ ~haped oo that when mount~d to ga~ ~onduotlon block 3 the lnner wall ~faclng thc mole-n motal) of hot hoat pro~ect~ closer to the molten met~l of the ~tlng than the runnlng 8urface of th- chlll, to for~ an overhang a ov~r the chlll where the chlll meets ~up~r~tructure The outer ~AO~ of overhang 1B separated from the lnn~r surface af g~ aonductlon block 3 to form an annular g~p 6 8lnce the ~nner ~urf~ce o~ qa~ conductlon block 3 ls ~u~tAntl~lly par~llel to running surface ~ of chlll t, Annul~r g-p 6 lo ~ub~tAntlally parallel to runnlng surface 7 GA6 channel 1~ communlaates wlth the upp-r end of annular g~p 6 ~t the upper ond of tho outor ur~ace of ov~rhang 8 Boro 4 lnt-ro~ct- ~nnul~r gap 6 at an acute angle at the lower end o~ th~ out-r ~ur~ace of overhang ~ Bore 4 lnter-~eot~ gAp 6 at an acute ~ngle allow the separating agent ~nd/or lubrlcant to roadily mlx wlth the gas ~lowlng through g~p 6 It l~ l~port~nt that runnlng surf~c- 7 and the urfaa- of the chlll ln th- vlalnlty of the outlet of ~nnulAr gap 6 b- fr~- fro~ off-et~, bor-- or groove- A smooth ourfsce ~- 'mportant to p-rmlt an approxlmAtely lamlnar ~low of tho mlxtur- of ~q~ratlng agont ~nd~or lubrlcant and gao Durln~ th- o~-tlng proao-~, molt~n motal 18 lntroduc-d to tho contlnuou- ca~tlng mold ~rom abov- The molton ~-t~l for~ A m nl-au- whor~ the low r outor edg~ of ov-rh-ng 8 moot~ ohlll 1 at A rlght ~ngl-. ~hls l- the ~Ame polnt wh-r- ~nnul~r gap 6 m -t- runnlng ~urfac- 7 In op-r-tlon, ~a- l~ ln~-ot-d through the ~nnul~r oh~nn-l 6 to the ~ nl-ou~ c~v~ty 9 Th- typo~ of g~ whlch oan bo u--a ar- dl~au--od ~olow. Tho forae of tho ga- trav~llng through ~p 6 cau~e~ th- part- o~ tho llqul~ opAra~lng a~nt or lubrlcant, e.g oll, to ntr~ln Wlth ~ho gA~. An ~oro~ol or omul~lon o~ gas and lubrlcany ~ - s 1 ~pa~tlng ~gon~ form~ ~nd trav~ n lamln~r flow below the o~erhang 8 ln tho dr~-o~f dlrection ~the dlrectlon of the flowlng ca~t motAl) an~ parallel to the chlll rur.nlng ~usSace 7.
A~ tho c~t ~et~l flow~ downwardly, the molton metAl ~t~rt~ to ~olldl~y. Along th- edge of the chlll 1, the cast ~otal 1- at lea~t pArtially solldlfled. ~t tho ~eginnln~ of a ca~tlng run the solld metal f ir3~ pre-~ents~ along the chlll 1~ c~lled the s~rter block. The ga~/lubrlc~nt em~l~lon travels ~long the gap pre3ent botwe~n the starter block an~ runnlng ~urface 7. Channel 5 located at a lowor edge of chlll 1 1~ dlreoted to~ards the ~tarter block and a wat~r ~et 18 forced thro~gh channel 5 towards the block. The ~lrectlon of flow of the water ~et c~u~-~ the form~tlon of a vacuum, drawing the gas/lubrlcant e~ul~lon downwardly along runnlng surf~Ge 7 and the edge of the ~tarter block. Iho v4cu~m cau~es the formatlon o~ an annula~ g~/oll vell, whlch completely shleld~ the chlll wall 7 from the ll~uld metal pre~ent above the ~tarter block.
~he provi~lon of an ~nnular gap in the dlrec-tlon of the runnlng ~urface of the chlll and the premlxlng of ~eparatlng ~nd/or lubrlcatlng agents wlth the g~ m~ke~
lt unnecessary to read~u-t the ca~t1ng parAmeter~ after they have b~en lnltlally ~et for the run. In partlcular, the volume of ga~ and lubrlcant do not havé to be read~ust-ed once ~et lnltlally, even at fluctuatlng metal level.
The m~thod sccordlng to the lnventlon ie ~pplled preforably to alloy group~ ~usceptlble to cracking, although other alloy~ and met~l~ can be successully used wlth the pre~ent lnventlon. Alu~lnum alloys are well ~u~ted to contlnuou~ ca~tl~g wlth the apparatus and method of the pre~-nt lnventlon.

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- 6 ~ 8Z~ZO

X~LE 1 1 In the ~ollowlng, an example l~ given for contlnuou~
ca~ting~ hav~ng a d~oto~ of 10 lnch~, where the ratlo O~ ~epAra~ing ~gent ~o ga- w~ 3 s 1000:
AlMg5 Ca~tlng r~t- ?O ~m/mln AlCuMgZ Ca~ting rate 65 mm/mln Al~nMgCul.S Cast~ng rAte 65 mm~mln AlCuM~P~ Ca~tl~g rate 6S ~m/mln.
It was po~iblc to keep tha~e c~eting rate~
constant ~mmed~ately after ~tartup, ~o other ca3tlng 0 parameter~ had to be read~u~ted. ~he billet ~urfaces obtalned ~howed a hlgh ~urface qu~llty.
FIG. 2 to 5 ~how addltlon~l embodiment~
oS the present Lnventlon. ~efer~lng to F~G. 2, there i6 shown a ~upor~truc~ure 22 mads ln one part, r~ter than 1S ln the two part~ ~hown in the super~tructure of FIG, 1.
Tho bore for the ga9 channel 14 run~ through ~uper~tructure 22 and dl~chargo~ lnto A wlde antechamber 15 betw~en o~er-hang 8 and runnlng ~urface 7. Oll l~ ed toward~ antechamber 15 through bore 4 ln chlll 1. A~ antechamber 1S the mlxture of the ~epara~lng agent and/or lubricant with ga~ takes place.
For coollng the blllet 10, water 11 is e~ected from re~ervoir thro~gh channel 5.
Anothcr embodlment of the apparatu~ according to the lnvention l~ ~hown ln FIG. 3. ~ere the ~uperstructure l~ divided horlzontally lnto two ~egments 22a and 22b. Ga~
llne 16 extend~ l draw-off dlrectlon ~rom upper part 22a snd 1- Lnterruptod only by a chamber 22c for ga~ dlstrlbu-tion. Chlll 1 na~ a upportlng wall 12 or sscure posltlon-1ng of th- ~uperstruoture 22a ~nd 22b ~galnst the chlll. ~he other component~ of the oontlnuous ca~t~ng mold, such a~
lubr~oant bore 4 an~ anteohambe~ ~S, aor~-~pond to the deslgn sh~wn in FIG, 2.
In FIG. 4, a differ~ntly shaped ga~ conduotlon block in the form of an ln~-rt 11 ls pro~lded b-t~een the ohlll 1 and the hot head 2. In ~ddltlon, gas llne 1~ l~ bored , . ........ ,.. ,,, , ,.. .. _. _._ ___ . _ . _ ._ , .. , _ . _ . _ __ ._. , _ . . . _ .... ,_, . __, . _ .. _ . .. .

_ 7 _ 1~82220 t ~t~aight ~hrough hot h-ad 2 lnto the g~ trlb~tlon ch~ber of ln~ert 17 In FIG 5, ~n ln-ort 18 ~ ~ ~rranged b-tween the chill 1 and the hot he~d 2 In oontra~t ~0 FIC. 4, S ln FIG S ~a~ l~ne 19 extena- ~orL~on~ally through chlll 1 and the ineert part 18 lnto ~n ~ntechumber 20, ~rom wh~ch t~e ga~ flow~ lnto annular g~p 6 The mlx~ng of the ga-wlth the lub~lcant and/or ~-p~ratlng agent, ~hlch ~
~upplled vls bore 4, occure varlably ~etwe-n 2 and 10 ~m before the outlet openlng of the annular gap orlflce All other features corr~pond to the part~ de~crlbed ln connec-tlon with the precodlng ~lguree In numerou~ te~ts u~lng the app~ratu~ and ~ethod of the pre~cnt lnv-ntlon, lt hss been found that the g~/oll ~lxture need not bc regul~ted by varlatlon of pump pre~eure or volume, even lf the metal level wlthln the mold fluctu~tee Evldently, the comblned actlon of the ~as/o~l vell ~nd euctlon e~f-ct along ~he r~nnlng surface le eo strong that e~en upon ~ari~tlon of the metallost~tlc pre--~ure , a buffor a¢tlon por~l~te betw-en the met~l and the runnlng ~urfao-. ~
~ . .. .__ .. ..

Claims

1. A process for continuous casting employing a chill equipped with a superstructure, the inner wall of which projects over the inner wall of the mold, wherein said inner wall is cooled and lubricated and compressed gas is introduced into the mold at the junction between the superstructure and the mold cavity, said process comprising mixing the separating and/or lubricating agent with the gas in a volumetric ratio of 1 to 4 : 1000 prior to the introduction into the mold cavity, wherein the mixture issues from the overhang of the superstructure and blows out in the direction of the draw-off parallel and over the running surface of the mold.

2. A process according to claim 1, further comprising creating a vacuum in the gap between a starter block and the mold running surface.

3. A process according to claim 1 or 2 further comprising maintaining a constant amount of the separating and/or lubricating agent and of the gas during the start and operation of the continuous casting.

4. A process according to claim 1 or 2 wherein the compressed gas is air or nitrogen.

5. A device to perform a process of continuous casting according to claim 1 comprising a superstructure placed on a chill wherein superstructure is provided with a channel-like aperture extending in parallel and alongside a meniscus cavity in the direction of billet draw-off.

6. A device according to claim 5 wherein an annular gap is provided in the overhang of the superstructure, the walls of which at least in the area of the outlet are essentially parallel to the draw-off direction and aligned to the mold running surface.

7. A device according to claim 6 comprising means to combine the separating and/or lubricating agent and the gas in the area 2 to 10 mm in front of the outlet of the annular gap opening.

8. A device according to claim 6 or 7 wherein the opening of the annular gap runs parallel to the mold axis for 10 to 30 mm to the outlet.

9. A device according to claim 6 or 7 wherein the running surface of the mold behind the overhang is smooth and totally enclosed.

10. A device according to claim 6 or 7 further comprising a gap of 2 to 5 mm between the running surface of the mold and a starting block, the starting block having the upper edge thereof an elevated lining extending over its entire perimeter.