US3850225A

US3850225A - Start-up method and apparatus for continuous casting

Info

Publication number: US3850225A
Application number: US00401436A
Authority: US
Inventors: R Mcnitt; E Fox
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1973-09-27
Filing date: 1973-09-27
Publication date: 1974-11-26
Anticipated expiration: 1991-11-26
Also published as: FR2246334A1; FR2246334B1; DE2442469B2; CA1011081A; DE2442469A1; JPS5060430A; DE2442469C3; AU7267174A; GB1449424A; JPS5223861B2

Abstract

Start-up apparatus and method for continuous casting apparatus including a relatively large holding or casting vessel having a relatively small casting outlet or channel at the base thereof to which is attached an open ended mold. The mold construction and a starter bar is arranged so that slag which prevents efficient start-up is kept out of the mold. When molten metal is poured into the casting vessel a fusable plug associated with the starter bar holds the molten metal within the vessel until a substantial non-turbulent head of molten metal has formed in the vessel to cause the slag to rise away from the channel leading to the mold. The mold structure includes a restrictive nozzle and a skim chamber ahead of the nozzle which are operative to trap residual slag in the molten metal. A starter bar sleeve feature insures effective sealing to prevent molten metal breakouts during start-up.

Description

[ 1 Nov. 26, 1974 ABSTRACT START-UP METHOD AND APPARATUS FOR CONTINUOUS CASTING [75] Inventors: Ralph R. McNitt, Okemos; Edward J. Fox Grand Ledge both of Mich Start-up apparatus and method for continuous casting apparatus including a relatively large holding or cast- Assignee: General Motors Corporation,

ing vessel having a relatively small casting outlet or Dem)", Mlchchannel at the base thereof to which is attached an open ended mold. The mold construction and a starter 22 Filed: Sept. 27, 1973 21 App]. No.: 401,436

bar is arranged so that s'lag which prevents efficient start-up is kept out of the mold. When molten metal is poured into the casting vessel a fusable plug associated. with the starter bar holds the molten metal within the vessel until a substantial non-turbulent head of molten metal has formed in the vessel to cause the 482 mm HUN 6 m 2 "4 H6 mmh 6 .r ""3 e "."S I M C d std U.mF. 111 2 2 00 555 [rl.|.

slag to rise away from the channel leading to the mold. [561 References Cited The mold structure includes a restrictive nozzle and a UNITED STATES PATENTS skim chamber ahead of the nozzle which are operative to trap residual slag in the molten metal. A starter bar sleeve feature insures effective sealing to prevent molten metal breakouts during start-up.

2,707,813 5/1955 164/85 X 3,286,309 11/1966 Brondyke.......,. 164/281 X FOREIGN PATENTS OR APPLICATIONS 1,235,374 6/1971 Great Britain...................... 164/281 6 Claims, 5 Drawing Figures Primary ExaminerAndrew R. Juhasz Assistant Examiner-John S. Brown Attorney, Agent, or FirmPeter P. Kozak Pmtmmnv'zslsn SHEET 2 OF 2 START-UP METHOD AND APPARATUS FOR CONTINUOUS CASTING BACKGROUND OF THE INVENTION This invention relates to the continuous casting of metals and more particularly to start-up apparatus and procedures therefor.

The US. Pat. Nos. 3,731,728; 3,730,251 and 3,726,333, assigned to the assignee of this invention, describe the continuous casting process and apparatus to which the present invention particularly pertains which includes a relatively large stationary casting vessel having an outlet opening at the base thereof and an open ended mold connected to the outlet opening. Molten metal is periodically poured into the vessel and the molten metal is at least partially solidified into a self-sustaining bar within the mold as the metal passes therethrough.

The mold includes a restricted nozzle portion adjacent the vessel outlet opening which leads to a primary solidification portion of substantially greater internal dimension which in turn leads to a further solidification portion of similar dimensions. In the operation of the process, the molten metal flows by gravity from the vessel through the vessel outlet opening and through the nozzle into the opened mold. The metal temperature in the vessel and nozzle is maintained sufficiently high to avoid any metal solidification therein. As the metal flows into the primary solidification portion, metal solidification begins at the junction of the nozzle and the primary solidification portion and proceeds as a thin skin layer downstream. At fixed regular time intervals a predetermined length or segment of the skin layer is pulled forward into the downstream portions of the mold. During the intermediate or dwell period the new skin layer segment which has solidified in the primary solidification portion during the pull period or extraction stroke welds on to the preceding segment.

At the start of the pull or extraction stroke the solidifying skin separates from the nozzle to which it is nonadherent at the junction of the nozzle and the primary solidification portion. Liquid steel then flows in behind the skin as it travels down the mold and new skin forms against the nozzle at the said junction, the metal primary solidification zone, and end of the preceding skin segment.

The new skin lying against the nozzle is stationary and that new skin solidifying from the end of the withdrawing skin is not. At the end of the extraction stroke a dwell of :12 to 0.20 seconds and a slight push back of the advanced skin is provided for the purpose of providing time and interface contact between these new skins. During this interval a weld of the skins and additional solidification on the inner surface occurs. At the beginning of the next extraction stroke the solidified and welded skin again separates from the nozzle and the cycle repeats. This solidification mechanism continues and further solidification results in a selfsustaining continuous bar.

Successful operation of the method requires that the integrity of the initial skin layer formed in the primary solidification zone be maintained. Small slag or refractory particles from the vessel linings may cause the skin layer to rupture and hence the molten metal to break through the skin layer and to run out of the mold. Since considerable slag is associated with metal initially poured into the vessel, the start-up of the casting method involves considerable problems.

SUMMARY OF THE INVENTION This invention provides apparatus means associated with a starter bar, the mold and the casting vessel to substantially eliminate the presence of slag in the mold during start-up and thereafter during casting and to prevent molten metal leakage about the starter bar whereby an efficient start-up is effected. More specifically, the starter bar is provided with a fusable plug means adapted for snug insertion in the vessel outlet opening to prevent the entry of molten metal into the mold for a predetermined time sufficient to permit the casting vessel to be filled with the molten metal to a sufficient height to enable the slag poured into the vessel to rise to the top of the molten metal charge away from the channel leading to the mold. Another feature of the invention is the provision of slag trap or skimmer ahead of the mold to prevent residual slag from entering the mold after the fusable plug has been melted to permit entry of the molten metal to the mold. The starter bar also includes a sleeve means for preventing molten metal run-out or leakage during start-up.

Other features and advantages of the invention will be apparent from the following description with reference to the accompanying drawings wherein:

FIG, 1 is a fragmentary cross-sectional view of a continuous casting vessel and associated mold containing a starter bar in operative position shown in elevation;

FIG. 2 is a fragmentary enlargement of FIG. 1 with the starter bar shown in cross-section illustrating the method and apparatus of the invention about 4 seconds after the beginning of start-up;

FIG. 3 is similar to FIG. 2 illustrating the method and apparatus about 12 seconds after start-up begins;

FIG. 4 is similar to FIG. 2 illustrating the method and apparatus of the invention about 16 seconds after startup begins; and

FIG. 5 is similar to FIG. 2 illustrating the method and apparatus of the invention after three extraction strokes.

As previously indicated, the continuous casting method and apparatus involved in this invention is disclosed in the aforementioned patents.

Referring to FIGS. 1 and 2, the method and apparatus includes a relatively large refractory vessel 10 having a downwardly extending channel 12 leading to a horizontally disposed channel portion 13 and the molten metal outlet 14 located in a recess 16 of the vessel. The outlet 14 is surrounded by a-frusto-conical refractory channel block 18 cemented in the recess 16 which provides the outlet with a smooth radial face 20. The

channels

12 and 13 are preferably of the same general cross-sectional configuration as outlet opening 14 but of substantially larger dimension.

The apparatus further includes a detachable open ended mold assembly 22 having a substantially symmetrical cross-sectional configuration along the longitudinal axis thereof, comprising sequentially a refractory spacer ring 24, a restricted internal dimension nozzle 26, a primary metal solidification portion 28 and a subsequent metal solidification portion 30. The drawings show apparatus for casting cylindrical bars so that the block 18, the spacer ring 24, the nozzle 26, and the

solidification portions

28 and 30 are shown to have cylindrical internal dimensions. These dimensions may have rectangular, triangular, oval or any other similar dimension to cast desired bars. The

metal solidification portions

28 and 30 are surrounded by a cooling water jacket 32 including the water inlet conduit 34 and the water outlet conduit 36. Cool water enters through the conduit 34, passes through the openings 35 into the inner annular chamber 33, around the end 37 of the baffle 39 into the outer annular chamber 41 to the outlet 36. The channel block 18 and spacer ring 24 are preferably formed of a refractory material such as zirconia which is resistant to erosion by the metal to be cast such as steel. The nozzle 26 is preferably formed of a material such as boron nitride which is inert to and nonwettable by molten steel. The nozzle 26 as well as the refractory channel block 18 and the spacer ring 24 are formed of materials having a relatively low coefficient of heat conductivity to insure that the molten metal does not solidify on the axial surfaces of these portions of the casting apparatus. The primary solidification portion 28 is formed of a high heat conductivity material such as a copper alloy and the subsequent solidification portion 30 is preferably formed of a suitable metal lined with graphite. The mold assembly 22 is sealingly attached to casting vessel by means of the annular cement layer 19 interposed between the radial face 20 of the block 18 and the spacer ring 24 and the bolts 21..

As described in the aforementioned patents, metal casting normally proceeds in the following manner. Molten metal is transferred to the vessel 10 by a suitable transfer ladle and it flows by gravity downwardly through the channel 12 through the outlet 14 of the channel block 18 and thence through the nozzle 26 to the mold. Molten metal solidification begins at the junction 25 of the nozzle 26 and the primary solidification portion 28. More specifically, solidification begins against the radial face of the nozzle at the junction 25. Initially a thin skin of metal is formed in the primary solidification portion and in accordance with the metod a method of the skin layer is pulled downstream a predetermined amount and permitted to remain stationary during a relatively short dwell period. During this pull period fresh molten metal flows through the nozzle 26 into the primary solidification zone 28 covering the area vacated by the advanced solidified skin segment and welds to the rear end thereof during the reverse and dwell period. The intermittent pull and dwell cycle is repeated continuously and eventually the metal solidifies sufficiently to form a self-sustaining rod as it is pulled from the subsequent solidification portion 30 by suitable roller means (not shown). The primary solidification portion 28 and the subsequent solidification portion 30 are preferably formed to have a progressively decreasing internal diameter to compensate for the shrinkage of the bar as it passes therethrough so that cast metal to mold contact is maintained substantially throughout the sojourn of the casting bar within the mold to maintain efficient heat transfer.

The casting process is commenced with the use of a starter bar assembly 38 comprising a hollow shank portion 40 of somewhat smaller diameter than the internal diameter of the mold which is capped by the insert 42 press welded thereto. The starter bar includes a chill ring 44 which is supported on the starter bolt 46 which is threaded into the insert 42 of the shank 40. An aluminum kill wire 48 is wrapped about the bolt 46 to deoxidize the initial steel poured which is usually high in oxygen content. The assembly includes a starter sleeve 50 having graphite seal rings 52 in the form of a tape wrapped around the sleeve which is separately inserted into the primary solidification portion 28 and is adapted to fit tightly and sealingly therein due to the graphite seals 52. The outer diameter of the sleeve 50 is approximately 0.140 inch smaller than the inner diameter of the primary solidification portion 28in the cold state to enable it to pass through the reduced diameter of the secondary mold portion 30. The starter bar assembly furtherincludes a fusable plug 54 supported by the rod 56 screwed into the bolt 46. When the starter bar assembly is in the assembled or operative condition the chill ring 44 is slidably received in the reduced diameter portion 51 of the sleeve 50.

As previously stated, the primary solidification portion 28 and the subsequent solidification portion 30 are preferably formed to have a progressively decreasing internal diameter. Since the starter sleeve taped diameter 52 is typically of a larger diameter than the exit end of the mold assembly, it is inserted separately within the primary solidification portion from the inlet side thereof during assembly of the mold.'The primary and

subsequent solidification portions

28 and 30 respectively of the mold are typically in the form of a unit. After the starter sleeve has been inserted within the primary solidification zone the nozzle 26 is next preferably press fitted therein. Thereafter the spacer ring 24 is assembled adjacent the nozzle 26 which is then clamped to the mold housing by means of the ring 58 bolted to mold housing by bolts (not shown). The mold is then bolted to the vessel with a ring of sealing compound 19 being interposed between the channel block 18 and the refractory spacer 24.

Before the molten steel can be cast the vessel 10 and mold assembly are preheated to thoroughly dehydrate their internal surfaces. Hot gases and flames from a gas fired torch is applied to vessel internal surfaces sufficiently to raise them to a temperatureabout 2,200 F. Part of the heating gases exhaust through the open end of the mold. Water is caused to flow through the water jacket 32 so as to maintain the water temperature leaving the water jacket at about 170 F. Under these conditions mold internal surfaces are above the boiling point. This results in complete dehydration which is highly desirable since any water remaining in the mold cavity will flash into steam on coming into contact with the molten steel, and cause excessive porosity which may disrupt initial solidification to such an extent that the start-up is unsuccessful.

The starter bar is then inserted into the mold assembly through the downstream end. When the starter bar is fully inserted the fusable plug 54 closes the opening 14 in the channel block 18 with the frusto-conical portions thereof extending into the channel and the frustoconical flange 53 of the chill ring 44 engages the starter sleeve 50 to support it in place centrally of the mold and positioned longitudinally so that the extreme end 60 of the starter sleeve 50 is in engagement with the nozzle 26. The plug 54 has the frusto-conical end which facilitates its entry into the opening 14. A slope of about 15 to the longitudinal axis is satisfactory for the frusto-conical portion.

The spacer ring 24 has substantially greater internal diameter or dimension than the channel block 18 or the nozzle 26 to provide an annular slag trap or skimmer 66 therebetween. The nozzle 26 must, of course, have an internal diameter large enough to permit the passage of the fusable plug 54 therethrough. In consequence of the preheating step described above, the plug heats up to about l,500 F just before the molten steel is poured into the vessel 10.

FIG. 1 shows the fusable plug 54 and the starter sleeve 50 within the mold in a proper position at startup. Molten steel heated to a superheated temperature of about 3,000 F is initially poured into the vessel 10. FIG. 2 illustrates the apparatus about 4 seconds after the pour has begun. The molten steel 62 with a slag overlay 64 flows into the channel 12 and extends into partial contact with the fusable plug 54. At this time the temperature of the moltensteel is about 2,800 F and the temperature of the fusable plug is about 2,700 F. The heat content of the fluid slag and the relatively low temperature of the steel initially poured into this vessel is insufficient to melt the plug.

FIG. 3 illustrates the system about 12 seconds after the beginning of the pour. The molten steel now covers the fusable plug completely and particles of slag 65 float upward away from the channel outlet opening 14. The downward slope of the channel 12 and its smooth contour facilitates the upward drift of the slag particles from the horizontal channel portion 13 as shown in FIG. 3. The turbulence and convectional currents within the flowing steel will continue to bring heat into the area of the fusable plug 54. Fusion of the plug typically occurs after about 12 seconds or more depending on the temperature of the steel, temperature of the preheated refractory of the vessel, the refractory contour, the rate of pour and the amount of slag present. Since the lower portions of the fusable plug are heated first the lower portions are melted away initially as shown in FIG. 3 permitting molten metal-to begin flowing into the channel block opening 14. The remainder of the plug fuses shortly thereafter. Meanwhile, particles 65 are caused to rise rather than flow into the channel block opening.

FIG. 4 illusrates the system about 16 seconds after the start-up has begun. The fusable plug has now melted completely away and residual slag 68 has been trapped in the skimmer or slag trap 66. As the molten metal enters the primary solidification portion 28, it is retained initially within the sleeve 50. The graphite ring seal 52 prevents the molten metal from leaking past the starter sleeve and the slidable connection between the chill ring 54 and the starter sleeve 50 is sufficiently tight to prevent the flow of the molten metal therethrough. Further, the chilling effect of the chill 44 causes solidification of any molten metal flowing through this slide connection. At this point, metal is solidifying on the inner surface of the starter sleeve 50, end of the chill ring 54, onto the head of the starter bolt 46, and the heat of the metal has caused the thin lip 60 of the starter sleeve 50 to approach or exceed the melting point. Nearly all of the fusable plug assembly has melted, and the aluminum kill wire 48 is reacting with oxygen present to prevent formation of carbon monoxide, which would interfere with initial solidification. This heat causes increases in temperature at the thermocouple 27, which through suitable electronic control initiates the first pull or extraction stroke; or, at the operators option, he may manually initiate that stroke. As the starter sleeve withdraws metal flows in behind and solidifies against the inner surface of the primary module 28 and against the radial face of the nozzle 26. The graphite tape 52 prevents overlapping of the molten steel between the outer diameter of the starter sleeve 50 and the inner diameter of the primary module 28, as is required to prevent scoring of these components during start-up. After the above-mentioned initial stroke, pull and dwell continues in a prescribed sequence and progressively increasing rate until full extraction conditions are achieved. Through the first several strokes, the temperature indicated by the thermo couple progressively increases to, and maintains at the steady state temperature of normal extraction. Sensitivity of this thermocouple is such that. it will indicate a slight temperature variation between the pull and dwell.

FIG. 5 illustrates the apparatus after three extraction strokes and dwell periods. The steel has previously solidified about the chill ring 44 and the bolt 46 and also against the internal surfaces of the sleeve 50. The molten metal has also solidified as a skin layer consisting of the three

segments

72, 73 and 74 respectively which were initiated at the junction 25 at the

ridges

75, 76 and 77 respectively and welded to one another at these ridges during the dwell periods.

In accordance with the casting method the intermittent extraction and dwell cycle is continued indefinitely with the casting vessel 10 being replenished periodically with sufficient frequency to maintain a substantial head of molten steel in the vessel 10 and hence to avoid the flow of slag into the channel area during normal casting.

Although the apparatus of this invention has been described in terms of a cylindrical bar it should be understood that the invention is applicable to molds of various shapes and sizes including rectangles, ovals, triangles and other polygonal shapes. Also, while the invention has been described in terms of certain specific embodiments, other forms may be adopted within the scope of this invention.

What is claimed is:

1. Continuous casting apparatus and a starting bar therefor comprising:

a holding vessel having an opening at the base thereof,

a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said opening; (c) a primary solidification chill mold positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; (d) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, and

a starter bar means including (a) a sleeve portion adapted for separate insertion into said primary mold portion having one larger dimensioned end thereof adapted in its operative position for engagement with said nozzle shoulder and for sealing engagement with said primary mold portion; (b) an elongated bar portion adapted for insertion into the said mold through the outlet end thereof to a fully inserted position including a fusable plug end portion adapted for snug insertion into said vessel opening in said fully inserted position; a chill portion receivable within at least a portion of said sleeve operative to locate and support said sleeve in its operative position and (d) an enlarged portion located within said sleeve in the said fully inserted position, said enlarged portion, said chill portion and said sleeve cooperatively forming a cavity for receiving molten metal and a mechanical grip for holding solidified metal.

2. Continuous casting apparatus and a starting bar therefor comprising:

a holding vessel having a horizontally disposed channel at the base thereof terminating in an outlet opening and a refractory block at said opening having an internal passage therethrough having a dimension substantially less than the dimension of said channel,

a detachable open ended mold assembly attached to said vessel about said block in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said block in sealing relation thereto and having a substantially greater internal dimension than said block; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said block; (c) a primary solidification chill mold positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; ((1) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, and starter bar means including (a) a sleeve portion adapted for separate insertion into said primary mold portion having one larger dimensioned end thereof adapted in its operative position for engagement with said nozzle shoulder and for sealing engagement with said primary mold portion; (b) an elongated bar portion adapted for insertion into the said mold through the outlet end thereof to a fully inserted position including a hollow fusable plug end portion adapted for snug insertion into said block passage in said fully inserted position; (c) a chill portion receivable within at least a portion of said sleeve operative to locate and support said sleeve in its operative position and (d) an enlarged portion located within said sleeve in the said fully inserted position, said enlarged portion, said chill portion and said sleeve cooperatively forming a cavity for receiving molten metal and a mechanical grip for holding solidified metal.

3. Continuous casting apparatus and a starting bar therefor comprising:

a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said opening, said block, said spacer ring and said nozzle forming a chamber therebetween; (c) a primary solidification chill mold positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; ((1) a further solidification mold portion adjacent said primary mold portion,said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, and

starter bar means including (a) a sleeve portion adapted for separate insertion into said primary mold portion having one larger dimensioned end thereof adapted in its operative position for engagement with said nozzle shoulder and for sealing engagement with said primary mold portion; (b) an elongated bar portion adapted for insertion into the said mold through the outlet end thereof to a fully inserted position including a hollow fusable plug end portion adapted for snug insertion into said vessel opening in said fully inserted position; (c) a chill portion receivable within at least a portion of said sleeve operative to locate and support said sleeve in its operative position and (.d) an enlarged portion located within said sleeve in the said fully inserted position, said enlarged portion, said chill portion and said sleeve cooperatively. forming a cavity for receiving molten metal and a mechanical grip for holding solidified metal,

said fusable plug being of a thickness so as to resist fusion by molten metal poured into contact therewith for a relatively short predetermined time necessary for slag contained in the molten metal to rise above said block passage and then fuse to permit the molten metal to pass into said mold assembly, said sleeve one end being relatively thin and fusable in contact with said molten metal.

4. A method for starting a continuous casting process which involves apparatus comprising a holding vessel having an outlet opening at the base thereof, a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said opening whereby an annular chamber is formed between said vessel, said spacer ring and said nozzle; (0) a primary solidification chill mold portion positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; (d) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, comprising the steps of:

inserting a metal sleeve portion into said primary mold portion, said sleeve being adapted in its operative position for providing sealing engagement with said primary mold portion,

inserting an elongated bar portion into said mold through the outlet end thereof to a fully inserted position, said bar portion including a fixed hollow fusable plug inserted into said vessel opening, said bar portion further including a fixed chill portion engaging at least a portion of said sleeve in said fully inserted position, locating and supporting said sleeve in its said operative position, said bar portion also including an enlarged portion within said sleeve in said fully inserted position, said enlarged portion and said chill portion and said sleeve operatively forming a cavity for receiving molten metal and providing a mechanical grip for holding solidified metal, I

pouring molten metal into said vessel with said plug being operative to hold back the molten metal from entering the mold until the slag has substantially risen above said opening,

continuing pouring molten metal into said vessel with said plug being fused to permit the flow of molten metal through said nozzle into said sleeve within said primary mold, said molten metal contacting said sleeve, chill portion and said enlarged portion, said molten metal contacting said primary mold portion at the junction of said nozzle and said primary mold and progressively solidifying within said primary mold and said chill portion,

pulling said starter bar a predetermined length whereby a new skin layer of molten metalsolidifies on the exposed surfaces of the primary mold, permitting the starter bar to dwell a sufficient time to permit the new segment of metal to weld to the segment previously pulled forward and continuing an intermittent pull and dwell cycle.

5. A method for starting a continuous casting process which involves apparatus comprising a holding vessel having an outlet opening at the base thereof, a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said opening whereby an annular chamber is formed between said vessel, said spacer ring and said nozzle; a primary solidification chill mold portion positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; ((1) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, comprising the steps of:

separately inserting a metal sleeve portion into said primary mold portion of larger dimension than the other end and being relatively thin, said sleeve being adapted in its operative position for engagement with said nozzle shoulder and seal ring thereon for providing sealing engagement with said primary mold portion,

inserting an elongated bar portion into said mold through the outlet end thereof to a fully inserted position, said bar portion including a fixed hollow fusable plug inserted into said vessel opening, said bar portion further including a fixed chill portion engaging at least a portion of said sleeve in said fully inserted position, locating and supporting said sleeve in its said operative position, said bar portion also including an enlarged portion within said sleeve in said fully inserted position, said enlarged portion and said chill portion and said sleeve operatively forming a cavity for receiving molten metal and providing a mechanical grip for holding solidified metal,

continuing pouring molten metal into saidvessel with said plug being fused to permit the flow of molten metal through said nozzle into said sleeve within said primary mold, said molten metal contacting said sleeve, chill portion and said enlarged portion, 7

said molten metal contacting said primary mold portion at the junction of said nozzle and said primary mold and progressively solidifying within said primary mold and said chill portion,

pulling said starter bar a predetermined length whereby a new skin layer of molten metal solidifies on the exposed surfaces of the primary mold, permitting the starter bar to dwell a sufficient time to permit the new segment of metal to weld to the segment previously pulled forward and continuing an intermittent pull and dwell cycle.

'6. A method for starting a continuous casting process which involves apparatus comprising a holding vessel having an outlet opening at the base thereof, a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refractory nozzle having an internal dimension substantially less than said spacer ringand at least as large as said opening whereby an annular chamber is formed between said vessel, said spacer ring and said nozzle; (0) a primary solidification chill mold portion positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; (d) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, comprising the steps of:

separately inserting a metal sleeve portion into said primary mold portion, said sleeve portion having one end of larger dimension than the other end and being relatively thin, said sleeve being adapted in its operative position for engagement with said nozzle shoulder and seal ring thereon for providing sealing engagement with said primary mold portion,

continuing pouring molten metal into said vessel with and said primary mold and progressively solidifying within said primary mold and said chill portion, so

that a partially solidified bar is formed which is mechanically gripped between said sleeve and said enlarged portion, said sleeve being operative to retain said molten metal sufficiently to permit its withdrawal from said mold through the outlet end of said mold,

UNITED STATES PATENT AND TRADEMARK OFFICE QEBTIFICATE OF CORRECTION PATENT NO. I 3 850 225 DATED November 26, 1974 v 0 (5) Ralph R. McNitt, Edward J. Fox

It is certified that error appears in the above-identified patent and that said Letters Patent 9 are hereby corrected as shown below:

Column 3, line 40, "metod" should read method Column 3, line 41, "method" should read segment Signed and Scaled this eighteenth D8) 0f May 1976 [sent Arrest:

RUTH c. msohi -rs. MARSHALL DANN Arresting Officer (ummissium'r nj'larenrs and Trademarks I

Claims

1. Continuous casting apparatus and a starting bar therefor comprising: a holding vessel having an opening at the base thereof, a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said opening; (c) a primary solidification chill mold positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; (d) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, and a starter bar means including (a) a sleeve portion adapted for separate insertion into said primary mold portion having one larger dimensioned end thereof adapted in its operative position for engagement with said nozzle shoulder and for sealing engagement with said primary mold portion; (b) an elongated bar portion adapted for insertion into the said mold through the outlet end thereof to a fully inserted position including a fusable plug end portion adapted for snug insertion into said vessel opening in said fully inserted position; (c) a chill portion receivable within at least a portion of said sleeve operative to locate and support said sleeve in its operative position and (d) an enlarged portion located within said sleeve in the said fully inserted position, said enlarged portion, said chill portion and said sleeve cooperatively forming a cavity for receiving molten metal and a mechanical grip for holding solidified metal.

2. Continuous casting apparatus and a starting bar therefor comprising: a holding vessel having a horizontally disposed channel at the base thereof terminating in an outlet opening and a refractory block at said opening having an internal passage therethrough having a dimension substantially less than the dimension of said channel, a detachable open ended mold assembly attached to said vessel about said block in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said block in sealing relation thereto and having a substantially greater internal dimension than said block; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said block; (c) a primary solidification chill mold positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; (d) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away fRom said vessel opening, and a starter bar means including (a) a sleeve portion adapted for separate insertion into said primary mold portion having one larger dimensioned end thereof adapted in its operative position for engagement with said nozzle shoulder and for sealing engagement with said primary mold portion; (b) an elongated bar portion adapted for insertion into the said mold through the outlet end thereof to a fully inserted position including a hollow fusable plug end portion adapted for snug insertion into said block passage in said fully inserted position; (c) a chill portion receivable within at least a portion of said sleeve operative to locate and support said sleeve in its operative position and (d) an enlarged portion located within said sleeve in the said fully inserted position, said enlarged portion, said chill portion and said sleeve cooperatively forming a cavity for receiving molten metal and a mechanical grip for holding solidified metal.

3. Continuous casting apparatus and a starting bar therefor comprising: a holding vessel having a horizontally disposed channel at the base thereof terminating in an outlet opening and a refractory block at said opening having an internal passage therethrough having a dimension substantially less than the dimension of said channel, a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said opening, said block, said spacer ring and said nozzle forming a chamber therebetween; (c) a primary solidification chill mold positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; (d) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, and a starter bar means including (a) a sleeve portion adapted for separate insertion into said primary mold portion having one larger dimensioned end thereof adapted in its operative position for engagement with said nozzle shoulder and for sealing engagement with said primary mold portion; (b) an elongated bar portion adapted for insertion into the said mold through the outlet end thereof to a fully inserted position including a hollow fusable plug end portion adapted for snug insertion into said vessel opening in said fully inserted position; (c) a chill portion receivable within at least a portion of said sleeve operative to locate and support said sleeve in its operative position and (d) an enlarged portion located within said sleeve in the said fully inserted position, said enlarged portion, said chill portion and said sleeve cooperatively forming a cavity for receiving molten metal and a mechanical grip for holding solidified metal, said fusable plug being of a thickness so as to resist fusion by molten metal poured into contact therewith for a relatively short predetermined time necessary for slag contained in the molten metal to rise above said block passage and then fuse to permit the molten metal to pass into said mold assembly, said sleeve one end being relatively thin and fusable in contact with said molten metal.

4. A method for starting a continuous casting process which involves apparatus comprising a holding vessel having an outlet opening at the base thereof, a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refraCtory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said opening whereby an annular chamber is formed between said vessel, said spacer ring and said nozzle; (c) a primary solidification chill mold portion positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; (d) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, comprising the steps of: inserting a metal sleeve portion into said primary mold portion, said sleeve being adapted in its operative position for providing sealing engagement with said primary mold portion, inserting an elongated bar portion into said mold through the outlet end thereof to a fully inserted position, said bar portion including a fixed hollow fusable plug inserted into said vessel opening, said bar portion further including a fixed chill portion engaging at least a portion of said sleeve in said fully inserted position, locating and supporting said sleeve in its said operative position, said bar portion also including an enlarged portion within said sleeve in said fully inserted position, said enlarged portion and said chill portion and said sleeve operatively forming a cavity for receiving molten metal and providing a mechanical grip for holding solidified metal, pouring molten metal into said vessel with said plug being operative to hold back the molten metal from entering the mold until the slag has substantially risen above said opening, continuing pouring molten metal into said vessel with said plug being fused to permit the flow of molten metal through said nozzle into said sleeve within said primary mold, said molten metal contacting said sleeve, chill portion and said enlarged portion, said molten metal contacting said primary mold portion at the junction of said nozzle and said primary mold and progressively solidifying within said primary mold and said chill portion, pulling said starter bar a predetermined length whereby a new skin layer of molten metal solidifies on the exposed surfaces of the primary mold, permitting the starter bar to dwell a sufficient time to permit the new segment of metal to weld to the segment previously pulled forward and continuing an intermittent pull and dwell cycle.

5. A method for starting a continuous casting process which involves apparatus comprising a holding vessel having an outlet opening at the base thereof, a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said opening whereby an annular chamber is formed between said vessel, said spacer ring and said nozzle; (c) a primary solidification chill mold portion positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; (d) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, comprising the steps of: separately inserting a metal sleeve portion into said primary mold portion of larger dimension than the other end and being relatively thin, said sleeve being adapted in its operative position for engagement with said nozzle shoulder and seal ring thereon for providing sealing engagement with said primary mold portion, inserting an elongated bar portion into said mold through the outlet end thereof to a fully inserted position, said bar portIon including a fixed hollow fusable plug inserted into said vessel opening, said bar portion further including a fixed chill portion engaging at least a portion of said sleeve in said fully inserted position, locating and supporting said sleeve in its said operative position, said bar portion also including an enlarged portion within said sleeve in said fully inserted position, said enlarged portion and said chill portion and said sleeve operatively forming a cavity for receiving molten metal and providing a mechanical grip for holding solidified metal, pouring molten metal into said vessel with said plug being operative to hold back the molten metal from entering the mold until the slag has substantially risen above said opening, continuing pouring molten metal into said vessel with said plug being fused to permit the flow of molten metal through said nozzle into said sleeve within said primary mold, said molten metal contacting said sleeve, chill portion and said enlarged portion, said molten metal contacting said primary mold portion at the junction of said nozzle and said primary mold and progressively solidifying within said primary mold and said chill portion, pulling said starter bar a predetermined length whereby a new skin layer of molten metal solidifies on the exposed surfaces of the primary mold, permitting the starter bar to dwell a sufficient time to permit the new segment of metal to weld to the segment previously pulled forward and continuing an intermittent pull and dwell cycle.

6. A method for starting a continuous casting process which involves apparatus comprising a holding vessel having an outlet opening at the base thereof, a detachable open ended mold assembly attached to said vessel about said opening in fluid flow relation, said assembly including (a) a refractory spacer ring disposed adjacent said opening in sealing relation thereto and having a substantially greater internal dimension than said opening; (b) a refractory nozzle having an internal dimension substantially less than said spacer ring and at least as large as said opening whereby an annular chamber is formed between said vessel, said spacer ring and said nozzle; (c) a primary solidification chill mold portion positioned in snug contact with said nozzle having an internal dimension substantially greater than said nozzle and forming a shoulder at the junction thereof; (d) a further solidification mold portion adjacent said primary mold portion, said mold portions having progressively diminishing internal dimensions in a direction away from said vessel opening, comprising the steps of: separately inserting a metal sleeve portion into said primary mold portion, said sleeve portion having one end of larger dimension than the other end and being relatively thin, said sleeve being adapted in its operative position for engagement with said nozzle shoulder and seal ring thereon for providing sealing engagement with said primary mold portion, inserting an elongated bar portion into said mold through the outlet end thereof to a fully inserted position, said bar portion including a fixed hollow fusable plug inserted into said vessel opening, said bar portion further including a fixed chill portion engaging at least a portion of said sleeve in said fully inserted position, locating and supporting said sleeve in its said operative position, said bar portion also including an enlarged portion within said sleeve in said fully inserted position, said enlarged portion and said chill portion and said sleeve operatively forming a cavity for receiving molten metal and providing a mechanical grip for holding solidified metal, pouring molten metal into said vessel with said plug being operative to hold back the molten metal from entering the mold until the slag has substantially risen above said opening, continuing pouring molten metal into said vessel with said plug being fused to permit the flow of molten metal through said chamber and said nozzle into said sleeve withiN said primary mold, said chamber being operative to retain residual slag, said molten metal contacting said sleeve, chill portion and said enlarged portion, said molten metal contacting said primary mold portion at the junction of said nozzle and said primary mold and progressively solidifying within said primary mold and said chill portion, so that a partially solidified bar is formed which is mechanically gripped between said sleeve and said enlarged portion, said sleeve being operative to retain said molten metal sufficiently to permit its withdrawal from said mold through the outlet end of said mold, pulling said starter bar a predetermined length whereby a new skin layer of molten metal solidifies on the exposed surfaces of the primary mold, permitting the starter bar to dwell a sufficient time to permit the new segment of metal to weld to the segment previously pulled forward and continuing an intermittent pull and dwell cycle.