US2049148A - Pouring practice and apparatus - Google Patents

Description

July 2s,1936. YW B, ARNESS 2,049,148

POURING PRACTICE AND APPARATUS Filed Oct. 17, 1955 Patented July 28, 1936 2,049,148 i PoURING PRACTICE AND APPARATUS William B. Arness, Baltimore, Md., assignor, by mesne assignments, to Rustless Iron and Steel Corporation, Baltimore, Md., a corporation of Delaware Application October 17, 1933, Serial No. 693,990 s claims. (c1. zit-209) Thisinvention relates to the production of a wrinkled, seamy unsound and cracked ingot metal ingots, especially ingots of chromium alloy surface ordinarily results. Particularly in the irons and steels, and to means and apparatus production of slab ingots of rustless irons and employed in the same. steels where a, chromium content of from about One of the objects of my invention is the sim- 12% to 30% is employed, either with or without I. 5 ple, economical and efficient production of metal nickel in substantial amounts and supplemeningots of relatively smooth surfaces, which are tary additions of copper, cobalt, titanium, molybfree of wrinkles, cracks, seams and scabs or cold denum, tungsten and the like as desired, the surshuts; which are likewise free of. sub-cutaneous faces of the ingots, especially along the narrow nonmetallic inclusions, blowholes and like desides, are wrinkled, cracked, seamy and unsound.

fects; and which readily lend themselves to an In, for example, top pouring a mold of comeiliciency and economy of rolling or otherwise paratively large sectional area, or a mold where working heretofore unknown. two or more of the walls are relatively remote Another object of my invention is the develfrom the center as in a slab mold where the end opment of a simple, economical and thoroughly walls are 15, 20, or more inches from the mold ,15

part pointed out hereinafter. sticky. This is particularly noticeable where the The invention, accordingly, consists in the comteemed metal is of high chromium content. Fur- 25 bination of elements, features of construction and thermore, during the teeming, non-metallic inarrangement of parts, and in the several steps clusions entering the mold tend to rise to the surand the relation of each of same to one or more face of the metal and form a sticky scum the of the others, as described herein, the scope of amount of which is increased by atmospheric the application of which is indicated in the foloxidation of the upper surface of. the metal. This .30

lowing claims. scum is carried with the surface flow of metal In the accompanying drawing, illustrating certoward the end-walls of the mold where the turtain features of my invention: bulent effect of the metal is at a minimum. As

Figure 1 is a front elevation of a mold ready surface metal and scum further cool a crust is for teeming, with associated hot-top and pourformed which sticks to the metal freezing against order to more clearly illustrate certain features ingot.

of my invention, Thus referring to A of Figure 5, metal I0 ris- Figure 2 is a plan view of mold, hot-top and ing along the side wall I I a of mold I I-is covered pouring crucible shown in Figure 1, by a, sticky layer of scum or a plastic crust gen- Figure 3 is an end elevation of mold, hot-top erany indicated at l2 which, for example, sticks and crucible shown in Figure 1 as seen from the at ma to the skin |01) of the forming ng0t The right rise of metal continues, as shown in B of Figure 5 Figure 4 is a frt eleg/atm? 0f alltlle'nd and under the ferro-static pressure of the rising 45 ingot mold' of the ig en up ype W 0 op metal the scum or crust I2 breaks. The molten and pouring crucible operatively associated theremetal ows to the mold Wan entrapping a Sec Wm? au reafy for teemmg and tion of scum or c rust of non-metallic inclusions,

Figure@ 1s. a diagrammatm represeltaton of generally indicated at I3, beneath the surface metil rnml fhglgglvearlsthe Supp y s rea'm skin of the fast forming ingot. 1S TE O As conducive to a clearer understanding of cer- The r 15mg mtal 110W? agout hentapped 111311 tain features of my invention it may be noted metalhc incluslol'ls mdlca ed a (see C 0f '1g' at this point that in casting ingots, especially slab ure 5) telldlrlg. m S measure, t0 reduce the 1ningots of relatively large slab sections, of iron cluded oxides with the consequent l1berat1on of or steel and more especially alloy iron and steel, gas. 'Ine metal contacting the 4mold walls 1s 5 5 heavy, sticky and viscous and quickly solidifies thereby entrappng the gas bubbles causing blowholes beneath the skin of the ingot.

As the metal in the mold continues to rise substantially uniformly and with minimum disturbance near the remote end-walls, successive sections of the scum or crust covering the rising metal adjacent these walls stick to the upper part of the continuously forming ingot skin, break from the main body of scum or crust and become entrapped by the rising metal. The metal, then, in contact with the mold walls rises not uniformly and at a substantially constant rate but discontinuously producing thereby an uneven, wrinkled surface covered with cracks and ssures. Immediately beneath the wrinkled surface of the ingot are entrapped the various sections of nonmetallicinclusions in the form of pieces of crust of various sizes together with entrapped gases, the whole forming an unsound and blowy sub-cutaneous layer.

In order to prepare the ingot for working into a desired intermediate form, such as a billet, bloom or slab suitable for 'finishing to sheet or plate, this wrinkled, seamy and cracked surface layer with sub-cutaneous oxide inclusions, blowhole sections and the like must be completely removed down to clean, sound metal. The removal of this outer layer of defective metal is slow, costly and inefficient.

It may be further noted at this point that in teeming ingots in accordance with heretofore known methods and pouring equipment, that in order to partially avoid the many defective ingot surface and sub-surface conditions a number of which are referred to above, the metal is poured into the mold in a large stream and at an excessive 'rate. Fast pouring, even when the metal is relatively cold, induces longitudinal surface cracks aswell as spots, scabs or cold shuts caused by metal splashed against the mold walls where the splashings immediately freeze and subsequently become incorporated in the skin of the ingot (ordinariy the metal contacting the mold walls is not sufficiently hot to melt these splashings). Furthermore in pouring the metal in a large stream, the edges of the stream may be as near as two or three inches of the side-walls of a mold. Such a stream under a high ferro-static pressure (even where this pressure is reduced and the stream accurately controlled by a pouring crucible between ladle and mold) causes .an excessive wash of metal against the bottom and side-walls of the mold, cutting into the mold bottom and Walls, decreasing the normal mold life, contaminating the fast forming skin of the ingot in localized areas with the high carbon cast iron of the mold and causing the ingot to stick in spots to the walls of the mold. The subsequent stripping of the ingot is slow and unduly dicult. The stripped ingot has a torn and scabby bottom, is objectionably contaminated with mold metal in sections adjacent the bottom and is inclined to have surface checks and cracks in addition to the many faults indicated above.

One of the objects of my invention is the production in a simple, economical and reliable manner with a minimum of expensive and/ or complex equipment, of smooth even surface ingots, free of seams, wrinkles and cracks; free of scabs, cold shuts and the like; free of sub-cutaneous nonmetallic inclusions, gas pockets and pits; and free of objectionable localized contamination of the ingot mold.

In the practice of my invention in casting a Slab ingot of rustless iron, for example, employing a slab mold having wide side-walls and narrow end-walls, the side-walls being relatively near the major lateral axis of the mold and the narrow-end walls being comparatively remote from the mold center, molten metal is poured into the mold in a plurality of spaced streams of reduced size. Each stream is maintained near the walls of the mold in order to assure a desired turbulence of metal washing the various walls of the mold and precluding the formation of a definite scum and subsequent crust of non-metallics on the surface of the rising metal, and to furthermore prevent the sticking of such a crust to the forming ingot or to the mold walls to be subsequently entrapped in the skin of the ingot as more particularly described abovefto form the wrinkled outer surface and the many sub-surface defects indicated. The turbulence of metal is not so great, however, as to cause a cutting of the mold bottom and walls with the many attendant injuries to mold and ingot a number of which are set forth above.

Thus, referring to the accompanying drawing and more particularly to Figures l, 2, and 3, an ingot mold I5, of cast iron,- illustratively of the Gathmann type, having an open top portion, indicated at I5a, and a closed bottom portion I5b (see Figure 1) is set up in a vertical position, handling of the mold being achieved by staple I6 embedded in the side-walls of the mold, on blocks I1 resting on a pit bottom generally indicated at I8. Mold I5 (see Figure 2 has opposite wide sidewalls I5c and I5d spaced relatively near the center of the mold and narrow side-walls I5e and ISI spaced remotely from the mold center. The inner Walls of lthe mold are tapered sufficiently to permit easy stripping of the fully formed ingot from the mold.

In teeming, a ladle (not shown) is suspended above the mold at a suitable height with the ladle nozzle substantially axial of the mold. By control of the ladle nozzle opening, metal is permitted to iiow into the mold.

In order to reduce the ferro-static pressure of the teemed metal, especially during the initial periods of teeming when the mold is empty and the tendency of splash is at a maximum, and to achieve a desired tubulent eiect of metal in the mold, thereby assuring A a continuous wash of metal along the various mold walls, a pouring crucible or pot I9, comprising a basin I 9a (see Figure 1) and utwardly extending nozzles illustratively I9b and I9c, 'is interposed between mold and ladle. Chilling and freezing of the metal in the pouring crucible is effectively prevented by employing a crucible pre-heated to approxi'- mately 1800* F. This pre-heating is carried out in any convenient manner, as by means of a gasfired oven. A number of crucibles are kept hot in the oven and are withdrawn for use in a pre-heated condition as indicated above.

The pouring crucible I9 is conveniently mounted upon the horizontal supporting bars 20 (see Figure 2) which rest upon the upper edge of a hot-top 2l. In accordance with standard pouring practice, hot-top 2| loosely ts within the open-end portion I5a of mold I5 where it is conveniently supported by bricks 22 engaging the projecting lugs 2Ia of the hot-top.

Crucible I9, preferably made of graphite bonded with nre-clay in order that it may withstand the necessary pre-heating, wash of metal and the high temperatures encountered, is of elongated section similar to the section of the mold with which it is Preferably, (see Figure 1) basin I9a and nozzles |9b and I9c are individually fashioned in order that the nozzles after being excessively Worn by the wash of teemed metal, or possibly frozen over with cold metal, may be readily replaced thus prolonging the life of the crucible.

Nozzles I9b and |9c extending outwardly from the basin of the Crucible are spaced at opposite ends of the bottom of the basin at such a distance that each of the nozzles, when the Crucible is in use, is at a permissible distance from the mold walls or is substantially equidistant from three of the walls of the mold.

Thus referring more particularly to Figure 2, Crucible I9 maintained in substantial axial alignment with mold I5 (see also Figure 1) with nozzles I 9b and I 9c in substantial alignment with the major lateral axis of the mold, has the pouring nozzles so spaced that the nozzle |9b is relatively near and substantially equidistant from mold walls I 5c, |5d, and l5! and nozzle |90 is likewise near and substantially equidistant from the mold walls |5c, |5d, and I5e.

. Metal flowing into Crucible I9 in a central stream from the ladle ows out of the Crucible by way of nozzles I9b and |9c in two streams adjacent the side Walls of the mold at a uniform, even rate. The falling streams of metal assure metallic scum or crust, thus assuring the production in a simple, inexpensive and thoroughly reliable manner, of an ingot of substantially smooth, continuous surface with a minimum of localized skin contamination with mold metal and a minimum of sub-cutaneous non-metallic inclusions, blowholes and the like. A substanmetal along the walls of of metal then maintaining a desired wash along the side-walls of the mold throughout substantiallyequal angles toward and away from the other stream. Thus, referring to Figure 2, nozzles |9b and |9c of the Crucible are spaced from and |5e respectively, when the Crucible is properly 'positioned over the mold, as more particularly described above. This construction assures a comparatively uniform and vigorous wash of metal against the mold sidewalls I5c and |5 throughout the extent of these Walls.

After teeming, Crucible |9 is moved to the next ingot mold where it is conveniently posi-` of the mold to a comparativelyformed with tapering holes |5g and lh (see Figure 1) in substantial alignment with the major lateral axis of the mold and spaced equidistant on opposite sides of the longitudinal axis I5g and |5h respectively are in substantially direct alignment with nozzles |9b and |9c of the pouring Crucible operatively associated with the mold.

The mold bottom is completed by cast iron plugs 23 and 24 respectively interiitting the tapered holes |59 and |5h. 'Ihese plugs are suiiciently large to catch the direct impact of the streams of metal initially falling into the empty In addition to minimizing metal splash by employing a, plurality of smaller streams of metal in teeming, and the accompanying decrease in scabs and cold shuts as well as curved wall sections, |5k, I 5m, |51, I 5p join bottom wall |5b with the respective side and end straight side and end walls of the mold thus assuring a smooth ingot butt free of scabs or cold shuts and with a minimum of sticking of ingot to the mold bottom.

Where a slab mold of the open-end type (see Figure 4) is employed, excellent results in casting an ingot of smooth surface and comparatively free of sub-Cutaneous defects is achieved by interposing between mold and ladle a pouring suiciently near the mold walls to maintain a turbulent condition of the metal with the consequent prevention of a wrinkled seamy or cracked ingot surface and the entrapping of sections of non-metallics and gas inclusions, all as more particularly described above.

Open-end mold 25 of the big end up type, is mounted upon a stool 26 having embedded therein a cast iron stool insert 21. In teeming, a pouring Crucible or pot 28 having a plurality of Crucible nozzles 28h and 28e is conveniently supported by bars resting upon the upper edges of hot-top 2 9 conveniently mounted upon the top of the mold. Crucible or pot 28 is designed with respect to 25 direct streams of molten metal adjacent the mold walls-in order to maintain a turbulence of metal washing the walls and assure the production of smooth surface ingots free of subcutaneous non-metallic inclusions and blowholes, all as more particularly described -The utilization of in filling the mold in a measure prevents the localized cutting away of the insert, as with a single stream of increased size, and in addition measurably ydecreases the amount of splash encountered with a single large stream of metal, thus permitting the production of an ingot having a minimum of scabs or cold shuts and the realization of maximum mold life.

Thus it will be seen that there has been provided in'this invention a method and apparatus for economically and elciently teeming ingots, in which the various objects hereinbefore noted together with many thoroughly practical advantages are successfully achieved.

While in the embodiment of my invention illustratively described above a slab mold having two bottom plugs and an associated pouring crucible having two nozzles are described it will be understood that three, four or more pouring nozzles spaced along the axis of the pouring crucible may be employed when desired and a mold of great width as compared to thickness may be used therewith, the mold bottom plugs preferably corresponding in number and in location to the nozzles of the associated pouring crucible.

Likewise, in teeming a mold of large cross section having substantially equal sides, it will be understood that many practical advantages may be achieved by employing a. pouring crucible operatively associated therewith wherein a plurality of crucible nozzles are used, spaced adjacent the projected walls of the mold, in. order to assure a desired wash of metal along the mold walls and to achieve a desired smooth surface ingct free of sub-cutaneous defects.

As many possible embodiments may be made of my invention and as many changes may be made in the embodiments hereinbefore set forth, it is to be understood that all matter described herein, or shown in the accompanying drawing, is to be interpreted as illustrative, and not in a l limiting sense.

I claim:

1. In the production of high chromium alloy iron and steel slab ingots, the art which includes, pouring molten high chromium alloy iron or steel into a slab mold a plurality of streams substantially evenly spaced along the major axis of the mold and maintained uniformly adjacent the side-walls and end-walls thereof, thereby creating a regular wash of metal against the walls of the mold and preventing the formation and entrapment of non-metallic inclusions in the forming ingot, whereby an igot free of subcutaneous blowholes, oxide inclusions and the like is effectively achieved.

2. In the production of rustless iron ingots in a slab mold, the art which includes, pouring molten rustless iron` into said mold in two streams evenly spaced opposite side walls and end-walls of the mold, thereby creating a uniform wash of metal along the walls of said mold and preventing the entrapment of a surface crust of non-metallic inclusions beneath the skin of the forming ingot, whereby an ingot free of sub-cutaneous defects is effectively achieved.

3. In the production of high chromium alloy iron and steel ingots in a slab mold, the art which includes, maintaining above said mold andin substantial alignment therewith a pouring crucible having a pair of nozzles thereinl each 5 by ingots free of sub-cutaneous defects are prol5 duced.

4. In the production of metal ingots of greater width than thickness, in combination, a slab mold having a plurality of hole portions spaced along the major axis of the bottom thereof, the 20 extreme hole portions being substantially equidistant from an end-wall and opposite sidewalls ofJthe mold, a corresponding plurality of plugs intertting the hole portionsof the' bottom of said mold, a pouring crucible having a plurality of nozzles so spaced as to correspond in number and arrangement with the hole portions of the bottom of said mold, and means supporting said crucible so as to space the nozzles thereof in substantial alignment with the plugs intertting the hole portions of said mold bottom and substantially equi-distant from the sidewalls of said mold, whereby metal poured into said crucible falls in a plurality of streams initially striking the plugs intertting the hole 35 portions of the mold bottom andthen deflecting against the walls ofsaid mold and from the outset creating a turbulence of metal washing the mold walls and assuring the production of ingots free of sub-cutaneous defects.

5. In the production of metal slab ingots, a pouring crucible comprising in combination, a refractory basin of elongated rectangular section, and a plurality of outward extending nozzles spaced along the major axis of said basin at intervals substantially equal to twice the spacing of the extreme nozzles from opposite sidewalls and an end-wall of the basin.

6. In the production of high chromium alloy iron and steel slab ingots, a slab mold comprising in combination, a bottom portion having wide side-wall and narrow end-wall portions rising therefrom, said bottom portion having a plurality of openings therein spaced along the major axis thereof at intervals substantially double the spacing between the extreme openings and the adjoining end-wall and side-wall portions of the mold, and plugs intertting said openings whereby molten high chromium iron and steel poured into said mold in a plurality 60 of streams corresponding in number and spacing to said plugs initially irnpinges upon said plugs creating a uniform wash of mold wall portions and assuring the production of slab ingots free of sub-cutaneous defects. 65

WHLIAM B. ARNESS.

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