US3192582A

US3192582A - Bottom pour ladle nozzle and stopper rod construction

Info

Publication number: US3192582A
Application number: US228188A
Authority: US
Inventors: Gerald R Cope; Robert K Scott; Jr Fred H Fanning
Original assignee: Harbison Walker Refractories Co
Current assignee: Harbison Walker Refractories Co
Priority date: 1962-10-03
Filing date: 1962-10-03
Publication date: 1965-07-06
Anticipated expiration: 1982-07-06
Also published as: GB995712A

Description

y 6, 1965 G. R. COPE ETAL 3,192,582

BOTTOM POUR LADLE NOZZLE AND STOPPER ROD CONSTRUCTION Filed Oct. 5, 1962 TEMPERATURE w 3 INVENTOR.

o GERALD R. COPE ROBERT K. sco'r'r BYF'RED H. F'ANNINC1,JR.

A T TOE/V5 Y United States Patent 3,192,532 BGTIOM POUR LADLE NQZZLE AND STGPPER non (IONSTRUCTKQN Gerald R. Cope, Pittsburgh, Robert K. Scott, Forest Hills, and Fred H. Fanning, .lr., lngomar, Pa, assignors to Harbison-Walher Refractories Company, Pittsburgh, Pa, a corporation of Pennsylvania Filed Oct. 3, 1962, Ser. No. 228,188 9 Claims. (Cl. 22-85) This invention relates to improved nozzle and stopper construction, and more particularly to improved bottompour-ladle stopper and nozzle construction.

Particularly in the manufacture of steel and steel alloys, it is conventional to tap molten metal from a furnace into a ladle in a pouring pit. The pouring pit is usually at a lower elevation than the floor on which the metallurgical furnaces reside, so that the molten metal may flow by gravity from the furnace to the ladle. Spaced from the furnace are a plurality of ingot molds, and the ladle of molten metal is moved through the pouring pit to a position above these ingot molds. Molten metal is poured from the ladle into the ingot molds to form ingots. Usually, the metal is poured from the ladle through a nozzle which opens through the bottom thereof. This nozzle is normally used for but one ladle charge, after which it is discarded and a new one substituted. These nozzles, and the stopper which is used therewith, are the source of many difiiculties. The refractories which are used in these pour ing nozzles, in the past, have worn at excessive rates or have had pieces crack and spall away by reason of heat shocking and contact with molten metal and slags. One of the primary problems is that these pieces of refractory find their way into the castings and form foreign inclusions and flaws, which harm the quality of a final product made from that casting.

Accordingly, it is an object of this invention to provide improved refractory pouring nozzles. It is another object of this invention to provide bottom-pour-ladle nozzle and stopper-rod assemblies. it is another object of this invention to provide improved pouring pit refractory nozzles, basic in composition.

Briefly, in one embodiment of this invention,'there is provided an improved bottom-pour-ladle nozzle and stopper assembly. The nozzle is fabricated of a basic refractory which resists attack by molten metal and slags, and which does not crack and spall away in contact therewith at operating temperatures. These nozzles are fabricated of a refractory composition which, after firing, exhibits the mineralogical phases periclase, dicalcium silicate, and spinel minerals (MgO-Fe O MgO-Al O MgOCr O etc. in a solid solution or as spaced inclusions). in a weight relationship, these mineral phases are present in the range of about 50% periclase, about to dicalcium silicate, the remainder being spinel. At operating temperatures, i.e. the temperature of molten metal, this composition is yieldable and, while it undergoes sorne permanent deformation, it tends to remain in the form of a self-sustaining body. By using a nozzle fabricated of this material, in cooperation with a stopper which is less yieldable and which is non-reactive or neutral to the nozzle, a tight seal which prevents leakage of molten metal is obtained during a series of pours. Suitable material for the stopper may be a clay-graphite mixture. The graphite is desirable in order to prevent wetting by the molten metal.

Other features and advantages of ladle nozzle and stopper construction, according to this invention, will become readily apparent to those skilled in the art from a study of the following detailed description, with reference to the drawings. in these drawings:

FIG. 1 is a side elevation in partial section of a bottom-pour-ladle nozzle and stopper assembly, according to the concepts or" this invention;

FIG. 2 is a schematic side elevation in partial section of the nozzle and stopper-head of the arrangement of FIG. 1; and

FIG. 3 is a plot which characterizes certain desirable physical properties of preferred compositions for fabrication of nozzles, according to this invention.

In FIG. 1 there is shown a bottom-pour-ladle, having a stopper and nozzle assembly, according to this invention. Such a ladle normally includes an outer metal shell it? lined with suitable refractory composition. It might be thought that the sidewalls 11 for ferrous metal such as iron, steel and steel alloys would be lined with a basic refractory composition-since the slags associated with production of the foregoing metals are themselves basic; but, in practice, it is far more common to use aluminasilica ladle brick, because they are cheap yet satisfactory in most instances. The bottom of the ladle includes an outer metal shell 12, also lined with a refractory com position 13, usually similar to that which is used to line the sides. A slag lip 14 opens through a portion of the upper periphery of the sidewall, and is usually fabricated of a refractory monolith.

Opening through the bottom, adjacent the sidewall, is a nozzle 15. A downwardly extending stopper-rod 16, terminating in a stopper-head i7, is axially aligned with the nozzle inlet.

As noted above, in the past, nozzles of the type shown in the ladle construction of FIG. 1 have tended to crack, spall way, or to wear or irregularly erode at excessive rates by reason of contact with flowing molten metal and slags. Heretofore, the trade has almost exclusively used fireclay refractories for these nozzles. They have been used because they are somewhat plastic at elevated temperatures, and are, therefore, expected to promote better sealing with the stopper. However, mineralogically, fireclay refractories are not best suited for contact with molten metal and slag. Such refractories are of relatively low refractoriness, and have tended to be very rapidly consumed during pouring with the eroded material lodging within the ingots. This has caused variation in nozzle orifice diameter as the pouring proceeds, thereby varying pouring rate and, in some instances, the irregular erosion has been so great that metal leakage can not be stopped between pours.

Basic refractory compositions have been recognized as theoretically more suitable as a nozzle composition. However, because of the relatively high thermal conductivity of basic refractory materials, they have caused an excessive cooling of the metal stream, which resulted in surface freezing and restriction of the orifice. Also, when subjected to the rapid heating, which occurs upon contact with molten metal, certain previously used fired basic nozzles have tended to crack excessively. Further, because of the rigidity of such previously used basic refractories, they have not been amenable to tight sealing relation with the stopper-head. Also, because of this rigidity, the stopper-heads have tended to tear away upon seating in the nozzle, still further lessening the adequacy of closure between pours.

In other attempts to up-grade nozzle compositions, clays of the highest refractoriness have been used, or even high alumina refractory compositions, such as alumina-silica blends with as much as A1 0 by analysis. In gen eral, however, when such mixes are chosen which are refractory enough to diminish nozzle erosion, small spaced metal deposits build up, probably due to the inherent thermal properties of such high alumina materials. The result is a poorly flowing stream of metal which is deflected or channeled by the deposits resulting in undesirable splattering.

Prior use of nozzle refractories has been predicated on the concept of controlled consumption of the constituents of the nozzle or stopper-head. This was, in effect, accepting the undesirable characteristics of the fireclay materials, and attempting to control them to obtain satisfactory service. The fire clay tends to wear away rapidly, or to melt because of its low refractoriness. With the much harder basic refractories, it was assumed the stopper head would Wear away and, in effect, continually reform a seat to close the nozzle inlet.

This invention is a departure from such technology and, in effect, provides a stopper and nozzle combination having what may be termed inherent resiliency at operating temperatures; which resiliency allows good seating be tween pours, without destruction of the nozzle or lessening of the ability of the stopper-head, to lie contiguously to the mouth of the nozzle inlet between successive pours. The composition selected for the nozzle, according to this invention, is yieldable at operating temperatures when under pressure; but self-sustaining. It can not be called elastic, because it has some permanent deformation under these conditions; but this actually is beneficial, according to the concepts of this invention. The stopper is preferably a clay-graphite mixture, which is less yieldable than the composition of the nozzle and which is substantially non-reactive or neutral thereto. Under actual service conditions, when a nozzle of the preferred composition is subjected to the temperature of molten metal, surface areas are yieldable or capable of being displaced to a limited degree under pressure. Thus, in operation, when the stopper-head is pressed against the nozzle inlet, there is some surface displacement of the nozzle material, providing a contiguous seat substantially conforming to the adjacent portions of the stopper-head. In a subsequent pour, upon Withdrawal of the stopper-head, the nozzle does not completely restore itself to its prior dimensions because of some permanent deformation, but it does again achieve the yieldable state discussed above. Thus, when the stopper-head is again pressed against the nozzle inlet, there is again some surface displacement of the material of which the nozzle is composed, to again assure good closure.

In FIG. 2, the nozzle 1.5 is shown closed by the stopperhead 17. When the stopper 17 is withdrawn for a pour, and then again seated in the inlet orifice of the nozzle, the peripheral lip A of the nozzle will be displaced as to the position shown by dotted line 153. During subsequent pours and closures, this lip configuration will yield somewhat each time, assuring a good closure. In

FIG. 2, the degree of deformation has beenexaggerated for purposes of clarity in explanation.

It is thought a better understanding of the character of the physical properties desired for nozzle composition, according to the concepts of this invention, will be had by a discussion of FIG. 3which represents the percent linear change undergone by refractories under controlled heating rate and constant load. In general, most basic refractory compositions tend to expand at an almost linear rate until a given temperature, at which time a shape fabricated thereof essentially collapses. This action is schematically shown by the dashed line 29 in FIG. 3. However, compositions according to this invention do not have the characteristic of such sudden failure. At an elevated temperature, under load, their rate of expansion decreases; and a shape made therefrom when under pressure and elevated temperature tends to have a period of gentle subsidence before failure.

. The line 21 in FIG. 3 is illustrative of this characteristic in compositions used according to this invention. The presence of this characteristic is determined in the labratory by fabricating small cylinders or test brick, and placing them under load and increasing temperature. Normally, the pressure will be a load of approximately 25 p.s.i. In general, and as shown by FIG. 3, the cylinders initially expand at an almost linear rate. If a specimen fails abruptly, it is squashed by the load. Such a resultis shown by the line 29. However, under similar test conditions, as shown by the line 21, compositions of this invention tend to have a gentle subsidence preceding actual failure. The significance of this for the instant invention is that the yielding range shown provides the physical characteristics needed for repeated yieldable seating of a stopper-head. The phenomenon, shown in FIG. 3, explains the yielding character of nozzles fabricated according to this invention, when they are subjected to the elevated temper- 1 O ature of in lten metal and then, subsequently, subjected to the downwardly exerted pressure of a stopper-head.

A preferred composition for refractory nozzles, according to this invention, is fabricated of a batch of pre- 15 fired clinker and a selected chrome ore. The chemical analysis of the clinker, and the composition of a batch for fabricating the nozzles, is shown in Table I. The clinker is usually subjected to iring to about 3000 F, as in a rotary kiln. The nozzle shapes are normally fired to be tween about 2450 to 250 Table I Chemical analysis of clinker 1:

Percent SiO 90.

CaO 21.9 1 8203 6.1 A1 0 1.4 Mg-O Most of the balance Chemical analysis of clinker II:

Al O 2.1

CaO 19.7 30 MgO 62.3 Cr 03 3-7 Batch composition:

Clinlter I 65 Clinlcer ll 25 Chrome ore 1 (6+2() mesh) 1O 1 This chrome ore was Turkish chrome ore having the typical analysis, by weight, and on the basis of an oxide analysis: A1203, about 17% CrzOs, about 4t8% FeO, about 15% MgO, about 17% the remainder, by difi'erence, S102, trace impurities, and ignition loss.

The size grading for the materials of Table I, when used to fabricate a nozzle, is according to the well established practices of the industry. However, a preferred and typical screen analysis can be as follows:

"' Table 11 Percent 6 on 10 mesh 25 10 on 28 mesh 2O 28 on mesh 15 65 mesh 40 The foregoing mesh sizes are all Tyler series.

In general, the fired nozzle, made of the foregoing composition, may be mineralogically characterized as com- (30 posed of the three phases periclase '(MgO), dicalcium silicate (ZCaO-SiO and spinel minerals (MgO-Fe O MgO-AI O MgO-Cr O and other spinels which form from the interreaction of the mineral constituents of the components of the batch). In general, it may be said that 35 the basic refractory compositions for fabrication of nozzles, according to this invention, are mixtures of basic refractory materials, which include about 2035%, by weight, of stabilized dicalcium silicate after firing. It is thought that this stabilized dicalcium silicate portion of the composition, in conjunction with the spinels, which is apparently primarily responsible for the yieldable character of the material at operating temperatures. The operating temperature, referred to in the foregoing discussion, will vary from operation to operation. In mak- 7 ing castings of molten metal from an electric furnace, the

temperature of metal being tapped may be as high as 3200 F. As a practical matter, the shapes of compositions according to this invention will initially exhibit their desired yieldable characteristic at about 2500" F., and the shapes will operate satisfactorily up to the normally encountered temperature of the electric furnace molten metal.

In an actual bottom-pour-ladle service installation, in which burned fireclay refractory nozzles of prior composition had been use-d, and which were resulting in many leaking closures and failures, nozzles, according to this invention were substituted. A graphite clay-type stopperhead was used therewith. A six-ton teapot ladle was filled from an acid electric furnace operating at about 3200 F. Metal was poured from the teapot ladle into a smaller ladle. The sma l er ladle had a nozzle and stopper, according to this invention. The metal was poured therefrom into a series of molds. The temperature at the beginning of the pouring was about 3100 F., and at the end was about 3050" F. The foregoing was repeated, and the small ladle was emptied and filled ten times during this particular test. The castings ranged from 200 to 700 lbs. each. The nozzle was subjected to 70 shutotfs. Examination of the nozzle after the test revealed no cracking, and no erosion of the 1 /2" internal nozzle diameter. Also, the interior of the nozzle was clean and free of metal or slag. The nozzle inlet or seat was found to be deformed to match the outer curvature of the stopper-head.

In another field trial, a ladle, of the type used with a basic open hearth operation, was subjected to extensive testing and gave good performance. This established the utility of the nozzles of this invention in both acid or basic environments.

The stopper-head may be fabricated according to any of many conventional techniques. In the United States, it is conventional to use a composition comprised of about 25% graphite and about 75% of a mixture of calcined and crude fire clay. A preferred mixture will be of fire clays of the Missouri type. In some portions of the United States metallurgical industry, where more aluminous fire clays are desired, bauxitic clay mixtures may be used. Also, a stopper-head of the type used in European practices is applicable, in which a straight fireclay mix is used. The composition used is a matter of choice, as long as the stopper-head which results is harder at operating temperatures than the composition of the nozzle, is substantially inert or neutral to the nozzle, and is sufiiciently smoothsurfaced in a finished shape as to prevent tearing of the inlet mouth of the nozzle.

Having thus described our invention in detail, and with suificient particularity as to enable those skilled in the art to practice it, what we desire to have protected by Letters Patent is set forth in the following claims.

We claim:

1. In vessels for handling molten metal, comprised of a shell, a refractory lining in the shell, a stopper-head and stopper-rod assembly operatively associated with said vessel, and a pouring nozzle, the improvement which comprises a fired basic refractory pouring nozzle having an inlet and an outlet, the surface areas of the nozzle which define said inlet being displaceable at operating temperatures to a degree surficient to provide a contiguous seat substantially conforming to adjacent portions of the stopper-head when under stopper-head pressure, at least those portions of the stopper-head which contact the dis placeable areas of the nozzle fabricated of a material which is substantially inert to said displaceable areas, said nozzle contacting portions of said stopper-head being sufficiently smooth surfaced as to prevent tearing of the stopper-head contacting surface areas of said nozzle, said nozzle mineralogically characterized by about 30 to 50%, by Weight, periclase, and about '20 to 35%, by weight, dicalcium silicate, and the remainder being spinel minerals.

2. The vessel of claim 1 in which the nozzle is mineralogically characterized by about 30% periclase, about 20 to 35% dicalcium silicate, and the remainder being spinel minerals.

3. In bottom pour ladle refractory nozzle and stopper construction, the improvement which comprises a fired, basic refractory nozzle which exhibits the mineralogical phases periclase, dicalciurn silicate, and spinel, said peri clase constituting at least about 30 to 50%, by weight, of the total weight of the nozzle, the dicalcium silicate constituting between about 20 and 35%, by weight, of the total wei ht of the nozzle, the spinel phase constituting the remainder of the nozzle composition.

4. A fired molten metal contacting basic refractory nozzle mineralogically characterized by the mineral phases periclase, dicalcium silicate, and spinel, the spinel phase being substantially entirely composed of members of the group MgO-Fe O MgO-Al O MgO-Cr O and mixtures thereof, the periolase constituting about 30 to 50% of the total weight of the nozzle, the dicalcium silicate constituting about 20 to 35%, by weight, of the total nozzle, and the remainder being spinel.

5. The fired molten metal contacting basic refractory nozzle of claim 4 in which the spinel is present as a solid solution of members of the group MgO-Fe O MgG -Al O MgO -Cr O and mixtures thereof.

6. The fired molten metal contacting basic refractory nozzle of claim 4 in which the spinel phase is formed in part from a minor amount of chrome ore.

7. The fired molten metal contacting basic refractory nozzle of claim 6 in which the chrome ore amounts to about 10%, by weight, of the total Weight of the nozzle.

8. In bottom pour ladle refractory nozzle and stopper construction, the improvement which comprises a fired nozzle which exhibits the mineralogical phases periclase, dicalcium silicate, and spinel, said periclase constituting at least about 30 to 50%, by weight, or" the total weight of the nozzle, the dicalcium silicate constituting between about 20 and 35%, by weight, of the total weight of the nozzle, the spinel phase constituting the remainder of the nozzle composition, said nozzle characterized by the ability to yield at operating temperatures when under pressure and to at least partially restore itself upon removal of the pressure, and said ability to yield characterizing the nozzle through a plurality of closures.

9. The bottom pour ladle refractory nozzle and stopper construction of claim 8 in which the nozzle has been fired to between about 2450 and 2550 F. before use.

References Cited by the Examiner UNITED STATES PATENTS 2,253,620 8/41 Heuer 10659 XR 2,268,279 12/41 Denbenham et al. 22-85 2,291,917 8/42 Pitt et al 10659 2,291,918 8/42 Pitt et al. 106-69 XR 2,311,970 2/43 Seil 10659 2,358,107 9/44 Sell 106-59 XR 2,599,565 6/52 Magri l0659 2,615,216 10/52 Slick 22-85 3,028,874 4/62 Burkett 22-35 XR 3,094,424 6/63 Ratclitfe 106-69 I. SPENCER OVERHOLSER, Primary Examiner.

MARCUS U. LYONS, Examiner.

Claims

1. IN VESSELS FOR HANDLING MOLTEN METAL, COMPRISED OF A SHELL, A REFRACTORY LINING IN THE SHELL, A STOPPER-HEAD AND STOPPER-ROD ASSEMBLY OPERATIVELY ASSOCIATED WITH SAID VESSEL, AND A POURING NOZZLE, THE IMPROVEMENT WHICH COMPRISES A FIRED BASIC REFRACTORY POURING NOZZLE HAVING AN INLET AND AN OUTLET, THE SURFACE AREAS OF THE NOZZLE WHICH DEFINE SAID INLET BEING DISPLACEABLE AT OPERATING TEMPERATURES TO A DEGREE SUFFICIENT TO PROVIDE A CONTIGUOUS SEAT SUBSTANTIALLY CONFORMING TO ADJACENT PORTIONS OF THE STOPPER-HEAD WHEN UNDER STOPPER-HEAD PRESSURE, AT LEAST THOSE PORTIONS OF THE STOPPER-HEAD WHICH CONTACT THE DISPLACEABLE AREAS OF THE NOZZLE FABRICATED OF A MATERIAL WHICH IS SUBSTANTIALLY INERT TO SAID DISPLACEABLE AREAS, SAID NOZZLE CONTACTING PORTIONS OF SAID STOPPER-HEAD BEING SUF-