US2883722A

US2883722A - Method and apparatus for freeing stopper rod in bottom pouring steel ladle

Info

Publication number: US2883722A
Application number: US776102A
Authority: US
Inventors: Bidner John
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-11-24
Filing date: 1958-11-24
Publication date: 1959-04-28
Anticipated expiration: 1976-04-28

Description

April 28, 1959 J. BIDNER ,8 ,7 1 METHOD AND APPARATUS FOR FREEZING STOPPER ROD IN BOTTOM POURING swam. LADLE Filed Nov. 24, 1958 United States PatefifQ F METHOD AND APPARATUS FOR FREEING STOPPER ROD IN BOTTOM POURING STEEL LADLE John Bidner, Youngstown, Ohio Application November 24, 1958, Serial No. 776,102

5 Claims. (Cl. 22-85) This invention relates to bottom pouring steel ladles, and, more particularly, is concerned vwith methods and apparatus for reducing the formation of a frozen sk of steel between the stopper rod'and the ladle nozzle, and for freeing the stopper rod for opening and closing movement.

In practically all basic open-hearth and electric furnaces steel is drawn in liquid form from the furnace into a bottom pour type ladle. The bottom pour ladle includes a nozzle in the bottom of the ladle closed by a stopper rod extending up vertically through the molten steel in the ladle and operated from above the ladle to move toward or from the nozzle to control the outflow of steel from the ladle into an ingot mold or the like.

Occasionally steel solidifies on the sides and bottom and in the nozzle of the ladle, and this is called a skull in the trade. The skull in the nozzle interferes with a smooth and solid stream flow of metal through the nozzle and causes turbulence and spraying of the steel in the stream which is undesirable from the standpoint of the quality of the ingot poured or the time required to empty the ladle.

A skull may also cause difiiculty in opening the stopper rod, i.e., moving it vertically, because of the steel frozen to and clinging to the stopper head. The skull may also interfere in the shut-off of the steel by interfering with a proper seal between the stopper head and the nozzle. At times the skull clings so tightly to the stopper head that the stopper head is pulled from the stopper rod upon lifting movement of the rod causing a full run of the steel, or the stopper head has to be burned out from underneath the nozzle with an oxygen lance thereafter making a shut-off of the nozzle impossible.

A skull clinging to the stopper head may suddenly release when heavy lifting pressure is put on the stopper rod, and the resulting springing efiect may cause the stopper rod to jump out of the well or nozzle opening making it impossible to shut off the steel.

It is the general object of my invention to avoid and overcome the difiiculties enumerated by the provision of improved means and methods for preventing the formation of a skull between the stopper rod and its nozzle in a bottom pouring steel ladle.

Another object of my invention is to provide relatively inexpensive, readily employed methods and apparatus in combination with a bottom pouring steel ladle so as to hold the stopper rod substantially free for vertical 2,883,722 Patented Apr. 28,, 1959 steel pouring ladle having a bottom nozzle of refractory material with a funnel-shaped passage therethrough, of a vertically movable stopper rod of refractory material positioned down in the funnel-shaped passage of the nozzle to stop off flow of molten steel through the nozzle,

the diameter of the rod being greater than the smallest the single figure is a fragmentary vertical cross-sectional view showing the nozzle portion of a bottom pouring steel ladle and with the lower end of a stopper rod being positioned in sealing relation therewith.

Having more particular reference to the drawing, the

. numeral 10 indicates generally a bottom pouring steel ladle which may be formed, for example, with a bucketshaped metal shell 12 lined with blocks of refractory material 14 and reinforced at the bottom with an additional steel plate 16 of dish-like shape.

One of the refractory blocks in the bottom of the ladle takes the form of a nozzle block, indicated as a whole by the numeral 18, and including a funnel-shaped well or nozzle opening 20 therethrough. The nozzle block 18 has a portion thereof extending through a hole in the bottom of plates 12 and 16, and a metal cap 22 sealed at its back with fire clay 24 may be provided to help support and strengthen the downwardly extending nozzle portion of the nozzle block, the cap 22 being held in position by suitable means not shown.

Associated with the nozzle block 18 is a stopper rod,

' indicated as a whole by the numeral 26, and normally movement away from the pouring nozzle thereby improvconstructed by sliding spool-shaped refractory sleeves 28 down over a metal rod 30 and into contact with a refractory body 32 forming the stopper rod head. The refractory head 32 of the rod has an axial bore 34 and a counterbore 36 to receive a headed pin 38 which extends up into a recess 40 in the lower end of rods 30, with the pin 38 being locked in the recess 40 by a wedge key 42 in mechanically obvious manner. The counterbore 36 of the stopper head 32 is closed with a plug 44 of suitable refractory material once the head 32 has been assembled on the lower end of the rod 30. The mechanism at the top of the ladle for raising and lowering the stopper rod is well known and has not been shown.

It will be recognized that the external diameter of the stopper rod 26 is greater than the smallest diameter of the funnel-shaped opening 20 of the nozzle 18, but the external diameter of the stopper rod 26 is less than the largest diameter of the funnel-shaped opening 20. There is thus provided a circular groove or trough 46 between the lower end of the stopper rod 26 and the opening in the nozzle, and in this trough or groove 46 is placed a body of lead or predominately lead. This can be accomplished in a variety of ways. Lead shot can be poured cold into the trough 46 after the stopper rod 26 has been positioned down in sealing relationwith the nozzle block 18 and before any molten steel is poured into the ladle 10. Lead wool can be placed in the trough 46 before any molten steel is poured into the ladle. A fabricated ring of lead or predominately lead can be placed into the trough in the empty ladle before setting the stopper rod into place. A fabricated ring of lead or predominately lead can be slid down the stopper rod in the empty ladle after the stopper rod has been placed in stop position. A fabricated ring of lead or predominately lead can be attached to the stopper rod or stopper head when the stopper rod is assembled. A fabricated ring of lead can be attached to the trough portion of the nozzle block before it is positioned into the ladle, all before any steel is poured into the ladle. Or molten lead can be poured around the stopper after the stopper is firmly seated in the nozzle. The poured lead after it has solidified holds the stopper in position during transportation of the ladle, and gives the crew assurance that steel would not leak from the ladle when first poured therein.

The lead eliminates the skull problems in this manner: With the lead in the trough as described, the molten steel is poured into the ladle, usually to substantially fill the ladle. As soon as the molten steel comes in contact with the lead the lead melts. But the lead being heavier than steel remains in the trough 46. The lead does not readily mix with the steel, nor does it easily oxidize. The molten lead between the lower end of the stopper rod 26 and the nozzle prevents steel from solidifying in this same area. Thus there is no bond or locking between the stopper rod and the nozzle, and the stopper rod, even after a considerable time interval, can be readily lifted from the mechanism at the top of the ladle to initiate the pouring of the steel. Of course, the lead flows out with the first steel poured and a portion thereof remains in the first dish of the mold stool, and a portion is partially oxidized when it comes in contact with the atmosphere.

It is believed that the invention results in an improvement over existing pouring practices for the reason that the steel is prevented when first poured into the bottom pouring steel ladle from flowing down between the stopper head and the tunnel-shaped nozzle. It is believed that in conventional ladle practice it is the flowing down of the molten steel into the wedge-shaped trough which causes the steel to tend to solidify between the stopper head and the nozzle block, it being recognized that the steel is cross-sectionally very thin and has very little body or mass and is in contact with considerable cold wall area in flowing down into the narrow, gradually decreasing wedge-shaped space between the stopper head and the funnel-shaped nozzle opening. It is this most objectionable type of skull formatiton which is prevented by the invention.

This specification will not be burdened with descriptions of the difiiculties experienced in having to tap an open-hearth furnace too early or too late and with the resulting effects thereof on the conventional bottom pouring ladle, nor will any further explanations be made with respect to the advantages of the elimination or reduction of the formation of a skull in the ladle after the ladle has been filled with molten steel and before any bottom pouring is done. Suflice it to note here that the greatest time delay and therefore the greatest tendency to form a skull is when the ladle is first filled and before metal is bottom poured therefrom. This delay is occasioned by the time required to fill the ladle and the time required to move the ladle to mold pouring position. Of course, inasmuch as the first pour from the ladle removes the molten lead, subsequent pours must be made with reasonable promptness, but by this time all parts of the ladle have been heated up towards the temperatures of ously provides new molten steel, a washing action at the 4 nozzle, and additional heat so that additional pours made with reasonable promptness encounter no skull problems.

While in accord with the patent statutes certain specific embodiments of my inventon have been illustrated and described in detail, it is to be particularly understood that I am not to be limited thereto or thereby, but that the scope of my invention is defined in the appended claims.

I claim:

1. The combination in a steel pouring ladle having a bottom nozzle of refractory material with a funnel-shaped passage of a vertically movable stopper rod of refractory material positioned down in the funnel-shaped passage of the nozzle to stop off flow of molten steel through the nozzle, the diameter of the rod being greater than the smallest diameter of the passage but less than the largest diameter of the funnel-shaped passage so that a circular trough is provided by the nozzle around the lower end of the stopper rod when it is in stop position, and a body predominately of lead substantially in and substantially filling the circular trough to prevent the formation of a steel skull in the ladle adjacent the rod.

2. The combination in a steel pouring ladle having a bottom nozzle of refractory material with a funnelshaped passage of a vertically movable stopper rod of refractory material positioned down in the funnel-shaped passage of the nozzle to stop off flow of molten steel through the nozzle, the diameter of the rod being greater than the smallest diameter of the passage but less than the largest diameter of the funnel-shaped passage so that a circular trough is provided by the nozzle around the lower end of the stopper rod when it is in stop position, and a body of lead in the circular trough to prevent the formation of a steel skull in the ladle adjacent the rod.

3. The combination in a steel pouring ladle having a bottom nozzle with a funnel-shaped passage of a vertically movable stopper rod positioned down in the funnel-shaped passage of the nozzle to stop off flow of molten steel through the nozzle, the diameter of the rod being greater than the smallest diameter of the passage but less than the largest diameter of the funnel-shaped passage so that a circular trough is provided by the nozzle around the lower end of the stopper rod when it is in stop position, and a body of lead in the circular trough to prevent the formation of a steel skull in the ladle adjacent the rod.

4. In combination, a steel pouring ladle, a nozzle positioned in the bottom of the ladle, a vertically movable stopper rod extending down into sealing relation with the nozzle, and a body of low melting metal heavier than steel and positioned between the nozzle and the stopper rod immediately above the area of sealing relation between the nozzle and rod.

5. That method of preventing the formation of a skull in a bottom pouring steel carrying ladle which includes the steps of depositing a collar of lead around the stopper rod of the ladle just above the nozzle but in contact therewith when the rod is in sealing position, and thereafter filling the ladle with molten steel to melt the lead but to leave it positioned as a ring around the stopper rod in contact with the nozzle.

References Cited in the file of this patent UNITED STATES PATENTS 2,348,199 Freeman May 9., 1944