US3327531A

US3327531A - Automatic expendable thermocouple lance

Info

Publication number: US3327531A
Application number: US416994A
Authority: US
Inventors: Ronald J Fradeneck
Original assignee: Bethlehem Steel Corp
Current assignee: Bethlehem Steel Corp
Priority date: 1964-12-09
Filing date: 1964-12-09
Publication date: 1967-06-27
Anticipated expiration: 1984-06-27

Description

June 27, 1967 R. J. FRADENECK 3,327,531

AUTOMATIC EXPENDABLE. THERMOCOUPLE LANCE Filed Dec. 9, 1964 4 Sheets-Sheet l INVENTOR Rona/d J. Fraoeneck June 2'7, 1967 R. J. FRADENECK AUTOMATIC EXPENDABLE THERMOCOUPLE LANCE 4 Sheets-Sheet 2 Filed Dec. 9, 1964 INVENTOR Rona/0 J Fradeneck June 27, 1967 R. J. FRADENECK 3,327,531

AUTOMATIC EXPENDABLE THEHMOCOUPLE LANCE Filed Dec. 9, 1964 4 Sheets-Sheet 3 INVENTOR. Rona/0' J Fradenec/r June 27, 1967 R. J. FRADENECK AUTOMATIC EXPENDABLE THERMOCOUPLE LANCE p Q? A W 3 4 5 a w Q I in. M Z Z 6 5 T: l i 5 3? A? II M I i 1 w T "7 5 w M w m m United States Patent 3,327,531 AUTQMATIC EXPENDABLIE THERMOCOUPLE LANCE Ronald J. Fradeneclt, Bethlehem, Pa, assignor, by mesne assignments, to Bethlehem Steel Corporation, a corporation of Delaware Filed Dec. 9, 1964, Ser. No. 416,994 3 Claims. (Cl. 73-359) This invention in general relates to a process and apparatus for determining the temperature of a molten metal bath in a furnace, and in particular a process and apparatus for determining the temperature of a molten metal bath in a basic oxygen furnace.

Modern steelmaking techniques require that the temperature of the molten metal bath in a furnace be known accurately. This is particularly true of oxygen lance equipped open-hearth furnaces and basic oxygen furnaces.

Several temperature measuring instruments have been developed to obtain and record the temperatures prevailing in metallurgical furnaces. These include the expendable immersion thermocouple, the immersion radiation pyrometer and the optical pyrometer. All of these devices have been used in open-hearth practices where it is a simple matter to insert the temperature measuring instruments into the molten metal bath in the furnace or to sight into the furnaces through openings in the furnace.

It is not, however, a simple matter to determine the temperature of the steel bath in a basic oxygen furnace. The oxygen injection of the molten metal in an oxygen furnace produces a large volume of smoke and fumes which must be exhausted from the shop. It is, therefore, imperative that an exhaust hood be placed over the fur nace to rid the shop of the smoke and fumes. As a result, it is not readily possible to discern or sight upon the flame in the furnace upon which to base an approximation of the bath temperature as has been done in the old Bessemer converters. Many of the present day furnaces, particularly the basic oxygen furnaces, are computer controlled. As a result, a temperature measurement is taken as close to the finish of the melting as possible. To obtain a temperature measurement of the molten metal, it is present practice to discontinue the oxygen injection, raise the oxygen lance above the hood of the furnace, tilt the furnace and manually insert an immersion thermocouple or radiation pyrometer into the bath to obtain the temperature thereof. If the temperature measurement shows that the temperature of the molten metal must be corrected to obtain the proper tapping temperature, the furnace must be returned to its upright operating position, the oxygen lance must be lowered into the furnace and the oxygen injection resumed or corrective addition made to the molten bath. This sequence of operations is lengthy resulting in a longer than normal blowing time and a loss of heat by the molten metal bath. As a result, the temperature obtained is not the actual temperature of the bath when the furnace is returned to the upright position. Allowances must be made and the melting schedule altered to obtain the desired tap temperature.

It is the primary object of this invention to provide an apparatus for determining the temperature of the molten metal bath in a basic oxygen furnace.

It is a further object of this invention to provide an apparatus for determining the temperature of the molten metal bath in a basic oxygen furnace while the furnace is in an upright operating position.

Broadly, the present invention provides a downwardly extending elongated liquid-cooled tubular guide sleeve adapted to be inserted into the basic oxygen furnace through the hood atop the furnace while the furnace is in an upright position. The elongated liquid-cooled tubular guide sleeve must be inserted into the furnace a suflicient distance so that a temperature sensing device can be inserted into the molten metal bath. Adjacent the lower open end of the tubular guide sleeve and concentrically arranged therein, is a specially constructed tip adapted to make electrical contact with the temperature sensing device. Adjacent the upper end of the tubular guide sleeve and aligned therewith is a magazine and a thermocouple drive mechanism adapted to drive the temperature sensing device downwardly through the tubular guide sleeve into the molten metal bath in the furnace so as to obtain a temperature measurement thereof. Air and/or an inert gas is introduced into the upper end of the downwardly extending elongated tubular guide sleeve and flows outwardly through the opened lower end of the said tubular guide sleeve.

FIG. 1 is a cross-sectional view of a basic oxygen furnace with the temperature determining instrument in posi tion atop the hood.

FIG. 2 is a view in elevation of the loading mechanism.

FIG. 3 is an isometric view of the drive mechanism.

FIG. 4 is a top view through 44, FIG. 2, of the loading mechanism.

FIG. 5 is a cross-sectional view of the depending elon gated tubular guide sleeve and its attendant tip.

Referring now to the drawings, FIG. 1 shows the general means employed in the invention to obtain the temperature of the molten metal bath in a basic oxygen fur nace. The entire assembly as shown in phantom lines, is positioned above the hood 11 atop the basic oxygen furnace 12 and adjacent to the oxygen lance equipment 12a. When a temperature measurement is required, the assembly is lowered into the furnace as shown. The loading mechanism is contained within the thermocouple housing 13. A substantially vertical elongated liquid-cooled tubular guide sleeve 14 which may be approximately 60 feet long, with its lower extremity 17 open, is attached to and aligned with the lower portion of the thermocouple housing 13. A superstructure 15 is built atop the thermocouple housing 13. Means (not shown for raising and lowering the assembly are attached to the superstructure 15. The temperature sensing device used in the process is an expendable immersion thermocouple, shown generally at 16. The thermocouples extend downwardly through the depending elongated tubular guide sleeve 14 so that the lowermost thermocouple extends through the open lower extremity 17 of the said depending elongated tubular guide sleeve 14. It will be noted that the assembly is lowered into the furnace a suflicient distance so that the hot junction 18 of the lowermost expendable immersion thermocouple extends below the slag 19 and into the molten metal bath 26.

FIG. 2 shows the loading mechanism in the thermocouple 13 housing and the upper portion of the elongated depending tubular guide sleeve 14 which includes two concentrically arranged pipes 48a and 47 and baffle plates 48. The elongated tubular guide sleeve 14 is attached to the underside of the housing 13 so as to effect an air-tight seal between the aforesaid two members. The loading mechanism within the thermocouple housing 13 consists of a thermocouple magazine 22 mounted on a metallic superstructure 22a and a thermocouple drive mechanism shown generally at 21 and hereinafter described. The magazine 22 can accommodate any desired number of any expendable immersion thermocouples which are sensitive to temperature differentials.

Turning now to FIG. 5, the expendable immersion thermocouple consists of an elongated cardboard tube approximately 4 feet in length, having a pair of spaced thermocouple wires 57a and 58a joined at one end to form a temperature sensing element usually called the hot junction 18, and the opposite ends of the thremocouple wires 57a and 5811 joined to thermocouple compensated

wires

57 and 58, usually copper and one of its alloys which extend to the rear (upper) portion of the cardboard tube. The thermocouple wires are platinum, platinumrhodium having their joined ends 18 encased in a protective quartz covering 18b. The joined ends of the thermocouple wires extend beyond the lower end of the cardboard tube are fixed to the end of the cardboard tube by means of a refractory plug 180 which fits inside the cardboard tube. A cap 18a of suitable material such as steel is placed over the hot junction 18 to protect it prior to its insertion into the molten metal. The said

wires

57 and 53 extend through the wall of the cardboard tube, at its upper portion, and are formed in staple-

like fashion

69 and 70 on the outside of the outboard tube opposite each other so as to form wiping contacts which engage the connector rings of the guide sleeve tip hereinafter described.

Returning now to FIG. 2, the expendable immersion thermocouple are urged forwardly to the front of the magazine into the breech 23 by means of pushers attached to and activated by constant torque springs 24 coiled on spools 24a. Although I have shown two springs attached to each pusher, one spring can be used. Each spring exerts a constant force on the pushers 25, to urge the thermocouples forwardly into the breech of the magazine. Assuming that a thermocouple has been ejected from the breech 23 of the magazine 22, the pushers 25 are urged forwardly by the springs 24 to move another thermocouple into the breech 23. This operation can be repeated until the last thermocouple has been ejected from the breech 23 and the magazine 22 is empty. The pushers 25 are connected to a reloading mechanism by means of a resilient member 28 which preferably is a steel wire but may be of any suitable material, such as nylon. When the last thermocouple has been fed to the depending elongated tubular guide sleeve 14, the magazine 22, which is hinged to the housing 13 by the piano hinge 13a, is tilted forward for reloading. To reload the mazazine 22, the pushers 25 are returned to the loading position by turning the eccentric cam 29 in a counterclockwise direction so that the pivotally mounted spring-loaded pawl 30 engages ratchet 31. The spring 30a exters a force on the pawl 30 sufficient to prevent the disengagement of the pawl from the ratchet while the magazine is being loaded. Ratchet 31 is turned in a clockwise direction by a nut turner (not shown) until the steel wire 28 is coiled on the spool 32. The pawl 30 engages the ratchet 31 to prevent the pusher 25 from being returned to the unload position. After the magazine is fully loaded, it is returned to its position in housing 13. The eccentric cam 29 is moved in a clockwise direction causing the pawl to be disengaged from ratchet 31. The pusher 25 is thus released and is now in position to push the thermocouples forwardly to the breech end of the magazine.

The expendable immersion thermocouples are urged downwardly, one at a time, until the lowermost immersion thermocouple extends beyond the open lower end of the depending elongated tubular guide sleeve 14, a suflicient distance so that the hot junction of the expendable immersion thermocouple will be inserted into the molten metal bath below the slag layer when the assembly is lowered into the furnace. FIG. 3 shows the drive mechanism used to urge the expendable immersion thermocouples downwardly from the breech 23 into the depending elongated tubular guide sleeve 14.

The drive mechanism comprises an endless chain 41 passing over two sprocket wheels driven by any wellknown means. Attached thereto, and activated by the chain 41 is a paddle 49. The paddle is connected to the chain 41 by a bracket arrangement shown generally at 40a, and is so designed that it will fit within, and pass through, the breech 23 of the magazine 22. Although I have shown only one paddle attached to the endless chain, it is possible to use two or more paddles to eject the expendable immersion thermocouples from the breech 23 in the magazine 22 and force their passage downwardly through the depending elongated tubular guide sleeve 14. As the paddle enters the top of the breech 23, it engages the upper portion 1dr; of an expendable immersion thermocouple which is positioned in the breech 23, forcing the said enpendable immersion thremocouple downwardly. The expendable immersion thermocouple is pushed downwardly from the breech 23 into the depending elongated tubular guide sleeve 14. The paddle arm 40]) is springloaded by tension spring 46. As the paddle reaches the lower portion of the breech, the cam follower 44 engages cam 45 forcing the paddle arm 45b and paddle 40 to move sidewardly on

guide rods

46a and 46b so as to clear the upper portion of the expendable immersion thermocouple. The paddle 4d proceeds around the lower sprocket for at which point the cam 45 terminates. The spring 46 exerts a force upon paddle arm 40b sufficient to return the said paddle arm 4% and the paddle 40 to the operating position on the endless chain.

Assuming the depending elongated tubular guide sleeve is empty, the expendable immersion thermocouples are ejected from the breech into the depending elongated tubular guide sleeve one at a time in such a manner that the tip of one thermocouple abuts the rear of the next lower thermocouple. As many thermocouples are ejected from the breech into the depending elongated tubular guide sleeve as are required to push the hot junction of the lowermost thermocouple a sufficient distance beyond the lower open end of the depending elongated tubular guide sleeve so that the said hot junction will extend below the surface of the molten metal bath when the assembly is lowered into the furnace.

As shown in FIG. 5, the depending elongated tubular guide sleeve 14 comprises two concentrically arranged pipes 48a and 47. The annular space between the outer pipes 431: and inner pipe 47 is divided into two equal semicircular chambers by baffle-plates 4-3 which extend substantially, but not all the way, to the lower end of the depending elongated tubular guide sleeve. Water is introduced at the rear of the one chamber by an inlet pipe 49, FIG. 2. The water flows to the tip end of the depending elongated tubular guide sleeve, around the forward edge of the battle-plates 48 and then backwardly to the outlet pipe 50, FIG. 2, of the second chamber.

The inner pipe 47 provides a passageway for the expendable immersion thermocouples as they move downwardly to the molten metal, and is a retaining member for the retarding devices shown generally at 47a. The said retarding devices are designed to have sufficient frictional retarding force to prevent the expendable immersion thermocouples from falling through the elongated depending tubular guide sleeve of their own weight, but not sufficient retarding force to prevent the passage of the expendable immersion thermocouples through the depending elon gated tubular guide sleeve when urged downwardly by the drive mechanism. Air and/or gas is introduced into the uppermost part of the inner tube 47 and flows downwardly through the said tube and is emitted through the open end of the depending elongated tubular guide sleeve at its tip. The retarding devices are aligned concentrically within the inner pipe 47 and are aligned axially one atop the other substantially the length of the inner pipe 47. The retarding device 47a is a thin-walled tubular member 51 having a flared end 52 to receive the lower edge 51a of the next higher retarding device. The walls of the tube 51 are provided with three equi-spaced holes 53, through which springs 54 extend inwardly to engage the sides of the expendable immersion thermocouple tubes. The springs 54 are riveted to the tubular wall of the retarding device as shown at 55. The equi-spaced holes 53 also allow the passage of the air and/ or inert gas fed into the elongated depending tubular guide sleeve.

Arranged concentrically within the inner pipe 47 at its lower end is a special tip shown generally at 56, in FIG. 5. The tip 56 is adapted to electrically connect the

wires

57 and 58, shown in exaggerated size for the sake of clarity, with an outside recording device for the purpose of recording the temperature measurements made of the molten metal bath. The tip 56 comprises a steel housing 59 and, arranged concentrically within the housing 59, are ring guides 60 and 61, which are fluted to aid in guiding the expendable immersion thercomouple and to allow the air and/or gas to flow through the lower end of the elongated depending tubular guide sleeve, retarding

devices

62 and 63, and insulating sleeves 64. Within the insulating sleeves are two

ring connectors

65 and 66 and their attendant connector springs 67 and 68. The ring guides 60 and 61 and the

retarding devices

62 and 63 may be made of any suitable material, such as steel. The connector rings 65 and 66 and their

attendant springs

67 and 68 may be made of any suitable material, such as copper and one of its alloys.

The expendable immersion thermocouple wires 57:? and 58a are connected to the

wires

57 and 58 which extend rearwardly axially within the expendable immersion thermocouple tube. The

Wires

57 and 58 are brought to the outside surface at the rear (upper) portion of the immersion thermocouple tube in a staple-like fashion shown at 69 and 70.

As the expendable immersion thermocouple tube is forced downwardly, it is guided into the tip 56 by the inside surface of ring guide 60 and is kept aligned by the ring guide 61 as it passes out of the open end of the depending elongated tubular guide sleeve. The

frictional retarding devices

62 and 63 prevent the expendable immersion thermocouple from falling through the tip 56 of its own weight. The staple-

like portions

69 and 70 of the

wires

57 and 58 make contact with the

springs

67 and 68 of the connector rings 65 and 66. The connector rings 65 and 66 are connected to an outside recording device by means of a paired thermocouple cable 73 such as Honeywells MegopaK. The paired wires of the cable are connected to the connector rings 65 and 66 by soldered

contacts

71 and 72.

When a temperature measurement is required, the oxygen injection of the molten metal bath is interrupted and the depending elongated tubular guide sleeve is lowered by means of a wire rope and drum assembly through the opening in the hood atop the furnace a suflicient distance so that the hot junction of the expendable immersion thermocouple is inserted into the molten metal bath in the furnace below the slag layer. The cap 18a which covers the hot junction of the expendable immersion thermocouple protects the hot junction from damage as it is urged downwardly through the slag layer into the molten bath. The cap is made of a suitable metal such as steel so that it will melt when exposed to the heat of the molten metal bath and will protect the hot junction from damage. A temperature measurement is then obtained. If for some reason several temperature measurements are required, the operator of the furnace can activate the drive mechanism in the thermocouple housing to insert an expendable immersion thermocouple into the depending elongated tubular guide sleeve from the breech of the magazine. As the expendable immersion thermocouple is driven into the top of the depending elongated tubular guide sleeve from the magazine, the lowermost thermocouple is ejected into the furnace. The operation may be repeated as often as required so long as there are thermocouples in the magazine. If the tip is inadvertently lowered into the slag layer, the air and/or gas flowing downwardly in the inner tube Will prevent the slag from entering the open end of the depending elongated tubular guide sleeve.

Although I have described this invention as pertaining to a basic oxygen furnace, it is within the scope of this invention to determine the temperature of a molten metal bath in other metallurgical furnaces in use today.

I claim:

1. Apparatus for determining the temperature of a molten metal bath comprising a housing for containing a plurality of elongated tubular thermocouple elements, an elongated, open-ended, tubular guide sleeve depending from and secured to said housing, frictional retaining means within said guide sleeve for engaging and holding said thermocouple elements located within said sleeve, a pair of electrical contacts at the lower end of said guide sleeve, and means for ejecting said thermocouple elements from said housing into said guide sleeve and for positioning the lowermost of the said thermocouple elements with its lower end projecting below the bottom of said guide sleeve and its upper end in electrical contact with said pair of contacts.

2. Apparatus as claimed in claim 1 in which the tip of the elongated, open-ended, tubular guide sleeve contains a pair of longitudinally spaced ring guides to guide the elongated, tubular thermocouple elements therethrough, and means associated with each of the ring guides to frictionally retard the passage of the thermocouple elements through the tip, and in which each of the pair of electrical contacts is secured to one of a pair of longitudinally spaced insulating members Within the sleeve.

3. Apparatus as claimed in claim 2 in which the pair of electrical contacts comprise a pair of connector springs to make contact with the staple-like portions of the thermocouple wires extending along the outside surface of the thermocouple as it is held in the tip, each of the pair of connector springs being secured to one of a pair of ring connectors, said ring connectors being connected by suitable means to an outside recording device.

References Cited UNITED STATES PATENTS 2,348,644 5/ 1944 Preziosi 22 l239 2,993,944 7/1961 Silver 136-234 3,038,951 6/1962 Mead l36235 LOUIS R. PRINCE, Primary Examiner. N. B. SIEGEL, Assistant Examiner.

Claims

1. APPARATUS FOR DETERMINING THE TEMPERATURE OF A MOLTEN METAL BATH COMPRISING A HOUSING FOR CONTAINING A PLURALITY OF ELONGATED TUBULAR THERMOCOUPLE ELEMENTS, AN ELONGATED, OPEN-ENDED, TUBULAR GUIDE SLEEVE DEPENDING FROM AND SECURED TO SAID HOUSING, FRICTIONAL RETAINING MEANS WITHIN SAID GUIDE SLEEVE FOR ENGAGING AND HOLDING SAID THERMOCOUPLE ELEMENTS LOCATED WITHIN SAID SLEEVE, A PAIR OF ELECTRICAL CONTACTS AT THE LOWER END OF SAID GUIDE SLEEVE, AND MEANS FOR EJECTING SAID THERMOCOUPLE ELEMENTS FROM SAID HOUSING INTO SAID GUIDE SLEEVE AND FOR POSITIONING THE LOWERMOST OF THE SAID THERMOCOUPLE ELEMENTS WITH ITS LOWER END PROJECTING BELOW THE BOTTOM SAID GUIDE SLEEVE AND ITS UPPER END IN ELECTRICAL CONTACT WITH SAID PAIR OF CONTACTS.