JP3500699B2 - Heating method of vacuum degassing tank - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention inserts a burner lance into a tank from a lance insertion port provided at the top of the tank, dissolves and removes the metal adhered in the vacuum degassing tank by the burner lance, and The present invention relates to an improvement in a heating method of a vacuum degassing tank that preheats and keeps heat.

[0002]

2. Description of the Related Art A vacuum degassing tank such as the RH method is not operated continuously, but is operated intermittently because it is used only for steel types requiring vacuum degassing treatment. Therefore, when a time interval with the pretreatment occurs, the temperature in the vacuum degassing tank is lowered, so the degassing tank is heated during non-operation.

This is to prevent the ingot from adhering to the inner wall by heating the refractory in the tank, to prevent spalling of the refractory, and to minimize the temperature drop of molten steel during the treatment. Has an aim. For heating in a vacuum degassing tank, a method is known in which a graphite electrode is inserted into the tank to conduct electricity, and the Joule heat is used to preheat or retain heat.

[0004] The graphite electrode has a problem in strength and is often broken and dropped during operation, which may mix into the molten steel to cause component separation and process troubles, and also to prevent graphite oxidation in a large amount. It is necessary to send the nitrogen gas in the tank into the tank, and it consumes expensive electric power.If there is a lot of metal adhered in the vacuum degassing tank, which is not economical, the adhered metal will fall into the molten steel. Since [C] was picked up by the molten steel and came out of [C], the metal was melted and removed by heating with a graphite electrode during non-operation. However, the metal other than the peripheral portion of the electrode cannot be removed, and the problem [C] pickup by melting the metal during degassing has been a problem.

In order to solve such a problem, Japanese Patent Laid-Open No. 58-
Japanese Patent No. 185704 discloses a technique of inserting a burner lance into a vacuum degassing tank such as RH to dissolve and remove the metal. That is, as shown in FIG. 7, a lance insertion opening 103 is provided on the top wall 102 of the vacuum degassing tank 101, and an opening / closing lid 104 is provided outside the lance insertion opening 103. The lid 104 is a burner lance
The opening 105 is opened when it is inserted into the tank, and is closed after it is taken out. As shown in FIG. 8, the center of the upper part is attached to the tip of the rotating member 106. The rotating member 106 has a rear end rotatably supported by a pin 108 on the front end of a pedestal 107 on the tank top wall 102 of the degassing tank 101 and an air cylinder 109 at the upper center.
It is rotatably connected with the tip of the piston rod of No. 1 and the pin 110, and the opening and closing operation is performed by moving the piston of the air cylinder 109 forward and backward. Air cylinder 109 is pin 111 on stand 107
It is rotatably supported by. 112 is a flexible tube.

After the opening / closing lid 104 is opened by the air cylinder 109 during non-operation, the electric motor 113 is rewound to lower the burner lance 105 along the elevating guide 114, and the burner lance 105 is inserted into the tank from the lance insertion opening 103. . When the tip of the burner lance 105 reaches the deposited metal 115, the oxygen gas supply pipe 11
By supplying oxygen gas from 6 and horizontally injecting oxygen from the injection nozzle, the adhered metal 115 is dissolved and removed.

When the work of removing the adhered metal 115 is completed, the burner lance 105 is taken out of the bath and stopped at a predetermined position, and is kept on standby until the next operation of removing the metal. The opening / closing lid 104 immediately closes the lance insertion opening 103 by taking out the burner lance 105 from the tank and immediately closing it by the air cylinder 109.
Also, Materials and Processes issued by the Iron and Steel Institute of Japan, Vol.7 (1994) −
241 The report entitled "Realization of RH multi-functional burner equipment" describes the prevention of metal adhesion in the RH degassing tank and the temperature compensation technology that enables temperature compensation regardless of steel grade, heating technology by de-carburization and molten steel. It has been reported that the heat can be raised. That is, as shown in FIG. 9, O ₂ and LNG (liquefied natural gas) are supplied to the burner lance 105 inserted in the vacuum degassing tank 101 to perform molten steel heating and refractory heating by the burner lance 105 under vacuum. The refractory is heated by the burner lance 105 under atmospheric pressure to prevent the adhesion of metal. The O ₂ by the burner lance 105 under vacuum
Is supplied to accelerate Al heating by top-blowing oxygen or promote decarburization by top-blowing oxygen.

[0008]

In the former means for removing metal by burner lance among the above-mentioned prior arts, the opening / closing operation of the lance insertion opening by the opening / closing lid and the subsequent insertion operation of the burner lance into the vacuum degassing tank are performed. is necessary. For this reason, it takes a long time to handle the lance, so that the burner lance cannot be used sufficiently in the interval between the pretreatment and the continuous degassing treatment in a short cycle. Therefore, the frequency of use of the burner lance tends to decrease, and the metal that adheres to the degassing tank grows, eventually closing the lance insertion port and making it difficult to use the burner lance. Met.

Further, in the latter multi-functional burner lance, during degassing treatment in a vacuum degassing tank, especially during decarburizing treatment, clogging due to adhesion of metal to the gas blowing port of the burner lance accompanying molten steel splash is apt to occur, If the gas injection port were blocked, it could lead to an explosion or other trouble, which is extremely dangerous. The present invention has been made in consideration of the above-mentioned circumstances, and after the vacuum degassing treatment of the molten steel in the vacuum degassing tank is completed, a burner lance is quickly inserted into the tank to start heating. It is an object of the present invention to provide a heating method for a vacuum degassing tank, which can prevent the metal from adhering to the gas blowing port of the burner lance.

[0010]

According to the present invention for achieving the above object, a burner lance is inserted into a tank through a lance insertion opening provided on a top wall of the tank , and the vacuum removal is performed by the burner lance. In the method of heating the vacuum degassing tank, which is designed to dissolve and remove the metal adhered in the gas tank and preheat and keep the temperature inside the tank, during the operation of vacuum degassing molten steel in the vacuum degassing tank, By making the burner lance stand by in a state of being faced in the pulling tank up to the vicinity of the lance insertion port, and blowing out an inert gas from the gas injection port of the burner lance at a linear velocity condition of 15 to 40 m / sec, A method for heating a vacuum degassing tank, characterized in that it prevents clogging due to adhesion of metal to the gas injection port due to splash of molten steel during operation.

Further, according to the present invention as set forth in claim 2, heating of the vacuum degassing tank according to claim 1 is characterized in that the burner lance is made to stand by in the lifting tank up to a lance insertion port within 2.0 m from the top of the tank. Is the way.

[0012]

In the present invention, since the burner lance is sealed by the sealing mechanism during the vacuum degassing operation, the burner lance can be pulled up to the vicinity of the lance insertion port and can be kept in a state of being faced in the tank. During operation, since it faces the vicinity of the lance insertion port and stands by, it is possible to immediately start the heating work by the burner lance at the time of non-operation after degassing.

In the burner lance, an inert gas is blown from a gas injection port during operation at a linear velocity condition of 15 to 40 m / sec. Therefore, even if molten steel splashes in the vacuum degassing tank, it invades into the gas injection port. It is possible to prevent gold from sticking and clogging. At a linear velocity of less than 15 m / sec, there is a possibility that the molten steel that has splashed may enter the gas injection port,
Further, even if the condition exceeds 40 m / sec, the effect does not change and it is wasted, so the linear velocity condition is set to 15 to 40 m / sec. Further, if the burner lance is made to stand by within 2.0 m above the lower surface of the tank top, the risk of metal sticking to the injection port of the burner lance increases, so it is preferable to wait at 2.0 m or below.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. When the present invention is applied to an RH type vacuum degassing apparatus, as shown in FIG. 1, a lance insertion port 2 penetrating the inside and the outside is provided in the central portion of the top wall 1a of the vacuum degassing tank 1, and the outside of the lance insertion port 2 is provided. A lance seal mechanism 3 is provided. The lance seal mechanism 3 hermetically seals the burner lance 4 when the burner lance 4 is inserted into the vacuum degassing tank 1 from the lance insertion port 2. In this way, the burner lance 4 is inserted into the vacuum degassing tank 1 from the lance insertion port 2 via the lance seal mechanism 3.
Are supported by a lance holder 6 attached to the lifting frame 5.

When the lance lift drive device 23 is driven, the lift frame 5 moves up and down along the lance lift guide 7, whereby the burner lance 2 is inserted into the vacuum degassing tank 1 from the lance insertion port 2 through the seal mechanism 3. It can be inserted and removed. A positioning guide 8 is provided below the lance lifting guide 7 to guide the burner lance 4 while aligning the position of the burner lance 4 with the center of the lance insertion opening 2.
Is provided.

The lance up-and-down guide 7 is fixedly supported at the tip of a horizontal support frame 9 arranged vertically.
Further, the rear end of the horizontal support frame 9 is rotatably supported between the operating position and the standby position by driving the lance turning drive device 24 about the vertical shaft 11 mounted on the upper part of the gantry 10 as a fulcrum. As shown in FIG. 2, a liquefied natural gas (LPG) supply pipe 12, an oxygen gas (O ₂ ) supply pipe 13, a water supply pipe 14 and a drain pipe 15 are connected to the burner lance 4 as shown in FIG. As shown in FIGS. 3 and 4, the burner lance 4 has an LPG channel 16 at the center and an oxygen channel 17 at the outside thereof.
Further, a water supply passage 18 and a drainage passage 19 having a double structure, which are communicated with each other at the tip of the lance, are formed on the outside thereof. LPG
The outlet of the channel 16 is provided with a single tubular LPG injection port 16a, and the outlet of the O ₂ channel 17 is provided with a narrowed O ₂ injection port 17a. As shown in FIG. 2, the LPG supply pipe 12 and the O ₂ supply pipe 13 can be switched to an inert gas such as Ar or N ₂ by using a switching valve (not shown) on the upstream side thereof. It has become. The cooling water supplied from the water supply pipe 14 is cooled through the water supply passage 18 and the drainage passage 19 formed in the burner lance 4 and then discharged to the drainage pipe 15.

Further, a pilot burner is provided in the LPG passage 16.
29 is inserted so that its tip end faces the injection port 16a. As shown in FIG. 5, the pilot burner 29 has a nozzle 32 arranged around a spark plug 31 provided inside a pilot lance body 30. The LPG gas supplied from the inside of the pilot burner body 30 is discharged from the nozzle 32 to the spark plug.
The pilot burner 29 is ignited by the spark supplied to the periphery of the spark plug 31 at the tip portion of the spark plug 31, and the combustion flame is formed from the burner tip 33 to the vicinity of the injection port 16a of the burner lance 4.

Thus, it is possible to ignite the burner lance 4 by supplying combustion air and LPG gas from the burner lance 4. As shown in FIG. 6, the seal mechanism 3 includes a gland packing 25 mounted on a lower pipe seat 27 between the burner lance 4 and the lance insertion port 2 and an upper pipe seat that is expanded by gas pressure and is in close contact with the burner lance 4. It is a structure in which a hollow elastic body 26 such as rubber attached to 28 is used for complete sealing. That is, when the burner lance 4 is inserted into the tank from the lance insertion port 2 via the seal mechanism 3, the hollow elastic body is
Release the gas pressure in 26 and insert it through the gland packing 25. When the burner lance 4 descends from the lower surface of the tank top wall 1a to a predetermined level of 2.0 m or less, the hollow elastic body 26 is pressurized with gas to expand and hermetically seal. In addition to the mechanical seal by the gland packing 25, the hollow elastic body 26 is sealed by gas pressurization, so that the hollow elastic body 26 can easily follow even if the burner lance 4 vibrates, and the vacuum degassing process can be performed. A perfect seal will be achieved during operation.

In the operation according to the present invention, the two immersion pipes 20 provided at the bottom of the vacuum degassing tank 1 are provided with molten steel 22 in a ladle 21.
During the operation of performing vacuum degassing by immersing the inside of the dipping tube 20 and blowing Ar gas into one dipping tube 20 and exposing the molten steel 22 in the ladle 21 to the vacuum in the vacuum degassing tank 1 according to the principle of the gas lift pump. ,
As shown in FIG. 1, the burner lance 4 is made to stand by in a state of being faced in the pulling tank up to the vicinity of the lance insertion port 2 within 2 m from the top wall 1a. At this time, it goes without saying that the burner lance 4 is cooled by flowing cooling water.

Then, the N ₂ gas from the LPG supply pipe 12 and the O ₂ supply pipe 13 is supplied from the gas injection port of the burner lance 4 at 15 to 20 m / m.
Even if the molten steel 22 splashes in the vacuum degassing tank 1 during the vacuum degassing operation by blowing under the linear velocity condition of 2 seconds, the LPG injection port 16a and the O ₂ injection port 17a provided at the tip of the burner lance 4 are introduced. It prevents jumping and depositing as bare metal. Since the burner lance 4 is inserted into the vacuum degassing tank 1 via the lance seal mechanism 3 during the degassing process while the vacuum degassing tank 1 is in a vacuum state, it is possible to prevent atmospheric air from leaking into the tank, so that the degree of vacuum is increased. There is no adverse effect.

In the present invention, when the vacuum degassing process in the vacuum degassing tank 1 is completed, the inside of the vacuum degassing tank is returned to the atmospheric pressure and the N ₂ gas supplied to the burner lance 4 is stopped. Continuing,
The ladle 21 containing the molten steel 22 is transported to the continuous casting plant in the next process. When the metal is adhered to the vacuum degassing tank 1, the burner immediately waits in the vicinity of the lance insertion port 2 provided on the top wall 1a of the vacuum degassing tank 1 so as to face the tank. The lance lifting drive device 23 is driven to lower the lance 4 to a required level in the tank.

When the lance lifting drive device 23 is driven, the lifting frame 5 is lowered along the lance lifting guide 7, so that the burner lance 4 supported by the lance holder 6 attached to the lifting frame 5 is lowered. When the lower end of the burner lance 4 reaches a required level position in the tank, the driving of the lance lifting drive device 23 is stopped. Next, LPG supply pipe 12
LPG and O ₂ gas are respectively supplied from the and O ₂ supply pipes 13, and after passing through the LPG channel 16 and the O ₂ channel 17, the LPG injected from the LPG injection port 17a of the burner lance 4 into the tank, O ₂
When the metal that adheres to the inside of the tank is heated by burning it with the O ₂ gas injected from the injection port 18a and the metal is melted, it flows downward and is removed. After the metal adhered in the vacuum degassing tank 1 is removed in this way, the interior of the vacuum degassing tank 1 is subsequently heated by the burner lance 4 to bring the tank to a required temperature in preparation for the next vacuum degassing process. Keep it warm.

In the RH degassing apparatus having a capacity of 180 t / minute, as shown in FIG. 1, a burner lance (maximum maximum) is inserted from a lance insertion port provided at the center of the top wall of the vacuum degassing tank through a sealing mechanism.
LPG amount 180 Nm ³ / hour, maximum O ₂ amount 940 Nm ³ / hour, combustion capacity 4
(00 × 10 ⁴ kcal / hour) is placed in the tank 1.0 m below the furnace top wall, and the LPG supply pipe and
Burner LPG by supplying N ₂ gas to each O ₂ supply pipe
The ultra low carbon steel was melted by decarburizing while injecting Ar gas from the injection port and the O ₂ injection port under the linear velocity condition of 15 to 40 m / sec.

Although the N ₂ gas was blown from the burner lance under the above conditions during the vacuum degassing process, the vacuum degree in the vacuum degassing tank during operation was 0.3 to 0.5 Torr.
The degassing process could be efficiently carried out. The degassing treatment time is 25 minutes, and ultra-low carbon steel can be melted in a short time. The reached [C] concentration of the molten steel is 10 ppm and the reached [H] concentration is 0.
It was 6 ppm.

After the degassing process, the gas injection port of the burner lance was inspected, but there was no metal adhesion due to splash. Therefore, according to the present invention, the burner lance can be made to stand by while facing the inside of the vacuum degassing tank during operation. Therefore, after the degassing process is completed, the N ₂ gas supplied to the burner lance is stopped and LPG and
When the supply of O ₂ gas is started, it is possible to immediately proceed to the work of melting and removing the metal adhered in the vacuum degassing tank, and the heating work for preheating or heat retention.

According to the present invention, the frequency of use of the burner lance can be increased from the conventional one time / day to eight times / day as compared with the conventional case where the burner lance is kept outside the tank. . According to the present invention, since the vacuum degassing treatment can be performed in a state where there is no adherent metal in the vacuum degassing tank and good heat retention, the life of the refractory in the vacuum degassing tank is 70
I was able to increase from 0 heat to 900 heat.

[0027]

As described above, according to the present invention, during the operation of the vacuum degassing process in the vacuum degassing tank, a burner lance is used to face the vicinity of the insertion port in the pulling tank. Inert gas from the gas injection port while waiting 15
It blows out at a linear velocity of ~ 40 m / sec. Therefore, it is possible to prevent blockage due to adhesion of metal to the gas injection port due to splash of molten steel during operation.

As a result, after the vacuum degassing process, the burner lance waiting in the tank near the lance insertion port can be immediately transferred to the heating work, and the frequency of use of the burner lance is improved. Also, since the vacuum degassing process can be performed in a state where there is no metal in the vacuum degassing tank and the heat retention is good, the efficiency of the vacuum degassing process can be improved and the life of the refractory in the tank can be extended. Can be achieved.

[Brief description of drawings]

FIG. 1 is a front view showing an apparatus according to an embodiment of the present invention.

FIG. 2 is a side view showing a burner lance according to the present invention.

FIG. 3 is a vertical cross-sectional view showing a burner lance tip portion according to the present invention.

FIG. 4 is a plan view showing an arrow AA of FIG.

FIG. 5 is a sectional view showing a pilot burner.

FIG. 6 is a sectional view showing a seal mechanism of a burner lance according to the present invention.

FIG. 7 is a side view showing a device according to a conventional example.

FIG. 8 is a side view showing an opening / closing lid structure of a lance insertion opening according to a conventional example.

FIG. 9 is a schematic side view showing an apparatus according to a conventional example.

[Explanation of symbols]

1 Vacuum degassing tank 2 Lance insertion port 3 Lance seal mechanism 4 Burner lance 5 Lifting frame 6 Lance holder 7 Lance lifting guide 8 Positioning guide 9 Horizontal support frame 10 Stand 11 Vertical shaft 12 LPG supply pipe 13 O ₂ Supply pipe 14 Water supply pipe 15 Drain pipe 16 LPG flow passage 17 O ₂ flow passage 18 Water supply passage 19 Drain passage 20 Dip pipe 21 Ladle 22 Molten steel 23 Lance lifting drive device 24 Lance swivel drive device 25 Gland packing 26 Hollow elastic body 27 Lower pipe seat 28 Upper pipe Seat 29 Pilot burner 30 Pilot burner body 31 Spark plug 32 Nozzle 33 Burner tip

Continuation of the front page (56) Reference JP-A-3-97807 (JP, A) JP-A-3-226515 (JP, A) JP-A-58-185704 (JP, A) Jitsukaihei 2-118746 (JP , U) (58) Fields investigated (Int.Cl. ⁷ , DB name) C21C 7/10

Claims (2)

(57) [Claims] 1. A burner lance is inserted into the tank from a lance insertion port provided on the top wall of the tank , and the burner lance dissolves and removes the metal adhered in the vacuum degassing tank, and preheats and keeps the temperature inside the tank. In the heating method of the vacuum degassing tank, the burner lance is exposed to the vicinity of the lance insertion port in the drawing tank during the operation of vacuum degassing molten steel in the vacuum degassing tank. In addition to making it stand by, the inert gas from the gas injection port of the burner lance is 15-40 m /
A method for heating a vacuum degassing tank, characterized in that by blowing out under a linear velocity condition of 2 seconds, blockage due to adhesion of metal to the gas injection port due to molten steel splash during operation is prevented. 2. The method for heating a vacuum degassing tank according to claim 1, wherein the burner lance is held in the drawing tank up to the vicinity of the lance insertion port within 2.0 m from the top of the tank.