JPH01195239A - Method and apparatus for heating in vacuum degassing vessel - Google Patents

Abstract

PURPOSE:To prevent sticking of metal by arranging plural pieces of gas combustion burners in a vessel, adjusting the positions of the burners, gas volume and gas injecting velocity, controlling oxygen for combustion and executing heating of the wall surface and melting of the metal at optional position in the vessel. CONSTITUTION:A lance 11 arranging plural pieces of the burners 12 is inserted as movable to vertical direction in the vacuum degassing vessel. A supplying pipe 15 for fuel gas and a supplying pipe 16 of air or oxygen for combustion are arranged in inside of the lance 11 and both are pre-mixed and injected at the parts of the burners 12. Then, gas quantity and gas injecting velocity are adjusted with an adjusting device 20, to control shape of flame 13. Further, by adjusting the air (or oxygen) ratio for combustion, the oxygen for combustion, which is less than the theoretical necessary quantity, is supplied to the burner 12, the combustion is continued while holding in the vessel under reducing atmosphere. By this method, oxidation of the stuck metal in the vessel is not developed and protection of the refractory and fluidity of melted metal are secured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vacuum degassing method and an apparatus thereof, and is particularly applicable to secondary refining of steel, particularly in a degassing tank of a vacuum degassing apparatus such as RH, DH, VOD, etc. It concerns the prevention of metal adhesion during scouring or non-scouring, and the removal technology by melting the metal.

[Conventional technology] FIG. 3 shows a conventional RH degassing tank as an example.

It is well known that the RH degassing tank is composed of a middle tank 1, a lower tank 2, a dipping tube 3, a top cover 4, a vacuum exhaust port 5, and a ferroalloy input port 6.

Secondary refining of the molten steel, especially removal of H and C10 from the steel, is carried out by immersing the degassing tank immersion tube 3 into the molten steel filled in a ladle (not shown), and blowing circulating gas into one side of the immersion tube 3. The molten steel in the ladle is degassed from the vacuum exhaust port 5 using a vacuum device (not shown) to reduce the tank internal pressure to about 0.5 Torr or less, and the molten steel in the ladle is removed from the lower tank 2 of the degassing tank. While circulating,
In addition, the molten steel bath surface in the lower tank 2 is stirred and disturbed to promote decarburization, deoxidation, and dehydrogenation reactions.

-M] and C10 are applied to high-grade steels, and the process is carried out while controlling the treatment contents and treatment time depending on the steel type. However, since the inside of the tank is vacuum, especially during rimmed treatment, The molten steel will be in a state of scattering or forming.

This scattered molten steel and the like will adhere to the refractory surface of the wall if the temperature of the refractory on the tank wall is lower than the solidification temperature of the molten steel. This amount varies depending on the molten steel temperature and wall surface temperature, but it is approximately 3~lo
kg/l (molten steel heat size), so if the steel type and composition of the next charge are not the same, for example, after refining general thick material (C = 0.18%), extremely low carbon material (C = 0.18%) is used.
If the scouring (30 ppm) continues, the deposited metal of the previous charge may be melted and mixed into the molten steel during the next charge treatment, and the C accuracy of the ultra-low carbon material will be significantly worse. Therefore, the processing time becomes longer and the temperature of the molten steel decreases.
This also makes it impossible to ensure the continuous casting temperature.

[Problem to be Solved by the Invention 1] Against this background, an electrode heating device having a carbon electrode 7 is installed in the degassing tank as shown in FIG. The surface temperature of the electrode 7 is maintained at about 2300°C by resistance heating in the tank through an electric current, and the radiant heat is used to heat the tank wall to a temperature higher than the solidification temperature of the molten steel. 8 Prevents steel adhesion or dissolves adhering base metal. Although the above-mentioned problems are aimed at being solved in this way, the following problems still remain.

(1) From the viewpoint of the insertion of the electrode into the tank and the power supply method, one electrode 7 is installed in the center of the tank.
It is insufficient to raise the temperature of the entire surface of the tank wall to the solidification temperature of the steel. In particular, the deposited metal 10, 10a is formed on the top cover and exhaust port of the tank, making it impossible to fundamentally solve the problem.

(2) Before the electrode reaches the end of its life due to consumption or oxidation, it is broken due to falling metal from the top cover or a defect in the electrode support (crimping) mechanism, which increases the unit consumption of the electrode.

(3) Since the broken electrode remains at the bottom of the tank, the C accuracy is particularly deteriorated in the current charge if processing is in progress, and in the next charge if non-processing is in progress.

(4) It takes time to replace or change the electrodes, and degassing cannot be performed during that time, which hinders a series of manufacturing processes from converter blowing to continuous casting. Therefore, even though the number of high-grade 'M' types is increasing, the processing time is reduced and the operating rate is lowered.

(5) During non-processing, it is necessary to seal N2 into the tank to prevent electrode consumption, and a device for this purpose is required.

(6) Electric heating requires approximately three times as much heating cost as heating by burning gas or fuel, and the equipment cost is also more than ten times as much.

The present invention attempts to solve the various problems mentioned above.

For this purpose, JP-A-62-1814 and JP-A-58-18
As shown in No. 5704 or Figure 3, an attempt was also made to heat the inside of the tank by inserting a simple coke oven gas (hereinafter referred to as C gas) burner 8.9 through the immersion tube 3 or ferroalloy inlet 6. However, the heat of combustion does not reach the entire area of the tank, or the combustion air oxidizes the metal deposited inside the tank and causes Fe.
It was not only difficult to flow, but also had drawbacks such as significant damage to wall refractories, so it was not put into practical use.

[Means for solving the problem] To solve the problem of the heating technology in the tank using electrodes, the burner υ-end thermal power type using gas or liquid fuel was used, although it had been used only on a trial basis and did not reach practical use. We determined that this was the best solution, and put it into practical use and developed it.

The main points of focus for achieving practical application are as follows.

(a) A plurality of burners are provided in the degassing tank.

The burner is installed in the tank so that it can be inserted and removed. Also, the burner vibe should be made of a material that will not be damaged by the heat of flames or molten steel, or should be coated with such a material.

(b) Combustion is performed at a low oxygen ratio and controlled so that excess oxygen does not exist in the tank to prevent oxidation of the deposited metal. This ensures the protection of the refractory and the fluidity of the molten metal.

Based on the above points of view, we specifically took the following technical measures. That is, in the method of the present invention, a plurality of gas combustion burners are placed in a vacuum degassing tank, and the position of the burners in the tank, the amount of gas, and the gas ejection speed are adjusted to adjust the shape of the flame. It is characterized by supplying a smaller amount of combustion oxygen than the theoretically required amount to the tank, and continuing combustion while maintaining the inside of the tank in a reducing atmosphere.

A device embodying this invention is a vacuum degassing tank, in which:
A device in which a lance that penetrates the top cover is suspended vertically into the tank, a plurality of burners distributed in the height direction are attached to the lance, and the amount of fuel and combustion air for each of the burners is controlled. A vacuum degassing tank heating method and apparatus or a vacuum degassing tank characterized in that a plurality of burners penetrating the side wall face the tank so as to be able to move forward and backward, and each burner has a fuel amount. and a device for heating a vacuum degassing tank, characterized in that a device for controlling the amount of oxygen for combustion is provided.

〔Example〕

FIG. 1 and FIG. 2 show an embodiment of the present invention.

In the embodiment shown in FIG. 1, a plurality of burner lances 11 are provided in the tank so as to be movable up and down from above (the lance lifting device is not shown). This lance 11 is water-cooled. This lance 11
are provided with burners 12 distributed in the height direction. Lance 1
A fuel supply pipe 15 that supplies gas to the inside of 1 and an air supply pipe (or oxygen supply pipe) that supplies combustion air or oxygen
Preferably, the gas and combustion air or oxygen are premixed in the burner section and then injected. Oxygen has an advantage over air in that it produces less exhaust gas, and because the gas burns faster, the flame becomes shorter and hotter, and the heat transfer effect by radiation is greater.

During combustion, the inside of the tank is kept well above the ignition temperature, so the injected premixed gas immediately forms a flame. The size and position of this flame are determined by the amount and speed of injection from the burner. Therefore, an adjustment device is provided to adjust these two elements. Also adjusts the combustion air (or oxygen) ratio. An adjustment device 20 is provided for these adjustments.

The specific embodiment of FIG. 1 is as follows.

A water-cooled lance 11 with a refractory coating on the surface was inserted into an RH degassing tank with a tank inner diameter of 2500 mmψ and a tank height of 9000 mm, and 12 premix burners 12 were installed in this lance 11.
C gas 2.0 Nrn'/min from each burner and combustion air ratio 0.8, that is, air amount 4.0 N m''/min
/min (enrichment rate: 50%), premixed, and ejected into the tank at a burner ejection speed of 30 m/s. At this time, the combustion flame 13 has a length of 500 to 700 mm and forms a flame with a combustion temperature of 2200°C. After continuing this combustion for 10 minutes,
The temperature of the refractory surface of the tank wall rose to 1650℃, and
It was possible to completely dissolve 700 kg of adhered metal.

Note that the conditions for ejection from the burner vary greatly depending on the scale of the degassing device.

Also, unlike the case of electrode heating, although there is the disadvantage of flame formation due to combustion under vacuum, the internal pressure of the tank is 1oOT.
orr or more, and since there is necessary time for handling the ladle and repairing the tank between treatments, the heating in the tank is fully possible.

The heating unit in the above example is about 11 in the case of electrode heating.
5 to 1/1O. Furthermore, as with electrode heating, the tank can be maintained in a reducing atmosphere, which prevents oxidation of the deposited metal and also keeps the flame short. heating method).

That is, with this one technique, many of the problems caused by electrode heating as described above can be solved at once.

FIG. 2 shows another embodiment of the present invention, in which from the side of the tank,
By inserting multiple burners so that they can move forward and backward, the flame of the nearby burners can be adjusted for each part of the tank.
It is effective for melting metal and heating walls depending on the condition of each part.

[Effect of the invention] C gas 2. ONrrr'/min, air 4Nrr
? /min 12 burners are installed in the degassing tank, and 10
As a result of heating in the tank for minutes, the wall temperature was 1600℃~169℃.
Since the temperature could be raised to 0° C. and 700 kg of adhered metal could be melted, the cost required for heating the tank and melting the metal was approximately 10 yen/l (molten WA).

From the above, the tank burner heating technology has the following advantages (effects) compared to the electrode heating method.

(b) The formation position of the burner can be changed freely by controlling the insertion mold of the burner lance and the amount and ejection speed of fuel gas and combustion air. Can melt gold.

(b) Burner combustion should be carried out at an air ratio of 1.0 or less, preferably 0.
．． Since the temperature is 9 or below, oxidation of the metal deposited in the tank does not occur.
The desired purpose is achieved without removing the bare metal or damaging the refractories.

(c) By heating the tank for each charge to be processed, the component accuracy, especially the C accuracy, is improved without being affected by the previous charge. Therefore, the degassing treatment time for each steel type is stable, the molten steel temperature can be easily controlled, and the process from converter to continuous casting can be managed consistently.'! The cost of the entire A steel process can be reduced.

(d) There is no need to maintain a reducing atmosphere inside the tank during non-processing.

(E) The equipment cost is less than 1/1 O of the electrode heating method.

Moreover, the operating cost is less than 1/I.

(f) Avoid the risk of explosion inside and outside the tank even if there is an excess of 1000-C gas by operating the exhaust system or installing another exhaust gas treatment device during combustion in the burner. be able to.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional views of a degassing tank according to an embodiment of the present invention, and FIG. 3 is a longitudinal sectional view of a conventional degassing tank. l...Middle tank, 2...Lower tank, 3...Immersion pipe, 4
...Top cover, 5.--Vacuum exhaust port, 6.--Ferroalloy input port, 7.--Heating electrode in the tank, 8.9.--Experimental burner, 10.--Basic metal deposited in the tank, 11... Lance, 1
2.14... Burner, 13... Flame, 15... Fuel (gas) supply pipe, 16... Air (oxygen) supply pipe.

Claims (1)

[Claims] 1. In a vacuum degassing method in which C, H, O, etc. in the molten steel are removed by suctioning and circulating molten steel in a ladle under vacuum, a plurality of gas combustion burners are installed in a vacuum degassing tank. The shape of the flame is adjusted by adjusting the position of the burner in the tank, the amount of gas, and the gas jetting speed, and the burner is supplied with a smaller amount of combustion oxygen than the theoretically required amount. A heating method in a degassing tank characterized by continuing combustion while maintaining a reducing atmosphere. 2. In a vacuum degassing tank, a lance that penetrates the top cover is suspended into the tank so as to be able to move vertically, and a plurality of burners distributed in the height direction are attached to the lance, and the amount of fuel and combustion of each of the burners is adjusted. A heating device for a vacuum degassing tank, characterized in that it is equipped with a device for controlling the amount of oxygen used. 3. A vacuum degassing tank, characterized in that a plurality of burners penetrating the side wall face the tank so as to be able to move forward and backward, and a device is provided for controlling the amount of fuel and the amount of oxygen for combustion in each of the burners. Heating device inside the degassing tank.