JPS6244520A - Method for maintaining aperature of tuyere - Google Patents

Abstract

PURPOSE:To check opening degree of tuyere aperture to always maintain the fixed degree and to prevent tuyere clogging, by connecting an oxygen supplying pipe and a gas supplying pipe for checking tuyere opening degree to a flux supplying pipe of an RH type vacuum degassing vessel. CONSTITUTION:The tuyere 5 is provided lower than molten steel level in the RH vacuum degassing vessel 1 and connected to a flux supplying pipe 6, the oxygen supplying pipe 10 and a supplying pipe 12 of a tuyere opening ratio checking gas 11 through cut-off valves 13, 14, 15 respectively. Preliminary refining is performed together with degassing refining by supplying flux for refining such as desulfurization, dephosphorization of molten steel from a tuyere 5 by a carrier gas 8. In this case, previously the valves 13, 14 are closed and the valve 15 is opened, and gas for checking tuyere opening ratio is supplied to the tuyere 5. If opening ratio is decreased by solidification and sticking of metal at the tuyere 5, since pressure at tuyere is raised, the value is measured by a pressure gauge 16, if the value is attained to >= a fixed value, the valve 15 is closed, 14 is opened to supply oxygen to the tuyere 5. Metal stuck to tuyere is melted and removed to raise opening ratio of tuyere to a prescribed value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for maintaining the opening of a tuyere, in particular, a method for controlling the tendency of the tuyere to become clogged when powder-containing gas is blown into molten steel from the tuyere. The present invention relates to a method for maintaining the tuyere porosity of the tuyere.

[Prior art]

Conventionally, a vacuum degassing method for molten steel in which oxygen is blown into the molten steel in a tank during heating during vacuum treatment is known from Japanese Patent Publication No. 53-81416 ``Vacuum Degassing Method for Molten Steel''. Here, a nozzle dedicated to oxygen blowing provided below the bath surface is shown. However, this method does not mention a nozzle for blowing refined flux.

In addition, in order to directly inject various refining fluxes (e.g., desulfurization agents, dephosphorization agents, composition adjustment agents, etc.) into the molten steel, the fluxes are injected directly into the molten steel through a special flags nozzle installed below the steel bath surface in the lower part of the vacuum degassing tank. There is a device that blows active gas as a carrier gas. For example, at the 109th lecture conference of the Japan Iron and Steel Institute, a method for desulfurization by injecting flux through a nozzle using an inert gas as a carrier gas was presented under the title "Flux in rRH tank, molten steel refining by injection."

However, when this dedicated nozzle is used, the nozzle often becomes clogged during non-blowing, and it becomes necessary to flow oxygen to open the nozzle, making the work complicated.

[Problem to be solved by the invention]

In this invention, when a powder mixture gas is directly blown into molten steel through the slats, if the powder blowing tuyere continues to blow powder, the solidified molten steel will adhere to the powder blowing tuyere and the pore opening will be reduced. The objective is to prevent this from decreasing, maintain a predetermined pore opening degree, and enable smooth powder injection.

[Means for solving problems]

This invention detects the pressure just before the tuyere of the blown gas conduit when blowing powder-containing gas into molten steel from the tuyere, and automatically automatically detects the pressure in front of the tuyere of the tuyere when the pressure exceeds the set pressure due to tuyere blockage. This method is characterized by blowing in oxygen gas to dissolve the clogging metal.

An example of this invention will be explained in detail based on FIG.

Figure 1 shows an example of an RH vacuum tank, where 1 is a vacuum degassing tank, 2 is an exhaust port, 3 is molten steel, 4 is a molten steel ladle, 5 is a powder desulfurization blowing tuyere, and 6 is a powder Body desulfurization agent supply piping, 7 is powder supply device, 8 is carrier body, 9 is oxygen, 10 is oxygen supply piping, 11 is gas for opening degree check, 12 is supply piping, 13, 14, 15 are shut off, respectively Valve 16 is a pressure measuring device.

This invention provides that when powder is directly blown into the molten steel 3 from the powder injection tuyere 5 from the powder supply device 7 via the powder supply piping 6 during vacuum degassing treatment, the powder injection tuyere It maintains a predetermined pore opening degree of 5 and enables smooth powder injection.

Here, the pore size measurement of the cutoff valve A1 is performed during non-vacuum processing.
3. Close the shutoff valve B14, open the shutoff valve C15, and flow the nozzle opening degree checking gas 11 through the supply pipe 12 to the powder injection tuyere 5. By measuring the pressure in front of the tuyere at this time with the pressure measuring device 16, the degree of pore opening of the tuyere is determined to be 1lllJ.
to be determined. The degree of pore opening of the lining can be calculated from this pressure by first investigating the relationship between the degree of pore opening and pressure as shown in Figure 2, or by calculating from the pressure loss of the piping and lining. As a result of the measurement in the above procedure, when the degree of pore opening is below a certain predetermined degree, oxygen is flowed to dissolve the metal blocking the tuyere and maintain the degree of pore size. Now, to open the tuyeres to allow oxygen to flow, close the cutoff valves A13, C, and 15, open the cutoff valve B14, and allow oxygen 9 to flow into the powder blowing tuyere 5, thereby causing the powder to adhere. The base metal etc. melts and increases the degree of porosity. In addition, during normal vacuum processing or powder injection, the shutoff valve A13 is opened, and the shutoff valve B14. The shutoff valve C15 is closed, and the carrier gas 8 is kept flowing through the powder injection tuyere 5 at all times.

Note that the pore opening degree set in the present invention is usually required to be about 70% or more, and when it is less than about 70%, the blowing of the powder carrier gas becomes considerably difficult due to increased tuyere resistance, and the operation becomes unstable.

To describe a preferred mode of use of the present invention, the timing of blowing oxygen to melt the metal around the first bird is preferably immediately after the vacuum treatment when the temperature inside the tank is highest and the metal can easily be melted, or It's not something you do. Regarding the oxygen flow rate, the higher the flow rate, the more effective it is, but if the flow rate is too high, it will have a negative effect on the opposing refractories, so it is necessary to set the flow rate appropriately based on the metal melting situation.

Further, although the effects of the present invention have been described in an example in which a cutoff valve and a supply pipe for measuring the pore size are installed, it is also possible to replace the gas for measuring the pore size with a carrier gas. In this case, an extra gas is required for the volume of the powder supply device, and it takes time to stabilize the pressure in front of the tuyere, so it is preferable to use a separate system when quick measurement is desired.

〔Example〕

As an example of the present invention, an example of an RH vacuum chamber for 250T treatment will be shown.

Example 1 Blow tuyere diameter: 18φ (made of SUS) Peracid amount: 200 N Bo/H for 30 seconds Acidification period Peracid starts 30 seconds after the end of vacuum treatment Tuyere opening degree Before 60% After 100% This As a result, almost 100% open pores were obtained, and vacuum degassing operation could be started smoothly.

Example 2 Blowing tuyere diameter 18φ (made of SUS) Peracid jl 20ON resistance/H for 60 seconds Acidification period When the pore opening degree is 70% or less, peracid starts 30 seconds after the end of the vacuum treatment Tuyere opening degree As shown in Figure 3, the opening work was carried out several times and the tuyere was always in a healthy state.

〔Effect of the invention〕

The present invention can always maintain a healthy tuyere porosity by blowing oxygen into the tuyere that blows powder into a vacuum chamber when the tuyere porosity deteriorates, and the powder injection process can be performed smoothly. This is an extremely useful invention.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the vacuum degassing tank used in the method of the present invention;
FIG. 2 is a diagram showing the tuyere opening degree and the pressure in front of the tuyere, and FIG. 3 is a diagram showing the change in the tuyere opening degree when the present invention is used. 1: Vacuum degassing Tsubaki 2: Exhaust port 3: Molten steel 4: Ladle 5: Powder injection tuyere 6: Supply piping 7: Supply device 8: Carrier gas 9: Oxygen 10: Check the degree of opening in oxygen supply arrangement 1 Gas 12: Supply piping 13: Shutoff valve A 14: Shutoff valve B 15: Shutoff valve C

Claims (1)

[Claims] When blowing powder-containing gas into molten steel from the tuyere, the pressure just before the tuyere of the blowing gas conduit is detected, and when the pressure exceeds the set pressure due to tuyere blockage, oxygen gas is automatically blown. A method for maintaining the opening of a tuyere, characterized by melting the ingot that is clogged.