FR2645543A1 - CALCINATED GAS WASHING BRICK AND USE THEREOF - Google Patents

Abstract

The invention relates to a calcined gas scrub brick 26 having a plurality of channels, approximately parallel to each other, which are formed by separately implanted tubes. This washing brick 26 can be integrated into the side wall 18 of a vacuum vessel, a short distance above the bottom 20 of the vessel, in a degassing installation, for the fine decarburization of the steel casting. .

Description

i Burning brick with calcined gas and use thereof

  The present invention relates to a brick of the

  calcined gas vage, oriented porosity, as well as its

particular use.

  For about 30 years, the vacuum treatment of steel castings has seen its field of application widen,

  in secondary metallurgy. Gas degassing of the-

  vage as well as vacuum decarburization are part of

these applications.

  The carbon-oxygen reaction, dependent on the

  is used for vacuum decarburization of

  unhardened steel flows. We can thus reach te-

  carbon values sometimes very low, less than 0.01%.

  The lower the partial pressure of CO, the lower the

  Carbon final nors are low.

  For fine decarburization of non-alloy steels, we

  knows among others, the RH process and the DH process.

  In the RH process (Ruhrstahl-Heraeus), the li-

  that from the ladle is sent to a

  riser, by means of a transport gas, in particular

  culier of argon, introduced into the ascending tube, au-

  above the level of the steel, and conveyed through the rising tube, under the effect of the increase in volume of the gas, then sent into the evacuation container, under the effect

  of the pressure difference between the atmospheric pressure

  that external and the depression reigning in this container of evacuation. The steel drawn into the discharge container is fragmented, which causes a large increase in the surface and therefore good degassing. The oxygen introduced at the same time and which, throughout the duration of the treatment, is supplied inter alia by the slag, gives rise to the formation of carbon monoxide which is released in the vacuum container, which makes it possible to obtain the

decarburization desired.

  By additional oxygen insufflation, we tried to optimize the fine decarburization to values also

as low as possible.

  In this context, we can also mention a

  of the cited RH process, namely the RH-OB process. To accelerate decarburization, we inject oxygen here

  in molten metal, by gas-cooled nozzles.

  A rapid decarburization is obtained in particular by a high speed of circulation of the molten metal,

  and therefore by increasing the flow of trans-

  port, as well as increasing the diameter of the riser

of the vacuum installation.

  By a controlled supply of oxygen, the carbon content can be reduced to values up to

  0.002%. But we have this drawback that the blowing of oxy-

  gene leads to high gas costs and above all very premature wear, in the region of gas introduction,

  compared to the rest of the refractory masonry.

  The invention proposes to provide means of per-

  processing the treatment of metal castings in vacuum installations, in particular increasing the service life while reducing costs and ensuring

  decarburization rates as high as possible.

  The invention is based on the discovery that this can be achieved by integrating a special calcined gas washing brick in the disposal container, this gas washing brick serving to inject an inert gas,

such as argon.

  It turned out, surprisingly, that in renouncing

  ering to inject oxygen separately, the carbon content can be reduced, for example from 0.03% to less

  0.0002%, in a few minutes, sometimes even at values

  their less than 0.001%. These carbon contents cannot

  can be obtained, even with known OB installations, only by the use of considerable quantities of oxygen,

  with the resulting drawbacks, as discussed above

  above. The invention therefore proposes a gas washing brick,

  oriented porosity, which unlike the bricks of the

  usual, such as those used for example in

  pocket metallurgy is calcined.

  This calcined gas washing brick must have several channels, roughly parallel to each other, which are

  formed by small tubes implanted separately.

  These small tubes are placed in a calcined gas washing brick, previously prepared, which

  has a corresponding number of practical passage channels

ticked to receive the tubes.

  Passage channels can be drilled, e.g.

  ple after the calcination of the wash brick, or

just before calcination.

  Tubes, in particular metal tubes (even

  also sintered ceramic tubes at maximum density) are glued in the passage channels, with a

  refractory glue, or sealed with a refractory mortar

  to hush up. The washing brick can be a washing brick

  with poured, crushed or pressed gas.

  The calcined gas washing brick, thus prepared,

  has a high resistance to erosion and infiltration

  trations. Thanks to the gas inlet tube, installed after calcination, during a separate process step,

  the inert gas stream, introduced through a supply line

  appropriate statement, can be infused, well

dosed, in molten metal.

  As already mentioned above, it has been found that by integrating a suitable gas washing brick into the wall of a vacuum container with degassing of quantities

  partial, it was possible to obtain, sur-

  taking, a fine and even very fine decarburization of

steel flows.

  This applies in particular in the case of a

  use of the gas washing brick in a container

  pient sous vide, for the implementation of a RH continuous degassing process or a RD-DH Heber degassing process. But the gas washing brick described can also

  be integrated in a vacuum container of an installation

  RH-OB relationship, as will be seen in more detail below.

  The gas washing brick is preferably integrated

  rigged in the side wall of the discharge vessel, in the region of the steel casting, preferably facing

  the entrance region of the molten metal.

  The inert gas, introduced by the gas washing brick, is distributed in an extremely fine form, in the

  degassing region of molten metal. Thanks to the use

  tion of a gas washing brick, with oriented porosity, high flow rates can be adjusted for the

  flow of inert gas, which is important for repair-

  uniform composition of the inert gas in the molten metal.

  To this end, it is also planned to have several gas washing bricks of the aforementioned type, which are placed in the discharge container, either close to each other, juxtaposed or spaced apart, or face to face. You can also distribute several washing elements

gas following a crown.

  The use of the gas washing bricks described prevents, almost completely, premature wear in the gas introduction region, facing the side wall of the

disposal container.

  It has been found, surprisingly, that the sending of the inert gas, in the manner described, is sufficient in itself to allow obtaining extremely low carbon contents of the steel casting, such as those mentioned more high, forgoing any separate external oxygen supply. Another advantage lies in the fact that it suffices to introduce into the ascending pipe of the installation reduced quantities of inert gas, which also reduces

wear and tear there.

  This is all the more important as this region is the most sensitive to the evacuation installation, in particular

  with regard to the durability of the refractory material.

  The gas washing brick can be easily integrated into the lower container of the installation

  evacuation, preferably a short distance above

  known from its bottom. An energy is thus introduced into the steel

  optimal brewing and mixing of the inert gas which

is evenly distributed there.

  As mentioned above, the integration of the gas washing brick mentioned makes it possible to dispense with a separate supply of oxygen. But it is obviously also possible to use the gas washing brick described, in the disposal container, for the implementation of a

  RH-OB process. In this case, we can reduce considerably-

  the amount of oxygen blown into the metal being smelled

  such that the described advantages are obtained in the same way, although to a slightly lesser extent. The invention is described below in more detail with reference to the accompanying drawing, in which: FIG. 1 shows in perspective and in section, the transition zone between the bag and the vacuum container of an RH installation; Figure 2 shows, on an enlarged scale and in section along II-II of Figure 1, a detail of this installation; FIG. 1 shows a tube 10 intended to suck the molten metal out of the ladle (not shown) as well as another tube 12, placed next to it, by which the molten metal returns to the ladle, in a continuous process, after passing through the container

Evacuation 14.

  The sectional view of the tube 10, in particular, shows the refractory masonry 16, placed inside the tube, while the reference 18 designates the masonry

  refractory inside the disposal container 14.

  A short distance above the bottom 20 of the vacuum container, a gas washing brick of the aforementioned type has been integrated in the side wall, facing the inlet zone 22. The gas connection pipe 24

  washing brick is visible here.

  In the enlarged sectional view of this portion given in Figure 2, we see how the gas washing brick 26 is integrated into the side wall of the vacuum container 14. It emerges from this view that the washing brick with gas is placed in the second row

  of bricks, above the bottom 20, and is aligned fronta-

  with the interior face of the refractory masonry

shut up 18.

  Placing the gas wash brick 26 right

  above the bottom 20 has been found to be particularly advantageous.

  geux, as regards the distribution of the gas in the molten steel, the height of the gas washing brick 26, above the bottom 20, having to correspond approximately to the

width of the brick 26 itself.

  By placing the gas washing brick 26 facing

  input 22, the flow of inert gas blown is repaired

  ti, optimally, in the flowing molten metal.

Claims (6)

- CLAIMS -   1. Brick gas washing, characterized in that it comprises a plurality of channels substantially parallel to each other, which are formed by small tubes which, in the form of separate elements, have been glued or sealed in channels passing through, prepared for this purpose,   after the calcination of the gas washing brick (26).   2. Use of a calcined gas washing brick (26) according to claim 1, in a vacuum container (14) with degassing of partial quantities, in view   fine decarburization of steel flows.   3. Use according to claim 2 in a vacuum container (14), for the implementation   of an RH, RH-DH or RH-OB degassing process.   4. Use according to claim 2 or 3, charac-   terized in that one or more washing bricks (26) are integrated in the side wall (18) of the container   discharge (14), in the region of molten steel.   5. Use according to claim 4, character-   in that the washing brick (s) (26) are integrated in the side wall (18), facing the area inlet (22) of the molten metal.   6. Use according to any one of the claims   cations 2 to 5, characterized in that the washing brick (26) is placed, a short distance above the bottom (20) of the discharge container (14), in the masonry refractory (18).