JPS6359995B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a nozzle hole filler for a sliding nozzle installed in a ladle, tundish, etc. [Prior art and its problems] The sliding nozzle device is composed of an upper nozzle, a fixed plate, a sliding plate, and a lower nozzle.The sliding nozzle device is composed of an upper nozzle, a fixed plate, a sliding plate, and a lower nozzle. This is to block or control outflow. However, when pouring molten metal into a ladle or tundish container, there was a problem in that the molten metal flowing into the upper nozzle and the nozzle hole of the fixed plate cooled and solidified, and the molten metal could not flow out even if the sliding plate was opened. For this reason, measures have been taken to prevent the molten metal from entering and sticking, and to fill the nozzle hole with powder that flows out together with the molten metal when the sliding plate is opened and the molten metal is poured out. This filler must have natural pores and be low cost, and to meet these conditions, a mixed powder using silica sand as the SiO ₂ source and feldspar as the alkali source is commonly used. used in When using this mixed powder, the reasons why pores do not open naturally when molten steel flows out are: (a) The amount of feldspar is too small, which causes it to react with silica sand.
SiO ₂ - The amount of alkaline glass produced decreases, causing metal to enter the nozzle filling layer, and the nozzle filling floating and being lost due to the flow of molten steel. (b) If the amount of feldspar is too large, SiO ₂ - This is thought to be due to the fact that the thickness of the sintered layer increases due to the formation of alkaline glass, making it difficult to break due to the head pressure of molten steel when opening the hole. Furthermore, quality requirements for steel have recently become stricter,
Various refining operations are increasingly performed in the ladle between receiving steel from a converter and casting it into a tundish, and the residence time of molten steel in the ladle is becoming longer. This extended residence time results in a thicker sintered layer of the nozzle filling, resulting in a reduction in natural porosity. Therefore, if an attempt is made to thin the sintered layer by reducing the amount of feldspar, the amount of SiO ₂ -alkaline glass produced will be too small, making it impossible for molten steel to flow out naturally due to factors such as intrusion of base metal. . [Object of the Invention] An object of the present invention is to provide a sliding nozzle packing that can maintain a good natural porosity even when molten steel is retained for a long time. [Structure of the Invention] The present invention solves the problem of using a mixed powder of silica sand and feldspar, which is a conventional filler, because the temperature at which SiO ₂ -alkaline glass produced during pouring of molten steel is low. This is based on the knowledge that by increasing the glass formation temperature, the natural porosity of the sliding nozzle can be maintained even when molten steel remains for a long time. In the present invention, a CaO- _SiO2- based glass-forming mixed powder is used as a filler. The formation temperature of CaO−SiO ₂ glass is 1400℃
It is in the above temperature range, which is considerably higher than the glass formation temperature of SiO ₂ -alkaline systems. Silica stone, silica sand, etc. can usually be used as the SiO ₂ raw material. However, the content of impurities, especially alkali metal oxides, in the SiO ₂ raw material has a large effect on lowering the glass formation temperature, so the content of alkali metal oxides in the mixed powder should be kept at 2% by weight or less. It is necessary to suppress it. CaO in the filling in the present invention is
It also has the effect of reacting with FeO at the contact surface with molten steel to form a FeO-CaO-based low-melting substance, which prevents molten steel from entering the nozzle filling layer. Although CaO powder is used as a CaO source, CaO
Lime carbonate or a mixed powder of both can be used instead of the powder. This mixing ratio is undesirable, even if the amount of SiO ₂ powder is less than 10% by weight or more than 95% by weight, the amount of glass formed is small and it may cause metal intrusion into the nozzle filling layer. . When lime carbonate powder is used, heating from molten steel causes decomposition of the carbonate, releasing carbon dioxide gas and suppressing sintering of the nozzle hole filling, making it especially effective against molten steel staying for a long time. It is. However, if only lime carbonate powder is used as a CaO source, the internal volume of the nozzle hole will increase, which is undesirable, especially in large pots, as volume stability will be lost due to carbonate decomposition. quantity
It needs to be 30% by weight or less in terms of CaO. Those using only CaO powder as a CaO source have good volume stability and are advantageously used in large pots. In addition to lime powder or lime carbonate powder, the CaO source of the present invention may contain 30% by weight or more of CaO.
Contains 30% by weight or more of SiO ₂ , and the total of both is
CaO- _SiO2 powders having a content of 65% by weight or more can also be used. In this case, each of CaO and _SiO2 is
If it is not 30% by weight or more, it will not be effective in preventing the intrusion of base metal, and if the total of both is not 65% by weight or more, the amount of impurities will be too large and sintering will occur, which is undesirable. In this way, CaO−SiO ₂ powder and
When used in combination with SiO ₂ powder
If the amount of CaO-SiO ₂ powder is less than 2% by weight, the amount of glass or low-melting material produced will be small, leading to the intrusion of base metal into the nozzle filling layer, which is undesirable.
If it exceeds 15% by weight, excessive sintering will result, which is not preferable. Furthermore, the present invention provides a method for combining CaO or CaCO ₃ with CaO-
It can be used in combination with SiO ₂ based powder. In this case, if the CaO-SiO ₂ powder is less than 5% by weight, the amount of glass produced will be small;
Moreover, if the amount is more than 15% by weight, excessive sintering will occur, which is not preferable. [Example] The effects of the present invention will be concretely illustrated by Examples below, but the present invention is not limited to these Examples. Tables 1 to 5 show examples of the filling material of the present invention and the effects when the filling material is applied to a sliding nozzle installed in an actual ladle, along with comparative examples. In either case, drying → classification → weighing → mixing →
It was adjusted by the process of cutting 0.5m/m or less and packing it into plastic bags.

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[Integrated effect]

The sliding nozzle filling of the present invention prevents metal intrusion into the nozzle filling layer even if the residence time of molten steel becomes long, and also forms a filling layer with a thin sintered layer that can be easily destroyed during pouring. However, the effect is that a good porosity can be obtained.

Claims (1)

[Scope of Claims] 1 Consists of a mixed powder of 10 to 95% by weight of SiO ₂ raw material powder and 5 to 90% by weight of either or both of CaO raw material powder and CaCO ₃ raw material powder, calculated as CaO. A sliding nozzle filler characterized in that the content of alkali metal oxide in the mixed powder is 2% by weight or less. 2 98 to 85% by weight of SiO ₂ raw material powder and 2 of CaO-SiO ₂ based powder containing 30% by weight or more of SiO ₂ and 30% by weight or more of CaO, and the total of both is 65% by weight or more.
15% by weight of a mixed powder, the content of alkali metal oxide in the mixed powder is 2% by weight or less. 3 CaO raw material powder or CaCO ₃ raw material powder, or a mixture of both, in terms of CaO, 95 to 85
% by weight, contains 30% by weight or more of SiO ₂ and 30% by weight or more of CaO, and the total of both is 65% by weight or more.
1. A sliding nozzle filling comprising a mixed powder with 5 to 15% by weight of CaO-SiO ₂ based powder, wherein the content of alkali metal oxide in the mixed powder is 2% by weight or less.