JP6287918B2 - Manufacturing method of container for high temperature - Google Patents

Description

  The present invention relates to a method for producing a high-temperature container used for holding, transporting, refining, etc., high-temperature objects of 900 ° C. or higher.

Zirconia (ZrO ₂ ) is widely used as lining refractories (also called “work refractories”) for high-temperature containers used for holding, transporting and refining hot objects such as hot metal and molten steel because of its high melting point and high corrosion resistance. It is used. However, pure zirconia is monoclinic at room temperature, but as the temperature is raised, the crystal transitions to tetragonal and cubic crystals at about 900-1100 ° C. Since it shows the change in volume expansion reached, it is easy to break in a pure and dense structure and difficult to use as a refractory. Therefore, stabilized zirconia in which calcium oxide (CaO) or yttrium oxide (Y ₂ O ₃ ) is dissolved in zirconia is used. This is because, when calcium oxide or yttrium oxide is dissolved in zirconia, tetragonal crystals and cubic crystals are stabilized at room temperature, so that volume changes can be avoided even when temperature changes are applied, and this is due to volume changes. This is because cracks can be prevented.

  Therefore, if a refractory compounded with such stabilized zirconia is applied as a lining refractory layer, a high-temperature container capable of responding to temperature changes can be obtained. However, since such stabilized zirconia is expensive, there has been a problem in using it for various purposes.

For this reason, means for using unstabilized natural zirconia as a refractory material has been proposed. For example, in Patent Document 1, calcium hydroxide (Ca (OH) ₂ ) is added to unstabilized natural monoclinic zirconia, this mixture is stirred and mixed, and calcined to stabilize zirconia. A method for producing a zirconia refractory by forming and firing using the refractory raw material as a refractory material is disclosed.

JP-A-2-1244763

  However, Patent Document 1 has the following problems. That is, in the method of Patent Document 1, since a relatively inexpensive natural zirconia and calcium hydroxide are used as raw materials, a reduction in manufacturing cost can be expected. However, once the raw materials are calcined, The process of molding and firing is required, and the problem that the zirconia refractory is relatively expensive cannot be solved.

  The present invention has been made in view of such circumstances, and its purpose is not to use expensive stabilized zirconia, but to inexpensively unstabilized zirconia without firing or preheating at high temperature. It is intended to provide a method for producing a high-temperature container used as a refractory for lining and used for holding, transporting, refining, etc., high-temperature objects.

The gist of the present invention for solving the above problems is as follows.
[1] In a method for manufacturing a high-temperature container for holding a high-temperature object of 900 ° C. or higher, which is provided with a permanent refractory layer and a lining refractory layer in this order inside a metal outer shell, calcium oxide (CaO), A zirconia stabilizing material composed of yttrium oxide (Y ₂ O ₃ ) or a compound thereof and an unstabilized zirconia (ZrO ₂ ) are combined with the mass of the zirconia stabilizing material in terms of CaO or Y ₂ O ₃ and 60% by mass or more of a mixture containing the stabilized zirconia in a mass ratio of 5:95 to 11:89 and having a silicon oxide (SiO ₂ ) content of 0.5% by mass or less And the balance is alumina (Al ₂ O ₃ ), magnesia (MgO), chromium oxide (Cr ₂ O ₃ ), graphite (C), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), and compounds thereof Out of Refractories that are seeds or two or more, as well as binders and inevitable impurities, and have a porosity of 15% or less, and are fired at a temperature of less than 900 ° C. or molded refractories that remain unfired Alternatively, a method for producing a container for high temperature, wherein an amorphous refractory is applied as the lining refractory layer.
[2] The molded refractory or the amorphous refractory applied as a lining refractory layer does not contain alumina, magnesia, chromium oxide, graphite, silicon carbide, silicon nitride, or a compound thereof. The method for producing a high-temperature container according to [1].
[3] A heat insulating layer having a heat transfer coefficient of 30 W / (m ² × K) or less between the outer shell and the permanent refractory layer or between the permanent refractory layer and the lining refractory layer. The method for producing a high-temperature container according to [1] or [2] above, wherein:

  According to the present invention, without using expensive stabilized zirconia as a raw material, inexpensive unstabilized zirconia is used as a lining refractory without firing or preheating at a high temperature, to hold and transport high-temperature objects. It is possible to manufacture a high-temperature container used for refining and the like.

It is side surface sectional drawing of the hot metal ladle manufactured by applying this invention.

  Hereinafter, the present invention will be specifically described. First, the background to the present invention will be described.

The present inventors examined the use of unstabilized zirconia (ZrO ₂ ) as a refractory for the lining refractory layer of a container for high temperature without firing or preheating at high temperature. A test based on the examination results was conducted. The results will be described below.

It is well known to those skilled in the art to use a divalent or trivalent metal oxide such as calcium oxide (CaO) or yttrium oxide (Y ₂ O ₃ ) as the zirconia stabilizer. A mixture of unstabilized zirconia powder and powder of zirconia stabilizing material such as calcium oxide or yttrium oxide (hereinafter also simply referred to as “stabilizing material”) is used as a lining refractory layer for a high-temperature container. In this case, the zirconia of the lining refractory layer is not stabilized at the start of use, but starts to stabilize when the temperature reaches 900 ° C. or higher after the start of use. Since stabilization of zirconia is accompanied by tissue transition, it causes defects such as cracks, cracks, and delamination.

In order to avoid defects such as cracks associated with this stabilization, conventionally, a low melting point material such as silicon oxide (SiO ₂ ) is added to sacrifice fire resistance, lower the elastic modulus, or increase the temperature slowly In some cases, firing is performed with time and cost.

  The inventors of the present invention, by covering the periphery with a metal outer shell, volume-expanding unstabilized zirconia by transferring crystals from monoclinic to tetragonal and cubic crystals, Based on the concept that cracks and cracks are avoided by the restraining force of the outer shell, and zirconia is stabilized by the coexisting stabilizing material, the stabilizing material powder and the unstabilized zirconia powder This mixture was applied as a lining refractory layer of a high-temperature container without firing in advance. In the test, calcium oxide was used as a stabilizing material.

  However, with a general zirconia refractory compound containing 0.5% by mass or more of silicon oxide, cracks and cracks were not eliminated. This is because the internal stress generated with the volume expansion due to crystal transition is eliminated by the plastic deformation of the zirconia refractory containing 0.5% by mass or more of silicon oxide, and is compressed by the metal outer shell. It was considered that the effect of reducing cracks and cracks was not exhibited because no stress was applied.

  Therefore, as a result of reducing the content of silicon oxide as much as possible to 0.5% by mass or less, a tendency to reduce defects such as cracks and cracks was confirmed in the vicinity of the working surface of the lining refractory layer.

  However, a crack in a direction parallel to the working surface may occur at an approximately intermediate position between the working surface of the lining refractory layer and the surface on the permanent refractory layer side. This crack in the direction parallel to the working surface occurred in a relatively dense lining refractory layer having a porosity of 15% or less, and the lining refractory layer having a porosity of 15% or more had very few cracks. However, when the porosity is 15% or more, the corrosion resistance is inferior, so it cannot be put into practical use as a lining refractory layer.

  As a cause of cracking in the direction parallel to the working surface, which occurs at approximately the middle position between the working surface and the surface on the permanent refractory layer side, the transition proceeds because the temperature is sufficiently high near the working surface, but the permanent refractory layer It was estimated that the transition was not progressed because the temperature became lower as it approached the side, and the structures with different thermal expansion coefficients coexisted.

  Therefore, for the purpose of increasing the temperature of the portion of the lining refractory layer close to the permanent refractory layer, the silicon oxide content of the lining refractory layer made of zirconia refractory is set to 0.5% by mass or less. The heat insulation layer was constructed between the outer shell, which is on the outer shell side of the lining refractory layer, and the permanent refractory layer. As a result, by installing the heat insulating layer, even in the case of a dense lining refractory layer having a porosity of 15% or less, cracks in the direction parallel to the working surface were eliminated.

This insulation layer heat transfer coefficient (thickness of the heat insulation layer thermal conductivity / heat insulating layer) is as low desirable, if both 30 W / (m ² × K) less high than 100mm equivalent of refractory lining layer Thus, the temperature of the portion of the lining refractory layer close to the permanent refractory layer is sufficiently raised to reduce cracking. Moreover, even if it installed the heat insulation layer between the lining refractory layer and the permanent refractory layer, the same effect was acquired.

  When the mass ratio of the mass of calcium oxide or yttrium oxide as the zirconia stabilizing material to the mass of unstabilized zirconia was 8 to 92, there were few cracks or cracks, but this mass ratio was 5 to 95. From 11 to 89, the durability was good.

The present invention has been made based on the above test results, and the method for producing a high-temperature container according to the present invention comprises a permanent refractory layer and a lining refractory layer in this order inside a metal outer shell. , A zirconia stabilizing material composed of calcium oxide (CaO), yttrium oxide (Y ₂ O ₃ ) or a compound thereof, and unstabilized zirconia (ZrO). ₂ ) in the range of 5:95 to 11:89, and the mass ratio of the mass of the zirconia-stabilized material in terms of CaO or Y ₂ O _{3 to} the mass of the unstabilized zirconia is oxidized. 60% by mass or more of a mixture having a silicon (SiO ₂ ) content of 0.5% by mass or less, with the balance being alumina (Al ₂ O ₃ ), magnesia (MgO), chromium oxide (Cr ₂ O ₃ ) , Lead (C), silicon carbide (SiC), silicon nitride (Si ₃ N ₄₎ and one or more of these compounds, as well as, a binder and inevitable impurities, porosity of 15% or less The molded refractory that has been fired at a temperature of less than 900 ° C. or that has not been fired or an unshaped refractory is applied as the lining refractory layer.

  The present invention is directed to a high-temperature container that holds a high-temperature object of 900 ° C. or higher. This is because when the temperature of the high-temperature object to be held is less than 900 ° C., zirconia transition does not occur and the effects of the present invention cannot be obtained. Moreover, the mixture of the zirconia stabilizing material and the unstabilized zirconia applied as the lining refractory layer may be a molded refractory (molded brick) or an irregular refractory. Can be applied.

  In the present invention, a mixture of a stabilizing material and unstabilized zirconia applied as a lining refractory layer is unfired, and is expanded by transition in a state of being restrained by a metal outer shell after the start of use. Since the stress is generated, the structure of the refractory becomes dense and the durability is improved.

  However, even if the mixture of the stabilizing material and the unstabilized zirconia is baked at a temperature of less than 900 ° C., the zirconia is not transferred and the above effect is not impaired. That is, as long as the firing temperature is less than 900 ° C., the mixture of the stabilizing material and the unstabilized zirconia may be fired before being applied as the lining refractory layer and after being applied as the lining refractory layer. Absent. That is, there is no problem in firing at a temperature of less than 900 ° C. in order to reduce the activity of CaO, which progresses in degradation such as digestion, in the air atmosphere.

As the zirconia stabilizer, for example, compounds such as calcium hydroxide (Ca (OH) ₂ ) and yttrium hydroxide (Y (OH) ₃ ) can be used in addition to the above-mentioned calcium oxide and yttrium oxide. . There is an optimum range for the blending ratio of the stabilizing material. In the present invention, the CaO equivalent mass or Y ₂ O ₃ equivalent mass of the stabilizing agent, including compounds such as calcium hydroxide and yttrium hydroxide, is not stabilized. The blending ratio of the stabilizing material is controlled based on the mass ratio with the mass of zirconia. That is, the mass ratio of the stabilizing material in terms of CaO or Y ₂ O _{3 and} the mass of unstabilized zirconia is in the range of 5:95 to 11:89.

Here, for example, when calcium hydroxide is converted to CaO, the CaO equivalent is 74 (Ca (OH) ₂ ) and the CaO formula is 56, so the mass of calcium hydroxide is 0. The value obtained by multiplying by 7568 (= 56/74) is the mass obtained by converting calcium hydroxide into CaO. Y ₂ O ₃ conversion is similarly calculated.

If the weight ratio of the stabilizing material to the unstabilized zirconia is less than 5:95, the transition to cubic crystals will not proceed sufficiently unless the temperature is increased to 1500 ° C. or higher. Unstabilized zirconia cannot be used as a lining refractory. In particular, in the range close to the permanent refractory layer, even if the heat insulating layer is installed, the temperature is lower than that of the operating surface, so that the stabilization effect cannot be obtained. On the other hand, when the blending amount of the stabilizing material is larger than 11:89, calcium oxide and yttrium oxide become excessive, a crystal phase such as CaZrO ₃ is generated, the structure becomes brittle, and the durability is excellent. A lining refractory layer cannot be formed.

  If the blending ratio of the mixture of zirconia-stabilized material and unstabilized zirconia in the lining refractory layer is low, cracks or cracks in the lining refractory layer due to the difference in expansion behavior between the transferred and non-transferred objects. Will occur. When the blending ratio of the mixture of the stabilizing material and unstabilized zirconia is less than 60% by mass and, for example, alumina is mixed in the balance, there is a gap at the interface between the mixture of the stabilizing material and unstabilized zirconia and the alumina. A form of wear was observed in which (crack) occurred and alumina dropped off.

  From this result, the blending ratio in the lining refractory layer of the mixture of the zirconia stabilizing material and the unstabilized zirconia is required to be 60% by mass or more. The balance other than the mixture of the stabilizing material and unstabilized zirconia may be one or more of alumina, magnesia, chromium oxide, graphite, silicon carbide, silicon nitride, and these compounds.

  Of course, it is also possible to apply only a mixture of a zirconia stabilizing material and an unstabilized zirconia, in which silicon oxide is 0.5% by mass or less, without being added as a lining refractory layer.

  In the present invention, a metal outer shell such as steel is an essential requirement. This is for restraining the occurrence of defects during transition by restraining the lining refractory with a metal outer shell and causing volume expansion to act as an internal stress. The material and dimensions of the metal outer shell are arbitrary. Such a thing is unsuitable because it becomes impossible to hold with keeping.

  For the same reason, silicon oxide that promotes plastic deformation with a low-melting-point material should be reduced as much as possible. However, if it is 0.5% by mass or less, there is no practical adverse effect. Moreover, the tendency for corrosion resistance to improve was recognized by reducing silicon oxide. Of course, it is not absolutely necessary to intentionally add silicon oxide.

In the present invention, a heat insulating layer having a heat transfer coefficient of 30 W / (m ² × K) or less is applied between the outer shell and the permanent refractory layer or between the permanent refractory layer and the lining refractory layer. Thus, application of unstabilized zirconia to the lining refractory layer becomes even more effective. It is considered that the crack of the lining refractory layer when the heat insulation layer is not provided is caused by a temperature gradient inside the lining refractory layer. In support of this, many cracks occur when the remaining thickness of the lining refractory layer becomes smaller than about 100 mm, and if the remaining thickness is larger than that, there are few cracks. This is presumably because when the remaining thickness of the lining refractory layer is large, the overall heat transfer coefficient is low, so the temperature gradient is small and the thermal stress is small.

  As described above, according to the present invention, without using expensive stabilized zirconia as a raw material, inexpensive unstabilized zirconia is used as a lining refractory without firing or preheating at a high temperature. It is possible to manufacture a high-temperature container used for holding, transporting, refining, and the like of high-temperature objects.

  FIG. 1 shows a side sectional view of a hot metal ladle manufactured by applying the present invention. The hot metal ladle 1 has an iron shell 2 as an outer shell, and a permanent refractory layer 3 and a lining refractory layer 4 are constructed in this order inside the iron shell 2. As the permanent refractory layer 3, conventional bricks such as magnesia bricks, alumina bricks, clay bricks and rhostone bricks are used.

  A permanent refractory layer 3 having a thickness of 50 mm was applied to the inner side of the iron skin 2 having a thickness of 30 mm, and a lining refractory layer 4 having a thickness of 160 mm was applied to the inner side thereof. The lining refractory layer 4 contains 80% by mass of unstabilized zirconia, 12% by mass of calcium hydroxide, and 8% by mass of binder except for the slag line part (not shown) on the upper end side of the hot metal ladle 1. An amorphous mixture was applied in the mold. All of the inevitable mixed components in the amorphous mixture were 0.5% by mass or less. Further, a commercially available sheet-like microporous heat insulating material having a thickness of 3 mm was applied as the heat insulating layer 5 between the iron skin 2 and the permanent refractory layer 3. In addition, the slag line part constructed the carbon containing refractory which is excellent in the corrosion resistance with respect to slag.

  In order to convert calcium hydroxide to CaO, it is only necessary to multiply the mass of calcium hydroxide by 0.7568 (= 56/74). Therefore, the content of calcium hydroxide converted to CaO is 9.1% by mass. (= 12 × 0.7568) The mass ratio of unstabilized zirconia to calcium hydroxide converted to CaO was 80 to 9.1, that is, 89.8 to 10.2.

The thermal conductivity of the sheet-like microporous heat insulating material was 0.03 W / (m × K) at the start of use, and 0.06 W / (m × K) at the time of dismantling after 1 year. The heat transfer coefficient (thermal conductivity / heat insulating layer thickness) in the heat insulating layer 5 during the pot use period is 10 to 20 W / (m ² × K).

  After constructing the lining refractory layer 4 having the above composition, a predetermined moisture drying step and mold removal were performed, and thereafter, the use was started as a high-temperature container for hot metal conveyance. During use of the hot metal ladle, no wear due to cracking or peeling of the lining refractory layer was observed, and the wear rate was reduced by 20% compared to the lining refractory layer using conventional stabilized zirconia.

1 Hot metal ladle 2 Iron skin 3 Permanent refractory layer 4 Lined refractory layer 5 Thermal insulation layer

Claims (3)

In the manufacturing method of the container for high temperature which hold | maintains the high temperature object of 900 degreeC or more provided with the permanent refractory layer and the lining refractory layer in this order inside the outer shell which consists of metal,
Calcium oxide (CaO), yttrium oxide (Y ₂ O ₃ ) or a zirconia stabilizing material composed of these compounds, and unstabilized monoclinic zirconia (ZrO ₂ ) are used as the CaO of the zirconia stabilizing material. The mass ratio of the converted or Y ₂ O ₃ converted mass to the mass of the unstabilized monoclinic zirconia is in the range of 5:95 to 11:89, and silicon oxide (SiO ₂ ) 60% by mass or more of a mixture having a content of 0.5% by mass or less, with the balance being alumina (Al ₂ O ₃ ), magnesia (MgO), chromium oxide (Cr ₂ O ₃ ), graphite (C), Silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ) and one or more of these compounds, as well as binders and inevitable impurities, are refractories with a porosity of 15% or less. 900 ℃ not yet If it were fired at a temperature, or a molded refractory or monolithic refractory remains unfired, characterized by construction as the refractory lining layer, the manufacturing method of high-temperature vessel.   The molded refractory or the amorphous refractory applied as a lining refractory layer does not contain alumina, magnesia, chromium oxide, graphite, silicon carbide, silicon nitride, or a compound thereof. The manufacturing method of the container for high temperature as described. A heat insulating layer having a heat transfer coefficient of 30 W / (m ² × K) or less is applied between the outer shell and the permanent refractory layer or between the permanent refractory layer and the lining refractory layer. The manufacturing method of the container for high temperature of Claim 1 or Claim 2 characterized by the above-mentioned.

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