Casting Ladle For Casting Aluminum Alloy

Abstract

Disclosed is a casting ladle for casting aluminum alloy in the present application. The casting ladle includes a liner contact layer, a first thermal insulation layer, a second thermal insulation layer, and a housing layer sequentially from inside to outside. The first thermal insulation layer includes first Al.sub.2O.sub.3 particles and at least one first oxide particle selected from the group consisting of first SiO.sub.2 particles, first CaO particles, and first MgO particles. The second thermal insulation layer includes at least one second oxide particle selected from the group consisting of second Al.sub.2O.sub.3 particles, second SiO.sub.2 particles, second CaO particles, and second MgO particles. The second thermal insulation layer has a porosity of 60-75% and a pore size of 2-5 mm.

Claims

1. A casting ladle for casting aluminum alloy, comprising a liner contact layer, a first thermal insulation layer, a second thermal insulation layer, and a housing layer sequentially from inside to outside, wherein: the first thermal insulation layer comprises first Al.sub.2O.sub.3 particles and at least one first oxide particle selected from the group consisting of first SiO.sub.2 particles, first CaO particles, and first MgO particles, wherein the first Al.sub.2O.sub.3 particles have a hollow spherical structure, a proportion of the first Al.sub.2O.sub.3 particles is 80-85 wt % based on a total weight of the first thermal insulation layer, and the first thermal insulation layer has a porosity of 55-65% and a pore size of 0.8-3.0 mm; and the second thermal insulation layer comprises at least one second oxide particle selected from the group consisting of second Al.sub.2O.sub.3 particles, second SiO.sub.2 particles, second CaO particles, and second MgO particles, wherein the second thermal insulation layer has a porosity of 60-75% and a pore size of 2-5 mm.

2. The casting ladle for casting aluminum alloy according to claim 1, wherein a sphere of the first Al.sub.2O.sub.3 particles has an inner hole diameter of 0.3-0.8 μm and a diameter of 40-80 μm.

3. The casting ladle for casting aluminum alloy according to claim 1, wherein the first oxide particles have at least two average particle sizes, in which a first average particle size is 40-60 μm and a second average particle size is 5-8 μm, wherein a proportion of the first oxide particles having the first average particle size is 8-13 wt %, and a proportion of the first oxide particles having the second average particle size is 3-5 wt %, based on a total weight of the first thermal insulation layer.

4. The casting ladle for casting aluminum alloy according to claim 2, wherein the first thermal insulation layer is composed of first Al.sub.2O.sub.3 particles, first SiO.sub.2 particles, first CaO particles, first MgO particles, and a first binder, wherein the first SiO.sub.2 particles have a size of 40-60 μm, the first CaO particles have a size of 5-8 μm, and the first MgO particles have a size of 5-8 μm; preferably, a proportion of the first SiO.sub.2 particles is 8-13 wt %, a proportion of the first CaO particles is 1-2 wt %, a proportion of the first MgO particles is 2-3 wt %, and a proportion of the first binder is 2-5 wt %, based on a total weight of the first thermal insulation layer.

5. The casting ladle for casting aluminum alloy according to claim 1, wherein the second Al.sub.2O.sub.3 particles have a size of 60-100 μm, and a proportion of the second Al.sub.2O.sub.3 particles is 40-50 wt % based on a total weight of the second thermal insulation layer.

6. The casting ladle for casting aluminum alloy according to claim 1, wherein the second oxide particles have at least two average particle sizes, in which a third average particle size is 50-65 μm and a fourth average particle size is 5-10 μm, wherein a proportion of the second oxide particles having the third average particle size is 36-46 wt %, and a proportion of the second oxide particles having the fourth average particle size is 6-10 wt %, based on a total weight of the second thermal insulation layer.

7. The casting ladle for casting aluminum alloy according to claim 1, wherein the second thermal insulation layer is composed of the second Al.sub.2O.sub.3 particles, the second SiO.sub.2 particles, the second CaO particles, the second MgO particles, and a second binder, wherein the second Al.sub.2O.sub.3 particles have a size of 60-100 μm, the second SiO.sub.2 particles have a size of 50-65 μm, the second CaO particles have a size of 5-10 μm, and the second MgO particles have a size of 5-10 μm; preferably, a proportion of the second Al.sub.2O.sub.3 particles is 40-50 wt %, a proportion of the second SiO.sub.2 particles is 36-46 wt %, a proportion of the second CaO particles is 3-5 wt %, a proportion of the first MgO particles is 3-5 wt %, and a proportion of the second binder is 4-8 wt %, based on a total weight of the second thermal insulation layer.

8. The casting ladle for casting aluminum alloy according to claim 1, wherein a proportion of ZrO.sub.2 particles in the liner contact layer is 88-93 wt % based on a total weight of the liner contact layer.

9. The casting ladle for casting aluminum alloy according to claim 8, wherein the liner contact layer has a porosity of 3-7% and a pore size of 10-15 μm.

10. The casting ladle for casting aluminum alloy according to claim 9, wherein in the liner contact layer, the ZrO.sub.2 particles have a size of 10-30 μm, third Al.sub.2O.sub.3 particles have a size of 40-80 μm, and third SiO.sub.2 particles have a size of 40-60 μm; preferably, a proportion of the third Al.sub.2O.sub.3 particles is 4-10 wt %, a proportion of the third SiO.sub.2 particles is 1-3 wt %, and a proportion of a third binder is 1-2 wt %, based on a total weight of the liner contact layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 is a structural schematic diagram of a casting ladle according to the present invention.

[0039] FIG. 2 is a photograph showing an entity that slag is adhered to an inner wall of a conventional casting ladle in one comparative example.

[0040] FIG. 3 is a photograph showing an entity that slag is adhered to an inner wall of a casting ladle according to one embodiment of the present invention.

[0041] The figures include: 1—liner contact layer; 2—first thermal insulation layer; 3—second thermal insulation layer; and 4—housing layer.

DETAILED DESCRIPTION

[0042] Technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the embodiments and accompanying drawings of the present invention. It will be apparent that the described embodiments are merely a part of the embodiments of the present invention and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0043] The present invention will be further illustrated below with reference to exemplary examples shown in the accompanying drawings. The advantages of various aspects of the present invention will be more apparent from the following description. Same reference numerals in the drawings refer to same components. The shapes and dimensions of the components in the schematic drawings are for illustration only and cannot be considered to embody actual shapes, dimensions and absolute positions.

[0044] The present invention provides a casting ladle for casting aluminum alloy. As shown in FIG. 1, the casting ladle of the present invention includes a liner contact layer 1, a first thermal insulation layer 2, a second thermal insulation layer 3, and a housing layer 4 sequentially from inside to outside.

[0045] A thickness of the liner contact layer 1 may be 70-110 mm, for example, the thickness of the liner contact layer 1 may be 75 mm or 90 mm, but is not limited thereto. A thickness of the first thermal insulation layer 2 may be 40-60 mm, for example, the thickness of the first thermal insulation layer 2 may be 47 mm or 50 mm, but is not limited thereto. A thickness of the second thermal insulation layer 3 may be 20-40 mm, for example, the thickness of the second thermal insulation layer may be 25 mm or 35 mm, but is not limited thereto. A thickness of the housing layer 4 may be 25-35 mm, for example, the thickness of the housing layer may be 30 mm.

[0046] According to one specific embodiment, the liner contact layer includes ZrO.sub.2 particles, Al.sub.2O.sub.3 particles, and SiO.sub.2 particles; the first thermal insulation layer includes Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, and MgO particles; the second thermal insulation layer includes Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, and MgO particles; and the housing layer is a steel housing. The proportion of each composition is calculated in parts by weight.

Example 1

[0047] A liner contact layer is composed of ZrO.sub.2 particles, Al.sub.2O.sub.3 particles, SiO.sub.2 particles and a binder aluminum dihydrogen phosphate. In the liner contact layer, a proportion of the ZrO.sub.2 particles is 88 wt %, a proportion of the Al.sub.2O.sub.3 particles is 10 wt %, a proportion of the SiO.sub.2 particles is 1 wt %, and a proportion of aluminum dihydrogen phosphate is 1 wt %. The size of the ZrO.sub.2 particles is 10 μm, the size of the Al.sub.2O.sub.3 particles is 40 μm, and the size of the SiO.sub.2 particles is 40 μm. The entire liner contact layer is required to have a refractoriness higher than 1650° C., with a porosity of 3% and a pore size of 10 μm.

[0048] The materials of the liner contact layer, namely the ZrO.sub.2 particles, the Al.sub.2O.sub.3 particles and the SiO.sub.2 particles specified above were preliminarily mixed by a stirrer at a speed of 500 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, aluminum dihydrogen phosphate needed to be added to be used as a binder, and a speed of the stirrer was 680 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 84 h. Finally, mold release was carried out to obtain the liner contact layer.

[0049] A first thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, MgO particles and a binder water glass. In the first thermal insulation layer, a proportion of a hollow Al.sub.2O.sub.3 sphere is 80 wt %, a proportion of the SiO.sub.2 particles is 13 wt %, a proportion of the CaO particles is 1.5 wt %, a proportion of the MgO particles is 2.5 wt %, and a proportion of the water glass is 3 wt %. The Al.sub.2O.sub.3 particles have a hollow spherical structure, in which an inner hole diameter of the sphere is 0.3 μm, and a diameter of the sphere is 40 μm. The size of the SiO.sub.2 particles is 40 μm. Both CaO and MgO are granular, with a size of 5 μm. The entire first thermal insulation layer has a refractoriness higher than 1560° C., a porosity of 55% and a pore size of 0.8 mm.

[0050] The materials of the first thermal insulation layer materials, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles and the MgO particles specified above were preliminarily mixed by a stirrer at a speed of 400 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, water glass needed to be added to be used as a binder, and a speed of the stirrer was 480 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 72 h. Finally, mold release was carried out to obtain the first thermal insulation layer.

[0051] A second thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, and MgO particles and a binder silica sol. In the second thermal insulation layer, a proportion of the Al.sub.2O.sub.3 particles is 40 wt %, a proportion of the SiO.sub.2 particles is 46 wt %, a proportion of the CaO particles is 5 wt %, a proportion of the MgO particles is 5 wt %, and a proportion of the silica sol is 4 wt %. The Al.sub.2O.sub.3 particles have a size of 60 μm, and the SiO.sub.2 particles have a size of 50 μm. Both CaO and MgO are granular, with a size of 5 μm. The entire second thermal insulation layer has a refractoriness higher than 1100° C., a porosity of 60% and a pore size of 2 mm.

[0052] The materials of the second thermal insulation layer, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles, and the MgO particles specified above were mixed by a stirrer at a speed of 300 r/min to obtain a mixed material, wherein to the stirring process, silica sol was added to be used as a binder. The resulting mixed material was injected into a mold cavity and then naturally cured for 12 h. Finally, mold release was carried out to obtain the second thermal insulation layer.

[0053] The liner contact layer, the first thermal insulation layer, and the second thermal insulation layer prepared above and a steel housing layer were combined and then heated and baked. In a low temperature stage (from room temperature to 180° C.), the heating was performed at a rate of 60° C./h, and after reaching the temperature, the temperature was maintained for 36 h. In an intermediate temperature stage (180° C.-850° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 48 h. In a high temperature stage (850° C.-1100° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 36 h. Finally, a casting ladle for casting aluminum alloy was obtained.

Example 2

[0054] A liner contact layer is composed of ZrO.sub.2 particles, Al.sub.2O.sub.3 particles, SiO.sub.2 particles and a binder aluminum dihydrogen phosphate. In the liner contact layer, a proportion of the ZrO.sub.2 particles is 90 wt %, a proportion of the Al.sub.2O.sub.3 particles is 5 wt %, a proportion of the SiO.sub.2 particles is 3 wt %, and a proportion of aluminum dihydrogen phosphate is 2 wt %. The size of the ZrO.sub.2 particles is 20 μm, the size of the Al.sub.2O.sub.3 particles is 60 μm, and the size of the SiO.sub.2 particles is 50 μm. The entire liner contact layer is required to have a refractoriness higher than 1650° C., with a porosity of 5% and a pore size of 12 μm.

[0055] The materials of the liner contact layer, namely the ZrO.sub.2 particles, the Al.sub.2O.sub.3 particles and the SiO.sub.2 particles specified above were preliminarily mixed by a stirrer at a speed of 500 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, aluminum dihydrogen phosphate needed to be added to be used as a binder, and a speed of the stirrer was 680 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 84 h. Finally, mold release was carried out to obtain the liner contact layer.

[0056] A first thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, MgO particles and a binder water glass. In the first thermal insulation layer, a proportion of a hollow Al.sub.2O.sub.3 sphere is 83 wt %, a proportion of the SiO.sub.2 particles is 8 wt %, a proportion of the CaO particles is 1.0 wt %, a proportion of the MgO particles is 3.0 wt %, and a proportion of the water glass is 5 wt %. The Al.sub.2O.sub.3 particles have a hollow spherical structure, in which an inner hole diameter of the sphere is 0.5 μm, and a diameter of the sphere is 60 μm. The size of the SiO.sub.2 particles is 50 μm. Both CaO and MgO are granular, with a size of 6 μm. The entire first thermal insulation layer has a refractoriness higher than 1560° C., a porosity of 60% and a pore size of 2.5 mm.

[0057] The materials of the first thermal insulation layer, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles and the MgO particles specified above were preliminarily mixed by a stirrer at a speed of 400 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, water glass needed to be added to be used as a binder, and a speed of the stirrer was 480 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 72 h. Finally, mold release was carried out to obtain the first thermal insulation layer.

[0058] A second thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, MgO particles and a binder silica sol. In the second thermal insulation layer, a proportion of the Al.sub.2O.sub.3 particles is 48 wt %, a proportion of the SiO.sub.2 particles is 38 wt %, a proportion of the CaO particles is 4 wt %, a proportion of the MgO particles is 4 wt %, and a proportion of the silica sol is 6 wt %. The Al.sub.2O.sub.3 particles have a size of 80 μm, and the SiO.sub.2 particles have a size of 60 μm. Both CaO and MgO are granular, with a size of 8 μm. The entire second thermal insulation layer has a refractoriness higher than 1100° C., a porosity of 70% and a pore size of 3 mm.

[0059] The materials of the second thermal insulation layer, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles, and the MgO particles specified above were mixed by a stirrer at a speed of 300 r/min to obtain a mixed material, wherein in the stirring process, silica sol was added to be used as a binder. The resulting mixed material was injected into a mold cavity and then naturally cured for 12 h. Finally, mold release was carried out to obtain the second thermal insulation layer.

[0060] The liner contact layer, the first thermal insulation layer, and the second thermal insulation layer prepared above and a steel housing layer were combined and then heated and baked. In a low temperature stage (from room temperature to 180° C.), the heating was performed at a rate of 60° C./h, and after reaching the temperature, the temperature was maintained for 36 h. In an intermediate temperature stage (180° C.-850° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 48 h. In a high temperature stage (850° C.-1100° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 36 h. Finally, a casting ladle for casting aluminum alloy was obtained.

Example 3

[0061] A liner contact layer is composed of ZrO.sub.2 particles, Al.sub.2O.sub.3 particles, SiO.sub.2 particles and a binder aluminum dihydrogen phosphate. In the liner contact layer, a proportion of the ZrO.sub.2 particles is 93 wt %, a proportion of the Al.sub.2O.sub.3 particles is 4 wt %, a proportion of the SiO.sub.2 particles is 1.5 wt %, and a proportion of aluminum dihydrogen phosphate is 1.5 wt %. The size of the ZrO.sub.2 particles is 30 μm, the size of the Al.sub.2O.sub.3 particles is 80 μm, and the size of the SiO.sub.2 particles is 60 μm. The entire liner contact layer is required to have a refractoriness higher than 1650° C., with a porosity of 7% and a pore size of 15 μm.

[0062] The materials of the liner contact layer, namely the ZrO.sub.2 particles, the Al.sub.2O.sub.3 particles and the SiO.sub.2 particles specified above were preliminarily mixed by a stirrer at a speed of 500 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, aluminum dihydrogen phosphate needed to be added to be used as a binder, and a speed of the stirrer was 680 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 84 h. Finally, mold release was carried out to obtain the liner contact layer.

[0063] A first thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, MgO particles and a binder water glass. In the first thermal insulation layer, a proportion of a hollow Al.sub.2O.sub.3 sphere is 85 wt %, a proportion of the SiO.sub.2 particles is 9 wt %, a proportion of the CaO particles is 2.0 wt %, a proportion of the MgO particles is 2.0 wt %, and a proportion of the water glass is 2 wt %. The Al.sub.2O.sub.3 particles have a hollow spherical structure, in which an inner hole diameter of the sphere is 0.8 μm, and a diameter of the sphere is 80 μm. The size of the SiO.sub.2 particles is 60 μm. Both CaO and MgO are granular, with a size of 8 μm. The entire first thermal insulation layer is required to have a refractoriness higher than 1560° C., with a porosity of 65% and a pore size of 3.0 mm.

[0064] The materials of the first thermal insulation layer, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles and the MgO particles specified above were preliminarily mixed by a stirrer at a speed of 400 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, water glass needed to be added to be used as a binder, and a speed of the stirrer was 480 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 72 h. Finally, mold release was carried out to obtain the first thermal insulation layer.

[0065] A second thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, MgO particles and a binder silica sol. In the second thermal insulation layer, a proportion of the Al.sub.2O.sub.3 particles is 50 wt %, a proportion of the SiO.sub.2 particles is 36 wt %, a proportion of the CaO particles is 3 wt %, a proportion of the MgO particles is 3 wt %, and a proportion of the silica sol is 8 wt %. The Al.sub.2O.sub.3 particles have a size of 100 μm, and the SiO.sub.2 particles have a size of 65 μm. Both CaO and MgO are granular, with a size of 10 μm. The entire second thermal insulation layer is required to have a refractoriness higher than 1100° C., with a porosity of 75% and a pore size of 5 mm.

[0066] The materials of the second thermal insulation layer, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles, and the MgO particles specified above were mixed by a stirrer at a speed of 300 r/min to obtain a mixed material, wherein in the stirring process, silica sol was added to be used as a binder. The resulting mixed material was injected into a mold cavity and then naturally cured for 12 h. Finally, mold release was carried out to obtain the second thermal insulation layer.

[0067] The liner contact layer, the first thermal insulation layer, and the second thermal insulation layer prepared above and a steel housing layer were combined and then heated and baked. In a low temperature stage (from room temperature to 180° C.), the heating was performed at a rate of 60° C./h, and after reaching the temperature, the temperature was maintained for 36 h. In an intermediate temperature stage (180° C.-850° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 48 h. In a high temperature stage (850° C.-1100° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 36 h. Finally, a casting ladle for casting aluminum alloy was obtained.

Comparative Example 1: Conventional Casting Ladle

[0068] A conventional casting ladle includes a composite ceramic brick, a heavy coke oven material layer, a thermal insulation layer, a cotton insulation layer and a furnace housing sequentially from inside to outside. The composite ceramic brick is formed from TiO.sub.2 and Al.sub.2O.sub.3 by sintering at 1450° C., and a major component thereof is Al.sub.2TiO.sub.5 generated. A heavy coke oven material is mainly Al.sub.2O.sub.3. The thermal insulation layer is a refractory fiberboard of 20 mm. The cotton insulation layer is an insulating cotton of 3-5 mm. The furnace housing is a steel housing.

Comparative Example 2

[0069] A liner contact layer is composed of ZrO.sub.2 particles, Al.sub.2O.sub.3 particles, SiO.sub.2 particles and a binder aluminum dihydrogen phosphate. In the liner contact layer, a proportion of the ZrO.sub.2 particles is 95 wt %, a proportion of the Al.sub.2O.sub.3 particles is 2 wt %, a proportion of the SiO.sub.2 particles is 0.5 wt %, and a proportion of aluminum dihydrogen phosphate is 1.0 wt %. The size of the ZrO.sub.2 particles is 8 μm, the size of the Al.sub.2O.sub.3 particles is 30 μm, and the size of the SiO.sub.2 particles is 30 μm. The entire liner contact layer is required to have a refractoriness higher than 1650° C., with a porosity of 2% and a pore size of 8 μm.

[0070] The materials of the liner contact layer, namely the ZrO.sub.2 particles, the Al.sub.2O.sub.3 particles and the SiO.sub.2 particles specified above were preliminarily mixed by a stirrer at a speed of 500 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, aluminum dihydrogen phosphate needed to be added to be used as a binder, and a speed of the stirrer was 680 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 84 h. Finally, mold release was carried out to obtain the liner contact layer.

[0071] A first thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, MgO particles and a binder water glass. In the first thermal insulation layer, a proportion of a hollow Al.sub.2O.sub.3 sphere is 90 wt %, a proportion of the SiO.sub.2 particles is 6.0 wt %, a proportion of the CaO particles is 0.5 wt %, a proportion of the MgO particles is 1.0 wt %, and a proportion of the water glass is 1.5 wt %. The Al.sub.2O.sub.3 particles have a hollow spherical structure, in which an inner hole diameter of the sphere is 0.2 μm, and a diameter of the sphere is 30 μm. The size of the SiO.sub.2 particles is 35 μm. Both CaO and MgO are granular, with a size of 4 μm. The entire first thermal insulation layer is required to have a refractoriness higher than 1560° C., with a porosity of 50% and a pore size of 0.6 mm.

[0072] The materials of the first thermal insulation layer, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles and the MgO particles specified above were preliminarily mixed by a stirrer at a speed of 400 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, water glass needed to be added to be used as a binder, and a speed of the stirrer was 480 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 72 h. Finally, mold release was carried out to obtain the first thermal insulation layer.

[0073] A second thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, MgO particles and a binder silica sol. In the second thermal insulation layer, a proportion of the Al.sub.2O.sub.3 particles is 56 wt %, a proportion of the SiO.sub.2 particles is 20 wt %, a proportion of the CaO particles is 7 wt %, a proportion of the MgO particles is 7 wt %, and a proportion of the silica sol is 10 wt %. The Al.sub.2O.sub.3 particles have a size of 40 μm, and the SiO.sub.2 particles have a size of 45 μm. Both CaO and MgO are granular, with a size of 3 μm. The entire second thermal insulation layer is required to have a refractoriness higher than 1100° C., with a porosity of 50% and a pore size of 1.5 mm.

[0074] The materials of the second thermal insulation layer, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles, and the MgO particles specified above were mixed by a stirrer at a speed of 300 r/min to obtain a mixed material, wherein in the stirring process, silica sol was added to be used as a binder. The resulting mixed material was injected into a mold cavity and then naturally cured for 12 h. Finally, mold release was carried out to obtain the second thermal insulation layer.

[0075] The liner contact layer, the first thermal insulation layer, and the second thermal insulation layer prepared above and a steel housing layer were combined and then heated and baked. In a low temperature stage (from room temperature to 180° C.), the heating was performed at a rate of 60° C./h, and after reaching the temperature, the temperature was maintained for 36 h. In an intermediate temperature stage (180° C.-850° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 48 h. In a high temperature stage (850° C.-1100° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 36 h. Finally, a casting ladle for casting aluminum alloy was obtained.

Comparative Example 3

[0076] A liner contact layer is composed of ZrO.sub.2 particles, Al.sub.2O.sub.3 particles, SiO.sub.2 particles and a binder aluminum dihydrogen phosphate. In the liner contact layer, a proportion of the ZrO.sub.2 particles is 80 wt %, a proportion of the Al.sub.2O.sub.3 particles is 12 wt %, a proportion of the SiO.sub.2 particles is 4 wt %, and a proportion of aluminum dihydrogen phosphate is 4 wt %. The size of the ZrO.sub.2 particles is 35 μm, the size of the Al.sub.2O.sub.3 particles is 90 μm, and the size of the SiO.sub.2 particles is 70 μm. The entire liner contact layer is required to have a refractoriness higher than 1650° C., with a porosity of 9% and a pore size of 20 μm.

[0077] The materials of the liner contact layer, namely the ZrO.sub.2 particles, the Al.sub.2O.sub.3 particles and the SiO.sub.2 particles specified above were preliminarily mixed by a stirrer at a speed of 500 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, aluminum dihydrogen phosphate needed to be added to be used as a binder, and a speed of the stirrer was 680 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 84 h. Finally, mold release was carried out to obtain the liner contact layer.

[0078] A first thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, MgO particles and a binder water glass. In the first thermal insulation layer, a proportion of a hollow Al.sub.2O.sub.3 sphere is 68 wt %, a proportion of the SiO.sub.2 particles is 15 wt %, a proportion of the CaO particles is 4.0 wt %, a proportion of the MgO particles is 5.0 wt %, and a proportion of the water glass is 8 wt %. The Al.sub.2O.sub.3 particles have a hollow spherical structure, in which an inner hole diameter of the sphere is 1.0 μm, and a diameter of the sphere is 100 μm. The size of the SiO.sub.2 particles is 75 μm. Both CaO and MgO are granular, with a size of 12 μm. The entire first thermal insulation layer is required to have a refractoriness higher than 1560° C., with a porosity of 70% and a pore size of 5.0 mm.

[0079] The materials of the first thermal insulation layer, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles and the MgO particles specified above were preliminarily mixed by a stirrer at a speed of 400 r/min to obtain a preliminary mixture. Then, the obtained preliminary mixture was rapidly mixed to obtain a preform, wherein in the rapid mixing stage, water glass needed to be added to be used as a binder, and a speed of the stirrer was 480 r/min. The obtained preform was injected into a mold cavity followed by jolt ramming, and then naturally cured for 72 h. Finally, mold release was carried out to obtain the first thermal insulation layer.

[0080] A second thermal insulation layer is composed of Al.sub.2O.sub.3 particles, SiO.sub.2 particles, CaO particles, MgO particles and a binder silica sol. In the second thermal insulation layer, a proportion of the Al.sub.2O.sub.3 particles is 30 wt %, a proportion of the SiO.sub.2 particles is 63 wt %, a proportion of the CaO particles is 2 wt %, a proportion of the MgO particles is 2 wt %, and a proportion of the silica sol is 3 wt %. The Al.sub.2O.sub.3 particles have a size of 120 μm, and the SiO.sub.2 particles have a size of 80 μm. Both CaO and MgO are granular, with a size of 15 μm. The entire second thermal insulation layer is required to have a refractoriness higher than 1100° C., with a porosity of 80% and a pore size of 7 mm.

[0081] The materials of the second thermal insulation layer, namely the Al.sub.2O.sub.3 particles, the SiO.sub.2 particles, the CaO particles, and the MgO particles specified above were mixed by a stirrer at a speed of 300 r/min to obtain a mixed material, wherein in the stirring process, silica sol was added to be used as a binder. The resulting mixed material was injected into a mold cavity and then naturally cured for 12 h. Finally, mold release was carried out to obtain the second thermal insulation layer.

[0082] The liner contact layer, the first thermal insulation layer, and the second thermal insulation layer prepared above and a steel housing layer were combined and then heated and baked. In a low temperature stage (from room temperature to 180° C.), the heating was performed at a rate of 60° C./h, and after reaching the temperature, the temperature was maintained for 36 h. In an intermediate temperature stage (180° C.-850° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 48 h. In a high temperature stage (850° C.-1100° C.), the heating was performed at a rate of 100° C./h, and after reaching the temperature, the temperature was maintained for 36 h. Finally, a casting ladle for casting aluminum alloy was obtained.

[0083] Thermal insulation performance test: used for testing a thermal insulation effect of casting ladles

[0084] An equal amount of molten aluminum alloy was charged into the casting ladles in Examples 1, 2 and 3 and Comparative examples 1, 2 and 3, respectively, an initial temperature of the molten aluminum alloy was measured, and then, a temperature of the molten aluminum alloy was measured at 1, 3, 5, 7, 9, 15 and 20 min, respectively, which were recorded in Table 1. The molten aluminum alloy in the casting ladle was subjected to a degassing and refining process within 20 minutes and then supplied to a die casting machine.

[0085] As shown in Table 1, the molten aluminum alloys in Examples 1, 2 and 3 have the initial temperatures of 735° C., 738° C., and 736° C., respectively. After 20 minutes, the temperatures of the molten aluminum alloys were decreased to 731° C., 734° C., and 732° C., respectively, with a temperature decrease rate of about 0.2° C./min. In Comparative example 1, the molten aluminum alloy in the conventional casting ladle has an initial temperature of 735° C., and after 20 minutes, the temperature was decreased to 705° C., with a temperature decrease rate of 1.5° C./min. Thus, it can be explained that compared with the conventional casting ladle, the casting ladle of the present invention may achieve a good thermal insulation effect by designing parameters such as the shape, size, proportion, and porosity of the thermal insulation materials. In Comparative example 2, the first and second thermal insulation layers of the casting ladle have the porosity and pore size less than those of the casting ladle of the present invention, and the temperature decrease rate is 1.55° C./min. In Comparative example 3, the first and second thermal insulation layers of the casting ladle have the porosity and pore size larger than those of the casting ladle of the present invention, and the temperature decrease rate is 1.65° C./min. It is further shown that the casting ladle of the present invention achieves a good thermal insulation effect by reasonably adjusting the porosity and pore size of the first and second thermal insulation layers of the casting ladle.

TABLE-US-00001 TABLE 1 Temperature Statistical Table of Molten Aluminum Alloy in Casting Ladles Initial At At At At At At At Data for Temperature 1 min 3 min 5 min 7 min 9 min 15 min 20 min comparison (° C.) (° C.) (° C.) (° C.) (° C.) (° C.) (° C.) (° C.) Example 1 735 734 734 734 733 733 732 731 Example 2 738 738 737 737 736 735 735 734 Example 3 736 735 735 734 734 733 733 732 Comparative 735 733 730 727 724 720 715 705 example 1 Comparative 735 733 729 727 723 720 714 704 example 2 Comparative 736 734 729 728 724 721 715 703 example 3

TABLE-US-00002 TABLE 2 Natural Gas Loss Statistical Table of Baking Casting Ladles Frequency Ladle Number of of ladle baking ladles for Usage Natural baking time producing amount of gas cost Data for (ladle(s) (min per aluminum natural gas (Yuan/ comparison per times) ladle) (ladle) (m.sup.3/day) day) Example 1 No ladle No ladle 160 0 0 baking baking Example 2 No ladle No ladle 160 0 0 baking baking Example 3 No ladle No ladle 160 0 0 baking baking Comparative 1 5 160 480 960 example 1 Comparative 1 5 160 480 960 example 2 Comparative 1 5 160 480 960 example 3

[0086] Table 2 is a statistical table showing the consumption of natural gas for on-site air-baking casting ladles in the workshop. As can be seen from Table 2, the casting ladles in Comparative examples 1, 2 and 3 have a greatly reduced inner temperature due to a poor thermal insulation effect, and the empty casting ladles need to be baked after return. However, in Examples 1, 2 and 3, the ladle baking process is not required, thereby reducing the factory cost, decreasing labor intensity of workers, saving energy while protecting the environment, and eliminating the safety hazard of scalding employees.

[0087] K-mold test: used for testing the slag content of molten aluminum alloy in casting ladle

[0088] Reference is made to Standard NO. YS/T1004-2014, entitled molten aluminum and aluminum alloy, of the Non-ferrous Metal Industry of the People's Republic of China, for a K-mold test method.

TABLE-US-00003 TABLE 3 Statistical table of K-mold test results of slag inclusions of molten aluminum alloy in casting ladles K-mold Sampling 1.sup.st time 2.sup.nd time 3.sup.rd time 4.sup.th time 5.sup.th time Average Example 1 0 0 0.1 0.1 0 0.04 Example 2 0 0.1 0.1 0 0 0.04 Example 3 0 0 0 0.1 0.1 0.04 Comparative 0.1 0.1 0.1 0.2 0.1 0.12 example 1 Comparative 0 0 0.1 0 0.1 0.04 example 2 Comparative 0.1 0 0 0.1 0 0.04 example 3

[0089] Table 3 shows K-mold test and analysis of the purity of molten aluminum alloy in casting ladles. In an actual production process in the workshops, a K-mold is usually used for quick analysis of slag inclusion in the molten aluminum. As can be seen from Table 3, in the conventional casting ladle of Comparative example 1, there are slag inclusions in the molten aluminum due to serious slag adhering on the wall of the casting ladle, and the average value of the K-mold test is 0.12. In Examples 1, 2, and 3 and Comparative examples 2 and 3, the average value of the K-mold test of the molten aluminum in casting ladles is 0.04 because aluminum slag is not adhered to the walls of casting ladles. Therefore, the present invention can achieve the effects of having no aluminum adhesion and improving the quality of the molten aluminum alloy.

[0090] As shown in FIG. 2, the amount of aluminum slag adhered to the inner wall of the conventional casting ladle in comparative example 1 is relatively large. As shown in FIG. 3, the amount of aluminum slag adhered to the inner wall of a casting ladle according to one embodiment of the present invention is significantly smaller than that of FIG. 2. Thus, it can be seen that the casting ladle of the present invention can indeed achieve the effects of having no aluminum adhesion and improving the quality of the molten aluminum alloy.

[0091] The foregoing description is only preferred embodiments of the present invention, and does not limit the patent scope of the present invention. Under the inventive concept of the present invention, the equivalent structure transformation made by using the contents of the description and accompanying drawings of the present invention, or the direct/indirect application in other related technical fields is included in the scope of patent protection of the present invention.