JP2006224114A - Member for molten metal and producing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic-made member for molten metal which has excellent strength, wear resistance, corrosion resistance, heat-shocking resistance and is drastically hard to be wet with the molten metal, and has profitability, durability and stable quality. <P>SOLUTION: A producing method for ceramic-made member for molten metal has: a first process, in which the slurry containing no component having wetness difficulty is poured into a porous mold having water-absorbability, and after sticking and solidifying by absorbing moisture into pores in the porous mold, a basic material layer is formed by removing the mud after elapse of a predetermined time; a second process, in which after the slurry containing component having wetness difficulty is made to flow into the basic material layer, an inner layer is formed on the inner surface of the basic material layer by discharging this slurry after elapse of a predetermined time; and a third process, in which after drying, the basic material layer is burned and sintered at a predetermined temperature to be made compact and simultaneously, integrated with the basic material layer and the inner layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is excellent for strength, corrosion resistance, wear resistance, thermal shock resistance, is difficult to get wet with high-temperature molten metal such as aluminum, copper, cast iron, etc., and has little adhesion to molten metal. It is related with a member and its manufacturing method.

  Silicon nitride ceramics are applied in many industrial fields because of their high strength, high hardness, thermal shock resistance, and corrosion resistance. For example, a method of manufacturing a member such as break ring by reactive sintering using silicon and boron as main raw materials is known (Japanese Patent Laid-Open Nos. 60-22676 and 59-107799). However, this method has a problem that it is easily damaged by thermal shock because of its low strength. Therefore, material development methods such as boron nitride can improve the wettability to metal melt, workability, corrosion resistance, thermal shock resistance and thermal shock resistance, but the strength is reduced. There is a problem that this is inevitable. For this reason, when measuring or conveying the high-temperature molten metal, the ladle may be damaged, leading to a serious accident. In addition, raw materials with high wettability are expensive, and it is necessary to minimize the amount used economically.

  In order to improve the hard wettability, conventionally, a layer containing a hard wettable component has been formed on the silicon nitride surface. As the simplest method, there is a method in which a boron compound powder having low wettability with respect to a molten metal is brushed or sprayed on a silicon nitride surface. In this method, since the base material layer and the boron compound powder are not integrated, peeling is easily caused by repeated use. As a method for imparting more durability, there is a method in which a component having poor wettability is sprayed onto the silicon nitride substrate layer. In Japanese Patent Application Laid-Open No. 8-141718, a porous layer is formed by spraying a material having poor wettability with molten metal onto a chute / trough of a centrifugal casting apparatus, and this porous layer is impregnated with a coating mold. Since the layer formed at this time is porous, a problem remains in durability.

  Further, there is a method of forming a surface layer composed of a composite structure in which boron nitride particles are dispersed and mixed in a base material ceramic as disclosed in Japanese Patent No. 3054978. In this method, a cold hydrostatic isostatic press is used, so it is suitable for shaping a circular tube such as stalk. Not suitable. In addition, it is impossible to form a structure that prevents the separation of the surface layer and the base material layer by realizing a structure in which the convex portions of the surface layer and the concave portions of the base material layer in which the hardly wettable component is dispersed are generally meshed. It is.

Japanese Patent Laid-Open No. 60-022676 JP 59-109779 A Japanese Patent Laid-Open No. 08-141718 Japanese Patent No. 3054978

  Metal melt members such as ladles, heater tubes, and stalks used in melting / casting lines that use molten metal must be resistant to getting wet with molten metal. For example, in the case of a ladle capable of transporting and reducing the weight of the molten metal, there is a problem that the measurement accuracy is reduced when the molten metal adheres. Further, when the molten metal adheres and solidifies by cooling, the solidified part is often removed using a hammer or the like, and depending on the impact, the ladle itself may be damaged. The present invention is excellent in strength, corrosion resistance, wear resistance, and thermal shock resistance so that it can solve these practical problems in the melting and casting line, and it is difficult to drastically wet the molten metal, and its economic efficiency. It is intended to provide a member for molten metal made of ceramic with stable durability and quality.

  The means taken by the present invention to solve the above problems is a heat-resistant member for molten metal produced by firing a laminate comprising a base material layer and an inner layer, and most of the outer surface of the base material layer is It is a fired surface that has not been machined, and an inner layer in which a component having difficulty in wettability with respect to the molten metal is dispersed is laminated on the inner surface of the base material layer. The layer and the inner layer are integrated. Further, an outer layer in which a component having poor wettability is dispersed may be laminated.

  Further, the layer in which the component having difficulty wettability is dispersed is integrated with the base material layer by an anchor structure, and the heat-resistant member is silicon nitride, sialon or a composite containing them as a main component. The material and the component having poor wettability are characterized in that the boron compound is a compound of B and an element selected from the element group of Ti, Zr, C, and N.

  Furthermore, a slurry that does not contain a component having poor wettability is poured into a porous mold having water absorption properties, and the porous mold is allowed to absorb moisture to solidify and solidify after a predetermined time. A first step of forming a base material layer by mud and after pouring a slurry containing a component having poor wettability into the base material layer, the slurry is discharged after a predetermined time and the inner layer is formed on the inner surface of the base material layer. It is characterized by comprising the second step of forming and the third step of integrating the base material layer and the inner layer simultaneously with sintering and densification after baking and sintering at a predetermined temperature.

  In place of the second step of injecting and discharging the slurry containing the hardly wettable component, the step of applying or spraying the slurry containing the hardly wettable component can be made dense in the sintering process. If the layer and the inner layer can be integrated, the object is achieved. Further, it is possible to further include a step of forming an anchor structure on the inner surface of the base material layer after the first step.

  By the first to third steps, for example, a hardly wettable component is dispersed on the inner surface of the ladle, and the wettability with the molten metal is reduced, thereby reducing the adhesion amount of the molten metal and increasing the measurement accuracy; At the same time, the base material layer does not contain a component having poor wettability, and the reliability of the member can be maintained only by the strength of the base material layer.

  According to this invention, it is excellent in strength, corrosion resistance, wear resistance, and thermal shock resistance, is not easily wetted by molten metal such as aluminum, copper, cast iron, etc., and is made of ceramics with little adhesion of molten metal to the inner or outer surface of the member. A member for molten metal and a method for producing the member can be provided.

  The ceramic metal melt member reduces the amount of molten metal adhering to the inner surface or the outer surface, and in particular for a metal melt member such as a ladle, the measurement accuracy can be increased, and the base material layer Since the reliability of the member can be maintained only by the strength of the metal, it can be used in a melting / casting line as a member for molten metal having stable economy, durability and quality.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The molten metal member of the present invention is excellent in strength, corrosion resistance, wear resistance, and thermal shock resistance, and is difficult to get wet with molten metal such as aluminum, copper, cast iron, etc., and the adhesion of molten metal to the inner surface of the member is small. The member for molten metal and its manufacturing method are provided.

  First, the raw material powder of the heat-resistant member to be the base material layer is slurried. The heat-resistant member is preferably composed mainly of ceramics, but more preferably silicon nitride, sialon, or a composite material composed mainly of them. When preparing a heat resistant member of silicon nitride or sialon, a mixed powder containing at least a part of metal silicon, silicon nitride, sialon, silicon oxide, metal aluminum, aluminum nitride, and aluminum oxide is used as a raw material powder. Metallic silicon and metallic aluminum are preferably powders having an average particle size of 30 μm or less. The silicon nitride powder preferably has an α-type crystal structure and an average particle size of 10 μm or less. Sialons having a β-type crystal structure and an average particle size of 1 μm or less are suitable. The silicon oxide, aluminum nitride and aluminum oxide powders preferably have an average particle size of 10 μm or less.

  In addition, it is preferable to add a metal oxide as a sintering aid in the raw material powder. As the sintering aid to be added, oxides such as yttria, ytterbia, alumina and magnesia are suitable, and the amount added is preferably in the range of 3 to 10% by mass with respect to the raw material powder. When the sintering aid to be added is too small, densification does not proceed and the strength becomes insufficient. Moreover, when there are too many sintering aids, the thermal shock resistance in high temperature falls. In addition, arbitrary methods are employable as a mixing method of raw material powder. For example, when adopting ball mill mixing, a solvent and a dispersant are added to the mixed powder to form a slurry. In addition, it is also possible to add a binder and an antifoaming agent as needed.

  Next, the slurry is poured into a porous mold having water absorption, preferably a gypsum mold or a resin mold, and the porous pores are allowed to absorb moisture to solidify, and after a predetermined time, the mud is discharged. Thereby, the base material layer which consists of a powder formation body is obtained. The thickness of the wall, that is, the thickness of the heat-resistant member serving as the base material layer can be adjusted by the porosity of the porous mold, the concentration of the slurry, and the time of the wall. If necessary, processing of the powder molded body, so-called raw processing, is performed to prepare the shape.

  At this time, a step of forming an anchor structure on the inner surface is taken if necessary. The anchor structure can be realized by forming grooves or dimples on the inner surface of the base material layer. Examples of the method for forming the anchor structure include machining and blasting using a mask, but are not limited thereto.

  Next, a slurry containing a component having hardly wettability (hereinafter simply referred to as “hardly wettable component”) is prepared. The slurry is prepared by adding a boron compound that is a hardly wettable component to the slurry of the base material layer. The boron compound content is desirably 5 to 50 mass%. When the content is small, the poor wettability with respect to the molten metal cannot be sufficiently exhibited, and when the content is large, the integrity with the base material layer is insufficient. The obtained slurry is poured into the base material layer and then drained after a predetermined time, or the slurry is coated or sprayed to disperse the hardly wettable component on the inner surface of the base material layer, and the base material An inner layer integrated with the layer is formed. In addition, when employ | adopting an anchor structure, the anchor structure as shown in FIG. 3 is formed by making the slurry containing a hardly wettable component spread in the recessed part formed in the base material layer.

  The powder molded body consisting of the base material layer and the inner layer obtained through the above steps is dried and fired at a predetermined temperature to disperse the base material layer and difficult-to-wet components simultaneously with sintering and densification. The heat-resistant member for molten metal can be obtained by integrating the inner layers. When the base material layer is silicon nitride or sialon and the hardly wettable component is boron nitride, firing in a pressurized nitrogen atmosphere is desirable to prevent decomposition. In this case, the firing temperature is preferably 1400 ° C. or higher, more preferably 1500 ° C. to 1900 ° C., and the firing time is desirably 30 minutes to 10 hours. When the firing temperature is too low, densification does not occur sufficiently, and the base material layer and the inner layer are not sufficiently integrated. When the firing temperature is too high, decomposition of the base material layer and difficult-to-wet components occurs. In addition, when other ceramics or a difficult-to-wet component is selected, it is necessary to select a firing temperature, a firing time, and an atmosphere according to the material and the component. EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to the examples.

  Add 3% alumina and 5% yttria as sintering aids to silicon nitride powder, add 40% water, 1% dispersant and 1% binder by weight with respect to the powder weight, The mixture was mixed with a ball mill to obtain a slurry for preparing the base material layer. This slurry was poured into a gypsum mold having a water content ratio of 60%, absorbed for 15 minutes to solidify, and then drained to obtain a powder molded body of the base material layer. Next, to the powder obtained by adding 3% by mass of alumina and 5% by mass of yttria as a sintering aid to the silicon nitride powder, boron nitride powder was added at a mass ratio of 3: 1. Mass% water, 1.5 mass% dispersant and 1 mass% binder were added and mixed in a ball mill to obtain a slurry for producing an inner layer. The slurry is poured into the powder molded body of the base material layer, water absorbed for 1 minute, solidified, and then drained to obtain a powder molded body in which the base material layer and the inner layer in which difficultly wet components are dispersed are integrated. It was. This powder molded body was dried, degreased, and then fired for 2 hours at a firing temperature of 1850 ° C. in an atmosphere of 9 atm nitrogen gas. Through the above steps, a member for molten metal such as aluminum in which the inner layer in which the component having poor wettability to the molten metal was dispersed was integrated with the base material layer was obtained.

  In order to confirm the wettability of the obtained member for molten metal, the contact angle with the AC4C aluminum alloy was measured at 750 ° C. and found to be 154 degrees. For comparison, the contact angle when measured on the outer surface of the base material layer was 121 degrees. Further, when the AC4C aluminum alloy was weighed using the member, the aluminum alloy did not adhere to the inner layer surface. On the other hand, when a measurement was performed using a commercially available silicon nitride aluminum melt member, an aluminum alloy slightly adhered to the inner surface of the member. Further, a ladle was prepared by the same method as in Example 1, and the AC4C aluminum alloy was weighed in the same manner as described above. As a result, it was confirmed that the same effect as in Example 2 was obtained.

  The slurry forming method for preparing the powder molded body of the base material layer and the inner layer is the same as in Example 1. The slurry for forming the inner layer was sprayed on the inner surface side of the powder molded body of the base material layer with an air spray gun to obtain a powder molded body in which the base material layer and the inner layer in which the hardly wettable component was dispersed were integrated. This powder molded body was dried, degreased and fired under the same conditions as in Example 1. Even in the method by spraying, a member for a molten metal such as aluminum in which an inner layer in which a hardly wettable component is dispersed is formed on the inner surface of the member and integrated with the base material layer is obtained as in Example 1. .

  In Example 2, after anchoring a groove having a width of 1 mm and a depth of 0.7 mm in a lattice shape with an interval of 2 mm by blasting using a mask on the inner surface of the base material layer, the slurry for creating the inner layer was sprayed. It was. The powder molded body is dried, degreased and fired under the same conditions as in Example 1, whereby the base layer and the inner layer in which the hardly wettable component is dispersed have an anchor structure, and the base layer and the inner layer Obtained a member for molten metal such as aluminum.

  In order to verify the durability of the member for molten metal obtained in Example 2 or 3, a test piece was cut out from the member and immersed in the molten AC4C aluminum alloy. For comparison, a flat plate was prepared by laminating a hard-wetting component-containing layer having the same composition and a base material layer by molding with a cold isostatic pressing device (hereinafter simply referred to as CIP molding), and simultaneously tested. . As a result, the test piece obtained by CIP molding was peeled over 400 times by immersion and the layer containing the hardly wettable component was peeled off, whereas the test piece cut out from Example 2 was immersed by more than 520 times, and Example 3 The test pieces cut out from the sample were peeled from the inner layer after 590 times. Further, in the test piece obtained by CIP molding and the test piece cut out from Example 2, the peeled inner layer was immediately dropped, whereas in the test piece cut out from Example 3, the peeled inner layer was immediately dropped due to the effect of the anchor portion. I never did.

The molten metal member is formed by forming a layer in which a hardly wettable component is dispersed only on the inner surface of the base material layer. However, the present invention is not limited to this. That is, as shown in FIGS. 4 and 5, in addition to the inner surface of the base material layer, a layer in which a hardly wettable component is dispersed may be formed on the outer surface. In this case, the manufacturing method is basically the same as that of the above embodiment, but in order to form a layer in which the hardly wettable component is dispersed on the outer surface of the base material layer, The base material layer is immersed in a slurry in which a hardly wettable component is dispersed, or the slurry is applied to or sprayed on the outer surface in addition to the inner surface of the base material layer. The hard-wetting component is dispersed, and a layer integrated with the base material layer is formed. At this time, as in the above embodiment, the inner layer and / or the outer layer may have an anchor structure. The other steps such as firing are the same as the above steps.

External view of molten metal parts Cross-sectional enlarged view of a member for molten metal Cross-sectional enlarged view of a member for molten metal having an anchor structure Cross-sectional enlarged view of a member for molten metal having an inner layer and an outer layer Cross-sectional enlarged view of a member for a molten metal in which the inner layer and the outer layer have an anchor structure

Explanation of symbols

(1) Molten metal parts
(2) Base material layer
(3) Inner layer
(4) Anchor structure
(5) Outer layer

Claims (14)

  A heat-resistant member for molten metal produced by firing a laminate composed of a base material layer and an inner layer, and most of the outer surface of the base material layer is a fired surface not subjected to machining, and the inner surface of the base material layer Unlike the base material layer, an inner layer in which a component having a wettability with respect to the molten metal is dispersed is laminated, and the base material layer and the inner layer are integrated. Materials.   The member for molten metal according to claim 1, wherein an outer layer in which a component having poor wettability is further dispersed is laminated on the outer surface of the base material layer.   The member for molten metal according to claim 1 or 2, wherein the layer in which the component having hardly wettability is dispersed is integrated with the base material layer by an anchor structure.   4. The molten metal member according to claim 1, wherein the heat-resistant member is made of silicon nitride, sialon, or a composite material containing them as a main component.   5. The molten metal according to claim 1, wherein the base material layer does not include a component having poor wettability and maintains the reliability of the member only by the strength of the base material layer. Element.   The member for molten metal according to any one of claims 1 to 5, wherein the component having poor wettability is a boron compound.   7. The member for molten metal according to claim 6, wherein the boron compound is a compound of B and an element selected from the element group of Ti, Zr, C, and N.   The member for molten metal according to any one of claims 1 to 7, wherein the member for molten metal is a ladle.   The member for molten metal according to any one of claims 1 to 7, wherein the member for molten metal is a heater tube.   The member for molten metal according to claim 1, wherein the member for molten metal is stalk.   After pouring a slurry that does not contain a component having poor wettability into a porous mold having water absorbency, and allowing the porous mold to absorb moisture into the porous mold, the slurry is drained after a predetermined time has elapsed. The first step of forming the base material layer and the slurry containing the component having poor wettability are poured into the base material layer, and then discharged after a predetermined time to form the inner layer on the inner surface of the base material layer. A method for producing a member for molten metal, comprising a second step and a third step in which, after drying, firing at a predetermined temperature to sinter and densify the base layer and the inner layer together. .   After pouring a slurry that does not contain a component having poor wettability into a porous mold having water absorbency, and allowing the porous mold to absorb moisture into the porous mold, the slurry is drained after a predetermined time has elapsed. A first step of forming a base material layer, a second step of applying or spraying a slurry containing a component having poor wettability in the base material layer to form an inner layer on the inner surface of the base material layer, and after drying A method for producing a member for molten metal, comprising a third step of firing at a predetermined temperature and integrating the base material layer and the inner layer simultaneously with sintering and densification.   The method for producing a molten metal member according to claim 11 or 12, further comprising a step of forming an anchor structure on at least an inner surface of the base material layer after the first step. 14. In the second step, the outer layer is formed by further laminating a slurry containing a component having poor wettability on the outer surface of the base material layer. The manufacturing method of the member for molten metal of description.

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