WO2013021677A1 - 黒鉛ルツボ - Google Patents
黒鉛ルツボ Download PDFInfo
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- WO2013021677A1 WO2013021677A1 PCT/JP2012/058254 JP2012058254W WO2013021677A1 WO 2013021677 A1 WO2013021677 A1 WO 2013021677A1 JP 2012058254 W JP2012058254 W JP 2012058254W WO 2013021677 A1 WO2013021677 A1 WO 2013021677A1
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- graphite
- graphite crucible
- crucible
- processed
- gas discharge
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B14/00—Crucible or pot furnaces
- F27B14/08—Details peculiar to crucible or pot furnaces
- F27B14/10—Crucibles
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D1/00—Casings; Linings; Walls; Roofs
- F27D1/0003—Linings or walls
- F27D1/0006—Linings or walls formed from bricks or layers with a particular composition or specific characteristics
Definitions
- the present invention relates to a graphite crucible, and more particularly to a graphite crucible for melting an object to be processed such as a metal.
- the target substance (object to be treated) is, for example, tin (melting point 232 ° C.), lead (melting point 328 ° C.), aluminum (melting point 660 ° C.), copper (melting point 1083 ° C.), silicon (melting point 1410 ° C.), iron ( Melting point 1539 ° C.) and nickel (melting point 1726 ° C.).
- the crucible is selected based on the heat resistance of the object to be processed and the reactivity between the object to be processed and the crucible.
- a crucible for melting an iron-based object or the like needs heat resistance and corrosion resistance of 1400 ° C.
- An object of the present invention is to provide a graphite crucible which can be melted and solidified safely and without scattering the object to be treated.
- the present invention is as follows. (1) A graphite crucible having a bottom part, a body part, and a processing part having an input port, having a gas discharge part closed at the lower end side and opened at the upper end side of the body part. (2) The graphite crucible according to (1), wherein the gas discharge part is formed in a groove shape. (3) The graphite crucible according to (1) or (2), wherein the thickness of the bottom is thicker than the minimum value of the distance between the gas discharge portion peripheral surface and the crucible inner peripheral surface. (4) The graphite crucible according to any one of (1) to (3), wherein the graphite crucible has a bulk density of 1700 to 1850 kg / m 3 .
- the graphite crucible is the graphite according to any one of (1) to (6), for melting an object to be processed selected from iron-based, silicon-based, nickel-based, titanium-based, and mixtures thereof.
- Crucible. A method for producing a solidified body of the object to be processed using the graphite crucible according to any one of (1) to (7).
- the gasification of impurities contained in the object to be treated can be similarly promoted, and the impurities contained in the object to be treated can be prevented from suddenly boiling and bumping from the graphite crucible. Since bumping of the object to be processed can be prevented, it is considered that the object to be processed can be prevented from being scattered and contaminated in an apparatus provided with a graphite crucible.
- the graphite crucible has a gas discharge part opened on the upper end side of the body part, when corrosive gas or reactive gas is generated from the object to be processed or by reaction between the object to be processed and graphite In this case, corrosive gas or reactive gas that permeates through the body of the graphite crucible can be introduced to the gas discharge part. For this reason, it can be made difficult to fill these corrosive gas or reactive gas inside the melting apparatus. For this reason, it is considered that corrosion of the melting apparatus can be prevented even if a porous graphite crucible is used.
- FIG. 1A is a cross-sectional view taken along line AA of FIG. 1B including the central axis of the graphite crucible of the first embodiment of the present invention
- FIG. 1B is the first embodiment of the present invention.
- It is a top view of a graphite crucible.
- 2A is a cross-sectional view including the central axis of the graphite crucible according to the second embodiment of the present invention
- FIG. 2B is a plan view of the graphite crucible according to the second embodiment of the present invention.
- An Si—C binary phase diagram is shown.
- An Fe—C binary phase diagram is shown.
- the polarization micrograph of the boundary region of a graphite crucible and a processed object (iron) of the section divided after heating concerning the embodiment of the present invention is shown.
- FIG. 1 shows a graphite crucible of Embodiment 1 of the present invention
- FIG. 1 (A) is a cross-sectional view taken along line AA of FIG. 1 (B) including the central axis of the graphite crucible of Embodiment 1 of the present invention
- FIG. 1B is a plan view of the graphite crucible according to the first embodiment of the present invention.
- the graphite crucible means that graphite is a substantial constituent.
- any graphite may be used.
- Anisotropic graphite CIP molding: Cold Isostatic Press
- anisotropic graphite such as an extrusion molding material or a die-molding material.
- Graphite material may be used.
- graphite obtained by CIP molding has high strength because a fine material (for example, coke having a particle diameter of 10 to 20 ⁇ m) can be used, and the structure becomes fine.
- an isotropic material can be obtained because it is pressurized with a liquid pressurizing medium, and since there is no directionality in the coefficient of thermal expansion, it is difficult to cause distorted deformation, and thermal stress due to distorted deformation is unlikely to occur, Troubles such as cracks can be made difficult to occur.
- a graphite crucible 1 according to Embodiment 1 of the present invention includes a treatment part 4 having a bottom part 2, a body part 3, and an inlet 4a, a gas discharge part that is closed at the lower end side and opened at the upper end side of the body part. 5.
- the graphite crucible 1 according to the first embodiment of the present invention is a graphite made by removing the gas discharge unit 5 from the space between the crucible inner peripheral surface 1a and the crucible outer peripheral surface 1b constituting the space of the processing unit 4. .
- the bottom portion 2 is a portion below the inner bottom surface when the surface including the inner bottom surface 2a which is the lower end portion of the inner peripheral surface 1a of the crucible is cut out to the outer peripheral surface of the crucible.
- the inner bottom surface 2a may be a curved surface as well as a flat surface as shown in FIG. Examples of the curved surface include a curved surface having an extreme value at the lower end of the inner peripheral surface of the crucible, and a contact surface of the extreme value coincides with the inner bottom surface 2a.
- the bottom 2 has an outer bottom surface 2b corresponding to the lower end surface of the crucible outer peripheral surface 1b.
- the body portion 3 is a portion between the crucible inner peripheral surface 1 a and the crucible outer peripheral surface 1 b and is a portion other than the bottom portion 2 of the graphite crucible 1.
- the gas discharge part 5 has a gas discharge function in a space (hole) opened at the lower end side and opened at the upper end side of the body part, its shape, size, position, number of closings, etc. are not particularly limited.
- Absent. 1 (A) and 1 (B) has a cylindrical shape, and has a closed end 5a on the lower end side, an opening 5b on the upper end side of the trunk, and 20 concentrically in the trunk. Provided, and they are provided at positions where the central angle is approximately 18 ° with respect to each other. The position of the closing port 5a is slightly below the inner bottom surface 2a.
- the thickness T of the bottom portion 2 is preferably thicker than the minimum value of the distance t between the gas discharge portion peripheral surface 5c and the crucible inner peripheral surface 1a.
- the distance t between the gas discharge portion peripheral surface 5c and the crucible inner peripheral surface is set to a certain range for each of the twenty gas discharge portions. Therefore, the smallest value is set as the minimum value.
- the minimum value is the minimum value of the distance t between the axial side of the gas discharge portion peripheral surface 5c and the inner peripheral surface of the crucible.
- the thickness T of the bottom portion 2 is a distance between the inner bottom surface 2a and the outer bottom surface 2b.
- the inner bottom surface 2a When the inner bottom surface 2a is a curved surface, it is a distance between the contact surface and the outer bottom surface 2b.
- the relationship between the thickness of the bottom portion 2 and the minimum value of the distance t is the same when the gas discharge portion is in the form shown in FIG.
- the graphite constituting the graphite crucible 1 is a porous body, it has many pores inside. Since it has pores, bubbles are generated in the process of elution of graphite to the object to be processed at the time of melting, and diffuses into the molten object to be processed. At this time, gasification of impurities contained in the object to be processed can be promoted, and the object to be processed can be prevented from bumping.
- the gas is generated CO or CO 2
- the gas is generated CO or CO 2
- the impurities contained in the object to be treated can be prevented from boiling suddenly and bumping. Since bumping can be prevented, it can be considered that the object to be processed can be prevented from being scattered and contaminated in the apparatus.
- the gas discharge part 5 functions as a gas discharge port as described above. Since the graphite crucible is made of graphite, which is a porous body, the graphite crucible has a property that gas easily permeates outside the graphite crucible. Depending on the components contained in the object to be treated, gas is generated from the object itself or by reaction with the graphite crucible. When the object to be processed contains chlorine such as polyvinyl chloride, chlorine-based gas is generated. For example, when fluorine such as polytetrafluoroethylene is contained, a fluorine-based gas is generated. When sulfate or sulfite is contained, it reacts with graphite to generate corrosive gas such as hydrogen sulfide.
- the gas generated by the reaction with the crucible can be discharged to the upper part of the crucible through the gas discharge part 5 of the body part 3.
- the gas discharged in this manner can be quickly led out of the melting apparatus by appropriately arranging the exhaust port of the melting apparatus on the graphite crucible.
- corrosive gas that can be generated from the object itself or by reaction with the graphite crucible is effectively prevented from filling the inside of the melting apparatus and corroding the inside of the melting apparatus. It is considered possible.
- the thickness T of the bottom portion 2 is preferably thicker than the minimum value of the distance t between the gas discharge portion peripheral surface 5c and the crucible inner peripheral surface 1a. The reason will be described.
- a solid (lump or powder) object to be treated is placed in the graphite crucible 1 and melted, the object to be treated is reduced in the process and easily gathers at the bottom of the graphite crucible.
- the addition of the object to be processed is repeated until the object to be processed is sufficiently filled in the processing unit 4 of the graphite crucible. For this reason, the bottom part 2 of the graphite crucible becomes longer in contact with the object to be processed.
- the graphite crucible 1 of the present invention preferably has a bulk density of 1700 to 1850 kg / m 3 .
- the bulk density is 1850 kg / m 3 or less, there is a sufficient amount of pores when graphite is eluted into the object to be treated, so that bubbles can be continuously supplied to the melt.
- the bulk density is 1700 kg / m 3 or more, the specific surface area of graphite can be reduced, so that the elution rate can be reduced and the graphite crucible can be made difficult to perforate.
- the graphite crucible 1 of the present invention preferably has an impurity content of 1.0% by mass or less.
- the impurity content is 1.0% by mass or less, it is possible to make it difficult to form an impurity layer due to residual impurities on the inner peripheral surface of the crucible even if the graphite is eaten.
- the graphite crucible 1 preferably has an impurity content of 0.1% by mass or less. When the impurity content is 0.1% by mass or less, even if graphite is eroded, it is possible to make it more difficult to form an impurity layer due to residual impurities on the inner peripheral surface of the crucible.
- the elution of graphite occurs continuously, and simultaneously with the elution, the gas contained in the pores is released as bubbles into the molten object to be processed. For this reason, it is thought that the component contained in the to-be-processed object becomes difficult to be overheated, and bumping can hardly occur. For this reason, it is considered that the inside of the apparatus due to bumping can be prevented from being damaged or damaged.
- action of the graphite crucible 1 is not limited to atmospheric pressure, It functions similarly even under pressure reduction.
- the impurity content of the graphite crucible 1 is preferably as small as possible if it is as small as 0% by mass.
- the graphite crucible 1 is preferably a graphite crucible for melting an object to be treated of iron, silicon, nickel, titanium, or a mixture thereof. Since these elements form carbides, bubbles can be generated while the graphite crucible is consumed when these elements are melted. For this reason, it is possible to make it difficult to cause bumping of the object to be processed.
- the graphite crucible 1 is effective in melting an iron-based object to be processed because the temperature is high and the graphite is easily eluted into the object to be processed, so that the graphite crucible 1 is easily consumed and bubbles are easily generated. It is possible to prevent bumping.
- the graphite crucible only needs to have a sufficient thickness so that the graphite material corresponding to 5.2% by mass of the melt may be eroded. .
- the concentration of saturated carbon increases. For example, in the case of 1600 ° C., the mass% of carbon at which the liquidus 13 from the eutectic point 12 and 1600 ° C.
- the mass of the object to be treated (iron) is M 1
- the mass of carbon (graphite) dissolved in the melt is M 2
- the densities are ⁇ 1 (7.8 g / cm 3 ) and ⁇ 2 (1.8 g / cm 3 )
- the volumes V 1 and V 2 of the object to be treated (iron) and the carbon dissolved in the object to be processed are calculated as follows when the dissolved carbon is 5.5% by mass. Can do.
- the graphite crucible 1 assumes the relationship between the distance between the gas discharge portion peripheral surface 5c and the crucible inner peripheral surface as described above, assuming about 25% erosion of the melted material and the melted graphite. It is considered that the thickness of the bottom portion to be filled should be provided.
- the object to be treated is an iron alloy
- the content of iron is less than that of pure iron, so the amount of graphite eluted to the object to be treated is smaller than that of pure iron.
- ceramics such as concrete or mortar
- these melts (slag) have high viscosity, so the reaction with graphite only occurs partially at the contact point with the slag, and the entire slag It is hard to react. For this reason, since the influence of the erosion of the graphite crucible by the slag is small, it is considered that the influence of the metal object to be treated should be considered.
- the size of the graphite crucible 1 is, for example, an outer diameter Ro of 975 mm, an inner diameter Ri of 795 mm, a height h of 900 mm, and a depth d0 of 795 mm.
- the barrel portion is provided with 20 rotationally symmetric gas discharge portions around the central axis of the graphite crucible.
- FIG. 2A is a cross-sectional view including the central axis of the graphite crucible of the second embodiment of the present invention
- FIG. 2B is a plan view of the graphite crucible of the second embodiment of the present invention.
- the graphite crucible 1 according to the second embodiment of the present invention is the graphite crucible 1 according to the first embodiment, in which the gas discharge portion 5 is provided in a groove shape continuously around the periphery of the trunk portion, and the gas discharge portion peripheral surface 5c and the crucible inside
- the minimum value of the distance t from the peripheral surface 1a is the same as that of the first embodiment except that it has an annular shape with a constant thickness, and has the same function as the first embodiment.
- the gas discharge portion is formed in a groove shape, the gas generated from the inside of the graphite crucible can be more easily captured than in the first embodiment. For this reason, corrosive gas can be made harder to reach the melting device around the crucible.
- channel of a gas exhaust part is not specifically limited, It is preferable to provide the depth which the closing port 5a reaches the bottom part of a graphite crucible. By providing the gas discharge portion with such a depth that reaches the bottom 2 of the graphite crucible, more gas generated from the inside of the graphite crucible can be captured.
- the graphite crucible 1 is similar to the first embodiment in the case of melting the object to be treated of silicon, iron, iron-based, silicon-based, nickel-based, titanium-based, or a mixture thereof. Since bubbles can be generated, it is considered that bumping can be made difficult to occur.
- the size of the graphite crucible of the second embodiment is, for example, an outer diameter Ro of 975 mm, an inner diameter Ri of 795 mm, a height h of 900 mm, a depth d0 of 795 mm, and an inner diameter Ri ⁇ of 900 mm.
- the gas discharge part having an outer diameter Ro ⁇ of 940 mm and a depth d1 of 500 mm is formed in a groove shape that circulates around the body part.
- the minimum value of t is constant and is 52.5 mm.
- the graphite crucibles of Embodiments 1 and 2 of the present invention are made of graphite having excellent heat resistance, thermal shock resistance, etc., they can be used in any heating device. Any melting apparatus such as induction heating, plasma heating, or radiation heating with a heater can be used. If the object to be processed contains a large amount of a ferromagnetic material such as iron or nickel, the object to be processed has a higher heat generation efficiency than a crucible with weak magnetism. Can be processed well. In the case of a plasma heating melting apparatus, graphite has a low coefficient of thermal expansion (4-5 ppm / K) and a high thermal conductivity (80-120 W / mK), so it is resistant to thermal shock.
- a graphite crucible has high emissivity and high thermal conductivity, so that the object to be processed can be efficiently heated.
- the object to be treated with the graphite crucibles of Embodiments 1 and 2 of the present invention is preferably composed mainly of iron, but may contain any substance other than iron.
- the object to be processed may contain a metal other than iron, slag, concrete, organic polymer, salt, halogen compound, and the like.
- Example 1 The graphite crucible of Embodiment 1 shown in FIG. 1 was used.
- the body of the graphite crucible is provided with eight rotationally symmetric gas discharge portions around the central axis of the graphite crucible.
- the PCD (Pitch Circle Diameter) of the gas discharge part is 36 mm, and each gas discharge part has ⁇ of 2 mm and a depth d1 of 35 mm.
- the minimum value of t is 2 mm.
- the internal volume (processing part volume) of the graphite crucible of this example is 21.2 ml, and the volume occupied by the graphite crucible (graphite volume) is 25.6 ml.
- the graphite crucible was prepared by cutting a fine carbon material (isotropic graphite): ET-10 manufactured by Ibiden Co., Ltd.
- the bulk density of ET-10 used for the crucible was 1750 kg / m 3 .
- 50 g of iron fragments were placed as an object to be processed and heated in a heating furnace in an argon atmosphere. At this time, the workpiece was filled up to the upper end of the graphite crucible.
- the heating furnace containing the graphite crucible of this example was heated at a heating rate of 500 ° C./H, held at 1600 ° C. for 6 hours, and then allowed to cool naturally.
- the graphite crucible of this example taken out after cooling had the same appearance as before heating, and no traces of iron scattered and scattered around the graphite crucible were observed.
- the object to be processed placed in the graphite crucible of this example was melted and reduced in volume.
- the graphite crucible of this example taken out after cooling was divided into two so as to include the central axis, and the cross section was observed. The thickness of the bottom part of the graphite crucible was greatly eroded until the thickness of 10 mm originally became 7 mm, but did not reach the outer surface.
- FIG. 5 shows a polarization micrograph of the boundary region between the graphite crucible and the object to be processed (iron), which is a cross section divided after heating in this example.
- the polarizing microscope was made by Nikon, and a 25x magnified image was taken by the collimating method.
- the left side in FIG. 5 is the graphite constituting the crucible, and the right side in FIG. 5 is considered to be cast iron in which the graphite constituting the crucible is dissolved in iron.
- the cast iron on the right side in FIG. 5 a linear structure is seen, and it can be seen that the once melted graphite is precipitated again as the temperature decreases.
- the object to be treated is gray cast iron with an increased carbon content.
- Example 2 The graphite crucible of Embodiment 2 shown in FIG. 2 was used.
- a gas discharge part having an inner diameter Ri ⁇ of 34 mm, an outer diameter Ro ⁇ of 38 mm, and a depth d1 of 20 mm is formed in a groove shape around the body.
- the minimum value of t is 2 mm.
- the internal volume (processing part volume) of the crucible in this example is 21.2 ml, and the volume occupied by the graphite crucible (graphite volume) is 24.6 ml.
- the graphite crucible was prepared by cutting a fine carbon material (isotropic graphite): ET-10 manufactured by Ibiden Co., Ltd.
- the bulk density of ET-10 used for the graphite crucible was 1750 kg / m 3 .
- An object to be processed similar to that in Example 1 was placed in the graphite crucible of this example, and was similarly heat-treated.
- the graphite crucible of this example taken out after cooling had the same appearance as before heating, and no traces of iron scattered and scattered around the graphite crucible were observed.
- the object to be processed placed in the graphite crucible of this example was melted and reduced in volume.
- the graphite crucible of this example taken out after cooling was divided into two so as to include the central axis, and the cross section was observed.
- the thickness of the bottom part of the graphite crucible was greatly eroded until the thickness of 10 mm originally became 7 mm, but did not reach the outer surface.
- a crucible without a gas discharge part was used in Example 1 or 2 in Example 1 or 2, a crucible without a gas discharge part was used.
- the constituent material of the crucible was not a graphite but a crucible made of magnesia mainly composed of magnesium oxide.
- the outer diameter Ro is 40 mm
- the inner diameter Ri is 30 mm
- the height h is 40 mm
- the depth d0 is 30 mm
- the inner volume of the crucible (processing part volume) is 21.2 ml
- the volume occupied by the crucible (magnesia volume) is 29. .1 ml.
- the present invention is not particularly limited as long as it is a graphite crucible that melts an iron-based, silicon-based, nickel-based, or titanium-based object, and a mixture thereof, and reduces the volume of crucibles and waste for casting production. It can be used for crucibles to do so.
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Abstract
Description
中でも鉄系等の被処理体を溶融するためのルツボは、1400℃以上の耐熱性と耐食性が必要であるため、アルミナ、マグネシアなど酸化物系セラミックスからなるルツボ、あるいは酸化物系セラミックスに黒鉛を添加した黒鉛系のルツボが使用される。
これらのルツボに使用される酸化物系セラミックスは、種々の溶融金属又はスラグに対して耐食性を示す最も適した化学組成のものが使用される。例えば、鋼、鋳鉄溶解に関してはアルミナ、マグネシア、ジルコニア、ジルコン、スピネルなどの骨材として使用される。さらに黒鉛系のルツボにおいては、高熱伝導、低弾性率である黒鉛を添加することにより、ルツボの耐熱衝撃性を高めることが記載されている。(特許文献1)
本発明の目的は、被処理体を安全、かつ飛散させることなく溶融、固化体ができる黒鉛ルツボを提供することにある。
(1)底部と、胴部と、投入口を有する処理部とを有し、下端側が閉口し、かつ胴部の上端側に開口したガス排出部を有する、黒鉛ルツボ。
(2)前記ガス排出部は、溝状に形成されている、(1)の黒鉛ルツボ。
(3)該底部の厚さは、該ガス排出部周面とルツボ内周面との距離の最小値よりも厚い、(1)又は(2)の黒鉛ルツボ。
(4)前記黒鉛ルツボは、かさ密度が1700~1850kg/m3である、(1)~(3)のいずれか1項の黒鉛ルツボ。
(5)前記黒鉛ルツボは、不純物含有量が、1.0質量%以下である、(1)~(4)のいずれか1項の黒鉛ルツボ。
(6)前記黒鉛ルツボは、不純物含有量が、0.1質量%以下である、(5)の黒鉛ルツボ。
(7)前記黒鉛ルツボは、鉄系、シリコン系、ニッケル系あるいはチタン系及びこれらの混合物から選択される被処理体を溶融するための、(1)~(6)のいずれか1項の黒鉛ルツボ。
(8)(1)~(7)のいずれか1項の黒鉛ルツボを使用して前記被処理体の固化体を製造する方法。
さらに、黒鉛ルツボは、胴部の上端側に開口したガス排出部を有しているので、被処理体からあるいは被処理体と黒鉛との反応によって、腐食性ガスあるいは反応性ガスが発生する場合には、黒鉛ルツボの胴部を透過する腐食性ガスあるいは反応性ガスをガス排出部に導くことができる。このため、溶融装置の内部にこれらの腐食性ガスあるいは反応性ガスが充満しにくくすることができる。このため多孔質の黒鉛ルツボを使用しても溶融装置の腐食を防止することができると考えられる。
図1は本発明の実施形態1の黒鉛ルツボを示し、図1(A)は本発明の実施形態1の黒鉛ルツボの中心軸を含む図1(B)のA-A線に沿う断面図であり、図1(B)は本発明の実施形態1の黒鉛ルツボの平面図である。
本発明の実施形態1の黒鉛ルツボ1は、処理部4の空間を構成するルツボ内周面1aとルツボ外周面1bの間の空間からガス排出部5を除いた空間を黒鉛としたものである。
底部2は、ルツボ内周面1aの下端部である内底面2aを含む面が、ルツボをルツボ外周面まで切り取ったときの該内底面以下の部分である。該内底面2aは、図1(A)のように平面の場合の他、曲面であってもよい。曲面としては、ルツボ内周面の下端に極値を有するものであって、その極値の接面が、該内底面2aと一致するような曲面が挙げられる。底部2は、ルツボ外周面1bの下端面に相当する外底面2bを有する。
胴部3は、ルツボ内周面1aとルツボ外周面1bの間の部分であって、黒鉛ルツボ1の底部2以外の部分である。
ガス排出部5は、下端側が閉口し、かつ胴部の上端側に開口した空間(穴)でガスの排出機能を有するのであれば、その形状、サイズ、閉口の位置、数等は特に制限はない。図1(A)及び図1(B)に示すガス排出部5は、円柱状であり、下端側に閉口5a、胴部の上端側に開口5bを有し、胴部に同心円状に20個備えられ、それらは互いに中心角がほぼ18°となるに位置に備えられている。閉口5aの位置は、内底面2aより若干下方となっている。
底部2の厚さTは、ガス排出部周面5cとルツボ内周面1aとの距離tの最小値よりも厚いことが好ましい。ガス排出部周面5cとルツボ内周面との距離tは、図1(A)及び図1(B)では、20個の各々のガス排出部について、各々の穴のtは一定の範囲であるため、その内で最小のものを該最小値とする。該最小値は、ガス排出部周面5cの軸側とルツボ内周面との距離tの内の最小のものとなる。底部2の厚さTは、内底面2aと外底面2bとの距離であり、内底面2aが曲面の場合は、上記接面と外底面2bとの距離である。なお、この底部2の厚さと該距離tの最小値の関係は、ガス排出部が図2の態様の場合も同様である。
さらに、被処理体に酸化物が含まれる場合には、黒鉛によって還元され、COあるいはCO2のガスが発生し、同様にCOあるいはCO2ガスが溶融した被処理体中に継続して気泡となって放出されるので、被処理体に含まれる不純物のガス化を促進し、被処理体に含まれる不純物が急激に沸騰し、突沸することを防止することが出来ると考えられる。突沸を防止できるので被処理体が装置内に飛散して汚染することを防止することができると考えられる。
被処理体に例えばポリ塩化ビニルなど塩素を含有する場合、塩素系のガスが発生する。例えばポリテトラフルオロエチレンなどフッ素を含有する場合、フッ素系ガスが発生する。硫酸塩あるいは亜硫酸塩が含まれる場合には、黒鉛と反応し硫化水素などの腐食性ガスを発生させる。
黒鉛ルツボ1は、ガス排出部5を有するので、ルツボとの反応により発生したガスを、胴部3のガス排出部5を介してルツボ上部へ排出することができる。このようにして排出されたガスは、溶融装置の排気口を黒鉛ルツボの上に適宜配置することにより速やかに溶融装置の外部に導き出すことができる。このようなガス排出部5を有することにより、被処理体そのものから、あるいは黒鉛ルツボとの反応により発生しうる腐食性ガスが溶融装置内部に充満し溶融装置内部を腐食させることを有効に防止することが出来ると考えられる。
黒鉛ルツボ1に固体(塊状あるいは粉末状)の被処理体を入れ溶融すると、その過程で被処理体が減容し、黒鉛ルツボの底に集まりやすくなる。多くの場合、効率的に黒鉛ルツボを使用するために、黒鉛ルツボの処理部4に充分に被処理体が充填されるまで、被処理体の追加投入を繰り返す。このため、黒鉛ルツボの底部2は、被処理体と接する時間が長くなる。特に鉄系の被処理体を溶融する場合には、黒鉛ルツボを構成する黒鉛が被処理体に溶出しやすくなる。このため、被処理体と長時間接する底部の厚さTを上述のように厚くすることにより、黒鉛ルツボに孔があく、あるいは破損することを防止することができる。
なお、黒鉛ルツボ1の前記作用は、大気圧下に限定されず、減圧下であっても同様に機能する。減圧下で黒鉛の気孔中に存在する気体の質量が小さくても、圧力が小さいので膨張し気泡を形成することができるからである。
なお、黒鉛ルツボ1の不純物含有量は0質量%と少なければ少ない方が好ましい。
尚、シリコンを黒鉛ルツボで溶融する際は、黒鉛ルツボの表層はSiC化するが、SiCであっても融液に溶け出すので、気泡を発生させることができる。
被処理体に含まれる金属がステンレスなどの鉄合金であっても、同様のメカニズムにより黒鉛が溶出する。
M1:M2=94.5:5.5 (式1)
M1=ρ1V1 (式2)
M2=ρ2V2 (式3)
(式1)~(式3)式より
V1:V2=94.5ρ2:5.5ρ1 (式4)
式4に実際の密度の数値(ρ1=7.8g、ρ2=1.8)を当てはめると、
V1:V2=80:20
となり、被処理体が鉄の場合、黒鉛ルツボ1は、鉄の約25%(20/80)の体積の黒鉛(炭素)を侵食しながら気泡を出し続けられると想定できる。その結果、黒鉛ルツボ1は、被溶融物と黒鉛の溶融した溶融液の約25%の侵食を想定した、上述のようなガス排出部周面5cとルツボ内周面との距離との関係を満たす底部の厚さを備えていればよいと考えられる。
図2(A)は本発明の実施形態2の黒鉛ルツボの中心軸を含む断面図であり、図2(B)は本発明の実施形態2の黒鉛ルツボの平面図である。
本発明の実施形態2の黒鉛ルツボ1は、実施形態1の黒鉛ルツボ1において、ガス排出部5を胴部周囲に連続して溝状に設けた態様で、ガス排出部周面5cとルツボ内周面1aとの距離tの最小値は、一定厚みの円環状をとる以外は実施形態1と同様であり、実施形態1と同様の機能を有する。
図1に示す実施形態1の黒鉛ルツボを用いた。
外径Roが40mm、内径Riが30mm、高さhが40mm、深さd0が30mmの黒鉛ルツボを用いた。
黒鉛ルツボの胴部には、黒鉛ルツボの中心軸を中心とする回転対称のガス排出部が8個備えられている。ガス排出部のPCD(ピッチ円直径:Pitch Circle Diameter)は36mmであり、個々のガス排出部は、それぞれφが2mmで深さd1が35mmである。tの最小値は2mmである。
本実施例の黒鉛ルツボの内容積(処理部容積)は21.2mlであり、黒鉛ルツボの占める体積(黒鉛の体積)は25.6mlである。黒鉛ルツボはイビデン株式会社製ファインカーボン材(等方性黒鉛):ET-10を切削加工して作製した。ルツボに使用したET-10のかさ密度は1750kg/m3であった。
本実施例の黒鉛ルツボに被処理体として50gの鉄の破片を入れ、アルゴン雰囲気の加熱炉内で加熱した。このとき被処理体は黒鉛ルツボの上端まで充填されていた。
本実施例の黒鉛ルツボを入れた加熱炉は500℃/Hの昇温速度で昇温し、1600℃で6時間保持した後、自然放冷した。
冷却後取り出された本実施例の黒鉛ルツボは、外観は加熱前と変わらず、黒鉛ルツボ周囲に溶融し飛散した鉄の痕跡は認められなかった。本実施例の黒鉛ルツボに入れられた被処理体は、溶融し容積が減っていた。冷却後取り出された本実施例の黒鉛ルツボを、中心軸を含むように2分割し、断面を観察した。黒鉛ルツボの底部の厚さはもともと10mmあった厚さが7mmになるまで大きく侵食されていたが、外面には到達していなかった。
本実施例の加熱後に分割された断面の、黒鉛ルツボと被処理体(鉄)の境界領域の偏光顕微鏡写真を図5に示す。偏光顕微鏡はニコン製であり、25倍の拡大像をコリメート法で撮影した。
図5中左側は、ルツボを構成する黒鉛であり、図5中右側は鉄にルツボを構成する黒鉛が溶け込んだ鋳鉄であると考えられる。図5中右側の鋳鉄には、線状の組織が見られ、一旦溶融した黒鉛が、温度が下がることによって再度析出していることがわかる。被処理体は、炭素含有量が増えてねずみ鋳鉄となっていると推定される。
図2に示す実施形態2の黒鉛ルツボを用いた。
外径Roが40mm、内径Riが30mm、高さhが40mm、深さd0が30mmの黒鉛ルツボを用いた。
黒鉛ルツボの胴部には、内径Riφが34mm、外径Roφが38mm、深さd1が20mmのガス排出部が、胴部を周回する溝状に構成されている。tの最小値は2mmである。
本実施例のルツボの内容積(処理部容積)は21.2mlであり、黒鉛ルツボの占める体積(黒鉛の体積)は24.6mlである。黒鉛ルツボはイビデン株式会社製ファインカーボン材(等方性黒鉛):ET-10を切削加工して作製した。黒鉛ルツボに使用したET-10のかさ密度は1750kg/m3であった。
本実施例の黒鉛ルツボに実施例1と同様の被処理体を入れ、同様に加熱処理した。
冷却後取り出された本実施例の黒鉛ルツボは、外観は加熱前と変わらず、黒鉛ルツボ周囲に溶融し飛散した鉄の痕跡は認められなかった。本実施例の黒鉛ルツボに入れられた被処理体は、溶融し容積が減っていた。冷却後取り出された本実施例の黒鉛ルツボを、中心軸を含むように2分割し、断面を観察した。黒鉛ルツボの底部の厚さはもともと10mmあった厚さが7mmになるまで大きく侵食されていたが、外面には到達していなかった。
[比較例1]
実施例1又は2において、ガス排出部が設けられていないルツボを用いた。ただし、ルツボの構成材料は、黒鉛ではなく、酸化マグネシウムを主成分とするマグネシア製のルツボであった。外径Roが40mm、内径Riが30mm、高さhが40mm、深さd0が30mm、ルツボの内容積(処理部容積)は21.2mlであり、ルツボの占める体積(マグネシアの体積)は29.1mlである。
本比較例のルツボに実施例1と同様の被処理体を入れ、同様に加熱処理した。
冷却後取り出された比較例1のルツボは、外観は加熱前と変わらなかった。被処理体は、突沸があったと見られ一部がルツボの外部に飛散していた。冷却後取り出された比較例1のルツボを、中心軸を含むように2分割し、断面を観察した。ルツボの内面は、侵食していなかった。
これに対し比較例1のルツボでは、材質が被処理体に溶融しにくいマグネシア製であるので、被処理体によってルツボは消耗しにくいものの、ルツボから気泡が発生しにくいので突沸が起こりやすくなったと考えられる。
Claims (8)
- 底部と、胴部と、投入口を有する処理部とを有し、下端側が閉口し、かつ胴部の上端側に開口したガス排出部を有する、黒鉛ルツボ。
- 前記ガス排出部は、溝状に形成されている、請求項1の黒鉛ルツボ。
- 該底部の厚さは、該ガス排出部周面とルツボ内周面との距離の最小値よりも厚い、請求項1又は2の黒鉛ルツボ。
- 前記黒鉛ルツボは、かさ密度が1700~1850kg/m3である、請求項1~3のいずれか1項の黒鉛ルツボ。
- 前記黒鉛ルツボは、不純物含有量が、1.0質量%以下である、請求項1~4のいずれか1項の黒鉛ルツボ。
- 前記黒鉛ルツボは、不純物含有量が、0.1質量%以下である、請求項5の黒鉛ルツボ。
- 前記黒鉛ルツボは、鉄系、シリコン系、ニッケル系あるいはチタン系及びこれらの混合物から選択される被処理体を溶融するための、請求項1~6のいずれか1項の黒鉛ルツボ。
- 請求項1~7のいずれか1項の黒鉛ルツボを使用して前記被処理体の固化体を製造する方法。
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