JPS61168567A - Manufacture of silicon carbide sintered body - Google Patents

Abstract

(57)【要約】本公報は電子出願前の出願データであるた
め要約のデータは記録されません。(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、炭化珪素焼結体の製造方法に関し、特に本発
明は、耐酸化性に優れた炭化珪素焼結体の製造方法に関
する。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a silicon carbide sintered body, and particularly the present invention relates to a method for manufacturing a silicon carbide sintered body having excellent oxidation resistance.

炭化珪素は、高い強度、優れた耐摩耗性、優れた耐酸化
性、優れた耐食性、良好な熱伝導率、低い熱膨張率、高
い耐熱衝撃性並びに高温での高い強度等の化学的および
物理的に優れた特性を有し、メカニカルシール中軸受は
等の耐摩耗材料、高温炉用の耐火材、熱交換器、燃焼管
等の耐熱構造材料、酸およびアルカリ等の強い腐食性を
有する溶液のポンプ部品等の耐食性材料として広く使用
することのできる材料である。Silicon carbide has chemical and physical properties such as high strength, good wear resistance, good oxidation resistance, good corrosion resistance, good thermal conductivity, low coefficient of thermal expansion, high thermal shock resistance and high strength at high temperatures. Mechanical seals have excellent properties, such as wear-resistant materials, refractory materials for high-temperature furnaces, heat-resistant structural materials such as heat exchangers, combustion tubes, and highly corrosive solutions such as acids and alkalis. This material can be widely used as a corrosion-resistant material for pump parts, etc.

〔従来の技術〕[Conventional technology]

ところで、炭化珪素は従来難焼結性の材料として知られ
ている。すなわち、この材料は酸化物セラミックスを製
造するのに一般に用いられている常温成形後無加圧下で
焼結する無加圧焼結方法によって高密度の焼結体を得る
ことは近年まで困難でめった。しかしながら、最近にな
って炭化珪素粉末とホウ素含有添加剤および炭素質添加
剤などの焼結助剤から成る混合粉末を成形し、不活性雰
囲気中で焼結する無加圧焼結方法が種々提案されている
。By the way, silicon carbide has been known as a material that is difficult to sinter. In other words, until recently, it was difficult and rare to obtain a high-density sintered body of this material using the pressureless sintering method, which is generally used to produce oxide ceramics, in which the material is molded at room temperature and then sintered under no pressure. . However, recently, various pressureless sintering methods have been proposed in which a mixed powder consisting of silicon carbide powder and sintering aids such as boron-containing additives and carbonaceous additives is compacted and sintered in an inert atmosphere. has been done.

例えば、特開昭５０−７８６０９号公報記載の発明によ
れば、（ａ）炭化珪素と、　０．３〜３．０重ｊｌｌ−
％の硼素に相当する量における硼素含有化合物と、そし
て０．１〜１．０重量％の炭素に相当する量における炭
素質添加剤とから成るミクロン以下の粉末の均質分散体
を形成する段階、（ｂ）該粉末混合物を生の物体に賦形
する段階、及び（Ｃ）該生の物体を１９００〜２１００
　Ｃの温度において不活性雰囲気中で理論密度の少なく
とも８５％の密度を持つセラミック物品を得るに充分の
時間焼結する段階を包含する高密度炭化珪素セラミック
を製造する方法が開示されている。For example, according to the invention described in JP-A-50-78609, (a) silicon carbide;
forming a homogeneous dispersion of submicron powder consisting of a boron-containing compound in an amount corresponding to % boron and a carbonaceous additive in an amount corresponding to 0.1 to 1.0% by weight carbon; (b) shaping the powder mixture into a green body, and (C) shaping the green body from 1900 to 2100
A method of making a high-density silicon carbide ceramic is disclosed that includes sintering in an inert atmosphere at a temperature of 500 ℃ for a sufficient time to obtain a ceramic article having a density of at least 85% of the theoretical density.

特開昭５４−６７５９９号公報記載の発明によれば、珪
素と炭素を主な骨格成分とする有機珪素高分子化合物を
真空または不活性ガス雰囲気中で１６００〜２２００　
Ｃの温度で熱分解して主としてβ−８ｉＣを主成分とす
る粉末を得、この粉末を酸化性雰囲気中で５００〜８０
０Ｃの温度に加熱した後、少なくとも弗酸を含む酸で処
理して不純物を溶解除去し高純度β−８ｉＣより成る粉
末とし、該粉末を用いた原料粉末に炭素および硼素を混
合物中のそれぞれの含有量が０．１〜５重量％となゝる
まで添加し、該混合物を所定形状に成形した後、真空中
、ＣＯガス雰囲気中または不活性ガス雰囲気中で２００
０〜２３００　Ｃの温度で密度が小なくとも２．６０汁
−３以上となるめに充分な時間焼結することを特徴とす
る炭化珪素焼結体の製造方法が開示されている。According to the invention described in JP-A-54-67599, an organosilicon polymer compound whose main skeleton components are silicon and carbon is heated to 1600 to 2200 in vacuum or an inert gas atmosphere.
A powder mainly composed of β-8iC is obtained by thermal decomposition at a temperature of
After heating to a temperature of 0C, it is treated with an acid containing at least hydrofluoric acid to dissolve and remove impurities to obtain a powder made of high-purity β-8iC, and carbon and boron are added to each raw material powder in the mixture. The mixture was added until the content was 0.1 to 5% by weight, and the mixture was molded into a predetermined shape.
A method for producing a silicon carbide sintered body is disclosed, which comprises sintering at a temperature of 0 to 2300 C for a sufficient time to have a density of at least 2.60 C or more.

特開昭５６−１６９１８１号公報記載の発明によれば、
炭化珪素微粉とホウ素含有添加剤と炭素質添加剤とを混
合し成形した後、無加圧焼結する炭化珪素焼結体の製造
方法において、β型結晶の炭化珪素８５重量％以上と残
部が２Ｈ型結晶の炭化珪素から実質的になる炭化珪素微
粉１００重量部とホウ素含有ｉｔに換算して０．１〜３
．０重量部のホウ素含有添加剤と固定炭素含有量に換算
して１．０重量部を越え４．０重量部以下の炭素質添加
剤とを均質混合する第１工程；前記均質混合物を任意の
生成形体に成形する第２工程；前記生成形体をアルゴン
、ヘリウム、ネオン、クリプトン、キセノン、水素のな
かから選択されるいずれか少なくとも１種からなるガス
雰囲気中で２０５０〜２２００　Ｃで焼結する第３工程
；上記第１〜３工程の組合せからなりβ型結晶を５０〜
８５重量％、残留遊離炭素を１・、０重量％を越え３．
０重量−以下含有し、３．Ｑｉ／ｃｍ３以上の密度を有
する高強度炭化珪素焼結体の製造方法が開示されている
。According to the invention described in JP-A-56-169181,
In a method for producing a silicon carbide sintered body in which silicon carbide fine powder, a boron-containing additive, and a carbonaceous additive are mixed, molded, and then sintered without pressure, 85% by weight or more of β-type crystal silicon carbide and the remainder are 100 parts by weight of silicon carbide fine powder consisting essentially of 2H-type crystalline silicon carbide and 0.1 to 3 parts by weight of boron-containing it.
．． A first step of homogeneously mixing 0 parts by weight of a boron-containing additive and a carbonaceous additive of more than 1.0 parts by weight and less than 4.0 parts by weight in terms of fixed carbon content; A second step of forming the formed body; a step of sintering the formed body at 2050 to 2200 C in a gas atmosphere consisting of at least one selected from argon, helium, neon, krypton, xenon, and hydrogen; 3rd step; consists of a combination of the above 1st to 3rd steps and produces 50 to 50 β-type crystals.
85% by weight, residual free carbon of 1., more than 0% by weight3.
0 weight or less; 3. A method for producing a high-strength silicon carbide sintered body having a density of Qi/cm3 or more is disclosed.

〔発明が解決しようとする問題点〕 ところで、前記特開昭５０−７８６０９号公報記載の発
明によれば、ホウ素を焼結助剤として炭化珪素に対し０
．３〜３．０重量％と比較的多量に含有させるため、得
られた焼結体は耐酸化性に劣るという欠点がある。[Problems to be Solved by the Invention] By the way, according to the invention described in JP-A-50-78609, boron is used as a sintering aid to reduce silicon carbide to zero.
．． Since it is contained in a relatively large amount of 3 to 3.0% by weight, the resulting sintered body has a drawback of poor oxidation resistance.

また−前記特開昭５４−６７５９９号公報記載の発明に
よれば、有機珪素高分子化合物を熱分解して得られる極
めて高価なβ−８ｉＣ粉末を出発原料とじて用いる方法
であるため、工業用材料として広く使用することが困難
であるという欠点がある。Furthermore, according to the invention described in JP-A-54-67599, the method uses extremely expensive β-8iC powder obtained by thermally decomposing an organosilicon polymer compound as a starting material. The drawback is that it is difficult to use widely as a material.

前記特開昭５６−１６９１８１号公報記載の発明は本願
人の出願に係る発明であり、その目的は炭化珪素無加圧
焼結法を改良し、高強度の焼結体を得るために、炭素質
添加剤を炭化珪素微粉の酸化含有量によって必要とされ
る量よりも過剰に添加し、積極的に炭化珪素焼結体内に
遊離炭素の形態で含有させることによってβ型結晶のα
型結晶への相変態を適正化し、β型結晶のα型化に伴う
粗大な微細結晶となるようにしたものである。しかしな
がら前記公報記載の発明は高強度の焼結体を得る上で出
発原料として８５重量％以上がβ型結晶よりなる炭化珪
素を必要としたシ、焼結助剤としてのホウ素や炭素の添
加蓋などに種々の制約を受ける欠点がある。The invention described in JP-A-56-169181 is an invention filed by the applicant, and its purpose is to improve the pressureless sintering method of silicon carbide and to obtain a high-strength sintered body. By adding the quality additive in excess of the amount required by the oxidation content of the silicon carbide fine powder and actively incorporating it in the form of free carbon into the silicon carbide sintered body, the
The phase transformation to the type crystal is optimized, and the β-type crystal becomes coarse and fine crystals as it changes to the α-type. However, the invention described in the above publication requires silicon carbide of which 85% by weight or more consists of β-type crystals as a starting material in order to obtain a high-strength sintered body, and the addition of boron or carbon as a sintering aid is necessary. It has the disadvantage of being subject to various restrictions.

本発明は、前述の如き従来知られた炭化珪素無加圧焼結
方法の欠点を除去し、特にガスタービン部品、高温熱交
換器、炉構造材料のような過酷な条件下で使用すること
のできる高密度でかつ耐酸化性に優れた炭化珪素無加圧
焼結体を安価にかつ容易に製造することのできる方法を
提供することを目的とする。The present invention eliminates the drawbacks of the previously known pressureless sintering methods for silicon carbide as described above, and is particularly suitable for use under harsh conditions such as gas turbine parts, high temperature heat exchangers, and furnace structural materials. It is an object of the present invention to provide a method that can inexpensively and easily produce a pressureless sintered body of silicon carbide having high density and excellent oxidation resistance.

〔問題を解決するための手段〕[Means to solve the problem]

本発明によれば、炭化珪素微粉を無加圧焼結する炭化珪
素焼結体の製造方法において、結晶の格子定数の平均値
が４，３５８４　Ａ以上のβ型炭化珪素を５０重量％以
上含有する炭化珪素微粉１００重量部とホウ素含有量に
換算して０．０１〜０．２５重量部のホウ素含有添加剤
と固定炭素含有量に換算して０．３〜５．０重量部の炭
素質添加剤とを均質混合した後、任意の形状を有する生
成形体に成形し１次いで非酸化性雰囲気中で１７００〜
２３００　Ｃで焼結し、２．８汁６３以上の密度を有す
る炭化珪素焼結体を製造することを特徴とする炭化珪素
焼結体の製造方法によって前記目的を達成することがで
きる。According to the present invention, in a method for producing a silicon carbide sintered body in which silicon carbide fine powder is sintered without pressure, the method contains 50% by weight or more of β-type silicon carbide having an average crystal lattice constant of 4,3584 A or more. 100 parts by weight of silicon carbide fine powder, 0.01 to 0.25 parts by weight of a boron-containing additive in terms of boron content, and 0.3 to 5.0 parts by weight of carbonaceous material in terms of fixed carbon content. After homogeneously mixing with the additives, it is molded into a formed product having an arbitrary shape, and then heated for 1700~
The above object can be achieved by a method for producing a silicon carbide sintered body, which is characterized by sintering at 2300 C and producing a silicon carbide sintered body having a density of 2.8 or more.

次に本発明の詳細な説明する。Next, the present invention will be explained in detail.

従来、炭化珪素の無加圧焼結法によれば、炭化珪素粉末
にホウ素および炭素を混合し焼結して焼結体が製造され
ている。ところで、前記ホウ素は焼結体内に残留して焼
結体表面のシリカ屡の融点を低下させて焼結体の耐酸化
性を劣化させるため、その添加量はなるべく少ないほう
が望ましい。しかしながら、従来知られた炭化珪素の無
加圧焼結法によれば、一部の特定の炭化珪素微粉例えば
特開昭５４−６７５９９号公報に記載されている有機珪
素高分子化合物を熱分解して得られる極めて高価なβ型
炭化珪素粉末および特開昭５６−１６９１８１号公報に
記載されている８５重量％以上がβ型結晶で残部が２Ｈ
型結晶から実質的になる炭化珪素微粉を除いては、少量
のホウ素添加量でもって高密度の炭化珪素無加圧焼結体
を得ることは困難であり、しかもそのホウ素添加量の最
少値はいずれも０．１重量％であシ、それ程少量ではな
かった。Conventionally, according to a pressureless sintering method of silicon carbide, a sintered body is manufactured by mixing silicon carbide powder with boron and carbon and sintering the mixture. By the way, since the boron remains in the sintered body and lowers the melting point of the silica on the surface of the sintered body, thereby deteriorating the oxidation resistance of the sintered body, it is desirable that the amount added is as small as possible. However, according to the conventionally known pressureless sintering method of silicon carbide, some specific silicon carbide fine powders, such as the organosilicon polymer compound described in JP-A-54-67599, cannot be thermally decomposed. The extremely expensive β-type silicon carbide powder obtained by
It is difficult to obtain a high-density non-pressure sintered body of silicon carbide with a small amount of boron added, except for silicon carbide fine powder that is essentially made of mold crystals, and the minimum value of the amount of boron added is Both amounts were 0.1% by weight, which was not a very small amount.

本発明者らは、結晶の格子定数の平均値が４．３５８４
　＆以上のβ型炭化珪素を主体とする炭化珪素微粉が焼
結性に極めて優れており、無加圧焼結法における出発原
料として使用することにより。The present inventors found that the average value of the crystal lattice constant was 4.3584.
& The silicon carbide fine powder mainly composed of β-type silicon carbide has extremely excellent sinterability, and can be used as a starting material in the pressureless sintering method.

極めて少量のホウ素添加量で炭化珪素粒子間にネックを
多数均一に発生させることができ、高密度で均一な微細
構造を有し、耐酸化性に優れた炭化珪素焼結体を得るこ
とのできることを新規に知見した。A large number of necks can be uniformly generated between silicon carbide particles with an extremely small amount of boron added, and a silicon carbide sintered body with a high density and uniform microstructure and excellent oxidation resistance can be obtained. We discovered something new.

本発明によれば、炭化珪素微粉は結晶の格子定数の平均
値が４．３４８４　＆以上のβ型炭化珪素を５０重量％
以上含有したものであるこ′とが必要である。その理由
は、ｍ記結晶の格子定数の平均値が４．３５８４　＆以
上のβ型炭化珪素は極めて焼結性に優れており、前記β
型炭化珪素を５０重量％以上含有する炭化珪素微粉を出
発原料として使用することにより、極めて少量のホウ素
添加量でもって高密度の焼結体を得ることができるから
であり、なかでも７０重量−以上含有する炭化珪素微粉
がよシ有利である。According to the present invention, the silicon carbide fine powder contains 50% by weight of β-type silicon carbide having an average crystal lattice constant of 4.3484 or more.
It is necessary that the content is as follows. The reason for this is that β-type silicon carbide whose m crystal has an average lattice constant of 4.3584 or more has extremely excellent sinterability;
This is because by using silicon carbide fine powder containing 50% by weight or more of type silicon carbide as a starting material, a high-density sintered body can be obtained with an extremely small amount of boron added. A silicon carbide fine powder containing the above amount is particularly advantageous.

本発明において使用されるβ型炭化珪素は、シリカと炭
素を出発原料として高温焼成してなるβ型炭化珪素であ
ることが好１しく、本出願人が先に出願した発明である
特公昭５７−４８４８５号公報に記載の製造装置を使用
して製造されろものが経済的に有利である。The β-type silicon carbide used in the present invention is preferably β-type silicon carbide obtained by firing silica and carbon at a high temperature as starting materials, and is an invention previously filed by the present applicant in Japanese Patent Publication No. 57 The product manufactured using the manufacturing apparatus described in Japanese Patent No. 48485 is economically advantageous.

なお、結晶の格子定数の平均値が４．３５８４　ｉ以上
のβ型炭化珪素が焼結特性に優れている理由としては、
結晶の格子定数の平均値が４．３５８４　＆以上のβ型
炭化珪素は焼結過程におけるネック形成時に粒子相互に
ネックが形成される確率が高く、しかも粒界を通しての
元素拡散が容易であることによるものと考えられる。The reason why β-type silicon carbide with an average crystal lattice constant of 4.3584 i or more has excellent sintering properties is as follows.
β-type silicon carbide with an average crystal lattice constant of 4.3584 & above has a high probability of forming necks between particles during neck formation during the sintering process, and elemental diffusion through grain boundaries is easy. This is thought to be due to

本発明において使用される結晶の格子定数の平均値が４
．３５８４　＆以上のβ型炭化珪素は、炭化珪素の生成
反応時にアルミニウムを固溶させることによって製造す
ることができ１例えばシリカと炭素と必要に応じて添加
されるアルミニウム含有添加剤とを出発原料として１８
００〜２２００　ｃの高温域で焼成することによって製
造することができる。The average value of the lattice constant of the crystal used in the present invention is 4
．． The β-type silicon carbide of 3584 & above can be produced by dissolving aluminum as a solid solution during the silicon carbide production reaction.1 For example, silica, carbon, and an aluminum-containing additive added as necessary are used as starting materials. 18
It can be produced by firing at a high temperature range of 0.00 to 2200 °C.

前記アルミニウム含有添加剤としては各種のアルミニウ
ム含有塩や金属アルミニウムを使用することもできるが
、アルミナ（酸化アルミニウム）。As the aluminum-containing additive, various aluminum-containing salts and metallic aluminum can be used, including alumina (aluminum oxide).

ムライト等を使用することが有利である。It is advantageous to use mullite or the like.

本発明によれは、前記β型炭化珪素はアルミニラＡ　２
０．０２〜１．０重量％含有したものであることが好ま
しい。その理由は、０．０２重量％より少ないと結晶の
格子定数を４．３５８４　Ａよりも大きくすることが困
難であるし、一方１．０重量％より多いと炭化珪素中に
固溶されないアルミニウムが多くなるため、焼結時にお
ける板状結晶の異常粒成長が起こり易く、高密度の焼結
体を得ることが困難になるばかりでなく、焼結体の高温
特性が劣化するからであり、なかでも０．１〜０．５重
ｆ％の範囲がより有利である。According to the present invention, the β-type silicon carbide is alumina A 2
It is preferable that the content is 0.02 to 1.0% by weight. The reason for this is that if it is less than 0.02% by weight, it is difficult to make the crystal lattice constant larger than 4.3584 A, while if it is more than 1.0% by weight, aluminum is not dissolved in silicon carbide. This is because abnormal grain growth of plate crystals is likely to occur during sintering, which not only makes it difficult to obtain a high-density sintered body, but also deteriorates the high-temperature properties of the sintered body. However, a range of 0.1 to 0.5 weight f% is more advantageous.

ところで、本出願人は先に特開昭５７−１７４６５号公
報により下記の発明を開示した。By the way, the present applicant previously disclosed the following invention in Japanese Unexamined Patent Publication No. 57-17465.

「　炭化珪素微粉を無加圧焼結する炭化珪素焼結体の製
造方法において、アルミニウムをＯ０１〜１．０重量％
含有し、／型結晶の炭化珪素が９０チ以上である炭化珪
素微粉１００重葦部とホウ素含有量に換算して０．１〜
３．０重量部のホウ素含有添加剤と固定炭素含有量に換
算して１．０重量部を越え４．０重量部以下の炭素質添
加剤を均質混合する第１工程；前記均質混合物を任意の
形状を有する生成形体に成形する第２工程；前記生成形
体をアルゴン。"In a method for manufacturing a silicon carbide sintered body in which silicon carbide fine powder is sintered without pressure, aluminum is added in an amount of O01 to 1.0% by weight.
Silicon carbide fine powder containing 90 units or more of silicon carbide in the / type crystal and 0.1 to 100% in terms of boron content
A first step of homogeneously mixing 3.0 parts by weight of a boron-containing additive and a carbonaceous additive in an amount exceeding 1.0 parts by weight and not more than 4.0 parts by weight in terms of fixed carbon content; A second step of molding into a green body having the shape; the green body is heated with argon.

ヘリウム、ネオン、クリプトン、キセノン、水素から選
択される少なくとも１種からなるガス雰囲気中で１９０
０〜２１００　Ｃで焼結する第３工程；前記第１〜３工
程の組合せからなる４Ｈ型結晶あるいは６Ｈ型結晶のい
ずれか少なくとも１種が８０〜９５％、残部は主として
β型結晶よりなり、残留遊離炭素を１．０重ｉｋ、％を
越え３．０重量−以下含有し、少なくとも３．Ｏ１ｉ１
−／ｃｒｎ３の密度を有する高強度炭化珪素焼結体の製
造方法」。190 in a gas atmosphere consisting of at least one selected from helium, neon, krypton, xenon, and hydrogen.
3rd step of sintering at 0 to 2100 C; 80 to 95% of at least one of the 4H type crystal or 6H type crystal formed by the combination of the first to 3rd steps, the remainder mainly consisting of β type crystal, Contains more than 1.0% by weight and less than 3.0% residual free carbon, and at least 3.0% by weight. O1i1
"A method for producing a high-strength silicon carbide sintered body having a density of -/crn3".

しかしながら前記公報記載の発明はβ型結晶の炭化珪素
が９０％以上である炭化珪素微粉を出発原料として、焼
結中にその結晶の大部分をα型結晶の炭化珪素に相変態
させα型結晶を８０〜９５　％含有する高強度の炭化珪
素焼結体を製造する発明であるのに対して、本願発明は
結晶の格子定数の平均値が４，３５８４　Ａ以上のβ型
炭化珪素を５０重ｔｅＩＪ以上含有する炭化珪素微粉を
出発原料とすることにより、極めて少量のホウ素添加量
でもって高密度の耐酸化性に優れた炭化珪素焼結体を製
造する方法であり、発明の目的および構成において太き
く異なる。However, the invention described in the above publication uses silicon carbide fine powder containing 90% or more of β-type crystal silicon carbide as a starting material, and phase-transforms most of the crystals into α-type crystal silicon carbide during sintering. In contrast, the present invention produces a high-strength silicon carbide sintered body containing 80 to 95% of This is a method for producing a high-density silicon carbide sintered body with excellent oxidation resistance with an extremely small amount of added boron by using silicon carbide fine powder containing teIJ or more as a starting material, and in accordance with the purpose and structure of the invention. Thick and different.

本発明によれば、得られる炭化珪素焼結体は少なくとも
２０重量％がβ型炭化珪素であることが好ましい。その
理由は、得られる炭化珪素焼結体に含有されるβ型炭化
珪素を２０重量％よりも少なくすると焼結時に伴う相変
態が著しく、相変態に伴って板状結晶の異常粒成長が顕
著になるため高密度の焼結体を得ることが困難になるか
らである。According to the present invention, it is preferable that at least 20% by weight of the resulting silicon carbide sintered body is β-type silicon carbide. The reason for this is that when the β-type silicon carbide contained in the obtained silicon carbide sintered body is less than 20% by weight, the phase transformation accompanying sintering is significant, and the abnormal grain growth of plate-like crystals is remarkable due to the phase transformation. This is because it becomes difficult to obtain a high-density sintered body.

本発明によれば、前記炭化珪素微粉は比表面積が５〜５
０　ｍ２／９−であることが好ましい。その理由は、前
記比表面積が５Ｉｎ”／９−より小嘔い炭化珪素を出発
原料とすると、焼結初期に形成されるネックの発生箇所
が少なく焼結時における収縮が不均一となるからであり
、一方５０ｍ”／９−より大きな比表面積を有する炭化
珪素微粉はネックの発生箇所も多く、　焼結性にも優れ
ていると考えられるが、このような炭化珪素微粉は入手
が困難であるからである。According to the present invention, the silicon carbide fine powder has a specific surface area of 5 to 5.
It is preferable that it is 0 m2/9-. The reason for this is that if silicon carbide, which has a specific surface area smaller than 5In"/9-, is used as a starting material, there will be fewer necks formed in the initial stage of sintering, and shrinkage during sintering will be uneven. On the other hand, fine silicon carbide powder with a specific surface area larger than 50m"/9- has many neck points and is considered to have excellent sinterability, but such fine silicon carbide powder is difficult to obtain. It is from.

本発明によれば、前記炭化珪素微粉は酸素含有率が０．
１〜１．０重ｉＬ％であることが好ましい。前起炎化珪
素微粉に含有される酸素は焼結時に炭素と反応し、次式
に示される如き機構で除去される。According to the present invention, the silicon carbide fine powder has an oxygen content of 0.
It is preferably 1 to 1.0 weight iL%. Oxygen contained in the preflamed silicon fine powder reacts with carbon during sintering and is removed by the mechanism shown in the following equation.

８ｉ０ｚ　＋　Ｃ−＋ＳｉＯ＋　ＣＯｆｌ）ＳｉＯ＋　
２Ｃ→ＳｉＣ＋　ＣＯ（２）したがって、前記酸素が１
．０重量％よりも多量に存在すると炭素質添加剤を多量
に使用しなければならないばかりでなく、焼結助剤とし
てのホウ素が酸化してし１つたり、ＣＯガスが大量に発
生するため焼結時にガス抜きの必要が生じる等焼結が困
難になるからである。一方前記酸素量が０．１本゛　量
チよりも少ない炭化珪素微粉は例えば弗酸と硝゛）酸の
混酸で処理することによって得ることができ−るが、こ
のようにして得た高純度の炭化珪素微粉は極めて活性で
あり、空気雰囲気中で乾燥したりすると常温でも容易に
酸化してしまゲため、酸素含有量を低く維持するには酸
処理後の雰囲気を非酸化性に保持したりしなければなら
ず実用的でないからである。8i0z + C-+SiO+ COfl)SiO+
2C→SiC+ CO(2) Therefore, the oxygen is 1
．． If the amount is greater than 0% by weight, not only will a large amount of carbonaceous additive have to be used, but also boron as a sintering aid will be oxidized and a large amount of CO gas will be generated, making it difficult to sinter. This is because sintering becomes difficult, such as the need for degassing during sintering. On the other hand, fine silicon carbide powder containing less than 0.1 liters of oxygen can be obtained, for example, by treatment with a mixed acid of hydrofluoric acid and nitric acid. Silicon carbide fine powder is extremely active and easily oxidizes even at room temperature when dried in an air atmosphere, so in order to maintain a low oxygen content, the atmosphere after acid treatment must be kept non-oxidizing. This is because it would be impractical to do so.

本発明によれば、炭化珪素微粉１００重量部に対してホ
ウ素含有添加剤をホウ素含有量に換算して０．０１〜０
．２５重量部添加することが必要である。According to the present invention, the boron-containing additive is 0.01 to 0 in terms of boron content per 100 parts by weight of silicon carbide fine powder.
．． It is necessary to add 25 parts by weight.

前記ホウ素含有添加剤をホウ素含有量に換算して０．０
１〜０．２５重量部にする理由は０．０１重量部よシ少
ないとネック形成時の接着作用が充分でなく高密度化が
困難であるからであり、一方０．２５重量部より多いと
焼結体内に残留するホウ素が焼結体表面のシリカ層の融
点を低下させて焼結体の耐酸化性を劣化させるからであ
る。前記ホウ素含有添加剤としては１例えばホウ素、炭
化ホウ素あるいはそれらの混合物から選択される少なく
とも１種を用いることが好ましい。The boron content of the boron-containing additive is 0.0
The reason why the amount is 1 to 0.25 parts by weight is that if it is less than 0.01 parts by weight, the adhesive effect during neck formation is insufficient and it is difficult to achieve high density.On the other hand, if it is more than 0.25 parts by weight, This is because boron remaining in the sintered body lowers the melting point of the silica layer on the surface of the sintered body, thereby degrading the oxidation resistance of the sintered body. As the boron-containing additive, it is preferable to use at least one selected from, for example, boron, boron carbide, or a mixture thereof.

なお１本発明によれば、ホウ素含有添加剤の添加量がホ
ウ素含有量に換算して０．１重量部より少ない場合に特
に耐酸化性に優れた炭化珪素焼結体を得ることができる
。According to the present invention, a silicon carbide sintered body particularly excellent in oxidation resistance can be obtained when the amount of the boron-containing additive added is less than 0.1 parts by weight in terms of boron content.

本発明によれば、炭化珪素微粉１００重景重量対して炭
素質添加剤を固定炭素含有量に換算して０．３〜５．０
重量部添加することが必要である。前記炭素質添加剤は
炭化珪素微粉に含有される酸素を除去し、かつ炭化珪素
粒子間に介在してＳｉＣの拡散を適正化させるために用
いられる。したがって炭素質添加剤は酸素含有量にみあ
う量を少なくとも添加し、さらに炭化珪素粒子間に均一
に介在するに充分な量を添加することが有利である。According to the present invention, the carbonaceous additive is converted into a fixed carbon content of 0.3 to 5.0 per 100 gram weight of silicon carbide fine powder.
It is necessary to add parts by weight. The carbonaceous additive is used to remove oxygen contained in the silicon carbide fine powder and to be interposed between the silicon carbide particles to optimize the diffusion of SiC. Therefore, it is advantageous to add the carbonaceous additive at least in an amount that matches the oxygen content, and further in an amount sufficient to be uniformly interposed between silicon carbide particles.

前記炭素質添加剤の添加量を固定炭素含有量に換算して
０．３〜５．０重量部にする理由は０．３重量部より少
ないと炭素質添加剤の大部分が酸素によって消費される
ため８ｉＣの拡散を適正化する作用が充分に発揮できな
いからであり、一方５．０重量部よりも多いと炭化珪素
粒子間に過剰の炭素が存在し、焼結を著しく阻害するか
らである。The reason why the amount of the carbonaceous additive added is 0.3 to 5.0 parts by weight in terms of fixed carbon content is that if it is less than 0.3 parts by weight, most of the carbonaceous additive will be consumed by oxygen. This is because the effect of optimizing the diffusion of 8iC cannot be sufficiently exerted due to the amount of carbon content, and on the other hand, if the amount exceeds 5.0 parts by weight, excessive carbon exists between silicon carbide particles, which significantly inhibits sintering. .

前記炭素質添加剤は、焼結開始時に少なくとも１００ｍ
”７％の比表面積を有するものであることが好ましい。The carbonaceous additive is present at least 100 m at the beginning of sintering.
``Preferably, it has a specific surface area of 7%.

その理由は前記焼結開始時における比表面積がｔｏｏｍ
２／Ｐよシも小さいとＳｉＣの拡散を適正化する作用が
弱いため、充分にＳｉＣの拡散を適正化する作用を発揮
させるには大量に添加しなければならず、焼結体中の介
在物層を増加させる結果となり高強度の焼結体を得難い
からである。The reason is that the specific surface area at the start of sintering is too
If 2/P is also smaller, the effect of optimizing the diffusion of SiC will be weak. Therefore, in order to fully exhibit the effect of optimizing the diffusion of SiC, it must be added in large quantities, and it may cause interference in the sintered body. This is because the number of layers increases, making it difficult to obtain a high-strength sintered body.

前記炭素質添加剤としては、焼結開始時に炭素を存在さ
せられるものであれば使用でき、例えばフェノール樹脂
、リグニンスルホン酸塩、ポリビニルアルコール、コン
スターチ、　糖蜜、　　コールタールピッチ、アルギン
酸塩、ポリフェニレンのような各種有機物質あるいは、
カーボンブラック。As the carbonaceous additive, any material that can cause carbon to be present at the start of sintering can be used, such as phenolic resin, lignin sulfonate, polyvinyl alcohol, cornstarch, molasses, coal tar pitch, alginate, and polyphenylene. Various organic substances or
Carbon black.

アセチレンブラックのような熱分解炭素が有利に使用で
きる。Pyrolytic carbon such as acetylene black can be advantageously used.

本発明によれば、炭化珪素微粉とホウ素含有添加剤と炭
素質添加剤を均質混合した後、任意の形状を有する生成
形体に成形し１次いで非酸化性雰囲気中で１７００〜２
３００　Ｃで焼結し、２．８？訳以上の密度を有する炭
化珪素焼結体が製造される。According to the present invention, silicon carbide fine powder, a boron-containing additive, and a carbonaceous additive are homogeneously mixed, and then molded into a formed body having an arbitrary shape, and then heated to a temperature of 1,700 to 2
Sintered at 300 C, 2.8? A silicon carbide sintered body having a density higher than the original density is produced.

本発明によれば、前記非酸化性雰囲気としてはアルゴン
、ヘリウム、ネオン、クリプトン、キセノン、水素から
選ばれるいずれか少なくとも１種からなるガス雰囲気で
あることが有利である。According to the present invention, it is advantageous that the non-oxidizing atmosphere is a gas atmosphere consisting of at least one selected from argon, helium, neon, krypton, xenon, and hydrogen.

ところで１本発明における焼結時には先にも記載した如
く、前記式（１）　、　（２＋に従ってＣＯガスが発生
する。前記ＣＯガスが多量に存在すると前記式の反応が
抑制され炭化珪素表面のシリカ膜除去が不充分となり、
充分な焼結収縮が得られないし、シリカ膜が残存すると
炭化珪素焼結体内で介在相を形成し焼結体の物性特に機
械的強度を劣化させるため、ＣＯガスを炉内より除去し
なければならない。従って本発明によれば炉内を前記ガ
ス気流雰囲気とすることが有利である。な訃前記焼結時
の炉内雰囲気のＣＯガス分圧は１０ＫＰａ以下に維持す
ることが有利である。By the way, during sintering in the present invention, as described above, CO gas is generated according to the above formulas (1) and (2+).If the CO gas is present in a large amount, the reaction of the above formula is suppressed, and the silica on the surface of silicon carbide is Film removal becomes insufficient,
Sufficient sintering shrinkage cannot be obtained, and if the silica film remains, it will form an intervening phase within the silicon carbide sintered body and deteriorate the physical properties, especially the mechanical strength, of the sintered body, so CO gas must be removed from the furnace. No. Therefore, according to the present invention, it is advantageous to provide the above-mentioned gas flow atmosphere inside the furnace. It is advantageous to maintain the CO gas partial pressure in the furnace atmosphere during the sintering to 10 KPa or less.

本発明によれば、前記生成形体を１７００〜２３００Ｃ
の範囲内で焼結することが必要である。その理由は焼結
温度が１７００　Ｃよシ低いと本発明の２，８？／ＦＦ
１３以上の密度を有する焼結体を得ることが困難であり
、逆に２３００　Ｃより高い温度では結晶粒の成長が著
しく、焼結体の物性例えば機械的強度が低下するからで
あり、特に均一な微細構造でかつ高強度の焼結体を得る
上では１９００〜２１００　ｔｅｌ’の温、度範囲内で
焼結することが有利である。According to the present invention, the formed body is heated at a temperature of 1700 to 2300C.
It is necessary to sinter within the range of The reason for this is that if the sintering temperature is as low as 1700 C, the sintering temperature of the present invention is 2.8? /FF
It is difficult to obtain a sintered body with a density of 13 or more, and conversely, at temperatures higher than 2300 C, crystal grains grow significantly and the physical properties of the sintered body, such as mechanical strength, decrease. In order to obtain a sintered body with a fine microstructure and high strength, it is advantageous to sinter at a temperature within the range of 1900 to 2100 tel'.

本発明によれば、前記焼結温度に至る昇温過程のうち１
５００〜１７００　ｔ：’の温度範囲内において、前記
シリカ膜の除去反応を速やかに進行させてネックの生成
反応を均一に発生させるために充分時間前記温度範囲に
おけるＣＯガス分圧をＩＫＰａより低く維持することが
有利である。According to the present invention, one of the heating steps leading to the sintering temperature
Within the temperature range of 500 to 1700 t:', maintain the partial pressure of CO gas lower than IKPa in the temperature range for a sufficient period of time to allow the silica film removal reaction to proceed quickly and the neck formation reaction to occur uniformly. It is advantageous to do so.

次に本発明を実施例および比較例について具体的に説明
する。Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

実施例１ 珪砂粉末（８ｉ０２　＝　９９．６％、全ＡＡ　＝０．
１　％、　　８０メツシユ以下）、無煙炭粉末（Ｃ＝　
８７．８　％、全Ｍ＝　０．４　％＋　　３２５メツシ
ユ以下）およびピッチ粉末（Ｃ＝　５０．４１．２００
メツシュ以下、珪砂に対して７重量％配合）をＣ／５ｉ
０２モル比が３．８になるように配合し、縦型スクリュ
ー混合機に入れて１０分間混合した。＃紀配合原料にＣ
ＭＣ００５チ水溶液をスプレーしながら皿型造粒機を用
いて成形し。Example 1 Silica sand powder (8i02 = 99.6%, total AA = 0.
1%, 80 mesh or less), anthracite powder (C=
87.8%, total M = 0.4% + 325 mesh or less) and pitch powder (C = 50.41.200
Below mesh, 7% by weight of silica sand) is added to C/5i
02 molar ratio was 3.8, and the mixture was placed in a vertical screw mixer and mixed for 10 minutes. ＃C in the compound raw materials
Molding was performed using a dish-type granulator while spraying an aqueous solution of MC005.

篩とバーグリズリ−で整粒した後、乾燥して平均粒径Ｉ
Ｑ、５ｍ、嵩比重０．６の成形原料を得た。次いで前記
成形原料を前記特公昭５７−４８４８５号公報に記載し
たと同様の製造装置の上部より装入し。After sifting with a sieve and burr grizzly, drying to obtain an average particle size of I
A molding raw material of Q, 5 m, and bulk specific gravity of 0.6 was obtained. Next, the forming raw material was charged from the top of a manufacturing apparatus similar to that described in Japanese Patent Publication No. 57-48485.

間接電気加熱して約１９００　Ｃの温度でＳｉＣ化反応
を行なわせた。さらに得られた生成物を精製、粒度分級
して炭化珪素微粉を調製した。The SiC formation reaction was carried out at a temperature of about 1900 C by indirect electric heating. Furthermore, the obtained product was purified and classified for particle size to prepare silicon carbide fine powder.

前記炭化珪素微粉は９６．７％がβ型結晶で残部が２Ｈ
型結晶よりなり、β型結晶の格子定数は４．３６０９　
Ａであり、０．３１重量％のアルミニウム。The silicon carbide fine powder has 96.7% β-type crystals and the remainder is 2H.
The lattice constant of β-type crystal is 4.3609.
A and 0.31% by weight aluminum.

０．３２重量−の遊離炭素、　　０．１８重量−の酸素
を含有し、１５．８　ｍ”／）の比表面積を有していた
。It contained 0.32 wt. free carbon, 0.18 wt. oxygen, and had a specific surface area of 15.8 m"/).

なお、前記β型結晶の格子定数は（４２０）の回折線よ
り求めた。The lattice constant of the β-type crystal was determined from the (420) diffraction line.

前記炭化珪素微粉９９．９　ｉと比表面積が２７．８ｍ
”／？の炭化ホウ素粉末０，１？と固定炭素含有率５ｔ
、６重ｔＪのノボラック型フェノール樹脂２．１との混
合物に対し、アセトン１５０ｄを添加し、振動ミルを使
用して２時間混合処理した。前記振動ミルより混合物ス
ラリーを排出し噴霧乾燥して。The silicon carbide fine powder has a specific surface area of 99.9 i and 27.8 m.
”/? boron carbide powder 0.1? and fixed carbon content 5t
, 150 d of acetone was added to the mixture with 2.1 tJ of novolac type phenolic resin, and the mixture was mixed for 2 hours using a vibration mill. The mixture slurry was discharged from the vibrating mill and spray-dried.

平均粒径が０．０９１１１１、粉体嵩密度が３ｓ％（ｘ
、１２Ｖ−）の顆粒を得た。The average particle size is 0.091111, the powder bulk density is 3s% (x
, 12V-) were obtained.

この顆粒から適量を採取し、金Ｗ４性押し型を用いて０
．１５　ｔ／ｍ２の圧力で仮成形し、次に静水圧プレス
機を用いて１．Ｂｔ／ｃ−の圧力で成形した。　前記成
形によって得られた生成形体の密度は６１チ（１，９５
Ｐｌｏｎ　）で６にとが！Ｉｆ’：＋れた。Take an appropriate amount of these granules and use a gold W4 mold to
．． Preliminary molding was performed at a pressure of 15 t/m2, and then 1. Molding was carried out at a pressure of Bt/c-. The density of the formed body obtained by the above molding was 61 inches (1,95 cm).
Plon) to 6! If': + got.

前記生成形体をタンマン型焼結炉に装入し、大気圧下の
アルゴンガス気流中で焼結した。昇温過程は常ｆｉ　〜
１６５０　Ｃは５　Ｃ／ｍｉｎ、１６５０　Ｃにて４０
分間保持した後、さらに５　Ｃ／ｍｉｎ、　　で昇温し
最高温度２０００　Ｇで３０分間保持した。焼結中のＣ
Ｏガス分圧は常温〜１６５０Ｇが５　ＫＰａ以下、１６
５０　Ｃで保持する際は０．５ＫＰａ以下、　１６５０
Ｃより高温域では５　ＫＰａ以下となるようにアルゴン
ガス流量を適宜調整した。The formed body was placed in a Tammann type sintering furnace and sintered in an argon gas stream under atmospheric pressure. The heating process is normally fi ~
1650 C is 5 C/min, 40 at 1650 C
After holding for a minute, the temperature was further increased at a rate of 5 C/min and held at a maximum temperature of 2000 G for 30 minutes. C during sintering
O gas partial pressure is 5 KPa or less at room temperature to 1650G, 16
0.5KPa or less when held at 50C, 1650
The argon gas flow rate was appropriately adjusted so that the temperature was 5 KPa or less in the higher temperature range than C.

得られた焼結体はアルミニウムを０．３１重量％、遊離
炭素を１．０重量％含有し、３．１２　Ｖａｎ３（相対
理論密度率９８．０％）の密度を有していた。またこの
焼結体の粉末Ｘ線回折測定の結果、この焼結体は９２．
１　％がβ型結晶であることが認められた。The obtained sintered body contained 0.31% by weight of aluminum and 1.0% by weight of free carbon, and had a density of 3.12 Van 3 (relative theoretical density rate 98.0%). Further, as a result of powder X-ray diffraction measurement of this sintered body, this sintered body has a 92.
It was found that 1% was β-type crystals.

前記焼結体を３０　Ｘ　３０　Ｘ　１　ｍの板状に加工
し、アセトンで洗浄して耐酸化性テスト用試料を作成し
た。前記試料を１４０００の空気雰囲気に保持された加
熱炉中で２０時間処理し、処理前後の重量増加量を測定
したところ処理前に比較して０．０２■／ｃｍ２の割合
であり、耐酸化性に優れていることが認められた。The sintered body was processed into a plate shape of 30 x 30 x 1 m, and washed with acetone to prepare a sample for oxidation resistance test. The sample was treated for 20 hours in a heating furnace maintained in an air atmosphere of 14,000 °C, and the weight increase before and after the treatment was measured, and the weight increase was 0.02 cm/cm2 compared to before the treatment, indicating that the oxidation resistance was recognized as being excellent.

実施例２、比較例１ 実施例ＩＫ記載したと同様であるが、無煙炭粉末に換え
て第１表に示した如くアルミニウム含有量の異なるオイ
ルコークス粉末を使用して第１表に示した温度で炭化珪
素微粉を調製した。Example 2, Comparative Example 1 Same as described in Example IK, but using oil coke powder with different aluminum content as shown in Table 1 instead of anthracite powder and at the temperature shown in Table 1. Silicon carbide fine powder was prepared.

得られた炭化珪素微粉の物性は第１表に示した。The physical properties of the obtained silicon carbide fine powder are shown in Table 1.

前記第１表に示した炭化珪素微粉を使用し、実施例１と
同様であるが第１表に示した如く炭化ホウ素の添加量を
変えて焼結体を得た。得られた焼結体の物性は実施例１
に示したと同様の方法で測定し、第１表に示した。Using the silicon carbide fine powder shown in Table 1 above, sintered bodies were obtained in the same manner as in Example 1, except that the amount of boron carbide added was changed as shown in Table 1. The physical properties of the obtained sintered body are as shown in Example 1.
The results are shown in Table 1.

第１表によれば、実権例２−１および２−２は全ｕ量が
それぞれ異なっているが、何れも高密度の焼結体が得ら
れており、−１だ耐酸化性もそれぞれ優れていることが
判る。また実施例２−３は特にＳｉＣ化反応温度を２１
００　Ｃに高めた例であるが、得られた炭化珪素粉末の
格子定数４．３６１８　Ａであり、この粉末から製造さ
れた焼結体は特に高密度になり、また耐酸化性が最も優
れていた。実権例２−４および２−５では実施例１で使
用した炭化珪素粉末を使用したが炭化ホウ素添加量をそ
れぞれ０．０５　Ｌ？、　０．１５１ｉ−とじて焼結体
を製造した。得られた焼結体は何れも高密度であり、耐
酸化性に優れていた。According to Table 1, although actual examples 2-1 and 2-2 have different total U amounts, they both yield high-density sintered bodies, and -1 has excellent oxidation resistance. It can be seen that In addition, in Example 2-3, the SiC formation reaction temperature was set at 21%.
In this example, the lattice constant of the silicon carbide powder obtained is 4.3618 A, and the sintered body produced from this powder has a particularly high density and has the best oxidation resistance. Ta. In Examples 2-4 and 2-5, the silicon carbide powder used in Example 1 was used, but the amount of boron carbide added was 0.05 L each. , 0.151i- to produce a sintered body. All of the obtained sintered bodies had high density and excellent oxidation resistance.

一方比較例１は炭化珪素粉末の結晶の格子定数の平均値
が４．３５８０　Ｘ、であり、これを用いて製造された
一焼結体の密度は２．７２　ｆ／ｃｒｒｔ３と低く、ま
た耐酸化性も実施例と比較して極めて劣っていた。On the other hand, in Comparative Example 1, the average value of the lattice constant of the silicon carbide powder crystal is 4.3580 The chemical properties were also extremely poor compared to the examples.

遺ｍ 出発原料として実施例ＩＫ記載した炭化珪素微粉９９．
９ｐと実施例１に記載した炭化ホウ素粉末をさらに粒度
分級し、比表面積を４７．８ｍ２／バ１製した炭化ホウ
素ｏ、ｉ　ｙと平均粒径２１ＯＮ、比表面積１２８　ｍ
２／９−のカーボンブラック１．５ｉとの混合物に対し
、アセトン１５０ｄ、ポリエチレングリコールＱ、７ａ
ｊを添加し、１０時間ボールミル処理した後スラリーを
噴霧乾燥した。この乾燥粉末を適量採取して実施例１と
同様に生成形体を作成し、焼結体を得た。The silicon carbide fine powder described in Example IK as a starting material 99.
9p and the boron carbide powder described in Example 1 were further classified by particle size, and the specific surface area was 47.8 m2/Ba1 made boron carbide o, i y, average particle size 21ON, specific surface area 128 m
For a mixture with 2/9 carbon black 1.5i, acetone 150d, polyethylene glycol Q, 7a
After ball milling for 10 hours, the slurry was spray dried. An appropriate amount of this dry powder was collected and a green body was prepared in the same manner as in Example 1 to obtain a sintered body.

得られた焼結体の密度は３．０１？／ｃｎ１３と高く。The density of the obtained sintered body is 3.01? /cn13 high.

９４．０％がβ型結晶であることが認められた。It was found that 94.0% were β-type crystals.

また実施例１と同様にして測定した耐酸化性テストによ
る重量増加量は０．０３　ｍｔｉ／ｃｍ２と少なく耐酸
化性に優れていた。Further, the weight increase in the oxidation resistance test measured in the same manner as in Example 1 was as small as 0.03 mti/cm2, indicating excellent oxidation resistance.

実施例４ 実施例１と同様であるが出発原料として実施例１に記載
した炭化珪素微粉６０重量部に市販のα型炭化珪素を粉
砕、精製、粒度分級して製造したα型炭化珪素微粉を４
０重量部の割合で混合した炭化珪素微粉を使用して焼結
体を得た。Example 4 Same as Example 1, but α-type silicon carbide fine powder produced by crushing, refining, and particle size classification of commercially available α-type silicon carbide was added to 60 parts by weight of the silicon carbide fine powder described in Example 1 as a starting material. 4
A sintered body was obtained using silicon carbide fine powder mixed in a proportion of 0 parts by weight.

なお、前記α型炭化珪素微粉は比表面積が１４．８ｍ２
／？であり、アルミニウムを００１重量％、遊離炭素を
０．３重量％、酸素な００２重量％含有していた。Note that the α-type silicon carbide fine powder has a specific surface area of 14.8 m2.
/? It contained 0.01% by weight of aluminum, 0.3% by weight of free carbon, and 0.02% by weight of oxygen.

得られた焼結体の密度は２．９０　ｉ／Ｃ’ｆｆ１３で
、β型炭化珪素の含有率は４０．４チであった。The density of the obtained sintered body was 2.90 i/C'ff13, and the content of β-type silicon carbide was 40.4 i/C'ff13.

また実施例１と同様にして測定した耐酸化性テストによ
る重量増加量は０．０４ｍｇ／ａｔ？と少なく、耐酸化
性に優れていた。Also, the weight increase in the oxidation resistance test measured in the same manner as in Example 1 was 0.04 mg/at? It had excellent oxidation resistance.

以上本発明によれば、高密度でかつ耐酸化性に優れ九炭
化珪素無加圧焼結体を安価に製造することができ′る。As described above, according to the present invention, a pressureless sintered body of silicon nine carbide having high density and excellent oxidation resistance can be produced at low cost.

Claims (1)

【特許請求の範囲】 １、炭化珪素微粉を無加圧焼結する炭化珪素焼結体の製
造方法において、 結晶の格子定数の平均値が４．３５８４Å以上のβ型炭
化珪素を５０重量％以上含有する炭化珪素微粉１００重
量部とホウ素含有量に換算して０．０１〜０．２５重量
部のホウ素含有添加剤と固定炭素含有量に換算して０．
３〜５．０重量部の炭素質添加剤と均質混合した後、任
意の形状を有する生成形体に成形し、次いで非酸化性雰
囲気中で１７００〜２３００℃で焼結し、２．８ｇ／ｃ
ｍ＾３以上の密度を有する炭化珪素焼結体を製造するこ
とを特徴とする炭化珪素焼結体の製造方法。 ２、前記β型炭化珪素はシリカと炭素を出発原料として
高温焼成してなるβ型炭化珪素である特許請求の範囲第
１項記載の方法。 ３、前記β型炭化珪素はアルミニウムを０．０２〜１．
０重量％含有したものである特許請求の範囲第１あるい
は２項記載の方法。 ４、前記炭化珪素微粉は比表面積が５〜５０ｍ＾２／ｇ
である特許請求の範囲第１〜３項のいずれかに記載の方
法。 ５、前記炭化珪素微粉は酸素含有率が０．１〜１．０重
量％である特許請求の範囲第１〜４項のいずれかに記載
の方法。 ６、ホウ素含有添加剤はホウ素、炭化ホウ素あるいはそ
れらの混合物から選択される少なくとも１種である特許
請求の範囲第１〜３項のいずれかに記載の方法。 ７、炭素質添加剤は焼結開始時に少なくとも１００ｍ＾
２／ｇの比表面積を有するものである特許請求の範囲第
１〜６項のいずれかに記載の方法。 ８、前記炭化珪素焼結体は少なくとも２０重量％がβ型
炭化珪素である特許請求の範囲第１〜７項のいずれかに
記載の方法。[Claims] 1. A method for producing a silicon carbide sintered body by pressure-free sintering of silicon carbide fine powder, comprising 50% by weight or more of β-type silicon carbide having an average crystal lattice constant of 4.3584 Å or more. It contains 100 parts by weight of silicon carbide fine powder, a boron-containing additive of 0.01 to 0.25 parts by weight in terms of boron content, and 0.01 to 0.25 parts by weight in terms of fixed carbon content.
After homogeneously mixing with 3 to 5.0 parts by weight of a carbonaceous additive, it is molded into a formed body having an arbitrary shape, and then sintered at 1700 to 2300°C in a non-oxidizing atmosphere to produce 2.8 g/c
A method for producing a silicon carbide sintered body, comprising producing a silicon carbide sintered body having a density of m^3 or more. 2. The method according to claim 1, wherein the β-type silicon carbide is a β-type silicon carbide obtained by firing silica and carbon at a high temperature as starting materials. 3. The β-type silicon carbide contains aluminum in an amount of 0.02 to 1.
The method according to claim 1 or 2, which contains 0% by weight. 4. The silicon carbide fine powder has a specific surface area of 5 to 50 m^2/g
The method according to any one of claims 1 to 3. 5. The method according to any one of claims 1 to 4, wherein the silicon carbide fine powder has an oxygen content of 0.1 to 1.0% by weight. 6. The method according to any one of claims 1 to 3, wherein the boron-containing additive is at least one selected from boron, boron carbide, or a mixture thereof. 7. The carbonaceous additive is at least 100 m^ at the beginning of sintering.
The method according to any one of claims 1 to 6, which has a specific surface area of 2/g. 8. The method according to any one of claims 1 to 7, wherein at least 20% by weight of the silicon carbide sintered body is β-type silicon carbide.