JPH11201654A - Induction furnace lined with glazed shaped material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To modify abnormal phenomenon due to a permeating material and to fully utilize the characteristic of the material by a method wherein ceramics blaze is applied on the back of a molding material sleeve and softened and molten, to provide a low permeability. SOLUTION: In a refractory for lining an electric type induction furnace, an innermost layer working layer is formed of a refractory molded integrally with a side wall. A ceramic glaze having a heat resisting temperature of 700 deg.C or higher is applied on the outer peripheral surface of the molded product, and a glassy layer is formed. Permeability (cm.cm/cm<2> , g/cm<2> , sec) of an integrally molded product is set to 15 or less to form a furnace interior material. The outer peripheral part of the electric type induction furnace is built of dry type amorphous refractories having the coefficiency of hot linear expansion equal to or higher than that of a shaped refractory with which the outer peripheral part thereof is lined.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は金属の溶解およびま
たは精錬を行なう時に用いられる施釉定形耐火材を内装
した誘導炉に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction furnace equipped with a glazed fixed type refractory material used for melting and / or refining metal.

【０００２】[0002]

【従来の技術】従来、主に鋳鉄の溶解およびまたは精錬
は主にキュポラでの溶解し前炉又は取鍋内での精錬処理
が行われていたが、近年、バラツキの無い品質を持つ
製品高い生産性より良い作業環境が求められている
昨今、これらの要求に対応するため、キュポラ操業に比
べ、溶解効率が高く炉および炉の内張り耐火材の保全機
会が少なく、且つ容易で、均一性の高い溶湯が得られる
と共に操炉時の作業環境のよい誘導炉が急速に普及して
きている。この誘導炉は外周部に電気炉の誘導コイルを
持ちこのコイルの内側に必要ならばコイルセメントによ
りコイルを被覆保護する耐火層を設け、湯もれセンサー
絶縁材および断熱材等等々を順次配設した後、最内側に
一般には一層の耐火物により炉床部、側壁部に内張り層
を構築して使用されている。2. Description of the Related Art Conventionally, melting and / or refining of cast iron has been mainly performed by melting in a cupola and refining in a pre-furnace or a ladle. In order to respond to these demands in recent years where a better working environment is required than productivity, compared to cupola operation, the melting efficiency is higher and the maintenance opportunities of the furnace and the refractory material of the furnace are less, easy and uniform. Induction furnaces that can obtain a high molten metal and have a good working environment during furnace operation are rapidly spreading. This induction furnace has an induction coil of an electric furnace on the outer periphery.If necessary, a refractory layer for covering and protecting the coil with coil cement is provided inside the coil, and insulation materials for heat leak sensor, heat insulating material, etc. are sequentially arranged. After that, a lining layer is generally formed on the innermost side of the hearth portion and the side wall portion by using one layer of refractory on the innermost side.

【０００３】この耐火物による内張り材の施工方法は一
般には乾式不定形耐火物を用いて先ず炉の底部を所定の
厚みだけつきかためるか、加振充填施工し、この上部に
所定の側壁の厚みを持たせるように設計された寸法の鋼
製の内枠（以下フォーマーと称する）を炉のほぼ中央部
に配設し、このフォーマーと炉本体と間隙部に乾式不定
形耐火物を投入した後、フォーマーの内側に直接振動を
与え、上下させながら投入した不定形耐火物を加振充填
させて施工する。In general, a method of applying a lining material with a refractory is to first dry the furnace to a predetermined thickness by using a dry amorphous refractory, or to carry out shaking and filling, followed by a predetermined thickness of a side wall on the upper portion. A steel inner frame (hereinafter referred to as a “former”) with dimensions designed to have a shape is placed at the approximate center of the furnace, and after the dry amorphous refractory is charged into the gap between the former and the furnace body. Vibration is applied directly to the inside of the former, and the refractory that has been injected while being moved up and down is vibrated and filled for construction.

【０００４】このようにして、施工された耐火物は充填
密度が低く、且つ均一性の高い施工体を構築しがたく、
炉の寿命のバラツキが出易いなどの不具合を持ち合わせ
ており、この施工の良否が炉材の寿命を大きく左右する
ため、予想外の保全作業が余儀なくされて突発的に工場
の操業停止となる大きな損失をまねく等工場の操業面で
の影響が大きいため、安定した操業を行なうには、より
確実な施工を行なう必要がある。それには高い熟練が必
要とされる。[0004] In this way, the refractory thus constructed has a low filling density and is difficult to construct a highly uniform construction.
Since the life of the furnace tends to fluctuate, the quality of the construction greatly affects the life of the furnace material, so unexpected maintenance work is required and the factory suddenly shuts down. Since the impact on the operation of the factory is large, such as causing loss, it is necessary to perform more reliable construction for stable operation. It requires a high level of skill.

【０００５】また、施工の良否と共にここに用いられる
耐火物も特に吟味された珪石質材、アルミナ質材、マグ
ネシア質材および、スピネル質材等の諸材料に必要なら
ば無水硼酸等の焼結助材を添加した乾式不定形耐火物を
使用条件にあわせて選定しながら使用されているが、均
一な充填密度や高い充填密度が得がたいのでガスや鋳鉄
材中に含まれる亜鉛等の低融点金属等が高温度中に存在
する場合は、非常に低粘性になるほか、一部気化現象を
生じ、炉の内張り耐火材の組織中に容易に浸透現象を起
こすことになる。[0005] In addition to the quality of the construction, the refractory used here is also examined especially for various materials such as siliceous material, alumina material, magnesia material and spinel material, and if necessary, sintering of boric anhydride or the like. Dry amorphous refractories to which auxiliary materials have been added are used while being selected according to the usage conditions.However, it is difficult to obtain a uniform or high packing density, so low melting point metals such as zinc contained in gases and cast iron materials When such substances are present at a high temperature, they become very low in viscosity and also cause a partial vaporization phenomenon, which easily causes a penetration phenomenon into the structure of the refractory material lining the furnace.

【０００６】現在誘導炉において溶解される鋳鉄用材料
は新材屑にかわり、亜鉛メッキ鋼板屑も多く使用される
ようになってきている。亜鉛金属は融点４１９．５℃、
沸点が９０６℃と非常に低耐熱性材であるため、鋳鉄材
の溶湯温度は１４５０〜１５５０℃と高く、溶解、精錬
されるため、内張り耐火材の組織中に容易に浸透して裏
側に配設されている湯もれセンサーに検知され作動する
こととなり、湯もれでなくても、湯もれか否かが判定で
きぬまま、継続使用することが安全操業上できず解体
し、新しく内張り材を張り替えねばならない。このため
内張り材の保全作業の機会が多くなり、３Ｋ作業を余儀
なくされていると共に、炉の操業はもとより上工程およ
び下工程にも影響が出て、工場全体の操業を低下させる
こととなる。尚、誘導コイル近傍にまで浸入してきたこ
れら亜鉛等の低融点金属は誘導コイルの寿命をも短くさ
せる原因となり、その損傷は大きくひいては製造コスト
を高めることとなっているのが現状である。現在このよ
うな問題点を解決し安定した操炉ができ且つ製造コスト
を引き下げられるようにすることが強く望まれているの
が現状である。[0006] At present, the cast iron material to be melted in the induction furnace is replaced by new scrap, and galvanized steel scrap is increasingly used. The melting point of zinc metal is 419.5 ° C,
Since the boiling point is 906 ° C, which is a very low heat-resistant material, the temperature of the cast iron material is as high as 1450-1550 ° C, and it is melted and refined, so that it easily penetrates into the structure of the lining refractory material and is distributed on the back side. It will be detected by the installed hot water leak sensor and will be activated.Even if it is not hot water leak, it can not be judged whether it is hot water leak or not, it can not be used continuously and it can not be safely operated and dismantled, The lining must be replaced. For this reason, there are many opportunities for the maintenance work of the lining material, and the 3K work is inevitable, and the operation of the furnace as well as the upper process and the lower process are affected, thereby lowering the operation of the entire factory. In addition, these low-melting metals such as zinc that have penetrated into the vicinity of the induction coil cause the life of the induction coil to be shortened, and at present, the damage is greatly increased and the manufacturing cost is increased. At present, it is strongly desired that such problems be solved so that a stable furnace operation can be performed and the production cost can be reduced.

【０００７】[0007]

【発明が解決しようとする課題】本発明者等はこのよう
な現状に鑑み、前述のごとく操業中に鋳鉄材中に混入す
る亜鉛等の低融点、低沸点金属が誘導炉の内張り耐火物
の組織内に浸透し、炉本体側に配設させている湯もれセ
ンサーが感知し、内張り材が充分に耐えられる状態にあ
るにもかかわらず、湯もれとして検知し、湯もれ警報を
発するため継続使用ができなくなると共に誘導コイルの
損傷を助長させる等の不具合を解決することを技術的課
題とするものである。In view of such a situation, the present inventors have considered that low melting point and low boiling point metals such as zinc mixed in cast iron material during operation as described above make refractory linings of induction furnaces. The water leak sensor, which has penetrated into the tissue and is located on the furnace body side, detects it and detects it as a water leak even though the lining material is in a state that can sufficiently withstand it. It is an object of the present invention to solve the problems such as the occurrence of such a problem that the continuous coil cannot be used continuously and the induction coil is damaged.

【０００８】[0008]

【課題を解決するための手段】本発明者等はこのような
現状に鑑み、炉の操業が安定してでき、且つ内張り用耐
火物が充分に使いきることができ、長い寿命を有するこ
とができるようにと種々調査検討を行なった結果、亜鉛
等の低融点低沸点の金属が耐火材の組織内を透過する現
象を起こすのは耐火物の組織、密度と通気率に起因する
ものであろうとの結論を得て、先ず、現在の乾式不定形
耐火物を用いての加振充填された炉の内張り用材の充填
密度と通気率を調べた結果、充填密度は７５〜８２％で
通気率（ｃｍ・ｃｍ／ｃｍ²，ｇ／ｃｍ²，ｓｅｃ）が８
００前後と高く、低密度で高通気性であることが判明し
た。この結果より、耐火物の密度と通気率、そして
小型の高周波誘導炉において鋳物銑９５重量％と亜鉛５
重量％を溶解して溶湯温度を１６００℃とし、６０分間
保持した後出湯する試験を繰り返し行い、調べた亜鉛
の浸透度とこの三者の関係につき種々研究と実用試験を
重ねた結果通気率（ｃｍ・ｃｍ／ｃｍ²，ｇ／ｃｍ²，ｓ
ｅｃ）が４０以下ならばほぼ亜鉛メッキ鋼板等の亜鉛の
混入材を鋳鉄の素材として使用して溶解された溶湯の温
度が１６００℃でも亜鉛等の低融点低沸点の金属が浸入
してきてもスリーブの裏面に施されたガラス質材により
止まり、誘導炉の操業上不具合の発生もなく、操炉する
ことが可能であること、また同じに実炉野呂本体内壁の
温度は炉内張り材が正常に溶損し、張り替えを必要とす
る時期でも最高７００℃までであることを知見し得た。SUMMARY OF THE INVENTION In view of such circumstances, the present inventors have found that the furnace can be operated stably, the refractory for lining can be used up sufficiently, and a long life can be attained. As a result of various investigations and studies to make it possible, it is found that the phenomenon that a metal with a low melting point and a low boiling point, such as zinc, penetrates the structure of the refractory material is caused by the structure, density and permeability of the refractory. After obtaining the conclusion of wax, firstly, the packing density and the permeability of the material for the lining of the furnace filled with vibration using the current dry type refractory were examined. (Cm · cm / cm ² , g / cm ² , sec) is 8
It was found to be as high as around 00, low density and high air permeability. The results show that the density and permeability of the refractory, 95% by weight of cast iron and 5% of zinc in a small high-frequency induction furnace.
The test was conducted by repeating the test of dissolving the weight percent, maintaining the melt temperature at 1600 ° C., holding the sample for 60 minutes, and then tapping, and repeating the various studies and practical tests on the relationship between the examined zinc permeability and these three factors. cm · cm / cm ² , g / cm ² , s
If ec) is 40 or less, a sleeve is used even if the temperature of the molten metal is 1600 ° C. even when a low melting point and low boiling point metal such as zinc enters, using a zinc-mixed material such as a galvanized steel plate as a cast iron material. The furnace is stopped by the vitreous material applied to the back surface of the furnace, and it is possible to operate the induction furnace without any trouble in the operation of the induction furnace. It was found that the temperature was up to 700 ° C. even at the time of melting and requiring replacement.

【０００９】このように通気率（ｃｍ・ｃｍ／ｃｍ²，
ｇ／ｃｍ²，ｓｅｃ）４０以下の低通気性の特性を具備
する内張り材を得ることは現在の施工方法の主流をなす
乾式不定形耐火物を炉性能上適正な厚みの内張り層を設
けるように設計されたフォーマーを底打ち後、炉のほぼ
中央部に配設した後、炉本体とフォーマーの間隙部に投
入しフォーマーの内側に直接、振動を与えながら加振充
填するのでは達成することができない。必要とする低通
気性材を得るためには、あらかじめ側壁一体成形体ある
いは側壁と底部を一体成形体として工場で製作すること
により達成出来たがより安定性を高めるには、更にこの
成形体（以下スリーブと称する）の裏面（外側の面）に
７００℃まで耐え得るセラミックス釉薬を施釉し、軟化
および溶融させる。この釉薬層により通気率（ｃｍ・ｃ
ｍ／ｃｍ²，ｇ／ｃｍ²，ｓｅｃ）１５以下とした高品質
で品質の安定した少なくとも側壁一体成形材スリーブを
製出することができた。As described above, the air permeability (cm · cm / cm ² ,
g / cm ² , sec) To obtain a lining material having a low air permeability of 40 or less, it is necessary to provide a dry-type amorphous refractory, which is the mainstream of the current construction method, with a lining layer having an appropriate thickness for furnace performance. After placing the former designed in the bottom and placing it almost in the center of the furnace, throw it into the gap between the furnace body and the former, and apply vibration to the inside of the former directly while applying vibration to achieve this. Can not. In order to obtain the required low-permeability material, it was achieved in advance by manufacturing the side wall integrally molded body or the side wall and the bottom as an integrally molded body at a factory. A ceramic glaze that can withstand up to 700 ° C. is glazed, softened and melted on the back surface (outer surface) of the sleeve. With this glaze layer, the air permeability (cm
m / cm ² , g / cm ² , sec) A high-quality, stable-quality at least side wall-integrated material sleeve of 15 or less could be produced.

【００１０】現在は一般の施工体は炉本体内に乾式不定
形耐火物とフォーマーを用いて直接加振充填施工を行な
うので内張り施工体の密度が低く、不均一性の生じやす
い内張り材であるため、大きな不具合を引き起こしてい
るが、このように製造された一体成形体も外表面に施釉
したスリーブ材を炉底最下部層に乾式不定形耐火物をつ
きかためた後、炉本体のほぼ中央部に設置し、その内周
部を成形体とほぼ同等以上の熱膨張率を有する乾式不定
形耐火物で高密度に充填する内張り材二層構造とするこ
とにより、従来の不具合を改善するに最も好ましい方法
であることを見い出した。[0010] At present, a general construction body is a lining material in which the density of the lining construction body is low and non-uniformity is liable to occur due to the fact that the vibrating and filling construction is directly performed by using a dry amorphous refractory and a former in the furnace body. Although this has caused a major problem, the integrally molded body manufactured in this way also used a non-refractory dry-type refractory on the lowermost layer of the furnace bottom after glazing the outer surface of the sleeve material. Installed in the center, the inner periphery of which has a two-layered lining material filled with high-density dry amorphous refractory having a coefficient of thermal expansion almost equal to or higher than that of the molded body, thereby improving conventional problems Was found to be the most preferred method.

【００１１】具体的には少なくとも側壁一体成形体とし
裏面に施釉された耐火物を炉の底部を施工した後、ほぼ
中央部に配置し、この定形体と炉本体との間隙部に乾式
不定形耐火物を投入し振動棒等で直接加振又はつきかた
めて充填施工することにより、 亜鉛等の低融点金属が内張り材（スリーブ）の組織中
への浸透を軽減することができると共にスリーブの裏面
釉薬層によりそれ以上外部への浸透がほぼ抑制される。 二層構造とすることにより万一浸透あるいは最内層材
に亀裂が入り、地金が浸入しても第二層目をなす不定形
耐火物が固まっていないため、割り込むことなく成形体
と不定形耐火物の間に薄く入り凝固するので安全に操炉
を行なうことが出来る。 亜鉛等の低融点金属がコイルセメントの組織内への浸
透や直接誘導コイル外表面への付着も軽減されることに
より誘導コイル自体の保全作業も少なくなり且つ寿命が
延長された。More specifically, at least a refractory glazed on the back surface is formed at the bottom of the furnace after being formed at least as an integral molded body of the side wall, and is disposed substantially at the center thereof. By injecting the refractory material and directly shaking it with a vibrating bar or filling it with a filling, the low melting point metal such as zinc can reduce the penetration of the lining material (sleeve) into the structure and the sleeve The back glaze layer substantially suppresses further penetration to the outside. In the unlikely event of infiltration or cracking of the innermost layer material due to the two-layer structure, even if the metal infiltrates, the irregular-shaped refractory that forms the second layer is not solidified. Since it enters thinly between the refractories and solidifies, the furnace can be safely operated. Since the low-melting-point metal such as zinc is less likely to penetrate into the tissue of the coil cement and directly adhere to the outer surface of the induction coil, the maintenance work of the induction coil itself is reduced and the life is extended.

【００１２】このような低通気性の成形体を最内層材と
し、その外周部に使用時に定形内装材を外回りより拘束
するには同等又は同等以上の熱膨張率を有し、使用時の
受熱により固まらない乾式不定形耐火物で構成すること
がより有効であることより、安全且つ安定した操業がで
きる、また誘導コイルの長寿命化が企れる効果をもたら
すことができて現在の問題点が解決し得る手段をここに
提供するものである。Such a molded article having low air permeability is used as the innermost layer material, and has a coefficient of thermal expansion that is equal to or greater than that of the outermost portion in order to restrain the fixed interior material from the outer periphery during use. Due to the fact that it is more effective to use a non-consolidated dry amorphous refractory, safe and stable operation can be achieved, and the effect of prolonging the life of the induction coil can be achieved. A solution that can be provided is provided here.

【００１３】 （限定理由） (1)稼働層を構成する少なくとも側壁一体の成形体耐火
物（スリーブ）の外周面に耐熱性７００℃以上のセラミ
ックス釉薬を施薬する。亜鉛等の低融点物が内張り材
（スリーブ）の組織内に浸透してもスリーブ内のみにと
どまり、浸透物による不具合を止めることができるため
である。尚、７００℃以上の耐熱性とするのは外周面の
最高温度に耐えさせるためである。 (2)稼働層に用いる定形耐火物の通気率（ｃｍ・ｃｍ／
ｃｍ²，ｇ／ｃｍ²，ｓｅｃ）が１５以下であること。通
気率が低くなるにつれ亜鉛等の低融点物の浸透が少なく
なり、しかもスリーブの裏面に施された釉薬により抑制
されるので、定形耐火物が電力の入りのバランスがと
れ、正常稼働している間は安全に使用ができる特性値を
示している。 (3)稼動層を少なくとも側壁一体の成形体耐火物とし、
外周部層を乾式不定形耐火物での二層方式とする。 (a)一体成形体とすることにより充填密度を高めること
ができ、低通気性材とすることができる。 (b)内張り用耐火物は稼動層が焼結度が高く高密度体と
なり、亀裂が発生せず、外周部は未焼結状態で自在性を
有することが操業上の安定性が高いことおよび解体
時に炉底部より押し抜き、又はこわしが楽にできる熱
の伝導度を低く保つことが出来る。 (4)定形耐火物の外周部に用いる乾式不定形耐火物の熱
間線膨張率が定形耐火物材に比べ、同等又は同等以上で
あること。内装された定形耐火物を背面より拘束して割
れの発生、発達も抑制することが背面部に充填する乾式
不定形耐火物の役目である。この役割をより確実とする
には熱間の膨張率が最内層を形成する定形耐火物を保護
するには高いことが望ましい。以下実施例を示す。(Reason for limitation) (1) A ceramic glaze having a heat resistance of 700 ° C. or more is applied to the outer peripheral surface of at least the molded body refractory (sleeve) integrated with the side wall constituting the operating layer. This is because even if a low-melting substance such as zinc permeates into the tissue of the lining material (sleeve), it stays only in the sleeve and can stop the trouble caused by the permeated substance. The heat resistance of 700 ° C. or more is intended to withstand the maximum temperature of the outer peripheral surface. (2) Permeability (cm · cm /
cm ² , g / cm ² , sec) is 15 or less. As the air permeability decreases, the penetration of low-melting substances such as zinc decreases, and is controlled by the glaze applied to the back surface of the sleeve, so that the fixed refractories are balanced with the power input and operate normally. The interval shows characteristic values that can be used safely. (3) The working layer is at least a molded body refractory integral with the side wall,
The outer peripheral layer is a two-layer system made of dry amorphous refractory. (a) The packing density can be increased by forming an integrally molded body, and a low air permeability material can be obtained. (b) The refractory for lining has a high operational stability in that the working layer has a high sintering degree and a high density body, no cracks are generated, and the outer peripheral portion has flexibility in an unsintered state, and During disassembly, it is possible to keep the heat conductivity low, which makes it easier to push out or stiffen from the furnace bottom. (4) The coefficient of linear thermal expansion of the dry amorphous refractory used for the outer periphery of the fixed refractory is equal to or greater than that of the fixed refractory. It is the role of the dry-type amorphous refractory to fill the rear part that the interior fixed refractory is restrained from the back to suppress the generation and development of cracks. To ensure this role, it is desirable that the coefficient of thermal expansion be high to protect the shaped refractory forming the innermost layer. Examples will be described below.

【００１３】[0013]

【実施例】１．実施例に用いた原料の化学成分値例を表
１に示す。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Table 1 shows examples of chemical component values of raw materials used in the examples.

【００１４】[0014]

【表１】 [Table 1]

【００１５】２．実施例に用いた耐火物の粒度構成を表
２に示す。2. Table 2 shows the particle size composition of the refractory used in the examples.

【００１６】[0016]

【表２】 [Table 2]

【００１７】３．実施例材の配合比率と耐火物の形態を
表３に示す。3. Table 3 shows the compounding ratio of the example materials and the form of the refractory.

【００１８】[0018]

【表３】 [Table 3]

【００１９】４．評価試験内材の製造方法 第一工程（内張り材の成形） 本発明の実施例は表１に示される原料を用い、表２、表
３に示される粒度構成に調製し、配合、混合又は混練を
行なう。 実施態様Ａ 、は定められた材料比を配合、混合し、この乾式不定形耐火 物に調製する。 実施態様Ｂ 、、、は定められた材料を配合、混合、混練し、湿式坏 土を調製する。 実施態様Ｃ は定められた材料を配合、混合、混練を行い、半乾式のラミン グ材を用い、調製する。4. Method of Manufacturing Inner Material for Evaluation Test First Step (Forming of Lining Material) In the examples of the present invention, the raw materials shown in Table 1 were used to prepare the particle sizes shown in Tables 2 and 3, and blended, mixed or kneaded. Perform In the embodiment A, the determined material ratio is blended and mixed to prepare a dry amorphous refractory. In Embodiment B, a predetermined material is blended, mixed, and kneaded to prepare a wet clay. Embodiment C is prepared by blending, mixing and kneading the specified materials, and using a semi-dry ramming material.

【００２０】以上の如く調製された材料を用いて、実施
態様Ａ、Ｂ、Ｃ共に２３０ｍｍ×１１４ｍｍ×６５ｍｍ
形状に充填し、加熱処理を行い、評価用材を製造する。
その評価用材の成形を実施態様Ａ、Ｂ、Ｃに詳記すれ
ば、 実施態様Ａ→調製された乾式不定形耐火物を所定の形
状に製出する。型内に１ｍｍのステンレス鋼板にてほぼ
同形状の薄鋼板枠を挿入して、振動台上に固定して加振
充填した後、内枠ごと電気炉中にいれ、８００℃で３時
間保持して硬化させ製造する。 実施態様Ｂ→調製された材料に、、材はリン酸
ソーダと水、材はコロイダルシリカと水を基定量添加
し、混合、混練を湿式材となし、容器内に厚み２０〜４
０ｍｍ位加振し、材料中の気泡をのぞきながら原料調製
を行い、所定の大きさの吸水性能を有する鋳込の粗型中
に順次投入しながら、加振鋳込み成形を行い、１６時間
以上放置、自然養生した後、脱型し、約２４時間２０〜
５０℃で予備乾燥を行なった後、１時間あたり３０℃の
昇温速度で１５０℃まで高め、１０時間保持し、乾燥後
１時間あたり４０℃で８００℃まで昇温させ、３時間保
持して製出する。 実施態様Ｃ→調製された材料をミキサー内にてリン酸
ソーダと水を添加、混練して、材料を調製し、所定の大
きさの型を用いて、エアーハンマーにてつき固めて製造
し、１６時間自然養生後、１時間あたり３０℃で１５０
℃まで昇温し、１０時間保持の乾燥を行った後、１時間
あたり４０℃で８００℃まで高めた後、３時間保持して
製出する。Using the materials prepared as described above, embodiments A, B, and C were all 230 mm × 114 mm × 65 mm
It is filled into a shape, heat-treated, and a material for evaluation is manufactured.
The molding of the evaluation material is described in detail in Embodiments A, B and C. Embodiment A → The prepared dry amorphous refractory is produced into a predetermined shape. Insert a thin steel sheet frame of almost the same shape with a 1 mm stainless steel sheet into the mold, fix it on a shaking table, fill it with vibration, place it in an electric furnace with the inner frame, and hold at 800 ° C for 3 hours. Hardened and manufactured. Embodiment B → To the prepared materials, sodium phosphate and water are added to the prepared materials, and colloidal silica and water are added to the prepared materials in a fixed amount. Mixing and kneading are performed as wet materials, and the thickness is 20 to 4 in a container.
Shake by about 0 mm, prepare the raw material while looking at the bubbles in the material, and shake and cast it while pouring it into a rough casting mold having a predetermined size of water absorption performance, and leave it for 16 hours or more After natural curing, demold, about 24 hours 20 ~
After pre-drying at 50 ° C., increase the temperature to 150 ° C. at a rate of 30 ° C./hour, hold for 10 hours, raise the temperature to 800 ° C. at 40 ° C./hour after drying, and hold for 3 hours. To produce. Embodiment C → The prepared material is mixed with sodium phosphate and water in a mixer and kneaded to prepare the material, and using a mold having a predetermined size, is compacted with an air hammer and manufactured. After natural curing for 16 hours, 150 at 30 ° C per hour
The temperature is raised to 0 ° C., drying is performed for 10 hours, the temperature is increased to 800 ° C. at 40 ° C. per hour, and then the product is held for 3 hours to produce.

【００２１】第二工程（スリーブ材の裏面（外周面）へ
のセラミックス釉薬の施釉工程） 成形体裏面（外周面）に施す釉薬の配合比率を表４に示
す。Second Step (Step of Glazing Ceramic Glaze on Back Side (Outer Peripheral Surface) of Sleeve Material) Table 4 shows the blending ratio of glaze applied on the back side (outer peripheral surface) of the molded product.

【００２２】[0022]

【表４】 [Table 4]

【００２３】表４に示すようにフリットに増粘性と粒子
の解膠性を高めるために有機物、デキストリンとリン酸
ソーダを添加し、水でもって泥漿状態とし、これをスリ
ーブの裏側の表面に塗る。１ｍｍ位の厚みでかけた後、
電気炉中にて１時間当たり１００℃で昇温し、最高７５
０℃とし、２時間保持して炉中冷却を行い、製出する。As shown in Table 4, an organic substance, dextrin and sodium phosphate are added to the frit to increase the viscosity and the deflocculating properties of the particles, and the frit is made into a slurry state with water, and this is applied to the back surface of the sleeve. . After applying with a thickness of about 1 mm,
Temperature rises at 100 ° C per hour in an electric furnace, up to 75
The temperature is kept at 0 ° C., and the temperature is kept for 2 hours to cool in a furnace to produce.

【００２４】以上のごとき製法により製出した各試験体
の品質特性値を同試験体を用いて、高周波誘導炉の内張
り用として張り分け、浸食、浸透試験を行なう。この張
り分け試験の条件は次の通りである。 １．溶解物 鋳物銑５０％、打ち抜き鋼材屑２５％、もどり材２０％、 亜鉛５％。 ２．溶解温度 １５４０℃ ３．溶解時間 ６０分 ４．保持時間 ３０分 ５．試験回数 ６．試料の大きさ 巾４０ｍｍ、厚み２５ｍｍ、高さ２５０ｍｍ ａ．試験材とは乾式不定形材一層で６０ｍｍ ｂ．試験材〜は定形試験材２５ｍｍ、乾式不定形材３５ｍｍで６０ｍ ｍとする。 で行い、その結果を表５に示す。The quality characteristic values of the test specimens produced by the above-described production method are separated from each other for the lining of a high-frequency induction furnace using the test specimens, and erosion and penetration tests are performed. The conditions of this split test are as follows. 1. Melted material Cast iron 50%, stamped steel scrap 25%, return material 20%, zinc 5%. 2. Melting temperature 1540 ° C 3. Dissolution time 60 minutes 4. Retention time 30 minutes 5. Number of tests 6. Sample size Width 40 mm, thickness 25 mm, height 250 mm a. The test material is a dry, irregularly shaped material of 60 mm b. The test material is a fixed test material of 25 mm and a dry irregularly shaped material of 35 mm and 60 mm. Table 5 shows the results.

【００２５】[0025]

【表５】 [Table 5]

【００２６】以上の結果に示されるように、一般に用い
られている乾式不定形耐火物との振動充填材は通気
率（ｃｍ・ｃｍ／ｃｍ²，ｇ／ｃｍ²，ｓｅｃ）がそれぞ
れ８１４、７１５と高く同材質でも湿式振動成形体と
では２７、１２と低く、成形方法の違いにより大きな
差を生じている。この通気率の差と組織内への浸透深さ
に相関特性を有していること、および裏面にセラミック
ス釉薬を施釉した本発明品Ｂ材は材と材は試料内に
とどまり、ほかの材質はガラス質の釉薬層の効果により
通気率（ｃｍ・ｃｍ／ｃｍ²，ｇ／ｃｍ²，ｓｅｃ）が
５．２〜７．３とすることができたことによりバック材
の部位までの浸透はなく、良好な結果を修めることがで
きた。この結果から考えれば通気率を１５以下にすれば
浸透の防止あるいは寿命に悪影響を及ぼすことはないこ
とを知り得た。この結果に基づき、本発明範囲内材の
内、実用実施例材として（２Ｂ）材、（４Ｂ）材、比較
例材として施釉していないＡ材として（２Ａ）材、と
（４Ａ）材として用いて実用実施例とする。As shown in the above results, the generally used dry-type refractory and vibratory filler have air permeability (cm · cm / cm ² , g / cm ² , sec) of 814 and 715, respectively. Even with the same material, it is as low as 27 and 12 with the wet vibration molded body, and a large difference occurs due to the difference in the molding method. The material B of the present invention, which has a correlation property between the difference in the air permeability and the penetration depth into the tissue, and the backside coated with a ceramic glaze, the material and the material remain in the sample, and the other materials are Due to the effect of the glassy glaze layer, the air permeability (cm · cm / cm ² , g / cm ² , sec) could be set to 5.2 to 7.3, so that there was no permeation to the part of the backing material , With good results. From these results, it was found that setting the air permeability to 15 or less would not prevent penetration or adversely affect the life. Based on this result, of the materials within the scope of the present invention, (2B) and (4B) as practical examples, (2A) as unglazed A and (4A) as comparative examples This is used as a working example.

【００２７】 実用試験の使用条件 １．炉の大きさ ５ＴＯＮ低周波誘導炉 ２．溶解材 鋳物銑２０％、亜鉛メッキ鋼板屑８０％、カーボン４％ ３．溶解精錬速度 １５４０℃±１０℃ ４．１日の溶解量 出湯時間（３ｔｏｎ＋３ｔｏｎ＋３ｔｏｎ＋５ｔｏｎ＝ 合計１４ｔｏｎ） 実用試験供試材の製造方法 実用試験用材は評価試験用材と同一の製造方法で行な
う。 第一次工程（一体成形体の製造） 実施例材材は実施態様Ｃの製法で材は実施態様Ｂの
製法により製造する。即ち実施例材は表３に示される
材の配合比率に調整された材料を所定の形状の成形用
型を用いてエアーハンマーにてつき固め成形した後、１
６時間の自然養生を行い、後、１時間当たり３０℃で１
５０℃まで昇温し、１０時間保持の乾燥を行なった後、
１時間当たり４０℃で８００℃まで１０時間保持製造す
る。実施例４材は実施態様Ｂの製法により製造する。即
ち実施例材４材は表３のに示される配合比率に調製さ
れた材料に所定のリン酸ソーダと水を添加し、混合、混
練を行なう。また材も同表３のに示された配合比率
に調製した材料に所定のコロイダルシリカと水を添加
し、混合、混練を行い、後に平型の原料用客器に漬け出
して振動台上で２０〜４０位の厚みにし、加振脱泡を行
い、調製された原料をそれぞれ定められた形状を製造す
る成形型を振動台上に設置して、この鋳込み成形用型を
振動させながら型中に順次投入した加振充填を行い、側
壁一体成形体を成形し、４８時間自然放置養生後、脱型
し、約４８時間を２０〜５０℃で予熱乾燥を行なった
後、１時間あたり３０℃の昇温速度で１５０℃まで高
め、１０時間保持して乾燥を行い、更に１時間当たり４
０℃の昇温速度で８００℃まで高め、１０時間保持して
成形体を製造する。 第二次工程（成形体の裏面側用面へのセラミックス釉
薬の施釉） 第一次工程で製造された成形体の裏面（外周面）に表４
に示す液状の釉薬をスプレー器により噴霧して約１．５
ｍｍの厚みで釉かけを行い、単独窯で焼成を行い、窒詰
して１時間あたり１００℃の昇温スケジュールで最高７
５０℃として３時間の保持を行い、セラミックス釉薬を
軟化およびまたは溶融状態とする。このようにして外周
面セラミックス釉薬を施した施薬成形体を製造して実用
供試材とする。本発明材の実施例材はこのように製造し
た一体成形体を、比較例材は表３、（２Ａ）材、（４
Ａ）材とし第一工程のみの工程で製造した一体成形体を
用いて、それぞれ炉底に所定の珪石質の乾式不定形耐火
物を定められた厚みに打設施工した上にほぼ炉の中央部
に設置し、炉本体と成形体との間隙に炉低施工材と同材
の乾式不定形耐火物を加振充填して固定した後、内底部
を側壁部と同材質の乾式不定形材で打設およびまたは加
振して充填施工を行なう。Use Conditions of Practical Test Furnace size 5TON low frequency induction furnace 2. 2. Melting material Cast iron 20%, Galvanized steel scrap 80%, Carbon 4% 3. Melting and refining rate 1540 ° C ± 10 ° C 4.1 amount of dissolving per day Dewatering time (3 ton + 3 ton + 3 ton + 5 ton = 14 ton in total) Manufacturing method of test material for practical test The material for practical test is performed by the same manufacturing method as the material for evaluation test. First Step (Manufacture of Integrated Molded Body) The materials of the examples are manufactured by the manufacturing method of the embodiment C, and the materials are manufactured by the manufacturing method of the embodiment B. That is, the example material was formed by hardening a material adjusted to the compounding ratio of the material shown in Table 3 with an air hammer using a molding die having a predetermined shape.
After 6 hours of natural curing, 1 hour at 30 ° C
After heating to 50 ° C. and drying for 10 hours,
Hold at 40 ° C per hour up to 800 ° C for 10 hours. The material of Example 4 is manufactured by the manufacturing method of Embodiment B. That is, the Example material 4 is prepared by adding predetermined sodium phosphate and water to the materials prepared in the mixing ratios shown in Table 3, and then mixing and kneading. In addition, the materials were prepared by adding predetermined colloidal silica and water to the materials prepared in the mixing ratio shown in Table 3 and mixing and kneading, and thereafter, immersed in a flat-type raw material container and placed on a shaking table. A thickness of about 20 to 40 is set, vibration degassing is performed, and a molding die for manufacturing the prepared raw materials in a predetermined shape is set on a shaking table. After shaking and filling, the molded product was molded into a side wall integrally, left to cure for 48 hours, then removed from the mold, and pre-heated and dried at 20 to 50 ° C. for approximately 48 hours. The temperature was raised to 150 ° C. at a heating rate of 10 ° C., and kept for 10 hours for drying.
The temperature is increased to 800 ° C. at a temperature rising rate of 0 ° C., and the temperature is maintained for 10 hours to produce a molded body. Second step (glazing of ceramic glaze on the back side of molded body) Table 4 shows the back surface (outer peripheral surface) of the molded body produced in the first step.
Spray the liquid glaze shown in
glazed with a thickness of mm, fired in a single kiln, squeezed, and heat-treated at a maximum temperature of 100 ° C per hour.
Hold at 50 ° C. for 3 hours to soften and / or melt the ceramic glaze. In this way, a molded drug product having the outer peripheral surface ceramic glaze applied thereto is manufactured and used as a practical test material. The example material of the present invention material is an integrally formed body manufactured as described above, and the comparative example material is Table 3, (2A) material, (4)
A) Using a single-piece molded body produced in only the first step as a material, a given siliceous dry amorphous refractory is cast into the furnace bottom to a predetermined thickness, and then substantially at the center of the furnace. After shaking and fixing a dry amorphous refractory of the same material as the furnace low work material into the gap between the furnace body and the molded body, fix the inner bottom to the dry amorphous material of the same material as the side wall Filling is performed by placing and / or vibrating.

【００２８】このようにして本発明実施例と比較例は共
にあらかじめ、成形された緻密な組織を有する成形体と
し、本発明の実施例材は外周面にセラミックス釉薬を施
工した外周面施釉成形体とした低通気性内張り材とし比
較例材は一体成形体としたのみで炉のほぼ中央部に配設
してその外周部を乾式不定形耐火物で充填し拘束した２
層構造とし、実用に供した。使用に際し共に低温での焼
結工程は全くなく、直ぐ溶解を行い、初溶解時のみ、溶
解後は通常の溶湯温度より１００℃上昇させ、２時間の
保持して、内張り材の安定を企った。このようにそれぞ
れの耐火物で施工され調製された誘導炉での実操業によ
る実施結果を表６に示す。As described above, both the examples of the present invention and the comparative examples were formed in advance into compacts having a dense structure, and the materials of the examples of the present invention were formed on the outer peripheral surface with a ceramic glaze applied thereto. The material of the comparative example, which was a low-permeability lining material, was only formed as an integral molded body, and was disposed almost at the center of the furnace, and its outer peripheral portion was filled with a dry type refractory and restrained.
A layer structure was used for practical use. There is no sintering process at low temperature at the time of use, and melting is performed immediately, and only at the time of initial melting, after melting, the temperature is raised by 100 ° C from the normal molten metal temperature and maintained for 2 hours to stabilize the lining material. Was. Table 6 shows the results of actual operation in the induction furnace prepared and constructed with each refractory.

【００２９】[0029]

【表６】 [Table 6]

【００３０】尚、実用実施例の炉の内張り材の構成は本
発明実施例も比較例も共に内装用スリーブ材が６０ｍｍ
厚み、バック材が４０ｍｍ厚みで合計１００ｍｍで構成
している。Incidentally, the construction of the lining material of the furnace of the practical embodiment is such that the sleeve material for the interior is 60 mm in both the embodiment of the present invention and the comparative example.
The thickness and the backing material are 40 mm thick and 100 mm in total.

【００３１】[0031]

【発明の効果】あらかじめ、一体成形体とし、組織の緻
密化を計るが、亜鉛等の低融点金属の溶融時には細孔中
に浸入し、深部まで到達すると湯もれセンサーの作動に
よる操業の中止や誘導コイル損傷が多発するがこの成形
材スリーブの裏面にセラミックス釉薬を施釉し、軟化お
よび溶融させて、低通気性とすることにより、浸透材に
よる異状現象を改善することができて、素材の特性を充
分生かしきるを可能にしたことにより、同材質の耐火物
を用いても本発明範囲内の（２Ｂ）材、（４Ｂ）材は同
材質比較例（２Ａ）材、（４Ａ）材に対して、特別な異
状も発生せず、それぞれ１５１％、１７６％の寿命を得
ることができ、操炉の省力化、安定且つ安全な操業がで
き、長寿命化が計れることにより、解体、操炉の３Ｋ作
業の軽減、計画的生産ができる等々、生産コスト削減に
も大きく寄与することができ、その効果は絶大なるもの
がある。According to the present invention, the structure is made in advance as an integrally formed body, and the density of the structure is measured. However, when a low melting point metal such as zinc is melted, it penetrates into the pores, and when it reaches a deep portion, the operation is stopped due to the operation of the leak sensor. However, damage to the induction coil occurs frequently, but glaze is applied to the back surface of the molded material sleeve to soften and melt it to make it less permeable. By making it possible to make full use of the characteristics, even if the refractory of the same material is used, the materials (2B) and (4B) within the scope of the present invention are the same material comparative examples (2A) and (4A). On the other hand, there is no special abnormality and the life of 151% and 176%, respectively, can be obtained, the labor saving of the furnace, stable and safe operation can be achieved, and the long life can be achieved. Reduction of furnace 3K work, planned Etc. which can produce, can also contribute significantly to reduce production costs, there is the effect with enthusiastic.

【手続補正書】[Procedure amendment]

【提出日】平成１０年１月２０日[Submission date] January 20, 1998

【手続補正１】[Procedure amendment 1]

【補正対象書類名】明細書[Document name to be amended] Statement

【補正対象項目名】０００８[Correction target item name] 0008

【補正方法】変更[Correction method] Change

【補正内容】[Correction contents]

【０００８】[0008]

【問題を解決するための手段】本発明者等はこのような
現状に鑑み、炉の操業が安定してでき、且つ内張り用耐
火物が充分に使いきることができ、長い寿命を有するこ
とができるようにと種々調査検討を行なった結果、亜鉛
等の低融点低沸点の金属が耐火材の組織内を透過する現
象を起こすのは耐火物の組織、密度と通気率に起因する
ものであろうとの結論を得て、先ず、現在の乾式不定形
耐火物を用いての加振充填された炉の内張り用材の充填
密度と通気率を調べた結果、充填密度は７５〜８２％で
通気率（ｃｍ・ｃｍ／ｃｍ^２，ｇ／ｃｍ^２，ｓｅｃ）が
８００前後と高く、低密度で高通気性であることが判明
した。この結果より、耐火物の密度と通気率、そし
て小型の高周波誘導炉において鋳物銑９５重量％と亜鉛
５重量％を溶解して溶湯温度を１６００℃とし、６０分
間保持した後出湯する試験を繰り返し行い、調べた亜
鉛の浸透度とこの三者の関係につき種々研究と実用試験
を重ねた結果通気率（ｃｍ・ｃｍ／ｃｍ^２，ｇ／ｃ
ｍ^２，ｓｅｃ）が４０以下ならばほぼ亜鉛メッキ鋼板等
の亜鉛の混入材を鋳鉄の素材として使用して溶解された
溶湯の温度が１６００℃でも亜鉛等の低沸点低融点の金
属が浸入してきても、誘導炉の操業上不具合の発生もな
く、操炉することが可能であること、また同じに実炉の
炉本体内壁の温度は炉内張り材が正常に溶損し、張り替
えを必要とする時期でも最高７００℃までであることを
知見し得た。SUMMARY OF THE INVENTION In view of the above situation, the present inventor has found that the furnace can be operated stably, the refractory for lining can be used up sufficiently, and a long service life can be attained. As a result of various investigations and studies to make it possible, it is found that the phenomenon that a metal with a low melting point and a low boiling point, such as zinc, penetrates the structure of the refractory material is caused by the structure, density and permeability of the refractory. After obtaining the conclusion of wax, firstly, the packing density and the permeability of the material for the lining of the furnace filled with vibration using the current dry type refractory were examined. (Cm · cm / cm ² , g / cm ² , sec) was as high as about 800, indicating low density and high air permeability. From these results, the refractory density and air permeability, and a test in which 95% by weight of cast iron and 5% by weight of zinc were melted in a small high-frequency induction furnace to a temperature of 1600 ° C., held for 60 minutes, and then poured out were repeated. As a result of various studies and practical tests on the relationship between zinc permeability and the three factors, the air permeability (cm · cm / cm ² , g / c)
If m ² , sec) is 40 or less, a low-boiling-point, low-melting-point metal such as zinc may enter even when the temperature of the molten metal is 1600 ° C. using a zinc-mixed material such as galvanized steel sheet as a material for cast iron. However, it is possible to operate the induction furnace without any trouble in the operation of the induction furnace .
It was found that the temperature of the inner wall of the furnace main body was up to 700 ° C. even at the time when the furnace lining material was normally melted and needed to be replaced.

【手続補正２】[Procedure amendment 2]

【補正対象書類名】明細書[Document name to be amended] Statement

【補正対象項目名】００１０[Correction target item name] 0010

【補正方法】変更[Correction method] Change

【補正内容】[Correction contents]

【００１０】現在は一般の施工体は炉本体内に乾式不定
形耐火物とフォーマーを用いて直接加振充填施工を行な
うので内張り施工体の密度が低く、不均一性の生じやす
い内張り材であるため、大きな不具合を引き起こしてい
るが、このように製造された一体成形体も外表面に施釉
したスリーブ材を炉底最下部層に乾式不定形耐火物をつ
きかためた後、炉本体のほぼ中央部に設置し、その外周
部を成形体とほぼ同等以上の熱膨張率を有する乾式不定
形耐火物で高密度に充填する内張り材二層構造とするこ
とにより、従来の不具合を改善するに最も好ましい方法
であることを見い出した。[0010] At present, a general construction body is a lining material in which the density of the lining construction body is low and non-uniformity is liable to occur due to the fact that the vibrating and filling construction is directly performed by using a dry amorphous refractory and a former in the furnace body. Although this has caused a major problem, the integrally molded body manufactured in this way also used a non-refractory dry-type refractory on the lowermost layer of the furnace bottom after glazing the outer surface of the sleeve material. was placed in the center, by a lining material two-layer structure in which densely packed in dry monolithic refractory having substantially the same or higher coefficient of thermal expansion the outer peripheral portion and the molded body, improving the conventional problem Was found to be the most preferred method.

【手続補正３】[Procedure amendment 3]

【補正対象書類名】明細書[Document name to be amended] Statement

【補正対象項目名】００２５[Correction target item name] 0025

【補正方法】変更[Correction method] Change

【補正内容】[Correction contents]

【００２５】以上のごとき製法により製出した各試験体
の品質特性値を同試験体を用いて、高周波誘導炉の内張
り用として張り分け、浸食、浸透試験を行なう。この張
り分け試験の条件は次の通りである。 １．溶解物 鋳物銑５０％、打ち抜き鋼材層２５％、もどり材２０％、 亜鉛５％。 ２．溶解温度 １５４０℃ ３．溶解時間 ６０分 ４．保持時間 ３０分 ５．試験回数 １００ ６．試料の大きさ 巾４０ｍｍ、厚み２５ｍｍ、高さ２５０ｍｍ ａ．試験材とは乾式不定形材一層で６０ｍｍ ｂ．試験材〜は定形試験材２５ｍｍ、乾式不定形材３５ｍｍで６０ｍ ｍとする。 で行い、その結果を表５に示す。The quality characteristic values of the respective specimens produced by the above-mentioned production method are separated from each other for the lining of a high-frequency induction furnace using the specimens, and erosion and penetration tests are performed. The conditions of this split test are as follows. 1. Melted material Cast iron 50%, punched steel layer 25%, return material 20%, zinc 5%. 2. Melting temperature 1540 ° C 3. Dissolution time 60 minutes 4. Retention time 30 minutes 5. 5. Number of tests 100 Sample size Width 40 mm, thickness 25 mm, height 250 mm a. The test material is a dry, irregularly shaped material of 60 mm b. The test material is a fixed test material of 25 mm and a dry irregularly shaped material of 35 mm and 60 mm. Table 5 shows the results.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】 金属を溶解およびまたは精錬する電気式
誘導炉の内張り用耐火物において最内側層（稼働層）を
少なくとも側壁一体成形耐火物とし、この成形物の外周
面に耐熱温度７００℃以上のセラミックス釉薬を施釉し
て、ガラス質層を形成し、一体成形物の通気率（ｃｍ・
ｃｍ／ｃｍ²，ｇ／ｃｍ²，ｓｅｃ）が１５以下として、
炉内装材となし、その外周部を熱間線膨張率が内装した
定形耐火物と同等または同等以上の乾式不定形耐火物で
築造されたことを特徴とする施釉定形材を内装した誘導
炉。1. A refractory for lining an electric induction furnace for melting and / or refining a metal, wherein an innermost layer (operating layer) is formed as a refractory integrally molded with at least a side wall, and an outer peripheral surface of the molded product has a heat resistant temperature of 700 ° C. or higher. Glazed with a ceramic glaze to form a vitreous layer, and the air permeability (cm
cm / cm ² , g / cm ² , sec) is 15 or less,
An induction furnace equipped with a glazed shaped material, characterized by being made of a furnace interior material and constructed of a dry amorphous refractory material whose outer peripheral portion is equal to or more than a fixed refractory material having a coefficient of linear thermal expansion therein.