JPH0333676B2 - - Google Patents
Info
- Publication number
- JPH0333676B2 JPH0333676B2 JP22626383A JP22626383A JPH0333676B2 JP H0333676 B2 JPH0333676 B2 JP H0333676B2 JP 22626383 A JP22626383 A JP 22626383A JP 22626383 A JP22626383 A JP 22626383A JP H0333676 B2 JPH0333676 B2 JP H0333676B2
- Authority
- JP
- Japan
- Prior art keywords
- silicon
- graphite
- refractory
- coating
- powder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 14
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 229910002804 graphite Inorganic materials 0.000 claims description 11
- 239000010439 graphite Substances 0.000 claims description 11
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 10
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 10
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 9
- 238000005245 sintering Methods 0.000 claims description 9
- 239000000843 powder Substances 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 7
- 229910052751 metal Inorganic materials 0.000 claims description 7
- 239000011819 refractory material Substances 0.000 claims description 7
- 239000011863 silicon-based powder Substances 0.000 claims description 7
- 239000002002 slurry Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 3
- 239000011248 coating agent Substances 0.000 description 17
- 238000000576 coating method Methods 0.000 description 17
- 238000005260 corrosion Methods 0.000 description 9
- 230000007797 corrosion Effects 0.000 description 9
- 229910052710 silicon Inorganic materials 0.000 description 8
- 239000010703 silicon Substances 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 4
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 4
- 239000004327 boric acid Substances 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229910010271 silicon carbide Inorganic materials 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 2
- -1 borax Chemical compound 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 238000005121 nitriding Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000011856 silicon-based particle Substances 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910001369 Brass Inorganic materials 0.000 description 1
- UMVBXBACMIOFDO-UHFFFAOYSA-N [N].[Si] Chemical compound [N].[Si] UMVBXBACMIOFDO-UHFFFAOYSA-N 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910021538 borax Inorganic materials 0.000 description 1
- 150000001642 boronic acid derivatives Chemical class 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 239000011449 brick Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 239000004328 sodium tetraborate Substances 0.000 description 1
- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
Landscapes
- Ceramic Products (AREA)
Description
【発明の詳細な説明】
この発明は耐酸化性、耐食性にすぐれた窒化珪
素被覆黒鉛質耐火物の製造方法に関する。
黒鉛−炭化珪素系もしくは黒鉛−アルミナ系な
どの黒鉛質耐火物の耐酸化性、耐食性を向上する
ため、耐火物表面に被覆膜を形成させることが従
来から行われている。被覆膜は耐火物表面に充分
な強度で密着すること、酸素との接触において充
分な気密性を有すること、膜自身が耐食性、耐火
性を有していることなどが必要であるが、従来か
ら行われている被覆膜は、密着性、気密性は充分
であつても耐食性が充分でないなど、一長一短が
あつて前記の諸性質を充分に満足させるものは未
だ見当らない。
この発明は、以上の実情に鑑みなされたもの
で、重量で金属珪素粉末75〜99％、アルミナ粉末
１〜25％に焼結助剤を加えた泥漿を黒鉛質耐火物
の表面に塗布したのち、窒素雰囲気中において高
温で加熱することを特徴とする窒素珪素被覆黒鉛
質耐火物の製造方法を要旨とするものである。
次にその詳細について説明すると、金属珪素は
高温の窒素雰囲気中で窒素と反応して窒化珪素を
生成する。窒化珪素は熱膨脹率が小さいので、耐
火物表面が加熱され被覆膜がいち早く急熱されて
も、また耐火物自体が高温になつたときでも両者
の膨脹差が小さいことから、それに伴う剥離は起
こさない。金属珪素は耐火物の生地界面では耐火
物中の炭素と反応して炭化珪素となるから、被覆
膜は耐火物と極めて強固に密着する。金属珪素粉
末は、粒度74μｍ以下のものを使用する。74μｍ
以上では窒化珪素化反応に長時間かかるので好ま
しくない。金属珪素粉末は前記粒度のものを重量
で75〜95％使用する。75％以下では窒化珪素被覆
膜の性質が充分に出ないので好ましくなく、また
99％以上では耐食性が悪くなるので好ましくな
い。
アルミナ粉末と金属珪素粉末を併用すると金属
珪素の反応焼結とアルミナの自己焼結との相乗効
果により低気孔で強固な窒化珪素被覆が形成さ
れ、溶融金属やスラグに対する耐食性が良好とな
るので、被覆した黒鉛質耐火物の耐食性が著しく
向上する。アルミナ粉末は粒度74μｍ以下のもの
を使用する。74μｍ以上では焼結性が悪くなるの
で気密で強固な被覆を形成せず、好ましくない。
アルミナ粉末は前記粒度のものを１〜25％、好ま
しくは５〜10％使用する。１％以下では耐食性が
悪くなつて好ましくなく、また25％以上では被覆
膜の熱膨脹率が大きくなり、被覆膜が剥離し易く
なるので好ましくない。
焼結助剤としては硼酸、無水硼酸、ホウ砂など
の硼酸塩等を使用する。これらの焼結助剤の水溶
液を前記粉末に混合すると、その泥漿物が耐火物
素地によく接着し、また乾燥強度が得られ、高温
では焼結助剤となる。焼結助剤はその量が少ない
と接着性等の効果がなく、過量では硼酸系ガラス
として残留し、耐火度を低下させる。重量濃度で
約10％水溶液が適当である。
前記金属珪素粉末、アルミナ粉末に硼酸水溶液
等を加えた泥漿を黒鉛質耐火物表面に被覆させた
のち、窒素ガスを流入させた炉内で950℃まで100
℃／hrで昇温し２時間保持する。この段階で金属
珪素の粒子表面を窒化させる。２時間保持しない
でそのまま昇温を続けると金属珪素は温度上昇と
共に表面が軟化し、窒化より先に珪素粒子間で焼
結するに至るため、窒素の拡散が著しく遅れ、均
一な膜厚の窒化珪素が生成しない。次に1350℃ま
で50℃／hrで昇温し、12時間保持する。このよう
な昇温パターンをとると金属珪素の約95％が窒化
珪素化し、膜厚が均一で、気密かつ強固な窒化珪
素被覆が形成される。
このようにして出来た耐火物は、耐酸化性およ
び耐食性にすぐれているから、この発明の方法は
黒鉛坩堝、浸漬ノズル、ロングノズル、同フラツ
クスライン部、キユポラ用れんがなどの溶融金
属、溶融スラグなどに対する侵食の防止に有効で
ある。
次に実施例について説明する。
93％の純度を有する74μｍ以下の金属珪素粉末
95重量％と、98％の純度を有する74μｍ以下のア
ルミナ粉末５重量％に重量濃度10％の硼酸水溶液
を加えた泥漿の黒鉛−炭化珪素系黒鉛坩堝表面に
膜厚1.5mmの被覆をした。被覆後充分に乾燥した
のち、内容積200の加熱炉に入れ、950℃まで
100℃／hrで昇温し２時間保持した。その後1350
まで50℃／hrで昇温し、12時間保持した。全加熱
中４／minの窒素ガスを炉内に流した。
冷却後、被覆物をｘ線回折にかけたところ、第
１図のようにSi3N4、Si2ON2、Si、Al2O3などが
みられるが、金属珪素の約95％が窒化珪素に変化
していることが判明した。
次に、上記条件で300番黒鉛坩堝（黄銅300Kgを
溶解できる容量をもつもの）の表面に被覆を形成
させ実炉試験をしたところ、第１表の結果を得る
ことができ、従来品に比較して良好な成績を収め
ることができた。
【表】DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a silicon nitride-coated graphite refractory having excellent oxidation resistance and corrosion resistance. BACKGROUND ART In order to improve the oxidation resistance and corrosion resistance of graphite refractories such as graphite-silicon carbide or graphite-alumina refractories, it has been conventionally practiced to form a coating film on the surface of the refractories. The coating film must adhere to the surface of the refractory with sufficient strength, have sufficient airtightness in contact with oxygen, and the film itself must have corrosion resistance and fire resistance. The coating films made from the above have advantages and disadvantages, such as insufficient corrosion resistance even though they have sufficient adhesion and airtightness, and so far no coating film has been found that fully satisfies the above-mentioned properties. This invention was made in view of the above circumstances, and after applying a slurry made by adding a sintering aid to 75-99% metal silicon powder and 1-25% alumina powder by weight on the surface of graphite refractories. The gist of this invention is a method for producing a nitrogen-silicon-coated graphite refractory, which is characterized by heating at high temperature in a nitrogen atmosphere. Next, the details will be explained. Metallic silicon reacts with nitrogen in a high temperature nitrogen atmosphere to produce silicon nitride. Silicon nitride has a small coefficient of thermal expansion, so even if the surface of the refractory is heated and the coating film is quickly and rapidly heated, or even when the refractory itself reaches a high temperature, the difference in expansion between the two is small, so the resulting peeling will not occur. I won't wake you up. Metallic silicon reacts with carbon in the refractory to form silicon carbide at the material interface of the refractory, so the coating film adheres extremely firmly to the refractory. The metal silicon powder used has a particle size of 74 μm or less. 74μm
The above is not preferable because the silicon nitride reaction takes a long time. Metallic silicon powder having the above particle size is used in an amount of 75 to 95% by weight. If it is less than 75%, it is not preferable because the properties of the silicon nitride coating film cannot be fully exhibited.
If it exceeds 99%, corrosion resistance deteriorates, which is not preferable. When alumina powder and metallic silicon powder are used together, a strong silicon nitride coating with low porosity is formed due to the synergistic effect of reactive sintering of metallic silicon and self-sintering of alumina, and it has good corrosion resistance against molten metal and slag. Corrosion resistance of coated graphite refractories is significantly improved. Use alumina powder with a particle size of 74 μm or less. If the thickness is 74 μm or more, the sinterability deteriorates and an airtight and strong coating cannot be formed, which is not preferable.
The alumina powder having the above particle size is used in an amount of 1 to 25%, preferably 5 to 10%. If it is less than 1%, the corrosion resistance deteriorates, which is undesirable, and if it exceeds 25%, the coefficient of thermal expansion of the coating film increases, making it easy to peel off the coating film, which is not preferred. As the sintering aid, boric acid, boric anhydride, borates such as borax, etc. are used. When an aqueous solution of these sintering aids is mixed with the powder, the slurry adheres well to the refractory substrate, provides dry strength, and serves as a sintering aid at high temperatures. If the amount of the sintering aid is small, there will be no effect on adhesive properties, and if the amount is excessive, it will remain as boric acid glass, reducing the fire resistance. An aqueous solution having a concentration of about 10% by weight is suitable. After coating the surface of the graphite refractories with a slurry made by adding boric acid aqueous solution to the metal silicon powder and alumina powder, the mixture was heated to 950°C in a furnace with nitrogen gas introduced.
Raise the temperature at ℃/hr and hold for 2 hours. At this stage, the surface of the metallic silicon particles is nitrided. If you continue to raise the temperature without holding it for 2 hours, the surface of metallic silicon will soften as the temperature rises, and sintering will occur between silicon particles before nitriding, which will significantly delay the diffusion of nitrogen and result in a uniform nitriding film thickness. Silicon is not produced. Next, the temperature was raised to 1350°C at a rate of 50°C/hr and held for 12 hours. When such a temperature increase pattern is used, approximately 95% of the metal silicon is converted to silicon nitride, and a uniform, airtight, and strong silicon nitride coating is formed. The refractory made in this way has excellent oxidation resistance and corrosion resistance, so the method of this invention can be applied to graphite crucibles, immersion nozzles, long nozzles, flux line parts, molten metals such as cupora bricks, etc. Effective in preventing erosion of slag, etc. Next, an example will be described. Metallic silicon powder below 74μm with 93% purity
The surface of a graphite-silicon carbide graphite crucible was coated with a slurry of 5% by weight of alumina powder of 74 μm or less with a purity of 95% by weight and a purity of 98% and an aqueous solution of boric acid with a concentration of 10% by weight to a thickness of 1.5 mm. After coating and drying thoroughly, put it in a heating furnace with an internal volume of 200 and heat up to 950℃.
The temperature was raised at 100°C/hr and held for 2 hours. then 1350
The temperature was raised to 50°C/hr and held for 12 hours. Nitrogen gas was flowed into the furnace at a rate of 4/min during the entire heating process. After cooling, the coating was subjected to X-ray diffraction, and as shown in Figure 1, Si 3 N 4 , Si 2 ON 2 , Si, Al 2 O 3 , etc. were observed, but about 95% of the metallic silicon was silicon nitride. It turned out that there was a change in. Next, under the above conditions, we formed a coating on the surface of a No. 300 graphite crucible (which has a capacity to melt 300 kg of brass) and conducted an actual furnace test, and the results shown in Table 1 were obtained and compared with the conventional product. I was able to achieve good results. 【table】
第１図は被覆物のｘ線回折図である。 FIG. 1 is an x-ray diffraction diagram of the coating.
Claims (1)
１〜25％に焼結助剤を加えた泥漿を黒鉛質耐火物
の表面に塗布したのち、窒素雰囲気中において高
温で加熱することを特徴とする窒化珪素被覆黒鉛
質耐火物の製造方法。1. A slurry made by adding a sintering aid to 75-99% metal silicon powder and 1-25% alumina powder by weight is applied to the surface of graphite refractories, and then heated at high temperature in a nitrogen atmosphere. A method for producing a silicon nitride-coated graphite refractory.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22626383A JPS60118685A (en) | 1983-11-30 | 1983-11-30 | Manufacture of silicon nitride-coated graphitic refractories |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22626383A JPS60118685A (en) | 1983-11-30 | 1983-11-30 | Manufacture of silicon nitride-coated graphitic refractories |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60118685A JPS60118685A (en) | 1985-06-26 |
| JPH0333676B2 true JPH0333676B2 (en) | 1991-05-17 |
Family
ID=16842457
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP22626383A Granted JPS60118685A (en) | 1983-11-30 | 1983-11-30 | Manufacture of silicon nitride-coated graphitic refractories |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60118685A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6148492A (en) * | 1984-08-17 | 1986-03-10 | 株式会社 ほくさん | Method of coating mold material for high temperature |
| US5909232A (en) * | 1992-02-27 | 1999-06-01 | Fuji Photo Film Co., Ltd. | Thermal recording system for preheating a thermosensitive recording medium and method therefor |
| CN114560707A (en) * | 2022-03-24 | 2022-05-31 | 湖南国发控股有限公司 | Formula, preparation and application process of silicon nitride impregnant for kiln furniture production |
-
1983
- 1983-11-30 JP JP22626383A patent/JPS60118685A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60118685A (en) | 1985-06-26 |
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