JP6735064B2 - Hot repair material for DC electric furnace - Google Patents
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- JP6735064B2 JP6735064B2 JP2015030428A JP2015030428A JP6735064B2 JP 6735064 B2 JP6735064 B2 JP 6735064B2 JP 2015030428 A JP2015030428 A JP 2015030428A JP 2015030428 A JP2015030428 A JP 2015030428A JP 6735064 B2 JP6735064 B2 JP 6735064B2
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- 239000000463 material Substances 0.000 title claims description 84
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 52
- 239000011449 brick Substances 0.000 claims description 42
- 229910052799 carbon Inorganic materials 0.000 claims description 40
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 36
- 239000000843 powder Substances 0.000 claims description 34
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 30
- 239000011398 Portland cement Substances 0.000 claims description 28
- 239000000395 magnesium oxide Substances 0.000 claims description 26
- 239000011822 basic refractory Substances 0.000 claims description 11
- 229910052742 iron Inorganic materials 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 229910045601 alloy Inorganic materials 0.000 claims description 4
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- 238000010276 construction Methods 0.000 description 15
- 229910000640 Fe alloy Inorganic materials 0.000 description 12
- 238000000034 method Methods 0.000 description 12
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 239000005011 phenolic resin Substances 0.000 description 9
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- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000000292 calcium oxide Substances 0.000 description 8
- 235000012255 calcium oxide Nutrition 0.000 description 8
- 239000010459 dolomite Substances 0.000 description 8
- 229910000514 dolomite Inorganic materials 0.000 description 8
- 239000002893 slag Substances 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 239000011230 binding agent Substances 0.000 description 7
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- 229920003986 novolac Polymers 0.000 description 5
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- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
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- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 239000004677 Nylon Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 238000013329 compounding Methods 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
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- 239000002994 raw material Substances 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 150000003505 terpenes Chemical class 0.000 description 2
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- 229910018134 Al-Mg Inorganic materials 0.000 description 1
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 229910018467 Al—Mg Inorganic materials 0.000 description 1
- 229910000915 Free machining steel Inorganic materials 0.000 description 1
- 235000019484 Rapeseed oil Nutrition 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000011083 cement mortar Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011280 coal tar Substances 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- 239000004567 concrete Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
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- 239000012535 impurity Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000003350 kerosene Substances 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 229940057995 liquid paraffin Drugs 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- -1 or the like Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
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- 238000000926 separation method Methods 0.000 description 1
- 238000004901 spalling Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000011271 tar pitch Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Landscapes
- Furnace Housings, Linings, Walls, And Ceilings (AREA)
- Ceramic Products (AREA)
Description
本発明は、直流電気炉電極部とその周辺部を補修するための直流電気炉用熱間補修材に関し、更に詳細には、電気伝導性を必要とされる部位である直流電気炉の炉底電極とその周辺部を補修するための直流電気炉用導電性熱間補修材に関するものである。 The present invention relates to a hot repair material for a direct current electric furnace for repairing a direct current electric furnace electrode part and its peripheral part, and more specifically, a bottom of a direct current electric furnace which is a portion where electrical conductivity is required. The present invention relates to a conductive hot repair material for a DC electric furnace for repairing an electrode and its peripheral portion.
直流電気炉は、炉底に設置された炉底電極と、炉蓋に設置された可動電極との間に直流電流を流し、ジュール熱を発生させ、そのジュール熱で鉄・スクラップを溶解して鋼を精練する炉である。炉底電極には３つのタイプがある。第１のタイプは、数本の径の大きい金属製の電極を設置し、その電極を通じて電流を流すと共に、電極の周囲を耐火物を施工するものである；第２のタイプは、カーボンを含有し、通電性を有する煉瓦を電極とするものである；第３のタイプは、多数の金属製のフィンあるいは丸棒を炉底煉瓦に埋め込む方法である。いずれの場合にも、炉底電極煉瓦は通電中に特に高温にさらされ、かつ溶融した鋼に接触する。また、その溶鋼を排出する際には、発生したスラグ成分とも接触して化学的反応が生じる。従って、炉底電極部付近の煉瓦は著しく損傷を受けることになる。 In a DC electric furnace, a DC current is passed between the furnace bottom electrode installed on the furnace bottom and the movable electrode installed on the furnace lid to generate Joule heat, and the Joule heat melts iron and scrap. It is a furnace for refining steel. There are three types of bottom electrodes. The first type is one in which several large-diameter metal electrodes are installed, a current is passed through the electrodes, and a refractory is installed around the electrodes; the second type contains carbon. However, a brick having electrical conductivity is used as an electrode; the third type is a method of embedding a large number of metal fins or round bars in a hearth brick. In each case, the bottom electrode brick is exposed to particularly high temperatures during energization and comes into contact with the molten steel. Further, when the molten steel is discharged, it also comes into contact with the generated slag component to cause a chemical reaction. Therefore, the brick near the bottom electrode of the furnace is significantly damaged.
直流電気炉の実炉の操業では、損傷した部位を吹付材や焼付材などの補修材により補修しながら操業が継続される。この際、第１のタイプの電気炉では、補修材に通電性が要求されないが、第２と第３のタイプの電気炉の場合には、補修材自体の電気伝導性が低いと炉底電極への通電が妨げられることになるため、このような電気炉を補修するための補修材は電気伝導性を有することが必須要件となる。 In the operation of an actual furnace of a DC electric furnace, the damaged part is repaired with repair materials such as sprayed materials and baked materials, and the operation is continued. At this time, in the first type electric furnace, the repair material is not required to have conductivity, but in the second and third type electric furnaces, if the repair material itself has low electric conductivity, the bottom electrode Since the power supply to the electric furnace is hindered, it is essential that the repair material for repairing such an electric furnace has electrical conductivity.
電気炉用補修材による補修は、通常以下のように行われる。すなわち、使用中に損傷が進行した部位を補修するに当たり、まず、溶鋼を排出して補修が必要な部位を露出させる。その露出部に常温の吹付材や焼付材を施工する。その後、炉熱で一定時間加熱したのち、通電によるスクラップ溶解作業を再開する。また、溶解熱を受けて、焼結が進む。このため、吹付材や焼付材の早急な強度発現が十分でない場合には、損傷が大きくなるため、早急な強度発現が求められる。 The repair with the repair material for the electric furnace is usually performed as follows. That is, when repairing a site where damage has progressed during use, first, molten steel is discharged to expose the site requiring repair. A spraying material or a baking material at room temperature is applied to the exposed part. After that, after heating with furnace heat for a certain period of time, the scrap melting work by energization is restarted. Further, the heat of dissolution causes the sintering to proceed. For this reason, if the rapid strength development of the sprayed material or the baked material is not sufficient, the damage becomes large, and thus the rapid strength development is required.
これまでの補修技術として、例えば、特許文献１には、上記第１のタイプの直流電気炉の補修方法として、炉体を例えばまず出鋼側に傾動して炉底電極のほぼ半数をホットヒールで覆い、残りの半数の電極を露出させた状態で不定形耐火物を吹付施工する方法が開示されており、特許文献１によれば、出鋼側の電極には不定形耐火物がコーティングされず、炉体を正立状態に戻した後にスクラップの装入を行って通電するとホットヒールによる通電が開始され、直立電気炉として直ちに機能し、また、非補修部の炉底耐火物は、次のチャージあるいは数チャージ後の非補修部耐火物に補修を要する段階で炉体を前回とは逆方向の排滓側に傾動して同様に補修を行った後、ホットヒールによる通電を再開することができるとしている。特許文献１に開示された直流電気炉の補修方法は、ドロマイト系吹付材のような電気伝導性を有しない不定形耐火物を使用することを前提としたものである。 As a conventional repairing technique, for example, in Patent Document 1, as a repairing method for the first type DC electric furnace, the furnace body is first tilted toward the tapped side to hot-heal almost half of the furnace bottom electrodes. Is disclosed, and a method of spraying an amorphous refractory in a state where the remaining half of the electrodes are exposed is disclosed, and according to Patent Document 1, the electrode on the tapped side is coated with the irregular refractory. However, when the furnace body is returned to the upright state and the scrap is charged and the power is turned on, the hot heel starts to turn on the power, and it immediately functions as an upright electric furnace. After repairing or after several charges, tilt the furnace body to the slag side in the direction opposite to the previous one at the stage where the non-repaired part refractory needs to be repaired and perform the same repair, and then restart the energization by hot heel. It is supposed to be possible. The method of repairing a DC electric furnace disclosed in Patent Document 1 is based on the assumption that an amorphous refractory material having no electrical conductivity, such as a dolomite spray material, is used.
また、特許文献２には、直流電気炉電極部等の高温で且つ電気伝導性を必要とされる部位に用いられる、体積抵抗率が１．０×１０−２Ω・ｃｍ以下である導電性材料２０〜７０重量％と、耐火性材料８０〜３０重量％と、コールタールピッチ等の石炭系、石油系タール・ピッチやフェノール樹脂等の樹脂のような加熱により炭素結合を形成する結合材とからなる導電性不定形耐火物が開示されている。
Further, in Patent Document 2, a conductive material having a volume resistivity of 1.0×10 −2 Ω·cm or less, which is used in a portion such as a DC electric furnace electrode portion where high temperature and electrical conductivity are required. 20 to 70% by weight of material, 80 to 30% by weight of refractory material, and a binder such as coal tar such as coal tar pitch, petroleum tar pitch, or a resin such as phenol resin that forms a carbon bond by heating. An electrically conductive amorphous refractory material is disclosed.
更に、特許文献３には、耐火物原料１００重量％のうち、０．１２５ｍｍ以下の微粉部を３０〜５０重量％を含み、ノボラック型フェノール樹脂を有機溶剤に溶解してなるノボラック型フェノール樹脂溶液を外掛けでフェノール樹脂成分が１０〜２０重量％となる範囲で混練することを特徴とする、高温下における自己流動性をもつ不定形耐火物が開示されている。特許文献３に開示された不定形耐火物は、コールタール・ピッチを用いず、ノボラック型フェノール樹脂とテルペン類のような有機溶剤を併用することにより、発煙を抑制し、硬化時間を短縮することができるものである。特許文献３には、不定形耐火物が導電性を有するか、否かについての明確な記述はないが、ノボラック型フェノール樹脂とテルペン類のような有機溶剤の熱分解によってカーボンボンドが形成され、ある程度の導電性が確保できるものと推定される。特許文献３によれば、発煙を抑制することができ、かつ硬化時間は短縮可能であるとしている。 Further, in Patent Document 3, a novolac type phenol resin solution obtained by dissolving a novolac type phenol resin in an organic solvent, containing 30 to 50% by weight of a fine powder portion of 0.125 mm or less, out of 100% by weight of a refractory raw material. Is disclosed and an amorphous refractory material having self-fluidity at high temperature is disclosed, which is characterized by kneading in the range of 10 to 20% by weight of a phenol resin component. The amorphous refractory disclosed in Patent Document 3 suppresses smoke generation and shortens the curing time by using a novolac type phenol resin and an organic solvent such as a terpene together without using coal tar pitch. Can be done. In Patent Document 3, there is no clear description as to whether or not the amorphous refractory has conductivity, but a carbon bond is formed by thermal decomposition of a novolac type phenol resin and an organic solvent such as a terpene, It is estimated that a certain degree of conductivity can be secured. According to Patent Document 3, smoke generation can be suppressed and the curing time can be shortened.
また、特許文献４には、特許文献２、３と同様に熱間で炭化結合する有機結合剤を用いた焼付補修材として、耐火性粉体と、有機結合剤とを含み、熱焼失性バッグに収容されて補修対象炉に投入される焼付補修材であって、前記耐火性粉体１００質量％中に、粒径が１ｍｍ以上の耐火れんが破砕物を最大で５０質量％、前記耐火れんが破砕物との嵩比重差が０．５以下で粒径１ｍｍ以上の球状化処理された球状化粒子を９質量％以上、それぞれ含む焼付補修材が開示されている。特許文献４によれば、この焼付補修材は、良好な展開性及び焼結性を有するとしている。 In addition, in Patent Document 4, as in Patent Documents 2 and 3, as a baking repair material using an organic binder that carbonizes hot, a refractory powder and an organic binder are included, and a heat-burnable bag is included. Which is a bake repair material that is housed in a furnace and put into a furnace to be repaired, in which 100% by mass of the refractory powder has a maximum of 50% by mass of crushed refractory bricks having a particle size of 1 mm or more, and the crushed refractory bricks. There is disclosed a baking repair material containing 9% by mass or more of spheroidized particles having a bulk specific gravity difference of 0.5 or less and a particle diameter of 1 mm or more. According to Patent Document 4, this seizure repair material has good spreadability and sinterability.
しかしながら、特許文献１に開示されている補修方法は、上記第１のタイプの直流電気炉の補修方法であり、導電性を有しない不定形耐火物を用いて補修すると、補修部位以外の部分に電流が集中し、局部的な損傷が発生しやすいという問題点があった。
また、特許文献２に開示されている導電性不定形耐火物は、不定形耐火物自体が電気伝導性を有しており、耐食性・施工性共に良好であるが、施工時にタール・ピッチや樹脂の熱分解に伴い、有色で異臭の強い発煙が激しく生じるため使用現場の作業環境が著しく悪化するという問題点があった。また、タール・ピッチの発煙には、ＣＯ、ＮＯｘ、ＳＯｘ等の有害物質が含まれるため、近距離での作業は危険でもある。さらに、タール・ピッチ等を含む不定形耐火物は炭素結合を生成して硬化・接着するが、加熱による熱分解の時間が十分に取れない場合では接着強度は低くなり施工体が剥離するという問題点があった。
更に、しかしながら、特許文献３においても、コールタール・ピッチを使用した場合と比較して発煙は少なくなるものの、多少の有色の発煙が発生し、また、ノボラック型フェノール樹脂の熱分解に伴う耐え難い異臭が発生するため、作業環境悪化の問題点を解決するには至っていない。
また、特許文献４の焼付補修材では、耐火れんが破砕物の一例としてマグネシア−カーボン質れんが（以下、「マグ・カーボンれんが」）破砕物が挙げられており、炭素を含有する耐火れんがを破砕した破砕物を耐火材料として活用することで、耐火れんがが、未使用・使用後のどちらの状態であっても、耐火物の炭素含有量が増加して溶鋼やスラグに対して優れた耐食性を示すことが開示されているが、特許文献４の焼付補修材においても、ピッチ、タールなどの有機結合剤が用いられており、発煙により作業環境の悪化するという問題点が依然として残っている。
上述のように、従来の直流電気炉用補修技術では、コールタール・ピッチやフェノール樹脂のような導電性を有するカーボンボンドを形成する炭素含有材料を活用した補修材が使用されてきた。しかし、それらの炭素含有材料は、補修後の加熱による熱分解で有色の発煙があったり、耐え難い異臭が発生してしまうという問題点がある。しかし、それらを使用しない場合には、導電性が確保できず、また、施工体の焼結性が低くなり強度を発現できないという新たな問題点が発生する。
However, the repair method disclosed in Patent Document 1 is a repair method for the DC electric furnace of the first type described above, and when repair is performed using an irregular shaped refractory that does not have electrical conductivity, a portion other than the repaired portion is repaired. There is a problem in that the current is concentrated and local damage is likely to occur.
Further, the conductive amorphous refractory disclosed in Patent Document 2 has electric conductivity of the irregular refractory itself, and has good corrosion resistance and workability, but tar, pitch and resin during construction. There was a problem in that the work environment at the site of use deteriorates remarkably because of the intense smoke that is colored and has a strong offensive odor due to thermal decomposition. Further, since fumes of tar and pitch contain harmful substances such as CO, NO x , and SO x , it is dangerous to work at a short distance. Furthermore, amorphous refractories containing tar, pitch, etc. form carbon bonds and harden and bond, but if the time for thermal decomposition due to heating is not sufficient, the adhesive strength will be low and the construction product will peel off. There was a point.
Further, however, in Patent Document 3 as well, although smoking is reduced as compared with the case where coal tar pitch is used, some colored smoking is generated, and the unpleasant odor associated with the thermal decomposition of the novolac type phenol resin is also generated. Therefore, the problem of deterioration of working environment has not been solved yet.
Further, in the baking repair material of Patent Document 4, a magnesia-carbonaceous brick (hereinafter referred to as "mag carbon brick") crushed material is mentioned as an example of the crushed refractory brick, and the crushed refractory brick containing carbon was crushed. By utilizing the crushed material as a refractory material, the refractory bricks show excellent corrosion resistance against molten steel and slag by increasing the carbon content of the refractory, whether it is unused or not used. However, the baking repair material of Patent Document 4 also uses organic binders such as pitch and tar, and the problem that the working environment is deteriorated due to smoking still remains.
As described above, in the conventional repairing technique for a DC electric furnace, a repairing material utilizing a carbon-containing material forming a carbon bond having conductivity such as coal tar pitch or phenol resin has been used. However, these carbon-containing materials have a problem in that they generate colored smoke due to thermal decomposition due to heating after repairing or generate an unbearable offensive odor. However, when they are not used, there is a new problem that the conductivity cannot be ensured and the sinterability of the construction body is low and the strength cannot be exhibited.
従って、本発明の目的は、使用時の発煙等による作業環境の悪化を防止し、かつ耐火物自体が導電性を有し、さらに耐用性の高い直流電気炉用導電性熱間補修材を得ることにある。 Therefore, an object of the present invention is to prevent the deterioration of the working environment due to smoke generation during use, and the refractory itself has conductivity, and to obtain a highly durable conductive hot repair material for a DC electric furnace. Especially.
上記課題を解決するために、本発明者らは、発煙や悪臭の原因となる上記炭素含有材料を含まない直流電気炉用導電性熱間補修材について鋭意研究を行った結果、以下のような知見を得た。
すなわち、直流電気炉用熱間補修材の導電性については、適当な量の導電性材料を配合すれば十分に確保することができ、特許文献２〜４のようなカーボン結合を有する必要がないことが判明した。
また、直流電気炉用導電性熱間補修材の強度の発現について、様々な焼結助剤について検討した結果、ポルトランドセメントを添加することで施工体に高強度を付与できることが判明した。
本発明者らは、かかる知見を基に、本発明を完成するに至った。
In order to solve the above problems, the inventors of the present invention have conducted diligent research on a conductive hot repair material for a DC electric furnace that does not contain the carbon-containing material that causes smoke and a bad odor, and the results are as follows. I got the knowledge.
That is, the conductivity of the hot repair material for a DC electric furnace can be sufficiently ensured by adding an appropriate amount of the conductive material, and it is not necessary to have a carbon bond as in Patent Documents 2 to 4. It has been found.
In addition, as a result of examining various sintering aids with respect to the development of the strength of the conductive hot repair material for a DC electric furnace, it was found that the addition of Portland cement can impart high strength to the construction body.
The present inventors have completed the present invention based on such findings.
すなわち、本発明は、鉄粉あるいは鉄を主成分とする合金粉を５〜３０質量％、ポルトランドセメントを５〜２５質量％を含み、残部が塩基性耐火性骨材から構成されることを特徴とする直流電気炉用導電性熱間補修材に係るものである。 That is, the present invention is characterized in that iron powder or alloy powder containing iron as a main component is contained in an amount of 5 to 30% by mass, Portland cement is included in an amount of 5 to 25% by mass, and the balance is composed of a basic refractory aggregate. The present invention relates to a conductive hot repair material for a DC electric furnace.
また、本発明の直流電気炉用導電性熱間補修材は、更に、マグネシア・カーボンれんがの破砕物を含有することを特徴とする。 Further, the conductive hot repair material for a DC electric furnace of the present invention is characterized by further containing a crushed material of magnesia carbon brick.
本発明の直流電気炉用導電性熱間補修材によれば、補修材自体が電気伝導性を有し、かつポルトラントセメントを活用することで発煙による作業環境の悪化を抑え、さらに低融点である特徴から養生時間による耐用性の低下を改善することができるという効果を奏するものである。 According to the conductive hot repair material for a DC electric furnace of the present invention, the repair material itself has electrical conductivity, and suppresses the deterioration of the work environment due to smoking by utilizing portant cement, and further has a low melting point. From a certain characteristic, it is possible to improve the deterioration of durability due to curing time.
本発明の直流電気炉用導電性熱間補修材は、鉄粉及び／または鉄（Ｆｅ）を主成分とする合金粉（以下、「鉄合金粉」と記載する）；ポルトランドセメント；及び塩基性耐火骨材から構成される。なお、本発明の直流電気炉用導電性熱間補修材では、ポルトランドセメントを使用しているにも拘わらず、水を一切使用せず、乾式の粉末状として使用することにも特徴がある。 The conductive hot repair material for a DC electric furnace of the present invention is an iron powder and/or an alloy powder containing iron (Fe) as a main component (hereinafter referred to as “iron alloy powder”); Portland cement; Composed of refractory aggregates. The conductive hot repair material for a DC electric furnace of the present invention is characterized by being used as a dry powder without using any water, although it uses Portland cement.
本発明の直流電気炉用導電性熱間補修材に使用される鉄粉または鉄合金粉は、熱間補修材に導電性を付与するための成分である。ここで、鉄粉、鉄合金粉は、安価であり、損耗により溶融して溶湯に混入しても不純成分とならない利点がある。更に、Ａｌ−Ｍｇ合金のように取扱い上で特別の注意を要するような危険性がない。なお、鉄粉、鉄合金粉は、それぞれを単独で使用しても、２種以上の混合物として用いても差し支えない。なお、鉄粉、鉄合金粉としては、例えば還元鉄粉、アトマイズ鉄粉、電解鉄粉等を挙げることができ、また、純鉄粉、快削鋼粉、低合金鋼粉、Ｃｒ系鉄合金粉、Ｎｉ系鉄合金粉、Ｃｒ−Ｍｏ系鉄合金粉、Ｃｏ系鉄合金粉等を挙げることができる。 The iron powder or iron alloy powder used in the conductive hot repair material for a DC electric furnace of the present invention is a component for imparting conductivity to the hot repair material. Here, the iron powder and the iron alloy powder are inexpensive and have the advantage that they are not impure components even if they are melted due to wear and mixed into the molten metal. Furthermore, there is no danger of requiring special handling in handling, unlike Al-Mg alloys. The iron powder and the iron alloy powder may be used alone or as a mixture of two or more kinds. Examples of the iron powder and iron alloy powder include reduced iron powder, atomized iron powder, electrolytic iron powder, and the like, and pure iron powder, free-cutting steel powder, low alloy steel powder, Cr-based iron alloy. Examples thereof include powder, Ni-based iron alloy powder, Cr-Mo-based iron alloy powder, and Co-based iron alloy powder.
鉄粉あるいは鉄合金粉の配合量は、５〜３０質量％、好ましくは８〜２０質量％の範囲内である。これらの成分の配合量が５質量％未満であると、施工体に十分な電気伝導性を付与することができないために好ましくなく、また、３０質量％を超えると、鉄粉または鉄合金粉の酸化により施工体の組織が悪くなったり、稼働面付近で溶鉄が生成して直流電気炉用導電性熱間補修材の強度低下を引き起こし、耐用性が低下するので好ましくない。 The blending amount of iron powder or iron alloy powder is in the range of 5 to 30% by mass, preferably 8 to 20% by mass. If the blending amount of these components is less than 5% by mass, it is not preferable because sufficient electrical conductivity cannot be imparted to the construction body, and if it exceeds 30% by mass, iron powder or iron alloy powder It is not preferable because the structure of the construction body is deteriorated due to oxidation or molten iron is generated in the vicinity of the operating surface to reduce the strength of the conductive hot repair material for a DC electric furnace and the durability is deteriorated.
なお、鉄粉、鉄合金粉の粒度は、特に限定されるものではないが、例えば０．０４５〜１．０ｍｍの範囲内に８５質量％以上含くまれることが好ましく、０．１５〜０．８ｍｍの範囲内に８５質量％以上含くまれることがより好ましい。ここで、０．０４５ｍｍ未満の粉末の割合が多くなると、後述する塩基性耐火骨材の粒度との差が大きくなって、分離しやすくなるため、導電性の不良や耐食性の悪化などが起こり易くなることがあるために好ましくない。また、１．０ｍｍより大きい粉末の割合が多くなると、施工体組織内に粉末が偏在してしまい、導電性が低下することがあるために好ましくない。 The particle size of the iron powder and the iron alloy powder is not particularly limited, but it is preferably contained in the range of 0.045 to 1.0 mm in an amount of 85% by mass or more, and 0.15 to 0. It is more preferable to include 85% by mass or more within the range of 8 mm. Here, when the ratio of the powder of less than 0.045 mm increases, the difference between the particle size of the basic refractory aggregate to be described later becomes large and the separation becomes easy, so that the poor conductivity and the deterioration of the corrosion resistance easily occur. It is not preferable because it may occur. Further, if the ratio of the powder larger than 1.0 mm increases, the powder is unevenly distributed in the structure of the construction body, which may reduce the conductivity, which is not preferable.
次に、本発明の直流電気炉用導電性熱間補修材は、ポルトランドセメントを含有する。ポルトランドセメントを添加することで、施工体を高強度化することができる。この理由は、以下のように考えられる。すなわち、ポルトランドセメントは、ＳｉＯ２、ＣａＯ、Ａｌ２Ｏ３、Ｆｅ２Ｏ３等から構成されるセメント化合物であり、セメントクリンカーの製造工程では、１５００℃程度の高温で焼成してセメント化合物を生成させると、１５〜２５質量％の液相もまた生成する。また、この液相を含む焼成物を急冷するため、ポルトランドセメント中には微細な結晶やガラス相が存在することとなる。これらの微細な結晶やガラス相は、加熱によって容易に再度液相となり、この液相が焼結助剤として働いて塩基性耐火骨材の焼結を促進して施工体の高強度化をもたらす。すなわち、ポルトランドセメントは、熱間で容易に溶融して塩基性耐火骨材の焼結を促進して施工体に強度を発現させることができる。 Next, the conductive hot repair material for a DC electric furnace of the present invention contains Portland cement. By adding Portland cement, it is possible to increase the strength of the construction body. The reason for this is considered as follows. That is, Portland cement is a cement compound composed of SiO 2 , CaO, Al 2 O 3 , Fe 2 O 3 and the like, and is burned at a high temperature of about 1500° C. to produce a cement compound in the manufacturing process of the cement clinker. If so, a liquid phase of 15 to 25% by mass is also produced. Further, since the calcined product containing this liquid phase is rapidly cooled, fine crystals and glass phase are present in the Portland cement. These fine crystals and glass phase easily become a liquid phase again by heating, and this liquid phase acts as a sintering aid to promote the sintering of the basic refractory aggregate, thereby increasing the strength of the construction body. .. That is, the Portland cement can be easily melted by heat to promote the sintering of the basic refractory aggregate and to make the construction body exhibit strength.
本発明の直流電気炉用導電性熱間補修材に使用されるポルトランドセメントは、上述のようにＳｉＯ２、ＣａＯ、Ａｌ２Ｏ３、Ｆｅ２Ｏ３等から構成されるセメント化合物であり、建築用モルタルやコンクリートなどで使用される慣用のポルトランドセメントを使用することできる。ここで、ポルトランドセメントには様々なタイプのものがあり、普通ポルトランドセメントの他、早強タイプ、超早強タイプ、中庸熱タイプ、低熱タイプ、耐硫酸塩タイプなどのポルトランドセメントが知れられているが、そのいずれも使用できる。これらの中でも、特に市販の普通ポルトランドセメントは、最も安価で効果的、経済的であるため、普通ポルトランドセメントを使用することが好ましい。 The portland cement used for the conductive hot repair material for a DC electric furnace of the present invention is a cement compound composed of SiO 2 , CaO, Al 2 O 3 , Fe 2 O 3, etc. as described above, Conventional Portland cement used in mortar and concrete can be used. Here, there are various types of Portland cement, and in addition to ordinary Portland cement, Portland cement such as early strength type, super early strength type, moderate heat type, low heat type, sulfate resistant type is known. However, any of them can be used. Among these, in particular, commercially available ordinary Portland cement is the most inexpensive, effective, and economical, and therefore it is preferable to use ordinary Portland cement.
本発明の直流電気炉用導電性熱間補修材において、ポルトランドセメントの含有量は５〜２５質量％の範囲内、好ましくは８〜２０質量％の範囲内である。ポルトラントセメントの含有量が５質量％未満の場合には、強度発現が十分でなく、耐用性が低下するために好ましくなく、また、２５質量％を超える場合には、施工体自体の焼結性は向上するものの、低融点物を多く生成するため耐食性が低下するため好ましくない。 In the conductive hot repair material for a DC electric furnace of the present invention, the content of Portland cement is in the range of 5 to 25 mass%, preferably in the range of 8 to 20 mass%. When the content of portrant cement is less than 5% by mass, strength development is not sufficient and durability is deteriorated, which is not preferable, and when it exceeds 25% by mass, the sintered body itself is sintered. Although the corrosion resistance is improved, a large amount of a low-melting point substance is generated, so that the corrosion resistance is deteriorated, which is not preferable.
本発明の直流電気炉用導電性熱間補修材の残部は、塩基性耐火骨材から構成される。塩基性耐火骨材としては、ＭｇＯ及び／またはＣａＯを主成分とするもので、例えば、マグネシア、カルシア、ドロマイト等を挙げることができ、これらは、焼成クリンカー、電融クリンカー、天然及び合成の鉱物として主に用いることができるが、成形された耐火物の破砕物や使用後耐火物の破砕物も使用可能である。 The balance of the conductive hot repair material for a DC electric furnace of the present invention is composed of a basic refractory aggregate. The basic refractory aggregate is mainly composed of MgO and/or CaO, and examples thereof include magnesia, calcia, dolomite, etc. These are calcined clinker, electromelting clinker, natural and synthetic minerals. However, a crushed material of the molded refractory or a crushed material of the refractory after use can also be used.
ここで、塩基性耐火骨材中のＭｇＯとＣａＯの合計含量は、８５質量％以上、好ましくは９０質量％以上である。ＭｇＯとＣａＯの合計含量が８５質量％未満では、不純物が多くなり耐食性が低下するために好ましくない。 Here, the total content of MgO and CaO in the basic refractory aggregate is 85 mass% or more, preferably 90 mass% or more. When the total content of MgO and CaO is less than 85% by mass, impurities increase and corrosion resistance decreases, which is not preferable.
また、塩基性耐火骨材の最大粒径は、４〜１０ｍｍの範囲内であり、好ましくは４〜８ｍｍの範囲内である。塩基性耐火骨材の最大粒径が４ｍｍより小さい場合には、充填性が低下するために好ましくなく、また、１０ｍｍより大きいと、分散性が悪くなって遍在することがあるために好ましくない。 The maximum particle size of the basic refractory aggregate is within the range of 4 to 10 mm, preferably within the range of 4 to 8 mm. If the maximum particle size of the basic refractory aggregate is smaller than 4 mm, the filling property is deteriorated, and if it is larger than 10 mm, the dispersibility is deteriorated and the particles may be ubiquitous. ..
更に、塩基性耐火骨材の粒度は、１ｍｍ以上の大きい粒子（粗粒部）が６０〜９０質量％、好ましくは６５〜８５質量％、１ｍｍ未満の小さい粒子（微粉部）が１０〜４０質量％、好ましくは１５〜３５質量％の範囲内である。ここで、１ｍｍ以上の大きい粒子が６０質量％未満の場合には、微粉部が多くなり過ぎて施工体の展開性が低下するため好ましくない。また、１ｍｍ以上の大きい粒子が９０質量％を超えると、微粉部が少なく、施工体組織がボソついた状態になって耐食性が低下するため好ましくない。 Further, the basic refractory aggregate has a particle size of 60 to 90% by mass for large particles (coarse particles) of 1 mm or more, preferably 65 to 85% by mass, and 10 to 40% for small particles of less than 1 mm (fine particles). %, preferably in the range of 15 to 35% by mass. Here, if the large particles of 1 mm or more are less than 60% by mass, the fine powder portion becomes too much and the deployability of the construction product is deteriorated, which is not preferable. Further, if the content of large particles having a size of 1 mm or more exceeds 90% by mass, the fine powder portion is small, and the structure of the construction body is in a rough state, and the corrosion resistance is deteriorated, which is not preferable.
更に、本発明の直流電気炉用導電性熱間補修材には、マグネシア・カーボンれんがの破砕物を配合して耐食性を向上させることができる。マグネシア・カーボンれんがの破砕物を添加することで耐食性をより向上させることが可能となる。ここで、マグネシア・カーボンれんがには様々な種類のものがあるが、いずれも高耐食性、高耐熱スポーリング性が要求される部位で使用される緻密な組織を有しかつ高耐食性を有する材質として知られており、本発明の直流電気炉用導電性熱間補修材と比較して極めて高い耐食性を有することから、いずれの種類のマグネシア・カーボンれんがの破砕物でも使用できる。さらには、マグネシア・カーボンれんがは、カーボンを含有するため適度な電気伝導性を有するため、マグネシア・カーボンれんがの破砕物を添加しても、得られる施工体の導電性を阻害することがない。なお、マグネシア・カーボンれんがの破砕物としては、未使用品のれんがを粉砕した破砕物、使用後れんがを回収して粉砕した破砕物のどちらでも使用することができる。例えば、転炉用、溶鋼取鍋用などに製造したれんが、あるいは使用後のれんがを利用することができる。 Further, the conductive hot repair material for a DC electric furnace of the present invention can be blended with a crushed material of magnesia carbon brick to improve the corrosion resistance. Corrosion resistance can be further improved by adding a crushed material of magnesia/carbon brick. Here, there are various types of magnesia carbon bricks, but all of them are materials with a dense structure and high corrosion resistance that are used in parts where high corrosion resistance and high heat resistance spalling are required. Since it is known and has extremely high corrosion resistance as compared with the conductive hot repair material for a DC electric furnace of the present invention, any kind of crushed magnesia carbon brick can be used. Furthermore, since the magnesia-carbon brick contains carbon, it has an appropriate electric conductivity. Therefore, even if the crushed material of the magnesia-carbon brick is added, the conductivity of the obtained construction body is not hindered. As the crushed product of magnesia/carbon brick, both a crushed product obtained by crushing an unused brick and a crushed product obtained by collecting and crushing a brick after use can be used. For example, a brick manufactured for a converter, a ladle for molten steel, or the like, or a brick after use can be used.
本発明の直流電気炉用導電性熱間補修材におけるマグネシア・カーボンれんがの破砕物の含有量は、特に限定されるものではないが、好ましくは４０質量％以下、より好ましくは３〜４０質量％、更に好ましくは２０〜３５質量％の範囲内である。マグネシア・カーボンれんがの破砕物の含有量が３質量％未満の場合には、配合効果が発現し難く、また、４０質量％を超えると、高温下の酸化雰囲気でカーボンが脱炭してしまい、得られる施工体の気孔率が増加して耐食性が低下することがある。 The content of the crushed material of magnesia-carbon brick in the conductive hot repair material for a DC electric furnace of the present invention is not particularly limited, but is preferably 40% by mass or less, more preferably 3 to 40% by mass. , And more preferably in the range of 20 to 35 mass %. When the content of the crushed material of magnesia/carbon brick is less than 3% by mass, the compounding effect is difficult to appear, and when it exceeds 40% by mass, carbon is decarburized in an oxidizing atmosphere at high temperature, The porosity of the obtained construction product may increase and the corrosion resistance may decrease.
なお、未使用のマグネシア・カーボンれんがの破砕物を使う場合には、フェノールレジンなどのバインダーの分解に伴う悪臭などが発生する可能性があるが、マグネシア・カーボンれんがの破砕品の添加量が上記範囲内であれば、バインダーなどの揮発分は、発煙、悪臭などの問題を発生し難い程度であり、たとえ発煙、悪臭などが発生したとしても問題とならない。しかしながら、マグネシア・カーボンれんがの破砕物としては、バインダーなどの揮発分の少ない使用後れんがの破砕物を使用することが好ましい。 In addition, when using unused crushed magnesia/carbon bricks, a bad odor may occur due to the decomposition of the binder such as phenol resin, but the added amount of crushed magnesia/carbon bricks is above. If it is within the range, the volatile matter such as the binder is less likely to cause problems such as smoke generation and malodor, and even if smoke generation and malodor occur, it does not cause a problem. However, as the crushed product of magnesia/carbon brick, it is preferable to use the crushed product of post-use brick having a small volatile content such as a binder.
マグネシア・カーボンれんがの粉砕物の粒度は、特に限定されるものではないが、好ましくは０．１〜１０ｍｍの範囲内、より好ましくは０．３〜５ｍｍの範囲内である。マグネシア・カーボンれんがの粉砕物の粒度が、０．１ｍｍより小さいと、焼結性を阻害することがあり、また、１０ｍｍより大きいと、破砕物が偏在して均一な組織にならないため強度や耐食性が局部的に弱い部分ができることがある。 The particle size of the crushed product of magnesia carbon brick is not particularly limited, but is preferably within the range of 0.1 to 10 mm, more preferably within the range of 0.3 to 5 mm. If the particle size of the crushed magnesia/carbon brick is less than 0.1 mm, the sinterability may be impaired, and if it is greater than 10 mm, the crushed material is unevenly distributed and a uniform structure may not be formed, resulting in strength and corrosion resistance. There may be a weak spot locally.
上述のように、本発明の直流電気炉用導電性熱間補修材は、ポルトランドセメントを含有するものであるが、通常のセメントモルタルのように水を添加することは好ましくない。この理由は、水の添加が補修部位を冷却して直流電気炉用導電性熱間補修材の焼結を阻害するのみならず、スクラップ溶解の際に水蒸気爆発の原因にもなり得るためである。 As described above, the conductive hot repair material for a DC electric furnace of the present invention contains Portland cement, but it is not preferable to add water like ordinary cement mortar. The reason for this is that the addition of water not only cools the repaired part and hinders the sintering of the conductive hot repair material for the DC electric furnace, but it can also cause steam explosion during melting of the scrap. ..
一方、発塵防止のために、本発明の直流電気炉用導電性熱間補修材に少量の油などの液体を加えることができる。この際、液体とポルトランドセメントが反応すると、粉状である本発明の直流電気炉用導電性熱間補修材が固化するため好ましくない。なお、油の添加量が多くなり過ぎると、発煙、悪臭などの問題が発生するとともに、本発明の直流電気炉用導電性熱間補修材を粉末状形態とすることが難しくなることがあるため、油を添加する場合でも、２質量％以下程度に抑えるべきである。なお、添加可能な油としては、例えば一号灯油、流動パラフィン、菜種油等を挙げることができる。 On the other hand, in order to prevent dust generation, a small amount of liquid such as oil can be added to the conductive hot repair material for a DC electric furnace of the present invention. At this time, when the liquid reacts with Portland cement, the powdery conductive hot repair material for a DC electric furnace of the present invention is solidified, which is not preferable. If the amount of oil added is too large, problems such as smoke generation and malodor may occur, and it may be difficult to make the conductive hot repair material for a DC electric furnace of the present invention into a powder form. Even if oil is added, it should be suppressed to about 2% by mass or less. Examples of oil that can be added include No. 1 kerosene, liquid paraffin, and rapeseed oil.
本発明の直流電気炉用導電性熱間補修材の製造方法は、特に限定されるものではなく、例えば、原料を秤量し、マラーミキサー、コナーミキサー、ナウターミキサー、オムニミキサーなどを用いて混合し、混合品をフレコンバッグ、プラスチック製の袋、紙袋などに入れて製品として出荷することができる。 The method for producing a conductive hot repair material for a DC electric furnace of the present invention is not particularly limited, and for example, the raw materials are weighed and mixed using a Muller mixer, a conner mixer, a Nauta mixer, an omni mixer, or the like. Then, the mixed product can be put in a flexible container bag, a plastic bag, a paper bag, or the like and shipped as a product.
また、本発明の直流電気炉用導電性熱間補修材の施工方法もまた特に限定されるものではなく、例えば直流電気炉の使用中に損傷の進んだ部位を補修する当たり、まず、溶鋼を排出して補修が必要な部分を露出させ、その露出部に本発明の直流電気炉用導電性熱間補修材を投入する。投入方法が限定されないが、例えば、プラスチック製袋に入れて投入する、スコップを用いて投入する、フレコンバッグごと直流電気炉に投入するなどの方法が採用できる。本発明の直流電気炉用導電性熱間補修材は粉体であっても、適度な流動性を有するので補修が必要な部位に、直流電気炉用導電性熱間補修材を供給することができる。なお、必要に応じて、投げ込まれた直流電気炉用導電性熱間補修材の表面をレーキなどによって均すこともできる。ここで、投入された直流電気炉用導電性熱間補修材は常温であるが、炉熱で一定時間加熱されることによって、焼結して強度が発現する。その後、直流電気炉にスクラップを投入して通電により溶解作業を再開することができる。溶解作業による熱で更に焼結が進み、高耐用な施工体（補修材層）を得ることが可能となる。 Further, the method for applying a conductive hot repair material for a DC electric furnace of the present invention is not particularly limited, for example, when repairing a damaged portion during use of a DC electric furnace, first, molten steel is used. The part that needs to be repaired is discharged to expose, and the conductive hot repair material for a DC electric furnace of the present invention is put into the exposed part. The charging method is not limited, but for example, a method of charging in a plastic bag, charging with a scoop, charging with the flexible container bag into a DC electric furnace, or the like can be adopted. Even if the conductive hot repair material for a DC electric furnace of the present invention is a powder, it has suitable fluidity, so that the conductive hot repair material for a DC electric furnace can be supplied to a site requiring repair. it can. If necessary, the surface of the thrown-in conductive hot repair material for a DC electric furnace can be leveled by a rake or the like. Here, the introduced conductive hot repair material for a DC electric furnace is at room temperature, but when it is heated by the furnace heat for a certain period of time, it is sintered and develops its strength. Then, the scrap can be put into the DC electric furnace and the melting operation can be restarted by energizing. Sintering is further promoted by the heat of the melting work, and it becomes possible to obtain a highly durable construction body (repair material layer).
以下、本発明の直流電気炉用導電性熱間補修材を更に具体的に説明する。
表１に、本発明品の配合例を示し、表２に、比較品の配合例を示す。
鉄粉１は、市販の鉄粉であり、粒度は１．０〜０.０７５ｍｍであり、０．５〜０．１５ｍｍ域に６０〜７０質量％が分布した。また，粒度の影響を見るために、篩い分けして粒度１ｍｍ超の鉄粉２と、粒度０．０４５ｍｍ未満の鉄粉３とした。
ポルトランドセメントは、市販のもので住友大阪セメント株式会社製の普通ポルトランドセメントと早強ポルトランドセメントを使用した。
塩基性骨材として、ドロマイトクリンカーを使用した。組成は、ＣａＯ＝６０質量％、ＭｇＯ＝３３質量％、Ｆｅ２Ｏ３＝６質量％であった。ドロマイトクリンカーは篩い分けして５〜１ｍｍのドロマイト１と、１ｍｍ未満のドロマイト２とした。
マグネシア・カーボンれんがの破砕物は、製鉄所で発生した使用後の取鍋用マグネシア・カーボンれんが（Ｃ＝１５質量％）と転炉用マグネシア・カーボンれんが（Ｃ＝２０質量％）であった：
ＭｇＯ−Ｃ破砕物１は、取鍋用マグネシア・カーボンれんがの破砕物であり、その粒度は５〜１ｍｍ＝６５質量％、１〜０．１ｍｍ＝３５質量％であった；
ＭｇＯ−Ｃ破砕物２は、転炉用マグネシア・カーボンれんがの破砕物であり、その粒度は５〜１ｍｍ＝６５質量％、１〜０．１ｍｍ＝３５質量％であった；
ＭｇＯ−Ｃ破砕物３は、取鍋用マグネシア・カーボンれんがの破砕物であり、その粒度は２５〜１０ｍｍであった；
ＭｇＯ−Ｃ破砕物４は、転炉用マグネシア・カーボンれんがの破砕物であり、その粒度は０．１ｍｍ未満であった。
Hereinafter, the conductive hot repair material for a DC electric furnace of the present invention will be described more specifically.
Table 1 shows a formulation example of the product of the present invention, and Table 2 shows a formulation example of the comparative product.
Iron powder 1 was a commercially available iron powder, the particle size was 1.0 to 0.075 mm, and 60 to 70 mass% was distributed in the 0.5 to 0.15 mm region. In addition, in order to see the influence of the particle size, it was sieved to obtain iron powder 2 having a particle size of more than 1 mm and iron powder 3 having a particle size of less than 0.045 mm.
Commercially available Portland cement was ordinary Portland cement and early strength Portland cement manufactured by Sumitomo Osaka Cement Co., Ltd.
Dolomite clinker was used as the basic aggregate. The composition was CaO=60 mass %, MgO=33 mass %, and Fe 2 O 3 =6 mass %. The dolomite clinker was sieved into 5 to 1 mm of dolomite 1 and less than 1 mm of dolomite 2.
Crushed magnesia carbon bricks were used ladle magnesia carbon bricks (C=15% by mass) and converter magnesia carbon bricks (C=20% by mass) generated at the steel mill:
The MgO-C crushed product 1 was a crushed product of magnesia carbon brick for ladle, and the particle size thereof was 5 to 1 mm=65% by mass and 1 to 0.1 mm=35% by mass;
The crushed MgO-C material 2 was a crushed material of a magnesia carbon brick for a converter, and its particle size was 5-1 mm=65 mass% and 1-0.1 mm=35 mass %;
MgO-C crushed product 3 was a crushed product of ladle magnesia carbon brick, and its particle size was 25 to 10 mm;
The MgO-C crushed product 4 was a crushed product of a magnesia carbon brick for a converter, and its particle size was less than 0.1 mm.
また、本発明品及び比較品の補修材の諸特性を表１及び２に併記する。なお、諸特性の評価方法は以下の通りである：
焼結性は、本発明品及び比較品の補修材をアルミナ質キャスタブル製の型枠に充填し、型枠ごと酸化雰囲気中、１３５０℃で３時間焼成して焼結体を得た。この際、型枠の内寸を幅３０ｍｍ、厚み３０ｍｍ、長さ１４０ｍｍとし、補修材の充填量を２５０ｇとした。冷却後、得られた焼結体を型枠から取り出して試験片し、外観を目視観察して焼結性の評価とした。しっかり形状を保っているものを◎、やや強く押すと角部が削れるものを○、形状が保たれず崩れてしまうものを×の３段階で評価した；
通電性は、上記試験片の１４０ｍｍ方向の電気抵抗値を絶縁抵抗計（三和電気計器製：ＤＭ−５２５７）で測定し、抵抗値が５０ＭΩ未満であれば◎、５０ＭΩ以上、１００ＭΩ未満であれば○として通電性ありと評価し、１００ＭΩより大きいものを×として通電性なしと評価した。なお、焼結性試験で形状が崩れたものについて、電気抵抗測定は行わなかった；
施工性は、本発明品及び比較品の補修材８００ｇをナイロン袋に詰め（四角いプラスチック製袋のコーナー部に詰めて）円錐状にしたものを、アルミナキャスタブル製の板（３００×３００×２０ｍｍ）の上に置き、１５００℃で３時間加熱した。加熱によりナイロン袋が破れ、補修材粉末が崩れ広がった形状の焼結体を得た。焼結体の広がり径により展開性を、また、骨材が偏りなく分散しているかどうかを目視により調べて、施工性の評価とした。施工性が極めて良好を◎、施工性が良好を○、施工性がやや劣るが許容範囲であるものを△、施工性が不十分なものを×とした（ただし、本発明品、比較品共×評価のものはなかった）；
圧縮強度は、焼結性を調査した試験片を用い、ＪＩＳ Ｒ ２５５３（キャスタブル耐火物の強さ試験方法）に準じて測定した；
耐食性の評価には、回転ルツボ法を用いた。試験条件は１６００℃（酸化雰囲気）で行い、スラグは一定時間経過する毎にルツボから排出し新鮮なスラグに交換した。スラグ交換の頻度は、６０分に１回の計４回行った。スラグはＣａＯ／ＳｉＯ２＝４．５の電気炉スラグを用いた。侵食量はポルトランドセメント無添加の侵食量を１００とした指数で示し、数値が多いほど耐食性に劣ることを示している。
In addition, various characteristics of the repair material of the invention product and the comparative product are also shown in Tables 1 and 2. The evaluation method of various properties is as follows:
As for the sinterability, the repair material of the product of the present invention and the comparative product were filled in a mold made of alumina castable, and sintered together with the mold in an oxidizing atmosphere at 1350° C. for 3 hours to obtain a sintered body. At this time, the inner dimensions of the mold were 30 mm in width, 30 mm in thickness, and 140 mm in length, and the filling amount of the repair material was 250 g. After cooling, the obtained sintered body was taken out of the mold and used as a test piece, and the appearance was visually observed to evaluate the sinterability. Those with a firm shape were rated as ◎, those with sharp corners that could be scraped were rated as ○, and those that collapsed because the shape was not retained were rated in three grades;
The electrical conductivity is obtained by measuring the electrical resistance value of the test piece in the 140 mm direction with an insulation resistance tester (manufactured by Sanwa Denki Keiki: DM-5257), and if the resistance value is less than 50 MΩ, ◎, 50 MΩ or more and less than 100 MΩ. If ◯, it was evaluated as having conductivity, and if larger than 100 MΩ, it was evaluated as not having conductivity. The electrical resistance was not measured for those whose shape was destroyed in the sinterability test;
The workability is as follows: 800 g of the repair material of the present invention product and comparative product is packed in a nylon bag (packed in the corner part of a square plastic bag) and made into a conical shape, and an alumina castable plate (300 x 300 x 20 mm) And heated at 1500° C. for 3 hours. By heating, the nylon bag was torn, and the repair material powder was broken and spread to obtain a sintered body. The spreadability of the sintered body was evaluated by the spreadability, and whether the aggregate was evenly dispersed was visually examined to evaluate the workability. The workability is extremely good, the workability is good, the workability is a little inferior but acceptable, and the workability is insufficient. × There were no evaluations);
The compressive strength was measured according to JIS R 2553 (casting refractory strength test method) using a test piece whose sinterability was investigated;
A rotary crucible method was used for the evaluation of corrosion resistance. The test conditions were 1600° C. (oxidizing atmosphere), and the slag was discharged from the crucible and replaced with fresh slag after a certain period of time. The frequency of slag replacement was 4 times, once every 60 minutes. As the slag, an electric furnace slag with CaO/SiO 2 =4.5 was used. The erosion amount is shown as an index with the erosion amount without addition of Portland cement being 100, and the larger the value is, the poorer the corrosion resistance is.
上記表１において、本発明例１〜１０は、鉄粉量と粒度を変化させたものである。また、本発明品１１〜１４は普通ポルトランドセメントの量を変化させたものであり、本発明品１５は、早強ポルトランドセメント使用したものである。本発明品１６〜１８は、ドロマイトの粒度を変更したものである。本発明品１〜１８は、いずれも焼結性、通電性、施工性、圧縮強度、耐食性に優れ、導電性を必要とされる直流電気炉用導電性熱間補修材として優れた特性を有することが解る。
更に、本発明品１９〜２５は、ＭｇＯ−Ｃ破砕物１の配合量を変えた場合あり，本発明品２６〜２８は、マグネシア−カーボンれんがの破砕品のソースと粒度を変えた場合である。ドロマイトクリンカーとマグネシア−カーボンれんがの破砕品を併用することで、一層の耐食性の向上を図ることができることが解る。
In Table 1 above, Examples 1 to 10 of the present invention are obtained by changing the amount of iron powder and the particle size. Further, the products 11 to 14 of the present invention are those in which the amount of ordinary Portland cement is changed, and the product 15 of the present invention is to use the early strength Portland cement. Inventive products 16 to 18 are obtained by changing the particle size of dolomite. The products 1 to 18 of the present invention are all excellent in sinterability, electrical conductivity, workability, compressive strength, and corrosion resistance, and have excellent properties as a conductive hot repair material for a DC electric furnace that requires conductivity. I understand.
Further, the products 19 to 25 of the present invention are cases where the compounding amount of the MgO—C crushed product 1 is changed, and the products 26 to 28 of the invention are the case where the source and particle size of the crushed product of magnesia-carbon brick are changed. .. It is understood that the combined use of the crushed product of dolomite clinker and magnesia-carbon brick can further improve the corrosion resistance.
上記表２において、比較品１は、鉄粉を含まない場合であるが、通電性が悪いだけではなく、焼結性も劣るものであった。焼結性が劣る原因は、鉄が酸化して生成する酸化鉄も焼結性に寄与するためと推定される。比較品２は、鉄粉の添加量が少ない場合であるが、焼結性はやや改善されるものの、通電性が不十分であった。比較品３は、鉄粉量が多い場合であるが、焼結性に劣るだけではなく、耐食性も劣る結果となった。比較品４及び５は、ポルトランドセメントを含まない場合と３質量％と少ない場合であるが、この場合は焼結性が劣り、耐食性も余りよい結果とはならなかった。比較品６及び７は、ポルトランドセメントの添加量が大きすぎる場合であるが、耐食性に劣る結果となった。
上述のように、本発明品の直流電気炉用導電性熱間補修材の効果は明確である。
In Table 2 above, Comparative product 1 was a case where iron powder was not included, but it was not only poor in electrical conductivity but also inferior in sinterability. It is presumed that the reason for the poor sinterability is that iron oxide produced by the oxidation of iron also contributes to the sinterability. Comparative product 2 had a small amount of iron powder added, but the sinterability was slightly improved, but the electrical conductivity was insufficient. Comparative product 3, which had a large amount of iron powder, was not only inferior in sinterability but also inferior in corrosion resistance. Comparative products 4 and 5 were the case where Portland cement was not included and the case where the content was as small as 3% by mass. In this case, the sinterability was inferior and the corrosion resistance was not so good. Comparative products 6 and 7 were cases where the amount of Portland cement added was too large, but the results were inferior in corrosion resistance.
As described above, the effect of the conductive hot repair material for a DC electric furnace of the present invention is clear.
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