JP2006009138A - Finish heat treatment method for iron powder and device therefor - Google Patents
Finish heat treatment method for iron powder and device therefor Download PDFInfo
- Publication number
- JP2006009138A JP2006009138A JP2004343552A JP2004343552A JP2006009138A JP 2006009138 A JP2006009138 A JP 2006009138A JP 2004343552 A JP2004343552 A JP 2004343552A JP 2004343552 A JP2004343552 A JP 2004343552A JP 2006009138 A JP2006009138 A JP 2006009138A
- Authority
- JP
- Japan
- Prior art keywords
- iron powder
- gas
- heat treatment
- furnace
- heated
- 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.)
- Pending
Links
Abstract
Description
本発明は、鉄粉の仕上熱処理方法および装置に関する。仕上熱処理とは、脱炭、脱酸、脱窒のいずれか１種または２種以上の処理を指す。仕上熱処理後の鉄粉は、焼結部品、磁性材料等の焼結製品の原料粉として使用され、あるいは、粉末のまま使用されることが多い。 The present invention relates to a method and apparatus for finishing heat treatment of iron powder. The finish heat treatment refers to one or more treatments of decarburization, deoxidation, and denitrification. The iron powder after the finish heat treatment is often used as a raw material powder for sintered products such as sintered parts and magnetic materials, or is often used as a powder.
一般に、鉄粉の仕上熱処理工程では、粗還元したミルスケール還元鉄粉やアトマイズしたままの鉄粉を処理対象とし、製品の用途に応じて脱炭、脱酸、脱窒のいずれか１種または２種以上の処理が施される。これらの処理では、移動床と呼ばれる連続的に移動するベルト上に鉄粉を積層し、この移動床を、温度および雰囲気が制御された水平炉（連続式移動床炉という）内に連続的に送り込んで、水平炉内を通過させる。移動床が炉内を通過中、移動床上の鉄粉は、雰囲気中の水蒸気ないし水素と反応し、下記の反応式に従って脱炭、脱酸ないし脱窒が行われる（例えば、特許文献１参照）。 Generally, in the finish heat treatment process of iron powder, rough reduced mill-scale reduced iron powder or atomized iron powder is treated, and any one of decarburization, deoxidation, and denitrification depending on the use of the product or Two or more types of processing are performed. In these processes, iron powder is laminated on a continuously moving belt called a moving bed, and this moving bed is continuously placed in a horizontal furnace (referred to as a continuous moving bed furnace) whose temperature and atmosphere are controlled. Feed it through the horizontal furnace. While the moving bed passes through the furnace, the iron powder on the moving bed reacts with water vapor or hydrogen in the atmosphere, and decarburization, deoxidation or denitrification is performed according to the following reaction formula (for example, see Patent Document 1). .
Ｃ（ｉｎ Ｆｅ）＋Ｈ２Ｏ（ｇ）＝ＣＯ（ｇ）＋Ｈ２（ｇ） （１）
ＦｅＯ（ｓ）＋Ｈ２（ｇ）＝Ｆｅ（ｓ）＋Ｈ２Ｏ（ｇ） （２）
Ｎ（ｉｎ Ｆｅ）＋３/２Ｈ２（ｇ）＝ＮＨ３（ｇ） （３）
図６は、従来の仕上熱処理装置の１例を示す側断面図である。鉄粉７はホッパ８からベルト９上に積層され、ベルト９はホイール１０で駆動されて炉（水平炉または連続式移動床炉）３０内を炉長方向に移動し、ベルト９上の鉄粉７の積層を連続的に炉内に搬入し炉内を通過させ炉外に搬出する。炉内はラジアントチューブ１１で所定の温度に加熱される。雰囲気ガスは炉出口側の雰囲気ガス導入口５から炉内に導入され、炉入口側の雰囲気ガス排出口６から炉外に排出され、燃焼された後、雰囲気ガス排気管１３を介して排気ダクト１４へ送られる。ラジアントチューブ１１内の燃焼ガスは燃焼ガス排気管１２を通じて炉外に排出され排気ダクト１４へ送られる。
C (in Fe) + H 2 O (g) = CO (g) + H 2 (g) (1)
FeO (s) + H 2 (g) = Fe (s) + H 2 O (g) (2)
N (in Fe) + 3 / 2H 2 (g) = NH 3 (g) (3)
FIG. 6 is a side sectional view showing an example of a conventional finish heat treatment apparatus. The iron powder 7 is laminated on the belt 9 from the hopper 8, and the belt 9 is driven by the wheel 10 to move in the furnace (horizontal furnace or continuous moving bed furnace) 30 in the furnace length direction. 7 is continuously carried into the furnace, passed through the furnace, and carried out of the furnace. The inside of the furnace is heated to a predetermined temperature by the radiant tube 11. The atmospheric gas is introduced into the furnace from the atmospheric gas inlet 5 on the furnace outlet side, discharged outside the furnace from the atmospheric gas outlet 6 on the furnace inlet side, burned, and then exhausted through the atmospheric gas exhaust pipe 13. 14. The combustion gas in the radiant tube 11 is discharged out of the furnace through the combustion gas exhaust pipe 12 and sent to the exhaust duct 14.
ベルト９上の鉄粉７は炉内を連続通過中に、雰囲気中の水素ないし水蒸気と反応し、上記の反応式で示される脱炭、脱酸ないし脱窒の反応が進行する。これらの反応はそれぞれ反応進行に最適の温度、雰囲気ガス組成の条件で行なわれ、脱炭では６００〜１１００℃、露点３０〜６０℃の還元ガス雰囲気、脱酸では７００〜１１００℃、露点４０℃以下の還元ガス雰囲気、脱窒では４５０〜７５０℃、露点４０℃以下のＨ２ガス雰囲気が最適とされている。このため、炉内は炉長方向に入口側から第一室２、第二室３、第三室４の三室に区分され、室間に仕切壁１が配設され、第一室２では脱炭、第二室３では脱酸、第三室４では脱窒が主反応になるように、各室の温度および雰囲気が制御される。 The iron powder 7 on the belt 9 reacts with hydrogen or water vapor in the atmosphere while continuously passing through the furnace, and the decarburization, deoxidation or denitrification reaction shown by the above reaction formula proceeds. These reactions are carried out under conditions of optimum temperature and atmospheric gas composition for the progress of the reaction, respectively, in decarburization at a reducing gas atmosphere of 600-1100 ° C. and dew point of 30-60 ° C., in deoxidation, 700-1100 ° C., dew point of 40 ° C. In the following reducing gas atmosphere and denitrification, an H 2 gas atmosphere having a temperature of 450 to 750 ° C. and a dew point of 40 ° C. or less is optimal. For this reason, the inside of the furnace is divided into three chambers of the first chamber 2, the second chamber 3, and the third chamber 4 from the inlet side in the furnace length direction, and a partition wall 1 is disposed between the chambers. The temperature and atmosphere of each chamber are controlled so that deoxidation is the main reaction in the charcoal, second chamber 3 and denitrification is in the third chamber 4.
効率よく仕上熱処理するためには、炉内各室での温度管理が重要である。しかし、通常規模の炉では、炉内で室温状態から鉄粉７を加熱すると、第一室２内を移動する鉄粉７の積層中心部が所定の温度に到達するのは同室の出口付近となる。このため、ベルト速度を上げたり、ベルト９上の鉄粉７の積層厚さを厚くするといった方法で生産性の向上を図ろうとしても鉄粉７の積層中心部の温度が所定の温度まで上昇することは困難である。 In order to efficiently perform the finish heat treatment, temperature control in each chamber in the furnace is important. However, in a furnace of a normal scale, when the iron powder 7 is heated from the room temperature in the furnace, the central part of the iron powder 7 moving in the first chamber 2 reaches a predetermined temperature near the outlet of the same chamber. Become. For this reason, even if it is intended to improve productivity by increasing the belt speed or increasing the lamination thickness of the iron powder 7 on the belt 9, the temperature at the center of the lamination of the iron powder 7 rises to a predetermined temperature. It is difficult to do.
そこで、仕上熱処理の効率を向上させるために、第一室に入る前の鉄粉を予熱し、第一室の入口通過時の積層の温度を高くしておく方法が提案され、具体的には、予熱の熱源として、炉内を加熱するときに排出される燃焼排ガスを用い（例えば、特許文献２参照）、鉄粉との熱交換は、図６、図７に示す間接加熱方式の熱交換器である予熱器１５を用いて行う（例えば、特許文献３参照）ことが知られている。 Therefore, in order to improve the efficiency of the finish heat treatment, a method of preheating the iron powder before entering the first chamber and increasing the temperature of the stack when passing through the inlet of the first chamber is proposed, specifically As the heat source for preheating, combustion exhaust gas discharged when heating the inside of the furnace is used (see, for example, Patent Document 2), and heat exchange with iron powder is performed by indirect heating system shown in FIGS. It is known to use a preheater 15 that is a heater (see, for example, Patent Document 3).
予熱器１５は、ホッパ８の下部と排気ダクト１４とを交叉させ、該交叉部内において排気ダクト１４を複数の熱交換用パイプ１６に分岐させた形態を有する。鉄粉７は、ホッパ８を出た後複数並んだ熱交換用パイプ１６の間を抜けてベルト９上に積層する。
排気ダクト１４内のいわゆる燃焼排ガスは、ラジアントチューブ１１内で燃焼したガス（燃焼ガス）を炉外に排出したガスおよび炉内で鉄粉と反応させた雰囲気ガス（反応排ガス）を炉外で燃焼させたガスの混合ガスである。
The preheater 15 has a form in which the lower part of the hopper 8 and the exhaust duct 14 are crossed and the exhaust duct 14 is branched into a plurality of heat exchange pipes 16 in the crossing part. After leaving the hopper 8, the iron powder 7 passes through a plurality of heat exchange pipes 16 and is stacked on the belt 9.
The so-called combustion exhaust gas in the exhaust duct 14 combusts the gas combusted in the radiant tube 11 (combustion gas) outside the furnace and the atmospheric gas (reaction exhaust gas) reacted with iron powder in the furnace outside the furnace. It is a mixed gas of gas.
予熱器１５を用いることで、鉄粉７は、内側に燃焼排ガスが流れている熱交換用パイプ１６の外面と接触して予熱されるので、酸化・固着することなくベルト９上に積層する。
しかしながら、上記従来の予熱方法では、熱交換用パイプを介して燃焼排ガスから鉄粉に熱が移動するため、熱交換用パイプの周囲の鉄粉にしか熱が伝わらないことや、熱交換用パイプの熱伝導率が熱移動の抵抗として働くことなどから、熱交換の効率が低いという問題があった。また、鉄粉が熱交換用パイプの間を移動するため、該移動する鉄粉により摩耗して熱交換用パイプに穴があくという問題や、鉄粉が熱交換用パイプとの接触により摩耗して球状化し、圧粉密度が低下するため、粉末冶金に使われる高密度材には適さなくなるという問題もあった。 However, in the above-described conventional preheating method, heat is transferred from the combustion exhaust gas to the iron powder through the heat exchange pipe, so that the heat is transmitted only to the iron powder around the heat exchange pipe, or the heat exchange pipe. Since the thermal conductivity of this works as a resistance to heat transfer, there is a problem that the efficiency of heat exchange is low. In addition, since iron powder moves between heat exchange pipes, the iron powder is worn by contact with the heat exchange pipe, and there is a problem that the heat exchange pipe wears out due to the moving iron powder. As a result, it becomes spheroidized and the density of the green powder is reduced, which makes it unsuitable for high-density materials used in powder metallurgy.
本発明は、上述の問題を解決し、予熱方法の改良により仕上熱処理の効率を向上させた鉄粉の仕上熱処理方法および装置を提供することを目的とする。 An object of the present invention is to provide a method and apparatus for finishing heat treatment of iron powder that solves the above-described problems and improves the efficiency of finishing heat treatment by improving the preheating method.
上記目的を達成した本発明は、以下のとおりである。
（発明項１）鉄粉を連続的に移動させつつ、これに脱炭、脱酸、脱窒のうち１種または２種以上の処理を施す鉄粉の仕上熱処理方法において、該鉄粉を加熱気体と直接接触させて予熱した後に前記処理を行なうことを特徴とする鉄粉の仕上熱処理方法。
（発明項２）前記加熱気体として、前記処理の反応排ガス、水素ガス、窒素ガス、不活性ガス、ＡＸガスのうち１種または２種以上のガスを用いることを特徴とする発明項１記載の鉄粉の仕上熱処理方法。
（発明項３）前記加熱気体は前記処理の反応排ガスを燃焼した燃焼排ガスと間接的に熱交換させて加熱されたものであることを特徴とする発明項１または２に記載の鉄粉の仕上熱処理方法。
（発明項４）前記加熱気体が鉄粉を予熱する時の同加熱気体の流速を１ｍ/ｓ以下とすることを特徴とする発明項１〜３のいずれかに記載の鉄粉の仕上熱処理方法。
（発明項５）鉄粉を連続的に移動させつつ、これに脱炭、脱酸、脱窒のうち１種または２種以上の処理を施す炉と、該炉に入る前の鉄粉を予熱する予熱手段とを有する鉄粉の仕上げ熱処理装置において、前記予熱手段が、前記鉄粉と加熱気体とを直接接触させて伝熱を行う予熱手段であることを特徴とする鉄粉の仕上げ熱処理装置。
（発明項６）前記予熱手段が、前記鉄粉の移動経路を挟んで相対する両側の一方の側から該移動経路内に気体を放出する気体供給部と、他方の側から該移動経路内の気体を回収する気体排出部とを有することを特徴とする発明項５記載の鉄粉の仕上熱処理装置。
（発明項７）前記移動経路の気体供給部と排出部の間の移動層の幅が１０〜３００ｍｍであることを特徴とする発明項５または６に記載の鉄粉の仕上熱処理装置。
（発明項８）前記予熱手段に入る前の加熱気体を前記炉から発生する反応排ガスを燃焼した燃焼排ガスと間接的に熱交換させる熱交換器を有することを特徴とする発明項５〜７のいずれかに記載の鉄粉の仕上熱処理装置。
The present invention that has achieved the above object is as follows.
(Invention Item 1) In a method of finishing heat treatment of iron powder in which the iron powder is continuously moved and subjected to one or more treatments among decarburization, deoxidation, and denitrification, the iron powder is heated. A method of finishing heat treatment of iron powder, characterized in that the treatment is carried out after preheating by direct contact with gas.
(Invention 2) The invention according to Invention 1, wherein the heating gas is one or more of reaction exhaust gas, hydrogen gas, nitrogen gas, inert gas, and AX gas in the treatment. Finish heat treatment method of iron powder.
(Invention 3) Finishing of iron powder according to Invention 1 or 2, wherein the heated gas is heated by indirectly exchanging heat with combustion exhaust gas obtained by burning the reaction exhaust gas of the treatment. Heat treatment method.
(Invention 4) The finish heat treatment method for iron powder according to any one of inventions 1 to 3, wherein the flow rate of the heated gas when the heated gas preheats the iron powder is 1 m / s or less. .
(Invention Item 5) A furnace in which iron powder is continuously moved and subjected to one or more treatments among decarburization, deoxidation, and denitrification, and the iron powder before entering the furnace is preheated. An iron powder finishing heat treatment apparatus comprising: a preheating means for heat treatment, wherein the preheating means is a preheating means for transferring heat by directly contacting the iron powder and a heated gas. .
(Invention 6) The preheating means includes a gas supply unit that discharges gas into the moving path from one side on both sides of the moving path of the iron powder, and the other side in the moving path. A finish heat treatment apparatus for iron powder according to claim 5, further comprising a gas discharge portion for collecting gas.
(Invention 7) The iron powder finishing heat treatment apparatus according to Invention 5 or 6, wherein the width of the moving layer between the gas supply section and the discharge section of the moving path is 10 to 300 mm.
(Invention 8) The invention according to any one of Inventions 5 to 7, further comprising a heat exchanger for indirectly exchanging heat with the combustion exhaust gas combusted by the reaction exhaust gas generated from the furnace before entering the preheating means. A finish heat treatment apparatus for iron powder according to any one of the above.
本発明によれば、鉄粉を連続的に移動させつつ、これに脱炭、脱酸、脱窒のうち１種または２種以上の処理を施す鉄粉の仕上熱処理方法において、前記処理を施される前（炉に入る直前）の鉄粉に、高温かつ非酸化性の気体を直接接触させるように流して該鉄粉を予熱するようにしたので、鉄粉は酸化されることなく、均等に予熱される。したがって、温度制御が的確にできるようになり、炉に入る時の鉄粉温度が従来よりも高くなって、仕上熱処理の燃料原単位を低減できる。また、鉄粉の所定の処理温度への到達時間が短縮するので、鉄粉の炉内通過速度を増すことができて生産性が向上する。 According to the present invention, in the finish heat treatment method for iron powder, in which the iron powder is continuously moved and at least one of decarburization, deoxidation, and denitrification is treated, the treatment is performed. Since the iron powder was preheated by flowing it in direct contact with high-temperature and non-oxidizing gas to the iron powder before it was entered (immediately before entering the furnace), the iron powder was not oxidized and evenly distributed. Preheated. Therefore, temperature control can be accurately performed, the iron powder temperature when entering the furnace becomes higher than before, and the fuel intensity of the finish heat treatment can be reduced. Moreover, since the time for the iron powder to reach a predetermined processing temperature is shortened, the passing speed of the iron powder in the furnace can be increased, and the productivity is improved.
また、鉄粉の移動経路と交叉する熱交換用パイプがなくなるから、その交換のための装置停止がなくなって稼動率が向上し、また、熱交換用パイプとの擦れによる鉄粉の球状化の問題がなくなって高密度材の製造が容易となる。 In addition, since there is no heat exchange pipe crossing the iron powder movement path, there is no need to stop the equipment for the exchange and the operating rate is improved, and the iron powder is spheroidized by rubbing with the heat exchange pipe. This eliminates problems and facilitates the production of high density materials.
本発明において、鉄粉を連続的に移動させつつ、これに脱炭、脱酸、脱窒のうち１種または２種以上の処理を施す工程については、従来と同様、水平炉を用いて行うことができる。その際、本発明では、処理を施される直前の鉄粉に、該鉄粉よりも高温の加熱気体を直接接触させるように流す。
水平炉を用いて仕上熱処理を行う場合、ホッパを出た鉄粉は移動経路内を下降してベルト上に到達し、移動経路内に鉄粉の充填層が形成されるので、この充填層内に該層を挟んで相対する両側の一方の側から加熱気体を送り込み、他方の側から回収するようにするのが好適である。鉄粉の充填層内に直接加熱気体を流すので、粉体粒子の間を加熱気体が流れ、粉体の表面積全体が熱伝導する面積となるため高効率で熱の交換ができる。例えば、互いに同じ体積の直径１０ｃｍの管と直径１００μｍの粉体とでは、表面積は粉体の方が１０００倍大きくなる。熱交換される熱の量は接触面積に比例するので、粉体粒子に気体を直接接触させる方が効率は格段によくなる。なお、加熱気体の温度は、鉄粉よりも高い温度であれば鉄粉の昇温に寄与し、熱処理炉へ供給する鉄粉の温度を上昇させて熱処理炉での生産性を向上させる効果を有するといえるが、実質的には、加熱気体の温度として２００℃以上程度であれば熱処理炉での投入熱量低減や装入鉄粉量増加による生産性向上に大きな効果があると考えられる。
In the present invention, while the iron powder is continuously moved, the step of performing one or more treatments among decarburization, deoxidation, and denitrification is performed using a horizontal furnace as in the past. be able to. In that case, in this invention, it flows so that heating gas higher temperature than this iron powder may be made to contact directly to the iron powder just before a process.
When finishing heat treatment is performed using a horizontal furnace, the iron powder that exits the hopper descends in the moving path and reaches the belt, and a packed bed of iron powder is formed in the moving path. It is preferable that the heated gas is fed from one side of the opposite sides of the layer and recovered from the other side. Since the heated gas flows directly into the packed bed of iron powder, the heated gas flows between the powder particles, and the entire surface area of the powder becomes a heat conducting area, so heat can be exchanged with high efficiency. For example, in a tube having a diameter of 10 cm and a powder having a diameter of 100 μm having the same volume, the surface area of the powder is 1000 times larger. Since the amount of heat exchanged is proportional to the contact area, the efficiency is significantly improved when the gas is brought into direct contact with the powder particles. If the temperature of the heated gas is higher than that of the iron powder, it contributes to the temperature increase of the iron powder, and the effect of increasing the temperature of the iron powder supplied to the heat treatment furnace and improving the productivity in the heat treatment furnace. Although it can be said that the temperature of the heated gas is about 200 ° C. or higher, it is considered that there is a great effect in improving productivity by reducing the amount of heat input in the heat treatment furnace or increasing the amount of charged iron powder.
また、前記したように、脱炭、脱酸、脱窒等の熱処理には、それぞれ最適の温度があるので、熱処理炉での最初の工程で熱処理に好適な温度以上の温度に鉄粉を加熱する必要はないので、加熱温度の上限も熱処理炉での最初の工程に応じて設定すればよい。
もっとも、高温の気体を直接鉄粉に接触させて予熱する場合、かかる高温の気体は、非酸化性の気体、すなわち、その温度で鉄を酸化させない気体でなければならない。
In addition, as described above, since there are optimum temperatures for heat treatment such as decarburization, deoxidation, and denitrification, the iron powder is heated to a temperature higher than the temperature suitable for heat treatment in the first step in the heat treatment furnace. Therefore, the upper limit of the heating temperature may be set according to the first step in the heat treatment furnace.
However, when preheating is performed by bringing a high-temperature gas into direct contact with iron powder, the high-temperature gas must be a non-oxidizing gas, that is, a gas that does not oxidize iron at that temperature.
鉄粉と熱交換した後の気体の温度が露点以下になると、気体に含まれている水蒸気が結露して、鉄粉表面に水滴ができ、これをもとに鉄粉が酸化される。また、反応式、
ＦｅＯ（ｓ）＋Ｈ２（ｇ）＝Ｆｅ（ｓ）＋Ｈ２Ｏ（ｇ） （１）
に従う反応は、２００℃では露点２５℃以上、５００℃では露点５５℃以上になると、反応が右から左に進み、鉄粉が酸化される。
When the temperature of the gas after heat exchange with the iron powder falls below the dew point, the water vapor contained in the gas is condensed to form water droplets on the surface of the iron powder, and the iron powder is oxidized based on this. Reaction formula,
FeO (s) + H 2 (g) = Fe (s) + H 2 O (g) (1)
When the dew point is 25 ° C. or higher at 200 ° C. and the dew point is 55 ° C. or higher at 500 ° C., the reaction proceeds from right to left, and iron powder is oxidized.
例えば、ラジアントチューブ内で燃焼させるガスとしてプロパンガスを用い、空燃比１.２として燃焼させた場合、燃焼排ガスの露点は４５℃となり、また、燃焼排ガス中に残留している酸素が３％程度となる。このため、燃焼排ガスは、温度が約９００℃である（高温の気体に該当する）が、直接鉄粉の充填層内に通すと予熱とともに鉄粉の酸化反応が進むので、非酸化性の気体に該当しない。 For example, when propane gas is used as the gas to be burned in the radiant tube and burned at an air-fuel ratio of 1.2, the dew point of the combustion exhaust gas is 45 ° C., and the oxygen remaining in the combustion exhaust gas is about 3%. It becomes. Therefore, the combustion exhaust gas has a temperature of about 900 ° C. (corresponding to a high-temperature gas), but if it is passed directly into the packed bed of iron powder, the oxidation reaction of the iron powder proceeds with preheating, so a non-oxidizing gas Not applicable.
非酸化性の気体としては、酸素を含まずかつ露点が２５℃以下であるという条件を満たす気体を用いることが好ましい。かかる非酸化性の気体としては、例えば、水素ガス、窒素ガス、不活性ガス（アルゴンガス等）、ＡＸガス（アンモニア分解ガス）のうちのいずれか１種または２種以上の混合ガスが挙げられる。なお、上記条件を満たすものであれば、可燃性ガスを不完全燃焼させたガスを用いてもよい。 As the non-oxidizing gas, it is preferable to use a gas that does not contain oxygen and satisfies the condition that the dew point is 25 ° C. or lower. Examples of the non-oxidizing gas include any one or a mixed gas of hydrogen gas, nitrogen gas, inert gas (argon gas, etc.), and AX gas (ammonia decomposition gas). . Note that a gas obtained by incomplete combustion of a combustible gas may be used as long as the above conditions are satisfied.
また、仕上熱処理の反応排ガスは、主に水素ガスと水蒸気の混合ガスであるが、処理前の鉄粉中の炭素濃度が低い（例えば０.５mass％以下）場合には、水蒸気の添加が少なくて済むので露点が２５℃以下となっており、温度も約９００℃で排出されるため、高温かつ非酸化性の気体として利用できる。
非酸化性の気体を高温にする手段としては、ボイラ等による加熱もあるが、炉から９００℃以上の高温で排出される燃焼排ガスを、非酸化性の気体と間接的に熱交換させ、燃焼排ガスの熱を非酸化性の気体に与えて該気体を高温にする方法が好ましく用いうる。
Further, the reaction exhaust gas for the finish heat treatment is mainly a mixed gas of hydrogen gas and water vapor, but when the carbon concentration in the iron powder before treatment is low (for example, 0.5 mass% or less), the addition of water vapor is small. Therefore, the dew point is 25 ° C. or less and the temperature is discharged at about 900 ° C., so that it can be used as a high-temperature and non-oxidizing gas.
As a means for increasing the temperature of the non-oxidizing gas, there is heating by a boiler or the like, but the combustion exhaust gas discharged from the furnace at a high temperature of 900 ° C. or higher is indirectly heat-exchanged with the non-oxidizing gas, and combustion is performed. A method in which the heat of exhaust gas is applied to a non-oxidizing gas to raise the temperature of the gas can be preferably used.
予熱温度（予熱後の鉄粉の温度）は、高温ほど仕上熱処理工程の生産性が向上するが、６００℃以上にすると鉄粉が焼結し、炉への供給が困難となるため、その上限を６００℃に設定するのが好ましい。
鉄粉がホッパから水平炉まで移動する移動経路中で加熱気体が鉄粉を予熱する時の同加熱気体の流速が大きすぎると鉄粉が流動化してしまい,鉄粉の移動を妨げることがある。あるいは、移動経路から加熱気体の排出管側へ鉄粉か吹き飛ばされて、ロスとなる虞もある。鉄粉の粒径は１００μｍ以下程度であることから、加熱気体が鉄粉を予熱する時の同加熱気体の流速を１ｍ/ｓ以下とすることが望ましい。
The preheating temperature (the temperature of the iron powder after preheating) increases the productivity of the finish heat treatment step as the temperature increases. However, if the temperature is 600 ° C. or higher, the iron powder sinters and becomes difficult to supply to the furnace. Is preferably set to 600 ° C.
When the heating gas preheats the iron powder in the moving path where the iron powder moves from the hopper to the horizontal furnace, if the flow rate of the heated gas is too large, the iron powder may fluidize and hinder the movement of the iron powder. . Alternatively, iron powder may be blown off from the moving path to the heated gas discharge pipe side, which may cause a loss. Since the particle size of the iron powder is about 100 μm or less, it is desirable that the flow rate of the heated gas when the heated gas preheats the iron powder is 1 m / s or less.
ここで加熱気体の流速は、加熱気体の気体供給部の温度、圧力での実ガス体積を気体供給部の開口面積で除した値で考えることができる。
図１は、本発明の仕上熱処理装置の一例を示す側断面図である。同図において、１７は熱交換器、１８は気体供給管、１９は気体排出管、５０は反応排ガス、５１は非酸化性の気体（反応排ガスを除く）、５３は燃焼排ガスであり、図６と同一または相当部材には同じ符号を付し説明を省略する。また、図２は、本発明で用いる予熱手段の一例を示す側断面図であり、図１と同一または相当部材には同じ符号を付し説明を省略する。図示のように、本発明の仕上熱処理装置は、炉３０に入る直前の鉄粉７を予熱する予熱手段として、ホッパ８からベルト９上に至る鉄粉７の移動経路を挟んで相対する両側の一方の側から該移動経路内に加熱気体（高温かつ非酸化性の気体）５２を放出する気体供給部と他方の側から該移動経路内の気体を回収する気体排出部とを有する。図２においては、気体供給部として複数の気体供給管１８、気体排出部として複数の気体排出管１９を設けた例を示している。
Here, the flow rate of the heated gas can be considered as a value obtained by dividing the actual gas volume at the temperature and pressure of the gas supply unit of the heated gas by the opening area of the gas supply unit.
FIG. 1 is a side sectional view showing an example of the finish heat treatment apparatus of the present invention. In FIG. 6, 17 is a heat exchanger, 18 is a gas supply pipe, 19 is a gas exhaust pipe, 50 is a reaction exhaust gas, 51 is a non-oxidizing gas (excluding reaction exhaust gas), 53 is a combustion exhaust gas, The same or corresponding members are denoted by the same reference numerals and description thereof is omitted. FIG. 2 is a side sectional view showing an example of the preheating means used in the present invention. The same or corresponding members as those in FIG. As shown in the figure, the finish heat treatment apparatus of the present invention is a preheating means for preheating the iron powder 7 immediately before entering the furnace 30, on both sides facing each other across the moving path of the iron powder 7 from the hopper 8 to the belt 9. A gas supply unit that discharges heated gas (high-temperature and non-oxidizing gas) 52 from one side into the movement path and a gas discharge unit that collects gas in the movement path from the other side are provided. In FIG. 2, the example which provided the some gas supply pipe | tube 18 as a gas supply part and the some gas discharge pipe 19 as a gas discharge part is shown.
これにより、加熱気体５２は気体供給管１８から鉄粉７の充填層内に放出され、該充填層内で鉄粉７と直接接触して流れながら鉄粉７に熱を与えた後、充填層を挟んで気体供給管１８と相対する気体排出管１９により回収される。該回収された気体は、仕上熱処理装置外に排出される。
この例では、加熱気体５２として、雰囲気ガス排気管１３内を通って流れてくる反応排ガス５０に外部から非酸化性の気体５１を加え、これを熱交換器１７に通して燃焼排ガス５３と間接的に熱交換させ、高温としたものを用いている。
As a result, the heated gas 52 is discharged from the gas supply pipe 18 into the packed bed of iron powder 7, and heat is applied to the iron powder 7 while flowing in direct contact with the iron powder 7 in the packed bed, and then the packed bed Is recovered by a gas exhaust pipe 19 facing the gas supply pipe 18. The recovered gas is discharged out of the finish heat treatment apparatus.
In this example, as the heated gas 52, a non-oxidizing gas 51 is added from the outside to the reaction exhaust gas 50 flowing through the atmosphere gas exhaust pipe 13, and this is passed through the heat exchanger 17 and indirectly with the combustion exhaust gas 53. Heat exchange is performed and the temperature is increased.
また、図３は、予熱手段のもう一つの例を示すものであり、この例では、気体供給管１８の気体放出口側が他の側よりも下方に位置し、かつ気体排出管１９の気体回収口側が他の側よりも下方に位置するように、両管を傾斜させて配置した。これにより、下向きに移動する鉄粉７が気体供給管１８や気体排出管１９に侵入しなくなるので、これらの管の詰まりを有効に防止することができる。 FIG. 3 shows another example of the preheating means. In this example, the gas discharge port side of the gas supply pipe 18 is located below the other side, and the gas recovery of the gas discharge pipe 19 is performed. Both pipes were inclined and arranged so that the mouth side was located below the other side. Thereby, since the iron powder 7 moving downward does not enter the gas supply pipe 18 and the gas discharge pipe 19, clogging of these pipes can be effectively prevented.
また、図４は、予熱手段のもう一つの例を示すものであり、この例では、気体供給管１８の気体放出口および気体排出管１９の気体回収口にそれぞれフィルタ２０を配設した。これにより、図３の例と同様、下向きに移動する鉄粉７が気体供給管１８や気体排出管１９に侵入しなくなるので、これらの管の詰まりを有効に防止することができる。フィルタとしては、耐熱性の点から焼結金属あるいはセラミックスが好ましく用いうる。 FIG. 4 shows another example of the preheating means. In this example, the filters 20 are disposed at the gas discharge port of the gas supply pipe 18 and the gas recovery port of the gas discharge pipe 19, respectively. Thereby, since the iron powder 7 moving downward does not enter the gas supply pipe 18 and the gas discharge pipe 19 as in the example of FIG. 3, clogging of these pipes can be effectively prevented. As the filter, sintered metal or ceramics can be preferably used from the viewpoint of heat resistance.
以上図示した例では気体供給部と気体排出部に管を使用した例を示したが、気体供給部、気体排出部には、その他、上下方向に複数の棚段を設けた構成や、鉄粉の移動経路の側面全体をセラミックフィルター等の多孔質体で形成しても良い。
鉄粉が加熱気体で予熱される移動経路では、気体供給部から気体排出部の間に充填される鉄粉の厚み（層厚）は１０〜３００ｍｍであることが好ましい。鉄粉の厚みが１０ｍｍを下回るような条件では、鉄粉を供給するホッパ内の棚吊り等が生じ易く、ホッパからの排出が不安定となることがある。また、３００ｍｍを超える層厚とすると、鉄粉の移動経路中での通気抵抗が大きくなるため、加熱気体を昇圧する必要があるので、設備的に過大なものとなってしまう。加えて、移動経路内の加熱気体の流通が偏りやすくなり、加熱むらが起りやすい。
In the example illustrated above, an example in which a pipe is used for the gas supply unit and the gas discharge unit has been shown. However, in addition to the gas supply unit and the gas discharge unit, a configuration in which a plurality of shelves are provided in the vertical direction, iron powder The entire side surface of the movement path may be formed of a porous body such as a ceramic filter.
In the movement path in which the iron powder is preheated with heated gas, the thickness (layer thickness) of the iron powder filled between the gas supply unit and the gas discharge unit is preferably 10 to 300 mm. Under the condition that the thickness of the iron powder is less than 10 mm, shelves in the hopper for supplying the iron powder are likely to occur, and the discharge from the hopper may become unstable. On the other hand, if the layer thickness exceeds 300 mm, the ventilation resistance in the moving path of the iron powder increases, so that it is necessary to increase the pressure of the heated gas, resulting in excessive facilities. In addition, the distribution of the heated gas in the movement path tends to be biased, and uneven heating tends to occur.
また、本発明に係る予熱手段では、鉄粉の移動経路に対して交叉する方向へ加熱気体を流すので、加熱気体が鉄粉の供給口から流出する虞がある。そこで、本発明では、加熱気体の供給口、排出口の上端部より上方に予熱対象である鉄粉を積層することで、粉体シールを形成し、この抵抗により加熱気体の流出を防ぐことが好ましい。このためには、鉄粉の供給口よりも上方に設けるホッパ８内の鉄粉の堆積高さを加熱気体の供給口から排出口までの間の距離に対して３倍以上に管理することが好ましい。 Moreover, in the preheating means which concerns on this invention, since heated gas is flowed in the direction which crosses with respect to the movement path | route of iron powder, there exists a possibility that heated gas may flow out from the supply port of iron powder. Therefore, in the present invention, a powder seal is formed by laminating iron powders to be preheated above the upper end of the heated gas supply port and discharge port, thereby preventing the heated gas from flowing out by this resistance. preferable. For this purpose, it is possible to manage the accumulation height of the iron powder in the hopper 8 provided above the iron powder supply port more than three times the distance from the heated gas supply port to the discharge port. preferable.
（比較例１）
比較例１では、図６に示した構成の仕上熱処理装置から予熱器１５を取り除いた構成の仕上熱処理装置を用い、鉄粉の予熱は行わず、以下の条件Ａで鉄粉の仕上熱処理を行った。
条件Ａ：炉内温度＝９５０℃、炉内通過時間＝６０分、鉄粉７の粒径＝１００μm以下、ベルト９上の鉄粉の積層厚さ＝４０ｍｍ
（比較例２）
比較例２では、図６に示した構成の仕上熱処理装置を用い、鉄粉の予熱を行いつつ、前記条件Ａで鉄粉の仕上熱処理を行った。なお、燃焼排ガス温度＝９００℃である。
（実施例）
実施例では、図１に示した構成の仕上熱処理装置を用い、鉄粉の予熱を行いつつ、前記条件Ａで鉄粉の仕上熱処理を行った。なお、燃焼排ガス温度＝９００℃である。
(Comparative Example 1)
In Comparative Example 1, a finish heat treatment apparatus having a configuration in which the preheater 15 is removed from the finish heat treatment apparatus having the configuration shown in FIG. 6 is used, and iron powder finish heat treatment is performed under the following condition A without performing iron powder preheating. It was.
Condition A: Furnace temperature = 950 ° C., Furnace passage time = 60 minutes, Particle size of iron powder 7 = 100 μm or less, Lamination thickness of iron powder on belt 9 = 40 mm
(Comparative Example 2)
In Comparative Example 2, the finish heat treatment of the iron powder was performed under the condition A while preheating the iron powder using the finish heat treatment apparatus having the configuration shown in FIG. In addition, it is combustion exhaust gas temperature = 900 degreeC.
(Example)
In the example, the finish heat treatment of the iron powder was performed under the condition A while preheating the iron powder using the finish heat treatment apparatus having the configuration shown in FIG. In addition, it is combustion exhaust gas temperature = 900 degreeC.
比較例１、２および実施例について、移動するベルト上の鉄粉の積層の厚さ中心位置に温度センサを配置し、炉内での鉄粉温度の時間変化を測定した。その結果を図５に示す。
予熱なしの比較例１では、鉄粉が常温で炉に入ってから２００℃まで昇温するのに７分、５００℃までで１５分、炉内温度の９５０℃に到達するのに３０分かかっている。従来の方法で予熱を行った比較例２では、炉に入った時の鉄粉温度が２００℃になっていたが、炉内温度の９５０℃に到達するのに２８分かかっている。これに対し、本発明の方法で予熱を行った実施例では、予熱手段の出側で鉄粉が５００℃まで昇温し、炉に入った時の鉄粉温度は４５０℃となり、２０分で炉内温度の９５０℃に到達した。
For Comparative Examples 1 and 2 and Examples, a temperature sensor was placed at the center of the thickness of the stack of iron powder on the moving belt, and the time change of the iron powder temperature in the furnace was measured. The result is shown in FIG.
In Comparative Example 1 without preheating, it took 7 minutes for the iron powder to enter the furnace at room temperature to rise to 200 ° C, 15 minutes to 500 ° C, and 30 minutes to reach the furnace temperature of 950 ° C. ing. In Comparative Example 2 in which preheating was performed by the conventional method, the iron powder temperature when entering the furnace was 200 ° C., but it took 28 minutes to reach the furnace temperature of 950 ° C. On the other hand, in the example in which preheating was performed by the method of the present invention, the iron powder was heated to 500 ° C. on the exit side of the preheating means, and the iron powder temperature when entering the furnace was 450 ° C. The furnace temperature reached 950 ° C.
実施例では、比較例１に比べて、炉内温度への到達時間が１０分短くなる。鉄粉を炉内温度に等しい温度に保持する時間は比較例１と同じでよいから、実施例では炉内通過時間を５０分にすることができ、そうすることで、２０％の増産を達成することができる。
上記実施例の条件で図１の気体排出管１９の経路中に排気ブロアを設置して加熱ガスの流速を０．５〜２ｍ/ｓに変更して実験を行い、各条件で、排出ガス中の粉塵量（含塵量）を測定した。測定結果を図８に示す。この結果より、移動層の気体供給部での加熱気体（鉄粉を予熱している加熱ガス）の流速が１ｍ/ｓを超えると排出ガス中の含塵量が増加するので、好ましくない。
In the example, compared with Comparative Example 1, the time to reach the furnace temperature is shortened by 10 minutes. Since the time for holding the iron powder at a temperature equal to the furnace temperature may be the same as in Comparative Example 1, in the example, the furnace transit time can be 50 minutes, and in that way, a 20% increase in production is achieved. can do.
Under the conditions of the above embodiment, an exhaust blower was installed in the path of the gas exhaust pipe 19 in FIG. 1 and the experiment was conducted by changing the flow rate of the heated gas to 0.5-2 m / s. The amount of dust (the amount of dust) was measured. The measurement results are shown in FIG. From this result, it is not preferable that the flow rate of the heating gas (heating gas preheating iron powder) in the gas supply part of the moving bed exceeds 1 m / s because the dust content in the exhaust gas increases.
本発明は、機械部品などを粉末冶金で製造する産業や磁性材料用などの焼結製品を製造する産業、あるいは化学反応用鉄粉、カイロ用鉄粉、脱酸素剤用鉄粉など粉末のままで使用される鉄粉を製造する産業などにおいて、仕上熱処理を行う工程を有するもの全てに利用でき、製造量の調整が容易にできて有利である。 The present invention is an industry that manufactures machine parts and the like by powder metallurgy, an industry that manufactures sintered products for magnetic materials, or powders such as iron powder for chemical reaction, iron powder for warmers, iron powder for oxygen scavengers, etc. In the industry for producing iron powders used in the above, it can be used for all the processes having a finish heat treatment, and the production amount can be easily adjusted, which is advantageous.
１ 仕切壁
２ 第一室
３ 第二室
４ 第三室
５ 雰囲気ガス導入口
６ 雰囲気ガス排出口
７ 鉄粉
８ ホッパ
９ ベルト
１０ ホイール
１１ ラジアントチューブ
１２ 燃焼ガス排気管
１３ 雰囲気ガス排気管
１４ 排気ダクト
１５ 予熱器
１６ 熱交換用パイプ
１７ 熱交換器
１８ 気体供給管
１９ 気体排出管
３０ 炉（水平炉または連続式移動床炉）
２０ フィルタ
５０ 反応排ガス
５１ 非酸化性の気体（反応排ガスを除く）
５２ 加熱気体（高温かつ非酸化性の気体）
５３ 燃焼排ガス
DESCRIPTION OF SYMBOLS 1 Partition wall 2 1st chamber 3 2nd chamber 4 3rd chamber 5 Atmospheric gas introduction port 6 Atmospheric gas discharge port 7 Iron powder 8 Hopper 9 Belt 10 Wheel 11 Radiant tube 12 Combustion gas exhaust pipe 13 Atmospheric gas exhaust pipe 14 Exhaust duct 15 Preheater 16 Heat exchange pipe 17 Heat exchanger 18 Gas supply pipe 19 Gas exhaust pipe 30 Furnace (horizontal furnace or continuous moving bed furnace)
20 Filter 50 Reaction exhaust gas 51 Non-oxidizing gas (excluding reaction exhaust gas)
52 Heating gas (high temperature and non-oxidizing gas)
53 Combustion exhaust gas
Claims (8)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004343552A JP2006009138A (en) | 2004-05-27 | 2004-11-29 | Finish heat treatment method for iron powder and device therefor |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004158015 | 2004-05-27 | ||
| JP2004343552A JP2006009138A (en) | 2004-05-27 | 2004-11-29 | Finish heat treatment method for iron powder and device therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2006009138A true JP2006009138A (en) | 2006-01-12 |
Family
ID=35776697
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2004343552A Pending JP2006009138A (en) | 2004-05-27 | 2004-11-29 | Finish heat treatment method for iron powder and device therefor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2006009138A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007211302A (en) * | 2006-02-10 | 2007-08-23 | Jfe Steel Kk | Finish heat treatment method for iron powder and finish heat treatment device |
| JP2009035793A (en) * | 2007-08-03 | 2009-02-19 | Sumitomo Metal Ind Ltd | Method for manufacturing hot pressed steel sheet member |
| CN102689008A (en) * | 2011-03-23 | 2012-09-26 | 杰富意钢铁株式会社 | Method of finish heat treatment of iron powder and apparatus for finish heat treatment |
| WO2012127760A1 (en) * | 2011-03-23 | 2012-09-27 | Ｊｆｅスチール株式会社 | Method of finish heat treatment of iron powder and apparatus for finish heat treatment |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS528255U (en) * | 1975-07-04 | 1977-01-20 | ||
| JPS5528420A (en) * | 1978-08-16 | 1980-02-29 | Iwao Kuwabara | Temperature adjusting device to pulverulent and granular body |
| JPS6144101A (en) * | 1984-08-07 | 1986-03-03 | Kawasaki Steel Corp | Finish heat treatment of iron and steel powder |
-
2004
- 2004-11-29 JP JP2004343552A patent/JP2006009138A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS528255U (en) * | 1975-07-04 | 1977-01-20 | ||
| JPS5528420A (en) * | 1978-08-16 | 1980-02-29 | Iwao Kuwabara | Temperature adjusting device to pulverulent and granular body |
| JPS6144101A (en) * | 1984-08-07 | 1986-03-03 | Kawasaki Steel Corp | Finish heat treatment of iron and steel powder |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007211302A (en) * | 2006-02-10 | 2007-08-23 | Jfe Steel Kk | Finish heat treatment method for iron powder and finish heat treatment device |
| JP2009035793A (en) * | 2007-08-03 | 2009-02-19 | Sumitomo Metal Ind Ltd | Method for manufacturing hot pressed steel sheet member |
| CN102689008A (en) * | 2011-03-23 | 2012-09-26 | 杰富意钢铁株式会社 | Method of finish heat treatment of iron powder and apparatus for finish heat treatment |
| WO2012127760A1 (en) * | 2011-03-23 | 2012-09-27 | Ｊｆｅスチール株式会社 | Method of finish heat treatment of iron powder and apparatus for finish heat treatment |
| JP2012211383A (en) * | 2011-03-23 | 2012-11-01 | Jfe Steel Corp | Method and apparatus for finish heat treatment of iron powder |
| EP2689871A1 (en) * | 2011-03-23 | 2014-01-29 | JFE Steel Corporation | Method of finish heat treatment of iron powder and apparatus for finish heat treatment |
| EP2689871A4 (en) * | 2011-03-23 | 2014-10-22 | Jfe Steel Corp | Method of finish heat treatment of iron powder and apparatus for finish heat treatment |
| US9321103B2 (en) | 2011-03-23 | 2016-04-26 | Jfe Steel Corporation | Finish heat treatment method and finish heat treatment apparatus for iron powder |
| US9815115B2 (en) | 2011-03-23 | 2017-11-14 | Jfe Steel Corporation | Finish heat treatment method and finish heat treatment apparatus for iron powder |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| RU2109070C1 (en) | Method for producing liquid conversion pig iron from iron ore and device for its embodiment | |
| JPH06501983A (en) | Method of preheating iron-containing reactor feed before processing in a fluidized bed reactor | |
| JP5095082B2 (en) | Method and equipment for transporting fine solids | |
| JPH06172835A (en) | Method and device for reducing iron ore | |
| JP4839869B2 (en) | Finishing heat treatment method and finishing heat treatment apparatus for iron powder | |
| AU747309B2 (en) | Method for continuous removal of oxides from metal | |
| JP2006009138A (en) | Finish heat treatment method for iron powder and device therefor | |
| JP2010159474A (en) | Method of finish heat treatment for iron powder and apparatus therefor | |
| ITUD980212A1 (en) | PROCEDURE AND RELATED APPARATUS FOR THE DIRECT REDUCTION OF IRON OXIDES | |
| JP3342670B2 (en) | Manufacturing method of iron carbide | |
| RU2213787C2 (en) | Process and installation for direct reduction of free-flowing ferrous oxide- containing material | |
| JP2005502790A (en) | Method for reducing particulate material containing metal, especially iron ore | |
| JPS5911649B2 (en) | Method and device for igniting sintered mixtures | |
| JP2006016688A (en) | Finish-heat treatment method for iron powder and apparatus therefor | |
| JPS6240323A (en) | Method and apparatus for producing high temperature briquet for refinery containing no binder | |
| US2331419A (en) | Furnace | |
| JP4727144B2 (en) | Method and apparatus for processing fine particulate feedstocks, particularly containing metals | |
| RU2294894C2 (en) | Method and the installation for production of the thermoextended graphite | |
| US4042226A (en) | Method and apparatus for producing metallic iron pellets | |
| JPH0545642B2 (en) | ||
| JP2001514701A (en) | Treatment method of reducing gas in ore reduction process | |
| JPS6126327Y2 (en) | ||
| RU2652684C1 (en) | Method and device for producing pellets | |
| JPS58110601A (en) | Belt type reducing furnace for metallic powder and operating method thereof | |
| JP2005300068A (en) | Method for control of oxygen concentration and temperature of exhaust gas from rotary hearth reducing furnace |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20070822 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20090827 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20091027 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20091224 |
|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20100914 |