CN100488673C - Method of manufacturing micro and sub-micron iron powder - Google Patents

Method of manufacturing micro and sub-micron iron powder Download PDF

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CN100488673C
CN100488673C CNB2007100636322A CN200710063632A CN100488673C CN 100488673 C CN100488673 C CN 100488673C CN B2007100636322 A CNB2007100636322 A CN B2007100636322A CN 200710063632 A CN200710063632 A CN 200710063632A CN 100488673 C CN100488673 C CN 100488673C
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iron powder
gas
volume content
passivation
nitrogen
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CN101011746A (en
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赵沛
郭培民
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Central Iron and Steel Research Institute
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Abstract

The invention relates to the making of micron and sub-micron metal powder, which firstly ball grinds the oxidized metal powder with heating environment, entering nitrogen or argon gas or their mixture till the content of metal powder <=10 micron, heating it to 200-400deg.C, feeding recovery gas H2 or mixture of H2 and CO to switch nitrogen and argon or their mixture for 30-6000 min, removing the water and CO2, boosting to back to the ball grinding for reaction, inactivating the recovered iron powder. It is low in cost and energy consumption, simple in production process, easy in making, suitable for mass production.

Description

The preparation method of a kind of micron order, submicron order iron powder
Technical field
The invention belongs to field of powder metallurgy preparation, particularly the preparation method of micron order, submicron order iron powder.
Background technology
In the prior art, micron order, submicron order iron powder are one of basic materials of powder metallurgy industry, and the granularity of micron order iron powder is that 1~10 micron, the granularity of submicron order iron powder are 0.1~1 micron.Micron order, submicron order iron powder have bigger specific area and activity, be mainly used in powder metallurgy, manufacturing machine part, produce fields such as friction material, antifriction material, superhard material, magnetic material, lubricant and goods thereof, in recent years, still have broad application prospects at numerous areas such as electromagnetism, biology, medical science, optics.
Tradition iron powder major part is by reducing process production.Reducing process mainly uses gas base or the coal-based pure iron oxide raw material that at high temperature reduces to obtain iron powder.Because the reduction temperature height, the granularity of iron powder is bigger, is difficult to prepare micron order, submicron order iron powder.In addition, atomization also can the production granularity iron powder suitable with reducing process.In order to prepare micron order, submicron order iron powder, adopt following several method usually:
(1) gas phase reduction process
Gas phase reduction process generally is with FeCl 2At high temperature evaporate in molysite, in gas phase, use H 2Or NH 3Make reducing agent and prepare superfine iron powder.Course of reaction is divided into molysite dehydration, evaporation and three steps of vapour phase reduction.α in the gas phase reduction process FeMoment nucleation, nucleation temperature is lower, the iron powder particle diameter is little, size distribution is concentrated; But because of it reacts when the gas phase, course of reaction is meticulous, is subjected to the influence of device etc. easily, and stability is bad, has not yet to see production in enormous quantities.
(2) solid phase reduction method
The solid phase reduction method generally refers at H 2Under the atmosphere, with FeC 2O 42H 2Presoma such as O or FeOOH decomposes, reduction is with the preparation superfine iron powder, reduction temperature 510 ℃ proper, this method requires high to the preparation of presoma, also be difficult at present make on a large scale.
(3) carbonyl process
The preparation method of carbonyl iron dust is generally the ordinary hot decomposition method, promptly allows Fe (CO) 5Directly decompose at a certain temperature and produce iron powder.The laser pyrolysis ratio juris is to utilize the continuous laser current system, with carbonyls Fe (CO) 5Cracking prepares superfine iron powder.But because the carbonyl process system cost is higher, and Fe (CO) 5Be poisonous explosive material, the complicated operation of whole process flow, these have hindered the application popularization of carbonyl process.
(4) vacuum vapor deposition method and sputtering method
Vacuum vapor deposition method is meant and makes evaporation of metal in a vacuum, then with its steam cooling with condense, and obtains the method for ultrafine metal powders.Sputtering method is to utilize sputtering phenomenon to replace evaporation to prepare dystectic super-fine metal powder, can be used for the preparation of metal iron powder.The advantage of these class methods is that the superfine powder size distribution of preparation is concentrated, uniform particles, and vacuum environment was difficult to realize when shortcoming was industrial production.
(5) high-energy ball milling method
High-energy ball milling method is rotation or the vibration that utilizes ball mill, makes hard sphere carry out strong bump, mill and stir metallic iron, powder is pulverized be the method for ultrafine dust.Because metallic iron has cold draw, the preparation micron order, submicron order iron powder difficulty is big, energy consumption is high.
Summary of the invention
The object of the present invention is to provide that a kind of cost is low, energy consumption is low, production process is simple to operate, easy preparation, be applicable to production in enormous quantities, the micron order that the iron powder reducing rate is high, the preparation method of submicron order iron powder.
According to above-mentioned purpose, the principle of the inventive method is:
The preparation method of the micron order that we proposed, submicron order iron powder mainly designs at the deficiency in the existing technology of preparing, for example, High Temperature Gas base and coal base reduction method reduction temperature height, iron particle size is big; High-energy ball milling method is because the distinctive ductility of iron powder is milled down to micron order or submicron order is quite difficult, and power consumption is high.The preparation method of micron order proposed by the invention, submicron order iron powder combines the advantage of gas base reducing process and ball-milling method, and iron oxide belongs to brittle substance, and iron powder belongs to ductile material, so easier micron order or the submicron order of being crushed to of iron oxide.In the iron oxide thinning process, mechanical energy partly is converted into surface energy, crystal boundary energy and the distortion of lattice energy etc. of ferric oxide powder, realizes the energy storage of ferric oxide powder.According to thermodynamics of reactions and dynamic law, the fine powder body of energy storage helps the reduction of reaction temperature, the quickening of reaction speed.Experiment according to us can be reduced to the reaction temperature of the thin iron oxide of gas reduction below 500 ℃, far below the reduction temperature of coal-based method or traditional gas base method.From H 2Reduction Fe 2O 3Thermodynamical equilibrium figure (Fig. 1) as can be known, when temperature was lower than 200 ℃, the utilization rate of hydrogen extremely low (being lower than 1%) was though H in theory 2Still can reducing iron oxides, but efficient is very low, has not had productive value.Therefore, the temperature in the ball mill should be controlled at more than 200 ℃.But too high temperature is too high to device, the material requirement of ball mill, and according to our research, it is relatively more suitable that the temperature in the ball mill is controlled at 200~400 ℃.
CO also is a reducibility gas preferably, and from the thermodynamical equilibrium figure (Fig. 2) of CO reducing iron oxides as seen, under equilibrium condition, CO compares H 2The utilization rate height, but the reaction speed of CO is lower than H under the low temperature 2, CO analyses the trend of carbon in addition under the low temperature simultaneously, hinders the carrying out of reaction.According to our result of study, the volume content percentage of CO is advisable to be lower than 30%.
Because reduction temperature is lower, the utilization rate of gas is still not high, and this meaning is left in the tail gas of ball mill except product H 2O and CO 2Still there are a large amount of H outward, 2, CO.If directly be discharged in the atmosphere, not only cause the waste of the energy, the more important thing is the production cost that has increased iron powder.Therefore, the present invention has designed the H that removes earlier in the tail gas 2O and CO 2, reducibility gas is reused through after the supercharging then.
The reducibility gas that the present invention uses is with H 2, CO is main, but steam, carbon dioxide, oxygen etc. had strict demand, because the carrying out that these gases hinder reduction reaction.According to our experiment, the volume content of steam should be less than 1% in the reducibility gas, and the volume content of oxygen should be less than 0.5%, CO 2Volume content should be less than 5%.Though gas such as nitrogen, argon gas does not participate in reduction reaction, they can dilute the concentration of reducibility gas, and then influence reaction speed, so their volume content is to be advisable less than 30%.
Ball mill apparatus in the actual fabrication process comprises agitating ball mill, vibrator and planetary mills etc.In order to satisfy the requirement of reduction temperature, need these devices are added heating function, can satisfy requirement of the present invention.
Circularly-supercharged equipment, as circulating pump, compressor and air blast series etc., these equipment in the market can satisfy supercharging requirement of the present invention.
According to above-mentioned purpose and method principle, concrete technical scheme of the present invention comprises following concrete steps:
A, pure raw iron oxide material powder put into the ball mill with heating function carry out ball milling, feed nitrogen or argon gas or its two mist simultaneously, until the croci granularity reach≤10 microns;
B, the ball milling built-in temperature is risen to 200-400 ℃, feed reducing gas H simultaneously 2Or H 2Reduce after switching nitrogen or argon gas or its two mist with the CO mist, the time is 30-600min;
C, the tail gas that will reduce are removed water and CO 2After utilize supercharger to feed again to participate in reaction in the ball mill;
D, the iron powder that reduces is carried out Passivation Treatment.The idiographic flow of this Passivation Treatment is to fill in the ball mill of superfine iron powder containing a certain amount of passivation gas feeding; utilize passivation gas and/or nitrogen, water quench means earlier the temperature of high temperature superfine iron powder to be reduced between room temperature~200 ℃; and then logical passivation gas and keep 30min~600min; make the surface of superfine iron powder form one deck protective oxide film; thereby reach the iron powder passivation effect, CO in the used passivation gas in the said method 2Volume content is 50-100%, and the M volume content is 0-50%, and wherein M is any one or any one the above volume content sum in oxygen, CO, steam, nitrogen or the argon gas.
In addition, guarantee atmosphere percentage in the ball mill: volume content percentage≤1% of steam, volume content percentage≤0.5% of oxygen, CO 2Volume content percentage≤5%, volume content percentage≤30% of nitrogen and argon gas, CO volume content percentage<30%, all the other are gas H 2
The 3rd, the volume content of oxygen≤5% in the passivation gas, CO and CO 2The ratio of volume content be 0~0.8, the volume content of steam≤5%, remaining gas do not participate in nitrogen, the argon gas of passivation reaction, its volume content is≤30%.
The present invention has compared with prior art that cost is low, energy consumption is low, production process is simple to operate, easy preparation, be applicable to production in enormous quantities, the advantage that the iron powder reducing rate is high.The percent reduction of the iron powder that is obtained 〉=98%.
In addition, the present invention compared with prior art has good passivation effect, sample and does not have that peroxidating, secondary oxidation rate are lower, the high advantage of degree of metalization of iron powder after the passivation.The advantage of this method is particularly in comparatively apace the surface oxidation of superfine iron powder being become Fe 3O 4Diaphragm, and needn't worry the peroxidating problem, and superfine iron powder is lower because of the secondary oxidation rate that passivation causes.
Description of drawings
Fig. 1 is the thermodynamical equilibrium figure of hydrogen reducing iron oxide.
Fig. 2 is the thermodynamical equilibrium figure of CO reducing iron oxides.
Fig. 3 obtains the shape appearance figure of trickle iron powder for adopting preparation method of the present invention.
The specific embodiment
The enforcement of the inventive method is earlier analytically pure brown iron oxide to be placed in the agitating ball mill with heating function, feeds nitrogen or argon gas the air in the ball mill is caught up with to the greatest extent.The starting agitating ball mill is milled down to brown iron oxide below 10 microns, and the ball milling built-in temperature is risen to 200~400 ℃.Switch nitrogen or argon gas with reducibility gas, begin to reduce, the tail gas that leaves ball mill removes H 2O/CO 2After, after the supercharging of coal gas supercharger, reuse.In the experimentation, hydrogen, CO, CO 2, nitrogen, argon gas, oxygen uses is 99.99% pure gas of commodity production, obtains steam by the steam generator, gas componant is regulated by the multipath gas control system, and uses the variation of online gas analyzer dynamic monitoring gas content.After the iron powder cooling after the reduction, the logical CO that contains 2Passivation gas iron powder is carried out passivation, implementation condition and result of implementation are all listed table 2 (experiment numbers 9~16) in.Except that passivation gas composition and passivation temperature are the variable, each heat of other experiment condition all is consistent, and contains CO 2Passivation gas prepare in advance, passivation time obtains by trial and error method, for example, as the passivation time deficiency, secondary oxidation will soon take place in the iron powder that takes out in air, should prolong passivation time this moment, secondary oxidation can not take place up to the iron powder that takes out in air, analyzes powder composition and pattern then.The inventive method prepares the implementation condition and the result of implementation of micron order, submicron order iron powder and all lists table 1 (experiment numbers 1~8) in.Table 3 is implemented and the comparison that has method now for the inventive method.
Prove that by the embodiment of the invention it is fully feasible using the inventive method production micron order, submicron order iron powder, the reducing rate of iron powder is very high, and the percent reduction of each heat has all surpassed 98%, and the part heat is up to more than 99.5%.
From embodiment as seen, along with the raising of reduction temperature, reaction speed is accelerated, corresponding shortening of reaction time.Because too high temperature is very high to device, the material requirement of ball mill, according to our research, it is relatively more suitable that the temperature in the ball mill is controlled at 200~400 ℃.
Though CO also can reducing iron oxides, find that in an embodiment CO content improves, the recovery time is elongated, this with low temperature under CO to analyse carbon relevant, therefore, it is more suitable that the volume content of CO is controlled at below 30%.
Oxygen, water vapour and carbon dioxide are unfavorable for the carrying out of reduction reaction, can prolong the recovery time.For carrying out smoothly of reduction reaction, the volume content of steam is less than 1% in the reducibility gas, and the volume content of oxygen is less than 0.5%, CO 2Volume content less than 5%.
Though nitrogen, argon gas do not participate in reduction reaction, can diluting reaction substrate concentration, thereby delayed response carry out, the production cycle is prolonged, their volume total content should be lower than 30%.
Table 1 the inventive method prepares the experiment condition and the result of micron order, submicron order iron powder
Figure C200710063632D00091
Table 2 contains CO 2The experiment condition and the result of gas passivation superfine iron powder
Figure C200710063632D00092
Table 3 the inventive method is implemented and the comparison that has method now
Tradition gas base method Coal-based method Atomization Carbonyl process The present invention
The major technique characteristics Logical hydrogen reducing pure iron oxide under the high temperature (as iron scale etc.) High temperature uses smart down.Coal reduction pure iron oxide In the atomising device of atmosphere protection, molten steel is atomized Iron pentacarbonyl is produced superfines through thermal decomposition The pure brown iron oxide of reduction in having the efficient ball mill of heating function
Smelting temperature 700~900 1000~1200 ℃ 1600~1800 ℃ 150~350 200~400 ℃
Product purity High Low High High High
Product granularity Tens of microns Tens of microns Tens of microns Several microns even thinner Several microns even thinner
Raw material sources Pure iron oxide, wide material sources, cost is low Pure iron oxide, wide material sources, cost is low Pure iron, wide material sources, cost is higher than pure iron oxide Iron pentacarbonyl, preparation is complicated, and severe toxicity is arranged, and is with high costs Pure iron oxide, wide material sources, cost is low
Capital equipment Fluid bed Tunnel cave Vacuum smelting furnace, atomising device The preparation equipment of iron pentacarbonyl, the iron pentacarbonyl pyrolysis device Efficient ball mill with heating function
Production cost Low Low Higher Very high Low

Claims (2)

1, the preparation method of a kind of micron order, submicron order iron powder is characterized in that this preparation method comprises following concrete steps:
A, pure raw iron oxide material powder put into the ball mill with heating function carry out ball milling, feed nitrogen or argon gas or its two mist simultaneously, until the croci granularity reach≤10 microns;
B, the ball milling built-in temperature is risen to 200-400 ℃, feed reducing gas H simultaneously 2Or H 2Reduce after switching nitrogen or argon gas or its two mist with the CO mist, the time is 30-600min;
C, the tail gas that will reduce are removed water and CO 2After utilize supercharger to feed again to participate in reaction in the ball mill;
D, the superfine iron powder that reduces is carried out Passivation Treatment, the idiographic flow of this Passivation Treatment is to contain a certain amount of CO 2Passivation gas feed and to fill in the ball mill of superfine iron powder; utilize passivation gas and/or nitrogen, water quench means earlier the temperature of high temperature superfine iron powder to be reduced between room temperature~200 ℃; and then logical passivation gas and keep 30min~600min; make the surface of superfine iron powder form one deck protective oxide film; thereby reach the superfine iron powder passivation effect, CO in the used passivation gas in the said method 2Volume content is 50-100%, and the M volume content is 0-50%, and wherein M is any one or any one the above mixture in oxygen, CO, steam, nitrogen or the argon gas.
2, the preparation method of micron order according to claim 1, submicron order iron powder is characterized in that guaranteeing having atmosphere percentage in the ball mill of heating function: volume content percentage≤1% of steam, volume content percentage≤0.5% of oxygen, CO 2Volume content percentage≤5%, volume content percentage≤30% of nitrogen or argon gas or its two mist, volume content percentage<30% of CO, all the other are H 2
CNB2007100636322A 2007-02-07 2007-02-07 Method of manufacturing micro and sub-micron iron powder Expired - Fee Related CN100488673C (en)

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CN1480539A (en) * 2002-09-04 2004-03-10 雨 赵 Method for preparing ferrous powder by using coke oven gas to deoxidize powder of iron ore
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