瑞典专利SE1750987A1 Method for producing water-atomized metal powder

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_ 53 _ ABSTRACTWater with a temperature of 30 °C or lower is preferably applied to a molten metal stream, the moltenmetal stream is divided and cooled into a metal powder, andthe metal powder is secondarily cooled, whereby a water-atomized metal powder is obtained. In the case of using jetwater for secondary cooling, the water temperature ispreferably 10 °C or lower. In the case of secondary coolingin which a container capable of storing and cooling themetal powder together with cooling water used to divide themolten metal stream or a collision plate capable of coolingthe metal powder by allowing the metal powder to collidetherewith together with the cooling water used to divide themolten metal stream is used, the water temperature ispreferably 30 °C or lower. Performing secondary coolingenables cooling from a transition boiling state or anucleate boiling state which were otherwise a film boilingstate, thereby enabling rapid cooling to be readilyperformed such that the metal powder can be amorphized. Thedivided metal powder is secondarily cooled after thetemperature of the metal powder reaches a temperature notlower than the cooling start temperature necessary for amorphization nor higher than the MHF point.
公开号:SE1750987A1
申请号:SE1750987
申请日:2016-03-14
公开日:2017-10-10
发明作者:Makoto Nakaseko；Naomichi Nakamura；Yukiko Ozaki
申请人:Jfe Steel Corp；
IPC主号:

专利说明:

[5] [0005] Therefore, several methods for quenching a metal powder have been proposed.
[6] [0006] For example, Patent Literature 1 describes a method forproducing a metal powder in such a manner that the coolingrate until solidification is set to 105 K/s or more when themetal powder is obtained by cooling and solidifying moltenmetal by scattering the molten metal. In a techniquedescribed in Patent Literature 1, the above cooling rate isobtained in such a manner that the scattered molten metal isbrought into contact with a coolant stream generated byswirling a coolant along the inner wall of a cylinder. Theflow Velocity of the coolant stream generated by swirlingthe coolant is preferably 5 m/s to 100 m/s.
[7] [0007] Patent Literature 2 describes a method for producing arapidly solidified metal powder. In a technique describedin Patent Literature 2, a coolant is supplied to a coolingcontainer having an inner surface that is a cylindricalsurface from the outside edge of the upper end of acylindrical portion of the cooling container in acircumferential direction and is dropped in such a mannerthat the coolant is swirled along the inner surface of thecylindrical portion, a layered swirl coolant layer having aspace in a central portion thereof is formed by thecentrifugal force due to the swirl, and molten metal is supplied on to the inner circumferential surface of the swirl coolant layer and is rapidly solidified. This allowsa high-quality rapidly solidified metal powder to beobtained with good cooling efficiency.
[8] [0008] Patent Literature 3 describes an apparatus forproducing a metal powder by a gas atomization method. Theapparatus includes a gas jet nozzle for dividing moltenmetal flowing down into molten droplets by ejecting a gasjet and also includes a cooling cylinder including a coolantlayer swirling down along the inner surface thereof. In atechnique described in Patent Literature 3, molten metal isdivided in two stages, with the gas jet nozzle and theswirling coolant layer, respectively, whereby a fine rapidlysolidified metal powder is obtained.
[9] [0009] Patent Literature 4 describes a method for producingfine amorphous metal particles in such a manner that moltenmetal is supplied into a liquid coolant, a vapor film isformed in the coolant so as to cover the molten metal, themolten metal is brought into direct contact with the coolantby disrupting the vapor film formed such that boiling iscaused by spontaneous nucleation, the molten metal israpidly cooled to be amorphized while the molten metal isbeing torn by the pressure wave of the boiling, and the fine amorphous metal particles are thereby obtained. The vapor film covering the molten metal can be disrupted by ultrasonic irradiation or in such a manner that thetemperature of the molten metal supplied to the coolant isadjusted such that, when the molten metal is in directcontact with the coolant, the interfacial temperature is not lower.than the spontaneous nucleation temperature nor higher than the minimum temperature of film boiling.[O0lO1Patent Literature 5 describes a method for producing fine particles in such a manner that the temperature of amolten material is set prior to supplying the moltenmaterial into a liquid coolant in the form of droplets or ajet stream such that the temperature of the molten materialis not lower than the spontaneous nucleation temperature ofthe liquid coolant and a molten state is kept when themolten material is brought into direct contact with theliquid coolant, the difference in relative speed between themolten material supplied in a stream of the liquid coolantand the liquid coolant stream is adjusted to 10 m/s or moresuch that a vapor film formed around the molten material isforcedly disrupted and boiling is caused by spontaneousnucleation, and atomization and solidification by coolingare caused, this enabling a conventionally and otherwisedifficult material to be atomized and amorphized.
[14] [0014] The techniques described in Patent Literatures 1 to 3are such that molten metal is supplied into a coolant layerformed by swirling a coolant and a vapor film formed aroundeach metal particle is removed. However, when thetemperature of the divided metal particles is high, filmboiling is likely to occur in the coolant layer and themetal pgrticles supplied into the coolant layer movetogether with the coolant layer. Therefore, the differencein relative speed between the coolant layer and each metalparticle is small and there is a problem in that it isdifficult to avoid film boiling. [00l5} In the technique described in each of PatentLiteratures 4 to 6, a vapor film covering molten metal isdisrupted by vapor explosion in which the chain oftransitions from film boiling to nucleate boiling occurs,whereby metal particles are atomized and are furtheramorphized. Removing the vapor film due to film boiling byvapor explosion is an effective method. In order to inducevapor explosion by causing the continuous transition fromfilm boiling to nucleate boiling, the surface temperature ofthe metal particles needs to be reduced to the MHF (minimumheat flux) point or lower at the start as is clear from aboiling curve shown in Fig. 6. Fig. 6 is a schematicillustration which is called a boiling curve and which showsthe relationship between the cooling capacity and thesurface temperature of a cooled material in the case where acoolant is liquid. As is clear from Fig. 6, when thesurface temperature of the metal particles is high, coolingto the MHF point corresponds to cooling in a film boilingregion. In cooling in the film boiling region, a vapor filmis present between a cooled surface and cooling water,resulting in weak cooling. Therefore, in the case wherecooling is started from the MHF point or higher for thepurpose of amorphizing a metal powder, there is a problem inthat the cooling rate for amorphization is too small and insufficient.
[16] [0016] In the technique described in each of PatentLiteratures 1 to 6, a metal powder is produced by a gastatomization method. The gas atomization method requires alarge amount of an inert gas for atomization and thereforehas a problem that an increase in production cost is caused.[0017] I The present invention solves these problems with theconventional techniques. It is an object of the presentinvention to provide a method for producing a water~atomizedmetal powder. In the method, a water atomization methodwhich is a method for producing a metal powder at low costis used, a metal powder can be rapidly cooled, and anamorphous metal powder can be obtained.
[19] [0019] Therefore, in order to achieve the above object, theinventors have intensively investigated various factorsaffecting the MHF point in cooling using jet water. As aresult, the inventors have found that the influence of thetemperature and ejection pressure of cooling water issignificant. [0O201 First, results of basic experiments carried out by the inventors are described.[002l}A base material used was a SUS304 steel plate (a size of 20 mm in thickness x 150 mm in width x 150 mm in length).
[22] [0022] Obtained results are shown in Fig. 1.
[23] [0023] As is clear from Fig. 1, in the case where coolingwater, used in a usual water atomization method, having atemperature of 30 °C is ejected at an ejection pressure of 1MPa, the MHF point is about 700 °C in such a state that the cooling water is ejected. However, in the case where cooling water having a temperature of 10 ”C or lower isejected at an ejection pressure of 5 MPa or higher, the MHFpoint is 1,000 °C or higher in such a state that the coolingwater is ejected. That is, the inventors have found thatreducing the temperature (water temperature) of coolingwater to 10 °C or lower and increasing the ejection pressurethereof to 5 MPa or higher increase the MHF point andincrease the temperature of transition from film boiling totransition boiling to 1,000 °C or higher. [00241 In usual, a metal powder obtained by atomizing molten metal has a surface temperature of about 1,000 °C to 1,300 °C. Starting cooling with water~jet cooling withcooling capacity having an MHF point not higher than thesurface temperature of the metal powder results in coolingin a film boiling region with low cooling capacity at thestart of cooling. Therefore, if cooling is started withwater-jet cooling having the MHF point higher than thesurface temperature of a metal powder including a moltenstate, then the cooling of the metal powder can be startedat least from a transition boiling region and cooling ispromoted as compared to that in the film boiling region,thereby enabling the cooling rate of the metal powder to besignificantly increased.
[25] [0025] However, in the usual water atomization method, thetemperature of Cooling water (water jet) injected into amolten metal stream is increased and therefore desired rapidCooling necessary to amorphize a metal powder cannot beachieved. Therefore, the inventors have appreciated that,in addition to cooling (primary Cooling) in which a moltenmetal stream is divided and cooled by applying a water jet(jet water) to the molten metal stream, a divided metalpowder is secondarily cooled.
[26] [0026] The inventors have found that, as secondary cooling, itis effective that fresh Cooling water, preferably Coolingwater with an ejection pressure of 5 MPa or higher and a temperature of 10 °C or lower is further supplied to a metal powder, divided by primary Cooling, including a molten state.
[27] [0027] The inventors have found that the MHF point of secondary Cooling is increased and Cooling capacity is increased in such a manner that a divided, cooled (primarily cooled) metal powder including a molten state is stored in acontainer together with cooling water and is secondarilycooled. Experiment results underlying this finding aredescribed below.
[28] [0028] A base material used was a SU8304 steel plate (a sizeof 20 mm in thickness X 150 mm in width x 150 mm in length).A thermocouple was inserted into the base material from theback surface thereof such that the temperature of a position(lateral center, longitudinal center) 1 mm in depth from thefront surface thereof could be measured. The base materialwas introduced into an oxygen-free furnace and was heated to1,200 °C or higher. The heated base material was taken out.A frame (a width of 148 mm x a length of 148 mm x a heightof 50 mm) was placed on the base material such that the basematerial and the frame formed a container storing coolingwater. Immediately, cooling water was applied to the basematerial from cooling nozzle for atomization in such amanner that the temperature and ejection pressure of waterwere varied, followed by measuring the change in temperatureof the position 1 mm in depth from the front surface. Thecooling capacity during cooling was estimated by calculationfrom obtained temperature data. A boiling curve wasprepared from the obtained cooling capacity. The point at which the cooling capacity increases sharply was judged to _]_5_ be the point of transition from film boiling to transitionboiling, whereby the MHF point was determined.[0029] Obtained results are shown in Fig. 2. Incidentally, thecase with no frame in Fig. l is shown together in Fig. 2.[0030] As is clear from Fig. 2, placing the frame on the basematerial (steel plate) to form the container (with a frame)increases the MHF point as compared to the case with noframe. From Fig. 2, the inventors have found that theincrease of the MHF point is significant when the watertemperature is 30 °C or lower. This is probably becausecooling water in the container is stirred by forming thecontainer (with a frame), a steam film is likely to beremoved by a stream along a cooled surface, and thereforethe cooling capacity is increased. This is also probablybecause shock waves generated when water collides with thesurface of a water pool at high speed facilitate thetransition from film boiling to transition boiling toincrease the cooling capacity. {003l] Considering that the influence of such shock waves iseffective, the inventors have further found that coolingwith high cooling capacity is similarly achieved by providing a collision plate serving as a secondary cooling means on a path where molten metal divided into powder by awater atomization method or a metal powder falls togetherwith cooling water.
[32] [0032] The inventors have found that cooling a metal powder bysuch a cooling method with high cooling capacity enablesquenching, essential to amorphize the metal powder, in acrystallization temperature range to be readily achieved.[0033] The present invention has been completed on the basisof the above findings and further investigations. That is,the present invention is as summarized below. (l) A method for producing a water-atomized metal powderincludes applying water to a molten metal stream, dividingthe molten metal stream into a metal powder, and cooling themetal powder. The metal powder is further subjected tosecondary cooling with cooling capacity having a minimumheat flux point (MHF point) higher than the surfacetemperature of the metal powder in addition to the cooling.The secondary cooling is performed from a temperature rangewhere the temperature of the metal powder after the coolingis not lower than the cooling start temperature necessaryfor amorphization nor higher than the minimum heat fluxpoint (MHF point). (2) In the method for producing the water-atomized metal _17.. powder specified in Item (1), the secondary cooling iscooling in which water ejection is performed using waterdifferent from water used to divide the molten metal stream.(3) In the method for producing the water-atomized metalpowder specified in Item (2), the cooling in which waterejection is performed is cooling in which jet water with atemperature of 10 °C or lower and an ejection pressure of 5MPa or higher is used. (4) In the method for producing the water-atomized metalpowder specified in Item (1), the secondary cooling iscooling by using a container placed on the fall path ofcooling water after the cooling, divided molten metalfalling together with the cooling water, and the metalpowder. (5) In the method for producing the water-atomized metalpowder specified in Item (1), the secondary cooling iscooling by a collision plate placed on the fall path ofcooling water after the cooling, divided molten metalfalling together with the cooling water, and the metalpowder. (6) In the method for producing the water-atomized metalpowder specified in Item (4) or (5), the cooling is suchthat water with a temperature of 30 °C or lower or waterwith a temperature of 30 °C or lower and an ejection pressure of 5 MPa or higher is ejected, the molten metal stream is divided into the metal powder, and the metalpowder is cooled. (7) In the method for producing the water-atomized metalpowder specified in any one of Items (1) to (6), the moltenmetal is composed of an Fe~B alloy or an Fe-Si-B alloy andthe water-atomized metal powder is powder containing 90% ormore of an amorphous metal powder.
[34] [0034]According to the present invention, a metal powder canbe rapidly cooled at 105 K/s or more by a simple method.
[35] [0035] The critical cooling rate for amorphization of an Fe-B _]_9_ alloy (FeæBn) is 1.0 x 106 K/s and that of an Fe-Si-B alloy(FewSi¿0Bn) is 1.8 x 105 K/s as exemplified, the Fe-B alloyand the Fe-Si-B alloy being typical amorphous alloys.According to the present invention, there is an effect thatthe critical cooling rate for amorphization of such valuesis readily ensured.
[36] [0036] [Fig. 1] Fig. 1 is a graph showing the influence of thetemperature and ejection pressure of cooling water on theMHF point.
[38] [0038] A method for melting the metal material need not beparticularly limited and any of melting means, such as anelectric furnace and a vacuum melting furnace, in common use can be used. _21_
[39] [0039] The molten metal is transferred to a container such asa tundish from a melting furnace and is then processed intoa water-atomized metal powder in a water-atomized metalpowder production apparatus. Fig. 3 shows an example of apreferable water~atomized metal powder production apparatusused in the present invention.
[40] [0040] The present invention, which uses a water atomizationmethod, is described with reference to Fig. 3. Fig. 3(a)shows the configuration of an entire plant. Fig. 3(b) showsdetails of a water-atomized metal powder productionapparatus 14.
[41] [0041] Molten metal l is dropped into a chamber 9 from acontainer such as a tundish 3 through a molten metal guidenozzle 4 in the form of a molten metal stream 8. Needlessto say, an inert gas valve ll is opened such that thechamber 9 has an inert gas atmosphere. A nitrogen gas andan argon gas can be exemplified as the inert gas.
[42] [0042] Jet water (water jet) 7 is applied to the fallingmolten metal stream 8 through nozzles 6 attached to a nozzleheader 5 such that the molten metal stream 8 is divided, followed by cooling, whereby a metal powder 8a is obtained. _22_ A position A where the molten metal stream 8 and the jetwater (water jet) 7 are brought into contact with each otheris preferably a position apart from the molten metal guidenozzle 4 at an appropriate distance from the viewpoint thatthe molten metal stream 8 is cooled to near the meltingpoint by heat radiation and the cooling action of the inertgas and the viewpoint that splashes of the jet water 7 areprevented from coming into contact with the molten metalguide nozzle 4.
[43] [0043] In the present ínvention, the ejection pressure ortemperature of the jet water (water jet) 7, which is used todivide the molten metal stream 8, is not particularlylimited as far as the jet water (water jet) 7 may have anejection pressure sufficient to divide the molten metalstream 8. The jet water (water jet) 7 preferably has atemperature of 30 °C or lower or has a temperature of 30 °Cor lower and an ejection pressure of 5 MPa or higher. Inparticular, when the water temperature is higher than 20 °C,the Cooling rate of a metal powder is low and therefore themetal powder cannot be maintained in an amorphous state evenwhen applying a secondary cooling. The water temperature ispreferably 10 °C or lower and more preferably 5 °C or lower.[0044] In the production of the metal powder by water _23_ atomization in the present invention, the jet water 7 isapplied to the molten metal stream 8 at the position A asdescribed above, whereby the molten metal stream is dividedand the divided metal powder (including those in a moltenstate) 8a is cooled (primarily cooled). Furthermore, themetal powder (including those in a molten state) 8a issecondarily cooled at a position B apart from the position Aat an appropriate distance.
[45] [0045] Secondary cooling is preferably performed in such amanner that cooling jet water 21 is ejected as shown in Fig.3(b). The temperature or ejection pressure of the coolingjet water 21, which is used for secondary cooling, is notparticularly limited. In order to achieve cooling to atransition boiling state or cooling to a nucleate boilingstate, cooling water with a temperature of 10 °C or lower ispreferably turned into cooling water with an ejectionpressure of 5 MPa or higher such that the MHF point ishigher than 1,000 °C. The ejection angle of the cooling jetwater 21 is preferably set to 5° to 45° such that thecooling jet water 21 can be uniformly applied to the metalpowder falling together with primary cooling water.Furthermore, the falling metal powder is preferably cooledfrom substantially all directions by arranging about two to eight nozzles 26 for performing secondary cooling. The cooling jet water 21 used may be in a system of water thatis different from one in which the jet water for dividingthe molten metal stream 8 is used.
[46] [0046] When the temperature (water temperature) of the coolingjet water 21 for secondary cooling is higher than 10 °C, theMHF point is low and a desired cooling rate can hardly beensured. Therefore, the temperature (water temperature) ofthe cooling jet water 21 for secondary cooling is preferablylimited to 10 °C or lower. The temperature thereof is morepreferably 8 °C or lower. When the ejection pressure of thecooling jet water 21 for secondary cooling is lower than 5MPa, cooling cannot be performed such that the MHF point isa desired temperature, even if the temperature of coolingwater is 10 °C or lower. Thus, a desired cooling rate canhardly be ensured. Therefore, the ejection pressure of thecooling jet water 21 is preferably limited to 5 MPa or higher. Even if the ejection pressure of the cooling jet water 21 is increased to higher than 10 MPa, the increase of. the MHF point is saturated. Therefore, the ejectionpressure thereof is preferably set to 10 MPa or lower.[0047] The term "desired cooling rate" as used herein refersto the minimum cooling rate at which amorphization can be achieved, that is, an average cooling rate of about 105 K/s _25.. to 106 K/s in a cooling temperature range necessary toprevent crystallization.[0048] The term "cooling temperature range necessary toprevent crystallization" as used herein refers to a rangefrom the cooling start temperature necessary foramorphization to a first crystallization temperature (forexample, 400 °C to 600 °C) that is a cooling stoptemperature. The cooling start temperature necessary foramorphization varies depending on the composition of moltenmetal and may be, for example, 900 °C to 1,100 °C.
[52] [0052] Secondary cooling is preferably set such that thedivided metal powder 8a can be cooled to a transitionboiling state or a nucleate boiling state. Therefore, thestart position of secondary cooling (the position B: theposition of a nozzle for secondary cooling) is preferablyset such that the surface temperature of the water-atomizedmetal powder 8a is not lower than the cooling starttemperature necessary to prevent crystallization nor higherthan the MHF point of secondary cooling. The surfacetemperature of the metal powder 8a can be adjusted byvarying the distance between the atomization position A andthe cooling start position of secondary cooling (theposition B). Therefore, the nozzles 26 for secondarycooling are preferably arranged to be vertically movable.[0053] Secondary cooling is preferably cooling by using a container 41 placed downstream of the position A instead ofCooling by the cooling jet water. An example of the water-atomized metal powder production apparatus in this case isshown in Fig. 4. Fig. 4(a) shows the whole of a plant. Fig.4(b) shows details of the water-atomized metal powderproduction apparatus 14.
[54] [0054] The container 41 is placed at the position B, which isin the fall path of cooling water (atomízing cooling water)used to divide the molten metal stream 8 and subsequentlyused to cool the metal powder, the divided molten metal, andthe metal powder in cooling and which is downstream of theposition A. The position B is a position where the surfacetemperature of the metal powder 8a is not lower than thecooling start temperature necessary to preventcrystallization nor higher than the MHF point, that is, asecondary cooling start position. Since the container 41 isplaced at the position B (preferably such that the positionof the bottom surface of the container corresponds to theposition B), cooling water is stored in the container toform a water pool and is stirred in the container and asteam film on the surface of the metal powder is likely tobe removed by a stream along the surface of the metal powderstored at the same time. It is conceivable that shock waves generated when water collides with the surface of the water _29_ pool formed in the container at high speed facilitate thetransition from film boiling to transition boiling.[0055] The placed container 41 preferably has a sizesufficient to store cooling water (atomizing cooling waterused to divide the molten metal stream 8 and subsequentlyused to cool the metal powder, the divided molten metal,and/or the metal powder. When the container is too large, ashock wave is unlikely to be generated. When the flow rateof atomizing cooling water is about 200 L/min, a containerhaving an inside diameter of about 50 mm to 150 mm and adepth of about 30 mm to 100 mm is enough. The container ispreferably made of metal in terms of strength and may bemade of ceramic.
[58] [0058] The collision plate 42 has only to be capable ofäblocking the fall path of atomizing cooling water, themolten metal, and the metal powder in cooling. The shapethereof is not particularly limited and may probably be adisk shape, a conical shape, an inverted conical shape, orthe like. Since a shape capable of forming a surfaceperpendicular to the fall path is effective in generating ashock wave, an inverted conical shape (Fig. 5(c)) ispreferably avoíded.
[61] [0061] Raw materials were blended (partly containingimpurities is inevitable) such that an Fe-B alloy (FeæB1ﬂwith a composition of 83% Fe-17% B and an Fe-Si-B alloy(Fewsilﬁhl) with a composition of 79% Fe-10% Sie1l% B on anatomic basis were obtained, followed by melting the rawmaterials at about 1,550 °C in a melting furnace 2, wherebyabout 50 kgf of each molten metal was obtained. Theobtained molten metal 1 was slowly cooled to 1,350 °C in themelting furnace 2 and was then poured into a tundish 3. Aninert gas valve 11 was opened in advance such that a chamber9 had a nitrogen gas atmosphere. Before the molten metalwas poured into the tundish 3, cooling water was supplied toa nozzle header 5 from a cooling water tank 15 (a volume of10 m3) by operating a high-pressure pump 17, whereby jetwater (fluid) 7 was ejected from water ejection nozzles 6.Furthermore, cooling water was supplied to nozzles 26 forsecondary cooling from the cooling water tank 15 (a volumeof 10 ma) in such a manner that a high-pressure pump 27 forsecondary cooling water was operated and valves 22 forsecondary cooling water were opened, whereby cooling jetwater 21 was ejected.
[62] [0062] _32- A position A where a molten metal stream 8 was incontact with the jet water T was set to a position 80 mmapart from a molten metal guide nozzle 4. The nozzles 26for secondary cooling were placed at a position B. Theposition B was set to each position 100 mm to 800 mm apartfrom the position A. The ejection pressure of the jet water7 was set to l MPa or 5 MPa and the temperature thereof wasset to 30 °C (rå °C) or 8 °C (i2 °C). The ejection pressureof the cooling jet water 21 used for secondary cooling wasset to 5 MPa and the temperature thereof was set to 20 °C(r2 °C) or 8 °C (i2 °C). The water temperature was adjustedwith a chiller 16 placed outside the cooling water tank 15.[0063] The molten metal l poured into the tundish 3 wasdropped into the chamber 9 through the molten metal guidenozzle 4 to form the molten metal stream 8, which wasbrought into contact with the jet water (fluid) 7 in such amanner that the temperature and ejection pressure of the jetwater (fluid) 7 were varied as shown in Table l, whereby themolten metal stream 8 was divided into a metal powder. Themetal powder was cooled while being mixed with cooling water,was further secondarily cooled with the cooling jet water 21ejected from the nozzles 26 for secondary cooling, and wascollected from a collection port 13. Incidentally, an example in which no secondary cooling was performed was a _33.. comparative example. The surface temperature of the metalpowder before secondary cooling was estimated from resultsof a separately performed primary cooling experiment. TheMHF point of secondary cooling was estimated from aseparately performed experiment and was listed in the table.[0064] After contaminants other than the obtained metal powderwere removed, an amorphous halo peak and a crystallinediffraction peak of the metal powder were measured by X-raydiffractometry.i The degree of crystallinity was determinedfrom the ratio between the integrated intensity of adiffracted X-ray from the amorphous halo peak and that fromthe crystalline diffraction peak. The percentage ofamorphousness (the degree of amorphousness: %) wascalculated from (l - the degree of crystallinity). The casewhere the degree of amorphousness (the degree ofamorphization) was 90% or more was rated ”A” and others wererated "B".
[65] [0065]Obtained results are shown in Table 1.
[66] [0066] 0000000000 0000000000 < 00000000 0000005000 00003 0 5000 000000000 00.0. P:.00 000 00 0000000000050 00.0 000000000 0000000050000000 0000000 000 0000 02 000 x 0.0 00 0000000000050 000 0000000000 0000 000000 000 P.00000 00 0000000000050 ._00 000000000 0000000050000000 0000000 000 0000 0.2 000 x 0.0 00 0000000000050 000 000000000 0000 0000000 000 0, 00050000 0000000500 0 00 0 000 0 0 000 000000000 0000>> 000 0 0 S00050000 000000050 00. 00 0000 0 0 000 000000000 000005 000 0 0 00005000 000000050 00. m0 0000 0 0 000 000000000 0000000 000 0 0 000050000 0000000000 < 00 0000 0 0 000 000000000 000000 0000 0 0 000050000 0>0000>0_ < 0.0 0 000 0 0 000 000000000 0000000 0000 0 0 000050000 00000050 000 00 000 00 0 000 000000000 0000000 000 0 0 .z 000050000 0000000050 < 00 0000 0 0 000 000000000 0000000.. 000 0 0 0000000 000050000 0>0000>00 < 00 0000 0 0 000 000000000 00000.. 000 0 0 000050000 0>0000>00 < 00 000 00 0 000 000000000 000000. 000 00 0 0 00050000 0000000500 0 00 - - - - - - 0 0 0 N 00000000 0000000000 0 00 - - - , - - 00 0 00 0000 000 0 0000 000000 00000 00.0000000 0030000500 00000000 0550 0000 0500000500 0000000000000=00>m 0000. 0500 0000>> 00000000 50 00000000 00005 0000000 0500000500 000000 00000000 .0z000005000 00.02 00%0HM000000%0@0%0000>> 000000000000 00000 0000000 0000000000. 000000000 0000000 0000000500 0000000000 000 00050 00. 000 00005000000 00000000 0000000 >0000o00w 000000000000000000000S 0000000 _35_ {0067] ln every inventive example, the degree of amorphousnessof a water-atomized metal powder is 90% or more. This showsthat in the present invention, a cooling rate of l.8 x l05K/s to 1.0 x 106 K/s or more, which is the critical coolingrate for amorphization, is obtained. However, incomparative examples (Powders No. l and No. 2) in which nosecondary cooling was performed, the degree of amorphousnessis less than 90%.
[68] [0068] In some of inventive examples, the degree ofamorphousness is slightly low. In Powders No. 3 and No. 6,the temperature of cooling jet water for secondary coolingis high. In Powder No. 7, the ejection pressure of jetwater for dividing a molten metal stream is lower than apreferable scope. In Powders No. 8 and No. 9, the coolingstart position of secondary cooling is close to the positionA; hence, the cooling start temperature of secondary coolingis close to the MHF point and the degree of amorphousness isslightly low though the degree of amorphousness is 90% ormore. In Powder No. 10, the cooling start position ofsecondary cooling is far apart from the position A; hence,the time until the start of secondary cooling is long,cooling is slow because the surface temperature of the powder is too low, and the degree of amorphousness is _ 36 _ slightly low though the degree of amorphousness is 90% ormore. In Powder No. 11, the secondary cooling startposition (position B) is too far apart from the position A,the temperature of the metal powder is lower than anecessary cooling start temperature, and it is conceivablethat crystallization proceeded.
[69] [0069] Raw materials were blended (partly containingimpurities is inevitable) such that an Fe-B alloy (FeæB1ﬂwith a composition of 83% Fe~17% B and an Fe-Si-B alloy(FewSi1ﬁﬁ1) with a composition of 79% Fe-10% Si-11% B on anatomic basis were obtained, followed by melting the rawmaterials at about 1,550 °C in a melting furnace 2, wherebyabout 50 kgf of each molten metal was obtained. Theobtained molten metal 1 was slowly cooled to 1,350 °C in themelting furnace 2 and was then poured into a tundish 3. Aninert gas valve 11 was opened in advance such that a chamber9 had a nitrogen gas atmosphere. Before the molten metalwas poured into the tundish 3, cooling water was supplied toa nozzle header 5 from a cooling water tank 15 (a volume of10 m3) by operating a high~pressure pump 17, whereby jet water (fluid) 7 was ejected from water ejection nozzles 6. _37,_ A container 41 made of metal was placed on the fall path ofcooling water and a metal powder, the fall path beingdownstream of a position A, such that cooling water and thedivided metal powder were stored therein after wateratomization. The container 41 made of metal had a size of100 mm in outside diameter x 90 mm in inside diameter X 40mm in depth. 1
[70] [0070] The position A where a molten metal stream 8 was incontact with the jet water 7 was set to a position 80 mmapart from a molten metal guide nozzle 4. The container 41for secondary Cooling was placed at a position B. Theposition B was set to each position (the position of thebottom of a container) 100 mm to 800 mm apart from theposition A. The ejection pressure of the jet water 7 wasset to 3 MPa or 5 MPa and the temperature thereof was set to40 ”C (i2 °C) or 20 °C (i2 °C). The water temperature wasadjusted with a chiller 16 placed outside the cooling watertank 15.
[71] [0071] The molten metal 1 poured into the tundish 3 wasdropped into the chamber 9 through the molten metal guidenozzle 4 to form the molten metal stream 8, which wasbrought into contact with the jet water 7 in such a manner that the temperature and ejection pressure of the jet water _38.. (fluid) 7 were varied as shown in Table 2, whereby themolten metal stream 8 was divided into a metal powder. Thedivided metal powder was mixed with cooling water, fellwhile being cooled, was stored in the container 41, wasstirred in the container 41 together with cooling water, wascooled, and was collected from a collection port 13. Themetal powder stored in the container was exposed to shockwaves generated when falling cooling water collided with thesurface of a water pool in the container at high speed.Incidentally, an example in which no secondary cooling wasperformed was a comparative example. The surfacetemperature of the metal powder before secondary cooling andthe MHF point of secondary Cooling were estimated insubstantially the same manner as that used in (Example 1)and were listed together in the table.
[72] [0072] After contaminants other than the obtained metal powderwere removed, an amorphous halo peak and a crystallinediffraction peak of the metal powder were measured by X-raydiffractometry. The degree of crystallinity was determinedfrom the ratio between the integrated intensity of adiffracted X-ray from the amorphous halo peak and that fromthe crystalline diffraction peak in substantially the samemanner as that used in Example l. The_percentage of amorphousness (the degree of amorphousness: %) was _39- calculated from (l - the degree of crystallinity). The casewhere the degree of amorphousness was 90% or more was rated"A" and the case where the degree of amorphousness was lessthan 90% was rated "B" in substantially the same manner.[0073] IObtained results are shown in Table 2.
[74] [0074] .Éoﬂowoﬂo Éomtmå < cOEmOQ cowwﬂrcowm komm w mocmﬂwzu mfE. Fä.Oo CNG 2 cOﬁwNEEOEm oc* Émwwwomc mozﬂmomacowo tmﬁm 95000 m5 Ucm m2 oO_. X OA. w_. cowmﬁcaoøEm ko» Émmwmom: wwmo 95000 mf. Ta.Oo Omm wo cowmﬂcaooocm oo* Émmwmow: mozﬂmomnEmﬁ tmﬁm mc=ooo m5 Ucm m2 om: X w_ coumNmcaooEm oc”. Émwwmom: Emo mrEOOo me: f. wasoxw maoßmoeoo o wo oooF ooo omšmëoo :o om o m Ymæasoä m>o=mw>:_ < oo oooP oow öEmEQo Ko om o Emmassa. mzoâšs < oo oooﬁ oo* öswëoo ooo om o ofm29:93 wzëmoëoo o mo ovo ooo .wsmëoo omof ow o omQoëwxm mëëwš < wo oooﬁ ooo .wsmëoo ooo om o r omwaëëæ ozmumoëoo o oo - - - - om o :omæwm mmoaëmxw mëmæoëoo o oo omo ooo öemëoo mmo om o ommaEmxw w>==o>E < fo. omo oow .ösoëoo Eo om o omwaëmxw wzëmš < mo omo , oo_. .wemëoo ooo om o Ymmooëoxw mzoåmoëoo o oo oom ooo öEmEoo moo ow o omwa Emä .ﬂšoošs < oo omo ooo omsmëoo ooo om o ,, mmwEEmxw w>_om._moëoo o oo - - - - om o :moooﬁwm _.-mGo Amnâcoomamsm oš _ Amooo Émímäßwoo .Uwﬁoﬁwﬁoë mooowíowﬁoëwo oooomoooëmo ïïowmoomwﬁmoo .wvrmEwm _ Eb oxå =o=o=oooo_ ._ o :Em ošooo o >> _ . :oåwooëoo ozwcetocoo oooowï. öﬁš .mošom:oohwfﬁooëm Aošooo rmëfåoooooo aoocoowo.ö wmöwo oc__ooo.ooou_zomm mšnmä vlàwﬁfi [0075} In every inventive example, the degree of amorphousnessof a water-atomized metal powder is 90% or more. However,in comparative examples (Powders No. 2-1 and No. 2-7) inwhich no secondary Cooling was performed, the degree ofamorphousness is less than 90%. Incidentally, in some ofthe inventive examples that are outside a preferable scopeof the present invention, the degree of amorphousness isslightly low. [0076l In Powders No. 2-3 and No. 2-9, the temperature of jetwater (primary oooling water) for dividing a molten metalstream is higher than the preferable scope, the secondaryCooling start temperature is high, the time of Cooling in afilm boiling region is long, and the degree of amorphousnessis low, less than 90%.
[77] [0077] In Powders No. 2-4 and No. 2~10, the installationposition of the container 41 is close to the position A,which is a position where a molten metal stream is divided,and therefore the cooling start temperature of secondarycooling is high; hence, the degree of amorphousness isslightly low though the degree of amorphousness is 90% ormore. Å [00781 _ 42 _ In Powders No. 2-5 and No. 2-11, the installationposition of the container 41 is far apart from the positionA, which is a position where a molten metal stream isdivided; hence, the time until the start of secondarycooling is long, the surface temperature of the metal powderis low, cooling is slow, and the degree of amorphousness isslightly low though the degree of amorphousness is 90% ormore. In Powders No. 2-6 and No. 2-12, the secondarycooling start position (position B) is too far apart fromthe position A, the temperature of the metal powder is lowerthan a necessary cooling start temperature, crystallizationproceeds, and the degree of amorphousness is less than 90%.(EXAMPLE 3) Each metal powder was produced using a water-atomizedmetal powder production apparatus shown in Fig. 5.
[79] [0079] Raw materials were blended (partly containingimpurities is inevitable) such that an Fe-B alloy (FeæB1ﬂwith a composition of 83% Fe-17% B and an Fe-Si-B alloy(FewSi1&ﬁ1) with a composition of 79% Fe-10% Si-11% B on anatomíc basis were obtained, followed by melting the rawmaterials at about 1,550 °C in a melting furnace 2, wherebyabout 50 kgf of each molten metal was obtained. Theobtained molten metal 1 was slowly cooled to 1,350 °C in the melting furnace 2 and was then poured into a tundish 3. An _43_. inert gas valve ll was opened in advance such that a chamber9 had a nitrogen gas atmosphere. Before the molten metalwas poured into the tundish 3, cooling water was supplied toa nozzle header 5 from a cooling water tank (a volume of l0 mÜ by Operating a high-pressure pump, whereby jet water(fluid) 7 was ejected from water ejection nozzles 6. Acollision plate 42 made of metal was placed on the fall pathof cooling water and a metal powder, the fall path beingdownstream of a position A, such that secondary cooling wasperformed in such a manner that falling cooling water afterwater atomization and the divided metal powder collided withthe collision plate 42. After secondary cooling, the metal powder was collected from a collection port l3.
[80] [0080] The size of the collision plate 42 made of metal wassuch that a surface perpendicular to the falling direction of the metal powder had an area with a diameter of 100 mm o This size is sufficient to allow substantially the wholeof the falling metal powder after water atomization tocollide therewithl[0081] The shape of the collision plate 42 was one of aninverted conical shape (a), a disk shape (b), and a conicalshape (c) as shown in Fig. 5. Needless to say, every shape was formed such that the plane perpendicular to the falling direction of the metal powder had substantially the abovearea.[0082] A position A where a molten metal stream 8 was incontact with the jet water 7 was set to a position 80 mmapart from a molten metal guide nozzle 4. The collisionplate 42 for secondary cooling was placed at a secondarycooling start position (position B). The position B was setto each position 100 mm to 800 mm apart from the position A.The ejection pressure of the jet water 7 was set to 3 MPa or5 MPa and the temperature thereof was set to 40 °C (i2 °C)or 20 °C (i2 °C). The water temperature was adjusted with achiller placed outside the cooling water tank. Incidentally,an example in which no collision plate 42 was placed (nosecondary cooling was performed) was a comparative example.The surface temperature of the metal powder before secondarycooling and the MHF point of secondary cooling wereestimated in substantially the same manner as that used inExample l and were listed together in a table.
[83] [0083] After contaminants other than the obtained metal powderwere removed, an amorphous halo peak and a crystallinediffraction peak of the metal powder were measured by X-raydiffractometry. The percentage of amorphousness (the degree of amorphousness: %) was calculated from the ratio between the integrated intensity of a diffracted X-ray from theamorphous halo peak and that from the crystallinediffraction peak in substantially the same manner as thatused in Example 1. The case where the degree ofamorphousness was 90% or more was rated "A" and the casewhere the degree of amorphousness was less than 90% rated"B" in substantially the same manner.
[84] [0084] Obtained results are shown in Table 3.
[85] [0085] Ém .om 9 _29 d 9% ooﬁæoo m 6,. Em "Som .om 2 EE .o 2.2o ooüæoo m ë Åmvm .om 9 .EE .m Ewa =om2__8 o En. rf:.Eomomšo ﬁuﬁwa < Ešwoo =o=m2Eoom 22.92, m 59,. oëßwä m5 f: .oo oßo 2 oo=m~EQ__oEm .Q ëmmowow: Qoowæoëwo :Em ošoâ m5 Em WE mo x o; 2 oommwzëosm ö.. 9.9 ošooo _9225 m5 F,.oo omo 2 EšmNEEoEo .om rwwooow: wšmowoswo :om oo=o8 2: Em 22 now x o; 2 =o=m~Eo._oEm å 29 oëooo _3226 E» o. wasmxm mëëwoëoo o oo ooow ooo m 22.. E22=oo Nå oo m m ﬁowaemxw m>_o._._.w>c_ < No ooow ooo. m wowa 8.260 oßo oo m mvo29:95 wàcmš < -o ooof oo* m Ewa 22260 Noof om m ïowaemxm mèmæosoo o Nß .mmaš ooo 0 wšo comhšoo ooo om m o fomaemxm o>o=w>5 < No oooo ooo m Ewa E22=oo Noo oo m Nfowaëwxo wëoæwoeoo o oo oå oom w Boa äašoo äo oo. m :oåeﬂm 2,==2,=_ < No 92 0% m 2% äﬁšoo G8 om m x o Eoaëwxw wšmæoëoo m om - - - - om m :omâm oowasmxm šoßmosoo o wo oßo ooo m moma =o_m.___oo ooo om o omwacæxm mzoššs < Fo oßo oow m Boa =o._2=oo Fmo oo o Wowwoemxw wëcw>s < Fo oßo oo m mäa 222200 moo om o oowaemxm wëoäoëoo o No æ2o5 ooo Q Qwa :oašoo moo oo m momasmxw wzëwš < wo oßo ooo n 2.2.. ._0200 ooo om o YoQašßæ mëﬁåeoo m æ Om: 0% m 2% Coaëö 29 3 m wowaëmxm ozëoš < mo oßo ooo w wšo 222260 woo om o _, oowasææ Émowaeoo m om - - - - 8 m ffooäæï EG0 . EÉ 0 GL _ ïmâv=Q29æ>m å ocêoo šo2cooowoa :äwﬂwoe ææwwæﬁeæ mšmﬁmoﬁswo .ozwšoëom HE: :ooowæﬁws . uﬂw ošooo ÉOÉES oooußo: owomš Ešmooëoo .öošom:oomwšñooew ošoov .cmooooww Aofšooo b.2523oo wmoowo . ošooo-o=_o_>_oHm mÅQmÉ
[86] [0086] In every inventive example, the degree of amorphousnessof a water-atomized metal powder is 90% or more. However,in comparative examples (Powders No. 3-1 and No. 3-9) inwhich no secondary cooling was performed, the degree ofamorphousness is less than 90%. Incidentally, in some ofthe inventive examples that are outside a preferable scopeof the present invention, the degree of amorphousness isslightly low. [00871 In Powders No. 3-3 and No. 3-ll, the temperature of jetwater (primary cooling water) for dividing a molten metalstream is higher than the preferable scope, the secondarycooling start temperature is higher than the MHF point, thetime of cooling in a film boiling region is long, and thedegree of amorphousness is low, less than 90%.
[88] [0088] In Powders No. 3-5 and No. 3-13, the shape of thecollision plate 42 is conical (Fig. 5(C)) and is outside thepreferable scope; hence, the effect of secondary cooling islittle and the degree of amorphousness is low. However, thedegree of amorphousness is higher than that of the casewhere no secondary cooling was performed. [00891 In Powders No. 3-6 and No. 3~l4, the installation _48_ position of the collision plate 42 is close to the positionA, which is a position where a molten metal stream isdivided; hence, the cooling start temperature of secondarycooling is high and the degree of amorphousness is slightlylow though the degree of amorphousness is 90% or more.[0090] In Powders No. 3-7 and No. 3-15, the installationposition of the collision plate 42 is far apart from theposition A, which is a position where a molten metal streamis divided; hence, the time until the start of secondaryCooling is long, the surface temperature of the metal powderis low, cooling is slow, and the degree of amorphousness isslightly low though the degree of amorphousness is 90% ormore. In Powders No. 3-8 and No. 3-l6, the cooling start temperature is lower than a necessary cooling start temperature and the degree of amorphousness is less than 90%.
[91] [0091]l Molten metal fmolten metal)2 Melting furnace3 Tundish4 Molten metal guide nozzle5 Nozzle header6 Water ejection nozzles 7 Jet water 8 Molten metal stream Ba Metal powder 9 Chamber lO Hopper ll Inert gas valve 12 Overflow valve 13 Metal powder collection valve 14 Water~atomized metal powder production apparatus15 Cooling water tank 16 Chiller (low-temperature cooling water production apparatus) I 17 High-pressure pump 18 Cooling water pipe 21 Secondary cooling water (cooling jet water) 22 Valves for secondary cooling water 26 Secondary cooling water ejection nozzles 27 High-pressure pump for secondary cooling water28 Cooling water pipe for secondary cooling water41 Container 42 Colliejion plate

权利要求:
Claims (7)
[1] 1. [Claim l] A method for producing a water-atomized metal powder,comprising applwing water to a molten metal stream, dividingthe molten metal stream into a metal powder, and cooling themetal powder, wherein the metal powder is further subjectedto secondary cooling with cooling capacity having a minimumheat flux point (MHF point) higher than the surfacetemperature of the metal powder in addition to the coolingand the secondary cooling is performed from a temperaturerange where the temperature of the metal powder after thecooling is not lower than the cooling start temperaturenecessary for amorphization nor higher than the minimum heatflux point (MHF point).
[2] 2. [Claim 2] The method for producing the water-atomized metalpowder according to Claim l, wherein the secondary coolingis cooling in which water ejection is performed using waterdifferent from water used to divide the molten metal stream.[
[3] 3. Claim 3] The method for producing the water-atomized metalpowder according to Claim 2, wherein the cooling in whichwater ejection is performed is cooling in which jet waterwith a temperature of 10 ”C or lower and än ejection pressure of 5 MPa or higher is used. _51..
[4] 4. [Claim 4] The method for producing the water-atomized metalpowder according to Claim 1, wherein the secondary coolingis cooling by using a container placed on the fall path ofcooling water after the cooling, divided molten metalfalling together with the cooling water, and the metalpowder.
[5] 5. [Claim 5] The method for producing the water~atomized metalpowder according to Claim 1, wherein the secondary coolingis cooling by a collision plate placed on the fall path ofcooling water after the cooling, divided molten metalfalling together with the cooling water, and the metalpowder.
[6] 6. [Claim 6] The method for producing the water-atomized metalpowder according to Claim 4 or 5, wherein the cooling issuch that water with a temperature of 30 °C or lower orwater with a temperature of 30 °C or lower and an ejectionpressure of 5 MPa or higher is ejected, the molten metalstream is divided into the metal powder, and the metalpowder is cooled. {
[7] 7. Claim 7]The method for producing the water-atomized metal powder according to any one of Claims 1 to 6, wherein the molten metal is composed of an Fe-B alloy or an Fe-Si-Balloy and the water-atomized metal powder is powder containing 90% or more of an amorphous metal powder.

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法律状态:

优先权:

申请号 | 申请日 | 专利标题

JP2015068227|2015-03-30|

PCT/JP2016/001412|WO2016157762A1|2015-03-30|2016-03-14|Method for manufacturing water-atomized metal powder|

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