CA1040894A - Method of manufacture of metallic powder - Google Patents
Method of manufacture of metallic powderInfo
- Publication number
- CA1040894A CA1040894A CA215,172A CA215172A CA1040894A CA 1040894 A CA1040894 A CA 1040894A CA 215172 A CA215172 A CA 215172A CA 1040894 A CA1040894 A CA 1040894A
- Authority
- CA
- Canada
- Prior art keywords
- metal
- speed
- gas
- jet
- injector
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
- B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
- B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention is concerned with the preparation of a metallic powder from a liquid metal by projection on to a jet of this metal of a gas under pressure, delivered by at least one injector in the form of a jet which causes the metal to burst into fine droplets, the molecules of gas being projected by the injector with a speed which, in the axis of this injector and in a so-called shock-wave zone is initially substantially constant and equal to the local speed of sound and then decreases beyond this zone. The local speed of sound is that calculated under local conditions of temperature and pressure; the injected gas is preferably of the inert type and the invention finds a special but not restrictive application in the production of steel powder.
The present invention is concerned with the preparation of a metallic powder from a liquid metal by projection on to a jet of this metal of a gas under pressure, delivered by at least one injector in the form of a jet which causes the metal to burst into fine droplets, the molecules of gas being projected by the injector with a speed which, in the axis of this injector and in a so-called shock-wave zone is initially substantially constant and equal to the local speed of sound and then decreases beyond this zone. The local speed of sound is that calculated under local conditions of temperature and pressure; the injected gas is preferably of the inert type and the invention finds a special but not restrictive application in the production of steel powder.
Description
- -1~)4()894 The present invention relates to the manufacture of a metallic powder from a liquid metal.
It relates especially to a method of manufacture of a metallic powder by projection, on a jet of liquid metal, of a gas -under pressure delivered by at least one injector in the form of a jet which causes the metal to burst into fine droplets, the mol-ecules of gas being projectèd by the inj~ctor at a speed which, in the axis of this injector, is initially and in a so-called "shock-wave zone" substantially con~tant and equal to the local speed of sound,and decreases beyond this zone.
It is known that it is possible to obtain metallic powder by such a process, known as an "atomization process" by introduc-ing into the upper portion of large vertical receptacles known as "reactors", a jet of liquid metal obtained from a melting fur.nace through the intermediary of a casting.ladle, and subjecting this liquid jet at the inlet of the reactor to a powerful atomization by jets of gas, preferably chemically neutral, which cause the jet of metal to burst into fine droplets which become cooled as -. .
they p~oduce powder, which is collected at the base of the:reactor.
The practical application of this known process results however in a large number of disadvantages, and especially:
- ~n upward movement of the metallic droplets towards the atomization injectors, which can cause the obstruc-tion of these injectors - An excessive bursting of the spray of droplets, some of which strike against the walls of the receptacle before.so~idification;
~k -' ~040894 - A defective form of some of the particles of the pow-der obtained (in the form of needles, flakes, etc) which are troublesome in certain cases and especially in sieving.
This method of atomization by jets of gas furthermore results most frequently in excessively-high consumption of gas.
The essential object of the present invention is to pro-vide a method of manufacture of metallic powder which avoids the above-mentioned drawbacks, while at the same time reducing the consumption of the atomization gases.
Studies carried out by various authors, for example by Abramovitch in his work "Theory of turbulent jets" (MIT Press, 1963), have shown the existence of a so-called "shock-waves zone", the length of which is a function essentially of the nature of the ga~, of the injection pressure and of the injector diameter. These -studies have established that in this shock-wave zone, the speed of the gas is constantly equal, in the axis of the injector, to the local speed of sound, and that it progressively decreases ~~
beyond the said zone. - -By "local speed of sound", there is understood in this case the speed of sound under local conditions of temperature and pressure.
The studies and tests carried out by the authors of the present invention have led to the conclusion that the various dis-advantages referred to above were intimately associated wi~h the existence of a shock-wave zone, and in particular with the posi-tion of the point of impact of the jet of gas on the liquid metal with respect to this zone.
'.
1~4~)894 The above-mentioned object is achieved by a method of manufacture of a metallic powder by projection on to a jet of liquid metal of a gas under pressure delivered from at least one injector in the form of a jet which causes the metal to burst into fine droplets, the molecules of gas being projected from said injector with a speed which, in the axis of said injector, is initially and in a so-called shoc~-wave zone, substantially constant and equal to the local speed of sound, decreasing beyond said zone, in which the distance between the outlet extremity of said injector and the jet of metal is regulated in such manner that, at the moment of impact with the metal, the molecules of gas have a speed V between 50%
and 100% of the local speed of sound.
For this reason, the point of impact of the gaseous molecules is therefore outside the shock-wave zone, which eliminates the undesirable effect of these shock-waves.
The range of speed determined by experience, makes it possible to obtain satisfactory results with regard to the behaviour of the droplets of liquid metal and to the form of the solid particles.
In accordance with a further characteristic feature of the method according to the invention, the above-mentioned dis-tance is regulated in such manner that the speed V is in the vicinity of 90% of the local speed of sound.
The point of impact of the molecules of gas is thus situated in this case slightly beyond the limit of the shock-wave zone. The fact of choosing a speed close to the speed of sound has the advantage of involving a minimum consumption of gas, since a maximum speed of the molecules permits a minimum flow- -rate of gas.
By way of a new industrial product, the invention is also directed to the metallic powder obtained by the .~
, ~ .
above-mentioned method, this powder being characterized by the fact that, on the contrary to the powders obtained by known method, it is practically free from flakes and needles.
The method according to the invention will be illustrated below by examples given purely by way of explanation and without any restrictive character.
In accordance with one form of embodiment, a powder is manufactured from liquid steel by utilizing an injector of 2.5mm.
in diameter, supplied with argon under a under a pressure of 20 bars. me above-mentionned studies by Abramovitch make it pos-sible to conclude that for such an injector and for such a pres-sure of argon, the length of the shock-wave zone is 87.5mm. The ``
distance between the outlet extremity of the nozzle and the jet of liquid metal was then chosen at the value of lOOm~., which corres-ponds to a speed of the gaseous molecules of 238 m/sec., that is to say to a speed slightly less than the local speed of sound in `
argon, which is about 265 m/sec. ` -`
Under these conditions, no substantial rise of the met-allic droplets toward the injectors was observed, and the spread ;
of the spray of droplets was sufficiently moderate to avoid any projection of the droplets on the walls of the receptacle before their solidification. Furthermore, The powder obtained was free `
or practically free from particles in the form of plates or nee- `
dles, as has been shown by microscopic examination.
It has further been found that for the conditions defin-ed above for the speed of the gaseous molecules during the impact with the liquid metal, that is to say when V is less than the loc-al speed of sound, there exists an optimum value of the ratio ~
;: :
between the mass flow-rate of the gas (A) and the mass flow-rate of liquid metal(M), which makes it possible to obtain in particu-lar a ~inimum consumption of atomization gas.
.
.
. : ~ , . . : , .. . , ~ . . . . .. .. ... .
104~894 This optimim value of the ratio A is obtained by re~-pecting the following relation:
(1) log dm = K log A ` ~ , in which: -da M
dm is the mean ponderal diameter of the particles of powder ob-tained;
da is the diameter of the jet of liquid metal to ~e atomized;
We is the We~er number, that is to say:
We = ~ =, in which:
~ is the density of the liquid metal V is the qpeed of each jet of gas upon its impact with the liquid metal;
6 is the superficial energy of the liquid metal.
~ is a coefficient which is slightly variable in depen-dence of the nature of the atomization gas in particular, always comprised between -0.5 and -0.7 and is preferably chosen in the vicinity of -0.57.
According to another form of embodiment of the inven-tion, ~aking account of this optimum value, there was obtained from liquid steel a powder formed of spherical particles having a mean granular size in the vicinity of 140 microns, with values of the ratio A of the mass flow-rate of gas to the mass flow-rate of metal of 0,2 for atomization by means of nitrogen, and 0~3 for atomization by means of argon, utilizing an atomization devi-ce provided with injectors, the characteristics of which (diame-ter, distance from an injector to the point of impact, etc.) are calculated from the above relation (1), these injectors being 4 in number.
,, , , ,, . , ,. , . j . . . , -, .
104~894 The invention is not in any way limited to the produc-tion of steel powders, nor to the use of nitrogen or argon, but is also applicable under the same conditions to other metals or metallic alloys, and also to other gases, although the neutral gases are preferred by reason of their chemical inactivity.
In addition, the orientation of the injectors with respect to the direction of flow of the metal may be in any desired direc-tion, as may also be their number and their distribution.
.. , ,. . , . :, . . ..
It relates especially to a method of manufacture of a metallic powder by projection, on a jet of liquid metal, of a gas -under pressure delivered by at least one injector in the form of a jet which causes the metal to burst into fine droplets, the mol-ecules of gas being projectèd by the inj~ctor at a speed which, in the axis of this injector, is initially and in a so-called "shock-wave zone" substantially con~tant and equal to the local speed of sound,and decreases beyond this zone.
It is known that it is possible to obtain metallic powder by such a process, known as an "atomization process" by introduc-ing into the upper portion of large vertical receptacles known as "reactors", a jet of liquid metal obtained from a melting fur.nace through the intermediary of a casting.ladle, and subjecting this liquid jet at the inlet of the reactor to a powerful atomization by jets of gas, preferably chemically neutral, which cause the jet of metal to burst into fine droplets which become cooled as -. .
they p~oduce powder, which is collected at the base of the:reactor.
The practical application of this known process results however in a large number of disadvantages, and especially:
- ~n upward movement of the metallic droplets towards the atomization injectors, which can cause the obstruc-tion of these injectors - An excessive bursting of the spray of droplets, some of which strike against the walls of the receptacle before.so~idification;
~k -' ~040894 - A defective form of some of the particles of the pow-der obtained (in the form of needles, flakes, etc) which are troublesome in certain cases and especially in sieving.
This method of atomization by jets of gas furthermore results most frequently in excessively-high consumption of gas.
The essential object of the present invention is to pro-vide a method of manufacture of metallic powder which avoids the above-mentioned drawbacks, while at the same time reducing the consumption of the atomization gases.
Studies carried out by various authors, for example by Abramovitch in his work "Theory of turbulent jets" (MIT Press, 1963), have shown the existence of a so-called "shock-waves zone", the length of which is a function essentially of the nature of the ga~, of the injection pressure and of the injector diameter. These -studies have established that in this shock-wave zone, the speed of the gas is constantly equal, in the axis of the injector, to the local speed of sound, and that it progressively decreases ~~
beyond the said zone. - -By "local speed of sound", there is understood in this case the speed of sound under local conditions of temperature and pressure.
The studies and tests carried out by the authors of the present invention have led to the conclusion that the various dis-advantages referred to above were intimately associated wi~h the existence of a shock-wave zone, and in particular with the posi-tion of the point of impact of the jet of gas on the liquid metal with respect to this zone.
'.
1~4~)894 The above-mentioned object is achieved by a method of manufacture of a metallic powder by projection on to a jet of liquid metal of a gas under pressure delivered from at least one injector in the form of a jet which causes the metal to burst into fine droplets, the molecules of gas being projected from said injector with a speed which, in the axis of said injector, is initially and in a so-called shoc~-wave zone, substantially constant and equal to the local speed of sound, decreasing beyond said zone, in which the distance between the outlet extremity of said injector and the jet of metal is regulated in such manner that, at the moment of impact with the metal, the molecules of gas have a speed V between 50%
and 100% of the local speed of sound.
For this reason, the point of impact of the gaseous molecules is therefore outside the shock-wave zone, which eliminates the undesirable effect of these shock-waves.
The range of speed determined by experience, makes it possible to obtain satisfactory results with regard to the behaviour of the droplets of liquid metal and to the form of the solid particles.
In accordance with a further characteristic feature of the method according to the invention, the above-mentioned dis-tance is regulated in such manner that the speed V is in the vicinity of 90% of the local speed of sound.
The point of impact of the molecules of gas is thus situated in this case slightly beyond the limit of the shock-wave zone. The fact of choosing a speed close to the speed of sound has the advantage of involving a minimum consumption of gas, since a maximum speed of the molecules permits a minimum flow- -rate of gas.
By way of a new industrial product, the invention is also directed to the metallic powder obtained by the .~
, ~ .
above-mentioned method, this powder being characterized by the fact that, on the contrary to the powders obtained by known method, it is practically free from flakes and needles.
The method according to the invention will be illustrated below by examples given purely by way of explanation and without any restrictive character.
In accordance with one form of embodiment, a powder is manufactured from liquid steel by utilizing an injector of 2.5mm.
in diameter, supplied with argon under a under a pressure of 20 bars. me above-mentionned studies by Abramovitch make it pos-sible to conclude that for such an injector and for such a pres-sure of argon, the length of the shock-wave zone is 87.5mm. The ``
distance between the outlet extremity of the nozzle and the jet of liquid metal was then chosen at the value of lOOm~., which corres-ponds to a speed of the gaseous molecules of 238 m/sec., that is to say to a speed slightly less than the local speed of sound in `
argon, which is about 265 m/sec. ` -`
Under these conditions, no substantial rise of the met-allic droplets toward the injectors was observed, and the spread ;
of the spray of droplets was sufficiently moderate to avoid any projection of the droplets on the walls of the receptacle before their solidification. Furthermore, The powder obtained was free `
or practically free from particles in the form of plates or nee- `
dles, as has been shown by microscopic examination.
It has further been found that for the conditions defin-ed above for the speed of the gaseous molecules during the impact with the liquid metal, that is to say when V is less than the loc-al speed of sound, there exists an optimum value of the ratio ~
;: :
between the mass flow-rate of the gas (A) and the mass flow-rate of liquid metal(M), which makes it possible to obtain in particu-lar a ~inimum consumption of atomization gas.
.
.
. : ~ , . . : , .. . , ~ . . . . .. .. ... .
104~894 This optimim value of the ratio A is obtained by re~-pecting the following relation:
(1) log dm = K log A ` ~ , in which: -da M
dm is the mean ponderal diameter of the particles of powder ob-tained;
da is the diameter of the jet of liquid metal to ~e atomized;
We is the We~er number, that is to say:
We = ~ =, in which:
~ is the density of the liquid metal V is the qpeed of each jet of gas upon its impact with the liquid metal;
6 is the superficial energy of the liquid metal.
~ is a coefficient which is slightly variable in depen-dence of the nature of the atomization gas in particular, always comprised between -0.5 and -0.7 and is preferably chosen in the vicinity of -0.57.
According to another form of embodiment of the inven-tion, ~aking account of this optimum value, there was obtained from liquid steel a powder formed of spherical particles having a mean granular size in the vicinity of 140 microns, with values of the ratio A of the mass flow-rate of gas to the mass flow-rate of metal of 0,2 for atomization by means of nitrogen, and 0~3 for atomization by means of argon, utilizing an atomization devi-ce provided with injectors, the characteristics of which (diame-ter, distance from an injector to the point of impact, etc.) are calculated from the above relation (1), these injectors being 4 in number.
,, , , ,, . , ,. , . j . . . , -, .
104~894 The invention is not in any way limited to the produc-tion of steel powders, nor to the use of nitrogen or argon, but is also applicable under the same conditions to other metals or metallic alloys, and also to other gases, although the neutral gases are preferred by reason of their chemical inactivity.
In addition, the orientation of the injectors with respect to the direction of flow of the metal may be in any desired direc-tion, as may also be their number and their distribution.
.. , ,. . , . :, . . ..
Claims (3)
1. A method of manufacture of a metallic powder by projection on to a jet of liquid metal of a gas under pressure delivered from at least one injector in the form of a jet which causes the metal to burst into fine droplets, the mole-cules of gas being projected from said injector with a speed which, in the axis of said injector, is initially and in a so-called shock-wave zone, substantially constant and equal to the local speed of sound, decreasing beyond said zone, in which the distance between the outlet extremity of said in-jector and the jet of metal is regulated in such manner that, at the moment of impact with the metal, the molecules of gas have a speed V between 50% and 100% of the local speed of sound.
2. A method as claimed in Claim 1, in which the said distance is regulated in such manner that the speed V is in the vicinity of 90% of the local speed of sound.
3. A method as claimed in Claim 1, in which the ratio between the mass flow-rate A of the gas and the mass flow-rate M of the metal has a value which satisfies the relation:
in which:
- dm = the mean ponderal diameter of the particles of powder which it is desired to obtain;
- da = diameter of the jet of metal;
- K = a coefficient depending on the nature of the gas;
- We = the Weber number, - ? = density of metal - V = speed of the molecules of the gas at the point of impact;
- ? = superficial energy of the liquid metal.
in which:
- dm = the mean ponderal diameter of the particles of powder which it is desired to obtain;
- da = diameter of the jet of metal;
- K = a coefficient depending on the nature of the gas;
- We = the Weber number, - ? = density of metal - V = speed of the molecules of the gas at the point of impact;
- ? = superficial energy of the liquid metal.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7343159A FR2252886B1 (en) | 1973-12-04 | 1973-12-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1040894A true CA1040894A (en) | 1978-10-24 |
Family
ID=9128672
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA215,172A Expired CA1040894A (en) | 1973-12-04 | 1974-12-03 | Method of manufacture of metallic powder |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5086467A (en) |
| CA (1) | CA1040894A (en) |
| CH (1) | CH579959A5 (en) |
| FR (1) | FR2252886B1 (en) |
| GB (1) | GB1472549A (en) |
| IT (1) | IT1025518B (en) |
| SE (1) | SE403979B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4917852A (en) * | 1988-04-29 | 1990-04-17 | Norton Company | Method and apparatus for rapid solidification |
| US5830944A (en) * | 1994-03-31 | 1998-11-03 | Basf Aktiengesellschaft | Preparation of polymeric polyesterols |
-
1973
- 1973-12-04 FR FR7343159A patent/FR2252886B1/fr not_active Expired
-
1974
- 1974-11-07 IT IT29214/74A patent/IT1025518B/en active
- 1974-12-02 CH CH1597974A patent/CH579959A5/xx not_active IP Right Cessation
- 1974-12-03 CA CA215,172A patent/CA1040894A/en not_active Expired
- 1974-12-03 SE SE7415112A patent/SE403979B/en unknown
- 1974-12-04 JP JP49138540A patent/JPS5086467A/ja active Pending
- 1974-12-04 GB GB5251874A patent/GB1472549A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| SE403979B (en) | 1978-09-18 |
| IT1025518B (en) | 1978-08-30 |
| FR2252886B1 (en) | 1976-10-08 |
| FR2252886A1 (en) | 1975-06-27 |
| SE7415112L (en) | 1975-06-05 |
| DE2456682B2 (en) | 1977-05-12 |
| GB1472549A (en) | 1977-05-04 |
| CH579959A5 (en) | 1976-09-30 |
| DE2456682A1 (en) | 1975-06-05 |
| JPS5086467A (en) | 1975-07-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4988464A (en) | Method for producing powder by gas atomization | |
| US4619597A (en) | Apparatus for melt atomization with a concave melt nozzle for gas deflection | |
| US4124377A (en) | Method and apparatus for producing atomized metal powder | |
| US4772315A (en) | Hydrometallurgical process for producing finely divided spherical maraging steel powders containing readily oxidizable alloying elements | |
| US3951577A (en) | Apparatus for production of metal powder according water atomizing method | |
| US5114471A (en) | Hydrometallurgical process for producing finely divided spherical maraging steel powders | |
| Goudar et al. | Effect of atomization parameters on size and morphology of Al-17Si alloy powder produced by free fall atomizer | |
| Gummeson | Modern atomizing techniques | |
| KR20040067608A (en) | Metal powder and the manufacturing method | |
| JP2004183049A (en) | Method and apparatus for producing fine metal powder by gas atomization method | |
| US4818279A (en) | Method and device for the granulation of a molten material | |
| CA1040894A (en) | Method of manufacture of metallic powder | |
| Schade et al. | Atomization | |
| Dixon | Atomizing molten metals—a review | |
| JPH0754019A (en) | Production of powder by multistage fissure and quenching | |
| JP2580616B2 (en) | Method for producing spherical metal powder | |
| JP7328796B2 (en) | METHOD AND APPARATUS FOR MANUFACTURING METAL POWDER | |
| JPH07102307A (en) | Production of flaky powder material | |
| EP1434666B1 (en) | Method for producing metallic powders consisting of irregular particles | |
| JPH06172817A (en) | Production of quenched metal powder | |
| KR100594761B1 (en) | Apparatus and Method for Manufacturing Inflammable metal powder | |
| CA1082413A (en) | Production of metal powder | |
| DE2260868A1 (en) | METAL POWDER MANUFACTURING PROCESS AND DEVICE | |
| JPS63241104A (en) | Production of fine spherical metal powder | |
| Wang et al. | Comparison of gas atomization on A6060 Al alloy powders produced by internal and external mixing type nozzles |