CN112828296A - Preparation method of chromium powder - Google Patents
Preparation method of chromium powder Download PDFInfo
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- CN112828296A CN112828296A CN202011642770.8A CN202011642770A CN112828296A CN 112828296 A CN112828296 A CN 112828296A CN 202011642770 A CN202011642770 A CN 202011642770A CN 112828296 A CN112828296 A CN 112828296A
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- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims abstract description 290
- 238000002360 preparation method Methods 0.000 title claims abstract description 40
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 174
- 239000011651 chromium Substances 0.000 claims abstract description 174
- 239000007788 liquid Substances 0.000 claims abstract description 75
- 238000002844 melting Methods 0.000 claims abstract description 60
- 230000008018 melting Effects 0.000 claims abstract description 59
- 230000006698 induction Effects 0.000 claims abstract description 37
- 230000007246 mechanism Effects 0.000 claims abstract description 25
- 239000011261 inert gas Substances 0.000 claims description 39
- 238000000034 method Methods 0.000 claims description 39
- 239000007789 gas Substances 0.000 claims description 31
- 239000002245 particle Substances 0.000 claims description 21
- 238000010438 heat treatment Methods 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000012216 screening Methods 0.000 claims description 3
- 238000003825 pressing Methods 0.000 claims description 2
- 230000000977 initiatory effect Effects 0.000 claims 1
- 239000000155 melt Substances 0.000 claims 1
- 238000000889 atomisation Methods 0.000 abstract description 12
- 239000012535 impurity Substances 0.000 abstract description 11
- 238000010146 3D printing Methods 0.000 abstract description 4
- 230000008569 process Effects 0.000 description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 239000000843 powder Substances 0.000 description 7
- 230000009471 action Effects 0.000 description 4
- 229910052786 argon Inorganic materials 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 230000002349 favourable effect Effects 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000005484 gravity Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000005204 segregation Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000000635 electron micrograph Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000001746 injection moulding Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 238000004372 laser cladding Methods 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 238000000879 optical micrograph Methods 0.000 description 1
- 238000004663 powder metallurgy Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000007751 thermal spraying Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- 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
-
- 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
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/06—Metallic powder characterised by the shape of the particles
- B22F1/065—Spherical particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y70/00—Materials specially adapted for additive manufacturing
-
- 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
- B22F2009/0824—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 with a specific atomising fluid
-
- 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
- B22F2009/0848—Melting process before atomisation
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Nanotechnology (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
Abstract
The invention discloses a preparation method of chromium powder, relates to the technical field of 3D printing, and aims to solve the problems of high impurity content and low efficiency in the prepared chromium powder. The preparation method of the chromium powder comprises the following steps: a chromium rod is provided. Feeding the chromium rod to a melting start station by using a feeding mechanism. And melting the chromium rod by using a high-frequency induction coil to obtain chromium liquid. And utilizing the feeding mechanism to lift the rest chromium rods from the melting ending station to a blanking starting station. The speed of the pulling is greater than the speed of the feeding. And carrying out atomization treatment on the chromium liquid by using a circular seam type atomization device to obtain chromium powder.
Description
Technical Field
The invention relates to the technical field of 3D printing, in particular to a preparation method of chromium powder.
Background
Through the rapid development of the last 30 years, 3D printing technology has become one of the most interesting advanced manufacturing technologies at present. However, in the metal 3D printing process, the requirements for metal powder are high, such as high sphericity, low oxygen content, narrow particle size distribution, and the like. Therefore, the preparation of high quality metal powder is a key factor for expanding the application of metal powder.
In the prior art, a mechanical crushing method and a spheroidizing method are generally used for crushing chromium blocks to obtain chromium powder, but the prepared chromium powder has high impurity content, large particle size and low efficiency.
Disclosure of Invention
The invention aims to provide a preparation method of chromium powder, which is used for preparing chromium powder with low impurity content, and the prepared chromium powder has small particle size, high efficiency and low cost.
In order to achieve the above object, the present invention provides a method for preparing chromium powder, which is used for preparing chromium powder with low impurity content. The preparation method of the chromium powder provided by the invention comprises the following steps:
a chromium rod is provided.
Feeding the chromium rod to a melting start station by using a feeding mechanism. And when the chromium rod reaches the melting starting station, the chromium rod is in contact with the high-frequency induction coil.
And melting the chromium rod by using a high-frequency induction coil to obtain chromium liquid. When the feeding mechanism feeds the chromium rod from the melting starting station to the melting finishing station, the high-frequency induction coil finishes melting the chromium rod. The heating power of the high-frequency induction coil is 50 kW-200 kW.
And utilizing the feeding mechanism to lift the rest chromium rods from the melting ending station to a blanking starting station. The speed of the pulling is greater than the speed of the feeding.
And carrying out atomization treatment on the chromium liquid by using a circular seam type atomization device to obtain chromium powder. The atomizing device comprises a chromium liquid channel to be atomized, wherein the chromium liquid channel has a Laval structure, and the pressure of atomizing gas of the annular seam type atomizing device is 2 Mpa-8 Mpa.
Compared with the prior art, in the preparation method of the chromium powder, the feeding mechanism drives the chromium rod to be fed from the melting initial station to the melting end station and then pulled from the melting end station to the blanking initial station, and because the chromium rod is already melted when being pulled from the melting end station to the blanking initial station, the pulling speed is higher than the feeding speed, so that the working efficiency can be improved. In addition, because the content of chromium in the chromium rod is high, the melting point of the chromium rod is higher, and therefore, the chromium rod is melted by using a high-frequency induction coil with the heating power of 50 kW-200 kW and the frequency of 50 kHz-300 kHz, the melting of the chromium rod can be accelerated, the superheat degree of chromium liquid is improved, chromium liquid drops with small particle size can be obtained more favorably, the gas content in the chromium liquid can be reduced, the gas content in the prepared chromium powder is reduced, the segregation is reduced, and the impurity content in the prepared chromium powder is reduced. The annular seam type atomizing device is used for atomizing the chromium liquid, so that gas can be guaranteed to gather at one point to act on the chromium liquid, and the particle size of the obtained chromium powder is smaller. Simultaneously, the annular seam formula atomizing device is favorable to the breakage of chromium liquid including treating the atomizing chromium liquid passageway that has the laval structure, has reduced the risk that chromium liquid blockked up atomizing device, and has increased chromium liquid surface wave intensity for the chromium liquid surface produces liquid film or liquid area more easily, more is favorable to the atomizing breakage of chromium liquid, thereby improves work efficiency. And because the viscosity of the chromium liquid is higher, the pressure of the atomizing gas filled in the annular-seam type atomizing device is 2-8 Mpa, the flow velocity of the atomizing gas is increased, and the chromium liquid with high viscosity is easier to atomize.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic partial structural view of a circular seam type atomizing apparatus according to an embodiment of the present invention;
FIG. 2 is a first optical microscope photograph of the chromium powder obtained in example 1;
FIG. 3 is a second optical microscopic view of the chromium powder obtained in example 1;
FIG. 4 is an electron micrograph of chromium powder obtained in example 1;
FIG. 5 is a particle size distribution diagram of the chromium powder obtained in example 1.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise. The meaning of "a number" is one or more unless specifically limited otherwise.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Pure chromium is a material having higher purity and better ductility, and in recent years, spherical chromium powder has been put to industrial use in the field of powder metallurgy, such as the production of chromium-containing alloy materials and the injection molding of small parts. In the field of thermal spraying, the demand of spherical chromium powder is increasing due to the advantages of good fluidity, compact coating texture structure and the like.
The prior chromium powder preparation process comprises a mechanical crushing method and a spheroidizing method. The mechanical crushing method mainly crushes chromium blocks through a crushing machine to obtain chromium powder, but gas containing oxygen and nitrogen elements and solid inclusions are inevitably introduced in the crushing process, so that the purity of the obtained chromium powder is low. The spheroidization method generally adopts radio frequency plasma to partially melt the surface of the non-spherical chromium powder, and utilizes the surface tension of chromium liquid to realize the preparation of the spherical chromium powder, but the spheroidization method firstly needs to obtain the non-spherical chromium powder, and has the disadvantages of multiple preparation procedures, low yield and higher cost.
The embodiment of the invention provides a preparation method of chromium powder, and the chromium powder prepared by the preparation method of chromium powder provided by the embodiment of the invention has the advantages of low impurity content, small particle size, low cost and high efficiency. The preparation method of the chromium powder is applied to chromium powder preparation equipment. The chromium powder preparation equipment can comprise a feeding mechanism, a high-frequency induction coil, an atomization device, an exhaust system, an inert gas supply device and a vacuum system. Wherein, feed mechanism drives the chrome stick and carries out the rotation and upwards or make rectilinear motion downwards along the axial. The high-frequency induction coil is used for carrying out melting treatment on the chromium rod. The atomization device is used for carrying out atomization treatment on the chromium liquid. The exhaust system is used for exhausting gas in the cavity at the lower part of the atomization device. The inert gas supply device is used for supplying inert gas to the chromium powder preparation equipment. The vacuum system is used for vacuumizing the chromium powder preparation equipment. As the chromium powder preparation equipment is the existing equipment, the method is not described in detail.
The preparation method of the chromium powder provided by the embodiment of the invention comprises the following steps:
s200: a chromium rod is provided. It should be noted that, in order to ensure that the impurity content in the prepared chromium powder is low and the stability of the chromium powder preparation process is ensured, the density of the chromium rod is 85-90% of the theoretical density of the chromium rod.
S210: and (4) blanking the chromium rod to a melting starting station by using a feeding mechanism. When the chromium rod reaches the melting initial station, the chromium rod is in contact with the high-frequency induction coil.
In practical application, the feeding mechanism is used for feeding the chromium rod to a melting initial station, and in the feeding process, the chromium rod can rotate at the speed of 40 r/min-200 r/min. When the chromium rod reaches the melting initial station, the chromium rod enters a conical high-frequency induction coil area of the high-frequency induction coil, namely the chromium rod and the high-frequency induction coil are in a contact state.
S220: and melting the chromium rod by using a high-frequency induction coil to obtain chromium liquid. When the feeding mechanism feeds the chromium rod from the melting initial station to the melting end station, the high-frequency induction coil finishes melting the chromium rod. The heating power of the high-frequency induction coil can be 50kW to 200kW, and the heating frequency of the high-frequency induction coil can be 50kHz to 300 kHz.
In practical application, when the chromium rod is in contact with the high-frequency induction coil, the high-frequency induction coil can start to melt the chromium rod to obtain chromium liquid. In order to improve the melting efficiency of the chromium rod, the high-frequency induction coil is a conical high-frequency induction coil, the conical angle of the conical high-frequency induction coil can be 45-120 degrees, the number of turns of the conical high-frequency induction coil can be 3-6 turns, the inner diameter of the top part (the end far away from the circular seam type atomizing device) of the conical high-frequency induction coil can be 45-130 mm, and the inner diameter of the bottom part of the conical high-frequency induction coil can be 25-45 mm. The conical high-frequency induction coil of the high-frequency induction coil can be coaxially arranged with a to-be-atomized chromium liquid channel of the circular seam type atomization device, the coaxiality is less than or equal to 2mm, and the axial distance can be 5-30 mm. It should be noted that the chrome bar can rotate during the feeding process from the melting start station to the melting end station, and the rotation speed can be 40 r/min-200 r/min.
S230: and (4) lifting the rest chromium rod from the melting end station to the blanking start station by using a feeding mechanism. The speed of the pull is greater than the speed of the feed. For example, the speed of the drawing may be 1000mm/min to 2000mm/min, and the speed of the feeding may be 20mm/min to 150 mm/min. In the process that the feeding mechanism lifts and pulls the rest chromium rods from the melting end station to the blanking start station, the chromium rods are not melted, and only the position is changed, so that the working efficiency can be improved by setting the lifting speed to be higher than the feeding speed.
S240: and carrying out atomization treatment on the chromium liquid by using a circular seam type atomization device to obtain chromium powder. The circular seam type atomizing device comprises a chromium liquid channel to be atomized, wherein the chromium liquid channel has a Laval structure, and the pressure of atomizing gas of the circular seam type atomizing device is 2 Mpa-8 Mpa.
Fig. 1 illustrates a schematic partial structure diagram of an annular slot type atomizing device provided by an embodiment of the invention. As shown in FIG. 1, the diameter A of the opening of the chromium liquid channel to be atomized with the Laval structure can be 15 mm-25 mm, the diameter B of the throat part can be 10 mm-15 mm, and the diameter C of the lower opening can be 20 mm-25 mm.
In practical application, the chromium liquid falls into the annular-gap type atomizing device through the opening of the chromium liquid channel to be atomized of the annular-gap type atomizing device. At this time, the inert gas supply device can be used to introduce the atomizing gas into the annular-slot type atomizing device to atomize the chromium liquid, so as to obtain the chromium powder. In order to ensure the crushing strength of the atomizing gas on the chromium liquid and obtain the chromium liquid with smaller particle size, the pressure of the introduced inert gas can be 2 MPa-8 MPa. It should be noted that, in order to ensure the crushing strength of the atomizing gas on the chromium liquid and obtain the chromium liquid with smaller particle size, the temperature of the introduced inert gas can be increased. Specifically, the inert gas introduced into the annular slot type atomizing device can be heated by using a heating device. It will be appreciated that when the temperature of the introduced inert gas is higher than room temperature, the pressure of the introduced inert gas may be adaptively reduced accordingly. For example, when the temperature of the inert gas is 50 to 300 ℃, the pressure of the inert gas introduced may be 2 to 4 Mpa. For another example, when the temperature of the inert gas is room temperature or lower, the pressure of the introduced inert gas may be 5Mpa to 8Mpa to ensure the crushing effect on the chromium solution.
In the preparation method of chromium powder provided by the embodiment of the invention, the feeding mechanism drives the chromium rod to be fed from the melting initial station to the melting end station and then to be lifted from the melting end station to the blanking initial station, and because the chromium rod is already melted when being lifted from the melting end station to the blanking initial station, the lifting speed is higher than the feeding speed, so that the working efficiency can be improved. In addition, the melting point of the chromium rod is higher due to the high content of chromium in the chromium rod, the chromium rod is melted by using a high-frequency induction coil with the heating power of 50-200 kW, the melting of the chromium rod can be accelerated, the superheat degree of chromium liquid is improved, chromium liquid drops with small particle sizes can be obtained more favorably, the gas content in the chromium liquid can be reduced, the gas content in the prepared chromium powder is reduced, the segregation is reduced, and the impurity content in the prepared chromium powder is reduced. The annular seam type atomizing device is used for atomizing the chromium liquid, so that gas can be guaranteed to gather at one point to act on the chromium liquid, and the particle size of the obtained chromium powder is smaller. Simultaneously, the annular seam formula atomizing device is favorable to the breakage of chromium liquid including treating the atomizing chromium liquid passageway that has the laval structure, has reduced the risk that chromium liquid blockked up atomizing device, and has increased chromium liquid surface wave intensity for the chromium liquid surface produces liquid film or liquid area more easily, more is favorable to the atomizing breakage of chromium liquid, thereby improves work efficiency. And because the viscosity of the chromium liquid is higher, the pressure of the atomizing gas filled in the annular-seam type atomizing device is 2-8 Mpa, the flow velocity of the atomizing gas is increased, and the chromium liquid with high viscosity is easier to atomize.
In a possible embodiment, after providing a chromium rod, the method for preparing chromium powder provided by the embodiment of the present invention further includes:
s200-1: along the extending direction of the chromium rod, one end of the chromium rod is processed into a circular truncated cone shape with gradually reduced diameter. For example, one end of the chromium rod may be machined to have a tip taper angle of 45 to 135 ° and a head diameter of 10 to 20 mm. The diameter of the bar stock is 20 mm-105 mm, and the length is 100 mm-1000 mm. Since the high-frequency induction coil in practical application is generally designed to be conical, one end of the chromium rod in the embodiment of the invention can be processed to be round table shape in order to be more fit with the conical coil. And the circular truncated cone-shaped chromium rod can improve the melting efficiency of the chromium rod, and meanwhile, the material utilization rate is higher.
In a possible embodiment, the preparation environment of the chromium powder in the preparation method of chromium powder of the embodiment of the present invention is an inert gas environment, and the gas pressure of the inert gas environment is-0.005 Mpa to 0.005 Mpa. The inert gas environment is used as the preparation environment, so that the content of nitrogen and oxygen impurities in the chromium powder prepared by the preparation method of the chromium powder provided by the embodiment of the invention can be reduced, and the purity of the prepared chromium powder is improved. And when the air pressure of the inert gas environment is in a micro negative pressure state of-0.005 Mpa to 0.005Mpa, the molten chromium liquid can be ensured to rapidly enter a chromium liquid channel to be atomized under the action of the air pressure and the self gravity, and the aggregation of the chromium liquid is reduced, so that the formation of satellite powder is reduced. It should be understood that the inert gas can be one or a combination of nitrogen, argon, helium.
In practical application, the inert gas environment is obtained by vacuumizing chromium powder preparation equipment through a vacuum system, and when the vacuum degree is 10-2When the pressure is between Pa and 10Pa, the controller controls the inert gas supply device to introduce inert gas into the chromium powder preparation equipment to obtain the chromium powder.
In one possible embodiment, the feeding of the chrome bar to the melting start station using the feeding mechanism includes:
s210-1: and (4) blanking the chromium rod from the blanking starting station to the melting starting station by using a feeding mechanism. When the chromium rod reaches the melting initial station, the chromium rod is in contact with the high-frequency induction coil. The speed of blanking is greater than the speed of feeding. So as to reduce the blanking time and improve the working efficiency. The blanking speed can be 1000 mm/min-2000 mm/min. Because the chromium rod is not melted in the blanking process and only the position of the chromium rod is changed, the blanking speed is set to be higher than the feeding speed, and the preparation efficiency of chromium powder can be improved. It should be noted here that the chrome rod can rotate during the blanking process, and the rotation speed can be 40r/min to 200 r/min. The chromium rod can also only rotate in the process from the melting starting station to the melting finishing station so as to ensure that the chromium rod is uniformly melted, and the melted chromium liquid can be driven to fall into the annular-slot type atomizing device as fast as possible by rotation.
In a possible embodiment, after the chromium rod reaches the melting start station, the preparation method of chromium powder provided by the embodiment of the invention further comprises the following steps:
s210-1: and (4) carrying out exhaust treatment on the cavity at the lower part of the circular seam type atomizing device by using an exhaust system.
In practical application, the exhaust system can be used for carrying out exhaust treatment on the cavity at the lower part of the circular seam type atomizing device, so that the air pressure of the cavity at the lower part of the circular seam type atomizing device is basically consistent with the atmospheric pressure. The exhaust system may include an exhaust duct, an exhaust fan, an exhaust valve, and the like. The power of the exhaust fan can be 15 kW-22 kW, the exhaust pressure can be 10000 Pa-20000 Pa, and the exhaust air volume can be 1000m 3/h-2000 m3/h。
S210-2: and introducing inert gas into the cavity at the upper part of the annular seam type atomizing device by using an inert gas supply device. The inlet pressure of the inert gas is 0.1-0.3 Mpa, and the inlet flow is 20m3/h～100m3/h。
In practical application, inert gas with pressure can be introduced into the cavity at the upper part of the circular seam type atomizing device by using the inert gas supply device, so that a certain pressure difference is generated between the upper cavity and the lower cavity of the circular seam type atomizing device, and the molten chromium liquid moves to an atomizing gas gathering point in an accelerating manner under the action of the pressure difference between the upper cavity and the lower cavity of the circular seam type atomizing device, the gravity of the molten chromium liquid and the suction force of the gas outlet of the circular seam type atomizing device, so that the preparation efficiency of the chromium powder is improved. And in the process of the accelerated motion of the chromium liquid, the surface liquid film is more easily peeled off under the turbulent flow action of the atomizing gas and is dispersed into the chromium liquid with smaller particle size.
In an alternative mode, when the feeding mechanism feeds the chromium rod from the melting start station to the melting end station, the preparation method of chromium powder provided by the embodiment of the invention further comprises the following steps:
s220-1: and stopping the exhaust system to exhaust the cavity at the lower part of the circular seam type atomizing device, and stopping the inert gas supply device from supplying inert gas to the cavity at the upper part of the circular seam type atomizing device. When the chromium bar is fed to the end-of-melting station, the bar needs to be replaced. At this time, in order to save cost, the exhaust system and the inert gas supply device may stop operating, wait for the replacement of the chromium rod, and then continue operating according to the above steps S210 and S220.
In a possible implementation manner, after the chromium solution is atomized by using the circular seam type atomization device to obtain chromium powder, the preparation method of chromium powder provided by the embodiment of the present invention further includes:
s240-1: and screening the chromium powder according to the particle size to screen the chromium powder which does not meet the requirement. It should be understood that the requirements for particle size sieving herein may include: when the chromium powder is applied to a laser selection melting process, the grain diameter meeting the requirement is 15-53 mu m, when the chromium powder is applied to a laser cladding process, the grain diameter meeting the requirement is 53-150 mu m, when the chromium powder is applied to a laser injection molding process, the grain diameter meeting the requirement is 0-15 mu m, and the like.
S240-2: preparing the chromium rod by using chromium powder which does not meet the requirement. Because the density of the chromium rod prepared by the method in the embodiment of the invention is 85-90% of the theoretical density of the chromium rod, the method can be directly applied to the preparation method of chromium powder in the embodiment of the invention to prepare chromium powder, thereby saving the cost and reducing the waste of resources.
In an alternative form, the above preparing a chromium bar using an unsatisfactory chromium powder comprises:
S240-2A: and pressing the chromium powder which does not meet the requirements by using a hydraulic device to obtain the chromium rod. Because the hardness of the chromium powder is higher, the pressure of a hydraulic device can be 80-150 tons to ensure that the chromium powder can be pressed to obtain the chromium rod. The effective working area of the hydraulic device is not less than 650mm multiplied by 650mm, and the diameter of the die can be 50 mm-150 mm. It should be understood that the hydraulic device may be a hydraulic machine or other hydraulic device meeting the requirements of the present invention, and the specific type and the like are not specifically limited herein, and are within the optional range as long as the working requirements can be met.
For ease of understanding, the following detailed description will be made with reference to specific examples in conjunction with the method of the present invention.
Example 1
The method comprises the steps of processing a chromium rod raw material with the density of the chromium rod being 85% -90% of the theoretical density of the chromium rod into a chromium rod with the diameter of 40mm, the length of 600mm and one end provided with a circular truncated cone on a machine tool, and then installing the processed chromium rod on a feeding mechanism. And then, carrying out vacuum pumping treatment on the chromium powder preparation equipment by using a vacuum system, and when the vacuum degree meets the requirement, filling argon protective gas into the chromium powder preparation equipment by using an inert gas supply device to obtain an inert gas environment. At the moment, the feeding mechanism drives the chromium rod to feed to a melting initial station at the autorotation speed of 140r/min and the blanking speed of 1000mm/min, an exhaust fan and an exhaust valve are opened to maintain the micro negative pressure state in the system, and meanwhile, an inert gas supply device is used for filling gas into the upper cavity of the circular seam type atomizer, so that the pressure difference between the upper cavity and the lower cavity of the circular seam type atomizer is kept between 0.03MPa and 0.05 MPa. And (3) starting a heating power supply, adjusting the power supply power to 55kW, heating the tip of the chromium rod in a conical high-frequency induction coil, gradually melting the chromium rod into chromium liquid, and converging the chromium liquid to the top of the rod. And introducing high-pressure argon gas into the annular seam type atomizing device by using an inert gas supply device to serve as atomizing gas, wherein the pressure of the high-pressure argon gas is 3.5 MPa. The molten chromium liquid flows into a chromium liquid channel to be atomized below the conical high-frequency induction coil under the action of gravity and the suction force of the circular seam type atomizing device, atomizing gas and the chromium liquid are interacted below an air outlet of the circular seam type atomizing device to break the chromium liquid into small liquid drops, and the small liquid drops are spheroidized and solidified through the surface tension of the small liquid drops in the downward flying process to obtain chromium powder.
Fig. 2 and 3 are optical microscope images of the chromium powder prepared in this example. FIG. 4 is an electron micrograph of the chromium powder prepared in this example. As can be seen from FIGS. 2, 3 and 4, the chromium powder prepared by the method in the embodiment of the invention has good sphericity, almost spherical or nearly spherical shape, and satellite powder is very little, and the adhesion phenomenon between the powder is almost not existed. Fig. 5 is a particle size distribution diagram of chromium powder prepared using the preparation method of chromium powder in this example. As can be seen from FIG. 5, the median particle size of the chromium powder prepared by the method of the present invention is 40 μm to 50 μm, and the particle size distribution of the chromium powder is 0 μm to 130 μm, i.e., the chromium powder prepared by the method of the present invention has a small particle size and a uniform particle size. The detection of the gas content in the chromium powder prepared by the embodiment of the invention shows that the chromium powder in the grain size section of 15-53 mu m has the oxygen content of 350ppm and the nitrogen content of 25ppm, which both meet the standard in the industry, i.e. the chromium powder prepared by the method of the embodiment of the invention has less gas and other impurities, and can reduce segregation. In conclusion, the chromium powder prepared by the method in the embodiment of the invention has good sphericity, less satellite powder, less impurity content and small particle size.
In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A preparation method of chromium powder is characterized by comprising the following steps:
providing a chromium rod;
utilizing a feeding mechanism to feed the chromium rod to a melting starting station; when the chromium rod reaches the melting starting station, the chromium rod is in a contact state with the high-frequency induction coil;
melting the chromium rod by using a high-frequency induction coil to obtain chromium liquid; when the feeding mechanism feeds the chromium rod from a melting starting station to a melting finishing station, the high-frequency induction coil finishes melting the chromium rod; the heating power of the high-frequency induction coil is 50 kW-200 kW, and the frequency of the high-frequency induction coil is 50 kHz-300 kHz;
pulling the rest of the chromium rod from the melting end station to a blanking start station by using the feeding mechanism; the speed of the pulling is greater than the speed of the feeding;
atomizing the chromium liquid by using a circular seam type atomizing device to obtain chromium powder; the annular seam type atomizing device comprises a chromium liquid channel to be atomized, wherein the chromium liquid channel has a Laval structure, and the pressure of atomizing gas of the annular seam type atomizing device is 2 Mpa-8 Mpa.
2. A method of preparing chromium powder as claimed in claim 1 wherein after said providing a chromium bar, the method further comprises:
and processing one end of the chromium rod into a circular table shape with the diameter gradually reduced along the extension direction of the chromium rod.
3. A method for producing chromium powder as claimed in claim 1, wherein the production atmosphere of chromium powder is an inert gas atmosphere having a gas pressure of-0.005 Mpa to 0.005 Mpa.
4. A method of making chromium powder as claimed in claim 1 wherein said feeding said chromium rod to a melting start station with a feed mechanism comprises:
utilizing the feeding mechanism to feed the chromium rod from the feeding starting station to a melting starting station; when the chromium rod reaches the melting starting station, the chromium rod is in a contact state with the high-frequency induction coil; the blanking speed is greater than the feeding speed.
5. A chromium powder production method as claimed in any one of claims 1 to 4 wherein, after the chromium rod reaches the melt initiation station, the chromium powder production method further comprises:
carrying out exhaust treatment on the cavity at the lower part of the circular seam type atomizing device by using an exhaust system;
and introducing inert gas into the cavity at the upper part of the annular seam type atomizing device by using an inert gas supply device, wherein the inlet pressure of the inert gas is 0.1-0.3 Mpa, and the inlet flow is 20m 3/h-100 m 3/h.
6. A chromium powder producing method as claimed in claim 5, wherein when said feeding mechanism feeds said chromium rod from a melting start station to a melting end station, said chromium powder producing method further comprises:
and stopping the exhaust system from exhausting the cavity at the lower part of the circular seam type atomizing device, and stopping the inert gas supply device from supplying inert gas to the cavity at the upper part of the circular seam type atomizing device.
7. The method for preparing chromium powder according to claim 1, wherein after the atomizing of the chromium liquid by the circular seam type atomizing device to obtain chromium powder, the method further comprises:
screening the chromium powder according to the particle size, and screening out the chromium powder which does not meet the requirement;
and preparing the chromium rod by using the chromium powder which does not meet the requirements.
8. A chromium powder preparation method as claimed in claim 7 wherein the density of the chromium rod is from 85% to 90% of the theoretical density of the chromium rod.
9. A method of producing chromium powder according to claim 7 or 8 wherein said producing the chromium bar from the unsatisfactory chromium powder comprises:
and pressing the chromium powder which does not meet the requirements by using a hydraulic device to obtain the chromium rod.
10. A method of producing chromium powder as claimed in claim 9, wherein the pressure of said hydraulic means is 50 to 100 tons.
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Application publication date: 20210525 |