Disclosure of Invention
The invention provides a method for preparing fine powder by close coupling gas atomization for preventing a flow guide pipe from being blocked, which adopts an electromagnetic acceleration vacuum gas atomization device, and metal droplets are refined into powder under the combined action of high-pressure hot air flow and magnetic field force by heating and pressurizing inert gas injection and additional electromagnetic acceleration in the atomization process of molten metal, so that the blockage of an atomization nozzle and the flow guide pipe can be effectively avoided, the continuous production of metal fine powder is realized, and the yield of fine powder is improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a close coupling gas atomization fine powder preparation method for preventing a flow guide pipe from being blocked is realized based on an electromagnetic acceleration vacuum gas atomization device; the electromagnetic acceleration vacuum gas atomization device consists of a smelting furnace, an electromagnetic accelerator and an atomization chamber; an electromagnetic accelerator is arranged at the periphery of the connection part of the smelting furnace and the atomizing chamber;
the gas atomization fine powder preparation method comprises the following steps:
1) smelting metal;
2) pouring the smelted molten metal into a tundish, starting an inert gas heating device, and heating inert gas for atomization;
3) starting an electromagnetic accelerator, setting the current intensity to be 40-50A and the frequency to be 45-50 Hz; the molten metal in the tundish is introduced into the atomizing chamber through the molten metal guide pipe; pressurizing the heated inert gas for atomization by an inert gas pressurizing device, wherein the pressure is 3-4 MPa, then spraying the high-pressure inert gas through an atomizing nozzle, crushing molten metal flowing out of a molten metal guide pipe into fine molten metal droplets, and solidifying the molten metal droplets into spherical powdery particles in the flight process;
4) and collecting the cooled metal powder by a powder collector, and drying and grading to obtain a metal powder finished product.
An induction furnace, a vacuum pumping system and a tundish are arranged in the smelting furnace; an atomizing chamber is arranged below the smelting furnace, and a molten metal guide pipe communicated with the atomizing chamber is arranged at the bottom of the tundish; a plurality of atomizing nozzles are arranged on the outer side of the molten metal guide pipe, and air inlet holes of the atomizing nozzles are connected with the inert gas pipeline; an inert gas heating device and an inert gas pressurizing device are arranged on the inert gas pipeline; and the bottom of the atomizing chamber is provided with a powder collector and an exhaust hole.
The step 1) specifically comprises the following steps: putting a metal raw material into an induction furnace, and starting a vacuum pump in a vacuum pumping system to enable the vacuum degree to reach 1-8 Pa; simultaneously, supplying electricity to heat up, and when the metal raw material in the induction furnace is melted and the air pressure reaches 30-35 kPa, closing the vacuum pump to melt the metal; inert protective gas is introduced in the smelting process.
In the step 2), the aperture of the molten metal draft tube at the bottom of the tundish is 7-10 mm.
The metal raw material comprises pure metal and alloy.
The inert protective gas and the inert gas comprise one or a mixture of helium and argon.
Compared with the prior art, the invention has the beneficial effects that:
the electromagnetic acceleration vacuum gas atomization device is adopted, metal molten drops are refined into powder under the combined action of high-pressure hot air flow and magnetic field force by injecting heated and pressurized inert gas and externally adding electromagnetic acceleration in the atomization process of metal liquid, so that the blockage of an atomization nozzle and a flow guide pipe can be effectively avoided, the continuous production of metal fine powder is realized, and the yield of fine powder is improved.
Detailed Description
The following further describes embodiments of the present invention with reference to the accompanying drawings:
as shown in figure 1, the method for preparing fine powder by close coupling gas atomization for preventing the blockage of the flow guide pipe is realized based on an electromagnetic acceleration vacuum gas atomization device; the electromagnetic acceleration vacuum gas atomization device consists of a smelting furnace 1, an electromagnetic accelerator 3 and an atomization chamber 2; an electromagnetic accelerator 3 is arranged at the periphery of the connection part of the smelting furnace 1 and the atomizing chamber 2;
the gas atomization fine powder preparation method comprises the following steps:
1) smelting metal;
2) pouring the smelted molten metal 4 into a tundish 12, starting an inert gas heating device, and heating inert gas for atomization;
3) starting the electromagnetic accelerator 3, setting the current intensity to be 40-50A and the frequency to be 45-50 Hz; the molten metal 4 in the tundish 12 is introduced into the atomizing chamber 2 through a molten metal draft tube 13; pressurizing the heated inert gas for atomization by an inert gas pressurizing device, wherein the pressure is 3-4 MPa, then spraying the high-pressure inert gas through an atomizing nozzle 14, crushing the molten metal 4 flowing out of a molten metal guide pipe 13 into fine molten metal drops, and solidifying the molten metal drops into spherical powdery particles in the flight process;
4) and collecting the cooled metal powder 5 by a powder collector, and drying and grading to obtain a metal powder finished product.
An induction furnace 11, a vacuum pumping system and a tundish 12 are arranged in the smelting furnace 1; an atomizing chamber 2 is arranged below the smelting furnace 1, and a molten metal draft tube 13 is arranged at the bottom of the tundish 12 and communicated with the atomizing chamber 2; a plurality of atomizing nozzles 14 are arranged on the outer side of the molten metal draft tube 13, and air inlet holes 15 of the atomizing nozzles 14 are connected with an inert gas pipeline; an inert gas heating device and an inert gas pressurizing device are arranged on the inert gas pipeline; the bottom of the atomizing chamber 2 is provided with a powder collector and an exhaust hole 21.
The step 1) specifically comprises the following steps: putting a metal raw material into an induction furnace 11, and starting a vacuum pump in a vacuum pumping system to enable the vacuum degree to reach 1-8 Pa; simultaneously, supplying electricity to heat up, and when the metal raw material in the induction furnace 11 is melted and the air pressure reaches 30-35 kPa, closing the vacuum pump to melt the metal; inert protective gas is introduced in the smelting process.
In the step 2, the aperture of the molten metal draft tube 13 at the bottom of the tundish 12 is 7-10 mm.
The metal raw material comprises pure metal and alloy.
The inert protective gas and the inert gas comprise one or a mixture of helium and argon.
As shown in fig. 2-4, the electromagnetic accelerator of the present invention is a split structure, and comprises 2 semicircular shells 31, an iron core 36, a coil 37 and a connecting member; one end of each of the 2 semicircular shells 31 is connected through a connecting plate 32 and a connecting bolt 33, and the other end is connected through a fastening plate 34 and a fastening bolt 35; the connecting plate 32 is fixedly connected to the semicircular shell 31 by a connecting bolt 33. The semicircular case 31 has a certain thickness, and the inside thereof is composed of a ferrite core 36 and a coil 37 wound around the ferrite core 36. In order to meet the requirement of working in a high-temperature environment, a copper pipe can be used as a coil, and water is introduced into the copper pipe for cooling; or adopting a copper wire soaked with insulating paint as a coil, and introducing water to the outside for cooling; the electromagnetic accelerator may be powered by a two-phase power supply or a three-phase power supply.
The following examples are carried out on the premise of the technical scheme of the invention, and detailed embodiments and specific operation processes are given, but the scope of the invention is not limited to the following examples.
[ example 1 ]
In the embodiment, the method for preparing the fine powder by the close coupling gas atomization of the invention is used for preparing the 27Cr4Mo super ferrite stainless steel fine powder, and the specific process is as follows:
1) according to the chemical composition of 27Cr4Mo super ferritic stainless steel, material calculation and raw material weighing are carried out, and alloy raw materials are put into an induction smelting furnace. Starting a vacuum pump, electrically heating to ensure that the vacuum degree reaches 2Pa, closing a vacuum pumping system when the alloy in the induction smelting furnace is molten and the air pressure reaches 30kPa, and smelting the alloy. Introducing mixed gas of argon and helium as inert protective gas in the smelting process;
2) pouring the molten alloy into a tundish, wherein the diameter of a molten metal guide pipe at the bottom of the tundish is 7mm, and the molten alloy guide pipe is used for controlling the flow of the molten alloy and ensuring the particle size distribution of powder particles; starting an inert gas heating device, and heating inert gas for atomization, wherein the inert gas is mixed gas consisting of helium and argon;
3) and opening a switch of the electromagnetic accelerator, setting the current intensity to be 40A and the frequency to be 50Hz, and introducing the alloy melt into the atomizing chamber through the metal liquid guide pipe. Pressurizing the inert gas to 4MPa, spraying the high-pressure inert gas through an atomizing nozzle, atomizing and crushing the alloy melt into a large number of fine alloy liquid drops, and solidifying the alloy liquid into spherical powder particles in the flight process;
4) and collecting the cooled powder by a powder collector, and then drying and grading to obtain a metal powder finished product.
In the embodiment, the proportion of the prepared 27Cr4Mo super ferrite stainless steel fine powder with the diameter ranging from 0 to 50 mu m is 70%, the phenomena of blockage of an atomizing nozzle and a guide pipe are not generated in the whole atomizing powder preparation process, the continuous production of alloy fine powder is realized, and the yield of the 27Cr4Mo super ferrite stainless steel fine powder is 28%.
[ example 2 ]
In the embodiment, the method for preparing the H13 die steel fine powder by the close coupling gas atomization is adopted to prepare the H13 die steel fine powder, and the specific process is as follows:
1) according to the chemical composition of the H13 die steel, calculating materials and weighing raw materials, and putting the alloy raw materials into an induction smelting furnace. Starting a vacuum pump, electrically heating to ensure that the vacuum degree reaches 2Pa, closing a vacuum pumping system when the alloy in the induction smelting furnace is molten and the air pressure reaches 31kPa, and smelting the alloy. Introducing mixed gas of argon and helium as inert protective gas in the smelting process;
2) pouring the molten alloy into a tundish, wherein the diameter of a molten metal guide pipe at the bottom of the tundish is 8mm, and the molten alloy guide pipe is used for controlling the flow of the molten alloy and ensuring the particle size distribution of powder particles; starting an inert gas heating device, and heating inert gas for atomization, wherein the inert gas is mixed gas consisting of helium and argon;
3) and opening a switch of the electromagnetic accelerator, setting the current intensity to be 45A and the frequency to be 45Hz, and introducing the alloy melt into the atomizing chamber through the metal liquid guide pipe. Pressurizing the inert gas to 4.5MPa, spraying the high-pressure inert gas through an atomizing nozzle, atomizing and crushing the alloy melt into a large number of fine alloy liquid drops, and solidifying the alloy liquid into spherical powder particles in the flight process;
4) and collecting the cooled powder by a powder collector, and then drying and grading to obtain a metal powder finished product.
In the embodiment, the proportion of the prepared H13 die steel fine powder with the diameter ranging from 0 to 50 microns is 52%, the phenomena of blockage of an atomizing nozzle and a guide pipe do not occur in the whole atomizing powder preparation process, the continuous production of alloy fine powder is realized, and the yield of H13 die steel fine powder is 32%.
The chemical composition of the iron-based metal powders described in examples 1 and 2 is shown in table 1.
Comparative example 1 (no electromagnetic accelerator, no heating and pressurizing of inert gas, and the same other process and process parameters as example 1), example 2 (no electromagnetic accelerator, no heating and pressurizing of inert gas, and the same other process and process parameters as example 2), the atomizing nozzle and the flow guide pipe are easily blocked by molten metal, the average blocking rate reaches 30%, and the molten metal blocking phenomenon does not occur in examples 1 and 2.
The iron-based metal powders obtained in examples 1 and 2 and comparative examples 1 and 2 were respectively sieved and weighed to obtain data shown in table 2. It can be seen that the ratio of the diameters of the iron-based metal powders obtained in examples 1 and 2 in the range of 0 to 50 μm is significantly increased by 25% and 10%, respectively, compared to the comparative example, indicating that the overall particle size of the iron-based metal powder prepared according to the method of the present invention is smaller.
TABLE 1 iron-based metal powder chemistry (wt%)
|
C
|
Ni
|
Mo
|
Cr
|
Al
|
Si
|
Mn
|
Nb
|
Ti
|
Example 1
|
0.012
|
2.12
|
3.87
|
27.2
|
0.03
|
0.27
|
0.11
|
0.26
|
0.21
|
Example 2
|
0.32
|
-
|
1.55
|
4.8
|
-
|
1.0
|
0.3
|
-
|
- |
TABLE 2 product particle size distribution (%)
|
0-50μm
|
50-100μm
|
100-200μm
|
>200μm
|
Example 1
|
70%
|
19%
|
5%
|
6%
|
Comparative example 1
|
45%
|
14%
|
26%
|
15%
|
Example 2
|
52%
|
22%
|
19%
|
7%
|
Comparative example 2
|
42%
|
23%
|
27%
|
8% |
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.