CN104004930A - Magnesium alloy melt refining method - Google Patents

Abstract

The invention relates to a magnesium alloy melt refining method, which belongs to the technical field of alloy melt processing. The method comprises the steps of melting a magnesium alloy billet; inserting a hollow tool head with an inert gas into the magnesium alloy melt in a thermal insulation container; starting a high-intensity sound cavitation system to process the alloy melt, and the like.

Description

A kind of magnesium alloy melt refining method

technical field

The invention belongs to the technical field of metal materials and metallurgy, and in particular relates to a magnesium alloy melt refining method.

Background technique

Magnesium alloys are widely used in automobiles, communication equipment and It has broad application prospects in the electronics industry. However, due to the chemical properties of magnesium alloys and their liveliness, the affinity between magnesium and oxygen is much higher than that between aluminum and oxygen. During the melting process of magnesium alloys, it is very easy to chemically react with oxygen, nitrogen, and water vapor, resulting in a large number of inclusions. Magnesium The content of inclusions during smelting is as high as about 20 times that of aluminum alloy. In addition, due to the great solubility of hydrogen in magnesium alloy melts, the solubility of hydrogen in magnesium melts is two orders of magnitude larger than that in aluminum melts, and the solubility of hydrogen changes greatly during its solidification. In addition, unlike the hydrogen in the aluminum alloy, which is in a free state, there is also a MgH ₂ compound between the hydrogen and the matrix in the magnesium alloy. It is precisely because of the high content of inclusions and hydrogen in the melt of magnesium alloys that not only makes the structure of magnesium alloys loose after solidification, but also seriously affects the mechanical properties, plastic deformation ability and corrosion resistance of magnesium alloys. Yield rate. Therefore, in the magnesium alloy smelting process, effective measures must be taken to control the melt quality in order to improve product quality.

Since the density of the inclusions in the magnesium alloy melt is similar to that of the magnesium melt, most of the inclusions are suspended in the magnesium melt, and it is very difficult to remove the inclusions. In addition, the hydrogen content in magnesium alloys is much greater than that in other metal melts. Therefore, it is much more difficult to remove inclusions and hydrogen in magnesium alloy melt than other metal melts such as steel and aluminum. At present, the industrial smelting of magnesium alloys mainly adopts flux refining method, filter filtration method and gas blowing method to achieve purification, but basically they are operated manually or with simple tools, so the amount of flux used in flux refining It is relatively large, and the pollution is relatively large, and it is easy to produce flux inclusions; when the blowing method is used, the gas consumption is large and the cost is high. The bubbles generated by the air blowing method are larger in size and faster in floating speed, which requires a longer degassing time, and the distribution in each area of the melt is not uniform and cannot fully contact with the entire melt, and the degassing efficiency is low; The French filter is easy to react with the chemically active magnesium melt and cannot be used for a long time. Therefore, based on the above situation, it is necessary to develop an efficient composite purification method for magnesium alloy melts to greatly improve the quality of magnesium alloy melts.

Contents of the invention

Aiming at the problems existing in the existing methods, the invention provides a magnesium alloy melt refining method, which is simple, easy to operate, high refining efficiency, short refining time, less pollution, and can realize magnesium alloy melting and slag and gas removal at the same time.

In order to achieve the above object, a kind of magnesium alloy melt refining method provided by the present invention mainly comprises the following steps:

(1) Melting the magnesium alloy billet put into the thermal insulation container, and standing at a certain temperature after melting;

(2) Insert the hollow tool head which is preheated to the melt temperature equivalent to the inert gas with the set flow rate and pressure into the magnesium alloy melt in the heat preservation container;

(3) Start the flux quantitative supply system after adjusting the gas flow and pressure, and quickly adjust the flux quantitative given control device;

(4) Start the high-intensity acoustic cavitation system, set the acoustic cavitation frequency and power, and process the alloy melt for a period of time by modulating the resonance state of the system;

(5) After the treatment of the magnesium alloy melt, first turn off the high-intensity acoustic cavitation system, then turn off the flux quantitative supply system, then quickly remove the hollow tool head inserted into the melt, and finally turn off the inert gas supply system.

The above-mentioned method for refining a magnesium alloy melt, wherein the standing temperature of the alloy after melting is 50-100° C. above the liquidus line of the alloy.

The above-mentioned method for refining a magnesium alloy melt, wherein the distance between the end face of the hollow tool rod inserted into the melt of the heat preservation container and the bottom of the heat preservation container is 30-500 mm.

The above-mentioned method for refining a magnesium alloy melt, wherein the inert gas fed into the melt is argon or a gas that does not react with the magnesium melt, the gas pressure is 0.02-0.8MPa, and the flow rate is 0.01-5.0L/min .

The above-mentioned method for refining a magnesium alloy melt, wherein the amount of flux fed is 10-3000 g/min.

The above-mentioned method for refining a magnesium alloy melt, wherein the high-intensity acoustic cavitation frequency is 15-50 kHz, and the power is 0.1-10 kW.

The above-mentioned method for refining a magnesium alloy melt, wherein the refining treatment time is 10s-50min.

The above-mentioned method for refining a magnesium alloy melt, wherein after the melt treatment is completed, the cavitation system and the flux supply system should be stopped first, then the tool bar should be lifted out of the melt, and finally the inert gas supply device should be closed.

When using the method described in this application, the present invention also provides a magnesium alloy melt refining device, which consists of four parts: a high-intensity acoustic cavitation system, a flux quantitative supply system, an inert gas supply system and a melt insulation system.

The high-intensity-acoustic cavitation system is composed of a high-intensity-acoustic cavitation generator 7 , a high-intensity-acoustic cavitation transducer, a hollow tool rod 6 , and a tool head 22 . The high-intensity-acoustic cavitation generator 7 is connected with the high-intensity-acoustic cavitation transducer formed by the coil 3 and the magnetostrictive body 9 through the electric wire 8, and a cooling high-intensity-acoustic cavitation transducer is installed outside the high-intensity-acoustic cavitation transducer The water tank 23 has a water inlet pipe 11 and a water outlet pipe 13 on the water tank. The high-intensity sound cavitation transducer is connected to the hollow tool bar 6, and the lower part of the hollow tool bar 6 is connected to the tool head 22. The hollow tool of the tool head 22 is installed when the melt is processed. The rod 6 needs to be inserted into the molten metal 25 in the heat preservation container 24; the flux quantitative supply system includes a funnel-shaped flux reservoir (10) with a moisture-proof function equipped with flux 14 and a flux quantitative given control device 12 connected below it, Among them, the flux quantitative setting control device 12 must be connected to the pipeline 26 that the hollow tool bar 6 is connected to the gas supply system; the inert gas supply system includes an inert gas generator 20, a pressure reducing valve 19, an inert gas that is equipped with a desiccant 17 The drying device 16 and the flow meter 15 for controlling the flow of gas, the relevant devices need to be connected by pipelines; the melt insulation system includes a thermocouple 5, a heat preservation container 24, a heating body 21 and a temperature control cabinet 1, wherein the temperature control cabinet 1 uses a cable 2 is connected with the thermocouple 5 and the heating body 21, and the heat preservation container 24 needs to be fed with protective gas through the ventilation pipe 4 when in use.

In the above-mentioned magnesium alloy melt refining device, the coil of the high-intensity acoustic cavitation transducer is made of copper wire wound with a water-resistant, heat-resistant and voltage-resistant film.

The said magnesium alloy melt refining device, wherein the magnetostrictive body is made of nickel thin plate or high magnetostrictive material.

According to the magnesium alloy melt refining device, the diameter of the hollow pipe inside the hollow tool rod is Φ2mm-Φ20mm.

In the aforementioned magnesium alloy melt refining device, when the lower part of the hollow tool rod is connected to the tool head, the lower end surface of the hollow tool rod must be in close contact with the upper end surface of the tool head.

The magnesium alloy melt refining device described above, wherein holes with a diameter of Φ0.5 mm to Φ8 mm are opened on the lower end wall of the tool head, and the number of holes on the wall is 10 to 300; the diameter of the gas outlet on the end surface of the tool head is Φ0.5 mm to Φ5 mm , the quantity is 1-50 pieces; the diameter of the tool head (6) is Φ20mm-Φ250mm.

The magnesium alloy melt refining device described above, wherein a water tank for cooling the high-intensity acoustic cavitation transducer is installed outside the high-intensity acoustic cavitation transducer, and the temperature of the water in the water tank must be kept between 5°C and 40°C.

Compared with prior art, the beneficial effect of the present invention is:

(1) Compared with other methods in the magnesium alloy melt refining method of the present invention, the cavitation effect of the high-intensity acoustic cavitation system in the melt can make the inert gas and solvent mixture passed into the alloy melt become dispersed and fine , under the combination of sound flow and air flow, the dispersed fine inert gas and solvent mixture are quickly ejected through the holes on the tool head wall, effectively ensuring that all the melt is fully mixed and contacted, which is conducive to the realization of full refining of the melt.

(2) The cavitation effect produced in the melt by the high-intensity acoustic cavitation system of the inventive method can make the inert gas and the solvent mixture passed into the alloy melt become dispersed and small, so that compared with other methods, the same In the case of the amount of solvent and gas used, the contact area and diffusion area are significantly increased; in addition, the cavitation effect makes the inert gas and solvent mixture into the alloy melt become dispersed and fine, which also makes it in the melt The movement speed in the body is greatly reduced, that is, the residence time in the melt becomes longer. Therefore, based on these two points, the method can greatly improve the refining efficiency of the magnesium alloy melt.

(3) The dispersed tiny inert bubbles and the solvent mixture that the inventive method forms during work disperse slowly and float up, which can keep the liquid level stable and not roll over, effectively avoiding the slag entrainment on the surface of the melt; in addition, the evenly floating inert gas is The liquid surface forms a protective layer to effectively prevent the liquid surface from oxidizing and burning.

(4) The method of the present invention is simple, easy to operate, greatly improves the use efficiency of flux and gas, reduces the use of flux and gas, has little pollution and low cost, and is an ideal device for purifying magnesium alloy melts.

(5) The magnesium alloy prepared by the method of the present invention has excellent yield strength, tensile strength and elongation.

Description of drawings

Fig. 1 is the schematic diagram of the device adopting the refining method of the present invention.

Detailed ways

The present invention is further illustrated below by way of examples. It should be understood that the embodiments of the present invention are used to illustrate the present invention rather than limit the present invention. The simple improvements made to the present invention according to the essence of the present invention all belong to the protection scope of the present invention.

Example 1:

Put 5kg of ordinary commercially purchased AZ91 magnesium alloy into the heat preservation container for melting, and after melting, keep it at 678°C for 8 minutes (conventional treatment method); Insert the hollow tool head of the inert gas into the magnesium alloy melt in the heat preservation container; start the flux quantitative supply system after adjusting the gas flow and pressure, and quickly adjust the flux quantitative setting control device; start the high-intensity sound cavitation system, set the sound Cavitation frequency and power, the system modulates the resonance state to process the alloy melt for a period of time; after the treatment of the magnesium alloy melt, first turn off the high-intensity acoustic cavitation system and then turn off the flux quantitative supply system, and then quickly insert the magnesium alloy into the melt The hollow tool head is removed and finally the inert gas supply system is turned off.

The relevant parameters of this embodiment are as follows: the diameter of the tool head is 30mm, and the hole with a diameter of 1.0mm is opened on the lower end wall, and the number of holes on the wall is 10; the diameter of the air outlet on the end surface of the tool head is 0.8mm, and the number is 3; The distance between the end surface of the hollow tool rod in the melt of the heat preservation container and the bottom of the heat preservation container is 50mm; the inert gas fed into the melt is argon, the gas pressure is 0.08MPa, and the flow rate is 1.2L/min; the amount of flux fed is 10g/min min; the high-intensity acoustic cavitation frequency is 20kHz, and the power is 800W; after 3 minutes of treatment under the above parameters. According to stop the sound cavitation system and flux supply system first, then lift the tool head out of the melt, and finally close the inert gas supply device. The solidified alloy was then tested.

Compared with the conventional treatment method, the purification effect of the AZ91 magnesium alloy melt processed by the method of the present invention is that the hydrogen content is reduced from 31.6ml/100g to 8.9ml/100g during the conventional treatment, and the degassing rate reaches about 71.8%; the slag discharge rate is reduced About 17%; tensile strength, yield strength and elongation are respectively increased by about 33%, 27% and 21% compared with conventional treatment.

Example 2:

Put 10kg of ordinary commercially purchased AZ91 magnesium alloy into the heat preservation container for melting, and after melting, keep it at 693°C for 15 minutes (conventional treatment method); Insert the hollow tool head of the inert gas into the magnesium alloy melt in the heat preservation container; start the flux quantitative supply system after adjusting the gas flow and pressure, and quickly adjust the flux quantitative setting control device; start the high-intensity sound cavitation system, set the sound The frequency and power of the cavitation, the system modulates the resonance state to process the alloy melt for a period of time; after the treatment of the magnesium alloy melt, first turn off the high-intensity acoustic cavitation system and then turn off the flux quantitative supply system, and then quickly insert the magnesium alloy into the melt The hollow tool head is removed and finally the inert gas supply system is turned off.

The relevant parameters of this embodiment are as follows: the diameter of the tool head is 40mm, and the hole with a diameter of 1.0mm is opened on the lower end wall, and the number of holes on the wall is 15; the diameter of the air outlet on the end surface of the tool head is 0.8mm, and the number is 5; The distance between the end face of the hollow tool rod in the melt of the heat preservation vessel and the bottom of the heat preservation vessel is 40mm; the inert gas fed into the melt is argon, the gas pressure is 0.1MPa, and the flow rate is 1.3L/min; the flux amount is 50g/min. min; the frequency of high-intensity acoustic cavitation is 15kHz, and the power is 2000W; after 10min of treatment under the above parameters. According to stop the sound cavitation system and flux supply system first, then lift the tool head out of the melt, and finally close the inert gas supply device. The solidified alloy was then tested.

Compared with the conventional treatment method, the purification effect of the AZ91 magnesium alloy melt processed by the method of the present invention is that the hydrogen content is reduced from 29.7ml/100g to 9.3ml/100g during the conventional treatment, and the degassing rate reaches about 68.7%; the slagging rate decreases About 13%; tensile strength, yield strength and elongation are respectively increased by about 29%, 31% and 17% compared with conventional treatment.

Example 3:

Put 20kg of ordinary commercially purchased AZ80 magnesium alloy into the heat preservation container for melting, and after melting, keep it at 687°C for 15 minutes (conventional treatment method); Insert the hollow tool head of the inert gas into the magnesium alloy melt in the heat preservation container; start the flux quantitative supply system after adjusting the gas flow and pressure, and quickly adjust the flux quantitative setting control device; start the high-intensity sound cavitation system, set the sound Cavitation frequency and power, the system modulates the resonance state to process the alloy melt for a period of time; after the treatment of the magnesium alloy melt, first turn off the high-intensity acoustic cavitation system and then turn off the flux quantitative supply system, and then quickly insert the magnesium alloy into the melt The hollow tool head is removed and finally the inert gas supply system is turned off.

The relevant parameters of this embodiment are as follows: the diameter of the tool head is 50mm, and the hole with a diameter of 1.5mm is opened on the lower end wall, and the number of holes on the wall is 20; the diameter of the air outlet on the end surface of the tool head is 1.0mm, and the number is 7; The distance between the end face of the hollow tool rod in the melt of the heat preservation container and the bottom of the heat preservation container is 70mm; the inert gas fed into the melt is argon, the gas pressure is 0.2MPa, and the flow rate is 1.5L/min; the amount of flux fed is 80g/min min; the frequency of high-intensity acoustic cavitation is 20kHz, and the power is 2000W; after 5 minutes of treatment under the above parameters. According to stop the sound cavitation system and flux supply system first, then lift the tool head out of the melt, and finally close the inert gas supply device. The solidified alloy was then tested.

Compared with the conventional treatment method, the purification effect of the AZ80 magnesium alloy melt processed by the method of the present invention is that the hydrogen content is reduced from 26.3ml/100g to 7.7ml/100g during the conventional treatment, and the degassing rate reaches about 70.7%; the slagging rate decreases About 15%; tensile strength, yield strength and elongation are respectively increased by about 26%, 24% and 19% compared with conventional treatment.

Example 4:

Put 70kg of ordinary commercially purchased AZ80 magnesium alloy into the heat preservation container for melting, and after melting, keep it at 695°C for 20 minutes (conventional treatment method); Insert the hollow tool head of the inert gas into the magnesium alloy melt in the heat preservation container; start the flux quantitative supply system after adjusting the gas flow and pressure, and quickly adjust the flux quantitative setting control device; start the high-intensity sound cavitation system, set the sound Cavitation frequency and power, the system modulates the resonance state to process the alloy melt for a period of time; after the treatment of the magnesium alloy melt, first turn off the high-intensity acoustic cavitation system and then turn off the flux quantitative supply system, and then quickly insert the magnesium alloy into the melt The hollow tool head is removed and finally the inert gas supply system is turned off.

The relevant parameters of this embodiment are as follows: the diameter of the tool head is 60mm, and the hole with a diameter of 2mm is opened on the lower end wall, and the number of holes on the wall is 26; the diameter of the air outlet on the end surface of the tool head is 1.5mm, and the number is 9; The distance between the end face of the hollow tool rod in the container melt and the bottom of the heat preservation container is 100mm; the inert gas fed into the melt is argon, the gas pressure is 0.2MPa, the flow rate is 2.0L/min; the amount of flux fed is 240g/min ; The high-intensity sound cavitation frequency is 30kHz, and the power is 3000W; after 20 minutes of treatment under the above parameters. According to stop the sound cavitation system and flux supply system first, then lift the tool head out of the melt, and finally close the inert gas supply device. The solidified alloy was then tested.

Compared with the conventional treatment method, the purification effect of the AZ80 magnesium alloy melt processed by the method of the present invention is that the hydrogen content is reduced from 25.9ml/100g to 7.3ml/100g during the conventional treatment, and the degassing rate reaches about 71.8%; the slagging rate decreases About 18%; tensile strength, yield strength and elongation are respectively increased by about 28%, 25% and 21% compared with conventional treatment.

Example 5:

Put 500kg of ordinary commercially purchased AZ91 magnesium alloy into the heat preservation container for melting, and after melting, keep it at 685°C for 30 minutes (conventional treatment method); Insert the hollow tool head of the inert gas into the magnesium alloy melt in the heat preservation container; start the flux quantitative supply system after adjusting the gas flow and pressure, and quickly adjust the flux quantitative setting control device; start the high-intensity sound cavitation system, set the sound Cavitation frequency and power, the system modulates the resonance state to process the alloy melt for a period of time; after the treatment of the magnesium alloy melt, first turn off the high-intensity acoustic cavitation system and then turn off the flux quantitative supply system, and then quickly insert the magnesium alloy into the melt The hollow tool head is removed and finally the inert gas supply system is turned off.

The relevant parameters of this embodiment are as follows: the diameter of the tool head is 120mm, and the hole with a diameter of 3.0mm is opened on the lower end wall, and the number of holes on the wall is 30; the diameter of the air outlet on the end surface of the tool head is 3.0mm, and the number is 15; The distance between the end face of the hollow tool rod in the melt of the heat preservation container and the bottom of the heat preservation container is 150mm; the inert gas fed into the melt is argon, the gas pressure is 0.3MPa, and the flow rate is 2.3L/min; the amount of flux fed is 1500g/ min; the frequency of high-intensity acoustic cavitation is 20kHz, and the power is 4000W; after 20min of treatment under the above parameters. According to stop the sound cavitation system and flux supply system first, then lift the tool head out of the melt, and finally close the inert gas supply device. The solidified alloy was then tested.

Compared with the conventional treatment method, the purification effect of the AZ91 magnesium alloy melt processed by the method of the present invention is that the hydrogen content is reduced from 37.6ml/100g to 11.2ml/100g during the conventional treatment, and the degassing rate reaches about 70.2%; the slag discharge rate is reduced About 21%; tensile strength, yield strength and elongation are respectively increased by about 27%, 23% and 18% compared with conventional treatment.

Claims (6)

1. A method for refining magnesium alloy melts, characterized in that: the preparation method comprises the steps of: (1) Melting the magnesium alloy billet put into the thermal insulation container, and standing at a certain temperature after melting; (2) Insert the hollow tool head which is preheated to the melt temperature equivalent to the inert gas with the set flow rate and pressure into the magnesium alloy melt in the heat preservation container; (3) Start the flux quantitative supply system after adjusting the gas flow and pressure, and quickly adjust the flux quantitative given control device; (4) Start the high-intensity acoustic cavitation system, set the acoustic cavitation frequency and power, and process the alloy melt for a period of time by modulating the resonance state of the system; (5) After the treatment of the magnesium alloy melt, first turn off the high-intensity acoustic cavitation system, then turn off the flux quantitative supply system, then quickly remove the hollow tool head inserted into the melt, and finally turn off the inert gas supply system. 2. The method for refining magnesium alloy melt according to claim 1, characterized in that the resting temperature of the alloy after melting is 50-100°C above the alloy liquidus line; The distance between the end surface of the hollow tool rod and the bottom of the heat preservation container is 30-500mm; the inert gas introduced into the melt is argon or a gas that does not react with the magnesium melt, the gas pressure is 0.02-0.8MPa, and the flow rate is 0.01- 5.0L/min; the amount of flux introduced is 10-3000g/min. 3. The method for refining magnesium alloy melts according to claim 1, characterized in that the frequency of the high-intensity acoustic cavitation is 15-50 kHz, and the power is 0.1-10 kW. 4. The magnesium alloy melt refining method according to claim 1, characterized in that the processing time is 10s-50min. 5. The method for refining magnesium alloy melts according to claim 1, characterized in that the cavitation system and the flux supply system should be stopped first after the treatment of the melt is finished, and then the tool head is proposed from the melt, and finally Turn off the inert gas supply. 6. A magnesium alloy, characterized in that the magnesium alloy is prepared by the method according to any one of claims 1-8.