A method for controlling the precipitation phase structure of aluminum-zirconium master alloy

Abstract

The present invention discloses a method for controlling the precipitated phase structure of an aluminum-zirconium master alloy. The method of the present invention comprises the following steps: heating and remelting the aluminum-zirconium master alloy in a medium frequency induction furnace; keeping the remelted aluminum-zirconium master alloy liquid warm for a certain period of time, stirring it with a stirrer, and then treating the metal liquid with ultrasound; treating the aluminum-zirconium master alloy liquid after ultrasound treatment with high-purity argon gas; casting the treated aluminum-zirconium master alloy liquid into a water-cooled copper mold, and taking it out after it is completely solidified under the continuous action of ultrasound and cooled, so as to obtain an aluminum-zirconium master alloy ingot with a fine precipitated phase and uniform distribution. The method of the present invention can overcome the problem that the precipitated phase of the aluminum-zirconium master alloy is coarse and affects the subsequent performance of the aluminum alloy, improve the quality of the aluminum-zirconium master alloy, and eliminate the inheritance of the solidification structure of the aluminum alloy.

Description

Technical Field

[0001] The invention relates to a method for controlling the precipitated phase structure of an aluminum-zirconium master alloy, and belongs to the field of metallurgy and new alloy materials. Background Art

[0002] Aluminum-zirconium master alloy is an important alloy required for the production of heat-resistant aluminum alloy, high-strength heat-resistant conductive aluminum alloy, etc. In the production process of aluminum alloy, zirconium is usually added through aluminum-zirconium master alloy; the solubility of zirconium in aluminum is very low, only about 0.28% in equilibrium state; during the solidification of zirconium-containing aluminum alloy, most of the zirconium precipitates in the form of Al3Zr; when the precipitated Al3Zr is dispersed in the aluminum alloy matrix, it is beneficial to improve the heat resistance and mechanical properties of the alloy.

[0003] The zirconium content in commercial aluminum-zirconium master alloys is usually 3%~5%, far exceeding the solubility of zirconium in aluminum. Most of the zirconium exists in the form of Al3Zr precipitation phase; the higher the Zr content, the easier it is to precipitate in the form of coarse primary Al3Zr precipitation phase. In the production of aluminum alloys, the particle size, morphology, and quantity of the Al3Zr precipitation phase of the master alloy will directly affect the microstructure of the alloy after solidification, and then affect the microstructure and performance after subsequent processing and forming; therefore, the control of the size, morphology, and quantity of Al3Zr in the aluminum-zirconium master alloy is extremely critical; however, Al3Zr in the aluminum-zirconium master alloy melt has a fast precipitation speed, a high melting point, is difficult to decompose, and is easy to grow. Once formed, it is difficult to eliminate, resulting in the alloy quality being difficult to meet the needs of high-performance aluminum alloy production; reducing the size of Al3Zr in the aluminum-zirconium master alloy and improving its morphology and distribution are the keys to improving the quality of the aluminum-zirconium master alloy.

[0004] Existing aluminum-zirconium master alloys are usually prepared by a molten salt reaction method by adding zirconium powder or zirconium-containing salts, zirconium-containing waste materials, etc. to aluminum liquid. For example, Chinese invention patent CN201510627513.X discloses a method for preparing an aluminum-zirconium master alloy, wherein one or more of potassium fluorozirconate, zirconium sponge, zirconium alloy scraps, and zirconium chips are uniformly mixed in proportion, and the prepared raw materials are added to the molten aluminum liquid at 700°C to 900°C using a bell jar or a feeder to perform a molten salt reaction. After the reaction is completed, the melt is continuously and fully stirred and refined, and then cast into ingots at 700°C to 1300°C to obtain an aluminum-zirconium master alloy. Chinese invention patent CN201010585739.5 discloses a method for preparing an aluminum-zirconium master alloy, wherein zirconium sponge powder is added to molten aluminum and stirred to react completely, followed by degassing, slag removal and cooling, and the cooled melt is cast into cast rods by a semi-continuous casting method, and then sawn into car bodies and extruded to obtain an aluminum-zirconium master alloy. These disclosed methods only describe the production of the aluminum-zirconium master alloy, and do not involve methods for eliminating the coarse Al3Zr phase in the structure of the aluminum-zirconium master alloy and further improving the quality. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention discloses a method for controlling the precipitated phase structure of an aluminum-zirconium master alloy. The method realizes the control of the Al3Zr phase structure in the aluminum-zirconium master alloy according to the melting and solidification precipitation characteristics of Zr in Al liquid through ultrasonic wave and cooling rate optimization processing and control, and obtains an Al3Zr precipitated phase with a small size and uniform morphological distribution. The method can overcome the problem that the precipitated phase of the aluminum-zirconium master alloy is coarse and affects the subsequent performance of the aluminum alloy, thereby improving the quality of the aluminum-zirconium master alloy and eliminating the inheritance of the solidification structure of the aluminum alloy.

[0006] The technical solution of the present invention is: a method for controlling the precipitation phase structure of an aluminum-zirconium master alloy, which specifically comprises the following steps:

[0007] (1) The aluminum-zirconium master alloy is heated and remelted in a medium frequency induction furnace.

[0008] (2) After the remelted aluminum-zirconium master alloy liquid is kept warm for a certain period of time, it is stirred with a stirrer and then the metal liquid is treated with ultrasound.

[0009] (3) The aluminum-zirconium intermediate alloy liquid after ultrasonic treatment is treated with high-purity argon gas.

[0010] (4) The treated aluminum-zirconium master alloy liquid is cast into a water-cooled copper mold, and is completely solidified under the continuous action of ultrasonic waves and taken out after cooling, thereby obtaining an aluminum-zirconium master alloy ingot with a fine precipitate phase and uniform distribution.

[0011] Preferably, the heating temperature of the aluminum-zirconium master alloy in step (1) of the present invention in the medium frequency induction furnace is 1050-1150°C.

[0012] Preferably, in step (2) of the present invention, the insulation temperature of the aluminum-zirconium intermediate alloy liquid is 1050-1150° C., the insulation time is 5-10 min, the stirrer during the stirring process is a graphite stirrer, and the stirring time is 2-5 min.

[0013] Preferably, the ultrasonic generator used in the ultrasonic treatment in step (2) of the present invention has a power of 50-200 W, a frequency of 40-60 Hz, and a treatment time of 2-5 min.

[0014] Preferably, the temperature of the aluminum-zirconium alloy liquid during treatment in step (3) of the present invention is 1050-1150°C.

[0015] Preferably, the specific process of the high-purity argon treatment of the present invention is: use high-purity argon (99.999%) to insert into the bottom of the treated aluminum-zirconium alloy liquid through a porous graphite tube with a diameter of 0.5~1.0mm for bottom blowing, with a flow rate of 1.0L~2.5L / s, a pressure of 0.15~0.2MPa, and a bottom blowing time of 3~5min.

[0016] Preferably, in step (4) of the present invention, the aluminum-zirconium intermediate alloy liquid is cast into a water-cooled copper mold at 850-900°C, the water temperature of the cooling water of the water-cooled copper mold does not exceed 30°C, the flow rate and pressure are adjusted to ensure that the cooling rate of the ingot is 100-150°C / s in the temperature range of 900-600°C, and during this process, an ultrasonic generator with a power of 100-200W and a frequency of 20-40Hz is continuously applied to the surface of the ingot until the ingot is completely solidified and the temperature is cooled to below 200°C.

[0017] Beneficial effects of the present invention:

[0018] The present invention firstly dissolves the coarse Al3Zr precipitate phase in the Al-Zr master alloy before treatment at high temperature and diffuses it into aluminum liquid, then mechanically and ultrasonically stirs the aluminum liquid to uniformly refine the Zr-rich area and Al3Zr atomic clusters in the aluminum-zirconium master alloy liquid, and then controls the nucleation and growth of Al3Zr in the solidification process through argon purification treatment and the synergistic effect of rapid cooling and ultrasound, so as to finally obtain fine and uniform Al3Zr precipitate phase and improve the quality of the aluminum-zirconium master alloy. The method disclosed by the present invention can overcome the problem that the precipitation phase of the aluminum-zirconium master alloy is coarse and affects the subsequent performance of the aluminum alloy, improve the quality of the aluminum-zirconium master alloy, and eliminate the inheritance of the solidification structure of the aluminum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a scanning electron microscope photograph of an aluminum-zirconium intermediate alloy having a coarse Al3Zr precipitation phase before the implementation of the present invention.

[0020] Figure 2 This is a scanning electron microscope photograph of the aluminum-zirconium master alloy obtained after being processed using the method disclosed in the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the described contents.

[0022] Example 1

[0023] The aluminum-zirconium master alloy used in this embodiment is Al-5Zr master alloy. The scanning electron microscope photo of its solidification structure before treatment is as follows: Figure 1 As shown, it can be seen that before treatment, the Al3Zr precipitation phase in the Al-5Zr master alloy is coarse and long, with a size of more than 200μm.

[0024] This aluminum-zirconium intermediate alloy was heated to 1050°C in a medium-frequency induction furnace for remelting and then kept at 1050°C for 10 minutes. During the holding process, a graphite stirrer was used to fully stir for 5 minutes, and then an ultrasonic generator with a power of 200W and a frequency of 40Hz was inserted for treatment for 5 minutes; then, high-purity argon gas with a content of 99.999% was inserted into the bottom of the remelted aluminum-zirconium alloy liquid through a porous graphite tube with a pore diameter of 0.5mm, and argon bottom blowing with a flow rate of 1.0L / s and a pressure of 0.2MPa was started for 5 minutes.

[0025] After the bottom blowing is completed, the aluminum-zirconium master alloy liquid is cast into a water-cooled copper mold at 850°C. The cooling water temperature does not exceed 30°C. The flow rate and pressure are adjusted to ensure that the ingot is cooled at a rate of 100°C / s within the temperature range of 900~600°C. During this process, an ultrasonic generator with a power of 200W and a frequency of 20Hz is continuously applied to the surface of the ingot until the ingot is completely solidified. When the ingot temperature drops below 200°C, it is taken out of the mold to obtain an aluminum-zirconium master alloy ingot with a fine precipitate size and uniform distribution. The scanning electron microscope photograph of the solidification structure of the aluminum-zirconium master alloy after treatment is shown in FIG. Figure 2 shown; contrast Figure 1 and Figure 2 It can be seen that after being treated by the method disclosed in the present invention, the Al3Zr precipitated phase in the master alloy is transformed into fine particles or petal-shaped, the size of which decreases to 5-25 μm and is evenly distributed in the matrix, and the quality of the master alloy is greatly improved.

[0026] Example 2

[0027] The aluminum-zirconium master alloy used in this embodiment is an Al-5Zr master alloy. Before treatment, the Al-5Zr master alloy Al3Zr is in the shape of thick strips and blocks, and the size of Al3Zr exceeds 300 μm.

[0028] The aluminum-zirconium master alloy was heated to 1150°C in a medium-frequency induction furnace for remelting and then kept at 1150°C for 5 minutes. During the insulation process, a graphite stirrer was used to fully stir for 2 minutes, and then an ultrasonic generator with a power of 50W and a frequency of 60Hz was used to insert the treatment for 2 minutes; then a porous graphite tube with a pore diameter of 1mm and high-purity argon gas with a content of 99.999% was inserted into the bottom of the remelted aluminum-zirconium alloy liquid, and argon bottom blowing with a flow rate of 1.0L / s and a pressure of 0.15MPa was started for 3 minutes.

[0029] After the bottom blowing is completed, the aluminum-zirconium master alloy liquid is cast into a water-cooled copper mold at 900°C. The cooling water temperature does not exceed 30°C. The flow rate and pressure are adjusted to ensure that the ingot is cooled at a rate of 150°C / s within the temperature range of 900~600°C. During this process, an ultrasonic generator with a power of 100W and a frequency of 40Hz is continuously applied to the surface of the ingot until the ingot is completely solidified. When the ingot temperature drops below 200°C, it is taken out of the mold to obtain an aluminum-zirconium master alloy ingot with a fine and uniformly distributed precipitate phase. The Al3Zr precipitate phase is transformed into fine particles and petal-shaped, with a size reduced to 5~20μm, which is evenly distributed in the matrix, and the quality of the master alloy is greatly improved.

[0030] Example 3

[0031] The aluminum-zirconium master alloy used in this embodiment is an Al-3Zr master alloy. Before treatment, the master alloy Al3Zr is in the form of thick strips and blocks with a size of more than 170 μm.

[0032] The aluminum-zirconium master alloy was heated to 1000°C in a medium-frequency induction furnace and remelted, and then kept at 1000°C for 8 minutes. During the insulation process, a graphite stirrer was used to fully stir for 4 minutes, and then an ultrasonic generator with a power of 100W and a frequency of 50Hz was inserted for treatment for 3 minutes; then a porous graphite tube with a pore diameter of 0.5mm and high-purity argon gas with a content of 99.999% was inserted into the bottom of the remelted aluminum-zirconium alloy liquid through a porous graphite tube with a pore diameter of 0.5mm, and argon bottom blowing with a flow rate of 2.0L / s and a pressure of 0.15MPa was started for 4 minutes.

[0033] After the bottom blowing is completed, the aluminum-zirconium master alloy liquid is cast into a water-cooled copper mold at 880°C. The cooling water temperature does not exceed 30°C. The flow rate and pressure are adjusted to ensure that the cooling rate of the ingot is 130°C / s in the temperature range of 900~600°C. During this process, an ultrasonic generator with a power of 150W and a frequency of 30Hz is continuously applied to the surface of the ingot until the ingot is completely solidified. When the ingot temperature drops below 200°C, it is taken out from the mold to obtain an aluminum-zirconium master alloy ingot with a fine and uniformly distributed precipitate phase. The Al3Zr precipitate phase is transformed into fine particles with a size reduced to 3~15μm, which are evenly distributed in the matrix, and the quality of the master alloy is greatly improved.

Claims

1. A method for controlling the precipitation phase structure of an aluminum-zirconium master alloy, characterized in that: The following steps are involved: (1) Heating and remelting the aluminum-zirconium master alloy in a medium frequency induction furnace; the heating temperature of the aluminum-zirconium master alloy in the medium frequency induction furnace is 1050~1150℃; (2) After the remelted aluminum-zirconium master alloy liquid is kept warm for a certain period of time, it is stirred with a stirrer, and then the metal liquid is treated with ultrasound; the ultrasonic generator used in the ultrasonic treatment has a power of 50-200 W, a frequency of 40-60 Hz, and a treatment time of 2-5 min; (3) Treating the aluminum-zirconium intermediate alloy liquid after ultrasonic treatment with high-purity argon gas; using high-purity argon gas to blow the aluminum-zirconium alloy liquid from the bottom after treatment, with a flow rate of 1.0L~2.5L / s, a pressure of 0.15~0.2MPa, and a bottom blowing time of 3~5min; (4) The treated aluminum-zirconium master alloy liquid is poured into a water-cooled copper mold at 850-900°C. The water temperature of the cooling water in the water-cooled copper mold does not exceed 30°C. The flow rate and pressure are adjusted to ensure that the cooling rate of the ingot is 100-150°C / s in the temperature range of 900-600°C. During this process, an ultrasonic generator with a power of 100-200W and a frequency of 20-40Hz is continuously applied to the surface of the ingot until the ingot is completely solidified and the temperature drops below 200°C. Then, the ingot is taken out to obtain an aluminum-zirconium master alloy ingot with fine precipitate size and uniform distribution.

2. The method for controlling the precipitation phase structure of the aluminum-zirconium master alloy according to claim 1, characterized in that: In step (2), the aluminum-zirconium master alloy liquid is kept at a temperature of 1050-1150° C. for a time of 5-10 min. During the stirring process, the stirrer is a graphite stirrer for a stirring time of 2-5 min.

3. The method for controlling the precipitation phase structure of the aluminum-zirconium master alloy according to claim 1, characterized in that: In step (3), the temperature of the aluminum-zirconium alloy liquid during treatment is 1050-1150°C.

4. The method for controlling the precipitation phase structure of the aluminum-zirconium master alloy according to claim 1, characterized in that: The specific process of high-purity argon treatment is: high-purity argon is inserted into the bottom of the treated aluminum-zirconium alloy liquid through a porous graphite tube with a diameter of 0.5~1.0mm and blown at the bottom.

Images