Preparation method of high-performance die-cast zinc alloy

Abstract

The invention discloses a high-performance die-cast zinc alloy preparation method which comprises the following steps that S1, a mold is placed in a circulating water tank, cooling water is arranged in the circulating water tank, and a pouring robot, an ultrasonic device and a peeling robot are sequentially arranged in the water flow direction in the circulating water tank; s2, a pouring robot injects the alloy liquid into a mold through a pouring manipulator; s3, an ultrasonic tool head in an ultrasonic device is inserted into the mold, one end of the ultrasonic tool head is connected with an ultrasonic electric box, the other opposite end extends into the mold, and the alloy liquid in the mold generates ultrasonic vibration; s4, an oxidation film on the alloy liquid level in the mold is removed through the scalping robot; and S5, after the alloy liquid is completely solidified, demolding is conducted, and the die-cast zinc alloy ingot is obtained. Compared with the prior art, the problem that crystal grains of die-cast zinc alloy ingots obtained through an existing preparation technology are not uniform is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous alloy smelting, and in particular relates to a method for preparing a high-performance die-cast zinc alloy. Background Art

[0002] Zinc alloys have been widely used in many fields due to their low melting point, good fluidity, and easy forming. In the casting process of die-cast zinc alloys, the focus is usually on the qualified zinc alloy composition and the reduction of inclusion content. The requirements for zinc alloy ingots are only reflected in the surface cleanliness, without bubbles, oil stains, inclusions, etc. The requirements for the performance of zinc alloy ingots, especially the requirements for grain size, are ignored.

[0003] The grain size of zinc alloy ingots is improved, and the plastic strength of the alloy ingots is improved, and the product quality of zinc alloy die-castings is also significantly improved. Since there are no mechanical properties and metallographic structure requirements for die-cast zinc alloy ingots in the national standards GB / T13818 "Die-cast zinc alloys" and GB / T13821 "Zinc alloy die-castings", as well as GB / T8738 "Zinc alloy ingots for casting", there are only composition and surface quality requirements for die-cast zinc alloy ingots, and die-cast zinc alloy ingots need to be remelted before die-casting into die-castings in die-casting production. The internal quality and mechanical properties of die-cast zinc alloy ingots have not received enough attention. However, downstream die-casting manufacturers have found that under the same die-casting process, the zinc alloy products die-cast from the more brittle zinc alloy ingots are significantly more brittle, and in severe cases, loose molds occur.

[0004] The grain-refined zinc alloy ingot not only improves the brittleness of the alloy ingot, but more importantly, it is easier to melt and has a more uniform composition during the zinc alloy remelting process. Therefore, the grain size of the zinc alloy ingot is an important link in whether high-performance zinc alloy die-castings can be obtained. In the smelting process of zinc alloy, in addition to ensuring high-quality zinc alloy liquid with qualified chemical composition and minimal gas and slag content, the grain size of the zinc alloy ingot is also equally important during casting.

[0005] At present, the casting process of the zinc alloy ingot production line is to scoop the alloy liquid out of the holding furnace with a metal spoon, cast it into the zinc alloy ingot mold in turn, and then use a metal sheet to remove the oxide scale on the alloy liquid surface in the mold, which is also called skinning. After that, the mold carrying the alloy liquid moves to the other end of the circulating water tank until the alloy liquid is completely solidified and then demolded, stacked and packaged.

[0006] When the zinc alloy liquid is cast into a metal mold, the grains of the alloy ingot become uneven due to the uneven cooling intensity at the edge and the core. Coarse columnar crystals and equiaxed crystals are easily formed inside, which affects the performance of the zinc alloy ingot and the performance of downstream zinc alloy die-casting products. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing a high-performance die-cast zinc alloy to solve the problem of uneven grains of die-cast zinc alloy ingots obtained by the existing preparation process.

[0008] In order to achieve the above object, the present invention adopts the following technical scheme: a method for preparing a high-performance die-cast zinc alloy, comprising the following steps:

[0009] S1. Place the mold in a circulating water tank with cooling water, and arrange the casting robot, ultrasonic device, and peeling robot in sequence along the water flow direction in the circulating water tank;

[0010] S2, the casting robot injects the alloy liquid into the mold through the casting robot arm;

[0011] S3, inserting an ultrasonic tool head in the ultrasonic device into the mold, connecting one end of the ultrasonic tool head to an ultrasonic electric box and extending the other end thereof into the mold, so that the alloy liquid in the mold generates ultrasonic vibration;

[0012] S4, the peeling robot removes the oxide film on the alloy liquid surface in the mold;

[0013] S5. The mold continues to be transported along the circulating water tank. After the alloy liquid in the mold is completely solidified, the mold is demolded to obtain a die-cast zinc alloy ingot.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0015] 1. In the present invention, by introducing ultrasonic waves at the beginning of casting, the nucleation rate during the solidification of the zinc alloy is increased, thereby increasing the grain size of the zinc alloy ingot to meet the requirements of producing high-performance die-cast zinc alloy products. The traditional idea of ​​controlling the inclusion content during the smelting process is changed to improve the performance of the zinc alloy ingot from another direction.

[0016] 2. In the present invention, after casting and before peeling, a metal rod is placed in the alloy liquid in the mold, and the metal rod is connected to an ultrasonic transmitting device, that is, after the alloy liquid is cast into the mold, ultrasonic vibration is introduced into the metal liquid in the early stage of solidification to improve the nucleation efficiency of the metal liquid, thereby refining the grain structure of the alloy ingot, increasing the grain size of the zinc alloy ingot, and improving the performance of the die-cast zinc alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1A schematic diagram of the structure of an alloy ingot preparation device for a high-performance die-casting zinc alloy preparation method Figure 1 .

[0019] Figure 2 A schematic diagram of the structure of an alloy ingot preparation device for a high-performance die-casting zinc alloy preparation method Figure 2 .

[0020] Legend:

[0021] 1. Mould; 2. Circulating water tank; 3. Casting robot; 31. Casting robot arm; 4. Ultrasonic tool head; 41. Ultrasonic electric box; 5. Peeling robot. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] Principle of ultrasonic grain refinement:

[0026] According to the nucleation driving force formula:

[0027]

[0028] ΔG V ——nucleation driving force, J / m;

[0029] ΔH——latent heat of fusion, J / m;

[0030] T m ——theoretical nucleation temperature, K;

[0031] T——time temperature of melt, K.

[0032] The latent heat of melting is related to the material properties. For alloy materials, the latent heat of melting is a constant. Therefore, if you want to increase the nucleation rate, that is, to increase the driving force for crystallization, you must either increase the theoretical crystallization temperature of the melt or lower the actual temperature of the melt, that is, increase the supercooling of the melt solidification.

[0033] First, ultrasonic vibration produces cavitation in the melt, forming cavitation bubbles. During the expansion process, the cavitation bubbles absorb a large amount of heat from the metal around the bubble wall, causing the micro-area melt to instantly decrease in temperature, increase the supercooling degree of solidification, increase the nucleation driving force, increase the number of nuclei, and meet the driving force for crystallization nucleation of the melt alloy.

[0034] Second, when these cavitation bubbles collapse, the melt is quickly replenished, the momentum of the melt flow is large, and a very high pressure is generated. When the pressure increases, the melting point temperature of the solidified alloy increases, thereby increasing the supercooling of solidification, increasing the nucleation driving force, and increasing the number of nuclei;

[0035] Third, the continuous impact force generated by the closing of cavitation bubbles causes the grown dendrites to break. The thermal fluctuations in the melt caused by the acoustic flow melt the necking part at the root of the dendrite. At the same time, the violent scouring effect causes a large number of dendrites to fall off the mold wall, promoting the refinement and uniform distribution of the dendrites.

[0036] See also Figure 1-2 The present invention provides a technical solution: a method for preparing a high-performance die-cast zinc alloy, comprising the following steps:

[0037] S1. Place the mold 1 in a circulating water tank 2, in which cooling water is provided. The casting robot 3, the ultrasonic device, and the peeling robot 5 are arranged in sequence along the water flow direction in the circulating water tank 2;

[0038] S2, the casting robot 3 injects the alloy liquid into the mold 1 through the casting robot arm 31;

[0039] S3, inserting the ultrasonic tool head 4 in the ultrasonic device into the mold 1, one end of the ultrasonic tool head 4 is connected to the ultrasonic electric box 41, and the other end of the ultrasonic tool head 4 is extended into the mold 1, so that the alloy liquid in the mold 1 generates ultrasonic vibration;

[0040] S4, the peeling robot 5 removes the oxide film on the alloy liquid surface in the mold 1;

[0041] S5, the mold 1 continues to be transported along the circulating water tank 2, and after the alloy liquid in the mold 1 is completely solidified, the mold is demoulded to obtain a die-cast zinc alloy ingot.

[0042] In step S3, since the ultrasonic tool head 4 is placed in the alloy liquid for a short time, in order to improve the ultrasonic vibration effect, high-frequency and high-energy ultrasonic waves can be used.

[0043] In step S3, the ultrasonic tool head 4 is made of TC4 titanium alloy. The tool head and horn in the ultrasonic device are made of TC4 titanium alloy with slow heat transfer and stable physical properties, and the zinc alloy composition is effectively controlled to be qualified. The transducer is protected by a shell and has a built-in cooling fan to ensure long-term use. The ultrasonic electric box 41 has the functions of continuous wave generation and protective alarm.

[0044] The diameter of the ultrasonic tool head 4 is ≤10 mm, and the ultrasonic frequency working range of the ultrasonic tool head 4 is greater than 20 Hz, ensuring the ultrasonic vibration effect.

[0045] Working principle: Under normal conditions, a large amount of nucleation occurs at the mold wall in the early stage of solidification due to low temperature. When ultrasonic treatment is used, the nucleation position of the alloy in the early stage of solidification is not only at the mold wall, but the high-energy ultrasonic wave generates energy disturbance to the alloy liquid, causing it to nucleate in a non-equilibrium state and even complete the solidification process, thereby achieving the effect of refining the alloy ingot structure.

[0046] By introducing ultrasound at the beginning of casting, the nucleation rate during the solidification process of the zinc alloy is increased, thereby increasing the grain size of the zinc alloy ingot to meet the requirements of producing high-performance die-cast zinc alloy products. Change the traditional idea of ​​controlling the inclusion content in the smelting process and improve the performance of the zinc alloy ingot from another direction. After casting and before peeling, place the metal rod in the alloy liquid of the mold. The metal rod is connected to the ultrasonic transmitter. That is, after the alloy liquid is cast into the mold, ultrasonic vibration is introduced into the metal liquid in the early stage of solidification to improve the nucleation efficiency of the metal liquid, thereby refining the grain structure of the alloy ingot, increasing the grain size of the zinc alloy ingot, and improving the performance of the die-cast zinc alloy.

[0047] Example 2

[0048] This embodiment further makes the following improved technical solutions on the basis of the above embodiments: in step S3, the ultrasonic tool head 4 is taken out before the oxide film is formed on the surface of the alloy liquid, so as to fully ensure the ultrasonic vibration effect and avoid affecting the oxide film formation.

[0049] Example 3

[0050] This embodiment further makes the following improved technical solutions on the basis of the above embodiments: in step S3, the bottom amplitude of the ultrasonic tool head 4 is 30-55 μm, which ensures the ultrasonic vibration effect of the bottom alloy liquid in the mold 1 and improves the grain size of the alloy ingot.

[0051] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a high-performance die-cast zinc alloy, characterized in that: The following steps are involved: S1. Place the mold in a circulating water tank with cooling water, and arrange the casting robot, ultrasonic device, and peeling robot in sequence along the water flow direction in the circulating water tank; S2, the casting robot injects the alloy liquid into the mold through the casting robot arm; S3, inserting an ultrasonic tool head in the ultrasonic device into the mold, connecting one end of the ultrasonic tool head to an ultrasonic electric box and extending the other end thereof into the mold, so that the alloy liquid in the mold generates ultrasonic vibration; S4, the peeling robot removes the oxide film on the alloy liquid surface in the mold; S5. The mold continues to be transported along the circulating water tank. After the alloy liquid in the mold is completely solidified, the mold is demolded to obtain a die-cast zinc alloy ingot.

2. A method for preparing a high performance die-casting zinc alloy according to claim 1, characterized in that: In step S3, the ultrasonic tool head is taken out before an oxide film is formed on the surface of the alloy liquid.

3. The method for preparing a high performance die-casting zinc alloy according to claim 1, characterized in that: In step S3, the ultrasonic tool head is made of TC4 titanium alloy.

4. The method for preparing a high performance die-casting zinc alloy according to claim 1, characterized in that: In step S3, the diameter of the ultrasonic tool head is ≤10 mm.

5. The method for preparing a high performance die-casting zinc alloy according to claim 1, characterized in that: In step S3, the ultrasonic frequency operating range of the ultrasonic tool head is greater than 20 Hz.

6. The method for preparing a high performance die-casting zinc alloy according to claim 1, characterized in that: In step S3, the bottom surface amplitude of the ultrasonic tool head is 30-55 μm.

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