阅读说明：本技术 具有均匀显微组织和较高力学性能的ZZnAl4Y锌合金制备方法 (Preparation method of ZZnAl4Y zinc alloy with uniform microstructure and higher mechanical property ) 是由 王建华 张凯 彭浩平 刘亚 苏旭平 于 2019-10-15 设计创作，主要内容包括：本发明公开了一种控制金属型温度提高ZZnAl4Y锌合金力学性能的方法,将熔融锌合金液浇铸到内腔尺寸分别为Φ10*100和Φ30*80毫米的预热金属型中。通过控制金属型温度和延长凝固时间,在改善锌合金显微组织的均匀性,提高该合金的抗拉强度、延伸率和冲击韧性等力学性能的可以减少工业生产成本。采用本发明能制备出显微组织均匀和力学性能较高的ZZnAl4Y锌合金,适合于该锌合金的工业生产。(The invention discloses a method for improving the mechanical property of ZZnAl4Y zinc alloy by controlling the temperature of a metal mold, which comprises the step of casting molten zinc alloy liquid into a preheated metal mold with the sizes of phi 10 × 100 and phi 30 × 80 mm respectively. By controlling the metal mold temperature and prolonging the solidification time, the uniformity of the microstructure of the zinc alloy is improved, and the mechanical properties of the alloy, such as tensile strength, elongation, impact toughness and the like, can be improved, so that the industrial production cost can be reduced. The invention can prepare ZZnAl4Y zinc alloy with uniform microstructure and higher mechanical property, and is suitable for industrial production of the zinc alloy.)

1. A method for preparing ZZnAl4Y zinc alloy with uniform microstructure and higher mechanical property is characterized in that: the method comprises the steps of casting a ZZnAl4Y zinc alloy liquid prepared by rapid smelting into a metal mold with the preheating temperature of 200-350 ℃, and then cooling to the room temperature along with the casting mold to prepare the ZZnAl4Y zinc alloy.

2. A method of making ZZnAl4Y zinc alloy of uniform microstructure and higher mechanical properties as defined in claim 1, wherein: the rapid smelting method comprises the following steps: the ZZnAl4Y zinc alloy raw material is rapidly smelted at 680 +/-5 ℃, then cooled to 620 +/-5 ℃, degassed, deslagged and refined, and then kept warm and kept stand for 30 +/-3 minutes.

3. A method of making ZZnAl4Y zinc alloy of uniform microstructure and higher mechanical properties as defined in claim 1, wherein: the preheating temperature of the metal mold is 200 ℃, 250 ℃, 300 ℃ or 350 ℃.

Technical Field

The invention relates to a preparation technology of zinc alloy, in particular to a preparation method of ZZnAl4Y zinc alloy with uniform microstructure and higher mechanical property.

Background

The zinc alloy material has various excellent characteristics, such as good casting performance, can be used for producing precision parts with complex shapes and thin walls by die casting, has smooth casting surfaces, can be used for surface treatment such as electroplating, spraying, paint spraying and the like, and has the advantages of low casting energy consumption, low raw material cost and no environmental pollution in the production process. The Zn-Al alloy is widely applied to die-casting production in the fields of motorcycle carburetors, automobile parts, hardware products and the like due to good wear resistance, superplasticity and creep resistance. The low aluminum zinc alloy such as ZZnAl4Y die casting zinc alloy is widely applied to daily equipment superior to instruments and equipment due to the characteristics of low melting point, good casting performance and the like. The die-casting zinc alloy products are over 500, and can be widely applied to automobiles, tractors, daily building hardware, electromechanical equipment, instruments, stationery toys and the like. The die-casting zinc alloy is originated from the Zn-4Al-3Cu alloy developed and developed by New Jersey company in the beginning of 20 th century, and then a series of researches and researches on the performance improvement are carried out around the Zn-4Al-3Cu alloy. Through a series of subsequent improvements, a series of Aamak alloys are successfully developed.

To date, Zn-Al alloys have been developed to the point where the furnace fire is pure green, with ZZnAl4Y zinc alloy being widely used in industry. However, the domestic ZZnAl4Y zinc alloy has low quality, and the high-quality ZZnAl4Y zinc alloy is greatly imported. The main reason why the domestic ZZnAl4Y zinc alloy has lower quality is that: 1) the content of impurities in the alloy is too high; 2) the control precision of the alloy components is low; 3) the uniformity of the alloy structure is poor; 4) the mechanical property of the alloy is lower. Therefore, innovative technologies are needed to improve the quality of the zinc alloy, so as to improve the structural uniformity and mechanical properties of the zinc alloy.

In the traditional casting process, the metal mold is usually adopted to cast and refine the alloy structure, thereby achieving the purpose of improving the mechanical property of the alloy. Generally speaking, it is generally recognized that the lower the temperature of the metal mold, the faster the cooling speed, the finer the microstructure of the alloy, and the higher the mechanical properties. The invention is completely different from the traditional cognition, obviously improves the uniformity of alloy structure by adopting the method of increasing the temperature of the metal mold, greatly improves the mechanical property of the zinc alloy, saves the subsequent heat treatment process and saves the production cost.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a preparation method of ZZnAl4Y zinc alloy with uniform microstructure and higher mechanical property, so that the uniformity of the alloy microstructure is obviously improved, and the mechanical property of the alloy is obviously improved.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a method for preparing ZZnAl4Y zinc alloy with uniform microstructure and high mechanical property comprises the following steps: and casting the ZZnAl4Y zinc alloy liquid prepared by rapid smelting into a metal mold at 200-350 ℃, and then slowly cooling to room temperature along with the casting mold to prepare the ZZnAl4Y zinc alloy with uniform microstructure and high mechanical property.

Further, the rapid smelting method comprises the following steps: the ZZnAl4Y zinc alloy raw material is rapidly smelted at 680 +/-5 ℃, then cooled to 620 +/-5 ℃, degassed, deslagged and refined, and then kept warm and kept stand for 30 +/-3 minutes. The solidifying point of the ZZnAl4Y zinc alloy is about 390 ℃, the pouring temperature after smelting is about 620 ℃, the temperature of the metal mold in the embodiment is controlled to be about 200-350 ℃, the temperature difference is about 270-400 ℃, the cooling effect of the metal mold on the zinc alloy liquid is greatly weakened, and therefore the zinc alloy liquid is slowly cooled to the solidifying point of 390 ℃ from 620 ℃, so that the dendritic primary aluminum phase disappears and is further converted into the whole spherical primary aluminum phase. Meanwhile, the temperature difference in the casting section is obviously reduced, so that more uniform primary aluminum phase is obtained. In the case of non-equilibrium solidification, the faster the cooling rate, the lower the solidification point of the alloy, as compared with the equilibrium cooling conditions. In the examples, the cooling rate of the zinc alloy liquid was slow, so the freezing point depression of the alloy was small.

Further, the preheating temperature of the metal mold is 200 ℃, 250 ℃, 300 ℃ or 350 ℃.

In the common casting process of the zinc alloy, the metal mold is not preheated normally, the preheating temperature is lower or the cooling time is too short, when the zinc alloy liquid is poured into the metal mold, the outer layer of a common casting is fine isometric crystal, the middle part of the common casting is columnar crystal, the center of the common casting is thick isometric crystal, and the microstructure of the casting from the outer layer to the inner part is very uneven. The preheating temperature of the metal mold is below the liquidus of ZZnAl4Y zinc alloy and is 200-350 ℃, and the technical effects are as follows:

1. with the increase of the metal mold temperature, the initial solidification point of the zinc alloy liquid is increased due to the great reduction of the cooling speed, a relatively coarse spherical primary aluminum phase is obtained, and the dendritic crystal primary aluminum phase is eliminated. Meanwhile, the temperature gradient of the casting from the surface layer to the center is obviously reduced, so that the casting tends to be solidified simultaneously, and the structure uniformity of the casting from the center to the outer layer is obviously improved. Under the action of tensile stress, the alloy with good tissue uniformity can be deformed more uniformly without fracture, so that the comprehensive mechanical property of the alloy is obviously improved.

2. The invention has the outstanding effect that although the primary spherical aluminum phase in the alloy solidification structure is obviously coarse, higher mechanical property can be obtained due to good uniformity.

3. Because the temperature of the metal mold is higher, the casting can be slowly cooled in the casting mold, and the spherical primary aluminum phase becomes more round and smooth due to the sufficient atomic diffusion, which is equivalent to the homogenization annealing effect of the alloy, and the elongation of the alloy can be further improved.

Drawings

The invention is further illustrated with reference to the following figures and examples:

FIG. 1 is a photograph of the microstructure at the center of the cross section of a specimen of a zinc alloy ZZnAl4Y of a comparative example.

FIG. 2 is a photograph of the microstructure of a test specimen 1/2R of a zinc alloy of ZZnAl4Y in a comparative example.

FIG. 3 is a photograph of the microstructure at the surface of a test piece of a zinc alloy of ZZnAl4Y of a comparative example.

FIG. 4 is a photograph of the microstructure at the center of the cross section of a specimen of the zinc alloy of example 1ZZnAl 4Y.

FIG. 5 is a photograph of the microstructure of a test specimen 1/2R of the zinc alloy of EXAMPLE 1ZZnAl 4Y.

FIG. 6 is a photograph of the microstructure at the surface of a sample of the zinc alloy of example 1ZZnAl 4Y.

FIG. 7 is a photograph of the microstructure at the center of the cross section of a specimen of zinc alloy ZZnAl4Y of example 2.

FIG. 8 is a photograph of the microstructure of a zinc alloy specimen 1/2R of EXAMPLE 2ZZnAl 4Y.

FIG. 9 is a photograph of the microstructure at the surface of a sample of zinc alloy of example 2ZZnAl 4Y.

FIG. 10 is a photograph of the microstructure at the center of the cross section of a specimen of zinc alloy ZZnAl4Y of example 3.

FIG. 11 is a photograph of the microstructure of a zinc alloy specimen 1/2R of EXAMPLE 3ZZnAl 4Y.

FIG. 12 is a photograph of the microstructure at the surface of a test piece of the zinc alloy of example 3ZZnAl 4Y.

FIG. 13 is a photograph of the microstructure at the center of the cross section of a specimen of zinc alloy ZZnAl4Y of example 4.

FIG. 14 is a photograph of the microstructure of a zinc alloy specimen 1/2R of example 4ZZnAl 4Y.

FIG. 15 is a photograph of the microstructure at the surface of a zinc alloy specimen of example 4ZZnAl 4Y.

Detailed Description

The invention is described in more detail below with reference to the following examples:

the cross-sections of the ZZnAl4Y zinc alloy specimen 1/2R were taken as microstructural photographs of the cross-sections of the ZZnAl4Y zinc alloy specimen in the following examples and comparative examples, wherein the ZZnAl4Y zinc alloy specimen was a cylinder, R was the radius of the cross-section of the cylinder, and the cross-section at 1/2R was the cross-section at 1/2R from the end of the cylinder (i.e., the cross-section was taken perpendicular to the axis of the cylinder).

Comparative example:

step 1, zinc alloy raw material proportioning: the raw materials adopted are industrial pure zinc (99.9%) and industrial pure aluminum (99.9%). The mass ratio of each component is calculated, and the components are weighed by adopting a Mettler XS105 electronic balance, and the weight percentage of the components is as follows: 95.9 percent of industrial pure zinc and 4.1 percent of industrial pure aluminum.

Step 2, smelting zinc alloy

The prepared zinc alloy raw material and the covering agent are put into a high-temperature-resistant corundum crucible, and the crucible is put into a furnace when the temperature in the furnace reaches 680 ℃. And after the sample is completely melted, fully stirring the melt by using a high-temperature-resistant quartz rod to prevent component segregation. Stopping supplying power, reducing the temperature of the metal liquid to 620 ℃, refining the alloy liquid by hexachloroethane, and then keeping the temperature and standing for 30 minutes.

Step 3, tapping and casting

And pouring the zinc alloy liquid into metal molds with the sizes of inner cavities of phi 10 x 100 (tensile and impact test samples) and phi 30 x 80 (metallographic analysis samples) at the non-preheating temperature respectively to obtain the required alloy samples.

The tensile test sample adopts a standard test sample (GB-T228-.

The microstructure of the zinc alloy is shown in FIGS. 1 to 3, and the microstructure is mostly non-equiaxed crystals such as dendrites and quincunx crystals, and the size difference of primary aluminum phase crystal grains from the center of the cross section to the surface structure is large. The tensile strength of the alloy is 245MPa, and the elongation is 2.5%; the impact work of the alloy was 23J.