阅读说明：本技术 一种锌合金铸件及其制备方法 (Zinc alloy casting and preparation method thereof ) 是由 金华君 章晓海 于 2020-05-28 设计创作，主要内容包括：本发明涉及一种锌合金铸件及其制备方法,属于合金加工领域。本发明通过对锌合金成分含量的合理配置,加入微量Zr,不仅提高了锌合金的硬度,还保证了锌合金具有优异的整体力学性能,分多次添加合金原料,一定程度上避免了直接加锌锭熔化时发生大幅度温度变化,导致合金材料出现气泡和成分不稳定现象,优化了压铸工艺参数,最大限度提高了锌合金的性能。(The invention relates to a zinc alloy casting and a preparation method thereof, belonging to the field of alloy processing. According to the invention, through reasonable configuration of the component content of the zinc alloy and addition of trace Zr, the hardness of the zinc alloy is improved, the excellent overall mechanical property of the zinc alloy is ensured, alloy raw materials are added for multiple times, the phenomena of bubbles and unstable components of the alloy material caused by large-amplitude temperature change during direct zinc ingot melting are avoided to a certain extent, the die-casting process parameters are optimized, and the performance of the zinc alloy is improved to the maximum extent.)

1. The zinc alloy casting is characterized by comprising the following components in percentage by mass: al: 4.0-5.4%, Mg: 0.3-0.8%, Cu: 0.5-0.7%, Zr: 0.02-0.06%, and the balance of zinc and inevitable impurity elements.

2. A method of making a zinc alloy casting according to claim 1, comprising the steps of:

(1) firstly, preparing the components and the mass percentage of the zinc alloy casting;

(2) firstly, placing 80-90% of high-purity zinc ingots by mass in a crucible, heating to 450-460 ℃, vacuumizing, heating to 830-850 ℃, adding an Al-Cu intermediate alloy until the zinc ingots are completely melted, cooling to 620-630 ℃, adding industrial pure magnesium, and filling inert gas for uniform mixing;

(3) heating the melt to 700-720 ℃, adding a refining agent into the crucible alloy liquid for refining, then adding the remaining 10-20 mass percent of high-purity zinc ingot, stirring, slagging off, and then adding Zr to obtain a zinc alloy mixed solution;

(4) putting the zinc alloy mixed solution into a die casting machine for die-casting treatment to obtain a zinc alloy casting blank;

(5) and (3) cooling the zinc alloy casting blank in cooling water, and carrying out homogenization annealing treatment to obtain the zinc alloy casting.

3. A method of making a zinc alloy casting according to claim 2 wherein in step (3) the refining agent is zinc chloride.

4. A method of producing a zinc alloy casting according to claim 2, wherein the Zr element in the step (3) is added in the form of a Zn — Zr master alloy.

5. The method for preparing a zinc alloy casting according to claim 2, wherein the temperature of the zinc alloy mixture is reduced to 315-450 ℃ before the step (4) of die casting, the specific pressure during the die casting is 13-20Mpa, the injection speed is 25-35m/s, and the filling time is 0.8-1 s.

6. A method of producing a zinc alloy casting according to claim 2,

and (5) carrying out homogenization annealing treatment, namely heating the zinc alloy casting blank to 350 ℃, preserving heat for 2-3h, and cooling to room temperature by water.

Technical Field

The invention relates to a zinc alloy casting and a preparation method thereof, belonging to the field of alloy processing.

Background

The metal zinc is a very important nonferrous metal in national and economic development. The research and development of zinc-based alloy originate from the beginning of the twentieth century, mainly Zn-4Al die-casting alloy is widely applied to the aviation industry and the automobile industry, and the development of thin-wall die-casting technology drives the development of zinc die-casting parts later. The zinc-base alloy material takes zinc as a base and is added with other elements, and the commonly added elements comprise aluminum, copper, magnesium, cadmium, lead, titanium and the like. Although the zinc-based alloy has the characteristics of good mechanical property, excellent friction property, good wear resistance and the like, the creep strength is low, and the dimensional change caused by natural aging is easy to occur, because the zinc-based alloy structure mainly comprises a zinc-rich solid solution containing Al and Cu and an Al-rich solid solution containing Zn, the solubility of the zinc-based alloy structure is reduced along with the reduction of the temperature, but because the solidification speed of a die casting is extremely high, the solubility of the solid solution is greatly saturated at room temperature, and after a period of time, the saturation phenomenon is relieved, so that the shape and the size of the casting are changed.

The zinc alloy contains harmful impurities such as lead, cadmium, tin and the like, intergranular corrosion is generated at the boundary of crystal grains, intergranular corrosion and cracking of a metal matrix and intergranular corrosion in plating solution are accelerated, so that the expansion of an intergranular corrosion part is caused, the plating layer is jacked up, and the surface of a casting is foamed. Intergranular corrosion, particularly in humid environments, can cause the casting to deform, crack, or even fail.

In the process of die casting of the zinc alloy die casting, a die casting material, a die casting machine and a die are three major factors of die casting production, and one of the three major factors is not enough. The die casting process comprehensively uses the three elements, so that qualified castings with good appearance and internal quality can be stably and efficiently produced in a rhythmic manner. The zinc alloy die casting is easy to generate air holes, oxidized slag inclusions and other defects. When in die casting, because the filling speed of the liquid alloy is extremely high, gas in a cavity is difficult to completely remove, so that the internal quality of a die casting is reduced, and because the gas in the gas hole expands at high temperature, the surface of the die casting can bubble, so that the general die casting can not be subjected to heat treatment.

At present, the existing zinc-based alloy has low hardness, and the phenomena of air bubbles and unstable form often occur in the die-casting process, so that the qualification rate of zinc alloy castings is low, and the industrial requirements are difficult to meet.

Disclosure of Invention

Aiming at the existing problems of the zinc alloy casting, the invention provides the zinc alloy casting and the preparation method thereof, which are used for improving the hardness of the zinc alloy casting and solving the technical problems of bubbles and unstable casting shape in the die-casting process.

The purpose of the invention is realized by the following technical scheme:

a zinc alloy casting comprises the following components in percentage by mass: al: 4.0-4.4%, Mg: 0.3-0.8%, Cu: 0.5-1.2%, Zr: 0.02-0.06%, and the balance of zinc and inevitable impurities.

When Al in the zinc alloy casting is molten, the melting point of the alloy can be reduced, the fluidity of the alloy solution is changed, and the mechanical property of the alloy casting is enhanced. Mg can inhibit intergranular corrosion, refine metal structures, increase hardness, and when the content is too high, an alloy casting becomes brittle and the fluidity is reduced. Cu can refine grains and increase the tensile strength and hardness of the alloy, but when the content is too high, the size and the mechanical strength of the alloy casting are changed due to aging.

The invention also provides a die-casting method of the zinc alloy casting, which comprises the following steps:

(1) firstly, preparing the components and the mass percentage of the zinc alloy casting;

(2) firstly, placing 80-90% of high-purity zinc ingots by mass in a crucible, heating to 450-460 ℃, vacuumizing, heating to 830-850 ℃, adding an Al-Cu intermediate alloy until the zinc ingots are completely melted, cooling to 620-630 ℃, adding industrial pure magnesium, and filling inert gas for uniform mixing;

(3) heating the melt to 700-720 ℃, adding a refining agent into the crucible alloy liquid for refining, then adding the remaining 10-20 mass percent of high-purity zinc ingot, stirring, slagging off, and then adding Zr to obtain a zinc alloy mixed solution;

(4) putting the zinc alloy mixed solution into a die casting machine for die-casting treatment to obtain a zinc alloy casting blank;

(5) and (3) cooling the zinc alloy casting blank in cooling water, and carrying out homogenization annealing treatment to obtain the zinc alloy casting.

During the melting process, the interaction of the metal with the gas and the interaction of the metal bath with the crucible cause a change in composition, resulting in inclusions and gettering. When the smelting temperature is too high, the iron crucible reacts with the zinc liquid, and the oxidation reaction of iron occurs on the surface of the crucibleFormation of Fe₂O₃And the oxides and the iron element can also react with the zinc liquid to generate zinc slag, the zinc slag is dissolved in the zinc liquid, and the alloy raw materials are added for multiple times, so that the phenomena of bubbles and unstable components of the alloy material caused by large-amplitude temperature change when the zinc ingot is directly added for melting can be avoided.

In the above die casting method of a zinc alloy casting, the refining agent in the step (2) is zinc chloride. Since the density of the zinc chloride is lower than that of the alloy, the zinc chloride is added under the pressure of a bell jar so as to ensure that the refining agent and the alloy fully react. The refining agent is generally wrapped by paper and then pressed in, and slag is removed by a slag removing spoon after refining is finished.

In the die casting method of a zinc alloy casting as described above, the Zr element in the step (3) is added in the form of a Zn-Zr master alloy. The Zr element is added in a Zn-Zr intermediate alloy form, can be quickly melted in a short time to release the zirconium element, and trace Zr is added into the zinc alloy to generate a hard phase and improve the hardness of the alloy, but the addition of Zr can coarsen crystal grains, reduce the grain boundary area of the alloy and reduce the resistance of dislocation slippage, and when the Zr content is too high, the alloy hardness can be reduced on the contrary.

The method for die casting the zinc alloy casting comprises the step (4) of cooling the zinc alloy mixed liquid to 415-450 ℃ before die casting, wherein the specific pressure during die casting is 13-20Mpa, the injection speed is 25-35m/s, and the filling time is 0.8-1 s. The reason for cooling the zinc alloy before die casting is that in the subsequent pouring process, if the temperature is too high, the shrinkage large casting is easy to generate cracks and large crystal grains, and even die sticking can be caused; the temperature is too low, and the defects of cold shut, pattern on the surface, insufficient pouring and the like are easily generated. The injection plunger head pushes the alloy liquid to bypass the pouring gate to run at low pressure and low speed, so that the metal liquid is prevented from overflowing from the pouring gate, gas is discharged, the speed is increased along with the pressure rise, the metal liquid fills the pressure chamber to the inner pouring gate, the flow resistance is increased sharply due to the fact that the section area of the inner pouring gate is greatly reduced, and high injection pressure is needed to keep enough filling speed. And when the molten metal completely fills the die cavity, the filling is finished, the injection punch stops moving, the injection speed is rapidly reduced to zero, and the pressure is sharply increased. Wherein, too high filling speed can cause the sticking of the casting and increase the internal porosity of the casting, thereby causing the reduction of mechanical properties; when the filling rate is too low, the contour of the casting becomes unclear and even cannot be formed.

The pressure casting method of the zinc alloy casting comprises the step (5) of carrying out homogenization annealing treatment, namely heating the zinc alloy casting blank to 350 ℃, keeping the temperature for 2-3h, and cooling the zinc alloy casting blank to room temperature by water. The alloy structure is more uniform after the homogenization annealing, and the nonuniformity of chemical components in the grain size is reduced, so that the elongation and plasticity of the alloy casting are improved.

Compared with the prior art, the invention has the following advantages: according to the invention, through reasonable configuration of the component content of the zinc alloy and addition of trace Zr, the hardness of the zinc alloy is improved, the excellent overall mechanical property of the zinc alloy is ensured, alloy raw materials are added for multiple times, the phenomena of bubbles and unstable components of the alloy material caused by large-amplitude temperature change during direct zinc ingot melting are avoided to a certain extent, the die-casting process parameters are optimized, and the performance of the zinc alloy is improved to the maximum extent.

Detailed Description

The following are specific examples of the present invention and further describe the technical solutions of the present invention, but the present invention is not limited to these examples.