阅读说明：本技术 一种晶粒细化方法 (Grain refining method ) 是由 秦简 李一峰 王林生 刘方镇 毛志福 周维 朱晓华 于承斌 王孝国 长海博文 于 2021-09-15 设计创作，主要内容包括：本发明公开了一种晶粒细化方法,本发明提供的晶粒细化方法,在合金熔铸过程中,添加微量的B元素,与铝锭中不可避免的微量杂质元素：如Ti、V、Cr、Zr等充分反应,使其析出并生成等固体颗粒,再通过一定时间的保温搅拌的方式使得生成固体的颗粒均匀分布在熔体中,作为新的异质形核点。此方法生成的固体颗粒有着不团聚、尺寸小的优点,在使合金的晶粒尺寸得到大幅度的降低的同时提高了合金的导热性能及力学性能。本发明流程简单,仅涉及合金熔铸过程,适合工业化生产。(The invention discloses a grain refining method, which adds trace B element and inevitable trace impurity elements in aluminum ingots in the alloy casting process: such as Ti, V, Cr, Zr, etc., are fully reacted to precipitate and generate equal solid particles, and the generated solid particles are uniformly distributed in the melt as new heterogeneous nucleation points by a heat preservation stirring mode for a certain time. The solid particles generated by the method have the advantages of no agglomeration and small size, and the heat-conducting property and the mechanical property of the alloy are improved while the grain size of the alloy is greatly reduced. The invention has simple flow, only relates to the alloy casting process and is suitable for industrial production.)

1. A method of grain refinement, comprising the steps of:

(1) weighing pure aluminum, aluminum-boron intermediate alloy, other intermediate alloy and refining agent according to a certain proportion and drying completely;

(2) putting pure aluminum ingots into a smelting furnace, and heating until the pure aluminum ingots are completely melted;

(3) when the temperature is raised to 700-800 ℃, adding other intermediate alloys except the aluminum-boron intermediate alloy and completely melting the intermediate alloys;

(4) when the temperature reaches 740 and 760 ℃, adding a refining agent for degassing and slagging off;

(5) adding Al-B intermediate alloy when the temperature reaches 740-760 ℃;

(6) stirring the molten metal liquid after the aluminum boron intermediate alloy is completely melted;

(7) when the temperature is reduced to 710-730 ℃, the molten metal liquid is poured into the metal mold for molding.

2. The method for grain refinement according to claim 1, wherein in the step (4), the chemical component of the refining agent is hexachloroethane, and the refining agent is added in two times, wherein the adding amount of each time is 0.5-2.0% of the total mass of the pure aluminum, the aluminum boron intermediate alloy and the other intermediate alloy in the step (1).

3. A method for refining grains according to claim 2, wherein said refining agent is completely pressed into the molten metal and left to stand for 5 to 15 minutes at each time of addition.

4. A grain refining method according to claim 1, characterized in that: the adding amount of B in the aluminum-boron intermediate alloy added in the step (5) is 0.002-0.100% of the total mass of the pure aluminum, the aluminum-boron intermediate alloy and other intermediate alloys in the step (1).

5. A grain refining method according to claim 1, characterized in that: and (3) stirring for 5-120min in the step (5).

6. A method of grain refinement as defined in claim 1, characterized in that: the temperature of the molten metal is maintained at 720-750 ℃ during the stirring in the step (5).

Technical Field

The invention relates to the field of aluminum alloy materials, in particular to a grain refining method capable of improving the heat-conducting property and the mechanical property of aluminum alloy while refining alloy grains.

Background

It is known that grain refinement is one of the most effective methods for improving the toughness and other properties of aluminum alloys. In order to refine the grains of an aluminum alloy, a grain refiner is typically added to the molten metal during the fusion casting process. At present, the refiner containing Ti is most widely applied, such as Al-Ti-B, Al-Ti-C, Al-Ti-N refiner. However, such refiners are expensive and tend to produce excessive amounts of TiB₂And the solid particles are agglomerated and settled, so that the refining effect of alloy grains and the alloy performance are reduced.

Furthermore, the pure aluminium used in the fused cast alloy, as well as the corresponding master alloys, contain certain amounts of unavoidable impurities, such as traces of Ti, V, Cr, Zr, etc. These alloying elements are often used as impurities and are removed by a certain method, and the generated bottom particles are widely removed at present, so that the purity of the aluminum alloy is improved on one hand, and the heat-conducting property of the alloy is improved on the other hand. However, Ti, V, etc. dissolved in aluminum firstly reduce the purity of aluminum, and secondly, such transition metal elements have extremely adverse effects on the heat conductivity of the alloy, so that the above purpose is generally achieved by adding B to react to precipitate and finally remove the B. For example, in Chinese patent CN 111270110A named as "a corrosion-resistant high-strength high-toughness high-heat-conductivity aluminum alloy material and a preparation method thereof", B element is added, and reacts with the trace elements to generate solid particles which are removed by standing and bottom precipitation. However, this method results in a waste of these trace alloying elements and the base alloy is unusable.

Therefore, there is a need for a grain refinement method that can reduce the grain size of the alloy and improve the thermal conductivity and mechanical properties of the alloy.

Disclosure of Invention

Aiming at the problems, the invention provides a grain refining method, which can reduce the grain size of the alloy and simultaneously improve the heat-conducting property and the mechanical property of the alloy by only an alloy casting method without adding rare earth metals such as Ti and the like.

In order to achieve the purpose, the invention provides the following technical scheme:

a method of grain refinement comprising the steps of:

(1) smelting and batching, namely weighing pure aluminum, aluminum-boron intermediate alloy, other intermediate alloy and refining agent according to a certain proportion and drying all the materials;

(2) putting pure aluminum ingots into a smelting furnace, and heating until the pure aluminum ingots are completely melted;

(3) when the temperature is raised to 700-800 ℃, adding other intermediate alloys except the aluminum-boron intermediate alloy until the intermediate alloys are completely melted;

(4) when the temperature reaches 740 and 760 ℃, adding a refining agent twice for degassing and slagging off;

(5) adding Al-B intermediate alloy when the temperature reaches 740-760 ℃;

(6) stirring the molten metal liquid after the aluminum boron intermediate alloy is completely melted;

(7) when the temperature is reduced to 710-730 ℃, the molten metal liquid is poured into the metal mold for molding.

The ingredients are as follows: the content of B accounts for 0.002-0.100% of the total mass of the alloy comprising pure aluminum, the aluminum-boron intermediate alloy and other intermediate alloys, the mass of the refining agent accounts for 0.5-2.0% of the total mass of the melting stock, and the proportion of the pure aluminum and other intermediate alloys is prepared according to the actual performance requirement;

preferably, in the step (4), the chemical component of the refining agent is hexachloroethane, the adding amount of the hexachloroethane is 0.5-2.0% of the total mass of the alloy, and the total mass of the alloy is the total mass of the pure aluminum, the aluminum-boron intermediate alloy and other intermediate alloys in the step (1).

Preferably, the refining agent is completely pressed into the molten metal liquid at each time of addition, and is allowed to stand for 5 to 15 min.

Preferably, the adding amount of B in the aluminum boron intermediate alloy added in the step (5) is 0.002-0.100% of the total mass of the alloy, and the total mass of the alloy is the total mass of the pure aluminum, the aluminum boron intermediate alloy and other intermediate alloys in the step (1).

Preferably, the stirring time in the step (6) is 5-120 min.

Preferably, the temperature of the molten metal is maintained at 720-750 ℃ during the stirring in the step (6).

The other intermediate alloy in the step (3) is selected from one or more of aluminum iron, aluminum silicon, aluminum manganese, aluminum chromium, aluminum zinc, aluminum molybdenum, aluminum tin, aluminum copper, aluminum magnesium, aluminum cobalt, aluminum vanadium and aluminum nickel according to the actual performance requirement;

the grain refining method of the invention is different from the widely used boronizing treatment for impurity removal, the invention fully utilizes inevitable trace impurity elements in the alloy, adds trace B in the fusion casting process of the alloy, and reacts with inevitable trace impurities such as Ti, V, Cr, Zr and the like in pure aluminum and intermediate alloy to generate TiB₂、VB₂、CrB₂、ZrB₂The generated solid particles are uniformly dispersed in the melt by stirring and other modes to form new nucleation particles, so that the aggregation and sedimentation of the particles are avoided, the effect of grain refinement is achieved, and the mechanical property is improved by fine grain reinforcement.

In addition, after B reacts with Ti, V and the like to precipitate, standing and bottom precipitation are not needed, and the improvement of the heat conduction of the alloy can be achieved as well, because the adverse effect on the heat conduction performance of the alloy elements existing in a solid solution form is far more than that of a precipitation form. Therefore, Ti, V and the like are precipitated by adding B for reaction to improve the heat conduction of the alloy, and are uniformly distributed into heterogeneous nucleation points by stirring, so that the grain size is reduced, and the mechanical property is improved.

Meanwhile, compared with the existing refining method, the solid particles generated by the method have the advantages of no agglomeration and small sizeThe most common Al-5Ti-B refiner is taken as an example, and the refiner is composed of alpha-Al and Al₃Ti、TiB₂Composition is carried out; the invention directly adds B element, which does not introduce nucleation particles, but generates TiB in the melt through reaction₂Etc., directly generated TiB₂Does not generate agglomeration phenomenon, which is essentially different from the traditional addition of the refiner.

Compared with the prior art, the refining method has simple flow and only relates to the casting process; the aluminum alloy has low cost, does not additionally add rare earth metals and the like, has no metal loss, improves the heat-conducting property and the mechanical property of the alloy while refining grains, is suitable for all conventional aluminum alloy casting processes, and is suitable for industrial production.

Detailed Description

The technical solution of the embodiment of the present invention will be clearly and completely described below.

Example 1

A grain refinement method comprising the steps of:

preparing materials: 20g of Al20Fe, 12g of Al20Si, 5.4g of Al-3B, 1562.6g of 99% pure aluminum and two portions of 20g of hexachloroethane are weighed and dried completely. Adding 99% pure aluminum into a smelting furnace, heating to 750 ℃, adding Al-20Si and Al-20Fe intermediate alloy, completely melting the intermediate alloy, adding hexachloroethane refining agent twice at 750 ℃, one part at a time, completely pressing the refining agent into molten metal, and standing for 5 minutes for full reaction; and after refining, adding Al-3B intermediate alloy at 750 ℃, stirring for 30min after the temperature is reduced to 730 ℃, and pouring into a water-cooled copper mold when the temperature is reduced to 720 ℃, wherein the temperature of the water-cooled copper mold is 25 ℃.

The alloy refined by the grain refining method of the embodiment comprises the following chemical components in percentage by mass: 0.15% of Si, Fe: 0.25%, B: 0.007% of aluminum and the balance of inevitable impurities.

Example 2

A grain refining alloy comprising the steps of:

preparing materials: 24g of Al20Fe, 8g of Al20Si, 6.5g of Al-3B, 1561.5g of 99% pure aluminum and two portions of 20g of hexachloroethane are weighed and dried completely. Adding 99% pure aluminum into a smelting furnace, heating to 750 ℃, adding Al-20Si and Al-20Fe intermediate alloy, and completely melting; then adding the prepared hexachloroethane refining agent twice at 750 ℃, wherein one hexachloroethane refining agent is added at a time, and the refining agent is completely pressed into molten metal liquid and stands for 5 minutes for full reaction; adding Al-3B intermediate alloy at 750 ℃ after refining is finished; stirring for 30min after the temperature is reduced to 730 ℃, pouring into a water-cooled copper mold after the temperature is reduced to 720 ℃, wherein the temperature of the water-cooled copper mold is 25 ℃.

The alloy refined by the grain refining method of the embodiment comprises the following chemical components in percentage by mass: 0.10% of Si, Fe: 0.30%, B: 0.010 percent, and the balance of aluminum and inevitable impurities.

Example 3

A grain refining method comprises the following steps:

preparing materials: 5g of Al-3B master alloy, 1595g of 99% pure aluminum and two portions of 20g of hexachloroethane are weighed and dried completely. Adding 99% pure aluminum into a smelting furnace, heating to 750 ℃, adding the prepared hexachloroethane refining agent twice, one part at a time, completely pressing the refining agent into molten metal liquid, and standing for 5 minutes for full reaction; adding Al-3B intermediate alloy at 750 ℃ after refining is finished; stirring for 30min after the temperature is reduced to 730 ℃, pouring into a water-cooled copper mold after the temperature is reduced to 720 ℃, wherein the temperature of the water-cooled copper mold is 25 ℃. In this embodiment, no additional fe-containing and si-containing master alloy is added.

The alloy after grain refinement comprises the following chemical components in percentage by mass: 0.006 percent of B, and the balance of aluminum and inevitable impurities.

Comparative example 1

Preparing materials: 1600g of 99% pure aluminum and two portions of 20g of hexachloroethane are weighed and dried in their entirety. Adding 99% pure aluminum into a smelting furnace, heating to 750 ℃, adding the prepared hexachloroethane refining agent twice, one part at a time, completely pressing the refining agent into molten metal liquid, and standing for 5 minutes for full reaction; stirring for 30min after the temperature is reduced to 730 ℃, and pouring into a water-cooled copper mold when the temperature is reduced to 720 ℃, wherein the temperature of the water-cooled copper mold is 25 ℃; no master alloy, including Al-20Fe, Al-20Si, Al-3B master alloy, was added in this comparative example.

Comparative example 2

The casting process was substantially the same as that of example 1 except that the Al-20Si mass was weighed to be 24g and the 99% pure aluminum mass was 1545.6 g.

Comparative example 3

The casting process was substantially the same as that of example 3, except that the stirring temperature was 780 ℃.

The thermal conductivity and Vickers hardness of the alloys cast in examples 1-4 and comparative examples 1-3 were measured, and the results are shown in the following table.

As can be seen from the above table, the comparative example 1 contains only 99% pure aluminum, and compared with the comparative example 1, the grain sizes of the examples 1 to 3 in the invention are all significantly smaller than that of the comparative example 1, and the thermal conductivity and the hardness are both improved; in example 3, the grain size is reduced to 311 μm, and at the same time, the hardness is improved to some extent, and the thermal conductivity is greatly improved. In addition, the grain size is greatly reduced and the hardness is greatly improved in comparative example 2, but the heat conductivity is reduced because the addition amount of Fe and Si is too high. Compared with the embodiment 3, the stirring temperature in the comparative example 3 is too high, so that the generated solid particles are partially dissolved back to the matrix, the grain refining effect is obviously reduced, and the heat conductivity and the hardness are not obviously improved. The embodiment shows that the grain refining method provided by the invention has obvious refining effect, can improve the heat-conducting property and the mechanical property of the alloy at the same time, has simple process and only relates to the alloy casting process; low cost, no addition of any rare earth element and suitability for industrial production.

Therefore, the scope of the present invention should not be limited to the disclosure of the embodiments, but includes various alternatives and modifications without departing from the scope of the present invention, which is defined by the claims of the present patent application.