阅读说明：本技术 一种细化过共晶铝硅合金初生硅相的方法 (Method for refining hypereutectic aluminum-silicon alloy primary silicon phase ) 是由 廖恒成 陈浩 于 2020-06-29 设计创作，主要内容包括：本发明公开了一种细化过共晶铝硅合金初生硅相的方法,涉及金属铸造技术领域。首先通过高功率的电阻坩埚炉对过共晶铝硅合金进行熔炼,采用热电偶和可控硅温控仪对熔体进行控温,熔清后进行除气去渣精炼处理。随后进行低温熔体处理：先断电开炉盖自然冷却,接近设定温度630-660℃时通电调整电炉功率系数进行保温一定时间,之后再断电连续冷却同时施加轻微搅拌,至设定温度580-600℃时采用玻璃管吸液取样方法获取合金组织。本发明对过共晶铝硅合金中出现的初生硅有很好的细化和球化效果,初生硅颗粒尺寸细小、分布均匀；本发明不会在熔体中引入其他杂质,操作成本低,不会对环境造成污染。(The invention discloses a method for refining a hypereutectic aluminum-silicon alloy primary silicon phase, and relates to the technical field of metal casting. Firstly, hypereutectic aluminum-silicon alloy is smelted through a high-power resistance crucible furnace, a thermocouple and a silicon controlled temperature controller are adopted to control the temperature of a melt, and degassing, deslagging and refining treatment are carried out after the melt is completely melted. Then carrying out low-temperature melt treatment: and (3) powering off, opening the furnace cover, naturally cooling, electrifying when the temperature is close to the set temperature of 630-660 ℃, adjusting the power coefficient of the electric furnace, carrying out heat preservation for a certain time, then powering off, continuously cooling, and slightly stirring, and obtaining the alloy structure by adopting a glass tube imbibition sampling method when the temperature is up to the set temperature of 580-600 ℃. The invention has good refining and spheroidizing effects on primary silicon appearing in hypereutectic aluminum-silicon alloy, and primary silicon particles have small size and uniform distribution; the invention does not introduce other impurities into the melt, has low operation cost and does not cause pollution to the environment.)

1. A method for refining hypereutectic aluminum-silicon alloy primary silicon phase is characterized in that low-temperature melt is adopted to treat and refine the primary silicon, and the method comprises the following steps:

(1) placing the hypereutectic aluminum-silicon alloy raw material into a resistance crucible furnace, and heating to 600-620 ℃;

(2) heating the raw materials obtained in the step (1) to 750-770 ℃ for smelting, and preserving heat after melting down;

(3) cooling the alloy melt obtained in the step (2) to 720-730 ℃ in a furnace, and performing degassing, deslagging and purification treatment;

(4) continuing to preserve the heat of the alloy melt obtained in the step (3) at the temperature of 720-;

(5) cutting off the power of the alloy melt obtained in the step (4), opening the furnace and cooling to 580-600 ℃;

(6) and (5) carrying out liquid suction sampling on the alloy melt obtained in the step (5) through a glass tube to obtain a tissue state.

2. The method for refining the primary silicon phase of a hypereutectic aluminum-silicon alloy as claimed in claim 1, wherein in step (1), the hypereutectic aluminum-silicon alloy raw material is preheated at 300 ℃ and 250 ℃ for 30 minutes and then placed in a resistance crucible furnace.

3. A method for refining the primary silicon phase of a hypereutectic aluminum silicon alloy according to claim 1, wherein in step (2) the temperature is maintained for 20-40 minutes after melting down.

4. The method for refining the primary silicon phase of a hypereutectic aluminum-silicon alloy as claimed in claim 1, wherein in step (4), the alloy melt obtained in step (3) is further subjected to heat preservation at 720-730 ℃ for 20-40 minutes.

5. The method for refining the primary silicon phase of a hypereutectic Al-Si alloy as claimed in claim 1, wherein in step (4), the temperature is controlled within ± 2 ℃ of 630-660 ℃ for 5-15 minutes.

6. A method for refining the primary silicon phase of a hypereutectic aluminum silicon alloy according to claim 1, wherein during cooling in step (5) a slight stirring is applied at all times.

7. A method for refining the primary silicon phase of a hypereutectic aluminum silicon alloy according to claim 1, wherein in step (6), the inner diameter of the glass tube is 10 mm.

8. A method for refining a primary silicon phase of a hypereutectic aluminum silicon alloy according to claim 1, wherein the refined primary silicon has a size of 15-20 μm, a rounded morphology and a uniform distribution.

Technical Field

The invention belongs to the metal casting technology, and particularly relates to a method for refining a hypereutectic aluminum-silicon alloy primary silicon phase.

Background

In recent years, domestic economy has been rapidly developed, and environmental problems have been accompanied therewith. The country has already put a lot of policies to improve the environmental quality of China, and one of them is the light weight of automobiles. In the field of automobiles, in order to replace steel with aluminum, important parts of automobile pistons, cylinders and the like are replaced by aluminum alloys, and particularly, aluminum-silicon alloys are most widely applied. In automobile part materials, hypereutectic aluminum-silicon alloy in aluminum alloy has the advantages of high specific strength, good wear resistance, light weight, good heat resistance, low thermal expansion coefficient and the like, and gradually becomes a research hotspot of researchers. Compared with hypoeutectic aluminum-silicon alloy and eutectic aluminum-silicon alloy, the hypereutectic aluminum-silicon alloy has better fluidity, is an important casting alloy and wear-resistant material, and has been successfully applied in the automobile industry. However, the untreated hypereutectic aluminum-silicon alloy structure often has thick primary silicon in the shape of plate sheet, five-petal star and octahedron, which seriously reduces the mechanical property of the material and limits the application of the material, so that the refinement of the primary silicon phase in the hypereutectic aluminum-silicon alloy is very important, and the higher the silicon content is, the more important the refinement of the primary silicon phase is.

In order to improve the size, distribution and morphology of the primary silicon phase, researchers at home and abroad have adopted a number of methods. Mainly comprises methods of modification treatment, rapid solidification, melt overheating treatment, semi-solid treatment and the like.

The modification treatment is mainly to add a certain modifier into the hypereutectic aluminum-silicon alloy to change the distribution, the appearance and the size of primary silicon in the hypereutectic aluminum-silicon alloy. Sterner discovered that phosphorus (red phosphorus) can be used as a modifier for hypereutectic aluminum-silicon alloy to achieve the effect of refining primary silicon, and therefore applied for a patent. Liu et Al developed a novel Al-2.5% P master alloy, which was found to refine primary silicon particles in hypereutectic Al-Si alloys. Lin et Al investigated the effect of La-Ce on the Al-18Si-4Cu-0.5Mg alloy structure and found that primary silicon particles are significantly refined from coarse, blocky and irregular polygons to flakes. However, such methods have some disadvantages, such as: the addition of additional alterants tends to increase the cost of the phenanthrene; the deteriorated substances (P and the like) cause serious pollution to production and social environment; the deterioration effect is not very ideal, and related impurity elements are introduced.

Rapid solidification refers to a process in which a metal liquid is transformed into a solid state at an extremely rapid solidification rate at a cooling rate much greater than that of a general process. Shafizadeh et Al combines rapid solidification and semi-solid forming processes to refine primary silicon particles of Al-30Si-5Fe alloys. But the production and application of the actual casting are still technically difficult and the effect is limited.

The melt overheat treatment method is a method of overheating an alloy melt to a higher temperature higher than the melting point of the alloy, preserving heat for a period of time, and then directly casting the melt or casting the melt into a casting mold after cooling the melt to a certain temperature by adopting a certain method to achieve structure refinement. Li and the like study the influence of melt overheating treatment on the structure of the hypereutectic Al-20Si alloy, and as a result, the primary silicon of the hypereutectic Al-20Si alloy can be refined by increasing the melt overheating temperature. Although the primary silicon can be refined to a certain extent by the melt overheating treatment, the process method has the defects that the selection of the overheating temperature is blind, and the appearance and the distribution of the primary silicon are not ideal.

Semi-Solid Metal Forming (SSM) is generally classified into two types, namely rheoforming and thixoforming. Because the thixoforming semi-solid metal blank is convenient to convey and heat, the research and application of the metal semi-solid forming technology mainly focuses on the thixoforming process, and the application is the most widely in the industry at present. The main blank making method comprises electromagnetic stirring, mechanical stirring, ultrasonic vibration and the like, so that the solid-liquid mixed slurry with liquid metal containing a certain solid phase fraction is prepared, and the solid phase fraction is usually more than 30%. Haghayeghi et al studied the effect of electromagnetic stirring, ultrasonic treatment and combinations thereof on the refinement of primary silicon in A390 alloys. The result is a large variation in the morphology and size of nascent silicon. Kim et Al refined the primary silicon phase by applying mechanical stirring during the cooling of the hypereutectic Al-15.5Si alloy. The methods have good effect of refining the primary silicon, but all the methods need additional mechanical equipment for assistance, increase the process period and consume a large amount of energy.

In conclusion, the refinement, the shape and the distribution of the primary silicon in the hypereutectic aluminum-silicon alloy structure are improved, and the method has important engineering application value. Although many developments and obvious effects have been achieved in domestic and foreign research and invention, the refinement, morphology and distribution of nascent silicon still need to be improved continuously in order to obtain better effect, and the method has the advantages of no pollution, convenience and easy operation, no influence on productivity and the like.

In the invention, a common hypereutectic aluminum-silicon alloy is used, the primary silicon phase in the alloy is refined through low-temperature melt treatment, and the primary silicon phase in the alloy is uniformly distributed, complete in form and considerable in solid phase fraction. At present, no report related to the refining of the hypereutectic aluminum-silicon alloy primary silicon phase by the method is found.

Disclosure of Invention

The purpose of the invention is as follows: in view of the above problems in the prior art, the present invention provides a novel method for refining the primary silicon phase of hypereutectic aluminum-silicon alloys.

The technical scheme is as follows: the invention relates to a method for refining a primary silicon phase of a hypereutectic aluminum-silicon alloy, which adopts low-temperature melt to treat and refine the primary silicon and comprises the following steps:

(1) placing the hypereutectic aluminum-silicon alloy raw material into a resistance crucible furnace, and heating to 600-620 ℃;

(2) heating the raw materials obtained in the step (1) to 750-770 ℃ for smelting, and preserving heat after melting down;

(3) cooling the alloy melt obtained in the step (2) to 720-730 ℃ in a furnace, and performing degassing, deslagging and purification treatment;

(4) continuing to preserve the heat of the alloy melt obtained in the step (3) at the temperature of 720-;

(5) cutting off the power of the alloy melt obtained in the step (4), opening the furnace and cooling to 580-600 ℃;

(6) and (5) carrying out liquid suction sampling on the alloy melt obtained in the step (5) through a glass tube to obtain a tissue state.

The low-temperature melt treatment refers to the process treatment of the melt in a liquid-solid two-phase region of the hypereutectic aluminum-silicon alloy.

In the step (1), the hypereutectic aluminum-silicon alloy raw material is preheated at the temperature of 250 ℃ and 300 ℃ for 30 minutes and then is placed into a resistance crucible furnace.

In the step (2), heat preservation is carried out for 20-40 minutes after melting down.

In the step (4), the alloy melt obtained in the step (3) is continuously kept at 720-730 ℃ for 20-40 minutes.

In the step (4), the temperature is controlled within +/-2 ℃ of 630-660 ℃ for 5-15 minutes.

In the step (5), slight stirring is always applied in the cooling process, so that the final refining effect is prevented from being influenced by the agglomeration phenomenon of primary silicon phases in the melt.

Preferably, in the step (6), the inner diameter of the glass tube is 10 mm.

In the steps of the method, all materials and moulds in contact with the melt are preheated for more than 30 minutes at the preheating temperature of 250-300 ℃. Wherein all materials in contact with the melt include a strainer, a bell, a refining agent, and a mold used for casting.

Preferably, the method comprises the steps of:

(1) all materials and molds in contact with the melt need to be preheated for more than 30 minutes at the preheating temperature of 250 ℃. The hypereutectic aluminum-silicon alloy raw material is put into a resistance crucible furnace and heated to 600 ℃.

(2) Heating the raw materials obtained in the step (1) to 750-770 ℃ for smelting, and preserving heat for 30 minutes after melting down.

(3) And (3) cooling the alloy melt obtained in the step (2) to 720 ℃ in a furnace, and carrying out degassing, deslagging and purifying treatment.

(4) And (3) preserving the temperature of the alloy melt obtained in the step (3) at 720 ℃ for 30 minutes, then cooling, and controlling the temperature within +/-2 ℃ of the set temperature (630-.

(5) And (5) carrying out isothermal treatment on the alloy melt obtained in the step (4) for 10 minutes, then cutting off the power, opening the furnace and cooling to the set temperature (590-600 ℃). Slight stirring was applied throughout the cooling.

(6) And (5) carrying out liquid suction sampling on the alloy melt obtained in the step (5) through a glass tube to obtain a tissue state. Wherein the inner diameter of the glass tube is 10 mm.

The primary silicon refined by the method has the size of 15-20 mu m, round appearance and uniform distribution.

Has the advantages that: compared with the prior art, the invention has the following advantages: (1) the invention discloses a novel method for refining a hypereutectic aluminum-silicon alloy primary silicon phase, which has good refining and spheroidizing effects on primary silicon appearing in the hypereutectic aluminum-silicon alloy, the size of the refined primary silicon is 15-20 mu m, the appearance is rounded, edges and corners are not clear any more, and the distribution is uniform. (2) In the invention, no alterant is added in the operation process, so that the serious pollution of the past method for adding the alterant to the environment is avoided, other impurities cannot be introduced into the melt, and the operation cost is low.

Drawings

FIG. 1 shows the structure of a hypereutectic Al-Si alloy obtained by holding the melt at 640 ℃ for 10 minutes and then cooling the melt to 590 ℃ for 5 minutes in a glass tube in example 1;

FIG. 2 shows the structure of a hypereutectic Al-Si alloy obtained by holding the melt at 640 ℃ for 10 minutes and then sampling the melt through a glass tube cooled to 600 ℃ for 5 minutes in example 2;

FIG. 3 shows the structure of a hypereutectic Al-Si alloy obtained in a metal mold by direct casting of the melt at 720 ℃ in example 3;

FIG. 4 shows the structure of the hypereutectic Al-Si alloy obtained in example 4 by holding the melt at 640 ℃ for 10 minutes and then cooling the melt to 590 ℃ for 10 minutes and pouring the melt into a metal mold.

Detailed Description

In order to make the technical solutions of the present invention more clearly understood by those skilled in the art, the technical solutions of the present invention will be described in detail below with reference to specific embodiments:

the substantial connotation and the remarkable effect of refining the primary silicon by the method are clarified by different examples by taking Al-16Si-4.2Cu-0.6Mg-0.8Fe alloy as an example.