CN111996409A - A kind of grain refinement method for preventing silicon poisoning of aluminum-silicon alloy - Google Patents

Abstract

The invention belongs to the technical field of metal material application, and relates to a method for refining grains for preventing silicon poisoning of aluminum-silicon alloys. The silicon content of the aluminum-silicon alloy described in the present invention is 5-11 wt.%, and it is difficult to refine crystal grains with traditional titanium-boron-based refiners due to the poisoning effect of silicon. The present invention forms a large number of nucleated embryos with the refiner as the core and wraps the aluminum atoms by adding a refiner to the high-purity aluminum in advance, and then adds silicon to diffuse into the aluminum liquid to form an aluminum-silicon alloy, thereby avoiding the combination of silicon and titanium. The "silicon poisoning effect" occurs, which can effectively refine the grains and play the role of grain refinement strengthening.

Description

A kind of grain refinement method for preventing silicon poisoning of aluminum-silicon alloy

technical field

The invention belongs to the technical field of metal material application, and relates to a method for refining grains for preventing silicon poisoning of aluminum-silicon alloys.

Background technique

Cast aluminum-silicon alloys are an important class of lightweight materials, which are widely used in the manufacture of thin-walled parts of automobile bodies, engine parts, transmission system parts, radiators with complex shapes, and oil pipelines. Without any treatment, the coarse α-Al dendrites and a large number of brittle Al-Si eutectic structures in Al-Si alloys will greatly weaken the strength and plasticity of the alloys, which limits their applications in transportation and aerospace industries. In order to improve the strength and plasticity, various methods have been used to refine Al-Si alloys. By adding a refiner alloy containing heterogeneous nucleation particles to control the nucleation and growth of crystals during solidification, the solidification structure is refined. This method is widely used in aluminum-silicon industrial production. However, when the silicon concentration is greater than 5 wt.%, the grain refinement efficiency of the traditional Al-Ti-B refiner is significantly weakened, which is the silicon poisoning effect. Due to the influence of silicon poisoning, traditional aluminum-titanium-boron refiners have poor effect on the grain refinement of aluminum-silicon alloys. Therefore, this patent provides a method for refining grains for preventing silicon poisoning of aluminum-silicon alloys. Before the occurrence of "silicon poisoning" A titanium diboride hetero core wrapped by aluminum atoms was introduced as an effective embryo, thereby improving the grain refinement effect.

SUMMARY OF THE INVENTION

Based on this, the purpose of the present invention is to provide a method for refining grains for preventing silicon poisoning of aluminum-silicon alloys. The present invention preferentially generates bismuth particles wrapped by aluminum atoms by adding a titanium-boron-based refiner to high-purity aluminum in advance. The effective embryo of the titanium boride heterogeneous core is then diffused into the aluminum liquid by adding silicon atoms to avoid the "silicon poisoning" effect caused by the combination of silicon atoms and titanium atoms, and solve the problem of aluminum-silicon alloys with a silicon content of 5-11wt.%. difficult problem.

The technical solution adopted in the present invention is as follows

A method for refining grains for preventing silicon poisoning of aluminum-silicon alloys, the steps are as follows:

(1) Add a certain proportion of titanium-boron-based refiner to the high-purity aluminum melt;

(2) Refining and degassing, removing scum;

(3) Pour the aluminum melt mixed with the titanium-boron-based refiner into a high-purity silica glass container, heat it to 800 °C for a certain period of time, and cool it to 600 °C by means of step cooling and thermal diffusion. During the process, keep stirring to ensure that the silicon atoms generated by the reaction between the aluminum liquid and the silicon dioxide can fully diffuse into the aluminum liquid and form an aluminum-silicon alloy with a uniform silicon content of 5-11wt.%;

(4) The aluminum-silicon alloy liquid is poured into different molds to obtain a grain-refined alloy ingot or casting.

The method for refining grains for preventing silicon poisoning of aluminum-silicon alloys as claimed in claim 2, wherein step (1) comprises: adding a certain proportion of a compound capable of producing titanium diboride isotopes into the high-purity aluminum melt. A refiner of the mass core, the titanium diboride hetero core is wrapped by aluminum atoms to form a crystal embryo.

A method for refining grains for preventing silicon poisoning of aluminum-silicon alloys as claimed in claim 2, wherein step (3) comprises: pouring the aluminum melt mixed with the refining agent into a high-purity silica glass container In the process, silicon atoms are generated by the reaction between aluminum liquid and silicon dioxide. The silicon atoms diffuse in the aluminum liquid, but cannot be combined with titanium atoms due to the isolation of aluminum atoms, thus avoiding the occurrence of "silicon poisoning effect".

A method for refining grains for preventing silicon poisoning of aluminum-silicon alloys as claimed in claim 2, wherein step (3) comprises: after heating to 800 °C for a certain period of time, cooling to a temperature of 600°C. Keeping at 800°C for a certain period of time is to accelerate the reaction of aluminum and silicon dioxide to generate silicon atoms. Step cooling and thermal diffusion means that each time the temperature drops to a step temperature, the temperature is kept warm and diffused for a period of time. The purpose is to ensure that the aluminum-silicon melt remains semi-solid, and the liquid aluminum continues Reacts with silica and continuously generates silicon atoms.

The method for refining grains for preventing silicon poisoning of aluminum-silicon alloys as claimed in claim 2, wherein step (3) comprises: stirring constantly, which means using mechanical rod stirring, electromagnetic stirring, mechanical vibration, ultrasonic Vibration and other contact or non-contact agitation of the melt accelerates the uniform distribution of silicon atoms in the melt.

The method for refining grains for preventing silicon poisoning of aluminum-silicon alloys according to claim 2, wherein step (3) comprises: adjusting the speed and time of the reaction between aluminum and silicon dioxide by using the holding temperature and holding time , so as to control the content of silicon at 5-11wt.%.

Description of drawings

Fig. 1 is the microstructure morphology of the method for refining grains for preventing silicon poisoning of aluminum-silicon alloys prepared in Example 1

Fig. 2 is the microstructure morphology diagram of the method for refining grains for preventing silicon poisoning of aluminum-silicon alloy prepared in Example 2

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

A method for refining grains for preventing silicon poisoning of aluminum-silicon alloys, the steps are as follows:

(1) Put 99 grams of aluminum ingots with a purity of 99.95% into a crucible, and then put them into a pit furnace to heat up to 800 °C to melt, add 1 gram of aluminum five titanium boron refiner, and stir evenly; Put a high-purity silica glass container inside;

(2) Use argon gas with a purity of 99.5% to refine and degas to remove scum;

(3) Pour the aluminum liquid mixed with the refining agent into the high-purity silica glass container in step (1), keep the temperature at 800 °C, and continuously stir the mixed molten liquid during this process;

(4) Controlling the step cooling speed of the molten aluminum in step (3). For the first 2 hours, the temperature dropped by 10°C, 15°C, 15°C, and 20°C every 30 minutes; after that, the temperature dropped by 20°C every 30 minutes, and cooled to 600°C after a total of 9 hours, and then air-cooled;

(5) During the cooling process of step (4), the aluminum liquid is continuously stirred to ensure that the silicon atoms generated by the reaction between the aluminum liquid and the silicon dioxide can fully diffuse into the aluminum liquid and form a high-silicon aluminum-silicon alloy liquid with uniform composition;

(6) Pouring the high-silicon aluminum-silicon alloy liquid into a graphite mold to obtain an ingot with refined grains;

(7) The microstructure diagram is shown in Figure 1. The silicon content of the sample is about 8%, and the grain diameter is 200-400 μm, which can effectively prevent the occurrence of "silicon poisoning effect".

Embodiment 2

A method for refining grains for preventing silicon poisoning of aluminum-silicon alloys, the steps are as follows:

(1) Put 98 grams of aluminum ingots with a purity of 99.95% into a crucible, and then put them into a pit furnace to heat up to 800 ℃ to melt, add 2 grams of aluminum five titanium boron refiner, and stir evenly; Put a high-purity silica glass container inside;

(2) Use argon gas with a purity of 99.5% to refine and degas to remove scum;

(3) Pour the aluminum liquid mixed with the refining agent into the high-purity silica glass container in step (1), keep the temperature at 800 °C, and continuously stir the mixed molten liquid during this process;

(4) Controlling the step cooling speed of the molten aluminum in step (3). For the first 2 hours, the temperature dropped by 10°C, 15°C, 15°C, and 20°C every 30 minutes; after that, the temperature dropped by 20°C every 30 minutes, and cooled to 600°C after a total of 9 hours, and then air-cooled;

(5) During the cooling process of step (4), the aluminum liquid is continuously stirred to ensure that the silicon atoms generated by the reaction between the aluminum liquid and the silicon dioxide can fully diffuse into the aluminum liquid and form a high-silicon aluminum-silicon alloy liquid with uniform composition;

(6) Pouring the high-silicon aluminum-silicon alloy liquid into a graphite mold to obtain an ingot with refined grains;

(7) The microstructure diagram is shown in Figure 2. The silicon content of the sample is about 8%, and the grain diameter is 200-300 μm, which can effectively prevent the occurrence of "silicon poisoning effect".

Claims (8)

1. Firstly, adding a titanium boron refiner into high-purity aluminum, melting and fully mixing, pouring into a high-purity silica glass container, heating to 800 ℃, preserving heat for a certain time, cooling to 600 ℃ by adopting a stepped cooling and heat preservation diffusion mode, so that aluminum liquid reacts with silica, silicon atoms are replaced to diffuse into an aluminum solution, and the aluminum-silicon alloy with the refined crystal grains and the silicon content of 5-11wt.% is obtained.

2. A method for refining crystal grains to prevent silicon poisoning of aluminum-silicon alloy comprises the following steps:

(1) adding a titanium boron refiner in a certain proportion into the high-purity aluminum melt;

(2) refining, degassing and skimming dross;

(3) pouring the molten aluminum mixed with the titanium boron refiner into a high-purity silica glass container, heating to 800 ℃, preserving heat for a certain time, cooling to 600 ℃ in a stepped cooling and heat preservation diffusion mode, and stirring continuously in the process to ensure that silicon atoms generated by the reaction of the aluminum liquid and the silica can be fully diffused into the aluminum liquid and form an aluminum-silicon alloy with uniform components and silicon content of 5-11 wt%;

(4) and pouring the aluminum-silicon alloy liquid into different casting molds to obtain the grain refined alloy ingot or casting.

3. A method of refining grains to prevent poisoning of the silicon of the aluminium silicon alloy according to claim 2, wherein step (1) comprises: adding a refiner capable of generating a titanium diboride heterogeneous core into the high-purity aluminum melt in a certain proportion, wherein the titanium diboride heterogeneous core is wrapped by aluminum atoms to form a crystal blank.

4. A method of refining grains to prevent poisoning of the silicon of the al-si alloy as claimed in claim 2, wherein step (3) comprises: pouring the aluminum melt mixed with the refiner into a high-purity silicon dioxide glass container, and utilizing the reaction of aluminum liquid and silicon dioxide to generate silicon atoms, wherein the silicon atoms are diffused in the aluminum liquid but cannot be combined with titanium atoms under the isolation action of the aluminum atoms, thereby avoiding the occurrence of silicon poisoning effect.

5. A method of refining grains to prevent poisoning of the silicon of the al-si alloy as claimed in claim 2, wherein step (3) comprises: heating to 800 deg.C, holding for a certain time, and cooling to 600 deg.C by stepped cooling and heat-preserving diffusion.

The heat preservation at 6.800 ℃ is to accelerate the reaction of aluminum and silicon dioxide to generate silicon atoms, the step cooling and heat preservation diffusion means that heat preservation diffusion is carried out for a period of time when the temperature is lowered to one step, so as to ensure that the aluminum-silicon melt keeps semi-solid, and the liquid aluminum continuously reacts with the silicon dioxide and continuously generates silicon atoms.

7. A method of refining grains to prevent poisoning of the silicon of the al-si alloy as claimed in claim 2, wherein step (3) comprises: stirring continuously refers to stirring the melt by using a mechanical rod, electromagnetic stirring, mechanical vibration, ultrasonic vibration and other contact or non-contact methods to accelerate the silicon atoms to be uniformly distributed in the melt.

8. A method of refining grains to prevent poisoning of the silicon of the al-si alloy as claimed in claim 2, wherein step (3) comprises: the reaction speed and time of aluminum and silicon dioxide are adjusted by using the holding temperature and holding time, so that the content of silicon is controlled to be 5-11 wt.%.

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