CN112626392A

CN112626392A - Cast aluminum-silicon alloy and preparation method thereof

Info

Publication number: CN112626392A
Application number: CN202011486592.4A
Authority: CN
Inventors: 孙自来
Original assignee: Chengdu Huiteng Chuangzhi Information Technology Co ltd
Current assignee: Chengdu Huiteng Chuangzhi Information Technology Co ltd
Priority date: 2020-12-16
Filing date: 2020-12-16
Publication date: 2021-04-09
Anticipated expiration: 2040-12-16
Also published as: CN112626392B

Abstract

The invention discloses a cast aluminum-silicon alloy and a preparation method thereof. The cast aluminum-silicon alloy comprises the following components in percentage by mass: si: 8.5-10.5%; fe: 0.1-0.2%; co: 0.15 to 0.32 percent; b: 0.04-0.15%; mixing rare earth: 0.2-0.3%; zn: 0.1-0.5%; unavoidable impurities: less than 0.15%; the balance being Al. The aluminum-silicon alloy has high thermal conductivity and toughness and good fluidity, is easy to form complex thin-wall parts, and can meet the use requirements in the photovoltaic field.

Description

Cast aluminum-silicon alloy and preparation method thereof

Technical Field

The invention relates to the technical field of metal materials, in particular to a cast aluminum-silicon alloy and a preparation method thereof.

Background

The rapid popularization of photovoltaic power generation has increasingly high requirements on the heat dissipation capacity of a photovoltaic inverter. The photovoltaic inverter is often required to be installed in outdoor severe environment, the product sealing performance of the photovoltaic inverter needs to meet the level above IP67, and the high sealing performance provides good protection for the internal electronic components of the inverter and simultaneously causes the internal high heat and high voltage to be difficult to release in extreme cases. In order to avoid brittle rupture of the inverter in extreme cases, the die-cast aluminum-silicon alloy heat dissipation shell is also required to have good toughness so that the die-cast aluminum-silicon alloy heat dissipation shell releases pressure through sufficient deformation under the explosive impact load, namely, ductile rupture is realized, and brittle rupture is avoided. This high requirement for toughness is also not met by these conventional die-cast aluminum-silicon alloys. In addition, along with the rapid improvement of the integration degree of electronic components, the inverter shell and the communication die casting shell are designed to have a large number of complex thin-wall radiating teeth, high-low bosses and deep cavity structures for adapting to the high integration degree of the electronic components, and have complex shapes with larger sizes, and the die casting of the complex shapes needs the aluminum-silicon alloy to have good fluidity.

The general thermal conductivity of the existing die-casting aluminum-silicon alloy is 90-150W/(m.K), the most widely used ADC12 aluminum-silicon alloy has excellent die-casting manufacturability, but the thermal conductivity is only 96W/(m.K), and the elongation is only 1%. The thermal conductivity of the die-casting aluminum-silicon alloy EN AC-44300 widely used for the heat-conducting shell can reach 150W/(m.K) in the casting state, but the elongation is only 1% -2%. The heat conductivity and toughness of these conventional die-cast aluminum-silicon alloys are completely unable to meet the requirements of the above-mentioned products with high heat loss density, high power and high sealing performance. Some aluminum-silicon alloys can reach the thermal conductivity of 180W/(m.K), but the content of Si element is only about 5%, and serious die sticking problem is difficult to avoid due to insufficient fluidity and no Fe element during die casting, and complicated thin-wall parts such as radiating teeth and the like are difficult to prepare through a die casting process.

Therefore, it is a research direction of those skilled in the art to design an aluminum-silicon alloy which has high thermal conductivity and toughness, good fluidity, and is easy to form complicated thin-walled parts.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to solve the problems that the existing aluminum-silicon alloy is poor in heat dissipation and toughness and cannot meet the requirements of the photovoltaic field on the aluminum-silicon alloy, and the like, and provides a cast aluminum-silicon alloy and a preparation method thereof.

In order to solve the technical problems, the invention adopts the following technical scheme:

the cast aluminum-silicon alloy comprises the following components in percentage by mass:

si: 8.5-10.5%; fe: 0.1-0.2%; co: 0.15 to 0.32 percent; b: 0.04-0.15%; mixing rare earth: 0.2-0.3%; zn: 0.1-0.5%; unavoidable impurities: less than 0.15%; the balance being Al.

Preferably, the mixed rare earth comprises Eu and La, wherein the Eu accounts for 0.1-0.15% and the La accounts for 0.08-0.15% in percentage by mass. The mass ratio of Si to the mixed rare earth is 37-43: 1.

further, the mass ratio of Co to Fe is 1.5-1.6: 1.

the inevitable impurities include elements of Cr, Mn, V and Ti, and the total amount is not more than 0.01%.

The silicon content influences the die casting fluidity and the solidification shrinkage rate of the aluminum-silicon alloy, when the silicon content is close to the vicinity of a eutectic point, the aluminum-silicon alloy has a narrower solidification interval, the fluidity of the aluminum-silicon alloy is best, the solidification shrinkage rate is also smaller, the aluminum-silicon alloy is ensured to have good casting forming performance and low hot cracking tendency, and the aluminum-silicon alloy can be used for forming complex thin-walled parts through a die casting process. But too high a silicon content reduces the toughness and thermal conductivity of the material. Therefore, the Si content in the present invention is 8.5 to 10.5%.

The plasticity of the aluminum-silicon alloy is mainly influenced by the quantity and the shape of eutectic silicon and impurity phases (such as iron-rich phase). When eutectic silicon or impurity phase exists in a coarse needle sheet shape, a severe stress concentration exists in a local area of a phase interface with an aluminum matrix, thereby causing crack initiation. Therefore, the eutectic silicon is changed from a coarse needle sheet to a fine fiber to reduce stress concentration, and the iron-containing phase should be prevented from growing into a coarse sheet β phase.

The Fe element is added mainly for preventing die sticking in die casting, although the Fe element has no obvious influence on the thermal conductivity, the content of the Fe element is strictly controlled to be 0.1-0.2% for obtaining high plasticity of the material, and the excessive Fe element is prevented from forming thick needle sheet-shaped beta to generate serious fracture relative to an aluminum matrix so as to reduce the toughness of the aluminum-silicon alloy.

In industrial application, Mn is generally added into the iron-containing aluminum-silicon alloy according to the Mn/Fe value of 0.6-0.83, an AlFeSiMn phase can be formed, the harm of iron elements to plasticity can be weakened to a certain extent, but the heat-conducting property of the aluminum-silicon alloy can be seriously reduced by the manganese elements. The addition of Co prevents Fe from forming harmful needle-like beta phases on the one hand, and on the other hand, Co does not combine with silicon, so that fewer additional phases (impurity phases) are formed in the aluminum-silicon alloy, and the elongation of the material is higher. The invention relates to a method for preparing aluminum-silicon alloy, which comprises the following steps of: co element is added according to the proportion of 1.5-1.6 of Fe to neutralize the harm of the Fe element, and the aluminum-silicon alloy with higher heat-conducting property is obtained.

The Zn element has slight influence on the thermal conductivity, and can improve the strength of the material and meet wider application.

The invention adopts mixed rare earth, and the mixed rare earth comprises La and Eu. Eu is the best refining and modifying element of eutectic Si, and has the advantages of good refining and modifying effect, long duration, good reproducibility and the like. Eu is added, so that the problem of air suction caused by the deterioration of the traditional Na and Sr elements can be avoided, the form of eutectic Si is changed from thick needles to fine uniform particles, the secondary dendrite spacing of aluminum is reduced, and the casting fluidity, strength and plasticity of the aluminum-silicon alloy are improved. However, too high a Eu concentration may cause a decrease in thermal conductivity of the Al-Si alloy. The added La element can react with elements such as Si, Fe and the like to generate La-Si-Fe compound, and the solid solution of Si and Fe in an aluminum matrix is reduced, so that the heat conduction performance is improved, and meanwhile, La can obviously refine eutectic silicon.

Through a large amount of researches and experiments, the fact that due to the fact that a proper amount of Eu and La are added at the same time, not only can the eutectic silicon be deteriorated, but also the elongation rate is improved, and meanwhile, the thermal conductivity can be improved. When the Eu + La content is 0.2-0.3%, and Si: (Eu + La) is 37-43: 1, the eutectic silicon is fully and completely deteriorated, and meanwhile, the heat conduction performance of the aluminum-silicon alloy is obviously improved, and the effect is better than that when Eu or La is singly added. When the mass ratio of Si to (Eu + La) is significantly less than 37: 1, the eutectic silicon can be insufficiently deteriorated, the elongation is obviously influenced, the plasticity of the material is reduced, and meanwhile, the thermal conductivity is also influenced to a certain extent. When the mass ratio of Si to (Eu + La) is obviously more than 43: 1, the deterioration of the eutectic silicon is guaranteed, but the thermal conductivity of the alloy is remarkably reduced by the excessive rare earth.

The thermal conductivity of an alloy corresponds to the electrical conductivity, and can be expressed by the wedgeman-franz law (WFL) which describes the correspondence between the electrical conductivity and the thermal conductivity of a metal, namely:

in the formula: λ is the thermal conductivity, δ is the electrical conductivity, L is the lorentz constant, and for aluminum L ═ 2.2 × 10W · K, T is the absolute temperature.

The defects, solid solution atoms or precipitated phases in the metal crystal lattice can cause lattice distortion to cause the change of the electric field period, thereby increasing the scattering probability of free electrons, reducing the mean free path of the electrons and causing the reduction of the heat conduction and the electric conduction of the alloy. By reducing the number of solid solution atoms in the aluminum matrix, the lattice distortion of the aluminum matrix is reduced, and the probability of scattering free electrons in the aluminum matrix crystal is reduced, so that the thermal conductivity of the aluminum alloy can be improved. Meanwhile, the scattering of free electrons can be influenced by the morphology of the eutectic silicon, the scattering probability of the eutectic silicon to the free electrons is reduced when the eutectic silicon is changed from a thick sheet shape to a thin and small fiber shape, and the thermal conductivity of the material can be further improved. The solid solution of Cr, Mn, V, Ti and other elements has obvious damage to the heat conduction and the electric conduction of the aluminum, and the solid solution not only causes the lattice distortion of the aluminum matrix, but also strongly absorbs free electrons in the aluminum matrix for filling the incomplete electron layers of the Cr, Mn, V and Ti, thereby leading to the remarkable reduction of the free electrons for the heat conduction and the electric conduction. In the solid solution state, the harmful effect of every 1 percent (Cr + Mn + V + Ti) on the conductivity is 5 times of the harmful effect of every 1 percent of silicon on the conductivity of aluminum, so the content of Cr + Mn + V + Ti in the aluminum-silicon alloy is less than 0.01 percent.

The added B element can be combined with impurity elements commonly found in aluminum-silicon alloys such as Ti, V and Cr to form TiB₂、V₂B₃、Cr₂B and high-melting-point refractory boride are precipitated, so that the impurity elements are converted into a boride precipitation state from a solid solution state in an aluminum matrix, the damage of the impurity elements on the thermal conductivity is eliminated, and high thermal conductivity is obtained.

The invention also provides a preparation method of the cast aluminum-silicon alloy, which adopts the components and the mixture ratio of the cast aluminum-silicon alloy, and specifically comprises the following steps:

(1) weighing industrial pure aluminum, crystalline silicon, Al-20Fe intermediate alloy, Al-10Co intermediate alloy, Al-3B intermediate alloy, Al-La intermediate alloy, pure zinc and Al-Eu intermediate alloy according to a set chemical component according to a metering ratio;

(2) putting industrial pure aluminum preheated to 150-200 ℃ into a smelting furnace for melting, wherein the melting temperature is 760-790 ℃, adding a deslagging agent accounting for 0.4% of the mass of an aluminum ingot after melting, stirring for 30 minutes, deslagging and keeping the temperature for 30 minutes;

(3) cooling the melt in the step (2) to 750 ℃, adding crystalline silicon, Al-20Fe intermediate alloy and Al-10Co intermediate alloy, cooling to 720 ℃ after the melt is completely melted, adding Al-3B intermediate alloy, stirring and standing for 10 minutes, and removing bottom sediment and surface scum; cooling to 680-700 ℃, protecting the melt with inert gas, adding Al-La intermediate alloy, Al-Eu intermediate alloy and pure zinc, pressing the mixture into the bottom of a smelting furnace for smelting, and standing for 10 minutes after the smelting is finished to remove bottom sediment and surface scum;

(4) heating the melt in the step (3) to 710-720 ℃, weighing a sodium-free powdery refining agent according to the proportion of 1-2 per mill of the total amount of the furnace charge, performing blowing refining, skimming after refining for 5-10 minutes, and standing for 10-20 minutes;

(5) and (4) die-casting the melt obtained in the step (4), controlling the furnace temperature at 660-680 ℃, controlling the temperature of the die at 180-210 ℃, introducing cooling water after the die is normal, pressing the aluminum liquid into a die cavity of the die, and obtaining the cast aluminum-silicon alloy, wherein the injection speed is 0.5-3 m/s, and the casting pressure is 80-130 MPa.

Further, in the step (1), the method also comprises the steps of washing and drying the weighed raw materials. In the step (3), the method also comprises the step of performing stokehole composition analysis on the melt after all materials are added and melted. The steps of the stokehole component analysis are as follows: sampling in the melt, cooling to room temperature, analyzing chemical components, calculating and adding corresponding raw materials by taking alloy element components as targets, and enabling the melt components and the proportion to reach the designed range.

In the preparation of aluminium-silicon alloys, the alloy is strictly controlledAdding time of the gold element. Adding crystalline silicon, Al-20Fe intermediate alloy and Al-10Co intermediate alloy after the aluminum ingot is melted, adding Al-3B intermediate alloy after the aluminum ingot is completely melted, fully and uniformly stirring and standing the mixture to ensure that B can fully react with impurity elements such as Cr, Mn, V, Ti and the like in the melt to generate CrB₂、TiB₂、VB₂And MnB₂And the compounds are stood and precipitated to the bottom, so that the harmful precipitates are discharged out of the melt, and the heat-conducting property of the aluminum-silicon alloy is improved. After the step of removing impurity elements such as Cr, Mn, V, Ti and the like, adding Al-La intermediate, Al-Eu intermediate alloy and pure zinc to reduce solid solution of Si and Fe in an aluminum matrix, fully modifying eutectic silicon and moderately strengthening the matrix, thereby preparing the die-casting aluminum-silicon alloy with high heat conductivity and high toughness.

Compared with the prior art, the invention has the following beneficial effects:

1. in the cast aluminum-silicon alloy, the content of Si element is 8.5-10.5%, so that the aluminum-silicon alloy has better fluidity, the aluminum-silicon alloy has good casting forming performance and low hot cracking tendency, and the aluminum-silicon alloy can be formed into complex thin-walled parts through a die-casting process; the modification of eutectic Si and the purification of a matrix are realized by adopting the mixed rare earth Eu + La, the defects of air suction and the like caused by modification of Sr are avoided, the elongation rate can be greatly improved, and the secondary dendrite spacing of aluminum can be reduced, so that the strength of the material is improved; zn is adopted to improve the strength of the material; co is adopted to improve the morphology of the Fe phase, reduce the cracking of the Fe-containing phase relative to the matrix, improve the toughness of the material and do not damage the thermal conductivity; and B is adopted to eliminate impurities such as Ti, V, Mn, Cr and the like. Through the comprehensive action of the elements, the prepared cast aluminum-silicon alloy has higher thermal conductivity and toughness in the casting state, and meets the application requirements in the industries of communication, automobiles, photovoltaic and the like.

2. Compared with the existing cast aluminum-silicon alloy, the cast aluminum-silicon alloy has higher thermal conductivity and fracture elongation (namely toughness), can achieve yield strength of 135MPa, tensile strength of 285MPa and elongation of 12.6 percent in an as-cast state, and has thermal conductivity of 185W/(m.K).

3. The preparation method provided by the invention has the advantages that the aluminum ingot is melted firstly, the Al-20Fe intermediate alloy and the Al-10Co intermediate alloy are added, and then the Al-3B intermediate alloy, the Al-La intermediate alloy, the Al-Eu intermediate alloy and the pure zinc are sequentially added, so that all the components can fully participate in the reaction, harmful impurities in the melt are effectively removed, the burning loss of raw materials is reduced, the preparation time of the die-casting aluminum-silicon alloy is shortened, and the preparation cost is reduced.

Detailed Description

The present invention will be described in further detail with reference to examples.

Example 1

The cast aluminum-silicon alloy comprises the following components in percentage by mass: si: 8.5 percent; fe: 0.1 percent; co: 0.15 percent; eu: 0.12 percent; b: 0.04 percent; la: 0.09%; zn: 0.2 percent; unavoidable impurities Cr + Mn + V + Ti: less than 0.01%; the balance being Al.

The preparation method of the cast aluminum-silicon alloy comprises the following steps:

(1) according to the set chemical components, weighing industrial pure aluminum, crystalline silicon, Al-20Fe intermediate alloy, Al-10Co intermediate alloy, Al-3B intermediate alloy, Al-La intermediate alloy, pure zinc and Al-Eu intermediate alloy according to the metering ratio. And cleaning and drying the weighed raw materials for later use.

(2) Putting the industrial pure aluminum preheated to 150 ℃ into a smelting furnace for melting, wherein the melting temperature is 780 ℃, adding a deslagging agent accounting for 0.4 percent of the mass of the aluminum ingot after melting, stirring for 20 minutes, and keeping the temperature for 30 minutes after deslagging;

(3) cooling the melt in the step (2) to 750 ℃, adding crystalline silicon, Al-20Fe intermediate alloy and Al-10Co intermediate alloy, cooling to 700 ℃ after the melt is completely melted, adding Al-3B intermediate alloy, stirring and standing for 20 minutes, and removing bottom sediment and surface scum; cooling to 680 ℃, protecting the melt with inert gas, adding Al-La intermediate alloy, Al-Eu intermediate alloy and pure zinc into the melt, and pressing the mixture into the bottom of a smelting furnace for melting. And standing for 20 minutes after the melting is finished, and removing bottom sediments and surface floating slag. And performing stokehole component analysis after melting, detecting the component content of the alloy melt, and feeding or diluting the melt with unqualified component content to enable the component content to reach the qualified range.

(4) Heating the melt in the step (3) to 710 ℃, weighing a sodium-free powdery refining agent according to 1 per mill of the total amount of the furnace charge, performing blowing refining, skimming after refining for 10 minutes, and standing for 20 minutes;

(5) and (4) die-casting the melt obtained in the step (4), controlling the furnace temperature at 660 ℃, the mold temperature at 210 ℃, introducing cooling water after the mold is normal, pressing the molten aluminum into a mold cavity, and obtaining the aluminum-silicon alloy, wherein the injection speed is 1.8m/s, and the casting pressure is 85 MPa.

Example 2

The cast aluminum-silicon alloy comprises the following components in percentage by mass: si: 9.0 percent; fe: 0.1 percent; co: 0.16 percent; eu: 0.13 percent; b: 0.04 percent; la: 0.08 percent; zn: 0.3 percent; unavoidable impurities Cr + Mn + V + Ti: less than 0.01%; the balance being Al.

The preparation method is the same as example 1.

Example 3

The cast aluminum-silicon alloy comprises the following components in percentage by mass: si: 9.5 percent; fe: 0.15 percent; co: 0.23 percent; eu: 0.14 percent; b: 0.04 percent; la: 0.1 percent; zn: 0.4 percent; unavoidable impurities Cr + Mn + V + Ti: less than 0.01%; the balance being Al.

The preparation method is the same as example 1.

Example 4

The cast aluminum-silicon alloy comprises the following components in percentage by mass: si: 10 percent; fe: 0.2 percent; co: 0.3 percent; eu: 0.15 percent; b: 0.04 percent; la: 0.12 percent; zn: 0.5 percent; unavoidable impurities Cr + Mn + V + Ti: less than 0.01%; the balance being Al.

The preparation method is the same as example 1.

Example 5

The cast aluminum-silicon alloy comprises the following components in percentage by mass: si: 10.5 percent; fe: 0.2 percent; co: 0.3 percent; eu: 0.1 percent; b: 0.04 percent; la: 0.08 percent; zn: 0.5 percent; unavoidable impurities Cr + Mn + V + Ti: less than 0.01%; the balance being Al.

The preparation method is the same as example 1.

Example 6

The cast aluminum-silicon alloy comprises the following components in percentage by mass: si: 8.5 percent; fe: 0.2 percent; co: 0.3 percent; eu: 0.15 percent; b: 0.04 percent; la: 0.15 percent; zn: 0.5 percent; unavoidable impurities Cr + Mn + V + Ti: less than 0.01%; the balance being Al.

The preparation method is the same as example 1.

The components and contents of the cast aluminum-silicon alloys in examples 1 to 6 are shown in table 1.

TABLE 1

Composition (I)	Si	Fe	Co	Eu	B	La	Zn	Cr+Mn+V+Ti	Al
										Example 1	8.5	0.1	0.15	0.12	0.04	0.09	0.2	＜0.01	Balance of
Example 2	9.0	0.1	0.16	0.13	0.04	0.08	0.3	＜0.01	Balance of
										Example 3	9.5	0.15	0.23	0.14	0.04	0.1	0.4	＜0.01	Balance of
Example 4	10	0.2	0.3	0.15	0.04	0.12	0.5	＜0.01	Balance of
										Example 5	10.5	0.2	0.3	0.1	0.04	0.08	0.5	＜0.01	Balance of
Example 6	8.5	0.2	0.3	0.15	0.04	0.15	0.5	＜0.01	Balance of

The performance of the cast aluminum-silicon alloy prepared in the examples 1 to 4 in the as-cast state is compared with the performance of the currently common die-cast aluminum-silicon alloy ADC12 and EN AC-44300 in the as-cast state, as shown in Table 2. From the results in table 2, it can be seen that the thermal conductivity and elongation of the cast aluminum-silicon alloy prepared by the invention in the as-cast state are obviously higher than those of the traditional die-cast aluminum-silicon alloy ADC12 in the as-cast state, the thermal conductivity is higher than 160W/(m · K) in the most ideal state of EN AC-44300, and can reach 185W/(m · K) at most, and the elongation can reach 12.6%, and is 12.6 times higher than that of EN AC-44300 by 1%, so that the cast aluminum-silicon alloy has good thermal conductivity and elongation, the yield strength and tensile strength are basically equivalent to those of ADC12 and EN AC-44300, and the tensile strength can reach 283 MPa. Therefore, the cast aluminum-silicon alloy prepared by the invention has good thermal conductivity and elongation and higher strength. The content of Si is 8.5-10.5%, so that the casting aluminum-silicon alloy has good fluidity, can be used for molding complex thin-wall parts, and widens the application range of casting aluminum-silicon alloy.

TABLE 2

Performance of	Yield strength (MPa)	Tensile strength (MPa)	Elongation (%)	Thermal conductivity (W/(m.K))
					Example 1	121	268	12.6	185
Example 2	123	278	12.3	181
					Example 3	128	281	11.2	180
Example 4	135	283	10.1	175
					Example 5	122	251	6.5	164
Example 6	129	278	12.1	160
					ADC12	154	228	1.5	96
ENAC-44300	130	240	1	160

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.

Claims

1. The cast aluminum-silicon alloy is characterized by comprising the following components in percentage by mass:

2. The cast aluminum-silicon alloy according to claim 1, wherein the misch metal is Eu and La, wherein Eu is 0.1 to 0.15% and La is 0.08 to 0.15% by mass.

3. The cast aluminum-silicon alloy according to claim 1 or 2, wherein the mass ratio of Si to misch metal is 37 to 43: 1.

4. the cast aluminum-silicon alloy according to claim 3, wherein the mass ratio of Co to Fe is 1.5 to 1.6: 1.

5. the cast al-si alloy according to claim 1, characterised in that the unavoidable impurities include elements Cr, Mn, V and Ti and the total amount does not exceed 0.01%.

6. A preparation method of a cast aluminum-silicon alloy is characterized in that the components and the mixture ratio of the cast aluminum-silicon alloy according to any one of claims 1 to 5 are adopted, and the preparation method specifically comprises the following steps:

7. The method for producing a cast aluminum-silicon alloy according to claim 6, characterized in that in step (1), the method further comprises the steps of washing and drying the weighed raw materials.