CN112301259A

CN112301259A - High-strength die-casting aluminum alloy, and preparation method and application thereof

Info

Publication number: CN112301259A
Application number: CN202011076668.6A
Authority: CN
Inventors: 李新涛
Original assignee: Institute Of Materials And Processing Guangdong Academy Of Sciences
Current assignee: Institute Of Materials And Processing Guangdong Academy Of Sciences
Priority date: 2020-10-10
Filing date: 2020-10-10
Publication date: 2021-02-02

Abstract

The invention discloses a high-strength die-casting aluminum alloy, a preparation method and application thereof, and relates to the technical field of die-casting aluminum alloys. The high-strength die-casting aluminum alloy comprises the following components in percentage by weight: 11.0 to 15.0 percent of Si, 2 to 12 percent of Zn, 1.0 to 3 percent of Cu, 0.3 to 0.85 percent of Mg, 0.1 to 0.3 percent of Ti, 0.01 to 0.05 percent of Zr, 0.01 to 0.06 percent of Sr, 0.01 to 0.05 percent of P, inevitable impurities and Al. Combines the advantages of Al-Si series, Al-Cu series and Al-Zn series cast aluminum alloys, and precipitates Al at room temperature₂Cu、MgZn₂And the like, which have good natural aging effect. The casting does not need high-temperature solid solutionAnd the artificial aging and other heat treatment, the tensile strength and the yield strength of the material are ideal only through natural aging, and the size requirement of the shell type casting can be met.

Description

High-strength die-casting aluminum alloy, and preparation method and application thereof

Technical Field

The invention relates to the technical field of die-casting aluminum alloys, in particular to a high-strength die-casting aluminum alloy, and a preparation method and application thereof.

Background

The aluminum-silicon alloy has the characteristics of good casting performance and wear resistance, high compactness, low expansion coefficient and the like, and the die-casting product is widely applied to automobile parts, such as differential mechanism shells, air compressor shells, pump shells and other shell parts. The conventional aluminum alloy die casting has high filling speed and high cooling strength, so that gas in the die is difficult to remove completely, residual gas is easy to be involved in the casting, and air holes are formed in the casting. These gases can form bubbles during heat treatment, which can affect the surface quality and, in severe cases, can cause the castings to be scrapped.

At present, ADC12 alloy is generally adopted for automobile shell type die castings, the as-cast tensile strength of the alloy is less than or equal to 300MPa, and the yield strength of the alloy is less than or equal to 160 MPa. For the casting with high requirement on mechanical property, the blank is produced by adopting a vacuum die casting or low-pressure casting mode and the like, and then the strength of the casting is improved by heat treatment of T4, T5, T6 and the like. Therefore, the process is complex, the working procedures are multiple, and the production cost is high; in addition, during heat treatment, the castings with complex structures or thin-wall castings are easy to deform due to uneven temperature and stress, and the dimensional precision requirements and the assembly requirements of the castings can be met only through large processing amount.

Therefore, on the basis of the aluminum-silicon alloy, the high-strength die-casting aluminum alloy which does not need heat treatment and has the natural aging characteristic is developed, and the method has important significance for optimizing the production process of the casting, meeting the size requirements of the structural part with a complicated shape or the thin-wall casting and the like.

Disclosure of Invention

The invention aims to provide a high-strength die-casting aluminum alloy and a preparation method thereof, aiming at meeting the requirement of high strength only by natural aging treatment without heat treatment such as high-temperature solid solution, artificial aging and the like.

The invention also aims to provide application of the high-strength die-casting aluminum alloy in preparing a shell type casting.

The technical problem to be solved by the invention is realized by adopting the following technical scheme.

The invention provides a high-strength die-casting aluminum alloy which comprises the following components in percentage by weight: 11.0 to 15.0 percent of Si, 2 to 12 percent of Zn, 1.0 to 3 percent of Cu, 0.3 to 0.85 percent of Mg, 0.1 to 0.3 percent of Ti, 0.01 to 0.05 percent of Zr, 0.01 to 0.06 percent of Sr, 0.01 to 0.05 percent of P, inevitable impurities and Al.

The invention also provides a preparation method of the high-strength die-casting aluminum alloy, which comprises the step of carrying out raw material proportioning according to the components of the high-strength die-casting aluminum alloy to form the high-strength die-casting aluminum alloy.

The invention also provides application of the high-strength die-casting aluminum alloy in preparing shell castings.

The embodiment of the invention provides a high-strength die-casting aluminum alloy and a preparation method thereof, and the high-strength die-casting aluminum alloy has the beneficial effects that: the method combines the advantages of Al-Si series, Al-Cu series and Al-Zn series cast aluminum alloys by adjusting the dosage of Si, Zn, Cu, Mg, Ti, Zr, Sr and P, and precipitates Al at room temperature₂Cu、MgZn₂And the like, which have good natural aging effect. The casting does not need to be subjected to heat treatment such as high-temperature solid solution, artificial aging and the like, and the tensile strength and the yield strength of the material are ideal only through natural aging.

Wherein, Si is the main component of the alloy and plays a role in improving the fluidity in the alloy; zn element is added into the alloy, the alloy can be completely dissolved in an Al matrix in a solid solution mode under the casting cooling condition, automatic quenching is realized, and the weight increment caused by Zn addition can be reduced by adding 11.0-15.0% of Si; cu has a solid solution strengthening effect in the alloy, so that the tensile strength of the alloy can be improved; p and Sr are alterants, and respectively play a role in modifying and refining primary crystal Si and eutectic Si in the alloy; 0.1-0.3% Ti is added to the alloy to form Al₃The Ti crystal nucleus can keep a fine energy structure at the thick wall of the die casting and reduce the thick wall effect of the alloy; adding Zr 0.01-0.05% into the alloy can form fine Al₃Zr can play a role in refining energy and reducing the hot cracking tendency of the casting.

The embodiment of the invention also provides the application of the high-strength die-casting aluminum alloy in preparing the shell castings, and as the high-temperature solid solution, artificial aging and other heat treatments do not exist in the preparation process, the stress non-uniformity phenomenon cannot be generated, the castings are not easy to deform, and the size requirements of structural parts with complex shapes or thin-wall castings are met.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a pictorial view of a die-cast differential housing provided in an embodiment of the present invention;

FIG. 2 is a pictorial view of a die-cast differential housing provided in a comparative example of the present invention;

FIG. 3 is a pictorial view of a die-cast differential housing provided in a comparative example of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The high-strength die-cast aluminum alloy provided by the embodiment of the invention, the preparation method and the application thereof are specifically described below.

The embodiment of the invention provides a high-strength die-casting aluminum alloy which comprises the following components in percentage by weight: 11.0 to 15.0 percent of Si, 2 to 12 percent of Zn, 1.0 to 3 percent of Cu, 0.3 to 0.85 percent of Mg, 0.1 to 0.3 percent of Ti0.01 to 0.05 percent of Zr, 0.01 to 0.06 percent of Sr, 0.01 to 0.05 percent of P, inevitable impurities and Al.

The inventor shows that the raw material proportion of the aluminum alloy is optimized, so that the casting does not need to be subjected to heat treatment such as high-temperature solid solution, artificial aging and the like, and the tensile strength of the material reaches 380MPa, the yield strength reaches 300MPa and the elongation after fracture is more than 1.1% only by natural aging.

Specifically, Si is the main component of the alloy, the content is 11.0-15.0%, and the alloy is ensured to have good fluidity near the eutectic point of the Al-Si alloy, so that the forming of a die casting with a complex structure and a thin-wall die casting is facilitated; under the condition of die casting, fine eutectic silicon is precipitated from the alloy in the temperature reduction process, so that the strength of the material can be improved.

Specifically, Zn element is added into the alloy, and the alloy can be completely dissolved in an Al matrix under the casting cooling condition, so that the automatic quenching is realized. MgZn is separated out during natural aging₂The strengthening phases are equal, and the natural aging strengthening effect is achieved. Meanwhile, Mg added into the alloy reacts with Si to separate out Mg₂Si compound is favorable for improving the alloy strength. As the density of Zn is far greater than that of a base material, the weight increase caused by Zn addition can be reduced by adding 11.0-15.0% of Si, and when the content of Si exceeds 15%, more primary crystal silicon can be precipitated, the tensile property of the material is deteriorated, and the processing difficulty of a casting is increased.

Specifically, Cu has solid solution strengthening effect in the alloy, can improve the tensile strength of the alloy, and can precipitate Al during natural aging₂Cu and other strengthening phases, and has obvious natural aging effect. Since Cu has a higher chemical potential than aluminum, intergranular corrosion is likely to occur when the copper content is too high.

Specifically, P and Sr are alterants, and respectively play a role in changing and refining primary crystal Si and eutectic Si in the alloy. 0.1-0.3% Ti is added to the alloy to form Al₃The Ti crystal nucleus can keep a fine grain structure at the thick wall of the die casting and reduce the thick wall effect of the alloy; when the Ti content exceeds 0.3%, the castability of the alloy is lowered. Adding Zr 0.01-0.05% into the alloy can form fine Al₃Zr can play a role in refining crystal grains and reducing the hot cracking tendency of the casting.

In a preferred embodiment of the invention, the high-strength die-cast aluminum alloy comprises the following components in percentage by weight: 11.0 to 15.0 percent of Si, 2 to 12 percent of Zn, 1.0 to 3 percent of Cu, 0.3 to 0.85 percent of Mg, 0.1 to 0.4 percent of Mn, 0.2 to 0.6 percent of Fe, 0.1 to 0.3 percent of Ti, 0.01 to 0.05 percent of Zr, 0.01 to 0.06 percent of Sr, 0.01 to 0.05 percent of P, less than or equal to 0.25 percent of the total amount of impurities and the balance of Al. More preferably, the high-strength die-cast aluminum alloy consists of the following components in percentage by weight: 11.0 to 13.5 percent of Si, 2 to 12 percent of Zn, 1.0 to 3 percent of Cu, 0.3 to 0.85 percent of Mg, 0.1 to 0.4 percent of Mn, 0.2 to 0.6 percent of Fe, 0.1 to 0.3 percent of Ti, 0.01 to 0.05 percent of Zr, 0.01 to 0.03 percent of Sr, 0.01 to 0.03 percent of P, less than or equal to 0.25 percent of the total amount of impurities and the balance of Al.

It should be noted that, adding a proper amount of Fe can make the surface oxide film of the casting discontinuous, which is beneficial to demoulding, and the phenomenon of sticking the die can occur when the Fe content in the alloy is too low or not added. However, Fe can reduce the mechanical property of the alloy, particularly the elongation, the harmful effect of Fe can be relieved by adding a proper amount of Mn, the Mn/Fe ratio is preferably controlled to be 0.5-0.8, and a coarse alpha (AlFeMn) phase is easily generated when the Mn/Fe ratio is too high, so that the mechanical property of the material is reduced.

The embodiment of the invention also provides a preparation method of the high-strength die-casting aluminum alloy, which comprises the step of carrying out raw material proportioning according to the components of the high-strength die-casting aluminum alloy to form the high-strength die-casting aluminum alloy. Due to the improvement of the proportion of the aluminum alloy raw materials, the high-strength die-casting aluminum alloy can be formed only through natural aging without high-temperature solid solution, artificial aging and other heat treatments in the preparation process. The method specifically comprises the following steps:

(1) melting

Firstly, smelting an aluminum ingot and raw materials of Si, Cu, Mn, Fe, Mg, Zn, Zr and Ti which are proportioned to obtain a smelting mixture. Preferably, the smelting mixture is to heat and melt an aluminum ingot, sequentially add Si, Cu, Mn, Fe, Mg and Ti, and add Zn and Zr after the added raw materials are melted. By optimizing the feeding step, raw materials such as Mg and the like are prevented from volatilizing to influence the performance of the product.

Specifically, Si is a silicon-aluminum intermediate alloy or instant silicon; cu is aluminum-copper intermediate alloy or pure copper; mn is an aluminum-manganese intermediate alloy or a manganese additive; fe is an aluminum-iron intermediate alloy or an iron additive; ti is an aluminum-titanium intermediate alloy; zr is an aluminum zirconium intermediate alloy; p is copper-phosphorus intermediate alloy or aluminum-phosphorus intermediate alloy. The manganese additive and the iron additive are common raw materials in the preparation process of the aluminum alloy and are not described in detail.

(2) Modification treatment

And then mixing the smelting mixture with raw materials of Sr and P for modification treatment, and modifying the form of silicon in the structure through modification treatment to improve the fluidity of the silicon. Specifically, the modification treatment is to heat the smelting mixture to 750-780 ℃ and then add Sr and P for modification for 15-45min, so as to effectively change the unfavorable form of silicon and improve the mechanical property.

(3) Refining treatment

Refining by introducing refining agent and inert gas, refining the aluminum alloy melt for 5-15min, skimming scum, and standing for 10-30 min; the refining temperature is 720-760 ℃. After refining, the inclusion is floated or sunk sufficiently, and then the scum is removed.

Specifically, the refining agent is a powdery refining agent, and is sprayed into the melt for refining by adopting a powder spraying refining mode and taking inert gas as a carrier. The inert gas is nitrogen or argon.

(4) Die casting

The die casting is carried out under the condition of 700-760 ℃, the casting does not need to be subjected to heat treatment such as high-temperature solid solution, artificial aging and the like, only through natural aging, the tensile strength of the material reaches 380MPa, the yield strength reaches 300MPa, and the elongation after fracture is more than 1.1 percent.

The embodiment of the invention also provides the application of the high-strength die-casting aluminum alloy or the high-strength die-casting aluminum alloy prepared by the preparation method in preparing shell castings, and as the high-temperature solid solution, artificial aging and other heat treatments do not exist in the preparation process, the stress non-uniformity phenomenon can not be generated, further the castings are not easy to deform, and the size requirements of structural parts with complex shapes or thin-wall castings are met.

The features and properties of the present invention are described in further detail below with reference to examples.

Examples 1 to 4

Examples 1 to 4 each provide a high-strength die-cast aluminum alloy having a chemical composition shown in table 1, wherein Si, Mn, Fe, Ti, Zr, Mg, Zn are used as raw materials as an intermediate alloy with aluminum, and P is a copper-phosphorus intermediate alloy.

Examples 1 to 5 each provide a method for producing a high-strength die-cast aluminum alloy, which is different only in the mixture ratio of raw materials, and includes the steps of:

(1) smelting: adding an aluminum ingot into a melting furnace, heating, sequentially adding Si, Cu, Mn, Fe, Mg and Ti after the aluminum ingot is completely melted, adding all Zn and Zr materials after the added raw materials are melted, and uniformly stirring.

(2) Modification treatment: and (2) heating the melt prepared in the step (1) to 770 ℃, adding an Al-Sr intermediate alloy and a P-Cu intermediate alloy for modification, wherein the modification time is 15 min.

(3) Refining: and introducing a powdery refining agent and argon, and performing degassing, deslagging and refining treatment on the aluminum alloy melt, wherein the refining time is 10min, the refining time is 750 ℃, and scum is removed.

(4) Die casting: and (4) cooling the melt obtained in the step (3) to 720 ℃, and then preparing the differential shell by using a 630-ton die casting machine.

Example 6

This example provides a high-strength die-cast aluminum alloy, which has a chemical composition different from that of example 1 only in that: mn and Fe are not contained.

It should be added that in other embodiments, parameters such as temperature and time in the preparation method can also be changed, which are not listed here, and the performance is not greatly affected by adjusting within the parameter range specified in the embodiments of the present invention.

Comparative examples 1 to 3

Comparative examples 1 to 3 provide a high-strength die-cast aluminum alloy and a method for preparing the same, which are different from example 1 only in that: the chemical composition of the aluminum alloy is shown in Table 1.

TABLE 1 chemical composition of aluminum alloy (wt.%)

Test examples

The aluminum alloys prepared in examples 1 to 6 and comparative examples 1 to 3 were tested for properties, wherein the test standards for tensile strength and yield strength were referred to GB/T16865-2013, and the test standard for elongation after fracture was referred to GB/T16865-2013, and the results are shown in Table 2.

TABLE 2 Properties of the aluminum alloys

It can be seen that after 60 days of natural aging, the tensile strength of the alloy is more than or equal to 370MPa, the yield strength is more than or equal to 300MPa, and the elongation is more than or equal to 1.1%.

In comparative example 1, the Si content was 9.2%, the Zn content was 13.1, the fluidity of the alloy was decreased, and the defect of insufficient casting occurred on the casting. Meanwhile, the Cu content exceeds the upper limit of 3 percent, and the Mn/Fe ratio is less than 0.5, so that the mechanical property of the alloy is reduced.

In comparative example 2, the Si content was 16.3%, and the Zn and Cu contents were low, resulting in a significant drop in the as-cast strength of the casting, with insignificant natural aging effects.

In comparative example 3, the Si content was 16.6%, the contents of Zn, Cu and Ti were high, resulting in cracks on the surface of the casting and insignificant natural aging effect.

Test example 2

Physical diagrams of the housings of the differentials die-cast in example 1 and comparative examples 1 and 3 were tested, as shown in fig. 1, 2 and 3.

FIG. 1 is a pictorial view of a differential case die-cast in accordance with example 1 without showing defects; FIG. 2 is a diagram of a differential case die-cast in comparative example 1, in which the Si content in the alloy is low, the Cu content reaches 3.5%, the fluidity of the alloy is reduced, and the casting has a defect of insufficient casting. FIG. 3 is a diagram of a differential case die-cast in comparative example 3, in which the fluidity of the alloy is decreased due to the high contents of Zn, Cu and Ti in the alloy, so that the casting has an undercasting defect, and meanwhile, the internal stress of the casting is increased with the increase of the content of the alloying elements, so that cracks appear on the surface of the casting.

In summary, the high-strength die-casting aluminum alloy and the preparation method thereof provided by the invention combine the advantages of Al-Si series, Al-Cu series and Al-Zn series casting aluminum alloys by adjusting the dosage of Si, Zn, Cu, Mg, Ti, Zr, Sr and P, and precipitate Al at room temperature₂Cu、MgZn₂And the like, which have good natural aging effect. The casting does not need to be subjected to heat treatment such as high-temperature solid solution, artificial aging and the like, and the tensile strength and the yield strength of the material are ideal only through natural aging.

The high-strength die-casting aluminum alloy provided by the invention is applied to the preparation of shell castings, and because the high-temperature solid solution, artificial aging and other heat treatments do not exist in the preparation process, the stress non-uniformity phenomenon cannot be generated, the castings are not easy to deform, and the size requirements of structural parts with complex shapes or thin-wall castings are met.

The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Claims

1. The high-strength die-casting aluminum alloy is characterized by comprising the following components in percentage by weight: 11.0 to 15.0 percent of Si, 2 to 12 percent of Zn, 1.0 to 3 percent of Cu, 0.3 to 0.85 percent of Mg, 0.1 to 0.3 percent of Ti, 0.01 to 0.05 percent of Zr, 0.01 to 0.06 percent of Sr, 0.01 to 0.05 percent of P, inevitable impurities and Al.

2. The high-strength die-cast aluminum alloy according to claim 1, comprising the following components in percentage by weight: 11.0 to 15.0 percent of Si, 2 to 12 percent of Zn, 1.0 to 3 percent of Cu, 0.3 to 0.85 percent of Mg, 0.1 to 0.4 percent of Mn, 0.2 to 0.6 percent of Fe, 0.1 to 0.3 percent of Ti, 0.01 to 0.05 percent of Zr, 0.01 to 0.06 percent of Sr, 0.01 to 0.05 percent of P, less than or equal to 0.25 percent of the total amount of impurities and the balance of Al.

3. The high-strength die-cast aluminum alloy according to claim 2, which is composed of the following components in percentage by weight: 11.0 to 13.5 percent of Si, 2 to 12 percent of Zn, 1.0 to 3 percent of Cu, 0.3 to 0.85 percent of Mg, 0.1 to 0.4 percent of Mn, 0.2 to 0.6 percent of Fe, 0.1 to 0.3 percent of Ti, 0.01 to 0.05 percent of Zr, 0.01 to 0.03 percent of Sr, 0.01 to 0.03 percent of P, less than or equal to 0.25 percent of the total amount of impurities and the balance of Al.

4. A method for producing a high-strength die-cast aluminum alloy, characterized in that the high-strength die-cast aluminum alloy is produced by compounding raw materials according to the composition of the high-strength die-cast aluminum alloy according to any one of claims 1 to 3.

5. The method for preparing a high-strength die-cast aluminum alloy according to claim 4, comprising: sequentially carrying out smelting, modification, refining and die casting on raw materials to form the high-strength die-cast aluminum alloy;

preferably, firstly, smelting an aluminum ingot and raw materials of Si, Cu, Mn, Fe, Mg, Zn, Zr and Ti which are proportioned to obtain a smelting mixture, then mixing the smelting mixture with raw materials of Sr and P for modification treatment, and then sequentially carrying out refining treatment and die casting;

more preferably, the die casting is performed at 700-.

6. The method for preparing the high-strength die-cast aluminum alloy according to claim 5, wherein the smelting mixture is prepared by heating and melting an aluminum ingot, then adding Si, Cu, Mn, Fe, Mg and Ti in sequence, and adding Zn and Zr after the added raw materials are melted.

7. The method for preparing a high-strength die-cast aluminum alloy according to claim 6, wherein Si is a silicon-aluminum intermediate alloy or instant silicon;

preferably, Cu is an aluminum copper master alloy or pure copper;

preferably, Mn is an aluminum manganese master alloy or manganese additive;

preferably, Fe is an aluminum-iron master alloy or an iron additive;

preferably, Ti is an aluminum titanium master alloy;

preferably, Zr is an aluminum zirconium master alloy;

preferably, P is a copper-phosphorus master alloy or an aluminum-phosphorus master alloy.

8. The method for preparing the high-strength die-cast aluminum alloy according to claim 5, wherein the modification treatment comprises heating the smelting mixture to 750-780 ℃ and then adding Sr and P for modification for 15-45 min.

9. The method for preparing the high-strength die-cast aluminum alloy according to claim 5, wherein the refining treatment comprises introducing a refining agent and an inert gas, refining the aluminum alloy melt for 5-15min, skimming the dross, and standing for 10-30 min;

preferably, the refining temperature is 720-760 ℃;

preferably, the inert gas is nitrogen or argon.

10. Use of the high-strength die-cast aluminum alloy according to any one of claims 1 to 3 or the high-strength die-cast aluminum alloy prepared by the preparation method according to any one of claims 4 to 9 in preparation of a casting of the shell type.