A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and its preparation method

Abstract

A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting, and its components and weight percentages are respectively: Si: 7-10.5 wt%, Mg: 0.3-1.5 wt%, Mn: 0.6-1.2 wt%, Zn: 0.5-1.5 wt%, Ti: 0.05-0.25 wt%, Sr: 0.05-0.1 wt%; the total amount of other impurities ≤ 0.4 wt%, and the balance is Al. The present invention also relates to a preparation method of a heat-treatment-free high-strength aluminum-silicon alloy for gravity casting, which includes the following steps: S1, preparing materials; S2, pre-treatment before melting; S3, melting; S4, refining; S5, refining; S6, modification; S7, gravity casting. The heat-treatment-free high-strength aluminum-silicon alloy for gravity casting is applied to gravity casting or the production of gravity-cast castings. The present invention can be used in the process of gravity casting. After melting and pouring, it can be directly formed without forming an alloy ingot and then die-casting. The alloy composition ratio is simple, and the casting performance and material performance indicators are excellent; the production efficiency is high; and the comprehensive technical effect is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and particularly relates to a heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and a preparation method thereof. Background Art

[0002] With the continuous development of the economy and society, fields such as aerospace, weaponry, and automobiles have also entered a stage of high-quality requirements. Many current high-demand castings are gradually developing towards integration, large size, thin walls, and complex structures.

[0003] Heat treatment is a commonly used method in the casting industry to improve mechanical properties, enhance corrosion resistance, improve machining performance, and obtain dimensional stability. However, for large-sized and thin-walled castings formed integrally, there are problems such as deformation, cracking, and overburning during the heat treatment process. If a heat-treatment-free alloy can be developed, it can not only avoid the deformation of the casting itself during the heat treatment process and subsequent related shaping processes, but also reduce production costs and save production time. Most common heat-treatment-free alloys are used for aluminum alloy die-cast structural parts in the automotive industry. This alloy needs to have high strength, toughness, good filling ability, little gas absorption and oxidation, no reaction between the material and the mold, and light weight and other performance requirements. For example: the Silafont-36 alloy developed by Rhein Company in Germany (Patent Publication No.: US 6364970B1), the elongation rate of this alloy at room temperature is not higher than 6%, and this alloy needs to use special high-vacuum die-casting and heat treatment strengthening to meet the requirements of improving the comprehensive mechanical properties of the casting. The non-heat-treatment-strengthened high-strength and high-toughness die-cast Al-Mg-Si alloy developed by Shanghai Jiao Tong University (Patent Publication No.: CN108754256A), this alloy has excellent mechanical properties, but the Mg content in the Al-Mg-Si alloy is relatively high, and its casting performance is worse than that of the Al-Si alloy. It has a great erosion on the die-casting mold, reduces the mold life, and has higher requirements for die-casting process design and manufacturing technology. In addition, this alloy also adds strengthening elements such as Zr, Be, Ca, and RE, which has a greater impact on the production cost of die-cast structural parts and the material recycling and preparation.

[0004] In addition, die-casting is also a available technical means. However, die-cast castings are prone to porosity and looseness defects, and the weight of the castings is limited by the die-casting machine; and the investment in die-casting equipment is high, the mold manufacturing is complex, the cycle is long, and the cost is high, which is not suitable for small-batch production and casting research and development.

[0005] Compared with die casting, gravity casting is one of the most common methods in aluminum alloy casting. It has the advantages of convenient operation, simple process, low equipment and mold costs, and is suitable for both the development of castings and small-batch production of castings. Therefore, developing a heat-treatable aluminum-silicon alloy for gravity casting and studying its preparation and forming process to make the alloy have good properties, casting performance, and recyclability, and meet the usage requirements of large integrated formed structural parts in industries such as aerospace and automotive, is of great significance for the development of heat-treatable aluminum-silicon alloys. Summary of the Invention

[0006] Under the technical background conditions of gravity casting, the present invention provides a heat-treatable high-strength aluminum-silicon alloy for gravity casting and its preparation method. On the premise of ensuring good casting performance, it has excellent comprehensive mechanical properties under gravity casting conditions and can well meet the requirements of large-size, thin-wall, and integrated formed structural parts.

[0007] The technical solution of the present invention is as follows:

[0008] To achieve the goal of heat-treatable high performance, in the research of heat-treatable aluminum-silicon alloys, the present invention found that the addition of Mg can significantly improve the strength of the alloy. However, when the Mg content is too high, Mg and Al will form the Al3Mg2 phase, and the morphology and distribution of this phase have a great influence on the mechanical properties of the alloy. At the same time, when Mg and Si are added simultaneously, the hard and brittle Mg2Si phase can be generated. When there is too much Mg2Si phase, the plasticity of the alloy will be severely reduced. To obtain better alloy properties, the present invention adds Mn, Ti, and Sr refinement elements to improve the alloy structure, uses Mn to replace Fe, reduces the generation of β-AlFeSi needle-shaped phases in the alloy, and transforms the needle-shaped iron-containing phases into Chinese character-shaped or small and rounded α-AlFeMnSi phases to improve the toughness of the alloy. In addition, Zn element is creatively introduced. The Zn element is mainly solid-solved in the α-Al phase, which plays a solid-solution strengthening role in the alloy. Moreover, Zn has a low melting point and the same crystal structure as Mg, having a dual role of solid-solution strengthening and age hardening. However, the excessive addition of Zn increases the size of eutectic Si and reduces the elongation rate of the alloy.

[0009] The present invention claims to protect a heat-treatable high-strength aluminum-silicon alloy for gravity casting. The composition components and their weight percentages in the heat-treatable high-strength aluminum-silicon alloy for gravity casting are as follows:

[0010] Si: 7wt%-10.5wt%, Mg: 0.3wt%-1.5wt%, Mn: 0.6wt%-1.2wt%, Zn: 0.5wt%-1.5wt%, Ti: 0.05wt%-0.25wt%, Sr: 0.05wt%-0.1wt%; the total amount of other impurities is ≤0.4wt%, and the balance is Al.

[0011] The present invention also claims the preparation method of the above-mentioned heat-treatable high-strength aluminum-silicon alloy for gravity casting. When preparing the heat-treatable high-strength aluminum-silicon alloy, the following steps are included:

[0012] S1. Material preparation: Alloying elements are proportioned by weight percentage; among them: the alloy materials are required to be A100 refined aluminum, industrial pure Mg, single crystal silicon Si, zinc ingot, Al-10wt%Mn master alloy, Al-10wt%Sr master alloy, and Al-5wt%Ti-1wt%B master alloy;

[0013] S2. Pretreatment before melting: The melting is carried out in a cast iron crucible. Before melting, it is required to clean the cast iron crucible and the ingate of the metal mold, and at the same time preheat the cast iron crucible, tools and various raw materials; preheat at 250°C for 2 hours;

[0014] S3. Melting: Add the preheated refined aluminum and Al-10Mn master alloy into the melting furnace, and raise the temperature to 680-700°C to completely melt them; then keep the furnace temperature at 680-700°C and add Si. After Si is completely melted, stir for 2-3 minutes; then add Mg and Zn, and use a ladle to press them below the melt surface to fully melt them, and slowly stir for 2-3 minutes;

[0015] S4. Refinement: When the melt temperature is raised to 730-740°C, add Al-5Ti-1B master alloy, stir for 3-4 minutes, and let it stand for 10-20 minutes;

[0016] S5. Refining: When the melt temperature is lowered to 700-730°C, introduce argon gas into the melt for refining, and control the argon gas flow rate at 1-3 L / min; after refining for 20-30 minutes, let it stand for 20-30 minutes, and skim the scum on the melt surface;

[0017] S6. Modification: When controlling the melt temperature at 720-730°C, add Al-10Sr master alloy. After it melts, stir, and after standing, skim the scum on the melt surface;

[0018] S7. Gravity casting: Pour the molten metal liquid after step S6 into a metal mold preheated to 200°C at a temperature of 725-735°C to complete the production of the casting.

[0019] The preferred technical requirements for the preparation method of the heat-treatable high-strength aluminum-silicon alloy for gravity casting are as follows:

[0020] The preparation method of the heat-treatable high-strength aluminum-silicon alloy for gravity casting meets one or a combination of the following requirements:

[0021] First, when preparing materials in step S1, the requirements for the selected A100 refined aluminum are a purity > 99.9 wt%, the purity of industrial pure Mg > 99.9 wt%, and the purity of zinc ingots > 99.9 wt%.

[0022] Second, when using a cast iron crucible for melt smelting, it is required to uniformly apply ZnO coating inside the crucible in advance, and the coating thickness is controlled within 1 - 3 mm.

[0023] Third, in step S2, the requirements for preheating the cast iron crucible, slag removal tools, and various raw materials are: preheat at 250 °C for 2 hours.

[0024] Fourth, in step S4, when using Al - 5Ti - 1B master alloy as a grain refiner during the preparation of the melt, the addition amount of the grain refiner is 1% - 5% of the alloy weight.

[0025] Fifth, in step S6, when using Al - 10Sr master alloy as a modifier during the preparation of the melt, the addition amount of the modifier is 0.5% - 1% of the alloy weight. Add the Al - 10Sr master alloy as a modifier when the melt temperature is 720 - 730 °C. After adding, stir for 3 - 4 min, let it stand for 20 - 30 min, and skim the scum on the surface of the melt.

[0026] Further preferably: in the preparation method of the gravity - casting heat - treatment - free high - strength aluminum - silicon alloy, the pouring speed of the alloy in step S7 is 1 kg / s - 11 kg / s.

[0027] The present invention also claims to protect the gravity - casting heat - treatment - free high - strength aluminum - silicon alloy, which is applied to gravity casting or the production of gravity - castings.

[0028] The beneficial effects of the present invention are:

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. The heat - treatment - free high - strength aluminum - silicon alloy of the present invention can be used in the gravity - casting process. After melting and pouring, it can be directly formed without forming an alloy ingot and then die - casting.

[0031] 2. The composition ratio of the heat-treatment-free high-strength aluminum-silicon alloy of the present invention is simple. Without rare-earth alloys, etc., at least 5% can be saved in terms of comprehensive cost. Moreover, the casting performance of the aluminum-silicon alloy is significantly superior to that of the magnesium-based and aluminum-copper-based alloys in terms of fluidity, hot-cracking resistance, and airtightness, and its product design and casting process resources are better. In the aluminum-silicon alloy, silicon can improve the fluidity of the alloy, reduce the tendency of hot cracking, reduce porosity, and improve airtightness; aluminum-copper alloy belongs to a solid-type alloy with a wide solidification range, resulting in poor casting performance; aluminum-magnesium alloy is prone to oxidation during the melting process, forming oxide inclusions, and a special melting process is required. The fluidity of ZL101A alloy is 350 mm at 700 °C, the fluidity of ZL201A alloy is 165 mm at 700 °C, and the fluidity of ZL303A alloy is 300 mm at 700 °C; ZL101A alloy can reach crack-free at 713 °C, the crack ring width of ZL201A alloy reaches 37.5 mm at 710 °C, and the crack ring width of ZL303A alloy reaches 16 mm at 720 °C.

[0032] 3. The as-cast properties of the heat-treatment-free high-strength aluminum-silicon alloy of the present invention are described as follows: tensile strength 230 - 260 MPa, yield strength 120 - 150 MPa, elongation 8 - 10% (for AlSi10MnMg alloy, as-cast tensile strength 200 - 220 MPa, elongation 5 - 8%).

[0033] 4. The heat-treatment-free high-strength aluminum-silicon alloy of the present invention can be used in large thin-walled structural parts. The heat treatment of the casting is avoided, which avoids the problems of dimensional deformation and surface defects caused during the heat treatment process, and the quality of the casting is increased by 10 - 20% as measured.

[0034] 5. Using the heat-treatment-free high-strength aluminum-silicon alloy casting of the present invention patent can reduce the heat treatment process, optimize production efficiency, and the production time of the casting can be shortened by 20 - 30%. The heat treatment (T6 state) of ZL101A alloy requires 10 - 30 hours, and the production time of the casting (under the condition of stable process, without processing and inspection links) is 50 - 70 hours. Description of the Drawings

[0035] Figure 1 It is the metallographic diagram of the microstructure of Example 1 (500X);

[0036] Figure 2 It is the metallographic diagram of the microstructure of Example 2 (500X);

[0037] Figure 3 It is the metallographic diagram of the microstructure of Comparative Example 1 (500X);

[0038] Figure 4 It is the metallographic diagram of the microstructure of Comparative Example 2 (500X). Detailed Embodiments

[0039] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope protected by the present invention.

[0040] The present invention will be further described below in conjunction with embodiments and the accompanying drawings of the specification, but not limited thereto.

[0041] Example 1

[0042] A gravity-casting heat-treatment-free high-strength aluminum-silicon alloy, with the weight ratio of each component being: Si: 9.0 wt.%; Mn: 0.6 wt.%; Mg: 0.5 wt.%; Zn: 0.5 wt.%; Ti: 0.15 wt.%; Sr: 0.06 wt.%; the total amount of other impurities is less than or equal to: 0.4 wt.%, and the rest is Al.

[0043] The gravity-casting heat-treatment-free high-strength aluminum-silicon alloy and its preparation method of this embodiment include the following steps:

[0044] (1) Preparation before furnace: Clean the cast-iron crucible and the inner runner of the metal mold, evenly coat ZnO coating on its inner wall, and preheat the cast-iron crucible, slag skimming tools, etc. at 250 °C for 2 hours;

[0045] (2) Batching: Considering the burn-off during the melting process, prepare raw materials such as A100 refined aluminum (purity > 99.9 wt%), industrial pure Mg (purity > 99.9 wt%), single-crystal silicon Si, zinc ingot (purity > 99.9 wt%), Al-10 wt% Mn master alloy, Al-10 wt% Sr master alloy, and Al-5 wt% Ti-1 wt% B master alloy according to the above alloy component ratio, and preheat the prepared raw materials at 250 °C for 2 hours;

[0046] (3) Alloy melting: Add the preheated refined aluminum and Al-10Mn master alloy to the melting furnace and heat up to 680 - 700 °C to completely melt them. Keep the furnace temperature at 680 - 700 °C and add Si. After Si is completely melted, stir for 2 - 3 min, then add Mg and Zn, and use a ladle to press them below the melt surface to fully melt them, and slowly stir for 2 - 3 min;

[0047] (4) Refinement and refining: The alloy is refined using Al-5Ti-1B master alloy and refined by introducing argon gas. When the melt temperature is raised to 730-740 °C, the Al-5Ti-1B master alloy is added, stirred for 3-4 minutes, and left standing for 10-20 minutes. Subsequently, when the melt temperature is lowered to 700-730 °C, argon gas is introduced into the melt for refining. The argon gas flow rate is controlled within 1-3 L / min. After refining for 20-30 minutes, it is left standing for 20-30 minutes, and the dross on the surface of the melt is skimmed off;

[0048] (5) Modification: When the melt temperature is controlled at 720-730 °C, the Al-10Sr master alloy is added. After it melts, it is stirred for 3-4 minutes, and after standing for 20-30 minutes, the dross on the surface of the melt is skimmed off;

[0049] (6) Gravity casting: After the in-furnace composition analysis is qualified, the molten metal is poured into a metal mold preheated to 200 °C at a temperature of 725-735 °C to obtain a heat-treatment-free casting.

[0050] Example 2

[0051] A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting, with the weight ratio of each component as follows: Si: 9.0 wt.%; Mn: 0.6 wt.%; Mg: 0.3 wt.%; Zn: 0.5 wt.%; Ti: 0.15 wt.%; Sr: 0.06 wt.%; the total amount of other impurities is less than or equal to: 0.4 wt.%, and the rest is Al.

[0052] A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and its preparation method, including the following steps:

[0053] (1) Furnace front preparation: Clean the cast iron crucible and the in-gate of the metal mold, evenly coat their inner walls with ZnO coating, and preheat the cast iron crucible, slag skimming tools, etc. at 250 °C for 2 hours;

[0054] (2) Batching: Considering the burn-off during the melting process, prepare the raw materials of A100 refined aluminum (purity > 99.9 wt%), industrial pure Mg (purity > 99.9 wt%), single crystal silicon Si, zinc ingot (purity > 99.9 wt%), Al-10wt%Mn master alloy, Al-10wt%Sr master alloy, and Al-5wt%Ti-1wt%B master alloy according to the above alloy component ratio, and preheat the prepared raw materials at 250 °C for 2 hours;

[0055] (3)Alloy melting: Preheated refined aluminum and Al-10Mn master alloy are added to the melting furnace and heated to 680 - 700 °C to completely melt them. While maintaining the furnace temperature at 680 - 700 °C, Si is added. After Si is completely melted, it is stirred for 2 - 3 min. Subsequently, Mg and Zn are added and pressed below the melt surface with a skimmer to fully melt them, and then slowly stirred for 2 - 3 min;

[0056] (4)Refinement: The alloy is refined using Al-5Ti-1B master alloy and refined by passing argon gas. When the melt is heated to 730 - 740 °C, Al-5Ti-1B master alloy is added, stirred for 3 - 4 min, and left standing for 10 - 20 min. Subsequently, when the melt temperature is lowered to 700 - 730 °C, argon gas is passed into the melt for refining. The argon gas flow rate is controlled within 1 - 3 L / min. After refining for 20 - 30 min, it is left standing for 20 - 30 min, and the scum on the melt surface is skimmed off;

[0057] (5)Modification: When controlling the melt temperature at 720 - 730 °C, Al-10Sr master alloy is added. After it melts, it is stirred for 3 - 4 min, and after standing for 20 - 30 min, the scum on the melt surface is skimmed off;

[0058] (6)Gravity casting: After the in-furnace composition analysis is qualified, the molten metal is poured into a metal mold preheated to 200 °C at a temperature of 725 - 735 °C to obtain a heat-treatment-free casting.

[0059] Example 3

[0060] A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting, with the weight ratio of each component as follows: Si: 9.0 wt.%; Mn: 0.6 wt.%; Mg: 0.5 wt.%; Zn: 1.0 wt.%; Ti: 0.15 wt.%; Sr: 0.06 wt.%; the total amount of other impurities is less than or equal to: 0.4 wt.%, and the rest is Al.

[0061] A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and its preparation method, including the following steps:

[0062] (1)Before-furnace preparation: Clean the cast iron crucible and the inner runner of the metal mold, and evenly coat their inner walls with ZnO coating. At the same time, preheat the cast iron crucible, slag skimming tools, etc. at 250 °C for 2 hours;

[0063] (2)Ingredients: Considering the loss during melting, prepare A100 refined aluminum (purity > 99.9wt%), industrial pure Mg (purity > 99.9wt%), single crystal silicon Si, zinc ingot (purity > 99.9wt%), Al-10wt%Mn master alloy, Al-10wt%Sr master alloy, and Al-5wt%Ti-1wt%B master alloy raw materials according to the above alloy component ratios, and preheat the prepared raw materials at 250°C for 2 hours;

[0064] (3)Alloy melting: Add the preheated refined aluminum and Al-10Mn master alloy to the melting furnace and heat up to 680 - 700°C to completely melt them. Keep the furnace temperature at 680 - 700°C and add Si. After Si is completely melted, stir for 2 - 3 min, then add Mg and Zn, and use a ladle to press them below the melt surface to fully melt them, and slowly stir for 2 - 3 min;

[0065] (4)Refinement: The alloy is refined using Al-5Ti-1B master alloy and refined by passing argon gas. When the melt temperature is raised to 730 - 740°C, add Al-5Ti-1B master alloy, stir for 3 - 4 min, let it stand for 10 - 20 min, then when the melt temperature is lowered to 700 - 730°C, pass argon gas into the melt for refining. Control the argon gas flow rate within 1 - 3 L / min, refine for 20 - 30 min, and then let it stand for 20 - 30 min, and skim the scum on the surface of the melt;

[0066] (5)Modification: When controlling the melt temperature at 720 - 730°C, add Al-10Sr master alloy. After it melts, stir for 3 - 4 min, let it stand for 20 - 30 min, and then skim the scum on the surface of the melt;

[0067] (6)Gravity casting: After the in-furnace component analysis is qualified, pour the molten metal into a metal mold preheated to 200°C at a temperature of 725 - 735°C to obtain heat-treatment-free castings.

[0068] Example 4

[0069] A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting, with the weight ratio of each component being: Si: 7.0wt.%; Mn: 0.6wt.%; Mg: 0.5wt.%; Zn: 0.5wt.%; Ti: 0.15wt.%; Sr: 0.06wt.%; the total amount of other impurities is less than or equal to: 0.4wt.%, and the rest is Al.

[0070] A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and its preparation method, including the following steps:

[0071] (1)Pre - furnace preparation: Clean the cast iron crucible and the inner runner of the metal mold, evenly coat their inner walls with ZnO coating, and preheat the cast iron crucible, slag - skimming tools, etc. at 250 °C for 2 hours.

[0072] (2)Batching: Considering the losses during melting, prepare the raw materials of A100 refined aluminum (purity > 99.9 wt%), industrial pure Mg (purity > 99.9 wt%), single - crystal silicon Si, zinc ingot (purity > 99.9 wt%), Al - 10wt%Mn master alloy, Al - 10wt%Sr master alloy, and Al - 5wt%Ti - 1wt%B master alloy according to the above alloy component ratios, and preheat the prepared raw materials at 250 °C for 2 hours.

[0073] (3)Alloy melting: Add the pre - heated refined aluminum and Al - 10Mn master alloy into the melting furnace and heat up to 680 - 700 °C to completely melt them. Keep the furnace temperature at 680 - 700 °C and add Si. After Si is completely melted, stir for 2 - 3 min, then add Mg and Zn, and use a ladle to press them below the melt surface to fully melt them, and slowly stir for 2 - 3 min.

[0074] (4)Refinement and purification: The alloy is refined with Al - 5Ti - 1B master alloy and refined by passing argon gas. When the melt temperature is raised to 730 - 740 °C, add Al - 5Ti - 1B master alloy, stir for 3 - 4 min, let it stand for 10 - 20 min. Then, when the melt temperature is lowered to 700 - 730 °C, pass argon gas into the melt for refining. Control the argon gas flow rate within 1 - 3 L / min, refine for 20 - 30 min, and then let it stand for 20 - 30 min, and skim the scum on the surface of the melt.

[0075] (5)Modification: When the melt temperature is controlled at 720 - 730 °C, add Al - 10Sr master alloy. After it melts, stir for 3 - 4 min, let it stand for 20 - 30 min, and then skim the scum on the surface of the melt.

[0076] (6)Gravity casting: After the in - furnace component analysis is qualified, pour the molten metal into the metal mold pre - heated to 200 °C at a temperature of 725 - 735 °C to obtain heat - treatment - free castings.

[0077] Comparative Example 1

[0078] This comparative example relates to a heat - treatment - free high - strength aluminum - silicon alloy for gravity casting and its preparation method. The weight ratios of its components are: Si: 9.0 wt.%; Mn: 0.6 wt.%; Mg: 0.5 wt.%; Ti: 0.15 wt.%; Sr: 0.06 wt.%; the total amount of other impurities is less than or equal to: 0.4 wt.%, and the rest is Al.

[0079] A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and its preparation method in this comparative example include the following steps:

[0080] (1)Preparation before melting: Clean the cast iron crucible and the inner runner of the metal mold, evenly coat their inner walls with ZnO coating, and preheat the cast iron crucible, slag skimming tools, etc. at 250 °C for 2 hours;

[0081] (2)Batching: Considering the burn-off during the melting process, prepare raw materials such as A100 refined aluminum (purity > 99.9 wt%), industrial pure Mg (purity > 99.9 wt%), single crystal silicon Si, Al-10wt%Mn master alloy, Al-10wt%Sr master alloy, and Al-5wt%Ti-1wt%B master alloy according to the above alloy component ratios, and preheat the prepared raw materials at 250 °C for 2 hours;

[0082] (3)Alloy melting: Add the preheated refined aluminum and Al-10Mn master alloy into the melting furnace and heat up to 680 - 700 °C to completely melt them. Keep the furnace temperature at 680 - 700 °C and add Si. After Si is completely melted, stir for 2 - 3 min, then add Mg, press it below the melt surface with a ladle to fully melt it, and slowly stir for 2 - 3 min;

[0083] (4)Refinement and refining: The alloy is refined with Al-5Ti-1B master alloy and refined by passing argon gas. When the melt temperature is raised to 730 - 740 °C, add Al-5Ti-1B master alloy, stir for 3 - 4 min, let it stand for 10 - 20 min, then when the melt temperature is lowered to 700 - 730 °C, pass argon gas into the melt for refining. Control the argon gas flow rate within 1 - 3 L / min, refine for 20 - 30 min and then let it stand for 20 - 30 min, and skim the scum on the surface of the melt;

[0084] (5)Modification: When controlling the melt temperature at 720 - 730 °C, add Al-10Sr master alloy. After it melts, stir for 3 - 4 min, let it stand for 20 - 30 min, and then skim the scum on the surface of the melt;

[0085] (6)Gravity casting: After the in-furnace composition analysis is qualified, pour the molten metal into the metal mold preheated to 200 °C at a temperature of 725 - 735 °C to obtain a heat-treatment-free casting.

[0086] Comparative Example 2

[0087] This comparative example relates to a heat - treatment - free high - strength aluminum - silicon alloy for gravity casting and its preparation method. The weight ratios of its components are as follows: Si: 9.0 wt.%; Mn: 1.2 wt.%; Mg: 0.5 wt.%; Zn: 1.0 - 0.15 wt.%; Ti: 0.15 wt.%; Sr: 0.06 wt.%; the total amount of other impurities is less than or equal to: 0.4 wt.%, and the rest is Al.

[0088] A heat - treatment - free high - strength aluminum - silicon alloy for gravity casting and its preparation method in this comparative example include the following steps:

[0089] (1) Preparation before melting: Clean the cast - iron crucible and the inner runner of the metal mold, evenly coat ZnO coating on its inner wall, and preheat the cast - iron crucible, slag - skimming tools, etc. at 250 °C for 2 hours;

[0090] (2) Batching: Considering the loss during melting, prepare raw materials such as A100 refined aluminum (purity > 99.9 wt%), industrial pure Mg (purity > 99.9 wt%), single - crystal silicon Si, zinc ingot (purity > 99.9 wt%), Al - 10 wt% Mn master alloy, Al - 10 wt% Sr master alloy, and Al - 5 wt% Ti - 1 wt% B master alloy according to the above alloy component ratios, and preheat the prepared raw materials at 250 °C for 2 hours;

[0091] (3) Alloy melting: Add the pre - heated refined aluminum and Al - 10Mn master alloy into the melting furnace and heat up to 680 - 700 °C to completely melt them. Keep the furnace temperature at 680 - 700 °C and add Si. After Si is completely melted, stir for 2 - 3 min, then add Mg and Zn, press them below the melt surface with a ladle to fully melt them, and slowly stir for 2 - 3 min;

[0092] (4) Refinement and purification: The alloy is refined with Al - 5Ti - 1B master alloy and refined by passing argon gas. When the melt temperature rises to 730 - 740 °C, add Al - 5Ti - 1B master alloy, stir for 3 - 4 min, stand for 10 - 20 min, then when the melt temperature drops to 700 - 730 °C, pass argon gas into the melt for refining. Control the argon gas flow rate within 1 - 3 L / min, refine for 20 - 30 min and then stand for 20 - 30 min, and skim the scum on the surface of the melt;

[0093] (5) Modification: When controlling the melt temperature at 720 - 730 °C, add Al - 10Sr master alloy. After it melts, stir for 3 - 4 min, stand for 20 - 30 min, and then skim the scum on the surface of the melt;

[0094] (6) Gravity casting: After the in-furnace composition analysis is qualified, the molten metal is poured into a metal mold preheated to 200 °C at a temperature of 725 - 735 °C to obtain a heat-treatment-free casting.

[0095] Comparative Example 3

[0096] This comparative example relates to a heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and its preparation method. The weight ratios of the components are as follows: Si: 9.0 wt.%; Mn: 0.6 wt.%; Mg: 0.5 wt.%; Zn: 1.5 wt.%; Ti: 0.15 wt.%; Sr: 0.06 wt.%; the total amount of other impurities is less than or equal to: 0.4 wt.%, and the rest is Al.

[0097] A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and its preparation method in this comparative example include the following steps:

[0098] (1) Furnace preparation: Clean the cast iron crucible and the in-gate of the metal mold, evenly coat their inner walls with ZnO coating, and preheat the cast iron crucible, slag skimming tools, etc. at 250 °C for 2 hours;

[0099] (2) Batching: Considering the loss during melting, prepare raw materials such as A100 refined aluminum (purity > 99.9 wt%), industrial pure Mg (purity > 99.9 wt%), single crystal silicon Si, zinc ingot (purity > 99.9 wt%), Al-10wt%Mn master alloy, Al-10wt%Sr master alloy, and Al-5wt%Ti-1wt%B master alloy according to the above alloy component ratios, and preheat the prepared raw materials at 250 °C for 2 hours;

[0100] (3) Alloy melting: Add the preheated refined aluminum and Al-10Mn master alloy to the melting furnace and heat up to 680 - 700 °C to completely melt them. Keep the furnace temperature at 680 - 700 °C and add Si. After Si is completely melted, stir for 2 - 3 min, then add Mg and Zn, and use a skimmer to press them below the melt surface to fully melt them, and slowly stir for 2 - 3 min;

[0101] (4) Refinement and refining: The alloy is refined with Al-5Ti-1B master alloy and refined by passing argon gas. When the melt temperature is raised to 730 - 740 °C, add Al-5Ti-1B master alloy, stir for 3 - 4 min, and let it stand for 10 - 20 min. Then, when the melt temperature is lowered to 700 - 730 °C, pass argon gas into the melt for refining. Control the argon gas flow rate within 1 - 3 L / min, refine for 20 - 30 min, and then let it stand for 20 - 30 min, and skim the scum on the surface of the melt;

[0102] (5) Degeneration: When controlling the melt temperature at 720 - 730 °C, add Al-10Sr master alloy. After it melts, stir for 3 - 4 min, let it stand for 20 - 30 min, and then skim the dross on the surface of the melt.

[0103] (6) Gravity casting: After the in-furnace composition analysis is qualified, pour the molten metal into a metal mold preheated to 200 °C at a temperature of 725 - 735 °C to obtain a heat-treatment-free casting.

[0104] Comparative Example 4

[0105] This comparative example relates to a heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and its preparation method. The weight ratios of each component are as follows: Si: 7.0 wt.%; Mn: 0.6 wt.%; Mg: 0.5 wt.%; Ti: 0.15 wt.%; Sr: 0.06 wt.%; the total amount of other impurities is less than or equal to: 0.4 wt.%, and the rest is Al.

[0106] A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting and its preparation method in this comparative example include the following steps:

[0107] (1) Preparation before furnace: Clean the cast iron crucible and the inner runner of the metal mold, evenly coat ZnO coating on its inner wall, and preheat the cast iron crucible, slag skimming tools, etc. at 250 °C for 2 hours.

[0108] (2) Batching: Considering the loss during melting, prepare raw materials such as A100 refined aluminum (purity > 99.9 wt%), industrial pure Mg (purity > 99.9 wt%), single crystal silicon Si, Al-10wt%Mn master alloy, Al-10wt%Sr master alloy, and Al-5wt%Ti-1wt%B master alloy according to the above alloy component ratios, and preheat the prepared raw materials at 250 °C for 2 hours.

[0109] (3) Alloy melting: Add the preheated refined aluminum and Al-10Mn master alloy into the melting furnace and heat up to 680 - 700 °C to completely melt them. Keep the furnace temperature at 680 - 700 °C and add Si. After Si completely melts, stir for 2 - 3 min, then add Mg, press it below the melt surface with a ladle to fully melt it, and slowly stir for 2 - 3 min.

[0110] (4)Refinement and refining: The alloy is refined using Al-5Ti-1B master alloy and refined by introducing argon gas. When the melt temperature is raised to 730 - 740 °C, add Al-5Ti-1B master alloy, stir for 3 - 4 min, let it stand for 10 - 20 min, then when the melt temperature is lowered to 700 - 730 °C, introduce argon gas into the melt for refining. Control the argon gas flow rate within 1 - 3 L / min, after refining for 20 - 30 min, let it stand for 20 - 30 min, and skim the dross on the surface of the melt;

[0111] (5)Modification: When the melt temperature is controlled at 720 - 730 °C, add Al-10Sr master alloy. After it melts, stir for 3 - 4 min, let it stand for 20 - 30 min, and then skim the dross on the surface of the melt;

[0112] (6)Gravity casting: After the in-furnace composition analysis is qualified, pour the molten metal into a metal mold preheated to 200 °C at a temperature of 725 - 735 °C to obtain heat-treatment-free castings.

[0113] The castings obtained from the above examples and comparative examples were subjected to room-temperature tensile mechanical property tests, and the performance is shown in Table 1.

[0114] Table 1 Room-temperature tensile mechanical properties of castings obtained from examples and comparative examples

[0115] Name Tensile strength (MPa) Yield strength (MPa) Elongation (A) Example 1 258 148 8.5 Example 2 238 125 9.5 Example 3 241 139 8 Example 4 239 135 8 Comparative Example 1 230 128 7 Comparative Example 2 190 115 3.5 Comparative Example 3 229 111 5 Comparative Example 4 202 107 5

[0116] It can be seen from Example 1, Example 3, Comparative Example 1 and Comparative Example 3 that adding Zn element can significantly improve the alloy performance, but when the addition amount of Zn element exceeds 1.0 wt.%, the alloy performance significantly decreases, especially the elongation. It can be seen from Example 1, Example 2 and Comparative Example 2 that adjusting the Mn / Mg element content has an important impact on the alloy performance. When the Mn content is too high, it has a greater impact on the elongation of the alloy. It can be seen from Comparative Example 1 and Comparative Example 4 that the Si content has a greater impact on the tensile strength and yield strength of the alloy. When the alloy composition range is within the composition range required by Claim 1 of this patent. The range of room-temperature tensile mechanical properties of the casting is: tensile strength 230 - 260 MPa, yield strength 120 - 150 MPa, elongation 8 - 10%.

[0117] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0118] It should be understood that the present invention is not limited to what has been described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A heat-treatment-free high-strength aluminum-silicon alloy for gravity casting, characterized in that, The components and their weight percentages in the heat - treatment - free high - strength aluminum - silicon alloy for gravity casting are as follows: Si: 9wt%, Mg: 0.5wt%, Mn: 0.6wt%, Zn: 0.5wt%, Ti: 0.15wt%, Sr: 0.06wt%, or Si: 9wt%, Mg: 0.3wt%, Mn: 0.6wt%, Zn: 0.5wt%, Ti: 0.15wt%, Sr: 0.06wt%, or Si: 9wt%, Mg: 0.5wt%, Mn: 0.6wt%, Zn: 1wt%, Ti: 0.15wt%, Sr: 0.06wt%, or Si: 7wt%, Mg: 0.5wt%, Mn: 0.6wt%, Zn: 0.5wt%, Ti: 0.15wt%, Sr: 0.06wt%; The total amount of other impurities is ≤0.4wt%, and the balance is Al; The preparation method of the heat - treatment - free high - strength aluminum - silicon alloy for gravity casting includes the following steps: (1) Preparation before melting: Clean the cast - iron crucible and the inner runner of the metal mold, evenly coat the inner wall with ZnO coating, and pre - heat the cast - iron crucible, slag - skimming tools, etc. at 250°C for 2 hours; (2) Batching: Considering the burn - off during the melting process, prepare raw materials such as A100 refined aluminum with a purity > 99.9wt%, industrial pure Mg with a purity > 99.9wt%, single - crystal silicon Si, zinc ingot with a purity > 99.9wt%, Al - 10wt%Mn master alloy, Al - 10wt%Sr master alloy, and Al - 5wt%Ti - 1wt%B master alloy according to the above alloy component ratio, and pre - heat the prepared raw materials at 250°C for 2 hours; (3) Alloy melting: Add the pre - heated refined aluminum and Al - 10Mn master alloy into the melting furnace, heat up to 680 - 700°C to completely melt them, keep the furnace temperature at 680 - 700°C and add Si. After Si is completely melted, stir for 2 - 3 min, then add Mg and Zn, press them below the melt surface with a ladle to fully melt them, and slowly stir for 2 - 3 min; (4) Refinement and purification: The alloy is refined with Al - 5Ti - 1B master alloy and refined by passing argon gas. When the melt temperature is raised to 730 - 740°C, add Al - 5Ti - 1B master alloy, stir for 3 - 4 min, stand for 10 - 20 min. Then, when the melt temperature is lowered to 700 - 730°C, pass argon gas into the melt for refining. Control the argon gas flow rate within 1 - 3 L / min, refine for 20 - 30 min and then stand for 20 - 30 min, and skim the scum on the surface of the melt; (5) Modification: When controlling the melt temperature at 720 - 730°C, add Al - 10Sr master alloy. After it melts, stir for 3 - 4 min, stand for 20 - 30 min and then skim the scum on the surface of the melt; (6) Gravity casting: After the in - furnace component analysis is qualified, pour the molten metal into the metal mold pre - heated to 200°C at a temperature of 725 - 735°C to obtain heat - treatment - free castings.

2. The preparation method of the heat-treatment-free high-strength aluminum-silicon alloy for gravity casting according to claim 1, wherein: In the preparation method of the heat-treatment-free high-strength aluminum-silicon alloy for gravity casting, the pouring speed of the alloy in step 6 is 1 kg / s to 11 kg / s.

3. The heat-treatment-free high-strength aluminum-silicon alloy for gravity casting according to claim 1 is applied to gravity casting or the production of gravity-castings.

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