A heat treatment method for semi-solid casting

Abstract

The present application relates to the field of heat treatment of semi-solid castings, and specifically to a heat treatment method for semi-solid castings. The present application provides a heat treatment method for semi-solid castings, comprising performing semi-solid isothermal heat treatment on the casting and ultrasonic treatment on the second region. The present solution improves the existing heat treatment method by combining semi-solid isothermal heat treatment technology with ultrasonic treatment technology, thereby overcoming the problem of a large number of bubbles generated during high-temperature heat treatment, and is particularly suitable for castings with a thicker second region, such as the manufacture of high-performance wheels.

Description

Technical Field

[0001] The present application relates to the field of heat treatment of semi-solid castings, and in particular to a heat treatment method of semi-solid castings. Background Art

[0002] With the increasing demand for lightweight automobiles, aluminum alloy wheels are increasingly used. The automobile wheel is the central part of the rim, connecting the tire and the vehicle's suspension system. The design and material of the wheel can affect the car's handling, comfort and overall performance. Wheels are usually made of aluminum alloy, steel or magnesium alloy. Aluminum alloy wheels are widely used because of their lightweight and good heat dissipation performance. The preparation methods of aluminum alloy wheels mainly include solid forging, low-pressure casting, gravity casting, liquid die forging and semi-solid die casting, among which semi-solid die casting has received extensive attention from researchers.

[0003] Semi-solid casting is an advanced metal processing technology that combines the advantages of traditional metal casting and metal injection molding. By controlling the solidification process of the metal, casting is performed in a partially solidified state to obtain metal parts with excellent performance. Semi-solid die casting is to cool the semi-solid slurry to 10%~50% solid content and then perform die casting to obtain the desired finished parts close to the required size. When semi-solid die casting is applied to complex castings such as wheels, it is easy to introduce gas and inclusions during the extrusion process, and it is easy to generate bubbles on the surface during the heat treatment process.

[0004] In the preparation process of semi-solid castings such as automobile wheels, bubbles are mainly generated in the solid solution stage of heat treatment. The higher the temperature or the longer the time of solid solution treatment, the easier it is to generate bubbles. However, if the temperature of solid solution treatment is too low or the time is too short, the alloy elements are not completely dissolved, and it is impossible to obtain a casting that meets the strength requirements. For example, patent CN109763080A avoids the generation of bubbles by lowering the temperature of solid solution treatment, which makes it difficult to improve the toughness of the casting; for another example, patent CN114959521B avoids the generation of bubbles by performing multiple high-temperature short-time solid solution heat treatments. However, this method is only suitable for thinner castings. For some thicker castings, the above method cannot fully diffuse the alloy elements inside the casting and fully discharge the bubbles.

[0005] Therefore, it is necessary to propose a heat treatment method for semi-solid castings. Summary of the invention

[0006] Based on this, an embodiment of the present application provides a heat treatment method for a semi-solid casting. The semi-solid casting obtained by the heat treatment method has fewer bubbles and stronger mechanical strength.

[0007] On the one hand, the present application provides a method for heat treatment of a semi-solid casting, comprising the following steps:

[0008] Providing metal raw materials according to the composition of the aluminum alloy, mixing the metal raw materials and heating them to 10° C. to 20° C. above the liquidus to form a melt;

[0009] The melt is stirred to obtain a semi-solid slurry, wherein the solid fraction of the semi-solid slurry is 30% to 50%;

[0010] transferring the semi-solid slurry into a mold to prepare a casting including a first region and a second region, and then heat treating;

[0011] The ratio of the average thickness of the first region to the average thickness of the second region is 1:(5-20);

[0012] The heat treatment comprises performing semi-solid isothermal heat treatment on the casting and simultaneously performing ultrasonic treatment on the second region;

[0013] The temperature of the semi-solid isothermal heat treatment is 5-15° C. above the solidus of the aluminum alloy, and the duration of the semi-solid isothermal heat treatment is 5 min to 10 min.

[0014] In one embodiment, the ratio of the average thickness of the first region to the average thickness of the second region is 1:(5-12).

[0015] In one embodiment, the semi-solid isothermal heat treatment is performed once or more times.

[0016] In one embodiment, the semi-solid isothermal heat treatment is multiple treatments;

[0017] The number of the multiple treatments is 5 to 20 times, and the duration of each treatment is 5 to 10 minutes.

[0018] In one embodiment, the stirring process includes electromagnetic stirring.

[0019] In one embodiment, the parameters of the ultrasonic treatment include: ultrasonic frequency of 40kHz~50kHz, ultrasonic power of 1000W~2000W.

[0020] In one embodiment, the aluminum alloy comprises one or a mixture of aluminum, silicon, nickel, magnesium, copper, iron, zinc, titanium, manganese and strontium. In one embodiment, the aluminum alloy is A356.2.

[0021] Another aspect of the present application provides a semi-solid casting, at least a partial area of ​​which is treated by the above-mentioned heat treatment method for a semi-solid casting.

[0022] In one embodiment, the semi-solid casting comprises a semi-solid automobile wheel hub.

[0023] The present application provides a method for heat treatment of a semi-solid casting, comprising performing semi-solid isothermal heat treatment on the casting and performing ultrasonic treatment on the second region. The present application first uses a semi-solid isothermal heat treatment technology with a higher temperature than the solution treatment to treat the casting. The casting is in a semi-solid state at a higher temperature, and the alloy elements of the casting can be fully diffused and dissolved in a short time. At the same time, the casting is maintained at a liquid phase volume ratio of less than 5% by a short-term heat treatment and controlling the temperature of the heat treatment, thereby avoiding the semi-solid isothermal heat treatment from causing a significant impact on the shape accuracy of the casting. At the same time, the liquid phase components in the casting provide a channel for gas overflow, which is conducive to the overflow of gas in the casting; on the other hand, during the heat treatment process, hydrogen atoms in the second region with a larger thickness are concentrated near the inclusions and migrate with the inclusions and deposited in the deep layer of the casting. The present scheme applies ultrasonic treatment to the second region with a larger thickness, and the ultrasonic treatment can produce ultrasonic cavitation at the solid-liquid interface of the casting, thereby avoiding the aggregation of inclusions at the solid-liquid interface, on the one hand, inhibiting the aggregation of hydrogen atoms to produce bubbles, and on the other hand, preventing inclusions from being deposited in the deep layer of the casting, making it difficult to discharge bubbles. This solution improves the existing heat treatment method by combining semi-solid isothermal heat treatment technology with ultrasonic treatment technology, overcoming the problem of a large number of bubbles generated during high-temperature heat treatment. It is particularly suitable for castings with a thicker second area, such as the manufacture of high-performance wheels.

[0024] On the other hand, the present application provides a semi-solid casting, which is treated by the above-mentioned heat treatment method for semi-solid castings.

[0025] In one embodiment, the semi-solid casting comprises a semi-solid automobile wheel hub.

[0026] The semi-solid casting obtained by the heat treatment method of the present application has fewer bubbles and stronger mechanical strength.

[0027] The details of one or more embodiments of the present application are set forth in the description which follows, and other features, objects, and advantages of the present application will be apparent from the description and its claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0029] Figure 1 This is a schematic diagram of the automobile wheel hub product prepared in Example 1.

[0030] Figure 2 This is a schematic diagram of the automobile wheel hub product prepared in Comparative Example 2. DETAILED DESCRIPTION

[0031] Below in conjunction with embodiment and example, the application is further described in detail.It should be understood that these embodiments and examples are only used to illustrate the application and are not used to limit the scope of the application, and the purpose of providing these embodiments and examples is to make the understanding of the disclosure of the application more thorough and comprehensive.It should also be understood that the application can be implemented in many different forms, is not limited to the embodiment and example described herein, and those skilled in the art can make various changes or modifications without violating the connotation of the application, and the equivalent form obtained also falls within the protection scope of the application.In addition, in the description below, a large number of specific details are given in order to provide a more comprehensive understanding of the application, and it should be understood that the application can be implemented without one or more of these details.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0033] the term

[0034] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0035] The terms "and / or", "or / and", and "and / or" used in this article include any one of two or more related listed items, and also include any and all combinations of related listed items, and the arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in this application, the technical solution undoubtedly includes technical solutions that are all connected by "logical and", and undoubtedly includes technical solutions that are all connected by "logical or". For example, "A and / or B" includes three parallel solutions of A, B and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, the technical solution that is all connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, the combination of any two or any three of A, B, C, and D, and also includes the combination of four of A, B, C, and D (that is, the technical solution that is all connected by "logical AND").

[0036] In the present application, "plurality", "multiple", "multiple times", "multiples", etc., unless otherwise specified, refer to a number greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0037] As used herein, "combination thereof", "any combination thereof", "any combination thereof" etc. include all suitable combinations of any two or more of the listed items.

[0038] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0039] In the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0040] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0041] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0042] In the present application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1 to 10, indicating that t is any integer selected from the integer group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0043] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0044] In the present application, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass volume percentage.

[0045] All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the invention purpose and / or technical solution of this application, the cited documents involved in this application are cited with all contents and all purposes. When the cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When the cited documents are involved in this application, the examples and preferred methods of the cited relevant technical features can also be incorporated into this application as references, but are limited to the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be modified adaptively according to the description of this application.

[0046] On one hand, the present application provides a method for heat treatment of a semi-solid casting, comprising the following steps: providing metal raw materials according to the composition of the aluminum alloy, mixing the metal raw materials and heating to 10°C to 20°C above the liquidus to form a melt;

[0047] The melt is stirred to obtain a semi-solid slurry, wherein the solid fraction of the semi-solid slurry is 30% to 50%;

[0048] transferring the semi-solid slurry into a mold to prepare a casting including a first region and a second region, and then heat treating;

[0049] In a specific example, the semi-solid casting of the present application includes a relatively complex casting such as a wheel hub, which has a relatively thick region inside.

[0050] The ratio of the average thickness of the first region to the average thickness of the second region is 1:(5-20);

[0051] The heat treatment comprises performing semi-solid isothermal heat treatment on the casting and simultaneously performing ultrasonic treatment on the second region;

[0052] The temperature of the semi-solid isothermal heat treatment is 5-15° C. above the solidus of the aluminum alloy, and the duration of the semi-solid isothermal heat treatment is 5 min to 10 min.

[0053] The ratio of the average thickness of the first region to the average thickness of the second region is 1:5, 1:10, 1:15, or 1:20.

[0054] For example, the solid fraction of the semi-solid slurry is 30%, 35%, 40%, 45%, or 50%; the temperature of the semi-solid isothermal heat treatment is 520°C, 530°C, or 540°C; and the duration of the semi-solid isothermal heat treatment is 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min.

[0055] It is understandable that during the semi-solid isothermal heat treatment, hydrogen atoms are concentrated near the inclusions and migrate with the inclusions. The ultrasonic cavitation effect promotes the movement of the inclusions so that they are evenly distributed in the thicker second region to avoid their aggregation at the solid-liquid interface to produce larger inclusions and more hydrogen atoms. It also prevents inclusions from settling in the inner layer of the casting, making it difficult to discharge hydrogen. At the same time, the higher the temperature or the longer the time of the semi-solid isothermal heat treatment, the easier it is to produce bubbles. However, if the time of the semi-solid isothermal heat treatment is too short and the alloy elements are not completely dissolved, it is impossible to obtain a casting that meets the strength requirements. If the temperature of the semi-solid isothermal heat treatment is too low, it is impossible to transform the casting into a partial liquid phase.

[0056] In a specific example, the ratio of the average thickness of the first region to the average thickness of the second region is 1:(5~12).

[0057] In a specific example, the number of times of the semi-solid isothermal heat treatment includes one or more times.

[0058] Optionally, the semi-solid isothermal heat treatment is performed multiple times.

[0059] Further optionally, the number of treatments is 5 to 20 times, and each treatment lasts 5 to 10 minutes.

[0060] In a specific example, the stirring process includes electromagnetic stirring.

[0061] In a specific example, the parameters of the ultrasonic treatment include: ultrasonic frequency of 40kHz to 50kHz, and ultrasonic power of 1000W to 2000W. For example, the ultrasonic frequency is 40kHz, 42kHz, 44kHz, 46kHz, 48kHz, 50kHz; the ultrasonic power is 1000W, 1200W, 1400W, 1600W, 1800W, 2000W.

[0062] In a specific example, the aluminum alloy includes a mixture of one or more of aluminum, silicon, nickel, magnesium, copper, iron, zinc, titanium, manganese and strontium;

[0063] Optionally, the aluminum alloy is A356.2 alloy.

[0064] Another aspect of the present application provides a semi-solid casting, at least a partial area of ​​which is treated by the above-mentioned heat treatment method for a semi-solid casting.

[0065] In one specific example, the semi-solid casting includes a semi-solid automobile wheel hub.

[0066] On the other hand, the present application further provides a semi-solid casting, at least a partial area of ​​which is treated by the above-mentioned heat treatment method for semi-solid casting.

[0067] In one embodiment, the semi-solid casting includes but is not limited to a semi-solid automobile wheel hub.

[0068] The embodiments of the present application will be described in detail below in conjunction with examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are preferably referred to the guidance provided in the present application, and can also be based on the experimental manual or normal conditions in this area, can also be based on the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0069] In the following specific embodiments, the measured parameters of raw material components may have slight deviations within the range of weighing accuracy unless otherwise specified. For temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed.

[0070] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0071] Embodiment 1: This embodiment provides a heat treatment method for a semi-solid casting. It can be understood that this embodiment takes a semi-solid automobile wheel hub as an example, and other semi-solid castings are also suitable for the heat treatment method of this application.

[0072] Various pure metals were weighed according to the composition of A356.2 aluminum alloy (solidus 555°C, liquidus 615°C, the same below), including silicon: 6.91%, nickel: 0.009%, magnesium: 0.320%, copper: 0.004%, iron: 0.109%, zinc: 0.014%, titanium: 0.104%, manganese: 0.003%, strontium: 0.0001%, and the rest was aluminum.

[0073] After mixing the metal raw materials, heating to 10° C. above the liquidus to form a melt;

[0074] The melt is stirred to obtain a semi-solid slurry, wherein the solid phase fraction of the semi-solid slurry is 40%.

[0075] The slurry was transferred to a mold with a mold temperature of 300°C and an injection speed of 0.2 m / s.

[0076] The automobile wheel hub obtained by die casting was heat treated, the temperature of semi-solid isothermal heat treatment was 565°C, the time of semi-solid isothermal heat treatment was 5 min, and the spokes, the connection between the rim and the spokes, and the mounting plate (i.e., the second area) of the wheel hub were ultrasonically treated simultaneously. The ratio of the average thickness of the rim (i.e., the first area) to the average thickness of the spokes of the wheel hub was 1:8, the ratio of the average thickness of the rim to the average thickness of the rim of the wheel hub was 1:5, and the ratio of the average thickness of the rim to the average thickness of the spoke connection of the wheel hub was 1:12.

[0077] The ultrasonic parameters were as follows: ultrasonic frequency was 40kHz and ultrasonic power was 1000W.

[0078] The solid solution and ultrasonic treatment were performed 10 times, and then artificial aging treatment was performed. The temperature of artificial aging treatment was 180°C and the time was 1h.

[0079] Embodiment 2: This embodiment provides a method for heat treatment of a semi-solid casting.

[0080] Various pure metals were weighed according to the composition of A356.2 aluminum alloy, including silicon: 6.91%, nickel: 0.009%, magnesium: 0.320%, copper: 0.004%, iron: 0.109%, zinc: 0.014%, titanium: 0.104%, manganese: 0.003%, strontium: 0.0001%, and the rest was aluminum.

[0081] After mixing the metal raw materials, heating to 10° C. above the liquidus to form a melt;

[0082] The melt is stirred to obtain a semi-solid slurry, wherein the solid fraction of the semi-solid slurry is 40%;

[0083] The slurry was transferred to a mold with a mold temperature of 300°C and an injection speed of 0.2 m / s.

[0084] The automobile wheel hub obtained by die casting was heat treated, the temperature of semi-solid isothermal heat treatment was 565℃, the time of semi-solid isothermal heat treatment was 5min, and the spokes, the connection between rim and spoke, and the mounting plate of the hub were ultrasonically treated simultaneously. The ratio of the average thickness of the rim to the average thickness of the spokes of the hub was 1:8, the ratio of the average thickness of the rim to the average thickness of the rim of the hub was 1:5, and the ratio of the average thickness of the rim to the average thickness of the spoke connection of the hub was 1:12.

[0085] The ultrasonic parameters were as follows: ultrasonic frequency was 50 kHz and ultrasonic power was 2000 W.

[0086] The solid solution and ultrasonic treatment were performed 10 times, and then artificial aging treatment was performed. The temperature of artificial aging treatment was 180°C and the time was 1h.

[0087] Embodiment 3: This embodiment provides a method for heat treatment of a semi-solid casting.

[0088] Various pure metals were weighed according to the composition of A356.2 aluminum alloy, including silicon: 6.91%, nickel: 0.009%, magnesium: 0.320%, copper: 0.004%, iron: 0.109%, zinc: 0.014%, titanium: 0.104%, manganese: 0.003%, strontium: 0.0001%, and the rest was aluminum.

[0089] After mixing the metal raw materials, heating to 10° C. above the liquidus to form a melt;

[0090] The melt is stirred to obtain a semi-solid slurry, wherein the solid fraction of the semi-solid slurry is 30%;

[0091] The slurry was transferred to a mold with a mold temperature of 300°C and an injection speed of 0.2 m / s.

[0092] The automobile wheel hub obtained by die casting was heat treated, the temperature of semi-solid isothermal heat treatment was 570°C, the time of semi-solid isothermal heat treatment was 5 min, and the spokes, the connection between the rim and the spoke, and the mounting plate of the hub were ultrasonically treated simultaneously. The ratio of the average thickness of the rim to the average thickness of the spokes of the hub was 1:8, the ratio of the average thickness of the rim to the average thickness of the rim of the hub was 1:5, and the ratio of the average thickness of the rim to the average thickness of the spoke connection of the hub was 1:12.

[0093] The ultrasonic parameters were as follows: ultrasonic frequency was 40 kHz and ultrasonic power was 1000 W.

[0094] The solid solution and ultrasonic treatment were performed 10 times, and then artificial aging treatment was performed. The temperature of artificial aging treatment was 180°C and the time was 1h.

[0095] Embodiment 4: This embodiment provides a method for heat treatment of a semi-solid casting.

[0096] Various pure metals were weighed according to the composition of A356.2 aluminum alloy, including silicon: 6.91%, nickel: 0.009%, magnesium: 0.320%, copper: 0.004%, iron: 0.109%, zinc: 0.014%, titanium: 0.104%, manganese: 0.003%, strontium: 0.0001%, and the rest was aluminum.

[0097] After mixing the metal raw materials, heating to 10° C. above the liquidus to form a melt;

[0098] The melt is stirred to obtain a semi-solid slurry, wherein the solid fraction of the semi-solid slurry is 50%;

[0099] The slurry was transferred to a mold with a mold temperature of 300°C and an injection speed of 0.2 m / s.

[0100] The automobile wheel hub obtained by die casting was heat treated, the temperature of semi-solid isothermal heat treatment was 560°C, the time of semi-solid isothermal heat treatment was 10 min, and the spokes, the connection between the rim and the spoke, and the mounting plate of the wheel hub were simultaneously ultrasonically treated. The ratio of the average thickness of the rim to the average thickness of the spokes of the hub was 1:8, the ratio of the average thickness of the rim to the average thickness of the rim of the hub was 1:5, and the ratio of the average thickness of the rim to the average thickness of the spoke connection of the hub was 1:12.

[0101] The ultrasonic parameters were as follows: ultrasonic frequency was 40 kHz and ultrasonic power was 1000 W.

[0102] The solid solution and ultrasonic treatment were performed 5 times, and then artificial aging treatment was performed. The temperature of artificial aging treatment was 180°C and the time was 1h.

[0103] Comparative Example 1: Compared with Example 1, this comparative example does not perform ultrasonic treatment, and the remaining steps are the same as those of Example 1.

[0104] Various pure metals were weighed according to the composition of A356.2 aluminum alloy, including silicon: 6.91%, nickel: 0.009%, magnesium: 0.320%, copper: 0.004%, iron: 0.109%, zinc: 0.014%, titanium: 0.104%, manganese: 0.003%, strontium: 0.0001%, and the rest was aluminum.

[0105] After mixing the metal raw materials, heating to 10° C. above the liquidus to form a melt;

[0106] The melt was stirred to obtain a semi-solid slurry, and the slurry was transferred to a mold with a mold temperature of 300° C. and an injection speed of 0.2 m / s.

[0107] The automobile wheel hub obtained by die casting is heat treated, the temperature of semi-solid isothermal heat treatment is 565°C, and the time of semi-solid isothermal heat treatment is 5 minutes.

[0108] The semi-solid isothermal heat treatment was performed 10 times, and then artificial aging treatment was performed. The temperature of artificial aging treatment was 180°C and the time was 1h.

[0109] Comparative Example 2: Compared with Example 1, the semi-solid isothermal heat treatment in the heat treatment is changed to solution treatment, the temperature of the solution treatment is 400°C, and the remaining steps are the same as those in Example 1.

[0110] Various pure metals were weighed according to the composition of A356.2 aluminum alloy, including silicon: 6.91%, nickel: 0.009%, magnesium: 0.320%, copper: 0.004%, iron: 0.109%, zinc: 0.014%, titanium: 0.104%, manganese: 0.003%, strontium: 0.0001%, and the rest was aluminum.

[0111] After mixing the metal raw materials, heating to 10° C. above the liquidus to form a melt;

[0112] The melt was stirred to obtain a semi-solid slurry, and the slurry was transferred to a mold with a mold temperature of 300° C. and an injection speed of 0.2 m / s.

[0113] The automobile wheel hub obtained by die casting is heat treated, the heat treatment is solution treatment, the solution treatment temperature is 400℃, the solution treatment time is 5min, and the spokes, the connection between the rim and the spoke, and the mounting plate of the hub are simultaneously ultrasonically treated. The ratio of the average thickness of the rim to the average thickness of the spokes of the hub is 1:8, the ratio of the average thickness of the rim to the average thickness of the rim of the hub is 1:5, and the ratio of the average thickness of the rim to the average thickness of the spoke connection of the hub is 1:12.

[0114] The ultrasonic parameters were as follows: ultrasonic frequency was 40kHz and ultrasonic power was 1000W.

[0115] The solid solution and ultrasonic treatment were performed 10 times, and then artificial aging treatment was performed. The temperature of artificial aging treatment was 180°C and the time was 1h.

[0116] Comparative Example 3: Compared with Example 1, the temperature of the semi-solid isothermal heat treatment is 580°C, and the remaining steps are the same as those in Example 1.

[0117] Various pure metals were weighed according to the composition of A356.2 aluminum alloy, including silicon: 6.91%, nickel: 0.009%, magnesium: 0.320%, copper: 0.004%, iron: 0.109%, zinc: 0.014%, titanium: 0.104%, manganese: 0.003%, strontium: 0.0001%, and the rest was aluminum.

[0118] After mixing the metal raw materials, heating to 10° C. above the liquidus to form a melt;

[0119] The melt was stirred to obtain a semi-solid slurry, and the slurry was transferred to a mold with a mold temperature of 300° C. and an injection speed of 0.2 m / s.

[0120] The automobile wheel hub obtained by die casting was heat treated, the temperature of semi-solid isothermal heat treatment was 580°C, the time of semi-solid isothermal heat treatment was 5 min, and the spokes, the connection between the rim and the spoke, and the mounting plate of the hub were simultaneously ultrasonically treated. The ratio of the average thickness of the rim to the average thickness of the spokes of the hub was 1:8, the ratio of the average thickness of the rim to the average thickness of the rim of the hub was 1:5, and the ratio of the average thickness of the rim to the average thickness of the spoke connection of the hub was 1:12.

[0121] The ultrasonic parameters were as follows: ultrasonic frequency was 40 kHz and ultrasonic power was 1000 W.

[0122] The solid solution and ultrasonic treatment were performed 10 times, and then artificial aging treatment was performed. The temperature of artificial aging treatment was 180°C and the time was 1h.

[0123] Results verification: The bubble generation of Examples 1 to 4 and Comparative Examples 1 to 3 was detected. The photo product schematic diagram of the automobile wheel hub prepared in Example 1 is shown in FIG. Figure 1 As shown, there are only a few bubbles at the junction of the spoke and rim, and almost no bubbles in other parts. The schematic diagram of the automobile wheel hub product prepared in Comparative Example 2 is shown in Figure 2 As shown, there are not only a few bubbles at the junction of the spoke and rim, but also a large number of flocculent bubbles can be observed in the middle area.

[0124] Mechanical property tests were performed on the spoke regions of the automobile wheels prepared in Examples 1 to 4 and Comparative Examples 1 to 3, and the tensile strength and elongation were tested in accordance with GB / T 23301-2009.

[0125] The results are shown in Table 1 and Table 2:

[0126] Table 1

[0127] Table 2

[0128] From the above results, it can be seen that in Examples 1 to 4, the semi-solid isothermal heat treatment method for semi-solid castings provided by the present application is used to perform semi-solid isothermal heat treatment on the automobile wheel hub, and ultrasonic treatment is simultaneously performed on the spokes of the wheel hub, the connection between the rim and the spoke, and the mounting plate. At the same time, the liquid phase volume ratio of the casting is maintained below 5% by short-term heat treatment and controlling the temperature of the heat treatment, thereby avoiding the semi-solid isothermal heat treatment from causing a significant impact on the shape accuracy of the casting. At the same time, the liquid phase components in the casting provide a channel for gas overflow, which is conducive to promoting the overflow of gas in the casting; on the other hand, during the heat treatment process, hydrogen atoms in the second region with a larger thickness are concentrated near the inclusions and migrate with the inclusions and deposited in the deep layer of the casting. In this scheme, ultrasonic treatment is applied to the second region with a larger thickness. The ultrasonic treatment can produce ultrasonic cavitation at the solid-liquid interface of the casting, thereby avoiding the aggregation of inclusions at the solid-liquid interface. On the one hand, the aggregation of hydrogen atoms is suppressed to generate bubbles, and on the other hand, the inclusions are prevented from being deposited in the deep layer of the casting, making it difficult to discharge the bubbles. The automobile wheel hub prepared in this way can be observed to have fewer bubble defects in appearance, and at the same time, it shows better effects in terms of tensile strength and elongation.

[0129] Comparative Example 1 does not perform ultrasonic treatment, but only performs semi-solid isothermal heat treatment on the automobile wheel hub with the same parameters as those in Example 1. It can be observed that more bubbles appear, especially in thicker areas such as spokes, which is not conducive to the refinement level of the product. At the same time, due to the generation of more bubbles, the tensile strength and elongation of the prepared automobile wheel hub are not as good as those in Example 1, so that the casting performance does not meet the standards.

[0130] Compared with Example 1, the heat treatment of Comparative Example 2 is solution treatment, and the temperature of the solution treatment is 400°C. In the traditional solution treatment process, the casting is in a solid solution (pure solid phase), and cannot provide a liquid phase to promote gas overflow. There is no solid-liquid phase interval, and it is difficult to produce ultrasonic cavitation to inhibit the aggregation of inclusions. Although ultrasonic treatment can promote the dissolution and diffusion of casting elements, its rate is far less than the synergistic effect of semi-solid isothermal heat treatment and ultrasonic action. Therefore, the casting of Comparative Example 2 not only has lower mechanical strength, but also has more bubbles.

[0131] Compared with Example 1, Comparative Example 3 increases the temperature of semi-solid isothermal heat treatment. Although a higher temperature is conducive to the dissolution and diffusion of casting elements, the excessive temperature drop leads to an excessively high liquid phase fraction of the casting. Although it is conducive to the overflow of bubbles, shrinkage cavities are easily generated after subsequent cooling, and the shape accuracy of the casting is affected. Therefore, the casting performance of Comparative Example 3 still does not meet the requirements.

[0132] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solution of the present application in detail, but it cannot be understood as a limitation on the scope of protection of the patent application. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several deformations and improvements can be made, which all belong to the protection scope of the present application. In addition, it should be understood that after reading the above-mentioned teaching content of the present application, the technicians in this field can make various changes or modifications to the present application, and the equivalent forms obtained also fall within the protection scope of the present application. It should also be understood that the technical solutions obtained by the technicians in this field through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the protection scope of the claims attached to the present application. Therefore, the protection scope of the patent of the present application shall be based on the content of the attached claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A method for heat treatment of a semi-solid casting, characterized in that: The following steps are involved: Providing metal raw materials according to the composition of the aluminum alloy, wherein the aluminum alloy is A356.2, and the components include silicon: 6.91%, nickel: 0.009%, magnesium: 0.320%, copper: 0.004%, iron: 0.109%, zinc: 0.014%, titanium: 0.104%, manganese: 0.003%, strontium: 0.0001%, and the rest is aluminum, and the metal raw materials are mixed and heated to 10° C. to 20° C. above the liquidus to form a melt; The melt is stirred to obtain a semi-solid slurry, wherein the solid fraction of the semi-solid slurry is 30% to 50%; The semi-solid slurry is transferred into a mold to prepare a semi-solid casting including a first region and a second region, wherein the semi-solid casting is a car wheel hub, the first region is a rim, and the second region is a spoke of the hub, a connection between the rim and the spoke, and a mounting plate, and then heat treated; The ratio of the average thickness of the first region to the average thickness of the second region is 1:(5-20); The heat treatment comprises performing semi-solid isothermal heat treatment on the casting and simultaneously performing ultrasonic treatment on the second region; The temperature of the semi-solid isothermal heat treatment is 5-15°C above the solidus of the aluminum alloy; The semi-solid isothermal heat treatment is multiple treatments; The number of multiple treatments is 5 to 20 times, and the duration of each treatment is 5 to 10 minutes; The parameters of the ultrasonic treatment include: ultrasonic frequency of 40kHz-50kHz, and ultrasonic power of 1000W-2000W.

2. The heat treatment method for a semi-solid casting according to claim 1, characterized in that: The stirring process includes electromagnetic stirring.

3. A semi-solid casting, characterized in that: The semi-solid casting is treated by the heat treatment method for semi-solid casting according to any one of claims 1 to 2.

4. The semi-solid casting according to claim 3, characterized in that: The semi-solid casting comprises a semi-solid automobile wheel hub.

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