A kind of semi-solid gravity casting process of aluminum alloy

Abstract

The invention provides an aluminum alloy semi-solid gravity casting process, comprising: putting a finished A356 aluminum alloy block into a crucible to melt it to 650°C to form aluminum alloy liquid; scooping out the liquid aluminum alloy liquid with a spoon, blowing nitrogen gas on the surface of the aluminum alloy liquid inside the spoon and stirring the aluminum alloy at a uniform speed; monitoring the temperature in real time through an infrared thermometer during the stirring process until the temperature in the spoon drops to the range of 630°C-640°C, and aluminum alloy semi-solid slurry with a solid-liquid ratio of 7:3 is formed in the spoon; a gravity pouring machine drives the mold to tilt and preheat the mold; putting the treated aluminum alloy liquid into a mold ladle and introducing it into a mold cavity, waiting for 120S, and the gravity pouring machine drives the mold to reset, and the mold is opened to clamp the formed product. In the conventional gravity casting process, only the semi-solid slurrying process needs to be added, so that the product qualification rate can be improved, the solidification time of the casting is shortened, the process cycle is shortened, the manufacturing efficiency is improved, the manufacturing cost is reduced, and it is suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to the field of foundry, in particular to the field of semi-solid die-casting technology, and specifically to a semi-solid gravity casting process for an aluminum alloy. Background Art

[0002] Semi-solid casting technology is in the trial and exploration stage in the field of high-pressure die casting, and its purpose is to improve the organizational density and performance of die castings. The mainstream casting technology in China is gravity casting, low-pressure casting and high-pressure casting. The semi-solid high-pressure casting process of semi-solid die casting technology is still in the trial and exploration stage of small batches. It has made some progress in the high-pressure die casting industry, but the yield rate of the existing public semi-solid high-pressure casting process is the same as that of gravity casting, which is not as good as low-pressure casting. The present invention mainly studies the common aluminum alloy casting process in the industry, combines the advantages and disadvantages of each process with the cutting-edge semi-solid die casting technology, and conducts research and innovation. Summary of the invention

[0003] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a semi-solid gravity casting process for aluminum alloy to solve the difficulties of the prior art.

[0004] To achieve the above-mentioned and other related purposes, the present invention provides a semi-solid gravity casting process for aluminum alloy, the process comprising:

[0005] S1: Put the finished A356 alloy aluminum block into a crucible and melt it to 650℃ to form aluminum alloy liquid;

[0006] S2: scooping out the liquid aluminum alloy with a spoon, blowing air on the surface of the aluminum alloy liquid inside the spoon and stirring the aluminum alloy at a uniform speed;

[0007] S3: The stirring time is generally 4-7 seconds. During the stirring process, the temperature is monitored in real time by an infrared thermometer until the temperature in the spoon drops to the range of 630℃-640℃. At this time, a semi-solid aluminum alloy slurry with a solid-liquid ratio of 7:3 will be formed in the spoon;

[0008] S4: The gravity pouring machine drives the mold to tilt and preheat the mold;

[0009] S5: Put the processed aluminum alloy liquid into the mold ladle and introduce it into the mold cavity.

[0010] S6: Wait for 120 seconds, the gravity pouring machine drives the mold to reset, and the mold is opened to clamp the molded product.

[0011] According to the preferred embodiment, the surface of the aluminum alloy liquid inside the spoon is blown with nitrogen. During the blowing and cooling process, the nitrogen atoms in the nitrogen do not react with the chemical elements in the A356 aluminum alloy liquid. The nitrogen atoms will leave the aluminum liquid along with the gas to prevent the aluminum liquid from oxidation.

[0012] According to the preferred solution, the mold is heated to 380°C+ before casting, and the mold temperature needs to be maintained at 380°C throughout the entire casting process. The solidus of A356 aluminum alloy is 550°C, and the aluminum alloy liquid for semi-solid casting is 630°C. When the mold temperature is lower than 380°C, due to heat conduction, the A356 aluminum alloy liquid will quickly cool down and move closer to the solidus, the fluidity will deteriorate, and the product cannot be formed.

[0013] The present invention is a semi-solid gravity casting process for aluminum alloy compared with conventional gravity casting; the following beneficial effects are achieved:

[0014] (1) The grain size of semi-solid gravity casting is finer than that of conventional liquid gravity casting, the aluminum liquid has better fluidity, the casting is easier to form, and it can effectively solve casting defects such as insufficient pouring;

[0015] (2) Semi-solid gravity casting aluminum liquid temperature is lower, which can greatly reduce the amount of gas generated by the shell core for parts with shell core auxiliary molding, effectively solving casting defects such as insufficient pouring and gas marks caused by trapped gas;

[0016] (3) The semi-solid gravity casting process has better mechanical properties;

[0017] (4) The semi-solid gravity casting process has lower melting and holding temperatures, and lower energy consumption per ton of molten metal, which can significantly reduce manufacturing costs. The semi-solid gravity casting process has lower casting temperatures, shortened solidification time, reduced process cycles, and improved production efficiency.

[0018] The best embodiment for carrying out the present invention will be described in more detail below with reference to the accompanying drawings so that the features and advantages of the present invention can be easily understood. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Shown are specific processing parameters for tilting gravity casting of liquid aluminum in Example 1;

[0020] Figure 2 The data are shown as experimental verification data on tilting gravity casting of liquid aluminum in Example 1;

[0021] Figure 3 Shown are experimental verification data for the present invention in Example 1;

[0022] Figure 4 Shown are experimental verification data for the present invention in Example 1;

[0023] Figure 5 Shown is the internal quality comparison CT of the castings manufactured by the prior art and the present invention in Example 1;

[0024] Figure 6Shown is the metallographic structure comparison of the castings of the present invention and the conventional gravity casting process;

[0025] Figure 7 Shown is a comparison of the mechanical properties of castings made by the present invention and conventional gravity casting processes;

[0026] Figure 8 The casting mold used in the process comparison and verification of Example 1 is shown;

[0027] Fig. 9 The castings required to be processed for process comparison and verification in Example 1 are shown;

[0028] Fig.10 It is shown as a schematic diagram of the process of the present invention.

[0029] Description of symbols DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the technical solution of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described in conjunction with the drawings of specific embodiments of the present invention. The same figure marks in the drawings represent the same parts. It should be noted that the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Compared to the embodiments shown in the drawings, feasible embodiments within the scope of the present invention may have fewer components, other components not shown in the drawings, different components, differently arranged components, or differently connected components, etc. In addition, two or more components in the drawings may be implemented in a single component, or a single component shown in the drawings may be implemented as multiple separate components.

[0032] Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not necessarily indicate a quantity limitation. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0033] The present invention provides a semi-solid gravity casting process for an aluminum alloy, which is used in a casting molding process. The present invention does not limit the types of specific parts required to be processed in the casting molding.

[0034] Example 1: The same automobile valve body is processed by the tilting gravity casting process of conventional liquid aluminum in the prior art and the aluminum alloy semi-solid gravity casting process proposed in the present invention. The same mold and the same gravity casting machine operation method are used to compare and verify the processes. Each process is subjected to three rounds of test processing. The temperature is increased gradually in the three rounds, with 20 pieces in each round. The processed valve body needs to undergo a sealing test. The test medium is water and the test pressure is 0.3MPa. The product appearance is not allowed to have cracks, pores, and through shrinkage cavities and shrinkage.

[0035] The specific processing parameters of liquid aluminum for tilting gravity casting are as follows: Figure 1 The experimental verification data is shown in Figure 2 Liquid aluminum is used for tilting gravity casting. The main appearance defects are insufficient pouring and gas marks. The main defects of X-ray flaw detection are shrinkage and penetration of the wall thickness between the airway and the inner cavity. The main airtight defect is leakage in the inner cavity. The leakage position is as follows: Figure 5 The X-ray flaw detection defects shown in the box are located in the same position.

[0036] The specific parameters of the aluminum alloy semi-solid gravity casting process proposed in the present invention are as follows: Figure 3 The experimental verification data is shown in Figure 4 As shown, the appearance is well formed because the casting aluminum liquid temperature is lower. Compared with conventional liquid aluminum liquid gravity castings, the surface flow lines and insufficient pouring of semi-solid slurry gravity castings are significantly reduced. X-ray inspection of a very small number of products shows slight shrinkage of the wall thickness structure between the airway and the inner cavity.

[0037] And if Figure 6 As shown in the figure, by comparing the metallographic results of qualified parts made by tilting gravity casting of liquid aluminum and semi-solid gravity casting of aluminum alloy, we can find that compared with conventional liquid aluminum gravity castings, the semi-solid slurry gravity castings have smaller grain size and finer grains.

[0038] Finally Figure 7 As shown, the mechanical properties of castings produced by tilting gravity casting of aluminum alloy semi-solid gravity casting process are higher than those of castings produced by tilting gravity casting of liquid aluminum.

[0039] The above embodiment proposes using A356.0, a common aluminum alloy casting material, to perform tilting gravity casting under certain process conditions using semi-solid slurry technology and conventional liquid metal states, and compares and analyzes the two process results. It only requires adding a semi-solid slurrying process to improve the product qualification rate, shorten the solidification time of the casting, and shorten the process cycle, thereby improving manufacturing efficiency and reducing manufacturing costs, and is also suitable for large-scale production.

[0040] The present invention provides a semi-solid gravity casting process for an aluminum alloy, the process of which is as follows:

[0041] S1: Put the finished A356 alloy aluminum block into a crucible and melt it to 650℃ to form aluminum alloy liquid;

[0042] S2: Use a spoon to scoop out the liquid aluminum alloy, blow air on the surface of the aluminum alloy liquid inside the spoon and stir the aluminum alloy at a uniform speed. The gas used for blowing is nitrogen. During the process of blowing and cooling, the nitrogen atoms in the nitrogen will not react with the chemical elements in the A356 aluminum alloy liquid. The nitrogen atoms will leave the aluminum liquid along with the gas to prevent the aluminum liquid from oxidation.

[0043] S3: The stirring time is generally 4-7 seconds. During the stirring process, the temperature is monitored in real time by an infrared thermometer until the temperature in the spoon drops to the range of 630℃-640℃. At this time, a semi-solid aluminum alloy slurry with a solid-liquid ratio of 7:3 will be formed in the spoon;

[0044] S4: The gravity pouring machine drives the mold to tilt and preheat the mold;

[0045] S5: Put the processed aluminum alloy liquid into the mold ladle and introduce it into the mold cavity.

[0046] S6: Wait for 120 seconds, the gravity pouring machine drives the mold to reset, and the mold is opened to clamp the molded product.

[0047] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A semi-solid gravity casting process for aluminum alloy, the process comprising: S1: Put the aluminum alloy block into the crucible and melt it to 650℃ to form aluminum alloy liquid; S2: scooping out the liquid aluminum alloy with a spoon, blowing air on the surface of the aluminum alloy liquid inside the spoon and stirring the aluminum alloy at a uniform speed; S3: The stirring time is generally 4-7 seconds. During the stirring process, the temperature is monitored in real time by an infrared thermometer until the temperature in the spoon drops to the range of 630℃-640℃. At this time, a semi-solid aluminum alloy slurry with a solid-liquid ratio of 7:3 will be formed in the spoon; S4: The gravity pouring machine drives the mold to tilt and preheat the mold; S5: Put the processed aluminum alloy liquid into the mold ladle and introduce it into the mold cavity. S6: Wait for 120 seconds, the gravity pouring machine drives the mold to reset, and the mold is opened to clamp the molded product.

2. The aluminum alloy semi-solid gravity casting process according to claim 1, characterized in that: A356.0 aluminum alloy is used as the casting material for the semi-solid gravity casting process.

3. The aluminum alloy semi-solid gravity casting process according to claim 1, characterized in that: The surface of the aluminum alloy liquid inside the spoon is blown with nitrogen. During the cooling process, the nitrogen atoms in the nitrogen do not react with the chemical elements in the A356 aluminum alloy liquid. The nitrogen atoms will leave the aluminum liquid along with the gas to prevent the aluminum liquid from oxidation.

4. The aluminum alloy semi-solid gravity casting process according to claim 1, characterized in that: The mold is heated to 380°C+ before casting, and the mold temperature needs to be maintained at 380°C throughout the entire casting process. The solidus line of A356 aluminum alloy is 550°C, and the aluminum alloy liquid of semi-solid casting is 630°C. When the mold temperature is lower than 380°C, due to heat conduction, the A356 aluminum alloy liquid will quickly cool down and move closer to the solidus line, the fluidity will deteriorate, and the product cannot be formed.

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