Aluminum-based material for piston of internal combustion engine and preparation method of aluminum-based material

Abstract

The invention provides an aluminum-based material for a piston of an internal combustion engine and a preparation method of the aluminum-based material, the aluminum-based material contains TiB2 with the mass fraction of 1-5%, and the content of the TiB2 in the piston is reduced and changed in a gradient mode from bottom to top.

Description

Technical Field

[0001] The invention belongs to the technical field of pistons, and in particular relates to an aluminum-based material for an internal combustion engine piston and a preparation method thereof. Background Art

[0002] The explosion pressure that an internal combustion engine piston can withstand is directly related to key indicators such as engine performance and emissions. When the explosion pressure of a heavy-duty diesel engine piston reaches above 18 MPa, the operating temperature of the piston top combustion chamber will reach 300-320°C. As the explosion pressure of the piston reaches above 20 MPa, the operating temperature of the piston top combustion chamber will reach 320-350°C.

[0003] Currently, the main pistons for internal combustion engines are aluminum alloy pistons and steel pistons. Aluminum alloy pistons are the most widely used type of piston in internal combustion engines due to their low density (which significantly reduces the piston's mass and the inertial force of reciprocating motion), good thermal conductivity, and excellent casting properties. However, as the demand for internal combustion engine explosion pressure indicators increases, the inherent disadvantage of aluminum alloy's low high-temperature strength becomes apparent. When the explosion pressure exceeds 18 MPa, aluminum alloy pistons are no longer able to meet actual demand.

[0004] Therefore, researchers have improved the performance of aluminum alloy pistons for heavy-duty diesel engines from multiple aspects such as piston design and aluminum-based material development to meet the requirements of high explosion pressure.

[0005] Existing technical research shows that adding TiB2 to silicon-aluminum alloys can significantly improve the material's overall performance, particularly in high-temperature, high-load applications like engine pistons. Generally, TiB2 is poured into the mold along with the molten aluminum, resulting in a relatively uniform distribution throughout the piston. Therefore, to achieve optimal high-temperature resistance, a relatively large amount of TiB2 is required. Summary of the Invention

[0006] In order to solve the above technical problems, this application proposes an aluminum-based material for internal combustion engine pistons and a preparation method thereof. The specific technical solutions are as follows:

[0007] An aluminum-based material for an internal combustion engine piston contains 1-5% TiB2 by mass, wherein the TiB2 content in the piston decreases gradually from the bottom to the top, and the particle size of the TiB2 should be limited to 2-10 μm.

[0008] As a preferred embodiment of the above scheme, the aluminum-based material includes the following components in mass percentage: the aluminum-based composite material is made of the following components in mass percentage: Si 12-13.5%, Cu 3-4%, Mn 0.1-0.3%, Mg0.8-1.45%, Ni 1.75-2.5% and unavoidable impurities, and the balance is Al.

[0009] As a preferred embodiment of the above solution, the aluminum-based material further comprises S with a mass fraction of 0.1 to 0.5%. C .

[0010] As a preferred embodiment of the above scheme, the TiB2 and S C The mass ratio is 8:1.

[0011] As a preferred embodiment of the above scheme, the preparation method of the piston is:

[0012] (1) Except for TiB2, the raw materials of aluminum-based materials are melted and the temperature of the molten aluminum is maintained at not less than 750°C;

[0013] (2) sequentially performing slag removal, modification, refining and degassing on the molten aluminum;

[0014] (3) Casting molten aluminum in a protective atmosphere, and spraying TiB2 powder into the casting liquid flow with inert gas, controlling the addition amount of TiB2 powder to gradually decrease.

[0015] As a preferred embodiment of the above scheme, the TiB2 powder is preheated to a temperature exceeding that of molten aluminum.

[0016] As a preferred embodiment of the above scheme, the temperature difference between the TiB2 powder preheating temperature and the aluminum liquid does not exceed 100°C.

[0017] The beneficial effects of the present invention are:

[0018] The aluminum-based material for internal combustion engine pistons and its preparation method of the present application adopt a method of adding TiB2 powder during casting, so that the TiB2 heterogeneous crystal nuclei formed inside the piston show a gradient change. Combined with this method, more TiB2 heterogeneous crystal nuclei can be enriched in the part of the piston close to the combustion chamber when the TiB2 addition amount is smaller, thereby showing better high-temperature resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Shown is a reference schematic diagram of a truncated piston in an embodiment. DETAILED DESCRIPTION

[0020] In the following description, certain specific details are set forth in order to provide a thorough understanding of the various embodiments. However, it will be understood by those skilled in the art that the present invention can be practiced without these details. In other cases, well-known structures are not shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. Unless the context requires otherwise, throughout the specification and the appended claims, the word "comprising" should be interpreted in an open, inclusive sense, that is, as in "including but not limited to."

[0021] In the following embodiments:

[0022] The slag cleaning agent was purchased from Xuzhou Siyuan Aluminum Co., Ltd. with the product number SY-QJ;

[0023] Modifier was purchased from Xuzhou Siyuan Aluminum Co., Ltd., product number SY-PB1;

[0024] The refining flux was purchased from Xuzhou Siyuan Aluminum Co., Ltd. with the product number SY-HBJ1.

[0025] Example 1

[0026] The piston is made as follows:

[0027] (1) Except for TiB2, the raw materials of aluminum-based materials are melted and the temperature of the molten aluminum is maintained at not less than 750°C;

[0028] (2) The aluminum liquid is sequentially subjected to slag removal, modification, refining and degassing; wherein the slag removal is to add a slag removal agent to the aluminum liquid and press it below the liquid surface, react for 2 to 3 minutes, stir the aluminum liquid and then remove the slag, and the amount of the slag removal agent is 0.2% of the total weight of the aluminum-based material; modification is to add a modification agent to the aluminum liquid, press it below the liquid surface, react for 13 to 15 minutes, and the amount of the modification agent is 0.4% of the total weight of the aluminum-based material; refining is to add a refining agent to the aluminum liquid, press it below the liquid surface, react for 8 to 10 minutes, and the amount of the refining agent is 0.3% of the total weight of the aluminum-based material; degassing is to use a degasser to degas the aluminum liquid for 8 to 10 minutes, with a gas volume of 15L / min, and after the degassing is completed, the slag removal agent is sprinkled on the liquid surface and left to stand for 10 minutes, and the amount of the slag removal agent is 0.04% of the total weight of the aluminum-based material.

[0029] (3) Molten aluminum is cast in an argon protective atmosphere, and TiB2 powder is sprayed into the casting liquid flow using argon, and the amount of TiB2 powder added is controlled to gradually decrease.

[0030] In this embodiment, the total weight of the piston is 1.5 kg, the mass fraction of TiB2 is 1%, the particle size of TiB2 is 2 to 10 μm, the mass fractions of the other components are Si 12%, Cu 3%, Mn 0.1%, Mg 0.8%, Ni 1.75% and unavoidable impurities (such as iron), and the balance is Al.

[0031] See also Figure 1 , press the piston Figure 1 The section A is the side close to the combustion chamber. The metallographic images of the three sections were observed and the density of TiB2 metallographic particles on different sections was counted. The actual observed density of TiB2 metallographic particles on section A was 0.8×10 6 Particles / cm 2 The metallographic particle density of TiB2 on section B is 0.5×10 6 Particles / cm2 The metallographic particle density of TiB2 on the C section is 0.1×10 6 Particles / cm 2 .

[0032] Example 2

[0033] This embodiment differs from embodiment 1 in that the mass fraction of TiB2 is 2%.

[0034] Press the piston Figure 1 The metallographic images of the three sections were observed and the density of TiB2 metallographic particles on different sections was counted. The actual observed density of TiB2 metallographic particles on section A was 1.5×10 6 Particles / cm 2 The metallographic particle density of TiB2 on section B is 1×10 6 Particles / cm 2 The metallographic particle density of TiB2 on the C section is 0.2×10 6 Particles / cm 2 .

[0035] Example 3

[0036] This embodiment differs from embodiment 1 in that the mass fraction of TiB2 is 5%.

[0037] A high-temperature tensile strength test was performed on the piston A side at 350°C, and the high-temperature tensile strength was measured to be 121 MPa.

[0038] Comparative Example 1

[0039] This embodiment differs from embodiment 3 in that: in step (1), TiB2 and the raw materials of the aluminum-based material are melted simultaneously.

[0040] The high temperature tensile strength test of the piston side A at 350°C was performed, and the high temperature tensile strength was measured to be 104 MPa.

[0041] It can be seen that the method of adding TiB2 simultaneously during casting and controlling the gradual reduction of the amount of TiB2 powder added in this application can make the TiB2 heterogeneous crystal nuclei formed inside the piston change in a gradient. Combined with this method, when the amount of TiB2 added is smaller, the part of the piston close to the combustion chamber is enriched with more TiB2 heterogeneous crystal nuclei, thereby showing better high-temperature resistance.

[0042] However, when the mass fraction of TiB2 is larger, TiB2 agglomeration will occur, which is more difficult to handle.

[0043] Example 4

[0044] This embodiment is different from embodiment 2 in that 0.1% S is added. C .

[0045] Press the piston Figure 1 The metallographic images of the three sections were observed and the density of TiB2 metallographic particles on different sections was counted. The actual observed density of TiB2 metallographic particles on section A was 1.57×10 6 Particles / cm 2 The metallographic particle density of TiB2 on section B is 1.05×10 6 Particles / cm 2 The metallographic particle density of TiB2 on the C section is 0.21×10 6 Particles / cm 2 .

[0046] Example 5

[0047] This embodiment differs from embodiment 2 in that 0.25% of S is added. C .

[0048] Press the piston Figure 1 The metallographic images of the three sections were observed and the density of TiB2 metallographic particles on different sections was counted. The actual observed density of TiB2 metallographic particles on section A was 1.67×10 6 Particles / cm 2 The metallographic particle density of TiB2 on section B is 1.15×10 6 Particles / cm 2 The metallographic particle density of TiB2 on the C section is 0.23×10 6 Particles / cm 2 .

[0049] Example 6

[0050] This embodiment differs from embodiment 2 in that 0.5% S is added. C .

[0051] Press the piston Figure 1 The metallographic images of the three sections were observed and the density of TiB2 metallographic particles on different sections was counted. The actual observed density of TiB2 metallographic particles on section A was 1.7×10 6 Particles / cm 2 The TiB2 metallographic particle density on the B section is 1.2×10 6 Particles / cm 2 The metallographic particle density of TiB2 on the C section is 0.24×10 6 Particles / cm 2 .

[0052] Combining Examples 4 to 6, it can be seen that adding an appropriate amount of S to the molten aluminum C It is beneficial to improve the metallographic particle density of TiB2, indicating that the addition of S C To a certain extent, it can overcome the agglomeration phenomenon caused by adding TiB2 powder during casting, and thus increase the metallographic particle density of TiB2 with the same addition amount of TiB2 powder.

[0053] Example 7

[0054] This embodiment differs from embodiment 6 in that the TiB2 powder is preheated to 750°C before adding the TiB2 powder.

[0055] Press the piston Figure 1 The metallographic images of the three sections were observed and the density of TiB2 metallographic particles on different sections was counted. The actual observed density of TiB2 metallographic particles on section A was 1.88×10 6 Particles / cm 2 The metallographic particle density of TiB2 on section B is 1.23×10 6 Particles / cm 2 The metallographic particle density of TiB2 on the C section is 0.24×10 6 Particles / cm 2 .

[0056] Example 8

[0057] This embodiment differs from embodiment 6 in that the TiB2 powder is preheated to 800°C before adding the TiB2 powder.

[0058] Press the piston Figure 1 The metallographic images of the three sections were observed and the density of TiB2 metallographic particles on different sections was counted. The actual observed density of TiB2 metallographic particles on section A was 1.91×10 6 Particles / cm 2 The metallographic particle density of TiB2 on section B is 1.26×10 6 Particles / cm 2 The metallographic particle density of TiB2 on the C section is 0.25×10 6 Particles / cm 2 .

[0059] Combining Examples 7 and 8, it can be seen that preheating the TiB2 powder before adding it is also beneficial to overcome the agglomeration phenomenon caused by adding TiB2 powder during casting, and thus improve the metallographic particle density of TiB2 under the same addition amount of TiB2 powder, but its effect is not as good as adding SC obvious.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same.

Claims

1. Aluminum-based material for internal combustion engine piston, characterized in that: The aluminum-based material contains TiB2 with a mass fraction of 1 to 5%, and the content of TiB2 in the piston decreases gradually from the bottom to the top.

2. The aluminum-based material for an internal combustion engine piston according to claim 1, characterized in that: The aluminum-based material includes the following components by mass percentage: the aluminum-based composite material is made of the following components by mass percentage: Si 12-13.5%, Cu 3-4%, Mn 0.1-0.3%, Mg 0.8-1.45%, Ni 1.75-2.5% and inevitable impurities, with the balance being Al.

3. The aluminum-based material for an internal combustion engine piston according to claim 1, characterized in that: The aluminum-based material further comprises S with a mass fraction of 0.1 to 0.5%. C .

4. The aluminum-based material for an internal combustion engine piston according to claim 3, characterized in that: The TiB2 and S C The mass ratio is 8:

1.

5. The aluminum-based material for an internal combustion engine piston according to claim 1, characterized in that: The preparation method of the piston is as follows: (1) Except for TiB2, the raw materials of aluminum-based materials are melted and the temperature of the molten aluminum is maintained at not less than 750°C; (2) sequentially performing slag removal, modification, refining and degassing on the molten aluminum; (3) Casting molten aluminum in a protective atmosphere, and spraying TiB2 powder into the casting liquid flow with an inert gas, controlling the amount of TiB2 powder added to gradually decrease.

6. The aluminum-based material for an internal combustion engine piston according to claim 5, characterized in that: The TiB2 powder is preheated to a temperature higher than that of the molten aluminum.

7. The aluminum-based material for an internal combustion engine piston according to claim 6, characterized in that: The temperature difference between the TiB2 powder preheating temperature and the aluminum liquid should not exceed 100°C.

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