A hybrid composite aluminum-based heat-resistant piston and its manufacturing method

Abstract

The present invention discloses a hybrid composite aluminum-based heat-resistant piston and a manufacturing method thereof. The formula includes: a piston body component and a piston head component. The piston body component is a heat-resistant aluminum alloy powder, including Fe, V, Si, Zr, and Al. The piston head component is an Al2O3 particle-reinforced aluminum-based composite material powder, including the following two types: the first type is Al2O3 and heat-resistant aluminum alloy powder, and the second type is graphite powder, Al2O3, and heat-resistant aluminum alloy powder. The manufacturing method includes: Step 1, preparing the heat-resistant aluminum alloy powder; Step 2, preparing the Al2O3 particle-reinforced aluminum-based composite material powder; Step 3, cold isostatic pressing to form a blank; Step 4, vacuum hot pressing; Step 5, hot forging and forming; Step 6, machining. The piston prepared by the present invention is composed of an Al2O3 particle-reinforced heat-resistant aluminum alloy-based composite material piston head and a heat-resistant aluminum alloy piston body, and has the advantages of high strength, light weight, heat resistance, wear resistance, and small expansion coefficient.

Description

Technical Field

[0001] The present invention relates to the technical field of metal matrix composites, and particularly to a hybrid composite aluminum-based heat-resistant piston and a manufacturing method thereof. Background Art

[0002] A piston is a reciprocating part in the cylinder block of an automobile engine. Its basic structure can be divided into a top part, a head part and a skirt part. The top of the piston is the main part that forms the combustion chamber. With the development of modern engines towards high power, high speed, high thermal efficiency and low energy consumption, the piston material has evolved from commonly used cast iron, cast steel and aluminum alloy to a new type of aluminum-based composite piston. Since the traditional aluminum alloy piston has reached or approached the limit of use, the development of aluminum-based composite pistons has received high attention at home and abroad. However, due to the poor formability of aluminum-based composites, it is difficult to machine some complex structures of the piston body. Therefore, using composites to locally strengthen aluminum alloy pistons to improve the wear resistance of piston ring grooves and the ability of the entire piston top to withstand thermal loads can well meet the requirements of current high-power diesel engines.

[0003] Al-Fe-V-Si aluminum alloy is a heat-resistant aluminum alloy developed by AlliedSignal Corporation of the United States. Its service temperature can reach 350°C and it has good thermal stability. It is a new type of aluminum alloy with very promising applications. Research has found that appropriate volume fractions of Al2O3 or SiC particles as reinforcements can endow Al-Fe-V-Si alloy with higher specific strength, specific stiffness and elastic modulus, better thermal stability, and more excellent corrosion and wear resistance. However, its formability deteriorates, thus limiting its application. Patent ZL201510456406.5 discloses an aluminum matrix composite reinforced with silicon carbide particles for an automobile piston and a processing technology, which has the advantages of heat resistance, wear resistance and small expansion coefficient. However, it is quite difficult to prepare an integral piston with a complex shape using silicon carbide particle-reinforced aluminum matrix composites.

[0004] In summary, it is necessary to develop a new type of lightweight piston with heat resistance, wear resistance and a small expansion coefficient and its manufacturing technology in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a hybrid composite aluminum-based heat-resistant piston and a manufacturing method thereof, so as to solve the problems of large expansion coefficient and poor wear resistance of a single aluminum alloy integral piston, and the difficulty in forming a single aluminum-based composite integral piston as mentioned in the above background art.

[0006] To achieve the above object, the present invention provides the following technical solution: A hybrid composite aluminum-based heat-resistant piston, the formula of which includes: a piston body component and a piston head component. The piston body component is a heat-resistant aluminum alloy powder, including Fe, V, Si, Zr and Al; the piston head component is an Al2O3 particle-reinforced aluminum matrix composite powder, including the following two types: the first is Al2O3 and heat-resistant aluminum alloy powder, and the second is graphite powder, Al2O3 and heat-resistant aluminum alloy powder.

[0007] Preferably, the mass percentages of the components of the heat-resistant aluminum alloy powder are respectively: 8-12% of Fe, 1.2-2.5% of V, 1.5-2.5% of Si, 0.1-0.3% of Zr, and the rest is Al.

[0008] Preferably, the particle size of the heat-resistant aluminum alloy powder is 10-20 μm.

[0009] Preferably, the mass percentages of the components of the first type of Al2O3 particle-reinforced aluminum matrix composite powder are respectively: 1-5% of Al2O3 and 95-99% of heat-resistant aluminum alloy powder, and the mass percentages of the components of the second type of Al2O3 particle-reinforced aluminum matrix composite powder are respectively: 1-1.5% of graphite powder, 1-5% of Al2O3 and 95-99% of heat-resistant aluminum alloy powder.

[0010] Preferably, the particle size of the Al2O3 is 1-3 μm, and the particle size of the graphite powder is 2-3 μm.

[0011] A manufacturing method of a hybrid composite aluminum-based heat-resistant piston includes Step 1, preparing heat-resistant aluminum alloy powder; Step 2, preparing Al2O3 particle-reinforced aluminum matrix composite powder; Step 3, cold isostatic pressing to form a blank; Step 4, vacuum hot pressing; Step 5, hot forging forming; Step 6, machining;

[0012] Among them, in the above Step 1, based on the sum of the mass percentages of the components being 1, raw materials are weighed according to the formula of the heat-resistant aluminum alloy powder. After alloying, melting and refining, the heat-resistant aluminum alloy powder is prepared by nitrogen atomization method. After classification according to the particle size, it is reserved for use;

[0013] Among them, in the above Step 2, based on the sum of the mass percentages of the components being 1, raw materials are weighed according to the formula of the Al2O3 particle-reinforced aluminum matrix composite powder, and the Al2O3 particle-reinforced aluminum matrix composite powder is prepared by high-energy ball milling method;

[0014] Among them, in the above Step 3, the heat-resistant aluminum alloy powder prepared in Step 1 and the Al2O3 particle-reinforced aluminum matrix composite powder prepared in Step 2 are taken, and according to the mass or volume ratio of the piston body to the piston head, they are layered and loaded into a cold isostatic pressing mold for cold isostatic pressing to form a blank, obtaining a cold isostatic pressing blank;

[0015] In the above step 4, the cold isostatic pressing blank obtained in step 3 is loaded into a hot pressing die, and a hot pressed forging blank of the integral piston is obtained through vacuum hot pressing;

[0016] In the above step 5, the integral piston forging blank obtained in step 4 is hot forged and formed to obtain an integral piston forging. The forging temperature is 480 - 500 °C, and the compression ratio is not less than 1.5;

[0017] In the above step 6, the integral piston forging obtained in step 5 is machined to obtain a hybrid composite aluminum-based heat-resistant piston.

[0018] Preferably, in step 1, the nitrogen atomization method is specifically as follows: Using heated and pressurized nitrogen gas to pass through an atomizer, the molten alloy is sprayed into mist-like alloy droplets. The ambient nitrogen gas quickly absorbs the heat of the alloy droplets, and the alloy droplets in the shape of mist beads rapidly condense and shrink into spherical shapes, and then are subjected to classification treatment by a classification device to be separated into various particle size grades.

[0019] Preferably, in step 2, the ball milling time is 6 - 8 h, and the rotation speed is 150 - 160 rpm.

[0020] Preferably, in step 3, the pressure is 160 - 180 MPa, and the pressure holding time is 15 - 20 min.

[0021] Preferably, in step 4, the vacuum hot pressing process is as follows: the vacuum degree is 10 -3 Pa, the heating temperature is 580 - 600 °C; the pressure is 60 - 80 MPa, and the pressure holding time is 60 - 70 min.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The piston prepared by the present invention is composed of an Al2O3 particle-reinforced heat-resistant aluminum alloy-based composite piston head and a heat-resistant aluminum alloy piston body, and has the advantages of high strength, light weight, heat resistance, wear resistance, and small expansion coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a process flow chart of the present invention;

[0024] Figure 2 is a front view sectional view of the hybrid composite aluminum-based heat-resistant piston in the embodiment of the present invention;

[0025] In the figure: 1. Piston body main body; 2. Piston head main body. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Please refer to Figure 1-2 , an embodiment provided by the present invention: a hybrid composite aluminum-based heat-resistant piston, the formula includes: a piston body component and a piston head component. The piston body component is a heat-resistant aluminum alloy powder, including Fe, V, Si, Zr, and Al; the piston head component is an Al2O3 particle-reinforced aluminum-based composite material powder, including graphite powder, Al2O3, and heat-resistant aluminum alloy powder; the mass percentages of the components of the heat-resistant aluminum alloy powder are respectively: 8.614% of Fe, 1.493% of V, 1.726% of Si, 0.182% of Zr, and the rest is Al; the particle size of the heat-resistant aluminum alloy powder is 15 μm; the mass percentages of the components of the Al2O3 particle-reinforced aluminum-based composite material powder are respectively: 1% of graphite powder, 4% of Al2O3, and 95% of heat-resistant aluminum alloy powder; the particle size of Al2O3 is 3 μm, and the particle size of graphite powder is 2 μm.

[0028] A manufacturing method of a hybrid composite aluminum-based heat-resistant piston includes Step 1, preparing heat-resistant aluminum alloy powder; Step 2, preparing Al2O3 particle-reinforced aluminum-based composite material powder; Step 3, cold isostatic pressing to form a blank; Step 4, vacuum hot pressing; Step 5, hot forging; Step 6, machining;

[0029] Among them, in the above Step 1, taking the sum of the mass percentages of each component as 1, raw materials are weighed according to the formula of the heat-resistant aluminum alloy powder. After alloying, melting, and refining, the heat-resistant aluminum alloy powder is prepared by nitrogen atomization method. After classification according to particle size, it is reserved for use; among them, Fe and V are added in the form of Al-40Fe and Al-40Fe-10V master alloys. The melting process is specifically: first, Al-40Fe and Al-40Fe-10V master alloys are respectively melted and prepared in an intermediate frequency induction furnace at 1600 °C, and then an Al-5Zr master alloy, aluminum ingots, and a quick-dissolving silicon agent are added at 1020 °C to melt and alloy; the nitrogen atomization method is specifically: using heated and pressurized nitrogen to pass through an atomizer to spray the molten alloy into mist-like alloy droplets. The ambient nitrogen quickly absorbs the heat of the alloy droplets, and the alloy droplets in the shape of mist beads rapidly condense and shrink into spherical shapes, and then are classified by a classification device to be separated into various particle size grades;

[0030] In the above step 2, taking the sum of the mass percentages of each component as 1, raw materials are weighed according to the formula of the Al2O3 particle-reinforced aluminum matrix composite powder, and the Al2O3 particle-reinforced aluminum matrix composite powder is prepared by high-energy ball milling. The ball milling time is 8 h and the rotation speed is 160 rpm.

[0031] In the above step 3, the heat-resistant aluminum alloy powder prepared in step 1 and the Al2O3 particle-reinforced aluminum matrix composite powder prepared in step 2 are taken, and they are layered and loaded into a cold isostatic pressing mold according to the mass or volume ratio of the piston body to the piston head for cold isostatic pressing to obtain a cold isostatic pressed blank with a diameter of 100 mm. The pressure is 180 MPa and the pressure holding time is 20 min.

[0032] In the above step 4, the cold isostatic pressed blank obtained in step 3 is loaded into a hot pressing mold, and an integral piston hot pressing forging blank is obtained by vacuum hot pressing. The vacuum hot pressing process is as follows: the vacuum degree is 10 -3 Pa, the heating temperature is 600 °C; the pressure is 80 MPa, the pressure holding time is 30 min, and it is cooled in the furnace until the temperature is lower than 200 °C and then taken out of the furnace.

[0033] In the above step 5, the integral piston forging blank obtained in step 4 is hot forged to form an integral piston forging; specifically: the integral piston hot pressing blank with a diameter of 100 mm is hot forged into an integral piston hot forging blank with a diameter of 125 mm. The forging temperature is 500 °C and the compression ratio is 1.5625.

[0034] In the above step 6, the integral piston forging obtained in step 5 is machined into a hybrid composite aluminum-based heat-resistant piston with a diameter of 120 mm, as Figure 2 shown, including a piston body main body 1 and a piston head main body 2.

[0035] Samples are taken from the piston body main body 1 and the piston head main body 2 of the hybrid composite aluminum-based heat-resistant piston prepared in the above embodiments for room temperature and 315 °C high-temperature tensile tests, and the linear expansion coefficient is measured, and the performance is compared with that of the aluminum alloy piston of the standard YS / T 493-2005. Among them, the high-temperature tensile test of the aluminum alloy piston refers to the standard GB / T1148-93, and the results are shown in Table 1:

[0036]

[0037]

[0038] Table 1 Performance comparison of the piston head and piston body of the hybrid composite aluminum-based heat-resistant piston and the aluminum alloy piston

[0039] Based on the above, the advantages of the present invention are as follows: The piston designed by the present invention is composed of a piston head made of Al2O3 particle-reinforced heat-resistant aluminum alloy matrix composite material and a heat-resistant aluminum alloy piston body, which solves the problems of large expansion coefficient and poor wear resistance existing in the single aluminum alloy integral piston in the prior art, as well as the problem of difficult forming of the single aluminum matrix composite integral piston; The present invention uses powder metallurgy method to integrally form the piston head and the piston body by cold isostatic pressing blanking, vacuum hot pressing and hot forging. The powder metallurgy method adopted is nitrogen atomization method, which has the advantages of high fine powder rate, high forming rate of spherical aluminum alloy powder and production safety. The isostatic pressing blanking, vacuum hot pressing and hot forging processes adopted can make the grains of the integral piston refined and distributed in a streamline, which is beneficial to improving the mechanical properties, wear resistance, heat resistance and high-pressure resistance of the integral piston, and increasing the reliability of the piston operation.

[0040] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

Claims

1. A hybrid composite aluminum-based heat-resistant piston, the formula includes: Piston body component and piston head component, characterized in that: the piston body component is a heat-resistant aluminum alloy powder, including Fe, V, Si, Zr and Al; the piston head component is an Al2O3 particle-reinforced aluminum matrix composite powder, including the following two types: the first is Al2O3 and heat-resistant aluminum alloy powder, and the second is graphite powder, Al2O3 and heat-resistant aluminum alloy powder.

2. The hybrid composite aluminum-based heat-resistant piston according to claim 1, wherein: The mass percentages of the components of the heat-resistant aluminum alloy powder are respectively: 8-12% of Fe, 1.2-2.5% of V, 1.5-2.5% of Si, 0.1-0.3% of Zr, and the rest is Al.

3. The hybrid composite aluminum-based heat-resistant piston according to claim 2, wherein: The particle size of the heat-resistant aluminum alloy powder is 10-20 μm.

4. A hybrid composite aluminum-based heat-resistant piston according to claim 1, characterized in that: The mass percentages of the components of the first type of Al2O3 particle-reinforced aluminum matrix composite powder are respectively: 1-5% of Al2O3 and 95-99% of heat-resistant aluminum alloy powder, and the mass percentages of the components of the second type of Al2O3 particle-reinforced aluminum matrix composite powder are respectively: 1-1.5% of graphite powder, 1-5% of Al2O3 and 95-99% of heat-resistant aluminum alloy powder.

5. A hybrid composite aluminum-based heat-resistant piston according to claim 4, characterized in that: The particle size of the Al2O3 is 1-3 μm, and the particle size of the graphite powder is 2-3 μm.

6. A manufacturing method of a hybrid composite aluminum-based heat-resistant piston, including Step 1, preparing heat-resistant aluminum alloy powder; Step 2, preparing Al2O3 particle-reinforced aluminum matrix composite powder; Step 3, cold isostatic pressing to form a blank; Step 4, vacuum hot pressing; Step 5, hot forging forming; Step 6, machining; characterized in that: In the above Step 1, based on the sum of the mass percentages of the components being 1, raw materials are weighed according to the heat-resistant aluminum alloy powder formula, and after alloying, melting and refining, the heat-resistant aluminum alloy powder is prepared by nitrogen atomization method, and after being classified according to the particle size, it is reserved for use; In the above Step 2, based on the sum of the mass percentages of the components being 1, raw materials are weighed according to the Al2O3 particle-reinforced aluminum matrix composite powder formula, and the Al2O3 particle-reinforced aluminum matrix composite powder is prepared by high-energy ball milling method; In the above Step 3, the heat-resistant aluminum alloy powder prepared in Step 1 and the Al2O3 particle-reinforced aluminum matrix composite powder prepared in Step 2 are taken, and according to the mass or volume ratio of the piston body to the piston head, they are layered and loaded into a cold isostatic pressing mold for cold isostatic pressing to form a blank, and a cold isostatic pressing blank is obtained; In the above Step 4, the cold isostatic pressing blank obtained in Step 3 is loaded into a hot pressing mold and vacuum hot pressed to obtain an integral piston hot forging blank; In the above Step 5, the integral piston forging blank obtained in Step 4 is hot forged to form an integral piston forging, and the forging temperature is 480-500 °C, and the compression ratio is not less than 1.5; In step six above, the overall piston forging obtained in step five is machined to obtain a hybrid composite aluminum-based heat-resistant piston; in step one, the nitrogen atomization method specifically is: using heated and pressurized nitrogen to pass through an atomizer to spray the molten alloy into mist-like alloy droplets, and the ambient nitrogen rapidly absorbs the heat of the alloy droplets, and the alloy droplets in the shape of mist beads rapidly condense and shrink into spherical shapes, and then are subjected to classification treatment by a classification device to be separated into various particle size grades; in step two, the ball milling time is 6-8h and the rotation speed is 150-160rpm; in step three, the pressure is 160-180MPa and the pressure holding time is 15-20min; in step four, the vacuum hot pressing process is: the vacuum degree is 10 -3 Pa, the heating temperature is 580-600°C; the pressure is 60-80MPa and the pressure holding time is 60-70min.

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