Powder metallurgical piston and method for producing the same

Abstract

The application discloses a powder metallurgy piston and a preparation method thereof. The raw material of the powder metallurgy piston comprises the following components in percentage by weight: 63.5-89% of aluminum-silicon alloy powder, 1.5-5% of electrolytic copper powder, 1.0-3.5% of nickel powder, 0.6-1.5% of magnesium powder, 0.05-0.1% of zirconium powder, 0.05-0.1% of vanadium powder, 0.1-0.15% of titanium powder, 0.05-0.11% of scandium powder, 0.05-0.1% of chromium powder, and the rest is gas atomized aluminum powder; and the weight ratio of the aluminum-silicon alloy powder to the gas atomized aluminum powder is greater than or equal to 2.2. The powder metallurgy piston is made of aluminum alloy material and has the advantages of high heat-resistant strength, excellent welding performance, light weight, good wear resistance, low thermal expansion coefficient, good heat conductivity and the like, and has important application prospect in the field of automobile engine piston materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder metallurgy, in particular to a powder metallurgy piston and a preparation method thereof. BACKGROUND

[0002] The piston is one of the most important parts in the automobile engine, and is also called the "heart" of the engine. The function of the piston is to bear the gas pressure and to transmit the energy to the connecting rod through the piston pin to drive the crankshaft movement, so the piston is one of the important factors to determine the overall quality of the engine. At present, with the continuous improvement of technical indicators such as diesel engine power and explosion pressure, the working environment of the piston becomes quite severe, and it simultaneously bears high pressure, high speed, high temperature mechanical load and thermal load. The piston in this working environment has special requirements for its material.

[0003] At present, the diesel engine piston at home and abroad is formed by gravity casting, and the piston material mostly uses eutectic Al-Si alloy. The representative Al-Si alloy piston material is ZL109. In order to further improve the heat resistance of the material, the composition of ZL109 material is optimized, the content of strengthening elements such as Cu and Ni is increased, and the piston alloy AlSiCuMgNi material is improved. The piston of national I to national V diesel engine mainly uses aluminum alloy material.

[0004] With the demand for high reliability and high strengthening of the vehicle power system, higher requirements for high power and high explosion pressure of the diesel engine are put forward, and the piston will work under higher temperature and higher friction and wear conditions, and bear higher thermal load and mechanical load. The traditional piston aluminum alloy material cannot meet the high technical index requirements of the diesel engine, so the piston material of national VI and above diesel engine mainly uses steel material, such as 42CrMo4, 34CrNiMo6 and 38MnVS6.

[0005] The steel material piston can bear an explosion pressure as high as 25 MPa or more, and the thermal expansion coefficient is also small, so the full steel piston has lower fuel consumption rate, higher strength, longer service life and smaller noise. However, the above-mentioned steel piston material has a large density, which is 3 times that of the aluminum alloy material, and a small thermal conductivity, which is 1 / 3 of the thermal conductivity of the aluminum alloy piston material, resulting in problems such as large weight, large inertia, poor heat dissipation capacity, high surface temperature and much rust of the steel piston, which seriously affect the development of vehicle lightweight and high mobility. SUMMARY

[0006] The present application provides a powder metallurgy piston and a preparation method thereof, to solve the technical problem that the steel material piston has large weight, large inertia and poor heat dissipation capacity, which seriously affects the development of vehicle lightweight and high mobility.

[0007] To achieve the above object, the technical scheme provided by the present application is as follows:

[0008] In the first aspect of the present application, a powder metallurgy piston is provided, raw materials of which include the following components in percentage by weight: aluminum-silicon alloy powder 63.5% to 89%, electrolytic copper powder 1.5% to 5%, nickel powder 1.0% to 3.5%, magnesium powder 0.6% to 1.5%, zirconium powder 0.05% to 0.1%, vanadium powder 0.05% to 0.1%, titanium powder 0.1% to 0.15%, scandium powder 0.05% to 0.11%, chromium powder 0.05% to 0.1%, and the rest is gas atomized aluminum powder; the weight ratio of the aluminum-silicon alloy powder to the gas atomized aluminum powder is greater than or equal to 2.2.

[0009] Further, the raw materials include the following components in percentage by weight: aluminum-silicon alloy powder 65%, electrolytic copper powder 4.5%, nickel powder 3%, magnesium powder 1.5%, zirconium powder 0.05%, vanadium powder 0.05%, titanium powder 0.12%, scandium powder 0.1%, chromium powder 0.05%, and the rest is gas atomized aluminum powder.

[0010] 4. Further, the powder metallurgy piston includes the following components in percentage by weight: Si 12.7% to 17.8%, Cu 1.5% to 5.0%, Ni 1.0% to 3.5%, Mg 0.6% to 1.5%, Ti 0.11% to 0.15%, Sc 0.05% to 0.11%, Cr 0.05% to 0.1%, Zr 0.05% to 0.1%, V 0.05% to 0.1%, Fe and O are inevitable impurity elements, Fe is not greater than 0.7%, O is not greater than 0.5%, and the rest is Al.

[0011] Further, the powder metallurgy piston includes the following components in percentage by weight: Si 15%, Cu 1.5%, Ni 1.0%, Mg 0.6%, Ti 0.13%, Sc 0.07%, Cr 0.08%, Zr 0.08%, V 0.05%, Fe 0.68%, O 0.29%, and the rest is Al.

[0012] In the second aspect of the present application, a preparation method of the above-mentioned powder metallurgy piston is provided, which includes the following steps:

[0013] S1, mixing raw materials according to the proportion, loading into a ball mill tank and adding an auxiliary agent to obtain a mixed powder;

[0014] S2, hot-press sintering the mixed powder to obtain a blank, the hot-press sintering including five stages: the first stage is to heat to 450-505 DEG C and keep for 25-35 min; the second stage is to heat to 511-545 DEG C and keep for 41-53 min, while applying a pressure of 25-30 MPa; the third stage is to heat to 552-566 DEG C and keep for 62-78 min; the fourth stage is to heat to 573-593 DEG C and keep for 81-106 min, after keeping, applying a pressure of 30-40 MPa; the fifth stage is to heat to 597-608 DEG C and keep for 254-329 min, after keeping, applying a pressure of 50-60 MPa;

[0015] S3, after die forging forming the blank obtained in the step S2, obtaining a piston top blank and / or a piston skirt blank; welding the piston top blank and the piston skirt blank to form a powder metallurgy piston.

[0016] Further, in the step S1, the additive is stearic acid, the weight of the stearic acid is 1.2-1.6 wt% of the total weight of the raw materials, the ball-to-material ratio is 5-6, the ball milling speed is 223-427 rpm, and the ball milling time is 6-8 h.

[0017] Further, in the step S3, the die forging forming includes: heating pretreatment of the blank, heating to 501-552 DEG C and keeping for 6.5-9.5 h; fixing the die on a die forging equipment, upsetting the blank after keeping, and then three times of forging forming to obtain the piston top blank and / or the piston skirt blank.

[0018] Further, the longitudinal upsetting ratio of the blank is 1.2-1.8, and the transverse deformation amount is 23-65%.

[0019] Further, in the three times of forging forming, the speed of the first hammer is 821-867 m / min, the speed of the second hammer is 714-754 m / min, and the speed of the third hammer is 596-621 m / min.

[0020] Further, before the welding forming in the step S3, the piston top blank and / or the piston skirt blank is subjected to heat treatment, specifically including: primary solid solution treatment at a temperature of 475-485 DEG C for 0.5-1 h; secondary solid solution treatment at a temperature of 505-525 DEG C for 3-4 h; and aging treatment at a temperature of 175-185 DEG C for 7-8 h.

[0021] The powder metallurgy piston is made of aluminum alloy material, has high heat-resistant strength, excellent weldability, light weight, good wear resistance, low thermal expansion coefficient, good thermal conductivity and the like, and has important application prospect in the field of automobile engine piston materials.

[0022] The powder metallurgy piston is prepared by powder metallurgy, the piston top blank and / or the piston skirt blank are prepared by ball milling, five-stage sintering and die forging process, the densification degree of the alloy is improved, the porosity is effectively reduced, the grain is refined, the material structure is more uniform, the strength, toughness and fatigue resistance of the piston blank are improved, the performance of the piston blank is better than that of the traditional piston, and the use requirement of the current and future high-performance diesel engine piston is met. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] Figure 1 It is a piston structure schematic diagram in the embodiment of the present application.

[0025] Figure 2 It is a mixed powder XRD diffraction pattern in embodiment 1 of the present application.

[0026] Figure 3 It is a mixed powder DSC curve in embodiment 1 of the present application.

[0027] Figure 4 It is a metallographic structure diagram of blank sintering state in embodiment 1 of the present application.

[0028] Figure 5 It is a metallographic structure diagram of piston blank forging state in embodiment 1 of the present application.

[0029] Reference signs:

[0030] 1, piston top blank; 2, piston skirt blank; 3, inner cooling oil channel. DETAILED DESCRIPTION

[0031] In order for the person skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] It should be noted that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or indirectly disposed on the other element; when an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0033] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0034] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of", "several" is two or more, unless otherwise explicitly specified.

[0035] It should be understood that the structures, proportions, sizes and the like shown in the drawings of the present application are only used to cooperate with the content disclosed in the description, to enable the person skilled in the art to understand and read, and do not define the limiting conditions for the implementation of the present application, and therefore do not have technical significance. Any modification of structure, change of proportion relationship or adjustment of size, which does not affect the effect and purpose that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application.

[0036] The first aspect of the embodiment of the present application provides a powder metallurgy piston, raw materials of the powder metallurgy piston include the following components in percentage by weight: aluminum-silicon alloy powder 63.5%-89%, electrolytic copper powder 1.5%-5%, nickel powder 1.0%-3.5%, magnesium powder 0.6%-1.5%, zirconium powder 0.05%-0.1%, vanadium powder 0.05%-0.1%, titanium powder 0.1%-0.15%, scandium powder 0.05%-0.11%, chromium powder 0.05%-0.1%, and the rest is gas atomized aluminum powder; the weight ratio of the aluminum-silicon alloy powder to the gas atomized aluminum powder is greater than or equal to 2.2.

[0037] With the continuous improvement of technical indicators of diesel engines, the working environment of the piston has also changed, and the piston needs to have the characteristics of small density, light weight, good heat conductivity, poor heat absorption, and small thermal expansion coefficient, and needs to have sufficient high-temperature strength, wear resistance, corrosion resistance, and good dimensional stability.

[0038] Although the steel material piston can withstand a burst pressure of up to 25 MPa or more, the thermal expansion coefficient is also small, and it has lower fuel consumption and higher strength, but the steel piston has a large density (7.8 g / cm 3 ), which is 3 times the density of the aluminum alloy piston and 1 / 3 of the thermal conductivity of the aluminum alloy piston, causing problems such as large weight and large inertia of the steel piston. In addition, the increase in the weight of the steel piston directly increases the reciprocating inertia force when the engine is working, thereby increasing the volume of the engine and the weight of the engine, which seriously hinders the development of vehicle power towards lightweight and high mobility. At the same time, the steel piston has a small thermal conductivity (40-45 W / mK) and poor heat dissipation, and has problems such as high surface temperature and severe corrosion, causing engine defects such as cylinder scoring.

[0039] Although the traditional aluminum alloy piston is light in weight, it has poor high-temperature mechanical properties and has been unable to withstand increasingly high mechanical and thermal loads. The material used in the current domestic forged aluminum piston is 4032 aluminum alloy, which has poor welding performance and is prone to welding defects such as pores and cracks during the welding process. At the same time, the forging temperature range is narrow, the deformation temperature range is small, and the forming is difficult, requiring a larger impact force to form, which can easily cause the forging to crack. The high-temperature performance of the 4032 aluminum alloy is limited, and when the temperature exceeds 200C, the strength of the material will decrease significantly.

[0040] The powder metallurgy piston of the embodiment of the present application is made of aluminum alloy material and has the advantages of high heat-resistant strength, excellent welding performance, small weight, good wear resistance, low thermal expansion coefficient, and good thermal conductivity, and has important application prospects in the field of automobile engine piston materials.

[0041] In the embodiment of the present application, the aluminum-silicon alloy powder is spherical, and compared with the silicon powder, the aluminum-silicon alloy powder has a lower melting point, so that the alloy powder has better flowability in the hot-pressing sintering process, can improve the filling rate, and has a small shrinkage rate when solidified, which helps to reduce the internal stress in the hot-pressing sintering process and improve the density, so the weight ratio of the aluminum-silicon alloy powder to the gas-atomized aluminum powder is greater than or equal to 2.2. In the embodiment of the present application, the aluminum-silicon alloy powder is Al20Si.

[0042] In the embodiment of the present application, the main alloy raw materials such as the aluminum-silicon alloy powder, the electrolytic copper powder, the nickel powder and the magnesium powder can form the second phase Mg2Si (for solid solution strengthening) and the Al7Cu4Ni and Al5Cu2Mg8Si6 metal compounds (for dispersion strengthening), which can improve the high-temperature performance and heat-resistant strength performance of the alloy.

[0043] In the embodiment of the present application, the main functions of the titanium powder, the vanadium powder, the zirconium powder and the scandium powder are to refine the grains and improve the welding performance and the strength and toughness of the alloy. Titanium and vanadium can refine the grains of the aluminum alloy, and in the welding process, the fine grain structure helps to reduce the crack tendency of the welding heat-affected zone. Because the finer grains can make the material deform more uniformly under the action of thermal stress, the crack resistance of the welding material and the strength and toughness of the alloy are improved. Zirconium (Zr) is also an effective grain refiner. The addition of zirconium elements can improve the welding solidification structure of the aluminum alloy, reduce the welding hot crack sensitivity, and make the quality of the welding joint higher. Scandium (Sc) can form highly dispersed compounds Al3Sc in the aluminum alloy, which can refine and strengthen the structure of the aluminum alloy. In welding, these dispersed phases can inhibit grain growth, improve the welding performance, and significantly improve the high-temperature strength.

[0044] 5. Further, the powder metallurgy piston comprises the following components in terms of weight percentage: Si 12.7% to 17.8%, Cu 1.5% to 5.0%, Ni 1.0% to 3.5%, Mg 0.6% to 1.5%, Ti 0.11% to 0.15%, Sc 0.05% to 0.11%, Cr 0.05% to 0.1%, Zr 0.05% to 0.1%, V 0.05% to 0.1%, iron elements and oxygen elements are inevitable impurity elements, iron is not more than 0.7%, oxygen is not more than 0.5%, and the balance is Al. The powder metallurgy piston of the embodiment of the present application comprises the above components after forming.

[0045] In a second aspect of the embodiment of the present application, a preparation method of the above-mentioned powder metallurgy piston is provided, comprising the following steps:

[0046] S1, mixing raw materials according to the proportion, loading into a ball mill tank and adding an auxiliary agent to obtain a mixed powder;

[0047] S2, hot-pressing sintering the mixed powder to obtain a blank, and the hot-pressing sintering comprises five stages:

[0048] The first stage is to heat to 450-505 DEG C and keep for 25-35 min;

[0049] The second stage is to heat to 511-545 DEG C and keep for 41-53 min, and meanwhile, 25-30 MPa pressure is applied;

[0050] The third stage is to heat to 552-566 DEG C and keep for 62-78 min;

[0051] The fourth stage is to heat to 573-593 DEG C and keep for 81-106 min, and after the keeping, 30-40 MPa pressure is applied;

[0052] The fifth stage is to heat to 597-608 DEG C and keep for 254-329 min, and after the keeping, 50-60 MPa pressure is applied;

[0053] S3, the blank obtained in the step S2 is subjected to die forging forming to obtain a piston top roughcast 1 and / or a piston skirt roughcast 2; the piston top roughcast 1 and the piston skirt roughcast 2 are welded and formed, and the powder metallurgy piston is obtained.

[0054] In the embodiment, the first stage is to heat to 450-505 DEG C and keep for 25-35 min, so that the additives added in the mixing and ball milling process are fully volatilized.

[0055] The second stage is to heat to 511-545 DEG C and keep for 41-53 min, and meanwhile, 25-30 MPa pressure is applied. At the above temperature, the aluminum-silicon alloy powder and the gas atomized aluminum powder have been softened, and under the pressure of 25-30 MPa, the aluminum-silicon alloy powder and the gas atomized aluminum powder are combined more closely, which is beneficial to the reaction and the mass transfer process, and also beneficial to increasing the density of the alloy.

[0056] The third stage is to heat to 552-566 DEG C and keep for 62-78 min. In this process, no pressure is applied, so as to prevent the liquid phase component from being squeezed out, which leads to change of the overall component of the alloy and damage of the structure, and the squeezed-out liquid also pollutes the mold.

[0057] The fourth stage involves heating to 573℃–593℃ and holding at that temperature for 81–106 minutes, followed by applying a pressure of 30 MPa–40 MPa. This stage is the pressure densification stage. Heating to 556℃–582℃ and holding for 81–106 minutes allows the liquid to completely solidify. Applying a pressure of 30 MPa–40 MPa then increases the alloy's density. Shrinkage cavities can occur during liquid-phase solidification, making it difficult to maintain alloy density; therefore, this step is crucial for ensuring alloy density. At this stage, the alloy density reaches 85.2%–90.5%.

[0058] The fifth stage is the pressure densification stage, where the temperature is raised to 597℃~608℃ and held for 254min~329min, followed by the application of 50MPa~60MPa pressure. This allows sufficient time and energy for the alloy to fully react with the various powder elements in the raw materials, ensuring complete solidification of the alloy liquid and the formation of the desired phase composition, thereby increasing the alloy's density. Similar to the purpose of the fourth stage, this further increases the alloy's density to 92.7%~96.2%.

[0059] In the embodiments of this application, the metal compounds and primary silicon microstructures in the billet prepared by the liquid-phase multi-stage hot pressing sintering method are relatively coarse, such as... Figure 4 As shown, the alloy is in the form of large plates or irregularly overlapping pieces, and is unevenly distributed in the matrix, resulting in porosity, reduced density, and adverse effects on the mechanical and thermophysical properties of the alloy.

[0060] To address the aforementioned issues, a forging process is employed to forge the billet, thereby increasing its density. Simultaneously, the size, morphology, and distribution of the metal compound and primary silicon are optimized, resulting in finer metal compounds and primary silicon, blunted sharp corners, and more uniform distribution.

[0061] Diesel engines meeting China VI emission standards and above all include internal cooling oil passages in their pistons. Additionally, the piston also includes a top and a skirt. (See reference...) Figure 1 The powder metallurgy piston preparation method of this application embodiment can be used to manufacture one or both of the piston top blank 1 and piston skirt blank 2, and the selection can be made according to the actual situation. The piston top blank 1 and piston skirt blank 2 are formed by welding, such as electron beam welding, laser welding, friction stir welding, etc.

[0062] In some embodiments, the die forging process includes: preheating the billet to 501°C–552°C and holding it at that temperature for 6.5h–9.5h; fixing the die on the die forging equipment; upsetting the billet after the holding period; and then forging it three times to obtain the piston top blank 1 and / or piston skirt blank 2.

[0063] In the embodiment of the present application, the blank is heated and pretreated in the box-type electric furnace before forging. When the blank is heated to a temperature of 501-552℃, in order to uniformly heat the material inside, eliminate the stress generated by heating, and make the material structure uniform, the blank is kept for 6.5-9.5 hours. Then the die is fixed on the die forging equipment. After the blank is kept for the preset time, the blank is upset. Upsetting at a high temperature can reduce the deformation resistance of the base material, improve its plastic deformation capacity, thereby reducing the required load for forging and reducing the possibility of cracks, so that the material can be forged into a well-shaped and high-density part at a lower pressure.

[0064] In the embodiment of the present application, the three-step forming forging is performed by using an electric screw press. In the initial stage of forging, the density of the blank is relatively low, and the forming load slowly increases with the increase of the pressing amount of the upper die. When the forging is about to end, the blank is densified due to the constraint of the die wall, which leads to the increase of the deformation resistance, and the load rapidly rises. With the increase of the strain rate, the initial deformation resistance increases. Therefore, the forging speed is reduced in stages during the three-step forming forging, and the density increases to 98.1%-99.2%.

[0065] During the forging process, one blank is hooked out from the furnace every time after one part is forged, and multiple blanks are not allowed to be hooked out at one time. The forged part is checked once every 20 parts, and the adjustment is made in time when an abnormality is found. The mixed lubricating liquid of graphite and machine oil is sprayed into the die cavity once every time after one part is forged. The blank is polished after forging, and the inner cavity and the periphery of the blank are polished by using the air-driven grinding machine, and the frame is cooled.

[0066] Further, the longitudinal upsetting ratio of the blank is 1.2-1.8, and the transverse deformation amount is 23%-65%. In the three-step forging forming process, the speed of the first hammer is 821-867 m / min, the speed of the second hammer is 714-754 m / min, and the speed of the third hammer is 596-621 m / min.

[0067] In some embodiments, before the step of welding forming in step S3, the piston top blank 1 and / or the piston skirt blank 2 is subjected to heat treatment, which specifically includes: first-stage solid solution treatment at a temperature of 475-485℃ for 0.5-1 hours; second-stage solid solution treatment at a temperature of 505-525℃ for 3-4 hours; and aging treatment at a temperature of 175-185℃ for 7-8 hours.

[0068] In the embodiment of the present application, the blank after forging needs to be subjected to heat treatment, i.e., solid solution strengthening and aging treatment, to strengthen the performance of the blank. The heat treatment process parameters are shown in Table 1.

[0069] Table 1 Heat treatment process parameters

[0070]

[0071] The reagents used in the following examples are commercially available.

[0072] Example 1

[0073] The raw materials for the powder metallurgy piston include the following components: 3250 g of aluminum-silicon alloy powder, 1281.5 g of gas atomized aluminum powder, 225 g of electrolytic copper powder, 150 g of nickel powder, 75 g of magnesium powder, 2.5 g of zirconium powder, 2.5 g of vanadium powder, 6 g of titanium powder, 5 g of scandium powder, and 2.5 g of chromium powder. The weight ratio of the aluminum-silicon alloy powder to the gas atomized aluminum powder is 2.5. The particle size range and purity of the above raw materials are shown in Table 2.

[0074] Table 2 Particle size range and purity of raw materials

[0075] Name Particle size range (μm) and purity Aerosolized aluminum powder 10-30, purity > 99.8% Aluminum-silicon alloy powder (Al20Si) 50-100, purity > 99.8% Electrolytic copper powder 30-60, purity > 99% Nickel powder 20-50, purity > 99% Magnesium powder 50-100, purity > 99% Zirconium powder 15-45, purity > 99% Vanadium powder 20-50, purity > 99% Titanium powder 50-100, purity > 99% Chromium powder 50-100, purity > 99% Scandium powder 50-100, purity > 99%

[0076] The method for preparing the powder metallurgy piston includes the following steps:

[0077] The raw materials are weighed according to the above weights, and the powders are loaded into a ball mill jar in a vacuum glove box for ball milling. Argon is filled into the ball mill jar, and the above raw materials are mixed on a ball mill, and 62 g of stearic acid is added as an additive to improve the powder yield of the powders. The ball milling time is 6.2 h, the ball milling speed is 398 rpm, and the ball-to-powder ratio is 5.8, to obtain a mixed powder.

[0078] The mixed powder is subjected to hot-press sintering to obtain a blank, and the mixed powder is subjected to XRD analysis (see Figure 2 ) and DSC analysis (see Figure 3 ). Figure 3 In the DSC curve, the endothermic peak appears at about 582°C, which indicates that the melting point of the mixed powder is 582°C, and the temperature at which eutectic silicon is formed is 556°C. The temperatures at which Mg2Si and Al7Cu4Ni metal compounds are formed are 539°C and 546°C, respectively. The temperature at which Al5Cu2Mg8Si6 metal compound is formed is 501°C.

[0079] The mixed powder after ball milling is subjected to hot-press sintering to obtain a blank, and the metallographic structure of the sintered state is shown in Figure 4 Hot-press sintering includes five stages:

[0080] The first stage is to heat to 455°C and hold for 26 min;

[0081] The second stage is to heat to 501°C and hold for 42 min, while applying a pressure of 26 MPa;

[0082] The third stage is to heat to 546°C and hold for 65 min;

[0083] The fourth stage is to heat to 556℃ and keep for 87min, and then apply a pressure of 32MPa;

[0084] The fifth stage is to heat to 582℃ and keep for 267min, and then apply a pressure of 53MPa.

[0085] The sintered blank is heated and pre-treated, heated to 507℃ and kept for 7.5h; the mold is fixed on the die forging equipment, and the blank after keeping is upset, the longitudinal upsetting ratio of the blank is 1.3, and the transverse deformation is 31%, and the temperature after upsetting is 507℃. The blank is formed and forged three times by using an electric screw press, in the steps of three times of forging forming, the speed of the first hammer is 863m / min, the speed of the second hammer is 752m / min, and the speed of the third hammer is 618m / min, different molds are used to obtain a piston top blank and a piston skirt blank. The metallographic structure diagram of the forged state is shown in Figure 5 .

[0086] From the comparison of the metallographic structures of the sintered state and the forged state, it can be seen that the forging process has obvious improvement effect on the reduction of pores and the increase of density, the pores of the powder forged alloy are uniform and small, most of the regions are completely dense, and the coarse metal compounds and silicon phase are obviously small, the average size of the silicon phase is reduced from 15μm to below 3μm, and the blank density is increased from 93.4% in the sintered state to 98.9% in the forged state.

[0087] The piston top blank and the piston skirt blank are heat treated, specifically including: first stage solid solution treatment, temperature is 475℃, holding time is 0.5h; second stage solid solution treatment, temperature is 505℃, holding time is 3h; water cooling to 52℃; aging treatment, temperature is 175℃, holding time is 7h, air cooling.

[0088] After heat treatment, the piston top blank and the piston skirt blank are welded to obtain a powder metallurgy piston.

[0089] Example 2

[0090] The raw materials of the powder metallurgy piston include the following components: 4250g of aluminum-silicon alloy powder, 388g of gas atomized aluminum powder, 125g of electrolytic copper powder, 150g of nickel powder, 65g of magnesium powder, 4.5g of zirconium powder, 4.5g of vanadium powder, 3.5g of titanium powder, 3g of scandium powder, and 4.5g of chromium powder. The weight ratio of the aluminum-silicon alloy powder to the gas atomized aluminum powder is 11.

[0091] The above-mentioned method for preparing the powder metallurgy piston comprises the following steps:

[0092] The raw materials were weighed according to the above, and the powders were loaded into a ball mill tank in a vacuum glove box for ball milling. Argon was filled into the ball mill tank, and the above raw materials were mixed on the ball mill, and 68 g of stearic acid was added as an additive to improve the powder yield of the powder. The ball milling time was 6.8 h, the ball milling speed was 421 rpm, the ball-to-powder ratio was 6, and the mixed powder was obtained.

[0093] The mixed powder after ball milling was subjected to hot-press sintering to obtain a blank, which included 5 stages:

[0094] The first stage was to heat to 475°C and keep for 28 min;

[0095] The second stage was to heat to 515°C and keep for 42 min, while applying a pressure of 26 MPa;

[0096] The third stage was to heat to 559°C and keep for 65 min;

[0097] The fourth stage was to heat to 583°C and keep for 86 min, and after the holding was completed, a pressure of 34 MPa was applied;

[0098] The fifth stage was to heat to 601°C and keep for 275 min, and after the holding was completed, a pressure of 53 MPa was applied.

[0099] The sintered blank was subjected to heating pretreatment, heated to 515°C and kept for 8.1 h; the mold was fixed on the die forging equipment, and the blank after the holding was completed was upset, the longitudinal upsetting ratio of the blank was 1.5, and the transverse deformation amount was 45%, and the temperature after upsetting was 515°C. The blank was subjected to three times of forming forging using an electric screw press, and in the three times of forging forming steps, the speed of the first hammer was 851 m / min, the speed of the second hammer was 741 m / min, and the speed of the third hammer was 601 m / min. Different molds were used to obtain a piston top blank and a piston skirt blank. The density of the blank was increased from 94.2% in the sintered state to 99.1% in the forged state.

[0100] The piston top blank and the piston skirt blank were subjected to heat treatment, which included: primary solid solution treatment at a temperature of 478°C for 0.7 h; secondary solid solution treatment at a temperature of 510°C for 3.2 h; water cooling to 58°C; aging treatment at a temperature of 177°C for 7.2 h, and air cooling.

[0101] After the heat treatment, the piston top blank and the piston skirt blank were welded to obtain a powder metallurgy piston.

[0102] Example 3

[0103] The raw materials of the powder metallurgy piston include the following components: 3750 g of aluminum-silicon alloy, 1074 g of gas atomized aluminum powder, 75 g of electrolytic copper powder, 50 g of nickel powder, 30 g of magnesium powder, 4 g of zirconium powder, 2.5 g of vanadium powder, 6.5 g of titanium powder, 3.5 g of scandium powder, and 4 g of chromium powder. The weight ratio of the aluminum-silicon alloy powder to the gas atomized aluminum powder is 3.5.

[0104] The method for preparing the powder metallurgy piston includes the following steps:

[0105] The raw materials are weighed according to the above, and the powders are loaded into a ball mill tank in a vacuum glove box for ball milling. Argon is filled into the ball mill tank, and the above raw materials are mixed on the ball mill, and 70 g of stearic acid is added as an additive to improve the powder yield of the powders. The ball milling time is 7 h, the ball milling speed is 325 rpm, the ball-to-powder ratio is 5.5, and the mixed powders are obtained.

[0106] The mixed powders after ball milling are subjected to hot-pressing sintering to obtain a blank, and the hot-pressing sintering includes five stages:

[0107] The first stage is to heat to 485°C and keep for 30 min;

[0108] The second stage is to heat to 523°C and keep for 45 min, while applying a pressure of 27 MPa;

[0109] The third stage is to heat to 557°C and keep for 68 min;

[0110] The fourth stage is to heat to 589°C and keep for 94 min, and after the keeping, a pressure of 35 MPa is applied;

[0111] The fifth stage is to heat to 604°C and keep for 291 min, and after the keeping, a pressure of 55 MPa is applied.

[0112] The sintered blank is subjected to heating pretreatment, heated to 521°C and kept for 8.5 h; the blank after the keeping is upset on a die forging equipment, the longitudinal upsetting ratio of the blank is 1.6, and the transverse deformation amount is 51%, and the temperature after upsetting is 521°C. The blank is subjected to three times of forming forging using an electric screw press, and in the three times of forging forming, the speed of the first hammer is 846 m / min, the speed of the second hammer is 734 m / min, and the speed of the third hammer is 615 m / min. Different dies are used to obtain a piston top blank and a piston skirt blank. The density of the blank is increased from 92.9% in the sintered state to 98.3% in the forged state.

[0113] The piston top blank and the piston skirt blank are heat treated, specifically including: first solution treatment, temperature is 480℃, holding time is 0.8h; second solution treatment, temperature is 515℃, holding time is 3.5h; water cooling to 65℃; aging treatment, temperature is 180℃, holding time is 7.5h, air cooling.

[0114] After the heat treatment, the piston top blank and the piston skirt blank are welded to obtain the powder metallurgy piston.

[0115] Example 4

[0116] The raw materials of the powder metallurgy piston include the following components: 3500g of aluminum-silicon alloy powder, 1089g of gas atomized aluminum powder, 175g of electrolytic copper powder, 175g of nickel powder, 40g of magnesium powder, 3g of zirconium powder, 3g of vanadium powder, 7g of titanium powder, 4.5g of scandium powder, and 3.5g of chromium powder. The weight ratio of the aluminum-silicon alloy powder to the gas atomized aluminum powder is 3.2.

[0117] The preparation method of the powder metallurgy piston includes the following steps:

[0118] According to the above weight, each raw material is weighed, and the powders are loaded into a ball mill jar in a vacuum glove box for ball milling. Argon is filled into the ball mill jar, and the above raw materials are mixed on the ball mill, and 75g of stearic acid is added as an additive to improve the powder yield of the powder. The ball milling time is 7.5h, the ball milling speed is 298rpm, the ball-to-powder ratio is 5.7, and the mixed powder is obtained.

[0119] The mixed powder after ball milling is heat pressed and sintered to obtain a blank, and the heat pressing and sintering includes 5 stages:

[0120] The first stage is to heat to 491℃ and hold for 32min;

[0121] The second stage is to heat to 531℃ and hold for 47min, while applying a pressure of 28MPa;

[0122] The third stage is to heat to 562℃ and hold for 73min;

[0123] The fourth stage is to heat to 576℃ and hold for 101min, and after the holding is completed, a pressure of 37MPa is applied;

[0124] The fifth stage is to heat to 599℃ and hold for 278min, and after the holding is completed, a pressure of 53MPa is applied.

[0125] The sintered blank is heated and pre-treated, and the temperature is raised to 533℃ and kept for 9h; the mold is fixed on the die forging equipment, and the blank after the heat preservation is upset, the longitudinal upsetting ratio of the blank is 1.7, and the transverse deformation is 55%, and the temperature after upsetting is 533℃. The blank is formed by three times of forging by using an electric screw press, and in the three times of forging forming, the speed of the first hammer is 831m / min, the speed of the second hammer is 725m / min, and the speed of the third hammer is 607m / min. Different molds are used to obtain a piston top blank and a piston skirt blank. The density of the blank is increased from 94.5% in the sintered state to 99.2% in the forged state.

[0126] The piston top blank and the piston skirt blank are heat treated, specifically including: first-stage solid solution treatment, temperature is 482℃, holding time is 0.8h; second-stage solid solution treatment, temperature is 520℃, holding time is 3.7h; water cooling to 75℃; aging treatment, temperature is 182℃, holding time is 7.8h, air cooling.

[0127] After heat treatment, the piston top blank and the piston skirt blank are welded to obtain a powder metallurgy piston.

[0128] Example 5

[0129] The raw materials of the powder metallurgy piston include the following components: 4000g of aluminum-silicon alloy powder, 703g of gas-atomized aluminum powder, 100g of electrolytic copper powder, 125g of nickel powder, 50g of magnesium powder, 3.5g of zirconium powder, 3.5g of vanadium powder, 7.5g of titanium powder, 4g of scandium powder, and 3g of chromium powder. The weight ratio of the aluminum-silicon alloy powder to the gas-atomized aluminum powder is 5.7.

[0130] The preparation method of the above-mentioned powder metallurgy piston includes the following steps:

[0131] According to the above-mentioned weights, each raw material is weighed, and the powders are loaded into a ball mill jar in a vacuum glove box for ball milling. Argon is filled into the ball mill jar, and the above-mentioned raw materials are mixed on the ball mill, and 79g of stearic acid is added as an additive to improve the powder yield of the powder. The ball milling time is 7.8h, the ball milling speed is 257rpm, the ball-to-powder ratio is 5.8, and the mixed powder is obtained.

[0132] The mixed powder after ball milling is hot-pressed and sintered to obtain a blank, and the hot-pressing sintering includes five stages:

[0133] The first stage is to raise the temperature to 500℃ and keep for 35min;

[0134] The second stage is to raise the temperature to 538℃ and keep for 49min, while applying a pressure of 29MPa;

[0135] The third stage is to raise the temperature to 555℃ and keep for 78min;

[0136] The fourth stage is to increase the temperature to 581℃ and keep for 105 min, and then apply a pressure of 40 MPa;

[0137] The fifth stage is to increase the temperature to 602℃ and keep for 322 min, and then apply a pressure of 60 MPa.

[0138] The sintered blank is subjected to a heating pretreatment, and the temperature is increased to 550℃ and kept for 9.5 h; the mold is fixed on a die forging equipment, and the blank after the keeping is upset, the longitudinal upsetting ratio of the blank is 1.8, and the transverse deformation is 63%, and the temperature after upsetting is 550℃. The blank is subjected to three times of forming forging by using an electric screw press, and in the three times of forging forming, the speed of the first hammer is 822 m / min, the speed of the second hammer is 715 m / min, and the speed of the third hammer is 597 m / min. Different molds are used to obtain a piston top blank and a piston skirt blank. The density of the blank is increased from 95.8% in the sintered state to 98.9% in the forged state.

[0139] The piston top blank and the piston skirt blank are subjected to heat treatment, specifically including: first-stage solid solution treatment, the temperature is 485℃, and the keeping time is 1 h; second-stage solid solution treatment, the temperature is 525℃, and the keeping time is 4 h; water cooling to 80℃; aging treatment, the temperature is 185℃, and the keeping time is 8 h, and air cooling.

[0140] After the heat treatment, the piston top blank and the piston skirt blank are welded to obtain a powder metallurgy piston.

[0141] Comparative Example 1

[0142] The raw materials of the powder metallurgy piston include the following components: 3250 g of aluminum-silicon alloy powder, 1281.5 g of gas-atomized aluminum powder, 225 g of electrolytic copper powder, 150 g of nickel powder, 75 g of magnesium powder, and 2.5 g of chromium powder. The weight ratio of the aluminum-silicon alloy powder to the gas-atomized aluminum powder is 2.5.

[0143] The preparation method of the powder metallurgy piston includes the following steps:

[0144] According to the above weight, each raw material is weighed, and the powders are loaded into a ball mill jar in a vacuum glove box for ball milling. Argon is filled into the ball mill jar, and the above raw materials are mixed on the ball mill, and 62 g of stearic acid is added as an additive to improve the powder yield of the powder, the ball milling time is 6.2 h, the ball milling speed is 398 rpm, and the ball-to-powder ratio is 5.8, to obtain a mixed powder.

[0145] The mixed powder after ball milling is subjected to hot-pressing sintering to obtain a blank, and the hot-pressing sintering includes five stages:

[0146] The first stage is to increase the temperature to 455℃ and keep for 26 min;

[0147] Stage 2 is to heat to 501℃ and keep for 42min, while applying a pressure of 26MPa;

[0148] Stage 3 is to heat to 546℃ and keep for 65min;

[0149] Stage 4 is to heat to 556℃ and keep for 87min, after the end of keeping, applying a pressure of 32MPa;

[0150] Stage 5 is to heat to 582℃ and keep for 267min, after the end of keeping, applying a pressure of 53MPa.

[0151] After sintering, the blank is heated for pretreatment, heated to 507℃ and kept for 7.5h; the mold is fixed on the die forging equipment, the blank after keeping is upset, the longitudinal upsetting ratio of the blank is 1.3, and the transverse deformation is 31%, the temperature after upsetting is 507℃. The blank is formed by three times of die forging by using an electric screw press, in the steps of three times of forging forming, the speed of the first hammer is 863m / min, the speed of the second hammer is 752m / min, and the speed of the third hammer is 618m / min, different molds are used to obtain a piston top blank and a piston skirt blank.

[0152] The forging process has obvious improvement effect on the reduction of porosity and the increase of density, the porosity of the powder forged alloy is uniform and small, most of the regions are completely dense, and the coarse metal compounds and silicon phase are obviously small, and the density is increased from 92.7% to 98.8%.

[0153] The piston top blank and the piston skirt blank are heat treated, specifically including: first-stage solid solution treatment, temperature is 475℃, keeping time is 0.5h; second-stage solid solution treatment, temperature is 505℃, keeping time is 3h; water cooling to 52℃; aging treatment, temperature is 175℃, keeping time is 7h, air cooling.

[0154] After heat treatment, the piston top blank and the piston skirt blank are welded to obtain a powder metallurgy piston.

[0155] Comparative Example 2

[0156] In the present comparative example, the raw material of the piston is AlSiCuMgNi material, which is made by gravity casting forming method, and the weight percentage of each component in the piston is shown in Table 3. The specific manufacturing method is as follows:

[0157] (1) charging and melting.

[0158] After charging according to the component table, slow heating should be carried out, after keeping at 500℃ for 55min, heating to 795℃ again, and keeping for 2.5h.

[0159] (2) rotary refining and degassing

[0160] The alloy is discharged and the temperature is lowered to 770°C, the degassing machine is started, and the degassing time is 15 min, while the alloy melt is stirred; the rotor and the baffle automatically sink, and automatically enter the refining stage; after degassing, the rotor rises, the air hole of the rotor is immediately dredged with a tool, the molten slag on the liquid surface is stirred with a slag scoop, and the floating dross on the surface of the aluminum liquid is scooped clean.

[0161] (3) Slagging

[0162] According to the separation of the aluminum slag after refining, 0.55wt% of the total weight of the raw materials of the slagging agent can be added to the surface of each aluminum water, and the molten slag on the liquid surface is stirred for 4 minutes with a slag scoop, and the floating dross on the surface of the aluminum water is scooped clean, the scooped molten slag is poured into the slag roasting platform or the slag roasting barrel, and the molten slag is spread as much as possible.

[0163] (4) Adding magnesium blocks and phosphorus and other modification alloys

[0164] For the molten alloy, when the temperature drops to 750°C, the surface oxide film of the aluminum liquid is scraped off with a preheated sample mold, a composition sample is taken for spectral analysis, and after calculation, an appropriate amount of phosphorus alloy modifier and magnesium block is added, and if necessary, other components can be adjusted by adding corresponding alloys.

[0165] (5) Composition inspection and blank (piston) pouring

[0166] The surface oxide film of the aluminum liquid is scraped off with a preheated composition sample mold, a composition sample is taken for spectral analysis, and the results are compared with the corresponding material discharge composition requirements for judgment. If the composition is unqualified, the material needs to be adjusted, and the sample is taken for spectral analysis again. After the composition is qualified, the power of the intermediate frequency furnace is adjusted, so that the alloy liquid temperature reaches the range of 772°C, and then the casting blank pouring can be carried out.

[0167] (6) Blank heat treatment process

[0168] The piston blank is heat treated, which specifically includes: solid solution treatment, temperature is 520°C, holding time is 6h; water cooling to 60°C; aging treatment, temperature is 220°C, holding time is 8h, air cooling.

[0169] Comparative Example 3

[0170] In this comparative example, the piston raw material is 4032 forged material, which is made by forging method, and the weight percentage of each component in the piston is shown in Table 3. The specific manufacturing method is as follows:

[0171] 4032 bar material is discharged according to a certain proportion to obtain a bar blank, the blank is heated and pretreated, the temperature is raised to 507℃ and kept for 7.5h; the mold is fixed on the die forging equipment, the blank after keeping is upset, the longitudinal upsetting ratio of the blank is 1.3, and the transverse deformation is 31%, the temperature after upsetting is 507℃. The blank is three times of forming forging by using an electric screw press, in the steps of three times of forging forming, the speed of the first hammer is 863m / min, the speed of the second hammer is 752m / min, the speed of the third hammer is 618m / min, and the piston blank is obtained by using the mold.

[0172] The piston blank is heat treated, specifically including: first solid solution treatment, the temperature is 475℃, the holding time is 0.5h; second solid solution treatment, the temperature is 505℃, the holding time is 3h; water cooling to 52℃; aging treatment, the temperature is 175℃, the holding time is 7h, air cooling.

[0173] The weight percentage of each component in the powder metallurgy pistons of examples 1 to 5 and the pistons of comparative examples 1 to 3 is shown in table 3 (unit %).

[0174] Table 3 Comparison of components of examples 1 to 5 and comparative examples 1 to 3

[0175]

[0176] The powder metallurgy pistons of examples 1 to 5 and the pistons of comparative examples 1 to 3 are respectively tested for performance, including hardness, tensile strength, yield strength, elongation at break, tensile strength of welded joint, fatigue strength, Young's modulus, thermal conductivity, thermal expansion coefficient, density and relative wear rate, and the test results are shown in table 4. The Brinell hardness at room temperature is tested according to GB / T 231-2012 "Metallic Materials Brinell Hardness Test Method"; the tensile strength, yield strength and elongation at break at room temperature are tested according to GB / T 228.1-2010 "Metallic Materials Tensile Test Method"; the tensile strength, yield strength and elongation at break at high temperature are tested according to GB / T 228.2-2015 "Metallic Materials High Temperature Tensile Test Method"; the bending fatigue strength is tested according to GB / T 4337-2015 "Metallic Materials Fatigue Test Rotary Bending Method"; the Young's modulus is tested according to GB / T 22315-2008 "Metallic Materials Elastic Modulus and Poisson's Ratio Test Method"; the thermal conductivity is tested according to GB / T 22588-2008 "Flash Method for Measuring Thermal Diffusivity or Thermal Conductivity"; the thermal expansion coefficient is tested according to GB / T 4339-2008 "Determination of Thermal Expansion Characteristics of Metallic Materials"; the density is tested according to GB / T 1423-1996 "Test Method for Density of Precious Metals and Their Alloys"; and the relative wear rate is tested according to GB / T 12444-2006 "Metallic Materials Wear Test Method".

[0177] Table 4 Comparison of the active performance of Examples 1 to 5 and Comparative Examples 1 to 3

[0178]

[0179]

[0180] The powder metallurgy piston of the embodiments of the present application comprises an aluminum-silicon alloy powder material, and has the advantages of high heat-resistant strength, excellent welding performance, light weight, good wear resistance, low thermal expansion coefficient, good thermal conductivity, etc. At 300℃, the tensile strength is 110-145 MPa, the yield strength is 71-85 MPa, the elongation at break is 13-25%, the fatigue strength is 45-62 MPa, the Young's modulus is 69000-72000 MPa, the thermal conductivity is 166-178 W / mK, the relative wear rate is 0.7-1, the tensile strength of the welded joint at 300℃ is 88-116 MPa, the linear expansion coefficient of the aluminum alloy at 20-100℃ is 19.2x10 -6 -19.7x10 -6 m / mK, the linear expansion coefficient of the aluminum alloy at 20-200℃ is 20.4x10 -6 -20.6x10 -6 m / mK, and the linear expansion coefficient of the aluminum alloy at 20-300℃ is 21x10 -6 -21.5x10 -6 m / mK.

[0181] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A powder metallurgy piston, characterized in that, The raw materials comprise the following components by weight percentage: 63.5%–89% aluminum-silicon alloy powder, 1.5%–5% electrolytic copper powder, 1.0%–3.5% nickel powder, 0.6%–1.5% magnesium powder, 0.05%–0.1% zirconium powder, 0.05%–0.1% vanadium powder, 0.1%–0.15% titanium powder, 0.05%–0.11% scandium powder, 0.05%–0.1% chromium powder, and the remainder being gas-atomized aluminum powder; the weight ratio of the aluminum-silicon alloy powder to the gas-atomized aluminum powder is greater than or equal to 2.

2. The method for preparing the powder metallurgy piston includes the following steps: S1. Mix the raw materials according to the ratio, put them into a ball mill jar, add the additives and ball mill to obtain mixed powder; S2. The mixed powder is hot-pressed and sintered to obtain a blank. The hot-pressing and sintering includes 5 stages: The first stage involves heating to 450℃~505℃ and holding at that temperature for 25min~35min. The second stage involves heating to 511℃~545℃ and holding at that temperature for 41min~53min, while applying a pressure of 25MPa~30MPa. The third stage involves heating to 552℃~566℃ and holding at that temperature for 62min~78min; The fourth stage involves heating to 573℃~593℃ and holding for 81min~106min, followed by applying a pressure of 30MPa~40MPa after the holding period. The fifth stage involves heating to 597℃~608℃ and holding at that temperature for 254min~329min, followed by applying a pressure of 50MPa~60MPa after the holding period. S3. The blank obtained in step S2 is die-forged to obtain a piston top blank and / or a piston skirt blank; the piston top blank and the piston skirt blank are welded together to obtain the powder metallurgy piston.

2. The powder metallurgy piston according to claim 1, characterized in that, Its raw materials include the following components by weight percentage: 65% aluminum-silicon alloy powder, 4.5% electrolytic copper powder, 3% nickel powder, 1.5% magnesium powder, 0.05% zirconium powder, 0.05% vanadium powder, 0.12% titanium powder, 0.1% scandium powder, 0.05% chromium powder, and the remainder is gas-atomized aluminum powder.

3. The powder metallurgy piston according to claim 1 or 2, characterized in that, The powder metallurgy piston comprises the following components by weight percentage: Si 12.7%–17.8%, Cu 1.5%–5.0%, Ni 1.0%–3.5%, Mg 0.6%–1.5%, Ti 0.11%–0.15%, Sc 0.05%–0.11%, Cr 0.05%–0.1%, Zr 0.05%–0.1%, V 0.05%–0.1%, with iron and oxygen as unavoidable impurities, iron not exceeding 0.7%, oxygen not exceeding 0.5%, and the balance being Al.

4. The powder metallurgy piston according to claim 3, characterized in that, The powder metallurgy piston comprises the following components by weight percentage: Si 15%, Cu 1.5%, Ni 1.0%, Mg 0.6%, Ti 0.13%, Sc 0.07%, Cr 0.08%, Zr 0.08%, V 0.05%, Fe 0.68%, O 0.29%, with the balance being Al.

5. The powder metallurgy piston according to claim 1, characterized in that, The auxiliary agent in step S1 is stearic acid, the weight of which is 1.2wt% to 1.6wt% of the total weight of the raw materials, the ball-to-material ratio is 5 to 6, the ball milling speed is 223 rpm to 427 rpm, and the ball milling time is 6 h to 8 h.

6. The powder metallurgy piston according to claim 1, characterized in that, The forging step in step S3 includes: The billet is preheated by heating to 501℃~552℃ and held at that temperature for 6.5h~9.5h; The mold is fixed on the forging equipment, the billet after the heat preservation is completed is upset, and then it is forged three times to obtain the piston top blank and / or piston skirt blank.

7. The powder metallurgy piston according to claim 6, characterized in that, The longitudinal upsetting ratio of the billet is 1.2 to 1.8, and the transverse deformation is 23% to 65%.

8. The powder metallurgy piston according to claim 6, characterized in that, In the three forging steps, the speed of the first hammer is 821-867 m / min, the speed of the second hammer is 714-754 m / min, and the speed of the third hammer is 596-621 m / min.

9. The powder metallurgy piston according to claim 1, characterized in that, Before the welding and forming step in step S3, the piston top blank and / or the piston skirt blank are subjected to heat treatment, specifically including: first-stage solution treatment at a temperature of 475℃~485℃ and a holding time of 0.5h~1h; second-stage solution treatment at a temperature of 505℃~525℃ and a holding time of 3h~4h; and aging treatment at a temperature of 175℃~185℃ and a holding time of 7h~8h.

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