Wear-resistant zinc-based alloy bearing bush and ultrasonic casting method thereof

Abstract

The invention discloses a wear-resistant zinc-based alloy bearing bush and an ultrasonic casting method thereof and belongs to the field of alloy bearing bushes. The wear-resistant zinc-based alloy bearing bush comprises the following components in percentage by weight: 28%-32% of Al, 1%-2.5% of Cu, 0.01%-0.03% of Co, 0.01%-0.03% of Er, 0.02%-0.05% of Ti, less than or equal to 0.01% of Fe and the balance of Zn, and the total content of impurities is less than 0.1%. In the smelting process, Co, Er and Ti elements are added to carry out microalloying treatment on the alloy, and the high-temperature service performance of the alloy can be remarkably improved. According to the wear-resistant zinc-based alloy bearing bush and the preparation method thereof, through specific alloy component design and combination of burdening, smelting and ultrasonic casting processes, the prepared wear-resistant zinc-based alloy bearing bush has high toughness and high wear resistance, meanwhile, the strength, hardness and high-temperature strength of the wear-resistant zinc-based alloy bearing bush are effectively improved, finally, comprehensive optimization of the comprehensive mechanical property of the bearing bush is achieved, and the use requirement in a higher-temperature environment is met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of alloy bearing, in particular, it relates to a wear-resistant zinc-based alloy bearing and an ultrasonic casting method thereof. BACKGROUND

[0002] Zamak 2, 3, 5 and 7, which are zinc-based commercial alloys, have been produced since the late 1920s. These alloys are mainly used in the industrial production of different components of automobiles, electrical and electronic products. After the 1940s, Alzen 305 alloy (30% aluminum and 5% copper) and Alzen 501 alloy (50% aluminum and 1% copper) were developed. Subsequently, in the 1970s and 1980s, a series of zinc-based wear-resistant alloys were developed and have been used to date, including ZA8, ZA12 and ZA27. Zinc-based alloys can be divided into eutectic alloys (Zn-4Al), eutectoid alloys (Zn-22Al) and segregation alloys (Zn-40Al) according to the different aluminum contents. It has been proven that among these alloys, the segregation-based zinc-based alloy has higher hardness, higher strength and higher wear resistance than the eutectic and eutectoid-based zinc-based alloys. In recent years, in order to develop alternative materials for traditional bearing alloys such as bronze and brass, researchers have conducted in-depth research on zinc-based alloys and developed a series of ternary and quaternary alloys based on Zn-15Al, Zn-25Al, Zn-27Al, Zn-30Al and Zn-40Al, which have better performance than traditional bearing materials. Experiments have shown that the strength and wear resistance of zinc-based alloys can be significantly improved by adding appropriate additives such as copper and silicon and appropriate heat treatment.

[0003] Zinc-based wear-resistant alloys have good overall mechanical properties at room temperature, but the problem of high-temperature softening of zinc-based alloys has always restricted their work in the medium and high temperature range. The service temperature of zinc-based alloys is generally less than 100℃, and when it exceeds 100℃, the performance loss is very large, especially the tensile strength is only 10%-30% of that at room temperature. Although the working temperature of ZA27 alloy can reach 150℃, it cannot work for a long time at high temperature, and its toughness is only 1-3%, and the overall performance is poor. In view of the above shortcomings, the use range of zinc-based wear-resistant alloys is severely limited.

[0004] The existing wear-resistant zinc-based alloy bearing has high strength and wear resistance at room temperature, but it can only work under low-speed conditions and serve at a temperature below 100℃. The effect of refining the grain by adding intermediate alloy to improve the medium and high temperature service conditions of zinc-based wear-resistant alloys is not obvious.

[0005] The main components of the existing zinc-based wear-resistant alloy bearing bush are 20-40% of Al, 1.0-5.0% of Cu, 0.01-0.015% of Mg, and the balance of Zn, and Ti, B and Si elements are added to improve the performance, but the high-temperature performance is not significantly increased. The zinc-based wear-resistant alloy is smelted below 800 DEG C and poured into a mold at 560 DEG C. The mold can be a metal mold or a sand mold. The strength of the obtained zinc-based alloy material is up to 400 MPa or more, the hardness value is 184 HB, and the dry friction coefficient measured by the wear experiment of 45# steel is 0.1. The tensile strength at 100 DEG C is only about 15% of that at room temperature.

[0006] The existing wear-resistant zinc-based alloy bearing bush casting process cools the metal mold by cooling liquid, which has a fast cooling and solidification speed, resulting in a decrease in the precipitated strengthening phase of the alloy and uneven distribution of the alloy components. In addition, the precipitated phase has limited heat resistance, and coarsens seriously under high temperature conditions, resulting in a significant decrease in the strength of the zinc-based alloy when working at a temperature greater than 100 DEG C. SUMMARY

[0007] The present application aims to provide a wear-resistant zinc-based alloy bearing bush and an ultrasonic casting process thereof. The core objective is to significantly improve the service temperature of the bearing bush while ensuring sufficient toughness, so that it can be used for a long time at a temperature above 150 DEG C, and to improve the comprehensive mechanical properties through component design and process optimization. The present application uses specific alloy component design, combined with batching, smelting and ultrasonic casting process, to make the prepared wear-resistant zinc-based alloy bearing bush have high toughness and high wear resistance, while effectively improving its strength, hardness and high-temperature strength, ultimately realizing the overall optimization of the comprehensive mechanical properties of the bearing bush, and meeting the use requirements in higher temperature environments.

[0008] In order to achieve the above technical problems, the present application adopts the following technical solutions: The present application aims to provide a wear-resistant zinc-based alloy bearing bush, which has the following components in terms of mass percentage (unit: wt.%): Al: 28-32%, Cu: 1-2.5%, Co: 0.01-0.03%, Er: 0.01-0.03%, Ti: 0.02-0.05%, Fe≤0.01%, and the balance of Zn, with the total impurity content being less than 0.1%.

[0009] The materials used in the above components are: zinc ingots with a mass purity of 99.99%; aluminum ingots with a mass purity of 99.90%; intermediate alloys including aluminum-copper intermediate alloy AlCu50, aluminum-cobalt intermediate alloy AlCo10, aluminum-titanium intermediate alloy AlTi10 and aluminum-erbium intermediate alloy AlEr10.

[0010] Another object of the present application is to provide an ultrasonic casting method for the above-mentioned wear-resistant zinc-based alloy bearing bush, which comprises the following steps: Step 1: Heat the aluminum ingot and intermediate alloy until the metal is completely melted; Step 2: Add zinc ingots, lower the temperature to a certain level, and after the alloy has completely melted, stir thoroughly, remove slag, let stand for a certain time, and after the melt composition is found to be qualified, pour the molten metal into the intermediate ladle. Step 3: After the molten metal is poured into the tundish, it is kept at a certain temperature. After the temperature is maintained at a certain temperature, it is left to stand for a certain period of time. Argon gas and ultrasonic combined action are introduced. Argon gas is stopped, and ultrasonic action is continued on the melt for a certain period of time. Ultrasonic action is stopped, and it is left to stand for a certain period of time. The molten metal is then poured into the bearing mold through the tundish. The mold is preheated before casting and the coating is brushed on and dried thoroughly. The mold temperature is maintained at 200°C during casting. When the temperature drops below 200°C, the mold is opened and the bearing is removed to obtain the zinc alloy bearing. The intermediate packaging includes a heating and insulation system and an ultrasonic generator with an argon gas blowing device. Before the molten metal is poured into the intermediate packaging, the heating and insulation system is turned on to ensure that the temperature in the intermediate packaging remains constant at a certain level. Argon gas is blown in simultaneously with the ultrasonic generator. This is because the invention designs the argon gas inlet on the ultrasonic inlet rod and controls the argon gas blowing in simultaneously through the ultrasonic generation and control system; the argon gas and ultrasound work together to act on the molten metal.

[0011] Step 4: After rough machining, the zinc alloy bearing obtained in Step 3 is subjected to solution treatment, hardening treatment, and after being completely cooled to room temperature, it is subjected to aging treatment, followed by air cooling, and finally wear-resistant zinc-based alloy bearing is obtained.

[0012] Further specifying, in step 1, a melting furnace is used for heating. The heating process is as follows: hold at 200℃ for 1 hour, then raise the temperature to 750-780℃, and strictly control the furnace temperature to ≤800℃.

[0013] Further specifying the steps, step 2 involves lowering the temperature to 650℃-680℃, allowing it to stand for 10-20 minutes, maintaining an argon flow rate of 15-25 L / min, and setting the ultrasonic emission power density to 150 W / cm². 2 -200W / cm 2 The emission frequency is 20KHz-24KHz, the combined action is 10min-20min, the melt is then subjected to ultrasonic action for 10min-20min, and after the ultrasonic action is stopped, it is left to stand for 10min-20min.

[0014] Further specifying, in step 3, after maintaining the temperature at 580℃, let it stand for 10-20 minutes.

[0015] Further specifying step 4, the solution treatment is carried out at 350℃ for 10-24 hours.

[0016] Further limitation, in step 4, the quenching treatment is carried out in water at 20-40℃.

[0017] Further limitation, in step 4, the aging treatment is carried out in a heat treatment furnace at a temperature of 150℃ for 2-4h.

[0018] The mechanical properties of the wear-resistant zinc-based alloy bushing are shown in Table 1.

[0019] Table 1 Mechanical properties of the wear-resistant zinc-based alloy bushing

[0020] During the smelting process, the alloy is micro-alloyed by adding Co, Er and Ti elements, which can significantly improve the high-temperature service performance of the alloy. The existing invention of wear-resistant zinc alloy bushing mainly refines the grain by adding Co element and strengthens the alloy by adding Cu element, but does not involve the micro-alloying design of Er and Ti elements to improve the high-temperature performance. In addition, the existing technical solution does not effectively control the content of Fe element, while Fe as a harmful impurity element will significantly deteriorate the performance of wear-resistant zinc-based alloy, especially having a serious negative impact on its high-temperature performance. Therefore, when optimizing the performance of the alloy, the content of Fe element must be strictly controlled.

[0021] The smelting process of the present application first puts aluminum ingots and intermediate alloy into the melting furnace for heating, after the alloy is melted, zinc ingots are added, and after cooling and holding, the alloy is completely melted, after stirring and slagging, it is placed for 10-20min, after the melt composition is qualified, it is poured into a tundish, the tundish has a heating and holding function, under the condition that the temperature of the metal liquid is unchanged, 10-20min of argon degassing and ultrasonic treatment are carried out, then the argon gas is stopped, the ultrasonic action is continued for 10-20min, then it is placed for 10-20min, and the bushing is poured. The existing technology is to pour the zinc alloy liquid into the mold through a pouring ladle, but the pouring ladle does not have a heating and holding function, which makes it difficult to meet the set requirements of pouring temperature. Moreover, the existing technology is to carry out degassing and ultrasonic treatment of zinc alloy in the smelting furnace, but due to the complex atmosphere in the smelting furnace, the degassing and ultrasonic refining treatment in the smelting furnace cannot achieve the desired effect, and it will also seriously affect the quality of the alloy.

[0022] The present application is for alloy refining of zinc alloy bearing shell in tundish, argon gas degassing and ultrasonic refining are combined, cavitation and vibration effect of ultrasonic is used to improve atomization effect and dispersion state of argon gas, so as to improve degassing effect of argon gas in metal liquid, after stopping degassing, further ultrasonic effect is carried out, not only can the residual gas in metal liquid be quickly removed, but also the grain can be refined through ultrasonic cavitation, so as to improve comprehensive performance of the bearing shell. The existing process is implemented in steps, argon gas degassing process is used first, and then ultrasonic treatment is carried out. The traditional degassing process needs special equipment, and the atomization and dispersion of argon gas are realized by accurately adjusting the rotating speed of the gas outlet head. The degassing-ultrasonic composite process of the present application can save special degassing equipment, and only ultrasonic generating device is needed to complete the process. Only the structure of the ultrasonic guide rod needs to be improved to have the dual functions of ultrasonic conduction and argon gas introduction. In addition, the original technology needs to strictly control the rotating speed of the gas outlet head, and the degassing effect is not obvious when the rotating speed is too low, and the metal liquid will be gas-entrained when the rotating speed is too high, which seriously affects the alloy quality.

[0023] After the wear-resistant zinc alloy bearing shell is completed, the following heat treatment process of step 4 is used to further improve the medium-high temperature service performance of the bearing shell. The bearing shell casting process diagram is shown in Figure 1 and 2 .

[0024] For a better understanding of the features and technical contents of the present application, please refer to the detailed description and the accompanying drawings. It should be noted that the accompanying drawings are provided for illustrative purposes only and are not intended to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a bearing shell casting process diagram; Figure 2 is an A-A sectional view of Figure 1 , 1 is a rain pouring gate box, 2 is a bearing shell outer mold, 3 is a metal core, 4 is a cavity, and 5 is a metal backing plate; Figure 3 is a bearing shell schematic diagram of example 1; Figure 4 is a bearing shell schematic diagram of example 2; Figure 5 is a bearing shell schematic diagram of example 3. DETAILED DESCRIPTION

[0026] The present application will be described in detail below in combination with specific examples. These examples are helpful for those skilled in the art to further understand the present application, but should not be regarded as limiting the present application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These all belong to the protection scope of the present application.

[0027] Example 1: The present embodiment is a wear-resistant zinc-based alloy bushing composition control and ultrasonic casting process, which specifically includes the following steps: (1) Melting: aluminum ingots and intermediate alloy are added to the melting furnace and heated to 200°C for 1 hour, then heated to 780°C. After the metal is completely melted, zinc ingots are added, and the furnace temperature is reduced to 680°C. After the alloy is completely melted, it is fully stirred and slagged, and the tool is coated with paint to ensure that iron elements enter the alloy. After detecting that the melt composition is qualified, the metal liquid is poured into the tundish. The composition of the obtained wear-resistant zinc-based alloy bushing is as follows: aluminum accounts for 29.4%, copper accounts for 2.1%, cobalt accounts for 0.015%, erbium accounts for 0.024%, titanium accounts for 0.028%, iron accounts for 0.006%, and the balance is zinc.

[0028] (2) Casting: After the metal liquid is poured into the tundish, the metal liquid is heat treated through the tundish, and the temperature is maintained at 580°C. After 15 minutes of standing, argon-ultrasonic combined action is performed, with an argon flow rate of 20 L / min, an ultrasonic emission power density of 170 W / cm 2 , an emission frequency of 22 KHz, and a combined action time of 15 min. Stop the argon flow, and further perform ultrasonic action on the melt. After 15 min of action, stop the ultrasonic action, and stand for 10 min. Pour the metal liquid into the bushing mold through the tundish. The mold used for casting the zinc alloy bushing is a metal mold. Before casting, the mold is preheated, and the paint is thoroughly dried. The mold temperature is maintained at 200°C during casting. When the temperature drops below 200°C, open the mold and take out the zinc alloy bushing.

[0029] (3) Heat treatment: After the wear-resistant zinc alloy bushing is roughed, it is placed in a heat treatment furnace for 15h of solid solution treatment at 350°C. Then, the bushing is placed in a water tank at 25°C for quenching treatment. After completely cooling to room temperature, the bushing is placed in a heat treatment furnace for 3h of aging treatment at 150°C, followed by air cooling. Finally, a wear-resistant zinc-based alloy bushing is obtained. The wear-resistant zinc-based alloy bushing is shown in Figure 3 .

[0030] Example 2: The present embodiment is a wear-resistant zinc-based alloy bushing composition control and ultrasonic casting process, which specifically includes the following steps: (1) Melting: aluminum ingot and intermediate alloy are added into a melting furnace and heated to 780℃, after the metal is completely melted, zinc ingot is added, and the furnace temperature is reduced to 680℃, after the alloy is completely melted, it is fully stirred and slagged, and then it is placed for 10 minutes. After the composition of the melt is qualified, the metal liquid is poured into a tundish. The composition of the obtained wear-resistant zinc-based alloy bearing shell is 30.1% aluminum, 1.9% copper, 0.018% cobalt, 0.026% erbium, 0.031% titanium, 0.007% iron, and the balance is zinc.

[0031] (2) Casting: After the metal liquid is poured into the tundish, the metal liquid is heat treated through the tundish, and the temperature is maintained at 580℃, then it is placed for 10 minutes. Under the combined action of argon and ultrasonic waves, the argon flow is 15L / min, the ultrasonic emission power density is 150W / cm 2 , the emission frequency is 20KHz, the combined action time is 10min, the argon flow is stopped, and the melt is further subjected to ultrasonic action, the action time is 10min, then it is placed for 10min, and the metal liquid is poured into the bearing shell mold through the tundish. The mold used for casting the zinc alloy bearing shell is a metal mold, the mold is preheated before casting, and the paint is brushed and dried, and the mold temperature is maintained at 210℃ during casting. When the temperature drops to below 200℃, the mold is opened, and the zinc alloy bearing shell is taken out.

[0032] (3) Heat treatment: after the wear-resistant zinc alloy bearing shell is coarsely processed, it is placed in a heat treatment furnace, and then it is subjected to solid solution treatment at 350℃ for 12h, then the bearing shell is placed in a water tank at 25℃ for quenching treatment, and then it is cooled to room temperature. After the whole is placed in a heat treatment furnace for aging treatment at 150℃ for 2h, it is air cooled, and finally the wear-resistant zinc-based alloy bearing shell is obtained. The wear-resistant zinc-based alloy bearing shell is shown in Figure 4 .

[0033] Example 3 In this embodiment, the composition control and ultrasonic casting process of a wear-resistant zinc-based alloy bearing shell are specifically as follows: (1) Melting: aluminum ingot and intermediate alloy are added into a melting furnace and heated to 780℃, after the metal is completely melted, zinc ingot is added, and the furnace temperature is reduced to 680℃, after the alloy is completely melted, it is fully stirred and slagged, and then it is placed for 20 minutes. After the composition of the melt is qualified, the metal liquid is poured into a tundish. The composition of the obtained wear-resistant zinc-based alloy bearing shell is 30.1% aluminum, 1.9% copper, 0.018% cobalt, 0.026% erbium, 0.031% titanium, 0.007% iron, and the balance is zinc.

[0034] (2) Casting: After the molten metal is poured into the tundish, the molten metal is kept warm by the tundish, and the temperature is maintained at 580℃. After 20 minutes of standing, argon-ultrasonic combined action is performed, the argon flow is 25L / min, the ultrasonic emission power density is 200W / cm 2 , the emission frequency is 24KHz, the combined action is performed for 20min, the argon is stopped, and the ultrasonic action is further performed on the melt. After 20min of action, the molten metal is poured into the bearing bush mold through the tundish after 10min of standing. The metal mold is used for casting the zinc alloy bearing bush, the mold is preheated before casting, the paint is brushed and dried, and the mold temperature is maintained at 200℃ during pouring. When the temperature drops below 200℃, the mold is opened, and the zinc alloy bearing bush is taken out.

[0035] (3) Heat treatment: After the wear-resistant zinc alloy bearing bush is roughed, it is put into a heat treatment furnace as a whole, and is subjected to solid solution treatment at 350℃ for 20h. Then, the bearing bush is put into a water tank at 20℃ for hardening treatment. After being completely cooled to room temperature, the bearing bush is put into a heat treatment furnace for aging treatment at 150℃ for 4h, and is then air-cooled. Finally, the wear-resistant zinc-based alloy bearing bush is obtained. The wear-resistant zinc-based alloy bearing bush is shown in Figure 5 .

[0036] Table 2 Comparison of mechanical properties of wear-resistant zinc-based alloy bearing bush castings in different embodiments

[0037] The specific embodiments of the present application are described in detail above. It should be noted that the present application is not limited to the above specific embodiments. Those skilled in the art can make various modifications or changes without departing from the protection scope defined by the claims, and these modifications or changes all belong to the technical scheme of the present application.

Claims

1. A wear-resistant zinc-based alloy bearing bush, characterized in that, By mass percentage, its composition is Al: 28%-32%, Cu: 1%-2.5%, Co: 0.01%-0.03%, Er: 0.01-0.03%, Ti: 0.02%-0.05%, Fe≤0.01%, with the balance being Zn, and the total impurity content is less than 0.1%.

2. The zinc-based alloy bearing bush according to claim 1, characterized in that, Its composition is Al: 29.4%, Cu: 2.1%, Co: 0.015%, Er: 0.024%, Ti: 0.028%, Fe: 0.006%, with the balance being Zn.

3. The zinc-based alloy bearing bush according to claim 1, characterized in that, The materials used in the composition are: zinc ingots with a purity of 99.99%; aluminum ingots with a purity of 99.90%; and the master alloys are aluminum-copper master alloy AlCu50, aluminum-cobalt master alloy AlCo10, aluminum-titanium master alloy AlTi10, and aluminum-erbium master alloy AlEr10.

4. The ultrasonic casting method for wear-resistant zinc-based alloy bearing bushes as described in claim 1, 2, or 3, characterized in that, Includes the following steps: Step 1: Heat the aluminum ingot and intermediate alloy until the metal is completely melted; Step 2: Add zinc ingots, lower the temperature to a certain level, and after the alloy has completely melted, stir thoroughly, remove slag, let stand for a certain time, and after the melt composition is found to be qualified, pour the molten metal into the intermediate ladle. Step 3: Then, the molten metal is kept at a certain temperature through an intermediate ladle. After the temperature is maintained at a certain temperature, it is left to stand for a certain period of time. Argon gas and ultrasonic combined action are introduced. Argon gas is stopped, and ultrasonic action is continued on the melt for a certain period of time. Ultrasonic action is stopped, and it is left to stand for a certain period of time. The molten metal is then poured into the bearing mold through the intermediate ladle. The mold is preheated before casting and the coating is brushed on and dried thoroughly. The mold temperature is maintained at 200°C during casting. When the temperature drops below 200°C, the mold is opened and the metal is removed to obtain the zinc alloy bearing. Step 4: After rough machining, the zinc alloy bearing obtained in Step 3 is subjected to solution treatment, hardening treatment, and after being completely cooled to room temperature, it is subjected to aging treatment, followed by air cooling, and finally wear-resistant zinc-based alloy bearing is obtained.

5. The method according to claim 3, characterized in that, In step 1, a smelting furnace is used for heating. The heating process is as follows: hold at 200℃ for 1 hour, then raise the temperature to 750-780℃, and strictly control the furnace temperature to ≤800℃.

6. The method according to claim 3, characterized in that, Step 2: Reduce the temperature to 650℃-680℃, let it stand for 10-20 minutes, maintain an argon flow rate of 15L / min-25L / min, and set the ultrasonic emission power density to 150W / cm³. 2 -200W / cm 2 The emission frequency is 20KHz-24KHz, the combined action is 10min-20min, the melt is then subjected to ultrasonic action for 10min-20min, and after the ultrasonic action is stopped, it is left to stand for 10min-20min.

7. The method according to claim 3, characterized in that, In step 3, after maintaining the temperature at 580℃, let it stand for 10-20 minutes.

8. The method according to claim 3, characterized in that, In step 4, a solution treatment is performed at 350℃ for 10-24 hours.

9. The method according to claim 3, characterized in that, In step 4, the water is quenched at 20℃-40℃.

10. The method according to claim 3, characterized in that, In step 4, the aging treatment is carried out in a heat treatment furnace at a temperature of 150℃ for 2-4 hours.

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