A bimetallic cylinder liner based on a casting-modification forging process

Abstract

This application relates to the field of cylinder liner technology, specifically to a bimetallic cylinder liner based on a casting-to-forging process. The bimetallic cylinder liner is manufactured through the following steps: heating steel, then upsetting it in a pre-forging die, followed by primary and secondary extrusion molding, removing the connecting skin at the bottom of the cup-shaped part to form a through hole, and then heat-treating and cooling to obtain a forged outer sleeve; centrifugally casting a high-silicon aluminum alloy, followed by precision machining of the outer diameter to obtain an inner liner; cleaning the inner surface of the outer sleeve and the outer surface of the inner liner, placing the outer sleeve in a heating furnace for heating, and then placing the room-temperature inner liner into the hot outer sleeve for cooling, thus obtaining a bimetallic cylinder liner based on a casting-to-forging process. The cylinder liner prepared in this application exhibits high impact resistance and strong pressure-bearing capacity.

Description

Technical Field

[0001] This application relates to the field of cylinder liner technology, specifically to a bimetallic cylinder liner based on a casting-to-forging process. Background Technology

[0002] As the working chamber for the reciprocating piston, the performance of the cylinder liner directly determines the service life, efficiency, and reliability of the equipment. To balance cost and performance, bimetallic cylinder liners have become the mainstream technical solution, which uses a steel outer shell to ensure structural strength and an inner lining of wear-resistant alloy to ensure the wear resistance of the inner surface.

[0003] Traditional bimetallic cylinder liner manufacturing processes typically employ a "casting + composite" approach. This involves first casting the outer casing blank, and then bonding a wear-resistant alloy inner liner to the inner wall of the outer casing using methods such as centrifugal casting, friction welding, or interference fit. However, cylinder liners manufactured using traditional methods frequently experience cylinder explosions and cracks at operating pressures of 20-30 MPa. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this application is to provide a bimetallic cylinder liner based on a casting-to-forging process, in order to solve the problems of cylinder explosion and cracking under working pressure.

[0005] To achieve the above objectives, this application provides a bimetallic cylinder liner based on a casting-to-forging process, which is manufactured through the following steps: S1. The steel is heated and then upsetting in a pre-forging die. It is then formed by first extrusion and second extrusion. The connecting skin at the bottom of the cup-shaped part is punched off to form a through hole. Then it is heat-treated and cooled to obtain a forged outer jacket. In the above process, upsetting in the pre-forging die allows for large plastic deformation, which welds together the internal micropores, making the material denser and increasing its density. This provides a reasonable allocation of metal volume for subsequent extrusion processes. Through two-step extrusion, metal filling can be precisely controlled to obtain complex shapes while reducing material waste. Extrusion molding causes the metal to flow along the die cavity, forming continuous and complete fiber flow lines whose direction is consistent with the cylinder liner's outline. This greatly improves the fatigue strength and stress corrosion resistance of the parts. Intense plastic deformation at high temperatures promotes dynamic recrystallization of grains, resulting in a fine and uniform grain structure, which significantly improves strength and toughness. Heat treatment eliminates the internal stress generated during forging, preventing deformation and cracking during subsequent processing or use. It also makes the potentially uneven structure after forging uniform and further refines the grains, thereby stabilizing and optimizing the material's comprehensive mechanical properties.

[0006] S2. High-silicon aluminum alloy is centrifugally cast, and then the outer circle is precision machined to obtain the inner lining. In the above process, through centrifugal casting, the high-silicon aluminum alloy undergoes directional solidification of the molten metal under centrifugal force, resulting in good feeding effect and the acquisition of high-density inner lining castings. Impurities and oxides are pushed to the inner surface due to their different densities and are removed in subsequent processing, resulting in a clean working layer material with good wear resistance.

[0007] S3. Clean the inner surface of the outer jacket and the outer surface of the inner liner. Place the outer jacket in a heating furnace and heat it. Place the room temperature inner liner into the hot outer jacket and cool it to obtain a bimetallic cylinder liner based on the casting-to-forging process.

[0008] In the above process, the outer jacket is heated, and the inner hole of the heated outer jacket expands, creating a gap with the lining at room temperature, making it easy to insert. After cooling, the outer jacket shrinks, generating huge and uniform radial compressive stress on the lining, achieving a firm mechanical bond, so that the inner and outer layers will not separate or move.

[0009] Furthermore, the heating temperature in step S1 is 1150-1200℃, and the time is 2-3 hours.

[0010] Furthermore, the upsetting ratio is 1.8-2.2.

[0011] Furthermore, the extrusion speed is 20-40 mm / s for each extrusion.

[0012] Furthermore, the secondary extrusion is carried out at a speed of 10-20 mm / s, and the pressure is maintained for 3-5 seconds after molding.

[0013] Furthermore, the heat treatment is performed at a temperature of 840-860℃ for 1-1.5 hours.

[0014] Furthermore, the cooling described in step S1 involves reducing the temperature to room temperature at a rate of 1-2°C / min.

[0015] Furthermore, the centrifugal casting process involves a casting temperature of 700-750℃ and centrifugal parameters of 50G-80G.

[0016] Furthermore, the finishing process involves machining the outer diameter of the inner lining to be larger than the inner diameter of the outer lining, with an interference fit of 0.1%-0.3% of the mating diameter.

[0017] Furthermore, the heating described in step S3 is carried out at a temperature of 350-450℃ for 1-2 hours.

[0018] In summary, this application has the following beneficial effects: 1. Material densification: This application completely eliminates the inherent defects of casting such as porosity, sand holes, and shrinkage porosity through the forging process, thus eliminating the source of cracks from the root.

[0019] 2. Optimized structure: The forged fiber has complete streamlines and refined grains, which makes the mechanical properties of the outer casing, especially the fatigue strength and impact toughness, much higher than those of the casting.

[0020] 3. Strong and tough bonding: This application uses interference-fit hot-fit composite technology to manufacture a high-strength and high-reliability bimetallic interface, ensuring that the inner and outer layers do not separate or move under high pressure. Detailed Implementation

[0021] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this invention.

[0022] The steel described in the specific embodiments of this application is 45# steel, and the high-silicon aluminum alloy is A390. Example 1

[0023] A bimetallic cylinder liner based on a casting-to-forging process is manufactured through the following steps: S1. Heat 45# steel (temperature 1150℃, time 2h), then upset it in a pre-forging die (upsetting ratio 1.8), then extrude it once (extrusion speed 20mm / s), and then extrude it twice (extrusion speed 10mm / s, holding pressure for 4s after forming). Remove the connecting skin at the bottom of the cup-shaped part to form a through hole, then heat treat it (temperature 840℃, holding for 1h), and then cool it down to room temperature at 1℃ / min to obtain the forged outer jacket. S2. The high-silicon aluminum alloy is centrifugally cast (casting temperature is 700℃, centrifugation parameter is 50G), and then the outer circle is precision machined. The outer diameter of the inner liner is machined to be larger than the inner diameter of the outer sleeve, with an interference of 0.1% of the fitting diameter, to obtain the inner liner. S3. Clean the inner surface of the outer jacket and the outer surface of the inner liner until the surface is smooth. Place the outer jacket in a heating furnace and heat it (temperature 350℃, time 1.5h). Place the room temperature inner liner into the hot outer jacket and cool it to room temperature to obtain a bimetallic cylinder liner based on the casting-to-forging process. Example 2

[0024] A bimetallic cylinder liner based on a casting-to-forging process is manufactured through the following steps: S1. Heat 45# steel (temperature 1170℃, time 2h), then upset it in a pre-forging die (upsetting ratio 2), and then extrude it once (extrusion speed 30mm / s) and twice (extrusion speed 15mm / s, holding pressure for 4s after forming). Remove the connecting skin at the bottom of the cup-shaped part to form a through hole, and then heat treat it (temperature 850℃, holding for 1h), and cool it down to room temperature at 1℃ / min to obtain the forged outer jacket. S2. The high-silicon aluminum alloy is centrifugally cast (casting temperature is 730℃, centrifugation parameter is 65G), and then the outer circle is precision machined. The outer diameter of the inner liner is machined to be larger than the inner diameter of the outer sleeve, with an interference of 0.2% of the fitting diameter, to obtain the inner liner. S3. Clean the inner surface of the outer jacket and the outer surface of the inner liner until the surface is smooth. Place the outer jacket in a heating furnace and heat it (temperature 400℃, time 1.5h). Place the room temperature inner liner into the hot outer jacket and cool it to room temperature to obtain a bimetallic cylinder liner based on the casting-to-forging process. Example 3

[0025] A bimetallic cylinder liner based on a casting-to-forging process is manufactured through the following steps: S1. Heat 45# steel (temperature 1200℃, time 2h), then upset it in a pre-forging die (upsetting ratio 2.2), then extrude it once (extrusion speed 40mm / s), then extrude it twice (extrusion speed 20mm / s, pressure held for 4s after forming), then remove the connecting skin at the bottom of the cup-shaped part to form a through hole, then heat treat it (temperature 860℃, holding for 1h), and then cool it down to room temperature at 1℃ / min to obtain the forged outer jacket; S2. The high-silicon aluminum alloy is centrifugally cast (casting temperature is 750℃, centrifugation parameter is 80G), and then the outer circle is precision machined. The outer diameter of the inner liner is machined to be larger than the inner diameter of the outer sleeve, with an interference of 0.3% of the fitting diameter, to obtain the inner liner. S3. Clean the inner surface of the outer jacket and the outer surface of the inner liner until the surface is smooth. Place the outer jacket in a heating furnace and heat it (temperature 450℃, time 1.5h). Place the room temperature inner liner into the hot outer jacket and cool it to room temperature to obtain a bimetallic cylinder liner based on the casting-to-forging process.

[0026] Compare with Example 1 The difference between this comparative example and Example 3 is that the outer sleeve is manufactured using a traditional casting method. The bimetallic cylinder liner of this comparative example is obtained by the following steps: S1. Heat the 45# steel raw material to 1600℃ to melt it, then cast it. After casting, cool it down to room temperature at 1℃ / min to obtain the casting jacket. S2. The high-silicon aluminum alloy is centrifugally cast (casting temperature is 750℃, centrifugation parameter is 80G), and then the outer circle is precision machined. The outer diameter of the inner liner is machined to be larger than the inner diameter of the outer sleeve, with an interference of 0.3% of the fitting diameter, to obtain the inner liner. S3. Clean the inner surface of the outer jacket and the outer surface of the inner liner until the surface is smooth. Place the outer jacket in a heating furnace and heat it (temperature 450℃, time 1.5h). Place the room temperature inner liner into the heated outer jacket and cool it to room temperature to obtain a bimetallic cylinder liner.

[0027] Performance testing Functional tests were performed on the bimetallic cylinder liners prepared in Examples 1-3 and Comparative Example 1.

[0028] Impact toughness test: Samples of 55mm×10mm×10mm were taken from the center of the wall thickness of the forged outer casing along the axial and radial directions. A V-shaped notch with a depth of 2mm, an angle of 45°, and a root radius of 0.25mm was machined at the middle of the sample length using a special milling cutter. Using a pendulum impact testing machine, the sample was placed horizontally on the two supports of the testing machine, ensuring that the V-shaped notch faced away from the impact edge of the pendulum and was located in the middle of the two supports. The pendulum was raised to a certain height, and the impact absorption energy when the sample was broken was recorded in J. Pressure resistance test: The test was conducted using a high-pressure hydraulic burst test bench. The burst pressure was recorded when the cylinder liner underwent permanent deformation or rupture. The results are shown in Table 1. Table 1 Group Impact absorption work J Explosion pressure MPa Example 1 43 95 Example 2 45 98 Example 3 41 92 Comparative Example 1 33 81 As shown in Table 1, the bimetallic cylinder liners prepared by the method used in the embodiments of this application have high strength in terms of impact toughness and strong performance in terms of pressure bearing capacity. In particular, the bimetallic cylinder liner prepared in Example 2 has the best effect. Compared with Example 3, the bimetallic cylinder liner outer sleeve prepared by the traditional casting method in Comparative Example 1 has poor impact performance and pressure bearing capacity. Comparative Example 1 is not as good as Example 3, indicating that the method used in this application is superior to the traditional casting method.

[0029] The above description is merely an example and illustration of the concept of this application. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the inventive concept or exceed the scope defined in the claims, they should all fall within the protection scope of this application.

Claims

1. A bimetallic cylinder liner based on a casting-to-forging process, characterized in that, It is prepared by the following steps: S1. The steel is heated and then upsetting in a pre-forging die. It is then formed by first extrusion and second extrusion. The connecting skin at the bottom of the cup-shaped part is punched off to form a through hole. Then it is heat-treated and cooled to obtain a forged outer jacket. S2. High-silicon aluminum alloy is centrifugally cast, and then the outer circle is precision machined to obtain the inner lining. S3. Clean the inner surface of the outer jacket and the outer surface of the inner liner. Place the outer jacket in a heating furnace and heat it. Place the room temperature inner liner into the hot outer jacket and cool it to obtain a bimetallic cylinder liner based on the casting-to-forging process.

2. A bimetallic cylinder liner based on a casting-to-forging process according to claim 1, characterized in that, The heating temperature in step S1 is 1150-1200℃, and the time is 2-3 hours.

3. A bimetallic cylinder liner based on a casting-to-forging process according to claim 1, characterized in that, The upsetting process has an upsetting ratio of 1.8-2.

2.

4. A bimetallic cylinder liner based on a casting-to-forging process according to claim 1, characterized in that, The extrusion speed is 20-40 mm / s.

5. A bimetallic cylinder liner based on a casting-to-forging process according to claim 1, characterized in that, The secondary extrusion is performed at a speed of 10-20 mm / s, and the pressure is maintained for 3-5 seconds after molding.

6. A bimetallic cylinder liner based on a casting-to-forging process according to claim 1, characterized in that, The heat treatment is performed at a temperature of 840-860℃ for 1-1.5 hours.

7. A bimetallic cylinder liner based on a casting-to-forging process according to claim 1, characterized in that, The cooling described in step S1 involves reducing the temperature to room temperature at a rate of 1-2°C / min.

8. A bimetallic cylinder liner based on a casting-to-forging process according to claim 1, characterized in that, The centrifugal casting process involves a casting temperature of 700-750℃ and centrifugal parameters of 50G-80G.

9. A bimetallic cylinder liner based on a casting-to-forging process according to claim 1, characterized in that, The finishing process involves machining the outer diameter of the inner lining to be larger than the inner diameter of the outer lining, with an interference fit of 0.1%-0.3% of the mating diameter.

10. A bimetallic cylinder liner based on a casting-to-forging process according to claim 1, characterized in that, The heating described in step S3 is performed at a temperature of 350-450℃ for 1-2 hours.