Method for inverted casting of copper spherical friction pair of plunger pump

Abstract

The application relates to the technical field of pump body part machining, and particularly discloses a method for inverting melt casting of a copper spherical friction pair of a plunger pump. The method comprises the steps of steel base body machining, stamping a die, installing the die, casting, cooling and demolding, etc., utilizes the spherical surface structure of a spherical die, changes a center hole into a pouring opening, and inverts the steel base body for casting, so that the technical problem of copper alloy waste and high production cost caused by the fact that the copper alloy needs to be first made into a column structure and then turned into a spherical surface structure when the copper alloy is combined with the steel base body in the process of manufacturing a plunger pump cylinder body in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of pump body parts processing technology, specifically a method for inverted casting of copper spherical friction pairs for plunger pumps. Background Technology

[0002] Piston pumps are core components of hydraulic equipment, and the cylinder block, as a key friction pair part of the piston pump, is its core. The performance and quality of the cylinder block directly affect the transmission efficiency and service life of the piston pump. Currently, the most widely used material for piston pump cylinder blocks is copper-steel bimetallic composite material. Copper alloy (especially lead bronze) serves as the working layer of the friction pair, while steel alloy serves as the piston pump's matrix. The working layer made of copper alloy has excellent friction reduction, wear resistance, and fatigue resistance properties, while its soft and hard phase structure determines its good anti-galling, embedding, and compliance properties. The steel material, as the piston pump cylinder block's matrix material, plays a role in load bearing and impact resistance. The copper-steel bimetallic composite material formed by combining these two materials possesses the excellent properties of both.

[0003] During production, two processes are typically used to bond the copper alloy to the steel matrix: casting and melting. The casting process usually involves first machining a cylindrical steel matrix, then machining a recessed annular molten copper pool on one end face of the steel matrix. Molten lead-bronze alloy is then poured into the heated copper pool of the steel matrix, and after solidification, a bimetallic cylinder blank is obtained. The molten copper pool is then machined away. Figure 4 Similar to the cylinder structure of the plunger pump, the copper alloy layer is machined into a spherical friction pair working layer. While the casting process also requires machining a molten copper pool, the copper alloy is directly placed into the molten copper pool, and the entire workpiece is placed in a multi-temperature zone sintering furnace for heating. Because the melting point of the copper alloy is lower than that of the steel substrate, when the melting point temperature of the copper alloy is reached, the copper alloy melts into a liquid state and spreads evenly in the molten copper pool of the steel substrate. After being removed and cooled, a bimetallic cylinder blank is obtained. Then, the molten copper pool is machined away using a turning process, and the copper alloy layer is machined into a spherical friction pair working layer.

[0004] Both of the above methods involve forming a columnar copper alloy working layer in a molten copper bath when bonding copper alloys with steel substrates. Only after the bimetallic composite is completed are processes such as drilling a center hole and machining the working layer into a spherical surface performed. These processes require drilling, turning, and grinding. Copper alloy waste is generated during the processing of the copper alloy working layer. The turned copper alloy waste can only be sold as scrap, resulting in a waste of copper alloy. In addition, the high price of copper alloy leads to high production costs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for inverted casting of copper spherical friction pairs for plunger pumps, in order to solve the technical problem mentioned above in the prior art of manufacturing plunger pump cylinder bodies, where the copper alloy needs to be first made into a cylindrical structure and then machined into a spherical structure, resulting in copper alloy waste and high production costs when the copper alloy is combined with the steel substrate.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows: a method for inverted casting of a copper spherical friction pair for a plunger pump, comprising the following steps:

[0007] Step 1: Steel substrate processing: Cut a cylindrical steel substrate blank from the steel bar with a pre-machining allowance, turn the copper molten pool on the steel substrate blank and drill a center hole along the steel substrate axis;

[0008] Step 2: Stamping Die: Based on the spherical friction pair structure, design a spherical die with a machining allowance of 1-2mm, and stamp the steel plate into the spherical die;

[0009] Step 3: Install the mold: Weld the spherical mold to the edge of the molten copper pool;

[0010] Step 4: Casting: Invert the steel substrate so that the molten copper pool faces downwards, and add the copper alloy into the molten copper pool through the central hole, so that the copper alloy and the steel substrate are cast together as a whole;

[0011] Step 5: Cooling and Demolding: After the copper alloy and steel substrate have completely cooled and bonded together in Step 4, the spherical mold is cut off to obtain the bimetallic cylinder blank.

[0012] The beneficial effects of this implementation plan are as follows:

[0013] 1. In existing technologies, when copper alloys are bonded to steel substrates, a cylindrical copper alloy working layer with a flat upper surface is formed in a molten copper pool. After the bimetallic composite is completed, a center hole is drilled, and the working layer is machined into a spherical surface. These processes require turning, drilling, and grinding, which generates copper alloy waste during the processing of the copper alloy working layer. The turned copper alloy can only be discarded and recycled, resulting in waste of copper alloy and high production costs. In contrast, in this application, a center hole is machined first and used as the entrance for copper alloy during casting or melting. A spherical mold with a spherical friction pair is designed and welded to the molten copper pool to form a closed space. After the steel substrate is inverted, the copper alloy working layer is formed by melting and casting. Compared with the cylindrical copper alloy working layer with a flat upper surface in existing technologies, the copper alloy working layer formed in this application is spherical. Therefore, the amount of turning is greatly reduced, the amount of copper alloy waste generated is reduced, the amount of copper alloy used is saved, and resources are conserved while reducing production costs.

[0014] 2. In existing methods, when the cylinder body is in the composite copper alloy layer, not only is a working surface of the composite friction pair required, but also cylindrical cylinder holes arranged circumferentially around the central hole on the composite cylinder body. As in the patent document with application number CN201510001327.5, a sealing plate needs to be welded below the cylinder hole to seal it. However, this application inverts the steel substrate, moves the sealing plate to one end of the molten copper pool, and stamps it into a spherical mold. In this way, without adding too many processes, the spherical structure of the friction pair working surface can be cast during the melting and casting process, and the cylinder hole can also face upwards, eliminating the need for a sealing plate.

[0015] 3. Because the spherical surface of the spherical friction pair is a concave sphere, and molten copper alloy can only be spread flat in the molten copper pool to form a plane, it is impossible to cast the spherical curvature without inverting the steel substrate. Even if a mold is made, only a flat end face can be formed in the mold. However, the ingenious center hole structure in this application, which requires subsequent machining, inverts the steel substrate, making the spherical surface of the spherical friction pair the bottom surface. Under the action of gravity, it covers the mold, thus allowing the spherical structure of the spherical friction pair to be cast / melted, reducing the amount of copper alloy machining required later.

[0016] Furthermore, in step 2, the center of the spherical mold is recessed downwards to form a cylindrical shell. The diameter of the cylindrical shell is smaller than the diameter of the central hole, ensuring that after the spherical mold is welded to the molten copper pool, the cylindrical shell extends into the central hole. Since the central hole of the bimetallic cylinder blank needs to penetrate through the steel substrate and the copper alloy working layer later, setting a cylindrical shell at the center of the spherical mold can reduce the waste copper generated during the later central hole penetration machining of the copper alloy working layer, further saving copper alloy material and reducing costs.

[0017] Furthermore, in step 4, the copper alloy is first melted into a liquid state and then cast into a molten copper pool through a central hole. For industries with smaller investments, casting requires a lower initial investment compared to smelting, making this application suitable for small-scale production.

[0018] Furthermore, before using the casting composite process, the steel substrate must be preheated to the melting point of the copper alloy. Heating the steel substrate first, followed by casting and cooling together, ensures a more stable bond between the copper alloy working layer and the steel substrate.

[0019] Furthermore, in step 4, the composite process involves adding a solid copper alloy into the molten copper pool through a central hole, then placing the entire workpiece into a sintering furnace and heating it to 1080-1100℃ for melting and casting. Compared to casting, melting and casting has higher processing efficiency, lower production costs, and a more stable bimetallic bond.

[0020] Furthermore, during cooling, the temperature should be controlled at a rate of 5°C / min. An appropriate cooling rate helps to form good intermetallic bonding. Cooling too quickly may lead to inhomogeneous microstructure, while cooling too slowly may cause large grain growth, affecting the bonding strength.

[0021] Furthermore, in step 1, the center hole is machined first, and then the copper molten pool is machined out. This avoids the need for slotting. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a steel-based structure in the prior art.

[0023] Figure 2 A schematic diagram of the steel substrate and mold in Embodiment 1 of the present invention.

[0024] Figure 3 This is a schematic diagram of the steel substrate and mold in Embodiment 2 of the present invention.

[0025] Figure 4 This is a schematic diagram of the structure of a conventional plunger pump. Detailed Implementation

[0026] The following detailed description illustrates the specific implementation method:

[0027] The reference numerals in the accompanying drawings include: steel substrate 1, central hole 11, copper melting pool 2, spherical mold 3, and cylindrical shell 31.

[0028] Implementation, for example, attached Figures 1-4 As shown:

[0029] Example 1

[0030] The method for inverted casting of the copper spherical friction pair of a plunger pump includes the following steps:

[0031] Step 1: Steel substrate 1 processing: Cut the steel bar into a cylindrical steel substrate 1 according to the specified dimensions, and first use a grooving tool to make a groove on the end face of the steel substrate 1. The grooving position is to move along the edge of the end face of the steel substrate 1 to the center position at a distance equal to the thickness of the annular sidewall. The purpose is to retain the annular sidewall of the copper molten pool 2. After grooving, the copper molten pool 2 is machined out along the grooving position. Then, the central hole 11 penetrating the steel substrate 1 is drilled along the axis of the steel substrate 1.

[0032] The cylinder block of the plunger pump is a bimetallic composite material of steel and copper. The steel alloy serves as the base of the plunger pump, providing structural support, while the copper alloy offers excellent friction reduction, wear resistance, and fatigue resistance. During processing, the raw steel bar is typically cut into the cylindrical structure of the steel base 1. Then, a copper bath 2 is machined into one end face of the cylindrical shape. In existing technology, this step usually completes the machining of the steel base 1, and its structure is as follows: Figure 1 As shown, the existing technology then directly casts or melts copper alloy in the copper molten pool 2, so that the copper alloy and the steel substrate 1 are combined into a whole to obtain a bimetallic blank cylinder body, and then performs machining on the center hole 11 and the spherical working layer of the friction pair.

[0033] In this application, when processing the steel substrate 1, not only is the steel bar cut into a cylindrical steel substrate 1 and the copper melting pool 2 processed, but the central hole 11 of the steel substrate 1 is also directly machined out, and its structure is as follows: Figure 2 As shown.

[0034] Step 2: Stamping Die: Stamp the steel plate into a spherical die that matches the structure of the spherical friction pair, but leave a machining allowance of 1-2mm in size;

[0035] like Figure 2 As shown, after the steel substrate 1 completes the machining of the center hole 11 and the copper melting pool 2, it is also necessary to process the mold. The mold is made of steel plate and is directly stamped into a spherical structure. Since the spherical surface of the friction pair is a concave spherical surface, the spherical mold 3 is also stamped into a concave spherical structure.

[0036] Step 3: Install the mold: Weld the spherical mold to the edge of the copper melting pool 2;

[0037] After the spherical mold 3 is stamped, the concave side of the spherical mold 3 is placed on the copper melting pool 2 and the spherical mold 3 is welded together along the edge of the circumferential wall of the copper melting pool 2. The welding position is sealed to prevent leakage.

[0038] Step 4: Casting: Invert the steel substrate 1 so that the molten copper pool 2 faces downward, and add the copper alloy into the molten copper pool 2 through the central hole 11, so that the copper alloy and the steel substrate 1 are combined into a whole;

[0039] After the spherical mold 3 is welded, the steel substrate 1 is inverted. Since the central hole 11 penetrates the steel substrate 1, it has an opening at the other end of the steel substrate 1. After inversion, the copper alloy can be added to the molten copper pool 2 through the central hole 11. The copper alloy is then composited with the steel substrate 1. Before composite, the steel plate of the steel substrate 1 is cleaned and dried.

[0040] Composite processes can be divided into two types: casting and melting.

[0041] The casting process is as follows: The steel substrate 1, after being welded to the spherical mold 3, is preheated to the melting point of the copper alloy, 800-860℃, and then held at that temperature. This holding process ensures that the temperature inside and outside the steel substrate 1 is uniform. Temperature differences in different areas of the steel can lead to uneven thermal expansion and contraction, generating internal stress. If this stress exceeds the yield strength of the material, it may cause structural damage. By holding the steel at that temperature to ensure uniform internal and external temperatures, this uneven stress is prevented, thus ensuring that the strength of the steel substrate 1 is not compromised.

[0042] While the steel substrate 1 is preheated, the copper alloy is melted. After preheating, the copper alloy is also melted into a liquid. At this point, molten copper alloy can be added to the molten copper pool 2 through the central hole 11. After the molten copper alloy flows into the molten copper pool 2 and slowly fills it, the addition of molten copper alloy is stopped, and the whole thing is cooled. During the gradual cooling process, the copper alloy and the steel substrate 1 become a whole.

[0043] The casting process is as follows: After inverting the steel substrate 1, solid copper alloy is added directly into the copper molten pool 2 through the central hole 11. The amount of copper alloy added should be calculated and not less or more than required. After the copper alloy is added, the entire workpiece is placed in a multi-temperature zone sintering furnace for heating. After the temperature reaches 1080 to 1100°C, the molten copper alloy is held at this temperature for 30-60 minutes. Since the melting point of the copper alloy is lower than that of the steel 1 in the steel substrate 1, when the melting point temperature of the copper alloy is reached, the copper alloy melts into a liquid state, while the steel substrate 1 remains solid. Therefore, the molten copper alloy will spread evenly in the copper molten pool 2 of the steel substrate 1. After the melting point temperature of the copper alloy is reached, it is held at this temperature for 30-60 minutes to ensure the stability of the composite between the alloy and the steel substrate 1. After the holding period, the multi-temperature zone sintering furnace begins to cool down. During the gradual cooling process, the entire workpiece gradually cools down, and the copper alloy and the steel substrate 1 are combined into a whole to obtain a bimetallic cylinder blank.

[0044] Because the spherical surface of the spherical friction pair is concave, casting cannot be performed without inverting the steel substrate 1. This is because the molten copper alloy would spread evenly in the copper molten pool 2, and even with a mold, only a flat end face could be formed within the mold. However, the ingenious center hole 11 structure in this application, which requires subsequent machining, inverts the steel substrate 1, making the spherical surface of the spherical friction pair the bottom surface. Under gravity, this surface covers the mold, allowing for casting / melting of the spherical surface and reducing the amount of machining required for the copper alloy later.

[0045] Step 5: Cooling and Demolding: After the copper alloy and steel substrate 1 have completely cooled and bonded together in step 4, the spherical mold is machined off to obtain the bimetallic cylinder blank.

[0046] After the copper alloy melts into a liquid state, the entire piece is gradually cooled, controlling the cooling rate. An appropriate cooling rate helps form a good intermetallic bond. Too rapid cooling may lead to uneven microstructure, while too slow cooling may cause large grain growth, affecting the bond strength. Therefore, the cooling rate is controlled at 5℃ / min. When cooled to below 500℃, the workpiece is removed and air-cooled to room temperature. After cooling, the weld between the spherical mold 3 and the molten copper pool 2 is broken using a tool, and the spherical mold 3 is removed, obtaining a bimetallic cylinder blank. This significantly reduces the amount of copper alloy that needs to be turned when the bimetallic cylinder blank enters the machining spherical friction pair.

[0047] Example 2

[0048] The difference between Example 2 and Example 1 is that in Example 2, when processing the steel substrate 1 in step 1, a central hole 11 is drilled first. After the central hole 11 is drilled, the copper molten pool 2 is machined out along the inner side of the central hole 11, which can avoid grooving.

[0049] And as Figure 3 As shown, in Embodiment 2, a cylindrical shell 31 is stamped out from the center of the spherical mold 3. The outer diameter of the cylindrical shell 31 is smaller than the diameter of the central hole 11 on the steel substrate 1. The maximum diameter of the spherical mold 3 is consistent with the outer diameter of the steel substrate 1. It is ensured that after the spherical mold is welded to the copper melting pool 2, the cylindrical shell 31 should extend at least into the central hole 11. Since the outer diameter of the cylindrical shell 31 is smaller than the diameter of the central hole 11, a gap is left between the cylindrical shell 31 and the central hole 11. Copper alloy particles can be added to the copper melting pool 2 through the gap for melting and casting, or copper alloy liquid can be added for casting. The width of the gap is 2mm. Since the central hole 11 of the bimetallic cylinder blank needs to penetrate through the steel substrate 1 and the copper alloy working layer in the later stage, the cylindrical shell 31 is set at the center of the spherical mold 31. This can reduce the waste copper generated when the central hole 11 is penetrated through the copper alloy working layer in the later stage, further saving the use of copper alloy materials and saving costs.

Claims

1. A method for inverted casting of a copper spherical friction pair for a plunger pump, characterized in that: Includes the following steps: Step 1: Steel substrate processing: Cut a cylindrical steel substrate blank from the steel bar with a pre-machining allowance, turn the copper molten pool on the steel substrate blank and drill a center hole along the steel substrate axis; Step 2: Stamping Die: Based on the spherical friction pair structure, design a spherical die with a machining allowance of 1-2mm, and stamp the steel plate into the spherical die; Step 3: Install the mold: Weld the spherical mold to the edge of the molten copper pool; Step 4: Casting: Invert the steel substrate so that the molten copper pool faces downwards, and add the copper alloy into the molten copper pool through the central hole, so that the copper alloy and the steel substrate are cast together as a whole; Step 5: Cooling and Demolding: After the copper alloy and steel substrate have completely cooled and bonded together in Step 4, the spherical mold is cut off to obtain the bimetallic cylinder blank. In step 2, the center of the spherical mold is recessed downward to form a cylindrical shell. The diameter of the cylindrical shell is smaller than the diameter of the central hole, ensuring that after the spherical mold is welded to the copper molten pool, the cylindrical shell extends into the central hole.

2. The method for inverted casting of the copper spherical friction pair of the plunger pump according to claim 1, characterized in that: In step 4, the composite process involves first melting the copper alloy into a liquid state, and then casting it into a molten copper pool through a central hole.

3. The method for inverted casting of the copper spherical friction pair of the plunger pump according to claim 2, characterized in that: Before using the casting composite process, the steel substrate must be preheated to the melting point of the copper alloy.

4. The method for inverted casting of the copper spherical friction pair of the plunger pump according to claim 1, characterized in that: In step 4, the composite process involves adding a solid copper alloy into the molten copper pool through a central hole, then placing the entire workpiece into a sintering furnace and heating it to 1080-1100℃ for melting and casting.

5. The method for inverted casting of the copper spherical friction pair of the plunger pump according to claim 1, characterized in that: In step 5, the cooling process requires controlling the temperature to decrease at a rate of 5°C / min.

6. The method for inverted casting of the copper spherical friction pair of the plunger pump according to claim 1, characterized in that: In step 1, the center hole is machined first, and then the copper molten pool is machined out.

7. The method for inverted casting of the copper spherical friction pair of the plunger pump according to claim 1, characterized in that: Before casting in step 4, the steel substrate must be cleaned and dried.

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