Plunger pump cylinder body and machining method thereof

Abstract

The machining method comprises the steps that S1, a plunger hole is machined in a steel base body, and the roughness of the inner surface of the plunger hole is not larger than Ra1.6; s2, a plunger bushing capable of being in interference fit with the plunger hole is machined according to the size of the plunger hole; s3, the plunger bushing is put into liquid nitrogen to be soaked and then taken out, then the plunger bushing is pressed into the plunger hole smeared with the soldering paste, a steel pin is embedded into the plunger hole, and a plunger assembly is obtained; through the thermal expansion effect of the steel pin, the plunger hole and the copper bush, the plunger bush is pressed to enter the plunger hole in the sintering process. And S4, the press-fitted plunger assembly is put into a sintering furnace to be sintered, the plunger lining and the plunger hole are subjected to diffusion welding, and the plunger pump cylinder body is obtained after cooling. According to the method, the plunger bushing is placed in the ultralow-temperature environment to be shrunk, mechanical press fitting is easier, then diffusion welding is combined, metallurgical bonding between the copper alloy bushing and the steel base body is achieved, and the service life of materials is prolonged.

Description

Technical Field

[0001] The invention relates to the field of hydraulic plunger pumps, in particular to a plunger pump cylinder body and a processing method thereof. Background Art

[0002] The plunger pump relies on the reciprocating motion of the plunger in the plunger hole of the cylinder to produce volume changes to achieve oil pressure and oil suction. Due to the advantages of high rated pressure, compact structure, high efficiency and convenient flow regulation, the plunger pump has been widely used in engineering machinery, ships and other fields. Since the cylinder is the key core part of the plunger pump, its service life and stability directly affect the service life and quality of the entire plunger pump. At present, the plunger pump cylinder mainly adopts a bimetallic material composed of a steel matrix + copper alloy. The copper alloy layer of the flow distribution surface of the cylinder is prepared by a melt casting method, and the copper alloy layer of the plunger hole is prepared by inlaying a copper alloy plunger bushing. Chinese patent CN113464420A discloses a plunger pump cylinder structure and its assembly method, and the copper alloy layer of the plunger hole is prepared by cold pressing and extrusion inlaying a copper alloy plunger bushing. Although this preparation method has been improved and optimized compared with the currently commonly used room temperature mechanical pressing copper alloy plunger bushing method, the combination between the copper alloy plunger bushing and the steel matrix is ​​still mechanical bite. Summary of the invention

[0003] In view of this, the present invention provides a plunger pump cylinder and a processing method thereof to solve the problems raised in the above-mentioned background technology. The plunger bushing is placed in an ultra-low temperature environment to shrink, making mechanical pressing easier. Then, combined with diffusion welding, metallurgical bonding between the copper alloy bushing and the steel matrix is ​​achieved, thereby improving the service life of the material.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention discloses a method for processing a plunger pump cylinder, comprising the following steps:

[0006] S1. Processing a plunger hole on a steel substrate, wherein the inner surface roughness of the plunger hole is not greater than Ra1.6; the material of the steel substrate is alloy structural steel, such as 42CrMo used in the specific embodiment;

[0007] S2. A plunger bushing is processed according to the size of the plunger hole to achieve an interference fit with the plunger hole; the bushing is made of a copper alloy consisting of lead, tin, and copper in a ratio of 10:10:80, and its melting point is close to 750°C;

[0008] S3. Soak the plunger bushing in liquid nitrogen and take it out, then press it into the plunger hole coated with solder paste to obtain a plunger assembly; through the thermal expansion effect of the steel pin, the plunger hole and the copper sleeve, the plunger bushing is pressed into the plunger hole during the sintering process.

[0009] S4, placing the pressed plunger assembly into a sintering furnace for sintering, so that the plunger bushing and the plunger hole are diffusion welded, and after cooling, a plunger pump cylinder body is obtained;

[0010] S5. After natural cooling, remove the steel pin from the plunger bushing.

[0011] As a further solution of the present invention: under normal temperature environment, the inner diameter of the plunger hole and the outer diameter of the plunger bushing differ by 0.06-0.08 mm.

[0012] As a further solution of the present invention: the solder paste is a copper-based solder paste or a silver-based solder paste.

[0013] The copper in the copper-based solder paste will diffuse into the copper in the copper sleeve during the sintering process, forming a metallurgical bond, which helps to improve the bonding between the copper sleeve and the plunger hole. The silver solder paste can improve the wettability of the welding interface, allowing the solder to better cover the metal surface being welded, reducing welding defects.

[0014] As a further solution of the present invention: in step S3, the plunger bushing is immersed in liquid nitrogen for 5-10 minutes.

[0015] As a further solution of the present invention: in step S4, the sintering temperature is 720-800° C., the sintering time is 30-60 min, and the protective atmosphere is nitrogen or argon.

[0016] The plunger hole and plunger bushing are made of steel and copper, which will produce thermal expansion between 720℃-800℃. On the one hand, it makes the plunger hole and the copper sleeve tightly bonded. On the other hand, it also increases the mutual diffusion flux of copper and steel between the plunger hole and the plunger bushing, making it easier for copper and steel to diffuse, thereby forming a metallurgical bond at the interface.

[0017] As a further solution of the present invention: before step S1, the process also includes melting and cooling the steel substrate and the copper alloy layer.

[0018] As a further solution of the present invention: the melting and cooling specifically include:

[0019] A molten pool is opened on the surface of a steel substrate, a flux is coated on the surface of the molten pool, a copper alloy is placed in the molten pool covered with a solvent, a protective cover is placed on the molten pool, and then the molten pool is placed in a sintering furnace for sintering, so that the copper alloy melts and spreads in the molten pool; and the base material of a plunger pump cylinder is obtained by cooling.

[0020] The protective cover is a mullite cover plate, and its main function is to keep the copper warm so that it can be fully melted during the sintering process.

[0021] As a further solution of the present invention: cooling specifically includes: directional cooling from bottom to top, and then medium-high temperature tempering treatment.

[0022] In a second aspect, the present invention discloses a plunger pump cylinder manufactured by the above-mentioned processing method.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention utilizes the principle of thermal expansion and contraction. The copper alloy plunger bushing shrinks under ultra-low temperature cryogenic treatment of liquid nitrogen. On the one hand, the plunger bushing is easily pressed into the plunger hole of the steel substrate. On the other hand, by controlling the cryogenic treatment time, the copper alloy plunger bushing can achieve a certain amount of shrinkage, leaving a certain space for the applied solder paste, thereby avoiding scratches when the plunger bushing is pressed. After the cryogenically treated plunger bushing is pressed into the plunger hole of the steel substrate, its temperature rises rapidly and expands. The copper alloy plunger bushing and the steel substrate plunger hole achieve an interference fit. After diffusion welding treatment, the copper alloy plunger bushing and the steel substrate achieve metallurgical bonding, thereby improving the service life of the plunger pump cylinder. The method for preparing a plunger pump cylinder provided by the present invention does not have typical casting defects such as pores, cracks, and sand holes in the plunger hole of the plunger bushing. At the same time, even if the cylinder body prepared by this method has a problem of poor bonding between the copper alloy plunger bushing and the steel substrate, the bad plunger hole can be reworked and repaired. Therefore, the method for preparing a plunger pump cylinder provided by the present invention has the advantages of reliable technology and economical cost.

[0025] Due to the different thermal expansion coefficients of copper and steel (copper's thermal expansion coefficient is usually greater than steel), thermal stress is generated at the copper-steel interface. Steel pins have high strength and rigidity and can withstand large stresses. Embedding them in copper bushings can significantly enhance the overall strength and stability of the bushing and its connected parts, optimize the force transmission path, reduce stress concentration and energy loss, and avoid interface cracking or failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the plunger pump cylinder in the present invention;

[0027] Figure 2 is a cross-sectional view of the plunger hole in the present invention;

[0028] Figure 3 The metallographic structure diagram of the interface between the plunger bushing and the steel base plunger hole of the plunger pump cylinder body processed in Example 1;

[0029] Figure 4 This is the metallographic structure diagram of the interface between the plunger bushing and the steel base plunger hole obtained by processing in Comparative Example 1;

[0030] In the figure, 1-steel substrate, 2-molten pool, 3-plunger hole, 4-bushing, 5-steel pin. DETAILED DESCRIPTION

[0031] For ease of understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] Example 1

[0034] S1. Rough machining of steel base: Design the steel base 1 structure of the cylinder body, such as Figure 1 As shown, the steel substrate is roughly machined to form a molten pool 2 on one side of the distribution surface of the steel substrate.

[0035] S2. Surface cleaning of materials: Surface cleaning of the steel substrate 1 and the copper alloy block used for the distribution surface is performed to remove pollutants on the surface of the materials.

[0036] S3. Preparation of copper alloy layer on distribution surface: coating flux on the surface of molten pool 2 of steel substrate 1, placing copper alloy block into molten pool 2 of steel substrate, adding insulation layer above molten pool 2, placing material into sintering furnace and sintering at 1050°C for 60min, so that copper alloy is melted and spread in molten pool 2, after sintering, directionally cooling material from bottom to top to realize directionally solidification of copper alloy melt, finally performing medium-high temperature tempering on material, and cooling medium used for cooling is water.

[0037] S4, blank processing: the flow distribution surface of the material blank prepared in step S3 is machined to make the flatness of one side of the flow distribution surface within 0.05mm, and at the same time, the plunger hole 3 is processed on the steel substrate. The size specification of the plunger hole 3 in this embodiment is φ27 0 -0.02 mm*52±0.1mm (diameter D0*depth H0), the surface roughness of the plunger hole 3 is within Ra1.6.

[0038] S5. Processing of copper alloy plunger bushing: According to the structure of the steel base plunger hole 3, the copper alloy plunger bushing 4 is designed and processed. The structure of the plunger bushing 4 is as follows: Figure 2 As shown, the size of the copper alloy plunger bushing 4 in this embodiment is φ27 + 0.060mm*φ24±0.1mm*52±0.1mm (outer diameter D1*inner diameter D2*length H1), the copper alloy plunger bushing 4 and the steel base plunger hole 3 can achieve interference fit in size.

[0039] S6. Solder paste application: evenly apply a layer of copper-based solder paste in the plunger hole 3 of the steel substrate.

[0040] S7. Cryogenic treatment and mechanical pressing of the copper alloy plunger bushing: Soak the copper alloy plunger bushing 4 in liquid nitrogen for 5 minutes for cryogenic treatment to cause it to shrink. After the cryogenic treatment, quickly press the plunger bushing 4 into the steel base plunger hole 3, and then embed the steel pin into the bushing 4.

[0041] S8, diffusion welding: put the copper alloy plunger bushing 4 mechanically pressed in step S7 into a sintering furnace for sintering to achieve diffusion welding of the copper alloy plunger bushing 4 and the steel substrate, the sintering temperature is 720°C, the sintering time is 60 minutes, and the protective atmosphere is nitrogen. The schematic diagram of the cylinder blank after diffusion welding is as follows Figure 3 shown.

[0042] S9, take out the steel pin;

[0043] S10, Finishing: Finish the product according to the finished product requirements of the plunger pump cylinder.

[0044] The copper-steel interface of the cylinder plunger hole prepared in this embodiment was subjected to metallographic structure analysis. Figure 4 As shown, it was found that a good metallurgical bond was formed between copper and steel.

[0045] Example 2

[0046] A method for preparing a plunger pump cylinder comprises the following steps:

[0047] S1. Rough machining of steel substrate: design the structure of the steel substrate 1 of the cylinder body, and perform rough machining on the steel substrate 1, and machine a molten pool 2 on one side of the distribution surface of the steel substrate.

[0048] S2. Surface cleaning of materials: Surface cleaning of the steel substrate 1 and the copper alloy block used for the distribution surface is performed to remove pollutants on the surface of the materials.

[0049] S3. Preparation of copper alloy layer on distribution surface: coating flux on the surface of molten pool 2 of steel substrate 1, placing copper alloy block into molten pool 2 of steel substrate, adding insulation layer above molten pool 2, and then placing the material into sintering furnace for high temperature sintering at 1150°C for 30 minutes to melt the copper alloy and spread it in the molten pool. After sintering, the material is directionally cooled from bottom to top to realize directional solidification of copper alloy melt, and finally the material is subjected to medium-high temperature tempering treatment. The cooling medium used for cooling is PAG quenching liquid with concentration of 10-12%.

[0050] S4, blank processing: the flow distribution surface of the material blank prepared in step S3 is machined to make the flatness of one side of the flow distribution surface within 0.05mm, and at the same time, the plunger hole 3 is processed on the steel substrate. The size specification of the plunger hole 3 in this embodiment is φ27 0 -0.02 mm*52±0.1mm (diameter D0*depth H0), the surface roughness of the plunger hole 3 is within Ra1.6.

[0051] S5. Processing of copper alloy plunger bushing: According to the structure of the steel base plunger hole 3, the copper alloy plunger bushing 4 is designed and processed. The size specification of the copper alloy plunger bushing 4 in this embodiment is φ27 +0.06 0mm*φ24±0.1mm*52±0.1mm (outer diameter D1*inner diameter D2*length H1), the copper alloy plunger bushing 4 and the steel base plunger hole 3 can achieve interference fit in size.

[0052] S6. Solder paste application: Apply a layer of copper-based solder paste evenly in the steel substrate plunger hole.

[0053] S7. Cryogenic treatment and mechanical pressing of the copper alloy plunger bushing: Soak the copper alloy plunger bushing 4 in liquid nitrogen for 10 minutes for cryogenic treatment to cause it to shrink. After the cryogenic treatment, quickly press the plunger bushing 4 into the plunger hole of the steel base, and then embed the steel pin into the bushing 4.

[0054] S8, diffusion welding: put the material after mechanical pressing of the copper alloy plunger bushing 4 in step S7 into a sintering furnace for sintering to achieve diffusion welding of the copper alloy plunger bushing 4 and the steel substrate 1, the sintering temperature is 760°C, the sintering time is 45 minutes, and the protective atmosphere is nitrogen.

[0055] S9, take out the steel pin;

[0056] S10, Finishing: Finish the product according to the finished product requirements of the plunger pump cylinder.

[0057] Example 3

[0058] A method for preparing a plunger pump cylinder comprises the following steps:

[0059] S1. Rough machining of steel substrate: design the structure of the steel substrate 1 of the cylinder body, and perform rough machining on the steel substrate 1, and machine a molten pool 2 on one side of the distribution surface of the steel substrate.

[0060] S2. Surface cleaning of materials: Surface cleaning of the steel substrate 1 and the copper alloy block used for the distribution surface is performed to remove pollutants on the surface of the materials.

[0061] S3. Preparation of copper alloy layer on distribution surface: coating flux on the surface of molten pool 2 of steel substrate 1, placing copper alloy block into molten pool 2 of steel substrate, adding insulation layer above molten pool 2, placing material into sintering furnace and sintering at 1100°C for 45min, so that copper alloy is melted and spread in molten pool, finally directionally cooling material from bottom to top, so as to realize directionally solidification of copper alloy melt, and cooling medium used for cooling is nitrogen.

[0062] S4, blank processing: the flow distribution surface of the material blank prepared in step S3 is turned to make the flatness of one side of the flow distribution surface within 0.05mm, and at the same time, the plunger hole is processed on the steel substrate. The size specification of the plunger hole in this embodiment is φ27 0 - 0.02 mm*52±0.1mm (diameter D0*depth H0), the surface roughness of the plunger hole is within Ra1.6.

[0063] S5. Processing of copper alloy plunger bushing: According to the structure of the steel base plunger hole 3, the copper alloy plunger bushing is designed and processed. The size specification of the copper alloy plunger bushing 4 in this embodiment is φ27 +0.06 0mm*φ24±0.1mm*52±0.1mm (outer diameter D1*inner diameter D2*length H1), the copper alloy plunger bushing 4 and the steel base plunger hole 3 can achieve interference fit in size.

[0064] S6. Solder paste application: evenly apply a layer of silver-based solder paste in the plunger hole 3 of the steel substrate.

[0065] S7. Cryogenic treatment and mechanical pressing of the copper alloy plunger bushing 4: Soak the copper alloy plunger bushing 4 in liquid nitrogen for 8 minutes for cryogenic treatment to cause it to shrink. After the cryogenic treatment, quickly press the plunger bushing 4 into the plunger hole of the steel base, and then embed the steel pin into the bushing 4.

[0066] S8, diffusion welding: put the material after mechanical pressing of the copper alloy plunger bushing 4 in step S7 into a sintering furnace for sintering to achieve diffusion welding of the copper alloy plunger bushing 4 and the steel substrate 1, the sintering temperature is 800°C, the sintering time is 30 minutes, and the protective atmosphere is argon.

[0067] S9, take out the steel pin;

[0068] S10, Finishing: Finish the product according to the finished product requirements of the plunger pump cylinder.

[0069] Although this specification is described according to implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0070] Comparative Example 1

[0071] Except that the sintering temperature of diffusion welding in step S8 is 600° C., the rest is the same as that of embodiment 1.

[0072] The metallographic structure of the copper-steel interface of the cylinder plunger hole prepared in this comparative example was analyzed. Figure 4 As shown, obvious hole defects were found between copper and steel.

[0073] Table 1 Bonding strength of samples of various embodiments and comparative examples

[0074] Example 1 Example 2 Example 3 Comparative Example 1 Bonding strength 156 161 167 92

[0075] The test method for the bonding strength in Table 1 is as follows:

[0076] The sample was cut into strips of 15 mm in length and 2 mm in thickness (width is unlimited), and the strips were tested by shear test. A gradually increasing shear force was applied to the strips until relative sliding occurred between the bushing and the steel substrate, and the bonding strength was recorded.

[0077] Therefore, the above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application; that is, all equivalent changes made according to the scope of the claims of the present application are within the protection scope of the claims of the present application.

Claims

1. A method for processing a plunger pump cylinder, characterized in that: The following steps are involved: S1. Process the plunger hole on the steel substrate, and the inner surface roughness of the plunger hole shall not exceed Ra1.6; S2. Processing a copper plunger bushing according to the plunger hole size to achieve an interference fit with the plunger hole; S3. Soak the plunger bushing in liquid nitrogen and then take it out. Then, press it into the plunger hole coated with solder paste, and embed a steel pin in the plunger hole to obtain a plunger assembly. S4, placing the press-assembled plunger assembly into a sintering furnace for sintering to diffusely weld the plunger bushing and the plunger hole, and obtaining a plunger pump cylinder after cooling; S5. After natural cooling, remove the steel pin from the plunger bushing.

2. The method for processing a plunger pump cylinder according to claim 1, characterized in that: Under normal temperature conditions, the difference between the inner diameter of the plunger hole and the outer diameter of the plunger bushing is 0.06-0.08mm.

3. The method for processing a plunger pump cylinder according to claim 1, characterized in that: The solder paste is copper-based solder paste or silver-based solder paste.

4. The method for processing a plunger pump cylinder according to claim 1, characterized in that: In step S3, the plunger bushing is immersed in liquid nitrogen for 5-10 minutes.

5. The method for processing a plunger pump cylinder according to claim 1, characterized in that: In step S4, the sintering temperature is 720-800° C., the sintering time is 30-60 min, and the protective atmosphere is nitrogen or argon.

6. The method for processing a plunger pump cylinder according to claim 1, characterized in that: Before step S1, the process also includes melting and cooling of the steel base and the copper alloy layer.

7. The method for processing a plunger pump cylinder according to claim 6, characterized in that: Melting and cooling specifically include: A molten pool is opened on the surface of the steel substrate, a flux is coated on the surface of the molten pool, a copper alloy is placed in the molten pool covered with the solvent, a protective cover is added above the molten pool, and then the substrate is placed in a sintering furnace for sintering to melt and spread the copper alloy in the molten pool; and the substrate is cooled to obtain a plunger pump cylinder base material.

8. The method for processing a plunger pump cylinder according to claim 7, characterized in that: Cooling specifically includes: directional cooling from bottom to top, followed by medium and high temperature tempering.

9. A plunger pump cylinder manufactured by the processing method according to any one of claims 1 to 8.

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