A method of welding a cylinder block of a dissimilar alloy automotive hydraulic piston pump

Abstract

The present application relates to the technical field of welding, in particular to a welding method of dissimilar alloy automobile hydraulic plunger pump cylinder body. The welding method of dissimilar alloy automobile hydraulic plunger pump cylinder body comprises the following steps: pretreatment, vacuum sealing, hot isostatic pressing forming of alloy steel base body, copper bush and cladding sleeve to obtain copper-steel dissimilar alloy welding cylinder body. The present application realizes high-quality welding of copper-steel interface by specific surface pretreatment, copper bush structure design and combination of vacuum electron beam sealing and hot isostatic pressing diffusion connection, and has high bonding strength and good sealing property, which meets the use requirements of automobile hydraulic plunger pump cylinder body.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and specifically to a welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block. Background Technology

[0002] Hydraulic piston pumps are primarily used in the automotive industry to provide high-pressure hydraulic oil and control critical functions such as steering and braking systems. A hydraulic piston pump has many core components, with the cylinder block (pump body) being particularly important. The cylinder block contains multiple piston bores to accommodate the pistons and facilitate oil suction and discharge. Copper alloy bushings are embedded within these piston bores, commonly made of tin bronze, lead bronze, or lead-free environmentally friendly copper alloys, such as copper-based alloys containing tin, bismuth, and silver. This reduces friction between the pistons and the cylinder block and improves wear resistance. This structure is commonly found in steel cylinder block designs. Therefore, the complex connection between the copper and steel structures becomes extremely important to meet these requirements.

[0003] With the rapid development of modern industrial technology, traditional single-material systems are no longer sufficient to meet the diversified needs of high-end applications such as new energy vehicles and aerospace technology. Against this backdrop, research on multi-metal composite joining technology is particularly important. Taking the copper-steel composite system as an example, this combination fully leverages the outstanding electrical and thermal conductivity of copper and the excellent mechanical properties and economic advantages of steel. Copper-steel composite joints prepared using advanced joining processes demonstrate significant application value in fields such as automobiles, energy infrastructure, and building structures due to their unique performance combination.

[0004] Compared to fusion welding, solid-state welding and brazing can effectively reduce the generation of weld and heat-affected zone cracks due to their lower welding heat input. However, for some large dissimilar metal joints, which involve numerous welds, traditional solid-state welding or brazing processes are often inefficient and difficult to meet the needs of mass production in engineering. Hot isostatic pressing (HIP), as an advanced welding technology, has many advantages over other welding methods. It involves applying isotropic static pressure to the materials inside a sealed container using high-pressure gas (nitrogen, argon, etc.) as a medium, achieving a dense bond under high temperature and pressure. Compared to traditional solid-state welding, HIP diffusion bonding offers advantages such as higher density, better metallurgical bonding, and higher bond strength in joining dissimilar materials. Due to its significant advantages in diffusion bonding, HIP technology has broad prospects in dissimilar metal welding, especially in practical engineering applications. HIP technology can achieve one-time forming of large dissimilar metal components, ensuring reliable connection quality while greatly improving production efficiency.

[0005] To overcome the shortcomings of existing hot isostatic diffusion welding processes for copper alloys and alloy steels, such as numerous joint defects, low strength, short service life, and poor stability, this invention provides a welding method for dissimilar alloy automotive hydraulic plunger pump cylinder blocks to solve the problems in the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a welding method for the cylinder block of a dissimilar alloy automotive hydraulic plunger pump.

[0007] This invention provides a welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block, comprising the following preparation steps: The alloy steel substrate, copper bushing, and cladding are pretreated. The pretreated alloy steel substrate, copper bushing, and cladding are assembled in sequence, and after assembly, they are placed in a vacuum electron beam welding machine for vacuum sealing. The sealed sample was subjected to hot isostatic pressing, and the cooling rate was controlled. After the process was completed, a sample was taken to obtain a copper-steel dissimilar alloy welded cylinder body. The outer periphery of the copper bushing is fitted with the blind hole of the alloy steel substrate with a small clearance, and an annular groove is formed at the upper end of the copper bushing so that there is a volume expansion zone near the opening of the mating cavity, which is used to contain residual gas after vacuuming before hot isostatic pressing.

[0008] As a preferred aspect, the pretreatment of the aforementioned alloy steel substrate, copper bushing, and cladding is specifically as follows: the alloy steel substrate, copper bushing, and cladding are sanded with sandpaper, then rinsed with deionized water 3-5 times. The rinsed alloy steel substrate, copper bushing, and cladding are then completely immersed in a sodium hydroxide alkaline cleaning solution at 60-80℃ and ultrasonically soaked for 10-15 minutes. After that, they are rinsed with flowing deionized water 3-5 times. Then, the alkaline-washed alloy steel substrate, copper bushing, and cladding are immersed in a room temperature dilute hydrochloric acid solution. The alloy steel substrate is soaked for 5-10 minutes, and the copper bushing and cladding are soaked for 2-5 minutes. After soaking, they are rinsed with deionized water 3-5 times, and then rinsed with anhydrous ethanol 3-5 times. Finally, they are dried to obtain the pretreated alloy steel substrate, copper bushing, and cladding.

[0009] As a preferred aspect, the sodium hydroxide alkaline washing solution is a sodium hydroxide aqueous solution with a concentration of 5-10%.

[0010] As a preferred aspect, the dilute hydrochloric acid solution is a 10-15% aqueous solution of dilute hydrochloric acid.

[0011] As a preferred aspect, an annular inner groove is provided at the upper end of the copper bushing 0.3mm from the end face, with a groove depth of 0.2-0.6mm and a groove width of 0.3mm.

[0012] As a preferred aspect, the vacuum degree of the vacuum seal in the vacuum electron beam welding machine is 1×10⁻⁶.-3 -1×10 - 4 Pa.

[0013] As a preferred aspect, hot isostatic pressing specifically involves heating to 950-960℃ at a rate of 2-5℃ / min, applying a pressure of 120-160MPa, and holding the temperature and pressure for 2-3 hours.

[0014] As a preferred aspect, the cooling rate is 1-2℃ / min, and after cooling to 750-760℃, it is cooled in the furnace to 180-200℃ before being removed from the furnace.

[0015] The present invention has the following advantages: This invention first produces a blind-hole steel substrate with a certain depth, then prepares a copper alloy tube with the same height and diameter as the deep hole, and cuts an annular groove at a certain position from the upper end of the copper tube. A special sleeve is then placed inside, and after assembly, the three components are sealed using vacuum laser electron beam welding to ensure no gas or only a small amount of residual gas between the steel substrate and the copper tube. Finally, the sealed sample is placed in a hot isostatic pressing (HIP) apparatus for welding, ultimately forming a defect-free copper / steel dissimilar material welded cylinder. The complex structure of copper / steel dissimilar materials is connected through the HIP welding method using gas pressure. By creating a groove in the copper tube, even if the pre-weld vacuum cannot completely remove the gas, residual gas can be stored in the groove without affecting the welding quality of the main body. This reduces welding defects caused by residual gas between the copper and steel, achieving metallurgical welding of dissimilar materials between the copper tube and the steel substrate, resulting in a welded cylinder without significant defects. Attached Figure Description

[0016] Figure 1 This is a two-dimensional diagram of the alloy welded cylinder assembly used in an embodiment of the present invention.

[0017] Figure 2 The images show the microstructure of the alloy welded cylinder prepared in Examples 1-2 of this invention.

[0018] Figure 3 This is a microscopic morphology image of the alloy welded cylinder prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0020] In the embodiment, the alloy steel matrix is ​​30CrMoA, the copper bushing is tin bronze, and the cladding is Q235.

[0021] Example 1: A welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block, referenced. Figure 1 ,include: The material dimensions were designed using SolidWorks, and the alloy steel substrate, copper bushing, and cladding were manufactured using a CNC lathe. The inner annular groove of the copper bushing has a depth of 0.2 mm, a width of 0.3 mm, and is 0.3 mm from the top of the copper tube. The alloy steel substrate, copper bushing, and cladding were sanded with sandpaper, then rinsed three times with deionized water. The rinsed alloy steel substrate, copper bushing, and cladding were then completely immersed in a 5% sodium hydroxide aqueous solution at 60°C and ultrasonically soaked for 10 minutes. After that, they were rinsed three times with running deionized water. Then, the alkaline-washed alloy steel substrate, copper bushing, and cladding were immersed in a 10% dilute hydrochloric acid aqueous solution at room temperature. The alloy steel substrate was soaked for 5 minutes, and the copper bushing and cladding were soaked for 2 minutes. After soaking, they were rinsed three times with deionized water, and then rinsed three times with anhydrous ethanol. Finally, they were dried to obtain the pretreated alloy steel substrate, copper bushing, and cladding. The pretreated alloy steel substrate, copper bushing, and cladding are assembled sequentially. After assembly, the assembly is placed in a vacuum electron beam welding machine for vacuum sealing at a vacuum level of 1×10⁻⁶. -3 Pa, the sealed sample is subjected to hot isostatic pressing. The hot isostatic pressing is specifically performed by heating to 950°C at a rate of 2°C / min and a pressure of 120MPa, holding at the temperature and pressure for 2 hours, and then cooling to 750°C at a cooling rate of 1°C / min and then cooling to 180°C in the furnace before taking it out of the furnace. The welded sample is then wire-cut to obtain a tubular structure copper-steel dissimilar alloy welded cylinder.

[0022] Example 2: A welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block, see [link to example]. Figure 1 ,include: The material dimensions were designed using SolidWorks, and the alloy steel substrate, copper bushing, and cladding were manufactured using a CNC lathe. The inner annular groove of the copper bushing has a depth of 0.6 mm, a width of 0.3 mm, and is 0.3 mm from the top of the copper tube. The alloy steel substrate, copper bushing, and cladding were sanded with sandpaper, then rinsed five times with deionized water. The rinsed alloy steel substrate, copper bushing, and cladding were then completely immersed in a 10% sodium hydroxide aqueous solution at 80°C and ultrasonically soaked for 15 minutes. After that, they were rinsed five times with running deionized water. Then, the alkaline-washed alloy steel substrate, copper bushing, and cladding were immersed in a 15% dilute hydrochloric acid aqueous solution at room temperature. The alloy steel substrate was soaked for 10 minutes, and the copper bushing and cladding were soaked for 5 minutes. After soaking, they were rinsed five times with deionized water, and then rinsed five times with anhydrous ethanol. Finally, they were dried to obtain the pretreated alloy steel substrate, copper bushing, and cladding. The pretreated alloy steel substrate, copper bushing, and cladding are assembled sequentially. After assembly, the assembly is placed in a vacuum electron beam welding machine for vacuum sealing at a vacuum level of 1×10⁻⁶. -4Pa, the sealed sample is subjected to hot isostatic pressing. The hot isostatic pressing is specifically performed by heating to 960°C at a rate of 5°C / min and a pressure of 160MPa, holding at the temperature and pressure for 3 hours, and then cooling to 760°C at a cooling rate of 2°C / min and then cooling to 200°C in the furnace before being taken out of the furnace. The welded sample is then wire-cut to obtain a tubular structure copper-steel dissimilar alloy welded cylinder.

[0023] The microstructure of the welded joints of the alloy welded cylinders prepared in Examples 1-2 was examined using an optical microscope. The results are referenced. Figure 2 As can be seen from the figure, the copper atoms diffuse well and there are no obvious defects at the interface. The cylinder body is achieved by hot isostatic pressure welding of alloy copper tubes with inner ring grooves and alloy steel.

[0024] The microstructure of the welded joint of the alloy welded cylinder prepared in Comparative Example 1 was examined using an optical microscope. The results are referenced. Figure 3 As can be seen from the figure, the diffusion of copper atoms is not obvious, and the interface is discontinuous, containing defects such as pores, cracks, and lack of fusion. This indicates that copper atoms have not completely diffused at 850℃.

[0025] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block, characterized in that, The preparation steps include the following: The alloy steel substrate, copper bushing, and cladding are pretreated. The pretreated alloy steel substrate, copper bushing, and cladding are assembled in sequence, and after assembly, they are placed in a vacuum electron beam welding machine for vacuum sealing. The sealed sample was subjected to hot isostatic pressing, and the cooling rate was controlled. After the process was completed, a sample was taken to obtain a copper-steel dissimilar alloy welded cylinder body. The outer periphery of the copper bushing is fitted with the blind hole of the alloy steel substrate with a small clearance, and an annular groove is formed at the upper end of the copper bushing so that there is a volume expansion zone near the opening of the mating cavity, which is used to contain residual gas after vacuuming before hot isostatic pressing.

2. The welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block according to claim 1, characterized in that, The pretreatment of the alloy steel substrate, copper bushing, and cladding is as follows: the alloy steel substrate, copper bushing, and cladding are sanded with sandpaper, then rinsed with deionized water 3-5 times. The rinsed alloy steel substrate, copper bushing, and cladding are then completely immersed in a sodium hydroxide alkaline cleaning solution at 60-80℃ and ultrasonically soaked for 10-15 minutes. After that, they are rinsed with running deionized water 3-5 times. Then, the alkaline-washed alloy steel substrate, copper bushing, and cladding are immersed in a dilute hydrochloric acid solution at room temperature. The alloy steel substrate is soaked for 5-10 minutes, and the copper bushing and cladding are soaked for 2-5 minutes. After soaking, they are rinsed with deionized water 3-5 times, and then rinsed with anhydrous ethanol 3-5 times. Finally, they are dried to obtain the pretreated alloy steel substrate, copper bushing, and cladding.

3. The welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block according to claim 2, characterized in that, The sodium hydroxide alkaline washing solution is a 5-10% sodium hydroxide aqueous solution.

4. The welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block according to claim 2, characterized in that, The dilute hydrochloric acid solution is a 10-15% aqueous solution of dilute hydrochloric acid.

5. The welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block according to claim 1, characterized in that, An annular inner groove is provided at the upper end of the copper bushing, 0.3 mm from the end face. The groove is 0.2-0.6 mm deep and 0.3 mm wide.

6. The welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block according to claim 1, characterized in that, The vacuum degree of the vacuum seal in the vacuum electron beam welding machine is 1×10⁻⁶. -3 -1×10 -4 Pa.

7. The welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block according to claim 1, characterized in that, Hot isostatic pressing (HIP) involves heating the material at a rate of 2-5℃ / min to 950-960℃, applying a pressure of 120-160MPa, and holding the temperature and pressure for 2-3 hours.

8. The welding method for a dissimilar alloy automotive hydraulic plunger pump cylinder block according to claim 1, characterized in that, The cooling rate is 1-2℃ / min. After cooling to 750-760℃, the furnace is cooled to 180-200℃ before being removed from the furnace.

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