Assembly method of internal combustion engine nozzle

Abstract

The invention relates to assembly of parts of an internal combustion engine, in particular to an assembly method of a nozzle of the internal combustion engine, which comprises the following steps: S1, pretreating a connecting surface of a nozzle body and a nozzle sleeve of the nozzle of the internal combustion engine, and removing an oxide film and stains on the connecting surface; s2, the nozzle body and the nozzle sleeve are clamped and fixed to friction welding equipment, friction welding process parameters are set, and the nozzle body and the nozzle sleeve are connected and fixed through friction welding; s3, after friction welding is completed, post-welding tempering treatment is conducted, and the residual stress of a welding joint is reduced; and S4, cooling to room temperature to obtain a finished product. The nozzle body and the nozzle sleeve can be effectively connected, and the strength of the connector is high.

Description

Technical Field

[0001] The invention relates to the assembly of parts of an internal combustion engine, and in particular to an assembly method of a nozzle of an internal combustion engine. Background Art

[0002] The nozzles used in internal combustion engines need to be resistant to high temperatures, and have excellent oxidation resistance and corrosion resistance in high temperature environments, and the performance requirements for the nozzle sleeve are higher. Generally, the nozzles of internal combustion engines are composite nozzles, in which the nozzle body is made of high-carbon high-alloy tool steel with high hardness, wear resistance and hot hardness, and the nozzle sleeve is made of nickel-based high-temperature alloy with excellent oxidation resistance and corrosion resistance. The mechanical properties of these two materials are quite different. For workpieces with this structure of nozzles, conventional fusion welding methods cannot be used. When brazing is used for welding, pores are prone to appear, and a good connection of the joint cannot be achieved. Summary of the invention

[0003] The object of the present invention is to provide an assembly method for an internal combustion engine nozzle, which can realize effective connection between a nozzle body and a nozzle sleeve, and the strength of the connection joint is relatively high.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a method for assembling an internal combustion engine nozzle, which comprises the following steps: S1, pre-treating the connection surface between the nozzle body and the nozzle sleeve of the internal combustion engine nozzle to remove the oxide film and stains on the connection surface; S2, fixing the nozzle body and the nozzle sleeve clamp on the friction welding equipment, setting the friction welding process parameters so that the nozzle body and the nozzle sleeve are connected and fixed by friction welding; S3, after the friction welding is completed, post-weld tempering treatment is performed to reduce the residual stress of the welded joint; S4, cooling to room temperature to obtain a finished product.

[0005] Furthermore, the pretreatment of S1 includes a machining process and a cleaning process. The oxide film on the connecting surface of the nozzle body and the nozzle sleeve is first removed by the machining process, and then the stains on the connecting surface of the nozzle body and the nozzle sleeve are removed by the cleaning process.

[0006] Furthermore, the friction welding process parameters in S2 include: the workpiece connection surface pressure in the stable friction stage is 200~450MPa, the workpiece connection surface pressure in the upsetting stage is 1.2~3 times the workpiece connection surface pressure in the stable friction stage, the rotation speed is 1000~2000rpm, and the welding shortening is 3~8mm.

[0007] Furthermore, the post-weld tempering treatment temperature in S3 is 600-750° C., and the post-weld tempering treatment time is 100-200 min.

[0008] Furthermore, the cooling method in S4 is oil cooling.

[0009] Furthermore, the material of the nozzle body in S1 is W6Mo5Cr4V2 alloy, and the material of the nozzle sleeve is SCo65 alloy.

[0010] The present invention has the following unexpected beneficial effects: the present invention realizes effective connection between the nozzle body and the nozzle sleeve by friction welding, and reduces the residual stress of the connection joint by post-weld tempering treatment. In addition, by limiting the friction welding process parameters and the post-weld tempering process parameters, it is ensured that the entire connection surface of the nozzle body and the nozzle sleeve is welded through and no obvious cracking occurs in the joint area, the connection joint has high strength, and the position of the weld after forming can be accurately controlled to ensure the margin of subsequent machining of the internal combustion engine nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A flow chart of an assembly method of an internal combustion engine nozzle according to an embodiment of the present invention is shown; Figure 2 A schematic diagram showing the clamping of the nozzle body and the nozzle sleeve on the friction welding equipment according to the embodiment of the present invention is shown; Figure 3 A schematic diagram of the morphology of the internal combustion engine nozzle after stretching in the performance detection test according to an embodiment of the present invention is shown.

[0012] In the figure, 1 is the nozzle body, 2 is the nozzle sleeve, 3 is the rotating fixture, and 4 is the moving fixture. DETAILED DESCRIPTION

[0013] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0014] In one embodiment, see Figure 1 As shown, the present invention provides a method for assembling an internal combustion engine nozzle, which comprises the following steps: S1, pre-treat the connection surface of the nozzle body and nozzle sleeve of the internal combustion engine nozzle to remove the oxide film and stains on the connection surface. Because the oxide film and stains on the connection surface will affect the welding quality. The oxide film may prevent good fusion between metals, and the stains may cause defects such as pores during the welding process. Generally, mechanical grinding can be used, such as grinding the connection surface with sandpaper or grinding wheel to remove the surface oxide layer and dirt, or chemical cleaning can be used to clean the connection surface with an appropriate cleaning agent.

[0015] S2, fix the nozzle body and nozzle sleeve clamp on the friction welding equipment, set the friction welding process parameters, so that the nozzle body and nozzle sleeve are connected and fixed by friction welding. Friction welding is a method that uses the heat generated by the friction between the end faces of the workpieces to make the ends reach a thermoplastic state, and then quickly forges to complete the welding. In this process, it is necessary to set appropriate friction welding process parameters.

[0016] S3, after friction welding is completed, post-weld tempering treatment is performed to reduce the residual stress of the welded joint. After friction welding is completed, residual stress will exist at the welded joint due to the thermal stress generated during the welding process. The residual stress may cause defects such as cracks in the welded joint during use. The residual stress of the welded joint can be reduced by post-weld tempering treatment. The tempering temperature is generally determined according to the properties of the nozzle material, and is usually maintained within a certain temperature range for a period of time so that the internal structure of the material can be adjusted and the stress can be released.

[0017] S4, cooling to room temperature to obtain the finished product. During the cooling process, the internal structure of the material will be further stabilized, ensuring the dimensional accuracy and performance of the nozzle.

[0018] Generally, the nozzle of an internal combustion engine is a composite nozzle, in which the material used for the nozzle body is a high-carbon high-alloy tool steel with high hardness, wear resistance and hot hardness, and the material used for the nozzle sleeve is a nickel-based high-temperature alloy with excellent oxidation resistance and corrosion resistance. The mechanical properties of these two materials are quite different, and their weldability is poor. Conventional melting welding methods cannot obtain welded joints with excellent performance. When using the laser welding method, there may be problems with incomplete welding; when using the brazing method, there may be a large number of gaps in the weld and the joint connection strength is low. The present invention, taking into account the structural shape of the internal combustion engine nozzle, the welding performance of the material, the physical and chemical properties of the material and other factors, proposes a solid phase welding method, provides a combination of friction welding and post-weld tempering to connect the nozzle body and the nozzle sleeve, and can effectively avoid the above-mentioned series of problems after the joint is welded.

[0019] The present invention realizes effective connection between the nozzle body and the nozzle sleeve by friction welding, and reduces the residual stress of the connection joint by post-weld tempering treatment. In addition, by limiting the friction welding process parameters and the post-weld tempering process parameters, it is ensured that the entire connection surface of the nozzle body and the nozzle sleeve is welded through and no obvious cracking occurs in the joint area. The connection joint has high strength, and the position of the weld after forming can be accurately controlled to ensure the margin of subsequent machining of the internal combustion engine nozzle.

[0020] In a preferred embodiment, the pretreatment of S1 includes a machining process and a cleaning process. The oxide film on the connecting surface of the nozzle body and the nozzle sleeve is first removed by the machining process, and then the stains on the connecting surface of the nozzle body and the nozzle sleeve are removed by the cleaning process.

[0021] Through machining, such as using precision cutting tools or grinding equipment, the oxide film on the connection surface can be accurately removed or ground off to expose the fresh metal surface underneath. This ensures a tighter and higher-quality bond between the connection surfaces during the subsequent friction welding process.

[0022] After the machining process is completed to remove the oxide film, the cleaning process is carried out immediately. The purpose of this process is to remove the stains remaining on the connection surface of the nozzle body and the nozzle sleeve. These stains may come from oil, metal debris, dust, etc. during the processing process. If they are not removed, they will also cause many problems in the subsequent assembly process. For example, during friction welding, stains may carbonize at high temperatures and mix into the welded joint, affecting the strength and purity of the joint.

[0023] The cleaning process can use appropriate cleaning agents, such as special metal cleaning agents, combined with advanced tools such as ultrasonic cleaning equipment, to more efficiently and thoroughly remove stains on the connection surface, thereby providing a clean and good starting condition for subsequent assembly steps.

[0024] This preferred implementation method of dividing the pretreatment into a machining process and a cleaning process can more specifically solve the problem of different types of impurities existing on the connection surface, and help improve the overall quality and reliability of the internal combustion engine nozzle assembly.

[0025] In a preferred embodiment, the friction welding process parameters in S2 include: the workpiece connection surface pressure in the stable friction stage is 200~450MPa, the workpiece connection surface pressure in the upsetting stage is 1.2~3 times the workpiece connection surface pressure in the stable friction stage, the rotation speed is 1000~2000rpm, and the welding shortening is 3~8mm.

[0026] The pressure range of the workpiece connection surface in the stable friction stage is set at 200~450MPa. This pressure is a very critical parameter in the friction welding process. In the stable friction stage, the appropriate pressure can ensure that sufficient friction is generated between the workpiece connection surfaces, so that the connection surfaces can quickly heat up to reach a thermoplastic state. If the pressure is too low, the friction is insufficient, and the connection surface heats up too slowly, the temperature required for welding may not be reached; and if the pressure is too high, it may cause excessive wear of the connection surface or even damage the workpiece, causing cracks in the joint area. For example, when the pressure is 200MPa, for some smaller or softer nozzles, it can ensure that the connection surface heats up while avoiding excessive pressure on the workpiece; when the pressure is 450MPa, it is suitable for nozzles with harder materials or larger sizes to ensure that there is enough friction to heat up the connection surface.

[0027] The pressure of the workpiece connection surface in the upsetting stage is 1.2~3 times that of the workpiece connection surface in the stable friction stage. The upsetting stage is to make the connection surface tightly bonded by applying a large pressure after the connection surface reaches the thermoplastic state. Since the metals that are already in the thermoplastic state need to be better fused together at this stage, a higher pressure is required than in the stable friction stage. Assuming that the pressure in the stable friction stage is 200MPa, the pressure in the upsetting stage is between 240~600MPa. Higher pressure can make the metal on the connection surface fully flow and fuse, fill the possible small gaps, and thus improve the quality of the welded joint.

[0028] The rotation speed also plays an important role in the friction welding process. The appropriate rotation speed can ensure that the friction between the connection surfaces is uniform and sufficient. If the rotation speed is too low, the friction of the connection surface is not uniform enough, which may cause the local temperature to be too high or too low, affecting the welding quality; if the rotation speed is too high, it may produce unfavorable factors such as centrifugal force, making the connection process unstable. For example, at a rotation speed of 1000rpm, for some nozzles with high precision requirements, it can provide a relatively smooth friction process; while a rotation speed of 2000rpm is suitable for some situations that require rapid heating, or when the connection surface area is large, it can ensure sufficient friction heat generation.

[0029] The welding shortening is a parameter that measures the degree of plastic deformation of the metal on the connection surface during the upsetting and other stages of the welding process. This parameter reflects the fusion of the metal on the connection surface. If the welding shortening is too small, it may mean that the metal on the connection surface is not fully fused; if the welding shortening is too large, it may cause the workpiece size to not meet the requirements, or cause greater stress inside the metal. When the welding shortening is 3mm, for some nozzles with simpler structures, it may be able to meet the connection quality requirements; and the welding shortening of 8mm may be suitable for nozzles with complex structures and higher connection strength requirements, to ensure a good combination between the connection surfaces through greater plastic deformation.

[0030] In a preferred embodiment, the post-weld tempering treatment temperature in S3 is 600-750° C., and the post-weld tempering treatment time is 100-200 min.

[0031] The appropriate tempering temperature can promote a favorable change in the metal structure at the welded joint. When the temperature is 600°C, it is close to the lower limit. At this time, for some nozzle welded joints with small residual stress or relatively soft materials, the internal structure can be adjusted at a relatively mild temperature to release the stress to a certain extent. When the temperature reaches 750°C, it is close to the upper limit. For those nozzles with large residual stress, harder materials or higher welding quality requirements, higher temperatures can help to more fully change the lattice structure inside the metal, further eliminate residual stress, and improve the stability and quality of the welded joint.

[0032] The post-weld tempering treatment time is set to 100~200min. Sufficient tempering treatment time is one of the key factors to ensure the tempering effect. At 100min, it is close to the lower limit. For some welded joints with small size or relatively simple residual stress distribution, this period of time may be enough for the metal to complete the adjustment of the internal structure at the selected tempering temperature and release the stress. When the time reaches 200min, it is close to the upper limit. For larger welded joints or nozzles with more complex residual stress conditions, a longer time can ensure a more complete tempering process, make the internal structure of the metal more uniform, and eliminate the residual stress more thoroughly.

[0033] In a preferred embodiment, the cooling method in S4 is oil cooling. Oil cooling has unique advantages over other methods such as natural cooling. When the weld joint completes the tempering treatment, its internal temperature is relatively high. If natural cooling is used, the cooling speed is relatively slow, which may cause surface oxidation during the cooling process, affecting the final quality of the weld joint. The cooling speed of oil cooling is moderate. It will not cause defects such as cracks in the weld joint due to excessive cooling like water cooling (the cooling speed of water cooling is too fast, and the thermal stress inside the metal changes dramatically), nor will it cool too slowly like natural cooling. Oil cooling can cool the weld joint to room temperature at a more appropriate speed, which helps to maintain the good organizational structure of the weld joint after the tempering treatment, further stabilize the performance of the weld joint, and thus obtain a higher quality finished internal combustion engine nozzle.

[0034] In a preferred embodiment, the material of the nozzle body in S1 is W6Mo5Cr4V2 alloy, and the material of the nozzle sleeve is SCo65 alloy.

[0035] W6Mo5Cr4V2 alloy is a kind of high-speed steel with extremely high hardness. This allows the nozzle body made of this material to withstand the wear caused by the high-speed erosion of fuel or other media during the operation of the internal combustion engine during long-term use, effectively maintain the shape and dimensional accuracy of the nozzle, and extend its service life. In a high-temperature environment, the W6Mo5Cr4V2 alloy can still maintain a high hardness. When the internal combustion engine is running, the temperature around the nozzle body will rise, and the hot hardness of the W6Mo5Cr4V2 alloy ensures that it will not soften significantly at high temperatures, so that it can stably perform its injection function and ensure accurate injection of fuel and other media. Although the hardness is very high, the W6Mo5Cr4V2 alloy is not a brittle material and has a certain toughness, which means that in the case of some impact forces (such as vibration during the operation of the internal combustion engine), the nozzle body is not prone to brittle fracture and can maintain its structural integrity.

[0036] SCo65 alloy generally has excellent high temperature resistance. In internal combustion engines, the nozzle sleeve will also be in a high temperature environment. The alloy can withstand high temperatures without deformation, softening and other undesirable phenomena, providing a stable support structure for the normal operation of the nozzle. There may be some corrosive media in the working environment of the internal combustion engine, such as impurities in the fuel, combustion products, etc. The corrosion resistance of SCo65 alloy enables it to resist the erosion of these corrosive factors, prevent corrosion damage to the nozzle sleeve, and thus affect the performance of the entire nozzle. SCo65 alloy is selected as the nozzle sleeve material, and it is matched with the nozzle body made of W6Mo5Cr4V2 alloy. From the perspective of the thermal expansion coefficient and mechanical properties of the materials, the two can work well together. For example, their thermal expansion coefficients are relatively close, and they can expand or contract synchronously when the temperature changes, reducing the problems of fitting clearance changes and stress concentration caused by the difference in thermal expansion and contraction, and ensuring the close fit and stable connection between the nozzle body and the nozzle sleeve.

[0037] The following is an explanation with reference to specific examples.

[0038] Embodiment 1, a method for assembling an internal combustion engine nozzle, comprising the following steps: S1, first remove the oxide film on the connection surface of the nozzle body and the nozzle sleeve by a machining process, and then remove the stains on the connection surface of the nozzle body and the nozzle sleeve by a cleaning process. Wherein, the material of the nozzle body is W6Mo5Cr4V2 alloy, and the material of the nozzle sleeve is SCo65 alloy.

[0039] S2, fix the nozzle body and the nozzle set clamp on the friction welding equipment, specifically, see Figure 2As shown, the nozzle body 1 is clamped and fixed on the rotating fixture 3 of the friction welding equipment, and the nozzle sleeve 2 is clamped and fixed on the moving fixture of the friction welding equipment. The friction welding equipment drives the nozzle body 1 to rotate through the spindle motor and the rotating fixture 3, and the hydraulic system at the moving end drives the nozzle sleeve 2 to gradually approach and press on the high-speed rotating nozzle body 1 through the slide and the moving fixture 4.

[0040] The friction welding process parameters were set to 1400 rpm, 4.5 MPa initial friction pressure, 9 MPa secondary friction pressure, and braking when the interface shortening reached 7 mm in the stable friction stage, while applying 10 MPa upsetting pressure and maintaining the upsetting pressure for 5 seconds, so that the nozzle body and the nozzle sleeve were fixed by friction welding.

[0041] S3, after the friction welding is completed, post-weld tempering treatment is carried out, the post-weld tempering treatment temperature is 580℃, and the post-weld tempering treatment time is 120min to reduce the residual stress of the weld joint.

[0042] S4, the oil is cooled to room temperature to obtain the finished product.

[0043] The test results show that the friction welding joint strength between the nozzle body 1 and the nozzle sleeve 2 is ≥700MPa. Figure 3 As shown in the figure, the fracture after stretching is not located at the connection joint, but on the parent material matrix (W6Mo5Cr4V2 alloy).

[0044] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or change made by a person skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A method for assembling an internal combustion engine nozzle, characterized in that: The steps include: S1, pre-treating the connection surface between the nozzle body and the nozzle sleeve of the internal combustion engine nozzle to remove the oxide film and stains on the connection surface; S2, fixing the nozzle body and the nozzle sleeve clamp on the friction welding equipment, setting the friction welding process parameters so that the nozzle body and the nozzle sleeve are connected and fixed by friction welding; S3, after the friction welding is completed, post-weld tempering treatment is performed to reduce the residual stress of the welded joint; S4, cooling to room temperature to obtain a finished product.

2. The method for assembling an internal combustion engine nozzle according to claim 1, characterized in that: The pretreatment of S1 includes a machining process and a cleaning process. The oxide film on the connecting surface of the nozzle body and the nozzle sleeve is firstly removed by the machining process, and then the stains on the connecting surface of the nozzle body and the nozzle sleeve are removed by the cleaning process.

3. The method for assembling an internal combustion engine nozzle according to claim 1, characterized in that: The friction welding process parameters in S2 include: the workpiece connection surface pressure in the stable friction stage is 200~450MPa, the workpiece connection surface pressure in the upsetting stage is 1.2~3 times the workpiece connection surface pressure in the stable friction stage, the rotation speed is 1000~2000rpm, and the welding shortening is 3~8mm.

4. The method for assembling an internal combustion engine nozzle according to claim 1, characterized in that: The post-weld tempering treatment temperature in S3 is 600-750° C., and the post-weld tempering treatment time is 100-200 min.

5. The method for assembling an internal combustion engine nozzle according to claim 1, characterized in that: The cooling method in S4 is oil cooling.

6. The method for assembling an internal combustion engine nozzle according to claim 1, characterized in that: The material of the nozzle body in S1 is W6Mo5Cr4V2 alloy, and the material of the nozzle sleeve is SCo65 alloy.

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