Method for friction welding of a large steel piston

Abstract

The present application belongs to the technical field of internal combustion engine piston friction welding, and relates to a steel large piston friction welding method, which is used for welding a large-bore steel piston with a bore diameter of 160 mm or more and a welding area of 8000 mm2 or more. The large-bore steel piston comprises a piston head and a piston skirt, and the finished outer surface of the large-bore steel piston is provided with a weight-reducing groove and a plurality of ring grooves. The method comprises the steps of preparing a blank, machining a welding groove, preheating and welding. The method is simple and convenient to operate. The existing inertia friction welding machine for small-size piston welding is used to realize inertia friction welding of the steel large piston with a bore diameter of more than 160 mm and a welding area of 8000 mm2 or more, and the welding strength and performance can fully meet the design requirements of the large piston.

Description

Technical Field

[0001] This invention relates to the field of friction welding technology for internal combustion engine pistons, and more specifically, to a friction welding method for large steel pistons, which is particularly applicable to the marine electric piston industry, such as generator sets, ships, and yachts. Background Technology

[0002] As a critical Class A component of an engine, the piston's function is to withstand combustion gas pressure and, through the piston pin, drive the connecting rod to rotate the crankshaft and output power. Pistons operate under conditions of high temperature, high pressure, high speed, and poor lubrication, enduring alternating mechanical and thermal loads, direct contact with high-temperature gases, and chemical corrosion from the combustion gases. With the increasing combustion pressure and power output of internal combustion engines, and stricter emission requirements, higher demands are placed on engines and their components. Traditional aluminum pistons can no longer meet the needs of heavy-duty internal combustion engines, and the replacement of aluminum pistons with steel pistons in heavy-duty internal combustion engines is an irreversible trend in piston development.

[0003] Meanwhile, pistons for older heavy-duty internal combustion engines in marine electrical industries such as generator sets, ships, and yachts are currently mainly connected by hinged bolts due to limitations in existing friction welding equipment (small-scale equipment cannot meet the welding capabilities, meaning there is currently no equipment in China to weld pistons with a cylinder diameter of 160mm and a welding area of ​​8000mm² or more). Hinged connections are difficult to process, have low strength, and are prone to bolt loosening, requiring regular inspection and replacement. Sometimes, untimely replacement can lead to detachment and serious accidents. Furthermore, hinged connections increase the overall height of the piston, further increasing the engine height and weight, resulting in greater fuel consumption and energy waste. Therefore, friction-welded integrated pistons with a cylinder diameter greater than 160mm and a welding area of ​​8000mm² or more have become a key research focus for major OEMs, but no related technologies have yet emerged for industrial application.

[0004] Therefore, there is an urgent need in this field to develop a friction welding method for large steel pistons. Summary of the Invention

[0005] The purpose of this invention is to provide a friction welding method for steel large pistons. By adopting a special external welding surface structure design and induction preheating welding surface, this method enables inertial friction welding of steel large pistons with a cylinder diameter greater than 160mm and a welding area of ​​more than 8000mm² on existing small-scale piston welding equipment (i.e., existing small-scale inertial friction welding machines), while ensuring that the welding strength and performance fully meet the design requirements of the large piston.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A friction welding method for steel pistons with a cylinder diameter of 160mm or more and a welding area of ​​8000mm² or more is disclosed. The large-diameter steel piston includes a piston head and a piston skirt, and the finished outer surface of the large-diameter steel piston is provided with a weight-reducing groove and several annular grooves. The friction welding method includes the following steps: S1. Preparing blanks: Prepare piston head blanks and piston skirt blanks separately; S2. Machining welding grooves: Machining a welding groove on the outer welding surface of the piston head blank and the piston skirt blank respectively, so that the welding groove corresponds to the opening position of the weight reduction groove or ring groove on the outer surface of the finished product, and the depth of the two welding grooves is less than the depth of the corresponding weight reduction groove or ring groove, so that the total height of the special groove formed by the two welding grooves after welding is less than the groove height of the corresponding weight reduction groove or ring groove. S3. Preheating: The piston head blank and piston skirt blank with welding grooves are respectively loaded into the corresponding fixtures of the existing inertial friction welding machine, and the outer welding surface and inner welding surface of the piston head blank and piston skirt blank are preheated simultaneously by an induction preheating device. S4. Welding: When the temperature of the outer and inner welding surfaces of the piston head blank and piston skirt blank reaches the preset temperature, the rotation speed and pressure required for friction welding of the large-diameter steel piston are reduced to the capability range of the existing inertial friction welding machine. At this time, the induction preheating device is removed, and the existing inertial friction welding machine is started to complete the welding of the large-diameter steel piston and obtain the welded semi-finished product.

[0008] Furthermore, the welded semi-finished product undergoes fine processing (a small amount of processing is performed on the welded groove to form the corresponding piston ring groove or weight reduction groove), full-surface phosphating, screen printing of nano-coating on the skirt, and packaging and inspection to form the final finished piston.

[0009] Preferably, the ring groove includes a first ring groove, a second ring groove, or a third ring groove for mounting piston rings and a weight-reducing groove for reducing piston weight.

[0010] Preferably, in step S2, the upper and lower wall openings of the welding groove are provided with deburring chamfers.

[0011] Preferably, in step S4, the welding shrinkage of the piston head blank and piston skirt blank is 3-10 mm.

[0012] Preferably, in step S4, the preset temperature is 600-1000℃.

[0013] Preferably, in step S3, the induction preheating device includes a trolley guide rail, a track trolley, a heating coil, and a water-cooled integrated IGBT power supply cabinet. The trolley guide rail is located on one side of the existing inertial friction welding machine and is correspondingly located between the two clamps on the existing inertial friction welding machine. The track trolley is slidably connected to the trolley guide rail. The water-cooled integrated IGBT power supply cabinet is fixed on the trolley guide rail. Two parallel heating coils are fixed on the track trolley by brackets, and the heating coils are electrically connected to the water-cooled integrated IGBT power supply cabinet.

[0014] Preferably, in step S3, when the induction preheating device preheats the outer and inner welding surfaces of the piston head blank and the piston skirt blank, the two heating coils are respectively close to the outer and inner welding surfaces of the piston head blank and the piston skirt blank, and the distance between the heating coils and the corresponding outer and inner welding surfaces is 1-2 mm.

[0015] Preferably, in step S3, the induction preheating device includes an induction power supply cabinet, a truss control cabinet, and a truss installed above the existing inertial friction welding machine. A translation seat is slidably connected to the truss via a gear rack structure I and a linear module I. A lifting seat is slidably connected to the translation seat via a gear rack structure II and a linear module II. Two heating coils II are adjustablely connected to the bottom of the lifting seat. The induction power supply cabinet is electrically connected to the heating coils II. Both the gear rack structure I and the gear rack structure II are driven by motors, and each motor is electrically connected to the truss control cabinet. When the induction preheating device preheats the outer and inner welding surfaces of the piston head blank and the piston skirt blank, the two heating coils II are moved between the two clamps on the existing inertial friction welding machine, and the distance between the heating coils II and the corresponding outer and inner welding surfaces is adjusted to 1-2 mm.

[0016] Preferably, the first gear rack structure includes a linear rack fixed horizontally on the front side wall of the truss and a gear meshing with the linear rack. The translation seat is located above the truss, and a front side plate is provided on the front side of the translation seat. A motor is fixed in the middle of the front side plate. The output shaft of the motor is connected to the gear. The upper and lower ends of the rear side of the front side plate are slidably connected to the slide rails of two linear modules horizontally arranged on the front side of the truss through the sliders of the two linear modules. The second gear rack structure includes a linear rack vertically arranged on the lifting seat and a gear meshing with the linear rack. A motor is fixed on the translation seat. The output shaft of the motor is connected to the gear. The front side plate of the translation seat is fixedly connected to the slider of the linear module through a connecting plate. The slide rail of the linear module is vertically fixed on the lifting seat.

[0017] Preferably, the bottom of the lifting seat is provided with an installation plate, and two linear modules three are correspondingly arranged below the installation plate. Each of the sliders of the two linear modules three is connected to a heating coil two through a connecting rod. The linear modules three are driven by a motor, and the motor of the linear modules three is electrically connected to the truss control cabinet.

[0018] The present invention also includes other components that enable its normal use, all of which are conventional means in the art. In addition, devices or components not limited in the present invention, such as water-cooled integrated IGBT power cabinets, induction power cabinets, truss control cabinets, inertial friction welding machines, etc., all adopt existing technologies in the art.

[0019] Compared with the prior art, the invention has the following beneficial effects: The present invention has a simple process and is easy to operate. It realizes the inertial friction welding of large steel pistons with a cylinder diameter greater than 160mm and a welding area of ​​more than 8000mm² using an existing small-sized piston welding inertial friction welding machine, and can ensure that the welding strength and performance fully meet the design requirements of the large piston. Attached Figure Description

[0020] The invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a process flow diagram of the present invention in Example 1; Figure 2 This is a schematic diagram of the piston head blank after the welding groove is processed according to the present invention in Example 1; Figure 3 This is a schematic diagram of the piston skirt blank after the welding groove is processed according to the present invention in Example 1; Figure 4 This is a schematic diagram of the overall structure of the semi-finished product after welding according to the present invention in Example 1; Figure 5 This is a schematic diagram of the processing positions of the semi-finished product with a special groove after welding and the finished product annular groove and weight-reducing groove in Example 1 of the present invention; Figure 6 This is a schematic diagram of a cross-sectional sample of the semi-finished product after welding according to the present invention in Example 1; Figure 7 This is a schematic diagram showing the arrangement of the induction preheating device and the existing inertial friction welding equipment in Example 1; Figure 8 This is a schematic diagram of the overall structure of the induction preheating device in Example 1; Figure 9 This is a schematic diagram showing the arrangement of the induction preheating device and the existing inertial friction welding equipment in Example 2; Figure 10 yes Figure 9 Enlarged schematic diagram of part A in the diagram; Figure 11 yes Figure 9 Enlarged schematic diagram of section B in the diagram; Figure 12 This is a schematic diagram of a cross-sectional sample of the semi-finished product after welding according to the present invention in Example 3. Detailed Implementation

[0021] The invention will now be clearly described in conjunction with the accompanying drawings and specific embodiments. This description is merely for illustrative purposes and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made by those skilled in the art based on the embodiments of the invention without inventive effort to obtain all other embodiments should be included within the scope of protection of the invention.

[0022] Example 1 like Figures 1-8 As shown, this embodiment provides a friction welding method for a large steel piston, used to weld a large-diameter steel piston with a finished cylinder diameter of 175mm, an outer diameter of 178.5mm and an inner diameter of 150mm on the outer welding surface of the friction-welded semi-finished product, an outer diameter of 91mm and an inner diameter of 68mm on the inner welding surface, and an original welding area of ​​10220mm². The large-diameter steel piston includes a piston head and a piston skirt, and the finished outer surface of the large-diameter steel piston is provided with a weight reduction groove 4 and three annular grooves 5. The annular grooves include a first annular groove, a second annular groove, or a third annular groove for installing piston rings.

[0023] Please see Figure 1 The above friction welding method includes the following steps: S1. Preparation of blanks: Prepare piston head blank 1 and piston skirt blank 2 respectively; S2, Machining welding groove 3: such as Figure 2 As shown in Figure 3, a welding groove with a height of 2 mm and a depth of 6 mm is machined on the outer welding surface of the piston head blank and the piston skirt blank, respectively. The upper and lower walls of the welding groove are provided with deburring chamfers of (-0.1, -0.4) so ​​that the welding groove corresponds to the opening position of the annular groove three on the outer surface of the finished product (see [reference]). Figure 5 The height of the annular groove three is 3mm and the depth is 7mm. The total height of the special groove 6 formed by the two welding grooves after welding is 1mm. S3. Preheating: The piston head blank and piston skirt blank with welding grooves are respectively loaded into the corresponding fixtures of the existing inertial friction welding machine 7 (model MTI 300B), and the outer welding surface and inner welding surface of the piston head blank and piston skirt blank are preheated simultaneously by an induction preheating device. S4. Welding: When the temperature of the outer and inner welding surfaces of the piston head blank and piston skirt blank reaches 600-1000℃, the rotational speed and pressure required for friction welding of the large-diameter steel piston are reduced to the capability range of the existing inertial friction welding machine. At this point, the induction preheating device is removed, and the existing inertial friction welding machine is started to complete the welding of the large-diameter steel piston, obtaining the welded semi-finished product (e.g., Figure 4 , Figure 5 As shown), its cross-sectional sample is shown. Figure 6 .

[0024] By adopting the above-mentioned friction welding method, the welding shrinkage of the piston head blank and piston skirt blank is 5mm, and the actual welding area of ​​the large-diameter steel piston is reduced to 8790mm².

[0025] The above-mentioned welded semi-finished products are then subjected to fine processing (a small amount of further processing of the welded grooves to form corresponding piston ring grooves or weight reduction grooves), full-surface phosphating, skirt screen printing nano-coating, packaging and inspection, and finally formed into the finished piston.

[0026] like Figure 7 , Figure 8 As shown, in this embodiment, the induction preheating device includes a trolley guide rail 8, a track trolley 9, heating coils 10, and a water-cooled integrated IGBT power supply cabinet 11. The trolley guide rail is located on one side of the existing inertial friction welding machine and is correspondingly positioned between the two clamps on the existing inertial friction welding machine. The track trolley is slidably connected to the trolley guide rail, and the water-cooled integrated IGBT power supply cabinet is fixed to the trolley guide rail. Two parallel heating coils are fixed to the track trolley via brackets, and the heating coils are electrically connected to the water-cooled integrated IGBT power supply cabinet. The power supply in the water-cooled integrated IGBT power supply cabinet is a SHPS50kW / 10-20kHz power supply, i.e., rated power 50KV, rated frequency 10-20kHz, supplied by Luoyang Shenghua Induction Heating Co., Ltd.

[0027] Continuing with the above embodiment, in step S3, when the induction preheating device preheats the outer and inner welding surfaces of the piston head blank and the piston skirt blank, the two heating coils are respectively close to the outer and inner welding surfaces of the piston head blank and the piston skirt blank, and the distance between the heating coils and the corresponding outer and inner welding surfaces is 1-2mm.

[0028] Example 2 like Figure 9 , Figure 10 and Figure 11 As shown, the only difference between this embodiment and Embodiment 1 is that: In step S3, the induction preheating device includes an induction power supply cabinet 12, a truss control cabinet 13, and a truss 14 mounted above the existing inertial friction welding machine 7. A translation seat 15 is slidably connected to the truss via a gear rack structure I and a linear module I. A lifting seat 16 is slidably connected to the translation seat via a gear rack structure II and a linear module II. Two heating coils II 17 are adjustablely connected to the bottom of the lifting seat. The induction power supply cabinet is electrically connected to the heating coils II. Both the gear rack structure I and the gear rack structure II are driven by motors, and each motor is electrically connected to the truss control cabinet. When the induction preheating device preheats the outer and inner welding surfaces of the piston head blank and the piston skirt blank, the two heating coils II are moved between the two clamps on the existing inertial friction welding machine, and the distance between the heating coils II and the corresponding outer and inner welding surfaces is adjusted to 1-2 mm.

[0029] In this embodiment, the first gear rack structure includes a linear rack 18 horizontally fixed on the front side wall of the truss and a gear 1 (not shown in the figure) meshing with the linear rack 1. The translation seat is located above the truss, and a front side plate is provided on the front side of the translation seat. A motor 1 (not shown in the figure) is fixed in the middle of the front side plate. The output shaft of the motor 1 is connected to the gear 1 through a transmission. The upper and lower ends of the rear side of the front side plate are slidably connected to the slide rails 19 of the two linear modules 1 horizontally arranged on the front side of the truss through the sliders of the two linear modules 1, respectively. The second gear rack structure includes a linear rack 20 vertically arranged on the lifting seat and a gear 21 meshing with the linear rack 2. A motor 2 (not shown in the figure) is fixed on the translation seat. The output shaft of the motor 2 is connected to the gear 2 through a transmission. The front side plate of the translation seat is fixedly connected to the slider of the linear module 2 through a connecting plate 22. The slide rail 23 of the linear module 2 is vertically fixed on the lifting seat.

[0030] Specifically, the bottom of the lifting seat is provided with an installation plate 24, and two linear modules 25 are correspondingly arranged below the installation plate. Each of the sliders of the two linear modules 25 is connected to a heating coil 2 via a connecting rod. The linear modules 25 are driven by a motor, and the motor of the linear modules 25 is electrically connected to the truss control cabinet.

[0031] Example 3 The only difference between this embodiment and Embodiment 1 is that: The embodiment provides a friction welding method for a large steel piston, used to weld a finished steel piston with a cylinder diameter of 193mm, a semi-finished friction welded product with an outer welding surface outer diameter of 190mm and an inner diameter of 116.31mm, an inner welding surface outer diameter of 106.09mm and an inner diameter of 80mm, and an original welding area of ​​12169mm². In step 2, the height of the welding groove is 3.72 mm and the depth is 5 mm. The welding groove corresponds to the opening position of the second annular groove on the outer surface of the finished product. The height of the second annular groove is 2 mm and the depth is 7 mm. The total height of the special groove formed by the two welding grooves after welding is 2 mm.

[0032] By employing the above friction welding method, the welding shrinkage of the piston head blank and piston skirt blank is 4mm, and the actual welding area of ​​the large-diameter steel piston is reduced to 9218mm² (see the cross-sectional sample of the semi-finished product obtained after welding). Figure 12 ).

[0033] The above description is merely a preferred embodiment of the present invention and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A friction welding method for a large steel piston, used for welding large-diameter steel pistons with a cylinder diameter of 160mm or more and a welding area of ​​8000mm² or more, wherein the large-diameter steel piston includes a piston head and a piston skirt, and the finished outer surface of the large-diameter steel piston is provided with a weight-reducing groove and several annular grooves, characterized in that, Includes the following steps: S1. Preparing blanks: Prepare piston head blanks and piston skirt blanks separately; S2. Machining welding grooves: Machining a welding groove on the outer welding surface of the piston head blank and the piston skirt blank respectively, so that the welding groove corresponds to the opening position of the weight reduction groove or ring groove on the outer surface of the finished product, and the depth of the two welding grooves is less than the depth of the corresponding weight reduction groove or ring groove, and the total height of the special groove formed by the two welding grooves after welding is less than the height of the corresponding weight reduction groove or ring groove. S3. Preheating: The piston head blank and piston skirt blank with welding grooves are respectively loaded into the corresponding fixtures of the existing inertial friction welding machine, and the outer welding surface and inner welding surface of the piston head blank and piston skirt blank are preheated simultaneously by an induction preheating device. S4. Welding: When the temperature of the outer and inner welding surfaces of the piston head blank and piston skirt blank reaches the preset temperature, the rotation speed and pressure required for friction welding of the large-diameter steel piston are reduced to the capability range of the existing inertial friction welding machine. At this time, the induction preheating device is removed and the existing inertial friction welding machine is started to complete the welding of the large-diameter steel piston.

2. The friction welding method for a large steel piston according to claim 1, characterized in that: The ring groove includes a first ring groove, a second ring groove, or a third ring groove for installing piston rings, and a weight-reducing groove for reducing piston weight.

3. The friction welding method for a large steel piston according to claim 1, characterized in that: In step S2, the upper and lower wall openings of the welding groove are provided with deburring chamfers.

4. The friction welding method for a large steel piston according to claim 1, characterized in that: In step S4, the welding shrinkage of the piston head blank and piston skirt blank is 3-10mm.

5. The friction welding method for a large steel piston according to claim 1, characterized in that: In step S4, the preset temperature is 600-1000℃.

6. A method for friction welding a large steel piston according to any one of claims 1 to 5, characterized in that: In step S3, the induction preheating device includes a trolley guide rail, a track trolley, a heating coil 1, and a water-cooled integrated IGBT power supply cabinet. The trolley guide rail is located on one side of the existing inertial friction welding machine and is correspondingly located between the two clamps on the existing inertial friction welding machine. The track trolley is slidably connected to the trolley guide rail. The water-cooled integrated IGBT power supply cabinet is fixed on the trolley guide rail. Two parallel heating coils 1 are fixed on the track trolley by brackets, and the heating coils 1 are electrically connected to the water-cooled integrated IGBT power supply cabinet.

7. The friction welding method for a large steel piston according to claim 6, characterized in that: In step S3, when the induction preheating device preheats the outer and inner welding surfaces of the piston head blank and the piston skirt blank, the two heating coils are respectively close to the outer and inner welding surfaces of the piston head blank and the piston skirt blank, and the distance between the heating coils and the corresponding outer and inner welding surfaces is 1-2mm.

8. A method for friction welding a large steel piston according to any one of claims 1 to 5, characterized in that: In step S3, the induction preheating device includes an induction power supply cabinet, a truss control cabinet, and a truss installed above the existing inertial friction welding machine. A translation seat is slidably connected to the truss via a gear rack structure I and a linear module I. A lifting seat is slidably connected to the translation seat via a gear rack structure II and a linear module II. Two heating coils II are adjustablely connected to the bottom of the lifting seat. The induction power supply cabinet is electrically connected to the heating coils II. Both the gear rack structure I and the gear rack structure II are driven by motors, and each motor is electrically connected to the truss control cabinet. When the induction preheating device preheats the outer and inner welding surfaces of the piston head blank and the piston skirt blank, the two heating coils II are moved between the two clamps on the existing inertial friction welding machine, and the distance between the heating coils II and the corresponding outer and inner welding surfaces is adjusted to 1-2 mm.

9. A method for friction welding a large steel piston according to claim 8, characterized in that: The first gear and rack structure includes a linear rack I horizontally fixed on the front side wall of the truss and a gear I meshing with the linear rack I. The translation seat is located above the truss, and a front side plate is provided on the front side of the translation seat. A motor I is fixed in the middle of the front side plate. The output shaft of the motor I is connected to the gear I through a transmission. The upper and lower ends of the rear side of the front side plate are slidably connected to the slide rails of two linear modules I horizontally set on the front side of the truss through the sliders of two linear modules I, respectively. The second gear and rack structure includes a linear rack II vertically set on the lifting seat and a gear II meshing with the linear rack II. A motor II is fixed on the translation seat. The output shaft of the motor II is connected to the gear II through a transmission. The front side plate of the translation seat is fixedly connected to the slider of the linear module II through a connecting plate. The slide rail of the linear module II is vertically fixed on the lifting seat.

10. A method for friction welding a large steel piston according to claim 8, characterized in that: The bottom of the lifting platform is provided with an installation plate, and two linear modules three are correspondingly arranged below the installation plate. Each of the sliders of the two linear modules three is connected to a heating coil two through a connecting rod. The linear modules three are driven by a motor, and the motor of the linear modules three is electrically connected to the truss control cabinet.

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