Piston and welding process

Abstract

The application discloses a kind of piston and welding process, wherein the piston includes piston head and piston skirt, welding top joint and welding ring joint are equipped between the piston head and the piston skirt;Several pressure relief holes are opened in the piston skirt, the pressure relief hole extends from the inner cavity of the piston skirt to the junction of the welding top joint and the welding ring joint.The piston provided by the application can not only discharge the air sealed in the assembly gap and the gas generated during the welding process by setting the pressure relief hole at the junction of the welding top joint and the welding ring joint, but also the stress concentration is generated at the position of the pressure relief hole, so that the stress change tends to be gentle at the highest stress position of piston work, i.e., the junction of piston pin hole and pin seat, which is beneficial to improve the load-bearing capacity of piston pin seat.

Description

Technical Field

[0001] This invention relates to the field of piston manufacturing, and in particular to a piston and welding process. Background Technology

[0002] With the development of engines towards high performance, high reliability, and long service life, forged pistons are being used more and more. Forged pistons have a better microstructure and retain complete metal flow lines than cast pistons, resulting in better mechanical properties.

[0003] In the existing technology, when forging aluminum pistons, the piston head and forging skirt are generally cast first, and then the piston head and forging skirt are welded together to form a shape, followed by precision machining and surface treatment.

[0004] However, because welding is performed in a vacuum or low vacuum environment, during the assembly of the piston head and piston skirt, differences in the machining radius of the assembly surfaces, as well as factors such as the flatness and perpendicularity of the weld mating surfaces, result in a small amount of air being trapped in the weld gaps after piston assembly. This trapped air cannot be expelled during the vacuuming process, and as the molten metal solidifies, the gas within it cannot escape in time, creating porosity defects on the metal surface or inside, affecting weld quality. Furthermore, the small amount of gas generated during welding also creates porosity defects on the metal surface or inside, resulting in numerous porosity issues and a high scrap rate in existing piston welds.

[0005] Therefore, how to effectively improve the welding quality of pistons is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a piston and a welding process to improve the welding quality of the piston and reduce weld porosity and stress concentration.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A piston includes a piston head and a piston skirt, wherein a welded top seam and a welded circumferential seam are provided between the piston head and the piston skirt; a plurality of pressure relief holes are provided in the piston skirt, the pressure relief holes extending from the inner cavity of the piston skirt to the junction of the welded top seam and the welded circumferential seam.

[0009] Preferably, the pressure relief hole is a circular blind hole.

[0010] Preferably, the pressure relief hole is inclined from one side near the piston head to the other side toward a position close to the axis of the piston skirt.

[0011] A piston welding process for processing pistons as described above includes the following steps:

[0012] Step S1: Forge and rough machine the piston head and piston skirt of the piston;

[0013] Step S2: A pressure relief hole is machined on the piston skirt at the junction of the weld top seam and the weld circumferential seam;

[0014] Step S3: Assemble the piston head and the piston skirt;

[0015] Step S4: Weld the top weld and the circumferential weld;

[0016] Step S5: Perform finishing and surface treatment on the piston.

[0017] Preferably, step S3 includes:

[0018] Clean the piston head and the piston skirt;

[0019] The piston head and the piston skirt are placed in a heating furnace for assembly;

[0020] The piston is subjected to pressure holding treatment.

[0021] Preferably, the step between step S4 and step S5 further includes:

[0022] The pressure relief hole is polished to remove burrs and sharp corners from its edges.

[0023] Preferably, step S4 includes:

[0024] Preheating before welding;

[0025] Clamp the piston, close the welding chamber door, and evacuate the chamber.

[0026] Adjust the welding torch, align the center of the weld seam through the welding equipment viewing window, and weld using an electron beam or laser beam.

[0027] After the piston has been welded, it is removed, heat-insulated, and then cooled to room temperature.

[0028] Preferably, the step of evacuating the vacuum includes: evacuating the welding chamber to a vacuum level of 5*10. 2 Below Pa.

[0029] Preferably, the step of heat preservation treatment of the piston followed by cooling to room temperature includes:

[0030] The heat preservation temperature is 150℃~180℃, the heat preservation time is ≥1h, and then the furnace is cooled to room temperature.

[0031] Preferably, the preheating step includes: a preheating temperature of 150℃~190℃ and a holding time of ≥1.5h.

[0032] The piston provided by this invention includes a piston head and a piston skirt. A welded top seam and a welded circumferential seam are provided between the piston head and the piston skirt. A plurality of pressure relief holes are formed within the piston skirt, extending from the inner cavity of the piston skirt to the junction of the welded top seam and the welded circumferential seam. The piston provided by this invention, by providing pressure relief holes at the junction of the welded top seam and the welded circumferential seam, not only removes air trapped in the assembly gap and gas generated during welding, but also creates stress concentration at the location of the pressure relief holes. This makes the stress change at the point of highest stress during piston operation, i.e., the junction of the piston pin hole and the pin seat, more gradual, which is beneficial to improving the load-bearing capacity of the piston pin seat.

[0033] The piston welding process provided by this invention includes the following steps: Step S1: Forging and rough machining the piston head and piston skirt; Step S2: Machining a pressure relief hole at the junction of the weld top seam and the weld circumference seam on the piston skirt; Step S3: Assembling the piston head and the piston skirt; Step S4: Welding the weld top seam and the weld circumference seam; Step S5: Finish machining and surface treatment of the piston. In the piston welding process provided by this invention, during vacuuming after piston assembly, the pressure relief hole machined at the junction of the weld circumference seam and the weld top seam can expel air trapped in the assembly gap and gas generated during welding, preventing welding porosity and improving welding quality. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 A schematic diagram of a specific embodiment of the piston provided by the present invention;

[0036] Figure 2 A flowchart of the piston welding process provided by the present invention;

[0037] Wherein: 1-piston head, 2-welded top seam, 3-welded circumferential seam, 4-pressure relief hole, 5-piston skirt. Detailed Implementation

[0038] The core of this invention is to provide a piston and welding process that can achieve a more uniform stress distribution at the weld position, thereby improving the load-bearing capacity of the piston pin seat.

[0039] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Please refer to Figure 1 and Figure 2 , Figure 1 A schematic diagram of a specific embodiment of the piston provided by the present invention; Figure 2 A flowchart of the piston welding process provided by the present invention.

[0041] In this embodiment, the piston includes a piston head 1 and a piston skirt 5, with a welded top seam 2 and a welded circumferential seam 3 between the piston head 1 and the piston skirt 5; a plurality of pressure relief holes 4 are provided in the piston skirt 5, extending from the inner cavity of the piston skirt 5 to the junction of the welded top seam 2 and the welded circumferential seam 3.

[0042] Specifically, the piston is divided into two parts: the piston head 1 and the piston skirt 5. The piston head 1 and piston skirt 5 are machined separately first, and then assembled. The weld top seam 2 and weld circumferential seam 3 between the piston head 1 and piston skirt 5 are welded and fixed. The weld top seam 2 is located in the axial direction of the piston, and the weld circumferential seam 3 is located in the circumferential direction of the piston. Several pressure relief holes 4 are opened in the piston skirt 5. The number of pressure relief holes 4 can be set as needed, for example, 2-6, and distributed sequentially along the circumferential direction of the piston. The number of pressure relief holes 4 should be set as needed, and the structure and shape of the piston should also be considered. The pressure relief holes 4 extend from the inner cavity of the piston skirt 5 to the junction of the weld top seam 2 and the weld circumferential seam 3. That is to say, the pressure relief holes 4 are used to connect the gap of the weld top seam 2 and the gap of the weld circumferential seam 3 to the outside, so as to facilitate the air sealed in the gap and the gas generated during the welding process to be discharged from the pressure relief holes 4.

[0043] The piston provided by this invention, by setting a pressure relief hole 4 at the junction of the weld top seam 2 and the weld circumferential seam 3, can not only remove the air sealed in the assembly gap and the gas generated during the welding process, but also the position of the pressure relief hole 4 creates a certain stress concentration, so that the stress change at the highest stress point when the piston is working, that is, at the junction of the piston pin hole and the pin seat, tends to be gradual, which is beneficial to improving the load-bearing capacity of the piston pin seat.

[0044] In some embodiments, the pressure relief hole 4 is a circular blind hole with a smooth outer periphery, which can reduce stress concentration.

[0045] In some embodiments, the pressure relief hole 4 is inclined from one side near the piston head 1 towards the other side toward a position near the axis of the piston skirt 5. Specifically, this arrangement facilitates processing and makes it easier for the pressure relief hole 4 to connect to the junction of the weld top seam 2 and the weld circumferential seam 3, such as... Figure 1 As shown in the current view, the pressure relief hole 4 is inclined from top to bottom towards the direction close to the piston's central axis, which facilitates machining and makes the force distribution more uniform.

[0046] In addition to the piston described above, the present invention also provides a piston welding process.

[0047] The piston welding process includes the following steps:

[0048] Step S1: Forge and rough machine the piston head 1 and piston skirt 5 of the piston;

[0049] Step S2: On the piston skirt 5, at the junction of the weld top seam 2 and the weld circumferential seam 3, a pressure relief hole 4 is machined;

[0050] Step S3: Assemble the piston head 1 and piston skirt 5;

[0051] Step S4: Weld the top weld 2 and the circumferential weld 3;

[0052] Step S5: Perform finishing and surface treatment on the piston.

[0053] Specifically, after forging and rough machining the piston head 1 and piston skirt 5, a pressure relief hole 4 is opened. Then, after assembling the piston head 1 and piston skirt 5, the top weld 2 and the circumferential weld 3 are welded. During the vacuuming process, the gas in the gap between the top weld 2 and the circumferential weld 3, as well as the gas generated during the welding process, will flow out along the pressure relief hole 4.

[0054] The piston welding process provided by this invention allows for the removal of air trapped in the assembly gap and gas generated during the welding process when vacuuming after piston assembly, due to the through-hole 4 processed at the junction of the welding annular seam 3 and the welding top seam 2. This avoids the formation of welding porosity and improves welding quality.

[0055] In some implementations, step S3 includes:

[0056] Clean the piston head 1 and piston skirt 5;

[0057] The piston head 1 and piston skirt 5 are placed in the heating furnace for assembly;

[0058] The piston is subjected to pressure holding treatment.

[0059] Specifically, the piston head 1 and piston skirt 5 are assembled through cleaning, heat fitting, and pressure holding, which facilitates subsequent welding and fixing.

[0060] In some implementations, step S4 and step S5 may further include:

[0061] The pressure relief hole 4 is polished to remove burrs and sharp corners from its edges, thereby reducing stress concentration.

[0062] In some implementations, step S4 includes:

[0063] Preheating before welding;

[0064] Clamp the piston, close the welding chamber door, and evacuate the vacuum.

[0065] Adjust the welding torch, align the center of the weld seam through the welding equipment viewing window, and weld using an electron beam or laser beam.

[0066] After removing the welded piston and heat-insulating it, it is cooled to room temperature.

[0067] Specifically, welding in a vacuum environment improves welding quality. Furthermore, the presence of the pressure relief hole 4 during the formation of the vacuum environment facilitates the outflow of gas in the gap between the weld top seam 2 and the weld circumferential seam 3, as well as gas generated during the welding process, thereby improving welding quality.

[0068] In some embodiments, the vacuuming step includes: evacuating the welding chamber to a vacuum level of 5*10. 2 Below Pa, ensure sufficient vacuum to reduce slag and welding flux during the welding process.

[0069] In some embodiments, after the piston is kept at a constant temperature, it is cooled to room temperature, including:

[0070] The heat preservation temperature is 150℃~180℃, and the heat preservation time is ≥1h. After that, it is cooled to room temperature with the furnace. Sufficient heat preservation can ensure the strength of the piston, reduce the residual stress at the weld top seam 2 and weld ring seam 3, and reduce deformation.

[0071] In some implementations, the preheating step includes: a preheating temperature of 150℃~190℃ and a holding time of ≥1.5h; similarly, preheating can improve the melting rate of the metal and ensure welding efficiency and welding quality.

[0072] In one specific embodiment, the piston welding process includes the following steps:

[0073] Forged piston head 1, piston skirt 5;

[0074] Rough machining of piston head 1 and piston skirt 5;

[0075] A pressure relief hole 4 is machined at the junction of the top weld seam 2 and the circumferential weld seam 3 on the piston skirt 5.

[0076] Assemble piston head 1 and piston skirt 5; clean; heat fitting; pressure holding;

[0077] Welding of top seam 2 and circumferential seam 3; preheating before welding at 150℃~190℃ for at least 1.5 hours; clamping the piston, closing the welding chamber door, and evacuating to a vacuum level below 5*102Pa; adjusting the welding torch and aligning it with the center of the weld through the welding equipment's observation lens, then welding using an electron beam or laser beam; removing the welded piston and holding it at 150℃~180℃ for at least 1 hour, then cooling it to room temperature with the furnace; finishing the pressure relief hole 4, removing burrs and sharp corners;

[0078] Piston precision machining and surface treatment.

[0079] In this piston welding process, when vacuuming is performed after piston assembly, the through-hole 4 machined at the junction of the welding circumferential seam 3 and the welding top seam 2 can remove the air sealed in the assembly gap. At the same time, it can facilitate the discharge of welding gases such as hydrogen generated during the welding process, avoid the formation of welding porosity, and improve the welding quality.

[0080] The piston and welding process provided by this invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the welding process and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A piston welding process for machining pistons, characterized in that, The piston includes a piston head (1) and a piston skirt (5), and a welded top seam (2) and a welded circumferential seam (3) are provided between the piston head (1) and the piston skirt (5); characterized in that a plurality of pressure relief holes (4) are provided in the piston skirt (5), and the pressure relief holes (4) extend from the inner cavity of the piston skirt (5) to the junction of the welded top seam (2) and the welded circumferential seam (3); the pressure relief holes (4) are circular blind holes, and the outer periphery of the circular blind holes is smooth; the pressure relief holes (4) are inclined from one side near the piston head (1) to the other side toward a position close to the axis of the piston skirt (5); Includes the following steps: Step S1: Forge and rough machine the piston head (1) and piston skirt (5) of the piston. Step S2: On the piston skirt (5), at the junction of the weld top seam (2) and the weld circumferential seam (3), a pressure relief hole (4) is machined. Step S3: Assemble the piston head (1) and the piston skirt (5); Step S4: Weld the top weld (2) and the circumferential weld (3); Step S5: Perform finishing and surface treatment on the piston; Step S4 includes: Preheating before welding; Clamp the piston, close the welding chamber door, and evacuate the chamber. Adjust the welding torch, align the center of the weld seam through the welding equipment viewing window, and weld using an electron beam or laser beam. After the piston has been welded, it is removed, heat-insulated, and then cooled to room temperature. The step of vacuuming includes: evacuating the welding chamber to a vacuum level of 5*10. 2 Below Pa.

2. The piston welding process according to claim 1, characterized in that, Step S3 includes: The piston head (1) and the piston skirt (5) are cleaned; The piston head (1) and the piston skirt (5) are placed in a heating furnace for assembly; The piston is subjected to pressure holding treatment.

3. The piston welding process according to claim 2, characterized in that, The step between step S4 and step S5 also includes: The pressure relief hole (4) is polished to remove burrs and sharp corners from its edges.

4. The piston welding process according to claim 1, characterized in that, The step of heat preservation treatment of the piston followed by cooling to room temperature includes: The heat preservation temperature is 150℃~180℃, the heat preservation time is ≥1h, and then the furnace is cooled to room temperature.

5. The piston welding process according to claim 4, characterized in that, The preheating step includes: a preheating temperature of 150℃~190℃ and a holding time of ≥1.5h.

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