CN115822801A - Piston and welding process - Google Patents

Abstract

The invention discloses a piston and a welding process, wherein the piston includes a piston head and a piston skirt, and a welding top seam and a welding ring seam are arranged between the piston head and the piston skirt; Several pressure relief holes are opened, and the pressure relief holes extend from the inner cavity of the piston skirt to the junction of the welding top seam and the welding ring seam. In the piston provided by the present invention, by providing a pressure relief hole at the junction of the welding top seam and the welding ring seam, not only the air trapped in the assembly gap and the gas generated during the welding process can be eliminated, but also the pressure relief hole can be eliminated. The position of the pressure hole produces a certain stress concentration, which makes the stress change at the highest stress point when the piston is working, that is, the junction of the piston pin hole and the pin seat, tends to be gentle, which is conducive to improving the load-bearing capacity of the piston pin seat.

Description

A kind of piston and welding process

technical field

The invention relates to the field of piston processing, in particular to a piston and a welding process.

Background technique

With the development of high performance, high reliability and long life of the engine, forged pistons are used more and more. Compared with cast pistons, forged pistons have a better microstructure and retain complete metal streamlines, and their mechanical properties are better. good.

In the prior art, when forging an aluminum piston, the piston head and the forged skirt are generally cast first, and then the piston head and the forged skirt are welded and formed, and then finishing and surface treatment are performed.

However, due to the vacuum and low vacuum environment during welding, when the piston head and piston skirt are assembled, due to the difference in the size of the rounded corners of the assembly surface of the piston head and piston skirt; Degree, verticality and other factors, after the piston is assembled, a small part of air will be sealed in the gap of the weld. The air sealed in the gap cannot be discharged when the welding is evacuated. When the molten metal is solidified, the gas in it has no time to escape, resulting in pore defects on the metal surface or inside, which affects the welding quality; in addition, during the welding process, Due to the generation of a small amount of gas, pore defects will also be generated on the metal surface or inside, resulting in a large number of pores in the welding of the piston in the prior art, and a high rate of welding rejects.

Therefore, how to effectively improve the welding quality of the piston is currently a technical problem to be solved by those skilled in the art.

Contents of the invention

The object of the present invention is to provide a piston and a welding process for improving the welding quality of the piston and reducing welding pores and stress concentration.

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

A piston, comprising a piston head and a piston skirt, a welded top seam and a welded ring seam are arranged between the piston head and the piston skirt; several pressure relief holes are opened in the piston skirt, and the The pressure relief hole extends from the inner cavity of the piston skirt to the junction of the welding top seam and the welding ring seam.

Preferably, the pressure relief hole is a circular blind hole.

Preferably, the pressure relief hole is inclined from one side close to the piston head to the other side towards a position close to the axis of the piston skirt.

A piston welding process for processing the piston as described above, comprising the following steps:

Step S1: forging and rough machining the piston head and piston skirt of the piston;

Step S2: Process a pressure relief hole on the piston skirt at the junction of the welded top seam and the welded ring seam;

Step S3: assembling the piston head and the piston skirt;

Step S4: welding the welding top seam and the welding ring seam;

Step S5: Finishing and surface-treating the piston.

Preferably, said step S3 includes:

cleaning the piston head and the piston skirt;

putting the piston head and the piston skirt into a heating furnace for assembly;

The piston is subjected to pressure-holding treatment.

Preferably, between the step S4 and the step S5, further include:

Perform a finishing operation on the pressure relief hole to remove burrs and sharp corners on the edge of the pressure relief hole.

Preferably, said step S4 includes:

Preheating before welding;

Clamp the piston, close the door of the welding chamber, and evacuate;

Adjust the welding torch, aim at the center of the weld seam through the welding equipment observation mirror, and use electron beam or laser beam welding;

The piston that has been welded is removed, and after the heat preservation treatment is performed on the piston, it is cooled to room temperature.

Preferably, the step of evacuating includes: evacuating the welding chamber until the vacuum degree reaches below 5*10 ² Pa.

Preferably, the step is to cool the piston to room temperature after heat preservation treatment, including:

The holding temperature is 150°C to 180°C, the holding time is ≥1h, and then cooled to room temperature with the furnace.

Preferably, the step of preheating before welding includes: the preheating temperature is 150°C-190°C, and the holding time is ≥1.5h.

The piston provided by the present invention includes a piston head and a piston skirt, a welded top seam and a welded ring seam are arranged 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 welded top seam and the welded annular seam. In the piston provided by the present invention, by providing a pressure relief hole at the junction of the welding top seam and the welding ring seam, not only the air trapped in the assembly gap and the gas generated during the welding process can be eliminated, but also the pressure relief hole can be eliminated. The position of the pressure hole produces a certain stress concentration, which makes the stress change at the highest stress point when the piston is working, that is, the junction of the piston pin hole and the pin seat, tends to be gentle, which is conducive to improving the load-bearing capacity of the piston pin seat.

The piston welding process provided by the present invention comprises the following steps: step S1: forging and roughing the piston head and piston skirt of the piston; step S2: on the piston skirt at the junction of the welding top seam and the welding ring process a pressure relief hole; step S3: assemble the piston head and the piston skirt; step S4: weld the welding top seam and the welding ring seam; step S5: carry out the welding on the piston Finishing and surface treatment. In the piston welding process provided by the present invention, when the piston is evacuated after assembly, since the junction of the welding ring seam and the welding top seam is processed with the through pressure relief hole, it can eliminate the sealing in the assembly gap. Air, as well as the gas generated during the welding process, avoid welding porosity and improve welding quality.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a schematic structural view of a specific embodiment of the piston provided by the present invention;

Fig. 2 is the flow chart of the piston welding process provided by the present invention;

Among them: 1-piston head, 2-welding top seam, 3-welding ring seam, 4-pressure relief hole, 5-piston skirt.

Detailed ways

The core of the present invention is to provide a piston and a welding process, which can have a more uniform stress distribution at the welding seam position, thereby improving the load-bearing capacity of the piston pin seat.

In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Please refer to Figure 1 and Figure 2, Figure 1 is a schematic structural diagram of a specific embodiment of the piston provided by the present invention; Figure 2 is a flow chart of the piston welding process provided by the present invention.

In this embodiment, the piston includes a piston head 1 and a piston skirt 5, and a welded top seam 2 and a welded ring seam 3 are arranged between the piston head 1 and the piston skirt 5; The pressure hole 4 and the pressure relief hole 4 extend from the inner cavity of the piston skirt 5 to the junction of the welding top seam 2 and the welding ring seam 3 .

Specifically, the piston is divided into two parts, the piston head 1 and the piston skirt 5. After the piston head 1 and the piston skirt 5 are processed separately, the piston head 1 and the piston skirt 5 are assembled, and the piston head The welding top seam 2 and the welding annular seam 3 between the piston part 1 and the piston skirt 5 are fixed by welding, the welding top seam 2 is located in the axial direction of the piston, and the welding annular seam 3 is located in the circumferential direction of the piston; Several pressure relief holes 4, the number of pressure relief holes 4 can need to be set, for example, it can be 2-6, distributed sequentially along the circumference of the piston, the number of pressure relief holes 4 should be set according to needs, and it is necessary to consider The structure, shape and other factors of the piston are determined. The pressure relief hole 4 extends from the inner cavity of the piston skirt 5 to the junction of the welding top seam 2 and the welding ring seam 3, that is to say, the pressure relief hole 4 is used to weld the top seam Both the gap between the seam 2 and the gap between the welding ring seam 3 are connected to the outside, so that the air trapped in the gap and the gas generated during the welding process can be discharged from the pressure relief hole 4 .

The piston provided by the present invention, by setting the pressure relief hole 4 at the junction of the welding top seam 2 and the welding ring seam 3, not only can eliminate the air sealed in the assembly gap and the gas generated during the welding process, but also the pressure relief hole 4 The position of the piston produces a certain stress concentration, which makes the highest stress point when the piston is working, that is, the stress change at the junction of the piston pin hole and the pin seat tends to be gentle, which is conducive to improving the load-bearing capacity of the piston pin seat.

In some embodiments, the pressure relief hole 4 is a circular blind hole, and the outer periphery of the circular blind hole is smooth, which can reduce stress concentration.

In some embodiments, the pressure relief hole 4 is inclined from the side close to the piston head 1 to the other side towards the position close to the axis of the piston skirt 5. Specifically, such setting can facilitate processing on the one hand, and can Make it easier for the pressure relief hole 4 to connect to the junction of the welding top seam 2 and the welding ring seam 3, as shown in Figure 1, in the current view, the pressure relief hole 4 is inclined from top to bottom towards the direction close to the central axis of the piston, It is convenient to process and the force is more uniform.

In addition to the above-mentioned piston, the present invention also provides a piston welding process.

The piston welding process includes the following steps:

Step S1: forging and roughly machining the piston head 1 and the piston skirt 5 of the piston;

Step S2: Process a pressure relief hole 4 on the piston skirt 5 at the junction of the welded top seam 2 and the welded ring seam 3;

Step S3: assembling the piston head 1 and the piston skirt 5;

Step S4: welding the top welding seam 2 and the welding ring seam 3;

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

Specifically, after forging and rough machining the piston head 1 and the piston skirt 5, a pressure relief hole 4 is opened, and then after the piston head 1 and the piston skirt 5 are assembled, the top seam 2 and the welding ring are welded. Seam 3 is welded, and in the process of vacuuming, the gas in the gap between welding top seam 2 and welding ring seam 3, as well as the gas generated during the welding process, will flow out along the pressure relief hole 4.

In the piston welding process provided by the present invention, when the piston is evacuated after assembly, since the junction of the welding ring seam 3 and the welding top seam 2 is processed with a through pressure relief hole 4, the air sealed in the assembly gap can be eliminated, and The gas generated during the welding process can avoid welding porosity and improve welding quality.

In some embodiments, step S3 includes:

Cleaning the piston head 1 and the piston skirt 5;

Put the piston head 1 and the piston skirt 5 into a heating furnace for assembly;

Pressurize the piston.

Specifically, the assembly of the piston head 1 and the piston skirt 5 is completed by means of cleaning, heat-fitting and pressure maintaining, so as to facilitate subsequent welding and fixing.

In some embodiments, between step S4 and step S5 also includes:

Perform polishing operation on the pressure relief hole 4 to remove burrs and sharp corners on the edge of the pressure relief hole 4 to reduce stress concentration.

In some embodiments, step S4 includes:

Preheating before welding;

Clamp the piston, close the door of the welding chamber, and evacuate;

Adjust the welding torch, aim at the center of the weld seam through the welding equipment observation mirror, and use electron beam or laser beam welding;

Remove the welded piston, heat the piston and cool it down to room temperature.

Specifically, by welding in a vacuum environment, the welding quality is improved, and because the vacuum environment is formed, due to the existence of the pressure relief hole 4, it can be beneficial to the gas in the gap between the welding top seam 2 and the welding ring seam 3 and the welding process. The generated gas flows out, improving the welding quality.

In some embodiments, the step of evacuating includes: evacuating the welding chamber until the vacuum degree reaches below 5*10 ² Pa, ensuring sufficient vacuum degree, and reducing dross and welding slag during the welding process.

In some embodiments, the step of cooling the piston to room temperature after insulated treatment includes:

The heat preservation temperature is 150 ℃ ~ 180 ℃, the heat preservation time is ≥ 1h, and then cooled to room temperature with the furnace; sufficient heat preservation can ensure the strength of the piston, reduce the residual stress at the position of welding top seam 2 and welding ring seam 3, and reduce deformation.

In some embodiments, the step of preheating before welding includes: the preheating temperature is 150°C to 190°C, and the holding time is ≥1.5h; similarly, by preheating before welding, the melting speed of the metal can be increased to ensure welding efficiency and welding quality.

In a specific embodiment, the piston welding process includes the following steps:

Forged piston head 1, piston skirt 5;

Rough machining piston head 1, piston skirt 5;

A pressure relief hole 4 is processed at the junction of the welding top seam 2 and the welding ring seam 3 of the piston skirt 5;

Assembling the piston head 1 and the piston skirt 5; cleaning; hot charging; maintaining pressure;

Welding top seam 2 and welding ring seam 3; preheating before welding, preheating temperature: 150 ° C ~ 190 ° C, holding time for more than 1.5 hours; clamp the piston, close the welding chamber door, vacuumize, and the vacuum degree reaches 5* Below 102Pa; adjust the welding torch, align the welding seam center through the welding equipment observation mirror, and use electron beam or laser beam welding; remove the welded piston and keep it warm. The furnace is cooled to room temperature; the pressure relief hole 4 is repaired, and the burrs and sharp corners are removed;

Piston finishing, surface treatment.

In this piston welding process, when the piston is vacuumed after assembly, the through pressure relief hole 4 processed at the junction of the welding ring seam 3 and the welding top seam 2 can eliminate the air sealed in the assembly gap, and at the same time, it can be conveniently discharged during the welding process. The generated welding gas such as hydrogen can avoid welding porosity and improve welding quality.

The piston and the welding process provided by the present invention have been introduced in detail above. In this paper, specific examples are used to illustrate the principles and implementation methods of the present invention, and the descriptions of the above embodiments are only used to help understand the welding process and the core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (10)

1. A piston comprises a piston head (1) and a piston skirt (5), wherein a welding top seam (2) and a welding annular seam (3) are arranged between the piston head (1) and the piston skirt (5); the pressure relief structure is characterized in that a plurality of pressure relief holes (4) are formed in the piston skirt portion (5), and the pressure relief holes (4) extend from the inner cavity of the piston skirt portion (5) to the junction of the welding top seam (2) and the welding circular seam (3).

2. Piston according to claim 1, characterized in that said pressure relief hole (4) is a circular blind hole.

3. Piston according to claim 1 or 2, characterized in that the pressure relief hole (4) is inclined from one side close to the piston head (1) to the other side towards a position close to the axis of the piston skirt (5).

4. A piston welding process for machining a piston according to any one of claims 1 to 3, comprising the steps of:

step S1: forging and roughly machining a piston head (1) and a piston skirt (5) of the piston;

step S2: a pressure relief hole (4) is machined in the piston skirt (5) at the joint of the welding top seam (2) and the welding circular seam (3);

and step S3: -assembling the piston head (1) and the piston skirt (5);

and step S4: welding the welding top seam (2) and the welding circular seam (3);

step S5: and performing finish machining and surface treatment on the piston.

5. The piston welding process of claim 4, wherein the step S3 comprises:

-cleaning the piston head (1) and the piston skirt (5);

placing the piston head (1) and the piston skirt (5) into a heating furnace for assembly;

and carrying out pressure maintaining treatment on the piston.

6. The piston welding process of claim 4, further comprising, between step S4 and step S5:

and (4) performing a polishing operation on the pressure relief hole (4) to remove burrs and sharp corners at the edge of the pressure relief hole (4).

7. Piston welding process according to any one of claims 4 to 6, characterized in that said step S4 comprises:

preheating before welding;

clamping the piston, closing the welding chamber door, and vacuumizing;

adjusting a welding gun, aligning the welding gun to the center of a welding seam through an observation mirror of welding equipment, and welding by adopting an electron beam or a laser beam;

and disassembling the welded piston, carrying out heat preservation treatment on the piston, and cooling to room temperature.

8. The piston welding process of claim 7, wherein said step of drawing a vacuum comprises: evacuating the welding chamber to a vacuum of 5 x 10 ² Pa or less.

9. The piston welding process of claim 7, wherein said step of cooling said piston to room temperature after said step of maintaining said piston temperature comprises:

the heat preservation temperature is 150-180 ℃, the heat preservation time is more than or equal to 1h, and then the furnace is cooled to the room temperature.

10. The piston welding process of claim 7, wherein said step of pre-weld preheating comprises: the preheating temperature is 150-190 ℃, and the heat preservation time is more than or equal to 1.5h.

Images