CN112658596B

CN112658596B - Process for solving problem of unqualified parallelism of die-casting piston pin hole

Info

Publication number: CN112658596B
Application number: CN202011280954.4A
Authority: CN
Inventors: 祝文明; 李志国; 常帅
Original assignee: Shandong Zhenting Jinggong Piston Co ltd
Current assignee: Shandong Zhenting Jinggong Piston Co ltd
Priority date: 2020-11-16
Filing date: 2020-11-16
Publication date: 2022-09-09
Anticipated expiration: 2040-11-16
Also published as: CN112658596A

Abstract

The invention provides a process for solving the problem of unqualified parallelism of a die-casting piston pin hole, which comprises the following steps of: (1) casting a die-casting piston blank produced by a die-casting machine, and putting the die-casting piston blank into a shot blasting machine for shot blasting treatment, wherein the shot blasting time is 20 minutes; (2) carrying out heat treatment on the die-cast piston blank after shot blasting, heating the die-cast piston blank to 225 +/-5 ℃ in a pit furnace, and keeping the temperature for 8 hours; (3) the piston blank after heat treatment is processed and produced, the piston blank inner cavity is propped against in the process of processing the ring groove, a top process positioning table is processed, when a piston pin hole is processed, the top process positioning table is used as a reference and is closely matched with a fixing clamp, and the top of the piston inner cavity is pressed by a cylinder, so that the piston pin hole and the peripheral part thereof are not influenced by external force; (4) when the top plane is processed, the pin pulls the ring groove to process, so that the piston pin hole is not stressed, and the parallelism of the die-casting piston pin hole produced by the process is below 2um and below 4.5um which completely meets the standard requirement.

Description

Process for solving problem of unqualified parallelism of die-casting piston pin hole

Technical Field

The invention belongs to the technical field of piston processing, and particularly relates to a process for solving the problem of unqualified parallelism of a die-casting piston pin hole.

Background

The pressure casting piston is more and more on small engines, such as a mower, a chain saw and the like, engines produced by enterprises such as Steyr, Fuji, TTI and the like of world well-known brands are used in batches, the small engines are small in size, large in power, long in operation time and large in work load, the engines are required to have good working performance, the core part piston of the corresponding engine is required to be more excellent and involves the problems of strength, durability, emission and the like of the piston, the molten aluminum has higher strength after being formed into the piston by die casting under the pressure of 400 tons, the parallelism of a corresponding piston pin hole is not good, certain interference and space exist between the piston pin and the connecting rod, the durability is deteriorated, the emission does not reach the standard, therefore, the die casting piston is a product with strict requirements on various indexes, particularly on emission, fatigue resistance and power,

the share of the products reaches 30% at present, but the flatness of the piston pin hole is difficult to meet the technical requirements, and the piston produced by the existing production process has fewer qualified products, cannot meet the requirements of the existing orders, suffers from customer complaints and also causes great loss of profits of the company.

Disclosure of Invention

In order to solve the technical problems, the invention provides a process for solving the problem that the parallelism of the die-casting piston pin hole is unqualified, and the parallelism of the die-casting piston pin hole produced by the process is below 2um and below 4.5um which completely meets the standard requirement.

The technical scheme adopted by the invention is as follows: a process for solving the problem that the parallelism of a die-casting piston pin hole is unqualified is characterized by comprising the following steps of:

(1) casting a die-casting piston blank produced by a die-casting machine, putting the die-casting piston blank into a shot blasting machine, wherein the shot blasting machine is a Q326 crawler-type shot blasting machine, performing shot blasting treatment by using stainless steel shots with the diameter of 0.2mm, the stainless steel shots can avoid surface oxidation of the die-casting piston blank, simultaneously removing edge burrs, increasing the surface hardness, enhancing the tensile strength, and the shot blasting time is 20 minutes,

(2) and (3) performing heat treatment on the piston blank subjected to shot blasting, heating the piston blank to 225 +/-5 ℃ in a pit furnace, and preserving heat for 8 hours to ensure that the piston blank has uniform texture and fine metallographic structure, and simultaneously eliminating the internal stress of the piston blank and reducing the influence of the internal stress on the parallelism of pin holes in the process of processing the piston pin holes.

(3) The piston blank after heat treatment is processed and produced, the prior process that a top is directly propped against the top is changed, the new process props against the inner cavity of the piston blank in the process of processing the ring groove to process a top process positioning table, when a piston pin hole is processed, the top process positioning table is taken as a reference and is closely matched with a fixed clamp, and the top of the piston inner cavity is pressed by a cylinder, so that the piston pin hole and the peripheral parts thereof are not influenced by external force.

(4) When the top plane is processed, the prior process that a piston pin hole is pulled by a pin through a cylinder is changed, an annular groove clamping piece is clamped into an annular groove of the piston, the piston is arranged in an outer sleeve, the upper part of the outer sleeve is clamped at the annular groove clamping piece, the pin is inserted into the pull pin hole of the outer sleeve, the cylinder fixes the piston through the pull pin, and the pin essentially pulls the annular groove for processing, so that the piston pin hole is not stressed, and the phenomenon of unqualified parallelism caused by stress of the piston pin hole is eliminated.

Furthermore, stainless steel shots with the diameter of 0.2mm are used in the shot blasting treatment,

the piston hardness is enabled to meet the technical requirement of HBW100-140 through heat treatment, in the volume stability test, after the piston is heated to 250 +/-5 ℃ and is kept warm for 6 hours, the volume stability of the piston is measured to be 0-0.014%, and the technical requirement is less than or equal to 0.025%;

the parallelism of the piston pin holes of the product processed by the process is detected to be below 2um, the standard requirement is below 5um, and the technical requirement is completely met.

Drawings

FIG. 1 illustrates a tooling used in the prior art of the present invention;

FIG. 2 is a sectional view in the direction of FIG. 1A-A;

FIG. 3 shows a tooling used in the original process;

FIG. 4 is a sectional view in the direction of FIG. 3A-A;

the reference numbers in the figures illustrate: 1-piston 2-ring groove clamping piece 3-pulling pin 4-outer sleeve 5-piston pin hole 6-pulling pin hole 7-inner working shaft.

Detailed Description

The following examples further describe embodiments of the present invention in detail.

Example 1:

the process for solving the problem of unqualified parallelism of the pin hole of the die-casting piston is characterized by comprising the following steps of:

(2) and (3) performing heat treatment on the piston blank after shot blasting, heating the piston blank to 225 +/-5 ℃ in a pit furnace, and keeping the temperature for 8 hours to ensure that the piston blank has uniform texture and fine metallographic structure, simultaneously eliminating the internal stress of the piston blank and reducing the influence of the internal stress on the parallelism of the pin holes in the process of processing the piston pin holes.

(4) When the top plane is processed, the prior process that a pin is pulled by a cylinder and the pin pulls a piston pin hole is changed, an annular groove clamping piece is clamped into an annular groove of the piston, the piston is arranged in an outer sleeve, the upper part of the outer sleeve is clamped at the annular groove clamping piece, the pin is inserted into the pull pin hole of the outer sleeve, the cylinder fixes the piston by pulling the pin, and the fact that the pin pulls the annular groove to process is substantial, so that the piston pin hole is not stressed, and the phenomenon that the parallelism is unqualified due to the stress of the piston pin hole is eliminated.

The original process comprises the following steps:

1) the die casting machine is used for producing a piston blank and carrying out heat treatment, the heat treatment temperature is 200 ℃, the time is 9 hours, and the internal stress of the piston blank cannot be eliminated;

2) the tool supports the inner cavity of the piston blank, the center supports the top of the piston blank, the outer circle and the annular groove are machined, and when the center supports the top, the center gives an indirect force to the piston pin hole;

3) the cylinder presses the top of the piston to process a piston pin hole, and the pin hole indirectly bears the pressure from the cylinder;

4) when the top of the piston is machined, the pull pin is pulled by the cylinder, the piston pin hole is pulled by the pull pin, and the pulling force is not lower than 0.6MPa, so that the pin hole has certain deformation;

the comparison of the parameters of the die-casting piston processed by the process of the invention and the original processing technique is shown in table 1, and the table shows that the volume stability and the pin hole parallelism of the new technique are obviously better than the original processing technique.

TABLE 1 comparison of die-cast piston parameters processed using the original and inventive processes

Claims

1. The process for solving the problem of unqualified parallelism of the pin hole of the die-casting piston is characterized by comprising the following steps of:

casting a die-casting piston blank produced by a die-casting machine, and putting the die-casting piston blank into a shot blasting machine for shot blasting treatment, wherein the shot blasting time is 20 minutes;

performing heat treatment on the die-cast piston blank after shot blasting, heating the die-cast piston blank to 225 +/-5 ℃ in a pit furnace, and preserving heat for 8 hours;

the piston blank after heat treatment is processed and produced, the piston blank inner cavity is propped against in the process of processing the ring groove, a top process positioning table is processed, when a piston pin hole is processed, the top process positioning table is used as a reference and is closely matched with a fixing clamp, and the top of the piston inner cavity is pressed by a cylinder, so that the piston pin hole and the peripheral part thereof are not influenced by external force;

when the top plane is machined, the ring groove clamping piece is clamped into the ring groove of the piston, the piston is arranged in the outer sleeve, the upper portion of the outer sleeve is clamped at the ring groove clamping piece, the pin is inserted into the pin pulling hole of the outer sleeve, the piston is fixed by the cylinder through pulling the pin, the pin pulls the ring groove to be machined, the piston pin hole is not stressed, and the phenomenon that the parallelism is unqualified due to stress of the piston pin hole is eliminated.

2. The process for solving the problem of unqualified parallelism of the pin hole of the die-casting piston according to claim 1, wherein a stainless steel shot with the diameter of 0.2mm is used in the shot blasting treatment.