RU2828524C1 - Method of producing pistons for internal combustion engines with ni-resist ring - Google Patents

Abstract

FIELD: foundry.

SUBSTANCE: method for production of pistons for internal combustion engines with a ni-resist ring includes installation of ring (6) in the recess along the plane of the mould parting and its fixation, installation of the shaping insert forming the inner cavity of the piston, into the movable half-mould, the pressing plunger installation into the fixed half-mould, the mould heating, the metal pouring into the mould with the cavity axis horizontal arrangement, applying pressure to liquid and crystallizing metal, holding the workpiece until complete solidification of the metal, extruding it from the fixed half-mould, thermal and mechanical treatment of the obtained workpiece. Mould is heated to 220-250 °C, temperature of metal poured into mould is 180-200 K higher than liquidus temperature. Metal poured into the mould is compressed by pressing plunger (9) under pressure of 200 MPa for 2 s, then, during crystallisation development, metal is pressed by forming insert (4) under pressure increasing to 400 MPa, with provision of destruction of dendritic crystals and compensation of metal shrinkage.

EFFECT: obtaining a piston with a homogeneous fine-grained structure in the entire volume.

1 cl, 1 dwg

Description

The invention relates to foundry production, in particular to the production of piston blanks for internal combustion engines (ICE), including those with a Ni-resist ring, for subsequent thermal and mechanical processing.

The piston is one of the most loaded parts of the engine. The vast majority of pistons of internal combustion engines are made of aluminum alloys. Depending on the technical and economic requirements for the piston, the design is selected and, what is no less important, the method of its manufacture.

A method for producing pistons for internal combustion engines from aluminum alloys is known (Patent RU 2674543), in which the first stages include obtaining a measured blank, its isothermal stamping in a die containing a punch that corresponds to the rear cavity of the piston, thermal and mechanical treatment, where in the process of obtaining a measured blank, the melt of hypereutectic silumin AK-18 with a temperature of 150 ... 200 ° K higher than the temperature of the onset of its crystallization is poured into a mold heated to a temperature of 150 ... 200 ° K below the temperature of the onset of crystallization of the alloy, compressing it under a pressure of 200 ... 250 MPa between plungers moving towards each other and cooled from the inside by running water, pressing the metal by 8 ... 10% for 3-5 s, then over the next 30 ... 40 s the pressure is raised to 350 ... 400 MPa, bringing total metal compression up to 12...13% under conditions of unidirectional heat dissipation along the axis of the workpiece until the crystallization process is completely completed.

The main disadvantage of the method is the absence of a Ni-resist insert in the piston blank, which leads to a decrease in the performance characteristics of the piston, the destruction of the grooves for the piston rings, which, in turn, makes it impossible to use this technology in the production of pistons for high-powered internal combustion engines.

The closest method is for producing pistons for internal combustion engines from aluminum alloys with a Ni-resist insert (Patent RU No. 2773555), which includes the production of a measured blank, its stamping, thermal and mechanical processing of the piston, in which the measured blank with a Ni-resist insert is produced by installing the said insert in the cavity of the mold, followed by pouring molten aluminum alloy into the mold and pressing it under a pressure of 500 MPa for 60 s until the crystallization process is completely completed by means of pressing plungers as they move towards each other and subsequent cooling of the blank with water, while isothermal stamping of the measured blank with a Ni-resist insert is carried out in a die containing a punch corresponding to the rear cavity of the piston of the internal combustion engine.

The disadvantage of the method is the long production cycle, which includes the manufacture of a measured blank at the first stage and only after that isothermal stamping, thermal and mechanical processing. In addition, the presence of a Ni-resist insert in a measured blank during isothermal stamping can lead to displacement of the insert, and in some cases to its mechanical damage.

The objective of the claimed invention is to manufacture internal combustion engine pistons with a Ni-resist ring for subsequent thermal and mechanical processing in order to obtain internal combustion engine pistons with high physical, mechanical and operational properties, as well as to ensure higher resistance to temperature and impact mechanical loads during engine operation.

The technical result is the production of cast pistons with a ni-resist ring for internal combustion engines made of high-strength aluminum alloys with a homogeneous, fine-grained metal structure throughout the entire volume, with high mechanical properties.

The technical result is achieved by the fact that in the method for producing cast pistons for internal combustion engines with a Ni-resist ring, including installing the ring in a recess along the parting plane of the mold and fixing it by closing the movable half-mold with the fixed half-mold, as well as installing a mold-forming insert that forms the internal cavity of the piston in the movable half-mold and a pressing plunger in the fixed half-mold, heating the mold to a temperature of 220...250°C, pouring liquid metal into the mold, the temperature of which is 180...200 K higher than the liquidus temperature with a horizontal arrangement of the cavity axis, applying pressure to the liquid and crystallizing metal, bringing the compressibility of the poured metal to 12...13%, holding the piston blank until the metal completely hardens, pushing the blank out of the fixed half-mold during the movement of the pressing plunger and the withdrawal of the movable half-mold, thermal and mechanical processing of the obtained piston blank with a ni-resist ring, the piston is manufactured as follows:

Before starting work (see Fig. 1), a Ni-resist insert 6 with a diameter 2...3 mm greater than the piston diameter is installed in the right part 7 of the mold, then, based on preliminary experiments, the temperature of the liquid metal and the initial temperature of the mold are selected so that a hard crust of the poured metal does not form before pressure is applied. A layer of graphite-based paint is applied to the surface of the technological equipment in contact with the liquid metal by spraying, after which, due to the increased diameter of the insert, the insert is fixed relative to the parting plane by closing the left part 5 of the mold with the right part 7 of the mold by moving the press plate 1. The right plate 12 remains stationary. Next, the pouring cup 10 is installed, heated to a temperature of 200°C. In the initial state, the plunger 9 closes the pouring hole of the cup. By turning on the hydraulic cylinder with the rod 11, the plunger 9 is moved to the right, providing a laminar mode of filling the mold. A strictly defined volume of liquid metal is poured into the bowl, the metal enters the pressing chamber 8, after which, by moving the plunger to the left, a pressure of 200 MPa is applied to the liquid metal, and by moving the plate 1 of the press, the crystallizing metal is pressed by the mold-forming insert 4. After the technological holding, the plate 1 is moved to the left. The compressed damper 3 rests against the ring 2 and undermines the mold-forming insert. The plate 1 is moved to a distance sufficient for pushing the piston blank out by the plunger 9.

The fundamental difference of the invention from known analogues and prototypes is in the proposed technology for manufacturing a piston blank for an internal combustion engine, when, in order to ensure higher resistance to temperature and impact mechanical loads during engine operation, based on a combination of casting technology with pressure treatment and expansion of the range of alloys used for pistons, the metal poured into the mold is compressed for two seconds during the movement of the pressing plunger under a pressure of 200 MPa, after which the crystallizing metal is pressed during the time of crystallization development, destroying dendritic crystals and compensating for the shrinkage of the metal under the pressure of the molding insert, increasing to 400 MPa.

The invention is illustrated by the following illustrations:

Fig. 1 - Schematic diagram of the method for producing pistons for internal combustion engines on a horizontal hydraulic press

The diagram (Fig. 1) shows the following positions:

1 - left movable plate; 2 - ring; 3 - damper; 4 - forming insert; 5 - left part of the mold; 6 - Ni-resist ring; 7 - right part of the mold; 8 - pressing chamber; 9 - pressing plunger; 10 - pouring cup; 11 - rod; 12 - right fixed plate.

The piston manufacturing process proceeds in the following sequence:

- installation of a Ni-Resist ring in the right part of the form;

- heating the insert and the mold;

- closing of the form;

- pouring a measured portion of metal;

- switching on the pressing plunger;

- switching on the movement of the press plate and pressing the internal cavity of the mold with a mold-forming insert;

- technological holding to complete crystallization;

- pushing out the piston blank with a plunger.

Next, the cast blank undergoes the following technological operations:

- heat treatment;

- mechanical processing.

The method of producing pistons for internal combustion engines with a Ni-resist ring is carried out on specialized technological equipment for casting with crystallization under pressure, which is an automated complex based on a horizontal hydraulic press consisting of two coaxial, oppositely located hydraulic cylinders designed to move the press plunger and a plate for directly applying pressure to the crystallizing metal.

Thus, the method for producing pistons for internal combustion engines with a Ni-resist ring includes obtaining a piston blank with a Ni-resist ring by installing the Ni-resist ring along the parting plane of the mold and fixing the insert by closing the movable half-mold with the fixed half-mold, pouring liquid metal through a pouring cup, pressing the liquid metal with a pressing plunger and a mold-forming insert. This is followed by thermal and mechanical treatment of the obtained blank. As a result, higher resistance to temperature and impact mechanical loads during engine operation is ensured, hardness increases, operational properties of the ICE piston are improved, production costs are reduced.

The claimed invention allows to increase the service life of the piston by reducing the risks of piston destruction at the piston ring seating points, improves quality by forming a dense, uniform, fine-grained structure throughout the entire volume of the internal combustion engine piston, and reduces the number of technological operations.

The implementation of the claimed method solves the problems set by the authors.

Claims (1)

A method for producing pistons for internal combustion engines with a Ni-resist ring, comprising installing the ring in a recess along the plane of the mold joint and fixing it by closing the movable half-mold with the fixed half-mold, installing a mold-forming insert that forms the internal cavity of the piston in the movable half-mold, installing a pressing plunger in the fixed half-mold, heating the mold, pouring liquid metal into the mold with a horizontal arrangement of the cavity axis, applying pressure to the liquid and crystallizing metal, bringing the compressibility of the poured metal to 12-13%, holding the formed piston blank until the metal has completely solidified, pushing the blank out of the fixed half-mold during movement of the pressing plunger and withdrawal of the movable half-mold, thermal and mechanical processing of the resulting piston blank with a Ni-resist ring, characterized in that said heating of the mold is carried out to a temperature 220-250°C, the temperature of the liquid metal poured into the mold is 180-200K higher than the liquidus temperature, while the metal poured into the mold is compressed for two seconds by the action of the movement of the pressing plunger under a pressure of 200 MPa, after which the crystallizing metal is pressed during the time of crystallization development by a mold insert under a pressure increasing to 400 MPa, ensuring the destruction of dendritic crystals and compensation for metal shrinkage.