RU2462328C2 - Method of casting brake shoes and travelling chill casting plant to this end - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy. Proposed method is implemented at travelling chill casting plant comprising slide chill moulds arranged on transfer cars of vertically-closed conveyor chain. At pouring area, chill mould cavities are lined by 9-11 mm-thick rods to pour fused metal therein. After primary solid metal skin is formed on castings in conveyor motion, halves of chill mould are drawn apart by pneumatic cylinders arranged on transfer cars through preset gap of 2-3 mm. After crystallisation, castings are withdrawn from chill mould by magnet in unloading area.

EFFECT: higher quality.

7 cl, 2 dwg, 1 ex

Description

The invention relates to foundry. A method for manufacturing brake pads by casting in a chill mold is proposed, mainly for use in railway transport. To implement the method, a conveyor chill installation is proposed, which includes a simple, efficient and reliable casting conveyor design, which allows for high-performance and high-quality production of brake pads in mechanized production conditions.

The manufacture of brake pads by the method of chill casting is known from the prior art (see USSR copyright certificate: SU 80655).

In railway transport, cast-iron brake pads equipped with reinforcing inserts are mainly used (see patents RU 2040361, RU 56521). For the manufacture of high-quality castings of the brake pads, the technology of its manufacture should provide a given metal structure in the corresponding parts of the casting. In addition, in the mass production of such castings, technological methods that provide high-quality products should not be expensive and complicated.

A method is known from the prior art for manufacturing brake shoes by casting in a chill mold, mechanized using a chill machine, which allows the halves of the split chill to be pushed apart after the crystallization of the ingot begins to reduce (by 70%) the surface layer of the casting (FR 2583320, 09/18/1987).

The disadvantage of this method is that it is not possible to use a casting conveyor that increases the productivity of the process and provides the ability to quickly replace used foundry equipment. In addition, 20-30% of cementite and other carbides are retained in the surface structure of the casting, despite the use of an air gap during crystallization of the casting. The selection of the correct thermal regime for cooling the casting during its crystallization in the chill mold is a very difficult task, requiring the consideration of a large number of different thermophysical process parameters.

The prior art designs of horizontally-closed cart conveyors (RU 2090480, 09/20/1997 and RU 51603, 02/27/2006), but they are not intended for use in foundry conditions.

The closest analogue of the claimed device is a conveyor chill machine according to patent RU2090307, published on 09/20/1997. The conveyor chill installation includes a base, a vertically closed conveyor, chill molds with a vertical plane of the connector placed on it, a casting area and a conveyor drive. In this case, the conveyor is made in the form of two closed chains, on which semi-cockles are fixed, the upper branches of the conveyor chains in the area of the pouring area are inclined to ensure a tight fit of the chill molds.

This design provides for the fastening of semi-chills on the conveyor, which makes it difficult to carry out equipment change operations. In addition, this installation is not intended for the manufacture of castings of brake pads.

The claimed invention is aimed at solving the problem of reducing the complexity of manufacturing cast iron brake pads while improving the quality of casting and working conditions.

The technical result of the invention is to improve the quality of cast billets while ensuring increased wear resistance of the working surface of the brake pads while increasing the productivity of the process and reducing the cost of production.

The problem is solved as follows.

The claimed method of casting cast iron brake pads using a conveyor chill installation includes placing sliding chill molds on horizontal platforms of load-bearing trolleys of a vertically closed chain conveyor and feeding them to the casting area. In this case, before feeding to the casting site, lining of the chill cavities is carried out with rods 9-11 mm thick, then molten metal is cast, followed by crystallization of the casting. Moreover, during the movement of the conveyor from the casting area to the unloading area after the formation of the primary crust of solid metal on the castings, the components of the split molds are moved apart by a predetermined gap of 2-3 mm, and after the crystallization of the castings in the unloading area is completed, castings of cast-iron brake shoes are extracted magnet.

To increase the productivity of the method, when casting brake shoes, this technology uses a double sliding water-cooled chill mold with two connectors in the vertical plane with the possibility of producing two castings in one chill mold.

Before pouring molten iron, the internal cavities of the chill molds must be protected from direct contact with the metal. Plug-in facing rods to protect the working surfaces of the chill mold are made with a thickness of 9-11 mm from cold-hardening carbomidofuran or phenolofuran molding composition. The manufacture of rods for facing the walls of the chill mold is carried out on a vibrating table with filling the core box from a screw mixer. Changing the thickness of the facing core adversely affects the life of the chill mold and the quality of the surface of the casting.

When developing this technology, it was unexpectedly found that in order to obtain a given structure of the surface layer of the brake shoe casting, the gap by which the components of the demountable mold are extended in the manufacture of cast iron castings should be 2-3 mm. Only at a given gap value, the conditions of the heat balance during crystallization of the casting of this type of product provide complete decomposition of cementite and the absence of bleach on a given surface area. Changing the gap leads to a mixed structure in which residual cementite is present in a significant amount (20% or more).

The conveyor chill installation contains a base, which serves as a support for the placement of all its mechanisms. The longest part of the installation is a vertically-closed conveyor, on which are placed sliding molds made with a vertical plane of the connector. The installation comprises a casting section, a conveyor drive and a discharge section. A vertically closed conveyor is made in the form of two closed chains on which load-carrying trolleys are attached, equipped with horizontal platforms adapted for installation of chill molds on them. The sliding parts of the chill molds are connected to power pneumatic cylinders, providing an adjustable gap in the process of crystallization of the casting. The pneumatic cylinders are fixed on the platforms of the load-carrying trolleys, and a lifting device equipped with a magnet for extracting the castings is installed at the discharge site.

Sliding chill molds are made water-cooled and double with two connectors in the vertical plane.

The lifting device at the discharge site is equipped with an electromagnet for extracting castings.

In addition, a vertically enclosed conveyor is made in the form of a cart conveyor with a tilting construction of load-carrying carts. Using a conveyor of a different design complicates the installation, reduces its operational reliability. Moreover, in the process of movement of the conveyor from the casting area to the unloading area after the formation of the primary crust of solid metal on the castings, the components of the detachable molds are moved apart by a predetermined clearance of 2-3 mm

As the metal for casting brake pads for railway transport, mainly cast gray cast iron or cast iron with a modified structure of graphite inclusions is used. Other casting alloys may be used to make brake pads for other vehicles.

The invention is illustrated in figures 1 and 2 and an example.

The figure 1 shows a General view of the conveyor chill installation containing a vertically-closed conveyor with load-carrying trolleys and double sliding chill molds placed on it.

The figure 2 shows a double sliding chill mold equipped with pneumatic cylinders.

As shown in figure 1, the conveyor chill installation 1 contains a base 2, which serves as a support for the placement of its mechanisms. The longest part of the installation is a vertically closed conveyor 3, on which sliding chill molds 4 are placed, made with the vertical plane of the connector 5. Installation 1 contains a pouring section (not shown in the drawing), a conveyor drive and a discharge section 6. A vertically closed conveyor 3 is made in the form of two closed circuits 7, on which load-carrying trolleys 8 are mounted, equipped with horizontal platforms 9 adapted for installation of the chill molds 4. The sliding parts 10, 11 of the chill mold 4 are connected to the power pneumatic indram 12, 13, providing an adjustable gap in the process of crystallization of the casting. The pneumatic cylinders are fixed on the platforms 9 of the load-carrying trolleys 8, and a lifting device equipped with a magnet 14 for extracting the castings 15 is installed in the discharge section 6.

Sliding chill molds 4 are made water-cooled and double with two connectors 5 in a vertical plane, while the lateral sliding part of the chill mold 10, 11 is equipped with individual pneumatic cylinders 12, 13, mounted on load-carrying carts 8 of conveyor 3.

The lifting device at the discharge site is equipped with an electromagnet 14 for extracting castings, made in the form of a contact magnetic washer.

The vertically closed conveyor 3 is made in the form of a cart conveyor with a tilting construction of load-carrying carts 8.

Example.

A method of manufacturing brake pads was carried out by pouring a portion of molten cast iron into a prepared batch of lined chill molds using a casting conveyor to move the chill molds from the casting area to the unloading section, which allows for simple, efficient and reliable production of brake shoe castings under mechanized production conditions.

As a casting conveyor, a vertically closed cart conveyor 3 was used, which is made in the form of two closed circuits 7 with load-carrying trolleys 8 of a tipping structure fixed on them (for reverse movement along the lower branch of the conveyor). The load-carrying trolleys 8 are equipped with horizontal platforms 9 adapted for installation on them of the chill molds 4 with power pneumatic cylinders.

The method includes placing sliding chill molds 4 on horizontal platforms 9 of load-carrying trolleys 8 of conveyor 3 and supplying them to the casting area of molten iron. At the same time, to prevent direct contact of the jet of molten cast iron with the surface of the chill mold, before casting the chill molds to the casting area, they cover their foundry cavities with a rod mass (insert rods) of 9-11 mm thickness. The plug-in facing rods for the protection of the working surfaces of the chill mold are made of cold-hardening carbomidofuran or phenolofuran molding composition. The manufacture of rods for facing the chill mold is carried out at the molding section on the vibrating table with filling the core box from the screw mixer. A lined chill mold is served for filling.

To obtain castings in this installation, we used sliding water-cooled double chill molds 4, made with two vertical connectors 5, while the lateral sliding parts of the chill mold 10, 11 are equipped with individual pneumatic cylinders 12, 13, mounted on load-carrying carts 8 of conveyor 3.

Metal filling is carried out in "open" sliding chill molds. A sliding chill mold is shown in section in FIG. It is made with the ability to expand its lateral components 10, 11 during the crystallization of the casting by a small amount of 2-3 mm using individual pneumatic cylinders 12, 13 mounted on them. For casting, the example used a chill mold made in the form of a metal mold lined with a rod with a size cladding 420 × 145 × 95 mm. Thus, the working surfaces of the chill mold were insulated with core inserts with an average thickness of 10 mm.

For casting, the chill molds 4 are mounted on horizontal platforms 9 of the load-carrying trolleys 8 of a vertically closed chain conveyor 3 and are placed so that during movement the filled chill molds 4 maintain their horizontal position when moving along the upper branch of the conveyor.

To prevent the appearance of “bleached” on other (except working) surfaces of brake shoe castings, the method of pouring a water-cooled chill mold with cast iron with an adjustable air gap was used. For this, after pouring the chill mold 4 with molten metal 20-30 seconds after the formation of a hard crust on the casting, the two components of the chill mold move apart to form a small air gap: 2-3 mm. The heat sink from the crystallizing surface decreases sharply. Under the influence of heat transfer from gradually crystallizing cast iron inside the casting, heat is redistributed with heating of the surface of the brake pads to t ° = 850-950 ° C and with holding at this temperature. Primary cementite formed in the structure of cast iron casting disintegrates. This ensures the preservation of frictional properties with the formation of a given microstructure of the metal base containing graphite inclusions in accordance with the requirements of regulatory documentation. Under these conditions, the rest of the metal (cast iron) crystallizes.

The casting is extracted with an electromagnetic lifting device with a contact magnetic washer, with the help of which the brake shoe casting is overloaded for further processing. Empty chill molds are removed from the carts and sent for cleaning and lining. Empty trolleys in reverse stroke of the lower branch of the conveyor return to their original position to place a new batch of lined chill molds on them.

Using the inventive method, a reduction in the cycle of manufacturing brake pads, an increase in the quality of the surface to obtain a surface of grade 4-5 are obtained, the sanitary and hygienic conditions of the process are significantly improved.

Claims (7)

1. A method of casting cast iron brake pads using a conveyor chill installation, including placing sliding chill molds on horizontal platforms of load-bearing trolleys of a vertically closed chain conveyor and supplying them to the casting area, prior to feeding to the casting area, chill cavities are lined with rods 9-11 thick mm, then molten metal is poured, followed by crystallization of the casting, and in the process of conveyor movement from the casting section to the discharge section after On castings of the primary crust of solid metal, the components of split molds are pushed apart by a predetermined gap of 2-3 mm, and after the completion of the crystallization process of the castings at the discharge site, castings of cast-iron brake shoes are extracted using a magnet. 2. The method according to claim 1, characterized in that to obtain castings of the brake pads use a double sliding water-cooled chill mold with two connectors in a vertical plane with the possibility of obtaining two castings in one chill mold. 3. The method according to claim 1, characterized in that the plug-in facing rods for protecting the working surfaces of the chill mold are made of cold-hardening carbomidofuran or phenolofuran molding composition. 4. The method according to claim 3, characterized in that the manufacture of rods for facing the chill mold is performed on a vibrating table with filling of the core box from the screw mixer. 5. A conveyor chill installation containing a base, a vertically closed conveyor, sliding chill molds with a vertical plane of a connector placed on it, a casting area, a conveyor drive and an unloading section, while the vertically closed conveyor is made in the form of two closed chains on which load-carrying are fixed trolleys equipped with horizontal platforms for installing chill molds on them, the sliding parts of the chill molds are connected to pneumatic cylinders fixed on the platforms of the trolleys, and a lift is installed in the unloading area mnoe device provided with a magnet for extracting the castings. 6. Installation according to claim 5, characterized in that the sliding chill molds are made water-cooled and double with two connectors in the vertical plane. 7. Installation according to claim 5, characterized in that a lifting device equipped with an electromagnet for extracting the castings is installed in the discharge section.

Images