WO2017195018A1

WO2017195018A1 - A method of modifying a metal in a casting mold

Info

Publication number: WO2017195018A1
Application number: PCT/IB2017/000519
Authority: WO
Inventors: Roman Aleksandrovich SAVUSHKIN; Kirill Valterovich KYAKK; Oleg Arkadievich BROYTMAN; Stepan Aleksandrovich BORODIN
Original assignee: Rail 1520 Ip Ltd.
Priority date: 2016-05-12
Filing date: 2017-05-03
Publication date: 2017-11-16
Also published as: RU2016118299A

Abstract

The invention relates to foundry operation and may be used for in-mold modification of a metal (steel, crude iron, non-ferrous metals and alloys thereof) in the production of castings. The method includes arranging a modifier (3) in a cavity (1) of a casting mold by attaching it to a surface (1.1) and subsequently filling the casting mold with metal melt. The modifier (3) is arranged by attaching it in places in the cavity (1) of the casting mold which correspond to zones of the casting where zoned modification is necessary, or in places in the cavity (1) of the casting mold arranged upstream of these zones relative to the melt flow direction. Attachment of the modifier (3) to the surface (1.1) of the cavity (1) of the casting mold is possible by means of applying it to a double-sided adhesive tape (2) or spraying it together with an adhesive substance. Improved quality of castings, reduced modifier expenditure, increased casting yield ratio are achieved.

Description

DESCRIPTION

A METHOD OF MODIFYING A METAL IN A CASTING MOLD

Technical Field

The invention relates to foundry operation and may be used for in-mold modification of a metal (steel, crude iron, non-ferrous metals and alloys thereof) in the production of castings .

Background Art

A method of modifying a metal in a casting mold is known, wherein, in a reaction chamber having inlet and outlet runner channels for forming a melt flow in the form of an ascending spiral around a modifier, the modifier is arranged at a distance from the bottom of the chamber and spaced apart from its side walls (SU 1692733 Al , published 23.11.1991).

A method of in-mold modification of a casting metal is known, which includes placing a modifier in chambers that are provided in inlet runner channels of the casting mold, and shaping a melt flow with the modifier (US 2007246185 Al, published 25.10.2007).

A method of modifying a metal within a casting mold is known, which includes placing a modifier within a reaction chamber of a runner system, and filling metal melt into the casting mold under controlled pressure and filling rate (SU 749563 Al, published 23.07.1980).

Common drawback of known technical solutions is that modifier is used inside elements of a runner system, e.g. in a reaction chamber, through which liquid metal is provided into the casting mold. Such arrangement of a modifier insert results in uneven distribution of the modifier within the volume of the castings due to uneven flow rate of the modifier dissolved in the metal flow in the process of filling the casting mold; hydrodynamic properties degrade due to cooling of the metal melt when it contacts large volumes of modifiers; modifier flow rate in the runner system is increased; it is necessary to keep filling rate low. Presence of a reaction chamber in the runner system for placing the modifying element complicates the structure and reduces the casting yield ratio.

Disclosure of Invention

Technical problem, which is not solved by prior art analogues of the invention and is solved by the proposed invention consists in making it possible to arrange the modifier directly within the casting mold. Such solution enables homogeneous modification of the whole volume of castings that have relatively small sizes, and to perform zoned modification in castings with a complicated shape or a manifold configuration by precise and fine dosing of the amount of modifying additives directly in the necessary parts of the castings .

Technical result of the use of the invention consists in improved quality of castings, reduced modifier consumption, increased casting yield ratio.

The above-mentioned technical result is achieved in that, in the method of modifying a metal in a casting mold, which includes arranging a modifier and filling the casting mold with metal melt, according to the invention the modifier is arranged in a cavity of the casting mold by attaching it to the surface of the casting mold. The modifier is attached at the portions of the casting mold which correspond to the zones of the casting where zoned modification is required, or at the portions of the casting mold which are located upstream of these zones relative to the direction of metal melt flow. Modifier is attached, for example, by applying it to a double-sided adhesive tape. Modifier is attached, e.g., by spraying it together with the adhesive substance.

Arrangement of the modifier immediately inside the cavity of the casting mold provides numerous advantages, such as: improved quality of castings and their microstructure, and enhanced mechanical properties by virtue of deep purification of metal from non-metallic impurities and admixtures at temperatures proximate to the solidification range ,

reduced microstructure of castings by virtue of achieving a short time interval between the time of modifier introduction and beginning of solidification, which is manifested by providing thermodynamic conditions for the formation of active crystallization nuclei;

performing full-scope modification of simple castings with light weight, providing for enhanced and uniform quality of metal structure in different cross-sections;

providing for zoned modification of complex castings with a manifold configuration of walls;

obtaining, in case of using zoned modification, an enhanced level of mechanical properties in most operationally loaded elements of the casting, in particular without using heat treatment;

possible reduction of the risk of occurrence of such defects as liquation and microporosity in zones which are characterized by reduced solidification rate; reduced modifier expenditure by virtue of minimized oxidation losses of the same while staying in liquid metal; increased casting yield ratio by virtue of reducing metal expenditure in the runner system with a reaction chamber; possibility of arranging the modifier on any surfaces of the mold, in particular curvilinear surfaces;

no need for designing a special runner system and organizing the modification;

possibility of using computer modeling of a process of filling the casting mold with metal melt for the purpose of predicting the movement of modifier particles and defining the zone in the casting, where the amount of modifier will be maximum at the end of the filling;

increased filling speed by virtue of the absence of need for controlling the expenditure of liquid metal for the reaction with the modifier when using the reaction chamber.

The suggested use of known double-sided adhesive tapes or known adhesive, substance provide for the implementation of intended use of the invention and achievement of the technical result as specified on condition that the adhesive used therein has a high initial adhesion to silicate materials, has a gluing point at room temperature, high radiation resistance and high short-term heat resistance that depends on the temperature of the metal melt being filled into the mold, and does not contain flammable solvents among its components. Double-sided adhesive tape that can be used may be, in particular, an acrylic foam tape; its adhesive substance may be, in particular, a glue on the basis of copolymers of vinyl acetate with acrylates.

The suggested method with a modifier attached to a casting mold with a double-sided adhesive tape is preferable when castings are produced using a vacuum cast (VC) method. Use of the invention together with this method is advantageous in that it provides high adhesion of the adhesive layer of the tape with a polymer cover film, use of active removal of glue component destruction products from the surface of a casting mold, which makes it possible to place the modifier on any surface of the mold, as well as a possibility of organizing modifier placement operations with a high level of automation. The invention may be used in casting molds having surfaces formed of sand-clay and cold- curing mixtures, and also may be used in durable metal and ceramic casting molds. In the meantime, there is a restriction which is related to the mode of gas filtration of glue combustion products within the cavity of the casting mold, due to which elements of the adhesive tape with the modifier should be arranged only in the regions of the casting mold which are well ventilated by virtue of being connected to the environment .

The suggested method with the modifier being attached within the casting mold by an adhesive substance sprayed over its surface may be used when producing castings in non- reusable casting molds with surfaces formed by sand-clay and cold-curing mixtures. A mandatory condition for using the method is also the provision of good ventilation by connecting the places of modifier arrangement to the environment for extracting products of glue components' destruction.

Brief Description of the Drawings

The invention is illustrated by drawings, which show: Fig. 1 - a casting mold with a modifier attached by a double- sided adhesive tape in places that correspond to the casting zones to be modified, longitudinal section; Fig. 2 - the same, section A-A;

Fig. 3 - a casting mold with a modifier attached by means of a sprayed adhesive in regions of the casting mold, which correspond to the casting zones to be modified, longitudinal section;

Fig. 4 - casting mold with a modifier attached by a double-sided adhesive tape in places which are situated upstream of the casting zones to be modified, relative to the metal melt flow direction, a horizontal section of the lower half-mold.

Best Mode for Carrying Out the Invention

The casting mold (Figs. 1, 2) comprises a cavity 1 with a surface 1.1, on which pieces of double- sided adhesive tape are arranged in places that correspond to zones of the casting that require zoned modification, said pieces being glued with their side, from which protective film has been removed. A layer of granulated powder of the modifier 3 applied in advance is arranged on the other, open side of the adhesive tape 2.

The casting mold (Fig. 3) comprises a cavity 1 with a surface 1.1, on which a layer of adhesive substance is applied by spraying in places that correspond to zones of the casting to be modified, with granulated powder of the modifier 3 dissolved therein.

The casting mold (Fig. 4) comprises a cavity 1 with a surface 1.1, on which pieces of double- sided adhesive tape 2 with modifier 3 are arranged in places above the zones 4 to be modified, in the way of the metal melt flow. The invention is implemented as follows.

At the first step, prior to the assembly of the casting mold and to filling the casting mold with metal melt, modifier is attached within the cavity 1 of the casting mold.

The modifier is attached by applying it to a double-sided adhesive tape (Fig. 1) . Modifier inserts are prepared in advance, for which double- sided adhesive tape 2 is cut into pieces with pre-calculated length which is sufficient for applying the necessary amount of modifier 3. Protective films are removed from one of the sides of the pieces of adhesive tape 2, and a layer of modifier 3 granulated into a powder is applied; non-adhering modifier particles are removed (blown off) . Then protective films are removed from the opposite side, and pieces of the adhesive tape 2 with modifier 3 are attached to the surface 1.1 of the casting mold. When simple castings with a small volume are produced, pieces of adhesive tape 2 with modifier 3 are arranged in different places Within the cavity 1 such that they are evenly distributed over the surface 1.1. When complicated castings with a manifold configuration are manufactured, pieces of adhesive tape 2 with modifier 3 are arranged in those places within the cavity 1 where maximum amount of modifier 3 is required.

Attachment of modifier by spraying it together with an adhesive substance (Fig. 3). Adhesive substance is prepared in advance, by mixing the powdered modifier 3 with glue. When simple castings with small volume are produced, adhesive substance is uniformly sprayed over a surface 1.1 of cavity 1 of the casting mold. When complicated castings with a manifold configuration of walls are produced, adhesive substance is sprayed directly to those places within the cavity 1 where maximum amount of modifier 3 is required. Attachment of modifier by means of a double- sided adhesive tape 2 (Fig. 4) or by spraying together with an adhesive substance in places of the casting mold which are located upstream of the zones 4 to be modified relative to the metal melt flow direction, and through which the zones 4 of the casting to be modified are filled with liquid metal, is carried out similarly to the aforementioned. For the modifier 3 to be delivered with high precision by a flow of metal melt to zones 4 of the casting to be modified, distance between the location of the attached modifier and these zones is determined in each particular case by modeling the filling of the metal melt with regard to the configuration of the casting, rate of filling, and physical and chemical properties of the metal to fill the mold.

At the second step, after attaching the modifier 3, metal melt is provided into the casting mold through a runner channel, the flow of metal interacting with the modifier 3 within the cavity 1 and gradually and completely dissolving its layer, and actively mixing while the casting mold is filled. Uniform or local arrangement of the modifier 3 applied on the inner surface 1.1 of the casting mold in the form of a thin layer within the cavity 1 provides for high quality and homogeneity of metal microstructure over a cross- section of the casting, significantly reduces modifier consumption, increases the casting yield ratio.

The claimed method enables filling a casting mold with metal melt and modifying the metal immediately within the casting mold as a one-stage process. By using computer modeling of filling of the casting mold with metal melt, it is possible to predict the movement of modifier particles and to identify the zone of the casting where maximum amount of the modifier will be located at the end of the filling. Therefore, high-quality microstructure and high level of mechanical properties of metal may be achieved in the necessary zones of the casting by selecting a mode of filling the mold with metal melt and adjusting the locations of the modifier .

Claims

1. A method of modifying a metal in a casting mold including arranging a modifier and filling the casting mold with metal melt, characterized in that the modifier is arranged within a cavity of the casting mold by attaching it to a surface of the cavity of the casting mold.

2. The method of modifying according to claim 1, characterized in that the modifier is attached in those places of the casting mold which correspond to zones of the casting where zoned modification is necessary.

3. The method of modifying according to claim 1, characterized in that the modifier is attached in those places of the casting mold which are located upstream of the zones to be modified relative to the direction of metal melt flow .

4. The method of modifying according to claim 1, characterized in that the modifier is attached by applying it to a double- sided adhesive tape.

5. The method of modifying according to claim 1, characterized in that the modifier is attached by spraying it together with an adhesive substance.