RU2367539C2 - Method of receiving of steel castings - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes manufacturing of model blocks, receiving of shell block moulds by application of layers of fireproof suspension on block, moulding of shell mould into refractory backing material, its tempering, ignition of model block. Model blocks are manufactured by pressing of thermite charge, containing iron-aluminium termite, ferroalloys and binder material. Model block is ignited by gas-flame burner for implementation of exothermic reaction with formation in shell mould of steel casting.

EFFECT: improvement of steel casting method.

2 cl, 2 dwg

Description

The invention relates to methods for manufacturing castings using a thermite mixture and can be used in the engineering industry.

The closest in technical essence to the achieved result is a method for producing castings in multilayer shell one-piece single forms manufactured using smelted, soluble or burned single-use models. In the process of investment casting (LWM), the following technological operations are performed: models of parts and a gate-feeding system are made in molds, for which they use wax-like fusible materials, compositions based on resins and plastics, and alloys of salts. Models are connected into blocks (by soldering, gluing, mechanical bonding) and layers of a suspension of a binder solution and dusty refractory material are applied to them. The layers of the suspension are strewn with sand and dried for their hardening and better mutual connection. The number of layers applied varies: from three to four to 20 or more, depending on the intensity and purpose of the form. From the obtained multilayer inseparable shell mold, the model composition is removed by melting, dissolving or burning. In some cases, in order to protect the shell from power and thermal influences in subsequent operations, blocks with the finished shell before or after removal of the models are molded into a loose or containing a binder support filler.

The shells liberated from the model composition separately or in a support filler are calcined to remove organic residues of model and binder materials, after which hot or cooled molds are poured with melt [Special casting methods: Reference book / V.A. Efimov, G.A. Anisovich, V.N. Babich et al .; Under the total. ed. V.A. Efimova. - M .: Mechanical Engineering, 1991. - S.197-230].

The implementation of the method makes it possible to manufacture shaped castings from any cast alloys, including complex in configuration and thin-walled, as close as possible to the shape and size of the finished part, which reduces the complexity and cost of manufacturing products, reduces the consumption of metal and tools, the need for production facilities, machine tools and accessories.

The disadvantages of the known prototype method are: the lack of the possibility of using waste metallurgical production; the duration of the casting process; a large number of operations used in the technological cycle.

The objectives of the proposed method are: the use of metallurgical waste (scale, ferrous metal shavings) to obtain steel castings; reduction of the duration of the technological process for producing castings; reduction in the number of operations used in the process.

These tasks are achieved by the claimed method of producing steel castings, including the manufacture of a model block, obtaining a shell inseparable form by applying layers of refractory slurry to a model block, molding the shell form in a refractory filler and its calcination, while model blocks are made by pressing a thermite charge containing iron-aluminum termite, ferroalloys and a binder material, ignite a model block for an exothermic reaction to form a hundred flax melt. In addition, the ignition of the thermite mixture is produced in the upper part of the model block using, for example, a gas flame burner.

Known features of the proposed method: the manufacture of a model block, obtaining a shell integral form by applying layers of refractory suspension to a model block, molding the shell form into a refractory filler and its calcination.

Distinctive features: model blocks are made by pressing a thermite mixture containing iron-aluminum termite, ferroalloys and a binder material, the model block is ignited to carry out an exothermic reaction with the formation of a steel melt in the shell form.

A causal relationship between the distinguishing features and the obtained technical results is achieved through the use of metallurgical waste products, in particular scale and ferrous metal shavings, as components of the pressed thermite mixture; ignition of the model block for the exothermic reaction with the formation of a steel melt in the shell form allows to reduce the duration of the process and the number of operations, eliminating from the process the operations of smelting the model mass from the shell form and preparation of molten molten steel in furnaces. Due to the composition of the termite charge, including iron-aluminum termite and ferroalloys, in the process of exothermic reaction, a steel melt of a given chemical composition is obtained, which upon solidification forms the casting body.

The inventive method for producing steel castings is carried out using the device shown in figures 1 and 2, where figure 1 shows a section of a casting flask before ignition of the model block, and figure 2 is a section of a casting flask after forming a steel casting.

The figures show a model block 1 with a coated shell integral form 2 installed in the supporting filler 3, which is poured into the casting flask 4. A gas flame burner 5 is brought to the model block 1.

The inventive method for producing steel castings is as follows.

By pressing a metallothermal charge consisting of iron-aluminum termite (22% aluminum powder, 52% scale, 2% fluorspar, 19% ground fireclay, 5% molding clay), ferroalloys and a waxy model material, model block 1 is made with a gating system ( figure 1). As a ferroalloy, it can be used, for example, to obtain steel castings according to the chemical composition of the corresponding St45, FS-45 ferrosilicon powder with a fraction of 0.5 mm, with a silicon content of 44%, the remaining elements no more than: S = 0.02%, P = 0.05%, Al = 2%, Mn = 0.6%, Cr = 0.5%, C = 0.2%. Layers of a suspension of a binder solution and refractory material, such as graphite, are applied to the model block, forming a shell form 2. The layers of the suspension are sprinkled with graphite for their hardening and better mutual connection and dried. The number of layers applied varies: from three to four to 20 or more, depending on the intensity and purpose of the steel castings.

In order to protect the shell mold 2 from force and thermal influences in subsequent operations, the model block 1 with the finished shell mold 2 is placed in the flask 4 and molded into a loose or containing binder support filler 3. The shell mold 2 installed in the support filler 3 of the flask 4 is calcined to remove organic residues of model and binder materials, as a result of which pyrolytic carbon is formed, which is absorbed by the melt that forms later.

After that, in the hot shell form 2 located in the flask 4, the termite material of the gate-feeding system of the model block is ignited, for example, a gas-flame burner 5. The combustion process proceeds quickly, sequentially spreading over the entire volume of the termite material, and generally proceeds according to an exothermic reaction :

2Al + Fe ₂ O ₃ = 2Fe + Al ₂ O ₃ + Q ' _p ,

where Q ^' _p is the heat of the exothermic reaction occurring in shell form 2, providing the melting of all components of the model block 1.

In this case, a molten steel is formed in the shell mold 2, which then hardens, forming a steel casting. In the process of the termite reaction, slag is formed, which floats in full to the upper part of the shell mold 2. The steel casting is cooled in the shell mold 2 and is removed from it in the traditional way.

This method is carried out through the use of traditional equipment and available materials, which ensures its industrial applicability.

Claims (2)

1. A method of producing steel castings, including the manufacture of model blocks, obtaining shell integral forms by applying layers of refractory slurry to the block, molding the shell shape into a refractory filler and its calcination, characterized in that the model blocks are made by pressing a thermite charge containing iron-aluminum termite, ferroalloys and the binder material, after calcination, the model block is ignited for an exothermic reaction to form a steel melt in the shell form and the subsequent conductive its solidification. 2. The method according to claim 1, characterized in that the ignition of the thermite mixture is carried out in the upper part of the gating system using, for example, a gas flame burner.

Images