RU2731494C1 - Method of iron castings reinforcement - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates to casting of reinforced iron castings and their chemical-thermal treatment using high-frequency electromagnetic field and can be used for production of parts used in abrasive and chemically aggressive media. Method of iron castings reinforcement includes heating reinforcing steel frame to temperature of 600–800 °C and cast iron melting with high-frequency electromagnetic field, at that, crucible with cast iron and casting mold with reinforcing steel frame installed in it are placed into inductor connected to high-frequency generator, melting of iron and heating of steel reinforcing frame is carried out simultaneously by exposure to them by high-frequency magnetic field with frequency of 40–70 kHz, wherein the thickness or diameter of the components of the reinforcing frame is selected based on the condition of penetration of electromagnetic waves into them at depth of 30–50 %.EFFECT: invention is aimed at reducing labor intensity of parts manufacturing with improvement of their physical and mechanical properties.1 cl, 2 ex, 2 dwg

Description

The invention relates to the foundry production of iron castings and chemical-thermal treatment of parts using a high-frequency electromagnetic field of parts manufactured for operation in abrasive and chemically aggressive environments.

The intensity and value of the heating temperature of products made of ferromagnetic materials depends on the conditional depth of penetration of the electromagnetic wave into the metal. It is known that for each frequency of an alternating electromagnetic field there is its own depth of penetration of electromagnetic waves into the metal for the same materials. In addition, it has been experimentally established that at a smaller thickness than the penetration depth of the current into the metal or the diameter of the product heated by a high-frequency electromagnetic field, the temperature in such workpieces does not rise above 740-780 ° C (the effect of a "tin" can).

There is a known method (analogue) of obtaining castings with increased mechanical strength by installing a metal frame (reinforcement) in a casting mold and filling it with melt and subsequent solidification of the castings, which are then removed and subjected to annealing (production of stone castings). However, when the reinforcement is installed from room temperature (without preheating), oxides appear on its surface, along the reinforcement-alloy interface, which does not provide mechanical strength between the reinforcement and the alloy, in addition, when using reinforcement that has room temperature when it is poured with melt, stresses arise at the interface between the melt and the cold metal, due to the difference in the coefficients of thermal expansion of metals, which leads to the appearance of numerous micro- and macrocracks [Lipovsky I.E., Dorofeev V.A. The basics of petrurgy. M, metallurgy, 1972, p. 151-162].

There is also known a method of producing stone reinforced casting by preheating the frame to a temperature of 600-800 ° C and installing the heated frame in the solidifying melt (Inventor's Certificate No. 1033330, 08/07/1983).

The disadvantage of this method is the high labor intensity, due to the need to use two metallurgical furnaces: one for heating the frame, and the other for melting the reinforced material (analogue).

There is a known method of reinforcing the pusher plate (prototype) adopted at the Gorky Automobile Plant, which consists in the fact that a groove is carried out in the pusher plate and fused drill is poured onto it, then the pusher plate is placed in a variable high-frequency electromagnetic field of the inductor and heats up in it to a temperature of 1150- 1250 ° C. After that, special cast iron is melted and poured into a mold (plate), and to obtain a high-quality cast structure, the pusher is additionally heated. (Smelyakov N.N. Reinforced castings: M, "Mashgiz", 1958, p. 74).

The disadvantage of this method is the high labor intensity, due to the need to carry out technological operations from two sources of heating: for heating the valve for surfacing and melting the hardened metal.

Thus, a common technical problem of the known analogs and prototype is the high labor intensity of implementing methods of reinforcing castings from various materials.

The object of the present invention is to reduce the complexity of manufacturing castings.

The present problem is solved by the fact that in the method of reinforcing cast iron castings, which includes heating a reinforcing steel frame in a furnace to a temperature of 600-800 ° C and melting cast iron with a high-frequency electromagnetic field, a crucible with cast iron and a casting mold with a reinforcing steel frame installed in it is placed in an inductor connected to a high-frequency generator, melting of cast iron and heating of a steel reinforcing frame is carried out simultaneously by exposing them to a high-frequency electromagnetic field with a frequency of 40-70 kHz, while the thickness or diameter of the components of the reinforcing frame is selected from the conditions for the penetration of electromagnetic waves into them to a depth of 30-50% ...

The technical result of the invention is to reduce the labor intensity of obtaining reinforced castings from metals and alloys by melting the charge in a crucible with a bottom drain, the hole which is closed with a melting plug before melting the charge materials made in the form of a cylinder or other profile made of materials with a melting point of 100-300 ° C higher than molten metals, which, after melting, are poured into a mold containing a frame or its elements heated to the required temperature, located in the same inductor as the crucible.

The essence of the invention lies in the fact that the crucible with a hole in the bottom is closed by a melting plug having a melting point higher than the temperature of the charge to be melted by 100-300 ° C. A casting mold is installed under the crucible, at the bottom of which there is a reinforcement with a thickness (2 mm) less than the depth of penetration of an electromagnetic wave (δ _m = 2.2-2.5 mm, Babat G.I. Induction heating of metals: ML, Energy - 352 from.). The crucible and the mold are placed in a wrapping inductor connected to a high frequency generator. In the inductor, the operations of melting and pouring metal into a casting mold with a metal frame (reinforcement) installed in it, heated by a high-frequency electromagnetic field up to a temperature of 730-980 ° C, take place simultaneously.

The method of obtaining castings with increased physical and chemical properties was carried out as follows: a mixture was prepared (lining and molding consisting of quartz sand, clay, borax). Then, in the flasks, a crucible with a hole in the bottom part and a mold were molded, in which a frame was installed in the form of a plate (coated with P-066 flux) or a copper-coated welding wire. Then the crucible was installed on the casting mold and placed in a covering inductor connected to a high-frequency inverter ELSIT 100-40 / 70, after which the charge was melted and the fittings were heated and the molten metal was poured into the mold with the frame.

The invention is illustrated by the following materials.

FIG. 1, a diagram of obtaining reinforced castings for C17 cast iron is presented.

FIG. 2.microstructure of reinforced alloy S17 with Sv-08GS welding wire

The scheme for obtaining reinforced castings (Fig. 1) shows: 1 - crucible for melting metal; 2 - flux; 3 - cork; 4 - ferrosilide; 5 - casting mold; 6 - molding composition; 7 - element of the steel frame; 8 - cooled water in the inductor; 9 - inductor.

An example of implementation of the invention.

Example 1. Reinforced castings were made in the form of a plate, intended for brazing on a drill bit of a Primera DMC-9000 seeder manufactured by Aamazone, which operates under conditions of intense abrasive and impact-abrasive wear. For this, a lining mixture was prepared (90% quartz sand; 2-4% clay; 3-4% water and 1.5-2.5%) borax) for making a crucible in a special flask. The crucible was made with a hole in the bottom. The casting mold was made from the same mixture in the bottom of which, plates (steel 65G,) were molded with a cross-section of 1.8-2.0 mm and then they were placed in an oven and dried at a temperature of 850-870 ° C for 5 hours.

A melting plug made of steel 20 with a diameter of 6 mm was installed in the bottom of the crucible, after which the crucible was loaded: ferromanganese FMn-78 and cast iron of grade C17; the mass of the melting plug was 3.5-3.8% of the metal part of the charge.

The amount of molten metal was 10-15% more than necessary to ensure the production of a casting, which should remain in the crucible hole, taking into account its thickness in the bottom of the crucible, which together made it possible to obtain castings without a shrinkage cavity. The weight of the reinforced castings was 46-49 grams.

Example 2. Produced deep anode ground electrodes "GAZ-M" made of cast iron C17, as a frame element located along its axis, to increase the mechanical strength and to increase the efficiency of the device due to electrical contact between the electrical conductor and the electrode.

The mold and crucible were made in the same way as in example 1.

The difference consisted in the fact that a casting mold with a metal core (Sv-08G2S, with a copper-plated surface, 1.6 mm in diameter) was placed in the oven before drying them. The crucible was loaded with the charge materials shown in example 1.

To ensure the technological process of heating the frame in a casting mold. Pre-select equipment that creates an interval of high-frequency electromagnetic waves with a depth of penetration into the metal less than the cross-section of the heated frame elements. In this case, they can reach temperatures no higher than 740-780 ° C, which can be provided by the ELSIT 100-40 / 70 inverter creating frequencies of 40,000-70000 Hz, on which the experiments were carried out.

In accordance with the above method for determining the depth of penetration of an electromagnetic wave into a metal (Tkachev V.N. et al. Induction surfacing of hard alloys. M., Mechanical Engineering. 1970, p. 21), it was found that for this inverter, creating high-frequency electromagnetic waves with a frequency of 40,000 -70000 Hz, for them it ranges from 6.5-4.9 mm.

Therefore, our experiments have determined that if, when a part is heated in a high-frequency electromagnetic field, having a thickness less than the penetration of an electromagnetic wave into the metal by 30%, then the part heats up no higher than 780 ° C, and when it increases to a thickness of 10% (i.e. up to 20%) in relation to the depth of penetration of the electromagnetic wave into the metal, then its heating reaches temperatures of 900-950 ° C. In the case of a decrease in the cross-section of the heated part by 50% in relation to the depth of penetration of the electromagnetic wave into the metal, the temperature does not increase above 740 ° C, and when the cross-section of the part is reduced by 60% in relation to the depth of penetration of the electromagnetic wave into the metal, the heating of the part practically does not change.

The use of the invention will reduce the complexity of manufacturing reinforced castings by using one metallurgical furnace, both for heating the reinforcement and for melting the reinforcing alloy.

After solidification of the castings, increase the physical and mechanical properties and electrical contact between the elements of the frame and the casting.

Claims (1)

A method of reinforcing cast iron castings, including heating a reinforcing steel frame to a temperature of 600 - 800 ° C and melting cast iron by a high-frequency electromagnetic field, characterized in that a crucible with cast iron and a casting mold with a reinforcing steel frame installed in it are placed in an inductor connected to a high-frequency generator, melting of cast iron and heating of the steel reinforcing frame is carried out simultaneously by exposing them to a high-frequency magnetic field with a frequency of 40-70 kHz, while the thickness or diameter of the components of the reinforcing frame is selected from the condition that electromagnetic waves penetrate them to a depth of 30-50%.

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