RU2623390C1 - Cast-iron melt processing method by nanosecond electromagnetic impulses (nemi) - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: in the method the melt is heated up to the temperature of 1500°C, it is hold at this temperature for 5 min, and then the melt is cooled up to the temperature of 1350°C, at which the electromagnetic processing of the melt is performed by nanosecond electromagnetic impulses. After heating up to 1500°C add 8 wt % of the chromium in the form of ferrochromium grade FX025 into the melt, then after cooling and electromagnetic processing for 15…20 minutes introduce the silicon containing magnesium modifier, FSMg7 in the amount of 0.25 wt % with further cooling of the melt up to the solid state.

EFFECT: invention allows to increase the cast iron abrasion resistance and heat resistance.

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Description

The invention relates to foundry and can be used to produce castings from cast iron with high abrasion resistance and heat resistance.

Known methods for treating melts with vacuum, electric current, ultrasound and vibration [1-4], reducing gas saturation in aluminum and cast iron castings, which should help to increase their properties. There is also a method of processing melts with protective reducing fluxes that reduce the gas saturation in castings [4], which also leads to an increase in their properties.

The disadvantages of the above methods of processing melts are the use of expensive equipment and the deterioration of sanitary and hygienic working conditions when using fluxes.

All of the above methods do not allow to increase abrasion resistance and heat resistance.

The closest in technical essence and the achieved result is a method of processing the molten iron, which consists in heating the melt to a temperature of 1500 ° C, holding it at this temperature for 5 minutes, and then cooling the melt to a temperature of 1350 ° C, at which the melt is electromagnetically processed nanosecond electromagnetic pulses [5].

The disadvantages of this method are that:

- an electromagnetic field is applied with a frequency of 6-15 Hz and a strength of (1.5-2) ⋅10 ³ Oe;

- the influence of the electromagnetic field on the abrasion resistance and heat resistance of cast iron is not considered;

- the dependence of the change in properties on the volume of the metal being processed has not been studied.

The technical problem to which this invention is directed is to increase the abrasion resistance and heat resistance of cast iron.

When powerful electromagnetic pulses of current are passed through molten metal at certain instants of time, electromagnetic fields with very high intensities up to 10 ⁸ -10 ¹⁰ V / m arise. These fields lead to a change in the structure and properties of the molten and hardened metal.

EFFECT: obtaining chrome cast iron with enhanced properties: wear resistance and heat resistance during processing of its liquid phase by nanosecond electromagnetic pulses (NEMI) with subsequent modification.

The technical result of the invention is achieved by the fact that in the method of processing the molten iron, which consists in heating the melt to a temperature of 1500 ° C, holding it at this temperature for 5 minutes, and then cooling the melt to a temperature of 1350 ° C, at which the melt is electromagnetically treated with nanosecond electromagnetic pulses, according to the invention, after heating to 1500 ° C, 8 wt. % Cr in the form of ferrochrome grade ФХ025 (GOST 4757-91), then, after cooling and electromagnetic treatment with nanosecond electromagnetic pulses, silicon-containing magnesium complex modifier FSMg7 (TU 14-5-134-86) is introduced in an amount of 0.25 for 15 ... 20 minutes wt. % followed by cooling to a solid state.

The invention is illustrated by drawings, where in FIG. 1 shows a setup diagram, where 1 is an electromagnetic pulse generator; 2 - furnace casing; 3 - a crucible; molten metal; 5 - electrodes; 6 - alundum covers; 7 - connecting wires; in FIG. Figure 2 shows the graphs of the effect of the NEMI treatment of the liquid phase on the wear resistance and heat resistance of chrome cast iron.

In the course of work, cast iron of the following composition is used, wt. %: 2.7 C; 1.67 Si; 0.33 Mn; 0.05 S; 0.23 R.

The installation scheme, the technique for irradiating the melts and the main characteristics of the used NEMI generator (GNI-01-1-6) are given in the patent description [6].

Characteristics of equipment used to process the liquid phase with nanosecond electromagnetic pulses, methods for determining heat and wear resistance:

1. The NEMI generator (GNI-01-1-6) has the following characteristics: pulse polarity is positive; the amplitude of the pulses at a load of 50 ohms - 6000 V; pulse duration at half level - 0.5 ns; maximum permissible pulse repetition rate - 1 kHz; delay of the output trigger pulse - 120 ns; the maximum current consumed by the generator in the entire range of supply voltages is not more than 1.7 A at a frequency of 61 kHz.

2. Heat resistance studies were carried out by the thermogravimetric method, which consists in measuring the weight gain of the samples upon heating. A MOP Q-1000 derivatograph was used at atmospheric pressure in air and a heating rate of 10 deg / min to a temperature of ~ 1000 ° C. The error of temperature measurement did not exceed ± 1 ° C. Powder alunda Al ₂ O _{3 was used} as a reference. [7]

3. The study of wear resistance was carried out in accordance with GOST 23.208-79 "Method for testing materials for wear resistance on non-rigidly fixed abrasive particles" [8]. For testing, a setup was used that, using abrasive particles, produced wear of samples from the test and reference materials under the same conditions.

4. For the complete dissolution of ferrochrome and uniform distribution over the casting, the temperature-time regime of cast iron melting has been developed, which consists in heating it to 1500 ° C with holding it at the same temperature for 5 minutes [9, 10].

Example 1

Cast iron is heated to 1500 ° C, after a five-minute exposure, 8 wt. % Cr in the form of ФХ025 (GOST 4757-91) is cooled to a temperature of 1350 ° С, modified with the FSMg7 complex modifier (TU 14-5-134-86) and treated with NEMI for 5, 10, 15 and 20 minutes. After turning off the generator, the melt crystallizes at a rate of 20 ... 50 ° C / min.

As can be seen from FIG. 2, the heat resistance of cast iron varies with the duration of the processing of the NEMI melt in an exponential manner with a minimum of mass gain during a 20-minute treatment. Heat resistance increases by more than 8.0 times compared with untreated NEMI and cast iron modification.

Example 2

As can be seen from FIG. 2, the wear resistance of cast iron varies with the duration of the processing of the NEMI melt by extreme dependence with a maximum during 15-minute treatment. Wear resistance increases by more than 1.5 times in comparison with untreated NEMI cast iron and modification with cast iron.

In the above examples, with the optimal duration of the processing of the NEMI melt, the maximum wear resistance and heat resistance of cast iron are observed.

Thus, the addition of 8 wt. % Cr in the form of ferrochrome grade ФХ025 (GOST 4757-91) and then cooling and electromagnetic treatment with nanosecond electromagnetic pulses for 15 ... 20 minutes, followed by the introduction of silicon-containing magnesium complex modifier FSMg7 (TU 14-5-134-86) in an amount of 0, 25 wt. % leads to increased abrasion resistance and heat resistance of cast iron.

Information sources

1. Reference "Cast Iron". Edited by A.D. Sherman and A.N. Zhukov. - M.: Metallurgy, 1991, p. 92.

2. Guide to iron casting. 3rd edition, revised and supplemented. Edited by N.G. Girshovich. - L .: Engineering, 1978, p. 59-60.

3. M.V. Maltsev. Metallography of industrial non-ferrous metals and alloys. 2nd edition, revised and supplemented. - M.: Metallurgy, 1970, p. 129-130.

4. Muravyov V.I., Yakimov V.I., Ri Hosen and others. Production of cast billets in aircraft industry. - Vladivostok: Dalnauka, 2003, 611 p.

5. RF patent for the invention No. 2354496, B22D 27/20, publ. 05/10/2009, bull. No. 13.

6. RF patent 2287605 C1. A method of processing a melt of copper and its alloys by nanosecond electromagnetic pulses (NEMI) to increase their thermal conductivity. 03.21.2005 Authors: Ri E.Kh., Ri Hosen, Belykh VV

7. Wenland W. Thermal methods of analysis / W. Wenland. - M .: Mir, 1978.- 526 p.

8. GOST 23.209-79. Method for testing materials for wear resistance against loosely fixed abrasive particles. - M .: Publishing house of standards, 1980. - 6 p.

9. Ri Hosen, Khudokormov D.N., Tazikov E.B. The choice of temperature conditions for the treatment of cast iron melts based on the analysis of structurally sensitive properties. Foundry. 1982, No. 5.

10. Auth. St. USSR 954425 from 05/21/1980, the Method of alloying cast iron. Ri Hosen, Klochnev N.I., Teikh V.A. and etc.

Claims (1)

A method of processing a cast iron melt, including heating the melt to a temperature of 1500 ° C, holding it at this temperature for 5 minutes, and then cooling the melt to a temperature of 1350 ° C, at which the melt is electromagnetically treated with nanosecond electromagnetic pulses, characterized in that after heating up to 1500 ° C, chromium is added to the melt in an amount of 8 wt. % in the form of ferrochrome grade ФХ025, and after cooling and electromagnetic treatment for 15 ... 20 min, a silicon-containing magnesium modifier FSMg7 is introduced in an amount of 0.25 wt. % followed by cooling the melt to a solid state.

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