RU2354723C1 - Briquetting method of steel cuttings - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: steel cuttings are crushed till the size no more than 12 mm, blended, it is implemented cleaning against moisture and organic admixtures, heating, hot compaction in mould. Blending, cleaning and heating are implemented simultaneously in rotating inclined barrel by means of influence of high frequency electromagnetic field on movable flow of cuttings during 3-8 min. Additionally relation of height and length of the heated area of movable flow of cuttings is 1:(10-12).

EFFECT: improvement of briquettes, density increasing of briquettes and productivity improvement.

3 dwg, 2 tbl

Description

The invention relates to metallurgy, in particular to methods for processing metal chips, and can be used in the preparation of chip waste metalworking for metallurgical remelting.

A known method of the so-called cold briquetting of metal shavings (1), including its crushing, cleaning, heating, adding sludge, binders, mixing and compaction, in which water-cement paste is used as a binder in an amount of 4-7% by weight of the briquette .

The disadvantage of this method is that the addition of binder components in the briquettes requires additional material costs at the manufacturing stage and energy at the stage of subsequent melting. In addition, the production of briquettes using binders is a lengthy process associated with the need to harden the cement-based binder filler and the contamination of the briquettes used as a charge in melting.

A known method of briquetting metal chips, in particular the manufacture of briquettes from titanium chips and its alloys (2), comprising crushing chips to obtain two fractions, mixing, washing, drying and compaction in a mold.

The disadvantages of this method are the complexity and duration of the process of obtaining briquettes, which consists in the presence of two operations for separate grinding of chips, their subsequent mixing and the presence of two cleaning operations - washing and drying. In addition, the presence of two stages of cleaning (washing and drying) requires two separate systems for neutralizing the coolant residues removed in this case - for liquid residues formed during washing and for gaseous ones formed during drying. In addition, due to the difference in the lengths of the fractions, the chip elements cannot evenly warm up, therefore, they have different mechanical strengths, and the weight ratio does not ensure their good adhesion, so metal briquettes are of unstable quality.

Closest to the claimed invention is a method of briquetting metal chips (3 - prototype), including its crushing, mechanical squeezing of the cutting fluid, heating and pressing, chips with a filling density of 700-1000 kg / m ³ are heated at a speed of 7-9 ° C in an atmosphere of oil pyrolysis in a confined space with a ratio of the height and width of the heated layer (5-8): 1 to a temperature of 670-690 ° C and then, before hot briquetting, cold metal sludge is added to the heated chips in the amount of 5-25% of chips with content m cutting fluid (coolant) 2-5%.

The disadvantages of the prototype are the complexity of the manufacturing technology associated with the additional mixing of the heated and supplied cold chips, the duration of the cleaning process associated with low heating rates and restrictions on the density and area of the chip filling during its heating. The supply of coolant containing coolant to a previously heated chip leads to the evaporation and burnout of the coolant in the cold chip, which requires an additional device to remove and neutralize the products of burning coolant.

The objective of the proposed method of briquetting steel chips is to improve the quality of briquettes by improving the quality of cleaning, increasing the density of briquettes and increasing productivity.

The technical result of the invention is the complete removal of residual organic impurities and moisture from steel chips, eliminating the burning of alloying elements and decarburization of chips during cleaning, reducing chip losses during processing and transportation, as well as reducing the cost of electricity, materials and labor resources for obtaining briquettes and subsequent smelting metal from them.

The problem is achieved in that in the method of briquetting steel chips, including crushing, mixing, cleaning from moisture and organic impurities, heating and hot pressing in a mold, crushing is carried out to a size of not more than 12 mm, and cleaning, mixing and heating are carried out simultaneously in a rotating inclined drum by exposure to a high frequency electromagnetic field on a moving chip stream for 3-8 minutes, the ratio of the height and length of the heated chip stream is 1: (10-12).

Increasing the productivity and improving the quality of cleaning steel chips is achieved through the use of integrated heating using a high frequency electromagnetic field, which ensures the intensification of moisture evaporation, pyrolysis and burnout of organic impurities.

When a high-frequency electromagnetic field acts on a metal drum made of a ferromagnetic material, it intensely heats up. In addition, an electromagnetic field is formed in the flow of chips moving and mixing in an inclined drum, heating it. As a result, complex heating of the chip flow for cleaning occurs in the following directions:

- thermal conductivity upon contact of cold chips with the heated surface of the drum, between heated and cold chips with intensive mixing;

- by convective heat transfer between the heated surface of the drum and the cold moving stream of chips;

- a high frequency electromagnetic field located inside a heated drum, affecting the flow of chips, which is a ferromagnetic material.

In the process of complex heating of the chip stream in the drum, intensive evaporation of moisture occurs, pyrolysis and burning of residues of organic impurities throughout the cross section of the chip stream, and mixing of the chip stream during its movement along the drum provides an intensive and complete removal of gaseous products. In this case, intensive heating of the chip stream in the pyrolysis vapor of organic impurities and a short time spent in the high temperature range excludes chip burning or decarburization of its surface layer.

An increase in the density of briquettes is achieved by reducing the hardness of the chips obtained by heating during the cleaning process, which makes it possible to obtain briquettes of higher density with the same compression force during pressing operations. The chips generated during machining, and primarily steel twisted chips, are subjected to hardening, which leads to an increase in its hardness and a decrease in ductility. During heating, there is a decrease in hardness due to stress relieving of the metal structure in the hardened state. This increases the ductility of steel chips and, as a consequence, the density of briquettes during pressing.

The essence of the invention is illustrated by drawings, where:

figure 1 presents the sequence of the proposed method of briquetting steel chips;

figure 2 - section aa figure 1, shows the height of the heated layer of chips;

in Fig.3 is a graph of the percentage of moisture and organic impurities in the briquettes after cleaning the chips at a certain temperature (1 - pipe temperature - 180 ° C, 2 - 300 ° C, 3 - 500 ° C, 4 - 700 ° C).

The method of briquetting steel chips is as follows. Chip 1 after preliminary screening and removal of foreign objects is fed into the hopper 2, then the rolls of the crusher 3 are crushed to a maximum size of not more than 12 mm. The crushed chips along the feed tray 4 are fed into a rotating smooth-walled drum 5, preheated to a temperature of 500-750 ° C by a high frequency electromagnetic field of the inductor 6. Moreover, the chip flow parameters in the drum (height h in FIG. 2 and length L of the inductor figure 1) are in the ratio 1: (10-12). Thus regulated chip flow 7, continuously mixing, is heated to a predetermined temperature and at the same time moves along the heated smooth-walled drum to the discharge side. The products of evaporation and pyrolysis are removed to the neutralization device 8. Depending on the angle of inclination of the drum, its rotation speed and the amount of supplied chips, the temperature of its heating at the outlet can be in the range from 180 to 750 ° C.

Next, the chips after cleaning in the drum 5 through the receiving tray 9 enters the working chamber of the mold 10, where briquetting of steel chips is carried out at different temperatures. Ready briquettes 12 enter the container 11.

The essence of the proposed method is confirmed by the following examples. At the Minsk Automobile Plant, the authors carried out work on the briquetting of experimental batches of steel carbon and alloy steel chips according to the claimed method. Steel shavings made of carbon steel were fed into an inclined drum with a diameter of 220 mm and a wall thickness of 8 mm, where it was intensively induced to be heated using a multi-turn high-frequency inductor covering the heated drum from the outside. The experimental work was carried out on two types of inductors: one inductor 630-650 mm long and the second inductor 1200-1300 mm long. The consumed power of the high-frequency current for heating was 70-85 kW at a frequency of 8000 Hz. The angle of inclination of the smooth-walled drum ranged from 2 ° to 5 °. The amount of chips supplied to the drum ranged from 0.7 to 1.1 t / h, which corresponded to a degree of filling of 35-45% of the cross section of the drum. The results of the tests are presented in tables No. 1 and No. 2.

Example 1. The ratio of the maximum height h of chip flow in the drum to the length L was 1: 7 (inductor length 630-650 mm).

Table number 1 Example Number one 2 3 four 5 6 7 8 one 2 3 four 5 6 7 8 9 Chip heating temperature *, ° С 180 200 300 400 500 600 700 750 Chip heating time, min 8 8 6 6 four four 3 3 The moisture content and organic impurities in the chips,% 3.8 3.4 4.2 4.6 3,7 3.9 4,5 4.1 The residual moisture content and organic impurities in the briquettes,% 1.9 1,1 0.7 0.5 0.2 0.05 0.00 0.00 The density of the briquette, g / cm ³ 4.6 4.6 4.9 5.2 5.8 6.5 6.8 7.0 Briquette strength ** 12.5 10.7 6.4 3.2 0.9 0.2 0 0

Example 2. The ratio of the maximum height h of the flow of chips in the drum to a length L was 1:11 (inductor length 120-1300 mm).

Table number 2 Example Number one 2 3 four 5 6 7 8 one 2 3 four 5 6 7 8 9 Chip heating temperature *, ° С 180 200 300 400 500 600 700 750 Chip heating time, min 8 8 6 6 four four 3 3 The moisture content and organic impurities in the chips,% 3.8 3.4 4.2 4.6 3,7 3.9 4,5 4.1 The residual moisture content and organic impurities in the briquettes,% 1.7 0.9 0.3 0.04 0.00 0.00 0.00 0.00 The density of the briquette, g / cm ³ 4.6 4.7 4.9 6.2 6.6 6.8 6.8 7.0 Briquette strength ** 12.5 8.7 3.4 0.4 0.2 0.04 0 0 * - was measured in the middle of the chip flow at the outlet of the electromagnetic field of the inductor; ** - it is defined as crumbling after triple dropping the briquette from a height of 1 m onto a concrete slab,%.

From the analysis of the presented tables it can be seen that with an inductor length of 630-650 mm (the ratio of the maximum height h of the chip flow in the drum to the length L 1: 7), complete chip cleaning is achieved when heated above 700 ° C, which is an energy-consuming process (examples 7, 8 table No. 1). In addition, when the chips are heated to high temperatures, productivity decreases.

With an inductor length of 1200-1300 mm (the ratio of the maximum height h of chip flow in the drum to a length of L 1:11), complete chip cleaning is achieved at a heating temperature of 400 ° C and above (examples 4, 5, 6, 7, 8 of Table No. 2).

The briquette density of more than 6.0 g / cm ^{3 is} achieved by heating more than 400 ° C, with an inductor length of 1200-1300 mm, where a more uniform chip heating is achieved over the flow cross section (examples 4, 5, 6, 7, 8 of Table No. 2 ) When heating more than 400 ° C, with an inductor length of 1200-1300 mm, the density of the briquettes is lower, which is explained by the unevenness of its heating (examples 4, 5 of table No. 1).

Figure 3 presents a graph of the moisture content and organic impurities after passing the cleaned chips through the drum from the time spent by the chips in the heated drum. The composition of most coolant contaminating the chips is a mixture of water, special additives and oil in an amount up to 30%. The flash point of the oils is in the range of 170-200 ° C; therefore, heating the chips in the drum to a temperature of 180 ° C leads to the complete evaporation of water, while the oil evaporates only partially (item 1). An increase in the heating temperature of the drum leads to the complete removal of moisture and organic impurities from the chips, and the higher the surface temperature, the faster the cleaning process (pos. 2, 3, 4).

Briquetting of an experimental batch of cleaned chips by the proposed method. The chips were fed into the experimental die of a pneumatic press of the MAZ design with a force of 5.3 tf. The dimensions of the working chamber of the press were calculated from the conditions for creating an equivalent specific pressure created in the working chamber of a hydraulic press of modes. B 6238, used for cold briquetting chips at RUE "MAZ".

Information sources

1. Patent RB No. 7767, IPC С22В 1/248, 1/243. "The method of briquetting metal chips", publ. 02/28/2006 ABOUT RB №1.

2. RF patent No. 2267543, IPC С22В 1/248. "The method of briquetting metal chips", publ. 01/10/2006.

3. Patent RB No. 7394, IPC С22В 1/24, B22F 8/00. "The method of briquetting metal chips", publ. 09/30/2005 ABOUT RB No. 3 - a prototype.

Claims (1)

The method of briquetting steel chips, including its crushing, mixing, cleaning from moisture and organic impurities, heating, hot pressing in a mold, characterized in that crushing is carried out to a size of not more than 12 mm, and mixing, cleaning and heating are carried out simultaneously in a rotating the inclined drum by applying a high frequency electromagnetic field to the moving chip stream for 3-8 minutes, and the ratio of the height and length of the heated zone of the moving chip stream is 1: (10-12).

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