RU2360025C1 - Ligature for manufacturing of moulding made of cast iron - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy field and can be used in mechanical engineering and tractor construction for manufacturing of mouldings from gray cast iron with pearlite structure of metallic basis. Ligature contains, wt %: copper 45.0-55.0; tin 5.5-6.5; silicon 15.0-20.0; calcium 0.03-0.2; aluminium 0.1-1.0; iron - the rest, herewith it is used in crushed shape with grain size 3.2-16 mm.

EFFECT: ligature is uniform by chemical composition, provides reduction of expenditures for manufacturing of moldings made of pearlite cast iron and increasing of suitable fractional yield while grinding.

2 cl, 2 tbl, 1 ex

Description

The claimed invention relates to metallurgy and can be widely used in mechanical engineering and tractor manufacturing in the production of gray iron castings with a pearlite structure of a metal base.

In the manufacture of pearlitic iron castings, strong perlitizing elements such as tin and copper are used. Microalloying of cast iron with tin and copper is usually carried out in a ladle. However, the introduction of only perlitizing elements does not ensure their uniform distribution in the volume of molten iron and is accompanied by their significant fumes.

Therefore, ligatures are developed that contain, in addition to copper and tin, chemically active elements of calcium, aluminum, silicon (Ca, Al, Si), which have a high affinity for oxygen and protect valuable perlitizing elements from oxidation during ladle microalloying of cast iron.

Known ligature containing components in the following ratio, wt.%:

Calcium 8.0-18.0 Iron 20.0-35.0 Copper 0.5-20.0 Tin 0.2-5 Aluminum 0.2-2.5 Silicon rest

The known composition of the ligature is presented in the description of the invention "Ligature" to the USSR copyright certificate No. 395481 in the class MPK С22С 35/00.

A disadvantage of the known ligature is the significant content of calcium in it, the cost of which is high, which leads to a significant increase in the cost of the production of cast iron castings.

The well-known ligature according to the USSR copyright certificate No. 395481 was selected as a prototype, because is the closest in technical essence and the achieved effect to the claimed ligature for the production of castings from cast iron.

The objective of the present invention is to reduce the cost of manufacturing castings of gray cast iron perlite class.

The technical result in the implementation of the invention is to obtain a crushed and fractionated ligature of a homogeneous chemical composition with particle sizes, ensuring the optimal dissolution rate in molten iron.

This problem is solved due to the fact that the well-known ligature for the production of castings from cast iron, including copper, tin, silicon, calcium, aluminum and iron, according to the invention, contains in the following ratio these components, wt.%:

Copper 45.0-55.0 Tin 5.5-6.5 Silicon 15.0-20.0 Calcium 0.03-0.2 Aluminum 0.1-1.0 Iron rest

The inventive ligature is used in crushed form with a particle size of 3.2-16 mm.

Studies conducted on the sources of patent and scientific and technical information showed that the claimed alloy for the production of castings from cast iron is not known and does not follow explicitly from the studied prior art, i.e. meets the criteria of "novelty" and "inventive step".

The inventive ligature can be obtained in the metallurgical industry or at enterprises specializing in the manufacture of ligatures, because this requires well-known technologies, materials and standard domestic or imported equipment. It can be widely used in enterprises manufacturing gray iron castings.

Therefore, the claimed ligature meets the criterion of "industrial applicability".

The proposed set of essential features informs the claimed invention of new properties that make it possible to solve the problem.

The claimed copper content of 45-55% provides the maximum yield of the ligature fraction. When reducing the amount of copper below 45 wt.% Decreases the yield of grains of the required size and the amount of fines increases. Screenings of fines are remelted and crushed. If the ligature contains copper above 55% due to the deterioration of crushability, the amount of over-sizing product increases during crushing, which requires additional refinement of large pieces of the ligature. Going beyond the declared limits for the copper content in both cases leads to an increase in the cost of ligatures.

The amount of tin claimed in the ligature is dictated by the need to obtain the brand composition of pearlite cast iron. When the tin content in the ligature is lower than the stated limit, the required hardness of cast iron is not achieved, and treatment with a ligature with a tin content exceeding 6.5 wt.% Gives the cast iron increased hardness and brittleness.

Silicon is needed in the ligature to get the possibility of its subsequent crushing. Silicon burns less and is more fully absorbed by the ligature if it enters the charge as part of ferrosilicon, and not crystalline silicon. If the inventive ligature of silicon below 15.0 wt.% There is a low yield of fraction due to its poor crushing. The amount of silicon greater than 20.0 wt.% Is not allowed, primarily due to the fact that the grade of cast iron, which must be obtained, will not be maintained. In addition, with an amount exceeding 20.0 wt.%, The ligature has excessively increased crushability, as a result of which there is a low yield due to an increase in the amount of the fine fraction. In both cases, when the amount of silicon is outside the declared limits, the cost of the ligature increases.

Calcium and aluminum enter the ligature together with ferrosilicon. A decrease in the content of these elements in the ligature requires the refinement of ferrosilicon, and an increase requires its additional alloying with calcium and aluminum. In both cases, this will increase the price of ferrosilicon and increase the cost of ligature. Calcium in the amount of 8-18 wt.% In the ligature, selected as a prototype, leads not only to its appreciation, but also to its slagging, reduced dissolution and incomplete absorption of cast iron. Practice has shown that slagging can be avoided if the calcium content in the modifiers used for ladle processing of cast iron does not exceed 3 wt.%. The presence of calcium in the ligature in an amount of 2.0-3.0 wt.% Does not adversely affect its properties, at the same time it is not necessary, because liquid cast irons along with perlitizing ligature are additionally treated with graphitizing modifiers containing the optimal amount of calcium.

As a result of chemical analysis of the ligature of various fractional composition for the content of copper, tin and silicon, it was found that in the ligature particles less than 3.2 mm in size, the silicon content increases and the content of copper and tin decreases.

Studies performed under production conditions showed that a ligature with a particle size of more than 16 mm is not completely absorbed by molten iron. When microalloying cast iron with a particle size of 18 mm, particles of insoluble ligature were found in the castings.

The results of chemical analysis are presented in table 1.

Table 1 Particle size mm 0-1 1-2 2-3,2 3.2-10 10-16 16-20 Content, wt.% Si 26.3 23.1 20.8 17.8 17.4 17.6 Cu 40.1 44,2 49.5 51,2 51,4 51,2 Sn 4,5 5.1 5.7 6.3 6.2 6.2

Thus, the minimum particle size of the ligature 3, 2 mm is determined by the need to obtain a master alloy of uniform chemical composition, and the maximum 16 mm is limited by the rate of its dissolution in cast iron.

Comparative tests of ligatures for yield of a fraction of 3.2-16 mm were carried out during crushing of the inventive claimed composition (composition 1) (compositions 2-4) and two compositions (compositions 5, 6) with transcendent component contents. Ligatures of each composition, weighing 50 kg, were melted in an induction furnace, poured into cast-iron molds, crushed on a jaw crusher, the 3.2-16 mm fraction was weeded out and its mass content in the crushed material was determined. The results of the study are presented in table 2.

table 2 Composition number The content of components, wt.% Yield 3.2-16% Sa Si Cu Sn Al Fe one 12.7 35.5 19.2 2,3 0.98 rest 56.1 2 0,032 15,5 45.8 5,4 0.88 rest 85.5 3 0,044 17.6 50.8 5.9 0.91 rest 87.2 four 0.056 19,4 54.7 6.5 0.96 rest 86.8 5 0.24 25 40.1 4.8 1.01 rest 71.1 6 0.018 13 60.3 7.3 0.85 rest 80.5

From the presented data it follows that crushing of the ligature of known composition is accompanied by the formation of a large number of small fractions and is characterized by a relatively low yield of the product with the required particle sizes. The increased crushability of the known ligature is due to the high content of calcium and silicon in it. A trifle formed during crushing - about 44% must be re-melted and crushed, which leads to an additional increase in the cost of the known ligature.

Crushing the ligature of the claimed composition allows you to get the yield of the fraction at the level of 85-87%, which is significantly higher than that obtained by crushing the known ligature. At the same time, going beyond the declared limits in chemical composition, especially in the content of copper and silicon, leads to a decrease in the yield of the crushed ligature fraction.

An example of obtaining a ligature

The claimed ligature is melted in arc or induction electric furnaces. Pure copper scrap or cathode copper, elemental ingot tin, and industrial ferrosilicon are used as charge materials. To obtain 100 kg of marketable ligature grains with a particle size of 3.2-16 mm, 60 kg of copper, 7 kg of tin and 53 kg of FS45 grade ferrosilicon are loaded into the furnace. After the charge is melted and heated to form a homogeneous melt, the ligature is poured into cast-iron molds and, after cooling, it is crushed and sieved. The ligature with a particle size of 3.2-16 mm is packed in steel drums or soft specialized containers and sent to consumers.

The ligature obtained by the consumer in certain portions is loaded onto the bottom of the bucket with a measured capacity immediately before the release of molten iron from the smelter.

Calculation of costs when using known and claimed ligatures

For the production of Cylinder Block castings, it is necessary to obtain cast iron with a copper content of 0.62 wt.% And 0.082 wt.% Tin. Cast iron was smelted in an arc furnace using recycled waste in a charge with copper and tin contents of 0.19 and 0.03 wt.%, Respectively. To obtain the branded content of copper and tin in cast iron, 12.7 kg of the inventive composition containing wt.% Were loaded onto the bottom of the 1.5-ton bucket, containing wt.%: Cu 50.8; Sn 5.9; Si 18.9; Al 0.75; Ca 0.042; Fe is the rest. Ligature is melted using elemental tin, cathode copper and ferrosilicon grade FS45 in the charge. Thus, in the sample of the claimed ligature, spent on microalloying cast iron, contained 6.45 kg of copper, 0.75 kg of tin and 5.5 kg of ferrosilicon.

On the basis of silicocalcium grade SK15 melted known ligature containing wt.%: Cu 20; Ca 12.7; Si 35.5; Al 0.98; Sn 2.4; Fe is the rest. Copper, as can be seen from the example, the maximum quantity is taken.

To introduce an equivalent amount of copper and tin into cast iron, 33.6 kg of known ligature containing 6.45 kg of copper, 0.75 kg of tin and 26.4 kg of SK15 were required.

The difference in the cost of the samples of the known and claimed ligatures is determined by the difference in the value of silicocalcium and ferrosilicon contained in them. At a price of 1 kg ferrosilicon of the FS45 grade $ 0.77 and 1 kg of silicocalcium grade SK15 1.35 $ the difference in the cost of ligatures will be:

$ 1.35 × $ 26.4-0.77 × 5.5 = $ 31.41 per 1.5 tons of cast iron or 770 rubles.

Thus, the use of the claimed ligature will reduce the cost of producing 1 ton of iron castings by 513 rubles.

The use of the inventive ligature instead of the known one with a calcium content of 8-18 wt.% And a maximum copper content of 20 wt.%, Reduces the cost of producing a ton of cast iron castings by 250-650 rubles. Replacing the known master alloy with lower copper contents with the master alloy of the claimed composition will further reduce the cost of the production of cast iron castings.

The inventive ligature in comparison with the prototype has the following advantages:

- homogeneity of the chemical composition;

- improving the manufacturability of the process of microalloying cast iron;

- reduction of costs for the production of castings from pearlitic iron;

- increase the yield of fractions during crushing;

- increase the speed and degree of assimilation of the ligature.

Claims (2)

1. Ligature for the production of castings from cast iron, containing copper, tin, silicon, calcium, aluminum and iron, characterized in that it contains these components in the following ratio, wt.%:
copper 45.0-55.0 tin 5.5-6.5 silicon 15.0-20.0 calcium 0.03-0.2 aluminum 0.1-1.0 iron rest 2. The ligature according to claim 1, characterized in that it is obtained in crushed form with a particle size of 3.2-16 mm