SU1680778A1 - Process for preparing cast iron with vermicular graphite - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of pig iron with vermicular graphite (CVG). The purpose of the invention is to improve the mechanical and operational properties of cast iron. The proposed method for producing CVG involves melting the metal, releasing the melt into the dispensing bucket, spheroidizing modification of the melt into the ladle by adding a rare-earth metal containing ligature to its bottom, holding the melt at 1290–1300 ° C for 5–10 min and secondary melt processing in a pouring ladle with technical copper. The use of technical copper instead of ferrosilicon FS 75 makes it possible to obtain, by the proposed method, cast iron with increased mechanical properties 1.41-1.59 times and 1.19-9.3 times higher. 3 tab.

Description

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The invention relates to metallurgy, in particular to the development of methods for producing iron with a vermicular form of graphite.

The purpose of the invention is to improve the mechanical and operational properties of cast iron.

Copper was chosen as the material for secondary processing.

PRI me R. Under laboratory conditions, the pig iron is melted in an MHP 102 induction crucible furnace with a capacity of 150 kg with an acidic lining. Cast iron, LK5, LK6, steel 45, ferrosilicon, and ferromanganese are used as charge materials. After the charge is melted, the cast iron is superheated to 1480–1500 ° C and cooled after cooling to 1380–1400 ° C. The composition of the resulting iron,%: carbon 3.4-3.7;

silicon 1.45-2.5; manganese 0.65-1.0; sulfur 0.04-0.11 and phosphorus 0.04-0.2.

Modification at 1320-1330 ° С is continued by a ligature of the brand Spetsmish-2 (TU 15-5-78-76) of the composition,%: silicon 40.3; aluminum 5.5; iron 18.1; rare earth metals 36.1. For secondary melt processing, M1 grade copper is used (GOST 850-78), which is introduced to the bottom into a 10 kg bottling ladle. Cast iron is poured into the mold for 3-7 minutes.

To study the structure and properties of cast iron, obtained by the proposed method, use the additives of Scemish and copper at the lower, middle and high levels. The temperature and holding time of the melt are changed during the processing and casting of the metal.

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The microstructure of cast iron was studied according to GOST 3443-77 using a metallographic microscope MIM-7.

Mechanical properties studies are carried out according to the existing standards for test methods: bending - according to GOST 24804-81 on a set of three cast specimens with a diameter of 30 and a length of 340 mm; Brinell hardness - according to GOST 24305-81; for stretching - according to GOST 24506-91.

Thermal stability tests were carried out on samples with a diameter of 30 and a thickness of 5 mm collected in a bag, which are periodically immersed in a lead melt bath at a temperature of 720 ± 5 ° C for 45 minutes, cooled in running water for 8-10 seconds and then blown compressed air 40-60 s. After cooling in water, the surface temperature of the samples is 140-150 ° C. Heat resistance is estimated by the number of cycles before the destruction of the samples and the number of cracks along the edge of the thin section, depending on the number of cycles.

The tests for oxidation resistance are carried out in accordance with GOST 6130-71 by periodically weighing samples — cylinders with a diameter of 10 and a height of 20 mm. The tests were carried out in an electric muffle furnace at 820 ° C. Scale resistance is evaluated by the specific weight gain of the samples (g / m2) periodically after 10-hour exposure. Weigh the samples on the analytical balance of VLA-200 r / m with an accuracy of ± 0.1 mg.

Technological parameters of the known and proposed methods

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Average

Lower

Average

Upper

1320

1.1

1320 0.8 1325 1.1 1330 1.4

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Rotation tests were carried out on cylinder samples with a diameter of 20 and a length of 100 mm, and at the ends they had pins of stainless steel H18H10t. Temperature test 820 ° C. Cast iron growth is evaluated by measuring the length of the samples with a micrometer periodically after 10 hours exposure.

Technological parameters, structure, mechanical and operational properties of cast iron are given in table. 1, 2 and 3.

As follows from the data table. 1-3, the use of ferosilicon in the secondary processing of copper makes it possible to increase the mechanical properties (hardness — 1.48–1.59 times, strength ob — 1.44– 1.59 times, al — 1, 42-1.52 times), and also to improve operational properties (heat resistance - by 1.19-2.38 times, height-resistance - by 1.3-2.4 times and scaling resistance - by 2.7-9.3 times) .

Claims (1)

Invention Formula The method of producing iron with vermiculum graphite, including metal melting, melt production into a dispensing bucket, at the bottom of which a spheroidizing ligature is preliminarily inserted, the secondary melt modification in the casting ladle, characterized in that, in order to improve the mechanical and operational properties of the iron, after entering the spheroidizing ligature, the melt is kept for 5–10 min at 1290–1300 ° C, and the secondary modification is carried out with technical copper. 0 five 0 five Table 1 1290 0.5 1290 0.4 3 1295 0.65 L 1300 0.9 7 Table The structure and mechanical properties of cast iron by the known and proposed methods Lime Proposed Average 0.20 The operational properties of cast iron according to the known and proposed methods 80 1600 360 800 Table3