SU1421795A1 - Iron - Google Patents

Abstract

The invention relates to metallurgy and to be used in the production of castings operating under positive and negative (up to -60 ° C) temperatures. The purpose of the invention is to improve the mechanical properties and reduce chill. The proposed cast iron contains, wt%: C 3.3-3.7; Si 1.0-1.4; MP 0.004-0.01; Mg 0.01-0.04; Ca 0.015-0.03; Ce 0.005-0.07; A1 0.02-0.08; Ba 0.015- (f), 03; Cr 0.01-0.06, N 0.01-0.03, Zr 0.05-0.2, Fe balance. The additional input of N and Zr into the cast iron makes it possible to vary the mechanical properties: GB (MPa) 1.4-1.8 times, §, (;) 1.6-3 times, impact strength 1.3- 3.5 times and reduce chill in 1.5-8.0 times. Table 2.: (

Description

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The invention relates to metallurgy, in particular, to the time1) the working composition of cast iron for castings operating under conditions of positive and negative temperatures.

The purpose of the invention is to improve the mechanical properties and reduce the selection.

The selection of the boundary limits of the components in the composition of the proposed cast iron is based on the following. The upper limits of LB carbon and silicon (3.7 and 1.4; maco%, respectively) are chosen based on the need to ensure high mechanical properties, and also due to the formation of brittle complex eutectic carbides when the upper limit is exceeded. Lower limits of carbon content 3 , 3 wt.% And silicon wt.% Are determined by a decrease in the technological properties and, first of all, by the fluidity of the alloy.

Manganese forms stable carbides of manganese; therefore, its content in the alloy should be minimal. The content of manganese is 0.004-0.01 wt.%, Based on the technological conditions of melting and the content of manganese in charge materials.

Calcium and barium of iron-carbon alloys .. in an amount of 0.015–0.03 May,% k, each of the elements providing a shot for producing pig iron, possessing high plastic properties of w due to improving the shape of nonmetallic inclusions with simultaneous ferritization of the matrix. The upper limit of the content of calcium and barium in the iron (0.03 wt%) is due to a small increase in the positive effect with a higher degree of increase in their content, “Lower prev & on the form of non-metallic inclusions and does not provide graphitization of the alloy.

Strontium is introduced into the composition of cast iron to increase the graphitizing effect. The effect of strontium is especially effective when there is an element in the cast iron that has high KIM chemical affinity in sulfur and oxygen, such as cerium, barium, kalitsch. The content of strontium is less than OjOl May, l ne ensures the formation of additional crystallization centers and is not noticeable

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influence the number and size of the unit. tic grains. The modifying effect of strontium is manifested when it is contained in cast iron, 0.01-0.05 wt.%. The addition of strontium in the amount of more than 0.06 wt.% Due to the limited solubility in the iron leads to micronization of strontium at the grain boundaries, which reduces the ductility of the iron. I,.

When its content in the pig iron is within the range of Oi005-0.07 wt.%, The cerium performs the functions of a graphitizing element. In addition, cerium in the amount of 0.005 wt.%, Which corresponds to the lower limit of its content in the iron, eliminates the appearance of irregular graphitzes. The upper limit of the cerium content (0.04 m ac.%) Is limited by the possibility of chipping in the castings.

Magnesium with its residual content in the alloy of 0.01-0.04 wt,% in the presence of barium, calcium and cerium ensures the preparation of spherical forms in the graphite structure, which positively affects the strength characteristics of the alloy at both positive and negative temperatures. The upper limit of the magnesium content (0.04 wt.%) Is limited by the formation of structurally free carbides in the cast state. When the content of magnesium at the end limit (0.01 wt,%) in the structure, not less than 80% of spheroidal graphite inclusions are provided. Entering into the composition of aluminum cast iron in the amount of 0, wt,% ensures a deep deoxidation of the melt. The lower limit of the content in aluminum is due to the graphitizing effect of the latter. The aging in the furnace at the temperature of the modified nitrides and zirconium cast iron shows that the duration of the effect directly depends on the concentration of A1 in the metal. Increasing the concentration Ai (0, 08 wt.%) Lengthens the effect of modification, which is necessary when pouring a large number of forms. from the bucket. The oxygen coming from the surrounding atmosphere into the liquid metal promotes the formation of corundum. When the aluminum content is above 0.08 wt,%, the technological properties of cast iron are equivalent. Zirconium and nitrogen when they are introduced into the cast iron together form stable

, nitrides, reinforced iron structure. Preliminary introduction of quantity B in aluminum cast iron (0.02–0.08 May.%) Provides deep melt deoxidation and consumption of Zr mainly for reaction with nitrogen. During the metallographic study of the structure of cast iron, it was found that corundum particles serve as substrates for crystallization of Zr nitride. As a result of the modification with nitrides, the grain is substantially crushed over the cross section and height of the castings, which is accompanied by a decrease in the concentration of impurities at the grain boundaries, an increase in the mechanical properties and cold resistance of the iron. The upper limit of the zirconium content in the cast iron, up to 2 wt.%, Is limited by the presence of stabilized phases in the cast iron structure, which cause the appearance of cementite enriched in zirconium carbides. This leads to increased brittleness of the cast iron. The lower limit of the content of zirconium in the cast iron 0.05 wt.% Corresponds to the absence of the effect of increasing the ductility of the alloy.

Nitrogen when injected into cast iron from

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in P ductile,., auglerokivasiI melt and the introduction of ferroalloys and modifiers,

After refining the molten pig iron according to the content of the main components and modifying with the magnesium in the furnace, the melt at a temperature of 1380 ° C is poured into KOBLa, the plasma torch is turned on and the melt is blown with nitrogen plasma for 20 sec. The mode of operation of the plasma torch: current 180 A, arc voltage 100 V, nitrogen flow 1.1 M-V4.

15 After the specified time has elapsed, a zirconium powder was introduced into the plasma jet by a feeder. The total purge time is 30 seconds.

The cast iron's tendency to chill bleached is assessed by fracture of a wedge-shaped sample poured onto a cold metal plate. Samples for testing the mechanical properties of cast iron is cut from samples cast in raw materials

25 sandy-clay forms.

The study of mechanical properties was carried out on samples cut from cast samples. A tensile test is performed. car brand IRM-50

the eutectic grain becomes smaller, the stabilization capacity is 50 tons, the impact test hardens and strengthens perlite. Ferrite disappears from the metal base and

The dispersion of perlite increases dramatically. At the same time, the total microhardness of perlite increases from 274-278 to 340-, 356 kgf / mm, which makes the overall strength of the iron. The increase in the microhardness of perlite is explained by the microtreatment of perlite by dispersed zirconium nitrides. The nitrogen content is less than 0.01 wt,% does not have a noticeable effect on the hardening of the alloy. When nitrogen is introduced in more than 0.03 wt.%, The ductility of the iron decreases due to the formation of structurally free carbides. The optimum nitrogen content in cast iron is 0.01-0.03 wt.%.

To study the structure and properties of the proposed melted cast iron, containing the main components in the lower, middle and upper, as well as below the lower and higher upper levels and known alloy with an average content of ingredients.

The chemical composition of melted

cast iron are given in table. G,

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The cast iron melting technology consists in melting metallized pellets with a Redtst content of 89.1%

on the MK-ZOA trencher with a work margin of 30 kgm.

Cooling of the samples to a temperature of minus 100 ° C is carried out in a special thermostat. The temperature of the cooling bath is measured with a pentane thermometer with a Dividing price of 1 ° C. A mixture of liquid nitrogen and gasoline is used as a coolant. 06-. The differences before testing are kept in a thermostat at a given temperature for 20 minutes.

The test results of the mechanical properties, as well as the chill depth in the cast state, are shown h.

It follows from Table 2 that the tensile strength due to the introduction of nitrogen and zirconium into the composition of the iron does not increase by 1.4-1.8 times, plasticity by 1.6-3 times, and impact strength by 1.3. -2 times at + 29 ° С and 1.5-3.5 times at -60 ° С, and also the reduction of chill is provided in 1.5-8 times.

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Claims (1)

Invention Formula Cast iron, containing carbon, - silicon, manganese, magnesium, calcium, cerium, aluminum, barium, strontium and zha with a capacity of 50 tons, impact test - on the MK-ZOA trencher with a work margin of 30 kgm. Cooling of the samples to a temperature of minus 100 ° C is carried out in a special thermostat. The temperature of the cooling bath is measured with a pentane thermometer with a Dividing price of 1 ° C. A mixture of liquid nitrogen and gasoline is used as a coolant. 06-d samples before testing, incubated in a thermostat at a given temperature for 20 minutes. The test results of the mechanical properties, as well as the chill depth in the cast state, are shown h. It follows from Table 2 that the tensile strength due to the introduction of nitrogen and zirconium into the composition of cast iron increases 1.4-1.8 times, plasticity 1.6-3 times, impact strength 1.3- 2 times at + 29 ° С and 1.5-3.5 times at -60 ° С, and also the reduction of chill is achieved. 1.5-8 times. five 0 55 Invention Formula Cast iron, containing carbon, - silicon, manganese, magnesium, calcium, cerium, aluminum, barium, strontium and the same, 01 0.01 0.1 Content of components, May.% 0,005 0.008 0.04, 04 0.07 0.04 0.022 - Known Medium . Lower Middle. Upper Table 2 122201.821040 8310327060 33604390130 1.33905,5430140