SU1235973A1 - Cast iron - Google Patents

Description

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The invention relates to metallurgy, in particular, to finding gray cast iron for cast parts of an internal combustion engine, which are subject to increased requirements for the stability of frictional properties during friction with heating up to 700 ° C in a corrosive environment.

The purpose of the invention is to improve the stability of frictional properties during friction in a gaseous corrosive environment when heated to.

Example. The cast iron is smelted in open induction furnaces (crucible capacity 250 kg) by remelting from a charge based on scrap iron, pig iron, granulated nickel, copper, steel scrap, and ferroalloys. After the pig iron has been melted and the scrap is added, the additives are superheated, the melt is heated to 1500–1520 ° C, niobium and cerium carbonitrides and aluminum are introduced, and released into the ladle, where they are micro-alloyed with tin and modified by silicocalcium and ferrosilicon. at 1380-1,400 ° C.

The chemical composition of the known and proposed cast iron is given in table.1.

The introduction of niobium carbonite to cast iron makes it more stable. structure and hardness of cast iron, strengthens the metal base, facilitating the formation of phases in the structure, not prone to delamination with the matrix, resulting in increased stability of the frictional properties at elevated temperatures and in a corrosive environment. At a concentration of carbonitious reads of niobium up to 0.12 wt.%, Stable frictional properties are not achieved when in a corrosive environment, and with an increase in the content of carbonitrides of more than 0.85 wt.%, Their graphitizing effect begins to appear and interdendritic graphite inclusions appear. and carbonitrides, reducing the mechanical properties of cast iron in castings.

Hardening the matrix and increasing its stability, impact resistance and hardness provides microalloying with cerium carbonitrides in an amount of 0.03-0, 15 wt.%. With increasing carbonitride content more

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0.15 wt.% Significantly increases chill iron casting in castings, the deflection boom is removed, which affects the stability of friction properties of S. When the content of cerium carbonitrides is up to 0.03 wt.%, Their influence on the stability of the structure, friction -. mechanical and mechanical properties are negligible.

10, with the simultaneous introduction of carbon niobium and cerium carbonitrides, which are concentrated inside the cast grain, when rubbed at 700 ° C in a corrosive environment, they are not prone to the formation of cavities 55 by delamination with the metal matrix, and the stability of the friction properties of the cast iron increases more significantly. It was experimentally established that with an increase in the concentration of calcium to 0.10–0.16, when

and interdendritic inclusions of graphite and carbonitrides are enclosed in a calcium shell, the stability of the frictional properties of cast irons in a corrosive environment

25 at 700 C above.

In the iron, the upper limits of the concentration of manganese and phosphorus are increased in order to compensate for the graphitizing effect of niobium carbonitrides and calcium. In addition, I act as inoculum components, carbonitrides of iobi and cerium in a given combination of graphitizing and bleaching materials, which have a favorable effect on the amount of coli.

35, honestly, additional crystallization centers, hindering the development of transcrystallization zones, which also increases the stability of the frictional properties of cast irons in castings.

40 Thus, the introduction of carbonitrides of niobium and cerium into the composition of cast iron in reduced ratios at elevated calcium concentrations provides the complex with new frictional properties, which combine high stability under friction in corrosive environments with temperatures up to 700 ° C and increased resistance. bully and shock loads 50 cams.

The introduction of manganese in an amount of 0.7-1.3 wt.% In cast iron promotes hardening and grinding of the structure, which ensures an increase in the crack resistance, plasticity, and stability of frictional properties during friction in a corrosive environment at temperatures up to 700 C. In the proposed iron

The upper limit of the concentration of manganese is increased to 1.3 wt.%, in order to compensate for the graphitizing effect of niobium and calcium carbonitrides. When the content of manganese is more than 1.3 wt.%, The stability of the structure and frictional properties decreases, and when the concentration of manganese is up to 0.7 wt.%, The plastic properties, resistance to tearing and stability of the friction coefficient at 700 ° C in a corrosive environment are reduced.

The introduction of 0-, 3-0.5% by weight of chromium into the cast iron microlegates the metal base, stabilizes perlite in a wide temperature range and increases the frictional heat resistance and stability of the friction coefficient at 700 ° C in a corrosive environment. The chromium content is selected taking into account the following, when the chromium content is up to 0.3 wt.%, The frictional heat resistance decreases significantly, and with an increase in the chromium concentration of more than 0.5 May. 7, chill bones increase and the propeller boom decreases and the stability of the friction coefficient at 700 ° C corrosive environment.

Nickel in the amount of 0.6–1.2 May,% dopes the matrix and increases the resistance to tearing and stability of the friction coefficient. At a nickel concentration of up to 0.6 May.7, the resistance to tearing and stability of the coefficient 700 ° С

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an increase in the nickel content of more than 1.2% by weight increases friction wear and friction stability.

The content of molybdenum is increased to 0.5-0.9 wt.% Taking into account the fact that when the concentration of molybdenum to 0.5 wt. high wear under friction and low stability of friction properties in corrosive environments, and with an increase in the molybdenum content of more than 0.9 wt.%, the brittleness of cast iron increases, the flexural strength and the resistance of cast iron to tearing decrease.

Copper is introduced to improve ductility, tear resistance and friction stability in Corrosive environments. When the concentration of copper is up to 0.2 wt.%, Its influence is insufficient, and if the concentration of copper is more than 1.0 wt.%, The content of ferrite in the structure increases and the frictional heat resistance and stability of frictional properties decrease.

ten

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Aluminum is introduced as an effective micro-alloying additive, helping to stabilize the structure and frictional properties in corrosive environments at elevated temperatures. Its content, at which a significant increase in the stability of the structure and frictional properties is noted, is 0.1 wt.%, And with an increase in its concentration of more than 0.4 wt.%, The heterogeneity of the structure and stability of the frictional heat resistance increase.

The limits of the phosphorus content are chosen taking into account the fact that it is at a concentration of 0.05-0.2 wt.% That the high-temperature wear resistance in corrosive environments and the stability of the coefficient of friction are maximum.

Tin in an amount of 0.03-0.07 wt. / S has a perlite effect on the structure and a stabilizing effect on the coefficient of friction, and calcium in an amount of 0.1-0.16 May, 7, modifies the structure, clears the grain boundaries, improves the shape of graphite and the stability of frictional properties in corrosive environments.

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The content of the main components (carbon 2.7-3.2 wt.% And silicon 1j2-2.0 wt.%) Eliminates the formation of chill in friction castings, improves the stability of the structure, mechanical properties, wear resistance during friction in corrosive environments. With a carbon content of up to 2.7 wt.% And silicon up to 1.2 wt.%, Chisel significantly increases, the deflection boom, flexural strength and stability of the coefficient of friction decrease, and with a carbon concentration of more than 3.2 wt.% And silicon more 2.0 wt.%. There is an increase in graphite, a decrease in the resistance to tearing at temperatures of 20–700 ° C and frictional heat resistance.

The friction properties of cast irons of known and proposed compositions are determined on an MKF-1M installation with a reciprocating rotational movement with an amplitude of 50 ± 5 µm, a frequency of Hz, and loading in the axial direction of 1500-2500 N. The corrosive medium is sulfur dioxide, whose temperature varies from 20 to 700 s. The estimation of the frictional heat resistance of cast iron is determined on the UMT-III installation at. axial loading force512

MI 1500-3900 N. The test results are shown in Table. 2

Tests show that cast iron, additionally microalloyed with niobium and cerium carbonitrides, contains less process impurities and gases, has relatively dispersed and compact structural components and non-metallic inclusions and more stable and high operational durability, which provides in comparison with the known

Note. Carbon is determined chemically, and other components are determined by X-ray microanalysis.

cast iron increase-density castings and .nost1 | friction properties.

With a decrease and increase in the content of carbonitrides in predpagayem

5 cast iron friction stability

The properties of cast iron in castings are significantly reduced. Metallographic studies show that the microstructure of castings from the proposed iron

10, when casting in coconut and dry liquid glass forms, there is more fine-grained than in cast iron.

Table 1

Reduction of frictional heat resistance when heated from 20 to in a corrosive gaseous environment,%

Friction wear, mg / h, with

Editor N. Yatsola

Compiled H, Shepitko

Tehred V. Kadar Proofreader V. Sinitska

Order 3065/26 Circulation 567 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

Table 2

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23

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Claims (1)

CAST IRON containing carbon, silicon, manganese, chromium, nickel, molybdenum, copper, aluminum, phosphorus, tin, calcium and iron, 'characterized in that, in order to increase the stability of frictional properties during friction in a gas corrosive environment when heated to 700 ° C , it additionally contains niobium carbonitrides and cerium carbonitrides in the following ratio of components, May.%: Carbon 2.7-3.2 Silicon 1.2-2.0 Manganese 0.7-1.3 Chromium 0.3-0.5 Nickel 0.6-1.2 Molybdenum 0.5-0.9 Copper 0.2-1.0 Aluminum 0.1-0.4 Phosphorus 0.05-0.2 Tin 0.03-0.07 Calcium 0.10-0.16 G5 Carbonitrides <g niobium carbonitride 0.12-0.85 to cerium 0.03-0.15 from Iron Rest 5 GO with SL with © m with 0