SU1693112A1 - Cast iron - Google Patents

Abstract

This invention relates to a foundry, namely, to compositions of high carbon iron alloys, and can be used to produce responsible castings. The aim of the invention is to increase the fluidity, the resistance to tearing, while maintaining wear resistance. The proposed cast iron contains, wt%: carbon 3.2-3.6; silicon 1.8-2.8; manganese 0.5-1.0; chromium 0.2-0.35; nickel 0.1-0.6; copper 0.55-1.2; vanadium 0.05-0.2; titanium 0.02-0.08; niobium 0.05-0.2; phosphorus 0,25-0,6; barium 0.005-0.02; bismuth 0.002-0.015; iron - the rest. The proposed composition is expediently used for the manufacture of cylinder liners without subsequent quenching of high-frequency current for air-cooled diesel engines. 2 tab.

Description

The invention relates to metallurgy, in particular, to compositions of high carbon iron alloys, and can be used to produce responsible castings, such as cylinder liners of air-cooled diesel engines, the material of which has increased requirements in terms of durability and fluidity (because the wall of the liner cylinder thin, ribbed), resistance to bully.

The purpose of the invention is to increase the resistance to tearing, fluidity and cost reduction while maintaining wear resistance.

This goal is achieved by the fact that cast iron predominantly for cylinder liners of air-cooled diesel engines contains carbon, silicon, manganese, chromium, nickel, copper, vanadium, titanium, niobium,

phosphorus and iron, barium, bismuth in the following ratio of ingredients, wt.%:

Carbon

Silicon

Manganese

Chromium

Nickel

Copper

Vanadium

Titanium

Niobium

Phosphorus

Barium

Bismuth

Iron

The combined input of barium and bismuth within the specified limits improves the resistance to tearing while reducing the total wear of the friction pair due to the complex effect on the distribution and size of the inclusions of graphite and the structure of the metal matrix. In particular, the grinding of graphite inclusions up to 45-90 µm is provided, while at the same time eliminating churning off in thin sections characteristic of a ribbed cylinder liner of air-cooled engines. Grinding of eutectic grain due to joint

Evod bismuth and bari leads to improved phosphide eutectic structure, which plays an important role in the formation of resistance to wear and durability.

Niobium enhances the stabilizing effect of elements such as chromium, vanadium, titanium, and also changes the morphology of structurally free carbides and phosphide eutectics, which play an important role in the formation of resistance to durability, wear resistance and hardness of the metal base.

The presence in the composition of the proposed phosphorus pig iron within the specified limits (0.25-0.6 wt.%) Leads to the formation of a phosphide eutectic in the structure in the form of a broken mesh (Fd1, Fd2), increases the fluidity and hardness.

Copper (0.55-1.2%) in the proposed composition, together with nickel, eliminates unevenness of properties over the cross sections of the casting, improves the strength and technological characteristics of cast iron. Complex doping with the sum of niobium, bismuth, phosphorus. With the proposed concentration of .. copper and kpOMa it contributes to the reduction of wear | ring of high-strength cast iron, especially in the presence of abrasive particles, and an increase in the resistance to tearing. Vanadium, manganese, chromium and titanium within the indicated limits, having an effective effect on the primary crystallization, in the vectic and eutectoid transformation, contribute to the production of cast iron with a fine matrix and uniformly distributed inclusions of graphite, which, in turn, reduces the tendency of the alloy to chipping structure - typHbix components in the process of wear.

The lower limits for carbon (3.2 wt.%) And silicon (1.8 wt.%) Are due to the need to exclude structural-free cementite. Exceeding the upper limits of the concentration of these Elements leads to a deterioration in the shape, size and distribution of graphite. The presence of manganese in the iron below 0.5 wt.% Does not provide the required strengthening of the matrix, and with additives above 1.0 May. % increases the tendency of the alloy to shrink fission. When the concentration of vanadium, titanium, niobium and chromium is below the specified limits (0.05; 0.02; 0.05; 0.2 wt.%, respectively), the structure of cast iron shows ferrite, which significantly reduces the alloy hardness, wear resistance and tearing resistance. Additions to the alloy of these elements above the upper limits (0.2; 0.08; 0.2; 0.35 wt.%, Respectively) sharply worsen the workability and, moreover, lead to higher prices for the casting. The introduction of chromium more than 0.35 wt.% Can lead to the release of eutectic carbides, which causes a decrease in fluidity and wear resistance. The lower limits for nickel 0.1 wt.% And copper 0.55 wt.% Were selected, based on 5 d from obtaining uniform hardness in the sections of the casting. At concentrations of these elements above the upper limits (0.6 and 1.2 wt.%, Respectively), their degree of influence on the alloy perlitization is insignificant and is not economically viable. When the phosphorus content is 0.25–0.6 wt.%, A uniformly distributed eutectic is formed in the structure, which significantly affects the achievement of the goal. At 5 phosphorus concentrations below 0.25 wt.%, A broken phosphide mesh is not formed in the structure. The addition of the specified element above Ogb May. % embrittlement of the alloy, which leads to cracks in the cracks. 0 The selected limits for the content of barium (0.005-0.02 wt.%) And bismuth (0.002-0.015 wt.%) Ensure, due to effective modification, the elimination in thin sections of castings from the proposed alloy 5 of structural-free cementite and grinding of graphite. These elements favorably influence the shape and morphology of the folded phosphide eutectic. The optimal composition of the proposed chu-0 guna contains, wt%:

carbon3.4;

silicon2,3;

manganese 0.75;

chromium; 0.26;

5 o nickel; 0.35;

copper 0.85;

vanadium 0.12;

titanium 0.05;

barium; 0.012;

0 niobiy0,12;

bismuth = 0.0085;

phosphorus 0.42.

Example. In order to obtain cast iron, three compositions of the proposed cast iron 5 are melted at the lower, middle and upper limits, two compositions with the limits of the content of ingredients below the lower and above the upper limits. For comparative tests, renowned cast iron containing ingredients at the middle limit is used.

Melting is carried out in an acid-lined induction furnace. Foundry cast iron LZ, steel scrap, manganese ferroalloys, silicon, vanadium, titanium, chromium, niobium, phosphorus, granulated nickel, cathode copper, barium-containing ligature (such as Fs65Ba10, 10 wt.% Barium) and ligature are used as the charge. with bismuth based on copper (Bi up to 10 May%) The mixture is loaded into the furnace, after melting and overheating to 1460 ° C, ferroalloys are introduced in the required quantities taking into account the degree of their absorption (manganese, copper, nickel, chromium, vanadium 85-95 wt. .%, phosphorus, titanium, niobium 70-80 May.%). Before casting, the liquid metal is treated with a barium-containing ligature and a bismuth-based copper-based ligature, the absorption of 70-80 wt.%.

Cast iron is poured into single sand forms. Samples of 50 mm in width, 150 mm in length and 5 mm in thickness were cut from the obtained blanks for wear tests, which were performed on a reciprocating friction machine under boundary friction conditions. When tested, diesel oil is used at 400 double strokes per minute. High-strength cast iron HF50 (200 HB) is used as a counterbody. The criterion for the intensity of abrasion of the accepted amount of wear, expressed in mg / 100 h. The evaluation of the resistance to tearing of the proposed alloy is carried out on an installation equipped with a special device. Samples are fixed in

steel clips and pressed to the frame with a diameter of 40 mm and a width of 20 mm, made

steel 45 (hardness 55 HRc),

Before testing, which

d t without the use of grease, samples and ro

faces degreased with gasoline. Roller rotation speed 0.4 m / s, loading about

rastsiv carried out by increasing

specific pressure in steps of 5 MPa

every minute Moment of onset

the bully is determined by the specific load at which the coefficient

Carbon

friction cycle. The fluidity of the alloy is determined by a spiral sample with a cross-sectional area of 40 mm2.

The chemical composition and results of tests of alloys are given in table. 1 and 2. As can be seen from the table. 1 and 2, the introduction of barium and bismuth into the composition of the alloy allows a significant increase in wear resistance, tearing resistance and fluidity.

The structure of the proposed pearlite alloy with a uniformly distributed torn mesh of phosphide eutectic of complex composition and uniformly distributed graphite inclusions with a size of up to 90 microns.

The proposed composition is expediently used for the manufacture of cylinder liners without subsequent quenching of high-frequency current for air-cooled diesel engines.

Claims (1)

Invention Formula Cast iron is predominantly for cylinder liners of air-cooled diesel engines, containing carbon, silicon, manganese, chromium, nickel, copper, vanadium, titanium, niobium, phosphorus and iron, characterized in that, in order to increase fluidity, resistance to tearing and reduce cost while maintaining wear resistance, it additionally contains barium and bismuth in the following ratio of components, wt.%: 3.2-3.6 1.8-2.8 0.5-1.0 0.2-0.35 0.1-0.6 0.55-1.20-0.05-0.20 0, 02-0.08 0.05-0.20 0.25-0.60 0.005-0.020 0.002-0.015 Else. Table 1 k2 51 43 39 Continuation of table 1 table 2 390 550 630 660