SU1108124A1 - Cast iron - Google Patents

Abstract

CAST IRON containing carbon, silicon, manganese, vanadium, copper, nickel, chromium, magnesium, rare earth metals and iron, which is different in that it contains calcium in order to improve galling resistance, improve machinability, aluminum and tin in the following ratio of components, wt.%: Carbon 3.4-3.8 Silicon 2.9-3.7 Manganese O, 4-0.8 Vanadium 0.9-1.2 Copper 0.8-2.0 Nickel 0.01 -0.80 Chromium 0.01-0.50 Magnesium 0.01-0.05 rare earths 0.01-0.15 metals (I Calcium 0.01-0.08 0.05-0.30 Aluminum 0, 01-0.10 Tin Iron Else

Description

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This invention relates to the field of metallurgy, in particular to the development of a composition of cast iron with high resistance to the formation of air on rubbing surfaces, for example cylindrical bushings of internal combustion engines.

Known cast iron Ij the following chemical composition, wt.%

Carbon2,6-4,5

Silicon1.0-4.0

Manganese 0.1-1.2

Chrome 0,01-0,5

Nickel0.01-1.0

Copper0.01-1.0

Magnesium 0,015-0,1

Calcium 0,015-0,06

РЗМ0,005-0,15

Aluminum0.005-0.4

IronErest

As impurities, cast iron may contain sulfur in an amount up to 0.03% and phosphorus up to 0.2%.

Cast iron has a fairly high strength ((6-630-650 MPa) and good workability (hardness 207-217 HB).

The disadvantages of cast iron are low wear resistance and resistance to scuffing (anti-friction properties). This is due to the presence in the structure of ferrite, which impairs anti-friction properties, and the lack of components with high hardness.

The closest to the present invention is cast iron 2J of the following chemical composition, wt.%:

Carbon3,8-4,5

Silicon 2,5-4,2

Vanadium3,5-4,5

Copper0,1-1,5

Nickel 0.1-2.0

ManganeseDo O, 8

SeraDo Oh, 1

PhosphorUdO 15

ChromeDo Oh 10

Magnesium Up to 0.05

RZMDo 0.03

IronErest

Due to the spherical shape of graphite, cast iron has high mechanical properties: in the molten state of C-in g 650-850 MPa, after quenching with tempering 1200-1400 MPa, after annealing df, g 650-680 MPa. Cast iron has a pearlite matrix and contains a large amount of wear-resistant carbide phase, represented by vanadium VC carbides. This gives the cast iron high wear resistance. However, a large amount of vanadium carbides and their unfavorable form reduces the antifriction properties of cast iron and impairs its machinability.

Cast iron has a high cost due to the increased content of vanadium.

The purpose of the invention is to increase the resistance to scuffing on surfaces, improving machinability.

The goal is achieved by the fact that cast iron containing carbon, silicon, manganese, vanadium, copper, nickel chromium, magnesium, rare earth metals and iron, additionally contains calcium, aluminum and tin at the following ratio of components, wt.%: Carbon 3,4-3 ,eight

Silicon2.9-3.7

Manganese0.4-0.8

Vanadium0.9-1.2

Copper 0.8-2.0

Nickel0.01-0.8

Chrome 0,01-0,5

Magnesium0.01-0.05

P nitrile metals 0,01-0,15

Calcium0.01-0.08

Aluminum0.05-0.3

Tin 0,01-0,1

IronErest

As impurities, cast iron may contain sulfur in an amount up to 0.03% and phosphorus up to 0.15%.

In the proposed iron compared with the prototype significantly reduced the content of the vanadium of the main kabidoobraznogo element. Due to this, the amount of the carbide phase is reduced and its morphology is improved: the number of compact carbides is reduced relative to the proportion of branched ones, which increases the resistance of cast iron to scuffing.

However, reducing the amount of wear-resistant carbide phase can lead to a decrease in wear resistance of the pig iron. To prevent this, calcium, aluminum and tin are additionally introduced into the cast iron. Calcium and aluminum effectively refined and modified cast iron, thereby crushing the structure, including vanadium carbides. The mass of carbide crystals is reduced, and their number per unit of iron volume increases. These elements, especially aluminum, increase the degree of branching of carbide crystals. Such changes in the microstructure of the carbide phase provide increased wear resistance of cast iron, despite the decrease in the total amount of the carbide phase.

Tin is introduced to prevent the formation of structurally free ferrite and to obtain a fully pearlitic matrix.

The positive effect of the calcium modifying and refining element is manifested when its content in the iron is more than 0.01%. More than 0.08%, the efficiency of the effect of calcium decreases, the technology of introducing it into the cast iron becomes more complex and the cost of the cast iron is lost. Aluminum begins to grind carbides when its content in the iron is not less than 0.05%. Over 0.3% cast iron casting properties due to strong foaming are extinguished. The absence of ferrite in the cast iron structure and an increase in the anti-friction properties is observed at a tin content of 0.01%. At 0.1%, strength properties begin to fall noticeably with a simultaneous increase in hardness and deterioration in workability.

The limits of the contents of the remaining components are selected for the following reasons.

Carbon and silicon contribute to the formation of vanadium carbide. When the carbon content is below 3.4% and the yield is 2.9%, cementite is formed in the iron structure, as a result of which the mechanical properties of the iron decrease. When the carbon content exceeds 3.8% and silicon - 3.7%, the enlargement of graphite inclusions occurs, which reduces the hardness and wear resistance of cast iron.

When the vanadium content is less than 0.9%, no special vanadium carbides are formed (the critical vanadium content). Above 1.2%, substantial strengthening of vanadium carbides occurs, resulting in reduced drag resistance and reduced workability of the iron.

Copper and nickel have alloying effects, reduce the critical vanadium content, promote graphitization, and inhibit the bleaching of cast iron. The effect of these elements on the structure and properties of cast iron is identical, so they are interchangeable. Since nickel acts about 1.5 times stronger than copper, their reduced content can be estimated by the sum of Cu + 1.5Ni. in the proposed iron, this amount should not be lower than 0.8% and not higher than 3.2%. With a decrease in Cu l, 5Ni below 0.8%, the antifriction properties of cast iron deteriorate. Increasing this amount by more than 3.2% leads to the strengthening of graphite inclusions, which reduces the oil-holding capacity of the microrelief on the surface of the friction, and the iron production deteriorates. The upper limit of the copper content is 2%, since its further decrease does not lead to a significant improvement in the mechanical and antifriction properties. The remaining limits of the contents are chosen and the conditions are 0.8% Cu + l, 5Ni:, 3.2%, while taking into account that nickel can be completely replaced by copper.

Manganese and chromium contribute to improving the mechanical properties of cast iron by doping austenite. When the content of manganese is more than 0.8% and chromium is 0.5%, structural-free cementite can form in the iron, which impairs the processability of the iron. The lower limit for manganese (0.4%) is determined by its minimum content necessary to eliminate the harmful effects of sulfur by binding it to sulfides. The minimum chromium content is determined by the presence of silicon in the iron, and when the silicon content is 2.9%, chromium may not be introduced into the iron. The chromium content of 0.01% corresponds to its minimum amount in charge materials.

Magnesium and rare earth metals (REM) provide for the production of graphite iron of spherical or vermicular shape in the structure, which increases the strength properties of cast iron. Magnesium spheroidizes graphite more actively than REM, however, the presence of rare-earth elements makes it possible to preserve the modifying effect of magnesium for a longer period of long-term exposure of cast iron, therefore, they are effectively introduced together. The lower limits of the content of magnesium and rare-earth metals (0.01) correspond to their minimum concentrations at which the combined sphroidizing effect is manifested. The upper limits of the contents of magnesium (0.05%) and rare-earth metals (0.15%) ensure in all cases stable production of spherical graphite. A further increase in their content is impractical due to the lack of a positive effect on the properties of cast iron, while at the same time complicating the technology of its production.

An example. In order to obtain cast iron of the proposed composition, 5 mixtures of ingredients (alloys 3-7) were prepared, which differed by increasing calcium, aluminum and tin additives, including higher (alloy 7) and lower (alloy 3) of the proposed limits when the remaining components were kept at a constant level In alloys 8 and 9, the content of components was varied within the limits of the proposed composition of cast iron. Simultaneously melted alloy prototype.

Cast iron was melted by the well-known technology in an induction furnace H4T-2, J5M As pig materials, pig iron, steel and cast iron scrap, ferroalloys and additives, including silicocalcium SC20 (GOST 4762-71), aluminum A5 (GOST 11069-71 ), tin 04 (GOST 86060). REM was introduced in the form of the ligature SCTSISH-3, magnesium - in the form of ligature LCM-1 (TU 14-5-37-74). Cast iron was released from the furnace at a temperature of 14801500 ° С into a bottling ladle, at the bottom of which there were heated ligatures. At 1340-1360 ° С forms of cylinder sleeves of engines were poured

internal combustion. After knocking out, the castings were artificially aged at 580-620C for 6 hours. The specimens were cut from the body of the castings to study the properties.

Anti-friction properties - wear resistance (I) and resistance to bully (P). determined by the well-known method of the Central Research Institute of the Ministry of Railways on the MTV-1 friction machine with reciprocating motion and LIQUID lubricant (oil Ml4B according to TU 38-101-421-73). Wear resistance was determined by weight loss in mg per 100 hours of machine operation, and tearing resistance was determined by the value of the specific pressure causing damage to the surfaces and samples.

a sharp increase in the coefficient of friction and an increase in contact temperature feed rates of 0.5 mm / rev (for the studied alloys), to the maximum cutting speed of the known iron.

The chemical composition of the investigated alloys and the test results are shown in the table. 9 110812 Increased, against the proposed, content of calcium, aluminum, and tin (alloy 7) alloy introduced into the composition reduces the machinability of the cast iron due to its hardness. With the absence of these elements (alloy 3), the antifriction properties are reduced due to the increased content of ferrite in the iron structure. 410 The results of the tests showed that the proposed alloy wear is 3-26% less, the pouring resistance increased by 46-62%, and the processability improved in L4-1 6% The annual economic effect from introducing the proposed cast iron of engine-diesel engine cylinders 2,276 million rubles.

Claims (1)

PIG IRON containing carbon, silicon, manganese, vanadium, copper, nickel, chromium, magnesium, rare earth metals and iron, distinguishing- with i that, with aim of increasing resistance to scoring on rubbing surfaces; workability he additionally holds calcium. aluminum and tin in the following ratio of components tov, wt.%: Carbon 3.4-3.8 Silicon 2.9-3.7 Manganese 0.4-0.8 Vanadium 0.9-1.2 Copper 0.8-2.0 Nickel 0.01-0.80 Chromium 0.01-0.50 Magnesium 0.01-0.05 h Rare earth is metals 0.01-0.15 I Calcium 0.01-0.08 (/) Aluminum 0.05-0.30 Tin 0.01-0.10 Cz Iron The rest is 1 about 00 to> 4 ^