SU885323A1 - Cast iron with spherical graphite - Google Patents

Description

(5) CAST IRON WITH SPARKET GRAPHITE

The invention relates to metallurgists, in particular, to cast irons with improved physicomechanical and special properties for castings operating under gas corrosion and corrosion conditions in non-ferrous metal melts operated with impact loads. Known cast iron containing carbon, silicon, manganese, chromium, magnesium, calcium, rare earth metals, characterized by low mechanical properties at room and high temperatures, as well as low resistance to gas corrosion and corrosion in the melt of non-ferrous metals. Known cast iron of the following chemical composition, weight. s, og, o Carbon Silicon 0.5-2.5 0, i4-1, 0 Manganese Nitrogen 0.003-0.025 Magnesium 0.01-0.05 0.08-0.3 Calcium Rare-earth metals0.001-0 , 01 Titan0.0it-0.1 Vanadium 0.02-0.2 Iron Remaining Cast iron in the cast state has the following properties; Strength, bending, kgf / mm Tensile strength, kgf / mm 22-2 Deflection, mm 5.0-6.0 Relative elongation,% 1.4-1.6 Hardness, HB 165-173 Corrosion rate iron in the molten aluminum, mm / h 0, 233. During the tests it was found that the impact strength of a known chua is 0.3-0.5 kgcm / cm D. In the known cast iron, the presence of anadi titanium contributes to the formation of dendritic graphite and pearlite metal base, which reduces the impact strength and ductility. and, as a result, cracking, however, the cast iron has a low resistance to gas corrosion. The closest to the proposed technical essence and the achieved result is nodular cast iron of the following chemical composition, weight D: Carbon 3.5, 0 Silicon 3.25-5.0 Manganese 0.4-1, 5 Chromium 0.25-2.0 Copper: 0.75-1.0 Magnesium; 0.01-0.0 Iron; Others As the impurities, the cast iron contains wt.%: Phosphorus 0.2, sulfur to 0.02 and nickel to 0.5. The microstructure of cast iron is spherical graphite, perlite or ferrite, cementite (up to 20). This cast iron has high wear resistance, durability, heat resistance and works under pure friction conditions with heating without shock loads. The maximum operating temperature of cast iron is 600 C t2J

Table 1 34 A disadvantage of the known iron is low corrosion resistance to gas corrosion and corrosion in a melt of non-ferrous metals. The purpose of the invention is to increase resistance to gas corrosion and corrosion in a melt of non-ferrous metals with a high level of strength, ductility and impact strength. This goal is achieved that nodular cast iron, containing carbon, silicon, manganese, chromium, copper, magnesium and iron, additionally contains rare earth metals in the following ratio of components, weight 1: Carbon 2.5- , Silicon3.2-4.5 Manganese0.2-0., 5 Chrome0.3-0.5 Copper0.2-0, Magnesium0,, 08 Rare-earth 0.03-0.06 metals Else Iron Offered cast iron is intended for operation at temperatures of 700-900 ° C, its metallic matrix with the content of ingredients on three levels of ferritic, In the table. 1 shows the chemical composition of the proposed iron and known; in tab. 2 shows their mechanical and special properties.

Comparative tests of the proposed and known cast irons lead to the following conclusions:

1.When the contents of the ingredients of the famous 2 cast iron on the lower level, gray ferrite-pearlitic cast iron is obtained

with lamellar graphite, having a high (6.3 corrosion rate in air at a test temperature of 800 ° C, which is 11 times higher than the corrosion rate of the proposed cast iron. The corrosion rate in the molten aluminum at 860 ° C is well-known among the cast iron cast iron.

2.When the content of the ingredients of the famous 2 cast iron at an intermediate level, cast iron with vermicular graphite was obtained. The metal matrix of cast iron is pearlitic, prone to ferritization, structural free cementite 1015%. This cast iron has an increased

(1.5 g / m-h) corrosion rate in air at 800 ° C, which is 7 times more than that of the proposed pig iron. The corrosion rate of the known iron in the molten aluminum with almost 1.5 times higher than that of the proposed iron.

3 When the content of the ingredients of the famous iron at the top level is obtained nodular cast iron. The metal matrix of cast iron is pearlite-cementitic, structurally free

table 2

cementite to. Such a cast iron has a corrosion rate in the air environment (0.123) at the speed of the corrosion in the molten aluminum (О, 226 mm / h) at.

The value of all physicomechanical properties when the content of ingredients of known iron at three levels is significantly lower than that of the proposed iron for estimates of the high content of carbide-forming elements of chromium and manganese.

Comparative analysis shows that known cast iron has a low level of strength, ductility, toughness and special properties, which is explained by the high content of manganese, copper and chromium - elements that contribute to the stabilization of pearlite and the appearance of structurally free cementite in the metal matrix of cast iron.

It is well known that the maximum corrosion resistance is usually found in cast irons with a single-phase ferritic or austenitic structure, and in low-alloy irons (with the exception of siliceous), a single-phase structure cannot be obtained.

Claims (2)

Manganese, being a carbide-forming element, has a great influence on the structure and properties of nodular cast iron. In a ferritic structure cast iron, the content of marga7a is recommended to be no more than 0.6 since it reduces ductility and toughness and increases the hardness of cast iron due to an increase in the amount of perlite in the structure. Carbides are formed at a higher content of manganese. Doping silicon manganese with manganese up to 0.6% improves the stability and height resistance somewhat, but at the same time, the sensitivity of castings to thermal shocks sharply increases. In order to maintain the high ductility of ferritic nodular cast irons, the manganese content should not exceed 0.6. Copper is one of the most effective perlite stabilizers. After the addition of 0.6% Cu, nodular cast iron with ferritic matrix becomes pearlitic in castings up to 60 mm thick. Copper increases the strength and hardness of cast iron, the more noticeable the lower the silicon content in it. Chromium hinders both stages of graphitization, promotes the formation of cementite and an increase in the amount of perlite. Nickel crushes the structure of the metal base, increases the amount of perlite in the iron. The alloying of silicon iron with chromium in small amounts (0.3 O, 5%) most favorably improves their quality. The improvement in the structure of siliceous iron and the increase in the resistance to oxidation, which occurs under the influence of small additions of chromium, significantly increase the operating temperature range of the castings. The effect of copper1 and nickel on the properties of silicon iron is the same and reduces, mainly, to an improvement in its mechanical properties. The effectiveness of their influence on the scaling resistance and the resistance of cast iron is manifested only in the presence of chromium. Additives of both nickel and copper to cast iron in quantities from 0.5 to 2.5% are more harmful than beneficial, since both of these elements are more conducive to the deterioration of the quality of graphite. However, small additions (up to 0.51) of copper and nickel to silicon with nodular graphite in combination with a limited amount (up to 0%) of chromium give a positive result. 3 All of the above indicates that it is inexpedient to alloy the nodular nodular silicon with significant amounts of carbide forming elements (chromium, manganese), since it is associated with an increase in growth and an increase in the brittleness of the already fragile cast iron. In order to improve the quality of such cast irons, such a doping is necessary that does not disturb the homogeneity of the metal base and does not prevent the formation of spherical graphite. Consequently, the content of chromium, manganese, copper and nickel (as an impurity) should not exceed 0.5% of each element. The magnesium content in the known iron does not always ensure the complete spheroidization of graphite, thereby reducing the corrosion resistance of the iron and mechanical properties. Processing the cast iron with a complex modifier (ligature) due to the presence of REM in it eliminates the coarse form of graphite, provides the correct spherical shape of graphite, and, consequently, a sufficiently high mechanical properties. In addition, the additive of rare-earth metals in cast iron allows suppressing the harmful effects of the elements - deglobulizers S, O., UD; nLf-ie "4 - Hj, Bi, Pb, Sn, T |, A and Cu and eliminate graphitized treatment of liquid iron , and also significantly increase its strength and plastic properties in a cast state. The addition of cerium, yttrium or lanthanum in the amount of 0.2-0.3% in nodular nodular cast irons leads to an increase in their resistance to gas corrosion. On such cast irons, under the influence of REM, qualitative changes occur in the oxide layer due to the formation of complex spinels, which are the result of the interaction of the rare earth metal oxides and other components that make up the pig iron. The presence of REM in the iron eliminates the looseness and porosity of the metal matrix, which increases the corrosion resistance. REM is introduced into cast iron in the form of Fe-Si-Ce (V) ligature containing cerium (yttrium), lanthanum, praseodymium, neodymium. The tests for resistance to gas corrosion were carried out in accordance with the recommendations of GOST on samples with a diameter of 10 and a length of 20 m for 100 hours. Tests on the rate of corrosion (corrosive) of cast iron in molten aluminum were carried out in samples with a diameter of 10 mm and a length of 20 mm at. The application of the proposed cast iron provides increased resistance from molt not less than 2.1 times. The total economic effect from the implementation of the proposed iron in the enterprises of the Ministry of Nonferrous Metallurgy of the USSR will be 1183920. Invention formula Nodular cast iron containing carbon, silicon, manganese, chromium, copper, magnesium and iron, in order to increase the resistance against gas 3O corrosion and corrosion in the melt of non-ferrous metals with a high level of strength, ductility and toughness, it additionally contains rare-earth metals with the following ratio of ingredients, weight: 2.5-i, 0 Carbon 3,2-f, 5 Cre mnn 0.2-0.5 Manganese 0.3-0.5 0.2-0, C 0.04-0.08 Magnesium Rare-earth 0.03-0, 06 Metals Iron Else Sources of information taken into account when examination 1. The author's certificate of the USSR 622862, cl. C 22 C 37/10, 1978, 2. Authors certificate of the USSR -380737, cl. C 22 C 37 / Oi, 1971.