SU1036788A1 - Cast iron - Google Patents

Abstract

CAST IRON; containing carbon, silicon, manganese, nickel, chromium. molybdenum, magnesium, copper, cerium and iron, characterized in that, in order to increase the strength, hardness and heat resistance of cast iron, it contains components in the following ratio, wt.%; Carbon 2.2-2.8 0.7-1.4 Silicon 0.4-0.7 Manganese 1.5-1.9 Nickel 0.1-0.3 Chromium 0.3-0.5 Molybdenum 0, 03-0.05 Magnesium. 1.5-2.0 Copper Cerium 0.02-0.04 Iron Else

Description

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00 The invention relates to chemistry, in particular, to the search for materials for the manufacture of mountain-rolls rolling. Known cast iron Ts 3 rolling mill reflux, containing, in 3.3-3.5 Carbon 2.0-2.2 Silicon 0.4-0.6 Manganese 0.2-0.6 3.0-3.8 Nickel 0.3-0.5 Molybdenum 0.03-0.06 Magnesium Else Iron The disadvantages of the known iron are low thermal stability (150–200 thermal cycles) and the cost of iron due to the content of nickel in the amount of 3.0- 3.8 The closest to the proposed technical essence and the achieved result is cast iron containing components in the following ratio, wt.%: 3.4-3.7 Carbon 2.4-2.8 Silicon 0.8-1.2 Manganese 1.2-1.5 Nickel 0.35-0.8 0.6-1.1 Molybdenum 0.03-0.1 Magnesium 0.3-0.9 0.001-0.0 Osta Flax Iron Impurities: Sulfur up to 0.03 Phosphorus up to 0.1 The insufficiently high level of hardness and hardness of cast iron can be used to press rollers for hot products. The purpose of the invention is to improve the hardness and heat-resistant pig iron. This goal is achieved that the pig iron containing carbon, manganese, nickel, chromium, monomer, magnesium, copper, cerium and jelly contains components in the following ratio, wt.%: 2.2-2.8 Carbon Silicon 0.7 -1.4 0.4-0.7 Manganese. Nickel 1.5-1.9 0.1-0.3 Molybdenum 0.3-0.5 Magnesium 0.03-0.05 1.5-2.0 0.02-0.04 Iron Else With this amount Nickel and copper ranges from 3.2 to 3.5. The proposed smelting technology of pig iron does not change in comparison with the known one. To ensure the required level of properties, the cast iron is subjected to heat treatment according to the mode: heating up to 1000-1050 s at a speed, holding 2-4 hours, cooling in air to, further, at a speed of 25-30 sec / h. Selection of boundary parameters the need to form a beiite-graphite structure over the entire cross section of the casting, which allows to combine high strength, heat resistance and hardness in the alloy of the same chemical composition. The stable formation of a bainithographite structure in heat-treated iron is ensured by the introduction of 0.3-0.5%, molybdenum, 1.5-1.9%, nickel and 1.5-2.0% copper at a given ratio of nickel and copper The composition of cast iron is balanced in such a way that, with a total content of nickel and copper in the range of 3.2-3.5 (Table 1), the metal base of the cast iron in thermally treated condition consists of bainite and does not contain martensitic and pearlitic sections. The presence of molybdenum, nickel and copper in cast iron in the quantities proposed increases the strength, hardness and heat resistance of cast iron. These elements increase the stability of austenite and when the content of molybdenum mekee is 0.3%, and Cu + Ni is less than 3.2%, the formation of a bainite base in rolls with a diameter of 300-600 mm is difficult. With an increase in the molybdenum content of more than 0.5, and QJ + Ni more than 3.5% in the material of the working layer of such rolls, there are areas of residual austenite and martensite, which leads to a decrease in the strength and heat resistance of the iron. When the carbon content is 2.2-2.8% and silicon is 0.7-1.4%, a bainitic matrix is formed in the heat-treated cast iron, which does not contain structurally free cementite, which precipitates along the grain boundaries and degrades all the strength characteristics of the alloy. When the content of carbon and silicon is more than 2.8 and 1.4%, respectively, in the heat treatment process, an excess of carbon annealing is released, which also leads to a decrease in the hardness and strength of cast iron. In cast iron containing less than 2.2% of carbon and 0.7% of silicon, structurally free cementite is released throughout the mesh along the grain boundaries, which does not decompose even when heated to 1050 ° C, while heating to higher temperatures is not permissible, since causes grain growth, worsens the shape of raffit.

Chromium and manganese exert a stabilizing effect on structurally free cementite; therefore, when they are introduced into cast iron in quantities exceeding 0.3 and 6.7%, the total amount of cementite increases and the process of graphitization of the carbide grid during heat treatment is slowed down.

A decrease in the chromium and manganese content of less than 0.1 and 0.4%, respectively, leads to a deterioration in the resistance of the bainite matrix against tempering, a decrease in the level of hardness of the material in the operating temperature range of the hot-rolled rolls.

To obtain nodular graphite, cast iron is modified with cerium and magnesium. In iron with 0.03-0.05%, magnesium in the amount of 0.02-0.04% is a graphitizing modifier and the melt is refined. When less than 0.03% of magnesium and 0.02% of cerium are introduced into cast iron, a violation of the form of spherical graphite and the appearance of lamellar precipitates occurs. Magnesium and cerium introduced into the alloy in quantities of higher boundary values increase the stability of structurally free cementite, worsen the shape and nature of the distribution of non-metallic inclusions and do not have

positive effect on the properties of cast iron.

To determine strength, hardness and heat resistance, five alloys with boundary

0 jji optimal ratios of all. ingredients.

In order to provide a comparative analysis with the known iron, 5 also alloy was prepared with a known optimal ratio of ingredients. The results are summarized in table. 1. Each alloy is made by smelting 200 kg of induction furnace. The following materials are used as charge materials: steel scrap, cast iron LK-2, FeMn (45%), FeCr (72%), granulated nickel, copper electrolysis, FeMo (60%), FeSi (75%), nickel-magnesium ligature (17 % Md), Fed (45%).

Table 1

Note: F-ferrite, A - residual austenite, G - graph Castings are subjected to heat treatment in the following mode: heating to 30 ° C / h, holding for 2 hours, air cooling to, then at 25s / h Mechanical properties standard methods. Thermal stability tests are carried out on the proposed offer.

11190

21215

2380

353 2930 361 ollite, B - bainite, M. - marten.sit. This method is used for thermocycling by heating the samples up to about 10 ° C, followed by cooling with water up to 20 ° C, which reflects the conditions of heating and cooling of the rolls in hot rolling mills during their operation. The properties of the resulting cast irons in the heat-treated state are given in Table. 2. Table 2 As shown in the data table. 2, the obtained alloys have the following strengths of 950-1215 MPa, hardness 302-388 HB, heat resistance of 1500-2930 thermal cycles. According to the table. 2, cast iron of the proposed composition in comparison with the known one provides an increase in strength by 1 g3 times, hardness by 1.7 times and heat resistance by 4.7 times.

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Continued table. 2 Having a higher level of quality, the mill rolls from the proposed cast iron will ensure higher productivity of rolling mills. Higher grades of good-quality cast iron will increase, consumption will be reduced: metal in the manufacture of metal products, rhythm and production culture will be observed. The expected annual economic effect from the use of the invention will be 4.1 million rubles.

Claims (1)

PIG IRON, containing carbon, silicon, manganese, nickel, chromium, molybdenum, magnesium, copper, cerium and iron, characterized in that, in order to increase the strength, • hardness and heat resistance of cast iron, it contains components in the following ratio. weight.%: Carbon 2.2-2.8 Silicon 0.7-1.4 Manganese 0.4-0.7 Nickel 1.5-1.9 Chromium 0.1-0.3 Molybdenum 0.3-0.5 Magnesium 0.03-0.05 Copper 1.5-2.0 Cerium 0.02-0.04 Iron Rest In e ω a FO m x x ί