SU1636471A1 - Cast iron for rolls - Google Patents

Abstract

The invention relates to metanurgy and can be used in the production of iron rolling rolls. The purpose of the invention is to improve the wear resistance and increase the tensile strength at a temperature of 8QO & C. The proposed cast iron contains components in the following ratio, wt.%: C 3.6 - 3.9; Si 0.35-0.85; MP 1.4 - 1.9; Cr 0.05 - 0.3; Ni 0.3 - 0.8; Ti 0.01 - 0.05; Р 0, 2 - 0.4; Sy 1.8 - 2.6; N 0.01 - 0.03 and. Fe - the rest. The additional input of nitrogen into the composition of the proposed iron and the change in the ratio of Si, Mn, and Cu in it allow improving wear resistance by 4.1 - 4.3 times i. Owing to the ultimate strength at crushing 1.4 - 1.6 times, table 2. with s

Description

The invention relates to the field of metallurgy, in particular to the development of cast iron compositions for rolling rolls

The purpose of the invention is to improve the wear resistance and increase the tensile strength at 800 ° C.

The choice of the boundary limits of the content of components in the pig iron of the proposed composition is due to the following.

When the carbon content is less than 3.6%, the level of hardness (wear resistance) —the working layer of the rolls — decreases and the casting properties deteriorate (increase in wear and decrease fluidity). With an increase in carbon concentration of more than 3.9%, graphite-shaped graphite appears in the structure of the bleached layer, which is a rejection feature for castings from bleached cast iron.

Silicon is the main regulator of the degree of graphitization of cast iron. When the silicon content is less than 0.35%, cementite is formed in the structure of the necks, which leads to a decrease in their workability, and if the content is more than 0.85%, the required level of hardness and wear resistance of the working roll layer is not provided.

Manganese, together with nickel and copper, provides an increase in the degree of dispersion of the products of the austenichic eutectoid transformation. When the manganese content is less than 1.4%, sorbitol is released, which leads to a decrease in

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hardness of the working layer, with a content of more than 1.9%, slow-cooling, with part of the castings (roll neck) acquire the structure of half-iron, which leads to a decrease in their workability and an increase in trans-crumble.

Nickel together with manganese and caddy provides an increase in the degree of dispersion of the products of eutectoid transformation of austenite, and together with silicon and copper provides compensation for the whitening effect of chromium and manganese. When the nickel content is less than 0.3%, the degree of dispersion of the products of eutectoid transformation of austenite is not provided in the rapidly cooling parts of the casting, and cementite is released in the slow-cooling parts. When the nickel content is more than 0.8%, the cost of pig iron increases due to the high cost.

Chromium in the range of 0.05 - 0.3% helps to increase the hardness of the bleached working layer and the strength of the necks of the rolls. However, with a chromium concentration of more than 0.3%, the workability deteriorates and the transcrystallinity of the iron increases due to an increase in cementite crystals.

Titanium in the range of 0.01-0.05% is used to reduce the transcrystallinity of the macrostructure in the working layer of the rolls, with a content of less than 0.01%, this effect of titanium is insignificant, and with a content of more than 0.05%, the mechanical properties of cast iron decrease with elevated temperatures.

Phosphorus is used to prevent the formation of hot cracks in the working layer of the rolls. When the phosphorus content is less than 0.2%, the scrap reject decreases slightly, and if the content is more than 0.40%, the transcrystallinity increases and the workability decreases due to the formation of phosphide eutectic precipitates.

Copper, like manganese and nickel, increases the dispersion of products of ectoctoid transformation of austenite and in the proposed iron partially replaces manganese, not only does it stretch, but reduces the transition zone with the structure of half-iron, while not providing the necessary structure in metal

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the matrix of quick-cooling parts of the casting, but also improves the machining capacity of cast iron at a lower cost. When copper is introduced in more than 1.8%, part of it is released in free form in cast iron, which contributes to an increase in workability. The lower limit of the copper concentration (1.8%) is justified by its effective influence on the structure of the metal matrix with a decrease in the manganese content. With a content of more than 2.6% (due to the reduced silicon concentration in the separated iron), copper no longer has a strengthening effect on the cast iron, since its main mass is released in its free form.

Nitrogen within the specified limits (0.01–0.03%) has a hardening effect on cast iron at elevated temperatures and reduces transcrystallinity (respectively, the anisotropy of mechanical properties) about being a martensite-forming element, nitrogen allows reducing the content of nickel-manganese in cast iron, which reduces costs, improves machinability. When the nitrogen content is less than 0.01%, its effect is practically not manifested, and when the content is more than 0.03%, it increases. danger of gas porosity in castings.

Example. Cast iron of the following composition is melted in the ICM-6 induction furnace, wt%: C, 3.75; Si 0.60; Mp 1.7; Cg 0.18; Ni 0.55; TiO, 03; P 0.3; C 2.2; N 0.02; Fe - the rest is about. In the quality of the charge, cast iron B-2, chromium-nickel rolls and steel metal scrap are used. Silicon, manganese, titanium and nitrogen are introduced in the form of ferroalloys, nickel is in the form of cathode copper.

Cast iron is superheated in a furnace to a temperature of 1450 ± 5 ° С and technological tests are poured at 1320 +

5 ° C.

Alloys with boundary and optimum ratios of all ingredients were prepared to determine wear with a radial load of 21.5 kg and torsional resistance. ensuring comparative analysis smelted known cast iron with an optimal ratio of ingredients (Table 1). Physicomechanical properties at 800 ° C of cast iron known

and the proposed formulations are presented in table 2.

Claims (1)

As follows from Tables 1 and 2, the additional input of nitrogen in the compositions of the proposed cast iron allows to increase the tensile strength in torsion 1.4 - 1.6 times and to improve the wear resistance 4.1 - 4.3 times. Invention Formula Roller cast iron containing carbon, silicon, manganese, chromium, nickel, titanium, phosphorus, copper and iron, characterized in that, in order to improve wear resistance and increase the strength at. torsion at temperature BOO ° C, it additionally contains nitrogen in the following ratio, wt.%: five Carbon Silicon Manganese Chromium Nickel Titanium Phosphorus Copper Nitrogen Iron 3.6 - 3.9 0.35 - 0.85 1.4 - 1.9 0.05 - 0.30 0.3 - 0.8 0.01 - 0.05 0.2 - 0.4 1.8 - 2.6 0.01 - 0.03 Else Famous Offered Table 2 g 0.173 251