SU1468957A1 - Cast iron - Google Patents

Abstract

The invention relates to the field of metallurgy and can be used to produce cast parts operating at high temperatures under load. The purpose of the invention is to increase the critical load, which causes plastic deformation in the temperature ranges 673-813K, wear resistance, heat resistance and fluidity. The proposed cast iron contains components in the following ratio, wt.%: C 3.0-3.6; Si 1.8-2.4; -Mn 0.005-0.04; V 0.05-0.14; Mo 0.1-0.5; A1 0.1-0.5; Ni 0.1-0.6; Cr 0.1-0.5; Ta and / or Nb 0.15-0.35; Ti 0.01-0.50; Zr 0.2-0.8; Sb 0.05-0.10; As 0.1-0.4; Fe stop Cast iron has the following properties: fluid flowability of 128-135 mm; wear 0.093-0.0132 g, heat resistance 52-60 cycles to failure, critical load of plastic deformation at 673 K 301– 368 MPa, at 873 K 278–346 MPa. 2 tab. W

Description

one

The invention relates to metallurgy and can be used to produce cast parts operating at high temperatures under load.

The purpose of the invention is to increase the critical load, which causes plastic deformation in the temperature ranges of 673-873 K, wear resistance, heat resistance and fluidity.

The limits of the content of elements in the composition of cast iron are established experimentally. The carbon and silicon contents are determined based on the required graphitization of the alloy. Their minimum content is

: bakes production in cast iron with a maximum content of carbide-forming elements, not more than 10% of structurally free carbides .. The maximum content of carbon and silicon is caused by a decrease in wear resistance and the critical load, caused by plastic, deformation at the content of alloying elements at the lower level, and in heat treated form. The minimum content of vanadium and molybdenum provides the required margin of safety and wear resistance at high temperatures. The upper limits of the content of these elements are limited due to

4iab

ai

00

0 pr

their strong whitening effect, which reduces the critical load causing plastic strain.

Antimony in cast iron in quantities of 0.05-0.1% contributes to obtaining a highly dispersed pearlitic structure with an amount of ferrite of not more than 10%. An antimony content of less than 0.05% leads to the ferritization of the metal base of cast iron, and above 0.1% of the coarse pearlite component and reduces wear resistance and leads to a decrease in the critical load during plastic deformation.

Aluminum in the alloy composition is strong with a graphitizer. Aluminum oxides are substrates for the crystallization of graphite. The addition of aluminum above 0.5% leads to a strong ferritization of the matrix, and below 0.1% does not affect the effect of graphitization. The aluminum content in the range of 0.1-0.5% grinds inclusions of graphite. The positive effect of aluminum on wear resistance is associated with the appearance of eutectic structure of complex carbide in cast iron, instead of cementite. The presence of aluminum in the range of 0.1-0.5% also eliminates the formation of gas porosity in the castings.

Nickel introduced into the alloy in an amount of 0.1–0.6% due to a decrease in the temperature y – oi conversion slows down the diffusion of carbon atoms and the formation of graphite in the process of pearlite transformation, thereby increasing strength and hot solid. alloy rafting.

The presence in the alloy of the specified element contributes, in addition, a more uniform distribution of properties over the cross section of the casting.

Niobium and tantalum are very close to each other both in chemical properties and in their influence on the properties of alloys of the Fe – C system. The introduction of niobium and tantalum into the cast iron contributes to the perlitization of the metal matrix and increases the dispersion of the phases due to the formation of complex stable Nb carbides, Cg and Ta-C, the hardness of which is 83 and 82 units of HRA, respectively. Located along the boundaries of eutectic grains, they impede their growth, which increases the critical load of plastic deformation and contributes to a decrease in the wear resistance of cast iron. The content of niobium or (and) tantalum at the level of 0.15% corresponds to a significant increase in the threshold for the onset of plastic deformation. When the content is over 0.35%, these elements deteriorate the fluidity and wear resistance of the alloy due to the formation of a carbide mesh.

Titanium, starting with the addition of 0.01%, has a strong graphitizing effect on cast iron. Possessing a high affinity for nitrogen and oxygen dissolved in iron, it forms numerous substrates for the crystallization of the graphite phase, grinding graphite. When the content of CBbraie is 0.5%, titanium promotes the formation of primary carbides that reduce the critical load of plastic deformation.

Chromium with a content of up to 0.5% of the strength of the metallic base of cast iron. Concentration sludge 0.5% chromium increases wear resistance, but reduces the fluidity and critical load of plastic deformation due to the formation of a large number of carbides and, cubically, serving as stress concentrators during deformation and deteriorating the melt through the channels of the mold;

Zirconium when entering it into iron in the amount of 0.2-0.8% grinds the incorporation of graphite and has a positive effect on the metal base of the iron. Increasing the dispersion of the matrix and its homogenization leads to an increase in the critical load of plastic deformation and wear resistance. When the content of more than 0.8% zirconium leads to the formation of carbides. Such a structure helps to reduce the strength properties of the alloy at high temperatures. An additive of zirconium less than 0.2% contributes to the grinding of graphite inclusions, but does not strengthen the metal base of the alloy.

Entering the mouse in an O amount of 1–0.4% causes a decrease in the temperature of the eutectic transformation by 293 K and increases the temperature of the eutectoid transformation by 288 K and thus has a significant effect of the IR only on graphite formation, but also.

on the metal base of cast iron, which significantly increases the wear resistance, fluidity and heat resistance of the alloy, as well as increases the critical load at which plastic deformation begins.

The cast iron is produced in a LPZ-67 crucible furnace. Metallized pellets, return of own production, electrode breakdown, crystalline silicon, and ferroalloys are used as charge materials. After the pellets are melted and slag is loaded into the liquid bath, the return is refilled and the melt is heated to temperatures of 1723-1753 K, Chromium, molybdenum, vanadium and mice are introduced into the melt in the form of ferroalloys FM1 (58% Mo) and Eg - 1 (35% V ), ferromic acid (32% As) and ferrochrome PF,

Circium, antimony, aluminum and nickel in the form of crystalline antimony, SuO, electrolytic nickel H-3, aluminum AB97 and zirconium.

The charge for producing pig iron of the proposed composition is calculated taking into account the absorption of antimony, zirconium and aluminum silicon at the level of 85-90% of chromium, vanadium, nickel and molybdenum - 75-80%, Niobium and tantalum and alloy are introduced in the form of a ligature of the GNB (VTU) (KZF-6-67) with NbfTa content - 25%. The assimilation of the ligature of the GNB at a temperature of 1753 K is 65%. The absorption of a ferrom mouse is 70-80%.

The cast iron compositions are given in Table 1.

The wear resistance tests were carried out in the dry friction sliding mode (V 1.2 m / s, P 30 kg / cm) on an MT-2 machine.

The critical load of plastic deformation is determined by

five

0

five

0

with a diameter of 16 mm and a height of 100 mm according to the following procedure.

The sample, fixed in the fixture, is loaded in series with simultaneous heating in the center (673-873 k) and the load is fixed at which the cast iron is deformed.

The properties of the alloys are presented in Table 2. As can be seen from Table 2, the introduction of an alloy ka.i zirconium into the composition of the alloy increases the fluidity, the critical load of plastic deformation of the alloy, as well as its wear resistance and heat resistance.

Claims (1)

Invention Formula Cast iron containing carbon, silicon, manganese, vanadium, molybdenum, aluminum, nickel, chromium, niobium and / or tantalum, titanium, zirconium and iron,. characterized in that, in order to increase the critical load causing plastic deformation in the range of 673-873 K, wear resistance, heat resistance and railway resistance, it additionally contains antimony and mouse in the following ratio of ingredients, wt.%: 35 40 45 1468957 10 Gablitz2 2) 105 TZT 132 128 141 117 Oj, l28 295 3 4 5 6 0,0093301 0,0101319 0,0132368 0,0120287 0,0148356 295 270 M. 301 52 60 56 68 52