SU1585374A1 - High-strength cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of castings from high-strength cast iron. The purpose of the invention is to improve the mechanical properties, heat resistance and cavitation resistance. New cast iron contains, by weight. %: C 3.2-3.8

SI 2.6-3.0

MN 0.2-0.7

NI 0.4-1.2

AL 0.03-0.10

MO 0.8-1.1

V 0.3-0.7

CA 0,002-0,02

CR 0.03-0.33

CE 0.002-0.05

CU 0.71-1.1

MG 0.03-0.07

titanium diborides 0.05-0.25

Y 0.03-0.08

one element from the group containing zirconium and niobium 0.005-0.21

FE the rest. Additional input of titanium, yttrium and zirconium or niobium diborides into the cast iron made it possible to increase the tensile strength by 1.33-1.39 times, the relative elongation by 3.68-4 times, the heat resistance by 3.06-3.37 times and cavitation resistance 1.55-1.74 times. 2 tab.

Description

The invention relates to metallurgy, in particular to the development of cast iron compositions with a spherical shape of a gradient.

The purpose of the invention is to improve the mechanical properties, heat resistance and cavitation resistance.

The invention is illustrated by the following examples.

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

The optimum concentrations of the newly introduced elements are the following: Titanium diborides 0.05-0.25 wt.%, Yttrium 0.03-0.08, and a metal from the group containing zirconium and niobium - 0.005-0.21 wac. .

A new set of features provides a significant positive effect that can be achieved with the use of the invention in the operation process of the chill molds made of the proposed high-strength cast iron, molds and other parts of the tooling operating under heat shock conditions.

The additional introduction of titanium diborides is associated with their high multilink modifying ability. Folding of the introduction of a refractory high-temperature (T ′, C 200 s) germ phase of close crystal structural orientation in the first stage and the formation of dissd

00 ate

100

four

persian structure in the process of crystallization.

When the concentration of titanium diborides is up to 0.05 wt.%, The micronized grain size is insufficient, which does not lead to a significant increase in mechanical and operational properties, and when the concentration of titanium diborides is more than 0.25 wt.%, The enrichment of the boundaries of even small diboride grains increases. titanium, which adversely affects the plasticity of crack resistance, toughness and stability of service properties,

Yttrium enhances the modifying effect of titanium diborides, improves the form factor of micrograin, graphite and non-metallic inclusions, which improves the mechanical and operational properties. At a yttrium concentration of up to 0.03 wt.%, Its modifying effect is insufficient, and the mechanical and operational properties (heat resistance) of cast iron under heat exchange conditions are low. With increasing yttria concentration more than 0.08 wt. the content of non-metallic inclusions increases, the stability of the structure, mechanical and operational properties decreases.

A metal from the group containing zirconium and niobium, microlegates the metal base, crushes the matrix, increases the homogeneity of the structure, thermal and operational stability. When the concentration of the metal from the group containing zirconium and niobium is less than 0.005 masD, the micro-alloying effect is insufficient, and the thermal and operational resistance have low values, and with an increase in their soda | ezhani more than 0.21 wt. ductility of cast iron, resistance to thermal shock decreases, which leads to a decrease in crack resistance and operational durability.

Vanadium is introduced as an effective micro-and. nitride-forming component, enhancing the effect of inversion of the structure, substantially grinding the matrix and graphite inclusions, ensuring homogeneity of the structure and improving thermal stability and elastic-plastic properties and their stability. The upper limit of vanadium concentration (0.7 masd) is due to a decrease in the technological plasticity of chusun

Q

about g

five

and an increase in the tendency to cracks with its higher content and a decrease in the elastic-plastic properties and operational durability. When the vanadium concentration decreases below 0.3 wt.%, Its microalloying effect is insufficient, its strength, yield strength, thermal and operational durability of metal forms decrease.

Copper crushes the bainite structure and contributes to the improvement of plastic properties, thermal resistance and operational resistance. When copper concentration is up to 0.72 wt.%, Its microblocking effect and enhancement of plastic and operational properties are insufficient, while increasing copper concentration more than 1.1 wt.%, Segregation processes increase, heat resistance decreases, structure homogeneity and operational durability decrease.

The boundary parameters of carbon content (3.2–3.8 wt.%) And silicon (2.6–3.0 wt.%) Are determined based on the practice of producing high-strength cast irons with enhanced elastic-plastic properties and high thermal stability. At a concentration of carbon over 3.8 wt.% and silicon over 3.0 wt.%, the thermal resistance, impact viscosity and other mechanical and operational properties of cast iron are reduced, and at a carbon concentration of up to 3.2 wt.% and silicon to 2.6 wt.% chilling and thermal stress increase, crack resistance decreases, thermal resistance Th, toughness, and other plastic properties and stability of performance properties in the casting.

The content of alloying additives (manganese 0.2-0.7 May.%, Molybdenum 0.8-1.2 wt.%, Chromium 0.03-0.33 May.%, Nickel 0.4-1.2 May., aluminum 0.03-0.1 wt.%) due to a significant increase in thermal resistance, technological plasticity and strength and limited to the limits below which the heat resistance, the technological plasticity and strength properties are insufficient, and above which the thermal stresses increase, thermal stability and limit of firing

bending, which leads to a decrease in performance properties.

The introduction of cerium in the amount of 0.002 0.05 masD, calcium 0.002-0.02 masD and magnesium 0.03-0.07 wt.% Due to their high modifying efficiency and surface activity, which in these quantities provides cleaning of grain boundaries, increasing plastic properties , crack resistance, technological plasticity and operational durability. Their content is due to the limits that provide the dispersion and homogeneous structure in castings, spherical graphite in cast iron and the necessary mechanical and operational properties, as well as a stable structure after heat treatment and during operation. With an increase in their content above the upper limits, the carbon loss increases, the homogeneity of the structure, the stability of the mechanical and operational properties decrease. At a concentration of less than the lower limits, the shape of the graphite deteriorates and the operational durability is insufficient.

Example. The iron was smelted in induction furnaces using cast iron, steel scrap, copper, Ml, nickel refinery, titanium diboride briquettes, ferrovanadium Fvd2, ferromolybdenum FMto1, silicomanganese CM-I, ferroniobi, and metallic yttrmette-rit, etc, and testmetrits, as well as test-centr, and testmetrits, as well as test materials. and other ferroalloys. Microalloying with ferrovanadium, ferromolybdenum, nickel, silicomanganese CM-17 is carried out in a furnace, and modification with ferrocerium, titanium diboride, aluminum, magnesium ligature, ferroniobium or ferrozirconium, in distribution caster buckets. Technological samples, 10 mm samples for mechanical tests and molds for castings are cast from modified cast irons.

In tab. 1 shows the chemical composition of the cast iron experienced bottoms. Determination of the content of the components of the wire.

ten

15

58537

d t according to the method of differentiated quantitative chemical analysis.

In tab. 2 shows the mechanical and operational properties of iron castings experienced heats.

As follows from the table. 2, the addition of titanium diborides, yttrium, as well as one of the elements — zirconium or niobium — to the composition of the proposed cast iron allows to increase the tensile strength djg- by 1.33-1.39 times, the relative elongation tf - by 3.68-fold, heat resistance of 3.06-3.37 times and cavitation resistance of 1.55-1.7 times.

Claims (1)

Formula invented and 20 25 thirty 40 45 0 High-strength cast iron containing carbon, silicon, manganese, nickel, aluminum, molybdenum, vanadium, calcium, chromium, cerium, copper, magnesium and iron, characterized in that, in order to improve the mechanical properties, heat resistance and cavitation resistance, it additionally contains diborides titanium, yttrium and one element from the group containing zirconium and niobium, the following - the ratio of components, wt.%: Carbon3,2-3,8 Silicon 2.6-3.0 Manganese 0.2-0.7 Nickel0.4-1.2 Aluminum 0.03-0.10 Molybdenum 0.8-1.1 Vanadium 0.3-0.7 Calcium0,002-0,020 Chrome 0.03-0.33 Cerium0,002-0,030 Copper0.71-1.10 Magnesium 0.03-0.07 Diborides titanium 0.05-0.25 Yttrium 0.03-0.08 One element from the group consisting of zirconium and niobium 0.005-0.210 Iron Other