SU1079689A1 - Steel - Google Patents

Abstract

STEEL containing carbon, manganese, aluminium, silicon, and zhe-, so that, in order to improve mechanical properties after prolonged exposure to temperatures up to 6 O, it contains co-components at the following ratio,% by mass: 0 , 3-0.5 Carbon 25 -27 Manganese 4.0-4.5 Aluminum 2.0-2.5 Silicon Ostishny Iron

Description

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The invention relates to ferrous metallurgy, in particular, to nickel-free steel of austenitic grade of heat-resistant up to temperature

Steel can be used as a material for the manufacture of parts of thermal equipment operating under considerable loads at elevated temperatures,. These parts are; Brackets, heat treatment furnace trays, grates, etc. At present, the main material for their manufacture is X18H10T chromium-nickel austenitic steel l.

This steel has satisfactory mechanical properties at elevated temperatures and high resistance to corrosion in oxidizing environments at elevated temperatures.

The shortfall of this steel is the high cost, determined by the chemical composition of nickel-chrome steels, which require expensive charge materials, in particular, nickel-deficient nickel, the closest in technical essence and the achieved effect to the proposed steel is 2j, wt.% 5

Aluminum8.0-10., O

Manganese20-35

Carbon 0.75-1.10

Silicon .1-2

IronErest

This steel has high heat resistance, as well as strength and plastic characteristics at room and elevated temperatures up to 815 ° C. After quenching, it has the following mechanical properties: Tensile strength, kg / mm - 84 Yield strength, kg / mm 57.6 Relative elongation, Relative tapering,% 70 The disadvantage of this steel is a sharp decrease in mechanical properties after long-term exposure at elevated temperatures.

The loss of steel for 200 hours results in almost complete loss of ductility and a sharp decrease in strength. This applies to testing both at room and at elevated temperatures.

The purpose of the invention is to increase the mechanical properties of steel after prolonged aging at temperatures up to

The goal is achieved by the fact that carbon-containing steel

manganese, aluminum, silicon and iron, contains components in the following ratio, wt.%:

Carbon 0.3-0.5

Manganese 25-27 Aluminum 4,0-4,5

Silicon2.0-2.5

IronReal

The reduction in the amount of aluminum and carbon in comparison with the known steel is due to the need to prevent the occurrence of type P-ACC carbides at elevated temperatures, and manganese to prevent the release of the P-Mi phase. The indicated contents of aluminum and silicon are sufficient to provide the necessary level of heat resistance.

To substantiate the limits of the content of the components, a series of heats of steel of the 1st steel (heats 1-12), is carried out. their mechanical properties are determined, the effect of chemical composition and heat treatment on the stability of the austenitic structure is revealed, the heat resistance at 600 ° C in air is determined. For comparison, famous steel is smelted (smelting 13).

Melting is carried out in the main induction furnace according to conventional technology. .

The chemical composition of the bottoms is given in table. one.

Conventional industrial alloys (ferromanganese, ferrosilicon, secondary aluminum, etc.) can be used as charge materials in ratios that provide the necessary chemical composition. Castings made by pouring into a metal mold are forged into a bar with a diameter of 16 mm at 1050-1100 ° C. To determine the effect of long-term exposure at elevated temperatures, the structure and properties of the steels are subjected to an appropriate heat treatment, which consists of. pre-quenching from 1100 ° C into water and holding the blanks for 200 hours. The tests of heat resistance in air and mechanical tests at room and elevated temperatures are carried out according to standard methods.

. The results of the tests at room temperature are presented in Table below, in Table 3; herewith, the following designations are accepted: de tensile strength, MPa;

t: yield strength, MPa; relative extension,

(f relative narrowing,%; impact viscosity, KJ / m; OH heat resistance at, K g / m h.

As can be seen from the data table. 2, the optic complex mechanical

properties and resistance to oxidation at 600 ° C have samples of melting 3-7J An increase in the amount of manganese above 27 wt.% (melting l) at given ratios of the remaining elements leads to the release of (5-manganese long-term exposure to properties, especially on plastic: characteristics. Impact viscosity is sharply reduced. Reducing the amount of manganese is below 25 wt.% (smelting 2. A significant amount of ferrite forms in the steel structure, and the relative elongation and contraction is reduced by a factor of 2-3. Similarly, a decrease in the amount of carbon below 0.3 wt.% (smelting 8) is affected. An increase in the carbon content above 0.5 wt.% (smelting 9) results in the release of carbides during prolonged exposure at elevated temperatures, and this, in turn, adversely affects the ductility of the steel and the toughness. Undesirable is a reduction in the aluminum content less than 4.0 wt.% and silicon less than 2.0 wt.% In this case, there is a significant decrease in heat resistance G by a factor of 2-3), although The properties of the properties remain high (melts 10 and I). Increase in aluminum over 4.5 May.%

(smelting 8) and silicon in excess of 2.5 wt.% (smelting 12 improves heat resistance, however, ferrite appears in the steel structure, and the mechanical properties of the steel significantly decrease.

The test results of a well-known steel indicate that, in the state after quenching, steel is known to have high mechanical properties.

both at room telesheratura, and at (tab. 2 and 3). However, its exposure for 200 h when leads to such a significant reduction in mechanical properties,

that the practical use of this steel as part of furnace reinforcement becomes impossible.

Heat resistance of experienced steels is slightly inferior to heat resistance.

known steel, despite a twofold decrease in the aluminum content. This is due to the fact that the lower carbon content in steel, compared to the known, has

positive effect on oxidation resistance.

Taking into account the need for such materials of the production association MTZ, determined approximately in the amount of 80-100 tons, the economic efficiency from the implementation of the invention is 30000 rubles. .

Table 1

Table 2

. T a b l and c a 3

Claims (1)

STEEL containing carbon, manganese, aluminum, silicon and iron, characterized in that, in order to increase mechanical properties after prolonged exposure at temperatures up to 600 ° C, it contains components in the following May,%.: Carbon 0.3-0.5 Manganese 25 -27 Aluminum 4.0-4.5 Silicon 2.0-2.5 Iron Ostil