SU789626A1 - Steel - Google Patents

Description

(54) STEEL

The invention relates to the field of metallurgy, namely, to austeine-thio martensitic steel. Steel known is known, containing, in wt.% 6-2 Nitrogen 0.12-0.2 niobium 0.05-0.1 Cerium 0.05-0.08 Iron Other 1 The disadvantage of the known steel is the low level of strength characteristics after quenching. In order to achieve higher strength, this steel must be subjected to a combined treatment, including hardening and plastic deformation, which complicates the technological process and makes it impossible to use this steel for parts of complex configuration. The purpose of the invention is to increase the strength properties, while maintaining the plate. This is achieved by the fact that the proposed steel will be supplemented with aluminum, with the following ratio of the components' penetration -, weight. % G Carbon 0.05-0.10 Chromium. 13.0-14.0 Manganese5.0-6.5 Silicon0.2-0.5 Nitrogen0 / 03-0,13 Molybdenum0 3-1.0 Copper0.3-2.0 Aluminum. 0.05-0.1 Iron. Else The proposed steel is austenitic-martensitic class. The steel structure after quenching is martensite in an amount of from 20-25 to 75-80% austenite. f laptensit is a hardening phase. The carbon content of 0.05-0.10%. Provides for the production of mg-carbon doped martensite with high plasticity. An increase in the carbon content of above 0.10% leads to a decrease in the Mie and Mk points and, after quenching, the production of predominantly austenitic structures d. This reduces the yield strength to 70-80 kgf / mm.

A distinctive feature of the proposed steel is the ability of a destable austenite to turn into martensite in the deformation process when testing mechanical properties. This provides a high level of tensile strength. The specified phase composition and optimal stability of austenite are provided with a content of 13-14% Cr and 5-6.5 Mp. |

The lower limit of the chromium content is taken to ensure high corrosion resistance of the steel. With a chromium content of more than 14%, the amount of martensite in the structure is reduced to 5%, and the yield strength is reduced. In addition, this leads to the stabilization of austenite and the appearance of f-ferrite, which reduces the tensile strength.

When the manganese content is below 5%, an increase in the amount of quenching martensite occurs, which leads to a decrease in the plastic characteristics. When the content of manganese is more than 6.5%, austenite of increased stability is formed after quenching. At the same time, the limits of strength and fluidity are noticeably reduced, and plastic kapaKTeuristics increase.

The silicon content is less than 0.2% impossible due to the deoxidation of steel by ferrosilicon. Its content of more than 0.5% leads to a decrease in the solubility of carbide-forming elements in austenite.

When the nitrogen content is less than 0.03%, the hardening effect decreases due to

0.12 15 7.0 0.6 0.15 1.5 0.36 10.87 8.8 0.5 0.12 3.0

VI

Quenching from 1100 to oil, tempering 200 ° С

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nitrides and carbonitrides. The presence of more than 0.13% of nitrogen leads to a decrease in the amount of quenching martensite, stabilization of austenite and, accordingly, to a decrease in the strength and yield strength.

Molybdenum in the amount of 0.3-1.0% has a significant impact on the stability of austenite, and, accordingly, the properties of steel. When the content of molybdenum is less than 0.3%, its effect is insignificant. With a molybdenum content of more than 1%, the strength of the steel is significantly reduced, due to the stabilization of austenite. In addition, # -ferrite appears in the structure, which reduces the ductility of steel after aging.

With a copper content of less than 0.3%, the effect of hardening of the steel due to dispersion hardening is insignificant, and with a content of more than 2.0%, the toughness decreases after aging.

When the aluminum content is less than 0.05%, the effect of precipitation hardening decreases. An increase in its content whiter than 0.1% leads to the appearance of a Y-ferrite in the structure, which reduces plastic characteristics.

The chemical composition and mechanical properties of steels after heat treatment are given in Table. 1 and 2.

The developed steels have higher strength and plastic properties after simple treatment of quenching from 110 ° C to oil and low tempering.

Table 1

2.3 0.12

2.2 - 0.09 0.58 0.05 iT a b l and c a 2

85 122 23 42 12.5 400 132 1740 11 - -

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Claims (1)

1. USSR author's certificate 505742, cl, C 22 C 38/38, 1976..