RU2237102C2 - Fire-resistant steel - Google Patents

Abstract

FIELD: metallurgy, in particular fire-resistant steel for production of discs and rotors for gas- and steam-driven turbines.

SUBSTANCE: claimed steel contains (mass.%) carbon 0.08-0.13; chromium 11.0-13.0; molybdenum 1.5-1.75; nickel 2.0-3.1; vanadium 0.2-0.38; silicium 0.03-0.1; manganese 0.05-0.1; based not more than 0.02; nitrogen 0.01-0.1; niobium 0.05-0.09; optionally cerium; and balance iron; with the proviso that [chromium+molybdenum+niobium+vanadium]-[1,5 nickel+30(carbon+nitrogen)] = 4.2+6.7, and content of either phosphorus and oxygen is not more than 0.05. Said steel exhibits increased toughness and failure viscosity at temperature from -60⁰C to +20⁰C, as well as improved short-tine, long-time and cyclical strength at temperature from 20⁰C to 500⁰C.

EFFECT: fire-resistant steel of excellent physical characteristics.

3 cl, 3 tbl

Description

The invention relates to metallurgy, in particular to the production of heat-resistant steels and can be used in power engineering for the production of disks and rotors of gas and steam turbines.

Steel is known for auth. St. USSR No. 872592, published October 15, 1981, C 22 C 38/48, adopted as a prototype. Steel contains components in the following ratio, wt.%:

Carbon 0.11-0.15

Silicon 0.9-1.2

Manganese 0.2-0.6

Chrome 11.0-13.0

Nickel 1.6 - 2.2

Molybdenum 1.2 -1.5

Niobium 0.2-0.5

Nitrogen 0.02-0.05

Aluminum 0.2 -0.4

Cerium 0.2-0.3

Iron Else

The objective of the invention is to increase the impact strength and fracture toughness at t = (-60) - (+20) ° C short-term, long-term and cyclic strength at t = 20 ... 500 ° C.

The task is achieved in that the heat-resistant steel containing carbon, chromium, molybdenum, nickel, silicon, manganese, aluminum, niobium, nitrogen and iron, additionally contains vanadium in the following ratio, wt.%:

Carbon 0.08-0.13

Chrome 11.0-13.0

Molybdenum 1.5-1.75

Nickel 2.0-3.1

Vanadium 0.2-0.38

Silicon 0.03-0.1

Manganese 0.05-0.1

Aluminum Not more than 0.02

Nitrogen 0.01-0.1

Niobium 0.05-0.09

Iron Else

when performing the following ratio:

[chromium + molybdenum + niobium + vanadium] - [1.5 nickel + 30 (carbon + nitrogen)] = 4.2-6.7.

Also, heat-resistant steel is characterized in that it additionally contains cerium in an amount of up to 0.05 wt.%. In it, the content of sulfur, phosphorus and oxygen is limited to no more than 0.005 wt.% Each.

The Si content is <0.05 ... 0.07%, while the Si content is 10 [0], which is technologically necessary for the binding of O and S into rounded non-metallic inclusions during the crystallization of steel.

The desired Mn content is <0.05 - 0.10%, and the Mn≅15 [S] content is technologically necessary for the binding of O and S to rounded non-metallic inclusions during the crystallization of steel. Cerium is introduced in the case of smelting in open aggregates in order to control the distribution of inclusions and the binding of hydrogen.

The content of S, O, P should not exceed 0.005% of each, in order to avoid the formation of more inclusions and the accumulation of surface-active elements at the boundaries of cast and austenitic recrystallized grains.

The aluminum content should not exceed 0.02% to ensure the optimal composition of oxide inclusions.

The Nb content depends on the operating conditions of the rotor or disk. In high-temperature operation, the Nb content should be in the range of 0.05-0.09%.

The chemical composition of the steel of two heats (basic and experimental) is given in table 1.

A comparison of the results shows that the proposed steel has a significantly better combination of properties, especially at negative temperatures (embrittlement temperature is 60 ° C lower than that of known steel) and at operating temperatures (long-term tensile strength is higher by 100 MPa).

The use of the proposed steel significantly increases the isotropy of properties, the reliability of operation of energy machines, their durability. In addition, the proposed steel can be smelted not only by the ESR and VDP methods, but also in plants of the “ladle-furnace” type.

The mechanical properties of steels (after heat treatment according to the regime of 1050 ° C, tempering - 550-570 ° C) are presented in table 2.

Table 3 presents data on the anisotropy coefficients (the ratio of properties along and across the fiber for industrial disks from known and proposed steel of the same production method).

Claims (3)

1. Heat-resistant steel containing carbon, chromium, molybdenum, nickel, silicon, manganese, aluminum, niobium, nitrogen and iron, characterized in that it additionally contains vanadium in the following ratio, wt. %: Carbon 0.08-0.13 Chrome 11.0-13.0 Molybdenum 1.5-1.75 Nickel 2.0-3.1 Vanadium 0.2-0.38 Silicon 0.03-0.1 Manganese 0.05-0.1 Aluminum Not more than 0.02 Nitrogen 0.01-0.1 Niobium 0.05-0.09 Iron Else when performing the following ratio: [chromium + molybdenum + niobium + vanadium] - [1.5 nickel + 30 (carbon + nitrogen)] = 4.2 ÷ 6.7 2. Heat-resistant steel according to claim 1, characterized in that it further comprises cerium in an amount up to 0.05 wt. % 3. Heat-resistant steel according to claim 1, characterized in that in it the content of sulfur, phosphorus and oxygen is limited to a value of not more than 0.005 wt. % of each.