CS199374B1 - Stress corrosion and molten metal effects resistant steel - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to steel resistant to stress corrosion and the effects of molten metals. This steel is also suitable for enamelling and inchromination and has increased mechanical characteristics.

Steels of this kind are already known. Thus, for example, the known titanium-stabilized steel is resistant to corrosion cracking in nitrates and leaches. However, this steel has limited strength characteristics and can be brittle at reduced temperatures. For example, stabilized steel with 2.0 to 5.0 wt. manganese has high mechanical characteristics, toughness up to -40 ° C resp. even deeper, however, it does not have optimal corrosion cracking resistance, especially after overheating to high temperatures.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the drawbacks of both these steels and to provide a steel resistant to both corrosion cracking and molten metals, with increased strength properties and toughness at reduced temperatures while remaining suitable for enamelling and inchromination.

This task is solved by a steel resistant to stress corrosion and to the effects of molten metals, containing by weight 0.01 to 0.12% carbon, 0.01 to 0.6% silicon, up to 3.5% chromium, up to 2.5 % nickel, up to 1.5% molybdenum, and at least one carbide former, such as titanium, niobium, tantalum, zirconium or vanadium with a ratio of the weight of steel carbide to the weight of steel carbon

X.

199 374, at least one and at most two times the stoichiometric ratio of this metal to carbon in the carbide of the metal, further comprising 0.3 to 2.5% by weight of manganese.

It is preferred that the steel further comprises aluminum in metallic form in an amount of from 0.01 to 0.15% by weight, since the aluminum content enhances the stabilizing effect of the carbide-forming elements. Its optimum effect with respect to the nitrogen content of the steel becomes apparent if the ratio by weight of the amount of aluminum to the amount of steel contained in the nitrogen is at least one and at most two times the stoichiometric ratio of aluminum to nitrogen in the metal nitride.

The invention removes the drawbacks of the steels known to date, guarantees both the binding of carbon and nitrogen in the steel to carbides and nitrides, especially at relatively low carbon contents in the steel, as well as suitable mechanical properties.

The steel according to the invention is resistant to both corrosion cracking and the effects of molten metals, has increased strength and toughness at reduced temperatures and is also suitable for enamelling and inchromination.

Examples of steel compositions according to the invention:

ZZZZZZsZžZZSZřZZsijL.-ZiZřmoZZZčoZ _1 * __ ___ 2S * 2 2 * 2 * S2 ___ 22 "_O _A O2___o _and O2 ___ _ο Α χ§_

2. 0.06 ___ 0 _x 20 -___ 2 * 22 ___ 0 _x 02___0 _A 02 ___ 0.65, _2 * __ 2 * 2Z ___ 0 * 62 ___ 0 * 20 ___ ο _α 035__ο _α 02_ο _α π_ _4 .__ 0 _and 08___1 _x J0 ___ 0,18 ____2 _and 02___0 _A 02___0 _A 02

Ni% Mo% · «« »* · And? 0., 03. . ^A1 metal. 0.030 Ti% μ »« · «μ · μ 0 * 50 % in% Nb% 1 _« 0.08 2, 0.35 '0,03' 0.025 0.60 -2 * _ _o * o £ _ "O * 22" 0.040 - - , .- 2 * 22_ .. 4. 0.05 0.02 0,035 ..... 0 _A 80 —Λ-

For the above steels, the following mechanical properties were achieved at normal temperature:

A. Steel no. 2 in the state after controlled oval, product - seamless tubes and thick plates: Yield strength Strength limit Ductility Notch. houž. RV MPa MPa C ^ 5% J.em2 245 410 27 Mar: 111-126

199 37

Β.

Steels No. 1, 3, 4 in the normalized state, the products are thick sheets / steel No. 1 and 4 or. and seamless Z pipes: Yield strength Strength limit Ductility Notch. houž. PV MPa MPa </ 5% J. cm2 1. 206 340 30 125 - 154 3. 216 354 29 16? - 185 4. 235 384 23 101 - 118

All these steels exhibit optimum corrosion cracking resistance in nitrates and lye environments, resistance to molten metals and suitability for enamelling and inchromination, respectively. for other applications where their stabilization and increased mechanical characteristics can be applied.

They can be used in particular in the chemical industry in fertilizer plants, in the caustic processing industry, in the metallurgical industry and in the energy sector in low-melting metal environments, in chemical engineering for enamelled equipment and in general for mechanical engineering for diffusing surface treated parts.

Claims (3)

1. Steel resistant to stress and molten metals, containing by weight 0,01 to 0,12% carbon, 0,01 to 0,6% silicon, up to 3,5% chromium, up to 2,5% nickel, and at least one carbide-forming element, for example titanium, niobium, tantalum, zirconium or vanadium, with a ratio by weight of steel of the carbide-forming element to the weight of steel-containing carbon of at least one and at most twice the stoichiometric ratio of the metal % of carbon in the carbide of the metal, further comprising 0.3 to 3.0 2.5% by weight of manganese. 2. Steel according to claim 1, characterized in that it contains aluminum in metallic form in an amount of from 0.01 to 0.15% by weight. 3. Steel according to claim 2, characterized in that the ratio by weight of aluminum to the amount of nitrogen contained in the steel is at least one and at most two times the stoichiometric ratio of aluminum to nitrogen in the nitride of the metal.