CS231947B1 - Heat resisting alloy - Google Patents

Abstract

The invention relates to a refractory alloy, in particular for centrifugal cast tubes used for long-term work loads at temperatures of 850 to 1,150 °C as furnace cylinders in continuous annealing furnaces, furnace burners and other thermally stressed parts of equipment in the metallurgical and petrochemical industries. The refractory alloy contains by weight 23.0 to 25.0% chromium, 20.0 to 22.0% nickel, 1.0 to 1.5% silicon, up to 0.5% manganese, 0.05 to 0.2% titanium and 0.30 to 0.40% carbon and its essence lies in the fact that it contains 2.3 to 4.0% aluminum and the phosphorus content is limited to an amount of up to 0.04%, the sulfur content to an amount of up to 0.04% and the copper content to an amount of up to 0.3%.

Description

The invention relates to refractory alloys, in particular for centrifugal cast tubes containing iron, chromium and nickel as a base, as well as silicon, manganese, titanium, aluminum and carbon, used for long-term working load at temperatures of 850 to 1,150 ° C as furnace rolls in continuous annealing furnaces, furnace burners and other heat-stressed components of the metallurgical and petrochemical industry equipment.

Alloys known for this purpose are known, for example an alloy having a mass composition of 23.0 to 25.0% chromium, 20.0 to 22.0% nickel, 1.0 to 1.5% silicon, up to 0.5% manganese 0.05 to 0.2% titanium, 0.30 to 0.40% carbon and 1.0 to 1.5% aluminum. As a direct alloy, the alloy may contain up to 0.04% sulfur and up to 0.04% phosphorus.

Centrifugal cast tubes of this alloy are used, for example, for furnace rolls of continuous annealing furnaces operating at a temperature of 850 to 950 ° C.

The disadvantage of the furnace cylinders of this alloy is their short service life and furthermore, due to the working temperature and contact with the annealed material, the formation of non-adhesives occurs on their surface.

This also causes the furnace to be shut down frequently and the cylinders need to be replaced or reground.

The above-mentioned disadvantages are eliminated by the refractory alloy, in particular for centrifugal cast tubes, which, in addition to iron and the usual accompanying elements, contains in an amount by weight 23.0 to 25.0% chromium, 20.0 to 22.0% nickel, 1.0 to 1 5% silicon, traces up to 0.5% manganese, 0.05-0.2% titanium and 0.30-0.40% carbon. The refractory alloy comprises 2.3 to 4.0% aluminum and the phosphorus content is limited to a trace amount of up to 0.04%, the sulfur content to a trace amount of up to 0.04% and the copper content to a trace amount of up to 0.04%. 0.3%.

The essence of the formation of deposits is the eutectic anesthesia of metal oxides, characterized by a relatively low melting point. These mixtures are plasticized at operating temperatures, which allows them to be adhered to the surface of the furnace rolls. The increased aluminum content, which is characterized by a high oxygen activity, causes the formation of Al2O3, which limits the formation of other metal oxides and thus the formation of deposits. The increased aluminum content also causes it to precipitate to the surface of the furnace rollers under operating conditions, where it forms a very durable protective layer which increases the life of the thermally stressed parts of centrifugal cast tubes.

Higher mechanical values are expressed in Table 1.

As examples of the chemical composition of the refractory alloy according to the invention:

Exemplary heat resisting steel had the following composition in% weight: 23.54% chromium, 21.08% nickel, 1.24% silicon, 0.33% manganese, 0.33% carbon, 0.18% titanium, 3.62 % aluminum,

0.008% sulfur, 0.016% phosphorus, traces of copper and the rest iron.

Example 2

23.83% chromium, 21.21% nickel, 1.43% silicon, 0.34% manganese, 0.37% carbon, 0.19% titanium, 3.05% aluminum, 0.009% sulfur, 0.018 phosphorus and traces copper and the rest iron.

Example 3

23.69% overwhelming, 21.38% nickel, 1.03% silicon, 0.32% manganese, 0.31% carbon, 0.08% titanium, 2.99% aluminum, 0.008% sulfur, 0.017 phosphorus, traces media and the rest iron.

The refractory steel is melted on a mid-frequency induction furnace with a basic lining. The charge consisted of carbon scrap, ferro-chromium and cathode nickel. It is necessary to add grain ferrotitanium and aluminum to the furnace just before tapping.

heat resistant steel is tested long-term under operating conditions. The performance tests of the steel according to the invention show that it is a technologically advantageous material for the production of furnace rolls and indicates possibilities for further use for furnace burners and other thermally stressed parts made of centrifugal cast tubes.

Table ,

Mechanical properties of steels according to the invention and known steels

steel yield strength Re [MPe] strength R _m [MPej elongation and ₅ C% 1 of steel according to the invention in Examples 1 282 642 28.8 2 278 547 20.0 3 270 561 29.3 known steel 245 44, 5.0

Due to the balanced content of the elements in the exemplary heat-resistant steels, it can be stated that the effect of the increased aluminum content on the mechanical values, especially on the ductility, is considerable.

Claims (1)

a heat-resistant alloy particularly for centrifugal cast tubes which, in addition to iron and the usual accompanying elements, contains in an amount by weight 23.0 to 25.0% chromium, 20.0 to 22.0% nickel, 1.0 to 1.5% silicon, traces up to 0.5% manganese, 0.05-0.02% titanium and 0.30-0.40% carbon, characterized in that it contains 2.3-4.0% aluminum and the phosphorus content is limited to traces up to 0.04%, sulfur content per trace amount up to 0.04% and copper content per trace amount up to 0.3%.