Heat-resistant steels in turbine production. Main characteristics of the material

Heat-resistant steels and alloys as a special type of structural materials began to be used intensively enough in connection with the development of the turbo-building industry. Turbines in the form of a converter or power source are used in heat power equipment, aircraft and marine engines. More recently, gas turbine designs for ground-based rolling stock (trucks, locomotives) have become widespread.

As the temperature of the gas at the inlet increases, the specific fuel consumption per unit of power decreases. In this connection, heat-resistant steels appeared in a rather short time. Today, these materials in turbine designs constitute up to 50% of the total mass.

Heat-resistant steel is a material that works not only at elevated temperatures. It is applicable in the complex stress condition for a given time period. The main characteristic that determines the operability of this material is heat resistance.

By this quality is meant a stress that does not lead to the destruction of a given strain, which is capable of withstanding a metallic material in a certain structure at a given temperature for a specific time interval. When the time and voltage are specified, the characteristic is called the ultimate strength (long). If deformation, time and stress are determined, then the quality is called the creep limit.

Heat-resistant steels have, in addition to strength, plasticity, which must be maintained until the end of operation. In terms of the stock of ductility, the reliability of the metal is assessed.

An important characteristic of the material is the sensitivity to the notch. This quality is determined in the form of a ratio of time elapsed before the destruction of a smooth and notched specimen tested at the same stress temperature. Heat-resistant steels are considered insensitive to incision at a ratio equal to or greater than one.

Due to the fact that the rise to the operating temperature occurs over time, the beginning of the work corresponds, as a rule, to the external temperature, much attention is paid to the values of elasticity and strength. It is important that the values that the material possesses at room temperature are sufficiently high.

Due to the fact that heat-resistant steels work under conditions of a complex stress, which is characterized by a constant change in the sign and the magnitude of the loads, the high fatigue resistance index is also important.

Today, the use of complex technical solutions in the design creates the need to have metal materials that have high technological characteristics. Thus, in the manufacture of blades in gas turbine engines , forging, precision stamping, grinding, machining of finished products and bars, precision casting, polishing are used. The production of combustion chambers from heat-resistant metal sheets is carried out with the use of pressing, cold stamping, spot welding and other technologies. The most common technologies are electrode welding, friction, diffusion welding, soldering products. All these manipulations require high quality characteristics of the material used.

Heat-resistant alloys and steels are inherently able to maintain increased strength indicators, both before the working and before the technological temperatures. This, in turn, imposes a specific imprint on all the applied technology of metal conversion, from the deformation of the ingot itself and to the final operations for finishing the products to the required surface cleanliness and required dimensions.