Detailed Explanation of the Key Properties and Applications of Blade Steel Cores

　　Blade steel is a high-end special steel designed specifically for rotating blades in power machinery. It is primarily used in core blade components of steam turbines, gas turbines, aircraft engines, and wind turbines. Blade steel must simultaneously meet stringent performance requirements, including high strength, high toughness, temperature resistance, and fatigue resistance. Blade steels for different application scenarios exhibit significant differences in composition and manufacturing processes.

　　I. Core Performance Requirements for Blade Steel

　　As rotating components, blades are subjected over the long term to multiple factors, including centrifugal forces, alternating loads, high-temperature oxidation and corrosion, and media erosion. Therefore, the steel used must possess the following key properties:

　　1. Ultra-high mechanical performance

　　High strength (yield strength ≥ 600 MPa) + high toughness (impact energy ≥ 40 J) to prevent fracture during high-speed rotation;

　　Excellent fatigue resistance, capable of withstanding fatigue cracking caused by long-term alternating loads.

　　2. Temperature Resistance and Oxidation Resistance

　　Turbine/Gas Turbine Blade Steel: Must withstand high temperatures ranging from 400 to 1000°C, preventing high-temperature softening and oxidation-induced scaling.

　　Wind turbine blade steel: Must be resistant to low temperatures (below -40℃) to prevent brittle fracture in cold regions.

　　3. Resistance to media erosion and corrosion

　　Turbine blades must withstand erosion caused by water droplets in the steam.

　　Offshore wind turbine blades made of steel must be resistant to seawater salt spray corrosion.

　　4. Good machinability and weldability

　　Can be forged and precisely machined into shape;

　　Some blade components require welding, and the performance of the weld joints must match that of the base material.

　　II. Common Classification of Blade Steels and Typical Grades

　　According to application scenarios, they can be categorized into four major types: steam turbine blade steel, gas turbine blade steel, aeroengine blade steel, and wind turbine blade steel, as detailed below:

　　3. Key Manufacturing Processes for Blade Steel

　　The quality of blade steel hinges critically on the precise matching of its compositional design and heat treatment process. A typical process flow is as follows:

　　1. Raw material smelting: An electric arc furnace combined with vacuum degassing technology is employed to reduce the levels of sulfur, phosphorus, and oxygen, enhance steel purity, and minimize internal defects.

　　2. Forging and Forming: Using isothermal forging and precision forging processes, the grain size is refined, resulting in a dense microstructure of the steel and effectively preventing issues such as porosity and segregation, thereby ensuring uniform mechanical properties of the blades.

　　3. Heat Treatment Strengthening

　　Turbine blade steel: Employing tempering treatment (quenching + high-temperature tempering) to obtain a tempered sorbite microstructure, thereby achieving a balance between strength and toughness.

　　Superalloy blades: Employed solution treatment plus age hardening to precipitate fine strengthening phases (such as the γ' phase), thereby enhancing high-temperature strength.

　　4. Surface Treatment

　　Spraying an antioxidant coating: Ceramic coatings are sprayed onto the surfaces of gas turbine and steam turbine blades to enhance their resistance to high-temperature oxidation.

　　Shot peening: The blade surface undergoes shot peening to introduce residual compressive stress, thereby enhancing fatigue resistance.

　　IV. Key Points for Quality Inspection of Blade Steel

　　Blades are critical, wear-prone components of power machinery and must undergo rigorous, multi-dimensional testing before leaving the factory.

　　Nondestructive Testing: Ultrasonic Testing (UT) for detecting internal defects, and Magnetic Particle Testing (MT) for identifying surface cracks;

　　Mechanical Property Testing: Tensile Test, Impact Test, and Fatigue Test—verifying strength, toughness, and fatigue resistance;

　　Metallographic Examination: Observe grain size and microstructure to ensure the absence of abnormal microstructures (such as coarse martensite or network carbides).