Steel used for steam turbine blades and manufacturing method thereof

Abstract

The invention relates to steel used for steam turbine blades, which contains the following chemical components in percentage by weight: 0.18% to 0.24% of C, 0.60% to 1.00% of Si, 0.10% to 0.20% of Mn, 0.80% to 1.20% of Mo, 11.00% to 12.50% of Cr, 0.70% to 0.80% of Ni, 0.25% to 0.35% of V, 0.005% to 0.020% of Nb, 0.02% to 0.05% of N, not more than 0.03% of S, not more than 0.02% of P, and the balance of Fe and unavoidable impurities. The manufacturing method of the steel comprises the following steps of: smelting by combination of EF, AOD and LFV; casting to form an electrode steel ingot, wherein the casting superheat degree is 40 DEG C to 70 DEG C, and the demoulding temperature of the steel ingot is controlled to be 600 DEG C to 700 DEG C; performing heat-loaded annealing on the electrode steel ingot; performing electroslag remelting on the electrode steel ingot; forging and performing heat-loaded annealing after forging; and rolling and annealing after rolling. The method produces high-performance medium-carbon martensitic stainless steel which is suitable for being applied to steam turbine blades working in a temperature range of 560 DEG C to 580 DEG C.

Description

technical field [0001] The invention relates to a medium-carbon martensitic stainless steel, in particular to a high-performance medium-carbon martensitic stainless steel for steam turbine blades with an operating temperature in the range of 560-580°C and a manufacturing method thereof. Background technique [0002] The blade is one of the most important parts of a steam turbine (responsible for converting heat energy into mechanical energy; it works for 100,000 hours for a long time under extremely complex working conditions such as high temperature and high pressure, large centrifugal force and aerodynamic force, vibration, oxidation, and corrosive atmosphere above). In order to ensure the stable operation of the steam turbine, the selection of the steam turbine blade material (blade steel) is very important. [0003] Steam turbine blades with operating temperature in the range of 560-580°C are important components of steam turbines. A steam turbine usually consists of s...

AI Technical Summary

Problems solved by technology

[0008] The high-temperature transient tensile comprehensive performance is low (at 560°C, the high-temperature yield strength is less than 420MPa; the high-temperature tensile strength is less than 480MPa; the reduction of area is less than 80%); the high-temperature durability is low (after 100,000 hours at 560°C The high-temperature durable strength is less than 150MPa; the high-temperature durable strength is less than 100MPa after working at 580°C for 100,000 hours), and these steel types have low stability of carbides formed under high temperature and long-term stress, which directly affects the service life of the blade

[0009] Ductile-brittle transition temperature FATT 50 If the value is too high (greater than 26°C), it is easy to cause the blade to become brittle and fail during the unit and operation, reducing safety

[0010] To sum up, the existing blade steels (2Cr12MoV, 2Cr12NiMo1W1V) with service temperature in the range of 560-580 °C cannot meet the development requirements of blade steel

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