A Three-stage Welding Method for Cold Metal Transition of Hollow Stationary Blade of Steam Turbine

Abstract

The invention relates to the field of steam turbines, in particular to a three-stage cold metal transfer welding method for steam turbine hollow static blades. The method includes performing spot welding on a leading edge, performing spot welding on a trailing edge, cooling to the room temperature, performing full welding on the leading edge and performing full welding on the trailing edge. The full welding are performed on the leading edge and the trailing edge by the cold metal transfer method, welding joints on the back arc of the leading edge and welding joints on the inner arc of the leading edge are welded in a three-stage manner, and welding joints on the back arc of the trailing edge and welding joints on the inner arc of the trailing edge are welded in a two-stage manner. By the aid of the method, heat input during welding a steam turbine hollow blade can be reduced, welding residual stress and distortion can be controlled effectively, cooling time is reduced, the number of the welding joints is decreased, welding operation is simplified, and quality stability of welded parts is improved; technical requirements on welders are low correspondingly, production of domestic enterprises are facilitated, and technology level and localization rate of steam turbine core equipment are improved; the cold metal transfer method is adopted, and the three-stage method and relative welding sequence of 'three-segment + three-segment + two-segment + two-segment' and the welding method for each segment are adopted.

Description

technical field [0001] The invention relates to the field of steam turbines, in particular to a three-stage welding method for cold metal transition of hollow stationary blades of steam turbines. Background technique [0002] The hollow blade is the key part of the steam turbine, and it is also one of the most delicate and important parts. The working conditions of the blades are extremely harsh, and they are subjected to the combined effects of high temperature, high pressure, centrifugal force, steam force, steam excitation force, corrosion and vibration, and water droplet erosion in the wet steam area. The aerodynamic performance, machining geometry, surface roughness, installation clearance, operating conditions, fouling and other factors of steam turbine blades all affect the efficiency and output of steam turbines. The structural design, vibration intensity and operation mode of steam turbine blades have a decisive impact on the safety and reliability of the unit. ...

AI Technical Summary

Problems solved by technology

At present, the hollow static blades in many steam turbine power generation equipment in my country are imported from abroad. For example, the hollow blades of Siemens are basically welded by laser. The welding method has a small heat input and a small heat-affected zone. Imported blades are very expensive, resulting in increased manufacturing costs for steam turbine power generation equipment

In addition, the hollow blades of Alstom Company in France mainly adopt the five-stage or seven-stage flux-cored welding method, and the welding deformation can be effectively controlled, but due to the large number of welded joints, the welding quality is difficult to control

[0005] The existing automatic welding of hollow blades has the following problems: 1. The hollow blades are manually assembled, and there are assembly errors between each piece, resulting in different spatial positions of each weld, and repeated welding special machines and teaching reproduction welding It is difficult for robots to meet the requirements; 2. Each hollow blade has four straight-line welds in space that are not in the same plane with each other, and it is difficult to ensure that the welding seams are basically kept horizontal during welding; 3. The blades have a deformation limit, exceeding this limit It is a substandard product; 4. The welding process is not traceable, and problems cannot be found in time

Because it adopts the above structure, this form will lead to large differences in welding methods and processes, which is not conducive to the unification of the overall process and increases the difficulty of welding

In terms of welding process, the above-mentioned patent adopts manual argon tungsten arc welding, but argon tungsten arc welding has defects such as large heat input, serious deformation, and unavoidable spatter, which is not suitable for welding thin-plate workpieces

The above-mentioned patent uses two welds, and the welding method is five-section + five-section (abbreviated as five-section method). When this method is used for welding, the welding effect is not good.

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