Valve Stem Laser Build-Up Welding for Uniform Hardness
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Solution Overview
Problem
Existing welding methods for forming build-up layers on valve stems in thermal power plants result in insufficient wear resistance and uneven hardness along the longitudinal direction, leading to steam leakage and reduced thermal efficiency.
Innovation Solution
A welding method that controls the output of a laser beam based on the dimension of the molten pool formed during the build-up welding process, ensuring a dilution rate of components of the filler metal within a specific range (10% to 40%) to maintain desired hardness and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If build-up welding is performed on valve stem using conventional method, then wear resistance is improved, but hardness becomes insufficient from weld middle portion to weld end portion
Solution Approach 1:
The patent applies dynamic control of laser beam output during the welding process. The laser output is adjusted in real-time based on the welding position along the valve stem, transitioning from higher output at the start portion to lower output at the end portion. This dynamic adjustment compensates for heat accumulation effects and maintains consistent molten pool conditions throughout the welding process, ensuring uniform hardness distribution.
Solution Approach 2:
The patent changes the laser beam output parameter during the welding process. By reducing the laser output from the start portion to the end portion of the weld, the patent compensates for the cumulative thermal effects that would otherwise cause excessive melting and hardness reduction at the weld end. This parameter change ensures consistent wear resistance throughout the valve stem.
2Productivity
If laser beam output is increased to improve welding speed, then productivity is improved, but molten pool dimension becomes unstable
Solution Approach 1:
The patent implements a feedback control system where the laser beam output is continuously adjusted based on the welding position and accumulated thermal effects. The system monitors the welding progress along the valve stem and dynamically modifies the laser output to maintain stable molten pool dimensions, preventing both excessive melting and insufficient fusion while maintaining high welding speed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves a consistent hardness of the build-up layer within the range of Hv 320 to Hv 500, improving wear resistance and preventing steam leakage, thus enhancing the thermal efficiency of thermal power plants.
Implementation Method 1
applying a laser beam to a surface to be built-up along a longitudinal direction of the workpiece to melt a filler metal
Implementation Method 2
forming a build-up layer on the surface to be built-up by supplying a filler metal to the surface to be built-up along the longitudinal direction and by applying a laser beam thereto to melt the filler metal
Data Source
AI summary
A welding method for subjecting a surface to be built-up of an elongated workpiece to a build-up welding process along a longitudinal direction of the workpiece, the welding method includes a step of forming a build-up layer on the surface to be built-up by supplying a filler metal to the surface to be built-up along the longitudinal direction and by applying a laser beam thereto to melt the filler metal. In the step of forming the build-up layer, information on a dimension of a molten pool formed by the filler metal and the workpiece molten by the laser beam is obtained, and an output of the laser beam is controlled based on the information.