Wind Turbine Main Shaft Forging for Near-Net-Shape Inner Holes
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Solution Overview
Problem
The development of large wind turbine main shafts above 6 MW is restricted due to low mechanical properties and high casting defects in traditional forging methods, which result in increased material costs and prolonged production schedules, as well as challenges in processing irregular inner hole shapes and material segregation during forging.
Innovation Solution
A compound profiling forging method that uses special piercing punches and profiling mandrels designed through finite element calculations, combined with controlled heat and holding times, to achieve near-net-shape processing of inner holes, reducing deformation and improving mechanical properties by ensuring uniform temperature distribution and material homogenization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional free forging method is used for large-size thin-walled hollow main shafts, then the manufacturing process is simple, but composition segregation and temperature difference between interior and outer surface occur, leading to coarse grains and agglomeration of non-metallic inclusions
Solution Approach 1:
The forging process is divided into multiple controlled stages: initial heating to 1250°C, preliminary stamping with specific deformation ratios, spinning forming at 850°C, and shaft body drawing in four sections. This segmentation allows each stage to address specific material behavior requirements, preventing segregation while maintaining process control
Solution Approach 2:
The method performs preliminary heating and holding at 1250°C before forging to ensure uniform temperature distribution throughout the billet. This preliminary thermal action eliminates temperature differences between interior and outer surface that would otherwise cause composition segregation during deformation
2Ease of manufacture
If conventional hollow mandrel drawing-out forming method is used for billets with special-shaped inner holes, then the forming process is straightforward, but inner hole eccentricity and folding occur, requiring huge material investment and prolonged machining time
Solution Approach 1:
A specially designed mandrel with curved surface transition acts as an intermediary tool during the spinning forming process. This mandrel guides the material flow to achieve the complex inner hole shape while preventing folding and maintaining concentricity, eliminating the need for subsequent deep hole machining
Solution Approach 2:
The mandrel features a curved surface transition from the first forming part to the second forming part, which smoothly guides the material deformation. This curvature prevents sharp corners and stress concentrations that would cause folding, while accurately forming the irregular curve outlines of the inner hole
3Productivity
If traditional forging method with multiple machining steps is used for main shafts with irregular curve inner holes, then the billet can be formed, but three required steps need to be machined in the inner hole, prolonging production schedule
Solution Approach 1:
The profiling forging process preliminarily forms the final irregular curve inner hole shape directly during the forging operation itself, before final assembly. This preliminary shaping eliminates the need for subsequent machining steps, significantly shortening the production schedule while maintaining manufacturing quality
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
This method effectively reduces material waste, shortens manufacturing cycles, and enhances mechanical properties by minimizing deformation and segregation issues, while saving raw materials and reducing production costs compared to traditional methods.
Implementation Method 1
a radius of the piercing punch gradually decreases along a center axis from top to bottom, and a curved surface transits from the first forming part I to the forming part II
Implementation Method 2
step S1, carrying out first heat-up upsetting on a billet to make the billet into a flat square billet, returning the billet into a furnace and holding a temperature at 1250° C.
Implementation Method 3
reasonably setting holding temperatures and holding time, homogenizing local compositions of the billets
Implementation Method 4
operating an oil press to press the piercing punch to be flush with the billet
Implementation Method 5
with heating and forging large-size thin-walled hollow main shafts by free forging, it is not easy to eliminate composition segregation of raw materials
Data Source
AI summary
A compound profiling forging method for a wind turbine main shaft includes: making a billet into a flat square billet, returning the billet into a furnace and holding a temperature at 1250° C.; preliminary punching, including: upsetting and drawing out the billet twice, and carrying out punching and rolling; preparing a piercing punch and a punching block, putting the billet in the punching block, putting the piercing punch into a hole of the billet, and operating an oil press to press the piercing punch to be flush with the billet; heating the billet, holding a temperature at 850° C., putting the billet in the punching block, preparing a female die and a punch, and inserting the piercing punch into an inner hole of the billet to carry out flange upsetting; and drawing out the shaft body of the billet in sequence, with a forging temperature range of 850-1250° C.