Circumferential Rail Refurbishment Welding
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Solution Overview
Problem
Current rail refurbishment methods involving multiple radial layers are prone to cracking, chipping, and require post-heating to meet hardness requirements, leading to increased costs, time, and disruption to rail services, while also resulting in undesirable hardness variations and 'eggshell' configurations.
Innovation Solution
A method that applies a single fill layer circumferentially, using a progression of fill-welds with each layer providing a flow barrier and being properly tempered to achieve uniform hardness without the need for post-heating, thereby minimizing repair time and costs while eliminating susceptibility to cracking and chipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple radial layers of fill material are applied to refurbish the rail, then the wear pocket can be filled, but the layers become prone to cracking and chipping under train weight and vibration
Solution Approach 1:
The patent changes the welding direction from radial (perpendicular to rail surface) to circumferential (parallel to rail surface). The weld head traverses the rail circumference, depositing fill material in layers that follow the circumferential direction rather than building up radially. This dimensional change eliminates radial joints that are susceptible to cracking, as the weld metal is deposited continuously around the rail rather than in stacked radial layers with horizontal interfaces.
2Quantity of substance
If multiple radial layers of fill material are applied, then the wear pocket can be filled, but substantial hardness variations occur below the restored rail surface
Solution Approach 1:
By changing from radial to circumferential welding, the patent eliminates the layered radial structure that causes hardness variations. The circumferential deposition method creates a more homogeneous material distribution throughout the fill depth, as each circumferential pass contributes material throughout the wear pocket volume rather than confining it to a specific radial depth zone.
Solution Approach 2:
The patent applies preheating to the rail surface before circumferential welding begins. This preheating ensures uniform initial temperature distribution throughout the wear pocket region, which promotes uniform cooling rates and consistent hardness throughout the deposited fill material, preventing the hardness gradients that occur with radial layering where inner layers cool differently than outer layers.
3Manufacturing precision
If multiple radial layers and post-heating are applied to meet hardness requirements, then the AREMA hardness standard is achieved, but the refurbishment process becomes slower and more costly
Solution Approach 1:
The patent applies preheating to the rail surface before welding begins, which ensures that the base metal and deposited fill material cool at more uniform rates. This preliminary thermal preparation achieves the desired hardness distribution directly during the welding process itself, eliminating the need for subsequent post-heating operations while still meeting AREMA hardness standards.
Solution Approach 2:
The patent removes the post-heating step from the refurbishment process by incorporating all necessary thermal control into the welding operation itself. Through proper preheating and circumferential welding technique, the desired hardness is achieved during deposition, allowing the elimination of the separate post-heating operation that slows down traditional radial layering methods.
4Duration of action of stationary object
If the rail surface hardness exceeds the original rail surface hardness by 50%, then wear life is increased, but an 'eggshell' configuration is created where the outside surface can crush the inside rail under heavy stresses
Solution Approach 1:
The patent controls the chemical composition and cooling rates during circumferential welding to achieve a more uniform hardness profile throughout the fill material depth. By maintaining consistent preheating temperatures and using appropriate fill material compositions, the resulting structure has graduated hardness from surface to core rather than creating an overly hard surface layer, preventing the eggshell effect while still providing enhanced wear resistance.
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 approach allows for faster, less disruptive, and cost-effective rail refurbishment with uniform hardness, eliminating the need for post-heating and reducing the risk of cracking and chipping, resulting in a refurbished rail surface similar to a newly manufactured rail.
Implementation Method 1
a progression of fill-welds with each layer providing a flow barrier
Data Source
AI summary
A method and related system and apparatus for refurbishing worn rail transit rails to a desired refurbished rail surface profile substantially similar to the surface profile of a newly-manufactured rail, comprising: depositing a first line of fill material along a lower-inside section to be refurbished; in N−1 successive iterations thereafter, progressing circumferentially from the lower-inside section to be refurbished to an upper-outside section to be refurbished, depositing an n+1th line of fill material adjacent an nth line of fill material wherein the nth line of fill material substantially provides a flow barrier against the n+1th line of fill material flowing past the nth line of fill material.