Rail Thermal Treatment: Uniform Cooling via Localized Methods
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Solution Overview
Problem
Existing thermal treatment processes for rolled rails are inefficient, leading to low throughput, energy consumption, and non-uniform metallurgical structures, with manipulators causing bending and increased production costs due to the need for alloy elements.
Innovation Solution
An in-line thermal treatment process involving four cooling steps - two air and two fluid cooling steps - to achieve a uniform fine pearlitic structure in the rail head, combined with a device featuring mobile trolleys with longitudinal roller tables and cooling tanks for precise handling and cooling, allowing for higher throughput and reduced maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If spray nozzles are used for cooling, then cooling speed is improved, but rail warping occurs due to temperature inhomogeneity
Solution Approach 1:
The patent applies different cooling methods to different regions of the rail: spray nozzles are used for the rail head requiring fast cooling, while cooling rollers are used for the rail body to maintain uniform temperature distribution and prevent warping. This local differentiation resolves the contradiction between cooling speed and straightness maintenance.
2Manufacturing precision
If immersion tank is used for cooling, then cooling uniformity is improved, but manipulator rigidity is insufficient to counteract rail bending
Solution Approach 1:
The patent extracts the manipulator from the cooling process by using a fixed immersion tank system where the rail is cooled in place during the rolling line operation. This eliminates the need for manipulators to hold the rail during cooling, thereby removing the rigidity limitation while maintaining cooling uniformity through the immersion method.
3Ease of operation
If manipulators are used for handling, then rail positioning is achieved, but cold areas are generated on the rail surface
Solution Approach 1:
The patent employs cooling rollers that are self-regulating in their contact with the rail. The rollers are designed to apply cooling only where needed and to minimal extent, allowing the rail to maintain its temperature profile without creating harmful cold areas, while still achieving proper positioning through the rolling mechanism.
4Strength
If alloy elements are added to steel, then mechanical properties are improved, but production cost increases
Solution Approach 1:
The patent achieves improved mechanical properties by changing the thermal processing parameters (cooling speed, temperature control, cooling duration) rather than by adding alloy elements. This approach maintains the base steel composition while obtaining enhanced properties through precise thermal treatment, thereby avoiding increased material costs.
5Productivity
If in-line thermal treatment is implemented, then throughput is improved, but device complexity increases
Solution Approach 1:
The patent designs the thermal treatment device with multi-functional components: the same rolling line structure serves both for rail transport and for applying thermal treatment. The cooling rollers and spray nozzles are integrated into the existing rolling line infrastructure, allowing the device to perform multiple functions (transport, cooling, heating) without proportionally increasing complexity.
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 process achieves high hardness, wear resistance, toughness, and fatigue resistance, maintaining mechanical properties at low temperatures, with a uniform pearlitic structure up to 15-25 mm depth and improved straightness, while reducing thermal distortions and production costs.
Implementation Method 1
a second cooling step by means of a cooling fluid
Implementation Method 2
a second cooling step by means of a cooling fluid until reaching a surface temperature of the rail head from 50 to 150° C. above the Ar3 temperature
Implementation Method 3
a first cooling step in air of the rail until reaching a surface temperature of the rail head of at least 720° C.
Implementation Method 4
a first cooling step in air of the rail
Implementation Method 5
a fourth cooling step by means of a cooling fluid until reaching a surface temperature of the rail head lower than 500° C. whereby the phase transformation from austenite to pearlite occurs
Implementation Method 6
whereby the phase transformation from austenite to pearlite occurs wherein said pearlite has an uniform structure with fine granulometry
Data Source
AI summary
Process for the in-line thermal treatment of rolled rails which ensures to obtain a fine pearlitic structure which is uniform through a whole predetermined superficial thickness of the rail head. There is also disclosed a new device for the thermal treatment of rails in-line with a rolling system which, as compared to the known devices, is structurally much simpler, has a high sturdiness and requires less maintenance.