Steel Wire Cooling Process for Consistent Drawability
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Solution Overview
Problem
Existing methods for heat treating steel wires, particularly those with diameters between 3.5 mm and 20 mm, often result in inconsistent drawability and brittle behavior due to unwanted metallic structures like martensite or bainite, and fail to reliably control tensile strength and microstructure.
Innovation Solution
A controlled cooling method involving multiple coolant baths with a stabilizing additive and impinging liquid to create a steam film, followed by air cooling to prevent turbulence, ensuring a stable transformation from austenite to pearlite, allowing for precise control of cooling rates and microstructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cooling methods (direct water cooling or air cooling) are used for steel wires with diameter 3.5-20mm, then cooling speed can be controlled, but inconsistent drawability and brittle behavior occur due to unwanted metallic structures like martensite or bainite
Solution Approach 1:
The cooling process is divided into multiple sequential stages: initial rapid cooling stage, intermediate cooling stage, and final cooling stage. Each stage uses different cooling media (water spray, air, water) and cooling rates to progressively transform the microstructure, ensuring complete avoidance of martensite and bainite while achieving uniform pearlite
Solution Approach 2:
The patent employs periodic alternation between different cooling methods and media throughout the cooling process. This includes switching between water spray and air cooling, and between different water temperatures, to maintain optimal cooling rates that prevent unwanted phase transformations while ensuring uniform microstructure
2Strength
If high cooling speed is applied to achieve fine pearlite structure, then tensile strength is improved, but formation of martensite or bainite occurs causing brittleness
Solution Approach 1:
The patent systematically varies cooling parameters including cooling rate, water temperature, and exposure time across different cooling stages. By precisely controlling these parameters, the process achieves rapid enough cooling to form fine pearlite for high tensile strength, while staying within the safe parameter range that avoids martensite and bainite formation
Solution Approach 2:
The cooling process incorporates monitoring and adjustment mechanisms to maintain optimal cooling rates. This ensures that the cooling speed remains within the range that produces fine pearlite without exceeding the threshold that would cause brittle phase formation, allowing consistent achievement of high strength without brittleness
3Reliability
If alternating water and air cooling periods are used for wires with diameter less than 2.8mm, then formation of martensite or bainite is avoided, but the process complexity increases and cooling control becomes more difficult
Solution Approach 1:
The patent develops a multi-stage cooling process that can handle various wire diameters (3.5-20mm) with a single integrated system. The same basic apparatus configuration with adjustable parameters can process different wire sizes, eliminating the need for completely different cooling systems for different diameter ranges and reducing overall process 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
This method achieves a more reliable and consistent transformation to a fine pearlitic structure, enhancing the mechanical properties and stability of steel wires by preventing the formation of undesirable structures like martensite or bainite, thus improving tensile strength and drawability.
Implementation Method 1
The bath liquid and the multiple previously heated and substantially straight steel wires create a steam film around each steel wire itself
Implementation Method 2
the wire is subjected to uniform and stable film-boiled cooling along its entire immersion length
Implementation Method 3
Directing an impinging liquid immersed inside the first coolant bath/baths towards the previously heated and substantially straight steel wire/wires over a certain length L along individual path/paths, to cool down the previously heated and substantially straight steel wire/wires
Implementation Method 4
Guiding the previously heated and substantially straight steel wire/wires along individual path/paths out of the first coolant bath/baths to be further cooled down in air
Implementation Method 5
the substantially straight steel wire/wires are subjected to a cooling transformation from austenite to pearlite
Implementation Method 6
cooling the wires to a chosen temperature held for a sufficient period for generally isothermal decomposition of the austenite to be completed
Data Source
Figure 1~2
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Figure 5~6
AI summary
A method of controlled cooling of one or multiple previously heated and substantially straight steel wire/wires of diameter more than 2.8 mm to a predetermined temperature range, comprises the steps: - guiding the previously heated and substantially straight steel wire/wires along individual path/paths through one or multiple first coolant bath/baths comprising a bath liquid comprising water and a stabilizing additive. The bath liquid and the multiple previously heated and substantially straight steel wires create a steam film around each steel wire itself along each individual path; - directing an impinging liquid immersed inside the first coolant bath/baths towards the previously heated and substantially straight steel wire/wires over a certain length L along individual path/paths, to cool down the previously heated and substantially straight steel wire/wires, the impinging liquid decreases the thickness of the steam film or destabilizes the steam film, thereby increasing the speed of cooling over the length L along individual path/paths; - guiding the previously heated and substantially straight steel wire/wires along individual path/paths out of the first coolant bath/baths to be further cooled down in air; - after the further cooling in air, guiding the previously heated, substantially straight steel wire/wires along individual path/paths through one or multiple second coolant bath/baths. In the method, the substantially straight steel wire/wires are subjected to a cooling transformation from austenite to pearlite.