Spray Cooling Profile for Flat High-Strength Steel Strip
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rapid cooling methods in continuous annealing lines for high yield strength steels cause unevenness defects due to internal stresses resulting from thermal and metallurgical phase transformations, which are not adequately addressed by existing technologies.
Innovation Solution
Optimizing the relative position of thermal and metallurgical critical points by adjusting cooling intensity along the cooling zone to minimize internal stresses, using a method that involves determining a thermal profile and adjusting cooling parameters such as flow rate and pressure to synchronize Leidenfrost and metallurgical transformation temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rapid cooling by spraying liquid or gas-liquid mixture is applied to achieve high yield strength steels, then cooling rate exceeds 100°C/s and mechanical strength is improved, but internal stresses develop causing unevenness defects
Solution Approach 1:
The invention dynamically adjusts cooling intensity along the cooling zone by varying spray flow rates and pressures in different sections. The cooling system transitions from intensive cooling at the entrance to less intensive cooling toward the exit, adapting the cooling rate to the strip's temperature profile and metallurgical transformation stages to minimize thermal gradients and internal stresses.
Solution Approach 2:
The invention changes cooling parameters (flow rate, pressure, temperature) along the cooling zone to optimize the cooling process. By adjusting these parameters, the system synchronizes the Leidenfrost temperature with metallurgical transformation temperatures, reducing thermal shocks and internal stresses that cause unevenness defects while maintaining the required cooling rate for high yield strength.
2Productivity
If cooling intensity is increased to achieve faster cooling rates, then productivity and mechanical strength are improved, but thermal gradients increase causing greater internal stresses
Solution Approach 1:
The cooling zone is divided into multiple sections with different cooling intensities. The first section near the heating zone applies intensive cooling with higher spray flow rates and pressures, while subsequent sections apply progressively less intensive cooling. This segmentation allows the system to achieve the required overall cooling rate while distributing thermal gradients more evenly, reducing internal stresses.
Solution Approach 2:
The cooling system dynamically adapts its intensity along the cooling zone to match the strip's thermal state and metallurgical transformation progress. By varying cooling parameters spatially, the system maintains high productivity where needed while minimizing stress generation in critical transformation zones.
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
Reduces internal stresses and unevenness defects in high yield strength steels by synchronizing thermal and metallurgical transformations, ensuring uniform mechanical properties and flatness.
Implementation Method 1
cooling by spraying liquid or a mixture of gas and liquid
Implementation Method 2
the strip is cooled at cooling rates greater than 100° C./s, by spraying liquid or a mixture of liquid and gas
Implementation Method 3
The Leidenfrost phenomenon, which consists of a sudden increase in the heat transfer coefficient by convection during the transition between the vapor phase cooling regime and the phase cooling regime liquid
Implementation Method 4
transformations of metallurgical phases... transformations from the austenitic phase to the martensitic phase
Implementation Method 5
partial transformation of the austenite into ferrite and finally rapid cooling for transformation of the austenite into martensite
Implementation Method 6
the temperature distribution in the product, in the direction of travel, in the width of the product and possibly in the thickness of the product
Implementation Method 7
The stresses causing unevenness defects depend on... the temperature distribution in the product... transformations of metallurgical phases
Data Source
AI summary
Method for reducing unevenness in a strip subjected to cooling by spraying of liquid, or a mixture of gas and liquid, along a cooling zone of a continuous heat treatment one, the cooling intensity being adjusted in the direction of travel of the strip so as to achieve a relative position between the Leidenfrost temperature and at least one temperature at which the metallurgical structure changes such that said cooling intensity minimizes the internal stresses of the strip, and device for implementing the method.