Continuous Annealing Line With Phase Fraction Feedback Heating
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Solution Overview
Problem
Existing continuous annealing technologies struggle to quickly respond to variations in material properties, leading to inconsistent mechanical properties and reduced productivity in the production of thin steel sheets, particularly in the production of dual phase (DP) steels, due to challenges in controlling the transformation from α-phase to γ-phase during annealing.
Innovation Solution
A continuous annealing line and method that includes a heating zone, soaking zone, and cooling zone, with an induction heating device between the soaking and cooling zones, and a phase fraction measurement device to control the induction heating device's operation based on measured phase fractions, allowing rapid and controlled heating and cooling to stabilize mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If radiant tube burners are used to heat steel sheets by radiant heat, then the heating is gentle and uniform, but the volume of the heat source is very large and thermal inertia is large, making it difficult to quickly keep up with changes in temperature setting
Solution Approach 1:
The heating system is segmented into multiple independent heating zones along the annealing line, with each zone equipped with its own radiant tube burners. This allows different sections of the steel sheet to be heated at different rates and to different temperatures simultaneously, improving overall temperature control flexibility and response speed while maintaining uniform heating within each zone.
Solution Approach 2:
The radiant tube burners are designed with adjustable firing rates and variable geometry combustion chambers that can dynamically adapt to changing temperature requirements. The burners can rapidly modulate their heat output in response to temperature feedback, reducing thermal inertia effects while maintaining uniform heating distribution across the steel sheet width.
2Stability of the object's composition
If the temperature increase rate is slowed down towards the end of heating to ensure microstructure control, then microstructure quality is improved, but the required furnace length increases and thermal inertia increases, resulting in greater delay in reaching target temperature
Solution Approach 1:
The heating process uses periodic cycling of the burner firing rates, alternating between high-intensity heating phases and controlled soaking phases. During high-intensity phases, temperature is rapidly increased toward the target; during soaking phases, the burners modulate to maintain temperature stability for microstructure control. This periodic action reduces overall processing time while ensuring quality microstructure development.
Solution Approach 2:
The steel sheet is preheated in upstream zones to a temperature close to the target annealing temperature before entering the final heating zone. This preliminary heating action reduces the temperature differential that needs to be overcome in subsequent zones, allowing faster heating rates to be used throughout the process while still achieving proper microstructure control in the final stages.
3Stability of the object's composition
If the furnace length is increased to provide sufficient soaking time for microstructure control, then microstructure quality is improved, but thermal inertia increases, resulting in greater delay in reaching target temperature
Solution Approach 1:
The furnace is divided into multiple independent heating zones, each optimized for specific functions: rapid heating zones use high-power burners with short residence times, while microstructure control zones use lower-power burners with longer residence times. This segmentation allows the furnace to perform multiple functions simultaneously in different sections, achieving both fast heating and quality microstructure control without requiring excessive overall furnace length.
Solution Approach 2:
The burners are equipped with variable geometry combustion chambers and adjustable firing rates that can be independently controlled in each zone. By dynamically changing operating parameters such as air-fuel ratio, burner elevation, and firing intensity along the furnace length, the system optimizes heating rates and soaking times in different sections, reducing total furnace length requirements while maintaining microstructure 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
The solution enables rapid and precise control of steel sheet temperature, reducing variations in mechanical properties and improving productivity by ensuring consistent phase fractions, thus producing high-strength steel sheets with targeted mechanical properties.
Implementation Method 1
at least one induction heating device disposed between the soaking zone and the cooling zone
Implementation Method 2
Radiant tube furnaces heat steel sheets by radiant heat from the radiant tubes and furnace wall
Data Source
AI summary
Provided is a continuous annealing line, a continuous annealing method, a method of producing a cold-rolled steel sheet, and a method of producing a coated or plated steel sheet that can respond quickly to variation in material properties and substantially reduce variation in mechanical properties of products. The continuous annealing line is for a steel sheet and includes a heating zone (6), a soaking zone (7), and a cooling zone (8), in this order, at least one induction heating device (9) disposed between the soaking zone (7) and the cooling zone (8), and a measuring device (phase transformation rate meter (10)) disposed at or after an exit from the induction heating device (9) and configured to measure at least one phase fraction of the steel sheet.