Blade Steel Production via Batch and Continuous Annealing
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Solution Overview
Problem
Current methods for producing steel for blades using batch annealing furnaces struggle to achieve high carbide concentrations, which are essential for improved productivity and quenchability, especially with elongated coils.
Innovation Solution
A method combining batch annealing, continuous annealing, and cold rolling steps, where the batch annealing is performed at 500°C to 700°C for 3 to 30 hours, followed by continuous annealing above the Ac1 transformation point, and then cold rolling, to achieve carbide concentrations of 200 to 1,000 per 100 µm² in the ferrite structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If batch annealing is used for elongated coils to improve productivity, then productivity increases, but carbide concentration remains insufficient (at most 200 carbides/100 μm²)
Solution Approach 1:
The annealing process is divided into two distinct stages: batch annealing followed by continuous annealing. The batch annealing stage (500-700°C for 3-30 hours) provides preliminary carbide precipitation and improves productivity for elongated coils, while the subsequent continuous annealing stage (Ac1 transformation point or higher for 5-30 minutes) significantly increases carbide concentration to 200-1000 carbides/100 μm². This segmentation allows each stage to optimize for its specific function.
Solution Approach 2:
The batch annealing step serves as a preliminary action that prepares the material structure before the main continuous annealing step. By performing batch annealing first at lower temperature for extended time, carbides begin to precipitate and the microstructure is conditioned, which then enables the subsequent continuous annealing to achieve high carbide concentration more effectively and efficiently.
2Quantity of substance
If continuous annealing is used to increase carbide concentration to improve quenchability, then carbide concentration increases (140-600 carbides/100 μm²), but productivity decreases due to processing time and coil length limitations
Solution Approach 1:
The annealing process is divided into two distinct stages: batch annealing followed by continuous annealing. The batch annealing stage (500-700°C for 3-30 hours) provides preliminary carbide precipitation and improves productivity for elongated coils, while the subsequent continuous annealing stage (Ac1 transformation point or higher for 5-30 minutes) significantly increases carbide concentration to 200-1000 carbides/100 μm². This segmentation allows each stage to optimize for its specific function.
Solution Approach 2:
The invention utilizes significant parameter changes between the two annealing stages. Batch annealing operates at lower temperature (500-700°C) for long duration (3-30 hours), while continuous annealing operates at higher temperature (Ac1 transformation point or higher, typically 800-950°C) for short duration (5-30 minutes). This parameter change enables the system to achieve both high productivity and high carbide concentration.
3Quantity of substance
If batch annealing temperature is increased to improve carbide concentration, then carbide precipitation may improve, but excessive temperature causes carbide coarsening and reduces quenchability
Solution Approach 1:
The annealing process is divided into two distinct stages: batch annealing followed by continuous annealing. The batch annealing stage (500-700°C for 3-30 hours) provides preliminary carbide precipitation and improves productivity for elongated coils, while the subsequent continuous annealing stage (Ac1 transformation point or higher for 5-30 minutes) significantly increases carbide concentration to 200-1000 carbides/100 μm². This segmentation allows each stage to optimize for its specific function.
Solution Approach 2:
The invention exploits phase transitions at different temperature ranges. Batch annealing occurs in the ferrite phase region (500-700°C) where slow carbide precipitation occurs without austenite formation. Continuous annealing then heats to the Ac1 transformation point or higher, inducing austenite phase transition and rapid carbide precipitation, followed by quenching to achieve martensite structure with high carbide concentration and fine grain size.
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 significantly increases carbide concentration and productivity, allowing for the production of steel blades with enhanced quenchability and corrosion resistance, suitable for razor blades.
Implementation Method 1
a batch annealing step for batch annealing a material to be cold rolled having the metal composition under a temperature having a range of 500°C to 700°C for 3 to 30 hours
Implementation Method 2
a continuous annealing step for continuously annealing the batch annealed material over 5 to 30 minutes so that the batch annealed material is heated to at least an Ac1 transformation point of the metal composition
Implementation Method 3
a cold rolling step for cold rolling the continuously annealed material after the continuous annealing step
Data Source
AI summary
An object of the present invention is to provide a method for producing steel for blades capable of achieving a high concentration of carbides even using a batch annealing furnace. There is provided a method for producing steel for blades having a metal composition consisting of, by mass, 0.55% to 0.8% C, not more than 1.0% Si, not more than 1.0% Mn, 12.0% to 14.0% Cr, not more than 1.0% Mo, not more than 1.0% Ni, and the balance Fe with inevitable impurities, the method comprising: a batch annealing step for batch annealing a material to be cold rolled having the metal composition at a temperature of 500°C to 700°C for 3 to 30 hours to obtain a batch annealed material; a continuous annealing step for continuously annealing the batch annealed material for 5 to 30 minutes so that the batch annealed material is heated to at least an Ac1 transformation point of the metal composition after the batch annealing step to obtain a continuously annealed material; and a cold rolling step for cold rolling the continuously annealed material after the continuous annealing step, wherein the continuous annealing step and the cold rolling step are performed at least once, respectively.