Cold-Rolled Steel Strip TRIP Processing at Elevated Temperatures
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Solution Overview
Problem
The production of cold-rolled steel strips from high-strength manganese-containing steels with TRIP properties is limited by strong work hardening, requiring multiple cold rolling steps and recrystallization annealing, making the process time-consuming, expensive, and associated with high CO2 emissions.
Innovation Solution
Cold rolling is performed at elevated temperatures of 70°C to 250°C to suppress the TRIP conversion mechanism, allowing for higher forming degrees in a single pass and reducing rolling forces, while maintaining the steel's high strength and elongation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cold rolling is performed at room temperature on high-strength manganese-containing steel with TRIP properties, then the steel achieves high tensile strength through TRIP effect, but the strong work hardening limits the degree of deformation and requires multiple cold rolling passes with intervening recrystallization annealing
Solution Approach 1:
The patent applies parameter changes by performing cold rolling at elevated temperatures (70°C to 250°C) instead of room temperature. This temperature parameter change suppresses the TRIP conversion mechanism during rolling, reducing work hardening and enabling higher degrees of deformation in a single pass while maintaining the steel's high strength properties
Solution Approach 2:
The patent eliminates the periodic cycle of cold rolling followed by recrystallization annealing by implementing continuous cold rolling at elevated temperatures. This removes the need for intermittent heating and cooling cycles, significantly improving productivity and reducing CO2 emissions
2Manufacturing precision
If multiple cold rolling passes with recrystallization annealing are used to achieve high degrees of deformation, then the final thickness reduction is achieved, but the process becomes time-consuming and expensive with high CO2 emissions
Solution Approach 1:
The patent changes the temperature parameter during cold rolling to 70°C-250°C, which fundamentally alters the material's deformation characteristics. This enables achieving high degrees of thickness reduction in a single pass without the need for multiple passes and intermediate annealing treatments, dramatically reducing production time
Solution Approach 2:
The patent extracts and removes the recrystallization annealing step from the cold rolling process by performing cold rolling at elevated temperatures. This eliminates the time-consuming cycle of heating for annealing and subsequent cooling, achieving the same thickness reduction goal more efficiently
3Strength
If cold rolling is performed at room temperature, then the steel's high strength is maintained, but the rolling forces become excessively high due to strong work hardening
Solution Approach 1:
The patent applies parameter changes by increasing the temperature during cold rolling from room temperature to 70°C-250°C. This temperature parameter change suppresses the TRIP conversion mechanism that causes strong work hardening, thereby significantly reducing the rolling forces required while maintaining the steel's high strength properties in the final product
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 enables more economical and ecological production of cold-rolled steel strips with improved forming capacity and reduced rolling forces, eliminating the need for multiple cold rolling steps and subsequent annealing, thus enhancing the material's formability and reducing environmental impact.
Implementation Method 1
Depending on the alloy composition, this steel can exhibit a metastable austenite with the ability to form stress-induced martensite (TRIP effect)
Data Source
Figure 1
AI summary
The invention relates to a method for producing a cold-rolled steel strip made of a high-strength mangan-containing steel with TRIP-characteristics, containing (in wt.%) C: 0.0005 to 0.9, Mn: more than 3.0 to 12, with the remaining portion being iron including unavoidable steel-associated elements, with the optional addition of one or more of the following elements (in wt.%): AI: up to 10; Si: up to 6; Cr: up to 6; Nb: up to 1.5; V: up to 1.5; Ti: up to 1.5; Mo: up to 3; Cu: up to 3; Sn: up to 0.5; W: up to 5; Co: up to 8; Zr: up to 0.5; Ta: up to 0.5; Te: up to 0.5; B: up to 0.15; P: max. 0.1, in particular < 0.04; S: max. 0.1, in particular < 0.02; N: max. 0.1, in particular < 0.05; Ca: up to 0.1. According to the invention, in order to improve a corresponding method, the cold-rolling to a required end thickness occurs at a temperature of over 50°C to 400°C before the first impact.