Warm Control Rolling for Ultrafine Ferrite Steel
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Solution Overview
Problem
Existing methods for manufacturing ultrafine particle steel lack a quantitative control method for grain size, particularly in continuous multipass rolling processes, where processing heat generation and deformation resistance pose challenges in achieving ultrafine crystal structures of 3 μm or less.
Innovation Solution
A warm control rolling method that sets the rolling condition parameter Z to 11 or more, controlling the rolling temperature between 350° C. to 800° C., and managing material temperature to prevent excessive heat generation, allowing for stable production of ultrafine crystal steel with grain sizes of 3 μm or less, regardless of pass interval or strain speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If warm rolling is performed at 350-800°C to achieve ultrafine crystal structure, then grain size is reduced to 3 μm or less, but processing heat generation increases and material temperature rises excessively
Solution Approach 1:
The patent implements periodic cooling intervals between rolling passes to control material temperature. After each rolling pass that generates processing heat, the material is allowed to cool down before the next pass, preventing excessive temperature accumulation while maintaining the warm rolling temperature range of 350-800°C necessary for ultrafine grain structure formation
Solution Approach 2:
The patent applies preliminary cooling measures before certain rolling passes to prevent temperature from rising too high. By proactively controlling the temperature trajectory through intermediate cooling, the material remains within the optimal warm rolling temperature range, enabling consistent ultrafine grain refinement without excessive heat accumulation
2Manufacturing precision
If continuous multipass rolling is performed to achieve ultrafine crystal structure, then grain size is reduced to 3 μm or less, but deformation resistance increases
Solution Approach 1:
The patent incorporates periodic intermediate cooling between rolling passes to reduce material temperature and thereby increase deformation resistance. This controlled increase in deformation resistance through temperature management enables better grain refinement in subsequent passes while maintaining overall process feasibility for achieving ultrafine crystal structures
Solution Approach 2:
The patent dynamically adjusts rolling parameters including temperature, strain rate, and pass interval to optimize the balance between deformation resistance and grain refinement efficiency. By changing these parameters periodically throughout the multipass process, the material undergoes progressive grain refinement to achieve 3 μm or less while managing the increasing deformation resistance
3Strength
If rolling parameter Z is set to 11 or more to achieve ultrafine ferrite with grain size of 1 μm or less, then strength is enhanced, but pass duration and strain speed are limited reducing productivity
Solution Approach 1:
The patent divides the total rolling process into multiple passes with intermediate cooling intervals, allowing each pass to contribute to grain refinement without requiring excessively high strain rates or long pass durations in single operations. This segmented approach enables accumulation of sufficient cumulative strain to achieve parameter Z≥11 and ultrafine grain structure while maintaining reasonable productivity through efficient multi-pass processing
Solution Approach 2:
The patent implements periodic cooling between passes to control material temperature and manage processing heat generation. This periodic temperature control enables sustained rolling operations at parameters that achieve ultrafine grain structure (Z≥11) without excessive heat accumulation that would otherwise limit pass duration and strain speed, thereby maintaining productivity
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 the stable production of ultrafine crystal steel with grain sizes of 3 μm or less, enhancing strength and ductility without alloy additions, by precisely controlling the rolling conditions to manage processing heat and maintain optimal temperature ranges.
Implementation Method 1
processing it by one pass or two or more consecutive passes with interval of each pass of within 20 seconds, at temperature of 500 to 700° C., strain speed of 0.1 to 20/sec, and total strain amount of 0.8 to 5.0
Implementation Method 2
the deformation resistance of steel is large and the processing heat generation of material is large in this case, and the material temperature may rise several hundred degrees during continuous rolling
Data Source
AI summary
The invention presents a new warm control rolling method, in consideration of processing heat generation, as a method of stably manufacturing ultrafine crystal steel of 3 microns to 1 micron or less, without any limitation in pass interval or strain speed, being a rolling method of manufacturing steel mainly composed of fine ferrite particle texture with average ferrite grain size of 3 μm or less, in which, in the rolling process of one pass or more wherein the rolling temperature range is a temperature region of 350° C. to 800° C., the material temperature upon start of rolling of each rolling process does not exceed the maximum temperature of 800° C., and the material temperature during rolling and right after final rolling (within 1 second) is not lower than 350° C., temperature Tx-out right after rolling in each rolling process (within 1 second) is not higher than the temperature that is higher than rolling entry temperature Tx-in by 100° C. and the material temperature right after rolling (within 1 second) is not lower than the temperature that is lower than the temperature right before rolling by 100° C.