Austenitic Stainless Steel Plate Cross-Rolling for Uniform Low-Temperature Properties
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Solution Overview
Problem
Existing methods struggle to produce austenitic stainless steel plates thicker than 100 mm with uniform mechanical properties across the entire cross-section, as the production process faces challenges in introducing sufficient working strain and achieving a fine recrystallized structure, particularly at locations from 1/4 to 3/4 of the plate thickness, leading to areas with low strength and elongation.
Innovation Solution
Austenitic stainless steel plates with specific compositions (C: 0.08% or less, N: 0.10% to 0.22%, Si: 0.01% to 2.0%, Mn: 0.1% to 2.0%, Cr: 15% to 27%, Ni: 8% to 20%, Mo: 4% or less, Cu: 0.1% to 3%, Al: 0.001% to 0.10%, and Ti: 0.010% to 0.030%) are produced using a combination of forging and rolling processes, followed by solution heat treatment, to ensure strength and ductility across the entire thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the reduction ratio is increased to introduce working strain evenly across the cross-section, then the fine recrystallized structure is improved, but the thickness of the material before rolling is limited by rolling machine restrictions
Solution Approach 1:
The patent segments the deformation process into multiple stages: first hot rolling to an intermediate thickness, then cross-rolling (90° rotation and re-rolling) to distribute strain evenly across the entire cross-section including the center region. This multi-stage approach overcomes the limitation of single-pass rolling on thick materials while achieving uniform fine recrystallized structure throughout.
Solution Approach 2:
The patent introduces cross-rolling in a perpendicular dimension (rotating the slab 90° between passes) to apply working strain from different directions. This dimensional change ensures that even the center region (1/4 to 3/4 thickness from surface) receives sufficient strain to develop fine recrystallized structure, overcoming the limitation of conventional single-direction rolling.
2Ease of manufacture
If conventional hot rolling is used for thick-gauge products, then production is simpler, but work strain cannot be introduced to the center location resulting in coarse cast structure
Solution Approach 1:
The patent divides the rolling process into multiple sequential stages with cross-rolling in between, transforming a single complex operation into manageable segments. This maintains production feasibility while ensuring the center region receives adequate strain to eliminate coarse cast structure.
Solution Approach 2:
The patent implements periodic cross-rolling at intermediate stages to repeatedly apply strain from different directions. This periodic intervention ensures progressive refinement of the structure throughout the thick gauge material, achieving uniform fine structure without excessive complexity.
3Strength
If the thickness of the steel plate is increased to meet structural material requirements, then the strength and ductility at extremely low temperature are improved, but obtaining uniform properties over the entire cross-section becomes difficult
Solution Approach 1:
The patent segments the thick gauge material into multiple deformation zones through cross-rolling, ensuring each region (surface and center) receives appropriate strain. This produces uniform fine recrystallized structure throughout the 100mm+ thickness, guaranteeing consistent strength and ductility properties across the entire cross-section at extremely low temperatures.
Solution Approach 2:
The patent applies different rolling sequences and strain distributions to different regions of the thick plate. The cross-rolling process specifically targets the center region (1/4 to 3/4 thickness) with enhanced strain introduction, ensuring local quality uniformity throughout the thick gauge material while maintaining overall structural integrity.
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 approach enables the production of austenitic stainless steel plates with high strength and ductility at extremely low temperatures, suitable for superconductive coils and LNG structural materials, ensuring uniform mechanical properties and improved strength-ductility balance across the entire cross-section.
Implementation Method 1
austenitic stainless steel plate... stabilized in the γ-phase... high strength and ductility at an extremely low temperature
Implementation Method 2
even if heat treating is done for the steel, the cast structure remains... solution heat treatment
Data Source
AI summary
Austenitic stainless rolled steel plate of a thickness of 100 mm or more, characterised by: containing, by mass%, C: 0.08% or less, N: 0.10% to 0.22%, C+N: 0.12% or more, Si: 0.01% to 2.0%, Mn: 0.1% to 2.0%, Cr: 15% to 27%, Ni: 8% to 20%, Mo: 4% or less, Co: 0.1% or less, Cu: 0.1% to 3%, Al: 0.001% to 0.10%, and Ca: 0.0005% to 0.01%, having a calculated value of the amount of δ-ferrite defined by the following (I) formula (δcal; vol%) of -7% to 4%, and having an elongation in the width direction and length direction at any location in the thickness direction of 30% or more: δcalvol%=2.9×Cr+0.3Si+Mo-2.6×Ni+0.3×Mn+0.25×Cu+35×C+20×N-18 where [element abbreviations] means the content of the element (mass%), and the elongation is the value measured at 4K.