Ferritic Stainless Steel Sheet Annealing for Crack-Resistant Blanking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hot-rolled ferritic stainless steel sheets used for thick flanges often crack during blanking due to insufficient threshold stress intensity factor, preventing the attainment of a predetermined flange shape.
Innovation Solution
Increasing the threshold stress intensity factor by performing hot-rolled sheet annealing at appropriate temperatures and controlling the rolling reduction during finish rolling, specifically setting the threshold stress intensity factor to 35 MPa·m1/2 or more, to prevent cracks and enhance workability and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot-rolled ferritic stainless steel sheet is used for thick flanges, then corrosion resistance is improved, but cracks occur during blanking due to insufficient threshold stress intensity factor
Solution Approach 1:
The patent applies parameter changes by optimizing the chemical composition parameters (C: 0.015% or less, Si: 0.01% to 0.4%, Mn: 0.01% to 0.8%, Cr: 14.0% to less than 18.0%, Ni: 0.05% to 1%, Nb: 0.3% to 0.6%, Ti: 0.05% or less, N: 0.020% or less) and processing parameters (accumulated rolling reduction of final three passes: 25% or more, annealing temperature: 600°C to 1100°C) to simultaneously achieve both corrosion resistance and sufficient threshold stress intensity factor (35 MPa·m1/2 or more), preventing cracks during blanking while maintaining corrosion resistance
2Strength
If accumulated rolling reduction of final three passes is increased to 25% or more, then threshold stress intensity factor is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-planning and specifying the accumulated rolling reduction (25% or more) and annealing temperature (600°C to 1100°C) parameters in advance during the manufacturing process design stage. This allows the steel sheet to achieve the required threshold stress intensity factor (35 MPa·m1/2 or more) before blanking operations, preventing cracks during subsequent forming while maintaining a manageable manufacturing process through predetermined parameter specifications
3Strength
If annealing temperature is set to 600°C to 1100°C, then threshold stress intensity factor reaches 35 MPa·m1/2 or more, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by optimizing the annealing temperature parameter within the range of 600°C to 1100°C to achieve the minimum required threshold stress intensity factor (35 MPa·m1/2 or more) while avoiding excessive energy consumption. This balanced parameter selection ensures sufficient crack resistance during blanking without unnecessary energy waste, and the chemical composition parameters are also optimized to work synergistically with the annealing process
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 method results in a hot-rolled and annealed ferritic stainless steel sheet with sufficient corrosion resistance and toughness, preventing cracks during blanking into thick flanges and achieving a rust area ratio of 25% or less in cyclic salt spray tests.
Implementation Method 1
performing hot-rolled sheet annealing at an appropriate temperature on a hot-rolled steel sheet obtained by subjecting ferritic stainless steel having an appropriate chemical composition to finish hot-rolling
Data Source
AI summary
The present invention provides a hot-rolled and annealed ferritic stainless steel sheet which has sufficient corrosion resistance and in which cracks can be prevented during blanking into a thick flange, and a method for manufacturing the same. A hot-rolled and annealed ferritic stainless steel sheet has a chemical composition containing, in percent by mass, C: 0.001% to 0.020%, Si: 0.05% to 1.00%, Mn: 0.05% to 1.00%, P: 0.04% or less, S: 0.01% or less, Al: 0.001% to 0.100%, Cr: 10.0% to 19.0%, Ni: 0.65% to 1.50%, Ti: 0.10% to 0.40%, and N: 0.001% to 0.020%, with the balance being Fe and unavoidable impurities, and has a threshold stress intensity factor KIC of 35 MPa ·m1/2 or more.