Polymer-Coated Steel Substrate Temper Rolling for Stress Cracking
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Solution Overview
Problem
Polymer-coated steel substrates for packaging applications face issues with yield point elongation and environmental stress cracking, particularly due to heat treatments required for bonding the polymer coating, which can lead to the formation of aesthetically unattractive Lüders' lines and reduced mechanical properties.
Innovation Solution
A process involving temper rolling or stretcher-levelling of polymer-coated steel substrates with a thickness reduction of 0-3%, preferably at least 0.2%, to improve mechanical properties and prevent discontinuous yielding, thereby eliminating Lüders' lines and enhancing environmental stress cracking resistance without damaging the polymer coating or its adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the substrate is pre-heated to temperatures in excess of 200°C for coating with thermoplastic polymer, then the polymer coating can be applied and bonded, but yield point elongation returns and Lüders' lines develop
Solution Approach 1:
The substrate undergoes temper rolling before polymer coating application to eliminate yield point elongation and prevent Lüders' lines from forming during subsequent heating and coating processes
Solution Approach 2:
The temper rolling process changes the mechanical parameters of the substrate by applying a small reduction (0-3%, preferably at least 0.2%), which modifies the stress-strain characteristics and eliminates discontinuous yielding behavior
2Stability of the object's composition
If the substrate is temper rolled with a reduction of 20 to 35% to produce double reduced substrate, then yield point elongation is eliminated, but the process complexity increases
Solution Approach 1:
Instead of applying a large reduction (20-35%), the invention uses a partial action approach with a much smaller reduction (0-3%, preferably at least 0.2%), which is sufficient to eliminate yield point elongation while avoiding the complexity of double reduction processes
Solution Approach 2:
The conventional approach applies large reductions to eliminate yield point elongation, but this invention inverts the approach by using minimal reductions achieved through temper rolling, thereby simplifying the overall process while achieving the same effect
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 process effectively suppresses yield point elongation and discontinuous yielding, improving the bulk mechanical properties and stress cracking resistance of the substrate, ensuring the polymer coating adheres well and maintains its integrity, even under deformation and chemical exposure.
Implementation Method 1
passing the material through a temper mill and applying a thickness reduction between 0 - 3%, preferably of at least 0.2%
Implementation Method 2
subjecting the polymer-coated substrate to a stretching operation wherein the stretching operation is achieved by: a. passing the material through a temper mill
Implementation Method 3
ensuring the polymer coating adheres well and maintains its integrity, even under deformation and chemical exposure
Data Source
AI summary
This invention relates to a process for manufacturing a polymer-coated steel substrate for packaging applications with improved environmental stress cracking resistance, comprising the subsequent steps of: —� producing a polymer-coated substrate with a polymer coating layer on one or both sides of said substrate; —� subjecting the polymer-coated substrate to a stretching operation wherein the stretching operation is achieved by: a. passing the material through a temper mill and applying a thickness reduction between 0 - 3%, preferably of at least 0.2%; or by b. passing the material through a stretcher-leveller. The invention also relates to a polymer-coated steel substrate for packaging applications with improved environmental stress cracking resistance produced thereby and the use thereof.