Steel Sheet Reflectance Reduction for Radiant Heating
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Solution Overview
Problem
Existing methods for heating metal sheets, such as electrify heating and laser heating, face challenges in achieving uniform heating of non-square shapes and are costly and inefficient, while conventional radiant heat transfer methods are hindered by high reflectance of metal surfaces, leading to low productivity and high costs.
Innovation Solution
Applying a reflectance reducing treatment to metal sheets, such as painting or roughening, to lower reflectance and enhance radiant heat transfer efficiency, allowing for targeted heating of specific portions using near-infrared radiation, thereby improving heating efficiency and enabling the production of metal products with varying strength profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If gas heating furnace is used for hot stamping, then the steel sheet can be heated to austenite temperature, but the heating efficiency is low and productivity is poor
Solution Approach 1:
The patent replaces conventional gas heating furnaces with induction heating equipment that uses electromagnetic fields to directly heat the steel sheet. This substitution of heating mechanism achieves rapid heating to austenite temperature with significantly improved heating efficiency and productivity, while maintaining the required temperature for hot stamping
Solution Approach 2:
The patent introduces a heating efficiency improvement parameter by controlling the heating rate and temperature distribution during induction heating. By optimizing heating parameters such as frequency, power, and duration, the steel sheet is rapidly heated to the required austenite temperature range, resolving the contradiction between achieving target temperature and maintaining high productivity
2Productivity
If electrify heating is used to increase productivity, then heating efficiency improves, but the current concentrates on portions with small sectional area causing non-uniform heating of profile shapes
Solution Approach 1:
The patent applies local quality control by using induction heating coils configured to generate concentrated electromagnetic fields at specific locations. This allows different regions of the steel sheet with profile shapes to receive appropriate heating intensity, ensuring uniform heating across the entire surface while maintaining high heating efficiency
Solution Approach 2:
The patent employs dynamic control of the induction heating process by adjusting heating parameters in real-time based on the steel sheet's geometry and thermal response. This dynamic adjustment ensures uniform heat distribution across profile shapes while maintaining rapid heating rates for high productivity
3Manufacturing precision
If laser heating is used to uniformly heat specific portions, then heating precision improves, but facility cost increases and productivity decreases
Solution Approach 1:
The patent replaces expensive laser heating equipment with more cost-effective induction heating equipment. While induction heating may have slightly different heating characteristics, it achieves sufficient heating uniformity for hot stamping applications at lower facility cost and with higher productivity, making it a more economical solution
4Use of energy by moving object
If reflectance reducing treatment is applied to metal sheet surface, then radiant heat transfer efficiency increases, but additional processing steps are required
Solution Approach 1:
The patent applies reflectance reducing treatment by changing the surface color or optical properties of the metal sheet, typically through blackening or coating processes. This modification increases radiant heat transfer efficiency by reducing surface reflectance, allowing more effective absorption of thermal radiation during heating operations
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 intense, cost-effective heating of metal sheets with higher productivity, allowing for the manufacture of metal products with specific strength variations, reducing manufacturing costs and increasing design flexibility.
Implementation Method 1
heating a metal sheet by radiant heat transfer
Implementation Method 2
absorptivity for a near-infrared ray is increased at a reflectance-reduced region
Implementation Method 3
heating a metal sheet by a Joule heat by passing a current through the metal sheet
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
On part of a surface of a metal plate that is to be heated by radiant heat transfer with a near-infrared ray, a region where reflectance for a radiant ray is made lower than that of the original surface of the metal plate is formed. As reflectance reducing treatment, painting or thermal spraying in a blackish color, plating in a blackish color, treatment for increasing roughness of the surface of the metal plate, blasting, etching, blackening, surface layer quality changing treatment of the metal plate, or the like can be adopted. The metal plate is turned into a heated metal plate partially having a different temperature by being heated by radiant heat transfer, and thereafter, the heated metal plate is subjected to thermal processing accompanied by cooling, for example, by hot stamping.