Induction Heating Coated Steel Sheet Process
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Solution Overview
Problem
Current coating processes for steel sheets face issues such as uneven coatings, flash rust, and the challenge of achieving both high punchability and weldability, particularly in nonoriented electromagnetic steel sheets, while also dealing with resin adhesion to roll coaters and the limitations of existing heating methods.
Innovation Solution
A process involving a water-based coating liquid with an organic resin applied to a steel sheet, where the liquid is dried quickly to 100°C and then baked, using induction heating to prevent unevenness and flash rust, and ensuring the resin is heated on the side close to the steel sheet to enhance weldability and prevent adhesion to the roll coater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed coating process is implemented, then productivity is improved, but coating uniformity deteriorates due to rapid heating causing uneven coatings
Solution Approach 1:
The heating process is divided into two distinct stages: a drying stage at lower temperature (100-150°C) to remove moisture, and a baking stage at higher temperature (200-400°C) to cure the coating. This segmentation allows each stage to be optimized independently, preventing the coating uniformity deterioration that occurs when rapid heating is applied throughout the entire process.
Solution Approach 2:
The drying stage is performed as a preliminary action before the baking stage. By removing moisture from the coating first at a controlled lower temperature, the coating structure is prepared to withstand the subsequent rapid heating during baking without forming uneven coatings or defects.
2Speed
If radiation heating is used for rapid drying, then drying speed is improved, but moisture removal is insufficient causing appearance defects and poor film properties
Solution Approach 1:
The patent introduces an intermediary heating stage (the drying stage) that acts as a mediator between the initial coating application and the final high-temperature baking. This intermediate stage at 100-150°C provides the necessary conditions for complete moisture removal through controlled heating, which radiation heating alone cannot achieve without causing surface defects.
3Ease of manufacture
If conventional heating methods are used, then equipment cost is reduced, but heating speed is limited preventing high-speed coating operations
Solution Approach 1:
The patent merges conventional heating methods with high-frequency induction heating to create a hybrid system. The conventional heating provides cost-effectiveness and reliability, while the induction heating component delivers the rapid heating capability needed for high-speed coating operations, achieving both affordability and high performance.
4Area of stationary object
If vertical coating lines are used to reduce line length, then space occupation is reduced, but coating unevenness worsens due to gravity affecting coating application
Solution Approach 1:
The patent changes the temperature parameter during the drying stage to 100-150°C, which optimizes the viscosity and flow characteristics of the coating. This parameter change compensates for the gravitational effects in vertical coating lines, allowing the coating to level properly and achieve uniform appearance despite the vertical orientation.
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 process achieves high-speed baking without coating unevenness, prevents resin adhesion to roll coaters, and ensures excellent film properties, including improved punchability and weldability, even after temper-rolling, while maintaining a satisfactory appearance.
Implementation Method 1
a drying step of drying the applied liquid to form a coating layer in a manner in which the applied liquid is heated on the side close to the steel sheet
Implementation Method 2
the time elapsed until the temperature of the steel sheet is increased to 100° C. after the application is completed is 10 seconds or less
Implementation Method 3
a baking step of heating the dry coating layer to a predetermined temperature to bake the coating layer and form a coating film
Data Source
AI summary
In a process for manufacturing a coated steel sheet such as a coated electromagnetic steel sheet using a water-based coating liquid containing an organic resin, to perform steps subsequent to an annealing step continuously at high speed without causing appearance defects such as coating unevenness; to provide an electromagnetic steel sheet having an insulating film thereon, in which properties of the film are satisfactory, superior weldability and punchability can be obtained without deteriorating the space factor, and the satisfactory film properties can be maintained even if the electromagnetic steel sheet having the insulating film thereon is temper-rolled. A coating liquid is applied onto an untreated steel sheet. The applied liquid is heated on the side close to the steel sheet in such a manner that the time elapsed until the steel sheet temperature is increased to 100° C. after the application is completed is 10 seconds or less, thereby drying the coating liquid. The steel sheet temperature is further increased to a predetermined temperature, thereby forming a coating film. When insulating films for electromagnetic steel sheets are formed, the coating liquid preferably further contains a water based inorganic component.