Vertical Strip Coating Airlocks for Vapor Isolation and Drying
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Solution Overview
Problem
The existing methods for coating continuously moving metal strips, particularly electrical steel sheets with insulating varnish, face issues such as incomplete drying leading to sticking or adhesion problems and the risk of explosions and pollution due to solvent-based coatings, especially when using upward pass coating techniques.
Innovation Solution
A method and installation for coating a continuously moving steel strip in a descending vertical strand, utilizing aeraulic/aerodynamic airlocks to isolate the cooking unit and prevent contamination, with continuous extraction and reprocessing of residual vapors, and injecting hot gas to prevent condensation, ensuring the coating is not in contact with mechanical parts until it reaches ambient temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the steel strip is cooled rapidly after the curing unit, then the coating can be handled sooner, but the coating may condense or stick due to premature cooling
Solution Approach 1:
A water cooling unit is introduced as an intermediary between the curing unit and the accumulator. This water cooling unit provides controlled cooling through water spray or immersion, preventing premature condensation while achieving cooling faster than air cooling. The water cooling unit acts as a mediator that balances the need for rapid cooling with the requirement to maintain coating integrity during the cooling process.
2Reliability
If an air cooling section is inserted between the induction furnace and the upper roller, then the coating is protected from damage, but the installation height and cooling length increase significantly
Solution Approach 1:
The patent replaces the mechanical air cooling system with a water-based cooling system. Instead of using large volumes of air to cool the strip (which requires significant space and height), water spray or water immersion is used. Water has much higher specific heat capacity and heat transfer coefficient than air, enabling rapid cooling in a compact space, thus eliminating the need for tall installation structures while still protectinging the coating.
3Speed
If water cooling is used instead of air cooling, then the cooling efficiency increases, but solvent condensation and water contamination occur
Solution Approach 1:
The curing unit is designed to complete the drying and curing of the coating before the strip enters the water cooling unit. The curing unit operates at elevated temperatures to evaporate solvents and set the coating. By ensuring the coating is fully cured before water cooling begins, preliminary action prevents solvent condensation during the subsequent water cooling process. The system sequence is carefully arranged: curing first, then water cooling, to avoid contamination.
4Reliability
If the coating is not fully cured before reaching the upper roller, then adhesion problems occur, but extending the curing process increases energy consumption and production time
Solution Approach 1:
The curing unit utilizes phase transition (evaporation) of solvents at elevated temperatures to complete the curing process. By maintaining the strip at high temperature in the curing unit, solvents evaporate and the coating sets. The water cooling unit then rapidly removes this heat, bringing the strip to handling temperature. This phase transition-based curing ensures complete adhesion while the rapid water cooling minimizes the time the strip remains at high temperature, thus balancing quality with productivity.
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 prevents damage to the coating, reduces the risk of explosions and pollution, and maintains coating quality by ensuring complete drying before mechanical contact, while also allowing for efficient solvent management and safe operation.
Implementation Method 1
The strip is then cooled with water to prevent solvent condensation
Implementation Method 2
dry or bake the coating of the coated steel strip by passing it through a baking unit comprising at least one oven up to a temperature of at least 100°C
Implementation Method 3
The insulating varnish is therefore cured in two stages: first on this line and then at the motor manufacturer's facility
Implementation Method 4
a system of two air/aerodynamic airlocks, located respectively at the inlet and outlet of the curing unit to create a dynamic pressure on the belt and prevent contamination
Data Source
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AI summary
The present invention relates to a method of coating a substrate in the form of a steel strip with a liquid, in continuous flow at least partly in a vertical strand, comprising a step of at least partial isolation of the baking unit (3) by a system of two aerodynamic/airlocks (21, 22), located respectively at the inlet and outlet of the baking unit (3) to create a dynamic pressure on the strip and prevent contamination of the coating unit (4) by residual vapors emanating from the baking unit (3).