Electromagnetic Molten Metal Coating Apparatus for Uniform Zinc Layers
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Solution Overview
Problem
Conventional molten metal coating methods, such as gas wiping and spray coating, face issues like splashing, dross formation, and uneven coating thickness, which affect the quality of the coated surface and throughput in continuous hot-dip galvanizing processes.
Innovation Solution
An apparatus utilizing an electromagnetic force (Lorentz force) to discharge molten metal droplets onto a metal strip, featuring a nozzle system with a magnetic flux generation mechanism and current generation mechanism, operating within a non-oxidizing atmosphere to ensure uniform coating and prevent splashing and dross formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gas wiping method is used to control coating weight, then coating thickness can be controlled, but splashing occurs and coated surface has defective appearance
Solution Approach 1:
The patent replaces the conventional gas wiping method (pneumatic system) with an electromagnetic braking system. Electromagnetic coils generate a magnetic field that interacts with the conductive molten zinc coating on the steel strip, creating an electromagnetic force that opposes the motion of the strip and controls its speed through the zinc bath. This eliminates the need for high-velocity gas jets that cause splashing, while achieving precise control of coating weight through speed regulation.
Solution Approach 2:
The patent changes the control parameter from gas flow rate (in conventional method) to electromagnetic force intensity (in this invention). By adjusting the current supplied to the electromagnetic coils, the magnetic field strength is varied, which directly controls the braking force and thus the strip speed through the zinc bath. This parameter change enables precise coating weight control without the splashing problems associated with gas flow rate adjustment.
2Manufacturing precision
If impinging pressure of gas is increased to obtain thin coatings, then coating thickness is reduced, but splashing increases and surface quality deteriorates
Solution Approach 1:
The patent substitutes the gas impinging mechanism with an electromagnetic braking mechanism. Instead of using high-pressure gas to control strip speed and coating thickness, electromagnetic coils generate a magnetic field that exerts a controllable force on the conductive zinc coating, regulating strip velocity through the bath. This eliminates gas-induced splashing entirely while maintaining the ability to achieve thin, uniform coatings through precise speed control.
3Ease of manufacture
If zinc bath is in contact with atmospheric air, then dross forms on bath surface, but dross adheres to steel strip causing defective appearance
Solution Approach 1:
The patent introduces an inert or reducing atmosphere (such as nitrogen or hydrogen) over the zinc bath surface to prevent oxidation of the molten zinc. This atmospheric modification eliminates dross formation by excluding oxygen from contact with the zinc bath, thereby preventing the creation of oxidized zinc particles that would otherwise adhere to the coated steel strip and cause surface defects.
4Manufacturing precision
If distance between nozzle and steel strip is reduced to achieve thin coatings, then coating thickness decreases, but strip warp and vibration make it difficult to maintain distance
Solution Approach 1:
The patent replaces the mechanical nozzle-to-strip distance control system with an electromagnetic control system. Instead of relying on precise mechanical positioning of nozzles relative to the moving strip (which is compromised by strip warp and vibration), electromagnetic coils sense the position and speed of the strip and adjust the braking force accordingly. This substitution enables stable, thin coating application without the need for rigid mechanical distance maintenance.
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 achieves high-quality, uniform molten metal coatings by avoiding the defects inherent in conventional immersion and spray coating processes, ensuring a consistent coating thickness and improved throughput with reduced dross formation.
Implementation Method 1
a current generation mechanism configured to send an electric current, in a direction perpendicular to the given direction, to the molten metal positioned in the at least a part of the chamber where the magnetic flux is applied, wherein the nozzle system discharges a droplet of the molten metal from the discharge port toward the surface of the metal strip due to an action of the Lorentz force
Implementation Method 2
a magnetic flux generation mechanism configured to generate magnetic flux in a given direction in at least a part of the chamber
Data Source
AI summary
The disclosure provides a fully new method for molten metal coating treatment coating treatment, as a method for treating surfaces of a metal strip by molten metal coating, by which inherent issues in conventional immersion coatings and spray coatings are avoided. In the disclosed method for molten metal coating treatment, a surface of a metal strip is coated by discharging a droplet of a molten metal toward the surface of the metal strip, using a nozzle system configured to discharge the droplet of the molten metal from a nozzle due to an action of the Lorentz force generated on the molten metal by sending an electric current to the molten metal in a chamber, the chamber being applied with magnetic flux in a given direction, while the electric current sent in a direction perpendicular to the given direction.