Hot-Dip Coating Sheath Layout to Prevent Metal Strip Splash Defects
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Solution Overview
Problem
Existing continuous dipping coating installations for metal strips result in unsatisfactory coating quality due to liquid metal projection onto the side of the belt opposite the bottom roller, leading to high defect density on one face of the strip.
Innovation Solution
A coating installation with a sheath design featuring two discharge compartments and a rotating mechanism that adjusts the position and orientation of discharge compartments relative to the metal strip, ensuring a controlled flow of liquid metal and minimizing splashing, combined with a sealing system to maintain a clean liquid joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the sheath is immersed in the liquid metal bath to create a liquid seal, then the liquid seal cleans impurities from the coating, but liquid metal is projected onto the side of the belt opposite the bottom roller causing defects
Solution Approach 1:
The sheath is divided into multiple discharge compartments (first discharge compartment and second discharge compartment) with separate liquid metal discharge paths. This segmentation allows independent control of liquid metal flow from each compartment, preventing uncontrolled projection onto the belt while maintaining effective impurity removal from the coating surface.
Solution Approach 2:
The sheath is made rotatable around its longitudinal axis, transforming it from a static to a dynamic structure. This rotation enables active control of the liquid metal discharge direction, allowing the system to prevent liquid metal from projecting onto the belt side while maintaining effective coating cleaning, thereby resolving the contradiction between coating quality and harmful liquid metal projection.
2Device complexity
If the sheath structure is simplified with parallel outer walls, then the device complexity is reduced, but coating quality deteriorates due to liquid metal projection defects
Solution Approach 1:
The sheath incorporates segmented discharge compartments with separate discharge paths for liquid metal. This segmentation adds functional complexity that prevents liquid metal projection onto the belt while maintaining reasonable overall structural simplicity, resolving the contradiction between device complexity and coating quality.
Solution Approach 2:
The rotatable sheath design adds dynamic capability without significantly complicating the basic parallel wall structure. The rotation mechanism enables precise control of liquid metal discharge direction, improving coating quality while keeping the structural complexity manageable through a relatively simple rotational joint design.
3Reliability
If the discharge compartments are positioned to clean the liquid seal, then impurity removal is improved, but liquid metal splashes onto the belt causing high defect density
Solution Approach 1:
The discharge compartments are segmented into separate first and second compartments with independent discharge paths positioned at different locations. This segmentation allows liquid metal to be discharged and impurities to be removed from the liquid seal while the separated paths prevent splashing onto the belt, simultaneously improving liquid seal cleanliness and reducing coating defect density.
Solution Approach 2:
The rotatable sheath dynamically adjusts the position and orientation of the discharge compartments during operation. This dynamic positioning ensures that liquid metal discharge occurs in controlled directions that maintain liquid seal cleanliness while preventing splashes from reaching the belt, thereby improving both reliability of impurity removal and manufacturing precision of coating quality.
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 solution achieves low defect density on both faces of the coated strip, maintaining coating quality by preventing liquid metal splashing and ensuring consistent flow control, even with changes in the bottom roller's characteristics or position.
Implementation Method 1
liquid metal from the bath is discharged from the liquid seal to clean the liquid seal of impurities
Data Source
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AI summary
The invention relates to an apparatus for the continuous dip coating of a metal strip (1), comprising a vessel for containing a molten metal bath (12), a bottom roller and a duct (13) in which the metal strip (1) travels. At its lower end, the duct (13) bears an overflow container (49) delimiting a front molten metal overflow compartment (25) and a rear molten metal overflow compartment (29), each overflow compartment (25, 29) being delimited internally by an inner wall (20, 26) and externally by an outer wall (22, 28). The outer wall (28) of the rear overflow compartment (29) forms, along with the plane of travel of the metal strip (1), an angle (a) of at least 15° in the operational configuration.