Hot-Dip Coating Roller with Ceramic Plug and Plain Bearing
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Solution Overview
Problem
Existing hot-dip coating rollers experience high wear and short service life due to high bearing forces and aggressive molten metal, leading to coating defects and reduced quality, especially when coating thin metal strips.
Innovation Solution
The roller features coaxially arranged bearing journals with annular elevations coated with a plain bearing coating, forming a hydrodynamic lubricating cushion and a multi-material design with a gas-permeable plug element to prevent internal pressure and material removal, enhancing wear resistance and coating quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solid material rollers are used for hot-dip coating, then the rollers provide structural strength and stability, but the high weight makes it difficult for thin strips to rotate the rolls, causing relative movements (slip) between the strip and roll which lead to scratches and coating defects
Solution Approach 1:
The roller is divided into a hollow cylindrical shell structure rather than a solid material construction. This segmentation allows the roller to maintain structural strength through the shell while significantly reducing the overall weight, enabling thin metal strips to easily rotate the roller without causing slip or coating defects.
Solution Approach 2:
The roller employs a hollow cylindrical shell structure that provides the necessary structural strength while being lightweight. The shell design allows the roller to be rotated easily by thin metal strips without the high weight burden of solid material rollers, preventing relative movements and coating defects.
2Ease of operation
If jacket rollers with openings on end faces are used, then the rollers can be turned more easily compared to solid material rolls, but a pumping effect occurs when the jacket rollers rotate, resulting in a turbulent flow of molten metal in the area of the spoke-like webs or recesses, which leads to very significant material removal (wear)
Solution Approach 1:
The harmful spoke-like webs or recesses that cause turbulent flow and material removal are completely removed from the roller design. The roller consists of a smooth hollow cylindrical shell without internal structural elements that would disrupt the molten metal flow, eliminating the pumping effect and associated wear.
Solution Approach 2:
The roller is designed as a smooth hollow cylindrical shell without spoke-like webs or recesses. This streamlined shell structure eliminates the turbulent flow and pumping effect that occur in traditional jacket rollers, preventing significant material removal from the molten metal while maintaining rotational ease.
3Device complexity
If plain bearings are used for pivot bearings in rollers, then the structure is simple, but the bearing journals are subjected to very high levels of wear due to high bearing forces and the aggressiveness of the molten metal
Solution Approach 1:
The bearing journals are constructed using composite materials with a steel base structure providing mechanical strength and a ceramic coating layer providing exceptional wear resistance against the aggressive molten metal. This composite structure maintains the simplicity of plain bearings while dramatically improving reliability and service life in the harsh hot-dip coating environment.
Solution Approach 2:
The bearing journals undergo parameter changes through the application of a ceramic coating that fundamentally alters the surface properties. The coating changes the material parameters to provide high hardness and chemical inertness, enabling the plain bearings to resist wear from the aggressive molten metal while maintaining structural simplicity.
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 significantly increases the service life of the rollers by reducing wear and ensuring high coating quality, particularly for thin metal strips, with improved rotational properties and reduced material loss.
Implementation Method 1
a sliding film of the metallic hot-dip coating material, which can be, for example, aluminum or a coating material based on zinc or aluminum, forms in the indentations between the annular elevations. In this way, in particular, a hydrodynamic lubricating cushion is formed during operation, which leads to a reduction in the stress on the supporting surfaces of the pivot bearing.
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
The invention relates to a roller (5, 6) for deflecting or guiding a metal strip, which is to be coated, in a metal melt bath, comprising bearing journals (9) arranged coaxially to each other for rotationally supporting the roller (5, 6). In order to achieve high coating quality by means of such a roller in the hot-dip coating of metal strip, in particular steel strip, and to increase the service life of such a roller, each bearing journal (9), according to the invention, has a plurality of annular elevations (9.5; 12.1), which are axially spaced apart from each other and which have a plain-bearing coating (12) or are composed of a plain-bearing coating. The roller (5, 6) preferably has a roller shell (8) composed of steel, wherein a substantially cylindrical or circular-disk-shaped connecting segment (9.1) composed of steel is provided on each bearing journal (9), which connecting segment extends radially toward the roller shell (8), wherein at least one of the connecting segments (9.1) has at least one passage opening (9.3) leading to an end face of the roller shell (8), and wherein the at least one passage opening (9.3) is closed by means of a gas-permeable plug element (10) composed of ceramic material.