Hearth Roll Coating Laser Modification for Build-up Resistance
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Solution Overview
Problem
In metal sheet production facilities, particularly in steelmaking processes, hearth rolls experience build-up and fouling due to contaminating objects like iron or manganese oxide, leading to quality deterioration and reduced productivity, despite existing thermally sprayed coatings which do not sufficiently suppress these issues.
Innovation Solution
A hearth roll with a thermally sprayed coating modified by irradiating its surface with an energy beam to form a denser, harder modified coating with specific thickness and Vickers hardness, reducing the attachment of contaminants and enhancing build-up resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermally sprayed coating is applied on hearth rolls, then the build-up resistance is improved, but the attachment of contaminating objects is not sufficiently suppressed
Solution Approach 1:
The invention applies laser irradiation to change the physical and chemical parameters of the thermally sprayed coating surface, transforming it into a modified coating with enhanced properties. The laser energy modifies the surface structure, composition, and morphology, creating a denser, harder surface that effectively suppresses contaminant attachment while maintaining build-up resistance
Solution Approach 2:
The invention replaces conventional mechanical or chemical surface treatment methods with laser irradiation. The laser beam provides precise, controlled energy input that modifies the coating surface without mechanical contact, achieving superior surface properties that prevent contaminant attachment more effectively than traditional methods
2Object-affected harmful factors
If the thickness of modified coating is increased to suppress contaminant attachment, then the build-up resistance improves, but the manufacturing complexity increases
Solution Approach 1:
The laser irradiation process enables precise control of the modified coating thickness through parameter optimization (laser power, scanning speed, number of passes). This achieves the required thickness range (2-20 μm) with consistent quality without requiring complex multi-layer coating structures or additional processing steps
Solution Approach 2:
The laser modification is applied after the thermally sprayed coating is already in place, creating a surface-modified layer without requiring preliminary preparation of the base coating. This sequential approach simplifies the overall manufacturing process while achieving the desired contaminant attachment suppression
3Object-affected harmful factors
If the Vickers hardness of the coating is increased to prevent contaminant attachment, then the build-up resistance improves, but the manufacturing precision requirements increase
Solution Approach 1:
The laser irradiation process provides precise control over the modified coating hardness (achieving 1.2-1.4 times the original coating hardness) through controlled energy input. The laser parameters (power, speed, pattern) can be precisely adjusted to achieve the target hardness range, ensuring consistent contaminant attachment suppression without excessive hardness that could cause brittleness
Solution Approach 2:
Laser irradiation replaces conventional mechanical hardening methods (such as shot peening or mechanical polishing) that are difficult to control precisely. The laser provides non-contact, uniformly distributed energy that achieves consistent hardness enhancement across the entire coating surface with high manufacturing precision
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 modified coating effectively suppresses the attachment of contaminants, preventing build-up and transferred defects on steel sheets, improving steel sheet quality and extending the hearth roll's lifespan, while reducing maintenance needs and increasing production efficiency.
Implementation Method 1
modifying a part or the whole of a surface of the thermally sprayed coating by melting and solidification of the thermally sprayed coating, by irradiating a part or the whole of the surface of the thermally sprayed coating with an energy beam
Implementation Method 2
modifying a part or the whole of a surface of the thermally sprayed coating by melting and solidification of the thermally sprayed coating
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A hearth roll includes a base roll, a thermally sprayed coating formed on the base roll, and a modified coating formed on the thermally sprayed coating. The modified coating is formed by modifying a part or the whole of a surface of the thermally sprayed coating by melting and solidification of the thermally sprayed coating, by irradiating a part or the whole of the surface of the thermally sprayed coating with an energy beam. The thickness of the modified coating is from 2 to 20 µm, and the Vickers hardness HV of the modified coating is from 1.2 to 1.4 times larger than the Vickers hardness HV of the thermally sprayed coating.