Hot Rolling Roll Lower Cladding Hardness
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Solution Overview
Problem
The existing lower cladding layers in hot-rolling factory rolls have a Shore hardness less than 60, leading to denting and cracking when the overlying self-fluxing alloy thermally-sprayed layer is fused multiple times, resulting in decreased hardness and reduced durability.
Innovation Solution
A lower cladding layer with a Shore hardness of 60 or more is achieved by forming an Fe-based cladding layer with specific compositions, including 0.4 to 1.0 mass % C, 2.0 mass % or less Si, 3.0 mass % or less Mn, 1.0 to 15.0 mass % Cr, and 0.5 to 5.0 mass % Nb, and optionally containing Mo, V, Co, W, and Ti, which enhances mechanical strength and resistance to thermal fusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the lower cladding layer uses conventional compositions (as in Patent Literatures 1-3), then the manufacturing cost and complexity are controlled, but the Shore hardness remains below 60, causing the overlying self-fluxing alloy layer to dent and crack during threading operations
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the lower cladding layer. Specifically, it increases carbon content to 0.20-1.00 mass%, adds niobium (0.05-5.00 mass%), and adjusts chromium (1.00-15.00 mass%), manganese (0.10-3.00 mass%), and silicon (0.10-2.00 mass%) contents. These compositional parameter changes enable the lower cladding layer to achieve Shore hardness of 60 or more, preventing denting and cracking of the overlying self-fluxing alloy layer during multiple fusing operations and threading processes.
Solution Approach 2:
The patent employs composite materials by creating a multi-layered structure consisting of a lower cladding layer with specific high-hardness composition and an overlying self-fluxing alloy layer containing carbide particles. The lower cladding layer itself is a composite of multiple alloying elements (C, Si, Mn, Cr, Nb, and optional Mo, V, Co, W, Ti) that work synergistically to achieve the required Shore hardness of 60 or more while maintaining structural integrity under thermal and mechanical stresses.
2Reliability
If the overlying self-fluxing alloy layer is fused multiple times to improve coating quality, then the coating integrity is enhanced, but the hardness of the lower cladding layer decreases significantly when using conventional compositions
Solution Approach 1:
The patent applies preliminary action by pre-configuring the lower cladding layer with a specific high-hardness composition (0.20-1.00 mass% C, 0.05-5.00 mass% Nb, 1.00-15.00 mass% Cr, 0.10-3.00 mass% Mn, 0.10-2.00 mass% Si, and optional Mo, V, Co, W, Ti) before the thermal spraying and fusing processes. This preliminary compositional preparation ensures that the lower cladding layer maintains Shore hardness of 60 or more even after multiple fusing operations, providing a stable foundation that prevents hardness degradation while allowing the overlying self-fluxing alloy layer to be fused multiple times for improved coating integrity.
3Duration of action of stationary object
If the lower cladding layer hardness is increased to prevent denting and cracking, then the durability during threading is improved, but the resistance to thermal softening during multiple fusing operations may be compromised
Solution Approach 1:
The patent applies parameter changes by carefully balancing multiple compositional parameters to achieve both high initial hardness and thermal stability. The carbon content is set to 0.20-1.00 mass% for high hardness, niobium is added at 0.05-5.00 mass% to form hard carbides that resist thermal softening, chromium is optimized at 1.00-15.00 mass% for solid solution strengthening and oxidation resistance, and manganese (0.10-3.00 mass%) and silicon (0.10-2.00 mass%) are adjusted to control hardenability and prevent excessive carbide formation. This balanced compositional approach ensures the lower cladding layer maintains Shore hardness of 60 or more after multiple fusing operations, achieving both durability during threading and resistance to thermal softening.
Solution Approach 2:
The patent employs composite materials by creating a lower cladding layer that is itself a composite of multiple alloying elements working synergistically. The combination of carbon, niobium, chromium, manganese, silicon, and optional Mo, V, Co, W, Ti creates a complex microstructure with various strengthening mechanisms (solid solution strengthening, precipitation hardening, grain boundary strengthening) that operate differently under thermal and mechanical stresses. This composite structure allows the material to maintain high hardness and resist thermal softening during multiple fusing operations while providing the durability needed for threading applications.
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 maintains a Shore hardness of 60 or more even after multiple fusions, preventing denting and cracking of the overlying self-fluxing alloy thermally-sprayed layer, thus ensuring the rolls' durability and performance in high-carbon material and high-tensile strength steel plate applications.
Implementation Method 1
a self-fluxing alloy layer formed on the lower cladding layer by thermal spraying
Data Source
AI summary
A roll for winding equipment in a hot rolling factory is obtained by forming a base build-up layer on the surface of the body of the roll and forming on the base build-up layer a self-fluxing alloy thermal spraying layer, in which carbide particles are dispersed. The base build-up layer has a Shore hardness of 60 or higher and includes an iron-based build-up layer that contains, in terms of mass %, 0.4-1.0% of C, 2.0% or less of Si, 3.0% or less of Mn, 1.0-15.0% of Cr and 0.5-5.0% of Nb.