Composite Rolling Roll Structure for Wear-Resistant Shaft Portions
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Solution Overview
Problem
Centrifugally cast composite rolls experience premature damage and reduced lifespan due to wear and surface roughening, particularly in the shaft portions, leading to frequent grinding and reduced productivity.
Innovation Solution
The composite roll design incorporates an outer layer made of an Fe-based alloy with specific chemical composition and an inner layer of graphite cast iron, where hard MC carbides are transferred to the shaft portions without adding carbide-forming elements, enhancing wear resistance without compromising toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbide-forming elements such as V are added to the inner layer melt to improve wear resistance of shaft portions, then wear resistance is improved, but graphitization is hindered and toughness is reduced
Solution Approach 1:
The invention extracts carbide-forming elements (Cr, Mo, V) from the inner layer composition and concentrates them in the outer layer instead. The outer layer contains 3.0-10.0% Cr, 2.0-10.0% Mo, and 5.8-10.0% V, while the inner layer contains significantly less of these elements, allowing the inner layer to maintain graphitization and toughness while the outer layer provides wear resistance.
Solution Approach 2:
The invention applies different material compositions to different parts of the composite roll. The outer layer is designed with high carbide-forming element content for wear resistance, while the inner layer is designed with low carbide-forming element content for toughness and graphitization, creating local optimization of properties for each region's functional requirements.
2Productivity
If the outer layer is made more wear-resistant to extend roll life, then productivity is improved, but the shaft portions become more susceptible to damage
Solution Approach 1:
The invention divides the roll into functionally distinct segments: an outer layer optimized for wear resistance with high Cr, Mo, and V content, and an inner layer optimized for toughness and shaft portion durability with low carbide-forming element content. This segmentation allows each part to perform its specific function optimally without compromising the other.
Solution Approach 2:
The invention creates a composite roll structure where the outer layer and inner layer are made of different materials with complementary properties. The outer layer uses an Fe-based alloy with high carbide-forming element content for wear resistance, while the inner layer uses ductile cast iron with low carbide-forming element content for toughness, combining the advantages of both material systems.
3Manufacturing precision
If frequent grinding is performed to remove damages from the outer layer, then surface quality is maintained, but productivity is reduced and usable roll diameter is reduced
Solution Approach 1:
The invention performs preliminary action by designing the outer layer with inherently high wear resistance through optimized composition (3.0-10.0% Cr, 2.0-10.0% Mo, 5.8-10.0% V) before the roll is put into service. This preliminary optimization of material properties reduces the frequency and extent of grinding operations needed during the roll's service life, thereby maintaining productivity.
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
This design significantly improves the wear resistance and lifespan of the shaft portions, reducing the need for frequent grinding and lowering rolling costs by extending the roll's usable life.
Implementation Method 1
a centrifugally cast composite roll in which a centrifugally cast outer layer of a wear-resistant iron-based alloy is integrally fused to a tough inner layer of ductile cast iron
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4
AI summary
A composite roll for rolling comprising an outer layer and an inner layer integrally fused to each other; the outer layer being made of an Fe-based alloy comprising by mass 1-3% of C, 0.3-3% of Si, 0.1-3% of Mn, 0.1-5% of Ni, 1-7% of Cr, 1-8% of Mo, 5-10% of V, 0.005-0.15% of N, and 0% or more and less than 0.05% of B; the inner layer being made of graphite cast iron comprising by mass 2.4-3.6% of C, 1.5-3.5% of Si, 0.1-2% of Mn, 0.1-2% of Ni, less than 0.7% of Cr, less than 0.5% of Mo, 0.05-1% of V, and 0.01-0.1% of Mg; the inner layer having a core portion fused to the outer layer, and shaft portions integrally extending from both ends of the core portion; and at least one of shaft portions containing 200/cm2 or more of hard MC carbides having equivalent circle diameters of 5 µm or more.