Composite Rolling Roll Structure to Prevent Shrinkage Voids
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Solution Overview
Problem
Existing composite rolls for hot-finishing mills face issues with shrinkage voids at the boundary between the outer and inner layers, leading to reduced wear resistance, sticking resistance, and surface roughening resistance, which results in increased roll damage and maintenance costs.
Innovation Solution
A composite roll structure comprising a centrifugally cast outer layer of Fe-based alloy and an inner layer of ductile cast iron, with an intermediate layer of Fe-based alloy that is integrally fused to both, where the intermediate layer's composition and temperature control prevent shrinkage voids by ensuring proper bonding between layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an intermediate layer is added between the outer layer and inner layer, then bonding between layers is improved, but shrinkage voids are likely to be generated near the boundary during centrifugal casting
Solution Approach 1:
The invention changes the chemical composition parameters of the intermediate layer, specifically controlling the carbon content at 2.5-4.0% and silicon content at 1.0-3.0%, which are higher than conventional ranges. These parameter changes modify the solidification characteristics of the intermediate layer, enabling it to remain molten longer during centrifugal casting and thus prevent shrinkage void formation at layer boundaries while maintaining excellent bonding
Solution Approach 2:
The invention creates a three-layer composite structure with distinct material compositions: an outer layer with specific wear-resistant alloy composition, an intermediate layer with high carbon and silicon content for controlled solidification, and an inner layer with standard ductile cast iron composition. This composite material approach allows each layer to perform its specific function while ensuring seamless bonding without voids
2Reliability
If the outer layer is centrifugally cast with high alloy content, then wear resistance is improved, but production complexity increases due to difficult temperature control
Solution Approach 1:
The intermediate layer acts as a thermal intermediary during the centrifugal casting process. Its high carbon and silicon content gives it specific solidification characteristics that allow it to remain molten longer than the outer layer, creating a temperature buffer zone. This intermediary layer simplifies temperature control by naturally managing heat distribution and solidification sequencing, reducing the complexity of controlling the casting process for high-alloy outer layers
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 provides a composite roll with enhanced wear resistance, sticking resistance, and surface roughening resistance, preventing shrinkage voids and reducing roll damage, thereby improving operational efficiency and extending roll lifespan.
Implementation Method 1
A working roll used in such a hot strip mill comprises an outer layer coming into contact with a hot thin strip, and an inner layer integrally fused to an inner surface of the outer layer, and is produced by casting a melt for the inner layer after forming the outer layer by a centrifugal casting method.
Data Source
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Figure 3(a)~3(b)
Figure 4~5
AI summary
A composite roll for rolling having a structure comprising centrifugally cast outer and intermediate layers of an Fe-based alloy integrally fused to an inner layer of ductile cast iron; the outer layer having a composition comprising by mass 1-3% of C, 0.3-3% of Si, 0.1-3% of Mn, 0.5-5% of Ni, 1-7% of Cr, 2.2-8% of Mo, 4-7% of V, 0.005-0.15% of N, and 0.05-0.2% of B, the balance being Fe and inevitable impurities; the intermediate layer containing 0.025-0.15% by mass of B; the B content in the intermediate layer being 40-80% of that in the outer layer; and the total amount of Cr, Mo, V, Nb and W in the intermediate layer being 40-90% of that in the outer layer.