Centrifugal Cast Roll Outer Layer Material Fatigue Resistance
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Solution Overview
Problem
The harsher usage environment and increased productivity in hot rolling processes lead to surface deterioration and chipping of rolls, which existing technologies fail to adequately address, particularly in terms of fatigue resistance.
Innovation Solution
A cast-iron roll outer layer material with specific chemical composition and carbide morphology, containing small-size carbides (3-30 μm) and limited large-size carbides (≤20 pieces/mm²), and a composite roll with an outer layer formed through centrifugal casting, where Cr, Mo, and V contents satisfy a specific ratio to enhance fatigue resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high speed steel with V addition is used to increase abrasion resistance, then abrasion resistance is improved, but fatigue resistance deteriorates due to surface deterioration and chipping scars
Solution Approach 1:
The invention changes the chemical composition parameters by strictly controlling C content to 2.0-3.0% and V content to 3.0-10.0%, and controlling the ratio of V/(C-0.15Nb) to be 3.0-15.0. This parameter optimization ensures sufficient carbide formation for abrasion resistance while preventing excessive carbide growth that would cause surface deterioration and chipping, thus improving fatigue resistance
Solution Approach 2:
The invention creates a composite microstructure consisting of hard carbides dispersed in a steel matrix, where the carbide morphology and distribution are controlled through specific composition ratios. The composite structure provides both abrasion resistance from the hard carbides and fatigue resistance from the controlled carbide size and distribution, preventing surface deterioration
2Strength
If Nb and V are added to inhibit carbide segregation, then abrasion resistance and crack resistance are improved, but fatigue resistance still deteriorates under harsh usage conditions
Solution Approach 1:
The invention optimizes the parameters by controlling Nb content to 0.50-7.00% and V content to 3.0-10.0%, and crucially controlling the ratio of V/(C-0.15Nb) to be 3.0-15.0. This ratio control ensures that V provides sufficient carbide hardness for abrasion resistance while the Nb and controlled ratio prevent excessive carbide growth, thereby improving fatigue resistance under harsh conditions
Solution Approach 2:
The invention achieves local quality control by ensuring uniform distribution of carbides throughout the roll outer layer material through controlled composition. The carbides are evenly dispersed rather than segregated, providing consistent local properties that resist both abrasion and fatigue damage across the entire rolling surface
3Productivity
If centrifugal casting method is used to produce composite roll, then production efficiency is improved, but surface deterioration and chipping still occur due to carbide segregation
Solution Approach 1:
The invention changes the composition parameters to be compatible with centrifugal casting by controlling C to 2.0-3.0%, Nb to 0.50-7.00%, V to 3.0-10.0%, and the ratio V/(C-0.15Nb) to 3.0-15.0. These parameters ensure that during centrifugal casting, carbides form uniformly without severe segregation, maintaining both production efficiency and fatigue resistance
Solution Approach 2:
The invention achieves homogeneity in carbide distribution throughout the roll outer layer material produced by centrifugal casting. The controlled composition parameters ensure uniform mixing and distribution of alloying elements, preventing carbide segregation and creating a homogeneous microstructure that resists surface deterioration and chipping while maintaining high production efficiency
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 fatigue resistance of roll surfaces, leading to improved surface quality and extended roll life, even under high rolling loads and continuous rolling conditions.
Implementation Method 1
a composite roll produced through centrifugal casting method
Data Source
AI summary
A roll outer layer material contains small-size carbides having a circle equivalent diameter of 3 to 30 μm in a number of 500 to 2500 pieces/mm2 and large-size carbides having a circle equivalent diameter of 50 μm or more in a number of 20 pieces/mm2 or less, preferably having a chemical composition containing, by mass %, C: 2.4% or more and 2.9% or less, Si: 0.2% or more and 1.0% or less, Mn: 0.2% or more and 1.0% or less, Cr: 4.0% or more and 7.5% or less, Mo: 4.0% or more and 6.5% or less, V: 5.3% or more and 7.0% or less, Nb: 0.5% or more and 3.0% or less, and the balance being Fe and inevitable impurities, in which the contents of Cr, Mo, and V satisfy the relationship 1.5≦(Cr+Mo)/V≦2.4.