Composite Hot Rolling Roll Surface Layer Material
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Solution Overview
Problem
Conventional hot rolling mill rolls face challenges in simultaneously achieving wear resistance, heat shock resistance, and surface deterioration resistance, particularly in severe usage environments with increased rolling speeds and material quantities, where cobble and sticking issues are prevalent.
Innovation Solution
A composite roll surface layer material is developed by optimizing the chemical composition of nickel grain cast iron with specific ranges of C, Si, Mn, Cr, Mo, V, Nb, REM, Al, and B, controlling the REM/Al ratio, and using a centrifugal casting method to integrate a surface layer with an inner layer, enhancing wear resistance, heat shock resistance, and surface deterioration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nickel grain cast iron roll is used to achieve heat shock resistance and smooth surface, then heat shock resistance is improved, but wear resistance deteriorates
Solution Approach 1:
The invention uses composite materials by combining nickel grain cast iron with high-speed tool steel surface layer. The surface layer contains hard carbide precipitates (MC type carbides) in a martensitic matrix, providing high wear resistance, while the nickel grain cast iron substrate provides heat shock resistance and smooth surface. This composite structure resolves the contradiction between wear resistance and heat shock resistance.
Solution Approach 2:
The invention applies local quality by creating a surface layer with specific chemical composition (similar to high-speed tool steel) and microstructure (martensite with MC type carbides) only on the outer surface of the roll. The surface layer thickness is controlled at 5-20mm, providing localized wear resistance where needed, while the inner nickel grain cast iron provides heat shock resistance.
2Strength
If high-speed steel roll is used to achieve high wear resistance, then wear resistance is improved, but heat shock resistance deteriorates
Solution Approach 1:
The invention uses composite materials by combining nickel grain cast iron with high-speed tool steel surface layer. The surface layer contains hard carbide precipitates (MC type carbides) in a martensitic matrix, providing high wear resistance, while the nickel grain cast iron substrate provides heat shock resistance and smooth surface. This composite structure resolves the contradiction between wear resistance and heat shock resistance.
3Strength
If V and Nb are added to increase wear resistance, then wear resistance is improved, but surface deterioration resistance deteriorates
Solution Approach 1:
The invention applies parameter changes by precisely controlling the chemical composition parameters: V content at 1.0-5.0 wt.%, Nb content at 0.5-2.0 wt.%, Cr content at 1.0-3.0 wt.%, and effective C content at 0.5-2.5 wt.%. These parameter optimizations ensure that MC type carbides form with appropriate size and distribution, providing wear resistance while preventing surface deterioration through proper carbide morphology control.
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 optimized composite roll exhibits excellent wear resistance, heat shock resistance, and surface deterioration resistance, enabling stable operation in high-stress rolling conditions and extended roll life, while maintaining cost-effectiveness and suitable for both steel sheet and steel pipe applications.
Implementation Method 1
using a centrifugal casting method to integrate a surface layer with an inner layer
Data Source
Figure 1~2
Figure 3
AI summary
Provided are a surface layer material of a hot rolling mill roll and a hot rolling mill composite roll having high wear resistance, heat shock resistance, and surface deterioration resistance at the same time. The surface layer material has a chemical composition containing, by mass%, C: 2.4% or more and 3.5% or less, Si: 1.2% or more and 2.4% or less, Mn: 0.2% or more and 2.0% or less, Cr: 0.8% or more and 2.1% or less, Mo: 0.3% or more and 1.1% or less, Ni: 3.0% or more and 6.0% or less, V: 1.0% or more and 2.2% or less, Nb: 0.1% or more and 0.5% or less, REM: 0.0005% or more and 0.1% or less, Al: 0.003% or more and 0.05% or less, and the balance being Fe and inevitable impurities, in which the contents of C, Cr, V, Nb, REM, and Al satisfy the relationships Cr+0.2 ≤ C-(0.24×V+0.13×Nb) ≤ 3.0 and 0.01 ≤ REM/Al ≤ 3.2 (where C, Cr, V, Nb, REM, and Al respectively represent the contents (mass%) of corresponding chemical elements).