Hot-Rolling Roll Outer Layer Composition for Low Porosity Fatigue Resistance

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Solution Overview

Problem

Existing hot-rolling rolls face challenges with porosities and shrinkage cavities, which degrade wear resistance and fatigue resistance, particularly in severe usage environments, and existing countermeasures are inadequate.

Innovation Solution

Adjusting the chemical composition of the outer layer material by controlling the amounts of N, O, Al, and eutectic carbides within specific ranges to minimize porosities and shrinkage cavities, while maintaining wear resistance and fatigue resistance comparable to or exceeding that of existing technologies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the outer layer material uses conventional centrifugal casting method with existing chemical compositions, then wear resistance and crack resistance are improved, but porosities and shrinkage cavities form that degrade fatigue resistance

Engineering Contradiction:

Improvewear resistance and crack resistanceVSAvoidfatigue resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling chemical composition parameters (C: 1.5-3.5%, Si: 1.5% or less, Mn: 1.2% or less, Cr: 5.5-12.0%, Mo: 2.0-8.0%, V: 3.0-10.0%, Nb: 0.5-7.0%) and their relationships to eliminate porosities and shrinkage cavities while maintaining wear and crack resistance, thereby resolving the contradiction between strength and reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by combining multiple alloying elements (C, Si, Mn, Cr, Mo, V, Nb) in specific proportions to create an outer layer material that simultaneously achieves high wear resistance, crack resistance, and fatigue resistance, resolving the contradiction through material composition optimization

Inventive Principle:

Principle #40Composite materials

2Strength

If high-Cr-content outer layer material is used to improve wear resistance, then surface hardness increases, but deep cracks form due to hot-rolling contact fatigue

Engineering Contradiction:

Improvesurface hardness and wear resistanceVSAvoiddeep cracks from contact fatigue

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by optimizing the Cr content range (5.5-12.0%) and establishing specific relationships between Cr and other alloying elements (Mo, V, Nb) to achieve adequate surface hardness while preventing deep crack formation from contact fatigue, resolving the contradiction between surface hardness and fatigue resistance

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3859025B1Outer layer material for hot-rolling roll, and composite hotrolling roll

Publication Date: 2023.05.03 JFE STEEL CORP

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AI summary

To provide a composite hot-rolling roll and an outer layer material for a hot-rolling roll that have a wear resistance and fatigue resistance comparable to or higher than those of the related art and in which porosities and shrinkage cavities are reduced. An outer layer material for a hot-rolling roll, the outer layer material having a chemical composition that contains, in mass%, C: 1.6 to 2.5%, Si: 0.2 to 1.5%, Mn: 0.2 to 1.6%, Cr: 4.5 to 7.0%, Mo: 1.0 to 5.0%, V: 4.0 to 6.0%, and Nb: 0.5 to 2.5%, in which a sum of contents of N and O of the chemical composition is 100 to 400 mass ppm, and a balance of the chemical composition is Fe and incidental impurities.