Forged Roll Microstructure for Cold Rolling Wear Resistance
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Solution Overview
Problem
Current forged rolls used in the cold rolling industry face challenges in achieving low residual internal stresses, preventing roll explosions, and maintaining tribological properties equivalent to coated rolls without environmental hazards, while also ensuring high wear resistance and crack resistance.
Innovation Solution
A forged roll with a specific steel composition and production process that includes a solidification rate higher than 15°C/min, induction hardening, and tempering to achieve a microstructure of tempered martensite with low retained austenite and open eutectic carbide networks, resulting in a roll with improved hardness and internal compressive stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If chrome plating is applied to forged rolls to improve wear resistance and surface texture retention, then the roll lifespan is extended (2 to 8 times longer), but environmental restrictions make this practice increasingly unacceptable
Solution Approach 1:
The invention extracts and eliminates the harmful chrome plating layer while retaining the essential function of wear resistance through optimized base steel composition (2-6% Cr) and controlled solidification processes that create inherent surface durability without environmental hazards
Solution Approach 2:
The invention changes the chemical composition parameters of the roll steel, specifically optimizing chromium content (2-6%) and controlling solidification rate (>15°C/min) to achieve superior wear resistance and surface texture retention in the uncoated state, replacing the need for chrome plating
2Strength
If high chromium content steel is used to improve wear resistance, then surface texture retention is enhanced, but residual internal stresses increase making the roll prone to explosion
Solution Approach 1:
The invention optimizes the chromium content parameter within a specific range (2-6%) and controls the solidification rate parameter (>15°C/min) to achieve a balanced microstructure that provides adequate wear resistance while minimizing residual internal stresses through controlled carbide formation and distribution
Solution Approach 2:
The invention creates a composite microstructure consisting of tempered martensite matrix with dispersed carbides (including Cr-rich carbides), where the combination of phases provides both wear resistance from the carbides and toughness/stress resistance from the martensite matrix
3Reliability
If solidification rate is increased to achieve fine microstructure and reduce internal stresses, then crack resistance is improved, but production time and energy consumption increase
Solution Approach 1:
The invention specifies a minimum solidification rate parameter (>15°C/min) that achieves the necessary microstructure refinement and stress reduction while allowing for practical production timeframes, balancing quality requirements with 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 provides a roll with enhanced crack resistance, wear resistance, and safety in operation, maintaining surface texture and reducing dust pollution, thus improving mill performance and extending roll lifespan.
Implementation Method 1
d. Hardening the roll by induction heating
Implementation Method 2
e. Tempering the roll at a temperature between 450-530°C to reach hardness between 780 HV to 840 HV
Data Source
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AI summary
This invention relates in general to the field of forged rolls and to production of forged rolls. More particularly the present invention relates to forged rolls for use in the cold rolling industry. The present invention relates to a forged roll for use in the cold rolling industry and a method for production of such a roll. Said forged roll, comprises a steel composition and a microstructure that comprises: - tempered martensite with a retained austenite rate less than (<) 5 % per volume; and - an open eutectic carbide network with eutectic carbides of less than (<) 5 % per volume; and wherein the roll exhibits: - a hardness between 780-840HV; and - internal compressive between -300 to -500 MPa in absolute values.