Forged Steel Roll Composition for Thermal Shock Crack Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing forged steel rolls for cold rolling are prone to crack initiation due to thermal shock, leading to spalling and increased roll consumption, as they lack sufficient hardness and resistance to tensile stress at high temperatures.
Innovation Solution
A forged steel roll with a Vickers hardness of 400°C or more and a shrinkage start temperature of 300°C or more, achieved through a specific chemical composition and production process, enhancing durability against thermal shock-induced cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional forged steel rolls are used for cold rolling, then the rolls can perform basic rolling functions, but crack initiation occurs due to thermal shock leading to spalling and increased roll consumption
Solution Approach 1:
The patent applies parameter changes by optimizing the chemical composition parameters (C: 0.2-0.5%, Si: 0.5-1.5%, Mn: 0.5-1.5%, Cr: 1.0-2.0%, Mo: 0.5-1.5%, B: 0.0005-0.0050%) and heat treatment parameters (austenite transformation point, quenching temperature, tempering temperature) to achieve a Vickers hardness of 350-450 at 400°C, which significantly improves crack resistance and reduces roll consumption
Solution Approach 2:
The patent creates a composite microstructure consisting of tempered martensite as the base phase with dispersed carbides (Fe3C, Cr7C3, Mo2C, and VC) as reinforcement particles. This composite structure provides both the hardness needed to resist thermal shock-induced cracks and the toughness to prevent crack propagation, thereby improving reliability and reducing roll consumption
2Reliability
If the roll surface is ground down to remove cracks, then crack propagation is prevented temporarily, but the specific roll consumption deteriorates due to greater grinding amounts
Solution Approach 1:
The patent applies preliminary action by performing heat treatment (quenching and tempering) during the roll manufacturing process to pre-establish a microstructure with high crack resistance before the roll enters service. This prevents crack initiation in the first place, eliminating the need for subsequent grinding operations and maintaining high productivity
3Reliability
If the roll hardness is increased to resist thermal shock, then crack initiation is reduced, but the toughness may decrease making the roll more susceptible to other forms of damage
Solution Approach 1:
The patent applies local quality by creating a specific microstructure where tempered martensite provides hardness and thermal shock resistance in the matrix, while dispersed carbide particles (Fe3C, Cr7C3, Mo2C, VC) act as toughening agents that prevent crack propagation. The carbide distribution and size are controlled to locally enhance toughness without sacrificing overall hardness
Solution Approach 2:
The patent creates a composite material system where the tempered martensite matrix and dispersed carbide particles work synergistically. The martensite provides the hard, heat-resistant matrix while the carbides act as obstacles to crack propagation and provide toughness, achieving both high thermal shock resistance and maintained toughness
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 reduces crack initiation and propagation, thereby improving crack resistance and reducing roll consumption by maintaining high hardness and toughness even at elevated temperatures.
Implementation Method 1
a shrinkage start temperature in a temperature elevation process is 300° C. or more
Implementation Method 2
the practice has been to grind down the roll surface corresponding to the depth of the cracks so as to remove the cracks
Data Source
AI summary
Provided is a forged steel roll for cold rolling with a Vickers hardness Hy at 400° C. of 400 or more.