Cr5 Back Up Roll Heat Treatment for Equal Hardness Retention
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Solution Overview
Problem
Conventional forged steel back up rolls in modern rolling mills experience a rapid reduction in hardness, abrasion resistance, and contact fatigue during the middle and later use periods due to insufficient hardenability and uneven structure, leading to reduced performance and service life.
Innovation Solution
A method for manufacturing an equal-hardness Cr5 back up roll involving specific chemical compositions, improved smelting and forging processes, and thermal treatment techniques to achieve uniform hardness and enhanced carbide formation, including high-efficiency exothermic compounds and controlled cooling methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Cr5 forged steel back up roll is used, then initial hardness and strength are achieved, but hardness and abrasion resistance rapidly reduce in middle and later use period
Solution Approach 1:
The patent modifies the chemical composition parameters by increasing Cr content to 4.00-5.00% and adding alloying elements (Ni: 0.20-0.60%, Mo: 0.10-0.80%, V: 0.10-0.50%) to improve hardenability and carbide formation. The thermal treatment parameters are also changed with controlled cooling rates (10-50°C/min) to achieve uniform martensitic structure throughout the roll, preventing hardness reduction during service.
Solution Approach 2:
The patent creates a composite microstructure by combining martensitic matrix with dispersed carbides formed from Cr, Ni, Mo, and V alloying elements. This composite structure at the micro-level provides both high initial hardness and excellent hardness retentivity during the service period by preventing pearlite transformation.
2Reliability
If alloy element content is increased to improve hardenability, then hardness and abrasion resistance improve, but material cost and manufacturing complexity increase
Solution Approach 1:
The patent optimizes alloying element content within specific ranges (Cr: 4.00-5.00%, Ni: 0.20-0.60%, Mo: 0.10-0.80%, V: 0.10-0.50%) to achieve the required hardenability and abrasion resistance without excessive cost. The controlled cooling rate parameter (10-50°C/min) during thermal treatment ensures uniform carbide precipitation and martensitic structure formation, simplifying the manufacturing process while achieving the desired performance.
3Productivity
If conventional smelting and forging processes are used, then production efficiency is maintained, but material uniformity and structure homogeneity are insufficient
Solution Approach 1:
The patent introduces controlled cooling rates (10-50°C/min) during the thermal treatment process to ensure uniform temperature distribution and homogeneous martensitic structure formation throughout the back up roll. This parameter control prevents local variations in microstructure while maintaining efficient production throughput.
Solution Approach 2:
The patent performs preliminary alloying during the smelting stage to ensure uniform distribution of Cr, Ni, Mo, and V elements before forging. This preliminary action prevents segregation and ensures homogeneous material composition throughout the ingot, which then translates to uniform microstructure after thermal treatment.
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 method results in improved hardness retentivity, abrasion resistance, and contact fatigue strength, extending the comprehensive use period and service life of the back up roll by 20% compared to conventional Cr5 rolls.
Implementation Method 1
performing thermal treatment on the roller blank
Implementation Method 2
thermal treatment techniques to achieve uniform hardness and enhanced carbide formation
Implementation Method 3
enhanced carbide formation, including high-efficiency exothermic compounds and controlled cooling methods
Data Source
AI summary
The present disclosure discloses a method for manufacturing an equal-hardness Cr5 back up roll. The method comprises the following steps: 1) preparing a steel raw material according to chemical components and weight percentage contents in a Cr5 back up roll material, and preparing a steel ingot according to a smelting procedure production process; 2) preparing a roller blank from the steel ingot according to a forging procedure production process; 3) performing thermal treatment on the roller blank; and 4) processing and detecting the roller blank to obtain an equal-hardness forged steel back up roll. The present disclosure solves problems that a hardness, an abrasion resistance, and a contact fatigue of a conventional forged steel back up roll are rapidly reduced in a middle and later use period, and prolongs a comprehensive use period and a service life of the back up roll.