Thin Cast Steel Strip Microcracking Reduction
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Solution Overview
Problem
Thin steel strips produced by continuous casting often suffer from microcracking due to the formation of an oxide layer on the casting rolls, which acts as a thermal barrier, and sulfur content, which decreases ductility and weldability, with existing methods failing to effectively control microcracking through sulfur regulation or manganese-to-silicon ratios.
Innovation Solution
Regulating the manganese-to-sulfur and manganese-to-silicon ratios in the molten metal, along with controlling oxygen, nitrogen, and carbon content, and adjusting the casting temperature and speed to reduce microcracking in thin steel strips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sulfur content is reduced to minimize impurities, then steel purity is improved, but microcracking increases due to insufficient MnS inclusion formation
Solution Approach 1:
The invention changes the chemical composition parameters by establishing specific ranges for sulfur (0.003-0.008%), carbon (0.010-0.065%), manganese, and silicon, along with their ratios, to simultaneously achieve low sulfur content and reduced microcracking through optimized inclusion formation
Solution Approach 2:
The invention creates a composite chemical composition system where multiple elements (C, Mn, Si, S) work together in specific proportions to form beneficial MnS inclusions that prevent microcracking while maintaining overall steel purity
2Strength
If manganese-to-sulfur ratio is increased to improve steel quality, then ductility is improved, but manufacturing complexity increases due to precise ratio control requirements
Solution Approach 1:
The invention simplifies manufacturing control by establishing fixed target ranges for the manganese-to-sulfur ratio (250:1 to 500:1) and manganese-to-silicon ratio (3.5:1 to 5:1), converting complex multi-variable optimization into straightforward ratio control
3Reliability
If casting temperature is increased to improve solidification, then nucleation is enhanced, but energy consumption increases
Solution Approach 1:
The invention optimizes the casting temperature parameter to a specific range (1500°C to 1600°C) that achieves effective nucleation and solidification quality while minimizing energy consumption, representing an optimized balance point
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
Significantly reduces microcracking in thin steel strips by optimizing the chemical composition and process parameters, resulting in improved ductility and weldability, as demonstrated by reduced microcracking rates across various steel compositions and casting conditions.
Implementation Method 1
a pair of counter-rotated laterally positioned casting rolls, which are cooled, so that metal shells solidify on the moving roll surfaces
Implementation Method 2
metal shells solidify on the moving roll surfaces
Data Source
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AI summary
A thin cast steel strip and method of making thereof with improved resistance to microcracking is disclosed. The steel strip is produced by continuous casting and contains a carbon content between about 0.010% and about 0.065% by weight, less than 5.0% by weight chromium, at least 70 ppm of total oxygen and between 20 and 70 ppm of free oxygen, and manganese to sulfur ratio greater than about 250:1. The carbon content in the cast strip may be below 0.035%, less than 0.005% by weight titanium, and the average manganese to silicon ratio in the strip produced may be greater than 3.5:1. The carbon content may be less than 0.035%, the casting speed less than 76.68 meters per minute, and the tundish temperature of the molten metal is maintained below 1612°C (2933.7°F).