Low Density High Strength Steel Composition and Processing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing low-density, high-strength steel sheets face challenges in processability, deformation resistance during rolling, weldability issues, and the formation of undesirable martensite components, particularly with high aluminum content, making them difficult to produce using existing steel industry facilities.
Innovation Solution
A low-density, high-strength steel sheet composition of 0.15% to 0.25% C, 2.5% to 4% Mn, 0.02% or less P, 0.015% or less S, 6% to 9% Al, and 0.01% or less N, with specific ratios of Mn-Al and C to balance strength and ductility, along with optional additions of Si, Cr, Mo, Ni, Cu, B, Ti, Zr, Nb, W, and Ca, and a manufacturing process involving controlled reheating, hot rolling, cold rolling, and annealing to refine the microstructure and improve properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If high aluminum content (over 15%) is added to reduce steel density, then the steel becomes lighter, but processability deteriorates due to cracking and high deformation resistance during rolling
Solution Approach 1:
The patent optimizes the aluminum content parameter to a specific range (6-9%) rather than using excessive amounts, and combines it with controlled carbon (0.15-0.25%) and manganese (2.5-4%) content to achieve the desired balance between density reduction and manufacturability
Solution Approach 2:
The patent creates a composite alloy system combining aluminum with specific proportions of carbon and manganese, forming a multi-element steel composition that leverages the benefits of each element while mitigating their individual drawbacks
2Weight of moving object
If high aluminum content is used to reduce steel density, then the steel becomes lighter, but weldability deteriorates
Solution Approach 1:
The patent constrains the aluminum content to a moderate range (6-9%) rather than using high levels, and balances it with carbon content (0.15-0.25%) to maintain weldability while achieving density reduction
3Weight of moving object
If high aluminum content is added to reduce steel density, then the steel becomes lighter, but undesirable martensite components form
Solution Approach 1:
The patent optimizes the aluminum content (6-9%) in combination with carbon (0.15-0.25%) and manganese (2.5-4%) to control the microstructure and prevent the formation of undesirable martensite components
Solution Approach 2:
The patent develops a multi-element composite steel system where aluminum works synergistically with carbon and manganese to achieve a stable microstructure free of harmful martensite phases
4Strength
If carbon content is increased to increase steel strength, then the strength increases, but ductility decreases
Solution Approach 1:
The patent optimizes carbon content to a specific range (0.15-0.25%) rather than using high levels, and balances it with aluminum (6-9%) and manganese (2.5-4%) to achieve the desired strength-ductility balance
Solution Approach 2:
The patent creates a multi-element composite steel system where carbon works synergistically with aluminum and manganese to achieve both high strength and adequate ductility
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 achieves a steel sheet with a tensile strength of 600 to 900 MPa and excellent ductility, suitable for automotive applications, while being producible in existing steel industry facilities, with controlled chemical composition and processing steps ensuring balanced mechanical properties.
Implementation Method 1
aluminium, as a lightweight element, is sometimes added so as to reduce the density of the steel
Implementation Method 2
manganese increases the lattice constant of steel thereby decreasing the density of the steel
Implementation Method 3
Carbon is also an austenite stabilising element, and provides dispersion strengthening by forming precipitates
Implementation Method 4
a manufacturing process involving controlled reheating, hot rolling, cold rolling, and annealing to refine the microstructure
Data Source
AI summary
The present invention relates to a low density high strength steel sheet comprising 0.15% to 0.25% C, 2.5% to 4% Mn, 0.02% or less P, 0. 015% or less S, 6% to 9% Al and 0.01% or less N, the balance being iron and inevitable impurities, wherein 1.7.(Mn-Al) + 52.7.C is at least 3 and at most 4.5 and to a method of producing said low density and high strength steel sheet.