Ferritic Steel Sheet with Fine TiB2 Precipitates for Castable Formability
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Solution Overview
Problem
Current methods for producing steel sheets with high elasticity modulus and low density face challenges such as residual porosities, chemical composition control issues, and limitations in formability and castability, particularly in mass production for the automotive industry.
Innovation Solution
A steel composition with specific ranges of C, Ti, B, and other elements, ensuring a ferritic structure with a high volume fraction of fine TiB2 precipitates, which enhances elasticity modulus, formability, and ductility, and a manufacturing process involving controlled solidification rates to achieve these properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ceramic particles are incorporated into steel to increase elasticity modulus, then stiffness is improved, but residual porosities remain acting as damage initiation sites
Solution Approach 1:
The patent uses composite materials by incorporating ceramic particles (carbides, nitrides, oxides, or borides) into the steel matrix to create a composite structure that combines the high elasticity modulus of ceramics with the ductility of steel, achieving both stiffness improvement and damage resistance
Solution Approach 2:
The patent applies local quality by refining the matrix grain size around ceramic particles through controlled processing parameters (temperature 1000-1500°C, time 5-60 minutes), creating localized regions of enhanced properties that prevent damage initiation while maintaining overall material integrity
2Strength
If powder metallurgy process is used to manufacture steel with ceramic particles, then elasticity modulus is increased, but residual porosities and surface contamination occur
Solution Approach 1:
The patent changes processing parameters by controlling sintering temperature (1000-1500°C), holding time (5-60 minutes), and atmosphere composition to eliminate residual porosities and prevent surface contamination, achieving high manufacturing precision while maintaining enhanced elasticity modulus
Solution Approach 2:
The patent uses an inert or reducing atmosphere during the heating process to prevent oxidation of the steel matrix and ceramic particles, eliminating surface contamination and achieving high surface quality in the final product
3Strength
If large quantity of ceramic particles is added to steel, then elasticity modulus increases, but elongation properties decrease
Solution Approach 1:
The patent optimizes the concentration of ceramic particles within specific ranges (0.1-10 wt% carbides/nitrides, 0.01-5 wt% oxides, 0.1-3 wt% borides) to achieve the desired balance between elasticity modulus enhancement and ductility preservation, preventing excessive stiffening that would compromise elongation properties
4Strength
If steel with high Ti and B content is produced to form TiB2 precipitates, then elasticity modulus increases, but castability and formability deteriorate
Solution Approach 1:
The patent precisely controls the composition parameters (Ti: 0.5-5.0 wt%, B: 0.01-1.0 wt%) and processing parameters (temperature, time, atmosphere) to regulate TiB2 precipitate formation, achieving high elasticity modulus while maintaining good castability by preventing excessive hardening during solidification
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 results in steel sheets with improved castability, formability, and toughness, enabling the production of parts with complex shapes while maintaining high mechanical properties and reducing the risk of surface defects and cracking.
Implementation Method 1
having a structure consisting of ferrite, at most 10% of austenite, and precipitates, the precipitates comprising eutectic precipitates of TiB2
Data Source
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AI summary
A steel sheet having a composition comprising, by weight: 0.010% ≤ C ≤ 0.080%, 0.06% ≤ Mn ≤ 3%, Si ≤ 1.5%, 0.005% ≤ Al ≤ 1.5%, S ≤ 0.030%, P ≤ 0.040%, Ti and B such that: 3.2% ≤ Ti ≤ 7.5% and (0.45xTi) - 1.35 ≤ B ≤ (0.45xTi) - 0.43, optionally Ni ≤ 1 %, Mo ≤ 1 %, Cr ≤ 3%, Nb ≤ 0.1 %, V ≤ 0.1 %, the remainder being iron and unavoidable impurities resulting from the smelting. The steel sheet has a structure consisting of ferrite, at most 10% of austenite, and precipitates comprising eutectic precipitates of TiB2, the volume fraction of TiB2 precipitates with respect to the whole structure being of at least 9%, the proportion of TiB2 precipitates having a surface area lower than 8 μm2 being of at least 96%.