Hot Stamping Steel Composition for High-Fracture-Strain Components
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Solution Overview
Problem
Existing press hardening steels face challenges in achieving high fracture strain and uniform grain structure, leading to inadequate energy absorption and collision safety in automotive components, with issues like coarse grains, high production costs, and decarburized layers.
Innovation Solution
A boron-containing steel composition with specific alloying elements (C, Mn, Si, Nb, Ti, and controlled ratios) forms nano-scale second phase particles, combined with a tailored hot stamping process to enhance fracture strain and toughness, allowing for flexible production of components with varying strength grades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional press hardening steel is used, then strength can be achieved, but fracture strain is insufficient leading to inadequate energy absorption
Solution Approach 1:
The patent changes the chemical composition parameters by adding boron (0.0005-0.005 wt%) and optimizing the ratios of C, Mn, Si, Nb, and Ti to achieve a microstructure with fine grains and high fracture strain while maintaining ultra-high strength
Solution Approach 2:
The patent creates a composite microstructure consisting of martensite matrix with dispersed carbide and nitride precipitates formed by the interaction of multiple alloying elements, achieving both high strength and high fracture strain
2Strength
If high carbon content steel is used to increase strength, then tensile strength improves, but total alloying cost increases
Solution Approach 1:
The patent optimizes the chemical composition parameters by adding boron (0.0005-0.005 wt%) and controlling the ratios of C (0.23-0.38%), Mn (1.50-3.00%), Si (0.10-0.50%), Nb (0.020-0.065%), and Ti (0.025-0.070%) to achieve ultra-high strength with reduced total alloying content compared to conventional steels
Solution Approach 2:
The patent uses small amounts of microalloying elements (Nb, Ti) combined with boron to achieve grain refinement and precipitation hardening, reducing the need for large amounts of expensive alloying elements while maintaining ultra-high strength
3Productivity
If conventional hot stamping process is used, then production efficiency is maintained, but grain structure remains coarse reducing fracture strain
Solution Approach 1:
The patent performs preliminary grain refinement during hot rolling by adding Nb and Ti microalloying elements that form precipitates during cooling, creating a fine-grained austenite structure before hot stamping that transforms into fine martensite grains after quenching, eliminating the need for post-processing heat treatment
Solution Approach 2:
The patent utilizes phase transition during hot stamping by heating the steel to austenite phase, rapidly cooling it to transform into martensite phase with fine grain structure, achieving both high strength and high fracture strain while maintaining production efficiency
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 high-fracture strain steel with improved plasticity and toughness, achieving bending angles up to 150° and tensile strengths of 600-850MPa, suitable for energy-absorbing automotive parts, reducing production costs and enhancing collision safety.
Implementation Method 1
forms nano-scale second phase particles
Implementation Method 2
heated to the austenitizing temperature
Implementation Method 3
quickly stamped into shape by a press, and then quenched and held under pressure in the mold for a certain period of time to obtain ultra-high strength stamped parts
Data Source
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AI summary
The present disclosure discloses a hot stamped component with high fracture strain, a press hardening steel sheet and a hot stamping process. Through innovative alloy composition and hot stamping process, the structure and mechanical properties after hot stamping are flexibly controlled, and the fracture strain of press hardening steel is improved to ensure the energy absorption effect. By combining Ti and Nb elements with C and N atoms in steel, solid solution C/N atoms are consumed to form nano-scale second phase particles, which are uniformly and dispersedly distributed on the matrix, thereby reducing the hardness difference at the interface between ferrite and martensite, and effectively improving the plasticity and toughness of the material. The materials involved are relatively simple, and the alloy cost is low. The process of preparing the press hardening steel and the hot stamping process have a wide process window. Based on control of the transfer time of the hot stamping sheet, the flexible control of the content of epitaxial ferrite (oriented attachment ferrite) is achieved, and finally the preparation of hot stamped components with different strength grades after hot stamping is achieved, which is very beneficial to the promotion of integrated door rings and will effectively contribute to the lightweighting of automobiles and the management of safe energy absorption.