Hot-Stamping Steel Sheet Composition with Hydrogen-Trapping Precipitates
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Solution Overview
Problem
High-strength steel used in hot stamping processes faces challenges with press formability and hydrogen-delayed fracture due to residual stress and hydrogen infiltration, which complicates the formation of complex shapes and reduces the precision of high-strength parts.
Innovation Solution
A steel sheet composition with specific alloying elements (C, Si, Mn, P, S, Cr, B, and additives like Ti, Nb, V) and fine precipitates that trap hydrogen, formed through a reheating and hot rolling process, to enhance mechanical and hydrogen-delayed fracture characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high strength steel is used to increase strength characteristics, then strength is improved, but press formability deteriorates and the material may break or spring back during manufacturing
Solution Approach 1:
The patent applies parameter changes by controlling the chemical composition parameters (C: 0.28-0.50 wt%, Si: 0.15-0.70 wt%, Mn: 0.5-2.0 wt%, Cr: 0.1-0.5 wt%, B: 0.001-0.005 wt%) and processing parameters (heating temperature, cooling rate) to achieve a balance between strength and formability. The specific composition ranges and heat treatment conditions transform the material properties to resolve the contradiction between high strength and press formability.
2Reliability
If preheating is performed to form a thin oxide layer on the surface to block hydrogen inflow, then hydrogen-delayed fracture is reduced, but it is impossible to completely block hydrogen inflow and introduced hydrogen cannot be controlled
Solution Approach 1:
The patent converts the harmful effect of hydrogen into a beneficial one by intentionally introducing hydrogen during the heating process and then trapping it in fine precipitates formed during controlled cooling. The hydrogen that would normally cause delayed fracture is instead captured by precipitates of alloying elements (Ti, Nb, V, Cr, B), transforming the harmful factor into a controlled feature that prevents fracture.
Solution Approach 2:
The patent introduces intermediary substances (alloying elements Ti, Nb, V, Cr, B) that act as mediators between hydrogen and the steel matrix. These elements form fine precipitates that serve as hydrogen traps, intercepting hydrogen atoms and preventing them from causing delayed fracture. The intermediaries convert the direct harmful interaction between hydrogen and steel into a controlled interaction where hydrogen is bound in harmless precipitates.
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 provides improved tensile strength, bendability, and reduced hydrogen delayed fracture characteristics, enabling the precise formation of complex shapes with high-strength parts by effectively managing hydrogen and residual stress.
Implementation Method 1
fine precipitates distributed within the steel sheet... trap hydrogen
Implementation Method 2
a hot stamping method is a forming technology in which a boron steel sheet is heated to an appropriate temperature, formed in a press mold, and then rapidly cooled
Data Source
AI summary
Provided are a material for hot stamping, and the material includes: a steel sheet including carbon (C) in an amount of 0.28 wt% to 0.50 wt%, silicon (Si) in an amount of 0.15 wt% to 0.70 wt%, manganese (Mn) in an amount of 0.5 wt% to 2.0 wt%, phosphorus (P) in an amount less than or equal to 0.05 wt%, sulfur (S) in an amount less than or equal to 0.01 wt%, chromium (Cr) in an amount of 0.1 wt% to 0.5 wt%, boron (B) in an amount of 0.001 wt% to 0.005 wt%, an additive in an amount less than or equal to 0.1 wt%, balance iron (Fe), and other inevitable impurities; and fine precipitates distributed within the steel sheet. The additive includes at least one of titanium (Ti), niobium (Nb), and vanadium (V), and the fine precipitates include nitride or carbide of at least one of titanium (Ti), niobium (Nb), and vanadium (V) and trap hydrogen.