Hot Pressed Steel Sheet Antimony Decarburization
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Solution Overview
Problem
Hot-pressed steel sheet members with high tensile strength experience a significant decrease in surface hardness, leading to reduced wear resistance and other performance issues.
Innovation Solution
Incorporating antimony (Sb) in a steel sheet at a concentration of 0.002% to 0.03% by mass, along with specific carbon and other alloy content ranges, to prevent decarburization and maintain surface hardness during the hot pressing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a steel sheet is heated to high temperature for hot pressing to achieve high tensile strength, then the tensile strength increases to 980-2130 MPa, but a decarburized layer forms on the surface causing significant decrease in surface hardness and reduced wear resistance
Solution Approach 1:
Alloying elements (Ti, Nb, V, B, REM) are introduced as intermediary substances that form carbides and nitrides, acting as mediators to prevent carbon loss from the steel matrix during heating. These elements intercept carbon atoms that would otherwise diffuse to the surface and form a decarburized layer, thereby maintaining surface hardness while allowing high-temperature hot pressing to achieve the desired tensile strength
Solution Approach 2:
The steel sheet is designed as a composite material system containing multiple alloying elements (Ti, Nb, V, B, REM) in specific combinations. This composite composition creates a synergistic effect where different elements contribute to preventing decarburization through multiple mechanisms (carbide formation, grain boundary strengthening, diffusion control), enabling simultaneous achievement of high tensile strength and maintained surface hardness after hot pressing
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 method effectively maintains surface hardness and enhances the tensile strength of hot-pressed steel sheet members to 980 to 2,130 MPa, suitable for structural applications requiring high strength and wear resistance.
Implementation Method 1
a high strength is realized by working a heated steel sheet in a metal mold and simultaneously rapidly cooling the steel sheet
Implementation Method 2
quenching is performed with a water-cooled metal mold, the strength of a member can be increased by utilizing a transformation structure
Implementation Method 3
A cause of the decrease in a surface hardness is a decarburized layer having a thickness of several tens of micrometers to several hundred micrometers, the decarburized layer being formed on a surface layer portion of a steel sheet while the steel sheet is heated prior to hot pressing
Implementation Method 4
In order to prevent the formation of such a decarburized layer, it is effective to add Sb to a steel sheet in an amount of 0.002% to 0.03% by mass
Data Source
AI summary
Provided is a hot-pressed steel sheet member which has a TS of 980 to 2,130 MPa and in which a decrease in a surface hardness is small, a steel sheet for hot-press, and a method for manufacturing the hot-pressed steel sheet member. The hot-pressed steel sheet member has a composition containing, by mass, C: 0.09% to 0.38%, Si: 0.05% to 2.0%, Mn: 0.5% to 3.0%, P: 0.05% or less, S: 0.05% or less, Al: 0.005% to 0.1%, N: 0.01% or less, Sb: 0.002% to 0.03%, and the balance being Fe and inevitable impurities, wherein a tensile strength TS is 980 to 2,130 MPa.