Hot-Press Steel Plate Molding With Localized Hardness Control
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Solution Overview
Problem
Conventional hot-press molding methods produce products with uniform characteristics, failing to achieve localized variations in strength, ductility, and toughness, which are necessary for complex-shaped components like those in the automotive industry.
Innovation Solution
A hot-press molding method involving a first heating process to austenitize the steel plate, followed by differential cooling to create martensite and austenite regions, a reheating process to temper the martensite, and a final cooling process to stabilize the microstructure, allowing for the creation of regions with varying hardness and strength during the molding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the entire steel plate is uniformly cooled after heating to austenite, then high strength is obtained throughout the product, but uniform characteristics are produced which fail to achieve localized variations in strength, ductility, and toughness
Solution Approach 1:
The patent applies local quality by differentiating the cooling treatment for different regions of the steel plate. Specifically, a first region is rapidly cooled to produce martensite for high strength, while a second region is gradually cooled to maintain austenite for high ductility and toughness. This allows each part of the molded article to have optimized characteristics suited to its functional requirements.
2Adaptability or versatility
If different cooling rates are applied to different parts of the steel plate to achieve different strengths, then localized characteristics are obtained, but the process complexity increases
Solution Approach 1:
The patent segments the steel plate into distinct regions (first region and second region) with different cooling requirements. By dividing the cooling process into separate treatments for different areas, the patent achieves complex localized characteristics while managing process complexity through systematic regional differentiation.
Solution Approach 2:
The patent applies preliminary action by heating the entire steel plate to austenite region before cooling. This preliminary uniform heating ensures that the material is in the appropriate phase state throughout, enabling subsequent differential cooling to produce the desired microstructural variations without requiring complex real-time adjustments during cooling.
3Adaptability or versatility
If a steel plate is partially quenched and then reheated for press-molding, then different characteristics are obtained for each part, but the manufacturing process time increases
Solution Approach 1:
The patent merges the heat treatment processes with the press-molding operation. The reheating to austenite and the subsequent cooling with differential rates are integrated into the molding process itself, allowing microstructural control and shaping to occur simultaneously. This reduces total manufacturing time by combining multiple operations into a unified process sequence.
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
This method enables the production of hot-press molded products with distinct characteristics in different parts, such as high strength and high ductility, by controlling the cooling and reheating processes, resulting in a hardness difference of 100 HV or more between regions.
Implementation Method 1
a first heating process in which a steel plate is heated and the entire steel plate becomes austenite
Implementation Method 2
a first cooling process in which a cooling rate of the steel plate after the first heating process is partially changed, a first region which is a part of the steel plate is transformed into martensite and a second region other than the first region remains as austenite
Implementation Method 3
a second heating process in which the entire steel plate is reheated and the first region becomes tempered martensite
Implementation Method 4
a second cooling process in which the entire steel plate after the second heating process is cooled
Data Source
AI summary
A hot-press molding method of the present disclosure includes a first heating process in which a steel plate is heated and the entire steel plate becomes austenite, a first cooling process in which a cooling rate of the steel plate after the first heating process is partially changed, a first region which is a part of the steel plate is transformed into martensite, and a second region other than the first region remains as austenite, a second heating process in which the entire steel plate is reheated and the first region becomes tempered martensite, and a second cooling process in which the entire steel plate after the second heating process is cooled. At least one of the first cooling process and the second cooling process is performed during a molding process in which the steel plate is press-molded on a molding die.