Hot Press Die Clearance Control for Shape-Accurate Cooling
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Solution Overview
Problem
Conventional methods for manufacturing hot-press-formed products with local property variations face challenges in achieving shape accuracy while minimizing the bottom-dead-center holding time, leading to potential defects due to temperature differences and thermal contraction.
Innovation Solution
A hot press line with a first and second press device, each having die parts with clearance and abutment surfaces, allows for controlled cooling conditions by adjusting the abutment and non-abutment periods during the bottom-dead-center holding, ensuring a uniform temperature distribution and shape accuracy without prolonging the holding time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the formed product is kept in the die until uniform temperature is reached, then shape accuracy is improved, but the bottom-dead-center holding time is prolonged
Solution Approach 1:
The die is designed with different thermal conductivity regions: high thermal conductivity regions for rapid cooling of most areas, and low thermal conductivity regions (insulation portions) for maintaining temperature in specific areas. This local differentiation allows selective cooling rates across different portions of the formed product, enabling uniform temperature distribution without requiring excessive holding time.
Solution Approach 2:
The invention changes the thermal conductivity parameter of the die surface by applying insulation coatings or creating insulation portions in specific regions. This parameter modification enables control over heat transfer rates, allowing the die to achieve uniform temperature distribution in the formed product within a reduced holding time by preventing excessive heat loss in critical areas.
2Strength
If the cooling rate is lowered by keeping a gap between the die and the formed product, then low-strength portions are created, but the temperature of the formed product upon removal remains high
Solution Approach 1:
The die incorporates insulation portions in specific regions where low-strength portions are desired. These insulation portions create localized thermal barriers that reduce cooling rates in specific areas, forming low-strength portions with controlled microstructures. Meanwhile, other regions of the die maintain high thermal conductivity for rapid cooling, ensuring the overall temperature of the formed product is reduced upon removal.
Solution Approach 2:
Insulation materials or coatings are introduced as intermediary layers between the die and the formed product in specific regions. These intermediaries control heat transfer by providing thermal insulation where needed, enabling the creation of low-strength portions through reduced cooling rates while allowing the rest of the system to achieve uniform temperature distribution.
3Strength
If thermal conductivity distribution in the die surface is used to achieve local cooling rate adjustment, then property distribution is created, but temperature differences within the formed product increase
Solution Approach 1:
The die is designed with strategically placed insulation portions that provide localized thermal management. These insulation portions are positioned to create property distribution in specific areas while maintaining overall thermal balance. The high thermal conductivity regions compensate for the insulated areas, ensuring that temperature differences within the formed product remain minimal despite the localized property variations.
Solution Approach 2:
The invention modifies the thermal conductivity parameter of the die surface in a controlled manner by applying insulation coatings or creating insulation portions. This selective parameter change enables the creation of property distribution in the formed product while maintaining uniform temperature distribution, as the insulation portions are designed to prevent excessive temperature differences rather than create them.
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 ensures shape accuracy and uniform temperature distribution in hot-press-formed products with localized properties by controlling cooling rates through adjustable abutment and non-abutment periods, reducing the need for prolonged die holding.
Implementation Method 1
as these portions experience thermal contraction during cooling, the formed product may develop defects of shape
Implementation Method 2
a heating device adapted to heat a metal sheet
Implementation Method 3
The welded portions of the two sheets are cooled at lower cooling rates with respect to portions on both sides of each welded portion
Data Source
AI summary
A hot press line (100) includes: a heating device (30); a first press device (10) having first die parts (1A, 1B); a second press device (20) having second die parts (2A, 2B); a first transportation device (41) that transports a metal sheet (B) to the first press device; and a second transportation device (42) that transports the metal sheet (B) to the second press device. One of the pair of first die parts and the pair of second die parts includes a clearance portion (1Ac) recessed inwardly, whereas the other pair of die parts includes an abutment surface (2At) in at least part of the portion corresponding to the clearance portion (1Ac) of the one pair of die parts, where the abutment surface abuts the metal sheet (B) when the die is at the bottom-dead center.