Intermediate Store for Dual-Ductility Press Hardening
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Solution Overview
Problem
Existing methods for producing molded parts with regions of different ductility and strength are complex, energy-intensive, and difficult to control, often requiring separate temperature zones in furnaces, which complicates the formation of components with varying geometries and slows down throughput.
Innovation Solution
A method involving a continuous furnace followed by an intermediate store where one section is kept at austenitization temperature and the other section is cooled to form a ferritic-pearlitic structure, allowing for continuous furnace operation and intermittent processing in a press-hardening tool, enabling easy control and energy efficiency without affecting throughput speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If separate temperature zones with partition walls are used in the continuous furnace, then different temperature regions can be achieved, but the device complexity increases and throughput speed decreases
Solution Approach 1:
An intermediate store (buffer furnace) is introduced as a mediator between the continuous furnace and the press-hardening tool. This buffer furnace temporarily stores heated semi-finished products, allowing the continuous furnace to operate independently without being constrained by the processing cycle of the press-hardening tool. The buffer furnace acts as a thermal buffer that maintains austenitization temperature for stored parts while enabling continuous production flow.
Solution Approach 2:
The process is segmented into independent stages: continuous heating in the first furnace, temporary storage in the buffer furnace, and intermittent forming in the press-hardening tool. This segmentation allows each stage to be optimized independently and operate at different speeds, with the buffer furnace decoupling the throughput of the continuous furnace from the cycle time of the press-hardening tool.
2Strength
If the semi-finished product is cooled after heating to form ferritic-pearlitic structure, then ductility is improved in specific areas, but additional cooling equipment and process complexity are required
Solution Approach 1:
Different thermal treatments are applied to different regions of the semi-finished product. The buffer furnace provides selective cooling where parts protrude from the furnace chamber, creating local ferritic-pearlitic structures in specific areas while maintaining austenitization temperature in other regions. This enables spatially differentiated material properties (ductility vs. strength) within a single component.
Solution Approach 2:
The buffer furnace utilizes its own heating chamber and natural cooling environment to achieve the desired thermal treatment. Parts are positioned such that certain regions protrude from the heated chamber and cool in air, while other regions remain inside the furnace. The system uses its inherent thermal gradient and cooling capacity without requiring separate dedicated cooling equipment.
3Productivity
If the continuous furnace operates at high speed, then productivity is improved, but it becomes difficult to coordinate with the intermittent operation of the press-hardening tool
Solution Approach 1:
The buffer furnace serves as a temporal intermediary that decouples the continuous high-speed operation of the first furnace from the intermittent cycle-based operation of the press-hardening tool. It accumulates heated parts during periods when the press-hardening tool is processing, then supplies parts to the tool when ready, eliminating the need for speed coordination between the two furnaces.
Solution Approach 2:
The buffer furnace performs preliminary storage of heated semi-finished products in advance of the press-hardening operation. By maintaining parts at austenitization temperature in the buffer, the system prepares material ahead of time, allowing the press-hardening tool to operate at its own rhythm without waiting for continuous furnace cycles, thus simplifying operational coordination.
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 approach allows for the production of molded parts with desired ductility and strength profiles in a straightforward, energy-efficient manner, accommodating various geometries without slowing down the continuous furnace, and enables flexible timing for hardening tool operation.
Implementation Method 1
the semi-finished product is heated to austenitization temperature in the continuous furnace
Implementation Method 2
a first section of the semi-finished product is cooled to a temperature at which the structure of the section is converted into a ferritic-pearlitic structure
Implementation Method 3
the semi-finished product is subsequently formed into the molded part in a press-hardening tool and tempered
Data Source
AI summary
To create a process for manufacturing a shaped part with at least two microstructure regions of different ductility from a semi-finished product (1) made of steel, involving heating in a continuous furnace (2) and a hardening process, wherein the semi-finished product (1) is heated in the continuous furnace (2) to austenitizing temperature, subsequently a first sub-region (4) of the semi-finished product (1) is cooled to a temperature at which the microstructure of the sub-region is transformed into a ferritic-pearlitic microstructure, while a second sub-region (5) of the semi-finished product (1) is held at austenitizing temperature, subsequently the semi-finished product (1) is formed and tempered in a press hardening tool (6) to form the shaped part, which is easily controllable, can be operated energy-efficiently and enables the treatment and forming of corresponding semi-finished products or blanks in the cycle time of the press hardening tool without influencing the throughput speed through the continuous furnace,It is proposed that the semi-finished product (1), after passing through the continuous furnace (2), is placed with the second section (5) into a chamber of an intermediate storage unit (7), which maintains the second section (5) at austenitizing temperature, while the first section (4) protrudes from the chamber of the intermediate storage unit (7) and this protruding section is cooled with air to the temperature at which the ferritic-pearlitic microstructure is formed.