Dry Ice Blasting Intercooling for Sheet Steel Press Hardening
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The press-hardening method for sheet steel components often results in surface cracks due to liquid metal embrittlement, and existing intercooling methods using cooling plates with poor thermal conductivity lead to rapid heat dissipation, making process control challenging, especially with thin blanks.
Innovation Solution
The method involves using dry ice blasting for intercooling, allowing for precise control of cooling intensity and homogeneity across the blank's surface, enabling efficient and controllable pre-cooling while avoiding rapid cooling, and simultaneously cleaning the glass-like oxide layer formed during austenitization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cooling plates with poor thermal conductivity are used for intercooling, then the cooling process is controllable, but heat dissipation occurs too rapidly especially with thin blanks
Solution Approach 1:
The patent introduces dry ice particles as an intermediary cooling medium between the heated blank and the cooling plates. The dry ice particles are applied to the blank surface before placing it on the cooling plates, creating a controlled thermal interface that moderates the heat transfer rate and prevents excessive rapid cooling
Solution Approach 2:
The patent changes the physical state and temperature parameters of the cooling system by using dry ice (solid CO2 at -78.5°C) instead of conventional cold plates. This phase change material provides controllable cooling through sublimation, allowing precise control of the cooling rate while avoiding the runaway heat dissipation problem with direct thermal contact
2Productivity
If rapid cooling is applied during intercooling, then cooling efficiency is improved, but surface cracks occur due to liquid metal embrittlement
Solution Approach 1:
The patent applies dry ice particles to the blank surface as a preliminary cooling action before the blank contacts the cooling plates. This pre-cooling treatment reduces the blank temperature gradually, preventing the formation of liquid metal embrittlement conditions that cause surface cracks during subsequent forming operations
Solution Approach 2:
The patent uses the rapid sublimation of dry ice particles to quickly pass through the critical temperature range where liquid metal embrittlement occurs. The dry ice particles rapidly absorb heat and sublime, allowing the blank to quickly transition through the dangerous temperature zone without dwelling long enough for embrittlement to occur
3Speed
If the process window for cooling and handling is narrowed due to rapid cooling, then cooling speed is improved, but process control becomes difficult
Solution Approach 1:
The patent introduces dynamic control to the cooling process by using movable dry ice particle application systems. The amount, distribution, and timing of dry ice particle application can be dynamically adjusted based on blank thickness, material properties, and desired cooling rate, providing flexible process control despite high cooling speeds
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 significantly improves surface quality and controllability of the intercooling process, delaying cooling to prevent surface cracks and enhancing the cleaning of the oxide layer, thus preparing the surface for shaping without additional steps, reducing tool wear and costs.
Implementation Method 1
the sheet steel blank (3) is cooled by means of dry ice particles (6) from a temperature which is above the transformation temperature into martensite to a temperature which lies between the austenitization temperature and the transformation temperature into martensite
Data Source
AI summary
A method for producing a hardened sheet steel, in particular a sheet steel that is coated with a metallic anti-corrosion layer; the sheet steel is first heated to an austenitization temperature and the austenite transformation is completed and then the sheet steel is pre-cooled to a temperature that lies above the transformation temperature of the austenite to other phases and is then transferred to a press-hardening die and in the press-hardening die, is shaped and, for hardening purposes, is quenched; for pre-cooling purposes, the blank is blasted in at least some areas or zones with dry ice, dry snow, or a gas flow containing dry ice particles.