eliminate aluminum casting porosity, shrinkage via liquid hipping.

by:AAG     2020-11-04
Compared to conventional gas delivery, this process shortens the cycle time and is more economical as part of the production cycle of standard castings.
The need for the foundry to reduce costs and reduce the weight of the castings is a daily struggle. End-
Users, due to fuel economy standards and the need to provide economic terminals
When providing products to customers, it is the responsibility of the supplier to implement the technology, to provide components that maintain the necessary mechanical and physical performance, while achieving weight and cost savings.
For the automotive industry, the final result is
The user\'s demand is to convert many cast iron and steel components into aluminum. However, high-
The cost of raw materials and production processes and strict quality requirements make these conversions very highcost solutions.
When parts made for automotive applications are cast in aluminum, there is little error in mechanical properties such as tensile and fatigue strength.
In addition, the space for component defects such as air holes is very small.
In order to pursue the new technology to improve the quality of aluminum castings, the hot isostatic pressure method (HIPping)
Developed as a value
Increased Service to eliminate air holes in aluminum castings.
HIPpingIn commercial use, due to the increased cost of components in this process, the HIPping process is retained for both aerospace and automotive racing casting components.
In HIPping, the casting is placed in a chamber, and when the pressure increases, the residual gas experience around the casting is slowly heated.
This pressure that is then applied to the casting helps to collapse any internal air holes (
Inclusion or contraction)
Left in the assembly after casting.
After the process is completed, the components are cooled to room temperature.
This process is not the standard for aluminum castings due to the low rate of circulation per hour (typically 8-hr cycles)
The cost is high.
This is the driving force for the development of liquid packaging (LHIP)process.
As the name implies, LHIP uses liquid media instead of gas to apply equilibrium pressure on the casting parts during processing.
This liquid medium is capable of reaching every outer surface of the casting and applying uniform pressure around the casting.
The liquid medium used is a mixture of molten salt that heat treatment personnel often use.
Select a specific salt according to its operating temperature range.
Because the LHIP temperature is within the range of solution heat treatment of aluminum, the economy can be obtained by combining these two operations.
The water quenching procedure follows the LHIP process to complete the dissolution cycle.
As a result, the foundry does not have to use additional energy to heat the components for drawing.
In production, components are placed in high
Pressure chamber full of molten salt liquid medium.
The lid of the chamber is closed.
Then a piston is introduced from the lid to compress the liquid.
The short stroke of the piston through the hydraulic pressure will make the liquid pressure increase sharply.
Once the hydraulic force pushing the piston is equal to the reaction of the liquid, when the ideal liquid pressure is reached, the piston stops moving and can maintain the required length of time.
The following process parameters have been used to achieve successful results: * pressure: 1100-1200 bar;
* Solution temperature: 860-996F (460-535C)(
Depending on the alloy);
* Cycle Time: 200 seconds (
Including loading and unloading of the system.
Mechanical properties achieved through the combination of heat and pressure on the LHIPThe casting can eliminate shrinkage and hydrogen ([H. sub. 2])porosity.
The loosening will collapse under pressure and [force]H. sub. 2]
Air holes enter the solution due to heat and pressure.
However, nitrogen ([N. sub. 2])
This process cannot reduce the air holes generated by gas retention in the mold because [N. sub. 2]
The solution cannot be entered in the aluminum alloy, because once the pressure is reduced, the air hole will open again.
In addition, surface cracks and exposed shrinkage cavities cannot collapse during this process, as LHIP liquids fill the gaps without effect.
In the initial development of this process, a security
The critical ia66 suspension arm was selected as the sample to compare the components that have been and do not have LHIPped.
Table 1 and Table 2 detail the differences in bending and tensile strength, respectively.
In Table 1, please note the increase of deformation before the crack and the decrease of standard deviation.
Therefore, designers can use more reliable attributes on the LHIPped component.
Table 2 shows that the ultimate tensile strength and yield tensile strength after LHIPping have barely increased, but the elongation has increased by 41%.
In the fatigue Workbench test to measure the load of the component in use, the LHIPped hanging arm withstood the load that exceeded the load that would occur in the actual problem by 30%.
These results are described in Table 3.
In terms of actual production, LHIP increased fatigue by 35%.
Because the hanging arm of the test is low
These results show that components can be redesigned using reduced wall thickness.
Component density is another attribute of pre-and post-treatment examination of LHIP. Fig.
2 Display results.
The real economic benefits of the LHIP process will not be realized unless the high-
Production of sand making process.
LHIPping is used with low-
There may be no cost for pressure permanent molds-
It is beneficial to use the process with sand casting with lower cost. [Graph omitted]
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