With the improvement of industrial technology,the demand of customers for precision castings increases.In order to meet the market requirements and win in the fierce market competition, the
investment casting manufacturers must control the quality of precision casting.Because of some hardware facilities, management, casting cooling,and correcting the problems,
precision investment casting in the production process will produce castings deformation problem.
Casting distortion is divided into:Trace from deformation,deformation and flaring casting warpage.
Trace from deformation: alloy material,gray cast iron since most prone to micro-deformation.After cleaning off the sand gray cast iron, presence of residual stresses are mainly residual thermal stresses.Residual stress in addition to casting will produce cold cracking, deformation and other casting defects,but also produce small quantities from the main deformation.Even if the residual stress does not exceed the yield strength of the material,but its role,the gray cast iron with an extension of time,will occur slowly micro plastic deformation,the deformation is called trace from deformation.
Flaring deformation:The reason is formed at the opening size of the sand core or sand casting hinder contraction free opening of the casting structure portion is plastically deformed,resulting in a flared deformation defects.
Warpage:sand casting occurred after both ends or at one end or side peripheral edge warpage,the casting central concave,resulting in uneven casting, this form of distortion known as warpage.Its causes are:cooling the casting,the casting thickness,or uneven thickness, the temperature difference,resulting in various parts of the casting cooling rate,resulting in non-uniform plastic deformation,resulting in the formation of warpage.
For precision casting deformation problems,this paper put forward four proposals related measures:
1.out before wax injection molds for wax injection chamber preset until the wax injection mold temperature and room temperature until beginning the same wax injection;For behind the system shell when the temperature of the wax pieces do not need any more,and because there is no control well perhaps directly on the column, up shell it.
2.pieces of wax came out to be the first self-test,the main view from the model project for deformation,or other defects;wax pieces should be uniform placement neatly placed,and to avoid duplication,vacant;product shipments recommended to use Fixture checks to improve the detection speed and accuracy,according to a certain period of calibration fixture.
3.open furnace came out,the temperature is still high when the module should avoid overlap,so that a regular place to allow plastic deformation in the same direction to facilitate correction fashion folder.
4.correction casting jig hard materials should be used, the surface should wear a relatively large area for some parts to be reasonably calculated presses or press tonnage,in order to avoid waste or power is not enough equipment and so on.
Precision castings for machinery products have a huge impact on performance,poor quality precision castings will seriously affect the mechanical life of the product, so if it is found to deform precision castings and other issues,the need for timely correction,so as not to affect the mechanical precision casting products performance.
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