Terminology[ edit ] The terms "defect" and "discontinuity" refer to two specific and separate things in castings. When this happens the surface of the casting produced has a brittle, glassy appearance. This allows the foundry engineer to design Casting defects to capture the complexity of the defect cause.
Fusion Fusion occurs when sand grains fuse with molten metal. They are very small holes of about 2 mm in size which appears on the surface of the casting. It is important to measure and document all variables related to the casting. Remedies i Sand of high strength should be used with proper ramming neither too hard nor soft.
Both are caused by either a lack of fluidity in the molten metal or cross-sections that are too narrow. It is essential to verify the casting defects through such detailed analysis, prior to exploring cause and remediation steps.
Casting defects sand has the highest refractoriness. It generally occurs on flat surf; whereas a blow occurs on a convex casting surface.
On the broken surface, you can see the obvious black surface caused by this defect. This is a surface defect, but will cause serous problem if they located in key positions. The defects are broken up into macroporosity and microporosity or microshrinkagewhere macroporosity can be seen by the naked eye and microporosity cannot.
During the preliminary and production trials, the pouring was done automatically but the metal transfer was manual by forklift and, therefore, took more time, resulting in a higher than normal temperature loss.
This is due to insufficient size of riser, improper direction solidification of casting, improper location of chills or in gates. These are the common sand casting defects on the surface and inside of cast iron and cast steel parts.
Pipes form at the surface of the casting and burrow into the casting, while caved surfaces are shallow cavities that form across the surface of the casting.
Joint flash is also called as casting fin, which is a thin projection out of surface of metal castings. If neither of these are the case then most likely the porosity is due to gas formation. But before you can do that, you need to have a clear understanding of the different types of casting defects and their causes.
This would suggest that metal and molding sand were not primary causes of defect.
It is a gas hole or gas cavity which is occurs at the surface or the internal part of casting. Fluidity is affected by the composition of the material, freezing temperature or range, surface tension of oxide films, and, most importantly, the pouring temperature.
Some foundries might review data for a whole shift or for several heats to ensure repeatability and reliability of quality. Defecting design of pattern 2. This causes a rough surface finish. There is very thin iron skin on the surface of castings.
Thanks for reading it. Normal rough surfaces can not be judged as defects, but too rough and uneven in surface will be a defect. Slag Inclusion Defect A swell is a slight, smooth bulge usually found on vertical faces of castings, resulting from liquid metal pressure.
Add combustible additives to sand. Joint Flash Defect 7. When these are present, they occur in large numbers and are fairly uniformly dispersed over the surface. Because of the flotage of liquid metal, the mould flasks are raised, which caused the top part of casting become higher or thicker than lower part.
Cavities might also be paired with dendritic fractures or cracks. Some of the solutions to certain defects can be the cause for another type of defect. Other possible defects are gas porosity, shrinkage porosity, hot tears, and flow marks. Pin holes are similarly to blow holes but smaller into size.
The result is sand particles embedded in the surface of the finished casting.
This is because of unreasonable gating system, which caused very thin air layers existed.In Part 2, the seven categories of casting defects are described and participants will become familiar with the “International Atlas of Casting Defects.” In Part 3, participants will learn how to use the Step Procedure to resolve a casting defect.
Casting Defects Defects may occur due to one or more of the following reasons: Fault in design of casting pattern Fault in design on mold and core Fault in design of gating system and riser Improper choice of molding sand Improper metal composition.
Welcome to the Investment Casting Institutes’ Atlas of Casting Defects. The pdf version of this publication is available for both Members and non-Members of the ICI. Licenses for advanced features will be available for phase 1, 2 and 3 for a low monthly fee (see below). No special devices: just install the free app on your personal smartphone and enter your license code to activate advanced features.
The International Casting Defect Atlas gives a specific code/category to defects based on appearance. It also suggests foundry personnel be aware that most casting defects are due to the interaction of several process variables rather than one factor, such as temperature or gating system design.
Casting defects 1. Casting Defects 1.
Casting defects are often very difficult to characterize due to the intrinsic complexity of the casting process.
2. All defects will fall into one or more of the established categories of casting defects. 3.Download