The major objective of steel casting radiography testing of castings is the discovery of defects that adversely affect the strength of the product. Castings are a product form that often receive radiographic inspection since many of the defects produced by the casting process are volumetric in nature and are thus relatively easy to detect with this method.
These discontinuities of course, are related to casting process deficiencies, which, if properly understood, can lead to accurate accept-reject decisions as well as to suitable corrective measures. Since different types and sizes of defects have different effects of the performance of the casting, it is important that the radiographer can identify the type and size of the defects.
Radiography Testing Process
Film radiography is the method SSC uses compared to the more recent switch to digital imaging. The castings are exposed to radiation from an x-ray tube, where they absorb part of this radiation, and the remainder exposes the radiographic film.
Very dense material withstands penetration of the radiation and exposes the film to lesser degree. Any hole, void, crack, or inclusion that is less dense than the casting is revealed as a dark area on the film compared to surrounding casting area.
Sivyer Steel uses a 4 meV Linear Accelerator to radiograph our castings, with the ability to examine up to 13” thickness. Once the film is exposed, or “shot”, it is developed in a dark room and then examined by a Level II technician.
Each film is compared to a reference radiograph for each defect category to determine if it meets the acceptance level as set forth by the customer. All our radiography techniques are created on site by Level II technicians and overseen by our Level III engineer.
Benefits of Steel Casting Radiography
The main benefit of steel casting radiography is the speed and effectiveness it provides for non-destructive evaluation. Volumetric and the internal inspection of steel castings is performed using radiography, ultrasonic testing, or both. Radiography is the best NDE method for determining the presence of internal defects, such as shrinkage or foreign inclusions.
Another major benefit of steel casting radiography is that it provides a permanent record of the areas examined, compared to UT. It also provides a 2D picture of the area being tested that is easy for many to visualize. If the customer does not know the severity levels the castings should be provided to, you should call to discuss your options and we can make recommendations from past practices.
Parts with continuous x-ray frequency ensure process stability over time. Most of our first article sample castings go through a complete, 100% x-ray of the entire casting to prove out our engineering methods. From there, a sampling plan is established, and periodic checks of critical areas can be completed.