There are several methods of Non-Destructive Evaluation and Testing or NDE that are used in the production of steel castings. All of our NDE is overseen by our ASNT Level III engineer. By having these processes onsite, we keep costs lower and decrease lead time for first piece sample castings.
We can also use the NDE methods on continuous production orders where a pre-determined inspection frequency is prescribed by the customer. Each method has their own pros and cons and should be specified for the applicable need.
Magnetic Particle Inspection
Magnetic Particle Inspection or MPI is the best choice for ferromagnetic materials, such as carbon and low alloy steels. MPI detects small cracks on or near the surface of the casting. In a magnetized object, defects, such as blowholes, cracks, and inclusions, produce a distortion of the magnetic flux. Small magnetic particles show the path of the flux line, and the shape of the crack or void.
These particles can be applied dry or wet. The wet fluorescent method is the predominant method used on almost all carbon and low alloy castings at Sivyer Steel. This inspections method is quick and inexpensive to operate, and very sensitive.
Sivyer’s large Magnuflux units are capable of multidirectional fields and up to 20,000 Amps. Each casting goes through several MPI inspections during the upgrade process and meets the requirements set forth by the customer.
Steel Casting Radiography
Just like taking a medical x-ray, steel casting radiography allows us to inspect the casting for internal defects. Internal shrinkage, gas porosity, foreign inclusions, and entrapped slag that normally are not detectable by visual inspection can be detected by radiography.
Internal defects can be detected, within certain limitations, depending on the design of the casting, the size, shape, and location of the defect. All of our radiography techniques and safety procedures are overseen by our ASNT Level III engineer. Having onsite x-ray allows us to efficiently deliver castings with required x-ray inspection frequencies.
Ultrasonic testing is frequently used on heavy section castings where the time and equipment involved for radiography would be prohibitive. It works best on heat treat carbon, and alloy castings with relatively fine, uniform grain sizes.
To achieve better test results, a smooth surface is required, via machining or buffing. Sound waves are generated through a transducer and passed through the casting, where a monitor measures the loss of or reduction in the reflected sound if a defect is detected.
Ultrasonic inspection and radiography are not directly comparable; however, UT is invaluable in locating the depth of an indication in a heavy section. UT is often use in conjunction with radiography, with each method complementing the other.