Ultrasonic Testing of Forged Steel Products
Introduction
Ultrasonic testing (UT) is a non-destructive inspection method used to locate and identify discontinuities in forged steel products. In UT, sound waves are used to detect hidden defects in the material and provide a detailed cross-section of its internal structure. UT is the most accurate and reliable method to assess these products for quality assurance purposes.
Basic Principle
By using an ultrasonic transducer, electrical energy is converted into sound waves that penetrate into the material. If the part is free of defects or discontinuities, the sound waves are reflected back to the transducer. However, if there are defects present, the sound waves are scattered and reflected back as echoes that can be detected. The time elapsed between the pulse being transmitted and the echo being received is then used to measure the depth of the defect. Additionally, the received sound intensity is enough to determine if it is a significant defect.
Types of Defects Detected
UT is capable of detecting a range of defects in both internal and surface structures of the forged product. These include:
* Casting shrinkage defects
* Porosity
* Inclusions
* Cold shuts and seams
* Cracks
* Seams
* Laminations
Inspection Procedure and Equipment
During the inspection process, the inspector must first thoroughly examine the specimen for any visible surface indications that may not be detectable with UT. Once all visible defects are identified, the sample is placed in the inspection area and product specific UT techniques are employed. Wall thickness, surface integrity and other product dimensions may also be measured during the inspection process.
The equipment used to carry out the inspection typically consists of:
* Variable frequency ultrasonic transducers
* Ultrasonic flaw detectors
* Scanning systems
* Cable driven systems
* Wedge type transducers
Before the start of the inspection, the transducer is connected to the flaw detector which provides signal strength, depth, and other pertinent data that are used for analysis and reporting. The signal strength is also used to fine-tune the equipment for optimal detection of defects.
Advantages of UT
UT offers numerous advantages over other NDE techniques including:
* Ability to detect near-surface defects that are not visible to the naked eye
* Capability to detect extremely small defects
* Does not require access to both sides of the part
* Does not require access from both sides of the weld line
* Can find defects in complex geometries
* Possibility for testing the entire surface
* Can detect multiple types of flaws simultaneously
Conclusion
Ultrasonic testing is an invaluable tool for forged steel product quality assurance. This testing method can detect numerous types of flaws which may otherwise be difficult or impossible to detect with visual inspection. UT is also incredibly fast and accurate, allowing for quick, reliable results that improve product yield and quality.
