Ultrasonic Testing of Steel Castings
|Publication Date:||1 January 1976|
Ultrasonic flaw detection is a method of nondestructive testing that is finding increasing acceptance in the United States. This growth in the application of ultrasonics is intimately tied to the field of fracture mechanics and the scientifically based approaches to designing against failure. Ultrasonic flaw detection, as opposed to the more widely used radiography, permits the inspector to pinpoint accurately the location of the flaw and to determine its shape and size. These factors play an important role in fracture mechanics where the maximum safe stresses can be calculated for a given flaw size and location. Conversely, for a given flaw type, size and operating stress field, the maximum flaw size that can be tolerated safely can be determined. Thus the unique ability of ultrasonic inspection to assess flaw location and flaw geometry is vital to engineering approaches of fracture-safe design.
Further insight into the growth of nondestructive testing is gained by a historical review of developments. Radiography was developed early and achieved industrial status when a set of radiographs called, "Gamma Ray Radiographic Standards for Steam Pressure Service" was issued in 1938 by the Bureau of Engineering, U.S. Navy. Numerous ASTM specifications relative to radiography in steel casting production have been issued since then. Ultrasonics, in contrast, received its first major boost towards industrial application for steel castings in Britain when a study on its use and development possibilities was undertaken in 1958. ASTM specification A-609, "Standard Specification for Longitudinal Beam Ultrasonic Inspection of Carbon & Low Alloy Steel Castings" was published in 1970. This specification was followed in 1974 by the ASME Boiler & Pressure Vessel Code, Section V, T524.2, "Angle Beam Examination of Steel Castings." Other specifications of international importance are the Westinghouse Specification 600964, "Ultrasonic Testing of Steel Castings," and the Central Electricity Generating Board United Kingdom Standard 66011, "Turbine Castings (chromium, molybdenum, vanadium steel) ."
Increased acceptance and utilization of ultrasonic inspection are to be expected for the future. These trends are apparent from the extensive activity going on now in the United States and abroad. Three standards, in addition to ASTM A-609, are currently considered. These are the British IS0 Standard-"Draft Proposal for an International Standard for the Ultrasonic Inspection of Steel Castings," the German standard- "Introduction of Ultrasonic Testing and Standards and General Conditions of Delivery for Steel Castings," and a new proposed ASTM specification which will be similar to Westinghouse Specification 600964.
This booklet is published to present basic information on the nature of ultrasonic inspection principles with specific guidelines on flaw detection in steel castings. This information and the favorable economic aspects of flaw detection by ultrasonic means are presented for technical personnel and managers of casting producers and particularly the technical staff of casting users who control the level to which ultrasonic inspection will find acceptance in the future.