Effects of microstructure on ultrasonic examination of stainless steel

Conference · Thu Jan 01 04:00:00 EST 1976

OSTI ID:7313924

Kupperman, D S; Reimann, K J

Ultrasonic inspection of cast stainless steel components or stainless steel welds is difficult, and the results obtained are hard to interpret. The present study describes the effects of stainless steel microstructure on ultrasonic test results. Welded coupons, 2.5 and 5.0 cm thick, were fabricated from Type 304 stainless steel, with Type 308 stainless steel as the weld material. Metallography of the base material shows grain sizes of 15 and 80 ..mu..m, and dendrites aligned from the top to the bottom surface in cast material. X-ray diffraction and ultrasonic velocity measurements indicate a random crystal orientation in the base material, but the cast sample had aligned dendrites. The weld material exhibits a dendritic structure with a preferred (100) direction perpendicular to the weld pass. Spectral analysis of ultrasonic broad-band signals through the base materials shows drastic attenuation of higher frequencies with increasing grain size (Rayleigh scattering). Annealing and recrystallization increases the ultrasonic attenuation and produces carbide precipitation at grain boundaries. The microstructural differences of the base metal, heat-affected zone, and weld metal affect the amplitude of ultrasonic reflections from artificial flaws in these zones. Data obtained from two samples of different grain sizes indicate that grain size has little effect when a 1-MHz transducer is used. When going from a 15 to an 80-..mu..m crystalline structure, a 5-MHz unit suffers a 30-dB attenuation in the detection of a 1.2 mm deep notch. The anisotropy of the dendritic structure in stainless steel renewed the interest in the effect of shear-wave polarization. In the (110) crystallographic orientation of stainless steel, two modes of shear waves can be generated, which have velocities differing by a factor of two. This effect may be helpful in ''tuning'' of shear waves by polarization to obtain better penetration in large grain materials such as welds.

• Research Organization: Argonne National Lab., IL (USA)
• OSTI ID: 7313924
• Report Number(s): CONF-7609101-1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101* -- Metals & Alloys-- Preparation & Fabrication
ACOUSTIC TESTING
ALLOYS
CASTINGS
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-NICKEL STEELS
CORROSION RESISTANT ALLOYS
CRYSTAL STRUCTURE
CRYSTALS
DENDRITES
GRAIN ORIENTATION
GRAIN SIZE
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
IRON ALLOYS
IRON BASE ALLOYS
JOINTS
MATERIALS
MATERIALS TESTING
MICROSTRUCTURE
NICKEL ALLOYS
NONDESTRUCTIVE TESTING
ORIENTATION
SIZE
STAINLESS STEEL-304
STAINLESS STEEL-308
STAINLESS STEELS
STEELS
TESTING
ULTRASONIC TESTING
WELDED JOINTS