Electroabrasive Mirror Finishing of the Inner Surfaces of Stainless Steel Pipes of Small Diameter.

Austenitic stainless steels are widely used in the key components of major equipment and the welds can be the weakest parts of equipment made with these materials. Ultrasonic waves propagate in austenitic stainless steel welds with multiple paths and modes. This study employed a multi-view total focusing method using an ultrasonic phased array for defect detection in the welds of small-diameter austenitic stainless steel pipes. The detection capability of four different direct wave modes and eight different half-skip wave modes for typical defects were compared and analysed through numerical simulation. A fusion imaging method was developed using the preferred direct and half-skip wave modes. The process was further verified with a weld defect detection experiment carried out on small-diameter austenitic stainless steel pipes. The results show that the multi-view total focusing method can efficiently detect the defects in the welds of small-diameter tubes. Compared with the single-mode imaging method, the fusion total focusing imaging approach can not only improve the signal-to-noise ratio but can also reduce the number of image artefacts.

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Fatigue Design Criteria for Small Super Duplex Steel Pipes

23rd International Conference on Offshore Mechanics and Arctic Engineering, Volume 2 ◽

10.1115/omae2004-51619 ◽

2004 ◽

Author(s):

Steinar Kristoffersen ◽

Per J. Haagensen

Keyword(s):

Stainless Steel ◽

Wall Thickness ◽

Large Diameter ◽

Small Diameter ◽

High Strength ◽

Gas Production ◽

Steel Pipes ◽

Fatigue Design ◽

Duplex Steel ◽

Design Guidance

Stainless steel pipes ranging in sizes from approximately 10 to 100 mm OD are used extensively in umbilicals for the control and monitoring of underwater installations for oil and gas production. Umbilicals are subjected to tensile loads as well as variable amplitude loading from wave and current actions. Fatigue is therefore a critical issue in the design of umbilical components. Sea water resistant high strength super duplex steel with ultimate strength of typically 800 to 900 MPa is used to save weight and reduce the wall thickness. Some umbilicals installed by Statoil have design pressure up to 1035 bar, which in combination with large dynamic loads from floating production units makes fatigue design of the umbilicals a challenging issue. While the fatigue performance of butt welded pipes for pipelines and risers are established and implemented in design guidance and codes, the experimental basis for design of small diameter piping made of high strength materials is not well documented in the open literature. However, unpublished data from in-house investigations indicate that small pipes in super duplex steel perform significantly better than larger diameter pipes in lower strength materials. It is therefore apparently scope for a “thinness effect”, i.e. a bonus effect that could be applied to the data for large diameter pipes in current codes to account for the higher S-N curves for small stainless steel pipes. This paper reviews some of the fatigue data for piping and compares these data with experimental evidence from a joint industry project. Tentative fatigue design guidance for small diameter super duplex steel piping is presented. Questions concerning special issues such as the possible influence of wall thickness, mean stress and pre-straining due to reeling are discussed.

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CARPENTER CUSTOM 475

Alloy Digest ◽

10.31399/asm.ad.ss0974 ◽

2006 ◽

Vol 55 (9) ◽

Keyword(s):

Tensile Strength ◽

Stainless Steel ◽

Corrosion Resistance ◽

Small Diameter ◽

High Strength ◽

Heat Treating ◽

Good Corrosion Resistance ◽

Technology Corporation ◽

Peak Aged ◽

Carpenter Technology Corporation

Abstract Custom 475 stainless is a premium melted, high-strength, martensitic, precipitation-hardenable stainless steel. It provides good corrosion resistance and was designed to achieve a tensile strength up to 2000 MPa (290 ksi), combined with good toughness and ductility when in the H975 condition, peak aged at 525 deg C (975 deg F). Other combinations of strength are possible by applying aging temperatures up to 595 deg C (1100 deg F). The alloy is available in strip, wire, and small diameter bar. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and machining. Filing Code: SS-974. Producer or source: Carpenter Technology Corporation.

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