Improvement of Welding and Surface Properties of Carbon-Steel by Ultrasonic Peening

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Improvement of Welding and Surface Properties of Carbon-Steel by Ultrasonic Peening

ارائه دهنده: Provider: faeze shojaeyan

اساتید راهنما: Supervisors: Abbas Pak (Ph. D)

اساتید مشاور: Advisory Professors: Amir Hossein Mahmoudi (Ph. D)

اساتید ممتحن یا داور: Examining professors or referees: Faramarz Fereshte saniei (ph.D) - Yousef Mazaheri roudbali (ph.D)

زمان و تاریخ ارائه: Time and date of presentation: 1400/07/28

مکان ارائه: Place of presentation: virtual

چکیده: Abstract: Abstract Nowadays, among the various methods to improve the properties of welded joints, the new method "ultrasonic Peening" has found a special place in various industries to improve the properties of welding Joints, including increasing fatigue resistance, improving health and surface hardness and also reducing tensile residual stress. The purpose of this study is to investigate the high frequency (ultrasonic) Peening operation in improving the properties of API-5L-X65 grade carbon steel welded specimens. In this research, the effect of ultrasonic Peening operation has been investigated on welded samples of 48-inch pipe which is widely used in gas transmission industry due to its large size. In addition to investigating the effect of pin geometry on the depth and amount of stress using numerical modeling, we studied the mechanical and welding properties after ultrasonic Peening by performing various tests including residual stress measurement, tensile strength, Surface hardness, metallurgical structure and corrosion test. Based on the modeling of ultrasonic Peening process, the use of pins with smaller diameters and larger tip radii has created more compressive residual stress but less effect depth near the material surface. The use of ultrasonic Peening operation has caused compressive residual stress in the material and the amount of this stress has decreased from the surface to the depth so that at the surface, the stress is completely compressive and at depth is a reduced tensile stress, due to the initial tensile stress in the pipe. The maximum stress reduction in the Peened samples was 83%. The use of ultrasonic Peening, has caused a severe plastic deformation in the surface and reduced the grain size. The results also show that, the use of ultrasonic Peening process, has doubled the surface hardness, increased the tensile strength by 15% and improved the corrosion resistance of the specimens. As a result, Ultrasonic Peening Treatment (UIT) can be replaced by local stress relief methods due to its significant impact on tensile residual stress reduction, corrosion resistance improvement and tensile strength increase in a 48-inch, API-5L-X65 grade carbon steel pipe which improves the properties and life of welded joints in gas transmission pipelines

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