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A Study on CGHAZ Precipitates and Toughness of Underwater Welds on Pipeline Steels

Author: ShiYongHua
Tutor: WangGuoRong
School: South China University of Technology
Course: Welding
Keywords: Pipeline steel Micro-alloying Underwater welding Coarse grain heat affected zone Precipitate Toughness
CLC: TG441
Type: Master's thesis
Year: 1998
Downloads: 109
Quote: 0
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Abstract


In this paper , the three oil and gas pipeline steel X60 , X65 and X70 different conditions underwater welding and air welding coarse-grained precipitate , toughness and other mechanical properties were studied and compared with the base material . Focuses on the behavior of the different components of the precipitate is dissolved in the welding thermal cycle , precipitation and grew up , and these acts toughness of the coarse-grained . Using the extraction replica coarse grain zone precipitate extraction on the carbon film , the precipitate morphology was observed under transmission electron microscopy , distribution , size and number , and the precipitate was measured using X-ray energy dispersive spectroscopy ( EDX ) ingredient. Was found in the test steel precipitate mainly two types of Ti - rich particles and spherical , cube -shaped V - rich particles . Ti - rich particles almost does not dissolve in the weld thermal cycle , and the small size of the V - rich particles by dissolving soluble dimensions of the calculation results coincide with the different types of precipitates in the weld thermal cycle . The type of welding conditions have a significant impact on the behavior of precipitate . The wet welding CGHAZ organization M, otherwise some B ; increasing line energy , help to reduce the M ; the local dry CGHAZ B content higher than the wet welding ; air CGHAZ B and acicular ferrite . X60 and X70 molten steel wet HAZ toughness lower than the air in welding , local dry welding in between ; increase the welding energy , coarse grain zone toughness improvement . X65 molten steel welding and air HAZ toughness were lower ; increased wet welding line energy , toughness variation . Test steel HAZ toughness these laws it contains precipitate a great relationship.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > General approach
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