The Paton Welding Journal, 2014, №12



2014 №12 (09)

DOI of Article 10.15407/tpwj2014.12.01

2014 №12 (02)

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The Paton Welding Journal, 2014, #12, 2-7 pages  

Influence Of Non-Metallic Inclusions In Pipe Steels Of Strength Class X65-X80 On Values Of Impact Toughness Of Flash-Butt Welded Joints

S.I. Kuchuk-Yatsenko, Yu.V. Shvets and V.I. Shvets

E.O. Paton Electric Welding Institute, NASU. 11 Bozhenko Str., 03680, Kiev, Ukraine. E-mail: office@paton.kiev.ua
 
 
Abstract
The comprehensive mechanical tests of high-strength steel pipe joints produced using flash-butt welding were carried out. The quality of joints completely meets the requirements of the international standard API STANDARD 1104. During tests on impact bending the single dropouts of KCV-40 values lower than the level required by standards DNV-OS-F101 and STO Gazprom 2-3.7-380-2009 were observed. The decrease in KCV-40 was predetermined by formation of zones of 1-2 mm² area in the plane of a joint differed by structural heterogeneity, which is characteristic also for base metal and revealed in a sharply distinct anisotropy of its ductile properties. It is shown that the areas with structural heterogeneity do not form colonies, therefore they do not decrease the general serviceability of the welded joint. The sizes of such areas do not exceed the admissible values accepted by the standards for defects of welds made by arc welding. The presence of single local dropouts of KCV-40 values observed during tests of welded joints produced using FBW should not be considered as a sign of rejection. 8 Ref., 1 Table, 11 Figures.
 
 
Keywords: flash-butt welding, high-strength steel, impact toughness of welded joints, heat treatment of welds
 
 
Received:                29.10.14
Published:               29.12.14
 
 
References
1. Kuchuk-Yatsenko, S.I. (1986) Resistance butt welding of pipelines. Kiev: Naukova Dumka.
2. API STANDARD 1104: Welding of pipelines and related facilities. 21st ed.
3. DNV-OS-F101: Offshore standard. Submarine pipelines systems. Jan. 2000.
4. STO Gazprom 2-3.7-380-2009: Instruction on technology of welding of marine pipelines. Moscow.
5. Kuchuk-Yatsenko, S.I., Shvets, Yu.V., Zagadarchuk, V.F. et al. (2012) Flash-butt welding of thick-walled pipes from high-strength steels of K56 strength class. The Paton Welding J., 5, 2-7.
6. Kuchuk-Yatsenko, S.I., Shvets, Yu.V., Zagadarchuk, V.F. et al. (2013) Technology of heat treatment of pipe joints from steel of K56 grade produced by flash-butt welding. Ibid., 2, 2-7.
7. Kuchuk-Yatsenko, S.I., Kazymov, B.I., Zagadarchuk, V.F. et al. (1984) Formation of «dead spots» in joint produced by resistance welding. Avtomatich. Svarka, 11, 23-26.
8. STO Gazprom 22.4-359-2009: Instruction on non-destructive testing of welded joints in construction of land and underwater gas pipelines from steels X-80, X-100. Moscow.

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