Effect of Microstructure on CTOD of Welded Joints for Offshore High-Strength Steel

2011 ◽  
Vol 117-119 ◽  
pp. 1905-1911
Author(s):  
Li Na Niu ◽  
Zhang Mu Miao ◽  
Tao Ma ◽  
Gang Chen
Keyword(s):  
Welded Joints ◽  
Heat Input ◽  
High Strength Steel ◽  
High Strength ◽  
Point Of View ◽  
Welding Heat Input ◽  
The Matrix ◽  
Welding Procedure ◽  
Carbide Particles ◽  
Effect Of Microstructure

Based on the CTOD test, metallographic test is done. The effect of microstructure on CTOD of welded joints for offshore high-strength steel has been analyzed by SEM. The microstructure of different samples in a welding procedure and two different welding procedures are compared. From the microscopic point of view, the reasons why the toughness of the second group welded joints is better than the first group’s and why the toughness of the same group welded joints is different have been determined. And the main microstructure found in EQ70 steel welded joints is the ferrite, tempered sorbite and a small amount of pearlite. Besides some carbide particles are on the matrix of tempered sorbite. The material toughness with a small amount of acicular ferrite is better. Inclusions and pores also seriously affect the toughness of welded joints. Reducing the welding heat input appropriately can refine the grain of CGHAZ and improve toughness. But hardened microstructure may occur owing to too low welding heat input.

Laser and Hybrid Laser-Arc Welding of High Strength Steel N-A-XTRA-70

2016 ◽  
Vol 870 ◽  
pp. 630-635 ◽  
Author(s):  
O. Berdnikova ◽  
V. Pozniakov ◽  
O. Bushma
Keyword(s):  
Mechanical Properties ◽  
Welded Joints ◽  
High Strength Steel ◽  
Arc Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Point Of View ◽  
Flow Sheet ◽  
Hybrid Laser Arc Welding ◽  
Fine Grain

The advantages of laser and hybrid laser-arc welding in production of welded structures from high strength steels are increase of efficiency due to rise of the welding rate by order; significant (3 – 5 times) decrease of heat input; reduction of weld size; receiving of fine grain structures in the welds and the heat affected zone increasing strength of the joint and reducing susceptibility to crack formation. Research of the peculiarities of laser and hybrid processes, their effect on weld formation, revealing the advantages and eliminating the disadvantages of laser and arc constituents of the heat sources are currently the main problems for the production engineers and researchers. Therefore, the aim of the investigation lies in determination of the effect of process mode parameters of the hybrid laser-arc and laser welding in high-strength steel welding on formation of the structure of the welded joint metal as well as the analysis of effect of this structure on their mechanical properties. The investigation was focused on the high-strength steel N-A-XTRA-70 which is widely used in European Union countries for manufacture of critical structures of different designations. A laboratory bench was developed for experiments. It was used for carrying out investigation on the process flow sheet which provided location of a consumable electrode arc at some distance ahead of a laser beam during welding proceeding. The laser irradiation source was Nd:YAG-laser DY 044 of ROFIN company (Germany). For the first time the results of carried investigations allowed determining the process modes of laser and hybrid laser-arc welding for producing quality and sound welded joints of the high-strength steel from the point of view of the structure formation and metal phase composition providing high indices of mechanical properties and crack resistance of the welded joints.

Influence of low-temperature tempering on structure and properties of welded joints of high-strength steel 30Kh2N2MF

2020 ◽  
Vol 2020 (6) ◽  
pp. 20-26
Author(s):  
O.A. Gaivoronskyi ◽  
◽  
V.D. Poznyakov ◽  
O.M. Berdnikova ◽  
T.O. Alekseenko ◽  
...  
Keyword(s):  
Low Temperature ◽  
Welded Joints ◽  
High Strength Steel ◽  
High Strength ◽  
Structure And Properties

scholarly journals Low-cycle fatigue behaviour of laser welded high-strength steel DOMEX 700 MC

2018 ◽  
Vol 157 ◽  
pp. 05013 ◽  
Author(s):  
Peter Kopas ◽  
Milan Sága ◽  
František Nový ◽  
Bohuš Leitner
Keyword(s):  
Fatigue Life ◽  
Welded Joints ◽  
High Strength Steel ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Fatigue Behaviour ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Fatigue Life Analysis

The article presents the results of research on low cycle fatigue strength of laser welded joints vs. non-welded material of high-strength steel DOMEX 700 MC. The tests were performed under load controlled using the total strain amplitude ɛac. The operating principle of the special electro-mechanic fatigue testing equipment with a suitable clamping system was working on 35 Hz frequency. Fatigue life analysis was conducted based on the Manson-Coffin-Basquin equation, which made it possible to determine fatigue parameters. Studies have shown differences in the fatigue life of original specimens and laser welded joints analysed, where laser welded joints showed lower fatigue resistance. In this article a numerical analysis of stresses generated in bending fatigue specimens has been performed employing the commercially available FEM-program ADINA.

scholarly journals On the Low Cycle Fatigue Behavior in the Longitudinally Butt Welded Joints between High Strength Steel and Mild Steel

1977 ◽  
Vol 1977 (142) ◽  
pp. 236-244
Author(s):  
Kinichi Nagai ◽  
Mitsumasa Iwata ◽  
Kenhichiro Kurihara ◽  
Junkichi Yagi ◽  
Yasumitsu Tomita
Keyword(s):  
Mild Steel ◽  
Welded Joints ◽  
High Strength Steel ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
High Strength ◽  
Cycle Fatigue
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