scholarly journals Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

2020 ◽  
Vol 64 (12) ◽  
pp. 1997-2009
Author(s):  
Thomas Schaupp ◽  
Michael Rhode ◽  
Hamza Yahyaoui ◽  
Thomas Kannengiesser
Keyword(s):  
Weld Metal ◽  
Gma Welding ◽  
High Strength ◽  
Economic Benefits ◽  
Structural Steels ◽  
Test Series ◽  
Deposition Rates ◽  
The Past ◽  
Hydrogen Assisted Cracking ◽  
Implant Test

Abstract High-strength structural steels are used in machine, steel, and crane construction with yield strength up to 960 MPa. However, welding of these steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of microstructure, local stress/strain, and local hydrogen concentration. In addition to the three main factors, the used arc process is also important for the performance of the welded joint. In the past, the conventional transitional arc process (Conv. A) was mainly used for welding of high-strength steel grades. In the past decade, the so-called modified spray arc process (Mod. SA) has been increasingly used for welding production. This modified process enables reduced seam opening angles with increased deposition rates compared with the Conv. A. Economic benefits of using this arc type are a reduction of necessary weld beads and required filler material. In the present study, the susceptibility to HAC in the heat-affected zone (HAZ) of the high-strength structural steel S960QL was investigated with the externally loaded implant test. For that purpose, both Conv. A and Mod. SA were used with same heat input at different deposition rates. Both conducted test series showed same embrittlement index “EI” of 0.21 at diffusible hydrogen concentrations of 1.3 to 1.6 ml/100 g of arc weld metal. The fracture occurred in the HAZ or in the weld metal (WM). However, the test series with Mod. SA showed a significant extension of the time to failure of several hours compared with tests carried out with Conv. A.

Study on Hydrogen-Assisted Cracking in High-Strength Steels by Using the Granjon Implant Test

2017 ◽  
Vol 6 (3) ◽  
pp. 247-257 ◽  
Author(s):  
U. Yadav ◽  
C. Pandey ◽  
N. Saini ◽  
J. G. Thakre ◽  
M. M. Mahapatra
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Hydrogen Assisted Cracking ◽  
Implant Test

Effect of Corrosion on Crack Development and Fatigue Life

1998 ◽  
Vol 1624 (1) ◽  
pp. 110-117 ◽  
Author(s):  
John W. Fisher ◽  
Eric J. Kaufmann ◽  
Alan W. Pense
Keyword(s):  
Fatigue Life ◽  
Weld Metal ◽  
Fatigue Cracking ◽  
High Strength ◽  
Time Dependent ◽  
Structural Behavior ◽  
The Past ◽  
Fatigue And Fracture ◽  
Bridge Structures

Fatigue and fracture as well as loss of section caused by corrosion are time-dependent performance characteristics that have the potential to jeopardize the integrity of bridge structures. During the past 25 years these conditions have developed in a number of bridges, resulting in loss of service, costly repairs, and concern about the safety of these structures. A review of the experience with such time-dependent damage since 1970 is presented. The experience is grouped into three categories: fatigue cracking resulting from changes in structural behavior as a result of corrosion, fatigue cracking resulting from development of corrosion notches in members, and stress corrosion of high-strength steel and weld metal. The examples cited illustrate the role of corrosion phenomena in bridge service and the need to control the corrosion conditions on bridge structures.

scholarly journals Hydrogen-Assisted Cracking in GMA Welding of High-Strength Structural Steel—A New Look into This Issue at Narrow Groove

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 904
Author(s):  
Thomas Schaupp ◽  
Nina Schroeder ◽  
Dirk Schroepfer ◽  
Thomas Kannengiesser
Keyword(s):  
Structural Steel ◽  
Crack Formation ◽  
Gma Welding ◽  
Gas Metal Arc Welding ◽  
High Strength ◽  
Opening Angle ◽  
Diffusible Hydrogen ◽  
Weld Metals ◽  
Metal Arc Welding ◽  
Hydrogen Assisted Cracking

Modern arc processes, such as the modified spray arc (Mod. SA), have been developed for gas metal arc welding of high-strength structural steels with which even narrow weld seams can be welded. High-strength joints are subjected to increasingly stringent requirements in terms of welding processing and the resulting component performance. In the present work, this challenge is to be met by clarifying the influences on hydrogen-assisted cracking (HAC) in a high-strength structural steel S960QL. Adapted samples analogous to the self-restraint TEKKEN test are used and analyzed with respect to crack formation, microstructure, diffusible hydrogen concentration and residual stresses. The variation of the seam opening angle of the test seams is between 30° and 60°. To prevent HAC, the effectiveness of a dehydrogenation heat treatment (DHT) from the welding heat is investigated. As a result, the weld metals produced at reduced weld opening angle show slightly higher hydrogen concentrations on average. In addition, increased micro- as well as macro-crack formation can be observed on these weld metal samples. On all samples without DHT, cracks in the root notch occur due to HAC, which can be prevented by DHT immediately after welding.

scholarly journals Effect of weld metal composition on impact toughness properties of shielded metal arc welded ultra-high hard armor steel joints

2020 ◽  
Vol 29 (1) ◽  
pp. 186-194
Author(s):  
V. Balaguru ◽  
Visvalingam Balasubramanian ◽  
P. Sivakumar
Keyword(s):  
Impact Toughness ◽  
Weld Metal ◽  
Welded Joints ◽  
Weight Ratio ◽  
High Hardness ◽  
High Strength ◽  
Solidification Mode ◽  
Austenitic Phase ◽  
Ferrite Number ◽  
Steel Joints

AbstractNowadays, ultra-high hard armor (UHA) steels are employed in armor tracked vehicle (ATV) construction because of their high hardness, high strength to weight ratio, and excellent toughness. UHA steels are usually welded using austenitic stainless steel (ASS) welding consumables, to avoid hydrogen-induced cracking (HIC). The use of ASS consumables to weld the above steel was the only available remedy because of higher solubility of hydrogen in the austenitic phase. In this investigation, an attempt was made to investigate the effect of ASS consumables (with different Creq/Nieq ratio) on solidification mode, impact toughness and microstructural characteristics of shielded metal arc (SMA) welded UHA steel joints. The welded joints were characterised based on impact toughness properties, hardness, and microstructural features. As the ferrite number increases with an increase in Creq/Nieq ratio result in different solidification mode (A, FA, F). It is also found that ferrite number of weld metal has appreciable influence on impact toughness and has inversely proportional relationship with impact toughness of the welded joints.

High-strength nitrogen removal of opto-electronic industrial wastewater in membrane bioreactor - a pilot study

2003 ◽  
Vol 48 (1) ◽  
pp. 191-198 ◽  
Author(s):  
T.K. Chen ◽  
C.H. Ni ◽  
J.N. Chen ◽  
J. Lin
Keyword(s):  
Wastewater Treatment ◽  
Industrial Wastewater ◽  
Organic Nitrogen ◽  
Membrane Bioreactor ◽  
High Strength ◽  
Experimental Period ◽  
Ammonia Nitrogen ◽  
Nitrifying Bacteria ◽  
Biological Degradation ◽  
The Past

The membrane bioreactor (MBR) system has become more and more attractive in the field of wastewater treatment. It is particularly attractive in situations where long solids retention times are required, such as nitrifying bacteria, and physical retention critical to achieving more efficiency for biological degradation of pollutant. Although it is a new technology, the MBR process has been applied for industrial wastewater treatment for only the past decade. The opto-electronic industry, developed very fast over the past decade in the world, is high technology manufacturing. The treatment of the opto-electronic industrial wastewater containing a significant quantity of organic nitrogen compounds with a ratio over 95% in organic nitrogen (Org-N) to total nitrogen (T-N) is very difficult to meet the discharge limits. This research is mainly to discuss the treatment capacity of high-strength organic nitrogen wastewater, and to investigate the capabilities of the MBR process. A 5 m3/day capacity of MBR pilot plant consisted of anoxic, aerobic and membrane bioreactor was installed for evaluation. The operation was continued for 150 days. Over the whole experimental period, a satisfactory organic removal performance was achieved. The COD could be removed with an average of over 94.5%. For TOC and BOD5 items, the average removal efficiencies were 96.3 and 97.6%, respectively. The nitrification and denitrification was also successfully achieved. Furthermore, the effluent did not contain any suspended solids. Only a small concentration of ammonia nitrogen was found in the effluent. The stable effluent quality and satisfactory removal performance mentioned above were ensured by the efficient interception performance of the membrane device incorporated within the biological reactor. The MBR system shows promise as a means of treating very high organic nitrogen wastewater without dilution. The effluent of TKN, NOx-N and COD can fall below 20 mg/L, 30 mg/L and 50 mg/L.

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