scholarly journals Effects of Diffusible Hydrogen Content and Hardness on Cold Cracking in High Strength Weld Metal

2012 ◽  
Vol 26 (2) ◽  
pp. 33-38
Author(s):  
Won-Chan Seo ◽  
Kook-Soo Bang
Keyword(s):  
Weld Metal ◽  
Hydrogen Content ◽  
High Strength ◽  
Cold Cracking ◽  
Diffusible Hydrogen

Effect of Weld Metal Microstructure on Cold Crack Susceptibility of High Strength Weld

2008 ◽  
Vol 580-582 ◽  
pp. 13-16
Author(s):  
Hee Jin Kim ◽  
Jun Seok Seo ◽  
Jae Hak Kim ◽  
Ka Hee Kim ◽  
Jin Hyun Koh ◽  
...  
Keyword(s):  
Weld Metal ◽  
Hydrogen Content ◽  
High Strength ◽  
Cold Cracking ◽  
Diffusible Hydrogen ◽  
Fca Welding ◽  
Flux Cored Arc Welding ◽  
Metal Microstructure ◽  
Multipass Weld ◽  
Crack Susceptibility

Facing the practical difficulties in reducing the diffusible hydrogen content of fluxcontaining welding consumables like flux-cored arc welding (FCAW) wires, the present study investigated the microstructural aspect to improve the hydrogen-induced cold crack (HICC) resistance of multipass weld metal of 600MPa strength. Two FCA welding wires were prepared by controlling the Ni content to give different weld microstructure, but to have similar levels of hardness and diffusible hydrogen content. HICC susceptibility of those two consumables was evaluated by 'G-BOP test' and also by 'multi-pass weld metal cold cracking test'. As a result of this study, it was demonstrated that microstructural modification with decreased proportion of grain boundary ferrite (GF) improved cold crack resistance of weld metal. The detrimental effect of GF against HICC has also been addressed based on the characteristics of weld metal cold cracking.

Critical Condition for Hydrogen Induced Cold Cracking of High Strength Weld Metal

2014 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Hitoshi Sueyoshi ◽  
Shigeru Endo
Keyword(s):  
Residual Stress ◽  
Tensile Stress ◽  
Weld Metal ◽  
Hydrogen Concentration ◽  
Hydrogen Content ◽  
Weld Joint ◽  
High Strength ◽  
Cold Cracking ◽  
Critical Conditions ◽  
Delayed Fracture

The critical conditions of hydrogen content and residual stress in the high strength steel weld with the tensile strength level of over 980MPa were investigated. The critical hydrogen concentration for the cold cracking in the Y-grooved constraint weld joint was evaluated with intentionally introducing hydrogen gas. Residual stress conditions at the “root” portion in the weld joint were evaluated by the neutron diffraction technique. It was found that the root portion showed highest tensile stress of over 1110MPa in the transverse direction, and cracking occurred when the average hydrogen content was over 2ppm. In order to clarify the critical conditions of the principal tensile stress and local accumulated hydrogen concentration of the weld metal, the delayed fracture testing by using the notched round bar specimen with electrochemically hydrogen charged was conducted. It was seen that the cold cracking behavior in the Y-grooved weld joint was explained by the critical conditions of the maximum principal stress and the local accumulated hydrogen content obtained from the delayed fracture with the small specimen.

scholarly journals Comprehensive Analysis of Cold-Cracking Ratio for Flux-Cored Arc Steel Welds Using Y- and y-Grooves

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5349
Author(s):  
Hyunbin Nam ◽  
Jaeseok Yoo ◽  
Kwanghee Yun ◽  
Guo Xian ◽  
Hanji Park ◽  
...  
Keyword(s):  
Hydrogen Content ◽  
High Strength ◽  
Cold Cracking ◽  
Carbon Equivalent ◽  
Diffusible Hydrogen ◽  
Factors Affecting ◽  
Strength Grade ◽  
Groove Shape ◽  
Weld Metals ◽  
Steel Welds

This study investigates various factors that influence the cold-cracking ratio (CCR) of flux-cored arc welds through Y- and y-groove tests. Factors affecting the CCR include the alloy component, diffusible hydrogen content, microstructure, hardness, and groove shape. In weld metals (WMs; WM375-R and WM375-B) of a low-strength grade, the diffusible hydrogen content has a more significant effect on the CCR than the carbon equivalent (Ceq) and microstructure. However, the combined effects of the microstructure and diffusible hydrogen content on the CCR are important in high-strength-grade WM. The CCR of the WM increased upon increasing Ceq and the strength grade because hard martensite and bainite microstructures were formed. Moreover, y-groove testing of the 500 MPa grade WM revealed a more significant CCR than that of the 375 MPa grade WM. Therefore, in high-strength-grade WMs, it is necessary to select the groove shape based on the morphology in the real welds.

scholarly journals Effect of Electrode Waterproof Coating on Quality of Underwater Wet Welded Joints

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2947 ◽  
Author(s):  
Jacek Tomków ◽  
Dariusz Fydrych ◽  
Kamil Wilk
Keyword(s):  
Hydrogen Content ◽  
Welded Joints ◽  
High Strength ◽  
Industrial Applications ◽  
Cold Cracking ◽  
Diffusible Hydrogen ◽  
Deposited Metal ◽  
Covered Electrodes ◽  
Steel Joints

In this paper, the effects of different hydrophobic coatings on the surface of covered electrodes on the quality of wet welded carbon steel joints were discussed. Commonly available hydrophobic substances used in industrial applications were selected for the research. The aim of using waterproof coatings was to check the possibility to decreasing the susceptibility of high-strength low-alloy S460N steel to cold cracking. During experiments diffusible hydrogen content in deposited metal determination by mercury method, metallographic macro- and microscopic testing and hardness measurements were performed. Investigations showed that waterproof coatings laid on covered electrodes can improve the quality of wet welded joints, by decreasing the Vickers HV10 hardness in heat-affected zone and decreasing the diffusible hydrogen content in deposited metal, which minimalize possibility of cold cracking.

A Predictive Electrochemical Model for Weld Metal Hydrogen Pickup in Underwater Wet Welds

1998 ◽  
Vol 120 (4) ◽  
pp. 243-248 ◽  
Author(s):  
R. C. de Medeiros ◽  
S. Liu
Keyword(s):  
Weld Metal ◽  
Hydrogen Content ◽  
Ferric Oxide ◽  
Welding Parameters ◽  
Oxide Content ◽  
Metal Interface ◽  
Feed System ◽  
Diffusible Hydrogen ◽  
Hydrogen Pickup ◽  
Electrochemical Model

Weld metal hydrogen pickup in underwater wet welding is severe due to the presence and dissociation of water surrounding the welding arc. This undesirable behavior can be minimized, however, with the use of oxidizing-type electrodes. The purpose of this investigation has been placed on the fundamental understanding of the effect of hydrogen pickup by the slag on the weld metal diffusible hydrogen content in direct current, shielded metal arc welding (SMAW) for both electrode-positive polarity (DCEP), and electrode-negative polarity (DCEN). To accomplish this purpose, 20 experimental oxidizing electrodes containing systematic ferric oxide (Fe2O3) additions, ranging from 0 to 70 wt. percent, to the flux coating were investigated. The mole fraction ratio of CaO/SiO2 in the fluxes ranged from 0.05 to 0.35, independent of the ferric oxide additions. Underwater, bead-on-plate welds were deposited on ASTM A36 steel coupons at 0.27 m (city) water depth using a gravity feed system. Welding parameters were held constant throughout the experiments. Weld metal diffusible hydrogen content was determined using the mercury displacement method according to current AWS standard. To correlate weld metal hydrogen content with slag chemistry, the slag hydrogen contents were also determined. The measured diffusible hydrogen contents showed that Fe2O3 was effective in reducing weld metal hydrogen content. Higher hydrogen values were always related to lower Fe2O3 contents initially present in the flux, for instance, 71 mL/100g (DCEP − 0 wt. percent Fe2O3) as compared to 31 mL/100g (DCEP − 36 wt. percent Fe2O3). Amazingly, diffusible hydrogen as low as 13 mL/100g was obtained with the use of DCEN polarity along with 53 wt. percent Fe2O3 in the flux coating. X-ray diffraction (XRD) conducted on different slags showed that the lower diffusible hydrogen values were always associated with the presence of fayalite (2FeO·SiO2). Complementing XRD analysis, Mo¨ssbauer spectroscopy analyses carried out on different slags showed that all ferric (Fe3+) oxide initially present in the slags had transformed to ferrous oxide (FeO), free or combined. Chemical analyses showed that weld metal hydrogen pickup was strongly dependent on the solubility of water in the slag systems. The total and diffusible hydrogen content in the weld metal increased monotonically with increasing slag hydrogen content. Finally, variations in weld metal hydrogen as well as slag hydrogen content with both polarity and iron oxide content in the slag were successfully predicted using an electrochemical model that describes the slag/metal interface equilibrium. In this investigation, the slag/metal interface has been identified as responsible in controlling the weld metal hydrogen pickup. The model assumed that hydrogen was present in the slag as (OH)− ions and that FeO displayed ideal solution behavior.

Repair Weldability at Overlay/Base Metal Interface of Petroleum Pressure Vessel

2008 ◽  
Author(s):  
Rinzo Kayano ◽  
Hiroaki Mori ◽  
Kazutoshi Nishimoto
Keyword(s):  
High Temperature ◽  
Hydrogen Embrittlement ◽  
Hydrogen Content ◽  
Welding Process ◽  
Pressure Vessels ◽  
Cold Cracking ◽  
Diffusible Hydrogen ◽  
Repair Welding ◽  
Crack Susceptibility

In order to extend the life of petroleum pressure vessels operated in long term, it is needed to establish the reliable repair welding technique. Weld cold cracking sometimes occurred in long-term operated petroleum pressure vessels due to hydrogen embrittlement by thermal stress and diffusible hydrogen after repair welding. The cracking was caused by the hydrogen concentration at the base meal of 2.25Cr-1Mo steel/overlaying metal of austenitic stainless steels interface during the service with high temperature and hydrogen partial pressure. The tendency was accelerated by carbide precipitation at the interface due to the post weld heat treatment (PWHT) and the operation with high temperature. That is, the crack susceptibility at the interface became markedly higher owing to the hydrogen embrittlement with metallurgical degradation by thermal embrittlement. To make clear the effect of weld thermal cycles during repair welding on the hydrogen content and weld cold cracking at the interface in the structural material of petroleum pressure vessels, the crack susceptibility was estimated by y-groove weld cracking test with varying overlay thickness and hydrogen exposure conditions. In addition, the hydrogen distribution in the material was calculated by the theoretical analysis using the diffusion equation based on activity. The crack susceptibility was raised with increase in the hydrogen content at the interface. It was concluded that the cracking could be prevented by controlling the repair welding process to reduce the hydrogen content at the interface.

Weld Metal Hydrogen Cracking in Transmission Pipelines Construction

2010 ◽  
Author(s):  
Sheida Sarrafan ◽  
Farshid Malek Ghaini ◽  
Esmaeel Rahimi
Keyword(s):  
Weld Metal ◽  
Construction Projects ◽  
High Strength Steels ◽  
High Strength ◽  
Carbon Equivalent ◽  
Transverse Cracks ◽  
Diffusible Hydrogen ◽  
Hydrogen Cracking ◽  
Girth Welds ◽  
Welding Position

Developments of high strength steels for natural gas pipelines have been in the forefront of steelmaking and rolling technology in the past decades. However, parallel to such developments in steel industry, the welding technology especially with regards to SMAW process which is still widely used in many projects has not evolved accordingly. Decreasing carbon equivalent has shifted the tendency of hydrogen cracking from the HAZ to the weld metal. Hydrogen cracking due to its complex mechanism is affected by a range of interactive parameters. Experience and data gained from field welding of pipeline construction projects indicated that weld metal hydrogen cracking is related to welding position as it occurs more in the 6 o’clock position of pipeline girth welds. In this research an attempt is made to open up the above observation in order to investigate the contributory factors such as welding position and welding progression in terms of diffusible hydrogen and possibly residual stress considerations. It was observed that transverse cracks produced in laboratory condition may not be detected by radiography. But, the higher tendency for cracking at 6 o’clock position was confirmed through bend test. It is shown that more hydrogen can be absorbed by the weld metal in the overhead position. It is shown that welding progression may also have a significant effect on cracking susceptibility and it is proposed that to be due to the way that weld residual stresses are developed. The observations can have an important impact on planning for welding procedure approval regarding prevention of transverse cracking in pipeline girth welds.

Hydrogen Charging of High Strength Steel Specimens and Physical Simulation of Cold Cracking under Laser Beam Welding Conditions

2012 ◽  
Vol 706-709 ◽  
pp. 1391-1396
Author(s):  
Ossama Dreibati ◽  
R. Ossenbrink ◽  
Vesselin Michailov
Keyword(s):  
Laser Beam ◽  
High Strength Steel ◽  
Physical Simulation ◽  
Laser Beam Welding ◽  
High Strength ◽  
Cold Cracking ◽  
Tension Stress ◽  
Pure Hydrogen ◽  
Diffusible Hydrogen ◽  
Hydrogen Charging

Cold cracks occur during the cooling down of welded joint at low temperatures or later at room temperature after the end of welding. It is associated with the formation of brittle microstructures as martensite in the presence of diffusible hydrogen as well as of tension stresses. By using an enhanced Simulation-und Testing Center Gleeble 3500, a procedure for physical simulation of cold cracking under laser beam welding conditions is suggested. The approach reproduces combinations of the cold crack main parameters, a brittle microstructure, tension stress and high local hydrogen concentration under welding conditions which induce a cold crack. A specimen geometry and technique were developed to enable the gaseous hydrogen charging from pure hydrogen atmosphere. The amount of charged hydrogen can be adjusted through varying the charging parameters like temperature, gas pressure and charging time. The hydrogen charging technique and the cold crack testing procedure were proven with high strength steel specimens.

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