Diffusible hydrogen content in submerged arc welds of a S960 type steel

2016 ◽  
Vol 58 (6) ◽  
pp. 561-568 ◽  
Author(s):  
Mehmet Türker
Keyword(s):  
Hydrogen Content ◽  
Diffusible Hydrogen ◽  
Type Steel ◽  
Submerged Arc

The Influence of Diffusible Hydrogen in Weld Metal and Moisture Content Levels in Flux Related With Weld Metal Mechanical Properties in Submerged Arc Welding Process for Line Pipe Manufacturing

2015 ◽  
Author(s):  
Gautam Chauhan ◽  
Piyush Thakor ◽  
Satyanarayana Samavedam ◽  
Ramakrishnan Mannarsamy ◽  
Ashif Sheikh ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Moisture Content ◽  
Weld Metal ◽  
Hydrogen Content ◽  
Welding Process ◽  
Diffusible Hydrogen ◽  
Line Pipe ◽  
Arc Welding Process ◽  
Submerged Arc ◽  
Pipe Manufacturing

The mechanical properties of welding material is correlative with the diffusible hydrogen content in weld metal and level of moisture content in flux. Minitab16program to predict mechanical properties correlated to diffusible hydrogen content in weld metal and level of moisture content in flux, such as yield strength, tensile strength, elongation and average Charpy impact toughness of welding material is established by using submerged arc welding process in line pipe manufacturing. The present paper aims to experiment and investigate the line pipe SAW Flux used for offshore/onshore applications. Flux moisture content has been studied under Karl Fischer Coulometer method. Subsequently, flux was then used to make weld to analysis for ‘diffusible hydrogen content in weld metal’ through mercury displacement method. This detailed study envisages and explains the correlations between the mechanical properties and micro structures of weldments. Evaluating the variance of moisture level in flux and diffusible hydrogen content in weld metal proves the advantage of restricting the moisture content along with good practices to accomplish better weld quality.

Optimization of a Specimen Size for the Determination of the Diffusible Hydrogen Content in Metals

2014 ◽  
Vol 698 ◽  
pp. 466-471
Author(s):  
Oleg V. Panchenko ◽  
Alexey M. Levchenko ◽  
Victor A. Karkhin
Keyword(s):  
Hydrogen Content ◽  
Calculation Method ◽  
Specimen Size ◽  
Experimental Results ◽  
Diffusible Hydrogen ◽  
Measuring Methods ◽  
Deposited Metal ◽  
Calculation Results

Specimens of various sizes are used to determine hydrogen content in deposited metals in such standards as ISO 3690, AWS A 4.3, and GOST 23338 while measuring methods are the same. It causes problems in comparison of experimental results and brings up the following question: what kind of specimen size is optimal to determine hydrogen content? An optimal specimen size was estimated using a calculation method. Experimental and calculation results obtained by using specimens with estimated dimensions were compared to the results obtained by using the specimen with dimensions of 100*25*8 mm to determine hydrogen content in a deposited metal.

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.

Effect of preheat and post-heating on diffusible hydrogen content of welds

2012 ◽  
Vol 17 (5) ◽  
pp. 408-413 ◽  
Author(s):  
G K Padhy ◽  
V Ramasubbu ◽  
N Murugesan ◽  
C Remash ◽  
S K Albert
Keyword(s):  
Hydrogen Content ◽  
Diffusible Hydrogen

scholarly journals Evaluation of Crack Occurrence Probability of T-Shape Welded Structures

2011 ◽  
Vol 27 (2) ◽  
pp. 279-286
Author(s):  
Y. Hsu ◽  
W.-F. Wu ◽  
H.-T. Kuo
Keyword(s):  
Residual Stress ◽  
Chemical Composition ◽  
Hydrogen Content ◽  
Welded Joints ◽  
Occurrence Probability ◽  
Diffusible Hydrogen ◽  
Element Analysis ◽  
Welded Structures ◽  
Welded Structure ◽  
Major Factors

ABSTRACTWelded structures are vulnerable to fracture due to cracks, especially at the welds. To investigate the safety of T-Shape welded structures used in some construction sites, a method is proposed in this paper to evaluate the crack occurrence probabilities of the structures. Three major factors that affect the crack occurrence are taken into consideration. They are residual stress, diffusible hydrogen content and chemical composition of the weld metal. In the analysis, finite element analysis is performed to find the residual stress distribution of the structures. The uncertainties of diffusible hydrogen content and chemical composition are treated as random variables. The critical cooling time is found and utilized for evaluating the crack occurrence probability of the welded structure. Numerical results indicate that T-shape welded joints lead to higher residual stresses and higher crack occurrence probabilities in comparison with the traditional butt joints. Therefore, more attention should be paid to this kind of welded joints when they are used.

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