Failures Related to Welding

2021 ◽  
pp. 266-306
Author(s):  
Jorge J. Perdomo ◽  
Luis A. Ganhao
Keyword(s):  
Base Metal ◽  
Nondestructive Inspection ◽  
Incomplete Fusion ◽  
Service Failures ◽  
Critical Flaw ◽  
Weld Porosity ◽  
New Construction ◽  
Construction Inspection ◽  
Welding Processes

Abstract This article describes some of the welding discontinuities and flaws characterized by nondestructive examinations. It focuses on nondestructive inspection methods used in the welding industry. The sources of weld discontinuities and defects as they relate to service failures or rejection in new construction inspection are also discussed. The article discusses the types of base metal cracks and metallurgical weld cracking. The article discusses the processes involved in the analysis of in-service weld failures. It briefly reviews the general types of process-related discontinuities of arc welds. Mechanical and environmental failure origins related to other types of welding processes are also described. The article explains the cause and effects of process-related discontinuities including weld porosity, inclusions, incomplete fusion, and incomplete penetration. Different fitness-for-service assessment methodologies for calculating allowable or critical flaw sizes are also discussed.

Visual Evaluation of Cast Dental Alloys Welds Discontinuities in the Field of Fixed Prosthodontics

2011 ◽  
Vol 383-390 ◽  
pp. 4058-4064
Author(s):  
Sorin Porojan ◽  
Liliana Sandu ◽  
Florin Topală
Keyword(s):  
Laser Welding ◽  
Base Metal ◽  
Visual Inspection ◽  
Incomplete Fusion ◽  
Weld Quality ◽  
Dental Alloys ◽  
Visual Evaluation ◽  
Fixed Prosthodontics ◽  
Microplasma Welding

It is essential for a weld to satisfy the requirements of certain standards in the field where it is applied. The aim of the study was to highlight the discontinuities which can appear in the joints achieved by laser and microplasma welding of base metal dental alloys used in fixed prosthodontics. All types of discontinuities which are visible from visual inspection were searched: inclusions, inadequate joint penetration, incomplete fusion, undercuts, overlaps, underfills. Recognizing the defects and discontinuities and their delimitation was essential in determining the weld quality. The obtained results were satisfactory for the purpose both for microplasma and laser welding. Using these methods, welds without defects, which meet minimum acceptable standards for each case, could be obtained.

Role of welding processes on microstructure and mechanical properties of nuclear grade stainless steel joints

2019 ◽  
Vol 233 (11) ◽  
pp. 2335-2351 ◽  
Author(s):  
R Rajasekaran ◽  
AK Lakshminarayanan ◽  
M Vasudevan ◽  
P Vasantharaja
Keyword(s):  
Stainless Steel ◽  
Base Metal ◽  
Arc Welding ◽  
Gas Tungsten Arc Welding ◽  
Nuclear Grade ◽  
Lower Percentage ◽  
Weld Joints ◽  
Gas Tungsten Arc ◽  
Gas Tungsten ◽  
Welding Processes

Nuclear grade 316LN austenitic stainless steel weld joints were fabricated using conventional gas tungsten arc welding (GTAW), activated flux gas tungsten arc welding (AGTAW), laser beam welding (LBW) and friction stir welding (FSW) processes. Assessment of weld beads was done by mechanical and metallurgical characterizations. Bead geometry and weld zones were studied by taking macrographs along the transverse side of the weld joints. Metallurgical features of different weld joints were carried out using optical microscopy and scanning electron microscopy. Microhardness distribution across four weld joints was recorded and hardness variations were compared. All weld zone, heat affected zone (HAZ) of GTAW and LBW, thermo-mechanically affected zone (TMAZ) of FSW processes, exhibited higher hardness values than the base metal. Reduced hardness was recorded at HAZ of AGTAW process. This was the result of a considerable grain growth. LBW joint showed the highest hardness value at the center of the fusion zone due to fine equiaxed dendrite morphology. Tensile and impact properties of different welding processes were evaluated and comparisons were made at room temperature. All weld samples displayed high yield strength (YS) and ultimate tensile strength (UTS) with a lower percentage of elongation compared to that of the base metal. FSW joint showed improved YS, UTS and impact toughness compared to other weld joints. This is attributed to the formation of strain-free fine equiaxed grains at stir zone around 5 µm in size with subgrains of 2 µm in size by severe dynamic recrystallization mechanism. Among the fusion welding techniques, AGTAW process exhibited improved toughness, besides almost equal toughness of the base metal due to low δ-Ferrite with high austenite content. Fractography studies of the base metal and different weld samples were carried out by SEM analysis and features were compared.

Phenomenological Modeling of Fusion Welding Processes

MRS Bulletin ◽  
1994 ◽  
Vol 19 (1) ◽  
pp. 29-35 ◽  
Author(s):  
S.A. David ◽  
T. DebRoy ◽  
J.M. Vitek
Keyword(s):  
Solid State ◽  
Heat Source ◽  
Base Metal ◽  
Weld Pool ◽  
Welding Process ◽  
Poor Performance ◽  
Consumer Products ◽  
Phase Changes ◽  
Fusion Welding ◽  
Welding Processes

Welding is utilized in 50% of the industrial, commercial, and consumer products that make up the U.S. gross national product. In the construction of buildings, bridges, ships, and submarines, and in the aerospace, automotive, and electronic industries, welding is an essential activity. In the last few decades, welding has evolved from an empirical art to a more scientifically based activity requiring synthesis of knowledge from various disciplines. Defects in welds, or poor performance of welds, can lead to catastrophic failures with costly consequences, including loss of property and life.Figure 1 is a schematic diagram of the welding process showing the interaction between the heat source and the base metal. During the interaction of the heat source with the material, several critical events occur: melting, vaporization, solidification, and solid-state transformations. The weldment is divided into three distinct regions: the fusion zone (FZ), which undergoes melting and solidification; the heat-affected zone (HAZ) adjacent to the FZ, that may experience solid-state phase changes but no melting; and the unaffected base metal (BM).Creating the extensive experimental data base required to adequately characterize the highly complex fusion welding process is expensive and time consuming, if not impractical. One recourse is to simulate welding processes either mathematically or physically in order to develop a phenomenological understanding of the process. In mathematical modeling, a set of algebraic or differential equations are solved to obtain detailed insight of the process. In physical modeling, understanding of a component of the welding process is achieved through experiments designed to avoid complexities that are unrelated to the component investigated.In recent years, process modeling has grown to be a powerful tool for understanding the welding process. Using computational modeling, significant progress has been made in evaluating how the physical processes in the weld pool influence the development of the weld pool and the macrostructures and microstructures of the weld.

scholarly journals Welding Soundness of a Thick-Walled 9Cr-1Mo Steel

2010 ◽  
Vol 654-656 ◽  
pp. 408-411
Author(s):  
Woo Seog Ryu ◽  
Sung Ho Kim ◽  
Dae Whan Kim
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Base Metal ◽  
Hardness Test ◽  
Ultimate Tensile Stress ◽  
Narrow Gap ◽  
Martensitic Steels ◽  
Narrow Gap Welding ◽  
Self Energy ◽  
Welding Processes

High Cr ferritic/martensitic steels are demanded to join using favorable welding processes with economical and metallurgical advantages in order to apply to the thick-walled reactor pressure vessel of a very high temperature gas cooled reactor. Narrow gap welding technology was adopted to weld a thick-walled 9Cr-1Mo-1W steel with thickness of 110mm. The welding integrity was checked by non-destructive examination, optical microscopy and hardness test, and the homogeneity through welding depth was checked by absorbed impact energy and tensile strength. The optimizing welding conditions resulted that a narrow U-grooved gap with almost parallel edges was sound in actual practice, and the coarse grain zone was minimized in the heat affected zone. The absorbed energy of 75±25 J through welding depth was acceptable in scatter band to check the uniformity through the welding depth. The ultimate tensile stress and yield stress were about the same through welding depth at 650±10 MPa and 500±10 MPa, indicating no difference through welding depth. Elongation was also almost same through depth, and the fracture surface was appeared as a normal. The weld metal had similar mechanical properties to base metal. The upper self energy of weld metal was 194J, and the ductile-brittle transition temperature was 30°C. The tensile behavior was the typical trend with temperature, and YS and UTS of weldment were slightly higher than base metal by nearly below 10%. Thus, it concluded that the soundness of the narrow gap welding of a thick-walled 9Cr-1Mo-1W steel was confirmed in terms of the welding uniformity through the depth and mechanical properties.

Welding in Marine Engineering

1953 ◽  
Vol 167 (1) ◽  
pp. 48-61
Author(s):  
H. N. Pemberton
Keyword(s):  
Gas Turbines ◽  
Good Practice ◽  
Land Plant ◽  
General Interest ◽  
Repair Work ◽  
Welding Equipment ◽  
New Construction ◽  
Marine Engineering ◽  
Welding Processes ◽  
Marine Engineers

This lecture comprises a survey and commentary on the use of welding for the construction and repair of marine machinery for main propelling and ancillary purposes. The history of welding in relation to marine engineering is traced from the hammer welding of boiler seams in 1870 up to the present day, when welds made by modern processes are accepted for highly stressed components. Descriptions of welding processes are omitted since the lecture deals with welding applications rather than welding technique. Numerous examples are given and illustrated, and many of them relate to design details which are typical of good practice and are accepted by ship classification authorities. The lecture is divided under two main heads, namely, “New Construction” and “Repairs”. A further subdivision is made under “New Construction”, so that boilers, pipe-work, machinery components, turbines, gearing, electrical propulsion, refrigerating plant, and dredging craft are dealt with in that order. Also included in this section are some remarks of general interest on the subject of residual stresses and their relief by thermal treatment. Problems concerning the welding of alloy steels for gas turbines are discussed. There is need for research into the weldability of these steels, bearing in mind that not only the welds should be free from micro-cracks to start with, but they should also be equivalent to the parent metal in resistance to metallurgical and physical deterioration whilst operating at high temperatures over long periods. A field of welding which is always of interest to marine engineers is in repair work. Unlike land plant for which complete resources for repairs are usually available, marine machinery may be involved in mishaps and breakdown on the high seas and in remote parts of the world when repair facilities might be primitive, or even non-existent. Many ships now carry electric welding equipment, and sea-going marine engineers include welding in their many manual accomplishments. Several interesting examples of weld repairs are described, which in some cases have enabled ships to complete their voyages carrying valuable cargoes with a minimum of delay. Other examples are given which emphasize the discrimination that is necessary in deciding whether or not a welded repair is desirable. Unfortunate consequences have followed the ill-advised use of welding in some cases.

scholarly journals Effect of Rotational Speed on Static and Fatigue Properties of Rotary Friction Welded Dissimilar AA7075/AA5083 Aluminium Alloy Joints

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 99
Author(s):  
Agus Sasmito ◽  
Mochammad Noer Ilman ◽  
Priyo Tri Iswanto ◽  
Rifai Muslih
Keyword(s):  
Residual Stress ◽  
Aluminium Alloy ◽  
Base Metal ◽  
Weld Joint ◽  
Rotational Speed ◽  
Tensile Tests ◽  
Fatigue Properties ◽  
Weld Joints ◽  
Rotary Friction Welding ◽  
Welding Processes

In this work, rotary friction welding processes of dissimilar AA7075/AA5083 aluminium alloy rods with the diameter of 15 mm were performed at varying rotational speeds, typically 370 to 2500 rpm. The aim of this research is to improve mechanical properties, in particular, strength and fatigue performance of the weld joints. Several experiments including macro and microstructural examinations, Vickers microhardness measurements, tensile tests, fatigue tests and residual stress measurements were carried out. Results showed that at higher rotational speeds, typically 540 rpm or above, the dissimilar AA7075/AA5083 rotary friction weld joints revealed a static fracture in the AA5083 base metal side, indicating that the joint efficiency is more than 100%. It seemed that the best weld joint was achieved at the rotational speed of 1200 rpm, in which the friction heat was sufficient to form metallurgical bonding without causing excessive flash and burn-off. In such a condition, the fatigue strength of the weld joint was slightly higher than AA5083 base metal, but it was lower than AA7075 base metal. It was confirmed that the crack origin is observed at the interface followed by fatigue crack growth towards AA5083 side, and the growth of crack seemed to be controlled by microstructure and residual stress.

Effect of Corrosion of Stainless Steel Welded within Lithium Chloride

2016 ◽  
Vol 869 ◽  
pp. 470-473
Author(s):  
Juliete N. Pereira ◽  
David Márcio Macêdo Dias ◽  
Natal Nerímio Regone ◽  
Marcos A. Fernandes ◽  
Sandra Nakamatsu ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Base Metal ◽  
Lithium Chloride ◽  
Welding Process ◽  
Weld Bead ◽  
Mechanical Resistance ◽  
Martensitic Steels ◽  
Cyclic Potentiodynamic Polarization ◽  
Lithium Chloride Solution ◽  
Welding Processes

The difficulties experienced in welding processes of martensitic stainless steel led to development of a new class of them, known as stainless mild martensitic steels. Also, due to the current high demand for energy and materials to oil extraction at great depths, scientists have being developing specific researches about mechanical resistance and corrosion of steels and how these properties are influenced by high temperature processes. This research studies the effect of welding process over the corrosion resistance of the 13Cr4Ni0.02C steel in a lithium chloride solution with a concentration of 120,000 PPM Cl-. The corrosion tests were conducted by cyclic potentiodynamic polarization in the base metal, weld bead and heat affected zone (HAZ) areas of the steel, in average temperatures of 23°C (as reference) and 3°C. The results revealed that the weld bead and heat affected zones of the 13Cr4Ni0.02C steel in a temperature of 3°C are less resistant to corrosion in this environment than the base metal in the same conditions.

scholarly journals Uniform system for grouping of steels in welding manufacture by ISO/TR 15608

2020 ◽  
pp. 63-68
Author(s):  
T. I. Bendik ◽  
N. I. Urbanovich ◽  
D. A. Nazarov ◽  
F. K. Figurin
Keyword(s):  
Mechanical Properties ◽  
Base Metal ◽  
Qualification Test ◽  
Specific Group ◽  
Uniform System ◽  
Wide Range ◽  
Steel Grades ◽  
Technological Documentation ◽  
The Republic ◽  
Welding Processes

Recommendations to assign steel grades most commonly used in industry and energy of the Republic of Belarus to a specific group and subgroup of the international standard ISO/TR 15608 are presented. These recommendations were made on the basis of a comparative analysis of the base metal chemical composition and its mechanical properties, given in the national and foreign standards for sheet and pipe metal rolling. Analysis of mechanical properties have been included conditions of thermal and thermomechanical treatment of the base metal. The information presented in the article can be useful for a wide range of welding specialists in documentation development for welding processes (WPS, WPQR), issuing welders attestation certificates (qualification test certificate) and other technological documentation.

The Effect of Base Metal and Core Rod Carbon Content on Underwater Wet Weld Porosity

2010 ◽  
Author(s):  
Luciano G. D. Andrade ◽  
Ezequiel C. P. Pessoa ◽  
Alexandre Q. Bracarense ◽  
Weslley C. Dias ◽  
Leandro F. Ribeiro ◽  
...  
Keyword(s):  
Weld Metal ◽  
Carbon Content ◽  
Base Metal ◽  
Steel Plates ◽  
Current Electrode ◽  
Current Voltage ◽  
Weld Porosity ◽  
Molten Droplets ◽  
Core Rod ◽  
Porosity Measurements

Porosity is a common defect observed in underwater wet welding. Several research programs have been developed to understand how pores form in order to mitigate the problem. No superficial pores and a limited number of internal pores (based on size) are important requirements to classify underwater wet welds according to the American Welding Society – AWS D3.6M standard. The main objective of this work is to study the effect of base metal and core rod carbon content on weld metal porosity. A pressure chamber with 20 atmospheres capacity was used to simulate depth with fresh water. To perform the welds, a gravity feeding system able to open an electric arc and deposit the weld automatically was used. Beads-on-plate were made using Direct Current Electrode Negative (DCEN) configuration on two base metals with different carbon contents (C2 – 0.1 wt. pct. and C7 – 0.7 wt. pct.) at 50 meters water depth. Commercial E6013 grade electrodes were used to deposit the welds. These electrodes were produced with core rods with two different carbon content (E2 – 0.002 wt. pct. and E6 – 0.6 wt. pct.) and painted with varnish for waterproofing. Samples were removed from the beginning, middle and end of the BOP welds and prepared following metallographic techniques including macroetching and image analysis for weld porosity. A data acquisition system was used to record current, voltage and welding time at 1.0 kHz rate. The porosity measurements indicated an increase of about 85% and 70% when E6 electrodes were used instead of E2 electrode on C2 and C7 steel plates, respectively. Simultaneously, the increase in porosity was followed by an increase in short circuiting events, an increase in weld bead penetration and a decrease in welding voltage. These observations seem to confirm, a direct effect of carbon content of the core rod on weld metal porosity and that porosity is associated with the CO reaction that can occur during metal transfer in that molten droplets carry gas bubbles to the welding pool. On the other hand, the increase of carbon content in the base metal was seen to decrease the porosity in the weld metal. This result can be related with the decrease in penetration observed when changing C2 to C7 plates. The smaller participation of carbon from the base metal in the weld pool reactions should then reduce the CO formation and, consequently, the amount of pores in the weld.

How Validates Residual Stress Effect on Fatigue Strength and SCC Evaluations?

2004 ◽  
Author(s):  
Masahito Mochizuki ◽  
Masao Toyoda
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Process Control ◽  
Stress Corrosion ◽  
Base Metal ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Stress Effect ◽  
Residual Stress Effect ◽  
Welding Processes

The availability of several processes for residual stress control is discussed in order to verify residual stress effect on fatigue strength and SCC evaluations The effectiveness protecting from fatigue and stress-corrosion cracking is validated by numerical analysis and actual experiment. In-process control during welding is the easiest method to reduce residual stress without any treatment after welding process. Control of welding pass sequence for multi-pass weld is applied to cruciform joints and butt-joints with X-shaped groove. Other processes after welding are confirmed the validity of residual stress improvement. Water jet peening is useful for obtaining compressive residual stress on the surface, and the tolerance against both fatigue and stress-corrosion cracking is verified. Cladding of corrosion-resistant material is also effective for preventing stress-corrosion cracking by the metallurgical respect on the basis that residual stress at the interface to base metal should be considered carefully. The residual stress of the base metal near the clad edge is confirmed within the tolerance of crack generation. Controlling methods both during and after welding processes are found to be effective for assuring the integrity of the welded components.

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