scholarly journals Analisis Kegagalan Pembentukan Ellipsoidal Head Pressure Vessel dari Dua Pelat Dilas ASME SA516 Grade 70N dengan menggunakan Metode Fabrikasi Cold Forming

2021 ◽  
Vol 43 (1) ◽  
pp. 48
Author(s):  
Khairmen Suardi ◽  
Faris Fadli
Keyword(s):  
Stress Concentration ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Pressure Vessel ◽  
Heat Input ◽  
Martensite Phase ◽  
Cold Cracking ◽  
Carbon Equivalent ◽  
Forming Process ◽  
Cold Forming

AbstrakHead pada pressure vessel yang berbentuk melengkung, seperti: hemispherical, torispherical, dan ellipsoidal dapat dibuat dari pelat dengan lebar 2.5 m yang mengalami proses metal forming. Namun, pelat yang tersedia di pasaran pada umumnya memiliki lebar 1,6 m. Kondisi ini menjadi batasan apabila ingin menggunakan satu material pelat secara integral sehingga dibutuhkan pelat untuk membuat head dengan lebar yang lebih besar. Oleh karena itu, untuk membuat head dengan lebar 2,5 m dilakukan proses cold forming pada dua pelat yang dilas. Namun setelah proses dilakukan, terjadi kegagalan berupa timbulnya retakan di sekitar area las. Pada paper ini akan dibahas analisis kegagalan proses cold forming yang terjadi pada dua pelat ASME SA516 grade 70N yang digunakan sebagai base metal. Untuk menganalisis penyebab kegagalan, maka dilakukan pengujian kekerasan, tarik, metalografi, dan komposisi kimia. Selain itu juga dilakukan perhitungan untuk mengetahui nilai crack consists of hot (UCS), cold cracking (Pcm), dan carbon equivalent (CE). Hasil perhitungan menunjukkan bahwa material tersebut memiliki nilai UCS di bawah 30, nilai Pcm berada di antara 0,23-0,35%, serta berada di zona II pada diagram Graville dimana nilai tersebut menunjukkan bahwa material memiliki kemampulasan  yang baik. Sementara dari hasil pengujian mekanis didapatkan nilai kekerasan dan kekuatan tarik yang lebih besar dari standar, yaitu masing-masing sebesar 300 HBW dan 621 Mpa dengan nilai elongasi yang masih tinggi, yaitu  sebesar 21,8%. Hasil pengamatan metalografi menunjukkan terbentuk fase martensit namun dalam jumlah yang sedikit pada area heat affected zone (HAZ) dengan bentuk butir seperti jarum. Fase martensit ini berperan sebagai stress concentration yang menjadi titik awal retak ketika proses cold forming dilakukan. Terbentuknya fasa martensit ini disebabkan oleh proses preheat yang tidak sesuai serta heat input yang terlalu besar. Abstract             The head on a pressure vessel with curved shapes such as hemispherical, torispherical, and ellipsoidal is derived from the formed plate. Generally the plates available in the market have a width of 1.6 m, this condition becomes a limitation if you want to use one plate material integrally so that a plate is needed to make a head with a larger width. Therefore, to make a head with a width of 2.5 m, a cold forming process is carried out on two welded plates. However, after the process is carried out, failure occurs in the form of cracks around the weld area. In this paper, we will discuss the failure analysis of the cold forming process that occurred on two ASME SA516 grade 70N plates used as base metal. In order to analyze the causes of failure, hardness, tensile, metallographic, and chemical composition tests were carried out. In addition, calculations were also carried out to determine the value of crack consists of hot (UCS), cold cracking (Pcm), and carbon equivalent (CE). From the calculation results it is evident that the material has a UCS value below 30, the PCm value is between 0.23-0.35%, and is in zone II on the Graville diagram where this value indicates that the material has good weldability. Meanwhile, from the results of mechanical testing, the hardness and tensile strength values are greater than the standard, which are 300 HBW and 621 Mpa, respectively, with a high elongation value, which is 21.8%. The results of metallographic observations showed that the martensite phase was formed but in small amounts in the heat affected zone (HAZ) area with needle-like grain shapes. This martensite phase acts as a stress concentration which is the starting point for cracks when the cold forming process is carried out. The formation of the martensite phase is caused by an inappropriate preheat process and the heat input is too large.

Forming Process during Electron Beam Surfi-SculptTM on Ti-6Al-4V Alloy

2019 ◽  
Vol 813 ◽  
pp. 25-30
Author(s):  
Kai Li ◽  
Peng Fei Fu ◽  
Zhen Yun Tang ◽  
Bo Zhang ◽  
Yan Long Ma ◽  
...  
Keyword(s):  
Electron Beam ◽  
Fusion Zone ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Surface Region ◽  
Martensite Phase ◽  
Treatment Technique ◽  
Layer By Layer ◽  
Forming Process ◽  
Near Surface

Electron beam Surfi-SculptTM is a novel surface treatment technique applied to produce high level performance Composite-Metal-Weld (ComeldTM) joints. Investigation on forming process during electron beam Surfi-SculptTM on Ti-6Al-4V alloy showed protrusions were formed via a layer-by-layer mode like additive manufacturing process. The near-surface region of electron beam Surfi-Sculpted Ti-6Al-4V alloy was occupied by fusion zone, heat-affected zone and base metal from the outermost surface to the underlying bulk alloy. The microstructure of fusion zone was characterized by a high density of fine acicular martensite phase, leading to a higher micro-hardness. A heat-affected zone was sandwiched between fusion zone and the underlying base metal, with different microstructural features compared to both fusion zone and the base metal.

Application of FIB/SEM/EBSD for Evaluation of Residual Strains and Their Relationship to Weld Metal Hydrogen Assisted Cold Cracking

2012 ◽  
Author(s):  
W. L. Costin ◽  
I. H. Brown ◽  
L. Green ◽  
R. Ghomashchi
Keyword(s):  
Residual Stresses ◽  
Weld Metal ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Ion Beam ◽  
Base Material ◽  
Welding Process ◽  
Cold Cracking ◽  
Predictive Methods ◽  
Residual Strains

Hydrogen assisted cold cracking (HACC) is a welding defect which may occur in the heat affected zone (HAZ) of the base metal or in the weld metal (WM). Initially the appearance of HACC was associated more closely with the HAZ of the base metal. However, recent developments in advanced steel processing have considerably improved the base material quality, thereby causing a shift of HACC to the WM itself. This represents a very serious problem for industry, because most of the predictive methods are intended for prevention of HACC in the HAZ of the base metal, not in the weld metal [1]. HACC in welded components is affected by three main interrelated factors, i.e. a microstructure, hydrogen concentration and stress level [2–4]. In general, residual stresses resulting from the welding process are unavoidable and their presence significantly influences the susceptibility of weld microstructures to cracking, particularly if hydrogen is introduced during welding [5]. Therefore various weldability tests have been developed over the years which are specifically designed to promote HACC by generating critical stress levels in the weld metal region due to special restraint conditions [4, 6–8]. These tests were used to develop predictive methods based on empirical criteria in order to estimate the cracking susceptibility of both the heat-affected zone and weld metal [4]. However, although the relationship between residual stress, hydrogen and HACC has received considerable attention, the interaction of residual stresses and microstructure in particular at microscopic scales is still not well understood [5, 9–21]. Therefore the current paper focuses on the development and assessment of techniques using Focused Ion Beam (FIB), Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction for the determination of local residual strains at (sub) micron scales in E8010 weld metal, used for the root pass of X70 pipeline girth welds, and their relationship to the WM microstructure. The measurement of these strains could be used to evaluate the pre-existing stress magnitudes at certain microstructural features [22].

Ultranarrow Gap Welding with Constrained Arc by Flux Strips

2012 ◽  
Vol 472-475 ◽  
pp. 2814-2818
Author(s):  
Liang Zhu ◽  
Yan Li Pan ◽  
Yuan Bo Li
Keyword(s):  
Base Metal ◽  
Cross Sections ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Pipeline Steel ◽  
Welding Parameters ◽  
Weld Profile ◽  
The Cross

Ultranarrow gap welding with the gap of less than 5mm was executed successfully. In order to prevent the arc from being attracted by sidewall and going up along the sidewall, the flux strips consisting of the specified aggregates are placed onto the sidewalls to constrain the arc. This technique was tested on the welding experiment of pipeline steel with thickness of 30mm. The involved welding parameters were obtained. The width of gap is 4mm, the welding voltage 20~24V, and the heat input 0.6 KJ/mm. The cross sections of weld profile were analyzed. The width of heat affected zone is relatively narrow and about 1.3mm, and the weld hardness is much higher than that of HAZ and base metal.

Investigation of Failed Wheel Rim Weld Joints

2017 ◽  
Vol 891 ◽  
pp. 288-291
Author(s):  
Atila Drotár ◽  
Jaroslav Duška ◽  
Lucia Hrabčáková ◽  
Peter Kalmár ◽  
Alica Mašlejová
Keyword(s):  
Weld Joint ◽  
Heat Affected Zone ◽  
Input Power ◽  
Carbon Equivalent ◽  
Metallographic Analysis ◽  
Cold Forming ◽  
Joint Point ◽  
Micro Cracks ◽  
Transverse Weld

Material used for car sheet wheels production was analyzed due to limited weldability. During the manufacturing of wheel rims, during shaping - cold forming cracks were initiated in the weld joint and in its heat affected zone. The destruction of rims occurred during their shaping. The wheel rims were welded at their manufacturer's site applying the compression technology and using the direct current welding source. Five rims were supplied for the metallographic analysis of which two were with conforming weld joint, and in the case of three rims there was a rupture at the weld joint point; on one them along the whole width of the rim. The rupture of the rim weld joint across its whole width at the weld joint point that was made by diffusionless connection was caused by a low welding input power. The primary cause of the rim cracking initiation on the transverse weld joint was the presence of micro-cracks, micro-notches in the vicinity of the weld joint and the heat affected zone, the notch effect of which was manifested during the rim forming. The occurrence of micro-notches was shown in the heat affected zone as well as on the conforming weld joint of one rim. The carbon equivalent Ce from the measured values of the material chemical composition of all rims was in the range from 0.175 to 0.201. Given the declared weldability guaranteed up to the value of Ce = 0.45, all analyzed materials complied with the requirement. Material cleanliness, grain size and linearity met the requirements of specification for material MW 01. Given the insufficient quality of the material was not the primary cause of the defect, it was recommended to eliminate the occurrence of potential notches in the heat affected zone through slightly planning of the weld collar.

Fracture Toughness Evaluation of Heat-Affected Zone Under Weld Overlay Cladding in Reactor Pressure Vessel Steel

2018 ◽  
Author(s):  
Yoosung Ha ◽  
Tohru Tobita ◽  
Hisashi Takamizawa ◽  
Satoshi Hanawa ◽  
Yutaka Nishiyama
Keyword(s):  
Fracture Toughness ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Weld Overlay ◽  
Reactor Pressure Vessel Steel ◽  
Reactor Pressure

An evaluation of the fracture toughness of the heat-affected zone (HAZ), which is located under the weld overlay cladding of a reactor pressure vessel (RPV), was performed. Considering inhomogeneous microstructures of the HAZ, 0.4T-C(T) specimens were manufactured from the cladding strips locations, and Mini-C(T) specimens were fabricated from the distanced location as well as under the cladding. The reference temperature (To) of specimens that were aligned with the middle section of a cladding strip (HAZMCS) was ∼12°C higher than that of specimens that were aligned with cladding strips at the overlap (HAZOCS). To values of partial area in the HAZ were obtained using Mini-C(T) specimen. The To values obtained near the side of the cladding were ∼13°C higher than those away from the cladding. To values of HAZ for both 0.4T-C(T) and Mini-C(T) specimens were significantly lower than that of the base metal at a quarter thickness by 40°C–60°C. Compared to the literature data that indicated fracture toughness at the surface without overlay cladding and base metal of a quarter thickness in a pressure vessel plate, this study concluded that the welding thermal history showed no significant effect on the fracture toughness of the inner surface of RPV steel.

Mechanical and Microstructural Characterization of Heat-Affected Zone Materials of Reactor Pressure Vessel

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Jinya Katsuyama ◽  
Tohru Tobita ◽  
Yutaka Nishiyama ◽  
Kunio Onizawa
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Pressure Vessel ◽  
Postweld Heat Treatment ◽  
Microstructural Characterization ◽  
Reactor Pressure Vessel ◽  
Reactor Pressure

In order to provide the technical basis for the judgment of the needs of surveillance specimens of heat-affected zone (HAZ) in reactor pressure vessel (RPV) steels, we performed a research on the characterization of metallurgical and mechanical properties of the HAZ in RPV steels. The distributions of grain size and phases were drawn as a map based on temperature histories around HAZ obtained from welding simulation. Referring to the HAZ map, typical HAZ materials were made by simulating temperature histories including postweld heat treatment (PWHT) within the HAZ. Metallurgical and mechanical characteristics for those HAZ materials were compared with those of base metal. From the results, it is clear that mechanical properties of HAZ materials depend not on the prior austenitic grain size but mostly on the phases. Concerning on the fracture toughness in HAZ, HAZ materials close to weld metal indicated higher toughness than that of base metal due to mixed structure of martensite and lower-bainite, while HAZ materials close to base metal were equivalent or slightly lower toughness than that of base metal due to the same phase as base metal of upper-bainite.

Mechanical and Microstructural Characterization of Heat-Affected Zone Materials of Reactor Pressure Vessel

2010 ◽  
Author(s):  
Jinya Katsuyama ◽  
Tohru Tobita ◽  
Yutaka Nishiyama ◽  
Kunio Onizawa
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Pressure Vessel ◽  
Charpy Impact ◽  
Reactor Pressure Vessel ◽  
Irradiation Embrittlement ◽  
Reactor Pressure

In order to monitor the neutron irradiation embrittlement of the reactor pressure vessel (RPV) steels for the safe operation of light-water reactors, surveillance specimens of representative materials, i.e. base metal, weld metal and heat affected zone (HAZ), are installed in the RPV during reactor operation according to the regulation. Among these materials, HAZ specimens exhibit a relatively large scatter in Charpy impact properties because of the microstructural inhomogeneity due to multi-pass welding. ASTM E185 and JSME S NC1 stipulate the exception of HAZ specimens from surveillance test. However, the technical basis on the exception has not been established. Therefore, we have started a research on the irradiation embrittlement in HAZ material of RPV steels. Typical RPV steel plates with different impurity levels and their weldments were fabricated to characterize the microstructures and subsequent mechanical properties of typical HAZ materials. Simulated HAZ materials were also made by applying several heat treatments representative of HAZ. Finite element analysis was conducted to draw maps of distributions of grain size and phase-fraction. Using simulated HAZ materials with different grain size and phase before irradiation, mechanical properties such as hardness, Charpy impact property and fracture toughness were measured in comparison with those of base metals and actual HAZ materials. Through the comparison, it was indicated that mechanical properties such as fracture toughness in some simulated HAZ materials were different from base metal and dependent significantly on the metallurgical structure, particularly phase but prior austenitic grain size. Higher fracture toughness in CGHAZ (Coarse-Grain HAZ) materials compared to base metal is due to mixed structure of martensite and lower-bainite phases. Upper-bainite phase in FGHAZ (Fine-Grain HAZ) and base materials causes lower fracture toughness than CGHAZ materials.

Analytical Study on Microstructure and Mechanical Property in HAZ-Softened Weld Joint with High Heat Input of Low Carbon TMCP Steel

2017 ◽  
Vol 872 ◽  
pp. 99-106
Author(s):  
Rong Zhi Mai ◽  
Ze Xin Jiang ◽  
Jin Jun Ma ◽  
Yong Jun Zhang
Keyword(s):  
Tensile Strength ◽  
Base Metal ◽  
Heat Input ◽  
High Strength ◽  
High Heat ◽  
Carbon Equivalent ◽  
Low Carbon ◽  
Fine Grain ◽  
High Heat Input ◽  
Softened Zone

Three types of low-carbon TMCP steels with different strength of the same carbon equivalent were welded by the flux-cupper back for SAW(FCB) method in this work. The microstructure, hardness and tensile strength of the FCB welded joints were studied. Softening phenomenon occurs in the heat affected zone of low-carbon content and low carbon-equivalent TMCP EH36 steel after high heat input welding. The softened zone is mainly depended on the strength of the base metal (BM), which appears on the fine-grain zone and incomplete crystallize zone of BM with relative low strength, and on the coarse grain zone of BM with high strength. The ratio of the tensile strength between each FCB joint and BM is the same of 0.98 as the same carbon and carbon equivalent content of 0.5% and 0.315% of BM, which is almost independent of the strength of BM. The tensile strength of the incomplete crystallize zone depends on the strength of the BM, which results in the improved strength of the whole softened zone with the increasing strength of base metal.

scholarly journals Properties of a thick-section narrow-gap gas tungsten arc weld of cast Haynes 282

2021 ◽  
Author(s):  
Michael Santella ◽  
X. Frank Chen ◽  
Philip Maziasz ◽  
Jason Rausch ◽  
Jonathan Salkin
Keyword(s):  
Base Metal ◽  
Heat Affected Zone ◽  
Reference Data ◽  
Filler Metal ◽  
Stress Rupture ◽  
Narrow Gap ◽  
Weld Deposit ◽  
Gas Tungsten Arc ◽  
Gas Tungsten ◽  
Weld Heat

AbstractA 50.8-mm-deep gas tungsten arc weld was made with matching filler metal in cast Haynes 282 alloy. The narrow-gap joint was filled with 104 weld beads. Visual and dye-penetrant inspection of cross-weld specimens indicated that the cast base metal contained numerous casting defects. No visible indications of physical defects were found in the weld deposit. The weld heat-affected zone was characterized by microcracking and localized recrystallization. The cause of the cracking could not be determined. Hardness testing showed that a softened region in the as-welded heat-affected zone was nearly eliminated by post-weld heat treatment. Tensile testing up to 816 °C showed that cross-weld specimen strengths ranged from 57 to 79% of the cast base metal tensile strength. The stress-rupture strengths of cross-weld specimens are within 20% of base metal reference data. Failures of both tensile and stress-rupture specimens occurred in the base metal.

scholarly journals Formability study and metallurgical properties analysis of FSWed AA 6061 blank by the SPIF process

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Payam Tayebi ◽  
Ali Fazli ◽  
Parviz Asadi ◽  
Mahdi Soltanpour
Keyword(s):  
Base Metal ◽  
Strain Distribution ◽  
Thickness Distribution ◽  
Experimental Studies ◽  
Welding Process ◽  
Forming Limit ◽  
Forming Process ◽  
Friction Stir ◽  
Numerical Process ◽  
Tailor Welded Blank

AbstractIn this study, in order to obtain the maximum possible formability in tailor-welded blank AA6061 sheets connected by the friction stir welding (FSW) procedure, the incremental sheet forming process has been utilized. The results are presented both numerically and experimentally. To obtain the forming limit angle, the base and FSWed sheets were formed in different angles with conical geometry, and ultimately, the forming limit angle for the base metal and FSWed sheet is estimated to be 60° and 57.5°, respectively. To explore the effects of welding and forming procedures on AA6061 sheets, experimental studies such as mechanical properties, microstructure and fracture analysis are carried out on the samples. Also, the thickness distribution of the samples is studied to investigate the effect of the welding process on the thickness distribution. Then, the numerical process was simulated by the ABAQUS commercial software to study the causes of the FSWed samples failure through analyzing the thickness distribution parameter, and major and minor strains and the strain distribution. Causes of failure in FSWed samples include increased minor strain, strain distribution and thickness distribution in welded areas, especially in the proximity of the base metal area.

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