scholarly journals Stress corrosion resistance of welded joints of low-alloy pipe steel produced by high frequency welding

2020 ◽  
Vol 61 (4) ◽  
pp. 328-338
Author(s):  
Lyudmila Nyrkova ◽  
Sergiy Prokopchuk ◽  
Svetlana Osadchuk ◽  
Anatoliy Rybakov ◽  
Larisa Goncharenko
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Weld Metal ◽  
Stress Corrosion ◽  
Base Metal ◽  
Cathodic Protection ◽  
Welded Joints ◽  
High Frequency ◽  
Welded Joint ◽  
Stress Corrosion Resistance

The paper presents the results of stress corrosion resistance studies of welded joints of low-alloy steel 17G1SU, obtained by high-frequency welding (HFW). The potentiometry method has established that the welded joint in the state after welding and after linear heat treatment is resistant to corrosion, because the potential difference between the weld and the base metal does not exceed (30-50) mV. According to the results of accelerated corrosion-mechanical tests in 3% NaCl under conditions of constant load under different stress, it was found that the rate of uniform corrosion of both types of welded joints is almost the same as the base metal. Slightly higher corrosion rate of the welded junction after linear heat treatment correlates with the electrochemical data. In general, the welded joint, made according to the factory technology, has resistance to corrosion and mechanical destruction in a solution of 3% NaCl at the level of the base metal, in the absence of weld defects. In the range of protective polarization potentials normalized by the standard of Ukraine, the ratio of the cathodic protection current to the diffusion current limit for the base metal and for the weld metal practically does not differ. It can be expected that under the conditions of cathodic protection, the predominant local flooding of the weld metal or the parent metal is not expected.

scholarly journals Corrosion Behavior of Welded Joints of X70 Pipeline Steel Produced by High-frequency Welding

2019 ◽  
pp. 1-9
Author(s):  
Anatolii Klymenko ◽  
Svetlana Kovalenko ◽  
Vitalii Kuzmenko ◽  
Yurii Kovalenko
Keyword(s):  
Corrosion Resistance ◽  
Stress Corrosion ◽  
Kinetic Parameters ◽  
Base Metal ◽  
Corrosion Behavior ◽  
Stress Corrosion Cracking ◽  
Welded Joints ◽  
High Frequency ◽  
Welded Joint ◽  
Pipeline Steel

Corrosion behavior of welded joints of steel pipe category X70 produced by high-frequency welding, in different conditions, in which it is possible to initiate stress-corrosion cracking, hydrogen or sulfide cracking, was investigated. According to the results of electrochemical researches, the kinetic parameters of the cathode and anode processes on the surface of the welded joint of pipe in the investigated solutions are determined. Corrosion resistance of the welded joint HFW-pipe is similar to corrosion resistance of the base metal.

Creep Strength Evaluation of a New and a Used Grade 91 Welded Joints by Using a Miniature Specimen

2018 ◽  
Author(s):  
Takashi Ogata
Keyword(s):  
Weld Metal ◽  
Strain Rate ◽  
Creep Strain ◽  
Base Metal ◽  
Welded Joints ◽  
Welded Joint ◽  
Creep Damage ◽  
Creep Strain Rate ◽  
Standard Size ◽  
Grade 91

Grade 91 is widely used for steam pipes and tubes in high temperature boilers of ultra-super critical power plants in Japan. It was reported that creep damage may initiate at the fine grain region within the heat affected zone (HAZ) in welded joints prior to the base metal, so called “Type IV” damage, which causes steam leakage in existing power plants. Therefore, development of creep damage assessment methods is not only an important but also an urgent subject to maintain operation reliability. In order to evaluate creep damage of welded joints based on finite element analyses, creep deformation properties of a base metal, a weld metal and a HAZ have to be obtained from creep tests. However, it is difficult to cut a standard size creep specimen from the HAZ region. Only a miniature size specimen is available from the narrow HAZ region. Therefore, development of creep testing and evaluation technique for miniature size specimens is highly expected. In this study, a miniature tensile type solid bar specimen with 1mm diameter was machined from a base metal, a weld metal and a HAZ of a new and a used Grade 91 welded joints, and creep tests of these miniature specimens were conducted by using a special developed creep testing machine. It was found that creep deformation property is almost identical between the base metal and weld metal, and creep strain rate of the HAZ is much faster than that of these metals in the new welded joint. Relationships between stress and creep strain rates of the base metal and the HAZ in the used welded joint are within scatter bands of those in the new material. On the other hand, creep strain rate of the weld metal in the used welded joint became much faster than that in the new one. Then both the standard size and the miniature size cross weld specimens were machined from the new and the used welded joints and were tested under the same temperature and stress conditions. Rupture time of the miniature cross weld specimen is much shorter than that of the standard size cross weld specimen. The finite element creep analysis of the specimens indicates that higher triaxiality stress yields within the HAZ of the standard size specimen than that of the miniature specimen causing faster creep strain rate in the HAZ of the miniature cross weld specimen.

scholarly journals Effect of Microstructure on Hydrogen Diffusion in Weld and API X52 Pipeline Steel Base Metals under Cathodic Protection

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
R. C. Souza ◽  
L. R. Pereira ◽  
L. M. Starling ◽  
J. N. Pereira ◽  
T. A. Simões ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Weld Metal ◽  
Base Metal ◽  
Cathodic Protection ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Pipeline Steel ◽  
Sodium Thiosulfate ◽  
Hydrogen Flow ◽  
Electrochemical Tests

The aim of this research was to evaluate the influence of microstructure on hydrogen permeation of weld and API X52 base metal under cathodic protection. The microstructures analyzed were of the API X52, as received, quenched, and annealed, and the welded zone. The test was performed in base metal (BM), quenched base metal (QBM), annealed base metal (ABM), and weld metal (WM). Hydrogen permeation flows were evaluated using electrochemical tests in a Devanathan cell. The potentiodynamic polarization curves were carried out to evaluate the corrosion resistance of each microstructure. All tests were carried out in synthetic soil solutions NS4 and NS4 + sodium thiosulfate at 25°C. The sodium thiosulfate was used to simulate sulfate reduction bacteria (SRB). Through polarization, assays established that the microstructure does not influence the corrosion resistance. The permeation tests showed that weld metal had lower hydrogen flow than base metal as received, quenched, and annealed.

scholarly journals Microstructure, roughness, and corrosion resistance of X5CrNi18-10 austenite stainless steel welded joint

2021 ◽  
pp. 7-7
Author(s):  
Bojana Radojkovic ◽  
Bore Jegdic ◽  
Jovanka Kovacina ◽  
Sanja Stevanovic ◽  
Dunja Marunkic
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Weld Metal ◽  
Base Metal ◽  
Pitting Corrosion ◽  
Welded Joint ◽  
Electrochemical Testing ◽  
Limit Value ◽  
Before And After ◽  
Degree Of Sensitization

The influence of the microstructure of the X5CrNi18-10 stainless steel welded joint on its resistance to general, pitting, and intergranular corrosion was analysed. The structure of weld metal, heat affected zone (HAZ) and base metal before and after electrochemical testing was analysed using SEM/EDS. The influence of the roughness level of the welded joint on its resistance to the mentioned types of corrosion was examined as well. Although the degree of sensitization of HAZ was significantly lower than the limit value, HAZ showed a noticeably greater tendency to general and pitting corrosion than weld metal and base metal. Polishing has been shown to significantly improve the corrosion resistance of HAZ than in the case of other parts of the welded joint.

Structure of welded joints of 15Kh2MFA steel completed with low carbon surfacing without heat treatmen

2020 ◽  
pp. 35-43
Author(s):  
M. N. Timofeev ◽  
S. N. Galyatkin ◽  
R. I. Samoylenko ◽  
Yu. M. Markova
Keyword(s):  
Heat Treatment ◽  
Base Metal ◽  
Welded Joints ◽  
Welded Joint ◽  
Chemical Elements ◽  
Steel Structures ◽  
Low Carbon ◽  
15Kh2mfa Steel

The paper studies the 15Kh2MFA steel structures at various sections of the welded joint performed without heat treatment after welding with low-carbon surfacing. It is shown that there are three zones in lowcarbon surfacing, which differ in the content of chemical elements passing from the base metal to the deposited one, as well as in the tendency to form hardened structures during welding.

Microstructure and Properties of Lean Duplex Stainless Steel UNS S32101 Welded Joint by Hot Wire TIG Welding

2020 ◽  
Vol 993 ◽  
pp. 466-473
Author(s):  
Liang Liang Bao ◽  
Yong Wang ◽  
Tao Han
Keyword(s):  
Corrosion Resistance ◽  
Base Metal ◽  
Pitting Corrosion ◽  
Welded Joints ◽  
Welded Joint ◽  
Tig Welding ◽  
Hot Wire ◽  
Average Value ◽  
Pitting Corrosion Resistance ◽  
Temperature Heat

Lean duplex stainless steel UNS S32101 was welded by hot wire TIG welding and traditional TIG welding, and nice formed welds with no visible defects were obtained. Metallographic microstructure, phase ratio, mechanical properties and pitting corrosion resistance property of the welded joints were tested. Microstructure analysis showed that the hot wire TIG and traditional TIG welded joints had similar microstructures. The welded metal was composed of ferrite, grain boundary austenite (GBA), Widmanstatten austenite (WA), intragranular austenite (IGA). The high temperature heat affected zone (HTHAZ) consisted of ferrite, GBA and IGA. The low temperature heat affected zone (LTHAZ) had semblable microstructures with base metal. The phase ratio of welded joints was measured by manual point count method. The ferrite/austenite ratio of hot wire TIG welded metal was close to 1:1. The welded joints of hot wire TIG and traditional TIG had same hardness distribution. The hardness of hot wire TIG with an average value of 291 HV10 was a little higher than that of traditional TIG with an average value of 280 HV10. Charpy impact test at -40°C showed that the impact values of hot wire TIG and traditional TIG welded joints meet the standard requirements. The results of chemical weight loss method showed that the corrosion rate of hot wire TIG welded joint was less than 10 mdd. Potentiodynamic polarization method results showed that the pitting corrosion resistance of hot wire TIG welded joints was slightly lower than that of base metal. Solid solution treatment significantly increased the pitting corrosion resistance of welded joints and base metal. The hot wire TIG and traditional TIG had similar microstructure and properties under the same arc power, however the welding speed of hot wire TIG was 1.5 times higher than that of traditional TIG and the welding efficiency was greatly improved.

Influence of Heat Treatment on Stress-Corrosion Resistance of EN AW-AIZn5Mg1,5CuZr Alloy

2013 ◽  
Vol 199 ◽  
pp. 424-429
Author(s):  
Lesław Kyzioł ◽  
Kazimierz Czapczyk
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Corrosion Resistance ◽  
Stress Corrosion ◽  
Structural Changes ◽  
High Stress ◽  
Corrosion Properties ◽  
Stress Cracking ◽  
Suitable Heat Treatment ◽  
Stress Corrosion Resistance

The aim of this study is to determine mechanical properties and stress-corrosion resistance of EN AW-AIZn5Mg1,5CuZr alloy from the aspect of microstructure changes depending on the applied heat treatment. Stress corrosion is caused by the effect of corrosion environment parallel to mechanical stress. It occurs when cracks appear in the metal which is exposed to a corrosion environment and static stretching stresses. The effect of the corrosion environment and stresses on the metal surface cause cracks which are placed perpendicularly to the direction of stretching stresses and may be intercrystalline, intracrystalline or mixed. Stress cracking observations show that distinct cracks are often preceded by the incubation phase. The intensity of microcracks in this phase can be determined by examining changes in mechanical properties caused by changes in alloy structures after various time intervals of the stress-corrosion experiment. This study outlines changes in mechanical properties and resistance of the aluminium alloy in question depending on the heat treatment parameters. Changes in mechanical and corrosion properties are reflected in the structural changes of EN AW-AIZn5Mg1,5CuZr alloy. In order to enhance stress-corrosion resistance and obtain good mechanical properties in Al-Zn-Mg alloys (Zn+Mg>5%), a special heat treatment with cooling with a stop is used. This publication shows suitable heat treatment parameters which guarantee good mechanical properties and high stress-corrosion resistance.

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