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.

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.

Estimation of Some Mechanical Properties for Similar & Dissimilar Welded Joints

2014 ◽  
Vol 2 (1) ◽  
pp. 59-76
Author(s):  
Abdullah Daie'e Assi
Keyword(s):  
Stainless Steel ◽  
Carbon Steel ◽  
Austenitic Stainless Steel ◽  
Base Metal ◽  
Welded Joints ◽  
Plate Thickness ◽  
Low Carbon Steel ◽  
Dissimilar Metals ◽  
Low Carbon ◽  
Steel Type

This research deals with the choice of the suitable filler metal to weld the similar and dissimilar metals (Low carbon steel type A516 & Austenitic stainless steel type 316L) under constant conditions such as, plate thickness (6 mm), voltage (78 v), current (120 A), straight polarity. This research deals with three major parts. The first parts Four types of electrodes were used for welding of dissimilar metals (C.St A516 And St.St 316L) two from mild steel (E7018, E6013) and other two from austenitic stainless steel (E309L, E308L) various inspection were carried out include (Visual T., X-ray T., δ- Ferrite phase T., and Microstructures T.) and mechanical testing include (tensile T., bending T. and micro hardness T.) The second parts done by used the same parameters to welding similar metals from (C.St A516) Or (St.St 316L). The third parts deals with welding of dissimilar weldments (C.St And St.St) by two processes, gas tungsten are welding (GTAW) and shielded metal are welding (SMAW).        The results indicated that the spread of carbon from low carbon steel to the welding zone in the case of welding stainless steel elect pole (E309L) led to Configuration Carbides and then high hardness the link to high values ​​compared with the base metal. In most similar weldments showed hardness of the welding area is  higher than the hardness of the base metal. The electrode (E309L) is the most suitable to welding dissimilar metals from (C.St A516 With St.St 316L). The results also showed that the method of welding (GTAW) were better than the method of welding (SMAW) in dissimilar welded joints (St.St 316L with C.St A516) in terms of irregular shape and integrity of the welding defects, as well as characterized this weldments the high-lift and resistance ductility good when using the welding conditions are similar.

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.

Metallurgical and Mechanical Features of API 5L X65 Pipeline Steel Weldment

2002 ◽  
Author(s):  
Jang-Bog Ju ◽  
Jung-Suk Lee ◽  
Jae-Il Jang ◽  
Woo-Sik Kim ◽  
Dongil Kwon
Keyword(s):  
Mechanical Properties ◽  
Base Metal ◽  
Welded Joints ◽  
Pipeline Steel ◽  
Steel Structures ◽  
Welding Residual Stress ◽  
Engineering Structures ◽  
Steel Weldment ◽  
Mechanical Factors ◽  
Fracture Performance

Substantial differences amongst metallurgical and mechanical properties of base metal (BM), weld metal (WM) and heat-affected zone (HAZ) occur in general in welded steel structures It is common practice in various engineering structures to evaluate the fracture performance of welded structures by mechanical testing. Especially, the HAZ of steel welded joints shows a gradient of microstructure and mechanical properties from the fusion line to the unaffected base metal. This study is concerned with the effects of metallurgical and mechanical factors on the fracture performance of API 5L X65 pipeline steel weldments, as they are generally used for main natural gas transmission pipelines in Korea. First of all, we investigated the microscopic and macroscopic fracture behavior of the various micro-zones within the HAZ from the viewpoint of metallurgical factors. The effects of mechanical factors such as welding residual stress in steel weldment and strength mismatch between BM and WM, particularly in high strength steel weldments, are also analyzed. Therefore, the fracture performance of API 5L X65 pipeline steel weldment was mainly dependent on the change of macrostructure and its distribution in the welded joints.

Evaluation of Creep Strength Reduction Factors for Welded Joints of Modified 9Cr-1Mo Steel (P91)

2006 ◽  
Author(s):  
Masaaki Tabuchi ◽  
Yukio Takahashi
Keyword(s):  
Base Metal ◽  
Creep Strength ◽  
Welded Joints ◽  
Welded Joint ◽  
Rupture Strength ◽  
Reduction Factor ◽  
Creep Rupture ◽  
Type Iv ◽  
Rupture Data ◽  
Term Creep

In order to review the allowable creep strength of high Cr ferritic steels, creep rupture data of base metal and welded joints have been collected and long-term creep strength have been analyzed in the SHC committee in Japan since 2004. In the present paper, the creep rupture data of 370 points for welded joint specimens of modified 9Cr-1Mo steel (ASME Grade 91) offered from seven Japanese companies and institutes were analyzed. These data clearly indicated that the creep strength of welded joints was lower than that of base metal due to Type IV fracture in HAZ at or above 600°C. From the activities of this committee, the master curve for life evaluation of welded joints of Gr.91 steel could be represented as follows: LMP==34154+3494(logσ)−2574(logσ)2,C=31.4 The reduction factor of 100,000 hours creep rupture strength of welded joint to base metal was concluded to be 0.75 at 600°C and 0.70 at 650°C for the Gr.91 steel.

Study of the heat treatment effect on the structure and mechanical properties welded joints of aluminum-lithium alloys V-1461 and V-1469

2019 ◽  
Vol 85 (7) ◽  
pp. 28-35
Author(s):  
Aleksey A. Skupov ◽  
Aleksey V. Scherbakov ◽  
Svetlana V. Sbitneva ◽  
Eva A. Lukina
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Rare Earth ◽  
Welded Joints ◽  
Artificial Aging ◽  
Welded Joint ◽  
Filler Materials ◽  
Aluminum Lithium ◽  
Aluminum Lithium Alloys ◽  
Lithium Alloys

The use of rare earth elements for alloying of aluminum alloys is a promising direction nowadays — filler materials doped with rare earth metals (REM) improve the mechanical properties of welded joints of high-strength aluminum-lithium alloys compared to serial filler material. The results of studying the effect of the composition of alloyed filler materials Sv1209 and Sv1221 and heat treatment mode on the mechanical properties and structure of welded joints of high-strength aluminum-lithium alloys B-1461 and B-1469 are presented. It is shown that the use of filler materials alloyed with rare earth metals in combination with full heat treatment (quenching and artificial aging) carried out after welding provide an increase in the strength characteristics of the welded joint to the level of strength of the base material with sufficiently high ductility and toughness. Metallographic study of welded joints after heat treatment revealed a fine-grained structure in the center of welds attributed to alloying of the filler with REM. Transmission electron microscopy is used to study precipitated hardening phases in welded joints. The round-shaped phase Al3(Sc, Zr) and a fine δ’-phase precipitated upon cooling of the welded joint are present in weld adjacent zone of V-1469 alloy. At the same time, artificial aging after welding results in formation of copper-containing Ω’- and θ’-phases. Quenching and artificial aging of the welded joint resulted in an increase in the size of precipitated hardening T1’-, S’-, θ’-phases and density of their distribution in the grain volume in the heat-affected zone of V-1461 alloy. Thus, heating upon welding leads to uneven phase precipitation, whereas additional artificial aging aggravates the non-uniformity of decomposition through partial dissolution of some phases and coarsening of the other.

A Study for Proposal of Welded Joint Strength Reduction Factors of Modified 9Cr-1Mo Steel for Japan Sodium Cooled Fast Reactor (JSFR)

2013 ◽  
Author(s):  
Takashi Wakai ◽  
Takashi Onizawa ◽  
Takehiko Kato ◽  
Shingo Date ◽  
Koichi Kikuchi ◽  
...  
Keyword(s):  
Base Metal ◽  
Creep Strength ◽  
Welded Joints ◽  
Welded Joint ◽  
Polynomial Equation ◽  
Creep Rupture ◽  
Short Term ◽  
Type Iv ◽  
Rupture Data

This paper proposes provisional welded joint strength reduction factors (WJSRF) of modified 9Cr-1Mo steel (ASME Gr.91) applicable to the structural designing of “Japan sodium cooled fast reactor (JSFR)”. In the welded joints of creep strength enhanced ferritic steels including modified 9Cr-1Mo steel, creep strength may obviously degrade especially in long-term region. This phenomenon is known as “Type-IV” damage. The authors had proposed provisional allowable stress for the welded joints made of the steel in PVP 2010 conference, taking creep strength degradation due to “Type-IV” damage into account. Available creep rupture data of the welded joints made of the steel provided by Japanese steel venders were collected. The temperature range was from 500 to 650°C. The database was analyzed by stress range partitioning method. The creep rupture data were divided into two regions of short-term and long-term and those were individually evaluated by regression analyses with Larson Miller Parameter (LMP). The difference in the creep failure mechanisms between short-term and long-term regions is taken into account in this method. Boundary between these regions was half of 0.2% proof stress of the base metal at corresponding temperature. First order polynomial equation of logarithm stress was applied. For conservativeness, allowable stress was proposed provisionally considering design factor for each region. JSME (Japan Society of Mechanical Engineers) published a revised version of the elevated temperature design code in last year. Modified 9Cr-1Mo steel was officially registered in the code as a new structural material for sodium cooled fast reactors. The creep rupture curve for the base metal of the steel was standardized by employing stress range partitioning method, same as for the welded joint. However, second order polynomial equation of logarithm stress was applied in the analysis for the base metal. In addition, the creep rupture data obtained at 700°C were included in the database and data ruptured in very short term, i.e. smaller than 100 hours, were excluded from the analysis. Thus, there are some differences between the procedures to determine the creep rupture curves for base metal and welded joint made of modified 9Cr-1Mo steel. This paper discusses the most feasible procedure to determine the creep rupture curve of the welded joint of the steel by performing some case studies to focus on physical adequacy and harmonization with the determination procedure of the creep rupture curve for the base metal. Then, the WJSRF are provisionally proposed based on the design creep rupture stress intensities. In addition, the design of JSFR pipes was reviewed taking WJSRF into account.

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