scholarly journals On the Effect of Various Heat Treatments on Microstructure of AISI 4130 Steel Used in Sour Service Pipes

2020 ◽  
Author(s):  
Dmitry Vysochinskiy ◽  
Dmitri Rybakov
Keyword(s):  
Hydrogen Diffusion ◽  
Base Material ◽  
Heat Treatments ◽  
Heat Output ◽  
Transformation Rate ◽  
Martensite Formation ◽  
Steel Microstructure ◽  
Aisi 4130 ◽  
Steel Welds ◽  
Sour Service

Abstract Nowadays welding is the most common way to connect metal parts and structures. One of the challenges connected to welding it that heat output from the welding alters the microstructure of the metal creating the heat affected zone (HAZ) near the weld. In steel welds HAZ is often harder and more brittle than the base material due to formation of martensite. This might cause hydrogen induced cracking and speed up the fatigue of the weld. To mitigate the martensite formation in the HAZ different heat treatments, like preheat, interpass and PWHT are often applied. However, for 4130 steel, preheat and interpass temperatures are not expected to restrict martensite formation due to materials slow transformation rate. Preheat and interpass temperatures are still important for hydrogen diffusion and reduction of tension in the weld. This paper investigates the effect of different heat treatments on the microstructure of AISI 4130 steel used in sour service pipes. The welding and sample preparation were performed in accordance with ISO 15156 and ASME B31.3 standards. Two sample sets were produced: one with and one without preheating. The hardness tests of weld profiles were performed in accordance with ISO 15156-2 international standard. Comparison of hardness profiles indicated that preheat had virtually no effect on hardness of the steel in HAZ, although it affected hardness of fusion zone. Preheated samples were further heat treated in a furnace simulating PWHT effect. Three different PWHT condition were tested. The hardness profiles indicated that PWHT led to noticeable changes in steel microstructure. In order to understand those microstructure changes, the heat treatment of the steel during production process was reviewed and microscopic investigations of the weld profiles were performed.

Role of Residual Stresses and Strains Fields Generated by Heat Treatments on the Hydrogen Embrittlement of a Nuclear Reactor Pressure Vessel

2011 ◽  
Author(s):  
J. Toribio ◽  
D. Vergara ◽  
M. Lorenzo ◽  
J. J. Marti´n
Keyword(s):  
Hydrogen Embrittlement ◽  
Pressure Vessel ◽  
Nuclear Reactor ◽  
Hydrogen Diffusion ◽  
Operation Time ◽  
Heat Treatments ◽  
Reactor Pressure Vessel ◽  
Low Carbon ◽  
Tempering Temperature ◽  
Reactor Pressure

The wall of a nuclear reactor pressure vessel can undergo a reduction of its mechanical properties due to the presence of hydrogen, a process known as hydrogen embrittlement (HE). A numerical model of hydrogen diffusion assisted by stress and strain was used in this paper to evaluate the HE process in the wall of a real nuclear reactor pressure vessel, formed by a bimaterial (stainless steel and low carbon steel). In this sense, a quantitative analysis was carried out of the influence of tempering heat treatments conditions applied to these two steels on hydrogen concentration accumulated in the nuclear reactor vessel during its operation time. To this end, the most relevant parameters of these heat treatments were considered: (i) tempering temperature and (ii) tempering time.

Ultrasonic Inspection of Thin Duplex Steel Welds by Phased Array

2015 ◽  
Vol 818 ◽  
pp. 256-259
Author(s):  
Erika Hodúlová ◽  
Ingrid Kovaříková ◽  
Beáta Šimeková ◽  
Koloman Ulrich
Keyword(s):  
Weld Joint ◽  
Phased Array ◽  
Ultrasonic Inspection ◽  
Base Material ◽  
Outer Diameter ◽  
Experimental Sample ◽  
Inspection Method ◽  
Duplex Steel ◽  
Steel Welds ◽  
Weld Root

The non-destructive inspection of duplex steels is a big challenge, being composed of ferrite and austenite, have some particularities. When using ultrasound, for instance, its waves propagate well in ferrite, but suffer strong attenuation, scattering and refraction in austenite. The aim of this work is to use the Phased Array ultrasonic inspection method for the thin (4 mm) duplex steel weld joint inspection. The experimental sample was made ​​of duplex steel shaped tube with an outer diameter of 44 mm and a wall thickness of 3.8 mm welded with a laser beam. The experiment was necessary to verify attenuation of duplex steel. On the base material and the weld joint were made the artificial defects, in which the adjusted sensitivity of the ultrasonic device was set.The result of the measuring was the defect echo coming from the weld root layer. The length (about 25 mm) can only be estimated due to the inaccurate constant velocity of probe motion along the surface.

Potential Detrimental Consequences of Excessive PWHT on Pressure Vessel Steel Properties

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Cédric Chauvy ◽  
Lionel Coudreuse ◽  
Patrick Toussaint
Keyword(s):  
Heat Treatment ◽  
Base Metal ◽  
Base Material ◽  
Heat Treatments ◽  
Pressure Vessels ◽  
Critical Parameters ◽  
Thick Wall ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Stress Relieving

During fabrication of Pressure Vessels, steels undergo several heat treatments that aim to confer the required properties on the entire equipment, including welds and base metal. Indeed, the production heat treatment of the base material, which leads to achieve the target properties, is most of the time followed by post weld heat treatment (PWHT). The aim of such treatments is to insure a good behavior of the welded zones in terms of residual stresses and obviously properties such as toughness. Generally, many simulated PWHT (up to 4 or more) are required for the testing of the base material, which can affect its properties and even lead to unacceptable results. In some cases for fabrication purposes an intermediate Stress relieving treatment can be required. Special attention is paid on C-Mn steels (e.g., SA/A516 from ASME BPV Code) with the effect of thickness and Ceq (International Institute of Welding Carbon equivalent formula: see page 3) requirements on the final compromise between properties and heat treatments. In particular, toughness and ultimate tensile strength (UTS) are the critical parameters that will limit the acceptance of too high PWHT. Although micro-alloying is a mean to increase the resistance to PWHT, this leads to difficulties in softening the heat affected zones. This solution is therefore not the best one considering the whole equipment optimization. Finally, the manufacturing process can play a major role when specifications are stringent. Quenching and tempering (Q&T) can indeed provide better flexibility in terms of PWHT and improved toughness for given Ceq and thickness. The case of Cr-Mo(-V) steels, which are widely used in the energy industry, is also addressed. Indeed, PWHT requirements for increasing the toughness in the weld metal can lead to decrease the base metal properties below the specification limits. For example, the case of SA/A387gr11 is very typical of metallurgical changes that can occur during these high PWHT leading to a degradation of toughness in the base metal. Another focus is made on the Vanadium Cr-Mo grade SA/A542D that must withstand very high PWHT (705 °C and even 710 °C) because of welds toughness issues. Optimization has therefore to be done to increase the resistance to softening and to guarantee acceptable microstructure, especially in the case of thick wall vessels. Some ways for improvement are proposed on the basis of the equivalent Larson–Miller parameter (LMP) tempering parameter concept. The basic philosophy is to fulfil the need for discussion between companies involved in pressure vessels fabrication so that the best compromise can be found to ensure the best and safest behavior of the equipment as a whole. In particular, the tempering operation can sometimes be done at lower temperature than PWHT in order to offer the best properties to the final vessel.

scholarly journals Martensite Formation in the Metallographic Preparation of Austenitic Stainless Steel Welds

2013 ◽  
Vol 19 (S2) ◽  
pp. 1748-1749
Author(s):  
J.M. Rodelas ◽  
M.C. Maguire ◽  
J.R. Michael
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Martensite Formation ◽  
Metallographic Preparation ◽  
Steel Welds

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Carbon Steel X65QS Pipeline Qualification for Extreme Sour Service a Global Approach: Line Pipe, Welding, Eca Methodology and Diyab Pipeline Case Study

2021 ◽  
Author(s):  
Lam-Thanh Luc ◽  
Hamdi Saad ◽  
Matta Tanios ◽  
Dr. Al Bannay Aamer ◽  
Meer Mumtaz Ali Imtiaz Sirsimth ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Large Diameter ◽  
Base Material ◽  
Global Approach ◽  
Production Environment ◽  
Destructive Testing ◽  
Line Pipe ◽  
Steel Material ◽  
Pipe Welding ◽  
Sour Service

Abstract In the wake of failures of large diameter pipelines made from plates using the Thermo-Mechanically Controlled Process (TMCP), the suitability of carbon steel material for sour environments where the H2S partial pressure is largely over 1 bar has been questioned. Understanding that seamless quench and tempered material are not prone to the same phenomenon as large diameter TMCP pipes, it has been decided to ensure the integrity of the DIYAB pipeline by qualification using the actual production environment pH=3.5 at 24°C and 6.84 bar H2S plus 6.84 bar CO2. The global approach includes the qualification to sour service resistance under 6.84bar H2S of the base material and the welds without post weld heat treatment. Fracture toughness tests under 6.84bar H2S were also conducted, and the results fed into an Engineering Criticality Assessment (ECA) to define the Non-Destructive Testing (NDT) acceptance criteria. The NDT tools were selected for their ability to detect the critical flaws and validated. The global approach methodology and results are presented.

Improving Reliability of Carbon Steel Girth Welds in Sour Environment

2020 ◽  
Author(s):  
Harpreet Sidhar ◽  
Neerav Verma ◽  
Chih-Hsiang Kuo ◽  
Michael Belota ◽  
Andrew J. Wasson
Keyword(s):  
Carbon Steel ◽  
Base Material ◽  
Oil And Gas Industry ◽  
Critical Parameters ◽  
Welding Parameters ◽  
Pipe Material ◽  
Line Pipe ◽  
Weld Root ◽  
Girth Welds ◽  
Sour Service

Abstract The oil and gas industry has seen unexpected failures of sour service carbon steel pipelines in the recent past. Below par performance of girth welds and line pipe material have been identified as the root causes of such failures. Although mechanized welding can achieve good consistency, the weld region is more heterogeneous as compared to base material, which can lead to inconsistencies and poor weld performance. Overall, the effects of welding parameters on performance of carbon steel pipeline girth welds for sour service are not well understood. Furthermore, industry is moving towards more challenging environments, such as production of hydrocarbons from ultra-deepwater, which further necessitates the need to improve welding practices for additional high criticality applications. Many of the critical parameters for sour service performance will also improve general weld performance for ultra-deepwater. So, there is a clear need to understand the effects of various welding parameters on weld properties and performance. This effort aims at assessing the effects of key welding parameters on performance of girth welds to develop improved welding practice guidelines for sour service pipeline applications. In this study, several API X65 grade line pipe girth welds were made using commercially available welding consumables. The effects on weld root performance of preheat, wire consumable chemistry, hot pass tempering, single vs. dual torch, copper backing, root pass heat input, metal transfer mode, pipe fit-up (root gap, misalignment) were studied. Generally, carbon steel welds with hardness 250HV or below are considered acceptable for sour service. So, detailed microhardness mapping and microstructural characterization were conducted to evaluate the performance and reliability of welds. It was evident that the welding parameters studied have a significant impact on root performance. Preheat and pipe fit-up showed the most significant impact on weld root performance. Based on the results and understanding developed with this study, recommendations for industry are provided through this paper to improve reliability of pipeline girth welds in sour service application.

An Analysis of a Crack in Weld by Using Near-Field as Well as Far-Field Crack Parameters

1990 ◽  
Vol 112 (4) ◽  
pp. 304-312 ◽  
Author(s):  
M. Nakagaki ◽  
C. W. Marschall ◽  
F. W. Brust
Keyword(s):  
Stainless Steel ◽  
Crack Growth ◽  
Near Field ◽  
Base Material ◽  
Crack Tip ◽  
Ductile Material ◽  
Stress Strain ◽  
Material Interface ◽  
Steel Welds ◽  
Strain Interaction

A study of ductile crack growth characteristics in stainless steel welds is reported in this paper. A hybrid-type analysis of combined experimental, analytical, and predictive procedures on the subject is addressed. The study focuses on the effects of a stress/strain interaction phenomenon occurring between the crack tip and the weld-base material interface. Clear dependence of the crack initiation fracture characteristics on the weld size relative to the specimen size was found. Also, fracture toughness of a tungsten inert gas weld is shown to be comparable to that for the base stainless steel metal, whereas that of a submerged arc weld is shown to be significantly lower than the base metal. Because of the stress/strain nonproportionality associated with a local unloading due to crack growth in a ductile material, the use of a crack-tip parameter such as ΔTP* or Jˆ-integral was emphasized. On the other hand, prediction of a crack instability was attempted using a less rigorous J-estimation scheme procedure.

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