On the Relationship of Microstructure, Toughness, and Hardness Properties in a Submerged Arc Welded API-5L Grade X65 Pipeline Steel Section

2014 ◽  
Author(s):  
Lee Aucott ◽  
Shuwen Wen ◽  
Hongbiao Dong
Keyword(s):  
Mechanical Properties ◽  
Fusion Zone ◽  
Base Metal ◽  
Weld Joint ◽  
Small Volume ◽  
Pipeline Steel ◽  
Chemical Properties ◽  
Detailed Knowledge ◽  
Upper Bainite ◽  
Submerged Arc

In order to further improve welded pipeline performance, a detailed knowledge of the key and interlinking relationships between the chemistry, microstructure and mechanical properties of the weld joint is needed. In this paper, the results of optical emission spectroscopy analysis on the as welded chemical properties of a submerged arc welded API-5L grade X65 linepipe are first presented. The microstructure of the various weld regions is then assessed against the results of the chemical analysis using a series of microscopy techniques. A fine grained ferrite-degenerate pearlite microstructure was observed within the base metal of the linepipe along with large (1.5 μm) cuboidal Ti (C, N) precipitates. Within the heat affected zone (HAZ) close to the molten weld joint, grain growth occurred with small volume fractions of induced upper bainite present within the microstructure. The fusion zone of the submerged arc weld joint consists of predominantly acicular ferrite with a small volume of grain boundary phases and a high number of large (0.8 μm) spherical Ti (C, N) precipitates. The results of Vickers hardness tests carried out at two length scales (macro + micro) show clear relations between the hardening effects of the cementite enriched degenerate pearlite and induced upper bainite phases within the base metal and HAZ respectively. Fractography analysis of Charpy impact test samples across the submerged arc welded joint found that the large Ti (C, N) precipitates within the fusion zone appear to be acting as microvoid initiation sites for the ductile fracture and as such contributing to the relatively low toughness properties within the fusion zone. Finally, the potential benefits of reducing the Ti content in both the welding wires and X65 base metal for further improvement of the mechanical properties of the linepipe weld joint are discussed in regards to reducing the size of the coarse Ti (C, N) precipitates within the base metal, HAZ and fusion zone.

Statistical Distribution Analysis of Mechanical Properties of a Welded Pipeline Steel API X70 and Correlation between Hardness and other Mechanical Characteristics

2017 ◽  
Vol 30 ◽  
pp. 49-64 ◽  
Author(s):  
Adel Saoudi ◽  
Farida Khamouli ◽  
L'hadi Atoui ◽  
Mosbah Zidani ◽  
Hichem Farh
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Base Metal ◽  
Vickers Hardness ◽  
Pipeline Steel ◽  
Distribution Patterns ◽  
Extreme Value ◽  
Distribution Analysis ◽  
Extreme Value Distributions ◽  
Submerged Arc

The aim of this study is to model the distribution patterns of the different mechanical properties of a submerged arc welded pipeline steel API X70 and to investigate the relationship between Vickers hardness and other mechanical properties of API X70. In this study, serial mechanical properties of 70 pipes, formed by spiral submerged arc welding of high strength low alloy steel (HSLA) API X70, were measured in base metal and weldments. Four main statistical distributions: Normal, Log-normal, Weibull and smallest extreme value distributions were chosen to test the goodness of fit to the experimental data. As a result, normal and lognormal distributions can equally model the distribution patterns of the whole experimental data of studied mechanical properties except for the hardness and toughness of the base metal that can be approximated by Weibull and smallest extreme value distributions, respectively. Using the current data, a weak but statistically significant correlation is obtained only between the toughness of the fusion zone and the hardness of both the base metal and the heat affected zone. Consequently, the calculated regression models were unable to estimate impact toughness values based on future measures of Vickers hardness components.

scholarly journals Effect of Al Content in Magnesium Alloy on Microstructure and Mechanical Properties of Laser-Welded Mg/Ti Dissimilar Joints

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2743
Author(s):  
Wen Dong ◽  
Rongrong Huang ◽  
Hongyun Zhao ◽  
Xiangtao Gong ◽  
Bo Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fusion Zone ◽  
Base Metal ◽  
Chemical Potential ◽  
Pure Titanium ◽  
Potential Gradient ◽  
Fracture Load ◽  
Dissimilar Joints ◽  
Al Content ◽  
Microstructure And Mechanical Properties

Laser penetration welding of magnesium alloys and pure titanium TA2 with unequal thickness was performed. Mg base metal with different Al content (AZ31B, AZ61A, AZ91D) was used to investigate the influence of Al element in microstructure and mechanical properties of Mg/Ti dissimilar joints. The results revealed that the change of Mg base metal did not influence the weld appearance of the joints. Three kinds of joint all presented the best mechanical property when the laser power was 3500 W. With the increase content of Al elements in Mg base metal, a reaction layer was observed which was identified as Ti3Al. The highest enrichment of Al element was obtained and its fraction reached 19.31 at% at the AZ91/TA2 interface. The chemical potential gradient of Al from AZ91 to Ti alloy was higher than that from the other two base metals based on thermodynamic calculation. The maximum fracture load reached 3597 N when AZ61 was employed as the base metal and the fracture position was the Ti base metal. AZ31/TA2 joints failed at the weld seam without necking due to the rapid propagation of cracks at the Mg/Ti interface. The AZ91/TA2 joint failed inside the Mg fusion zone with necking at the middle area of the weld, which resulted from the precipitation of brittle phases such as Mg–Al, Ti–Al phases in the fusion zone of Mg alloys.

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.

Experimental Study on Mechanical Properties and Microstructure of 2.25Cr1Mo0.25V Steel by the Influence of Heat Treatment and Welding

2018 ◽  
Author(s):  
Qing Li ◽  
Guangxu Cheng ◽  
Mu Qin ◽  
Zaoxiao Zhang
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Base Metal ◽  
Arc Welding ◽  
Treatment Time ◽  
Welding Process ◽  
Heat Treatment Time ◽  
Evolution Of Microstructure ◽  
Welding Metal ◽  
Submerged Arc

In this paper, the mechanical properties and microstructural changes of 2.25Cr1Mo0.25V steel under different heat treatment and welding process were investigated. The heat treatment of steel during practical processing is taken as a reference. Different heat treatment time are used to obtain samples with different condition. Automatic submerged arc welding was used to obtain welding sample. The mechanical properties of different samples are obtained by tensile test; the evolution of microstructure and precipitates of different sample with heat treatment and welding was studied on scanning electron microscopy. The experimental results show that with the increase of heat treatment time, the strength of the samples decreases and the plasticity remains nearly constant. Heat treatment also affects the precipitation of carbides; the longer the heat treatment time is, the more precipitates are. Compared with the base metal, the welding metal sample has higher strength. The amount of precipitates in welding metal is much larger than it in base metal. The research on precipitation shows that there are different kinds of precipitates which have different morphologies in welding metal.

Study on the Microstructure and the Mechanical Properties of TA2

2012 ◽  
Vol 472-475 ◽  
pp. 2655-2658
Author(s):  
Xiao Dong Hu ◽  
Sen Zhang ◽  
Yong Zhang ◽  
Ya Jiang Li
Keyword(s):  
Mechanical Properties ◽  
Fusion Zone ◽  
Weld Joint ◽  
Arc Welding ◽  
Weld Zone ◽  
Base Material ◽  
Annealing Treatment ◽  
Welding Joint

The microstructure and the mechanical properties of welding joint with the material of TA2 have been studied in this paper with the specimens made with the method of argon-arc welding. The microhardness of the welding joint has been compared with the hardness in the same position of the weld joint after annealing. Conclusions have been obtained as follows: The organizations of the welding joint include base material, recrystallization zone, overheated area, fusion zone and the weld zone; the hardness tendency of the weld joint is depicted as M-shape with the softest point located at the center, and the hardest is located at the overheated zone; the annealing treatment can enhance the weld joint hardness mainly at the center, and the hardness of other zones change little.

Study on the Microstructure and the Mechanical Properties of Zr R60702

2012 ◽  
Vol 510 ◽  
pp. 679-682 ◽  
Author(s):  
Xiao Dong Hu ◽  
Sen Zhang ◽  
Yong Zhang ◽  
Ya Jiang Li
Keyword(s):  
Mechanical Properties ◽  
Fusion Zone ◽  
Weld Joint ◽  
Arc Welding ◽  
Weld Zone ◽  
Base Material ◽  
Annealing Treatment ◽  
Welding Joint

The microstructure and the mechanical properties of welding joint with the material of R60702 have been studied in this paper with the specimens made with the method of argon-arc welding, and the according mechanical properties of the weld joint have been compared with the annealed microstructure at the temperature of 600.Conclusions have been obtained as follows: The organizations of the welding joint include base material, normalizing zone, overheated area, fusion zone and the weld zone; the hardness tendency of the weld joint is depicted as W-shape with the hardest point located at the center, and the softest points is located at the normalizing zone; the annealing treatment can improve the ductility and soften the weld joint mainly at the center.

Investigation on Non-Preheating Welding Technology of X70 Pipeline Steel

2013 ◽  
Vol 333-335 ◽  
pp. 1836-1840
Author(s):  
De Fen Zhang ◽  
Jin Wang ◽  
Zheng Tao Jiang ◽  
Xiong Shi ◽  
Zeng Zhen Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Weld Joint ◽  
Pipeline Steel ◽  
Welding Process ◽  
Construction Cost ◽  
Construction Time ◽  
X70 Pipeline Steel ◽  
Welding Technology ◽  
Construction Efficiency ◽  
Interpass Temperature

Considering the mechanical properties of X70 pipeline steel after repeated welding heat cycles, preheating and interpass temperature controlling are often adopted in the welding technology, which widely increase the welding construction time and lower the construction efficiency, thus improve the construction cost of pipelines. According to the present welding process of X70 pipeline steel, non-preheating welding technology was proposed in this paper. The experiment results show that the properties of the weld joint of X70 pipeline steel with non-preheating achieves the requirement of specified standard. Furthermore, this method simplifies the welding construction processes and improves the construction efficiency. Key Words:X70 Steel; Non-Preheating; Welding Technology

Microstructures and Mechanical Properties on Laser Welded Joints of Automotive High Strength Complex Phase Steel

2010 ◽  
Vol 97-101 ◽  
pp. 3957-3962
Author(s):  
Lian Hai Hu ◽  
Qi Yan ◽  
Jian Huang ◽  
Yi Xiong Wu
Keyword(s):  
Mechanical Properties ◽  
Laser Welding ◽  
Fusion Zone ◽  
Base Metal ◽  
Automobile Industry ◽  
Welded Joint ◽  
High Strength ◽  
Uniaxial Tensile ◽  
Complex Phase ◽  
The Impact

Reducing car’s weight has become an important goal for automobile industry. Laser welding of automotive high-strength steel plays a significant role in producing light weight cars. Experiments of CO2 high power laser welding of 1000MPa grade complex phase steels with a thickness of 3mm for automobile were performed using a 15 KW CO2 laser. The macrostructure and microstructure of the welded joint were examined by optical microscope. Mechanical properties of the welded joint, fusion zone and base metal were assessed by microhardness distribution across the welded joint, uniaxial tensile test and charpy V-notch impact test. Fractographs of the impact specimens were studied by scanning electron microscopy (SEM). It is found that the fusion zone has a higher toughness than that of the base metal and fusion line. The test results show good mechanical properties of laser welds that can meet the technical requirements for automobile Industry.

Effect of Brazing Flux Pb on Microstructure and Mechanical Property of CMT Weld-Brazed Lap Joint of 5052 Aluminum Alloy to Galvanized Q235 Steel

2014 ◽  
Vol 789 ◽  
pp. 290-296 ◽  
Author(s):  
Hua Qing Lai ◽  
Sheng Lu
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Fusion Zone ◽  
Base Metal ◽  
Testing Machine ◽  
Galvanized Steel ◽  
Lap Joint ◽  
Cold Metal Transfer ◽  
Tensile Testing Machine ◽  
Q235 Steel

5052 aluminum alloy and galvanized Q235 steel sheets with thickness of 1mm were lap welded/brazed by cold metal transfer technology (CMT) with ER4043 as the filler wire and Pb foil as the brazing flux. Scanning electron microscope (SEM), microscope with super-depth, X-ray diffraction (XRD), electronic universal tensile testing machine and hardness tester were employed to study the microstructure and mechanical properties of the joint. The results indicate that Pb foil effectively improved the mechanical properties of the joint with tensile strength up to 160Mpa which is higher than that of the joint without the brazing flux of Pb foil. Intermetallic compound (IMC) layer in the brazing joint unequally distributed in the interface of aluminum alloy and galvanized steel. The thickness of IMC layer was about 1~3.5um. The main phases of the IMC layer were FeAl and AlFe6Si. Fine equiaxial crystals existed in the weld metal while columnar crystals existed in the fusion zone of aluminum alloy. The hardness of fusion zone was higher than base metal while the hardness of heat affected zone was lower than base metal. In most case, the lap joint was broken in the junction of base metal and fusion zone.

Tensile and Fracture Properties of X80 Steel Microstructures Relevant to the HAZ

2012 ◽  
Author(s):  
Michael J. Gaudet ◽  
Warren J. Poole
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Pipeline Steel ◽  
Thin Sheet ◽  
Detailed Knowledge ◽  
Tear Strength ◽  
Heat Treated ◽  
The Individual ◽  
Unit Propagation ◽  
Tensile Toughness

The girth welding of steel pipelines creates a substantial heat affected zone (HAZ) within the base pipeline steel. The HAZ can be considered to be a complex graded microstructure. While there is significant concern as to the fracture and mechanical properties of the HAZ as whole, detailed knowledge about the mechanical properties of the individual microstructures is lacking. For this study, X80 is heat treated in a Gleeble simulator to create samples of bulk microstructures with differing amounts and morphologies of bainite, ferrite and martensite-retained austenite (MA) with a total of 8 microstructures being investigated. The heat treatments were selected specifically to control the level of niobium in solid solution; that is to control whether niobium was fully in solution or contained mainly in niobium carbonitride precipitates. From the heat treated samples a matching tensile and fracture specimens were made. The strongest microstructure proved to be the finest bainitic microstructure, while the lowest strength microstructure was the coarsest bainite sample containing a significant amount of martensite-retained austenite connected along grain boundaries. The fracture behaviour at ambient temperature was studied using the Kahn tear test. The Kahn tear test is a machine notched, thin-sheet, slow strain rate fracture test which has the advantage of being a simple test to conduct. All Kahn tests failed in a ductile manner and it showed that the sample with the coarse bainite, with a connected martensite-retained austenite phase had the lowest unit propagation energy and tear strength while the fine, fully bainitic sample had the highest unit propagation energy and tear strength. Further investigation using SEM measurements of the final fracture surface from the tensile test to determine the tensile toughness. A comparison of the tensile toughness and unit propagation energies showed that there was a complex relationship between the two measurements. However, the samples which had the highest content of MA gave the in lowest unit propagation energy.

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