Inter-relationship between microstructure evolution and mechanical properties in inertia friction welded 8630 low-alloy steel

AbstractThe evolution of microstructure and mechanical properties in AISI 8630 low-alloy steel subjected to inertia friction welding (IFW) have been investigated. The effects of three critical process parameters, viz. rotational speed, friction and forge forces, during welding of tubular specimens were explored. The mechanical properties of these weld joints, including tensile and Charpy V-notch impact were studied for determining the optimum welding parameters. The weld joints exhibited higher yield strength, lower hardening capacity and ultimate tensile strength compared to base metal (BM). The maximum strength and ductility combination was achieved for the welds produced under a nominal weld speed of ~ 2900–3100 rpm, the highest friction force of ~ 680–720 kN, and the lowest axial forging load of ~ 560–600 kN. The measured hardness distribution depicted higher values for the weld zone (WZ) compared to the thermo-mechanically affected zone (TMAZ), heat-affected zone (HAZ) and BM, irrespective of the applied welding parameters. The substantial increase in the hardness of the WZ is due to the formation of microstructures that were dominated by martensite. The observed microstructural features, i.e. the fractions of martensite, bainite and ferrite, show that the temperature in the WZ and TMAZ was above Ac3, whereas that of the HAZ was below Ac1 during the IFW. The fracture surface of the tensile and impact-tested specimens exhibited the presence of dimples nucleating from the voids, thus indicating a ductile failure. EBSD maps of the WZ revealed the formation of subgrains inside the prior austenite grains, indicating the occurrence of continuous dynamic recrystallisation during the weld. Analysis of crystallographic texture indicated that the austenite microstructure (i.e. FCC) in both the WZ and TMAZ undergoes simple shear deformation during IFW.

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Effects of bottom plate in friction stir welding of AA6061-T6

Metallurgical Research & Technology ◽

10.1051/metal/2020087 ◽

2020 ◽

Vol 118 (1) ◽

pp. 108

Author(s):

M.A. Vinayagamoorthi ◽

M. Prince ◽

S. Balasubramanian

Keyword(s):

Mechanical Properties ◽

Axial Load ◽

Weld Zone ◽

Welding Process ◽

Bottom Plate ◽

Welding Parameters ◽

Nugget Zone ◽

Friction Stir ◽

Weld Joints ◽

Fine Grain

The effects of 40 mm width bottom plates on the microstructural modifications and the mechanical properties of a 6 mm thick FSW AA6061-T6 joint have been investigated. The bottom plates are placed partially at the weld zone to absorb and dissipate heat during the welding process. An axial load of 5 to 7 kN, a rotational speed of 500 rpm, and a welding speed of 50 mm/min are employed as welding parameters. The size of the nugget zone (NZ) and heat-affected zone (HAZ) in the weld joints obtained from AISI 1040 steel bottom plate is more significant than that of weld joints obtained using copper bottom plate due to lower thermal conductivity of steel. Also, the weld joints obtained using copper bottom plate have fine grain microstructure due to the dynamic recrystallization. The friction stir welded joints obtained with copper bottom plate have exhibited higher ductility of 8.9% and higher tensile strength of 172 MPa as compared to the joints obtained using a steel bottom plate.

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Evolution of microstructure and mechanical properties during quenching and tempering of ultrahigh strength 0.3C Si–Mn–Cr–Mo low alloy steel

Journal of Materials Science ◽

10.1007/s10853-009-4160-x ◽

2010 ◽

Vol 45 (6) ◽

pp. 1695-1708 ◽

Cited By ~ 10

Author(s):

Fawad Tariq ◽

Nausheen Naz ◽

Rasheed Ahmed Baloch ◽

Ashraf Ali

Keyword(s):

Mechanical Properties ◽

Alloy Steel ◽

Low Alloy Steel ◽

Ultrahigh Strength ◽

Microstructure And Mechanical Properties ◽

Evolution Of Microstructure ◽

Quenching And Tempering

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Interactions of the process parameters and mechanical properties of laser butt welds in thin high strength low alloy steel plates

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420720910442 ◽

2020 ◽

Vol 234 (5) ◽

pp. 665-680 ◽

Cited By ~ 1

Author(s):

Patricio Gustavo Riofrío ◽

Carlos Alexandre Capela ◽

José AM Ferreira ◽

Amilcar Ramalho

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Laser Welding ◽

Alloy Steel ◽

Heat Input ◽

High Strength ◽

Welding Parameters ◽

Bead Geometry ◽

Low Alloy Steel ◽

Weld Bead Geometry

High strength low alloy steels subjected to the thermomechanical control process present excellent strength–toughness combination, high strength/weight ratio, and weldability. Therefore, they are widely used in structural components, such as pressure vessels, oil/gas transportation pipes, lifting equipment, vehicles, shipbuilding and offshore industries, and in the automotive industry where low thickness (0.8–3 mm thickness) is of great importance. Usually, these steels are welded by conventional gas metal arc welding, which creates wide heat-affected zones, large residual stresses, and distortion in the welded parts. Laser welding is nowadays an alternative process to weld high strength low alloy steel parts due to its advantages. The aim of this work is to understand the effect of process parameters on defects, weld bead geometry, microstructure, and mechanical properties, namely hardness and tensile strength. We identify the main laser welding parameters and their influence on the weld bead geometry and defects, for a 3 mm thick high strength low alloy steel welded under a maximum power of 2 kW. A cross section of the weld seam was optimized achieving a good geometry without porosity. The threshold value of the heat input to achieve complete penetration was determined for different focus diameters. The microstructure, size, and hardness of the heat-affected zone and of the fusion zone are strongly influenced by the heat input. The values of the tensile strength achieved in butt welds were close to the base metal by an appropriate selection of the laser welding parameters and the heat input.

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WELDING OF S355J+N LOW ALLOY STEEL ELEMENTS IN RAILWAY CARRIAGES STRUCTURES

Scientific Journal of Silesian University of Technology Series Transport ◽

10.20858/sjsutst.2021.112.7.15 ◽

2021 ◽

Vol 112 ◽

pp. 191-200

Author(s):

Bożena SZCZUCKA-LASOTA ◽

Tomasz WĘGRZYN ◽

Bogusław ŁAZARZ ◽

Adam JUREK ◽

Krzysztof I. WILCZYŃSKI

Keyword(s):

Mechanical Properties ◽

Alloy Steel ◽

Steel Structures ◽

Bending Test ◽

Mag Welding ◽

Rolling Stock ◽

Welding Parameters ◽

Main Role ◽

Low Alloy Steel ◽

Welded Structures

Various types of structures and materials play an important role in the creation modern means of transport, including various grades of steel with different mechanical properties. For the rolling stock, proper operation and meeting the operational conditions is very important. Welded structures play an important role in the construction of various means of transport. Correct welding of carriages is important both in production and when carrying out various types of repairs. Each repair a carriage depends on its advancement and condition and the time of its operation. Each inspection for a refurbished carriage is defined either by the service life or the big distance traveled by the carriage. Important factor that may lead to damage is the effect of the load transported in the carriage. Therefore, the causes of the wear of the rolling stock are investigated and measures are taken to prevent any damage. The appropriate technical condition of the carriage also ensures safety on railroads for users and owners of the rolling stock. In the case of welded structures in carriages, it is influenced by poorly materials choice, incorrectly selected production processes and wrong selection of parameters. The goal of this paper is the mechanical properties analyse of weld low alloy steel structure of carriages after MAG welding using the parameters of the process. Thick-walled steel structures are used to build carriages, which is often a serious welding problem. The main role of welding conditions is connected with filer materials, welding technology, state of stress and temperature. In this paper, the properties of low alloy steel S3555J+N structures after MAG welding are presented. Furthermore, metallographic structure, tensile strength, bending test and impact toughness welded joints were analysed regarding welding parameters. The amount of acicular ferrite in WMD oxygen after welding was tested. Gas mixtures of argon and carbon dioxide with various percentage was used for shielding gas.

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MICROSTRUCTURE AND MECHANICAL PROPERTIES OF 1500 MPa GRADE ULTRA--HIGH STRENGTH LOW ALLOY STEEL

ACTA METALLURGICA SINICA ◽

10.3724/sp.j.1037.2010.00687 ◽

2010 ◽

Vol 46 (6) ◽

pp. 687-694 ◽

Cited By ~ 3

Author(s):

Lijun WANG ◽

Qingwu CAI ◽

Wei YU ◽

Huibin WU ◽

Aidi LEI

Keyword(s):

Mechanical Properties ◽

Alloy Steel ◽

High Strength ◽

Low Alloy Steel ◽

Microstructure And Mechanical Properties

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Influence of Post Weld Heat Treatment on the Grain Size, and Mechanical Properties of the Alloy-800H Rotary Friction Weld Joints

Materials ◽

10.3390/ma14164366 ◽

2021 ◽

Vol 14 (16) ◽

pp. 4366

Author(s):

Saqib Anwar ◽

Ateekh Ur Rehman ◽

Yusuf Usmani ◽

Ali M. Al-Samhan

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Grain Size ◽

Heat Affected Zone ◽

Tensile Testing ◽

Weld Zone ◽

Alloy 800H ◽

Weld Joints ◽

Heat Treated ◽

Friction Weld

This study evaluated the microstructure, grain size, and mechanical properties of the alloy 800H rotary friction welds in as-welded and post-weld heat-treated conditions. The standards for the alloy 800H not only specify the composition and mechanical properties but also the minimum grain sizes. This is because these alloys are mostly used in creep resisting applications. The dynamic recrystallization of the highly strained and plasticized material during friction welding resulted in the fine grain structure (20 ± 2 µm) in the weld zone. However, a small increase in grain size was observed in the heat-affected zone of the weldment with a slight decrease in hardness compared to the base metal. Post-weld solution heat treatment (PWHT) of the friction weld joints increased the grain size (42 ± 4 µm) in the weld zone. Both as-welded and post-weld solution heat-treated friction weld joints failed in the heat-affected zone during the room temperature tensile testing and showed a lower yield strength and ultimate tensile strength than the base metal. A fracture analysis of the failed tensile samples revealed ductile fracture features. However, in high-temperature tensile testing, post-weld solution heat-treated joints exhibited superior elongation and strength compared to the as-welded joints due to the increase in the grain size of the weld metal. It was demonstrated in this study that the minimum grain size requirement of the alloy 800H friction weld joints could be successfully met by PWHT with improved strength and elongation, especially at high temperatures.

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