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Control of Microstructures and Properties in Steel Arc Welds provides an overview of the most recent developments in welding metallurgy. Topics discussed include common welding processes, the thermal cycle during welding, defects that may occur during the welding process, the metallurgy of the material, metallurgical processes in the heat-affected zone and the fused metal, and the relationship between microstructures and mechanical properties. The book's final chapter presents examples of welded joints, illustrating how modern theories are capable of predicting the microstructure and properties of these joints. This book is an excellent resource for welding engineers, metallurgists, materials scientists, and others interested in the subject.
This book is a printed edition of the Special Issue "Advances in Welding Metal Alloys, Dissimilar Metals and Additively Manufactured Parts" that was published in Metals
The effect of nitrogen concentration in the shielding gas on microstructure and mechanical properties of autogenously plasma arc welded lean duplex Allegheny Ludlum ATI 2003® material was studied. Six single-pass plasma arc butt welds were produced for the evaluation. One weld was performed using 100% argon shielding and backing gas, while the other five utilized varying additions of nitrogen in the shielding and backing gas, from 1 to 5%, with argon as the primary gas. 100% argon was used as the plasma orifice gas for all welds. The coupons were labeled 0 through 5, which correlated with the concentration of nitrogen. The heat input was consistent for each weld and was representative of a typical value for production plasma arc welding of lean duplex stainless steel. Mechanical testing and evaluation was completed in accordance with typical customer requirements and industry standards. Each weldment was tested mechanically and analyzed microstructurally to investigate any correlations with the nitrogen additions in the weld shielding gas. Mechanical tests consisted of transverse and longitudinal tensile testing per ASME 2010 Section II, Part A, SA-370, Charpy impact testing per ASME 2010 Section II, Part A, SA-370 at -40° C, and micro-hardness testing per ASTM E384 with a test force level of 500 grams-force (gf). The microstructural analysis included ferrite testing, utilizing both the Fischer® Ferritescope and PAXit® software, and optical microscopy with focus on austenite formation and morphology, precipitate formation, and grain size comparison. The mechanical tests from this study revealed that only specific coupons met the requirements provided in ASME Boiler and Pressure Vessel Code. The transverse tensile tests revealed that all the coupons met the minimum requirements for the tensile strength of 620 MPa (90 ksi). Conversely, the elongation for each of the coupons except coupon 5, with 5% nitrogen in the shielding gas, fell short of the 25% elongation minimum specified for the base material. Charpy impact tests disqualified coupons 0 through 2, which were unacceptable due to lateral expansions less than the minimum of 0.38 mm (.015 inches) per ASME Section VIII. Vickers micro-hardness testing was found to be optimum and below the ATI 2003® base metal requirement of 293 BHN per ASME Section II, Part A, SA-240. During ferrite testing, both using the Fischer® Ferritescope and the PAXit® software, it was determined that coupons 2 through 5 had optimum ferrite values of between 40 and 60%, for each the fusion zone, HAZ, and base metal. Conversely, Coupons 0 and 1 had values that fell outside this range. Neither secondary austenite precipitation nor formations of detrimental second phases were detected in any of the weld microstructures. In conclusion, 5 percent nitrogen added to the shielding gas had a beneficial effect on autogenously plasma arc welded ATI 2003® Lean Duplex Stainless Steel and resulted in optimum mechanical properties and microstructure of the weldment. Alternatively, autogenous plasma arc welding with 100% argon as the backing, shielding, and orifice gas resulted in unacceptable mechanical properties and an unbalanced ferrite-austenite ratio.
This book presents the recent research results of the application of arc spectrum in the welding process. It sheds light on the fundamentals of monitoring welding quality using arc spectral information. By analyzing the topic both from a global and local perspective, it establishes a knowledge base of features characterizing welding statuses. Researchers, scientists and engineers in the field of intelligent welding can benefit from the book. As such, this book provides valuable knowledge, useful methods, and practical algorithms that are applicable in real-time detection of welding defects.
Gas Tungsten Arc Welding Handbook combines hundreds of illustrations with easy-to-understand instructions. The text explains the features of the gas tungsten arc welding process, as well as the proper welding procedures used on a variety of base materials. Content conforms with ANSI/AWS standards.
The laser powder bed fusion (L-PBF) process inherently accumulates interstitial gas elements during powder fabrication and laser deposition processes. Such elements can lead to localized variations in the weld pool and affect the solidification behavior (when compared with its wrought equivalent), in addition to chemical microsegregation within the fabricated material. This study was conducted to characterize the solidification behavior of gas tungsten arc (GTA) welds made on L-PBF 304L stainless steel. The effect of surface active elements on the local solidification rates was studied. An emphasis was placed on the role local solidification rates and temperature gradients throughout the weld play on the resultant weld solidification structure and microsegregation. It was determined that gas tungsten arc welds on L-PBF 304L stainless steel exhibited a vermicular ferrite solidification structure compared with a mix of vermicular and lathy ferrite structure in wrought 304L. The varying convective thermal gradients in the weld pool affected the solidification modes and partitioning of elements, leading to fluctuations of microsegregation in the L-PBF 304L. Macroscopically, such partitioning affected the surface tension within the weld pool, producing asymmetric weld pool geometries. The compositional differences between wrought and L-PBF fabricated 304L stainless steels resulted in irregular solidification behaviors during welding affecting the final weld microstructure.
The duplex stainless steels have been developed to provide a combination of tensile properties and resistance to pitting and stress corrosion cracking in comparison with the 300--series austenitic stainless steels. The optimum properties of duplex stainless steels are achieved when nearly equal proportions of aus-tenite and ferrite are present in the microstructure. Control of the ferrite/austenite balance in welds is not as straightforward as in the base metals since it depends on different welding parameters as well as type of welding process. This book is concerned with laser beam welding and its effect on size and microstructure of fusion zone then, on mechanical and corrosion properties of welded joints of the widely used 2205 duplex stainless steel plates. Results of laser welding process have been compared with that of tungsten inert gas (TIG) welding process. The results achieved in this investigation disclosed that laser welding parameters including laser power, welding speed, defocusing distance and type of shielding gas combinations play an important role in obtaining laser welded joint with acceptable fusion zone size and weld profile.