scholarly journals Laser Welding of Ultrahigh Strength Steels at Subzero Temperatures

2016 ◽  
Vol 83 ◽  
pp. 352-361 ◽  
Author(s):  
Benjamin Gerhards ◽  
Uwe Reisgen ◽  
Simon Olschok
Keyword(s):  
Laser Welding ◽  
Ultrahigh Strength ◽  
Subzero Temperatures ◽  
Ultrahigh Strength Steels

Fiber Laser Welding of Direct-Quenched Ultrahigh Strength Steels: Evaluation of Hardness, Tensile Strength, and Toughness Properties at Subzero Temperatures

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Farhang Farrokhi ◽  
Jukka Siltanen ◽  
Antti Salminen
Keyword(s):  
Tensile Strength ◽  
Impact Toughness ◽  
Fiber Laser ◽  
Welding Process ◽  
Fiber Laser Welding ◽  
Butt Joints ◽  
Ultrahigh Strength ◽  
Subzero Temperatures ◽  
Ultrahigh Strength Steels ◽  
Strength And Toughness

The recently developed direct-quenched ultrahigh strength steels (UHSS) possess an appropriate combination of high tensile strength and toughness properties at subzero temperatures down to −80 °C, while simultaneously having low carbon contents, which is beneficial for weldability. In this study, butt joints of Optim 960 QC direct-quenched UHSS with a thickness of 8 mm were welded with a 10 kW fiber laser to evaluate the characteristics of the joints within the range of low to high heat inputs possible for this welding process. The mechanical properties of the joints were studied by subjecting the specimens to a number of destructive tests, namely, hardness and tensile testing, as well as impact toughness testing at temperatures of −40 °C and −60 °C. It was found that high quality butt joints with superior tensile strength and good impact toughness properties at −40 °C could be obtained. However, having a high level of all these properties in the joint narrows the process parameters’ window, and the heat input needs to be strictly controlled.

scholarly journals The Effect of Electroslag Remelting on the Microstructure and Mechanical Properties of CrNiMoWMnV Ultrahigh-Strength Steels

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 262
Author(s):  
Mohammed Ali ◽  
David Porter ◽  
Jukka Kömi ◽  
Mamdouh Eissa ◽  
Hoda El Faramawy ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Laser Scanning ◽  
Electron Backscatter Diffraction ◽  
Laser Scanning Confocal Microscopy ◽  
Electroslag Remelting ◽  
Scanning Confocal Microscopy ◽  
Ultrahigh Strength ◽  
Microstructure And Mechanical Properties ◽  
Considerable Impact ◽  
Ultrahigh Strength Steels

The effect of electroslag remelting (ESR) with CaF2-based synthetic slag on the microstructure and mechanical properties of three as-quenched martensitic/martensitic-bainitic ultrahigh-strength steels with tensile strengths in the range of 1250–2000 MPa was investigated. Ingots were produced both without ESR, using induction furnace melting and casting, and with subsequent ESR. The cast ingots were forged at temperatures between 1100 and 950 °C and air cooled. Final microstructures were investigated using laser scanning confocal microscopy, field emission scanning electron microscopy, electron backscatter diffraction, electron probe microanalysis, X-ray diffraction, color etching, and micro-hardness measurements. Mechanical properties were investigated through measurement of hardness, tensile properties and Charpy-V impact toughness. The microstructures of the investigated steels were mainly auto-tempered martensite in addition to small fractions of retained austenite and bainite. Due to the consequences of subtle modifications in chemical composition, ESR had a considerable impact on the final microstructural features: Prior austenite grain, effective martensite grain, and lath sizes were refined by up to 52%, 38%, and 28%, respectively. Moreover, the 95th percentiles in the cumulative size distribution of the precipitates decreased by up to 18%. However, ESR had little, if any, the effect on microsegregation. The variable effects of ESR on mechanical properties and how they depend on the initial steel composition are discussed.

Influence of silicon content on ion nitriding of ultrahigh strength steels

2004 ◽  
Vol 20 (9) ◽  
pp. 1171-1178 ◽  
Author(s):  
L.C. Casteletti ◽  
R.M. Munoz Riofano ◽  
P.A.P. Nascente
Keyword(s):  
Silicon Content ◽  
Ion Nitriding ◽  
Ultrahigh Strength ◽  
Ultrahigh Strength Steels

Comparison of Mechanical and Microstructural Characteristics in Maraging 300 Steel Welded by PAW and GTAW Processes Submitted to Repair

2016 ◽  
Vol 1135 ◽  
pp. 255-264 ◽  
Author(s):  
Paulo Roberto Sakai ◽  
Deivid Ferreira da Silva ◽  
Sandro Lombardo ◽  
Antonio Jorge Abdalla
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Base Material ◽  
Welding Process ◽  
Repair Process ◽  
High Temperature Strength ◽  
Maraging Steels ◽  
Ultrahigh Strength ◽  
Ultrahigh Strength Steels ◽  
Welding Processes

Maraging steels are a special class of ultrahigh-strength steels which presents a combination of high mechanical strength, excellent toughness, high temperature strength and corrosion resistance. The joint of sheets/plates by welding processes are fundamental for aeronautical and industrial products in addition Brazil has been developing technologies in welding ultrahigh-strength steels such as AISI 4340ESR and SAE 300M steels for its domestic space launch program and has currently decided for the replacement of these steels by Maraging 300 steel in some projects. In this work, we studied the welding process of the Maraging 300 steel for two different routes: Tungsten Inert Gas (TIG or GTAW) and Plasma Arc Welding (PAW). Filler additions were used for both processes. Procedure after any welding demands non destructive testing and sometimes non approved defects considering the usage of the product require for welding repair. Verification of the effects of this operation was made through a simulation of a welding repair for both types of welding. Specimens were submitted to heat treatment consisting of a solution annealing and aging and their microstructures were examined. The microhardness measurements were made on samples with and without repair characterized the fusion and heat affected zones. Specimens were submitted to tensile testing and the fractured surfaces were examined by a scanning electron microscope. Results of microstructure exam revealed the presence of austenite (γ) in FZ (Fusion Zone). After the welding repair simulation, a new different colored zone appeared in the HAZ (Heat Affected Zone) for both processes due to reheating of the sheet provided by the repair process. In the HAZ near FZ an important grain growth due to the heating occurred. Also, close FZ that was submitted to new heating due to repair it was noted an apparent growing of grain size relative to original grain size. The microhardness measurements showed that there is a reduction in hardness in the FZ and the region immediately (fusion line) compared to base material values. After the aging heat treatment a recovery of hardness values took place in these regions but the values themselves remain smaller than the base material. It was observed an increase of values of the microhardness in dark regions in the HAZ provoked by a phenomenon of aging locally due to the dissipation of the heat of the welding process and posterior repair. After aging, those differences disappeared. It was observed that there was not a large difference between the yield and strength limits considering both processes of welding, as well as between both situations after repair. It could be seen that the rupture began in the region near FZ and followed in the direction of the weld bead. The analysis of the fracture surfaces showed that this happened by ductile way, forming dimples.

Controlling Hydrogen Embrittlement in Precharged Ultrahigh-Strength Steels

CORROSION ◽  
2007 ◽  
Vol 63 (7) ◽  
pp. 689-703 ◽  
Author(s):  
H. Dogan ◽  
D. Li ◽  
J. R. Scully
Keyword(s):  
Hydrogen Embrittlement ◽  
Ultrahigh Strength ◽  
Ultrahigh Strength Steels
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