Optimization of Parameters and Prediction of Response Values Using Regression and ANN Model in Resistance Spot Welding of 17-4 Precipitation Hardened Stainless Steel

17-4[Formula: see text]PH steel, also known as UNS 17400 steel or called SAE type 630 stainless steel, is a very important category of steel which has tremendous and extraordinary properties. The superior properties include high corrosion resistance, high hardness and high strength due to the conversion or phase change of the austenite to martensite by cooling the material to room temperature after heating to a temperature around 1030[Formula: see text]C. Normally, this procedure is called as precipitation hardening and hence the name. Due to its extensive properties, the 17-4[Formula: see text]PH steel finds its applications in a variety of industries including pump shafts, oil path, mechanical seals, and within the aerospace industry, parts of the aircrafts, chemical industries and petroleum industries. When a material is used in any kind of applications, fastening is the major process involved. Hence, there should be a standard welding procedure involved in generating a permanent fastening. In this work, resistant spot welding is considered as the welding process and the major parameters are considered which have a crucial effect on the whole process. The responses are considered to be the nugget diameter and tensile strength which denote the weld quality majorly. The process parameters with the help of literature are considered and they are electrode force, voltage and weld current. Taguchi method is used to design the experiments along with the NN tool to generate and predict the new response values. The results show that the major affecting factor is electrode force followed by current and then the voltage. Comparison is done to choose a better model for predicting the optimum responses with the given values of the input parameters. The results are pretty much accurate for both but still the regression model yields better results and almost similar values to the experimental values. Therefore, better results can also be obtained by ANN model by continuous training of the model.

FUNCTIONAL TESTING OF THIN AND STACK WELDED M400-50 A5 CRNGO ELECTRICAL STEEL

In this paper, the effect of gas tungsten arc (GTA) welding current on the mechanical–microstructural–magnetic (M[Formula: see text] properties of cold-rolled non-oriented electrical steel (CRNGO) are investigated. The thin CRNGO sheets of 0.5[Formula: see text]mm each are stacked, welded at a different range of welding current from 30 A to 110 A, and observed for mechanical testing (joint performance and micro-hardness), macroscopic (weld seam characterization), microscopic (grain size variation), and magnetic property evaluation of post-welded samples. The results showed that with the increase in weld current, significant variation in micro-hardness, weld strength, weld seam size, and grain size in the samples’ weld zone is observed. A massive increase in core loss and magnetic field strength, with a significant decrease in relative permeability, is observed for the welded samples compared to the non-welded sample. The samples’ weld strength was varying, depending on the size of the HAZ and fusion zone (FZ) region, for a different weld current range. The hardness in the samples’ weld region increases with the weld current, with relatively higher hardness values observed at the FZ region of weld. Besides, it is observed that the increase in weld current resulted in the formation of coarse-sized grains in the HAZ region of the weld sample, with fine grains existing at the FZ region for higher weld current. The study can be referred for determining the appropriate welding parameters for joining of stacked CRNGO sheets to achieve the desired material properties.

Forming Process of Wire and Arc Additive Manufacture

The forming process of wire and arc additively manufacture (WAAM) was studied using the self-developed and designed WAAM system. The single-pass and single-layer weld bead samples were prepared with different process parameters, and the cross-sectional dimensions of the weld bead were measured. The influence rules of weld current, welding speed, wire feed speed and welding height on the weld bead size were obtained. In addition, the overlap experiment of the WAAM forming process was also carried out. The multiple and multilayer lap samples with different overlap rates were prepared, and the cross-sections of the lap samples were observed and analyzed. Finally, the overlap rate range of 35-45% with good forming effect was obtained.

Gas Tungsten Arc Welding of Stainless Steel 304 and 202 Grades for Optimum Weld Bead Width and Hardness Value

Gas tungsten arc welding of two different stainless steel grades of 304 and 202 of 3 mm thickness is attempted through this experimentation to produce the weld joint without any weld defects. The pure argon is supplied to protect the molten weld pool from any form of contaminations. The welding factors like weld current and travel speed are chosen to prepare the welded joints. The response surface central composite experimental design is used to draw 10 numbers of welding conditions. The gas tungsten arc welded butt joint is produced in a single pass manually for complete penetration. The ranges of weld current are chosen as 86, 90, 100, 110, and 114amps. The welding speed is set as 1.54, 2.05, 4.64, 5.09, and 7.5mm/min. The welded sheets are evaluated for weld bead width which is measured with the help of a Vernier caliper. The hardness of the welded joints is also measured. The chosen factors and measured width of the weld bead and hardness value of the weld joints are analyzed by the use of different statistical terms such as R square, ANOVA analysis, lack of fit, t-test, F-test, and effect tests to state a regression expression at 95% assurance level. It is thus understood from the regression analysis that the welding current and travel speed having major influences upon the weld bead width and hardness of the welded joints. In the manual welding technique, both factors are supposed to be carefully matched by the welder otherwise the penetration depth and proper formation of weld bead width are quite difficult to obtain which further increases the total heat input leading to the degradation of mechanical properties. The current experiment is performed to get an optimum condition by optimizing the weld current and speed to get a well-formed weld bead structure by controlling the total heat input. Thus the experiment will be useful to get the desired quality gas tungsten arc welded joints which are most essential in particular for aerospace and automotive industries for various structural applications.

Tensile Strength of Interpulse Gas Tungsten Arc Welded Butt Joints of Nimonic Super Alloy C263

Nimonic C263 a nickel base super-alloy is generally used in the major components particularly in various structural and hottest sections of the gas turbine engine mainly in the combustor, exhaust sections including blades, discs, liners, and casings, etc. The interpulse gas tungsten constricted welding process is a modified controlled heat input arc welding technique. In this experiment response surface, rotatable central composite experimental design is methodically implemented for the evaluation of the impact of the key factors (i.e. interpulse current, weld current, weld speed and background current) on the tensile strength of butt-welded joints. The welded coupons are tested for tensile tests and obtained a maximum of 1152MPa. The outcome of this experimental examination and thorough optimization will be useful in choosing the most appropriate and suitable welding ranges of the above-mentioned factors for interpulse gas tungsten constricted arc welding of Nimonic superalloy C263 for automotive and aerospace applications.

The Effect of Welding Current and Electrode Force on the Heat Input, Weld Diameter, and Physical and Mechanical Properties of SS316L/Ti6Al4V Dissimilar Resistance Spot Welding with Aluminum Interlayer

Welding parameters obviously determine the joint quality during the resistance spot welding process. This study aimed to investigate the effect of welding current and electrode force on the heat input and the physical and mechanical properties of a SS316L and Ti6Al4V joint with an aluminum interlayer. The weld current values used in this study were 11, 12, and 13 kA, while the electrode force values were 3, 4, and 5 kN. Welding time and holding time remained constant at 30 cycles. The study revealed that, as the welding current and electrode force increased, the generated heat input increased significantly. The highest tensile-shear load was recorded at 8.71 kN using 11 kA of weld current and 3 kN of electrode force. The physical properties examined the formation of a brittle fracture and several weld defects on the high current welded joint. The increase in weld current also increased the weld diameter. The microstructure analysis revealed no phase transformation on the SS316L interface; instead, the significant grain growth occurred. The phase transformation has occurred on the Ti6Al4V interface. The intermetallic compound layer was also investigated in detail using the EDX (Energy Dispersive X-Ray) and XRD (X-Ray Diffraction) analyses. It was also found that both stainless steel and titanium alloy have their own fusion zone, which is indicated by the highest microhardness value.

Experimental investigation on resistance spot welding of dissimilar weld joints

In the present study, galvanized High Strength Interstitial Free (HIF) steel sheets, and Dual Phase (DP780) steel sheets were used for the investigations. Resistance spot weld joints were fabricated between dissimilar steel sheets. The variation in dynamic resistance (DR) with the change in welding process parameters such as weld current, weld time and electrode force were used for establishing the range of adequate weld nugget formation parameters. Effect of these parameters over tensile strength, nugget diameter and the observed failure mode was studied using one factor at a time (OFAT) approach. Microstructure and hardness of parent metal, fusion & HAZ region has also been studied.

Resistance spot weldability of TBF steel sheets with dissimilar thickness

This paper presents an experimental study on weldability of TBF steel sheets with dissimilar thickness. Nominal thickness of TBF sheets were 0.95 and 1.55 mm. Optical microscope was used to observe the cracks formed in the weld zone. The indentation depths were determined by ultrasonic technique. Tensile shear tests were applied to the welded specimens in order to determine the mechanical properties. Higher weld current and time resulted in higher nugget size and indentation depth. This increase in nugget size and indentation depth with increasing of weld current and weld time was almost linearly. The liquid metal embrittlement crack sensitivity in the HAZ was very high on TBF spot welds. The liquid metal embrittlement cracks were much deeper and wider along the weld periphery regions compared to the nugget regions. These cracks were occurred easily with a higher heat input and the crack depth increased almost linearly with increasing of heat input. Weld strength of the specimens was governed by crack formation in the HAZ. Lower weld currents and weld times resulted in higher tensile shear properties. The highest tensile shear load (18.50 kN) and energy absorption (37.5 J) were achieved at 6 kA for 20 cycles. This weld exhibited interfacial failure mode.