Effect Of Welding Current Research Articles

Resistance Spot Welding Behavior of Automotive Steels

In present-day automobiles, new high-strength steel grades are being extensively utilized, which have different alloy concentration, microstructure and properties, and results in different spot welding behavior. In the present work, the effect of weld current was studied on four widely used automotive grades, such as IF 270, TRIP 690, DP 780 and TRIP 980, in a laboratory welding machine. The welding current was varied between 5 and 15 kA. Weld quality was assessed based on tensile shear, mode of failure, weld nugget diameter, metallographic observations and hardness tests. Experimental results showed that weld strength increased with an increase in base metal tensile strength but with a drop at the point of expulsion. Variation in hardness along the cross section was found to be higher in high-strength steels. The initial microstructure and phase transformation during cooling affected the final properties. Critical currents for peak strength, expulsion, sticking and failure mode transition were determined for each grade for industrial applications. This study helped in determining the criterion-based optimized welding parameters for specific applications of these automotive-grade steels.

Investigation of thin sheet stainless steel resistance spot welds: Effect of weld current on nugget failure and microstructure

Thin stainless-steel sheets commonly used in food and beverage industry is resistance spot welded in the process of making leak proof containers. The spot-welding parameters are optimized to obtain maximum nugget size and weld strength. In contrast, least importance is given to the temperature developed at the sheet/electrode interface and subsequent oxidation of the weld. It is well known that the oxidation of the stainless-steel results in the depletion of the chromium in the material affecting its corrosion resistance properties. In this context, this paper is aimed at investigating the effect of resistance spot welding current on the chromium depletion and subsequently on the microstructure of 0.4 mm 304 stainless steel sheet weldments. Comparative study between the microstructures of the heat affected and weld zones were carried using optical microscope and scanning electron microscope. The effect of weld current on the morphology of the delta ferrite formed in the weld zone is presented in the paper with help of pseudo-binary phase diagram. An attempt is made to correlate the local chromium depletion with the microstructure and defect formation.

Investigation on the resistance spot-welded austenitic/ferritic stainless steel

In this work, the effect of weld current on joining capability of austenitic stainless steel (AISI 304) and ferritic stainless steel (AISI 430) sheets with application of resistance spot welding process was investigated. Macrostructure, microstructure, microhardness, tensile shear strength, and failure mode of welded materials were evaluated for different weld currents. The values of weld current were 2.5, 3.75, and 5 kA. It was found that when the weld current increased, the nugget size and the weld strength were increased. Two distinct failure modes including interfacial and pullout were observed during tensile shear test. Finally, an adequate weld current was obtained.