Correlation Among the Input Thermal Parameters and Thermography Measurements Data of the Resistance Seam Welding

Abstract

Resistance Seam Welding (RSEW) is commonly used in continuous steel processing for joining steel coils. Experimental studies focused on the welding process quality controls are justified by their wide application and influence on the performance of steelmaking processes. The present study focuses on the continuous annealing line welding process using as sample, a low carbon steel (0.07%C) with 0.21 mm thickness. The work proposes a correlation of thermal input, electric current parameter and thermogram monitoring during RSEW procedures. A methodology was developed to determine the real thermal profiles values by means of association of the thermograms with the sample emissivity curve. Three heat input levels were used, 3.64 J.mm-1 , 5.09 J.mm-1, and 6.38 J.mm-1 , respectively, for typical C-Mn steel. The thermal welding profile obtained experimentally exhibited linear correlation coefficients (R) of 0.99 with the electric current welding parameter and (R) of 0.99 with the calculated thermal input, respectively. The welds metallurgical characterizations results, expressed through the ductility and welds nuggets analysis, were conducted to correlate the welds quality with the welding thermal input. The Erichsen cupping test showed that the higher the thermal input corresponds to higher ductility of the welds. Nevertheless, the heat input of 5.09 J.mm-1 indicated better-balanced properties: ductility, weld nugget discontinuity, nugget size, and no expulsion of the melt material.

A Coupled Thermo-Mechanical-Metallurgical Model Capturing Essential Transformations in the Welding of High Strength Low-Alloy Steels

“…Paloposki and Liedquist [21] investigated the temperature dependency of emissivity for low carbon steels, but the available data limited for a narrow range of temperature (up to 700 o C). Recent data published by Deus et al [22] have indicated that a sigmoid function is suitable for applying under welding environment conditions. Thus, the available data by Paloposki and Liedquist [21] can be fitted as shown in Equation 4.…”

Prediction of the Emissivity Curve at High Temperatures of Low Carbon Steel

“…Although methods for measuring emissivity have already been proposed and applied for different materials, there is still no standard procedure or methodology universally accepted with suitable accuracy. It is recognized that the measurement of emissivity is difficult in practice due to the influence of variables such as material reflectivity, instrument calibration, surface homogeneity and interference from the environment (Novo et al 2014;Paloposki & Liedquist, 2005;Richmond & Harrison, 1962;Deus, 2019, Deus et al, 2020.…”

“…In order to base subsequent thermographic evaluations on welds made throughout the steel production process, the present research focused on the development of a methodology for the normal emissivity curve experimental determination, using, as the sample, a low carbon steel (0.07%C) with 0.21 mm thickness obtained from the productive stock of a continuous annealing line from the CSN steel plant (Deus, 2019;Deus et al, 2020). Subsequently, the results were compared with the data obtained through other methodologies developed from correlated researches.…”