scholarly journals Double Pulse Resistance Spot Welding of Dual Phase Steel: Parametric Study on Microstructure, Failure Mode and Low Dynamic Tensile Shear Properties

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 802
Author(s):  
Imtiaz Ali Soomro ◽  
Srinivasa Rao Pedapati ◽  
Mokhtar Awang
Keyword(s):  
Spot Welding ◽  
Mechanical Performance ◽  
Peak Load ◽  
Double Pulse ◽  
Dual Phase ◽  
Tensile Shear ◽  
Resistance Spot ◽  
Failure Energy ◽  
Pulse Welding

Resistance spot welding (RSW) of dual phase (DP) steels is a challenging task due to formation of brittle martensitic structure in the fusion zone (FZ), resulting in a low energy capacity of the joint during high-rate loading. In the present study, in situ postweld heat treatment (PWHT) was carried out by employing a double pulse welding scheme with the aim of improving the mechanical performance of DP590 steel resistance spot weld joint. Taguchi method was used to optimize in situ PWHT parameters to obtain maximum peak load and failure energy. Experiments were designed based on orthogonal array (OA) L16. Mechanical performance was evaluated in terms of peak load and failure energy after performing low dynamic tensile shear (TS) test. Microstructural characterization was carried out using a scanning electron microscope (SEM). The results show that improvements of 17 and 86% in peak load and failure energy, respectively, were achieved in double-pulse welding (DPW) at optimum conditions compared to traditional single-pulse welding (SPW). The improvement in mechanical performance resulted from (i) enlargement of the FZ and (ii) improved weld toughness due to tempering of martensite in the FZ and subcritical heat affected zone (SCHAZ). These factors are influenced by heat input, which in turn depends upon in situ PWHT parameters.

Resistance Spot Welding of Unequal Thickness Low Carbon Steel Sheets

2009 ◽  
Vol 83-86 ◽  
pp. 1205-1211 ◽  
Author(s):  
Majid Pouranvari ◽  
Pirooz Marashi
Keyword(s):  
Carbon Steel ◽  
Spot Welding ◽  
Peak Load ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Tensile Shear ◽  
Spot Welds ◽  
Resistance Spot ◽  
Resistance Spot Welds ◽  
Dissimilar Thickness

Resistance spot welding is the dominant process for joining sheet metals in automotive industry. Even-thickness combinations are rarely used in practice; therefore, there is clearly a practical need for failure behaviour investigation of uneven-thickness resistance spot welds. The aim of this paper is to investigate and analyze the failure mode and failure mechanism of dissimilar thickness low carbon steel resistance spot welds during tensile-shear overload test. Microstructural investigations, microhardness tests and tensile-shear tests were conducted. Mechanical properties of the joint were described in terms of peak load, energy absorption and failure mode. It was concluded that weld nugget size and the strength of the thinner base metal are the controlling factors of the peak load and energy absorption of dissimilar thickness spot welds.

EFFECTS OF HOLDING TIME ON HAZ-SOFTENING IN RESISTANCE SPOT WELDED DP980 STEELS

2012 ◽  
Vol 1485 ◽  
pp. 95-100 ◽  
Author(s):  
C.J. Martínez-González ◽  
A. López-Ibarra ◽  
S. Haro-Rodriguez ◽  
V.H. Baltazar-Hernandez ◽  
S.S. Nayak ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Spot Welding ◽  
Mechanical Performance ◽  
Martensite Phase ◽  
Holding Time ◽  
Dual Phase ◽  
Tempered Martensite ◽  
Dp Steel ◽  
Resistance Spot ◽  
Lap Shear

ABSTRACTResistance spot welding (RSW) of dual-phase (DP) steel subjected to various conditions of cooling rate (holding time) is studied in this work. Lap-shear tensile testing is used in order to evaluate the mechanical performance of the weldments. The microstructure is analyzed through optical and electron microscopy and the hardness is obtained through Vickers method. Results indicate an effective tempered region along the sub-critical heat affected zone in all the samples. A broken morphology accompanied with presence of small carbides within tempered martensite phase is consistently observed. Variations in the cooling rate (holding time) indicate minimal effect on the degree of softening and on the mechanical performance of the welds.

scholarly journals Effect of Double Pulse Resistance Spot Welding Process on 15B22 Hot Stamped Boron Steel

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1279
Author(s):  
Hwa-Teng Lee ◽  
Yuan-Chih Chang
Keyword(s):  
Heat Input ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
Welding Process ◽  
Double Pulse ◽  
Weld Nugget ◽  
Boron Steel ◽  
Welding Parameters ◽  
Tensile Shear ◽  
Resistance Spot

Double pulse resistance spot welding process by applying a second step welding current is a new pathway to alter the mechanical properties for advanced high strength steels. Herein, the resistance spot welding (RSW) of hot stamped boron steel 15B22 by one-step and two-step welding with different welding currents is investigated. The results of the tensile–shear test, size of the weld nugget, hardness distribution, microstructure, and failure mode of different welding parameters are analyzed. The weldment of the two-step RSW with a higher heat input exhibits a lower tensile–shear load and lower fracture energy when the size of the weld nugget is large. The microstructural study reveals the appearance of a partially melted zone and sub-critical heat affected zone in the weldment where the fracture readily occurred. Thus, the two-step RSW process weakens the strength of the sample, which is attributed to the partial softening in the weldment due to the higher heat input.

Investigation of Microstructure and Mechanical Properties of Resistance Spot Welded Dissimilar Joints Between Ferritic Stainless Steel and Weathering Steel

2015 ◽  
Vol 766-767 ◽  
pp. 770-779 ◽  
Author(s):  
A Subrammanian ◽  
D.B. Jabaraj ◽  
V.K. Bupesh Raja
Keyword(s):  
Stainless Steel ◽  
Fusion Zone ◽  
Ferritic Stainless Steel ◽  
Spot Welding ◽  
Peak Load ◽  
Weathering Steel ◽  
Tensile Shear ◽  
Dissimilar Joints ◽  
Resistance Spot ◽  
Mode Of Failure

Resistance spot welding is widely used in automobile and rail car manufacturing industries. In this research work, resistance spot welded dissimilar joints of ferritic stainless steel and weathering steel sheets is investigated for mechanical and metallurgical properties. Ferritic stainless steel AISI 409M and weathering steel corten A (ASTM A 242) of 2mm thickness were used in this work. Spot welding was done at different current values, keeping other parameters such as electrode force, electrode tip diameter and weld time as constant. Test specimens were subjected to tensile shear test and micro hardness test to assess the mechanical properties of the weld joints. The influence of welding current on nugget growth, fusion zone hardness, peak load, and failure energy and failure mode during tensile shear test, was investigated at various current ratings. The results showed that, with increasing value of current, peak load increased correspondingly. Nugget shape was found to be near symmetrical. Nugget diameter was found to be increasing with increase in current, in expulsion free welds. Interfacial mode of failure was noticed at low current values, whereas, at higher current values, pull out mode of failure was observed. Presence of martensite was observed in the fusion zone. Micro hardness values at fusion zone were found to be more than that of both heat affected zones and base metals.

scholarly journals Microstructural characterization of a double pulse resistance spot welded 1200 MPa TBF steel

2019 ◽  
Vol 64 (2) ◽  
pp. 335-343
Author(s):  
Manfred Stadler ◽  
Martin Gruber ◽  
Ronald Schnitzer ◽  
Christina Hofer
Keyword(s):  
Mechanical Performance ◽  
Bainitic Ferrite ◽  
High Strength Steels ◽  
Quality Criterion ◽  
High Strength ◽  
Microstructural Characterization ◽  
Double Pulse ◽  
Resistance Spot ◽  
Advanced High Strength Steels ◽  
Pulse Welding

AbstractIn the automotive industry resistance, spot welding is the dominant technology in sheet metal joining of advanced high strength steels (AHSS). In order to improve the mechanical performance of AHSS welds, in-process tempering via a second pulse is a possible approach. In this work, two different double pulse welding schemes were applied to a 1200 MPa transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steel. The different microstructures in the welds were characterized via light optical and scanning electron microscopy. Additionally, hardness mappings with several hundred indents were performed. It is shown that the second pulse, following a low first pulse which is high enough to produce a weld nugget that fulfills the quality criterion of a minimum spot weld diameter of 4*√t, leads to partial reaustenitization and consequently to a ferritic/martensitic microstructure after final quenching. Hardness mappings revealed that this inner FZ is harder than the surrounding FZ consisting of tempered martensite. In contrast, if the highest current without splashing is chosen for the first pulse, the same second pulse does not reaustenitize the FZ but only temper the martensite.

Resistance Spot Welding in Non-Combustible Magnesium Alloy

2020 ◽  
Author(s):  
Xuanyi Shao ◽  
Yukio Miyashita ◽  
Duriyathep Panwised ◽  
Rattana Borrisutthekul
Keyword(s):  
Magnesium Alloy ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
Shear Test ◽  
Dissimilar Materials ◽  
Maximum Load ◽  
Tensile Shear ◽  
Similar Material ◽  
Resistance Spot ◽  
Surface Polishing

Abstract Resistance spot welding (RSW) was applied to non-combustible magnesium alloy, AX41 (Mg-4%Al-1%Ca) to investigate its weldability. The similar material joint of AX41 and dissimilar materials joint between AX41 and aluminum alloy, AA6061 were welded. Tensile shear test was carried out to evaluate joining strength in the similar and dissimilar materials RSW joints. In case of similar material joints, the maximum load obtained with tensile shear test in AX41 similar material joint was higher than that obtained in AA6061 similar material joint. Moreover, higher maximum load was obtained in a similar material joint without surface polishing compared to joint welded with surface polishing in AX41. In case of the dissimilar materials joint, the maximum load obtained was almost comparable with AX41 similar material joint, however scatter in joint strength was large. Weldability of the dissimilar materials joint became poor by applying surface polishing.

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