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 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.

Experimental Investigation on Solid State Resistance Spot Welding

2017 ◽  
Author(s):  
Zhijun Wu ◽  
Guanlin Zhang ◽  
Bingxu Wang ◽  
Kelvin Shih
Keyword(s):  
Solid State ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
Mechanical Performance ◽  
Thin Sheet ◽  
Welding Current ◽  
Sheet Metals ◽  
Resistance Spot ◽  
Nugget Formation ◽  
State Resistance

Resistance Spot Welding (RSW) is one of the most common and dominant technologies utilized in the automotive industry to join the thin sheet metals together, and expulsion is a common phenomenon during the operation. How to ensure the high quality nugget formation and joining performance is essential to ensure the quality and integrity of structures. In this study, solid state resistance spot welding is introduced in order to prevent expulsion. The effect of welding current and welding time on the mechanical performance of the solid state RSW in terms of nugget size, tensile performance and nugget formation will be investigated experimentally by using steel sheet metals. Microstructure and micro-hardness of the nugget cross-section will be evaluated as well.

Resistance spot welding macro characteristics of the dissimilar thickness dual phase steels

2014 ◽  
Vol 63 ◽  
pp. 151-158 ◽  
Author(s):  
Hongqiang Zhang ◽  
Xiaoming Qiu ◽  
Yang Bai ◽  
Fei Xing ◽  
Haiyan Yu ◽  
...  
Keyword(s):  
Resistance Spot Welding ◽  
Spot Welding ◽  
Dual Phase ◽  
Dual Phase Steels ◽  
Resistance Spot ◽  
Dissimilar Thickness

Thermo-Mechanical Simulation of Ultra-High Strength Ferrite-Bainite Dual Phase Steel

2012 ◽  
Vol 184-185 ◽  
pp. 1367-1370
Author(s):  
Wei Lv ◽  
Di Wu ◽  
Zhuang Li
Keyword(s):  
Cooling Rate ◽  
Dual Phase Steel ◽  
High Strength ◽  
Solute Drag ◽  
Dual Phase ◽  
Drag Effect ◽  
Dp Steel ◽  
Mechanical Simulation ◽  
Austenite Grain ◽  
Fast Cooling

In the present paper, thermo-mechanical simulation of ultra-high strength ferrite-bainite dual phase (DP) steel was performed using a thermomechanical simulator. Continuous cooling transformation (CCT) diagram was constructed for DP steel. The effects of composition and cooling rate on the kinetics and products of phase transformation and the form of the CCT diagram were investigated. The results have shown that the α→γ transformation in DP steel was found to be more sluggish due to the addition of alloying elements. The segregation of manganese and niobium at austenite grain boundaries is expected to cause a solute drag effect, thereby reducing the rate of γ→α transformation in DP steel. The pearlite transformation region disappeared for cooling rates from 0.1 to 20°C/s. The microstructure comprises of bainite and martenite was obtained at fast cooling rate. The present steel is expected to have a higher hardenability.

Research on Resistance Spot Welding of DP980 Dual Phase Steel

2013 ◽  
Vol 860-863 ◽  
pp. 780-783
Author(s):  
Qiao Bo Feng ◽  
Yun Feng Zhu ◽  
He Xin Zhao
Keyword(s):  
Resistance Spot Welding ◽  
Spot Welding ◽  
Dual Phase Steel ◽  
Welding Current ◽  
High Resistivity ◽  
Dual Phase ◽  
Welding Joint ◽  
Resistance Spot ◽  
Electrode Force

The process parameters and quality of resistance spot welding for DP980 dual phase steel were studied through the orthogonal experiment method, and the influence of welding current, welding time and electrode force on the strength of welding joint has been discussed. The results show that the welding current has the greatest influence on the quality of welding joint for DP980 dual phase steel, and it needs relatively lower welding current for the DP980 dual phase steel as it has high resistivity, and appropriate increasing of electrode force is a feasible way to avoid the defect of shrinkage and it improves the joint strength.

scholarly journals MULTI-OBJECTIVE OPTIMIZATION OF THE RESISTANCE SPOT-WELDING PROCESS PARAMETERS FOR THE WELDING OF DUAL-PHASE STEEL DP500

2021 ◽  
Vol 55 (2) ◽  
pp. 201-206
Author(s):  
Aleksija Djuric ◽  
Dragan Milčić ◽  
Damjan Klobčar ◽  
Biljana Marković
Keyword(s):  
Automotive Industry ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
Dual Phase Steel ◽  
Mechanical Characteristics ◽  
Welding Process ◽  
Dual Phase ◽  
Multi Objective Optimization ◽  
Multi Objective ◽  
Resistance Spot

Resistance spot welding (RSW) is still the most used form of welding in the automotive industry, primarily for welding steel. One of the advanced steels used in the automotive industry is dual-phase steel, so it is important to properly select the welding parameter for these steels. Therefore, this paper presents multi-objective optimization in the RSW welding process of DP 500 steel. The paper considers three different mechanical characteristics i.e., the failure load (F), failure displacement (l) and weld nugget diameter (D), as all these welding characteristics play significant roles in evaluating the quality of spot welding. The results show that the welding current is the most influential parameter with respect to the mechanical characteristics. The effect of welding time on the weld quality is the least significant. The optimal parameters for welding DP 500 steel obtained in this paper are weld current 8 kA, electrode force 4.91 kN and weld time 400 ms.

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