Home Mechanical properties and nugget evolution in resistance spot welding of Zn–Al–Mg galvanized DC51D steel
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Mechanical properties and nugget evolution in resistance spot welding of Zn–Al–Mg galvanized DC51D steel

  • Linlin Zhao ORCID logo EMAIL logo , Yue Lu EMAIL logo , Ziliu Xiong EMAIL logo , Li Sun , Jianjun Qi , Xinjian Yuan and Jian Peng
Published/Copyright: March 23, 2023
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High Temperature Materials and Processes
From the journal High Temperature Materials and Processes Volume 42 Issue 1

Abstract

Zn–Al–Mg coating galvanized steel in resistance spot welded (RSW) in different configurations of DC51D was investigated to illustrate the nugget evolution process and mechanical properties of the joints. Results show that the microstructure of welded joints can be divided into nugget zone (FZ), heat-affected zone (HAZ), and base metal zone (BM). FZ was composed of lath martensite. The average hardness value of the weld joint was 110 HV0.2 while the FZ was up to 300 HV0.2 due to the formation of lath martensite. The failure modes can be divided into interface fracture (IF) and pull-out fracture occurred (PF) under different welding parameters, in which shear dimples showed had a typical plastic fracture morphology. The best range for welding parameters was found to be 12–18 cycles in which the nugget diameter reached 5.5 mm. The process of nugget evolution in HAZ and FZ was discussed.

Keywords: steel; RSW welding; microstructure; coating evolution; nugget formation

1 Introduction

Ultra-low carbon DC51D steel has been widely used in the automobile industry, due to its good corrosion resistance as well as stamping performance and high stiffness, which can avoid depression in the production process and absorb impact energy in collision accidents [1]. Different from the traditional alloying coating, Zn–Al–Mg coating has better corrosion resistance, wear resistance, better weldability, and better resistance to different service environments [2,3,4]. By increasing the contents of Al and Mg in the coating, the corrosion resistance of the car is prolonged under complex and harsh service conditions [5,6].

Good weldability of DC51D + ZM can ensure that the strength and performance of the welded parts in the welding process are kept as stable as possible. Resistance spot welding is the main method to connect parts of the car. RSW is mainly realized by using current through the contact surface of the welded joint and the resistance heat generated in the internal area [7,8]. It has been widely used in TRIP steel welding [9,10,11].

Feng [5] applied AZ31 magnesium alloy and galvanized DP600 steel as the research objects. Hot-dip galvanized Q235 steel was used as the interlayer for resistance spot welding. Under the optimized welding process parameters, the peak load was increased by about one–third, and the energy absorption was doubled compared to traditional resistance spot welding joints. Arghavani et al. [12] treated the effect of galvanized layer on resistance spot welding of aluminum/galvanized steel (GS–Al joint and aluminum/low carbon steel (PS–Al) joint. The melting and evaporation of the galvanized layer resulted in a decrease in the thickness of the Al–Fe alloy layer.

Ghatei Kalashami et al. [13] introduced the effect of silicon content on the embrittlement sensitivity of liquid metal in resistance spot welding of galvanized dual-phase steel. In dual-phase steel, the silicon content increased from 0.7 to 1.8%, which improved the embrittlement sensitivity of liquid metal. Kim et al. [14] reported that CO2 laser combined with arc welding was applied to zero gap lap welding of galvanized steel. The problem of the gas hole was solved, and the heat input of arc could be reduced by 40%. Selvamani et al. [15] investigated the thermal distribution of cold metal transfer welding galvanized steel in the welding process simulated by ANSYS. The thermal distribution of galvanized steel sheet was measured by an infrared thermometer and compared with the finite element analysis results of volume heat source model. Shreyas et al. [16] investigated the effect of zinc on the mechanical properties of welds of galvanized low carbon steel and 316L stainless steel. Ashiri et al. [17] reported the relationships of resistance spot welds of galvanized IF steels. Kim et al. [18] presented an innovative approach that uses a pulse profile to improve the welding quality of CP1180 steel in RSW. The maximum defect size of the welding procedure was 18.5% larger than that of the single pulse. The welding current range was increased by 130%.

However, due to different material thickness, microstructure, and coating, it is often necessary to find out the change of resistance spot welding parameters. In attempting to solve the welding problem of galvanized steel, many researchers have conducted a lot of research. Andrade et al. [19] revealed the effect of the thickness of galvanized layer on the thermal cycle. Steel structures and thin plates commonly used in the automobile industry were welded by different thicknesses of the galvanized layer. Ghatei Kalashami et al. [20] argued that compared to the receiving conditions, the formation of internal oxide during controlled atmosphere galvanizing reduces the resistance and heat input, resulting in the delay of nugget growth in resistance spot welding. Hamidinejad et al. [21] investigated the resistance spot welding (RSW) process of galvanized gapless (IF) steel plate and galvanized baking hardening (BH) steel plates used in automobile body manufacturing by modeling and optimization. Feng et al. [5] stated that AZ31 magnesium alloy and electrogalvanized DP600 steel were joined by resistance spot welding (RSW) using hot-dip galvanized Q235 steel as an interlayer. The tensile properties of welded joints with an intermediate layer were found to be better than those whose joints did not have an intermediate layer.

The above studies show that most of the studies on automobile galvanized steel focus on the influence of welding parameters and some macro- and micro-characteristics of welded joints. However, the effect of Zn–Al–Mg coating on resistance spot welding joint of steel plate remains unclear. In order to solve these problems, we have studied the RSW of DC51D + ZM to obtain the optimal welding process. The range of welding current, welding time, and electrode pressure was investigated.

Two significant aspects were highlighted. First, the welding parameters were studied to reveal the nugget formation process through. Macro and micro morphologies were acquired by optical microscope (OM), scanning electron microscope-replication (SEM), transmission electron microscope (TEM), and energy dispersive spectroscopy (EDS). The strength and tensile shear properties of microhard welded joints were also investigated. Second, the interface composition, chemical element composition, and fracture morphology of Zn–Al–Mg coating and welding joint were analyzed. The influence of coating phase composition on strength and the microstructure and properties of welded joints were also studied. DC51D with Zn–Al–Mg coating joint was obtained using RSW. Fe–Al phase was detected at the interface of HAZ. The mechanisms of nugget formation and mechanical properties were also discussed.

2 Materials and methods

DC01 Non-coated and Galvanized DC51D + ZM low carbon steel with a thickness of 1.0 mm were used as the BM. The chemical compositions and the mechanical properties of DC51D + ZM are given in Table 1. The configurations and welding parameters are listed in Tables 1 and 2, respectively.

Table 1

Chemical composition and mechanical properties of DC51D + ZM

Chemical composition (wt%) Ultimate tensile strength (MPa) Elongation (%)
Steel C Mn Si P S Ti
DC51D + ZM 0.12 0.6 0.50 0.1 0.05 0.30 357 25

Resistance spot welding machine (TCW-33E-LX) was used in the experiment (GWS-5A-2007). Figure 1 shows the tensile-shear specimens and metallographic specimens which were cut along the cross section. The tensile shear was tested using CMT-5105 universal mechanical testing machine (DIN EN ISO 14273-2016). Digital camera was used to take macro photographs and record the resistance spot welding process. Wire-electrode cutting was used to separate the welded sample from the center. The welded samples were ground via silicon carbide paper (mesh from 180 to 3,000). Samples were etched by corrosion with 4% nitric acid alcohol solution for roughly 8–10 s at room temperature (ASTM E3-2011, R2017). The nugget diameters and indentation rates were obtained from the resulting metallograph.

Figure 1 The schematic of welding samples.
Figure 1

The schematic of welding samples.

OM and SEM (TESCAN VEGA 3 LMH, Czech) were used to analyze the microstructures of the welded joints with a voltage of 20 kV. The microhardness from longitudinal and transverse directions was investigated through the Vickers hardness tester (HXS-1000AKY) with a load of 300 g (DIN EN ISO 14271-2018). The dwelling time was about 15 s, and indentations spaced were 0.2 and 0.5 mm relatively. The evolution of Zn–Al–Mg coating was investigated by EDS match by SEM.

3 Results and discussion

3.1 Macro characteristics of the welded joint

When the welding time and electrode pressure remain unchanged, the nugget diameter increased with the increase of welding current. As shown in Figure 2, when the welding current exceeded 9 kA, the color of the solder joint changed from gray to yellow. The color gradually deepened with the increase of welding current. Cr–Zr–Mn copper electrode was used in RSW. During the welding process, the electrode cap adhered to the sample when the copper element diffused. With the increase of welding current, the heat input increased with the increase of the adhesion. To avoid this problem, the electrode head should be replaced or cleaned on time.

Figure 2 Macrophotographs of the resistance spot welded joints in different configurations: (a) welding current, (b) welding time, and (c) electrode pressure.
Figure 2

Macrophotographs of the resistance spot welded joints in different configurations: (a) welding current, (b) welding time, and (c) electrode pressure.

Figure 3 shows the photographs of the resistance spot welded joints at different welding times (one–ten cycles). When the welding current and electrode pressures were 10 kA and 2.2 kN, the nugget diameter increased and the nugget was formed with the augmentation of welding time changing from one to ten cycles.

Figure 3 Macro photographs of the resistance spot welded joints in different configurations.
Figure 3

Macro photographs of the resistance spot welded joints in different configurations.

Figure 4 Macro photographs of the resistance spot welded joints in different configurations: (a) one cycle, (b) two cycles, (c) four cycles, (d) six cycles, (e) eight cycles and (f) ten cycles.
Figure 4

Macro photographs of the resistance spot welded joints in different configurations: (a) one cycle, (b) two cycles, (c) four cycles, (d) six cycles, (e) eight cycles and (f) ten cycles.

Figure 4 shows the process of nugget formation. The Joule's heating of different welding times can be calculated as follows:

(1) Q = I 2 RT .

According to the law, the welding heat input increases with welding time [13]. When welding time was one–two cycles, the heat was not sufficient to completely melt the base metal. Zn–Al–Mg coating immediately melt at the beginning of welding, and a enlargement of the electrothermal contact surface occurred. It only caused the growth of grain, which can be concluded to annealing-related phenomena.

As shown in Figure 4(a) and (b), the heating temperature was at Ac1–Ac3. The pearlite in BM was transformed into fine austenite, while the ferrite only partially melted into austenite, the remaining part of the ferrite continued to grow into coarse ferrite. Recrystallization and grain growth occurred in a place where the electrode cap had contact. Austenite became fine ferrite and pearlite during cooling while the coarse ferrite was retained. The grain size and structure were not uniform, which influenced the mechanical properties.

When the welding time changed to four–six cycles, the nugget began to form and the metallographic structure had an obvious contrast difference. The FZ was composed of lath martensite corresponding to Figure 4(d). The lath martensite was perpendicular to the fusion line along the direction of the fastest heat dissipation, namely the direction of the highest temperature gradient. These effects are discussed later.

Figure 4(e) and (f) show the metallographic structure of the weld joint under the welding time of eight cycles and ten cycles, respectively. With the increase of time, the microstructure of the FZ did not expand but the nugget diameter increased gradually while the thickness of the joint decreased gradually. The range of the HAZ remained unchanged because the width of the electrode cap was 6 mm which limited the increase of the diameter of the joint.

When the welding time was one–two cycles, the nugget diameter was unformed with the width of 1.58 and 2.73 mm, respectively, as shown in Figure 13. With the increase of time from four cycles to six cycles, the martensite appeared while the nugget was not penetrated. When increased to eight cycles, the joint was completely formed. The shape of the joint was regular and the color was also changed from gray to yellow because of the increase of heat input. The plastic ring expansion was normal while the copper electrode began to adhere. When the welding time was one–eight cycles, the nugget diameter increased and the nugget was formed without cracks and expulsion. In ten cycles, small expulsion emerged [22,23].

Figure 5 shows the microphotographs of the resistance spot welded joints at different welding parameters. The complexity of heat input and the thermal cycle during spot welding determine the microstructure of steel greatly [24]. From the metallographic diagram, there was a gradual increase in grain size from the base metal to the nugget zone. The weld microstructure was obviously different. The microstructure of welded joints can be divided into nugget zone, heat-affected zone, and base metal zone. The relatively long high-temperature time in HAZ made the austenitized structure have enough time to grow up, which made the C element fully diffuse to form carbon-rich austenite. It provided sufficient conditions for the formation of martensite.

Figure 5 Optical microstructure of welded spots in different zones.
Figure 5

Optical microstructure of welded spots in different zones.

The HAZ of the welded joint can be separated into three zones named Two-phase zone (HAZ-1), fine grain zone (HAZ-2), and coarse grain zone (HAZ-3). HAZ-1 was near the base metal, and the microstructure presented equiaxed grains smaller than the base metal grains. Studies have shown that the peak temperature is lower than Ac1 in the subcritical heat-affected zone.HAZ-2 was composed of fine lath martensite. The grain size of HAZ-2 was smaller than HAZ-3. The temperature in HAZ-2 was between Ac1 and Ac3 which limited the growth of austenite grain. Due to the distribution of carbon element, the hardenability of the region was higher than BM. The austenite transformed into fine lath martensite during the subsequent rapid cooling process. The hardness of HAZ-3 was close to FZ because of the higher cooling rate while the size of the martensite lath was smaller than FZ.

3.2 Microstructure of the RSW joint

Figure 6 shows the SEM images of the microstructure of DC51D + ZM joints (10 kA 16 cycles 2.6 kN). The base metal was ferrite and pearlite distributed at grain boundaries as shown in Figure 6(b). During welding, resistance heat melts base metal. There was a steep temperature gradient from FZ to BM. After welding, the molten pool cooled rapidly and martensitic transformation occurred. The microstructure evolution of FZ is the result of the combined effect of chemical composition and cooling rate during RSW. The chemical composition of FZ is affected by the chemical composition of base metal involved in spot welding and the mixing of molten base metal. The heat dissipation was the fastest along the vertical electrode direction. Because of the water-cooling electrode, the cooling rate of RSW was faster, which inhibited the diffusion decomposition of austenite. The austenite transforms into martensite at a lower temperature lower than Ms. FZ was formed with lath martensite which was perpendicular to the direction of sheets (Figure 6(f)).

Figure 6 SEM images of welded joints (10 kA 16 cycles 2.2 kN): (a) 100X joints, (b) BM, (c) HAZ-1, (d) HAZ-2, and (e) HAZ-3, (f) FZ.
Figure 6

SEM images of welded joints (10 kA 16 cycles 2.2 kN): (a) 100X joints, (b) BM, (c) HAZ-1, (d) HAZ-2, and (e) HAZ-3, (f) FZ.

The heating and cooling rates of RSW were significantly higher than laser welding and traditional welding. Studies [25] have shown that the structure and properties of the steel weld are influenced by the cooling rate in the range of 500–800°C. Phase transition which is crucial to the evolution of the final nugget microstructure occurs.

The complexity of heat input during spot welding can change the microstructure of steel greatly. HAZ-3 was also composed of martensite while the grain size was finer than FZ [26–28]. Because the temperature of HAZ-3 was less than Ac3 but lower than the liquidus, the microstructure of the base metal was completely austenitized and the austenite grain grew rapidly. The high temperature in HAZ-3 was relatively long enough to provide the austenitized structure sufficient time to grow up. It made the carbon element fully diffuse to form a carbon-rich austenite structure, which provides sufficient conditions for the formation of coarse lath martensite (Figure 6(e)).

The austenite grains in HAZ-2 did not grow significantly due to the distribution of carbon elements. The hardenability of the HAZ-2 was higher than BM. Which had the martensite grain decreased obviously (Figure 6(d)). The peak temperature was slightly higher than Ac3 so that base metal could be completely austenitized. However, due to the high welding speed of spot welding and the effect of cooling water, the grains could not grow up. The austenite transformed into fine lath martensite during the cooling process.

The peak temperature of HAZ-1 was between Ac1 and Ac3. The pearlite in BM was completely transformed into austenite. The austenitized grains were transformed into martensite. HAZ-1 was composed of fine martensite and ferrite (Figure 6(c)).

Figure 7 shows the SEM images of HAZ and FZ during the change of welding time (one–four cycles). It can be seen from Figure 7(a), (d), and (g) that with the increase of welding time, the joint gradually melted. At the same time, the fusion line gradually disappeared. Figure 7(b), (e), and (h) show the SEM images of HAZ-1 in one cycles, two cycles, and four cycles. The heat input of HAZ also increased [29,30]. The austenitizing of pearlite occurred, which transformed into martensite. The microstructure of HAZ was composed of martensite and residual ferrite.

Figure 7 SEM images of joints under different welding times: (a) 1 cycles, (b) 1 cycles-HAZ-1, (c) 1 cycles-FZ, (d) 2 cycles, (e) 2 cycles-HAZ-1, (f) 2 cycles-FZ, (g) 4 cycles, (h) 4 cycles-HAZ-1, and (i) 4 cycles-FZ.
Figure 7

SEM images of joints under different welding times: (a) 1 cycles, (b) 1 cycles-HAZ-1, (c) 1 cycles-FZ, (d) 2 cycles, (e) 2 cycles-HAZ-1, (f) 2 cycles-FZ, (g) 4 cycles, (h) 4 cycles-HAZ-1, and (i) 4 cycles-FZ.

Figure 7(c), (f), and (i) show the SEM images of FZ in one cycle, two cycles, and four cycles. FZ had the highest temperature gradient during the welding in which peak temperature exceeded the liquidus of BM. The ferrite and pearlite in the base metal were completely austenitized. In the process of rapid cooling at the end of welding, all martensite transformation occurred, and the lath martensite with the obvious direction was formed (Figure 8).

Figure 8 TEM images of BM coating: (a) Zn–Al–Mg coating (b) coating-steel substrates.
Figure 8

TEM images of BM coating: (a) Zn–Al–Mg coating (b) coating-steel substrates.

3.3 Change of Zn–Al–Mg coating

The DC51D + ZM coating was sampled and analyzed by EDS and Selected Area Electron Diffraction (SAED). According to the results of point scanning and SAED, point A was Zn-rich phase. Zn and Al elements were detected which may be Zn–Al–MgZn2 ternary eutectic phase. Point C was located by the interface between the coating and the matrix iron. Fe and a small amount of Al were detected due to the diffusion of Fe during the galvanizing process. It is generally considered that Al reacts with Fe to form Fe2Al5 phase, which can improve the adhesion of the coating on the matrix and prevent the mutual diffusion of elements and effectively inhibit the formation of Fe–Zn brittle phase [31]. Therefore, Fe–Al phase is called the inhibition layer. The coating was composed of Zn-rich phase and Zn–Al–MgZn2 ternary eutectic [32].

The HAZ between two sheets after welding was analyzed using TEM. The EDS line scanning between the unmelted part. The detection position is shown in Figure 9(a). According to Figure 9(b) showing the EDS and line scanning results, it can be seen that Al and Zn were distributed between the upper and lower sheets, and the farther away from the weld, the lower the content. The content of Zn was less than Al due to the melting point (Zn 420°C lower than Al 660°C). The evaporation loss was serious during spot welding. Results show that the unmelted part was mainly composed of Fe and Al. Combined with the SAED, FeAl phase was formed in this area.

Figure 9 TEM images of HAZ-1: (a) microstructural morphology of HAZ-1; (b) line scanning; (c) and (d) SAED of unintegrated areas.
Figure 9

TEM images of HAZ-1: (a) microstructural morphology of HAZ-1; (b) line scanning; (c) and (d) SAED of unintegrated areas.

Figure 10(b) shows the EDS and line scanning. Only Al in FZ was distributed between the upper and lower sheets while Zn and Mg were not detected. It is speculated that the temperature gradient in the FZ was the highest. The Zn and Mg evaporated and overflowed in the form of a splash. According to the XRD results in Figure 11, the Fe–Al phase and Fe3Al phase existed while the coating disappeared completely. The two sheets were connected by the matrix iron, and the metallurgical connection was realized. Combined with micro-XRD and SAED, the bright white phase in Figure 10(d) was FeAl phase [33]. The FeAl phase formed by Al and Fe in the coating inhibited the formation of a brittle Fe–Zn phase.

Figure 10 TEM images of HAZ-3: (a) microstructural morphology of HAZ-3; (b) line scanning; (c) and (d) SAED of unintegrated areas.
Figure 10

TEM images of HAZ-3: (a) microstructural morphology of HAZ-3; (b) line scanning; (c) and (d) SAED of unintegrated areas.

Figure 11 XRD analysis of FZ.
Figure 11

XRD analysis of FZ.

In the continuous hot dip galvanizing process, the addition of about 0.2 wt% Al can promote the formation of Fe2Al5 inhibition layer and prevent the severe reaction between steel plate and metal bath. Therefore, the element Al detected in the FZ came from the inhibition layer at the interface of galvanized steel. A small amount of Al and smaller relative phase had little effect on the mechanical property.

3.4 Micro-hardness profiles

Figure 12 shows the micro-hardness distribution of the nugget formation process from one cycles to ten cycles. Figure 12(a) shows the hardness values from BM to FZ in the horizontal direction.

Figure 12 Microhardness in nugget formation: (a) horizontal direction, (b) perpendicular direction.
Figure 12

Microhardness in nugget formation: (a) horizontal direction, (b) perpendicular direction.

The DC51D + ZM coating steel used in this experiment was processed by DC01. The hardness of DC01 steel before the coating was about 130 HV0.2. It was immediately galvanized after annealing. At this time, the dislocation density caused by recovery recrystallization decreases, which led to the decrease of hardness. The average hardness value of DC51D + ZM was 110 HV0.2 while the FZ was up to 300 HV0.2. Due to the formation of lath martensite, the micro-hardness values increased from the BM to the FZ. When the welding time was one–two cycles, the welding nugget was not formed. It was composed of ferrite and fine martensite. However, when the welding time increased to four cycles, the structure of FZ was lath martensite. The range of the nugget zone increased with the increase in welding time. The specimen of ten cycles had the widest range. Figure 12(b) shows the hardness values from BM to FZ in the vertical direction has the same result.

3.5 Mechanical properties of welded joint

Figure 13 shows the variation of welding time on mechanical properties of nugget formation. Nugget diameter, tensile shear, and welding thickness were tested. It reveals the evolution of nugget diameters from 1 to 20 cycles. Nugget diameter was expected to reach above = 5.5 t . The thickness of DC51D + ZM base metal is 1 mm, in which case a fine diameter of the nugget formed above 5.5 mm. When the welding time was eight cycles, the nugget diameter was 5.80 mm (Figure 13(a)).

Figure 13 The mechanical property in different welding times: (a) nugget diameter, (b) tensile-shear thickness, and (c) nugget thickness.
Figure 13

The mechanical property in different welding times: (a) nugget diameter, (b) tensile-shear thickness, and (c) nugget thickness.

Figure 13(b) indicates the relationship between tensile-shear load and welding time. When the welding time was less than four cycles, the nugget was not fully formed (Figure 4(b)) while the tensile shear load was 1.99 kN with a width of 2.73 mm.

When the cycle was four, the corresponding nugget diameter and tensile shear force were 3.72 mm and 6.71 kN, respectively, which were much lower than those of other parameters. With the increase of time, the nugget gradually formed. When the welding time was six–eight cycles, the nugget basically formed. At eight cycles, the tensile-shear force was 7.78 kN. When the time reached more than ten cycles, the nugget diameter and tensile shear force were relatively stable, reaching 6 mm and above 8 kN, respectively.

By measuring the thickness of the nugget, the reduction rate can be calculated [34]. According to the standard, the reduction rate should not exceed 30%. A high reduction rate reduces the bearing area of the joint and causes stress concentration. The thickness of the nugget gradually decreased with the increase in welding time. When the welding time was 20 cycles, the nugget thickness reached the maximum value but was still below 30%, as shown in Figure 13(c).

3.6 Tensile-shear properties and failure mode

According to the results of Figure 14, the surface scanning of Al in HAZ of 1–20 cycles joint was carried out. When the welding time was one cycle, the welding process started while the molten Zn–Al–Mg coating was not able to diffuse. The two sheets were not closely connected so the distribution of Al was compact. When the welding time increased to eight cycles, the welding joint was basically formed and the distribution of Zn was relatively orderly in the HAZ area. The tensile-shear force was 7.78 kN at 8 cycles. When the welding time increased to 16 cycles, the melting amount between the two sheets increased. The elements in the HAZ accelerated to diffuse. At this time, the tensile-shear force reached a peak of 8.61 kN. On reaching 20 cycles, the diffusion of Al was the most intense. Accompanied by splash, tensile shear decreased to 8.17 kN.

Figure 14 EDS face scanning analyses of the Zn element in different welding times: (a) 1 cycles, (b) 8 cycles, (c) 16 cycles, and (d) 20 cycles.
Figure 14

EDS face scanning analyses of the Zn element in different welding times: (a) 1 cycles, (b) 8 cycles, (c) 16 cycles, and (d) 20 cycles.

Figure 15 and Table 2 show the fracture mode of RSW joints and tensile-shear load ranging from 2 to 20 cycles. When the welding time was two cycles, interface fracture (IF) occurred due to the poor combination, and the tensile-shear load was 1.99 kN. When the welding time increased to 4–20 cycles, a pull-out fracture occurred (PF). At this time, the average tensile-shear load was 8.24 kN. However, the DC01 steel without coating was relatively stable in the one–eight cycles, which showed the fracture mode of PF. The average tensile shear was 5.71 kN.

Figure 15 Fracture mode and morphology of spot welded joint: (a) Morphology of interface fracture, (b) morphology of pull-out fracture, (c) fracture appearance of Interface fracture, and (d) fracture appearance of Interface fracture pull-out fracture.
Figure 15

Fracture mode and morphology of spot welded joint: (a) Morphology of interface fracture, (b) morphology of pull-out fracture, (c) fracture appearance of Interface fracture, and (d) fracture appearance of Interface fracture pull-out fracture.

Table 2

Chemical composition and mechanical properties of DC51D + Zm and DC01

Welding cycles 1 2 4 8 12 14 16 18 20
DC51D + ZM Tensile shear (kN) — 1.99 6.71 7.78 8.18 8.22 8.61 8.41 8.17
Fracture mode IF IF PF PF PF PF PF PF PF
DC01 Tensile shear (kN) 5.22 5.95 5.18 6.51 6.79 6.57 6.97 8.28 8.30
Fracture mode PF PF PF PF PF PF PF PF PF

Combined with TEM Figures 9 and 10, it can be seen that at two cycles, DC51D + ZM may have residual Fe–Zn brittle phase in HAZ which lead to low strength, while DC01 had higher strength by metallurgical connection.

By observing the specimens after tensile-shear test, the failure modes can be divided into IF and PF under different welding parameters, as shown in Figure 15(a) and (b). Short welding time caused low heat input. The effective nugget was not formed in the IF sample which led to poor mechanical properties. The step-like pattern was observed in the fracture which conveyed brittle fracture. The PF specimen has a good nugget formation, the tensile-shear load is higher than the former. The combination between the two plates was sufficient which leads to good mechanical properties.

The SEM shows that the dimple points to the shear direction which indicates typical ductile fracture. Figure 15(c) shows the quasi-cleavage fracture. High-density tearing edges and river-like equiaxed dimples were observed in local positions. Figure 15(d) shows the micro-void accumulation fracture. A large number of shear dimples were observed in which boundary was clear. The bottom was relatively flat with a ripple pattern pointing to the shear direction, showing a typical plastic fracture morphology.

4 Discussion

4.1 Nugget evolution process

According to the study on the influence of welding time in the microstructure of welding joint, the nugget evolution process can be demonstrated in Figure 16, and the processes are summarized as follows [35]:

Figure 16 Schematic of the nugget evolution: (a) HAZ evolution process, (b) FZ evolution process.
Figure 16

Schematic of the nugget evolution: (a) HAZ evolution process, (b) FZ evolution process.

For HAZ

  1. Base metal is formed with equiaxial ferrite and pearlite remaining at grain boundary.

  2. In pearlite, the Flake cementite has large surface area which leads to a high interface energy. Spheroidization of pearlite occurred under the influence of thermal cycle.

  3. The pearlite reaches AC1 temperature and partly austenitizing.

  4. When the spot welding is completed, the temperature decreases rapidly and the austenite transform to martensite. HAZ is composed of ferrite and martensite, in which the grain size and structure is not uniform

For FZ

  1. Base metal is formed with equiaxial ferrite and pearlite remaining at grain boundary.

  2. The temperature of pearlite rises between Ac1 and Ac3, which leads to austenitizing.

  3. The temperature of ferrite reaches AC3 which results in austenitic grain growth and eventually austenitizing.

  4. When the spot welding is completed, the temperature decreases rapidly and the austenite transform to lath martensitefine which has a certain direction.

4.2 Coating evolution

With the gradual formation of nugget, the Zn and Al elements in the coating were evaporated and burned. Increasing the melting time leads to the migration of Zn element and increases the Zn content gradient. The formation of Fe–Al phase hinders the formation of Fe–Zn brittle phase. Near the heat-affected zone is easy to form Zn segregation area, resulting in stress concentration, becoming the weak link of fracture.

5 Conclusion

The following conclusions were obtained from the and discussion presented previously:

  1. The results showed that the microstructure of the DC51D steel contains ferrite and pearlite. The microstructure of welded joints can be divided into nugget zone (FZ), heat-affected zone (HAZ), and base metal zone (BM). The microstructure of the FZ is martensitic.

  2. The results showed that when the welding time increased, the nugget gradually formed. The hardness in four–ten cycles welding time was relatively stable, up to 300 HV. The carbon content of martensite in FZ region played a decisive role in the microhardness of martensite.

  3. The results showed that Al reacted with Fe in coating to form Fe–Al phase inhibition layer. In HAZ, Al and Zn were distributed between the upper and lower sheets. The unmelted part was mainly composed of Fe and Al. Only Al was distributed between sheets while Zn and Mg were not detected in FZ. The sheets were connected by matrix iron in which Fe–Al phase was formed to inhibit the formation of brittle Fe–Zn phase.

  4. The results showed that the failure modes can be divided into IF and PF. The average tensile-shear load is 8.24 kN at PF. Low heat input leads to the quasi-cleavage fracture while high heat input showed the micro-void accumulation fracture. The former one exhibited the tearing edges while the other was shear dimples which shows a typical plastic fracture morphology.

Acknowledgments

The authors thank Ba Gen, a senior engineer of Tangshan Iron and Steel company, for their technical support and valuable suggestions.

  1. Funding information: This research was funded by HBIS Company Limited.

  2. Author contributions: Linlin Zhao: writing – review & editing, experimental guidance, investigation; Yue Lu: investigation, data curation, and writing, writing – review and editing; Li Sun: methodology; Jianjun Qi: resources; Xinjian Yuan: investigation and visualization; Jian Peng: software and conceptualization; Ziliu Xiong: supervision.

  3. Conflict of interest: The authors state no conflict of interest.

References

[1] Šebestová, H., P. Horník, L. Mrňa, and P. Doležal. Microstructure and mechanical properties of hybrid LasTIG welds of HSLA steel. Procedia CIRP, Vol. 74, 2018, pp. 743–747.10.1016/j.procir.2018.08.019Search in Google Scholar

[2] Xiong, Z., Z. Lin, J. Qi, L. Sun, G. Wu, S. Kuang, et al. Research on high-temperature oxidation resistance, hot forming ability, and microstructure of Al–Si–Cu coating for 22MnB5 steel. High Temperature Materials and Processes, Vol. 40, No. 1, 2021, pp. 397–409.10.1515/htmp-2021-0040Search in Google Scholar

[3] Ashiri, R., M. A. Haque, C.-W. Ji, M. shamanian, H. R. Salimijazi, and Y. D. Park. Supercritical area and critical nugget diameter for liquid metal embrittlement of Zn-coated twining induced plasticity steels. Scripta Materialia, Vol. 109, 2015, pp. 6–10.10.1016/j.scriptamat.2015.07.006Search in Google Scholar

[4] Pishva, P., S. S. Beni, M. Atapour, M. R. Salmani, and R. Ashiri. Study of corrosion behavior in resistance spot welds of thin sheets of zinc-coated interstitial-free steel. Journal of Materials Engineering and Performance, Vol. 30, No. 3, 2021, pp. 1723–1736.10.1007/s11665-021-05474-0Search in Google Scholar

[5] Feng, Y., Y. Li, Z. Luo, Z. Ling, and Z. Wang. Resistance spot welding of Mg to electro-galvanized steel with hot-dip galvanized steel interlayer. Journal of Materials Processing Technology, Vol. 236, 2016, pp. 114–122.10.1016/j.jmatprotec.2016.05.015Search in Google Scholar

[6] Zhu, J., Z.-H. Zhang, and J.-X. Xie. Relationship between martensite microstructure and ductility of H13 steel from aspect of crystallography. Journal of Iron and Steel Research International, Vol. 28, No. 10, 2021, pp. 1268–1281.10.1007/s42243-021-00595-1Search in Google Scholar

[7] Pan, B., H. Sun, S.-L. Shang, W. Wen, M. Banu, J. C. Simmer, et al. Corrosion behavior in aluminum/galvanized steel resistance spot welds and self-piercing riveting joints in salt spray environment. Journal of Manufacturing Processes, Vol. 70, 2021, pp. 608–620.10.1016/j.jmapro.2021.08.052Search in Google Scholar

[8] Hu, S., A. S. Haselhuhn, Y. Ma, Y. Li, B. E. Carlson, and Z. Lin. Influencing mechanism of inherent aluminum oxide film on coach peel performance of baked Al-Steel RSW. Materials & Design, Vol. 197, 2021, id. 109250.10.1016/j.matdes.2020.109250Search in Google Scholar

[9] Ashiri, R., S. P. Marashi, and Y. D. Park. Weld processing and mechanical responses of 1-GPa TRIP steel resistance spot welds. The size and geometry of the fusion zone was the most important factor affecting the mechanical performance of the welds. Welding Journal, Vol. 97, No. 5, 2018, pp. 157S–169S.10.29391/2018.97.014Search in Google Scholar

[10] Hajiannia, I., M. Shamanian, M. Atapour and R. Ashiri. Evaluation of weldability and mechanical properties in resistance spot welding of ultrahigh-strength TRIP1100 steel. SAE International Journal of Materials & Manufacturing, Vol. 12, No. 1, 2019, pp. 102–115.10.4271/05-12-01-0001Search in Google Scholar

[11] Ashiri, R., H. Mostaan, and Y.-D. Park. A phenomenological study of weld discontinuities and defects in resistance spot welding of advanced high strength TRIP steel. Metallurgical and Materials Transactions A, Vol. 49, No. 12, 2018, pp. 6161–6172.10.1007/s11661-018-4900-0Search in Google Scholar

[12] Arghavani, M. R., M. Movahedi, and A. H. Kokabi. Role of zinc layer in resistance spot welding of aluminium to steel. Materials & Design, Vol. 102, 2016, pp. 106–114.10.1016/j.matdes.2016.04.033Search in Google Scholar

[13] Ghatei Kalashami, A., C. DiGiovanni, M. H. Razmpoosh, F. Goodwin, and N. Y. Zhou. The effect of silicon content on liquid-metal-embrittlement susceptibility in resistance spot welding of galvanized dual-phase steel. Journal of Manufacturing Processes, Vol. 57, 2020, pp. 370–379.10.1016/j.jmapro.2020.07.008Search in Google Scholar

[14] Kim, C. H., Y. N. Ahn, and J. H. Kim. CO2 laser-micro plasma arc hybrid welding for galvanized steel sheets. Transactions of Nonferrous Metals Society of China, Vol. 21, 2011, pp. s47–s53.10.1016/S1003-6326(11)61059-5Search in Google Scholar

[15] Selvamani, S. T., S. Velmurugan, V. Balasubramanian, and K. Palanikumar. Effects of heat distribution during cold metal transfer arc welding on galvanized steel using volumetric heat source model. Journal of Materials Research and Technology, Vol. 9, No. 5, 2020, pp. 10097–10109.10.1016/j.jmrt.2020.07.004Search in Google Scholar

[16] Shreyas, P., B. Panda, and R. Kumar. Mechanical properties and microstructure of 316L-galvanized steel weld. Materials Today: Proceedings, Vol. 23, 2020, pp. 600–607.10.1016/j.matpr.2019.05.418Search in Google Scholar

[17] Salimi Beni, S., M. Atapour, M. R. Salmani, and R. Ashiri. Resistance spot welding metallurgy of thin sheets of zinc-coated interstitial-free steel. Metallurgical and Materials Transactions A, Vol. 50, No. 5, 2019, pp. 2218–2234.10.1007/s11661-019-05146-8Search in Google Scholar

[18] Kim, J. W., S. P. Murugan, J.-H. Yoo, R. Ashiri, and Y. D. Park. Enhancing nugget size and weldable current range of ultra-high-strength steel using multi-pulse resistance spot welding. Science and Technology of Welding and Joining, Vol. 25, No. 3, 2020, pp. 235–242.10.1080/13621718.2019.1680483Search in Google Scholar

[19] Andrade, D. G., S. S. Sabari, C. Leitão, and D. M. Rodrigues. Influence of the galvanized coating thickness and process parameters on heat generation and strength of steel spot welds. Thin-walled Structures, Vol. 160, 2021, id. 107401.10.1016/j.tws.2020.107401Search in Google Scholar

[20] Ghatei Kalashami, A., X. Han, F. Goodwin, and N. Y. Zhou. The influence of modified annealing during the galvanizing process on the resistance spot welding of the CMn1.8Si advanced high strength steel. Surface and Coatings Technology, Vol. 381, 2020, id. 125181.10.1016/j.surfcoat.2019.125181Search in Google Scholar

[21] Hamidinejad, S. M., F. Kolahan, and A. H. Kokabi. The modeling and process analysis of resistance spot welding on galvanized steel sheets used in car body manufacturing. Materials & Design, Vol. 34, 2012, pp. 759–767.10.1016/j.matdes.2011.06.064Search in Google Scholar

[22] Akulwar, S., A. Akela, D. Satish Kumar, and M. Ranjan. Resistance Spot Welding Behavior of Automotive Steels. Transactions of the Indian Institute of Metals, Vol. 15, 2021, pp. 42–50.10.1007/s12666-020-02155-9Search in Google Scholar

[23] Rajarajan, C., P. Sivaraj, and V. Balasubramanian. Role of welding current on mechanical properties and microstructural characteristics of resistance spot welded dual phase steel joints. Physics of Metals and Metallography, Vol. 121, No. 14, 2020, pp. 1447–1454.10.1134/S0031918X20140136Search in Google Scholar

[24] Park, A. Phenomenological study of weld discontinuities and defects in resistance spot welding of advanced high strength TRIP steel. Metallurgical & Materials Transactions A, Vol. 82, 2018, pp. 587–594.Search in Google Scholar

[25] Wang, T., M. Zhang, W. Xiong, R. Liu, W. Shi, and L. Li. Microstructure and tensile properties of the laser welded TWIP steel and the deformation behavior of the fusion zone. Materials & Design, Vol. 83, 2015, pp. 252–261.10.1016/j.matdes.2015.06.002Search in Google Scholar

[26] Yunzhao, L., T. Huaping, and L. Ruilin. Microstructure and mechanical performance of resistance spot welded martensitic advanced high strength steel. Processes, Vol. 9, No. 6, 2021, pp. 971–989.10.3390/pr9061021Search in Google Scholar

[27] Stadler, M., R. Schnitzer, M. Gruber, K. Steineder, and C. Hofer. Microstructure and local mechanical properties of the heat-affected zone of a resistance spot welded medium-Mn steel. Materials, Vol. 14, No. 12, 2021, pp. 1125–1141.10.3390/ma14123362Search in Google Scholar PubMed PubMed Central

[28] Li, W., J.-H. Chang, B.-F. Wen, and R. Cao. Joining of dissimilar metals between magnesium AZ31B and aluminum A6061-T6 using galvanized steel as a transition joining layer. Journal of Iron and Steel Research International, Vol. 43, 2021, pp. 1128–1137.10.1007/s42243-021-00589-zSearch in Google Scholar

[29] Afzal, A., M. Hamedi, and C. V. Nielsen. Numerical and experimental study of AlSi coating effect on nugget size growth in resistance spot welding of hot-stamped boron steels. Journal of Manufacturing and Materials Processing, Vol. 5, No. 1, 2021, id. 10.10.3390/jmmp5010010Search in Google Scholar

[30] Mahmud, K., S. P. Murugan, Y. Cho, C. Ji, D. Nam, and Y. D. Park. Geometrical degradation of electrode and liquid metal embrittlement cracking in resistance spot welding. Journal of Manufacturing Processes, Vol. 61, 2021, pp. 334–348.10.1016/j.jmapro.2020.11.025Search in Google Scholar

[31] Ashiri, R., M. Shamanian, H. R. Salimijazi, M. A. Haque, J. H. Bae, C. W. Ji, et al. Liquid metal embrittlement-free welds of Zn-coated twinning induced plasticity steels. Scripta Materialia, Vol. 114, 2016, pp. 41–47.10.1016/j.scriptamat.2015.11.027Search in Google Scholar

[32] Chen, R., M. Lou, Y. B. Li, and B. E. Carlson. A critical nugget size prediction model for Al-Si coated press hardened steel resistance spot welds. Journal of Manufacturing Science and Engineering, Vol. 17, 2021, pp. 64–76.10.1115/1.4051680Search in Google Scholar

[33] Chen, Z.-Y., Z.-Z. Chen, D.-X. Kou, Y. Q. Li, Y. L. Ma, and Y. M. Li. Evolution of microstructure in reheated coarse-grained zone of G115 novel martensitic heat-resistant steel. Journal of Iron and Steel Research International, Vol. 52, 2021, pp. 524–536.10.1007/s42243-021-00606-1Search in Google Scholar

[34] Mishra, D., K. Rajanikanth, M. Shunmugasundaram, A. P. Kumar, and D. Maneiah. Dissimilar resistance spot welding of mild steel and stainless steel metal sheets for optimum weld nugget size. Materials Today: Proceedings, Vol. 46, No. P1, 2021, pp. 378–389.10.1016/j.matpr.2021.01.067Search in Google Scholar

[35] Ning, J., L.-J. Zhang, B.-Y. Yang, R. Y. Ma, Y. J. Sun. Improved quality of resistance spot welded joints for molybdenum sheets in lap configuration by adding titanium interlayer. Materials Research Express, Vol. 8, No. 6, 2021, id. 066522.10.1088/2053-1591/ac083dSearch in Google Scholar
Received: 2022-05-16
Revised: 2022-07-20
Accepted: 2022-09-12
Published Online: 2023-03-23

© 2023 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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https://doi.org/10.1515/htmp-2022-0243
Keywords for this article
steel; RSW welding; microstructure; coating evolution; nugget formation
Creative Commons
BY 4.0

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