Softening Effect in the Heat-Affected Zone of Laser-Welded Joints of High-Strength Low-Alloyed steels

doi:10.21203/rs.3.rs-3343951/v1

The softening effect, which occurs as an undesirable consequence of microstructural changes in the heat affected zone (HAZ) as a result of the welding process, is an inherent aspect of welding high-strength low-alloyed (HSLA) steels. One of the recommended ways to minimize these changes is the application of laser beam welding (LBW) as a lower heat input technology. Hence, this work compares and investigates the effects of laser beam welding on the properties of weld joints made of the steels S690QL, S960QL, S1100QL, S700MC, S960MC, and S1100MC. The main objective of this work is to examine the variations in the mechanical properties, grain size, and microstructure of the HAZ of different structural materials welded under various conditions. For laser-welded HSLA steels, the results showed no significant changes in the weld joint properties when the heat input was increased. When individual steels are compared, more obvious changes in the softening effect, grain growth, and the extent of the coarse-grain HAZ (CGHAZ) are evident. According to measured values it has been demonstrated that as the amount of Nb, V, and Ti in material decreases, the grain size in the coarse-grain HAZ (CGHAZ) and the zones’ overall width increases. It was also further demonstrated that the Cr and Mo content had a significant impact on the weld metal's hardness in laser-welded weld joints. These variations can be explained by the initial microstructure and the different chemical composition, which have an impact on the softening characteristics, austenitic grain growth, and the size of the CGHAZ.

HSLA

softening effect

laser beam welding

grain size

Every year, there is an increasing demand for high-strength steels, which are used in the manufacturing of products such as cars, trucks, cranes, bridges, mining machinery, and other welded constructions [1, 2]. The effort to reduce the weight of welded structures is driven by the desire to lower the carbon footprint generated by these mechanisms during their lifetime. Among the steels employed for this purpose are the structural steels S690QL, S960QL, S1100QL, S700MC, S960MC, and S1100MC, which are used in the previously mentioned sectors owing to their high strength and ductility. These steels can be used with certainty in the manufacture of welded constructions due to the low carbon content and lower content of alloying elements. Practical experience, however, makes it evident that the requirement of verified weldability needs to be reconsidered for thin material thicknesses [3]. The reason for that is unsatisfactory heat transfer in thin materials, which results in the HAZ's microstructural changes being enforced. As an example, S960MC steel's thin sheets welded using the GMAW method fail to achieve the minimum requirements for yield strength (YS) and ultimate tensile strength (UTS), whereas thicker sheets do so despite requiring higher heat input [3–6]. For welding thin HSLA steel sheets, a LBW is therefore suggested. In addition, several studies have stated that the application of LBW is appropriate for quenched and tempered steels [7–10] and for steels that have undergone thermomechanical controlled processing [11–15].

Minimizing the heat input makes it possible to significantly reduce the area affected by irreversible microstructure changes in the HAZ, and at the same time it also affects the properties of this area. Since it follows from the theory that by inhibiting the soft zone, it is possible to increase the YS and UTS of the welded joints of HSLA steels. For instance, Maurer et al. [16], Amraei et al. [17], Rodrigues et al. [18], or de Meester [19] reported a comparable conclusion. The requirement to understand the soft zone's width forms the cornerstone for the application of theoretical findings. A possible approach for determining the soft zone's width is based on measurements of line hardness that were published by Mičian et al. [3] or Frátrik et al. [12]. In the particular instance, a section of the material that is softer than 90% of the base material (BM) hardness is thought to be the soft zone. With the assumption of a hardness drop, such an approach makes it feasible to precisely and unambiguously quantify the breadth of the soft zone of weld joints. In the case of laser-welded weld joints that show a minimal hardness drop in the HAZ, the given methodology may be unusable, and it is necessary to modify it (e.g., by shifting the soft zone criterion from 90–100%).

When compared to arc welding technologies, HAZ of laser-welded joints have different properties because of their higher heating and cooling rates and lower heat input. While a higher heating rate increases A_c1 and A_c3 temperature values, decreasing the width of the CGHAZ, FGHAZ, and ICHAZ subzones [20, 21], a higher cooling rate promotes the development of harder and stronger structures in these areas. The lower heat input has also a partial effect on the properties of the structures in the SCHAZ area, which, due to the narrowed temperature fields and lower soaking times, are less tempered as a result of the welding process [22].

The distribution of temperature fields and the cooling rate can be significantly influenced by changing the welding technology, where the best results can be achieved by a LBW. By applying LBW, it is possible to narrow the temperature fields, which narrows the soft zone, and increase the cooling rate, which results in more favorable decay structures in the HAZ. It is also important to consider the possibility of supercritical cooling rate in the case of LBW, which would lead to brittle and hard decay structures like martensite and bainite. Such features may significantly raise a given steel's susceptibility to cold cracking [23, 24].

An additional factor affecting the properties of the HAZ and the soft zone is the chemical composition of the BM. In the case of HSLA steels, the content of C, Mo, and Cr, or the content of microalloying elements Nb, Ti, V, and Al, is particularly important. While the elements C, Mn, Mo, and Cr have an impact on the hardenability of steel in the WM, CGHAZ, and FGHAZ, precipitates of Nb, Ti, V, and Al have an impact on the grain size of the recrystallized microstructure. In particular, the precipitates of Nb, V, and Ti are significant for the properties of the CGHAZ and FGHAZ because they remain stable even at high temperatures, contributing to the so-called Zener pinning, which controls grain growth in the CGHAZ and FGHAZ areas [25, 26].

It can be stated that, the presence of dispersed particles, which contribute to Zener pinning, can indirectly affect grain growth by influencing the grain boundary mobility. The interaction between the dispersed particles and the grain boundaries can result in a reduced mobility of the boundaries, hindering their migration and impeding grain growth. When particles are present at the grain boundaries, they can act as barriers or obstacles, restricting the movement of the grain boundaries. The particles pin the grain boundaries and prevent their migration, which limits the grain growth process. Moreover, the particles act as nucleation sites for new grains, leading to the formation of smaller and more numerous grains. The content of C, Mo, Cr, and V is particularly important for the SCHAZ, which is characterized by a significant decrease in hardness in welded joints of HSLA steels. These elements have an impact on the overall hardness of this zone exposed to tempering.

Despite the fact that there have been numerous research on the weldability of HSLA steels by laser welding, this work provides a distinctive overview based on a comparison of the characteristics of the weld joints of different steels. The characteristics of the soft zone and how they affect the overall mechanical properties of the welded joints are also the primary objective of the investigation of weld joints.

Materials

Experimental materials utilized for this study are quenched and tempered (QT) structural steels S690QL, S960QL, and S1100QL and thermo-mechanically controlled processed (TMCP) structural steels S700MC, S960MC, and S1100MC. Microstructure of quenched and tempered as well as S960MC and S1100MC is composed by the mixture of martensite, tempered martensite, bainite, and residual austenite. The amount of individual compounds and its ratio differs based on individual materials. Steel S700MC is composed by the mixture of fine-grained bainite and acicular ferrite. All materials were delivered in the form of rolled sheets with a thickness of 5 mm (S690QL, S960QL, S1100QL, S700MC) and 6 mm (S960MC, S1100MC), respectively. The chemical composition of the assessed steels obtained by own spectral analysis on the equipment Q2 ION is shown in Table 1. Mechanical properties of assessed steels obtained by own measurements are listed in Table 2.

Table 1

Chemical composition of assessed steels (wt.%).
	C	Si	Mn	P	S	Cr	Mo	Ni	Nb	Ti	V	Al
S690QL	0.066	0.250	1.557	0.003	0.003	0.530	0.166	0.017	0.024	0.003	0.003	0.096
S960QL	0.105	0.384	1.849	0.003	0.003	0.801	0.276	0.010	0.020	0.003	0.018	0.042
S1100QL	0.039	0.500	2.052	0.003	0.003	0.355	0.791	0.024	0.016	0.002	0.031	0.064
S700MC	0.035	0.020	2.270	0.003	0.003	0.052	0.005	0.004	0.050	0.126	0.003	0.035
S960MC	0.079	0.282	1.791	0.003	0.003	0.210	0.269	0.018	0.005	0.009	0.030	0.055
S1100MC	0.062	0.313	1.781	0.003	0.003	0.951	0.005	0.143	0.005	0.010	0.050	0.039

Table 2

Mechanical properties and CET values of assessed steels.
	YS [MPa]	UTS [MPa]	YS / UTS [-]	A₅₀ [%]	HV0.1	CET
S690QL	852	880	0.97	16.4	300	0.27
S960QL	999	1028	0.97	16.3	340	0.36
S1100QL	1289	1404	0.92	14.8	455	0.34
S700MC	764	829	0.92	22.7	290	0.20
S960MC	988	1083	0.91	17.8	361	0.30
S1100MC	1232	1352	0.91	15.8	420	0.29

Experimental welds

All welded joints were made as butt I-welded joints without filler material with zero root gap on the TRUMPF TruDisk 5001 device. Welding edges were aligned by milling and cleaned and degreased before welding. The sheets were clamped in the jig to prevent deformations during welding. The dimensions of the welded sheets were 150 mm × 150 mm × 5 mm and 150 mm × 150 mm × 6 mm, respectively. Welded joints were welded in two variants for each material. One variant was welded with lower heat input (without designation), while the second variant was welded with higher heat input designated with additional letter “H”. The welding parameters are listed in Table 3.

During welding, thermal cycles were measured from the root side. Thermal cycles were measured with K-type NiCr-NiAl thermocouples, which were placed on the surface of the welded sheet at a distance of 0.7–1.2 mm from the axis of the weld. The aim of the measurement was to determine the heating rate, cooling rate and time t_8/5 in the HAZ of the weld joints. The temperature was recorded at a frequency of 80 Hz. For all temperature cycles, a 1st derivative was constructed to evaluate the maximal heating rate and the maximal cooling rate. Figure 1 shows cross-sections of welded joints.

Table 3

Welding parameters for all assessed welded joints.
Weld joint	Power [W]	Travel speed [mm∙s^− 1]	Focus [mm]	Gas flow [l∙min^− 1]	Q [kJ∙cm^− 1]
S690QL	5000	25	+ 2.5	20	2.00
S690QL-H	5000	20	+ 3.5	20	2.50
S960QL	5000	25	+ 2.5	20	2.00
S960QL-H	5000	20	+ 3.5	20	2.50
S1100QL	5000	25	+ 2.5	20	2.00
S1100QL-H	5000	20	+ 3.5	20	2.50
S700MC	5000	25	+ 2.5	20	2.00
S700MC-H	5000	20	+ 3.5	20	2.50
S960MC	5000	22	+ 2.5	20	2.27
S960MC-H	5000	17	+ 2.5	20	2.94
S1100MC	5000	22	+ 2.5	20	2.27
S1100MC-H	5000	17	+ 2.5	20	2.94

Based on Fig. 1, it is possible to observe how an increase in the heat input leads to an increase in the width of the HAZ. With greater heat input, the fusion zone's characteristic shape does not alter appreciably.

Experimental methods

Two samples were taken from each weld joint for the purpose of a static tensile test. The preparation, shape, and dimensions of the samples and the test conditions corresponded to the requirements established by the EN ISO 4136 standard. The test was performed on the INSTRON 5985 device.

All considered weld joints were subjected to a microhardness test. Microhardness was measured by the Vickers method (HV0.1) in the form of line measurements. The line was guided in cross-section through the weld joint in the middle of the material thickness and covered the entire HAZ and WM area and part of the BM. The line consisted of a total of 121 measurements with a mutual distance of 0.1 mm between indentations. The purpose of the test was to measure the rate of hardness decrease and the width of the soft zone in all of the weld joints. The soft zone for every weld joint was defined as the area with a decrease in hardness below the hardness value of the BM. The width of this area was determined from the X-axis of the graphical plot. An example can be seen in Fig. 2.

A bend test was performed to obtain an overview of the ductility and deformability of the weld joints. 4 samples (2×TRBB, 2×TFBB) were tested on each weld joint, while the diameter of the load mandrel and the distance of the supports were calculated separately for each material according to the minimum ductility given by the product standard. The dimensions, preparation of the samples and the test procedure were made according to the EN ISO 5173 standard.

Microstructural analysis was performed by light optical microscopy (LOM) on samples etched with 2% Nital. The objective of the analysis was to determine the mean grain size in the CGHAZ and the width of the CGHAZ. The CGHAZ was considered to be the part of the HAZ with a coarsened grain from the fusion line to the area with a grain size equal to the original grain in the BM (Fig. 3). Mean grain size was determined by a linear intercept method. Both the CGHAZ width and the mean grain size were evaluated at the center of the material thickness.

The temperature cycles of welded joints have characteristic features for laser welding, which include a high heating rate and a high cooling rate. Figure 2 shows the temperature cycles for the S1100QL, S700MC-H, S960MC, and S960MC-H weld joints so that all thickness variations and all heat input variations are covered.

Table 4 shows selected parameters of weld joints thermal cycles. From the measured results it is possible to observe the effect of increasing heat input on the decreasing cooling rate. However, with respect to the measured values of the cooling rate and the characteristics of the CCT diagrams of the materials assessed, the observed differences can be considered as irrelevant for the resulting decay structures. According to the published CCT diagrams, the cooling rate for all materials leads to the formation of martensite in the HAZ.

Table 4

Selected thermal cycle parameters.
	Max. heating rate [°C∙s^− 1]	Max. cycle temperature [°C]	t_8/5 [s]	Cooling rate v_{800 − 500} [°C∙s^− 1]	Cooling rate v₃₀₀ [°C∙s^− 1]
S1100QL	3122	846	1.49	201	22.8
S700MC-H	3141	954	1.75	171	19.7
S960MC-	3970	1029	1.73	173	17.7
S960MC-H	2717	1041	2.44	123	18.7

By the static tensile test, the yield strength (YS), ultimate tensile strength (UTS), and elongation were evaluated. The results of the test are shown in the Table 5.

Table 5

Mechanical properties of all assessed weld joints.
	YS [MPa]	UTS [MPa]	YS / UTS [-]	A₅₀ [%]
S690QL	856	883	0.97	12.7
S690QL-H	858	886	0.97	11.7
S960QL	988	1030	0.96	11.7
S960QL-H	987	1027	0.96	12.2
S1100QL	1223	1276	0.96	3.1
S1100QL-H	1237	1287	0.96	3.8
S700MC	752	828	0.91	11.6
S700MC-H	758	817	0.93	8.7
S960MC	989	1096	0.90	11.4
S960MC-H	983	1087	0.90	10.6
S1100MC	1185	1255	0.94	3.9
S1100MC-H	1175	1275	0.92	4.3

From the given values, it can be observed that the amount of heat input does not directly affect the resulting values of YS, UTS, and elongation. In the case of steels S690QL, S960QL, and S960MC, this fact is confirmed by the location of the fracture during the static tensile test in the BM. In the case of welded joints of S700MC, S1100QL, and S1100MC, fracture initiation is localized to the SCHAZ. However, this fact was not significantly reflected in the YS and UTS values, which in the case of YS were at the level of 98–99% and in the case of UTS at the level of 99–100% of the values of the BM. Elongation values decreased for all considered weld joints in the range of 29–62%.

Based on the tests performed, it can be concluded that all welded joints of steels S690QL, S960QL, S700MC, and S960MC met the requirements for the fracture test and achieved the required bending angle without cracking. In the case of steels S1100QL and S1100MC, the test specimens did not meet the conditions specified in the standard as fracture occurred during the test.

The line microhardness measurements showed differences in the individual subzones of the welded joints. From the graphical plots (Fig. 5), a significant increase in hardness compared to the BM can be observed in the WM, CGHAZ, and FGHAZ for the welded joints of S690QL, S960QL, and S960MC steels. Hardening of the microstructure also occurred in the weld joints of S1100QL and S1100MC steels, however, due to the high hardness of the BM, there was observed no increase in hardness compared to the BM. At the same time, it is possible to observe a minimal decrease in hardness in the soft zone, which is less than 5% for steels S690QL and S960QL and in the range 15–30% compared to the BM for steels S700MC, S960MC, S1100QL, and S1100MC.

The width of the soft zone was measured using Fig. 5. The measured values of the width of the soft zone and the decrease in hardness are shown in Table 6.

Table 6

Values of the width of the soft zone and hardness drop of assessed weld joints.
	Width of the soft zone [mm]		Max. hardness decrease [ΔHV0.1]
	Left	Right	Max. hardness decrease [ΔHV0.1]
S690QL	0.60	0.44	38
S690QL-H	0.86	0.57	25
S960QL	0.43	0.37	18
S960QL-H	0.28	0.37	24
S1100QL	3.13	3.38	139
S1100QL-H	3.40	3.55	160
S700MC	2.03	1.16	40
S700MC-H	1.83	1.49	38
S960MC	0.85	0.64	39
S960MC-H	0.61	0.78	86
S1100MC	1.91	2.21	115
S1100MC-H	2.88	3.00	115

The mean grain size in the CGHAZ and the width of the CGHAZ were determined by the microstructural analysis (Fig. 6). The values of the mean grain size and the width of the CGHAZ are given in Table 7.

Table 7

Mean grain size and the width of the CGHAZ of the assessed steels.
	Actual mean grain size [µm]	Width of the CGHAZ [µm]
S690QL	72.00	335
S690QL-H	72.00	340
S960QL	65.50	345
S960QL-H	65.00	345
S1100QL	57.00	340
S1100QL-H	58.50	335
S700MC	47.20	280
S700MC-H	46.00	275
S960MC	52.00	345
S960MC-H	54.00	350
S1100MC	48.80	325
S1100MC-H	50.20	330

The analysis of the mechanical properties showed sufficient YS and UTS values of the welded joints, which reached values in the range of 94–100% of the BM values. The given values are sufficient for all welded joints in terms of normative requirements. In the case of elongation values, a decrease can be observed for all welded joints, which ranges from 23 to 79%. The most significant decrease in elongation (73–79%) was observed in welded joints of steels S1100QL and S1100MC. This decrease was also reflected in the bend test results, as neither of the S1100QL nor S1100MC steels met the test requirements. The other welded joint samples met the EN ISO 5173 fracture test criteria.

When investigating the impact of laser welding on the metallurgical changes of welded joints, a mutual comparison revealed a number of significant changes. The effects of laser welding were particularly noticeable in the properties of the weld joints made of the steels S690QL and S960QL, where there was no significant soft zone in the HAZ. Hardness tests for these types of steel also revealed significant hardening in the WM, CGHAZ, and FGHAZ. The instances can be explained by the very limited heat input and rapid cooling, which resulted in the hardening in the WM, CGHAZ, and FGHAZ and prevented considerable metallurgical changes in the ICHAZ and SCHAZ.

The steels S1100QL and S1100MC showed the biggest decrease in hardness between 115 and 160 HV0.1 compared to hardness of the BM. A paradox occurs in the case of S1100MC welded joints: experimental laser-welded joints indicate considerable softening, while in the study of GMAW welds published by Amraei et al. [27, 28], the HAZ exhibits hardening rather than softening. Further research is therefore needed to determine the causes of this phenomenon. For the steels stated, it is also possible to see a sizeable soft zone width in the range of 1.91 to 3.55 mm. In S690QL and S960QL steels, the smallest decrease in hardness was observed, as well as the smallest width of the soft zone. Based on these observations, it can be confirmed that the heat input and the cooling rate are not the only factors influencing the properties of the HAZ; the chemical composition of the materials or the microstructure of the base material must also be taken into account.

The hardness of the weld metal of S700MC steel, which only reaches approximately 70% of the hardness of the weld metal of steels S690QL and S1100QL, provides a demonstration of the influence of chemical composition (Fig. 7). This behavior occurs despite the same thickness, the same heat input, and the same cooling rate of the compared weld joints.

The effect of chemical composition can be observed mainly on the properties of the CGHAZ. Significant grain growth occurs during welding in this zone, which is influenced by the chemical composition among other factors. According to the theory, the precipitates of Nb, V, and Ti create an obstacle to the austenitic grain growth that develops during heating. As a result of this, their higher content can both inhibit considerable grain growth and narrow the CGHAZ. The mean grain size and CGHAZ width measurements have satisfactorily verified these hypotheses. In Fig. 8, the effect of Nb, V, and Ti content on the increase in the width of the CGHAZ and on the mean grain size in this zone can be observed.

Consequently, it is possible to state, on the basis of the knowledge obtained, that the chemical composition of the base material can have a substantial impact on the properties of welded joints. Differences in the content of individual elements can thus cause differences in the properties of individual HAZ subzones.

Acknowledgements

This research was funded by APVV, grant number APVV-20-0427; KEGA, grant number KEGA 008ŽU-4/2022; and VEGA, grant number VEGA 1/0741/21, VEGA 1/0044/22, and VEGA 1/0241/23.

Conflicts of interests

The authors declare no conflict of interests.

Jindal, S.; Chhibber, R.; Mehta, N.P. Issues in Welding of HSLA Steels. Advanced Materials Research, 2012, 365, 44-49. DOI: 10.4028/www.scientific.net/AMR.365.44
Górka, J. Properties of thermo-mechanically treated welds of high yield-point steel. Welding International, 2016, 30, 3, 196-201. DOI: 10.1080/09507116.2014.937624
Mičian, M.; Frátrik, M.; Kajánek, D. Influence of Welding Parameters and Filler Material on the Mechanical Properties of HSLA Steel S960MC Welded Joints. Metals, 2021, 11, 305. DOI: 10.3390/met11020305
Jambor, M.; Nový, F.; Mičian, M.; Trško, L.; Bokůvka, O.; Pastorek, F.; Harmaniak, D. Gas metal arc welding of thermo-mechanically controlled processed S960MC steel thin sheets with different welding parameters. Communications 2018, 20, 29–35. DOI: 10.26552/com.C.2018.4.29-35
Schneider, C.; Ernst, W.; Schnitzer, R.; Staufer, H.; Vallant, R.; Enzinger, N. Welding of S960MC with undermatching filler material. Weld. World 2018, 62, 801–809. DOI: 10.1007/s40194-018-0570-1
Hochhauser, F.; Ernst, W.; Rauch, R.; Vallant, R.; Enzinger, N. Influence of the Soft Zone on the Strength of Welded modern HSLA Steels. Weld. World 2012, 56, 77–85. DOI: 10.1007/BF03321352
Tuz, L. Evaluation of Microstructure and Selected Mechanical Properties of Laser Beam Welded S690QL High-Strength Steel. Advances in Materials Science, 2018, 18, 3, 34-42. DOI: 10.1515/adms-2017-0039
Nasiłowska, B., Ślęzak, T., Sniezek, L., Torzewski, J. Mechanical Properties of Laser-Welded Joints in the Difficult-to-Weld Steels. Proceedings of 8th International Conference ITELMS 2013, 2013, 173-178, Panevėžys, Lithuania.
Ślęzak, T.; Sniezek, L. Properties of welded joints made in high strength steel using laser technology. Bulletin of the Military University of Technology. 2017, 66, 1, 55-66. DOI: 10.5604/01.3001.0009.9484
Gerhards, B.; Reisgen, U.; Olschok, S. Laser welding of ultrahigh strength steels at subzero temperatures. Physics Procedia, 9^th International Conference on Photonic Technologies - LANE 2016, 2016, 83, 352-361. DOI: 10.1016/j.phpro.2016.08.037
Górka, J.; Stano, S. The structure and properties of filler metal-free laser beam welded joints in steel S700MC subjected to TMCP. Proc. of SPIE 2016, 2016, 10159.
Frátrik, M.; Mičian, M.; Brůna, M. Welding of thin sheets of S960MC steel by laser beam welding. Proc. of the 76th IIW Annual Assembly and Intl. Conf. on Welding and Joining (IIW 2023), 2023, 428-435.
Khanigi, A.F.; Farnia, A.; Ardestani, M.; Torkamany, M.J. Microstructure and mechanical properties of low power pulsed Nd:YAG laser welded S700MC steel. Sadhana, 2020, 45, 1. DOI: 10.1007/s12046-020-1279-6
Guo, W.; Crowther, D.; Francis, J.A.; Thompson, A.; Liu, Z.; Li, L. Microstructure and mechanical properties of laser welded S960 high strength steel. Materials and Design, 2015, 85, 534–548. DOI: 10.1016/j.matdes.2015.07.037
Kurc-Lisiecka, A.; Piwnik, J.; Lisiecki, A. Laser welding of new grade of advanced high strength steel STRENX 1100 MC. Archives of Metallurgy and Materials, 2017, 62, 3, 1651-1657. DOI: 10.1515/amm-2017-0253
Maurer, W.; Ernst, W.; Rauch, R.; Vallant, R.; Enzinger, N. Evaluation of the factors influencing the strength of HSLA steel weld joint with softened HAZ. Welding in the World, 2015, 59, 6, 809-822. DOI: 10.1007/s40194-015-0262-z
Amraei, M.; Skriko, T.; Björk, T.; Zhao, X.-L. Plastic strain characteristics of butt-welded ultra-high strength steel (UHSS). Thin-Walled Structures, 2016, 109, 227-241. DOI: 10.1016/j.tws.2016.09.024
Rodrigues, D.M.; Menezes, L.F.; Loureiro, A.; Fernandes, J.V. Numerical study of the plastic behavior in tension of welds in high strength steels. International Journal of Plasticity, 2004, 20, 1–18. DOI: 10.1016/S0749-6419(02)00112-2
De Meester, B. 1997. The weldability of Modern Structural TMCP Steels. ISIJ International, 1997, 37, 537–551. DOI: 10.2355/isijinternational.37.537
Celin, R., Kafexhiu, F., Klančnik, G., Burja, J. Properties of the Simulated Coarse-Grained Microstructure of Quenched and Tempered High-Strength Steel. Materials and technology, 2021, 55, 1, 115-120. DOI: 10.17222/mit.2020.144
Moravec, J.; Nováková, I.; Vondráček, J. Influence of Heating Rate on the Transformation Temperature Change in Selected Steel Types. Manufacturing Technology, 2020, 20, 2, 217-222. DOI: 10.21062/mft.2020.024
Saha, D.C.; Biro, E.; Gerlich, A.P.; Zhou, Y. Martensite tempering kinetics: effects of dislocation density and heating rates. Materials Characterization, 2020, 168, 110564. DOI: 10.1016/j.matchar.2020.110564
Winarto, W.; Anis, M.; Taufiqullah. Cooling Rate Control on Cold Cracking in Welded Thick HSLA Steel Plate. Materials Science Forum, 2011, 689, 269-275. DOI: 10.4028/www.scientific.net/MSF.689.269
Tomków, J.; Fydrych, D.; Rogalski, G. Dissimilar underwater wet welding of HSLA steels. The International Journal of Advanced Manufacturing Technology, 2020, 109, 717-725. DOI: 0.1007/s00170-020-05617-y
Foder, J.; Burja, J.; Klančnik, G. Grain Size Evolution and Mechanical Properties of Nb, V–Nb, and Ti–Nb Boron Type S1100QL Steels. Metals, 2021, 11, 3, 492. DOI: 10.3390/met11030492
Monschein, S.; Ragger, K.S.; Zügner, D.; Fasching, J.; Schnitzer, R. Influence of the Ti Content on the Grain Stability and the Recrystallization Behavior of Nb-Alloyed High-Strength Low-Alloyed Steels. Steel Research International, 2022, 93, 2200094. DOI: 10.1002/srin.202200094
Amraei, M.; Ahola, A.; Afkhami, S.; Björk, T.; Heidarour, A.; Zhao, X.-L. Effects of heat input on the mechanical properties of butt-welded high and ultra-high strength steels. Engineering Structures, 2019, 198, 109460. DOI: 10.1016/j.engstruct.2019.109460
Amraei, M.; Afkhami, S.; Javaheri, V.; Ghafouri, M.; Björk, T.; Salminen, A.; Zhao, X.-L. Weld HAZ in ultra-high strength steels. Proc. of the 76th IIW Annual Assembly and Intl. Conf. on Welding and Joining (IIW 2023), Singapore. 614-619.

Softening Effect in the Heat-Affected Zone of Laser-Welded Joints of High-Strength Low-Alloyed steels

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Version 1

Abstract

Figures

Introduction

Materials and Methods

Materials

Experimental welds

Experimental methods

Results and discussion

Summary

Declarations

References

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Version 1