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Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes
Materials Today: Proceedings xxx (xxxx) xxx
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Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes Yelamasetti Balram ⇑, T. Vishu Vardhan, B. Sridhar Babu, G. Venkat Ramana, Ch. Preethi CMR Institute of Technology, Kandlakoya, Medchal, Hyderabad, 501401, India
a r t i c l e
i n f o
Article history: Received 20 May 2019 Received in revised form 10 June 2019 Accepted 25 June 2019 Available online xxxx Keywords: Austenitic steels IR thermography Temperature measurement X-Ray Diffraction Residual stresses
a b s t r a c t An experimental investigation was made to measure and analyze the temperature distribution and residual stresses in TIG and pulse TIG weldments of AISI 316 stainless steels. Here, Infra-Red (IR) thermography was used to capture the surface temperature during welding processes. The IR images were captured during each welding pass at time intervals of 12 s, 25 s and 45 s. The captured images were analyzed using Forward Looking Infra-Red (FLIR) tool plus software. The surface residual stresses were measured using X-Ray Diffraction (XRD) technique. The nature of thermal fields and residual stresses were observed in both welding techniques and compared. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering.
1. Introduction In the arc welding process due to inherent local heating and rapid cooling process, residual stresses (RS) and strains are induced in the welded structure. These induced stress effects the service life of welded component. The weld-induced RS and distortions are unfavorable as they can cause serious problems, such as Stress Corrosion Cracking (SCC) and hydrogen-induced cracking [1]. The weld residual stresses either in compressive or tensile will either increase or decrease the strength of the welded components. The stresses in tensile nature will cause the brittle fracture, fatigue failure whereas the compressive nature of RS will improve the yield properties [2]. The magnitude and nature of RS mainly depends on parameters like heat input rates, welding torch speed, geometry of plates and type of weld joints [3–5]. In TIG welding, due to the continuous heat inputs to the metals will increase the weld pool dimensions which further effects on Heat Affected Zone (HAZ) [6,7]. This given heat inputs can be altered from low level to high level by employing pulse frequency which can further minimize the HAZ, distortions and RS [8]. The weld induced stresses can be measured in both destructive and non-destructive methods. One of the most used NonDestructive Technique (NDT) is XRD which is proven and useful for the measuring of micro and macro residual stresses. Osman ⇑ Corresponding author. E-mail address: [email protected] (Y. Balram).
Anderoglu [9] explained the measurement of RS distribution by employing XRD technique which can be used for both isotropic and anisotropic materials. Paul S. Prevey [10] explained the current applications on XRD for measuring residual stresses. The width obtained from diffraction technique during stress measurement can also predict the metal properties like yield strength, hardness and depth resolution. S.A.A. Akbari Mousavi et al. [11] measured the RS distribution along welding and transverse directions experimentally by employing XRD technique and concluded that the minimum stresses were observed when having U-groove design than the V-groove. Residual stresses along with the heat affected region, bead geometry is affected by temperature fields, and hence, this paper essences on the measurement of precise temperature profile characteristics and thermal field which form the prerequisite. Since, IRT (InfraRed Thermography) being one of the promising NDE methods to study the induced isotherms in welding [12], it is used to measure the temperature profiles during the welding method. It is well known as in-Situ temperature value logger, which measures the temperature by measuring the wavelengths of emitted infrared energy from the weldments [13]. The temperature distribution captured using IRT to simulate the numerical results is an indication that the temperature distribution given by IRT are close and precise enough to study the temperature distribution [2]. The temperature fields from the data logger and their validations were carried out for experimental analysis. K.C. Ganesh et al. [14] investigated on thermal fields and stress development in TIG weld-
https://doi.org/10.1016/j.matpr.2019.06.695 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering.
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
2
Y. Balram et al. / Materials Today: Proceedings xxx (xxxx) xxx
Table 1 The chemical composition in weight percentage of base and filler metals. Base/Filler metal
Ni
Fe
Cr
Mo
Mn
Cu
C
Si
P
AIS 316 ER316
10.4 10.4
Bal Bal
17.9 17.8
2.1 2.0
2.0 1.8
Nil –
0.08 0.08
0.4 0.4
0.002 0.019
Table 2 Welding process parameters used in TIG and pulse TIG. Welding methods
TIG Pulsed-TIG
Welding current (A) Main current
Low current
135 180
– 90
Pulse frequency (Hz)
Arc voltage, V (V)
Heat input, Q (W)
– 4
14 14
1323 1316
Fig. 1. LINCON 375 welding machine and (a) TIG weldment; (b) pulse TIG weldment.
Fig. 2. IR Thermography shows temperature values at 12, 27 and 56 s of TIG welding.
Fig. 3. IR Thermography shows temperature values at 12, 27 and 56 s of pulse TIG welding.
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
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3
process, IR thermography with attached data logger was used. After welding, the developed stresses were measured experimentally using XRD technique. 2. Experimental set-up
Fig. 4. XRD residual stress measurement set-up.
ments of AISI 316LN by employing Infrared thermography and XRD method. The IR temperature values were in a good agreement with numerical results. In this paper, an experimental investigation was carried out to measure the thermal fields during welding and RS in similar weldments of AISI 316 stainless steels. Here, constant and pulse current TIG welding processes were used for the development of weldments. For measuring temperature distribution during welding
The base metals, AISI 316 stainless steels of 150 mm 60 mm 5 mm dimensions were considered for Vgroove configuration using constant and pulse TIG welding processes. Here, ER309L filler wire of 1.6 mm diameter was used. The chemical composition in weight percentage of base and filler metals are listed in Table 1. Before welding process, the base and filler metals were cleaned with acetone using lint free cloth. The process parameters for both welding processes are listed in Table 2. The given heat input rates for both welding process are calculated by using Eqs. (1) and (2). For the development of weldments INCOLN 375 welding machine was used and the developed weldments are shown in Fig. 1
Q PCGTAW ¼ g Q GTAW ¼ g
V Im
v
V I
v
kJ mm
kJ mm
ð1Þ
ð2Þ
Fig. 5. Temperature distribution during TIG welding process.
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
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Y. Balram et al. / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 6. Temperature distribution during pulse TIG welding process.
Table 3 IR Temperature values of TIG and pulse TIG weldments at different time intervals. Welding method
Welding passes
Temperature (°C) At 12 s
At 28 s
At 54 s
TIG
Pass 1 – Root Pass 2 – Filling Pass 3 – Capping
1458.3 1544.5 1728.3
1494.6 1589.0 1752.1
1641.0 1692.4 1815.3
Pulse TIG
Pass 1 – Root Pass 2 – Filling Pass 3 – Capping
1473.3 1531.0 1642.4
1487.4 1563.8 1686.5
1563.1 1646.0 1724.8
ture in the range of 20 °C to 2000 °C. This Infra-Red camera is attached to the data logger which allows for in-situ imagining and captured files stores information regarding thermal field over the entire weld surface of the specimens under the visual zone. For the functioning of IR camera, the emissivity of the base metal has to be entered. From the scientific data, the emissivity of the AISI 316 was taken as e = 0.72. During welding process, a snapshot of IR images was captured during TIG and pulse TIG welding processes and shown in Figs. 2 and 3. 2.2. X-Ray Diffraction
where, Q = heat input, g = arc efficiency (gGTAW = 70% [15], gPCGTAW = 60% [16], Im = mean current which is calculated from following Eq. (3).
Im ¼
Ip T p þ Ib T b Tp þ Tb
ð3Þ
T p , and T b are time durations of pulse and background current. 2.1. Infra-red thermography IRT is well known for in-situ thermal field measurement technique which have the ability of capture and measuring tempera-
The X-Ray Diffraction technique (shown in Fig. 4) has been used to measure the weld induced stresses along welding and transverse directions. The X-rays used to measure stresses in isotropic and anisotropic materials which are interacting with lattice structure to cause the diffraction patterns. The inter-planar spacing of metal which is unstrained would produce a characteristic diffraction pattern that is different from the one which is strained due to heating as expansion and contractions that are produced within the crystal lattice change the inter-planar spacing of the {h k l} lattice planes [17]. This inter-planar spacing between any two lattices can be measured from the fundamental X-Ray Diffraction theory of Bragg’s equation (4). The residual stresses were assessed at fusion zone and on both sides of weld line at a distance of 10, 20 and 40 mm respectively.
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
Y. Balram et al. / Materials Today: Proceedings xxx (xxxx) xxx
0
Residual stress (MPa)
150
2
TIG Pulse-TIG
100
50
4
0
6
8
10
5
compressive RS away from the weld zone i.e., interface of weldments. The maximum RS value 157.4 MPa was observed in TIG welding process whereas in pulse TIG welding process the maximum value found to be 89.3 MPa. Residual stresses near the HAZ of TIG weldments observed more as compared to pulse TIG weldments which could be reasoned to continuous heat supply to the base metals. Due to the pulse effect during pulse TIG welding process, the temperature and its distribution quite low compared to that of TIG weldments which helps to minimization of residual stresses.
-50
4. Conclusion
-100
-60
-40
-20
0
20
40
60
Distance from the weld zone (mm)
Fig. 7. Residual stress distribution in TIG and pulse TIG welding processes.
gk ¼ 2dsinh
ð4Þ
where, n is order of reflection, k is wavelength (Å), d is Inter-planar space between lattice, and h is angle between incident beam and reflected planes. Vanadium filtered Mn-Ka radiation of wavelength k = 1.07542 Å was deflected from (3 1 1) plane of plate at 2h = 156.13°. For calculating the RS in specimen, the sin2w method was employed. The w-angles are taken from 45° to +45° for measuring lattice plane space. This diffraction technique was used to measure the surface strains and the induced RS r/ has been calculated using Eq. (5)
r/ ¼ m
E 1þ#
ð5Þ
where, m is slope value derived from lattice space D against sin2w. 3. Results and discussions 3.1. Temperature measurement The captured images were analyzed using FLIR tool plus software and the profiles for each pass shown in Figs. 5 and 6. The peak temperature during TIG welding process 1600 °C was recorded at weld zone where as 1550 °C was recorded during pulse TIG welding process. The thermal profiles along transverse direction were observed and shows (Figs. 5 and 6) the difference heat distribution rates during pulse and constant TIG welding process. The distribution of heat towards the base metals also observed and more heat energy has been accumulated at the HAZ which could be attributed to development of more stresses. The temperature values of TIG and pulse TIG weldments at different time intervals were given in Table 3. It is observed that from the Table 3, the incremental temperature values were observed welding pass wise and time incremental. 3.2. Residual stresses The developed residual stresses were measured experimentally in austenitic steels 316 grade by employing XRD technique. The RS distribution in TIG and pulse TIG welding along transverse directions are shown in Fig. 7. It is clearly observed that from the Fig. 7, the tensile stresses were observed at the weld zone in both welding processes. The nature of RS distribution was changed to
Temperature distribution during TIG and pulse TIG welding process was measured using IR Thermography successfully. The variations in peak temperatures and its distribution to base metals were observed in both welding processes. Due to the pulse effect during pulse TIG welding process, the solidification time and its distribution was less compared to TIG welding process. IR thermography was found to be efficient temperature measuring tool during both TIG and pulse TIG welding processes. Due to the variations in the arc characteristics in both welding processes, the distribution of RS and its magnitude also slightly vary with respect to welding process. The maximum tensile nature RS value was observed in TIG welding process which could be reasoned to accumulation of more heat at the weld zone due to resistance of heat during solidification process. The induced stresses were minimized by maintaining pulse arc mode and low frequency (4 Hz). References [1] D. Deng, H. Murakawa, W. Liang, Numerical and experimental investigations on welding residual stress in multi-pass butt-welded austenitic stainless steel pipe, Comput. Mater. Sci. 42 (2008) 234–244, https://doi.org/10.1016/ j.commatsci.2007.07.009. [2] B. Yelamsetti, R. Stresses, S. Welds, D. Welds, in: Thermal Stress Analysis of Similar and Dissimilar Welded Joints, 2018, p. 80. [3] D. Venkatkumar, D. Ravindran, 3D finite element simulation of temperature distribution, residual stress and distortion on 304 stainless steel plates using GTA welding, J. Mech. Sci. Technol. 30 (2016) 67–76, https://doi.org/10.1007/ s12206-015-1208-5. [4] H. Vemanaboina, G. Edison, S. Akella, R.K. Buddu, Effect of residual stresses of GTA welding for dissimilar materials, Mater. Res. 21 (2018), https://doi.org/ 10.1590/1980-5373-mr-2017-1053. [5] M. Chougule, M. Unhale, A. Walunj, S. Chavhan, S. Somase, Study of thermally induced residual stresses for stainless steel grade using GMAW process, Int. J. Technol. Enhancement Emerg. Eng. Res. 2 (2014) 17–25. [6] M. Aissani, S. Guessasma, A. Zitouni, R. Hamzaoui, D. Bassir, Y. Benkedda, Three-dimensional simulation of 304L steel TIG welding process: contribution of the thermal flux, Appl. Therm. Eng. 89 (2015) 822–832, https://doi.org/ 10.1016/j.applthermaleng.2015.06.035. [7] Y. Balram, T.V. Vardhan, G.V. Ramana, B.S. Babu, in: Effect of Heat Input on Weld Defects Using X-Ray Radiography, 2019, pp. 317–322. [8] N. Karunakaran, V. Balasubramanian, Effect of pulsed current on temperature distribution, weld bead profiles and characteristics of gas tungsten arc welded aluminum alloy joints, Trans. Nonferrous Met. Soc. China (Engl. Ed.) 21 (2011) 278–286, https://doi.org/10.1016/S1003-6326(11)60710-3. [9] O. Anderoglu, in: Residual Stress Measurement Using X-Ray Diffraction, 2004, pp. 1–64. [10] P.S. Prevéy, in: X-ray Diffraction Residual Stress Techniques. Met Handbook 10 Met Park, 1986, pp. 380–392, https://doi.org/10.1361/asmhba0001761. [11] S.A.A. Akbari Mousavi, R. Miresmaeili, Experimental and numerical analyses of residual stress distributions in TIG welding process for 304L stainless steel, J. Mater. Process. Technol. 208 (2008) 383–394, https://doi.org/10.1016/j. jmatprotec.2008.01.015. [12] G.M. Pittalà, M. Monno, A new approach to the prediction of temperature of the workpiece of face milling operations of Ti-6Al-4V, Appl. Therm. Eng. 31 (2011) 173–180, https://doi.org/10.1016/j.applthermaleng.2010.08.027. [13] Yelamasetti Balram et al., Mater. Res. Express (2019), https://doi.org/10.1088/ 2053-1591/ab23cf (in press). [14] K.C. Ganesh, M. Vasudevan, K.R. Balasubramanian, N. Chandrasekhar, P. Vasantharaja, Thermo-mechanical analysis of TIG welding of AISI 316LN stainless steel, Mater. Manuf. Process. 29 (2014) 903–909, https://doi.org/ 10.1080/10426914.2013.872266. [15] S. Dev, K.D. Ramkumar, N. Arivazhagan, R. Rajendran, Investigations on the microstructure and mechanical properties of dissimilar welds of inconel 718
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
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and sulphur rich martensitic stainless steel, AISI 416, J. Manuf. Process. 32 (2018) 685–698, https://doi.org/10.1016/j.jmapro.2018.03.035. [16] H. Mohammad Soltani, M. Tayebi, Comparative study of AISI 304L to AISI 316L stainless steels joints by TIG and Nd:YAG laser welding, J. Alloys Compd. 767 (2018) 112–121, https://doi.org/10.1016/j.jallcom.2018.06.302.
[17] M. Fitzpatrick, A. Fry, P. Holdway, F. Kandil, J. Shackleton, L. Suominen, in: Determination of Residual Stresses by X-ray Diffraction – Issue 2. Meas. Good Pract. Guide, 2005, p. 74, https://doi.org/10.1007/s00028-005-0194-y.
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes Yelamasetti Balram ⇑, T. Vishu Vardhan, B. Sridhar Babu, G. Venkat Ramana, Ch. Preethi CMR Institute of Technology, Kandlakoya, Medchal, Hyderabad, 501401, India
a r t i c l e
i n f o
Article history: Received 20 May 2019 Received in revised form 10 June 2019 Accepted 25 June 2019 Available online xxxx Keywords: Austenitic steels IR thermography Temperature measurement X-Ray Diffraction Residual stresses
a b s t r a c t An experimental investigation was made to measure and analyze the temperature distribution and residual stresses in TIG and pulse TIG weldments of AISI 316 stainless steels. Here, Infra-Red (IR) thermography was used to capture the surface temperature during welding processes. The IR images were captured during each welding pass at time intervals of 12 s, 25 s and 45 s. The captured images were analyzed using Forward Looking Infra-Red (FLIR) tool plus software. The surface residual stresses were measured using X-Ray Diffraction (XRD) technique. The nature of thermal fields and residual stresses were observed in both welding techniques and compared. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering.
1. Introduction In the arc welding process due to inherent local heating and rapid cooling process, residual stresses (RS) and strains are induced in the welded structure. These induced stress effects the service life of welded component. The weld-induced RS and distortions are unfavorable as they can cause serious problems, such as Stress Corrosion Cracking (SCC) and hydrogen-induced cracking [1]. The weld residual stresses either in compressive or tensile will either increase or decrease the strength of the welded components. The stresses in tensile nature will cause the brittle fracture, fatigue failure whereas the compressive nature of RS will improve the yield properties [2]. The magnitude and nature of RS mainly depends on parameters like heat input rates, welding torch speed, geometry of plates and type of weld joints [3–5]. In TIG welding, due to the continuous heat inputs to the metals will increase the weld pool dimensions which further effects on Heat Affected Zone (HAZ) [6,7]. This given heat inputs can be altered from low level to high level by employing pulse frequency which can further minimize the HAZ, distortions and RS [8]. The weld induced stresses can be measured in both destructive and non-destructive methods. One of the most used NonDestructive Technique (NDT) is XRD which is proven and useful for the measuring of micro and macro residual stresses. Osman ⇑ Corresponding author. E-mail address: [email protected] (Y. Balram).
Anderoglu [9] explained the measurement of RS distribution by employing XRD technique which can be used for both isotropic and anisotropic materials. Paul S. Prevey [10] explained the current applications on XRD for measuring residual stresses. The width obtained from diffraction technique during stress measurement can also predict the metal properties like yield strength, hardness and depth resolution. S.A.A. Akbari Mousavi et al. [11] measured the RS distribution along welding and transverse directions experimentally by employing XRD technique and concluded that the minimum stresses were observed when having U-groove design than the V-groove. Residual stresses along with the heat affected region, bead geometry is affected by temperature fields, and hence, this paper essences on the measurement of precise temperature profile characteristics and thermal field which form the prerequisite. Since, IRT (InfraRed Thermography) being one of the promising NDE methods to study the induced isotherms in welding [12], it is used to measure the temperature profiles during the welding method. It is well known as in-Situ temperature value logger, which measures the temperature by measuring the wavelengths of emitted infrared energy from the weldments [13]. The temperature distribution captured using IRT to simulate the numerical results is an indication that the temperature distribution given by IRT are close and precise enough to study the temperature distribution [2]. The temperature fields from the data logger and their validations were carried out for experimental analysis. K.C. Ganesh et al. [14] investigated on thermal fields and stress development in TIG weld-
https://doi.org/10.1016/j.matpr.2019.06.695 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering.
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
2
Y. Balram et al. / Materials Today: Proceedings xxx (xxxx) xxx
Table 1 The chemical composition in weight percentage of base and filler metals. Base/Filler metal
Ni
Fe
Cr
Mo
Mn
Cu
C
Si
P
AIS 316 ER316
10.4 10.4
Bal Bal
17.9 17.8
2.1 2.0
2.0 1.8
Nil –
0.08 0.08
0.4 0.4
0.002 0.019
Table 2 Welding process parameters used in TIG and pulse TIG. Welding methods
TIG Pulsed-TIG
Welding current (A) Main current
Low current
135 180
– 90
Pulse frequency (Hz)
Arc voltage, V (V)
Heat input, Q (W)
– 4
14 14
1323 1316
Fig. 1. LINCON 375 welding machine and (a) TIG weldment; (b) pulse TIG weldment.
Fig. 2. IR Thermography shows temperature values at 12, 27 and 56 s of TIG welding.
Fig. 3. IR Thermography shows temperature values at 12, 27 and 56 s of pulse TIG welding.
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
Y. Balram et al. / Materials Today: Proceedings xxx (xxxx) xxx
3
process, IR thermography with attached data logger was used. After welding, the developed stresses were measured experimentally using XRD technique. 2. Experimental set-up
Fig. 4. XRD residual stress measurement set-up.
ments of AISI 316LN by employing Infrared thermography and XRD method. The IR temperature values were in a good agreement with numerical results. In this paper, an experimental investigation was carried out to measure the thermal fields during welding and RS in similar weldments of AISI 316 stainless steels. Here, constant and pulse current TIG welding processes were used for the development of weldments. For measuring temperature distribution during welding
The base metals, AISI 316 stainless steels of 150 mm 60 mm 5 mm dimensions were considered for Vgroove configuration using constant and pulse TIG welding processes. Here, ER309L filler wire of 1.6 mm diameter was used. The chemical composition in weight percentage of base and filler metals are listed in Table 1. Before welding process, the base and filler metals were cleaned with acetone using lint free cloth. The process parameters for both welding processes are listed in Table 2. The given heat input rates for both welding process are calculated by using Eqs. (1) and (2). For the development of weldments INCOLN 375 welding machine was used and the developed weldments are shown in Fig. 1
Q PCGTAW ¼ g Q GTAW ¼ g
V Im
v
V I
v
kJ mm
kJ mm
ð1Þ
ð2Þ
Fig. 5. Temperature distribution during TIG welding process.
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
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Y. Balram et al. / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 6. Temperature distribution during pulse TIG welding process.
Table 3 IR Temperature values of TIG and pulse TIG weldments at different time intervals. Welding method
Welding passes
Temperature (°C) At 12 s
At 28 s
At 54 s
TIG
Pass 1 – Root Pass 2 – Filling Pass 3 – Capping
1458.3 1544.5 1728.3
1494.6 1589.0 1752.1
1641.0 1692.4 1815.3
Pulse TIG
Pass 1 – Root Pass 2 – Filling Pass 3 – Capping
1473.3 1531.0 1642.4
1487.4 1563.8 1686.5
1563.1 1646.0 1724.8
ture in the range of 20 °C to 2000 °C. This Infra-Red camera is attached to the data logger which allows for in-situ imagining and captured files stores information regarding thermal field over the entire weld surface of the specimens under the visual zone. For the functioning of IR camera, the emissivity of the base metal has to be entered. From the scientific data, the emissivity of the AISI 316 was taken as e = 0.72. During welding process, a snapshot of IR images was captured during TIG and pulse TIG welding processes and shown in Figs. 2 and 3. 2.2. X-Ray Diffraction
where, Q = heat input, g = arc efficiency (gGTAW = 70% [15], gPCGTAW = 60% [16], Im = mean current which is calculated from following Eq. (3).
Im ¼
Ip T p þ Ib T b Tp þ Tb
ð3Þ
T p , and T b are time durations of pulse and background current. 2.1. Infra-red thermography IRT is well known for in-situ thermal field measurement technique which have the ability of capture and measuring tempera-
The X-Ray Diffraction technique (shown in Fig. 4) has been used to measure the weld induced stresses along welding and transverse directions. The X-rays used to measure stresses in isotropic and anisotropic materials which are interacting with lattice structure to cause the diffraction patterns. The inter-planar spacing of metal which is unstrained would produce a characteristic diffraction pattern that is different from the one which is strained due to heating as expansion and contractions that are produced within the crystal lattice change the inter-planar spacing of the {h k l} lattice planes [17]. This inter-planar spacing between any two lattices can be measured from the fundamental X-Ray Diffraction theory of Bragg’s equation (4). The residual stresses were assessed at fusion zone and on both sides of weld line at a distance of 10, 20 and 40 mm respectively.
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
Y. Balram et al. / Materials Today: Proceedings xxx (xxxx) xxx
0
Residual stress (MPa)
150
2
TIG Pulse-TIG
100
50
4
0
6
8
10
5
compressive RS away from the weld zone i.e., interface of weldments. The maximum RS value 157.4 MPa was observed in TIG welding process whereas in pulse TIG welding process the maximum value found to be 89.3 MPa. Residual stresses near the HAZ of TIG weldments observed more as compared to pulse TIG weldments which could be reasoned to continuous heat supply to the base metals. Due to the pulse effect during pulse TIG welding process, the temperature and its distribution quite low compared to that of TIG weldments which helps to minimization of residual stresses.
-50
4. Conclusion
-100
-60
-40
-20
0
20
40
60
Distance from the weld zone (mm)
Fig. 7. Residual stress distribution in TIG and pulse TIG welding processes.
gk ¼ 2dsinh
ð4Þ
where, n is order of reflection, k is wavelength (Å), d is Inter-planar space between lattice, and h is angle between incident beam and reflected planes. Vanadium filtered Mn-Ka radiation of wavelength k = 1.07542 Å was deflected from (3 1 1) plane of plate at 2h = 156.13°. For calculating the RS in specimen, the sin2w method was employed. The w-angles are taken from 45° to +45° for measuring lattice plane space. This diffraction technique was used to measure the surface strains and the induced RS r/ has been calculated using Eq. (5)
r/ ¼ m
E 1þ#
ð5Þ
where, m is slope value derived from lattice space D against sin2w. 3. Results and discussions 3.1. Temperature measurement The captured images were analyzed using FLIR tool plus software and the profiles for each pass shown in Figs. 5 and 6. The peak temperature during TIG welding process 1600 °C was recorded at weld zone where as 1550 °C was recorded during pulse TIG welding process. The thermal profiles along transverse direction were observed and shows (Figs. 5 and 6) the difference heat distribution rates during pulse and constant TIG welding process. The distribution of heat towards the base metals also observed and more heat energy has been accumulated at the HAZ which could be attributed to development of more stresses. The temperature values of TIG and pulse TIG weldments at different time intervals were given in Table 3. It is observed that from the Table 3, the incremental temperature values were observed welding pass wise and time incremental. 3.2. Residual stresses The developed residual stresses were measured experimentally in austenitic steels 316 grade by employing XRD technique. The RS distribution in TIG and pulse TIG welding along transverse directions are shown in Fig. 7. It is clearly observed that from the Fig. 7, the tensile stresses were observed at the weld zone in both welding processes. The nature of RS distribution was changed to
Temperature distribution during TIG and pulse TIG welding process was measured using IR Thermography successfully. The variations in peak temperatures and its distribution to base metals were observed in both welding processes. Due to the pulse effect during pulse TIG welding process, the solidification time and its distribution was less compared to TIG welding process. IR thermography was found to be efficient temperature measuring tool during both TIG and pulse TIG welding processes. Due to the variations in the arc characteristics in both welding processes, the distribution of RS and its magnitude also slightly vary with respect to welding process. The maximum tensile nature RS value was observed in TIG welding process which could be reasoned to accumulation of more heat at the weld zone due to resistance of heat during solidification process. The induced stresses were minimized by maintaining pulse arc mode and low frequency (4 Hz). References [1] D. Deng, H. Murakawa, W. Liang, Numerical and experimental investigations on welding residual stress in multi-pass butt-welded austenitic stainless steel pipe, Comput. Mater. Sci. 42 (2008) 234–244, https://doi.org/10.1016/ j.commatsci.2007.07.009. [2] B. Yelamsetti, R. Stresses, S. Welds, D. Welds, in: Thermal Stress Analysis of Similar and Dissimilar Welded Joints, 2018, p. 80. [3] D. Venkatkumar, D. Ravindran, 3D finite element simulation of temperature distribution, residual stress and distortion on 304 stainless steel plates using GTA welding, J. Mech. Sci. Technol. 30 (2016) 67–76, https://doi.org/10.1007/ s12206-015-1208-5. [4] H. Vemanaboina, G. Edison, S. Akella, R.K. Buddu, Effect of residual stresses of GTA welding for dissimilar materials, Mater. Res. 21 (2018), https://doi.org/ 10.1590/1980-5373-mr-2017-1053. [5] M. Chougule, M. Unhale, A. Walunj, S. Chavhan, S. Somase, Study of thermally induced residual stresses for stainless steel grade using GMAW process, Int. J. Technol. Enhancement Emerg. Eng. Res. 2 (2014) 17–25. [6] M. Aissani, S. Guessasma, A. Zitouni, R. Hamzaoui, D. Bassir, Y. Benkedda, Three-dimensional simulation of 304L steel TIG welding process: contribution of the thermal flux, Appl. Therm. Eng. 89 (2015) 822–832, https://doi.org/ 10.1016/j.applthermaleng.2015.06.035. [7] Y. Balram, T.V. Vardhan, G.V. Ramana, B.S. Babu, in: Effect of Heat Input on Weld Defects Using X-Ray Radiography, 2019, pp. 317–322. [8] N. Karunakaran, V. Balasubramanian, Effect of pulsed current on temperature distribution, weld bead profiles and characteristics of gas tungsten arc welded aluminum alloy joints, Trans. Nonferrous Met. Soc. China (Engl. Ed.) 21 (2011) 278–286, https://doi.org/10.1016/S1003-6326(11)60710-3. [9] O. Anderoglu, in: Residual Stress Measurement Using X-Ray Diffraction, 2004, pp. 1–64. [10] P.S. Prevéy, in: X-ray Diffraction Residual Stress Techniques. Met Handbook 10 Met Park, 1986, pp. 380–392, https://doi.org/10.1361/asmhba0001761. [11] S.A.A. Akbari Mousavi, R. Miresmaeili, Experimental and numerical analyses of residual stress distributions in TIG welding process for 304L stainless steel, J. Mater. Process. Technol. 208 (2008) 383–394, https://doi.org/10.1016/j. jmatprotec.2008.01.015. [12] G.M. Pittalà, M. Monno, A new approach to the prediction of temperature of the workpiece of face milling operations of Ti-6Al-4V, Appl. Therm. Eng. 31 (2011) 173–180, https://doi.org/10.1016/j.applthermaleng.2010.08.027. [13] Yelamasetti Balram et al., Mater. Res. Express (2019), https://doi.org/10.1088/ 2053-1591/ab23cf (in press). [14] K.C. Ganesh, M. Vasudevan, K.R. Balasubramanian, N. Chandrasekhar, P. Vasantharaja, Thermo-mechanical analysis of TIG welding of AISI 316LN stainless steel, Mater. Manuf. Process. 29 (2014) 903–909, https://doi.org/ 10.1080/10426914.2013.872266. [15] S. Dev, K.D. Ramkumar, N. Arivazhagan, R. Rajendran, Investigations on the microstructure and mechanical properties of dissimilar welds of inconel 718
Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695
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Please cite this article as: Y. Balram, T. Vishu Vardhan, B. Sridhar Babu et al., Thermal stress analysis of AISI 316 stainless steels weldments in TIG and pulse TIG welding processes, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.695