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Effect Of Welding Speed On Weld Bead Geometry And Percentage Dilution In Gas Metal Arc Welding Of SS409L
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 18 (2019) 5032–5039
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ICMPC-2019
Effect Of Welding Speed On Weld Bead Geometry And Percentage Dilution In Gas Metal Arc Welding Of SS409L Sanjay Kumar Gupta1, Shivansh Mehrotra2, Avinash Ravi Raja3, M.Vashista4 and M.Z. Khan Yusufzai5* a-2 1,3,4,5*
Department of Mechanical Engineering, PDPM IIITDM Jabalpur- 482005, India
Department of Mechanical Engineering, Indian Institute of Technology (BHU), Varanasi - 221005, India
Abstract
Welding process parameters are the controlling factor for percentage dilution and weld bead geometry (bead width, bead height and penetration). Percentage dilution and weld bead geometry are very important factors to determine the quality of the joints. Present work aims to investigate the effect of welding speed (300, 400 and 500 mm/minute) on percentage dilution and weld bead geometry. Gas metal arc welding of ferritic stainless steel SS409L with austenitic stainless steel filler wire ER304L using pure argon gas has been done. The study of percentage dilution and weld bead geometry has been carried out. It has been found out that with increasing welding speed, bead width, bead height and penetration decreases but percentage dilution first increases with the welding speed parameter and then decreases with further increase in these values. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: Gas metal arc welding; Ferritic stainless steel; Welding speed; Weld bead geometry; Percentage dilution
1. Introduction Ferritic stainless steel (FSS) is one type of stainless steel in which amount of ferrite phase is dominated over other phases. Since its strength is less than mild steel but it possess more corrosion resistance property than mild steel, it is used as gap filler metal between carbon steel and stainless steel [1-3]. FSS is used in various industries *
Corresponding author E-mail address: [email protected]
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
S.K. Gupta et al./ Materials Today: Proceedings 18 (2019) 5032–5039
5033
Nomenclature GMAW
Gas metal arc welding
FSS
Ferritic stainless steel
SS409L
Stainless steel of grade 409L
ER304L
Electrode wire of grade 304L
such as automotive industry, paper industry, chemical industry, railway industry, sugar industry etc. at large scale due to its adequate mechanical strength as well as good corrosion resistance towards pitting corrosion, crevice corrosion and stress corrosion cracking (mainly in chloride atmospheres) [4, 5]. Chromium percentage decides its corrosion resistance and thus depending upon the percentage content of chromium by weight, FSS are classified into three types; low chromium, medium chromium and high chromium FSS. Low chromium FSS is used in automotive industry at large scale because of its sufficient mechanical strength, heat resistance property and adequate corrosion resistance property [6]. SS409L is one grade of low chromium FSS which is stabilized by titanium to prevent the sensitization effect during welding which improves its corrosion resistance property. Due to its high heat resistance property along with sufficient corrosion resistance and mechanical strength, it is used to manufacture components of exhaust system of automobiles such as mufflers, catalytic converters, exhaust tubing etc. Gas metal arc welding (GMAW) is widely used in many industries like railway, automobile, paper mills, chemical processing industries etc. because it offers many benefits over other welding processes such as high welding speed, good arc efficiency, uninterrupted continuous long welding speed, good quality of weld joints with less effort of the operator [7, 8]. GMAW is used quite prevalently to weld SS409L. The mechanical properties of the welded joints are determined by the chemical composition of the weld metal. Composition of the weld metal in turn depends on percentage dilution. The percentage dilution is the ratio of the volume of fused base metal to the volume of total weld deposit [9]. The percentage dilution and weld bead geometry (bead width, bead height and penetration) depend upon the welding process parameters such as welding speed, welding current, welding voltage etc.. In this competitive world, it is necessary to increase the productivity which in turn, strongly depends on the welding speed parameter to produce products at very fast rate with good quality. Therefore, it is necessary to study the effect of welding speed parameter on the percentage dilution and weld bead geometry. Tarng et al. (1998) determined welding process parameters for obtaining optimal weld bead geometry in gas tungsten arc welding. They used the Taguchi method to formulate the experimental layout to analyze the effect of each welding process parameter on the weld bead geometry, and to predict the optimal setting for each welding process parameter [10]. Murugan et al. (2005) studied the mathematical models developed for SAW of pipes for their adequacy and significance by using the F-test and the t-test, respectively and presented in graphical form the main and interaction effects of the process variables on bead geometry and shape factors using which the prediction of important weld bead dimensions, shape relationships and the controlling of the weld bead quality by selecting appropriate process parameter values is possible [11]. Benyounis et al. (2005) investigated laser butt-welding of medium carbon steel using CW 1.5kW CO2 laser. The experimental plan was based on Box–Behnken design and linear and quadratic polynomial equations were developed for predicting the heat input and the weld-bead geometry [12]. Nouri et al. (2007) studied the effect of pulsed variables on the dilution and weld bead geometry in cladding X65 pipeline steel with 316L stainless steel. They used a full factorial method to carry out a series of experiments to know the effect of wire feed rate, welding speed, distance between gas nozzle and plate, and the vertical angle of welding on dilution and weld bead geometry. They found that the dilution of weld metal and its dimension i.e. width, height and depth increase with the feed rate, but the contact angle of the bead initially decreases and then increases. Also, the welding speed has an opposite effect except for dilution [13]. Kolahan et al. (2010) used regression modeling in order to establish the relationships between input and output parameters for Gas Metal Arc Welding (GMAW) process. They checked the adequacies of the mathematical models developed using analysis of variance (ANOVA) technique and selected the best fitted model based on the ANOVA results and other statistical analysis [14]. Shen et al. (2012) carried out a series of measurements on submerged arc welded plates of ASTM A709 Grade 50 steel to determine how variation in heat input achieved using single and double wires affected bead
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reinforcement, bead width, penetration depth, contact angle, heat affected zone (HAZ) size, deposition area, penetration area and total molten area. They found that the bead reinforcement, bead width, penetration depth, HAZ size, deposition area and penetration area increased with increasing heat input, but the bead contact angle decreased with it [15]. Various researchers have established the relationship between welding process parameters and percentage dilution and weld bead geometry. There is little work done to establish the relationship between welding speed and percentage dilution as well as weld bead geometry in GMAW of SS 409L. 2. Experimentation Plates of SS 409L having dimensions 200x50x3 mm were cleaned by acetone. Austenitic grade electrode wire (filler wire) ER304L was selected with diameter 1.2 mm. Root gap of 1.2 mm was maintained during square butt welding by GMAW process. Welding was performed at three different welding speed i.e. 300, 400 and 500 mm/minute keeping all other welding parameters as constant. Chemical composition of base metal and filler wire is given in Table 1 and welding process parameters is shown in Table 2. Table 1. Chemical composition of base metal and filler wire Sample
%C
%Mn
%Si
%S
%P
%Cr
%Ni
%Cu
%Mo
%Nb
%Ti
%N
%V
Base metal
0.024
0.263
0.517
0.001
0.023
11.24
0.066
0.010
0.006
0.040
0.234
0.027
0.059
ER304L
0.015
1.65
0.243
0.013
0.031
18.46
8.14
0.434
0.352
0.050
0.008
0.220
0.061
Table 2. Welding process parameters and welding conditions Sample name
Welding speed
Current (A)
Voltage (V)
(mm/min)
Gas flow rate
Shielding Gas
(litre/min)
S1
300
130
20
18
Pure argon
S2
400
130
20
18
Pure argon
S3
500
130
20
18
Pure argon
The samples of proper dimension were sectioned from the welded plates. To reveal the shape of the weld bead, polishing of samples were carried out by emery papers followed by cloth polishing with diamond paste as abrasive particle. Samples were etched by Kalling’s reagent (10 ml hydrochloric acid, 10 ml ethanol and 0.5 gram cupric chloride) for 10 seconds. The weld bead profile has been shown schematically in figure 1. Different parts of the weld bead geometry such as bead width, bead height and penetration as well as areas of fused base metal (Afbm), upper reinforcement (Aur), lower reinforcement (Alr) and root gap (Arg) were measured by using Adobe Acrobat Reader DC software to calculate the percentage dilution (D) (Table 3) with the help of equations 1 & 2.
S.K. Gupta et al./ Materials Today: Proceedings 18 (2019) 5032–5039
Bead width
Bead height
upper reinforcement Fused base metal
Fused base metal
Base Metal
Base Metal
Penetration
5035
Lower reinforcement
Root gap
Figure 1. Schematic diagram of weld bead profile
Atwd = Afbm + Alr + Arg + Aur
.....……………… (1)
D = (Afbm / Atwd) X 100
…………………. (2)
Where Atwd represents the area of total weld deposition. 3. Results The values of bead width, bead height, penetration and percentage dilution has been tabulated in Table 3. Table 3. Weld bead geometry and percentage dilution Sample name
Bead width
Bead height
Penetration
Percentage dilution
S1
9.03
1.69
4.35
28.50
S2
7.04
1.10
3.77
31.49
S3
5.85
0.73
3.25
30.52
10.0 9.5 9.0
Bead width (mm)
8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 250
300
350
400
450
500
550
Welding speed (mm/minute)
Figure 2. Variation of bead width with welding speed
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S.K. Gupta et al./ Materials Today: Proceedings 18 (2019) 5032–5039
The relationship between welding speed and bead width has been shown in figure 2. It was observed that maximum value of bead width was possessed by sample 1 and followed by sample 2 and sample 3. An inversely proportional relationship was found between bead width and welding speed. 2.0
1.8
Bead height (mm)
1.6
1.4
1.2
1.0
0.8
0.6 250
300
350
400
450
500
550
Welding speed (mm/minute)
Figure 3. Variation of bead height with welding speed
The variation of bead height with welding speed is presented in figure 3. It was observed that bead height follows inverse relationship with the welding speed. 4.6 4.4
Penetration (mm)
4.2 4.0 3.8 3.6 3.4 3.2 3.0 250
300
350
400
450
500
Welding speed (mm/minute)
Figure 4. Variation of penetration with welding speed
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S.K. Gupta et al./ Materials Today: Proceedings 18 (2019) 5032–5039
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The effect of welding speed on penetration has been shown in figure 4. It can be easily seen that penetration and welding speed are also in inverse relationship with each other.
32
Percentage dilution
31
30
29
28
250
300
350
400
450
500
550
Welding speed (mm/minute)
Figure 5. Variation of percentage dilution with welding speed
From figure 5 it was observed that percentage dilution first increases then decreases with the increase of welding speed. The sample S2 possessed maximum value of percentage dilution followed by sample S3 and sample S1. 4. Discussions 4.1 Relation between welding speed and bead width The width of the weld bead should be small but must be sufficient to melt sufficient portion of the base material. The weld joints should have W/P ratio between 1.2 to 2.0 to possess good weld strength, where W refers to bead width and P refers to depth of penetration The width of the weld bead depends upon welding process parameters such as welding speed, welding current, welding voltage, gas flow rate, electrode diameter, nozzle to tip distance etc.. It is generally found that width of the weld bead increases with the increase in welding current, welding voltage, gas flow rate, electrode diameter, contact tip to work distance (CTWD). The reason of variation of width of the weld bead is the variation of distribution of heat between the base metal and electrode wire. On increasing welding speed, keeping all other parameters as constant, base metal received less heat input per unit length. Due to this reduced heat input less melting of the base metal took place and deposition of the filler metal per unit length was also reduced due to faster movement of welding head. Due to less melting of the base metal as well as less deposition of the filler metal, the smaller weld bead was formed. 4.2 Relation between welding speed and bead height Bead height is the height of upper reinforcement and is represented in figure 1 and Figure 2. To obtain good quality of the weld joints, it is necessary to avoid the production of very thick weld bead because it may cause distortion, burn-off at the edge, deep craters at the end, sagging of the weld pool as well as wastage of energy and filler wire. Due to larger bead height, the junction point of the upper reinforcement and surface of the base metal (also known as weld toe) is not smooth and it produces a notch effect. Notch effect (size effect) deteriorates the properties of the welded joints. Therefore it is necessary to produce welds having smaller bead height by proper selection of the welding process parameters. As shown in figure 3, bead height decreases with the welding speed. It was due to the fact that on increasing welding speed, the heat input per unit length given to the base metal is reduced and also deposition of the filler metal is reduced due to high welding speed. 4.3 Relation between welding speed and penetration Penetration is the distance measured perpendicular from the upper surface of the base metal to the end part of the weld metal which is shown in figure 1. Ideally, penetration should be equal to the thickness of the base metal,
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however excess penetration upto certain amount are also acceptable. The limit of the acceptance of excess penetration depends upon the type of metals, type of welding methods, type of joints, application of joints etc. Beyond the acceptable limit, excess penetration is not desired because it causes wastage of energy, deteriorates the quality of the product and increases the weight of the product as well as wastage of filler metal which results into reduction in productivity. Penetration depends upon the heat input provided to base metal per unit length which in turn depends upon the welding process parameters. More heat input per unit length provided to the base metal causes more melting of the base metal which results into more penetration. Due to faster movement of electrode by increasing the welding speed, lesser heat input was received by the base metal per unit length. It causes reduction in the melting of base metal which resulted into reduced penetration with increase in the welding speed as shown in figure 4. 4.4 Relation between welding speed and percentage dilution The competition between melting of base metal and filler wire due to variation of welding parameters result into variation percentage dilution. The part of the base metal which is melted and the metal which is deposited from melting of filler wire together form the total volume of weld metal. The extent of melting of the base metal and filler wire depends upon the distribution of the heat input between base metal and filler wire which in turn controlled by the welding process parameters. On increasing welding speed, the percentage dilution may be decreased or increased depending upon the distribution of heat input between base metal and filler wire. Figure 5 showed that percentage dilution first increases then decreases with increase in welding speed. The increase in percentage dilution on increasing welding speed was due to the fact that deposition of filler metal was more sharply decreased than the reduction in melted volume of base metal which resulted into increase the ratio of volume of fused base metal and volume of total weld metal. On further increase in welding speed, percentage dilution was decreased. It was due to the fact that more welding speed causes less melting of the base metal as well as less deposition of the filler wire. The volume of melted base metal and volume of deposited filler metal were distributed in such a way that the volume of fused base metal to the total volume of weld metal in fusion zone was reduced which led to reduction in value of percentage dilution. 5. Conclusions Following important conclusions may be derived from this experimental investigation: The weld bead width obtained during GMAW of SS409L gets reduced on increasing welding speed. There exists an inversely proportional relationship between welding speed and bead width The increase in welding speed leads to decrease in bead height and penetration. The variation of both with the welding speed are found in inverse proportion. Percentage dilution first increases then decreases with the welding speed and the maximum dilution was obtained at medium level of welding speed. Acknowledgements Authors are thankful to Mr. Pai Namit Narasimhan (PDPM IIITDM Jabalpur, India) for their assistance in sample preparation of metallography. References [1]
Bansod AV, Khobragade NN, Giradkar KV, Patil AP. Effect of concentration of hyaluronic acid and NaCl on corrosion behavior of 316L
[2]
Kumar SM, Shanmugam NS. Studies on the weldability, mechanical properties and microstructural characterization of activated flux TIG
[3]
Sanjay Kumar Gupta, Avinash Ravi Raja, Vashista M, Yusufzai MZK. Effect of heat input on microstructure and mechanical properties in
austenitic stainless steel. Mater Res Express. 2017;4(11):116508. welding of AISI 321 austenitic stainless steel. Mater Res Express. 2018;5(10):106524. gas metal arc welding of ferritic stainless steel. Mater Res Express. 2019;Volume 6(036516). [4]
Mamphekgo T, Matjeke V, Pillay K, editors. Investigation of abnormal corrosion of 10.5–12.5 chromium ferritic stainless steel used to fabricate railway coal wagons. IOP Conference Series: Materials Science and Engineering; 2018: IOP Publishing.
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Dan NE, Sabri SNSM, Hussain P, Mohebbi H, editors. The Influence of Nitrogen on The Wear Resistance of Ferritic Stainless Steel. Journal of Physics: Conference Series; 2018: IOP Publishing.
[6]
Chun-Xia L, Sui-Hu D, Li-Ping W, Cai-Li Z, Pei-De H. Effect of Cr, Mo, and Nb additions on intergranular cohesion of ferritic stainless steel: First-principles determination. Chinese Phys B. 2014;23(3):037102.
[7]
Gheonea M, Mihăilescu D, Florescu S, Scutelnicu E, editors. Experimental research on melting and deposition characteristics of wires during gas metal arc welding. IOP Conference Series: Materials Science and Engineering; 2018: IOP Publishing.
[8]
Murphy AB. The effects of metal vapour in arc welding. Journal of Physics D: Applied Physics. 2010;43(43):434001.
[9]
DuPont JN. Dilution in Fusion Welding. ASM Handbook, Volume 6A, Welding Fundamentals and Processes. 2011.
[10] Tarng Y, Yang W. Optimisation of the weld bead geometry in gas tungsten arc welding by the Taguchi method. The International Journal of advanced manufacturing technology. 1998;14(8):549-554. [11] Murugan N, Gunaraj V. Prediction and control of weld bead geometry and shape relationships in submerged arc welding of pipes. J Mater Process Tech. 2005;168(3):478-487. [12] Benyounis K, Olabi A, Hashmi M. Effect of laser welding parameters on the heat input and weld-bead profile. J Mater Process Tech. 2005;164:978-985. [13] Nouri M, Abdollah-zadeh A, Malek F. Effect of welding parameters on dilution and weld bead geometry in cladding. J Mater Sci Technol. 2007;23(6):817. [14] Kolahan F, Heidari M. A New Approach for Predicting andOptimizing Weld Bead Geometry in GMAW. International Journal of Mechanical Systems science and engineering. 2010;2. [15] Shen S, Oguocha I, Yannacopoulos S. Effect of heat input on weld bead geometry of submerged arc welded ASTM A709 Grade 50 steel joints. J Mater Process Tech. 2012;212(1):286-294.
ScienceDirect Materials Today: Proceedings 18 (2019) 5032–5039
www.materialstoday.com/proceedings
ICMPC-2019
Effect Of Welding Speed On Weld Bead Geometry And Percentage Dilution In Gas Metal Arc Welding Of SS409L Sanjay Kumar Gupta1, Shivansh Mehrotra2, Avinash Ravi Raja3, M.Vashista4 and M.Z. Khan Yusufzai5* a-2 1,3,4,5*
Department of Mechanical Engineering, PDPM IIITDM Jabalpur- 482005, India
Department of Mechanical Engineering, Indian Institute of Technology (BHU), Varanasi - 221005, India
Abstract
Welding process parameters are the controlling factor for percentage dilution and weld bead geometry (bead width, bead height and penetration). Percentage dilution and weld bead geometry are very important factors to determine the quality of the joints. Present work aims to investigate the effect of welding speed (300, 400 and 500 mm/minute) on percentage dilution and weld bead geometry. Gas metal arc welding of ferritic stainless steel SS409L with austenitic stainless steel filler wire ER304L using pure argon gas has been done. The study of percentage dilution and weld bead geometry has been carried out. It has been found out that with increasing welding speed, bead width, bead height and penetration decreases but percentage dilution first increases with the welding speed parameter and then decreases with further increase in these values. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: Gas metal arc welding; Ferritic stainless steel; Welding speed; Weld bead geometry; Percentage dilution
1. Introduction Ferritic stainless steel (FSS) is one type of stainless steel in which amount of ferrite phase is dominated over other phases. Since its strength is less than mild steel but it possess more corrosion resistance property than mild steel, it is used as gap filler metal between carbon steel and stainless steel [1-3]. FSS is used in various industries *
Corresponding author E-mail address: [email protected]
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
S.K. Gupta et al./ Materials Today: Proceedings 18 (2019) 5032–5039
5033
Nomenclature GMAW
Gas metal arc welding
FSS
Ferritic stainless steel
SS409L
Stainless steel of grade 409L
ER304L
Electrode wire of grade 304L
such as automotive industry, paper industry, chemical industry, railway industry, sugar industry etc. at large scale due to its adequate mechanical strength as well as good corrosion resistance towards pitting corrosion, crevice corrosion and stress corrosion cracking (mainly in chloride atmospheres) [4, 5]. Chromium percentage decides its corrosion resistance and thus depending upon the percentage content of chromium by weight, FSS are classified into three types; low chromium, medium chromium and high chromium FSS. Low chromium FSS is used in automotive industry at large scale because of its sufficient mechanical strength, heat resistance property and adequate corrosion resistance property [6]. SS409L is one grade of low chromium FSS which is stabilized by titanium to prevent the sensitization effect during welding which improves its corrosion resistance property. Due to its high heat resistance property along with sufficient corrosion resistance and mechanical strength, it is used to manufacture components of exhaust system of automobiles such as mufflers, catalytic converters, exhaust tubing etc. Gas metal arc welding (GMAW) is widely used in many industries like railway, automobile, paper mills, chemical processing industries etc. because it offers many benefits over other welding processes such as high welding speed, good arc efficiency, uninterrupted continuous long welding speed, good quality of weld joints with less effort of the operator [7, 8]. GMAW is used quite prevalently to weld SS409L. The mechanical properties of the welded joints are determined by the chemical composition of the weld metal. Composition of the weld metal in turn depends on percentage dilution. The percentage dilution is the ratio of the volume of fused base metal to the volume of total weld deposit [9]. The percentage dilution and weld bead geometry (bead width, bead height and penetration) depend upon the welding process parameters such as welding speed, welding current, welding voltage etc.. In this competitive world, it is necessary to increase the productivity which in turn, strongly depends on the welding speed parameter to produce products at very fast rate with good quality. Therefore, it is necessary to study the effect of welding speed parameter on the percentage dilution and weld bead geometry. Tarng et al. (1998) determined welding process parameters for obtaining optimal weld bead geometry in gas tungsten arc welding. They used the Taguchi method to formulate the experimental layout to analyze the effect of each welding process parameter on the weld bead geometry, and to predict the optimal setting for each welding process parameter [10]. Murugan et al. (2005) studied the mathematical models developed for SAW of pipes for their adequacy and significance by using the F-test and the t-test, respectively and presented in graphical form the main and interaction effects of the process variables on bead geometry and shape factors using which the prediction of important weld bead dimensions, shape relationships and the controlling of the weld bead quality by selecting appropriate process parameter values is possible [11]. Benyounis et al. (2005) investigated laser butt-welding of medium carbon steel using CW 1.5kW CO2 laser. The experimental plan was based on Box–Behnken design and linear and quadratic polynomial equations were developed for predicting the heat input and the weld-bead geometry [12]. Nouri et al. (2007) studied the effect of pulsed variables on the dilution and weld bead geometry in cladding X65 pipeline steel with 316L stainless steel. They used a full factorial method to carry out a series of experiments to know the effect of wire feed rate, welding speed, distance between gas nozzle and plate, and the vertical angle of welding on dilution and weld bead geometry. They found that the dilution of weld metal and its dimension i.e. width, height and depth increase with the feed rate, but the contact angle of the bead initially decreases and then increases. Also, the welding speed has an opposite effect except for dilution [13]. Kolahan et al. (2010) used regression modeling in order to establish the relationships between input and output parameters for Gas Metal Arc Welding (GMAW) process. They checked the adequacies of the mathematical models developed using analysis of variance (ANOVA) technique and selected the best fitted model based on the ANOVA results and other statistical analysis [14]. Shen et al. (2012) carried out a series of measurements on submerged arc welded plates of ASTM A709 Grade 50 steel to determine how variation in heat input achieved using single and double wires affected bead
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reinforcement, bead width, penetration depth, contact angle, heat affected zone (HAZ) size, deposition area, penetration area and total molten area. They found that the bead reinforcement, bead width, penetration depth, HAZ size, deposition area and penetration area increased with increasing heat input, but the bead contact angle decreased with it [15]. Various researchers have established the relationship between welding process parameters and percentage dilution and weld bead geometry. There is little work done to establish the relationship between welding speed and percentage dilution as well as weld bead geometry in GMAW of SS 409L. 2. Experimentation Plates of SS 409L having dimensions 200x50x3 mm were cleaned by acetone. Austenitic grade electrode wire (filler wire) ER304L was selected with diameter 1.2 mm. Root gap of 1.2 mm was maintained during square butt welding by GMAW process. Welding was performed at three different welding speed i.e. 300, 400 and 500 mm/minute keeping all other welding parameters as constant. Chemical composition of base metal and filler wire is given in Table 1 and welding process parameters is shown in Table 2. Table 1. Chemical composition of base metal and filler wire Sample
%C
%Mn
%Si
%S
%P
%Cr
%Ni
%Cu
%Mo
%Nb
%Ti
%N
%V
Base metal
0.024
0.263
0.517
0.001
0.023
11.24
0.066
0.010
0.006
0.040
0.234
0.027
0.059
ER304L
0.015
1.65
0.243
0.013
0.031
18.46
8.14
0.434
0.352
0.050
0.008
0.220
0.061
Table 2. Welding process parameters and welding conditions Sample name
Welding speed
Current (A)
Voltage (V)
(mm/min)
Gas flow rate
Shielding Gas
(litre/min)
S1
300
130
20
18
Pure argon
S2
400
130
20
18
Pure argon
S3
500
130
20
18
Pure argon
The samples of proper dimension were sectioned from the welded plates. To reveal the shape of the weld bead, polishing of samples were carried out by emery papers followed by cloth polishing with diamond paste as abrasive particle. Samples were etched by Kalling’s reagent (10 ml hydrochloric acid, 10 ml ethanol and 0.5 gram cupric chloride) for 10 seconds. The weld bead profile has been shown schematically in figure 1. Different parts of the weld bead geometry such as bead width, bead height and penetration as well as areas of fused base metal (Afbm), upper reinforcement (Aur), lower reinforcement (Alr) and root gap (Arg) were measured by using Adobe Acrobat Reader DC software to calculate the percentage dilution (D) (Table 3) with the help of equations 1 & 2.
S.K. Gupta et al./ Materials Today: Proceedings 18 (2019) 5032–5039
Bead width
Bead height
upper reinforcement Fused base metal
Fused base metal
Base Metal
Base Metal
Penetration
5035
Lower reinforcement
Root gap
Figure 1. Schematic diagram of weld bead profile
Atwd = Afbm + Alr + Arg + Aur
.....……………… (1)
D = (Afbm / Atwd) X 100
…………………. (2)
Where Atwd represents the area of total weld deposition. 3. Results The values of bead width, bead height, penetration and percentage dilution has been tabulated in Table 3. Table 3. Weld bead geometry and percentage dilution Sample name
Bead width
Bead height
Penetration
Percentage dilution
S1
9.03
1.69
4.35
28.50
S2
7.04
1.10
3.77
31.49
S3
5.85
0.73
3.25
30.52
10.0 9.5 9.0
Bead width (mm)
8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 250
300
350
400
450
500
550
Welding speed (mm/minute)
Figure 2. Variation of bead width with welding speed
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The relationship between welding speed and bead width has been shown in figure 2. It was observed that maximum value of bead width was possessed by sample 1 and followed by sample 2 and sample 3. An inversely proportional relationship was found between bead width and welding speed. 2.0
1.8
Bead height (mm)
1.6
1.4
1.2
1.0
0.8
0.6 250
300
350
400
450
500
550
Welding speed (mm/minute)
Figure 3. Variation of bead height with welding speed
The variation of bead height with welding speed is presented in figure 3. It was observed that bead height follows inverse relationship with the welding speed. 4.6 4.4
Penetration (mm)
4.2 4.0 3.8 3.6 3.4 3.2 3.0 250
300
350
400
450
500
Welding speed (mm/minute)
Figure 4. Variation of penetration with welding speed
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S.K. Gupta et al./ Materials Today: Proceedings 18 (2019) 5032–5039
5037
The effect of welding speed on penetration has been shown in figure 4. It can be easily seen that penetration and welding speed are also in inverse relationship with each other.
32
Percentage dilution
31
30
29
28
250
300
350
400
450
500
550
Welding speed (mm/minute)
Figure 5. Variation of percentage dilution with welding speed
From figure 5 it was observed that percentage dilution first increases then decreases with the increase of welding speed. The sample S2 possessed maximum value of percentage dilution followed by sample S3 and sample S1. 4. Discussions 4.1 Relation between welding speed and bead width The width of the weld bead should be small but must be sufficient to melt sufficient portion of the base material. The weld joints should have W/P ratio between 1.2 to 2.0 to possess good weld strength, where W refers to bead width and P refers to depth of penetration The width of the weld bead depends upon welding process parameters such as welding speed, welding current, welding voltage, gas flow rate, electrode diameter, nozzle to tip distance etc.. It is generally found that width of the weld bead increases with the increase in welding current, welding voltage, gas flow rate, electrode diameter, contact tip to work distance (CTWD). The reason of variation of width of the weld bead is the variation of distribution of heat between the base metal and electrode wire. On increasing welding speed, keeping all other parameters as constant, base metal received less heat input per unit length. Due to this reduced heat input less melting of the base metal took place and deposition of the filler metal per unit length was also reduced due to faster movement of welding head. Due to less melting of the base metal as well as less deposition of the filler metal, the smaller weld bead was formed. 4.2 Relation between welding speed and bead height Bead height is the height of upper reinforcement and is represented in figure 1 and Figure 2. To obtain good quality of the weld joints, it is necessary to avoid the production of very thick weld bead because it may cause distortion, burn-off at the edge, deep craters at the end, sagging of the weld pool as well as wastage of energy and filler wire. Due to larger bead height, the junction point of the upper reinforcement and surface of the base metal (also known as weld toe) is not smooth and it produces a notch effect. Notch effect (size effect) deteriorates the properties of the welded joints. Therefore it is necessary to produce welds having smaller bead height by proper selection of the welding process parameters. As shown in figure 3, bead height decreases with the welding speed. It was due to the fact that on increasing welding speed, the heat input per unit length given to the base metal is reduced and also deposition of the filler metal is reduced due to high welding speed. 4.3 Relation between welding speed and penetration Penetration is the distance measured perpendicular from the upper surface of the base metal to the end part of the weld metal which is shown in figure 1. Ideally, penetration should be equal to the thickness of the base metal,
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however excess penetration upto certain amount are also acceptable. The limit of the acceptance of excess penetration depends upon the type of metals, type of welding methods, type of joints, application of joints etc. Beyond the acceptable limit, excess penetration is not desired because it causes wastage of energy, deteriorates the quality of the product and increases the weight of the product as well as wastage of filler metal which results into reduction in productivity. Penetration depends upon the heat input provided to base metal per unit length which in turn depends upon the welding process parameters. More heat input per unit length provided to the base metal causes more melting of the base metal which results into more penetration. Due to faster movement of electrode by increasing the welding speed, lesser heat input was received by the base metal per unit length. It causes reduction in the melting of base metal which resulted into reduced penetration with increase in the welding speed as shown in figure 4. 4.4 Relation between welding speed and percentage dilution The competition between melting of base metal and filler wire due to variation of welding parameters result into variation percentage dilution. The part of the base metal which is melted and the metal which is deposited from melting of filler wire together form the total volume of weld metal. The extent of melting of the base metal and filler wire depends upon the distribution of the heat input between base metal and filler wire which in turn controlled by the welding process parameters. On increasing welding speed, the percentage dilution may be decreased or increased depending upon the distribution of heat input between base metal and filler wire. Figure 5 showed that percentage dilution first increases then decreases with increase in welding speed. The increase in percentage dilution on increasing welding speed was due to the fact that deposition of filler metal was more sharply decreased than the reduction in melted volume of base metal which resulted into increase the ratio of volume of fused base metal and volume of total weld metal. On further increase in welding speed, percentage dilution was decreased. It was due to the fact that more welding speed causes less melting of the base metal as well as less deposition of the filler wire. The volume of melted base metal and volume of deposited filler metal were distributed in such a way that the volume of fused base metal to the total volume of weld metal in fusion zone was reduced which led to reduction in value of percentage dilution. 5. Conclusions Following important conclusions may be derived from this experimental investigation: The weld bead width obtained during GMAW of SS409L gets reduced on increasing welding speed. There exists an inversely proportional relationship between welding speed and bead width The increase in welding speed leads to decrease in bead height and penetration. The variation of both with the welding speed are found in inverse proportion. Percentage dilution first increases then decreases with the welding speed and the maximum dilution was obtained at medium level of welding speed. Acknowledgements Authors are thankful to Mr. Pai Namit Narasimhan (PDPM IIITDM Jabalpur, India) for their assistance in sample preparation of metallography. References [1]
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