Al-Khwarizmi Engineering!!! Journal Al-Khwarizmi Engineering Journal, Vol. 7, No. 1, PP 76 - 81 (2011) Study the Factors Effecting on Welding Joint of Dissimilar Metals Abdul wahab H. Khuder Esam J. Ebraheam Department of Welding Engineering/ Technical College Baghdad (Received 8 April 2010; Accepted 4 April 2011) Abstract The aim of this work is to study the factors that affect the welding joint of dissimilar metals. Austenitic stainless steel-type AISI (316L) with a thickness of (2mm) was welded to carbon steel (1mm) using an MIG spot welding. The filler metal is a welding wire of the type E80S-G (according to AWS) is used with (1.2mm) diameter and CO2 is used as shielding gas with flow rate (7L/min) for all times was used in this work. The results indicate that the increase of the welding current tends to increase the size of spot weld, and also increases the sheer force. Whereas the sheer force increased inversely with the time of welding. Furthermore, the results indicate that increasing the current and time of welding increases the diameter of weld zone, and decreases the sheer force. Keyword: MIG spot, weld dissimilar metals, shielded gas. 1. Introdaction According to the good corrosion resistance and the good mechanical properties, the stainless steel, it has been used in many industrial applications, especially those, which need high corrosion resistance, since there are many aggressive mediums responsible for the corrosion of that alloy in chemical, petrochemical industries. The most common used series of stainless steel is austenitic type [1]. Some industries and for the reason of reducing the production cost use lining process (low carbon steel with stainless steel) especially with pressure vassals industry by some types of welding processes; one of these is MIG Spot Welding. Therefore, we study MIG Spot weldments of stainless steel AISI (316L) and low carbon steel in this research. The AISI (316L) stainless steel is a type of a high alloy steel; it is a very important type because it has certain amounts of the alloying element and these elements increase thermal resistance and strength; therefore; this type of steel is very recommended [2]. Steels with less than (0.15%) carbon, known as low carbon steels, are easily joined by welding; these steels have very low hardenability. Rapidly cooled welded joint in steel containing about (0.10%) carbon and higher can develop cracks during serves cold forming operations because the weld area is harder than the unaffected base metal. Spot weld hardness is not a serious problem with these steels except for some critical applications [2]. 1.1. Gas Metal Arc Welding (GMAW) It is a once welding process that uses an arc between a continuous filler metal electrode and a weld metal. The process is used with shielding from an externally supplied gas and without the application of a pressure; it was developed in the late 1940 s for welding aluminum and has become very popular. This process is also called metal in arc gas (MIG) welding .There are many variations depending on the type of shielding gas, type of the metal transfer, type of the metal welded and so on. It has been given many names for example (MIG Welding, Co2 welding, Fin wire welding, Spray arc welding, Pals arc welding, Dip transfer welding, Short circuit arc welding and various trade names) [3]. This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Abdul wahab H. Khuder Al-Khwarizmi Engineering Journal, Vol. 7, No. 1, PP 76 - 81 (2011) 77 1.2. Gas Metal Arc Spot Welding (MIG Spot) (GMAW) It is a process in which coalescence is produced by heating them with an arc between a continuous filler metal electrodes and the metal welded. Shielding is obtained entirely from an externally supplied gas or gas mixture. There is a number of variations of gas metal arc welding process and the process has been given many different trade names, which tend to create confusion. This method involves inert gas pumping during the welding process [4]. These inert gases are Argon, Helium or may be active gas such as Carbon-dioxide. Sometimes the gas used during the process is a mixture of two or more gases. The purpose of using inert gases is to prevent oxygen and waste gases from entering the welding region which causes failure in the welded joint [4]. 2. Experimental Work MIG spot welding process was selected to weld sheets of austenitic stainless steel – type AISI (316L) with thickness of (2mm) and the low carbon steel with thickness of (1mm). Tables (1) & (2) show the chemical compositions and the mechanical properties of the materials selected. Table 1, Chemical Compositions. Composition wt %Specimen Materials AlCuMoNiCrSPSiMnC 0.010.190.28.3318.330.010.0250.581.480.03Stainless steel 0.030.050.030.080.050.0140.010.260.920.14Carbon steel Table 2, Mechanical Properties. 2.1. Welding filler metal The type of filler metal used is AWS (E80S-G) of (1.2mm) diameter; this type consists of (Mn) (Si) as a deoxidize element added to obtain a high quality weldment using (Co2) as a protective gas. Table (3) shows the chemical composition and properties for a filler metal [5]. Table 3, Chemical Composition of the Welding Wire. Elements C Si Mn Mo Weight % 0.1 0.6 1.1 0.6 Yield strength = 460 (MPa). Tensile strength = 530 – 570 (MPa). Impact strength = 47J. Elongation =22% 2.2. Shielded Gas The shielding gas is (Co2) used with flow rate (7L/min.) for all times. (Co2) gas is a protective gas; it is used to weld the steel and low alloy steel because sweetening (Co2) to (Co + O). 2.3. Preparation of the Specimen Preparation of the welding specimens depends on standers; see Figure (1) [6] .Table (4) shows the dimensions of the specimen. Mechanical Properties Stainless steel Low Carbon steel Tensile Strength (N/mm2) 558.9 345 Yield Strength (N/mm2) 269.1 193.2 Elongation% 55 28 This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Abdul wahab H. Khuder Al-Khwarizmi Engineering Journal, Vol. 7, No. 1, PP 76 - 81 (2011) 78 Fig.1. Specimen Dimensions’ Dateless)[6]. Table 4, Specimen Dimensions. 3. Results and Discussions Table (5) shows the parameters used during welding and the results obtained from the share force test. Table 5, The Condition of Weld When the Flow Rate is (7L/min). Specimen No. Feed of wire (cm/min.) Time of feed wire (sec) Weld current (Amp) Diameter of spot (mm) 1 109 1.5 300 8.5 2 109 3 270 7.2 3 109 3 300 9.5 4 127 1.5 220 8 5 127 1.5 240 8.5 6 127 1.5 270 9.5 7 127 1.5 300 12.5 8 127 3 180 7.25 9 127 3 200 7.25 10 127 3 220 7.5 11 127 3 240 7.5 12 127 3 270 9 13 127 3 300 11 14 204 1.5 180 8 15 204 1.5 200 9.25 16 204 1.5 220 9.5 17 204 1.5 240 10 18 204 1.5 270 11 19 204 1.5 300 12.1 20 204 3 200 8.5 21 204 3 220 9.75 22 204 3 240 11.5 23 204 3 270 12.2 24 470 1.5 220 7.8 25 470 1.5 240 9.5 26 470 1.5 270 12.2 27 470 1.5 300 13.75 (t1) Thickness of St.St. strip (mm) (t2) Thickness of C.St. strip (mm) (w) Specimen width (mm) (W1) Lap width (mm) (L) Specimen length (mm) 2 1 25 25 102 This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Abdul wahab H. Khuder Al-Khwarizmi Engineering Journal, Vol. 7, No. 1, PP 76 - 81 (2011) 79 Figure (2) shows that the shear force increases when the current increases from (180Amp to 300) at weld time (3sec.). Fig.2. Relationship between Welding Current and the Max. Shear Force for Different Time of Weld With Wire Feed 127 cm/min. These increases depend on the welding penetration and the size of weld spot; see figures (3&4). 4 6 8 10 12 14 150 200 250 300 350 Weldin Current (Amp) W e ld in g S p o t D ia . (m m ) 127 cm/min. 204 cm/min. 109 cm/min. Fig.3. Relationship between Welding Current and Welding Spot Diameter for Different Wire Feeding at 3 Sec. Time of Weld. Fig.4. Relationship between Welding Current and Welding Spot Diameter for Different Wire Feeding at 1.5 Sec. Time of Weld. But, at weld time (1.5 sec.) and current from (180Amp to220), no welding happens, because this period of welding time is not enough for thermal energy to pass through metal; see figures (2 & 4). Figure (5) shows that increasing wire feed at (1.5 sec.) tend to increase shear force from (6821N at 180 Amp) to (7456 N at 300 Amp). Fig.5. Relationship between Welding Current and the Max. Shear Force for Different Time of Weld With Wire Feed 204 cm/min. So, when comparing figures (2 & 5), we found that welding took place at the rang ( 180 Amp to 220) when wire feed increased from (127 cm/min) to (204 cm/min). Welding time is an important factor as a result of the amount of heat input effects. The shear force is proportional with the time at different wire feeds (figure 6) until it reaches the max value at (270 Amp); then it is proportional inversely because more heat input (long time of current flow) gives spattering of electrode metal’s and over grain growth at the heat affected zone. Therefore, the failure occurs on the HAZ after welding in the range (270Amp to300) [7][8]. 20 30 40 50 60 70 80 90 150 200 250 300 350 Weldin Current (Amp) M a x . S h e a r F o rc e ( 1 0 0 N ) 127 cm/min. 204 cm/min. 470 cm/min. Fig.6. Relationship between Current and Shear Force for Different Wire Feeding at 1.5sec Welding Time. 4 6 8 10 12 14 16 150 200 250 300 350 Weldin Current (Amp) W ld in g S p o t D ia . (m m ) 127 cm/min. 204 cm/min. 470 cm/min. This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Abdul wahab H. Khuder Al-Khwarizmi Engineering Journal, Vol. 7, No. 1, PP 76 - 81 (2011) 80 4. Conclusion 1) Increase welding current tend to increase the size of spot weld, and also increases the shear force. 2) Shear force is proportional with welding time until it reaches the max value; then it is inversely proportional because of more heat input and over grain growth at heat affected zone with high current. 3) Increase the current and time of welding is proportional with the diameter of welding spot. 4) Increasing the wire feeding with the time of feed is proportional with diameter of spot. 5) The mig spot can be useful to lining process of stainless steel insipid of the traditional methods or process that be used recently. 5. References [1] Stuart W. Gibson, Gerted "Advance Welding" Macmillan an press LTD, 1997. [2] Donald R. Askeland & Pradeep P. Phule “The Science and Engineering of Materials”,Thomson Brooks/Cole,2004. [3] A.S.Gibson,"Advanced Welding", Macmillan Press LTD, 1997. [4] HB.Cary,''Modren Welding Technology'', 5th Edition, Prentice-Gall, 2002. [5] American Welding Society, “Specification for Carbon Steel Electrodes for Shielded Metal Arc Welding”, American Welding Society, Inc.1999. [6] Specimen diamensions ,"Welding in the world", vol. 18, 1980, pp. 39-40. [7] Sindo Kou "Welding Metallurgy" 2nd Edition, John Niley &Sons.Inc, 2003. [8] Thomas Bollinghaus, ''Hot Cracking Phenomena in Weld'', Spring verlag, Berlin Heidelberg, 2005. This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ - 81 ، صفحة1، العدد 7الخوارزمي الھندسیة المجلد مجلة عبد الوھاب حسن خضر 76 )2011( 81 دراسة العوامل المؤثرة على وصلة اللحام لمعادن مختلفة إبراھیمعصام جبار عبد الوھاب حسن خضر بغداد –الكلیة التقنیة / ھندسة تقنیات اللحام الخالصة وبسمك (316L)نوع –االوستنایتي تم استخدام الصلب المقاوم للصدأ . یھدف البحث الى دراسة العوامل المؤثرة على وصلة اللحام لمعادن مختلفة (2mm) 1(والصلب المنخفض الكاربون بسمكmm ( لحام من نوع سلكتم أستخدام .الغازات الواقیة باستعمالوتم لحامھا بطریقة لحام النقطة(E80S- G) وبقطر(1.2mm) األمریكیةباالعتماد على مواصفات جمعیة اللحامین (AWS) .ني أوكسید الكاربون كغاز عازل وبسرعة كما تم أستخدام غاز ثا .لكل االزمان المستخدمة في ھذا العمل (7L/min)جریان ى ان . اشارت النتائج الى ان الزیادة في تیار اللحام تؤدي الى زیادة في قطر نقطة اللحام والزیادة في قوة القص لوصلة اللحام ایضا ائج ال رت النت ا اظھ كم اد . زیادة قوة القص تتناسب عكسیا مع زمن اللحام للوصلة ى زی ؤدي ال ام ی ن اللح ؤدي كذلك اشارت النتائج الى ان زیادة تیار وزم ام وی ة اللح ر نقط ي قط ة ف .ذلك الى النقصان في قوة القص لوصلة اللحام This page was created using Nitro PDF trial software. 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