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46th ISTE Annual National Convention & National Conference 2017International Journal of Advance Research and Innovation (ISSN 2347 – 3258)

Experimental Investigation of Effect of Welding Parameters on Bead Geometry & Mechanical

Properties on Dissimilar MS-SS Joints by A-TIG Welding Process

Ravinder Goyal1 Kulvir Singh2 Manish Moonglia3 Akhilesh Kumar4

1,2,3Assistant Professor: Department of Automobile EngineeringGulzar College of Engineering

Ludhiana, Punjab, [email protected]

4Student of Production Engineering, Thapar University

Abstract - Steels are alloys of iron and carbon which are mostly used in construction work because they have high tensile strength and low cost. Mild steel is also known as carbon steel is a type of carbon steel having maximum carbon up to 0.25. Many everyday objects are made of mild steel like pots, pans etcetera. It is general term for range of low carbon steel having good strength that can be bent, worked and welded into variety of shapes for uses from vehicles to building materials. Most everyday items which are used in our daily life made of steel contain mild steel content, from cookware to vehicle chassis.Weldablity refers to the ability of the material to be welded. The variant of TIG welding process used i.e. A-TIG welding, a thin layer of activated flux is brushed on to the surface of the joint to be welded.The term Flux is overcome from Latin word fluxes and it means flow. It is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes are mainly used to remove oxide impurities of weld and also absorb impurities from slag. The activator in flux used to reduce corrosive effect at room temperature and increase the temperature of job at certain level. For most welding operation commonly used fluxes are SiO2, TiO2, Cr2O3, ZrO2, Al2F3 etc.Design of Experiments (DoE) was used to analyses the results of experiment. The design of experiment is a procedure of selecting number of trials and conditions running them, essential and sufficient for solving a problem that has been set with the required precision.Mild Steel and Stainless Steel grade 304 were selected as base materials for performing the experiments. In this study, effect of different welding parameters on penetration of weld, mechanical properties studied.Five different types of oxide based flux powders were used which are commercially available in the market. The Titanium dioxide flux enhances the mechanical properties evidently in the A- Tungsten inert gas welding of dissimilar MS-SS. In the present study was analyzed under different welding parameters i.e. welding speed, weld current, gas flow rate and fluxes SiO 2 and TiO2.Fine grain size were observed in the welded fusion zone prepared with a TiO2 flux. These characteristics led to high tensile strength compared to the welds prepared without the use of a flux. Elements containing in flux can change the coefficient of the surface tension of molten weld from negative to positive and further change the direction of flow in the weld pool cause deep and narrow weld pool, which help to enhance the mechanical properties of welded joint.Keywords—A-TIG, DoE, Oxide flux, Fusion zone, Mechanical properties.

I. INTRODUCTION

Steels are alloys of iron and carbon which are mostly used in construction work because they have high tensile strength and low cost. The carbon content in typical alloy steel is up to 2.1% of its weight. But in the cast iron that contain carbon content more than 2.1% does undergo eutectic reaction. When Carbon content is higher than those of steel it makes an alloy that is commonly known as pig iron which is brittle and not malleable. When there is too little carbon amount it leaves iron which quite soft, ductile and weak. Different alloying elements added to the steel to modify the properties of steel such as Manganese, Sulphur, Silicon and traces of Oxygen, Nitrogen and copper.

A. CLASSIFICATION OF STEELS

Steels are classified into three groups according to the carbon composition i.e. Low carbon steel ( <0.25% ) Medium carbon steel (0.3-0.6%) High carbon steel ( >0.6% )

B. MILD STEEL & ITS USAGESMild steel is also known as carbon steel is a type of carbon steel having maximum carbon up to 0.25% also other alloying elements such as 0.4%-0.9% manganese, 0.1%-0.5% silicon

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Gulzar Group of Institutes, Ludhiana, Punjab-141401 (INDIA)


and also there are some traces of other alloying elements such as phosphorous, lead and sulphur.Uses of mild steel Nuts and bolts Chains Knives Pipes Magnets etc.C. WELDABILITY

It refers to the ability of the material to be welded. Many metals and thermoplastics can be welded .Some materials are difficult to weld then others. Weldability is used to define the welding process and compare of weld the quality to the other materials.FACTORS AFFECTING WELDABILITY: Material type Travel speed Heat input Arc welding positions Welding techniques Welding procedure Weld metal composition

D. TIG WELDING:Tungsten inert gas arc welding, as the name suggests is a process in which the source of heat is an arc formed between a non-consumable tungsten electrode and the work piece, and the arc and the molten puddle are protected from atmospheric contamination (i.e. oxygen and nitrogen) with a gaseous shield of inert-gas such as argon, helium or argon-helium mixture. Filler metal, if required, is added externally to the arc in the form of a bare wire by the welder. It is often referred to in abbreviated form as TIG welding. Some authors prefer to call it inert-gas tungsten-arc welding.

Fig. 1: Schematic diagram of TIG welding process

Welding current, welding voltage, Inert gases & welding speed are the process parameters for TIG welding process.

E. ACTIVATED TUNGSTEN INERT GAS (A-TIG) WELDING

Activated tungsten inert gas (A-TIG) welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas (argon or helium), and a filler metal is normally used, though some welds, known as autogenous welds, do not require it. In A-TIG welding, a thin layer of activated flux is brushed on to the surface of the joint to be welded.Activated flux is used in the A-TIG welding, which is the only difference from the conventional TIG welding. Activated flux can be prepared by using different kind of component oxides packed in the powdered form with about 30-60 μm particle size. These powders mixed with acetone, methanol, ethanol etc to produce a paint-like consistency. Before welding, a thin layer of the flux, brushed on to the surface of the joint to be welded. The coating density of the flux should be about 5-6 mg/cm². Activated TIG welding can increase the joint penetration and weld depth-to-width ratio, thereby reducing the angular distortion of the weldment.

F. ACTIVATING FLUXThe term Flux is overcome from Latin word fluxes and it means flow. It is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes are mainly used to remove oxide impurities of weld and also absorb impurities from slag. The activator in flux used to reduce corrosive effect at room temperature and increase the temperature of job at certain level. For most welding operation commonly used fluxes are SiO2, TiO2, Cr2O3, etc.G. ADVANTAGES OF ACTIVATED TUNGSTEN INERT

GAS (A-TIG) WELDING1. The new process enables single pass welding of higher

thickness plates with higher welding speed and hence reduced heat input.Enhanced productivity and reduced consumption of filler wire

2. Residual stresses are reduced significantly (more than 70%) in A-TIG weld joints compare to conventional TIG weld joints and the weld joints are distortion free.

3. Significant improvement in creep-rupture life (more than 75%)

4. Significant reduction in the cost of fabrication

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5. Up to 25 mm thick plates can be welded using double side welding procedure with square edge preparation

II. WORK MATERIALMild Steel and Stainless Steel grade 304 were selected as base materials for performing the experiments. In this study, effect of different welding parameters on penetration of weld, mechanical properties and microstructure is studied.

Fig. 2: Base material selected for experimentation

Mild Steel and Stainless Steel were used as base metal, because in industries there many applications such as pipelines, boilers where dissimilar welds between these two metals are to be made. Also, these are the materials which have good strength. Due to their cheaper cost these are used when in large quantity steel is required.

A. SELECTION OF FLUX POWDERS

Five different types of oxide based flux powders were used which are commercially available in the market. Also one mixture of two flux powders was used as a sixth powder. Two flux powders were those which were not commonly used in the previous research works. The different flux powders used in the investigation are as follows: Chromium Oxide Green(Cr2O3) Silicon Dioxide(SiO2) Titanium Dioxide(TiO2) Aluminum Oxide(Al2O3) Cadmium Chloride (CdCl2)Acetone was used as a binder to form paint like solution which was applied on the mild steel and stainless steel 304 plates during experiments.

III. EXPERIMENTATIONA. PREPARATION OF THE BASE METAL

First of all, size of the base plates i.e. Mild Steel and Stainless Steel 304 was decided as 75mm x 50mm x 6mm on the basis of literature survey. Required number of specimens was cut from single plate of each base material with the help

of cutter, and then these specimens were made smooth with the help of grinder.B. APPLICATION OF ACTIVE FLUXES ON THE BASE

PLATESAfter preparing the base plates, oxide layer from all the

specimens of both materials was removed with the help of a hand grinder. After that, all the available fluxes {Chromium Oxide Green (Cr2O3), Silicon Dioxide (SiO2), Titanium Dioxide (TiO2), Aluminum Oxide (Al2O3), Cadmium Chloride (CdCl2)} were applied on the base material after making a paste by mixing them with Acetone.

Fig. 3: Application of Active Fluxes on Base Plates

To select the parametric range for actual experiments the trial runs were conducted over a wide range of parameters of TIG welding. From these trial runs, it was depicted that two Active Fluxes i.e. Silicon dioxide (SiO2) and Titanium dioxide (TiO2) were producing better results in terms of penetration than the rest of the fluxes. So, these two fluxes were selected for actual experiment.

Fig. 4: Welded Specimen after Trial RunIn this final phase of experimentation, all the four parameters i.e. welding current, welding speed, gas flow rate and active fluxes were varied to study their effect on depth of penetration, mechanical properties (Tensile Strength and Micro-hardness) and microstructure. Gap of 2 mm was kept between the base plates of MS and SS 304 and filler rod of SS was used to make a weld between the base plates.

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Fig. 5: Welded Specimens after Carrying out ExperimentIV. TESTING & RESULTS

Specimens for tensile test were prepared and the size of these specimens was decided as 150 mm x 20 mm x 6 mm. The specimens of Dumbbell shaped were made for tensile testing and gauge length of the specimens was 50 mm. These tensile testing specimens were made using Wire EDM.

Fig. 6: Dumbbell Shaped Specimens for Tensile TestingAfter that, testing specimens for Micro-hardness were prepared with the help of cutter and these were finished with grinder. Size of specimens was chosen as 20 mm x 15 mm x 6 mm.Then same sized specimens were prepared for carrying out microstructure testing.

Fig. 7: Interaction effect of welding current and type of weld on tensile strength

Main effects plots for tensile strength here are plotted between1. Tensile strength Vs. Welding current2. Tensile strength Vs. Oxide flux

3. Tensile strength Vs. Welding speed4. Tensile strength Vs. Gas flow rate

The effect of each parameter on the Tensile strength is plotted on the graph in form of lines.

Fig. 8: Probability Plot of Tensile StrengthThe probability plot shown that the all the experiments carried out were under the normal curve distribution.

V. CONCLUSION1. The Titanium dioxide flux enhances the mechanical

properties evidently in the A- Tungsten inert gas welding of dissimilar MS-SS. In the present study was analyzed under different welding parameters i.e. welding speed, weld current, gas flow rate and fluxes SiO2 and TiO2.

2. The maximum tensile strength achieved using activated flux TiO2 is 547.46 MPa at welding current 130 A, Welding speed 3 mm/sec and Gas flow rate of 12 L/min.

3. Fine grain size were observed in the welded fusion zone prepared with a TiO2 flux. These characteristics led to high tensile strength compared to the welds prepared without the use of a flux.

4. Elements containing in flux can change the coefficient of the surface tension of molten weld from negative to positive and further change the direction of flow in the weld pool cause deep and narrow weld pool, which help to enhance the mechanical properties of welded joint.

This study can be extended for other welding or alternate welding processes on same materials.

REFERENCES[1] TIG Torch - CK Worldwide TIG Welding Torches & Accessories.

2014. TIG Torch - CK Worldwide TIG Welding Torches &

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Accessories. [ONLINE] Available at: http://www.ckworldwide.com. [Accessed 05 July 2014].

[2] Liao Jinsun et al. (2014), Gas tungsten arc welding of fine-grained AZ31B magnesium alloys made by powder metallurgy. Journal of Materials and Science, Elsevier, 56, pp. 460-467.

[3] Vikesh et al. (2013), Effect Of A-Tig Welding Process Parameters On Penetration In Mild Steel Plates. International Conference on Mechanical and Industrial Engineering, pp. 8-11.

[4] Ahmadi E. and Ibrahim A.R., The effect of activating fluxes on 316L stainless steel weld joint characteristic in TIG welding using the Taguchi method.

[5] Tseng et al. (2011), Performance of activated TIG process in austenitic stainless steel welds. Journal of Materials Processing Technology, Elsevier, 211, pp. 503–512.

[6] Kumar Vinod (2011), Modeling of Weld Bead Geometry and Shape Relationships in Submerged Arc Welding using Developed

Fluxes. Jordan Journal of Mechanical and Industrial Engineering, 5, pp. 461-470.

[7] Sakthivel T. et al. (2011), Comparison of creep rupture behavior of type 316L(N) austenitic stainless steel joints welded by TIG and activated TIG welding processes. Materials Science and Engineering, Elsevier, 528, pp. 6971– 6980.

[8] Qing-ming L.I. et al. (2007), Effect of activating flux on arc shape and arc voltage in TIG welding. Trans. Noni'crrous Met. Soc. China, 17, pp. 486-490.

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