· Web viewFirst Step in this study we cut the Mild Steel and Stainless Steel in to small...
Transcript of · Web viewFirst Step in this study we cut the Mild Steel and Stainless Steel in to small...
TO STUDY THE MECHANICAL PROPERTIES OF WELDED JOINT OF MILD
STEEL & EN-31 WITH CHANGE PARAMETER OF MIG WELDING.
AUTHOR :- PAWAN KUMAR (M.TECH)
ABSTRACT
This study was carried out to investigate To study the mechanical properties of welded joint of mild steel & EN-31 with change parameter of MIG welding. The study reveals the influence of current and voltage on the weld bed of steel as well as the mechanical properties of the metal. The samples were welded together by metal inert gas welding process and wire feeder speed selected against the values of current and voltage after which various tests were performed on the welded samples. In large steel fabrication industries such as ship making, and train guide way, the problem of residual stresses and overall distortion has been and continues to be a major issue. In the last few decades, various research efforts have been directed at the control of the welding process parameters aiming at reducing the distortions and residual stress effects. Yet in actual practice, large amounts of resources are still being spent in reworking welds, which in turn increases the production cost and delays work completion.
It is assumed that in order to reduce the residual stresses and distortions from a welding
operation, it is necessary to understand the effects of welding process parameters on various
mechanical properties of material. In this dissertation, the effect of various process parameters on
hardness, impact strength, chemical composition and microstructure of material. Also, a study
has been conducted to assess the effects of welding current, welding voltage, wire feeder rate on
gas welding responses as applied to mild steel and EN-31 welding. A single pass butt joint gas
welding has been chosen in this study. The result shows that all parameters have a significant
effect on the various properties of material. Hence, after studying the effect of various
parameters on weld quality, it might be possible to select the best combination of various
parameters to get a good quality weld. It will help in reducing the residual stresses and distortion
in the welding.
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Introduction
1.1 Welding :-
Welding is a process of joining two similar or dissimilar metal by metal fusion, with or without
the help of pressure and with or without the use of filler metal. The fusion of metal takes place
by heat. That heat may be produced by chemically reaction, friction between two joining metal
& resistance. In the end of the 19th century, the process of joining was forge welding in which
black smith had used for to join metal by heating and hammering process. Arc welding were
among the 1st processes to develop late in 19th century and resistance welding after this. In 20th
century during world war I and world war II increase the demand for reliable and expensive
process of joining technique. During world war many welding process were developed it also
including manual techniques for example-shielded metal arc welding .many energy sources are
used for welding process like :- flame ,beam(electron),laser beam and friction of two joining
metals during process etc. Welding arc are performed in different -different environment. It may
be used in open place and can be under water. Many precautions are necessary for welding
process. These precautions to avoid burs, electricity shock, vision damage and from harmful
flames and gases .Now days semi-automatic , full automatic welding are very most popular in
industries work like - MIG welding, slag welding, flux welding and submerged welding etc.
Development continued with introduced of beam (laser ,Electric), welding, friction welding in
the late half of 20th century. Now days robot welding are most popular welding for industries
work. In this field researcher continue working for develop advice welding techniques and gain
greater understanding of welded quality. There are many types of welding process are used for
industries work. These welding process are very usefully for joining ferrous and non-ferrous
metals .Due to welding process industries work became easy. Various welding process are used
for industries purpose.
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In general, various welding and allied processes are classified follows :-
• Gas welding
• Arc welding
• Resistance welding
• Solid state welding
• Thermo- chemical welding process
• Radiant energy welding process
Application of welding :-
There are many type of application of welding like as:-
• Automobile construction
• Railroad equipment
• Ships
• Aircraft construction
• Building construction
• Pressure vessel
• Storage tanks
• Piping and pipe lines
• Household furniture
• Fabrication of jigs and fixture
• Bridge construction
• Fabrication of machine tools
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Metal Inert Gas welding (MIG):-
It developed in BM institute in year 1948,developed by H.E Kennedy .During development H.E
Kennedy used a small diameter electrode and a power source with constant voltage .But it had
high deposition rate .It had some limit like very use fully for non-ferrous material with high
cost. There also had some disadvantages like it was very costly with inert gases .In year 1953 it
was used with carbon dioxide gas. So Due to this gas it became popular in welding process and
gained same advantages such like economical for sheet metal work and also could be used easily
in thin material work with smaller electrode wires and more advanced power sources. It was
historical development in welding process. In the early year 1960 a small amount of oxygen with
carbon oxide was added in welding process it became popular in industries field. Now days its
known as pulsed spray arc variation welding. In 1950 and 1960 gave the process more
versatility. t is very most popular in welding process. Now days MIG welding performed by
robot in industries field. The metal inert gas welding is increase employed for fabrication in
many industries .This can used for all position welding. The basic necessary equipment is a
welding gun, a wire feed, power source, wire, and shielding gases.MIG welding can be
intergraded into the robotized, production canters .these advantages have motivated many
researcher to study MIG welding process in detail. Gas metal arc welding is an arc welding
process that used an arc between a continuously feed metal electrode and work piece .It is also
known MAG (metal active gas) welding involves the gases like carbon dioxide and oxygen. A
variant of the GMAW process uses a tubular electrode filled with metallic powders to make up
the bulk of the core material .Such electrode may or may not require a shield gas to protect the
molten weld pool from oxidation.MIG welding used for Al ,MS, EN-31,SS,copper and nickel
metal alloys .In which heat generate between electrode and work piece.MIG welding may be
automatic or full automatic welding.MIG welding also used with a constant direct voltage power
source. We can used it with constant current as well as AC source. Globular, short circuit, spray
and pulsed spray, are metal transfer method in MIG welding process. These all transfer methods
have advantages as well as limitations. There are following shield gases used for avoid oxidation
on weld pool like Argon ,carbon dioxide and helium gas these are mostly useable gases during
welding process.
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Welding polarity :- MIG welding done with reverse polarity that means electrode connected
with positive side of battery and negative with work piece .But in flux core (gas less) welding
done with straight polarity mean electrode connected with negative side of battery and work
piece connected with positive side of battery. According experiment electrons flow from
negative to positive side of battery and causes heat build up at the positive side. Electrode used
mean wire is ER70S6 wire thickness is like between 0.023 to 0.045 used for heavy industrial
purpose. Wire ER7OS6 used for steel work .Code ER7OS6 mean
ER-A filler rod used with wire feed or TIG welding
70-70,000 tensile strength /inch 2
S- solid wire.
6- Availability amount of cleaning and oxidation agents in feeding wire.
Chemical composition of the wire is given in Table 1. The pure Argon as shielding gas is used.
C M n Si p s Cu
0.060-0.16 % 1.40-1.8 % 0.8-1.14 % <0.025 % <0.025 % <0.05%
Table 1.1 Chemical Composition of Wire
1.8 Mild steel:-
Mild steel, also known as plain-carbon steel, is the most common form of steel because its price
is relatively low while it provides material properties that are acceptable for many applications,
more so than Fe Mild steel is the least expensive of all steel and the most common steel used.
Used in nearly every type of product created from steel, it is weld able, very hard and although it
easily rusts, very durable. Containing a maximum of 0.29% carbon this type of steel is able to be
magnetized and used in almost any project that requires a vast amount of metal. Its structural
strength prevents it from being used to create load-bearing girders and structural beams.
Many of the everyday objects that are created of steel are made using mild steel, including
automobile chassis, motorcycle frames, and most cookware. Due to its poor corrosion resistance,
it must be painted or otherwise protected and sealed in order to prevent rust from damaging it. A
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light coat of oil or grease is able to seal this steel and aid in rust control. Unlike high carbon,
mild steel is easily welded. The properties of the steel allow the electrical current to travel
through the metal without distorting the makeup of the material. Some types of high-carbon
steel, such as SS require special techniques in order to properly weld the material. Being less
brittle than high-carbon steels, the mild variant is able to flex and give in construction projects
where a higher-carbon version could simply break.
Most of the pipeline in the world is created using mild steel. This allows the pipe to not only be
easily welded into place, but also lets the pipeline flex and avoid cracking and breaking under
pressure. The corrosive properties of the steel pipeline mean that it must be properly sealed
through painting or a process often used on pipelines that involves wrapping the pipe with a
corrosive-resistant material. Mild steel is a type of steel alloy that contains a high amount of
carbon as a major constituent .An alloy is a mixture of metals and non-metals, designed to have
specific properties. Mild steel is the type of steel, which is used in 84% of all steel applications in
the United States of America. This article will talk about mild steel properties and enlighten you
about why exactly is it called 'mild' and what it really means.
Mild steel absorb shocks it is having bright fibrous structure. It can be easily forged and welded
and it is malleable and ductile. Its tensile strength is better than cast iron and wrought iron but
compressive strength is better than wrought iron but less than cast iron and melting point of mild
steel is 1400 C.
1 .EN-31
EN-31 is very important metal from EN series. It is very most popular in manufacturing
industries. It have good surface finishing and harness. EN having following series like EN-8,EN-
24 and EN-31 but it is very usefully in manufacturing .EN-31 have good machining properties .
It is used for ball bearing .shear blades , modeling die ,industrial gauges ,axles , spindle and for
high hardness components . EN-31 is a alloys steel that which is very popular in manufacturing
field. Alloys steel is defined as a steel alloyed have variety of elements in total amounts range
from 1 to 50 %. Alloys steel classified into two class that is low alloy and high alloy .Low alloys
steel have lower than 4-5% alloy and other hand high alloys steel have more than 8%alloys. EN-
31 have following elements like most common -Mn, Ni, Cr, V, Si, and boron & less used
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alloying elements are Al , Co, Cu , Nb , Ti and W.EN-31 have high carbon alloy steel which
that offer a high hardness with abrasion resistance and compressive strength . It is very popular
in manufacturing of industrial gauges and dies. EN-31 is a good quality steel and most useable
metal in world. It also have good wear resistance properties .Forging at 1000c° – 1050c° but heat
slowly and also cool slowly at forging process.EN-31 is supply in the annealed and machining
condition . It anneal solely at 800c~810c and also cool slowly. EN-31 heat at 700c° and carefully
cool.
Chemical elements :-
Fe- 98.721 , C-0.911Si-0.272, Mn-0.570,P-0.0344,S-0.0410,Cr-1.231,Mo-0.0035,Ni-0.0711,
V-0.0153, Cu-0.0618AL-0.0260, Nb-0.0051, Ti-0.0060, B-0.0001 Co-0.0108, W-0.0104, Sn-0.0022
Mechanical Properties of Steel :-
• Hardness
• Toughness
• Brittleness
• Malleability
• Ductility
• Tensile strength
The above listed properties help in determining how an alloy or a metal would behave under
load. Now explain one by one.
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Literature Survey
The principles of gas metal arc welding began to be understood in the early 19th century,
after Humphry Davy discovered the short pulsed electric arcs in 1800.VasilyPetrovindependently
produced the continuous electric arc in 1802. It was not until the 1880s that the technology
became developed with the aim of industrial usage. At first, carbon electrodes were used
in carbon arc welding. By 1890, metal electrodes had been invented by Nikolay HYPERLINK
"http://en.wikipedia.org/wiki/Nikolay_Slavyanov"Slavyanov and C. L. Coffin. In 1920, an early
predecessor of GMAW was invented by P. O. Nobel of General Electric. It used a bare electrode
wire and direct current, and used arc voltage to regulate the feed rate. In 1926 another forerunner
of GMAW was released, but it was not suitable for practical use. Many of investigators have
suggested various methods to explain the process parameters effecting on mechanical properties
of weld metal of steel.
M.St. Weglowski a, Y. Huang b, Y.M. Zhang b:-
The Measurements of metal transfer are presented in the GMAW process in the range of welding
wire speed from 150 inch/min to 240 inch/min[4]. The measurement system is based on a high
speed camera and it can measure the metal transfer at 3000 frames per second.Effect of welding
current on the metal transfer are evaluated using dimensional and kinetic analysis.
E. Mahdi, E. O. Eltai, A. Rauf:-The behavior of MIG welded and un-welded AA 6061 T6 were investigated using a series of
electrochemical measurements and mechanical tests. The Heat affected zone was more
susceptible to corrosion showing severe pitting corrosion comparing to the basemetal[5]. The
hardness of the welded specimens was increased as we moved away from the weld centre and
Torsion welded specimens were broken at the heat affected zone suggesting softness of this area
due to the impact of MIG welding.
G. Haragopal, P V R Ravindra Reddy and J V Subrahmanyam:-
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They presented a method to design process parameters that optimize the mechanical properties of
weld specimen for Al alloy, used for construction of aerospace wings. The process parameters
considered for the study were gas pressure, current, groove angle and pre-heat temperature.
Process parameters were assigned for each experiment. The experiments were conducted using
the L9 orthogonal array. Optimal process parameter combination was obtained. Along with this,
identification of the parameters which were influencing the most was also done[6]. This was
accomplished using the S/N analysis, mean response analysis . Mechanical properties obtained
for three samples of each run were obtained. Signal to noise ratio for each quality (S/N) ratio for
each quality characteristic was calculated, significant parameters were identified and optimum
input parameter for each quality characteristic were predicted from S/N values and mean
response. Analysis of variance ascertained significant parameters identified through S/N
analysis. A confirmation test was conducted at optimum conditions to ensure correctness of
analysis.
Suresh Kumar:-It discuss about micro structural development during MIG welding of copper with iron filler.
During the experimental work they consider voltage, current and travel speed as welding
parameter. They investigate needle shaped morphology of iron matrix typical of marten site and
at copper iron interface bended microstructure was observed which varied with travel speed.
Abbasi..K, Alam S Khan .M.J :-
MIG is carried on 144mm long x 31mm wide & 10mm thick bright drawn, mild steel .Increase in
pressure of shielding gas is studied through variation of welding parameters like feed rate and arc
voltage on penetration. The vessel was pressurized with argon-carbon dioxide mixture to
absolute pressure of 7,14, 29, 58, 115, & 230bars[7].The metal transfer modes were controlled
by changing the wire feed rates in the range of 3.81m/Min to 6.1mm/min. The result was found
that along with increase in pressure the arc voltage must be increased in order to get good weld
bead. Higher the pressure, density of fumes gets increases. MIG welding can be carried up to
pressure of gas 230bar.
M.AgkaKhani et al:-
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This research show studies for the material IS 2062 ES250 Mild steel and take input parameter as
wire feed rate(W),welding voltage(V),nozzle to plate distance(N),welding speed (s) and gas flow
rate (g) and the response was the relationships between the weld dilution and the five
controllable input welding parameters such as wire feed wire, welding voltage, nozzle-to-plate
distance, welding speed, gas flow rate[8]. And it was found that among main input welding
parameters the effect of wire feed rate is significant. Increasing the wire feed rate and arc voltage
increases the weld dilution where as increasing the nozzle to plate distance the welding speed
results in decreases weld dilution and gas flow rate did not affect the weld dilution.
M.Suban,J.Tusek:This research establish the influence of the shielding medium used on quantity of the filler
material melted. A comparison was made between the melting rate in welding with a solid wire
and a cored wire, respectively[9]. The melting rate in welding with the cored wire is higher than
in welding with the solid wire the condition being same. It is quite interesting that at high current
melting rates are higher in CO2.
Pawankumar, Dr.B.K.Roy:-In this study it was worked carried out on plate welds AISI 304 & Low Carbon Steel plates using
gas metal arc welding (GMAW) process. Taguchi method is used to formulate the experimental
design. Design of experiments using orthogonal array is employed to develop the welds .The
input process variables considered here include welding current,welding voltage & gas flow rate.
A total no of 9 experimental runs were conducted using an L9 orthogonal array the ideal
combination of controllable factor level was determined for the hardness to calculate the
signal-to noise ratio After collecting the data signal-to-noise ratios were calculated as used in
order to obtain optimum levels for every input parameter. The Nominal-the-better quality
characteristic is considered in the hardness prediction
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Problem Formulation
MIG is currently one of the most popular welding methods, especially in industrial
environments. It is used extensively by the sheet metal industry and by extension, the automobile
industry. There are the many type of problem found when change in mechanical properties
during welding like dimensional inaccuracies and misalignments of structural members, which
can result in corrective tasks or rework on the work piece. Due to this increases the cost of
production, waste material and leads to delays. In industries, for example, expenses for rework
such as straightening could cost money as well as time .The problem of change in properties, are
always of great concern in welding industry. In order to deal with this problem, it is necessary to
predict the amount of change in properties like hardness, impact strength, toughness,
microstructure etc. during welding operations. Once the techniques to predict the change the
properties are identified, then the problems can be controlled accordingly.
Within the welding procedures, there are many factors such as welding process type, welding
process parameters, welding sequence, preheat patterns, level of constraint and joint details that
contribute to the distortion of the welded structure. Knowing which parameters have an effect on
the quality of the weld and which parameters give the most significant effect on the weld quality
are the main issues in welding industry. There certain factors on which the selection of welding
process depends like volume of the material to be welded, types of joint obtained, base metal. In
every welding process there are certain parameters on which weld quality depends. In arc
welding also there are certain parameters on which weld quality depends. There are various
welding parameters on which various properties of weld depend. The objective of this research
is first, to weld the piece on the different parameters. Then, after to check the hardness, impact
strength, chemical composition and microstructure of steel on different parameters. The ultimate
objective of this research is to get a suitable set of welding parameters on which the properties of
the weld material and base should be almost same. There is not much difference in there
mechanical property. This will ultimately help in reducing residual stresses and distortion in
welding. So the main objective of this research is to provide a suitable set on parameters to get a
best possible weld.
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Experimental Analysis
In this chapter we are going to study the various machines and equipments like Welding
Machine, Hardness Tester, Impact Testing Machine and other equipments used during
experimentation.
Welding Machine:-We used MIG welding for joining MS and EN-31 metal with co2 gas cylinder .Model ESAB
MIGMATIC 400Amp.This is very popular in manufacturing field.
Welded Specimen:-
In this study Mild Steel SAE 350 and Stainless Steel SAE 304L Grade is used. First Step in this
study we cut the Mild Steel and Stainless Steel in to small pieces for welding the specimen. After
that we done MIG welding on these piece shown in the figure. In the figure shows that the butt
joint welding are used for this study. Before Welding LBH of pieces is (79*49*5) mm And After
.2 mm increment in length.
After the MIG welding operation we plan the weld bead on grinding machine in workshop for
various testing. These shows in below figure.(AG4 Grinder)
After preparing the various specimen, next step is to do various testing. For this various
specimen are cut from these welded pieces and perform various testing .
Testing:-
4.3.1 Hardness MeasurementTest:-There are three types of tests used with accuracy by the metals industry; they are the Brinell
hardness test, the Rockwell hardness test, and the Vickers hardness test. Since the definitions of
metallurgic ultimate strength and hardness are rather similar, it can generally be assumed that a
strong metal is also a hard metal. The way the three of these hardness tests measure a metal's
hardness is to determine the metal's resistance to the penetration of a non-deformable ball or
cone. The tests determine the depth which such a ball or cone will sink into the metal, under a
given load, within a specific period of time. There are the many type of Hardness test is used in
today’s technology but in this study Rockwell Hardness test is used.
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Rockwell Hardness Test:-Rockwell tester use small penetrators and smaller loads than does the Brinell tester. In this two
types of indenters. The Rockwell Hardness test is a hardness measurement based on the net
increase in depth of impression as a load is applied. Hardness numbers have no units. The higher
the number in each of the scales means the harder the material [20]. Hardness has been variously
defined as resistance to local penetration, scratching, machining, wear or abrasion, and yielding.
The multiplicity of definitions, and corresponding multiplicity of hardness measuring
instruments, together with the lack of a fundamental definition, indicates that hardness may not
be a fundamental property of a material, but rather a composite one including yield strength,
work hardening, true tensile strength, modulus of elasticity, and others. In the Rockwell method
of hardness testing, the depth of penetration of an indenter under certain arbitrary test conditions
is determined. The indenter may either be a steel ball of some specified diameter or a spherical
diamond-tipped cone of 120° angle and 0.2 mm tip radius, called Brale. The type of indenter and
the test load determine the hardness scale.
A load of 100 kg is first applied, which causes an initial penetration and holds the indenter in
place. Then, the dial is set to zero and the major load is applied. Upon removal of the major load,
the depth reading is taken while the minor load is still on. The hardness number may then be read
directly from the scale. The hardness of ceramic substrates can be determined by the Rockwell
hardness test, according to the specifications of ASTM E-18. This test measures the difference in
depth caused by two different forces, using a dial gauge. Using standard hardness conversion
tables, the Rockwell hardness value is determined for the load applied, the diameter of the
indentor, and the indentation depth. The hardness testing of plastics is most commonly measured
by the Rockwell hardness test or Shore hardness test. Both methods measure the resistance of the
plastic toward indentation. Both scales provide an empirical hardness value that doesn't correlate
to other.
3 Impact Test:-The property that is measured in impact test is the energy absorbed in fracturing the specimen of
standard dimensions and standard notch. This property measured in N-m or J IS also often
referred to as impact toughness or strength.
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The impact testing machine as shown in fig. is a rigid strong structure of two columns on a heavy
base. The columns carry a heavy swinging pendulum at their top which swings on frictionless
pins and a support platform at the buttons for the specimen. When the pendulum is in its vertical
position its striking edge is in level with the central cross section of the specimen. A circular disc
scale is mounted centric with the pin of the pendulum which reads its position.
Microstructure Testing:-Microstructure is defined as the structure of a prepared surface or thin foil of material as revealed
by a microscope. The microstructure of a material can strongly influence physical properties
such as strength, toughness, ductility, hardness, corrosion resistance, high/low temperature
behavior, wear resistance, and so on, which in turn govern the application of these materials in
industrial practice[21]. A microstructure is the way a material comes together on a very small
scale. An object's microstructure is not visible by the naked eye, although the patterns present at
the microscopic level may replicate at a larger level. This larger level is the macroscopic level; it
will give an observer a basic impression of the material’s underlying design. The object’s
microstructure determines the majority of its physical properties. There are four main categories
that materials fall into based on their microstructure: ceramic, metallic, polymeric and
composite.
A material’s physical structure will appear to change depending on how closely you look at it.
When an object is held at arm’s length, it looks different than if it is a hand’s width away from a
person’s face. The same is true when an object is observed under a microscope. In order to create
a standard definition of microstructure, the power of the magnification used to look at it is no
more than 25x. When the structure is observed at a higher or lower power, it looks different.
These other observable structures, particularly the smaller ones, can have a significant impact on
the properties of the object. Instead of expanding the definition of microstructure, the elements
that make up the microstructure are changed to accommodate differences in underlying structure.
4.3.5 Microstructure testing process :-
After the MIG welding operation welded pieces are cut out on the power hacksaw. The portion
cut out from the welded specimen is such that it contains weld bead with uniformity and with
high penetration. After cutting by the power hacksaw as shown above the specimen is cut in such
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a way that the weld bead remains in the centre and a good grip can be provided by the hand for
the further operations. Then a filing operation is provided to all the faces of the weld bead
sample. After filing by the help of hammery paper hamming process is carried out. In this we
use hammer paper of grade 1, grade2, grade3 and grade 4. By hamming process a very neat and
clean surface is obtained on which microstructure is to be seen. After using the hammery paper
buffing process is carried out by the help of buffing cloth on the buffing machine.
Result & DiscussionOn the basis of above experiments and research we can determine the effect of the various
process parameters on the mechanical properties of mild steel and stainless steel . During this
process we select various parameters and consider their effect on hardness, impact strength,
microstructure and chemical composition.
The various process parameters which we select in this study :-
1. Voltage
2. Current.
3. Wire feeder speed
In this dissertation I consider the effect of the above mentioned parameters on the following
properties of the mild steel and EN-31.
1. Hardness
2 .Impact strength
3. Microstructure
4. Chemical composition
The observation shows the effect of above mentioned parameters on hardness, impact strength,
microstructure and chemical composition.
Effect of various parameter on Hardness :- During the MIG welding operation wire feeder speed is selected against the voltage and current
and various readings are taken. The following table and graph shows the variation of harness
with current and voltage.
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Sr. No voltage Current Weld zone Hardness
HAZHardness
1 22 80 48 32
2 24 90 50 40
3 26 98 45 38
4 28 110 25 20
5 30 122 40 20
6 32 135 35 20
2Effect of wire feeder speed :-We took the reading by adjusting wire feeder speed during MIG welding process shown in table
below.
Sr.no Wire feeder speed
Weld zone Hardness
HAZ Hardness
Out come
1 4 48 32 Waviness of Bead
2 7 50 40 Good weld
3 10 45 38 Spatter on piece
4 13 25 20 Excessive deposit of
metal5 15 40 20 Crack on
weld zone6 19 35 20 Incomplete
fusion
Effect of Wire Feeder Speed on Impact Strength :-For examine the effect of wire feeder speed on impact strength .we took the values of wire feeder
speed and study their effect on impact strength. The following table and graph shows the
variation of impact strength with wire feeder speed.
Sr.no Wire feeder Impact strength (joule)
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speed1 4 95
2 7 110
3 10 85
4 13 76
5 15 70
6 19 65
Table 5.3 For Varying Wire Feeder Speed and Impact Strength
4 Microstructure Testing Results :-The microstructure tests are carried out on the microscopes equipped with inbuilt cameras.
During this research the microstructure of base metal, welded joint and Heat effected joint is
investigated..
The microstructure of Weld joint is shown in figure 5.10. The microstructure shown in figure
consist of martensite. Martensite named after the German metallurgist Adolf Martens. Most
commonly refers to a very hard form of steel crystalline structure but it can also refer to any
crystal structure that is formed by defussion less transformation. It includes a class of hard
minerals occurring as lath- or plate-shaped crystal grains. Martensite is present at grain
boundaries results in increase in hardness.
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Chemical composition testing results :- Weld Zone consist various types of elements like as :- Iron, Carbon, Silicon , Manganese,
Sulphar, Phosphorus, Nickel, Chromium ,Molybdenum, Copper, Cobalt Vanadiu .
Chemical composition of mild steel & EN-31:-
Average
Fe- 98.613, Fe- 98.721,
C-0.311, C-0.911,
Si-0.162, Si-0.272,
Mn-0.4977, Mn-0.570,
P-0.0365, P-0.0344,
S-0.0278, S-0.0410,
Cr-0.1087, Cr-1.231,
Mo-0.0010, Mo-0.0035,
Ni-0.0450, Ni-0.0711,
Cu-0.127, Cu-0.0618,
V-0.0059, V-0.0153,
AL-0.0116, AL-0.0260,
Nb-0.0078, Nb-0.0051,
Ti-0.0050, Ti-0.0060,
B-0.000 B-0.0001,
Co-0.0140, Co-0.0108,
W-0.0054, W-0.0104,
Sn-0.0131 . Sn-0.0022,
Pb-0.0075,
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CONCLUSION & FUTURE SCOPE
6.1 CONCLUSION :-
This research helps in determining the correct welding parameters in Gas Metal Arc Welding
process. During this research the change in hardness, impact strength ,microstructure and
chemical composition at various process parameters is investigated. The original properties and
the values of these the properties are different. This means that during welding there is always
some changes in the properties of material. . These parameters really affect the welding quality
which can be seen from above discussion. The following conclusions are derived from above
research.
• There is increase in hardness and small increment in impact strength when current
increases when we start our wire feeder speed from 2.2 to 7 according literature review.
In which observed that after wire feeder speed increase with current and voltage hardness
and impact strength 1st goes down then small increase .
• The microstructure also changes with increase in current. Originally mild steel contains
ferrite and pearlite at grain boundaries. As current increases ferrite is converted in
cementite and martensite. Due to this increment in hardness.
• There is small increase in hardness and impact strength with increase in current .
• There is small increase in hardness and impact strength with increase in voltage
SCOPE FOR FUTURE :-
• There is also a lot of future scope for Gas metal arc welding researches. During this
research only three parameters are investigated only for four properties. Similarly other
parameters can be used to find out the other mechanical properties .The effect of the
process parameters can be investigated in other welding processes also.
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References
• R.W. Messler, Principles of Welding, Processes, Physics, Chemistry, and Meallurgy,
Chapter 3, John Wiley & Sons, New York, 1999.
• http://www.wisegeek.org/what-is-mild-steel.htm
• .http://en.wikipedia.org/wiki/Carbon_steel.
• M.St. Wêglowski. Y. Huang , Y.M. Zhang (2008) “ Effect of welding current on metal
transfer in GMAW” International Scientific Journal, Vol-33 pp 49-56.
• E. Mahdi, E. O. Eltai, A. Rauf, (2014)”The Impact of Metal Inert Gas Welding on the
Corrosion and Mechanical behavior of AA 6061 T6”Int. J. Electrochem. Sci, Vol-9 pp
1087-1101.
• G. Haragopal, , P V R Ravindra Reddy, G Chandra Mohan Reddy and J V
Subrahmanyam, (2011)“Parametric design for MIG welding of Al-65032 alloy using
Taguchi Technique”, Journal of Scientific and Industrial Research, Vol. 70,, pp.844-8.
• Abbasi..K, Alam S Khan .M.J(2011),” An experimental study on the effect of increased
pressure on MIG welding arc”, International journal of applied engineering research,
Dindigul ,Vol2,No1.
• M. Aghakhani , E. Mehrdad, and E. Hayati (2011), "Parametric Optimization of Gas
Metal Arc Welding Process by Taguchi Method on Weld Dilution" International Journal
of Modeling and Optimization ,pp216-220
• M.Suban,J.Tusek (2001) “ Depedence of melting rate mig/mag welding type of shielding
gas used journal of material processing technology pp 185-192.
• Pawan Kumar (2013), “Parametric Optimization of Gas Metal Arc Welding of Austenitic
Stainless Steel (AISI 304) & Low Carbon Steel using Taguchi’s technique”, International
Journal of Engineering Research and Management research, Vol. 3, Issue 4, pp.18-22.
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