International Journal of Engineering Trends and Technology (IJETT) – Volume-41 Number-5 - November 2016

ISSN: 2231-5381 http://www.ijettjournal.org Page 300

A Study on Reduction of Welding Fumes in

GMAW for Various Shielding Gas Mixtures N.Sampathkumar

1, B.Parthiban

2, N.Thangavel

3

#Assisstant professor & Department of Mechanical Engineering & Jay Shriram group of Institutions

Avinashipalayam, Tirupur, India.

Abstract - This study was performed to

investigate the Fume Generation Rates (FGR’s) and

the effect of fumes on welders working i n a

c o n f i n e d working environment. In t h i s work,

suitable shielding gas is to be selected for GMAW

process. Experimentally the fume emission test has to

be done t o determine the contents in the fumes.

For various shielding gas mixtures, the fume content

is to be determined. By using the reducing agents,

FFR (Fume Formation Rate) is to be reduced for the

selected shielding gas mixtures.

Keywords - Gas metal arc welding, Gas

emissions, fume formation rate, shielding gas

mixtures.

I. INTRODUCTION

Welding is one of the most widely used

fabrication methods. One particular method that is

often utilized within the fabrication industry is arc

welding. The main concern in the past is the quality

control over joints and the productivity. The main

interest in welding industry is in the area of fumes

generated during welding processes, as the fumes are

known to be potentially hazardous to welder’s health.

The main aim is to clearly identify the factors which

influence welding fume levels in the breathing zone

and to evaluate the possibility of controlling exposure

to fumes. Welding fumes have posed a threat to health

since the first coated electrodes were introduced in the

early nineteen hundreds. Biological effects on the

health of the welders such as respiratory problems,

acute illness and the chronic threat of the fumes

containing carcinogenic substances have played an

important role in increasing the industrial awareness of

the health risks faced by welders. Some adverse health

effects are metal fume fever (from zinc exposure) and

irritation to lungs from ozone, to more severe

problems such as exposure to substances such as

beryllium. Shielding gases has different physical and

chemical properties, it has low ionization potential,

thermal conductivity, which affects filler metal

deposition rate and efficiency, welding fume

generation rate, weld metal mechanical properties. The

filler, base metal and base metal coating used during

welding operations and the subsequent gases formed

during the welding process release small, solid

particles into the air creating a plume. This plume is

called “welding fumes”. The welders in construction

industries are exposed to fumes which largely affect

the welder’s health and can cause serious health

problems. When inhaled welding fumes can enter the

lungs, bloodstream, brain nerve cells, spinal cord and

other organs and can cause both short and long-term

health effects. Methods of controlling fume at the

source by optimizing welding parameters, by selecting

consumables do not solve the problem completely.

The initial method to remove the contaminants from

breathing zone of the welder is by means of

ventilation. Ventilation is a mechanism of controlling

the quality of air within a working environment.

II. SPECIMEN AND EXPERIMENTAL

A. Materials

The studying material, aluminium 6063 which is

used in aircraft and military applications. Then IS

2062 which is having low carbon content is used in the

structural fabrications. The respective chemical

compositions of the above mentioned materials are

given the Table 1.

Table: 1.1Chemical Composition of Al 6063

ELEMENT GRADE 6063

MIN MAX

Si 0.2 0.6

Fe - 0.35

Cu - 0.1

Mn - 0.1

Mg 0.45 0.9

Cr - 0.1

Al - Balance

International Journal of Engineering Trends and Technology (IJETT) – Volume-41 Number-5 - November 2016

ISSN: 2231-5381 http://www.ijettjournal.org Page 301

Table: 1.2 Chemical Composition of IS 2062: (in % max

Values)

ELEMENT GRADE IS 2062

MIN MAX

C 0.23 0.25

Mn 1.5 1.55

S 0.045 0.05

P 0.045 0.05

Si 0.40 0.454

B. Basic Characteristics of Shielding Gases

1) Argon

Argon is a gas without color, odor and taste. It is

not flammable, non-toxic and it does not react with

other elements to form compounds. It is present in the

atmosphere only to the extent of 0.934%. It is 1.38-

times heavier than air and provides very efficient and

stable protection of the arc and molten metal. Because

of its low ionization energy, arc ignition under

protection of argon is highly reliable. Thermal

conductivity is very low which affects both the arc

shape and the weld shape. It is used as a basic

shielding gas with O2, CO2, He, H2 additions or as an

addition to CO2.

2) Carbon dioxide

Carbon dioxide has a very good heat transfer

properties and produce a very deep weld but somewhat

unstable arc and due to its reactivity and intense

spatter. Due to the presence of dissociated oxygen, the

weld zone has oxidizing properties and thus produces

more slag. The argon addition inhibits sputtering and

increases the width and depth of weld penetration. For

welding of stainless steels where carbon content

control is required an argon-helium blend with 1-2%

of CO2 can be used. Pure CO2 usage is limited to

short circuit and globular transfer welding.

3) Oxygen

Oxygen enhances arc stability and reduces the

surface tension of the molten metal, increasing wetting

of the solid

Metal. Oxygen is used for spray transfer welding of

mild carbon steels, low alloy and stainless steels and

also increases the amount of slag. Excessive oxygen,

especially when used in application for which it is not

prescribed can lead to brittleness in the heat affected

zone. Argon-Oxygen blends with 1-2% oxygen are

used for austenitic stainless steel where argon-CO2

cannot be used due to low content of carbon in the

weld.

4) Argon-Oxygen-Carbon Dioxide

Shielding Gas Mixtures Gas mixtures of argon

with up to 20% carbon dioxide and 3% to 5% oxygen

are versatile. It gives adequate shielding and then the

desirable arc characteristics for both spry and short-

Circuiting modes of Gas Metal Arc Welding.

5) Carbon Dioxide

Carbon dioxide is a reactive gas most commonly

used in its pure form for the gas metal arc welding of

carbon and low alloy steels. It is the only shielding gas

that can be used alone for welding. The general

characteristics are higher welding speed, greater joint

penetration and low cost. With carbon dioxide as

shielding gas, the metal transfer mode is either short-

circuiting or globular.

In overall comparison to the argon rich shielding

arc, the carbon dioxide shielded arc produces weld

bead of excellent penetration with rough surface

profile and less wetting action at the sides of weld

bead due to buried arc. Mechanical properties get

affected because of the oxidizing nature of the arc.

III. EXPERIMENTAL WORK

For measurement of the fume gases a closed

environment is to be needed, so that a fume hood is to

be designed and is fabricated. The fume hood used in

the experimental procedure is shown in fig 1.

Fig 1 Fume Hood Chamber

Fume formation rate (FFR) and gases emissions

are to be measured using the standard procedures

described in EN ISO 15011-2[1]. A turn table is used,

upon which the plates are to be fixed and the air flow

rate throughout the chamber is maintained at 100 m3/h.

International Journal of Engineering Trends and Technology (IJETT) – Volume-41 Number-5 - November 2016

ISSN: 2231-5381 http://www.ijettjournal.org Page 302

The fume emitted is collected on a pre-weighted fibre

filter of 240 mm diameter which is then re-weighted to

give the total weight of fumes produced. It is then used

along with the arc time to calculate the fume formation

rate. The arc time to be employed is 60s.

A detailed study of the influence of six shielding

gas mixtures (Ar, CO2, Ar + 8% CO2,Ar + 2%O2,Ar +

8% CO2 + 2%O2, Ar + 18% CO2 + 2%O2)on the

features of GMAW process was aimed at:

Analyzing the FFR (Fume Formation Rate).

Characterizing the mechanisms responsible for

the FFR.

For this purpose fume reducing agent is to be

added with along with the shielding gas mixtures and

is to be tested.

IV. RESULTS AND DISCUSSION

A. Welding fume generation rates

Many factors influence welding fumes

generation, including filler metal, base metal

composition, operating parameters and shielding gas.

High argon blends are less reactive than pure CO2 and

generally produce less welding fumes under similar

operating conditions. But lower fume generation

doesn’t always equal lower exposure, so be sure to

conduct measurements to ensure compliance with

applicable permissible exposure limits.

B. Influence of filler wire

To analyses the influence of different types of

filler wires on fumes produced during GMAW, four

carbon-manganese have to be selected. The results of

the test are presented in terms of fume generation rate

instead of fume formation rate. In order to calculate

the fume generation rate the following expression is to

be used.

FGRfume = MFume/Mfiller metal, [mg/kg]

Where

Mfume mass of the fume [mg]

Mfiller metal mass of filler metal- deposition, [kg]

The calculation of the mass of the deposited metal was

done according to the expression:

Mfiller metal = Vwire * γ * 10-3

,[kg]

Where Mfiller metal = mass of filler metal-deposit, [kg]

Vwire volume of wire (filler metal used in test), [dm3]

γ weight by volume, [kg/m3]

Vwire =0 .785d2 * v * t * 10

-3 , [dm

3]

Where, d is the wire diameter, mm; v is the wire

speed, m/s and t the time of test, s.

C. Influence of shielding gases

In order to study the influence of shielding gas

mixture two sets of experiments were made; one using

a metal green wire and the other using a solid wire

coated with copper. In order to achieve smaller fume

formation rates with high productivity, the user can

decide on cored wires and binary gas mixtures.

Minimum values can be achieved by reducing the CO2

content in the mixtures and using metal cored wires,

which lead to FFR very similar to solid wires and

higher productivities.

Shielding gas mixtures with higher CO2 contents

leads to higher fume generation rates. This fact is

related to:

– Decrease of arc stability. There is a higher

amount of spatter released during welding, which is

projected for

regions outside the influence of the shielding gas and

are oxidised and vaporised.

– Increase of thermal conductivity of the mixture,

which promotes a reduction of the conduction zone,

being almost all the generated heat concentrated in that

region. Therefore, there is a local and intense heating

of the molten droplet that enters rapidly in ebullition.

– Increase of the active (CO2) content of the

mixture. When the amount of carbon dioxide in the

mixture increases, the reaction rate that occurs in the

weld pool also increases. This is the result of the

decomposition

of CO2 into CO and O2.

– Oxidising content of the mixture. This increases

the arc temperature as a result of the exothermic

reactions between oxidising elements and the weld

pool elements.

V. CONCLUSION

Control of fumes at the source, by modification

of process, procedures or consumables, can be used for

existing control strategies. A systematic approach to

fume control by GMAW process modification

contributes to a reduction of fume emission and

provides a healthier environment for welders. This

paper attempts to point out ways of reducing the

potential harmful effects of gas metal arc welding

processes.

The expected results are based on the following

categories:

A. Relative to the shielding gas mixtures

– The NO addition to the shielding gas mixtures

also affects FFR and nitrogen oxide emission. The

fume formation rate increases and nitrogen oxides

emissions increase with the addition of NO to the

shielding gas.

– The fume formation rate increases with the

increase of CO2 and O2 in the mixture.

B. Relative to the filler wires – Metal cored or solid wires with shielding gas

mixtures with low CO2 content gives lower fume

emissions.

International Journal of Engineering Trends and Technology (IJETT) – Volume-41 Number-5 - November 2016

ISSN: 2231-5381 http://www.ijettjournal.org Page 303

– “Green” wires are quite “environmentally

friendly”, which leads to lower emissions than

conventional flux cored wires.

– For solid wire with or without copper coating

has no significant differences, although FGR with the

wire without Cu coating has slightly lower fume

generation rate

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