EXPERIMENTAL

INVESTIGATIONS ON

WELDING

CHARACTERISTICS OF

ALLOY STEEL(EN24)

WELDMENTS USING

TIG WELDING

PROJECT

ASSOCIATES

•ABHINAV KUMAR SINHA (10J41A0361)

•JETTEM SRIRAM (10J41A0378)

•K.VIDYADHAR (10J41A0379)

•K.BHASKAR REDDY (10J41A0381)

•KASTURIAKASH (10J41A0382)

Welding

Introduction • Welding is a fabrication or sculptural process that joins

materials, usually metals or thermoplastics, by

causing coalescence. This is often done by melting the

work pieces and adding a filler material to form a pool of

molten material (the weld pool) that cools to become a

strong joint, with pressure sometimes used in conjunction

with heat, or by itself, to produce the weld. This is in

contrast with soldering and brazing, which involve melting

a lower-melting-point material between the work pieces to

form a bond between them, without melting the work

pieces.

Welding

Parts are joined together by Fusion. Fusion is

brought about by a combination of heat and

pressure between parts being joined. In normal

welding processes very high temperatures and

little or no pressure is used.

Welding conditions • Smooth joint surfaces that match each other

• Surfaces clean and free from oxides, grease and dirt.

• Metals to be joined have same microstructure

Manual Metal Arc (MMA)

Metal Arc Gas Shielded (MAGS) MIG

Tungsten Arc Gas Shielded (TAGS) TIG

Submerged Arc Welding (SAW)

Types of Electric Arc Welding

Welding power source

•Positive (+) lead is connected to the torch

•Negative (-) lead is connected to the work piece

Sheilding Gas

• Purpose of shielding gas is to protect the weld area from the contaminants in the atmosphere

• Gas can be Inert, Reactive, or Mixtures of both

• Argon, Helium, and Carbon Dioxide are the main three gases used in MAGS

Tungsten Arc Gas Shielded (TAGS) TIG

TIG is similar to MMA in that

heat for welding is produced

by forming an arc between a

metal electrode and the

workpiece

Applications Used in joining magnesium and

Aluminium, stainless steels etc.

In the TIG process the arc

is formed between a

pointed tungsten

electrode and the work

piece in an inert

atmosphere of argon or

helium. The small intense

arc provided by the

pointed electrode is ideal

for high quality and

precision welding. The electrode is not consumed during welding. When filler metal

is required, it must be added separately to the weldpool. There

are two currents one for starting the arc the other switched on

using a trigger or foot pedal, this is a high frequency current

to maintain the arc, this is generated by a separte unit.

Advantages

• Superior quality welding

• Can be used in mechanised systems

• Used to weld aluminium and stainless

steels

• Free of spatter

• Low distortion

Equipment used in TAGS Power source

Electrodes

TIG must be operated with a

constant current power source -

either DC or AC

Electrodes for DC welding are normally pure

tungsten. In AC welding, as the electrode will be operating

at a much higher temperature, It should be noted that

because of the large amount of heat generated at the

electrode, it is difficult to maintain a pointed tip and the end

of the electrode assumes a spherical or 'ball' profile.

Sheilding Gas

• Argon

• Argon + Hydrogen

• Argon/Helium

Helium is generally added to increase heat

input (increase welding speed or weld

penetration). Hydrogen will result in cleaner

looking welds and also increase heat input,

however, Hydrogen may promote porosity

or hydrogen cracking.

Shielding gas is selected according to the material being welded.

Filler Rod

Filler rods are used when additional filler metal is

required in the weld area they come in different

diameters.

Alloy steel • Alloy steel is steel that is alloyed with a variety of elements in total

amounts between 1.0% and 50% by weight to improve its mechanical

properties. Alloy steels are broken down into two groups: low-alloy

steels and high-alloy steels..Most commonly, the phrase "alloy steel"

refers to low-alloy steels.

• Every steel is truly an alloy, but not all steels are called "alloy steels".

Even the simplest steels are iron (Fe) (about 99%) alloyed

with carbon (C) (about 0.1% to 1%, depending on type). However, the

term "alloy steel" is the standard term referring to steels

with other alloying elements in addition to the carbon. Common

alloyants include manganese (the most common one), nickel,

chromium, molybdenum, vanadium, silicon, and boron. Less common

alloyants

include aluminum,cobalt,copper,cerium,niobium,titanium,tungsten,

tin, zinc, lead, and zirconium.

Alloy steel EN24

EN24 is a high quality, high tensile, alloy steel . Usually supplied

readily machine able in ‘T’ condition, it combines high tensile

strength, shock resistance, good ductility and resistance to wear.

A nickel chromium molybdenum steel with high strength and

toughness. Used for gears axles and high strength studs. Supplied as

rolled, annealed and hardened and tempered. Supplied as black round

or square bar and bright round or square, and hexagons.

EN24 is available from stock in round bar, flat bar and plate.

EN24 alloy steel properties • EN24 is usually supplied in the finally heat treated condition

(quenched and tempered to "T" properties) up to a limiting ruling

section of 250mm, which is superior to grades 605M36, 708M40 or

709M40 .

• EN24 is a very popular grade of through-hardening alloy steel, which

is readily machinable in the "T" condition. (Refer to our machinability

guide). EN24T is most suitable for the manufacture of parts such as

heavy-duty axles and shafts, gears, bolts and studs. EN24T can be

further surface-hardened typically to 58-60 HRC by induction or

nitride processes, producing components with enhanced wear

resistance.

• In addition to the above, EN24T is capable of retaining good impact

values at low temperatures, hence it is frequently specified for harsh

offshore applications such as hydraulic bolt tensioners and ship borne

mechanical handling equipment.

Tensile test

• Tensile testing, also known as tension testing, is a

fundamental materials science test in which a sample is

subjected to a controlled tension until failure. The results

from the test are commonly used to select a material for an

application, for quality control, and to predict how a material

will react under other types of forces. Properties that are

directly measured via a tensile test are ultimate tensile

strength, maximum elongation and reduction in area. From

these measurements the following properties can also be

determined: Young's modulus, Poisson's ratio, yield strength,

and strain-hardening characteristics. Uniaxial tensile

testing is the most commonly used for obtaining the

mechanical characteristics of isotropic materials.

For anisotropic materials, such as composite

materials and textiles, biaxial tensile testing is required.

TENSILE TESTING

MACHINE

Microstructure test using (SEM)

Scanning electronic microscope)

• A scanning electron microscope (SEM) is a type of electron

microscope that produces images of a sample by scanning it with a

focused beam of electrons. The electrons interact with atoms in the

sample, producing various signals that can be detected and that contain

information about the sample's surface topography and composition.

The electron beam is generally scanned in a raster scan pattern, and the

beam's position is combined with the detected signal to produce an

image. SEM can achieve resolution better than 1 nanometer.

Specimens can be observed in high vacuum, in low vacuum, and (in

environmental SEM) in wet conditions.

• The most common mode of detection is by secondary electrons emitted

by atoms excited by the electron beam. The number of secondary

electrons is a function of the angle between the surface and the beam.

On a flat surface, the plume of secondary electrons is mostly contained

by the sample, but on a tilted surface, the plume is partially exposed

and more electrons are emitted. By scanning the sample and detecting

the secondary electrons, an image displaying the tilt of the surface is

created.

MICROSTRUCTURE OF EN24 ALLOY

CONCLUSION

Welding of EN24 specimen is done using TIG welding setup and

destructive and non destructive tests are performed to determine the

characteristics of the weldments.