Ministry of National Education [603907]

1
Ministry of National Education
University Polytechnic Bucharest
Faculty of Material Science and Engineering

A STUDY OF THE EFFECTS OF SOME TYPES OF
WELDING ON THE MECHANICAL PROPERTIES OF
304 AND 316L AUSTENITIC STA INLES S STEEL
SHEETS

Supervisor PhD Student: [anonimizat].Dr.Ing Ion Ciuca Alaa Abou Harb

2016

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Contents
1. Overview of alloy 304 and 316L
1.1. Introduction ––––––––––––––––––––––– 2
1.2. Applications ––––––––––––––––––––––- 2
1.2.1. Alloy 304 ––––––––––––––––––––– 2
1.2.2. Alloy 316L –––––––––––––––––––– 3
2. The influence of various factors on weldability for alloys 304 and 316L
2.1. The effect of alloying components –––– ––––––––––- 5
2.2. The effect of elements in weld zone –––––––––––––– 5
2.3. The effect of alloying elements ––––––––––––––– 6
2.4. The effect of alloying elements on weld structure –––- ––––– 6
2.5. Welding properties of 304 and 316L –––––––––––––- 6
3. Welding Processing for alloys 304 and 316L Austenitic Stainless Steel
3.1.Shielded Metal Arc Welding (SMAW) ––––––––––––– 8
3.2.Gas Tungsten A rc Welding (GTAW) or (TIG) –––––––––– 9
3.3.Gas Metal Arc Welding (GMAC) ––––––––––––––– 11
3.4.Submerged Arc Welding (SAW) ––––––––––––––– 11
3.5.Plasma Arc Welding (PAW) ––––––––––––––––– 12
3.6.Electron Beam Welding (EW) –––––––––––––––– 13
3.7.Laser Beam Welding (LW) –––––––––––––––––- 14
4. Some studies that show the influence of som e welding types on alloys 304 and
316L in different environments
4.1.Effect of welding on the corrosion ––––––––––––––– 17
4.2.Effect of welding parameters on alloys 304 and 316L ––––––– 18
5. Experimental research
5.1. Experime ntal procedures
5.1.1. Materials ––––––––––––––––––––- 20
5.1.2. Tensile testing –––––––––––––––––– 21
5.1.3. Hardness testing –––––––––––––––––– 26
5.1.4. Welding process es ––––––––––––––––- 28
5.2. Mechanical properties for welded specimens
5.2.1. Tensile testing ––––––––––––––––––- 29
5.2.2. Hardness testing –––––––––––––––––– 31
5.3. Comparison of results

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5.3.1. Tensile properties ––––––––––––––––– 32
5.3.2. hardness properties ––––––––––––––––- 37
5.4. Conclusions ––––––––––––––––––––––- 40
6. Refe rences ––––––––––––––––––––––––––– 41

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OVERVIEW OF ALLOYS 304 AND 316L

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1. Overview of alloy 304 and 316L
1.1. Introduction
Alloy 304 is the most commonly used types of austenitic stainless steel and versatile,
because it has a good mechanical properties as susceptibility formation and welding , so
this kind serves the industrial sector in a wide range. [1].
Alloy 316L is developed for a lloy 304 / 304L, it is characterized by excellent
mechanical properties, and it often called nickel, chromium and molybdenum alloy,
This alloy is used in the marine environment, and at low temperatures. It has excellent
corrosion resistance in the welding conditions [2].
Fig. 1.1 shows Chart for world production of stainless steel from 1970 to 2010, this
shows the growing demand and importance which occupied by stainless steel among
different types of materials [3].

Fig. 1.1 World production of stainless steel [3]
1.2. Applications
1.2.1. Alloy 304
This alloy is used in the following fields:
 Food processing equipment, particularly in beer brewing, milk processing and
wine making.
 Architectural paneling.
 Chemical containers, including for transport
 Heat Exchangers.
 water filtration
 Threaded fasteners
 Springs [1]

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1.2.2. Alloy 316L
 The basic material in the manufacture of pressure vessels, tanks, heat
exchangers, piping systems, valves and pumps
 In the field of food industry equipment.
 In the maritime field.
 In the field of pharmaceutical industry equipment.
 Power Generation equipment.
 Water Treatment equipment. [2].
Fig. 1.2 shows Chart for product forms of stainless steel. we notes that the sheets are
the most productive among the products by 60% and our st udies in this field
specializes in knowledge changes the characteristics of these products in the welding
conditions[3].

Fig. 1.2 product forms of stainless steel [3]

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THE INFLUENCE OF VARIOUS FACTORS ON
WELDABILITY FOR ALLOYS 304 AND 316L

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2. The influence of various factors on weldability for alloys
304 and 316L
2.1. The effect of alloying components
Based on the studies that have worked in this field, we note the existence of two types
of elements that form the ferrite (such as chromium, molybdenum, silicon and
niobium), or that form the austenite (such as nickel, manganese, carbon and nitrogen),
according to temperature changes. Affected of these elements on a nature of the welding
zone can be a great as shown in previous studie s. [4].
We can see the influence of elements that formed the ferrite and the austenite in the
following chart Figure 1.3. It is benefit us to estimate the structure of weld metal.

Figure 1.3. A Schaeffer diagram of the worked example [4]
2.2. Tte e ffect of elements in weld zone
Latest studies show that the most important element in the welding stainless steel is
chromium, which tends to union with oxygen and carbon, so it has to be taken into
account during the welding of stainless steel.
As for the other el ements also effect on the Properties of steel welded, oxygen in the
air binds with the molten metal to form a thick layer of oxide.
Carbon interacts with chromium and that can lead to carburization, this process reduces
the corrosion resistance in welded m etal. Hydrogen Causes porosity in welding zone,
while copper and lead can lead to brittleness in the basic metal [5].

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2.3. The e ffect of alloying elements
Reveal studies show that the steel consists of alloying elements where there are
aluminum , silicon, sulfur , phosphorus , selenium , nickel , manganese and
molybdenum . They cause effects on base metal, for example, presence of silicon lead
to melt the metal and make it more flow, either sulfur, phosphorus and selenium added
to steel to improve the mechanical properties but that lead to the decreasing of
weldability and increasing the porosity. [5].
2.4. The e ffect of alloying elements on weld structure
latest studies show that it possible to controll the structure of stainless steel through the
basic components o f the elements of alloys which used in the alloy where help to stable
of austenite, which is important to maintain the strength of the metal after welding.
the elements that help to stable austenite such as chromium, molybdenum and nickel,
carbon, nitrog en and manganese . [5].
2.5. Welding properties of 304 and 316L
latest studies show that during the welding of stainless steel, the temperature of the
metal take levels that affects to the crystal structure near the welding zone of the
elements, all of which aff ect the final shape of welding, mechanical properties and
corrosion resistance which relies on a range of factors, including the alloy content ,
thickness , and metal fillers etc. But there are three main zones which determine the
welding zone. The region containing the weld metal and basic metal, heat affected zone
and the area affected by the heat from the base metal or did not affect [5]. The following
figure shows that fig ure 1.5.

Figure 1.4 welding zones [4].

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WELDING PROCESSING FOR ALLOYS 304
AND 316L

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3. Welding Processing for alloys 304 and 316L Austenitic
Stainless Steel
Intruduction
Reference studies show the presence of tow methods for welding stainless steel. The
first one is fusion welding and the second one is resistence welding, however the most
common method is fusion welding between the electrode welding and the piece to be
welded. Through generating an electrical arc with a high v oltage. fusion welding is
divided into several types, evrey tybes is differnt from the other in the way it generate
the electrical arc.[4] Those type are:
 Shielded metal arc welding (SMAW)
 Gas tungsten arc welding (GTAW) or (TIG)
 Gas metal arc welding (GM AW) or MIG / MAG welding
 Submerged arc welding (SAW)
 Plasma arc welding (PAW)
 Electron beam welding (EW)
 Laser beam welding (LW)

3.1. Shielded Metal Arc Welding (SMAW)
This is the simplest kind of welding processes. It is a manual welding that means the
presence of electrode welding that is covered with a substances which protects the
welding area from external factors when starting the process, and formation of electric
arc between the electrode welding and the piece that is to be welded. The mod of
work depend one welding the metal locally and cover it with slag which has effect of
protecting the metal from oxidation process. This process is valid for conducting
welding in all circumstances and in any environment, and it is the most common type
used shor t or long term [4]. Fig. 1.5 demonstrates welding zone of this kind. Fig. 1.6
demonstrates the mechanism of this kind.

Fig. 1.5 welding zone of shielded metal arc welding [4]

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Fig. 1.6 the mechanism of shielded metal arc welding [6]
3.2. Gas Tungsten Arc Welding (GTAW) or (TIG)
It’s a method of welding with the use of filler material in the firm of a hand – held
rod. It is a mechanical way that has so many features. We use this method in welding
stainless steel, aluminum and its alloys and magnesium and i ts alloys. Thickness that
can be welded in this method vary between 0.5 mm to 3 mm. using this way in
welding alloys 304 and 316 is still under study in our scientific research.[4]. Fig. 1.7
demonstrates the mechanism of this kind. Fig. 1.8 demonstrates welding zone of this
kind.

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Fig. 1.7 the mechanism of gas tungsten arc welding [6]

Fig. 1.8 welding zone of gas tungsten arc welding [4]

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3.3. Gas Metal Arc Welding (GMAW) or MIG / MAG welding
This method has emerged in a developed from of the pervious tow meth ods. It depends
on generating a welding arc with the existence of an inert gas which is argon gas (MIG),
or the existence of an active gas which is Co 2 (MAG).
This method is based on basic parameters that can be controlled according to the
material that is to be welded such as: measuring the electrode, voltage, electric current,
wires feed speed, preservative gas flow rate, and welding angle. [4]. Fig. 1.9
demonstrates the mechanism of this kind.

Fig. 1.9 the mechanism of gas netal arc welding [6]

3.4. Submerged Arc Welding (SAW)
This method is used for stainless steel welding and it is based on welding along with an
external covering procedure using a material called ( flux ) that basing from the slag for
protecting the metal, and improving the electric arc, and controlling the flow of
properties of the molten weld metal. But this type of welding has a problem which is
rise of temperature and the reduction in the rate of cooling. All this will lead to an
increase in rigidity and the ability fir cracking [7]. Fig. 1.10 demonstrates the
mechanism of this kind.

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Fig. 1.10 the mechanism of submerged arc welding [6]

3.5. Plasma Arc Welding (PAW)
This way uses plasma gas in the presence of gas protection with an inert gas. During
this process, the plasma gas flows around the electrode that is made of tungsten, then
the inert gas flows in around to protect the welded area during the local smelting
process. The advantages of this method is that it is very fast and can be used in butt
welds in thickness of up to 8mm. it is also characterized by the occurring of a local
fusion ( 0.03 mm). This way is used in welding and cutting the alloys 304 and 316L in
our research. [4]. Fig. 1.11 demonstrates the mechanism of this kind.

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Fig. 1.11 the mechanism of plasma arc welding [6]

3.6. Electron Beam Welding (EW)
The mechanism of the electron beam welding depends on a local smelting through
high-speed electrons, which shocked a piece of work with its all the kinetic energy, the
electron beam is able to weld thicknesses ranging from 0.01 mm up to 150 mm of
stainless steel, and up to 500 mm of aluminum. Electron beam can be used in welding
dissimilar metals. [5, 6]. Fig. 1.12 demonstrates the mechanism of this kind.

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Fig. 1.12 the mechanism of electron beam welding [6]
3.7. Laser Beam Wel ding (LW)
The mechanism of the laser beam welding depends on a local smelting through high
energy of laser beam for piece of work. LW is used in wide fields such as welding of
aviation equipment, in the field of space, welding of communications equipment a nd
for joining a very small pieces.
Laser welding is characterized by the possibility of welding different materials, HAZ
is very tight and the possibility joining small pieces. The high cost of this type make it
only use in the private industrial sectors. [4, 6]. Fig. 1.13 demonstrates the mechanism
of this kind.
Laser beam welding can be used with another method of welding such as plasma or
MIG, as shown in Fig 1.14.

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Fig. 1.13 the mechanism of laser beam welding [4]

Fig 1.14. Principle of laser/MIG welding [4]

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SOME STUDIES THAT SHOW THE INFLUENCE
OF SOME WELDING TYPES ON ALLOYS 304
AND 316L IN DIFFERENT ENVIRONMENTS

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4. Some studies that show the influence of some welding
types on alloys 304 and 316L in different environments
4.1. Effect of welding on the corrosion
Latest studies in the field of welding for alloys 304 and 316L suggest that the most
important region is heat affected zone (HAZ), as we talked earlier, there are three areas
when we want to study the welding: the heat affected zone, the zone of weld metal and
the zone of base metal. Which it showed that the alloy 316L has greater resistance to
pitting corrosion compared to alloy 304 when welding in a method (MIG) and the
presence of an inert gas (argon ), but for the alloy 304 can be improve the corrosion
resistance by conducting heat treatment and that of the region containing the weld metal
[8].
Other Latest studies in the field of welding for alloys 304 show that affected of the
microstructure when we lding. In this regard, one of the studies conducted welding
comparison between (GTAW) and (LBM), where after conducting tests, they notice
when used a technique (GTAW) to alloy 304, the most affected areas are the heat
affected zone and the zone of weld me tal more than the base metal for pitting corrosion.
But technology (LBW) improve these areas to the pitting corrosion resistance. For
cracks start of the weld metal zone and extends into Surrounding areas, it is likely that
by using technology (GTAW) as a result of high thermal input and low cooling rate,
which led to hardening areas and the occurrence of chromium -free zones that helps to
occurrence stress corrosion cracking (SSC) [9].
One study showed in the field of welding for alloys 304 and 316L that th e most problem
common is sensitization in the HAZ, which leads to intergranular corrosion, due to the
precipitation of carbides at the grain boundaries, so we have to be careful when
conducting welding, taking into Consideration the occurrence of sensitiza tion, which
can happen above 400ο c. [10]. But alloy 316L has the best intergranular corrosion
resistance compared with alloy 304[11].
Reveal studies show, there are also other problems related with corrosion, such as the
migration of chromium to the grain boundaries and formation the iron – δ when these
boundaries in the smelting area, all this affects the corrosion behavior when conducting
of welding, this is other important point which must be taken into consideration. [12,
13]. Latest studies show to be consider the thermal input parameters which significantly
effect on the corrosion behavior. [9.14].
It was found in one of studies that used the laser welding of alloys 304 and 316L, that
the alloy 316L has remained the province of the austenitic structure compared with the
alloy 304 which is found in its structure, in addition of austenite, small amount of
ferrite, where all of these effect on the final characteristics of welded metal in terms of
corrosion resistance (pitting corrosion) in different enviro nments. [15].

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4.2. Effect of welding parameters on alloys 304 and 316L
Latest studies show about laser beam welding for alloys 304 and 316L, so LBW
includes many varieties; laser power, welding speed and defocusing distance and type
of shielding gas. Each of th ese may have a significant affection two factors: 1) heat
flow. 2) Fluid flow which in turn affect: penetration depth, shape and the final solidation
structure of the fusion area. The second and the third will have a considerable effect on
the characterist ics of the weldment. [16, 17].
The higher the laser power increased, the higher the penetration depth increased. But it
has less effect on weld profile [18].
Welding speed has its important effect on size and shape of the fusion zone, pitting
corrosion and the hardness of the metal. [18, 19].
An increase in weld depth / width ratio is shown as a result of increase in welding speed.
And therefore a decrease in the fusion area will be noticed. [18].
It is very important for the weld quality in terms of fusion and profile to minimize heat
and optimize energy density. [18]. to get an acceptable weld profile, helium is more
influential than argon. [18].
Change in heat input made no noticeable effect on fusion zone composition. A finer
solidification structure is resulted due to low heat input. [18].
For all welds, an austenitic structure that has no solidification cracking, was obtained.
This could be due to primary ferrite or mixed mode solidification based on Suutala and
Lippold diagrams. However, mechanical pro pertied at room temperature were not
affected by heat input [18].

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EXPERIMENTAL RESEARC H

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5. Experimental research
Our aim was to observe mechanical characteristics variations on welded samples which
were previously tensile tested. The tested samples, stainless steel type 304 and 316L,
were obtained from cutting on longitudinal and transverse direction in respect to th e
rolling direction of the steel sheet, and, on each directions two specimens were tested:
one in which a 5mm hole was drilled and one full specimen, Fig. 1. 15 showing the
schematics of the samples used.
From the tensile tested specimens the necked regions were cut and the specimen
remainder welded together using two methods: TIG and MMAW, then tensile tested
again.
The results allowed us to compare the mechanical characteristics and find stressed
regions on the test samples and decide on which method would be most convenient.

Fig. 1 .15 Tensile specimens used in research: full speci mens and specimens with a central 5
mm radius hole
5.1. Experimental procedures
5.1.1. Materials
From sheets, 2000×1000×3 mm, standard tensile specimens parallel and
perpendicular to the rolling direction were cut using a laser and on some specimens a
hole with a 5 mm radius was drilled using a conventional drilling machine in order to
mimic a defect.
The material used was 3 mm thick 304 and 316L stainless steels sheets. The chemical
compositions of the alloys are shown in Table 1.1.
Table 1.1 Chemical composition of the alloys (wt. %).
AISI C Si Mn P S Cr Ni Mo Cu
304 0.018 0.369 1.84 0.014 0.0007 18.29 8.3 0.328 0.415
316L 0.018 0.406 1.88 0.019 0.0029 17.04 9.55 1.85 0.391

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5.1.2. Tensile testing
The samples were tested in tension using a 300 KN servo -hydraulic universal testing
machine and, on failed specimens.
The ultimate tensile strength, yield tensile strength, Area of reduction, and elongation
of the used material are presented in Table 1.2. Standard specimens are used for tensile
testing of alloys, and that the presence with holes and without holes.
Fig. 1.16 indicate to Standard tensile specimens of AISI 304 and AISI 316L austenitic
stainless steels.
Fig. 1.17 indicate to Standard tensile specimens of AISI 303 and AISI 316L austenitic
stainless steels after tensile testing. Tensile curves for specimens with holes and wit hout
holes are presented in fig. 1.18 and fig. 1.19.
Table 1.2 Mechanical properties of AISI 316L and AISI 304.
specimens Tensile strength
Rm (Mpa) Yield strength
Rp 0.2 (Mpa) Elongation
(%) Reduction in area
(%)
Full specimens
T 304 745 421 51 67
L 304 760 425 45 68
T 316L 774 437 42 69
L 316L 774 458 41 70
Specimens with holes
HT 304 610 407 17 59
HL 304 627 441 16 57
HT 316L 630 402 12 73
HL 316L 621 404 12 68

Sample coding reflects the alloy, 304 or 316L and the sample orientation,
T – Transverse and L – longitudinal and H denotes the hole presence within specimen .

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Fig. 1.16 Standard tensile specimens of AISI 303 and AISI 316L austenitic stainless steels

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Fig. 1.17 Standard tensile specimens of AISI 303 and AISI 316L austenitic stainless steels
after tensile testing

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(A)

(B)

(C) (D)
Fig. 1.18 Tensile curves for specimens (A) T 304 (B) L 304 (C) T 316L (D) L 316L

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(E)
(F)

(G) (H)

Fig. 1.19 Tensile curves for specimens (E) HT 304 (F) HL 304 (G) HT 316L (H) HL 316L

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5.1.3. Hardness testing
Rockwell C hardness was determined on several regions after the tensile testing for
specimens without central holes and specimens with central holes. Five positions were
chosen to measure the hardness in both directions, the right -wing and left -wing. Shown
in Fig. 1.20 and fig.1.21. The results of this hardness testing (HRC) are present in the
table 1.3.

Fig. 1.20. Points of hardness testing for specimens without central holes

Fig.1.21. Points of hardness testing for specimens with central holes

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Table 1.3 Hardness testing (HRC) for specimens AISI 316L and AISI 304.
T 304 L 304
Nr Left Right Nr Left Right
1 5.12 17.67 1 22.38 19.79
2 16.26 20.52 2 22.48 15.20
3 15.59 17.40 3 18.61 18.66
4 18.87 19.55 4 18.58 19.24
5 16.17 17.10 5 15.64 16.43
L 316L T 316L
1 29.80 30.57 1 30.69 27.77
2 31.83 31.39 2 31.37 30.30
3 31.32 30.28 3 29.87 30.50
4 30.23 20.54 4 32.14 28.93
5 25.50 19.24 5 28.01 27.20
HT 304 HL 304
1 34.76 32.12 1 35.78 33.62
2 34.94 31.20 2 35.63 33.45
3 34.64 31.49 3 32.43 33.74
4 32.34 31.25 4 31.54 32.75
5 27.31 30.79 5 31.42 33.04
HL 316L HT 316L
1 3.41 12.83 1 18.85 19.85
2 20.88 19.86 2 15.76 15.88
3 16.97 16.51 3 17.84 15.10
4 16.46 18.39 4 17.13 18.54
5 15.73 15.10 5 14.65 16.17

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5.1.4. Welding process
The necked region was removed using a metallographic cutter and the remainders of
the specimens welded together by TIG and MMAW. Welding parameters are shown in
Table 1.4.
The chemical composition for electrodes were used for welding of specimens are shown
in Table 1.5.
Table 1.4 Welding parameters used
specimens Welding
method Welding
current (A) Shielding
gas Welding
voltage (V) Welding
electrode
Full specimens
ELT 304 MMAW 80 – 20 – 24 309L -17
ELL 304 MMAW 80 – 20 – 24 309L -17
ELT 316L MMAW 80 – 20 – 24 309L -17
ELL 316L MMAW 80 – 20 – 24 309L -17
specimens with holes
TIGHT 304 TIG 80 Argon 20 – 24 308L
TIGHL 304 TIG 80 Argon 20 – 24 308L
TIGHT 316L TIG 80 Argon 20 – 24 308L
TIGHL 316L TIG 80 Argon 20 – 24 308L
Sample coding reflects welding process used, EL – manual metal arc welding, TIG –
tungsten inert gas welding, the alloy, 304 or 316L and the sample orientation, T –
transverse and L – longitudinal and H denotes the hole presence within specimen.
Table 1.5. Chemical composition for of electrodes (W %) [ 7].
Chemical composition
C Cr Ni Mo Mn Si P S Cu
ER308L 0.03 19.5-22.0 9.0- 11.0 0.75 1.0 -2.5 0.30-0.65 0.03 0.03 0.75
ER309L 0.03 23.0-25.0 12.0- 14.0 0.75 1.0-2.5 0.30-0.65 0.03 0.03 0.75

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5.2. Mechanical properties for welded specimens
5.2.1. Tensile testing
The ultimate tensile strength, yield tensile strength, Area of reduction, and elongation
of the used material are presented in Table 1.6 after welding. Standard welded
specimens are used for tensi le testing of specimens. The dimensions of welded
specimen are shown in Fig. 1.22.
Welded specimens after tensile testing were shown in Fig. 1.23
Tensile curves for welded specimens with central holes and without central holes were shown
in fig. 1.24 and f ig.1.25.
Table 1.6 Mechanical properties of specimens after welding.
specimens Tensile strength
Rm (Mpa) Yield strength
Rp 0.2 (Mpa) Elongation
(%) Reduction in
area (%)
Full specimens
ELT 304 614 437 7 21
ELL 304 623 496 5 8
ELT 316L 494 363 3 33
ELL 316L 602 378 8 40
specimens with central holes
TIGHT 304 500 269 0.3 70
TIGHL 304 661 337 10 45
TIGHT 316L 555 375 17 78
TIGHL 316L 637 416 18 37

Fig. 1.22. The welded specimen dimensions of 304 and 316L austenitic steels

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Fig. 1.23 welded specimens after tensile testing (A) ELT 304 (B) ELL 304 (C) TIGHT 304
(D) TIGHL 304 (E) ELL 316L (F) ELT 316L (G) TIGHL 316L (H) TIGHT 316L

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Fig. 1.24 Tensile curves for all welded specimens, ELT304, ELL304, ELT316L, and
ELL316L

Fig. 1.25 Tensile cur ves for all welded specimens, TIGHT 304, TIGHL 304, TIGHT 316L, and
TIGHL 316L

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5.2.2. Hardness testing
The hardness testing (HRC) was conducted after the tensile testing for all welded
specimens. Three positions were chosen to measure the hardness in both directions.
The results of this hardness testing (HRC) are present in the table 1.7.
Table 1.7. HRC for welded specimens
ELT 304 ELL 304
Nr Left Right Nr Left Right
1 18. 2 19.52 1 22.03 19.05
2 17.31 21.8 2 23.36 16.54
3 – – 3 17.58 18.2
ELL 316L – Long ELT316L
1 29.92 30.79 1 28.08 22.65
2 30.41 30.9 2 30.23 27.44
TIGHT 304 TIGHL
1 32.6 34.7 1 34.68 33.1
2 36.15 33.9 2 34.18 34.53
3 33.08 – 3 31.15 32.48
TIGHL 316L TIGHT 316L
1 22.17 13.13 1 – 23.08
2 25.13 23.15 2 23.2 26.08
3 24.6 24.05 3 22.8 24.22

5.3. Comparison of results
5.3.1. Tensile properties
If we compare the results that have been obtained through curves tensile of specimens
before welding for (1), (2), (3) and (4) of 304 stainless steel and (1), (2), (3) and (4) of
316L stainless steel we find that decrease of tensile properties with central hole for
specimens 304, and the same for specimens 316L, we find decrease of tensile properties
with central hole. Fig.1.26 shows ten sile properties for all specimens 304 and 316L.
The bar charts shown in Fig. 1.27 and 1.28 show the comparison of the tensile
parameters obtained from initial testing.

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Fig.1.26. Tensile properties for all specimens 304 and 316L
Fig. 1.27 Tensile strength and yield strength comparison for tested samples

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Fig. 1.28 Elongation and reduction in area com parison for tested samples
Return to the tensile curves of specimens that were welded by (MMAW) in the figure
1.24, we find that the 304 stainless s teel has tensile properties better than 316L stainless
steel, and in both tensile properties decreased comparing with the specimens without
welding.
Return to the tensile curves of specimens that were welded by (TIG) in the figure 1.25,
we find that the 3 16L stainless steel has tensile properties better than 304 stainless steel,
and in both tensile properties decreased comparing with the specimens without welding.
Figure 1.29 shows the tensile curves of each welded specimens, we note that 316L
stainless st eel has the best tensile properties when using TIG welding technique, but
304 stainless steel has the best tensile properties when using MMAW welding
technique.
Figure 1.30 shows the tensile curves for each welded specimens and without welding,
we note tha t contraction occurred in the area of plasticity – elasticity and a reduction in
yield strength.
The bar charts shown in Fig. 1.31 and 1.32 show the comparison of the tensile
parameters obtained from testing for Welded specimens.

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Fig. 1.29 shows the te nsile curves of each welded specimens

Fig. 1.30 shows the tensile curves for each welded specimens and without welding

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Fig. 1.31 Tensile strength and yield strength comparison for welded samples

Fig. 1.32 Elongation and reduction in area comparison for welded samples

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5.3.2. hardness properties
On the failed specimens Rockwell C hardness tests were performed on the regions
depicted in Fig. 1.33.

Fig. 1.33 Elongation and reduction in area comparison for tested samples
In return to the Table 1.3 and mak ing a comparison between specimens (1, 3) for 304
alloy, and the specimens (2, 4) of the same kind, we notice an increase in characters of
hardness of the tensile specimens; with the existence of a central hole near the area of
the hole in the regular spec imens with no central hole. The variation being shown in
Fig. 1.34.

Fig. 1.34 Hardness variation on samples made of 304

41
This applies also to the comparison of the specimens (1, 3) and the specimens (2, 4) for
the 316L alloy; we notice that the opposite occurs. Where the properties of the tensile
specimens decrease with existence of some holes in the area near the hole from the
regular specimens without existence central holes. The variation b eing shown in
Fig. 1.35.

Fig. 1.35 Hardness variation on samp les made of 316L

Table 1.7 shows the characters of hardness of the specimens 304, 316L after doing
welding for these specimens, we notice after the comparison between (1, 2) of 304
before welding with specimens (1, 2) after welding, also for specimens (1, 2) of 316L
before welding and after it, there is no notice able change in the values of the hardness,
this leads to the conclusion that when using (MMA) there was no effect on the values
of hardness for (304, 316L).
Making a comparison between specimens ( 3, 4) of 304 before welding and after it,
shows that there is no change in the hardness. So there is no affection of welding (TIG)
on the hardness of 304 SS.
But when we compare specimens (3, 4) of 316L before welding and after it, we
recognize a notice ab le change in the hardness, values increase after welding in (TIG).
So, on the welded specimens the hardness did not vary considerably, ranging between
30-35 HRC for full specimens (304 specimens), while the welded specimens with a
previous hole a slight in crease was noticed, sign of a slight strain hardening ( 316L
specimens). These are shown in Fig. 1.36 and 1.37.

42

Fig. 1.36 Hardness variation on samples made of 304

Fig. 1.37 Hardness variation on samples made of 316L

43
5.4. Conclusions
 We concluded that was decrease in the properties of tensile for both specimens with
the existence of central holes.
 316L has tensile characteristics better than 304 when using the technique (TIG).
 304 has better tensile characteristics than 316L when using th e technique (MMA).
 The existence of central holes affected on the hardness characteristics of both kinds,
therefor the hardness increased in 304 but decreased in 316L.
 It also showed that there was no influence (MMA) on hardness of both kinds.
 It also show ed that there was no influence (TIG) on the hardness for 304, but on the
other hand these values increased for 316L.

44
6. References
[1] www.dm -consultancy.com /TR/dosya/1 -59/h/aisi -340-info.pdf.
[2] www.sandmeyersteel.com/images /316-316L -317L -Spec -Sheet.pdf.
[3] S. tryckeri, Sweden, Handbook of stainless steel , 1523EN -GB: 1, October 2013.
[4] Welding processes , Wood head Publishing Ltd, 2003.
[5] Welding of stainless steels and others joining methods , American iron and steel
Institute, 1989.
[6] http://www.substech.com
[7] Welding Handbook , Seventh Edition, Volume 4, Metals and Their
Weldability, 1997.
[8] C. Garcia, F. Martin, P. de Tiedra, Y. Blanco, M. Lopez, Pitting corr osion of
Welded Joints of austenitic stainless steels studied by using an electrochemical
Minicell, Corrosion Science 50 (2008) 1184 –1194.
[9] B.T. Lu, Z.K. Chen, J.L. Luo, B.M. Patchett, Z.H. Xu, Pitting and stress
Corrosion cracking behavior in welded austenitic stainless steel, Electrochimica
Acta 50 (2005) 1391 –1403
[10] A.H. Tuthill, Corrosion Testing of austenitic stainless steel weldments , Weld. J.5
(2005) 36–40.
[11] C. Garcia, M.P. de Tiedra, Y. B lanco, O. Martin, F. Martin, Intergranular
Corrosion of welded joints of austenitic stainless steels studied by using an
Electrochemical minicell , Corrosion Science 50 (2008) 2390 –2397.
[12] Y. Cui, Carl D. Lundin, Evaluation of initial co rrosion location in E316L
Austenitic stainless steel weld metals , Mater. Lett. 59 (2005) 1542 –1546.
[13] Y. Cui, Carl D. Lunding, Austenite – Preferential corrosion attack in 316
Austenitic stainless steel weld metals , Mater. Des. 28 (2007) 324 –328.
[14] M. Dadfar, M.H. Fathi, F. Karimzadeh, M.R. Dadfar, A. Saatchi, Effect of TIG
Welding on corrosion behaviour of 316L stainless steel , Mater. Lett. 61 (2007)
2343 –2346.
[15] C.T . Kwok, S.L. Fong, F.T. Cheng, H.C. Man, Pitting and galvanic corrosion
Behavior of laser -welded stainless steels , Journal of Materials Processing
Technology 176 (2006) 168 –178.

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[16] Klimpel, A. & Lisiecki, A. (2007). Laser Welding of Butt Joints of Austenitic
Stainless Steel AISI 321 . Journal of Achievements in Materials and
Manufacturing Engineering, 25, 1.
[17] Curcio, F.; et al. (2006). Welding of Different Materials by Diode Laser . Journal
Of Materials Processing and Technology, 175, 83-89.
[18] R. Kovacevic , Welding Processes, ISBN 978 -953-51-0854 -2, InTech November
21, 2012.
[19] W. Chuaiphan, L. Srijaroenpramong, Effect of welding speed on
Microstructures , Mechanical properties and corrosion behavior of GTA -welded
AISI 201 stainless steel Sheets , Journal of Materials Processing Technology 214
(2014) 402 – 408.