the effect of metal transfer modes on mechanical

Draft

The Effect of Metal Transfer Modes on Mechanical Properties of 3CR12 Stainless Steel

Journal: Transactions of the Canadian Society for Mechanical Engineering

Manuscript ID TCSME-2018-0125.R1

Manuscript Type: Article

Date Submitted by the Author: 17-Jan-2019

Complete List of Authors: KAYMAKCI, ABDULLAH; University of Johannesburg, Mechanical Engineering ScienceMadyira, Daniel; University of Johannesburg, Mechanical Engineering ScienceNkwanyana, Ntokozo; University of Johannesburg, Mechanical Engineering Science

Keywords: Welding, Microstructure, Hardness, Tensile strength, Metal transfer mode

Is the invited manuscript for consideration in a Special

Issue? :Not applicable (regular submission)

https://mc06.manuscriptcentral.com/tcsme-pubs

Transactions of the Canadian Society for Mechanical Engineering

Draft

The Effect of Metal Transfer Modes on Mechanical Properties of 3CR12 Stainless Steel

Daniel M. MadyiraUniversity of Johannesburg

Faculty of Engineering and the BuiltEnvironment

Department of Mechanical Engineering Science,

Johannesburg, South [email protected]

Abdullah KaymakciUniversity of Johannesburg

Faculty of Engineering and the Built Environment



Ntokozo Nkwanyana University of Johannesburg

Faculty of Engineering and the Built Environment



Page 1 of 15



mailto:[email protected]

mailto:[email protected]

Draft

ABSTRACT

The effect of metal transfer modes on mechanical properties of welded 3CR12 stainless steel were investigated. This was achieved

by butt welding 10 mm thick plates of 3CR12. The effect of the metal transfer modes on the microstructure and the mechanical

properties of the 3CR12 steel was then investigated as it was hypothesized that the change in welding positions will affect the

transfer modes partly due to the effect of gravity. The microscopic examination revealed that the substrate was characterized by

dual phase microstructure. Using the spectroscopic examination results, the ferritic factor calculation had shown that the

microstructure was expected to be ferritic-martensitic during air cooling process. The tensile strength and Charpy impact energy

were measured to be 498 MPa and 102 J. The heat input in the material was observed to be greater than 1 kJ/mm which is the

limiting factor for grain growth. Grain growths were observed in the heat affected zone of the welded materials. Ferritic-martensitic

microstructure was observed in the microstructure. The grain growth altered the mechanical properties of the test material. Globular

down hand had higher mechanical properties than spray down hand. Globular vertical up had better mechanical properties than

globular vertical down.

Keywords: Welding, Metal transfer mode, Microstructure, Hardness, Tensile strength

INTRODUCTION

Train wagons in South Africa are manufactured using 3CR12 corrosion-resistant steel since they carry corrosive materials such as

coal. 3CR12 is a ferritic stainless steel that has good mechanical properties in terms of strength, hardness and corrosion resistance.

In the past, the manufacturing process of the train wagons involved the rotation of the wagon during welding to allow welding only

in one direction and position, that is, flat or horizontal. The rotation of the wagon is now limited to certain directions hence welding

occurs in all welding positions. This could result in differing bonding strengths on the welds which can be more pronounced for

repair work (Transnet 2016). Figure 1 shows wagons manufactured by Transnet in Pretoria, South Africa.

Reduced weld bonding strength can lead to reduction in the wagon fatigue life necessitating further repair work. The manufacturing

and repairing processes are commonly implemented using arc welding processes. Arc welding is one of the most common methods

for joining metals, and it is important for the construction of steel structures and the fabrication of machinery. Arc welding has made

it possible to weld different types of materials such as carbon steels, low alloy steels, and aluminum. Dissimilar materials can also

be welded such as aluminum and steel, steel and magnesium and also magnesium alloys (Gharibshahiyan et al. 2012). The joining

of materials sensitive to heat has lately become an important issue during arc welding. Understanding of arc types and their inherent

properties can help enhance weld prediction and weld quality and reduce welding cost and production cycle times (P. Kah et al.

2013; Mohamat et al. 2012).

Page 2 of 15



Draft

One of the most used arc welding methods in the railway industry is the Gas Metal Arc Welding (GMAW) due to its fundamental

advantages such as adjustable penetration profiles, smooth bead, low spatter, and high welding speed. In GMAW, the metal transfer

mode due to the arc and hence the weld quality is influenced by the arc current and the arc voltage. The arc current also affects the

penetration depth. An increase in current increases the joint penetration. However, increased joint penetration also increases the

possibility of burn through and solidification cracking. That is not good, since this can lead to premature failure that can cause loss

of human lives or economic losses (Kapustka 2012; Gharibshahiyan et al. 2012; ASME 2010).

In general, the arc welding process is affected by several factors such as arc current and voltage, filler wire type and size, travel

speed of the torch and spin frequency. When selecting these parameters, the amount of heat input and the desired fusion should be

considered. One problem commonly faced by the welding industry is poor stability of the arc. Arc stability and arc length influence

the behavior of metal transfer modes. With a stable arc, metal transfer is uniform and the amount of spatter is minimal. The arc

stability and the arc length are controlled by the arc current and voltage. Another problem faced by the welding industry is the

shrinkage of the welded components which introduces residual stresses and distortion. This is due to the heating and cooling of the

welded components (Kah et al. 2014).

The common metal transfer modes during arc welding include short circuit transfer, globular transfer, spray transfer and pulsed arc

transfer. Under normal welding conditions, the welder relies on the specifications of the welding procedure. However, during repair

welding, it is common for the welder to adjust parameters on the go. This can have unintended effects especially on mechanical

properties of the weld. There is therefore, a need to investigate the effect of metal transfer modes on the mechanical properties of

the weld (Kobe Steel 2011). South African companies manufacture their train wagons mainly from 3CR12 steel. Furthermore, for

the repair of these wagons, welders mainly use the Submerged Arc Welding (SAW) and Gas Metal Arc Welding (GMAW) processes

(Transnet 2016). During the welding process, the welders set their own voltage and weld in all welding directions using constant

set voltage, presumably. However, during the welding, depending on the weld orientation, the metal transfer mode may change. The

transfer modes are dependent upon the voltage and a small change in the voltage can effectively produce a high welding current

which consequentially increases the heat generation that directly affects the microstructure and mechanical properties of the weld (

Martikainen et al. 2013). Therefore, this research focused on investigating the effect of metal transfer modes on the weld

microstructure and the mechanical properties of the weldments of 3CR12 steel under different welding conditions.

EXPERIMENTAL METHODS AND EQUIPMENT

Materials

Coal train wagons in South Africa are manufactured using 3CR12. The same material was used for this investigation. The material

was supplied by Columbus Stainless Steel, a steel making company in Middelburg, South Africa. The material was supplied in

Page 3 of 15



Draft

plates of dimensions 3000 × 1500 × 10 mm with a batch number of 3818673/ 1L 3CR12. The chemical composition of the material

according to the manufacturer certificate is given in Table 1.

Furthermore, the mechanical properties of the material as specified in the manufacturer’s certificate are given in Table 2.

Welding Machines and Welded Specimens

The ASME IX: 2010 (Welding and Brazing Qualifications) code was used as a basis for welding variables (ASME 2010). Welded

specimens were prepared on a Lincoln Electric Welding Machine (EWM), model DC 600. Its main features include full range output

voltage control for ease of operation and precision control, standard analog ammeter and voltmeter, VRD™ (Voltage Reduction

Device™) reduces OCV (open circuit voltage) when not welding for added safety (select models) and a mode switch for selecting

desired output. The welding electrode used on the machine was A5.9 ER309L, which is for GMAW.

For pulsed arc transfer modes, a special EWM machine was used to weld the test plates. The machine is specially designed to weld

in pulsed transfer modes only. The EWN machine used was the EWM Multimatrix (WPQR 1090) Phoenix Pulse welding machine.

A fluke clamp meter (Tong meter) was used to verify the voltage and current set on the GMAW machine whilst a measuring tape

was used to measure the length of the electrode during the determination of the wire feed rate. A stainless-steel brush was used to

clean the material before and after each single welding run.

To prepare the welds, the supplied material was cut into plates of dimensions 350 × 150 × 10 mm. The samples were prepared to be

welded in butt joint configuration. A 30˚ bevel angle was made on the plate, which resulted in a V-groove angle of 60˚ between the

weld plates. The geometry of the welded specimens is shown in Figure 2.

The prepared cut plates are shown in Figure 3(a).

Prepared plates were welded under different welding conditions. A welding wire (AWS A5.9 ER 390L) of 1 mm diameter was used

for all the welds. Welding was done under Argoshield 5 (Argon, oxygen and carbon dioxide) shielding gas. The shielding gas flow

rate was set between 15-20 L/min. Welding voltage was varied from 15 to 35 Volts while the current was varied from 100 to 350

Amps. This enabled the variation of the metal transfer modes. The corresponding metal transfer modes are given in Table 3. The

wire feed speed was determined by measuring the length of the wire over a span of 10 seconds. The wire feed speed was therefore

set at 0.114 m/s. The plates for each joint were tacked horizontally to maintain welding gap. They were then welding at the required

orientation to completion (see Table 4). Prepared samples were then used to prepare test specimens. Sample welded plates are shown

in Figure 3(b).

Metallurgical Analysis and Mechanical Testing

Welded samples were then cut into different specimens for metallurgical and mechanical testing procedures. Metallurgical

specimens were prepared and mounted using epoxy resin, ground and polished. These were prepared for microscopy, micro

Page 4 of 15



Draft

hardness, and spectroscopy tests. Optical microscopy was conducted using an Olympus optical microscope, spectroscopic analysis

was done on an ultraviolet spectroscopic machine and the micro hardness testing was conducted on a FM-800e micro-hardness

testing machine. For spectroscopy, an ultraviolet spectroscopic machine was used.

Tensile Test Specimens

Tensile test specimens were also prepared from the welded samples. Flat bars were cut using a band saw from the welded plates at

an orientation perpendicular to the weld. The bars were then shaped into doggy bone shape using a milling machine. The welded

joint appears in the centre of the gauge section of the specimens. Tensile testing was conducted on an MTS tensile testing machine

using a 100 kN load cell.

RESULTS AND DISCUSSION

Spectroscopic Examination

The spectroscopic examination confirmed that the material supplied was a 3CR12 stainless steel with carbon content less than 0.03%

as specified by the manufacturer. The chromium content was also in the range of the expected values i.e. 10.5-12.5%. The silicone

content was less than 1%; manganese 1.5%; phosphorus content 0.4%; sulphur content was greater than 0.015% and lastly nickel

content fell in the range of 0.3-1.5%.

Microscopic Examination

The microstructure of the parent material was found to be a ferritic stainless steel. This was characterized by two phase or dual

phase microstructure i.e., alpha phase and beta phase grain structures. The alpha phase appears to be light and beta phase appears to

be dark in color. This is clear in Figure 4(a). The microstructures observed for some of the metal transfer modes are shown in Figures

4(b) to (d). In all the figures, three zones can be distinguished i.e. the parent material, the heat affected zone with large grain sizes

and the weld metal. The size of the grains reflects the effect of the metal transfer modes on the microstructure. This is mainly

governed by the amount of heat input as the minimum heat input for grain growth in 3CR12 has been reported to be 1 kJ/mm.

However, the heat inputs computed for the test cases were 1.89 kJ/mm for globular down, 3.77 kJ/mm for globular up and 2.69

kJ/mm for spray down. The grain growth at higher voltages was also observed by Gharibshahiyan et al. (Gharibshahiyan et al.

2011).

Micro hardness Results

Micro hardness results for the test samples are presented in Table 5. These show the comparison for the hardness values of the

parent material (PM), weld material (WM) and the heat affected zone (HAZ). Acceptance criteria was developed based on the

literature from the previous studies done by Akinlabi et al. (Akinlabi 2014) ) where they presented the micro-hardness of 3CR12

steel as 146 HV and for the heat treated and air cooled 3CR12 specimen as ±150 HV for parent material values. Accordingly, these

Page 5 of 15



Draft

values were used as acceptance levels with a range or class of ±50 HV. The globular vertically down did not meet the acceptance

criteria for good weld performance. Higher hardness values were observed for the parent material and the welded material compared

to the heat affected zone. This was in agreement with the findings made by Gharibshahiyan et al. (Gharibshahiyan et al. 2012)

which they attributed to the increased grain growth size and the increased penetration depth of the heat, a phenomenon also observed

by Ibrahim et al. (Ibrahim et al. 2012).

Mechanical Test Results

The grains generally elongated in the casting direction hence the mechanical properties of the parent material were tested in the

longitudinal and transverse direction to determine the difference in Charpy and tensile test properties. The results of the longitudinal

and transverse samples are given in Table 6. The mechanical properties were found to be lower in the transverse direction compared

to the longitudinal direction. This is as expected. The obtained values were generally in agreement with the material certificate

supplied by the manufacturer.

The tensile test results for the specimens prepared at various metal transfer modes are summarised in Table 7. The results show that

the globular down hand (GDH) has the best performance compared to the other transfer modes in terms of mechanical performance

as shown by the ranking column in the table.

The UTS and yield strength of globular down hand were higher than those of spray down hand while the % elongation and the %

reduction of area of globular is lower than that of spray down hand. Globular vertical up had better mechanical properties than

globular vertical down. The results show that the globular transfer mode produces better mechanical properties in down hand

position. This is due to the lower heat input to the material during to the welding process. The current and voltage of the globular

transfer mode are lower than those of spray transfer mode. This results in more heat input when using spray transfer mode under

constant welding speed, which results in severe change in the mechanical properties of the stainless steel.

SUMMARY OF RESULTS

Table 8 shows the ranking criteria of the four test plates that were welded and tested using visual inspection, micro-hardness testing

and tensile testing.

Globular down hand had better results followed by spray down hand, globular vertical up and lastly globular vertical down. Table

9 shows the ranking of the transfer modes and the welding positions based on macroscopic examination according to ISO 5817.

CONCLUSIONS

This paper investigated the effect of metal transfer modes on the mechanical performance of 3CR12 stainless steel. Samples were

prepared using GMAW. Welding parameters (voltage and current) were varied to ensure the existence of four metal transfer modes.

These modes were then applied to different welding positions which, included vertically up and down. Specimens produced under

Page 6 of 15



Draft

these conditions were examined using microstructure, micro hardness, Charpy and tensile testing analysis. The results obtained led

to the following conclusions:

1. All specimens exhibited good welded joints

2. The heat input for all the test configurations were more than 1 kJ/mm hence this resulted in grain growth that was more

pronounced in the heat affected zone (HAZ)

3. Microstructural analysis verified that there was grain growth in the HAZ for all specimens

4. Grain growth was responsible for most of the changes in mechanical properties

5. Microhardness tests indicated higher values for the parent metal and the weld metal compared to the HAZ

6. Mechanical properties (Charpy and tensile) of the welds were lower than those of the parent material as expected

7. The globular down hand test plate produced better mechanical properties than spray down hand metal transfer mode due

to lower heat input

8. Spray vertical up, spray vertical down and spray overhead could not be welded due to high heat input. The plates were

burning during the penetration run

ACKNOWLEDGEMENTS

The authors would like to acknowledge Transnet Engineering (Pretoria) for the provision of materials and the welding and testing

facilities.

REFERENCES

Akinlabi, Esther T, and Stephen A Akinlabi. 2014. “Characterising the Effects of Heat Treatment on 3CR12 and AISI 316 Stainless

Steels” 2050 (2): 256–61.

ASME. 2010. Qualification Standard for Welding and Brazing Procedures, Welders, Brazers, and Welding and Brazing Operators.

2010 ed. New York, NY: ASME Pressure and Boiler Vessel Committee Subcommittee on Welding and American Society of

Mechanical Engineers.

Gharibshahiyan, Ehsan, Abbas Honarbakhsh Raouf, Nader Parvin, and Mehdi Rahimian. 2011. “The Effect of Microstructure on

Hardness and Toughness of Low Carbon Welded Steel Using Inert Gas Welding.” Materials and Design 32 (4): 2042–48.

https://doi.org/10.1016/j.matdes.2010.11.056.

Gharibshahiyan, Ehsan, Abbas Honarbakhsh Raouf, Nader Parvin, Mehdi Rahimian, Nick Kapustka, Paul Kah, Hamidreza Latifi,

et al. 2012. “The Effect of Flux Core Arc Welding (FCAW) Processes on Different Parameters.” Procedia Engineering 41

Page 7 of 15



Draft

(1): 1497–1501. https://doi.org/10.1007/s00170-012-4513-5.

Ibrahim, Izzatul Aini, Syarul Asraf Mohamat, Amalina Amir, and Abdul Ghalib. 2012. “The Effect of Gas Metal Arc Welding

(GMAW) Processes on Different Welding Parameters.” Procedia Engineering 41 (Iris): 1502–6.

https://doi.org/10.1016/j.proeng.2012.07.342.

Kah, P., R. Suoranta, and J. Martikainen. 2013. “Advanced Gas Metal Arc Welding Processes.” International Journal of Advanced

Manufacturing Technology 67 (1–4): 655–74. https://doi.org/10.1007/s00170-012-4513-5.

Kah, Paul, Hamidreza Latifi, Raimo Suoranta, Jukka Martikainen, and Markku Pirinen. 2014. “Usability of Arc Types in Industrial

Welding.” International Journal of Mechanical and Materials Engineering 9 (1): 1–12. https://doi.org/10.1186/s40712-014-

0015-6.

Kapustka, Nick. 2012. “Arc Welding Capabilities at EWI.”

Kobe Steel. 2011. “The ABC’s of Arc Welding and Inspection,” 93.

Mohamat, Syarul Asraf, Izzatul Aini Izatul Aini Ibrahim, Amalina Amir, Abdul Ghalib, Kobe Steel, P. Kah, R. Suoranta, et al.

2012. “The Effect of Gas Metal Arc Welding (GMAW) Processes on Different Welding Parameters.” Procedia Engineering

41 (April 2016): 1502–6. https://doi.org/10.1016/j.pnsc.2017.03.004.

Transnet. 2016. “Transnet Freight Rail.” 2016. http://www.transnetfreightrail-tfr.net.

Page 8 of 15



Draft

Table 1: Chemical composition of 3CR12 as supplied (in accordance to ASTM A240 and EN 10088-2)

Element C Si Mn P S Cr Ni Others

Content 0.03 1.0 2.0 0.04 0.03 10.5 1.5 0.6

Table 2: Mechanical properties of 3CR12 as supplied (in accordance to ASTM A240 and EN 10088-2)

Property Density

(kg/m3)

Elastic Modulus (GPa)

Yield Strength (MPa)

Ultimate Tensile Strength (MPa)

Max BHN

Value 7 680 200 300 460 220

Table 3: Experimental parameters

Parameters Arc Voltage Welding Current Transfer Modes

Units Volts Amps -

Test 1 15 150 Short Circuit

Test 2 25 250 Globular

Test 3 35 350 Spray

Test 4 30 100 Pulsed Arc

Table 4: Welding positions

Welding Positions Code Transfer Modes No. of Samples

Flat 1 G 4 4

Vertical up 2 G 4 4

Vertical down 3 G 4 4

Overhead 4 G 4 4

Page 9 of 15



Draft

Table 5: Micro hardness results for varying metal transfer modes

Table 6: Mechanical test results of parent material

Properties Transverse direction Longitudinal direction

Yield Strength (MPa) 319 352

Tensile Strength (MPa) 443 498

% Elongation 43 37

% Reduction Area 66 67

Impact Strength (J) @ room temperature

151 102

Table 7: Summary of tensile test results for varying metal transfer modes

3CR12 UTS (MPa) YIELD (MPa) EL (%) RA (%) Ranking

GDH 498 352 16.2 33.6 1

GVU 468 313.7 25.5 58.3 2

GVD 350 272.3 14.4 12.5 4

SDH 415 313.7 16.2 33.57 3

Test Plates LHAZ or PM WM HHAZ Acceptance criterion

GDH 181.65 HV 212.2 HV 173.35 HV

GVU 200.5 HV 223.85 HV 182.25 HV

GVD 196.3 HV 182.1 HV 232.1 HV x

SDH 177.2 HV 246.2 HV 170.85 HV

Page 10 of 15



Draft

Table 8: Ranking criteria of weld test plates

3CR12 Weld Plates

Macrostructure Micro-hardness Test

Tensile Test Score

GDH 4 4 4 12

GVU 2.5 3 3 8.5

GVD 1.5 3 1 5.5

SDH 4 3 2 9

Table 9: Weld soundness ranking

Parameters 1G 3G (Up) 3G (Down) 4G

Short Circuit Good Average Poor Poor

Globular Good Average Poor Poor

Spray Average Poor Poor Poor

Pulsed Good Average - -

List of Figures

Figure 1: Train wagons manufactured from 3CR12 stainless steel (Transnet 2016)Figure 2: Specimen geometryFigure 3: Prepared specimens (a) Blank plates (b) Welded sampleFigure 4: Microstructures (a) Parent materials (b) Globular down (GDH) (c) Globular up (GVU) (d) Spray down (SDH)

List of Tables

Table 1: Chemical composition of 3CR12 as supplied (in accordance to ASTM A240 and EN 10088-2)Table 2: Mechanical properties of 3CR12 as supplied (in accordance to ASTM A240 and EN 10088-2)Table 3: Experimental parametersTable 4: Welding positionsTable 5: Micro hardness results for varying metal transfer modesTable 6: Mechanical test results of parent materialTable 7: Summary of tensile test results for varying metal transfer modesTable 8: Ranking criteria of weld test platesTable 9: Weld soundness ranking

Page 11 of 15



Draft

Page 12 of 15



Draft

Page 13 of 15



Draft(a) (b)

Page 14 of 15



Draft(a) (b)

(c) (d)

Page 15 of 15



the effect of metal transfer modes on mechanical

Documents