Er

SD

a

ARRAA

KIDFHTFC

1

4TiFietdialiiaaooom

h0

Journal of Materials Processing Technology 236 (2016) 216–224

Contents lists available at ScienceDirect

Journal of Materials Processing Technology

journa l homepage: www.e lsev ier .com/ locate / jmatprotec

ffect of heat input on impact toughness in transition temperatureegion of weld CGHAZ of a HY 85 steel

anjeev Kumar, S.K. Nath ∗

epartment of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, India

r t i c l e i n f o

rticle history:eceived 7 March 2016eceived in revised form 15 May 2016ccepted 17 May 2016vailable online 19 May 2016

eywords:

a b s t r a c t

Physical weld simulated coarse grain heat affected zone (CGHAZ) specimens of HY 85 steel with heatinputs 15, 22, 50 kJ/cm were prepared by thermo mechanical simulator. Impact toughness was deter-mined at test temperatures from room temperature to −196 ◦C. Ductile to brittle transition temperature(DBTT) were determined by two methods (i) average impact toughness value of upper and lower shelfenergy and (ii) fracture appearance transition temperature (FATT) from the SEM fractographs. Impacttoughness and hardness values have been found to decrease with increase in heat input. This decrease is

mpact toughnessBTTATTigh strength steelransition temperatureractographs

attributed to slower cooling rate, increase in prior austenite grain size and increase in width of bainiticferrite lath. DBTT was determined for base metal and weld CGHAZ specimens based on upper and lowershelf energy criterion. FATT method based on SEM fractographs is applicable only for base metal butnot for weld CGHAZ specimens because they were fully brittle in character. Best impact toughness andhardness for heat input 22 kJ/cm observed are 66 J and 322 VHN respectively.

© 2016 Elsevier B.V. All rights reserved.

GHAZ

. Introduction

High strength low alloy steels having yield strength more than60 MPa are widely used for making hull of the ships (ABS, 2014).hese steels have a good combination of strength, ductility, and

mpact toughness at room temperature and subzero temperature.usion welding is the most important joining process of these steelsn the ship building industries (Ragu Nathan et al., 2015). How-ver, problem arises in the weld heat affected zone (HAZ) closeo the fusion line where coarse grain heat affected zone (CGHAZ)evelops (Kumar et al., 2015). Impact toughness in CGHAZ region

s found to decrease drastically and makes the welded joint brittlend unsuitable for applications (W.Y. Liu et al., 2011). The chal-enge is to minimize the decrease in the mechanical propertiesn the CGHAZ region. Attempts have been made to attain a min-mum impact toughness of 50 J at temperature −50 ◦C for saferpplications (Moorthy, 2011). For this purpose, better quality steelsnd selection of proper welding parameters are important. Onef the important parameters of welding is the heat input. Effect

f heat input on the mechanical properties of the weld CGHAZf high strength steel has shown that higher heat input causesore coarsening of prior austenite grain size (PAGS) due to slower

∗ Corresponding author.E-mail address: indiafmt@iitr.ac.in (S.K. Nath).

ttp://dx.doi.org/10.1016/j.jmatprotec.2016.05.018924-0136/© 2016 Elsevier B.V. All rights reserved.

cooling rate and decrease in mechanical properties (Kumar et al.,2016). Lambert-Perlade et al. (2004) have further reported thatapart from coarser PAGS in CGHAZ, increase in the width of bainiticferrite lath, decrease in the size of martensite/austenite (M-A) con-stituents, and more precipitation of carbides are also responsiblefor decrease in mechanical properties specially impact toughnessin a high strength low alloy steel (HSLA) steel. D. Liu et al. (2011)have also observed that impact toughness in the weld CGHAZ of anadvanced F460 high strength steel for shipbuilding, decreases withan increase in the heat input. For high strength steels, informa-tion pertaining to the impact toughness at transition temperaturefor different heat input corresponding to weld CGHAZ is relativelylimited. Zheng and Song (2013) have reported the effect of heatinput on ductile to brittle transition temperature (DBTT) in weldCGHAZ for low alloy steel. They have observed that DBTT increaseswith increasing in heat input. Lambert-Perlade et al. (2004) havereported the effect of heat input on the mechanical properties in theCGHAZ region of a HSLA steel and have observed the lower impacttoughness and higher DBTT of weld CGHAZ region as compared tobase metal. Further, they have observed lower impact toughness forhigher heat input in CGHAZ region. Cao et al. (2015) have reportedthe effect of four different heat inputs (15, 30, 50, 100 kJ/cm) onimpact toughness in the weld simulated CGHAZ for HSLA steel. They

have found that impact toughness decreases with increase in heatinput due to increase in PAGS. DBTT has also been found to increase.

S. Kumar, S.K. Nath / Journal of Materials Processing Technology 236 (2016) 216–224 217

Fig. 1. Typical weld simulated CGHA

Table 1Chemical composition of the present steel (wt%).

wtmaambfb

2

2

lpTs

2

wfHibsHsi

C Si Mn P S Cr Ni Nb V Cu Mo

0.08 0.25 0.5 0.015 0.01 0.54 2.1 0.05 0.03 0.5 0.3

In the present study, DBTT has been determined for HY 85 steelhich is a high strength low alloy steel used in the quenched and

empered condition specially developed for the hull of the ship. Twoethods have been used to determined DBTT (i) fracture appear-

nce transition temperature (FATT) from SEM fractographs, and (ii)verage impact toughness of lower and upper shelf energy for baseetal and weld CGHAZ at various heat inputs. No such work has

een reported where DBTT has been determined by two methodsor given steel. Limitations in determining DBTT for weld CGHAZy upper and lower shelf energy have also been discussed.

. Material and experimental procedure

.1. Material

The chemical composition of 28 mm thick plate of HY 85 steel isisted in Table 1. This plate was obtained in the quenched and tem-ered condition. The yield strength of the present steel is 560 MPa.he chemical composition of the steel was determined by sparkpectrometer, Thermo Jarrelash, USA.

.2. Weld HAZ simulation

Square x-section specimens of dimensions (10 × 10 × 85 mm)ere machined from transverse rolling direction of the steel plate

or weld HAZ simulation. The specimens were subjected to weldAZ simulation. The specimens were heated to 1300 ◦C with a heat-

ng rate of 200 ◦C/s with 0.1 s holding time at 1300 ◦C and followedy three different cooling rates 38 ◦C/s, 25 ◦C/s, and 15 ◦C/s corre-

ponding to heat input of 15, 22 and 50 kJ/cm respectively. WeldAZ thermal cycles in CGHAZ region at different heat input are

hown Fig. 1. It can be observed from this figure that as heat inputncreases cooling rate in the specimen decreases. This is because the

Z thermal cycle of HY 85 steel.

higher heat input causes wider HAZ and heats specimen in the basemetal to a longer distance as compared to lower heat input condi-tion. Therefore, the temperature difference decreases between thepoint of heat input and base metal and this causes slower coolingrate.

The simulated weld HAZ thermal cycle was designed on HAZmodule of QuickSim software of Gleeble ®3800 Thermo MechanicalSimulator corresponding to Rykalin-3D (for thick plate). Vacuum10−3 Pascal was maintained during the experiment in the chamber.The temperature was controlled with an K-type (Alumel–Chromel)thermocouple. Thermocouple wires were welded at the middle ofthe specimen by resistance welding. At the time of welding, 1 mmgap between thermocouple wires were maintained as per the stan-dard specification of model 35200 thermocouple welding machine.

2.3. Mechanical testing

Standard Charpy impact specimens (55 × 10 × 10 mm) weremachined from the weld simulated HAZ and base metal accordingto ASTM E23. An IT 30 kg m German make Charpy impact tester wasused for impact testing. Impact tests at room temperature (28 ◦C)and sub-zero temperatures (0 ◦C, −25 ◦C, −50 ◦C, −75 ◦C, −85 ◦C,−110 ◦C, −130 ◦C, −150 ◦C, −196 ◦C) were carried out on. In sub-zero Charpy impact test, specimens were first immersed in a bathcontaining mixture of liquid nitrogen and acetone (Kumar et al.,2016), and another mixture of ethanol and liquid nitrogen (Caoet al., 2015) to maintain a temperature range of 0 to −75 ◦C and−85 ◦C to −140 ◦C, respectively. All base metal and simulated spec-imen as per desired test temperatures were taken out after dippinginto the bath for 5 min and impact tests were carried out imme-diately. The average impact toughness value of three specimensin each transition temperature was determined. Ductile to brit-tle transition temperature (DBTT) curves for base metal and weldsimulated CGHAZ were plotted.

2.4. Microstructural characterization

One part of the broken impact tested specimens was used formicrostructural characterization and the other part was used for

218 S. Kumar, S.K. Nath / Journal of Materials Processing Technology 236 (2016) 216–224

d simu

fAu2cr1iTcuPdpfb

Fig. 2. Optical, SEM and TEM micrographs of base metal and wel

ractograph. The metallographic specimens were prepared as perSTM E3-11 standard technique. The specimens were polishedsing standard metallographic techniques and then etched with% Nital solution. However, to identify the morphology of M–Aonstituent in base metal and different CGHAZ, the specimen wase-polished and etched with modified LePera reagent (Girault et al.,998). A Leica DMI 5000 M optical microscope equipped with dig-

tal imaging facility was used to record the optical microstructure.he prior austenite grain size was measured by the line inter-ept method. Fracture surface observation was carried out by these of Carl Zeiss EVO 18 Scanning Electron Microscope (SEM).oint counting method was used to calculate the percentage of

uctile and brittle character in the fractographs in terms of dim-les and cleavage respectively by using a grid point of 100. Thin

oils for transmission electron microscopy (TEM) were preparedy Twin-Jet Electro Polisher, Model 110 in the electrolyte solution

lated CGHAZ specimens of HY 85 steel for different heat inputs.

of a mixture of 15% acetic acid and 85% methanol. TEM TECNAIG2 20 S-TWIN (FEI Netherlands) scanning/transmission electronmicroscope (S/TEM) was employed to reveal the fine details ofmicrostructure and carbide precipitates in the base metal and weldCGHAZ.

3. Results and discussion

3.1. Microstructure

Micrographs of optical microscopy (OM), SEM, and TEM of basemetal and weld simulated CGHAZ specimens at different heat input

(HI) are shown in Fig. 2a shows optical microstructure of base metal(BM). It shows a mixture of bainite and tempered martensite (M)with some amount of M-A constituents. This microstructure is inagreement with other HY 80, HY 100 and HY 85 series steels (Yue,

S. Kumar, S.K. Nath / Journal of Materials Processing Technology 236 (2016) 216–224 219

Fig. 3. Variation of average prior austenite grain size in CGHAZ with different heat input specimens.

nd (b

2BaimfhsmgmsPtdwcs

Fig. 4. Morphology of M-A constituents in (a) base metal, a

013; Kumar and Nath, 2016). In SEM and TEM micrographs ofM, the bainitic ferrite lath (BF), granular bainite (GB), carbides,nd M-A constituents can be easily observed and shown by arrowsn Fig. 2b,c respectively. Bu et al. (2015) have also found similar

icrostructure. For HI 15 kJ/cm, microstructure consists of bainiticerrite, granular bainite, martensite, and M-A constituents. For thiseat input, cooling rate is 38 ◦C/s that is maximum in the presenttudy. These microconstituents can be observed in the opticalicrograph (Fig. 2d) and SEM micrograph in Fig. 2e and TEM micro-

raph (Fig. 2f). Bainitic ferrite laths have been marked observed andeasured and it has been found to be 0.29 �m. Dislocation sub-

tructure can also be observed in the bainitic ferrite laths (Fig. 2f).resence of dislocation substructure in the bainitic ferrite validateshe findings of Bhadeshia (1999) which states the presence of highislocation density due to shear transformation. M-A constituents

ere observed between the bainitic ferrite lath and no inter-lath

arbides was observed. For HI 22 kJ/cm, the microconstituents areimilar to HI 15 kJ/cm (Fig. 2g–i). The changes in the microstructure

) weld simulated CGHAZ specimen at heat input 22 kJ/cm.

for HI 22 kJ/cm, are increase in width of bainitic ferrite (0.4 �m),increased amount granular bainite, decreased amount and size ofM-A constituents, and increased amount of carbides due to slowercooling rate (25 ◦C/s). For HI 50 kJ/cm, the microconstituents aresimilar to previous two HIs (Fig. 2j–l). However, the width ofbainitic ferrite lath increased to 0.46 �m, amount of granular bai-nite increased, amount of martensite decreased and the amountand size of M-A constituents also decreased due to still slower cool-ing rate (15 ◦C/s). Easterling (1983) has also established that high HIcauses slower cooling rate in the specimen. Due to this slower cool-ing rate, carbides and M-A constituents can be observed betweenthe bainitic ferrite laths (Fig. 2l). Yan et al. (2014) have suggestedfaster cooling rate after welding for high heat input welding toimprove impact toughness in the CGHAZ region for a high strengthsteel. This is attributed to lower PAGS and decrease in amount of

M-A constituents.

The variation of average prior austenite grain size (PAGS) withHI is shown Fig. 3. It is observed that PAGS increases with increase

220 S. Kumar, S.K. Nath / Journal of Materials Processing Technology 236 (2016) 216–224

AZ with different heat input specimens.

iaHvZAt

woaHiwam(

3

awa2aicdifctcish

Fig. 5. Variation of hardness in CGH

n HI. The average PAGS has been determined to be 86 �m, 99 �m,nd 102 �m for HIs of 15 kJ/cm, 22 kJ/cm, and 50 kJ/cm respectively.owever, the PAGS value of base metal is only 7 �m. Similar trend ofariation of PAGS with HI is also observed in micro alloyed steel byheng et al. (2012). The PAGS, width of bainitic ferrite lath, and M-

constituents are considered to play an important role on impactoughness as will be discussed in mechanical properties section.

Further, the presence of M-A constituents in base metal andeld CGHAZ region for different HI has been identified. It is

bserved that with increase in HI M-A constituents increased inmount. M-A constituents become finer in nature with increasingI. This is due to slower cooling rate observed with higher HI. This is

n agreement with the work of (Matusuda et al., 1995). For BM andeld CGHAZ region of HI 22 kJ/cm M-A constituents are shown with

rrow in Fig. 4. M-A constituents observed in weld CGHAZ speci-en of HI 22 kJ/cm are finer in nature as compared to BM specimen

Fig. 4a).

.2. Mechanical properties

Hardness of CGHAZ is found to decrease with increases in HI,s shown in Fig. 5. At HI 15 kJ/cm, the hardness value is 362 VHN,hereas at HIs 22 kJ/cm and 50 kJ/cm, hardness values are 322 VHN

nd 308 VHN respectively. However, the hardness value of BM is49 VHN. The hardness of all weld simulated CGHAZ specimensre higher than that of BM. It is because of increase in size of PAGS,ncreased amount of M-A constituents as well as martensite andarbides. However, the hardness values of weld HAZ specimensecrease with increase in HIs. This is due to the increase in PAGS,

ncrease in the amount of granular bainite and the width of bainiticerrite, and decrease in amount and size of M-A constituents. Slowerooling rate also promotes austenite transformation over a higheremperature range with a higher degree of auto-tempering during

ooling. As a consequence, the hardness decreases. Similar trendn the variation of hardness with HI has been observed for hightrength steel in the work of Shi et al. (2014). Liang et al. (2013)ave also reported that the hardness value decreases with increase

Fig. 6. Variation of impact toughness of base metal and weld CGHAZ simulatedspecimens at various heat input tested at different test temperatures.

in heat input in CGHAZ region of high strength low alloy steel. Shiand Han (2008) have also observed that the higher the heat inputthe lower the cooling rate. The variation of impact toughness ofBM and weld CGHAZ specimens of HY 85 steel at different testingtemperatures has been studied and shown in Fig. 6. Higher impacttoughness in term of upper shelf energy has been observed for theBM steel specimens as compared to weld CGHAZ specimens at dif-ferent HIs. However, the lowest impact toughness in terms of lowershelf energy for various specimens are almost the same (Fig. 6)The impact toughness values are more or less constant betweenroom temperature to minus 50 ◦C test temperature for BM and weld

CGHAZ specimens. Later, the impact toughness values show drasticdecreases with decrease in test temperature. The average impacttoughness for BM varies from 228 J to 10.3 J. The impact toughnessvalues for weld simulated CGHAZ specimens varies from 83 J to 9 J,

S. Kumar, S.K. Nath / Journal of Materials Processing Technology 236 (2016) 216–224 221

Fig. 7. Variation of DBTT and impact toughness of base metal and weld CGHAZ specimens at different heat input of HY 85 steel.

Table 2Transition temperatures of the base metal and weld simulated CGHAZs of HY 85 steel.

Weld thermal cycle Base metal HI 15 kJ/cm HI 22 kJ/cm HI 50 kJ/cm

DBTT (◦C) −93 −90 −81 −79Impact toughness (J) at DBTT 119 46 37 27Upper shelf energy (J) 228 83 65.7 45.5

6a

irmasibeid

toaD−a1Ft

s(bb

c

Lower shelf energy (J) 10.3

Temperature above which impact toughness is >50 J −123

FATT (◦C) −90

5.7 J to 8.5 J, and 45.5 J to 8.3 J corresponding to heat input 15, 22,nd 50 kJ/cm respectively.

The impact toughness of CGHAZs was found to decrease withncreasing heat input because higher HI causes slower coolingate in the specimen. Slower cooling rate is associated with

icrostructural features such as coarser bainitic ferrite, increasedmount of granular bainite and carbides, and finer M-A con-tituents as discussed in the microstructure section. Similar trendn impact toughness variation at different test temperature haseen observed for carbon and high strength low alloy steels (Caot al., 2015). They have reported decrease in impact toughness withncreasing heat inputs in CGHAZ of high strength steel welded jointsue to slower cooling rate.

The ductile to brittle transition temperature (DBTT) based onoughness equals the temperature corresponding to the half valuef the sum of the values on the upper shelf and lower shelf energys stated by Oldfield (1979). According to this, in the present study,BTTs for base metal and HI 15, 22, 50 kJ/cm are determined to be93 ◦C, −90 ◦C, −81 ◦C, −79 ◦C, respectively. However, temperaturebove which impact toughness is greater than 50 J for base metal, HI5 kJ/cm and 22 kJ/cm is −123 ◦C, −90 ◦C, and −65 ◦C respectively.or HI 50 kJ/cm, the impact toughness value observed is less thanhe 50 J (Table 2).

The DBTT and impact toughness of base metal and weld CGHAZpecimens have been found to decrease with increase in heat inputFig. 7). With increase in HI, variation in microstructure has alreadyeen explained based on coarsening of PAGS values, width of

ainitic ferrite lath, and M-A constituents in microstructure section.

Ductile to brittle transition temperature (DBTT) has also beenalculated from the SEM fractographs of broken impact tested

9 8.5 8.3−90 −65 –– – –

specimens. DBTT is now called fracture appearance transition tem-perature (FATT). This is defined as the test temperature at whichSEM fractographs has 50% ductile fracture and 50% brittle (cleav-age) fracture. The overall fracture process is governed by the shearmechanism of failure. Fractographs of broken impact tested spec-imens of base metal at different test temperatures are shown inFig. 8.

The variation of percent ductile fracture at different test tem-perature for BM is shown in Fig. 9. Similar trend of FATT for lowalloyed steel is also reported by Song and Zheng (2014) and Mouraet al. (2009). SEM fractographs of BM specimens show ductilecharacter (presence of dimples) up to test temperature −75 ◦C. Duc-tile fracture is explained on the basis of void nucleation, growthand coalescence. Void growth consumes maximum deformationenergy, which increases the upper shelf energy. At the end of voidgrowth, void coalescence begins, where the plastic instability setsin the region between the two adjacent voids, leading to necking.Factors like volume fraction, size of the precipitate particle, andinter-particle spacing affect chances of void-growth and their byaffecting the ductility and impact toughness of the steel (Ghoshet al., 2014). Mixed mode (ductile plus brittle) character are visibleupto −130 ◦C, and below this temperature, fracture mode is com-pletely brittle. Some cracks have also been observed and marked byarrows. FATT is −90 ◦C for BM, which corresponds to 126 J impacttoughness. This value is 3 ◦C less than determined from the averageof upper shelf and lower shelf energy.

For weld CGHAZ specimens, SEM fractographs are brittle in

character right from room temperature to subzero temperature(Fig. 10). Cracks are also visible and have been marked. The reasonfor brittle behavior is overall coarser PAGS value, increased width

222 S. Kumar, S.K. Nath / Journal of Materials Processing Technology 236 (2016) 216–224

of ba

osCamF

t(tc1mam5ist

4

1

Fig. 8. Fractographs of broken impact tested specimens

f bainitic ferrite lath, increased M-A constituents, and marten-ite as compared to BM. FATT could not be calculated for weldGHAZ specimens from the SEM fractographs as the fractographre fully brittle in character. For such specimens, DBTT was deter-ined based on upper and lower shelf energy criterion. DBTT and

ATT for BM and weld CGHAZ specimens are shown in Table 2.Researchers have established that in weld HAZ region, impact

oughness value should not be less than 50 J at minus 50 ◦CMoorthy, 2011; ABS, 2014), and hardness should not be morehan 350 VHN, which are considered safe from the point of view ofold cracking and safety of the welded joints (Harrison and Farrar,989). In the present work, impact toughness higher than 50 J atinus 50 ◦C is observed for base metal and heat inputs 15 kJ/cm

nd 22 kJ/cm but hardness less than 350 VHN is observed for baseetal and weld simulated HAZ specimens with HIs 22 kJ/cm and

0 kJ/cm. Therefore, it can be stated that for the present steel weld-ng with heat input 15 kJ/cm and 22 kJ/cm will give a safer weldedtructure except HI 50 kJ/cm. Because heat input 50 kJ/cm causeshe lower impact toughness than the recommended value.

. Conclusions

In the present study, the following are conclusions:

. Heat inputs 15 kJ/cm and 22 kJ/cm are found suitable for singlepass welding of the present HY 85 steel from the point of viewof impact toughness. Heat input 50 kJ/cm is found not suitablebecause it caused the coarser width of bainitic ferrite as well

se metal of a HY 85 steel at different test temperatures.

as PAGS value, increased amount of granular bainite, decreasedamount of martensite and M-A constituents.

2. Very high amount of coarsening in PAGS is reported in CGHAZregion for HI 50 kJ/cm as compared to other heat inputs. PAGSvalues observed are 86 �m, 99 �m, and 102 �m for HI 15, 22,50 kJ/cm respectively. PAGS value of base metal is only 7 �m.

3. The microstructure in the weld CGHAZ specimens are trans-formed from lath bainite and tempered martensite (base metal)to a mixture of coarse bainitic ferrite, granular bainite and tem-pered martensite. Width of bainitic ferrite lath has been foundto increase with increase in HI from 0.29 to 0.46 �m.

4. Impact toughness of the CGHAZ for different HIs was signifi-cantly decreased from the base metal because of the formation oflarger PAGS (86 �m–102 �m), increased width of bainitic ferritelath size, increased amount of M-A constituents. Impact tough-ness in upper shelf energy (83–46 J) decreases with increase inHIs. However, lower shelf energy is more or less constant atlowest test temperature (−196 ◦C).

5. Fractographs of the base metal specimens show ductile characterup to test temperature −75 ◦C, followed by mixed mode (−75 ◦Cto −110 ◦C) and then fully brittle character (−110 to −196 ◦C). Incase of weld simulated specimens for all three heat inputs frac-tographs were fully brittle in character for all test temperatures.

6. Ductile to brittle transition temperatures (DBTT) for base metal

and weld simulated specimens for heat input 15, 22, 50 kJ/cmare determined to be −93 ◦C, −90 ◦C, −81 ◦C, −79 ◦C, respectivelyon the basis of upper and lower shelf energy. FATT based onfractographs is observed −90 ◦C only for base metal. FATT could

S. Kumar, S.K. Nath / Journal of Materials Processing Technology 236 (2016) 216–224 223

Fig. 9. Percent ductile fracture of broken impact tested specimens for base metal at different test temperatures.

Fig. 10. Fractographs of broken impact tested weld simulated CGHAZ specimens of HY 85 steel at room temperature for (a) HI 15 kJ/cm, (b) HI 22 kJ/cm(c) HI 50 kJ/cm, and(d-i) HI 22 kJ/cm at different test temperatures.

2 ls Proc

7

8

A

TTT0

R

A

B

B

C

E

G

G

H

K

K

heat-affected zones in a Cr–Mo low-alloy steel. Philos. Mag. Lett. 93, 405–412,http://dx.doi.org/10.1080/09500839.2013.793459.

Zheng, L., Yuan, Z., Song, S., Xi, T., Wang, Q., 2012. Austenite grain growth in heataffected zone of Zr-Ti bearing microalloyed steel. J. Iron Steel Res. Int. 19,73–78, http://dx.doi.org/10.1016/S1006-706X(12)60063-6.

24 S. Kumar, S.K. Nath / Journal of Materia

not be calculated for weld HAZ simulated specimens as fracturewas fully brittle in character for all test temperature.

. Impact toughness higher than 50 J at −50 ◦C is observed forbase metal and weld simulated HAZ specimens for heat inputs15 kJ/cm and 22 kJ/cm. Hardness less than 350 VHN is observedfor base metal and weld simulated HAZ specimens with HIs22 kJ/cm and 50kJ/cm.

. As per literature review, in actual welding and simulated weldCGHAZ, a difference of 2–6% in the hardness value is observed.The difference in the microstructure between simulated CGHAZand actual weld CGHAZ decreases with decrease in peak tem-perature.

cknowledgement

The authors are grateful to the Department of Science andechnology (DST) New Delhi, Government of India for purchasinghermo-mechanical simulator Gleeble®3800 in Indian Institute ofechnology Roorkee from FIST grant (SR/FST/ETI-216/2007 Dated6.02.2008).

eferences

BS, 2014. Application of higher-Strength hull structural thick steel plates incontainer carriers. Am. Bur. Shipping.

hadeshia, H.K.D.H., 1999. The bainite transformation: unresolved issues. Mater.Sci. Eng. A 273–275, 58–66, http://dx.doi.org/10.1016/s0921-5093(99)00289-0.

u, F.Z., Wang, X.M., Chen, L., Yang, S.W., Shang, C.J., Misra, R.D.K., 2015. Influenceof cooling rate on the precipitation behavior in Ti–Nb–Mo microalloyed steelsduring continuous cooling and relationship to strength. Mater. Charact. 102,146–155, http://dx.doi.org/10.1016/j.matchar.2015.03.005.

ao, R., Li, J., Liu, D.S., Ma, J.Y., Chen, J.H., 2015. Micromechanism of decrease ofimpact toughness in coarse-Grain heat-affected zone of HSLA steel withincreasing welding heat input. Metall. Mater. Trans. A 46, 2999–3014, http://dx.doi.org/10.1007/s11661-015-2916-2.

asterling, K.E., 1983. Introduction to the Physical Metallurgy of Welding. Butter−worths & Co Ltd.

hosh, A., Sahoo, S., Ghosh, M., Ghosh, R.N., Chakrabarti, D., 2014. Effect ofmicrostructural parameters, microtexture and matrix strain on the Charpyimpact properties of low carbon HSLA steel containing MnS inclusions. Mater.Sci. Eng. A 613, 37–47, http://dx.doi.org/10.1016/j.msea.2014.06.091.

irault, E., Jacques, P., Harlet, P., Mols, K., Van Humbeeck, J., Aernoudt, E., Delannay,F., 1998. Metallographic methods for revealing the multiphase microstructureof TRIP-Assisted steels. Mater. Charact. 40, 111–118, http://dx.doi.org/10.1016/S1044-5803(97)00154-X.

arrison, P.L., Farrar, R.A., 1989. Application of continuous cooling transformationdiagrams for welding of steels. Int. Mater. Rev. 34, 35–51.

umar, S., Nath, S.K., 2016. Effect of weld thermal cycles on microstructures andmechanical properties in simulated heat affected zone of a HY 85 steel. Trans.Indian Institute Metals, 2016, http://dx.doi.org/10.1007/s12666-016-0880-1,

ISSN 0975-1645 (first online).

umar, S., Nath, S.K., Kumar, V., 2015. Effect of single and multiple thermal cycleson microstructure and mechanical properties of simulated HAZ in low carbonbainitic steel. Mater. Perform. Charact. ASTM 4, 365–380, http://dx.doi.org/10.1520/MPC20150007.

essing Technology 236 (2016) 216–224

Kumar, S., Nath, S.K., Kumar, V., 2016. Continuous cooling transformation behaviorin the weld coarse grained heat affected zone and mechanical properties ofNb-microalloyed and HY85 steels. Mater. Des. 90, 177–184, http://dx.doi.org/10.1016/j.matdes.2015.10.071.

Lambert-Perlade, A., Gourgues, A.F., Besson, J., Sturel, T., Pineau, A., 2004.Mechanisms and modelling of cleavage fractures in simulated heat-affectedzone microstructures in {HSLA} steel. Metall. Mater. Trans. A 35, 1039–1053.

Liang, G., Yang, S., Wu, H., Liu, X., 2013. Microstructure and mechanicalperformances of CGHAZ for oil tank steel during high heat input welding. RareMet. 32 (2), 129–133, http://dx.doi.org/10.1007/s12598-013-0036-y.

Liu, D., Cheng, B., Luo, M., 2011. Microstructure and impact fracture behaviour ofHAZ of F460 heavy ship plate with high strength and toughness. Acta. Metall.Sin. 47, 1233–1240, http://dx.doi.org/10.3724/SP.J.;1;1037.2011.00126.

Liu, W.Y., Liu, J.B., Zhu, C.M., Wang, H., 2011. Study in simulated heat-Affected zoneof ship steel. Adv. Mater. Res. 228–229, 1196––1200, http://dx.doi.org/10.4028/www.scientific.net/AMR.228-229.

Matusuda, F., Ikeuchi, K., Fukada, Y., Horii, Y., Okada, H., Shiwaku, T., Shiga, C.,Suzuki, S., 1995. Review of mechanical and metallurgical investigations of MAconstituent in welded joint in Japan. Trans. JWRI 24, 1–24.

Moorthy, A.L., 2011. Bullitin of defence research and development organisation:weld consumables for naval structural application. Technol. Focus DESIDOC 19,1–27.

Moura, C.M., Vilela, J.J., Rabello, E.G., Martins, D.G.P., Carneiro, J.R.G., 2009.Evaluation of the ductile-to-brittle transition temperature in steel low carbon.In: International Nuclear Atlantic Conference − INAC 2009, Rio de Janeiro,RJ,Brazil 27 September to 2 October (Associac ão Brasileira Deenergia Nuclear,Aben).

Oldfield, W., 1979. Fitting curves to Toughness data. J. Test. Eval. ASTM Int. 7,326–333.

Ragu Nathan, S., Balasubramanian, V., Malarvizhi, S., Rao, a. G., 2015. Effect ofwelding processes on mechanical and microstructural characteristics of highstrength low alloy naval grade steel joints. Def. Technol. 11, 308–317, http://dx.doi.org/10.1016/j.dt.2015.06.001.

Shi, Y., Han, Z., 2008. Effect of weld thermal cycle on microstructure and fracturetoughness of simulated heat-affected zone for a 800 MPa grade high strengthlow alloy steel. J. Mater. Process. Technol. 207, 30–39, http://dx.doi.org/10.1016/j.jmatprotec.2007.12.049.

Shi, M., Zhang, P., Wang, C., Zhu, F., 2014. Effect of high heat input on toughnessand microstructure of coarse grain heat affected zone in Zr bearing low carbonsteel. ISIJ Int. 54, 932–937, http://dx.doi.org/10.2355/isijinternational.54.932.

Song, S.H., Zheng, L., 2014. Effect of thermal cycling induced phosphorus grainboundary segregation on embrittlement of welding heat affected zones in2·25Cr–1Mo steel. Mater. Sci. Technol. 30, 1378–1385, http://dx.doi.org/10.1179/1743284713Y.;1;0000000482.

Yan, H.Q., Wu, K.M., Wang, H.H., Li, L., Yin, Y.Q., Wu, N.C., 2014. Effect of fastcooling on microstructure and toughness of heat affected zone in high strengthoffshore steel. Sci. Technol. Weld. Join. 19, 355–360, http://dx.doi.org/10.1179/1362171812Y.;1;0000000009.

Yue, X., 2013. Evaluation of heat-affected zone hydrogen-induced cracking inhigh-strength steels. J. Chem. Inf. Model., http://dx.doi.org/10.1017/CBO9781107415324.004.

Zheng, L., Song, S.H., 2013. Antimony-induced embrittlement in welding