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Validating the weldability with ux core arc weldingFCAW for deteriorated naval steels (FLUX CORED

ARC WELDING)

Validacin de la soldabilidad mediante alambre tubular con ncleo de fundente FCAW para acerosnavales deteriorados (FLUX CORED ARC WELDING)

Repairs and changes o steel plates in the structure o the vessels where it is possible to nd steels witha high degree o deterioration need reliable welded joints in naval steel o the type ASM A131 Gr.

A new to old. Due to the act that the variables associated to the weldability o the materials to berepaired are not known, it is necessary to make a study on the weldability o steel ASM A131 Gr A,in ull penetration seams or junctures, under the various parameters involved in the welding process,to determine the infuence o the corroding residues that aect the application o welding compoundsthrough the analysis o the metallurgical reactions o liquid condition in order to select the contributingmaterials with the alloy elements that are able to prevent these phenomena and to recommend the bestpractices or the electric arc welding process with tubular electrode with FCAW fux core.

Las reparaciones y cambios de lminas de acero en la estructura de los buques donde se presentan aceroscon alto grado de deterioro, requieren uniones soldadas conables en el acero naval ASM A131 Gr. Anuevo a viejo. Debido al desconocimiento de las variables asociadas con la soldabilidad de los materiales areparar, es necesario realizar el estudio de la soldabilidad del acero ASM A131 Gr A, en uniones o juntasde penetracin completa, bajo los dierentes parmetros del proceso de soldeo, determinar la infuenciade los residuos de corrosin que aectan la aplicacin de la soldadura, mediante anlisis de las reaccionesmetalrgicas de estado lquido para seleccionar los materiales de aporte con elementos de aleacin capacesde evitar estos enmenos y recomendar las mejores prcticas del proceso soldeo por arco elctrico conelectrodo tubular con ncleo de undente FCAW .

Key words:Weldability, corrosion, fux Cored Arc Welding.

Palabras claves: soldabilidad, corrosin, fux Cored Arc Welding.

Alonso Patarroyo1

Elvis Solano2

Fabio Cueca3

Fernando Rojas4

Alredo Morales5

Abstract

Resumen

1 Servicio Nacional de Aprendizaje SENA. e-mail: [email protected] Servicio Nacional de Aprendizaje SENA e-mail: [email protected] Servicio Nacional de Aprendizaje SENA. e-mail: [email protected] Servicio Nacional de Aprendizaje SENA. e-mail: [email protected] Corporacin de Ciencia y ecnologa para el Desarrollo de la Industria Naval, Martima y Fluvial COECMAR. e-mail: [email protected]

Date received: March 2nd, 2009 - Fecha de recepcin: 2 de marzo de 2009Date Accepted: October 6th, 2009 - Fecha de aceptacin: 6 de octubre de 2009

Ship Science & Technology - Vol. 3 - n. 6 - (41-52) January 2010 - Cartagena (Colombia)

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Studies on the weldability o ASM A-131grams,naval steel with a high degree o deterioration arescarce. Te objective o this study is to establish the

behavior o these steels when they are subject to theFCAW (Flux Cored Arc Welding) processes. Tisprocess stands out or its high productivity andwelding reduction costs as compared to manualprocesses. It is based on the act that FCAW is asemi automatic process that reduces the periods ousing welding, welding costs and also, they increaseproductivity by improving several indicators ascompared to the SMAW process.

In order to validate the weldability, mechanic

practices, micro structural behavior studies as wellas studies on the behavior o several commercialtubular wires in Colombia will be conducted.

Welding with an electric arc with tubular electrodewith fux core FCAW (Flux Cored Arc Welding)is a semi automatic welding process that takes

advantage o an electric arc between a continuouselectrode o ller metal and the welding electrodeand the welding puddle. Tis process is used withthe protection rom a fux that can be ound intothe tubular electrode, with or without an additional

gaseous protection rom the outside, and withoutapplying any pressure to it.

Te method that has been used to assess theweldability conditions o Steel o the type ASMA131 Gr. A, through the FCAW process in themanuacture and repair o vessels, by Cotecmarand Centro de Materiales y Ensayos del SENA,

has been based on the characterization o steels othe type ASM A131 Gr. A with steel sampleso ships built on dierent years. Te ollowingtubular wires were selected or this study in orderto be assessed in terms o their behavior beoreweldability o the naval steel as per the classicationANSI / AWS A 5.20; E71-1, E71-8 and E71-11, which was encoded in this document as -1, -8y-11 respectively.

Introduction

Basics of the process

Experimental Design

Fig. 1. A diagram of self- protected FCAW.

Source: Lincoln Electric.

Tubular electrode

Metal powders, materialvapors generators, dexosidantsand cleaning agents

Arc shield formed byvaporized compoundsand slag generators

Arc and metal transfer

Guide wire andcontact tube

Melten slag

Solidied slag

Weld metal

Weld puddle

Wieldingdirection


Patarroyo, Solano, Cueca, Rojas, Morales

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Tree stages were ollowed here: characterizationo the naval steel, selection o the ller materialsand the assessment o the weldability.

Creating the parameters o the welding equipment

was perormed in order to qualiy positions 2Gand 3G correspondingly as per code number AWSD1.1:2004

Te seam junctures were made with base materialsaccording to the production years and servicecondition o the vessel. Te nomenclature or thebase material was set as ollows: new material (N),old material (V) and old- welded material (VS);and the resulting combinations were N-VS, V-Vand N-V or each one o the junctures part o the

research.Te design o groove butt joints with root size aceequivalent to 0 a 5/

32 root opening equivalent to

5/64

a1/16

and bevel angle and chamer o 45.

Te result analysis was done bysimple comparisonwith: 18 observations in the tension test whichcorresponded to the 3 combinations per each oneo the designation and 2 test tubes per coupon asper the Regulation, 36 observations in the side 3combinations and 4 test tubes per coupon accordingto code AWS D1.1 and in the hardness test 36observations or a total o 720 points obtained, 20points per test tube). Te metallographic analysishad 27 metallographies (3 or each combinationand designation), or the base material, weldingjobs and the area that had been aected by heat,

done in the old material (V) and old welding jobs(VS) whose interest is to veriy the weldabilitybehavior in them or the FCAW process.

Fig. 2. Design of a typical joint.

Fig. 4. Cutting and tagging the test tubes for chemicaland metallographic analysis of the base metals.

Fig. 3. ASTM A131 G A. Naval steel ame-cutting

process.

NewMaterial

45

1/2

1/16

5/32

OldMaterial

Validating the weldability with a tubular wire FCAWfux cored or deteriorated naval steels

ASTM A131 G A. Naval steel.

1972 1969 2008


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Fig. 5. Test coupon for Naval Steel of the type ASTMA131 Gr A of Steel made in 2008 and steel made in 1972.

Prior to welding.

Fig. 6. Test coupon of naval steel of the type ASTM A131Gr A, steel manufactured in 2008 and one from 1972.

Fig. 7. Performing the tension tests on the test specimens.

Te AWS D1.1 code criteria were applied here,obtaining the design o the joint o Fig. 2 or whichthe fame- cutting process was perormed in orderto generate the coupons on which the welded jointswere done ollowing the FCAW process with three

electrode wires -1,-8 and -11.

Heat input H

Where:

H = Heat input in J/centimietersA = amperesV = electrical potencials in voltsVa = Advancing speed in inches / minutesA = current in amperesV = voltage in voltsva = advancing speed in inches per minutes60 = constant

Heat input for position 2G Root pass = 64,8 KJ/cm Filler pass = 61,8 KJ/cm Presentation pass = 60.800,11 J/m

Heat intake for position 3G Root pass = 53.647,05 J/m Filler pass = 52.258,06 J/m Presentation pass = 49.241,37 J/m

Te base material o the test tubes obtained romthe plates was characterized during the research, toveriy it with ASM A131 Gr A or Naval Steel,according to what is shown in Fig. 3. Chemicalanalysis tests were perormed by spectrometry thusgenerating the chemical composition o able 2,rom where it is easy to conclude that the navalsteels manuactured in 1969, 1972 and 2008, aretypical steels o designation ASM A131 Gr A.

=

(1)H

A.V. 60

Va

Parameter creation of the Welding Pro-cess and calculation of the Heat input (H)

Base material characterization



(1)

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Later, a metallographic analysis was perormed andnding bead like segregation bands in the navalsteel rom 1969 and 1972, (see Figs. 8 and 9) (boxes1 and 4) on a erritic matrix (box 3), supposedly dueto the aging process due to the precipitation and

migration o carbon on errite. Also sphere- shapedoxides were ound in the erritic structure (box 2),probably generated by corroding environments inan aqueous or gaseous environment.

Input Pass Amperes Volts Advancing Speed Polarity

-1

1 160 - 190 18 - 21 3,0 Negative

2 140 - 170 19 - 23 3,1 N3 140 - 170 19 - 23 3,7 N

-8

1 160 - 195 19 - 23 3,2 N

2 155 - 180 18 - 21 2,8 N

3 155 - 180 18 - 21 3,2 N

-11

1 150 - 180 18 - 21 3,5 N

2 140 - 170 17 - 20 3,3 N

3 140 - 170 17 - 20 3 N

Table 1. Parameter classication FCAW process.


Element C Si Mn P S Cr Mo Ni Cu V Nb

Steel vesselbuilt in 1969

.2098 .0242 .7724 .0175 .0181 .0010 .0010 .1526 .0167 .0010 .0026


.2490 .0342 .7621 .0123 .0215 .0010 .0010 .1878 .0492 .0010 .0027


.1549 .2227 .6974 .0106 .0295 .0199 .0010 .1804 .0785 .0010 .0028

Table 2. Chemical composition of the base material naval steel.

Fig. 8. Metallography ASTM A 131 Gr A steel from 1969.

1

2

3

4

Fig. 9. Metallography, ASTM A 131 Gr A steel from 1972.

1

2

3

4


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As compared with the micro structure o navalsteel rom 2008, that shows an evenly distributedbeaded erritic structure as can be seen in Fig. 10.

Te average Vickers analysis o hardness o thesamples o the naval steel rom 1969, 1972 and2008, is consistent with the metallographic analysis.It was possible to obtain hardness indexes greaterthan that o the steel rom 2008, supposedly dueto the aging phenomenon due to the precipitationand migration o carbon on errite.

By applying the parameters in able 1, andthe design o the joint in Fig. 2, the FCAWwelding process was applied with input -1, -8and -11, according to what was stated during theexperimental design the Joints welded using thevisual inspection techniques, colored penetratingfuids, tension destructive test, side crease,metallography and hardness prole.

Regarding the side crease tests, the test tubes withthe various combinations had a good behavior and

the behavior is acceptable under the criteria inCode AWS D1.1.

Fig. 10. Metallography ASTM A 131 Gr A steel from 2008.

Fig. 11. Behavior of the hardness prole for welded joints.

Year 1969 1972 2008

VickersHardness

143,51 143,41 134,45

Table 3. Hardness Comparison.

Table 4. Maximum load, tension practice.

Table 5. Parameters of the Vickers hardness test.

2

4

Characterization of a Welded Joint

Input Joint Amperes

-1

V-V 68

N-VS 68

N-V 72

-8

V-V 59

N-VS 58

N-V 69

-11

V-V 73

N-VS 68

N-V 76

Load (gm) 300

Load Constant 1854,4

Occular Constant 20 X 0,6234

310

Specimen

HardnessValues

290

270

250

230

210

190

170

-1VV

-1NVS

-1NV

-8VV

-8NVS

-8NV

-11VV

-11NVS

-11NV

0 1 2 3 4



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Micrograph of a naval steel of theType ASTM A- 131 Grade A withperlite (dark) dual phase on aferritic matrix, Attack with Nital at2 %, 200 x enlargement. epresence of some isolated carbons

is evident here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attack with Nital at2 %, 200 x enlargement. epresence of some isolated carbons

is evident here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A withperlite (dark) dual phase on aferritic matrix, attacked with Nitalat 2 %, 200 x enlargement. epresence of some embeddedhydrocarbons is evidenced.

Micrograph of a naval steel of theType ASTM A- 131 Grade A withperlite (dark) dual phase on aferritic matrix, enlargement 200 x.e presence of some embeddedhydrocarbons in the ferritic matrixand a ner perlite grain due to theame- cut and latter welding job.

INPUT 1

STEEL 1969 STEEL 1969

Fig. 12. Metallography - Input - 1 VV Joint.

Fig. 13. Metallography - Input - 1 Joint NV.

Micrograph of a naval steel of theType ASTM A- 131 Grade A withperlite (dark) dual phase on a

ferritic matrix. Attack with Nital at2 %, 200 x enlargement. A ningperlite grain condition is evidencedhere as well as some isolatedhydrocarbons.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on a

ferritic matrix, Attacked with Nitalat 2 %. 200 x enlargement. epresence of some isolated hydrocar-bons is evidenced here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, attacked with Nitalat 2 %, 200 x enlargement. epresence of some embeddedhydrocarbons is evidenced here.

Micrograph of a naval steel of theType ASTM A- 131Grade A, withperlite (dark) dual phase on aferritic matrix, Nital at 2 % attack,enlarged 200 x. Partiallytransformed, tempered perlite,some isolated oxides, micro poresand micro crevices can be seenhere.

INPUT 1



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Fig. 14. Metallography - Input - 1 NVS Joint.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement. Aning perlite grain trend is

evidenced here as well as someisolated hydrocarbons.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, attacked with Nitalat 2 %, 200 x enlargement. epresence of some isolated

hydrocarbons is evidenced here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement. Aning perlite grain trend isevidenced here, some isolatedhydrocarbons in the perlite grainslimits.

Micrograph of a naval steel of theType ASTM A- 131Grade A, withperlite (dark) dual phase on aferritic matrix, Nital at 2 % attack,enlarged 200 x. Partiallytransformed, tempered perlite,some isolated oxides, micro poresand micro crevices can be seenhere.

INPUT 1

STEEL 2008WELDED STEEL

1969


Micrograph of a naval steel of theType ASTM A- 131 Grade A, with

perlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement. epresence of some hydrocarbons isevidenced here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, with

perlite (dark) dual phase on aferritic matrix, attacked with Nitalat 2 %, 200 x enlargement. epresence of some hydrocarbons isevidenced here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 500 x enlargement. einclusion of slug together withsome hydrocarbons and groupedoxides is evidenced here.

Micrograph of a naval steel of theType ASTM A- 131Grade A, withperlite (dark) dual phase on aferritic matrix, Nital at 2 % attack,enlarged 200 x. Partiallytransformed perlite as well as someisolated hydrocarbons can be seenhere.

INPUT 8




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Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, attacked with Nitalat 2 %, 500 x enlargement. epresence of some acicular perlite

with some isolated hydrocarbons

embedded in the ferritic matrix isevidenced here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement. Aning perlite grain trend together

with some directed micro crevicesis evidenced here.

Micrograph of a naval steel of theType ASTM A- 131Grade A, withperlite (dark) dual phase on aferritic matrix, Nital at 2 % attack,enlarged 200 x. It is possible to seepores together with embeddedoxides in the ferritic matrix.

INPUT 8


1969

Fig. 17. Metallography - Input - 8 NV Joint.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on a

ferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, attacked with Nital

at 2 %, 500 x enlargement. Someoxides embedded in the grainlimits of the pearlitic phase areevidenced here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement. Aning grain trend of the pearliticphase, generalized porosity in theferritic matrix and some isolatedhydrocarbons in the limits of the

erlite rain can be seen here.

Micrograph of a naval steel of theType ASTM A- 131Grade A, withperlite (dark) dual phase on aferritic matrix, Nital at 2 % attack,200 x enlargement. Polygonalferrite with hydrocarbons includedand the presence of pores isevidenced here.

INPUT 8



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Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, attacked with Nitalat 2 %, 500 x enlargement. Someoxides embedded in the grainlimits of the pearlitic phase are

evidenced here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement. Aning grain trend of the pearliticphase is evidenced here.

Micrograph of a naval steel of theType ASTM A- 131Grade A, withperlite (dark) dual phase on aferritic matrix, Nital at 2 % attack,enlarged 200 X. It is possible to seeacicular perlite as well as someisolated oxides in the grain limits.

INPUT 11


1972




Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, attacked with Nitalat 2 %, 200 x enlargement. eveins on the ferrite grains limits areevidenced here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement. Aning pearlitic grain trend, ferritegrain limit veins as well as someisolated hydrocarbons areevidenced here.

Micrograph of a naval steel of theType ASTM A- 131Grade A, withperlite (dark) dual phase on aferritic matrix, Nital at 2 % attack,enlarged 200 X. It is possible to seeacicular perlite as well as someisolated oxides in the grain limits.

INPUT 11


1972


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Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement. epresence of some isolatedhydrocarbons, a ferritic matrix and

an acicular pearlitic matrix isevidenced.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, attacked with Nitalat 2 %, 200 x enlargement. epresence of some isolated hydrocar-bons, a ferritic matrix and acicular

perlite are evidenced here.

Micrograph of a naval steel of theType ASTM A- 131 Grade A, withperlite (dark) dual phase on aferritic matrix, Attacked with Nitalat 2 %, 200 x enlargement. Aning grain trend of tempered andpartially transformed perlite andsome isolated hydrocarbons can beseen here.

Micrograph of a naval steel of theType ASTM A- 131Grade A, withperlite (dark) dual phase on aferritic matrix, Nital at 2 % attack,200 x enlargement. A ning grainperlite trend and some isolatedhydrocarbons are evidenced here.

INPUT 11


Source: research results.

Te average Vickers hardness or all base materials,shows that or years 1969-(143,51) and 1972-(143,41), it is relatively similar and they are higherwhen compared to the year 2008-(134,45). Tisis due to the probable hardening caused by itsmicro component precipitation and the years thematerials have been used in the vessel.

Te base materials used in this study exhibiteda erritic matrix with perlite as the second microcomponent. Mechanical tension tests showedmaximum load values, maximum eort values,rupture load and rupture eort within the rangesset by regulation ASM A131 Grade A ordesignation -11. Designations -1 and -8 are belowthe values stated by the regulation and especially -8whose rupture occurred in the input material.

Analysis and Conclusions During welding process FCAW, some weldingprocedure specications were generated, as well asthe qualication o the welders. Te conclusionswere that the input materials designated as -1 and-8, require highly trained welders, because manag-ing the welding puddle and especially the slag fu-ency result in inclusions and lack o penetration inthe root o the joint.

Te Best behavior was exhibited by the inputmaterial designated as -11, since it generates cleanwelded joints and the welder needs an intermediatetraining level. It is possible to go rom manualcoated electrode applications SMAW, to theFCAW process.

Calculating the input heat or inputs -1,-8 and -11generates heat aected areas that are typical inclean steels like ASM A 131 Gr A.

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Te metallographic analysis concluded that thesteels rom 1969, 1972 and 2008, even thoughthe rst two exhibit pearlitic segregations, thisdoes not aect the welded joints, including the oldwelding jobs ound. A NV welding process should

be graded or maintenance cases.

FCAW welding process with AWS E71-11inputmaterial exhibits the best welding results. Itdeveloped clean ull penetration joints. Tisbehavior allows or unilateral welds in vessels, thusdisplacing the SMAW welding methods whichhave partial penetration and root clean up.

ORZAR, Ral. Mecnica de racturas enestructuras navales. En: Congreso Panamericanode Ingeniera Naval XVI COPINAVAL991988

CASILLA, Ivn J. UNFRIED, Jimmy S.Soldabilidad de un acero microaleado utilizandoel proceso SMAW y metal de aporte errtico dealta resistencia. Revista Ciencia y ecnologa deBuques Numero 3 Volumen 2. Julio de 2008.

AMERICAN WELDING SOCIEY AWS,D1.1/D1.1 M:2006 Structural Welding Code Steel No 1.3)

HERRERA MELO, Oscar Javier.FUNDAMENOS DEL PROCESO,Soldadura por arco con ncleo de undente"FCAW", 2007.

WELDING HANDBOOK. Volume 2. WeldingProcesses Chapter.5 p. 159.

WELDING HANDBOOK. Volume 2. WeldingProcesses Chapter.5 p. 159 - 174.








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