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LRSS – LABORATÓRIO DE ROBÓTICA, SOLDAGEM E SIMULAÇÃOLABORATÓRIO DE ROBÓTICA, SOLDAGEM E SIMULAÇÃO

Laboratório de Robótica, Soldagem e Simulação

“The low hydrogen covered electrode”

Alexandre Queiroz Bracarense Claudio Turani

Ezequiel Caires Pereira Pessoa Ivanilza Felizardo

Federal University of Minas GeraisBelo Horizonte, MG, BRAZIL



QUESTION:What could happens if the polymer is placed

directly on the coating as a binder and sealer?

It is an extreme condition, where

the electrode (usually E6013)

Everything started with underwater wet

welding

needs to be varnished

Could it eliminates the varnishing needs?

Many varnishes were tested including Expanded polystyrene (Styrofoam™) dissolved in chloroform



Electrodes produced in the laboratory

In the Laboratory



Manufacturing

Balance

Raw material

Mixer

Mixer

Binder

Dry mix area Wet mix area

Briquettepress

Bri

qu

ette

Dry mixDrymix

Wet mix

Covered electrode

Bri

qu

ette

WireExtrusion area

Electrode extruder

Drying 150°C 2hours

Air drying

Traditional flow

NEW FLOW (Impermeable E6013 covered electrode)

Drying area

Drying area

Air coolingPac

kag

e

Pac

kag

eVarnishing

For undewater



Evaluation of extrudability

E6013

E6013


Laboratório de Robótica, Soldagem e SimulaçãoWF +

WF +

PF+

PF+

500x

500x

100x

Microstructure of underwater wet weld made with E6013 electrode waterproofed with VINILIC varnish

Important surprise, yet inexplicable!

Typical!!!!



F P+

100x

500x

500x

Microstructure of underwater wet weld made with E6013 electrode binded with POLYSTYRENE AF

+

AF+



Full with ACICULAR FERRITE!!!!

Acicular ferrite is an indication of good mechanical properties.

It is difficult to obtain acicular ferrite in underwater wet welding!!

Using the polymer it was easily obtained!!!



The underwater project still goes on, however….

the focus turned to….

.....conventionalwelding with E7018

This new technology could eliminates redrying, maintenance and more......



Basic electrode fabrication

Balance

Raw material

Mixer

Mixer

Binder

Dry mix area Wet mix area

BriquettePress

Bri

qu

ette

Dry mixDrymix

Wet mix

Covered electrode

Bri

qu

ette

WireExtrusion area

Electrode extruder

Pac

kag

e

Drying 150°C 2hoursBaking 400°C 9hours

Air dryingNew flow (Impermeable E7018 covered electrode)

Drying area

Air cooling

Pac

kag

e



Methodology1st PHASE: Adjustments in the conventional formulation of basic type E7018 covered electrodes, replacing the silicate by polymer in solution and manufacturing in laboratory.

Electrodes produced in the laboratory



Methodology

2nd PHASE: Production, in industrial scale, of batches of impermeable E7018 electrodes.

Electrodes produced in the factory



Production Validation tests: Bead on plate

• Arc stability• Bead appearance• Chemical composition•Microstructure• Diffusible hydrogen• Hardness

Methodology

Validate formulae changes

Direction for new changes



First good results – Economy of water and energy!!!Results

Considering the annual E7018 (3,25mm) Brazilian market: 2,000 tons per month

In the factory

Conventional electrodesIn 12 months = 24,000 tons = 8,500 tons of powder = 2,300 tons of silicate = 1,400,000 liters of water + drying energy with natural gas =

Impermeable electrodesIn 12 months = 24,000 tons = 8,500 tons of powder =

Economy 648,000.00 USD/year

0 liters of water + no pre-drying

648,000.00 USD



Results

Welds of Electrodes produced in the

laboratory

Weld of Electrodes produced in the

factory



ResultsMore good results – Economy in maintenance

In the Client

Conventional electrodesPre-drying and maintenance: 538,700 KwH/year

Impermeable electrodesPre-drying and maintenance: 0 KwH/year

Economy 120,415.29 USD/year



Resultswelding current

Considering an E7018 (3,25mm) with a deposition rate of 1,09Kg/h

Conventional electrodesVoltage: 24Volts and Current: 130AConsume (24,000 Tons/year): 68,697,247 KwH/year

Impermeable electrodesVoltage: 24Volts and Current: 110AConsume (24,000 Tons/year): 58,128,440 KwH/year

Difference = Economy 10,568,807 KwH/year


Laboratório de Robótica, Soldagem e SimulaçãoWeld Metal chemical analyses

% C % Si % Mn % P % S % Cr % Ni % Mo % VStandard 0,15 0,75 1,60 0,04 0,04 0,20 0,30 0,30 0,08

Electrode 0,18 0,72 1,14 0,03 0,01 0,05 0,02 0,01 0,01

1 2 3 4 5 6 7 8 9 10 11 12

274 269 261 255 251 285 274 275 279 252 286 277

Hardness at acicular ferrite regions

~ 270 HV

Results

impermeable

conventional



100X

Top Center RootWeld metal microstructure – different positions

Nital 2%

500X

100

0X

Results



Still Acicular ferrite!!!!!

Results



Tensile test

Tensile stress 677,9 MPa

Yield stress 554,3 MPa

Elongation after rupture 29,1 %

Results



Impact Test– Charpy V

(- 30oC)

(- 45oC)Absorbed energy at -30o C = 68 J

Absorbed energy at -45o C = 50 J

Results



Impermeable

The slag analysis for the conventional electrode showed

that the compounds were not all used during the burning through the arc, probably indicating that

they are in excess in the formulae.

On the other side, for the impermeable covered electrode,

the x-ray pattern showed few peaks (an unusual morphology for

slags) indicating probably that most of the compounds were

burned during the welding.

SLAG X-ray DiffractometryConventional

This is probable the phenomena associated

with all the benefits observed in weld metal.

Results



Fume analysis – ion chromatographyConventional electrodeParticulates

Probable due CaF2 - tracesFumes

Went up until stabilize

Dangerous materials: aluminum, Fluor, iron oxides, magnesium, manganese and vanadium.

Results



Fume analysis – ion chromatographyImpermeable electrodeParticulates

Fumes

No indication

Larger scale

No indication

Gas flow was turned off

Results



Diffusible Hydrogen – Cromatography

Results



AWS Standard



Sample Fabrication date

Lot Tests date (ml/100g deposited metal)

1 07/26/2010 1 08/12/2010 3,42 07/26/2010 1 08/12/2010 3,93 07/26/2010 1 08/12/2010 4,74 07/26/2010 1 09/30/2010 2,15 07/26/2010 1 09/30/2010 1,86 07/26/2010 1 09/30/2010 2,17 07/26/2010 1 09/30/2010 1,8

8 09/01/2010 2 09/30/2010 1,99 09/01/2010 2 09/30/2010 1,7

10 09/01/2010 2 09/30/2010 1,911 09/01/2010 2 09/30/2010 1,9

Diffusible hydrogen (Commercial E7018 – 7,5m/100gr)

v

15 days

60 days

30 daysv

Lot 1 – mixer type “paddle mixer”Lot 2 – mixer type “screw blender”

Results



IMPORTANT OBSERVATION: Seems that the impermeable electrode “exposure” doesn’t promote the hydrogen content increase and even reduce it …..

Diffusible hydrogen

Results



• It is possible to be produced the electrode in large scale;

• Electrode with excellent operacionability (lower current);

• Undetermined durability – hydrophobic coating;

• Excellent coating mechanical resistance;

• Can save a lot of money;

• Waive special maintenance and conservation;

• Superior mechanical and metallurgical results related to conventional

electrodes;

• Technology applies for others coatings types;

• Very low hydrogen weld metal - the possibility of approval the electrode as

E7018-1H4R, H2(??) or whether the standard permits….

Remarks regarding to the findings

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