other arc welding techniques ctu in prague faculty of

CTU in Prague

Faculty of Mechanical Engineering

Ing. Petr Vondrouš, PhD., IWE

Other arc welding techniques

1st semester 2015/2016

Arc welding processes

• Welding processes that employ an electric arc are the most

prevalent in industry

• Already covered

– Shielded Metal Arc Welding

– Gas Metal Arc Welding

– Gas Tungsten Arc Welding

• For today

– Submerged Arc Welding

– Flux Cored Arc Welding

Deposition rates for various welding

processes (Uhrig, 1983)

Deposition rate comparison for

consumable used in welding duplex

stainless steels http://www.esab.com/

Arc welding processes – comparison of effectivity

• Selection of welding processes is done on base of

technological capability, quality and costs

SAW submerged arc welding

- use of granular flux which is fed into the joint from a flux hopper

- arc is struck between the wire and the workpiece beneath the flux

- arc and weld pool are shielded by the resulting envelope of molten flux

FSW – Friction stir welding

ČVUT, Fakulta strojní, Ústav strojírenské technologie, skupina svařování

SAW welding

SAW is defined as arc welding beneath

a bed of granulated flux.

Method no. acc. ČSN EN ISO 4063

12 – Submerged arc welding

121 with solid wire

122 with strip electrode

124 with metallic particle

125 with tubular electrode

126 with cored strip electrode



Basic parameters

Positions : all

Base material : MAG – structural steels

MIG- alloyed steels, Al, Cu, Ni alloys

Welded thickness : 2 - 100 mm

Current, voltage short circuit : I = 40 -190 A

U = 16 - 21 V

Spray : I = 120 - 500 A

U = 20 - 36 V

Diameter : 0,8 – 1,6 mm

Welding source : flat, solid wire mostly

DCEP, DC+



High power needed – 400-2000 A

-Transformers – AC current

-Rectifiers – DC current – ESAB LAF 631

-Invertors – most modern, AC, DC, Pulse

Welding source



DC(+ )

very stable arc for lower currents

Lower productivity

For low thickness sheet

DC(-) higher productivity

DC For higher currents – arc blow

Magnetic influence

AC – no arc blow - stability

Polarity - AC, DC +, DC-

SAW Welding polarity and productivity http://www.lincolnelectric.com/en-gb/support/process-

and-theory/Pages/minimizing-risk-offshore-saw.aspx



SAW is automated welding technique

1. Wire feed system

2. Movement system

Rotational welds - Often the movement of the welded structure, weld in position PA

Longitudinal welds – often movement of welding head

Automation



Consumables

Filler wire – solid wire,

flux cored,

metal cored wire,

stripe

Flux-



Flux

Granulated flux that is in solid state non conductive, while in molten

state conductive.

Functions:

Protection from gases

Metallurgy – desoxydation, purification of WM, alloying

Technology – slag forms weld, insulates arc and weld, no spatter

Electric – arc stability, ionization

Differently from SMAW – gas production should be low



Types of flux

Symbol Chem. Comp.

MS MnO + SiO2

CS CaO + MgO + SiO2

ZS ZrO2 + SiO2

AR Al2O3 + TiO2

AB Al2O3 + CaO + MgO

FB CaO + MgO + MnO +

CaF2

ST Metal containing

Terminology :flux is the powdered material used before a

welding. Its product after the welding is called slag.

Chemical compositionČSN EN ISO 14174 - Fluxes for submerged arc welding and electroslag welding – Classification

Metallurgy effectdescribed by Bazicity index –=reducing/oxidizing oxides

acidic – oxidation occures – Mn, Sineutralbasic – reduction of oxides to metals, little oxidic inclusions (500 ppm)

The higher the B.I. of a flux mix, the less the residual oxygen is in a weld, and the better the mechanical properties are; the welding performance, will be worse.

Production method –molten and groundsintered

network builder SiO2

viscosity controller CaF2

-liquid slag flow-inclusions-weld shape, surface tension-de-oxidation, de-nitridization-hydrogen removal-alloying



SAW

Thermal bilance:

High heat input

40 % WM melting

25 % heat flow into the WM

22 % flux melting

13 % wire melting



Use SAW



Twin, TANDEM, Multiwire

http://www.esab.com/automation/en/process/subarc-general/



Narrow gap welding



Material consumption

SAW submerged arc welding

Advantages

•high current (1000 A), high deposition rates – for thick materials

•Smooth, high quality weld

•Minimal smoke and fumes

•continuous wire electrode – high diameter (max 5-6 mm)

•no arc flash or glare

•flux and wire added separately - extra dimension of control

•easily automated

•joints can be prepared with narrow grooves

•twin wire, multiple torch …

Drawbacks - slag creation, much heat input, welding process not visible

FCAW Flux cored arc welding

Uses tubular wire with flux, metal powder inside.

Advantages

•High deposition rates (higher than SMAW, GMAW)

•Continuous electrode

•No creation

•Easily automated

Drawbacks

•Gun size

•Many process variables



Filler materials – solid and cored wires



FCAW

Method no. acc. ČSN EN ISO 4063

-not only 1 method

114 – self shielded tubular cored arc welding

no need for shielding gas

Part of GMAW

132 – MIG with flux cored electrode

133 – MIG with metal cored electrode

136 – MAG with flux cored electrode

138 – MAG with metal cored electrode

Part of SAW

124, 125, 126 – tubular electrode



Basic parameters

Positions : all positions

Base material : structural steels, alloyed steels,

Weld length :

Welded thickness : 2 - 20 mm

Current, voltage : I = 40 -500 A

U = 15-40 V

Diameter : wires 0,8 – 1,6 mm

Welding source : flat, AC, DC

Filling: rutile, bazic, metal



Core filling

Rutile – the best outlook, easy removal, good operational properties

All positions, shipyards – CO2

Bazic – pure metal, good ductility and CTOD – upto -60 ͦC, need ceramic

backing, all positions, yet welding is substantially different from solid wire,

bridges, seashore platforms,

Metal – metal powder inside, no slag – multilayer welds, thin and thick

plates welding suitable

Self shielding – no need for shielding gas, mainly only structural steels



Ceramic backing – for full penetration welding

www. http://www.kobelco-welding.jp/education-

center/abc/ABC_2008-02.html

Deposition rates for various welding

processes (Uhrig, 1983)

Arc welding processes – comparison of effectivity

• Selection of welding processes is done on base of

technological capability, quality and costs

FCAW characteristics

Advantages

•Less cleaning, good self shielding protection

•High deposition rates (higher than SMAW)

•Continuous electrode

•Easily automated

•Deeper penetration

Drawbacks

•Slag creation

•Fumes

•Price

•spatter

other arc welding techniques ctu in prague faculty of

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