Chapter 12-Flux Cored Arc Welding Equipment, Setup, and Operation

Question 1

List some factors that have left to the increased use of FCA welding.

Answer 1

• The improvements in the fluxes
• Smaller electrode diameters
• Reliability of the equipment
• Better electrode feed systems
• Improved Guns

Question 2

How is FCAW similar to GMAW?

Answer 2

Both processes use a constant-potential (CP) or constant-voltage (CV) power supply.

Question 3

What does the FCA flux provide to the weld?

Answer 3

The flux inside the electrode provides the molten weld pool with protection from the atmosphere, improves strength through chemical reactions and alloys, and improves the welds shape.

Question 4

What are the major atmospheric contaminations of the molten weld metal?

Answer 4

They come from oxygen and nitrogen.

Question 5

How does slag help an FCA weld?

Answer 5

Helps the weld by protecting the hot metal from the effects of the atmosphere, controlling the bead shape by serving as a dam or mold, and serving as a blanket to slow the welds cooling rate, which improves its physical properties.

Question 6

How can FCA welding guns be cooled?

Answer 6

Air-cooled or water-cooled.

Question 7

What problems does excessive drive roller pressure cause?

Answer 7

It can distort the electrode wire diameter, which can allow some flux to be dropped inside the electrode guide tube.

Question 8

List the advantages that FCA welding offers the welding industry.

Answer 8

• High deposition rate
• Minimum electrode waste
• Narrow groove angle
• Minimum pre cleaning
• All-Position welding
• Flexibility
• High Quality
• Excellent Control

Question 9

Describe the two methods of manufacturing FCA electrode wire.

Answer 9

Seamed Electrode- A thin sheet of metal is made into a U-Shape, a measured amount of flux is poured in and then squeezed shut. Then it is put through a series of dies to size it and further compact the flux.

Seamless Electrode- A seamless tube, normally 1 in. In diameter, one end is sealed which plus is poured into the open end. It’s vibrating while filling, ensuring it fills completely. Then it is put through dies for sizing.

Question 10

Why are the large diameter electrodes not used for all-position welding?

Answer 10

The large diameter electrode produces such large welds that they cannot be controlled in all-positions.

Question 11

How do deoxidizers remove oxygen from the weld zone?

Answer 11

Chemicals are added that react to the presence of oxygen in either form and combine to form a harmless compound.

Question 12

What do fluxing agents do for a weld?

Answer 12

Fluxing agents make the weld more fluid and allow it to flow outward, filling the undercut.

Question 13

Why are alloying elements added to the flux?

Answer 13

Because of the difference in the mechanical properties of metal that is formed by rolling or forging and metal is melted to form a weld bead, the metallurgical requirements of the two also differ. Some elements change the welds strength, ductility, hardness, brittleness, toughness, and corrosion resistance.

Question 14

How does the flux form a shielding gas to protect the weld?

Answer 14

As elements in the flux are heated by the arc, some of them vaporize and form voluminous gaseous clouds hundreds of times larger than their original volume. It forces the air around the weld zone away from the molten weld metal.

Question 15

What are the main limitations of the rutile fluxes?

Answer 15

The main limitation of the rutile fluxes is that their fluxing elements do not produce as high a quality deposit as do the T-5 systems.

Question 16

Why is it more difficult to use lime-based fluxes electrodes on out-of-position welds?

Answer 16

Their low melting temperature slag is fluid, which makes them generally unsuitable for out-of-position welding.

Question 17

What benefit does adding an externally supplied shielding gas have on some rutile-based electrodes?

Answer 17

With the weld being protected partially by the shielding gas, more elements can be added to the flux, which produces welds with the best of both flux systems, high-quality welds in all positions.

Question 18

How do excessive amounts of manganese affect a weld?

Answer 18

It can strengthen the weld metal too much and reduce its ductility.

Question 19

Why are elements added that cause ferrite to form in the weld?

Answer 19

It can control the hardness and brittleness of a weld.

Question 20

Why are some slags called refractory?

Answer 20

Because they solidify at a higher temperature than the weld metal.

Question 21

Why must a flux form a less dense slag?

Answer 21

So that they will float to the surface before the weld solidifies.

Question 22

WhT is the AWS classification for FCA welding electrodes for stainless steel according to Table 12-5?

Answer 22

A5.22

Question 23

E81T-5

Answer 23

E - Electrode
8 - Tensile Strength
1 - All-Position
T - Fluxed Cored Electrode

5 - Usability and performance capabilities

Question 24

What does the number 316 in E316T-1 mean?

Answer 24

316 -

Question 25

What is the advantage of using an argon-CO2 mixed shielding gas?

Answer 25

Weld penetration increases

Question 26

What can cause porosity in a FCA weld?

Answer 26

It can be caused by moisture in the flux, improper gun manipulation, or surface contamination.

Question 27

What happens to water in the welding arc?

Answer 27

Water breaks down into free hydrogen and oxygen in the presence of an arc, this can cause post-weld cracking.

Question 28

What is the thin, dark gray or black layer on new hot-rolled steel? How can it affect the weld?

Answer 28

Mill Scale

It may provide a source of enough oxygen to cause porosity.

Question 29

Why is uniformly scattered porosity hard to detect in the weld?

Answer 29

Because it’s under the weld surface.

Question 30

What cautions must be taken when chemically cleaning oil or paint from a piece of metal?

Answer 30

Must be done by the MSDS.

Question 31

What can happen to slag that solidifies on the plus ahead of the weld?

Answer 31

Porosity

Question 32

How is the electrode extension measured?

Answer 32

From the contact tip to the arc.