SERVICE WELDING GUIDE Caterpillar

Flux Core (FCAW) Flux Cored Arc Welding

Usage:

Principle Features

The benefits of FCAW are achieved by combining three general features.

1. The productivity of continuos wire welding.

2. The metallurgical benefits that can be derived from flux.

3. A slag that supports and shapes the weld bead.

FCAW combines the characteristics of Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW), and Submerged Arc Welding (SAW).

Advantages of FCAW

Flux Cored Arc Welding has many advantages over the manual SMAW process and provides certain advantages over the SAW and GMAW processes. In many applications, the FCAW process provides high quality weld metal at lower cost with less effort on the part of the welder than SMAW. These advantages can be listed as follows.

* High quality weld metal deposit.

* Excellent weld appearance and smooth, uniform welds.

* Excellent contour of horizontal fillet welds.

* Many welds weldable over a wide thickness range.

* High operating factor, easily mechanized.

* High deposition rate, high current density.

* Relatively high electrode deposit efficiency.

* Economical engineering joint design.

* Visible arc, easy to use.

* Less precleaning required than GMAW.

* Up to 4 times greater deposition rate than SMAW.

* Higher tolerance for contaminants that may cause weld cracking.

* Resistant to underbead cracking.

Limitations of FCAW

* FCAW is presently limited to welding ferrous metals and nickel based alloys.

* The process produces a slag covering which must be removed.

* FCAW electrode wire is more expensive on a weight basis than solid electrode wires, except for some high alloys steels.

* The equipment is more expensive and complex than that required for SMAW; however, increased productivity usually compensates for this.

* The wire feeder and power source must be fairly close to the point of welding.

* For gas shielded version, the external gas shield may be adversely affected by breezes and drafts.

* More smoke and fumes are generated (compared to GMAW and SAW).

Fundamentals of the process

Definition

The Flux-Cored Arc Welding process is a process in which coalescence is produced by heating with an arc between a continuous filler metal (consumable) electrode and the work. Shielding is obtained from a flux contained within the electrode. Additional shielding may or may not be obtained from an externally supplied gas or gas mixture.

Slang names

1. FabCo - Fabshield-Inner Shield - Dual Shield

Process Principles

1. Heat source - an arc between a continuous filler metal electrode and the weld spot.

2. Shielding - is obtained from flux contained within the tubular electrode and with or without additional shielding from an externally supplied gas.

3. Filler metal - is obtained from a continuously-feeding tubular electrode.

4. Flux - will provide deoxidizers, ionizers, purifying agents, and in some cases alloying elements.

Figure 21

Methods of Application

1. Manual - not applicable.

2. Semiautomatic - most popular method of application.

3. Machine - widely used.

4. Automatic - widely used.

Metals Weldable

Thickness Range

Figure 22

Position Capabilities

* Grooves - all positions depending on size and type.

* Fillets - all positions depending on size and type.

* Limitations - would depend on skill of the operator.

Electrical Requirements

Welding Circuit

Figure 23

Welding Current Types

* D.C.E.N. or D.C.E.P. depending on type of wire.

Power Source Types and Characteristics

* Constant voltage type with a flat volt amp curve.

* Constant speed system with a constant current machine. The wire feeder is a variable speed system.

Other Equipment Requirements

Additional Equipment Necessary

Welding guns - shielding gas - water cooling system. Welding guns are of two different types. The guns for externally gas shielded wires are identical to the guns for the Gas Metal Arc Process. For the self-shielding electrodes, the guns will contain wire guides that increase the electrical stickout. This is designed to preheat the wire.