ESAB Knowledge center.
MIG Wire Selection Guide
March 20, 2014
Welding performance of a MIG wire is described by the following:
- Weld metal soundness
- Weld puddle fluidity
- Bead shape and edge wetting
- Spatter tendency
Weld Metal Soundness
Soundness in weld metal is characterized by a lack of porosity, good fusion, and freedom from cracking. Porosity, the most frequently cited cause of poor weld soundness, is caused by excess oxygen from the atmosphere, the shielding gas, and any base plate contamination combining with carbon in the weld metal to form bundles of carbon monoxide (CO) gas. Some of the CO can become trapped as the weld cools forming pores called porosity. Typically, the MIG wire process is recognized as having very low hydrogen in the deposit. Factors, such as moisture in the shielding gas, atmospheric conditions, and plate condition, may have a varying degree of adverse effect on the actual diffusible hydrogen in the weld deposit.
Control Of Porosity
Sufficient deoxidation of the weld puddle is needed to minimize CO formation and porosity. To accomplish this, Spoolarc wires contain elements with which oxygen combines in preference to carbon to form harmless slags. These elements, called deoxidizers, are manganese (Mn), silicon (Si), titanium (Ti), aluminum (Al), and zirconium (Zr). Aluminum, titanium and zirconium are very powerful deoxidizers — perhaps five times as effective as manganese and silicon.
Weld Puddle Fluidity, Bead Shape And Spatter
Fluidity of the molten weld puddle is important for several reasons. Fluid puddles tend to wet out smoothly at the edges and produce a flat, smooth bead shape, especially on fillet welds. This is important on multi-pass, short arc welds where lack-of-fusion defects can occur if bead shape is poor. Flat, well-wet-in beads are also desirable where appearance is a primary concern and where post weld grinding may be necessary to meet job requirements.
Caution: Excessive puddle fluidity can cause performance difficulties in out-of-position welding or in making concave horizontal fillets.
Influence Of Manganese And Silicon
Choosing the manganese and silicon content of a MIG wire is usually the major decision an operator must make. Increasing manganese and silicon affects puddle fluidity, bead shape and other factors. The Al, Ti and Zr deoxidizers in Spoolarc 65 wire tend to make its puddle somewhat sluggish. The “stiff” puddle characteristic makes this wire ideal for pipe - especially small diameter pipe - and many other out-of-position welding jobs.
Influence Of Shielding Gas and Arc Voltage
CO2 shielding causes more turbulent wire-to-base plate metal transfer and tends to create a more crowned bead with greater spatter loss.
Argon-based shielding gases provide more stable, uniform wire-to-base plate metal transfer, well-shaped beads, minimal spatter loss and a lower fume generation rate.
Increasing arc voltage tends to increase puddle fluidity, flatten the weld bead, increase edge wetting and increase spatter. Higher voltages also reduce penetration and may cause additional loss of alloying elements.
Spoolarc wires are processed either copper-coated using the proprietary ESAB HI DEP III manufacturing process, or as “bare” (uncoppered) product. Spoolarc wires are available in a variety of alloys, diameters and packages to meet the most demanding customer applications.
Spoolarc wires, either copper-coated or “bare,” provide excellent feedability and arc stability under the roughest shop conditions and most demanding applications even at high wire feed speeds…that means less downtime, greater productivity.
Note: Spoolarc “bare” wires are a standard product for customers requiring or preferring no copper coating.
Why Feedability Is So Improved With ESAB
- All Spoolarc MIG wires are cleaned after the final drawing process to remove residual drawing lubricants and are then treated with a proprietary ESAB process to insure good feeding, arc stability and low weld deposit hydrogen.
- Spoolarc HI DEP III (copper-coated) wire has a matte finish with a low (typically 0.05% wt.) copper coating that is thin and tightly adherent - eliminating troublesome copper flaking.
- The matte-finish on the Spoolarc wire contrasts with many conventional MIG wires that are “shiny” in appearance. These “shiny” wires do not have any enhanced welding performance. In fact, these wires are generally higher in copper coating level (up to 0.30% wt.) and are prone to copper flaking which detracts from their performance.
- Higher tensile strength wire has a greater resistance to “buckling” under compression. ESAB draws most MIG wires directly from rod to final size resulting in a high tensile strength product that resists “birdnesting” when restrictions in the feed system occur.
Excellent Arc Characteristics
- Quick starting with Spoolarc wire from ESAB minimizes weld spatter - a common problem with other MIG wires.
- Spoolarc wires produce excellent spray arcs at lower voltages, providing precise control of the welding process, lower weld metal hydrogen levels and better penetration.
- Spoolarc wires increase contact tip life. ESAB’s proprietary manufacturing process results in better current transfer, less arcing, reduced contact tip erosion - especially at high current and wire feed speeds. Fewer worn out contact tips can mean a sizable saving not only in replacement parts but also in labor and downtime required to change them.
ESAB Spoolarc Wires For Low Hydrogen Welds
Hydrogen normally gets into welds through moisture on the electrode surface, particularly when stick electrodes are used. Spoolarc MIG wires have no absorbent coating and no moisture pickup. Tight control of surface residuals results in a high quality weld with no hydrogen problems. There is no need for drying ovens to recondition electrodes that may have absorbed moisture.
CAUTION: Don’t Forget to Test The Weld
Most of the data in this guide are based on AWS tests performed under standard conditions. In normal practice, however, the results usually differ to the extent that the job conditions differ from the standard. The following factors can affect the results produced by any wire/gas combination:
- Base plate chemistry
- Base plate thickness
- Weld bead size
- Dilution of base plate with weld metal
- Heat input (affects weld cooling rate)
That is why it is important to test the selected wire/gas combination in the same joint and under the same condition to be used during actual production. Depending on the job, the test may simply be to evaluate welding performance. It may also involve a full check on the weld’s service properties.