Page 37 - MetalForming June 2016

undercutting and a more fluid, con- trollable puddle. The preferred gas for short-circuiting transfer mode is 75- percent argon/25-percent CO2, which provides good arc transfer, lower levels of spatter and a nice appearance of the completed weld bead.
Common Types of Solid Wire
Each classification of solid wire has unique benefits, limitations and best uses. Following are some common types of solid wires, along with their attributes.
AWS ER70S-6
An ER70S-6 solid wire is the most common choice for welding mild steel. This widely available wire is found in general fabrication and automotive- welding applications, and can be used for robotic welding as well as to complete root passes for pipe welding and other critical or industrial applications. It offers smooth and consistent wire feeding, which helps support greater productivi- ty (less downtime to address feeding issues), and the wire helps increase con- sumable life. With proper use, it creates smooth weld beads with uniform tie-in.
Welding operators can use ER70S-6 solid wire with 100-percent CO2 to increase joint penetration or with an argon/CO2 blend to help minimize spatter. Note that these wires tend to generate silicon island deposits on the surface of the completed weld. Opera- tors must remove these deposits prior to painting or other types of surface conditioning, which may increase time required for post-weld cleaning.
While solid wires generally generate low spatter levels on clean base mate- rials, they may not be the best option for welding contaminated metals. If, however, there is no alternative, an ER70S-6 wire may be helpful for weld- ing through light rust or mill scale. This wire has greater percentages of silicon and manganese, which act as excel- lent deoxidizers.
AWS ER70S-3
ER70S-3 solid wire is another com- mon choice, used primarily in appli-
cations where a clean finished weld is important. Similar to an ER70S-6 prod- uct, this wire provides good wire feed- ing, but it also generates a clean weld deposit that can be ready to paint or plate with little post-weld cleaning. It’s a common choice for automotive and automated welding as well as general fabrication, light sheetmetal fabrica- tion and in applications requiring high wire-feed speeds.
Also like an ER70S-6, this wire can be used with 100-percent CO2 or with an argon/CO2 mix, depending upon whether greater joint penetration or low spatter is the desired outcome.
AWS ER80S-D2
When welding carbon and low-alloy steels, an ER80S-D2 low-alloy solid wire provides higher tensile and yield strength. This wire delivers quality welds matched to meet the require- ments of many high-strength applica- tions, such as welding construction equipment, pipe, trailers and more. The “D2” designator indicates that this wire is a manganese-molybdenum alloy. Manganese is a deoxidizer that makes this wire a good option for rusty or dirty metals while also helping increase tensile strength. Molybdenum also offers hardenability in addition to high-temperature strength.
Higher alloy content in ER80S-D2 wire can make the arc in a spray-trans- fer mode slightly more difficult to con- trol, resulting in increased spatter. To combat this issue, welding operators may prefer to use a pulsed-GMAW process instead.
Copper-Free Solid Wire
Most solid welding wires contain a small amount of copper plating, which helps prevent wire corrosion and enhances electrical conductivity between the contact tip (also copper) and steel base material. Adding copper to certain steel base materials, however, can cause problems. Here, welding oper- ators may prefer copper-free wire.
One benefit to copper-free wire: It can be used at a slightly lower voltage in spray-transfer mode as compared
When welding on clean base material, solid-wire filler metals deposit very little slag, resulting in minimal post-weld cleanup. Because of this, solid wire com- monly finds use for tack welding or other applications where a clean surface is important.
to the same wire with copper plating. For thinner materials, spray-transfer mode allows for quicker welding and a better deposition rate than short-circuit welding. This process change helps reduce spatter and minimize heat in the arc, thus lessening the chance of burnthrough.
When using a copper-free wire, be sure that the spool or coil of wire isn’t stored for long periods of time in the shop or on the jobsite, as the absence of copper can cause the product to rust. Copper-free wire may also cause arcing between the contact tip and base mate- rial should the surface finish or lubri- cant be incorrect. To defend against this problem, the welding operator may need to adjust welding parameters.
Many Options
for Solid-Wire Use
As with any welding operation, find- ing the right filler metal is key to gaining good productivity and quality, while also minimizing costs. Solid wires offer ver- satility in many general fabrication appli- cations that require the welding of mild and low-alloy steel. Take care to select the right classification of wire for the job— based on desired mechanical and chem- ical properties—and to consult with a distributor or filler-metal manufacturer for assistance when in doubt. MF
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