Hobart Brothers — Performance Welding.™

Increased labor and unessential equipment costs, expensive warranty work and decreased productivity are just some of the problems that manufacturers deal with as a result of silicon deposits in their welds.

A deoxidizing agent added to filler metals, silicon creates a cleaner, stronger weld by removing impurities that might be caused by surface contaminants, such as mill scale and light rust, and bringing them to the surface of the weld as the puddle solidifies. But it also has a downside.

Almost all companies manufacturing painted equipment, such as cranes, bulldozers, agricultural implements and scissor lifts, face extensive post-weld grinding and blasting to remove the silicon deposits. If not removed, the silicon eventually flakes off from the weld and causes the metal underneath to rust. Because the silicon deposits from most filler metals collect near the toes of the weld, they can be difficult to access with a grinder or other tools.

Removing silicon deposits from the toes of a weld typically requires shot blasting the part, grinding the silicon off with a grinding wheel or removing it with a chisel or needle gun. Each of these ways is a laborious and costly process.

Certain painting processes, such as enameling, are more forgiving of silicon deposits than other processes, such as powder coating, but nearly all require extensive silicon removal procedures to avoid future rust problems.

E70C-6M H4 wires, like Metalloy Vantage, greatly reduce the number of silicon islands that lead to costly post-weld  operations.

Because the benefits of silicon outweigh the disadvantages, however, some companies calculated that it was cheaper to remove the silicon deposits as a post-weld activity than to fully clean the material prior to welding.

Companies are now realizing that it’s not an either-or proposition, and that they can receive the deoxidizing benefits of silicon without the troublesome and costly islands.

Solving the Silicon Dilemma
Newly developed metal cored wires with silicon island control, categorized under the AWS classification E70C-6M H4, greatly reduce the problems caused by silicon deposits while still providing its benefits and the productivity and weld quality advantages of metal cored wire.

These categories of wire have been designed specifically for manufacturers of painted products who must chip, blast and grind away the silicon islands to avoid rust problems down the road.

The primary advantage of this E70C-6M H4 (like Tri-Mark^® Metalloy^® Vantage^™) wire with silicon control is that it causes the silicon islands to collect in the center of the weld, where they are much easier to remove than along the toes of the weld. These wires also greatly reduce the number of silicon islands and those that do form do not adhere as strongly to the weld metal, oftentimes peeling off without the use of additional tools.

E70C-6M H4 wire comes in four sizes, ranging from .035-in. up to 1/16-in., and can be welded with anywhere between 75 and 90 percent Argon, with the balance CO2. The lower Argon concentrations produce deeper penetration and cost less in gas usage. Higher Argon concentrations create a smoother arc and decrease spatter and fume levels, which makes it easier to use in the spray transfer process.

Using the spray transfer process, this wire can be used in the flat, horizontal and vertical down positions. In pulse or short circuit mode, the wire is suitable for all position welding.

This type of wire works best in applications requiring five or fewer passes, and has demonstrated tensile strength up to 97,000 psi with a 90 percent Argon mix and 90,200 psi with a 75 percent argon mix. The yield strength and elongation values at those gas mixes were 87,000 psi and 22.5 percent for a 90/10 gas mix and 80,000 psi and 25 percent for a 75/25 gas mix.

Best of Both Worlds
Using E70C-6M H4 wire with silicon control, companies are able to greatly reduce the amount of post-weld cleanup and cut down on the amount of quality problems associated with paint chipping off the weld due to silicon deposits.

An added benefit is that E70C-6M H4 wire produces almost no spatter compared to solid wire. This wire classification features a host of additional advantages: better wetting action and gap bridging, higher deposition rates, reduced burn through and better side wall fusion.

Of course, like all metal cored wire, E70C-6M H4 wire might cost slightly more than solid wire. When balanced against the time and materials savings, however, the financial benefits of eliminating silicon deposits greatly outweigh the increased cost of the wire.

The chart below shows an example of how the increased cost of metal cored wire is more than made up for by the savings in materials and labor.

Like most metal cored wire, at the same amperage it features higher deposition rates compared to solid wire, which can increase overall productivity. The chart shows a comparison of this type of metal cored wire and a comparable solid wire.

An E70C-6M H4 wire won’t be right for every application, however. Although this wire is designed to withstand a certain amount of mill scale, dirt, rust and other surface impurities on the base metal, high levels of contaminants will cause problems in the weld. In such situations, a flux core wire might be recommended.

For production environments where welds are painted over, though, this class of wire can offer significant labor and warranty work savings through unparalleled reduction of silicon deposits as well as increased productivity through the higher deposition rates afforded by metal cored wire. 

This entry was posted on Thursday, May 24th, 2007 and is filed under Articles.