Resolving the challenges of welding coated steels – the fabricator galvanic cell definition

The increased use of coated steels has resulted in an intensified search for solutions to the problems posed by joining these materials. Galvanized metal decor High levels of spatter and welding fume, weld porosity, and poor bead shape are common. Galvanized steel wire rope These problems lead to increased post-weld cleaning costs, reduced quality, greater rework, and an overall reduction in productivity.

Galvanized metal tub planter The right wire size and type, matched with the most appropriate shielding gas, can substantially improve gas metal arc welding (GMAW) performance on galvanized and coated steels.

The increased use of coated (particularly galvanized) steels has resulted in an intensified search for solutions to the problems posed by joining these materials. Galvanized steel railing High levels of spatter and welding fume, weld porosity, and poor bead shape are common. Galvanized steel pipe dimensions These problems lead to increased postweld cleaning costs, reduced quality, more rework, and an overall reduction in productivity.

The most frequently used coated materials include both hot-dipped galvanized and electrogalvanized carbon steel, zinc alloy-coated steel sheet (Galvanneal®), and aluminum-coated steel.

Electrolytically deposited coatings are thin, homogeneous, and provide the adherent coating needed in forming applications. Polish galvanized steel Hot-dipped sheet, coated in a bath of either molten zinc or aluminum, has a less uniform coating but still provides excellent corrosion resistance. Galvanized steel planters Galvannealed material, coated by either process, is heat-treated to increase coating adherence and improve its weldability

When welding galvanized material, welders often encounter the problems of spatter, porosity, fume generation, and potential weld cracking as a result of the volatilization of zinc in the coating.

When short-circuiting or spray metal transfer is used to join this material, the volatilized zinc rising from the plate surface causes the arc to become unstable and generate considerable spatter. Galvanized steel paint Zinc vapor sometimes can be trapped in the solidifying weld puddle, causing porosity.

The amount of welding fume generated during joining is a function of the coating composition and thickness and of the welding parameters used. Galvanized souls A thicker coating increases the amount of fume generated. Galvanized metal baskets Cracking also may result from zinc entrapment in the weld.

Unlike a galvanized coating, an aluminum coating is not volatile but it does produce a high-melting-point oxide that can interfere with arc stability and cause spatter. Galvanized steel wall decor This oxide also prevents good surface wetting, which can create poor bead shape. Galvanized structural steel Current Welding Methods Fall Short

Most galvanized steel is welded like its uncoated counterpart, with little modification to processes and parameters. Galvanized steel vs stainless Solid wire used with short-circuiting transfer and argon/25 percent CO 2 shielding gas (C-25) is common.

Zinc sometimes is removed from the joint surfaces before welding to improve weld quality, or the joint is gapped to allow zinc vapor to escape from the joint area during welding, which reduces spatter and porosity. Galvanized steel corrosion resistance chart Voltage and current may be increased slightly to help improve arc stability and to increase the removal of the zinc coating before the puddle reaches the joint area. Galvanized metal bins Quality may

improve slightly, but lower productivity and poor weld appearance and soundness are constant problems. Galvanized steel thickness Wire-Gas Combinations Improve Welding of Coated Steel

The right wire size and type, matched with the most appropriate shielding gas, can substantially improve gas metal arc welding (GMAW) performance on galvanized and coated steels.

An evaluation of different wire-gas combinations at Praxair’s technology center in Tonawanda, N.Y., determined that low-silicon solid wires (ER 70S-3, average 0.55 percent silicon) reduced the potential for hot cracks in weld metal where zinc was present in the coating. Galvanized metal 3 tier stand Using 0.045-inch-diameter wire—rather than the more commonly selected 0.035-in. Galvanized metal wall decor diameter for this material gauge—generated

Gas blend evaluation showed that argon/oxygen shielding produced a nonadherent oxide that reduced corrosion resistance in the area surrounding the weld joint. Galvanized steel uses Argon/CO 2 blends improved bead shape and weld quality as the CO 2 content increased, but this typically increased weld spatter and fume generation.

Continued evaluation found that an experimental blend of argon, CO 2, and a small amount of helium reduced spatter and weld fume generation, while also improving bead appearance. Galvanized steel fire ring This gas blend with low-silicon solid wire produced optimized performance in short-circuiting transfer (see “Playground Equipmentmaker Spins Better Welds”

Brenda Spubbe, welder, BCI Burke, and Chris Brownlee, productivity specialist, Praxair, try out playground equipment fabricated by BCI Burke at Lakeside Park, Fond du Lac, Wis.

BCI Burke, a designer and manufacturer of playground equipment in Fond du Lac, Wis., needed to reduce the amount of time it spent grinding to remove spatter and to improve weld appearance. Galvanized metal wash tub Painted, galvanized tubing is used for many of the company’s playset components, and since good weld quality and appearance are critical to this equipment’s acceptance and safe use, excessive spatter is a

big problem. Galvanic cell definition Its removal generates nonproductive labor cost, as well as significant expenditures associated with grinding wheels and other needed supplies.

To optimize its welding process, BCI used an argon/helium/CO 2 shielding gas blend in place of the argon/25 percent CO 2 blend it had been using. Galvanized steel table top In short-circuiting transfer, the new blend produced less spatter and enhanced arc stability, which minimized postweld grinding.

The company’s own production evaluation tests showed spatter was reduced by half, roughly, nearly eliminating any cleanup. Galvanized metal mail organizer In addition, welding fume levels and gas usage were reduced, while travel speeds increased.

Pulsed metal transfer GMAW can help improve galvanized steel weld quality even more. How is steel galvanized By reducing spatter, it increases process efficiency and minimizes cleanup. Galvanized metal rust The controlled fine droplet spray transfer produced by pulsed GMAW results in a more stable arc than with short-circuiting, so more joint types and a wider range of material thicknesses can be joined. Galvanized pipe lengths Its lower average current levels

and greater stability produce lower fume levels as less zinc is vaporized. Galvanized iron sheet Good results are obtained with a low-silicon wire and an argon/CO 2 gas blend.

In a case example 1, sheet material from 16 to 12 gauge (0.060 to 0.10 in.) was being joined using short-circuiting transfer. Galvanized steel grating Substituting pulsed GMAW with an argon/low CO 2 content gas blend reduced spatter and increased deposition efficiency from 85 percent to 98.5 percent. Galvanized steel for sale Little postweld recoating of the base material and weld joint was

Because of the extensive grinding and cleanup previously associated with welding coated steels, some fabricators are forced to produce components from uncoated steel and then clean and dip-galvanize before powder painting these parts to provide the needed corrosion resistance. Galvanized metal bathtub These additional operations significantly increase production cost and time to complete the fabrication. Galvanized steel pipe price list Now designs

that incorporate precoated or pregalvanized material and parts, such as tubing, can achieve corrosion resistance without postfabrication galvanizing and powder painting. Galvanized steel pipe shelves This greatly increases productivity and reduces cost. Galvanized steel roofing Joining Aluminized Sheet Steel

Aluminized steel presents different but more easily addressed welding problems. Galvanized steel welded wire Here, too, control of bead shape and spatter levels are key issues. Galvanized metal strap The aluminum coating forms a difficult-to-remove oxide that interferes with bead wetting and generates arc instability with spatter. Galvanized steel food safe Because this coating is not volatile like zinc-bearing coatings, weld soundness is not as much of a problem. Galvanized steel window wells Like

At the Praxair Technology Center, short-circuiting transfer with several wire-gas combinations was evaluated to improve aluminized steel weldability. Galvanized metal chandelier Weld bead shape and the depth of penetration were key factors in determining the best wire-gas combination. Non galvanized steel pipe Argon with a low CO 2 content (5 percent to 10 percent) performed best by minimizing spatter and

Pulsed metal transfer significantly reduced spatter when joining aluminized sheet steel. What is galvanized pipe A better overall bead shape—flatter, with less “humping”—was obtained with the argon/ CO 2 blends. Galvanized steel rod Argon/8 percent CO 2 was the best two-part gas mix. Galvanized metal pendant lights Of the three-part blends evaluated, an argon helium/CO 2 blend produced better bead shape and further reduced spatter when compared with conventional two-part argon/CO 2 mixes. What is galvanized metal MIG Brazing of Coated Steels

An alternative to welding coated steel (particularly galvanized) is brazing using low-melting-point (1,500-1,600 degrees F) copper silicon (bronze) or aluminum-copper-silicon (aluminum bronze) alloys (1,000-1,100 degrees F). Galvanized metal table top The lower operating temperatures for the process eliminate welded seam corrosion and reduce spatter and coating loss. Galvanized plating The low heat input lessens distortion and lowers fume

Historically, brazing has been performed using a flame for the heat source. 20 galvanized pipe Recent equipment developments have resulted in a variation of pulsed GMAW known as MIG brazing.

In MIG brazing of galvanized sheet, a 3 percent silicon-bronze alloy is recommended for enhanced puddle fluidity. What is galvanized sheet metal For aluminum-coated material, one of several aluminum-bronze alloys can be selected. Gi galvanized Argon or argon with a small CO 2 addition has been the shielding gases of choice with these alloys.

Critical to the success of this process is pulsed equipment that can regulate the transfer to one droplet of material per pulse. Galvanized steel gate A short arc length with stable metal transfer is needed to minimize heat input. Galvanized metal fence panels Optimal results can be achieved with an argon/ CO 2/hydrogen blend, as the enhanced arc control and a slightly reducing atmosphere can promote even

If the mechanical properties of the joint permit brazing to be used, and the cost for the consumable materials can be justified, this process can offer some considerable advantages over conventional arc welding. 4 galvanized steel pipe 2

While there are many challenges to be faced in the joining of coated steels, new consumables and process technologies can improve weld quality and increase productivity. Galvanized metal trash can New gas blends and the right welding processes can save fabricators both time and money as they face the challenge of being competitive in a global economy.

2. Cutting galvanized steel pipe M. Galvanized metal cleaner Ebbinghaus, Heinrich Hackl, and R. Galvanized metal letters Lahnsteiner, “MIG-Brazing of Galvanized Sheet Metals and Profiles,” in proceedings from International Institute of Welding (IIW) Commission XII, Document No. Galvanized coating 1501-97, San Francisco, 1997, pp. What is galvanized steel 121-137.