HOW TO MANAGE THE OPERATING COSTS OF MIG WELDING

One subject of particular interest is how to reduce and control costs for GMAW (MIG) welding operations. Assume a typical MIG shop that performs a lot of MIG welding generates about half of its work from higher-volume production while the other half consists of one-time special orders. Here are some areas to concentrate on in this sort of production environment that will help bring the costs of the MIG welding operations in line.

Procedure. Many shops allow too much procedural freedom to individual welders in the ways they set their machines for higher-volume production welding. For example, if we know that a quality weld can be made by setting a wire feed speed for .045 in ER70S-3 wire at 370 ipm, but a welder sets his machine to 335 ipm because they like the way it runs, over a year that decision could mean depositing 500 lb less weld metal. Depending on labor/overhead rates, that welder’s decision could mean over $8,000 extra cost per year.

Gas Leaks. Shielding gas is a high-cost consumable for GMAW (MIG) shops. Because most shielding gases are colorless and odorless, leaks are difficult to detect. By comparing gas consumption rate to actual weld time in a shop, leakage can be identified. One leak at 60cfh, at an average cost of $3.75/cf, can cost a shop over $20,000/year.

Here are some easy, helpful controls/practices:

• Close gas bottle valves when not in use. Even when the connections and hoses between the bottle and the welding gun are tight and fairly leak-free, a bottle of gas can be drained over a weekend if left on! This is especially the case for expensive, helium-based shielding gas bottles.
• Installing devices to reduce gas delivery pressure to the wire feeder solenoid, and locking flow rates to proper levels can produce excellent savings. This will control gas usage at each welding station and reduce gas surges at the start of a weld.
• Identify and fix leaks on gas hoses and plant-wide gas distribution systems. Many times these leaks can be identified by listening for them in the quiet time after the shop is shut down. Otherwise, soap-bubble testing the gas distribution system from the gas source to every welding station can pay large dividends.

Overwelding. Fillet welds require no groove preparation and are one of the most commonly used weld types. Overwelding the required leg size by 1/16 in may not sound like much. However, making a 5/16 in fillet weld versus the required ¼ in fillet weld, can increase the weight of weld metal per foot of weld by 55 percent. Combined with the 55 percent increase in labor required to overweld by 1/16 in, this decision can add almost $1 of extra cost per foot of weld.

These controls take extra time to implement and manage, but they will help your shop survive these tough economic times – and make you even more competitive when the good times return. Becoming more competitive means being able to effectively adapt to more changes as needed, such as the materials being welded. So what happens when our shop switches from type 304 stainless steel to type 201 stainless steel due to lower alloy surcharges?

Assume that the shop has experience with welding 304 stainless, but doesn’t know all of the process differences involved in welding 201. They will find out that 300 and 200 series stainless steels are both austenitic grades. The 300 series are Cr-Ni alloyed, while the 200 series are Cr-Ni-Mn alloyed. 200 series stainless is attractive due to its lower and more stable cost, primarily due to its lower Nickel content. Type 201 offers comparable corrosion performance and higher strength than 304, while containing approximately half the amount of Nickel (see Table 1). Manganese is added to partially replace the Nickel, in a 2:1 ratio. Manganese stabilizes the austenitic phase like Nickel, but is not as potent.

Type 201 stainless may be welded with 209, 219, or 308 filler metals. However, 200 series filler metals aren’t used as widely as 308. Conventional procedures and techniques used for welding the 300 series apply to the 200 series, too.