Ask the Experts
Industry experts answer practical welding questions covering equipment setup, electrode selection, aluminum design, and welding performance optimization.
What’s the best and most effective way to adjust the tension on wire feed roller and spool on a MIG welder?
Jose Rivera, Hernandez, Adjuntas Puerto Rico
Your adjustment should not be on the roller so much as the spool, where the primary tension control is the wingnut on the spool’s axis. If the tension is too tight, the rollers won’t be able to turn. If the tension is too slack, the spool will unwind and result in a bird’s nest inside the cabinet. The ideal tension is somewhere in the middle – a little bit slack, but not too much. You want just enough tension that the wire will come off the spool as you weld, but not all the way around the spool. When the spool is running and you stop welding, the wire should stop short but should not be overly tight. There should be a little bit of slack in the length of wire between the spool and the roller, but no slack around the spool.
Most stick electrode manufacturers provide guidelines for the recommended operating current for each particular
type and diameter of electrode. For example, the Lincoln Electric Filler Metals Selection Guide lists a typical current range of 90 to 160 amps for 1/8-inch Excalibur® 7018 MR®. How do I determine the optimum amperage to use for my particular application?
Ken Sanders, St. Louis, Missouri
The manufacturer’s typical recommended current range is a rough guideline that suggests the maximum and minimum current in which a particular electrode will satisfactorily operate. If the manufacturer suggests a current range of 90 to 160 amps, a good starting point for optimum operating characteristics would be the middle of the current range – 125 amps. Adjusting the current above 125 amps would work well and increase productivity on flat and horizontal welding of thicker plate, whereas turning the current down might be required to limit burn through on thinner materials or to control the puddle when welding in the vertical and overhead positions. Adjusting current above or below the manufacturer’s recommendation is usually not suggested, because it could lead to poor operating characteristics of the electrode.
A tighter set of guidelines might be the current range that a welder is required to operate within a welding procedure specification (WPS). For example, a WPS for a 3-G/4-G qualification test on 3/8-inch plate using a 1/8-inch 7018 electrode might define a current range of 105 to 135 amps. The more conservative current range for this particular test could be determined by a number of factors, including plate thickness, joint configuration and the fact that the welding is being done in the vertical and overhead positions. A good starting point would be right in the middle of the range, at 120 amps, and to adjust up or down for desired operating characteristics. When working to a code, it is important to operate within the current range defined in the WPS.
Several factors determine the best current to operate an electrode for a particular job. For best results, start in the middle of the range and adjust accordingly.
If I want to fabricate a product such as a steel trailer, but make it out of aluminum instead – and assuming my welds are sound – what thickness of aluminum would it take to match the strength of steel, and what grade would you use (6061, 3003, etc.)?
Dale Asher, Wichita, Kansas
The question is a little too complex for a simple answer like “use aluminum that is 50% thicker than steel,” but we can provide some general guidance.
Aluminum is lighter than steel by volume. In fact, aluminum weighs 1/3 what the same volume of steel would. But steel is stronger than aluminum, and its Elastic Modulus is higher than that of aluminum. So you can’t just replace steel with the same thickness and still have a safe design. In general, a good design in aluminum can save 40% over the same design in steel. This is done in two ways:
- Aluminum thickness should be 40% greater than material used in the corresponding steel design.
- For closed sections, such as square tubing, the aluminum section should be larger. For instance, if a 1-inch x 1-inch square tube was used for steel, the aluminum square tube should be 1-1/2-inch x 1-1/2-inch.
As far as which alloys you should use, the answer depends on what the specific part looks like. Closed sections such as squares or rounds should be made from extrusions. These will normally be 6061-T6 or 6063-T6. Parts that are sheets or plates should normally be made from one of the 5XXX structural plate alloys, such as 5052, 5454 or 5083.
The general guideline in this answer is just a starting point, and you should have a qualified engineer review the aluminum trailer design and load capacity to ensure it is adequate.
From the welding experts at
Lincoln Electric