The right process for structural welding
Jolson Welding deals in heavy steel. The company specializes in structural welding for bridge and highway work in one of the most seismically sensitive areas in the world: Northern California. Working with the state department of transportation and local contractors, Bob Jolson (owner, operator, welder) and his team have established welding processes that meet strict code requirements (CalTrans, AWS D1.8 and D1.5), and pass ultrasonic and x-ray tests without fail.
A recent job welding soldier pile highlighted the soup-to-nuts mobile welding system that Jolson has built for these applications. A soldier pile is a critical component of many highway projects in Northern California as soil makeup and varying terrain make earth retention necessary. On this particular project, beams of A709 bridge steel will be paired together and placed into holes drilled deep into the ground, serving as the structural backbone for a rebar and concrete retaining wall.
Flux-Cored Arc Welding (FCAW) is Jolson’s process of choice. There are structural steel welders who still rely on the Shielded Metal Arc Welding (SMAW, or Stick) process due to familiarity; however, flux-cored welding offers a number of advantages in terms of quality and productivity.
“If you don’t want to get a lot done in a hurry, Stick welding is the way to go,” says Jolson, “but running this process (Flux-Cored), the deposition rate is really high on it and you get a lot done in a day – probably five or six times more than you would with Stick.”
Advantages of self-shielded flux-cored welding
- Greater productivity through faster deposition rates — the .072-inch self-shielded Flux-Cored wire used in this application compared to a 7018 1/8-inch Stick electrode provides approximately a 249-percent increase in deposition rate in the flat and horizontal positions, and a 162-percent increase in vertical up and overhead positions.
- Greater deposition efficiency compared to Stick electrodes — the Flux-Cored wire discussed in this case presents a 75-83 percent deposition efficiency versus 65-73 percent in a comparable 7018 Stick electrode.
- Low hydrogen weld deposit (provides resistance to cracking, promotes X-ray quality welds) — the wire used in this application features less than 8 ml/100g of diffusible hydrogen.
- Welds out of position at high currents, also helping with productivity.
- Less cleanup through simplified slag removal.
Building a welding system: The power source
Jolson’s power source preference is large-frame, low-speed diesel engine-driven welder. Jolson operates a number of Miller engine-driven welders, including the Big Blue 500. The Big Blue 500 is a CC/CV power source – necessary for Flux Cored welding – that provides 14-40 volts of welding output in MIG and Flux-Cored processes.
“Our outputs will depend on what positions we’re welding in” says Jolson. “In flat positions we’ll run up around 23 volts and 300 inches per minute (ipm), and when welding vertical-up we run about 230, 240 ipm at about 22 volts.”
In addition to providing adequate weld output, Jolson chose this engine-driven welder for its ability to work at low RPM.
“We run the Big Blue engine drives because they run at 1,850 RPM, which helps us keep our fuel economy in check,” says Jolson. “I can get 35 to 40 hours of welding out of one tank of fuel.”
Jolson also runs deluxe models that provide 20,000 watts 3-phase power and 12,000 watts 1-phase power in addition to the machine’s standard power. This gives them the ability to run common jobsite tools and accessories, as well as equipment with 3-phase input requirements such as pumps, plasma cutters and portable welders that help turn one machine into a multi-arc work station.
“There have been a lot of times where we’re out on a pipeline job and we’ll have to plug in a three-phase pump to empty our ditch and be able to get down in there and do our welding,” says Jolson. “We also use that three-phase power to run our plasma cutters. They cut a lot quicker and everything stays nice and cool, as the duty cycle is increased (with the 3-phase power input power).”
Wire standardization drives quality, productivity
To give you an idea of how much welding goes into these structural projects, Jolson and colleague Brandon Hobbs burn through 40 to 45 pounds of wire each day, per man. To simplify inventory and handling, Jolson has standardized almost his entire structural operation on .072-inch Fabshield XLR-8 self-shielded Flux-Cored wire (AWS E71T-8JD H8).
“We stick with the .072 because we could turn it way up or way down, we could weld anything from a handrail to a four-inch thick piece of pipe,” says Jolson. “One wire does it all. And it’s user-friendly. It’s not finicky. You could be a few volts off, or off on your ipm, and it still welds (to standards). ”
The primary benefit of a flux-cored wire over a stick electrode is that it is continuously fed, whereas a Stick electrode requires the worker to continuously start and stop to replace electrodes. This improves productivity and minimizes the possibility of defects caused by more frequent starts and stops. There is also a higher percentage of lost material with Stick electrodes as filler metal in the stub is discarded. As such, 50 pounds of Flux-Cored wire compared to 50 pounds of Stick electrodes would yield a higher deposition efficiency: more of the filler metal is actually deposited into the joint. That efficiency ranges from 75-83 percent with this particular wire compared to 65-73 percent with a 7018 Stick electrode (when the product has been burned to a 2-inch stub).
“It’s a real high deposition welding wire, and it’s very clean,” says Jolson. “Very seldom do you have any slag inclusions or porosity or anything like that.”
The cleanliness Jolson refers to is due in part to easy slag removal. The slag produced by this wire is known to be self-peeling in many cases, improving productivity through less cleaning and helping to prevent potential defects caused by slag inclusions. It also features low levels of diffusible hydrogen (less than 8 mL/100g) and excellent mechanical properties for welding in seismic zones: 58 ksi minimum yield strength, 70 ksi minimum tensile strength, with 22 percent minimum elongation at 2 inches, and impact values of 40 ft*lbs at 70 degrees Fahrenheit.
“It has really great Charpy V-Notch impact values, and that’s important because of the critical work we do,” says Jolson.
New feeder technology improves feeding consistency
One of the concerns that face Flux-Cored welding applications in the field is the consistency of the wire feeding itself. Wire feed speed consistency is important in terms of controlling the deposition rate and heat input into the steel beam – voltage varies with the changing distance between the electrode and the work piece. The new Miller SuitCase X-TREME 12VS voltage-sensing wire feeder ensures wire feed consistency through new robust features and a design resilient to temperature swings throughout the day known to cause variations in feeder performance.
“The new feeder is the smoothest feeder I’ve ever ran,” says Jolson. “They have a little bit bigger motor in them, so they don’t get hot throughout the day. (With other feeders), the weather gets hotter and the motor gets hotter in the feeder. The new 12VS is very constant and doesn’t change around. Wherever you put it in the morning, it’s there at the end of the day. There’s no variation.”
The new feeder features a new drive motor assembly, motor control and integrated tachometer that provides electronic wire feed speed control and accuracy that rivals the performance of bench-top-style feeders found in shop environments. A new wire delivery system makes it easier to load the 12-inch wire spools and reduces drag on the wire by eliminating the inlet guide and allowing the wire to roll over the large radius of the drive rolls. It also features a new visual scale on the wire pressure knob that eliminates guesswork and allows welders to specifically dial in tension to settings they know provide the best feeding performance for the size and type of wire they are working with.
“Having the register on the scale is nice because you always know where you need to be,” says Jolson. “If somebody messes with your machine or puts different wire in it, you just dial it in and you’re up and running. You don’t have to guess and turn it a half-turn and back a half-turn. It makes it really user friendly.”
Jolson also claims the feeders allow him to more easily load in new spools of wire, and switch between different wire types/diameters through the elimination of guide tubes within the feeder.
“In the old days, we had to change out guide tubes (when changing wire diameters),” he says. “There is no guide tube on this feeder. You just open your feeder, feed your wire through right into the gun, cinch her down and you’re ready to go.
Setting parameters simplified through digital meters, wireless remotes
A focus of welding manufacturers has been to put as much knowledge and power into the hands of the welder at the point-of-use as possible. In an application like this, that includes the ability to know exactly what your machine settings are and to change them without having to go back to the engine-driven welder at the truck. Two technologies that help Jolson with this are digital meters on the wire feeder and wireless remote control technology matched up with the engine-driven welder. Together, these technologies help improve productivity by allowing welders to more quickly dial in their equipment and get to work faster.
“The (wire feeders) without the digital meters, you have to call over to your buddy to tell you where the needle is bouncing around at, and you’re never really accurate that way,” says Jolson. “With this feeder, you can make a practice pass, let off the trigger and look over (at the feeder) and it will hold its values. That way you know where you’re at and you don’t have to bother your partner to come and help you. You can really see them good, too, out in the sun. It’s got some special technology in there that, even out on a sunny day, you can still see your numbers – and that’s nice.”
With a voltage sensing wire feeder and CV power source, voltage is set at the power source while wire feed speed (amperage) is set at the feeder. In the past, after running his test pass, Jolson would have to get up and go back to the truck to adjust his voltage. Now, with wireless remote technology, Jolson has full control of that setting without leaving his workplace.
“If I’m up on a ladder and I’ve got to change my settings, I don’t want to crawl up and down all day,” says Jolson. “If I’m down in a ditch and I’ve got to turn the machine up and down, rather than spending ten minutes crawling in and out of there, I can turn it up or down and I’m good to go.”
Specialized flux-cored guns take the heat, provide optimal comfort
Rounding out Jolson’s structural welding system is the Bernard Dura-Flux Gun, built specifically for self-shielded Flux-Cored welding. Rated at 350 amps, these guns feature ergonomic handles, easy-change consumables and a robust design for working in hot and dusty outdoor applications.
“We like the long goosenecks because it keeps us away from the heat,” says Jolson. “And this sealed microswitch, If you’re out in a dusty environment where it’s laying on the ground all the time, it never gets any dirt or dust in it and it continues to work perfect every time.”
“I like the Bernard gun – how you hold it in your hands,” says Hobbs. “You don’t have any fingers that are pressed together, squeezing together, pinching themselves off, getting all tingly and numb. It’s easy to hold and move around. It’s comfortable in the grip of your hand and the trigger guard isn’t too bulky – it does its job without messing you up, without hindering your performance.”
Jolson also likes the ability to change out the contact tip without tools – a technology that Bernard calls its Centerfire™ Consumable System.
“You take off the little retainer, the tip comes out and you replace your tip,” says Jolson. “And, normally, the tip always wears the top and the bottom, it wears a groove in it. (With these) you can loosen this up, turn the tip 90 degrees, tighten it back down and you’ve got a brand new tip again – so you get two lives out of one tip.”
When put together, these varied components build a structural steel welding system that Jolson finds to be optimal for the work he does, ranging from bridge construction to pile splicing. Knowing that all of these components are designed by companies that work together to provide best-in-class, market-focused solutions, Jolson has peace of mind that he’s going to work with the best tools available.
“It’s nice because everyone seems to work together,” says Jolson. “If I have a problem with my wire and I’m talking to a Miller representative, they can help me out and vice versa. With Miller, Bernard and Hobart Brothers working together, it really helps us out as end users because everybody knows a little about everything. There’s always somebody there to help you out.”