Stronger material means more stress on tube mills and tooling

One of Addison Machine Engineering’s main services is regrinding and polishing customers’ old roll tooling.

Making high-frequency electric resistance welded (HF ERW) tube doesn’t look much different at first glance today from tube operations 50 years ago.

Appearances deceive.

With automotive customers and other high-volume users of metal tubing placing ever more emphasis on higher-strength, lower-weight tubing, mainly for the sake of fuel efficiency, the physical demands on tube mills—and especially the tooling that forms those tubes—has only increased.

The implications for tooling and tube mill design, machine maintenance, production schedules, product quality, and customer satisfaction are vast. So, how do mills and tooling producers keep up? How do they help their customers ensure both quality and speed, even as the strength-to-weight ratio demands work against both?

These and other questions keep Patrick Brunken of Addison Machine Engineering (AME) in Reedsburg, Wis., up at night as he wrestles with the limits of not only his new mills but also much older mills using new tooling and the high-strength weld boxes his and other companies are building to meet modern demands.

“Some material is more forgiving than others, so welding becomes easier,” said Brunken, who represents (with this brother, Jay) the third generation of Brunkens at the helm of the company. “Your high strengths and tensiles really stress out the weld—there's no margin for error.

“In the ideal world, there are no issues with the tube mill. The weld box is running great. But ... the mill that was built in 1930 can only run ’X’ and everybody’s pushing the limit. As a tooling designer or machine builder, can we do this? Can we push the envelope? Can we run tougher material? That’s the question.”

Brunken isn’t the only one fretting over those questions. About 200 miles from Reedsburg, Rick Olson, owner of Roll Machining Technologies & Solutions (RMTS) in Romeoville, Ill., looks at the range of products being requested out of tube mills these days as one of the most significant changes to hit the industry in a while. One case in point is the current wave of tubing being used for solar power generation and the inherent physicals demands it puts on tube mill tooling.

“With this big push for solar ... normally it would be 4-in.-OD tube, and now it’s 4-in.-OD tube with crazy corner radius specs and high-tensile materials and crazy straightness specs,” said Olson, who’s been in the roll tooling business for 31 years. “Things that we’ve never seen or that haven’t been done on a tube mill before are now being requested. And what happens is, just because you have 4-in.-OD tooling doesn’t mean you can run normal cold-rolled steel and then also run 90,000-yield HSLA [high-strength, low-alloy] material with crazy specs and get the same results.

“Everybody is having to kind of relearn how to be better at what they do to be able to make these tighter-tolerance materials on their same tube mill,” Olson added. “You see lots of tube mill rebuilding out there and [companies] making their machines better, because when you’re making a normal tube, there are things you can get away with [that you can’t] when you’re making these tight-tolerance tubes. You can’t have the play on the machines that you can [normally]—your tooling can’t be as worn. A lot of your tooling needs to be redesigned to be able to handle those higher-tensile materials because they bend more, and they resist bending more. So, you have to attack it in a different way.”

A crate of roll tooling awaits the next process at Addison Machine Engineering.

That redesign mindset, of course, stretches all the way to the weld box, Brunken pointed out—specifically the configuration of the tooling. At AME, what brought that to the fore was a customer in Texas producing oil country tubular goods that needed a heftier, four-roll weld box configuration to handle new specs.

“Just because you buy a bigger welder doesn’t mean the machine can do it,” Brunken said. “The weld boxes only have so much strength in them. What we’re seeing today in regard to pushing that envelope has caused us, as the designer, to build a heavy-duty weld box. It was totally re-engineered from the ground up with help from the customer. One of the things that came to us ... was the need for people that have three-row weld boxes to get more of a heavy-duty [design] versus a chuck style that you see out there.

“Hundreds of tube mills out there have your simple three-roll chuck style. Well, you get to those high-tensile strengths, they just can’t handle it. The clevis will break apart. The internal scroll will break apart. So, we had to come up with a high-strength weld box.”

For AME’s customer, the new weld box configuration incorporated jack screws to adjust the tooling and moved all the adjustment controls to the operator side, which requires far less operator interference in the machine during production. That created a safer environment as opposed to older designs in which operators often reached around the weld box and scarfing unit to adjust the machine.

“Now you take all that out,” Brunken said. “Operator safety, ease of use, and heavy duty—that’s the future. It’s getting to the point where people don’t even want your standard [machines] anymore.

“The drive to make things easier and safer and stronger is where everything is going today.”

Technological advances push changes, of course, but Olson noted that customer demand for certain kinds of tube and pipe actually can get driven by political winds, especially in regard to energy markets and the demand for tubing used in solar power generation. The products that customers focus on affects what they ask of their machinery suppliers, which then influences the technical specs that companies like RMTS must design to.

“Election years are always difficult,” said Olson, who’s seen his share of ideological swings in Washington, D.C., during his time in the business. “Nobody wants to put a bunch of tube in stock because they don’t know what is going to happen with the administration. Certainly the current administration is heavy on solar and renewables, so then you see lots of solar tubes. But if those incentives go away, then we go back to the previous administration, where we’re building ... more factories and more structural steels and more oil pipe.

“We get lots of questions: Can we do this on our tube mill? Can we handle these specifications? They come to us and say, ‘You can design the tooling—can we reliably make this product?’ So, there’s a lot of that right now because everybody’s kind of figuring out where things are going to go in November and then which way their business is going to turn and where their business is going to come from.”