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In November 2005 (Issue #11) we reported on the first trials of tube production using SCS coils. The product in that case was rectangular structural tubing and the SCS advantages of being clean enough to weld 'right off the mill' and eliminate rust claims were compelling.
Production trials for mechanical tubing and pipe have been performed since then and results are equally compelling. Cleanliness, excellent shape and weldability are all coming together to make SCS a problem-solver for a wide range of tube and pipe production applications. |
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SCS for Tube & Pipe a Winner !
Meeting Customer Expectations
for Material Cleanliness
SCS News Bytes |
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Two truckloads of SCS coils were recently delivered to a major US tubing producer to run trials of both round and rectangular mechanical tubes. Samples from these trials are shown in the photo to the left . The 1.90" OD round tube was made from 16 gauge SCS. It welded beautifully and came off the tube mill so clean that the customary SCS 'napkin wipe' test picked up practically no dirt or scale at all. Just as important, the operator reports that the SCS ran faster than their normal P&O material, although he stated, apologetically, that he did not record actual mill speeds.
The 1" x 1.5" rectangular tube was made from 14 gauge SCS. The customer for this product will use it 'as is' without cleaning or painting, so the SCS cleanliness and rust inhibitive qualities become especially valuable |
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Recent samples from SCS production trials of mechanical tubing and
pipe. Superior welding performance, cleanliness, resistance to rust
and potential to run faster combine to make SCS a winner for tube/pipe. |
to them. The tube ran wonderfully, but
wasn't quite as clean coming off the
mill as the round tube. Reason: the
oil-based coolant used was quite |
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dirty and fouled the surface of the |
tube. As expected, there was some scale powdering on the inside of the bends, but the producer felt this would not be of any concern to the customer.
Two weeks later, coils of 16 gauge SCS were delivered to a major pipe producer for their trials which resulted in the two large pipe sections shown in the photo above (one painted and one bare). This producer uses hot-rolled and applies a transparent protective coating to selected products. That coating doesn't apply as uniformly to hot rolled as the producer would like; he's counting on SCS' smoothness and cleanliness to give him the consistently uniform coverage and high quality finish you expect of a premium product.
The SCS coils certainly performed like a premium steel on the pipe mill. "This is, without a doubt, the nicest coil of 14 gauge I've ever run on this mill," the operator commented while running his first SCS coil, "and I've been runnin' this mill for 20 years!" He felt the smooth, even edge of the SCS coil made for better welding. He also felt the very smooth SCS surface, with just a thin layer of scale, would extend the life of the welding unit's copper contacts. "We've run pickled dry and it's so rough that you can almost watch the contacts being ground down. The scale on hot-rolled has some kind of a 'lubricating' effect and helps the contacts last longer. But normal hot-rolled surface is a lot rougher than the SCS and the heavier, loose scale on hot-rolled can be rough too, so I expect our contacts may last even longer with the SCS."
Additional tubing trials have been conducted by other US and Canadian producers who have been extremely impressed with SCS performance. That's not to say there aren't adaptations tube and pipe producers will need to make to get the most from SCS. For example, dirty oil-based coolants will leave deposits on the SCS tube and defeat the purpose of using such a clean material. Switching to a filtered water-based coolant would be the appropriate solution. Also, seam welding is usually the speed limitation of a tube or pipe mill, and the SCS coil's excellent shape and cleanliness appears to be a key to raising this limit. Still, careful monitoring of weld quality needs to accompany any increases in line speed to make sure there's no adverse tradeoff.
In summary, after trials from some of America's premier tube and pipe producers (who will remain anonymous in order to protect their competitive advantage) we feel confident stating that SCS offers an excellent opportunity for tube and pipe producers to simplify material sourcing, improve quality, and even increase throughput. Most importantly, it can let them provide their customers with a more consistent product that's practically 'ready-to-weld/ready-to-paint' right off the mill.
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SCS Grayscale Standards
Each of these 'standard napkins' show the maximum acceptable pickup from SCS. The leftmost napkin shows a 10% level of grayscale - the upper limit for material under 0.20" thick. The napkin to the right shows a 30% level of grayscale - maximum acceptable for material 0.20" and over.
To receive a copy of TMW's SCS Cleanliness Check Instruction, please contact Bob Hoffman at BobH@thematwks.com, or call Bob at (618) 282-4200 ext. 113 |
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An important selling feature of SCS is its cleanliness, as is often illustrated by the 'napkin wipe' comparison to P&O or hot-rolled. But even the cleanest SCS won't stay that way if downstream processing equipment deposits dirt, grime or scale on the SCS material, so SCS producers and processors who level, slit or blank SCS need to keep their processing equipment as clean as possible. Exactly how clean is this?
We've developed a 'grayscale" visual standard for maximum acceptable levels of pickup on a clean napkin wiped across SCS. There are actually two standards, as shown in the photo above. Thinner material (under 0.20") uses the 10% grayscale standard and thicker material (0.20" and greater) uses the 30% standard. The difference is due to inherent variation in scale composition with thickness of the hot-rolled substrate.
We use the 10% and 30% standard as the minimum acceptable to assure good SCS performance in subsequent fabrication or painting processes. Our experience is that our SCS lines will, in most cases, produce to levels better than these standards, and that's what customers have come to expect. Those expectations don't change when the SCS is slit or cut-to-length, so we encourage SCS producers and processors to use these same standards as a means to make sure their processing equipment is clean enough when running SCS. How? Contact us for our 'SCS Cleanliness Check Instruction.'
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Improved Specs for SCS Coil Line
The SCS Coil Line at TMW, as well as those of licensees, are now rated to handle coil widths
down to 12 inches. The previous minimum was
24 inches. This new width spec adds flexibility
to processing schedules as slitting prior to SCS
processing is now more practical.
New SCS Welding Guidelines
Additional testing and production experience has
resulted in an improved set of guidelines for
spot welding SCS. The new guidelines, available
for download through this link, provide initial
values for several welding parameters, such as
tip force, weld current, quench time, etc., that
have been shown to work particularly well for
welding SCS-to-SCS or SCS-to-P&O. Developed
by Richard Dunbar of Welding Engineering
Associates, the new guidelines include a useful section on weld quality inspection. |
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| Copyright 2006 The Material Works, Ltd. |
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