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Exactly the Same, Only Different

When steel flat products are thin, they are typically referred to as sheet and strip; as opposed to flats and plate. There are specific delineations separating the two types, however in general use distinction of the terms is pretty loose.

It is customary to describe flats and plate, or strip and sheet, from the smallest dimension through to the largest dimension. Thuse, 1/4″ x 48″ x 240″ would be how a quarter inch thick piece of 4ft wide 20ft long plate would be listed. It is fairly typical for the “grain” direction of the steel to run parallel to the length of the item. There is room for caution when grain is an important consideration; such as when forming is involved, since the plate may have subsequently been cut to a smaller size. In those instances, you can not be sure about grain direction unless it has been marketed. It is good practice to mark grain direction on remnants, or “drops”, once a plate has been cut. Grain is important for several reasons. First, when forming a steel plate it is generally advisable to form against (perpendicular to) the grain. In the case of wear plate, abrasive wear due to flow, may be diminished when the plate is installed so that the flow pattern is perpendicular to the grain. Unfortunately, many times this is theoretical rather than practical due to size and shape required.

Hollow materials may be pipes and tubes, or something like structural rectangular tubing. Tubes are generally more exacting in size, shape, and quality. Pipes are “big and ugly” hollow sections. Pipes are categorized as NPS, or National Pipe Size. Sizes up to 14″ NPS are described by their I.D. Or inside Diameter. At 14″ O.D. (outside diameter), the NPS refers to the O.D. Important information required would involve; O.D. I.D., and wall thickness. Generally, you would use only two of those measurements; not three. Caution must be exercised when “telescoping” one tube inside of another. Where a closer fit is desired, the two parts must be made, or fabricated in such a way to ensure that they are completely compatible; insured compatibility.

When dealing with pipe and tube you will doubtless encounter peripherals, such as elbows, flanges, laterals, T’s, etc. Configurations and cautions here are too numerous to list. If you will be involved with tubing or pipe it is recommended that you take the time to familiarize yourself with the materials and parts you will be encountering. Complex configurations require as much artistry and experience as technical knowledge.

Solid Steel Bars (Long bar products) are referred to as “bars” or “lengths”, or each (Ea). Hydraulic Pistons or shafts are referred to as “rods”.

Typically, there is a difference between the physical properties of a grade of steel and the mechanical properties. Generally, the physical properties are those properties that will be fairly uniform (common) to the grade. Those might include; thermal conductivity, thermal expansion, % elongation (%EL), %reduction in area (%RA), etc.

When discussing properties of steel, such as flatness, straightness, or out-of-round, it is best to avoid superlatives such as “perfectly flat”, or, “perfectly straight”. Presenting your requirements in that manner may result in a “No-Quote” from a potential supplier.

While there are many methods of determining hardness, it is fairly common in carbon and alloy steel to encounter Rockwell “C” hardness testing, or, Brinell (Bhn) testing. In sheet and coil you may encounter the Olson test, which involves an even larger ball impression than the Brinell ball. The Rockwell test is more appropriate for high surface finishes or finished parts, whereas the Brinell test method is used on “Big and Ugly” materials, such as hot rolled wear plate or bar.

Remember that surface decarb must be removed completely to obtain an accurate reading.

 

-Howard Thomas, July 8th 2020

 

General Steel Terms – “Talk the Talk”

You may have noticed every activity, workplace, social group, college, etc. seems to have its own language. One sure way to expose yourself as “new to the program” is to not use the approved language customary to the endeavor you are undertaking. In those cases, the dialog/language might be said to be “esoteric” (known by a certain group) to the group or business.

I remembered vividly the first time I had to call a steel source in New York. I had a hard time getting the person to understand what steel I was interested in. Finally, after a litany of clumsy attempts, he abruptly said; “Look kid, when you know what it is you want, call me back . . . dial-tone.” You don’t want to be that guy. Most institutional dialog will come with experience. This may be a small bit of help.

Steel products grouped by general type (service centers may carry multiple groups)

  • Carbon and flat roll – Perhaps the biggest grouping of suppliers. Most general category covering commercial grades of mild steel, carbon steel, and often structural steel. Does not generally include alloy steel, stainless steel, and premium exotic grades of steel.
  • Structural Steel – Angles, Channels, Rectangular Tube, perhaps flat bar, ductile plate products. Generally used in the building, construction, and manufacturing trades.
  • Wire & Cable – Small diameter rounds, shapes and wound products, in coil form. Cold header stock used to make small production quantity parts, bolts or wire based products.
  • Pipe & Tube – Long hollow products
  • Long Bar Products – Round bars, flat bars, some shapes (Hex, Square, etc.). Solid Steel bars.
  • Non ferrous – red metals – copper, brass, bronze. Note: “Yellow Metals” may refer to a specific type of  brass, or, it may refer to an industry rather than metal type. That group involves metals used in support of heavy construction equipment; typically to that produced by Caterpillar and John Deere.

Howard Thomas, June 9th 2020

Conclusion – Ten Things to Know About “Finish Size”

REMAINING FIVE POINTS – elaborated

  1. If the finish shaft involves substantial step downs, or, if only a small portion of the bar needs to finish… share that information.
  2. Remember, your supplier cannot be responsible for a third parties work, and/or mistakes.
  3. If liability on the shaft is considerable, consider parking it in another parties driveway.
  4. Try to “Talk the Talk” Phrases like, “a stick of steel”, or, “cold roll”, or, “a length of steel”, will get you in trouble.
  5. Share important ancillary facts with your suppliers; have you received steel in the past that has not been straight enough, hasn’t cleaned up, or was inappropriate in another way?

Why share info on details of a finished part with the supplier?

Well, you don’t need to go over everything, but statements like; “It’s going to be a long small diameter shaft with a big lollipop head on one end” will tip off an astute vendor to the potential of post machining stress related problems. On the other hand, a statement such as: “There is only a very small high spot near the middle of a short shaft that needs to finish to 8″ Dia. The rest of the shaft is 7” Dia. That might make a difference on how much stock is needed for allowance on the raw material.

The caution stated in number 2, above, is just a gentle nudge to limit how much responsibility you find yourself mentally assigning to the supplier. In the final phase, except for mill defect, unless the vendor is handling the job from cradle to grave, the responsibility for success or failure is really out of their hands.

Jobbing the actual machining to an outside source is not just about saving money, mostly because it will generally cost more. But, there are times when “potential problems are probable”. Who knows the product better than the supplier? You may want to see if they felt confident making a difficult piece. If so, why not let them. That eliminates lots of “finger pointing” if the job goes south. If the job goes wobbly, who’s wallet comes out? Their product, their method, their machining, their liability. If they screw it up the burden is on them to do it over at their expense.

TALK THE TALK

Like it or not, many terms are esoteric to specific industries. With hydraulic components, a bar of steel is a rod. When dealing with freight haulers and steel coils, they use terms like; “Eye to the sky”, or, “Suicide”. If you find yourself working within the maintenance steel industry, try to use the same terms you hear the suppliers using. It will go a long way to eliminating surprises. Surprises in maintenance are generally not good.

In closing, if you know some relevant history about a specific shaft or application, by all means share it. If the bar diameter did not clean up the last time, share that. If the shaft broke or bent, share that. If you encountered hard spots or glazing, share that.

Now, if your supplier is decidedly not interested in your ancillary comments, or, if they cut you short and enjoin you to just tell them the dimensions of the steel you want, perhaps you should try a second source. No harm no foul. You can always go with the first source. It is always nice to test the waters.

-Howard Thomas, April 1st 2019