The term “wear plate” doesn’t give you much by way of steel specification.
Nor do the terms “Overlay Plate or Clad-Plate”
Wear Plate, Abrasion Resistant (AR) plate, is primarily used in heavy industrial maintenance applications. (Note that “AR” may also refer to As Rolled plate, but that is not the context we are using here). If a job is banging, clanging, screeching, or in any way loud and offensive it most likely is tearing up steel and could use some sort of hardened plate to keep things from breaking and otherwise wearing out too soon. Clad (Overlay) Plate is a Wear Plate product that is basically the combination of two products bonded together and sold as a unit. Properly matched to the application, it may significantly outlast wear plate.
If you just make wear plate really hard, it will most likely be brittle. It may be great to resist all sorts of sliding wear, but any sort of expected or unexpected vibration or impact may crack the plate. Since most applications in heavy industry involve both sliding abrasion and gouging or impact, the trick is to make a wear plate hard with some degree of ductility. The combination of hardness and ductility is called “toughness”. The nature and degree of toughness will vary with each brand of wear plate, with each chemical recipe and with each individual thermal treatment (hardening) process. Keep in mind there is no specific description of alloy content or hardness contained in the terms; wear plate, AR plate, AR400, AR500, etc. Those descriptors mostly mean that the plate is hard. My “go-to phrase” is; “Wear Plate Is Big and Ugly”. Big and ugly things are generally hard to manage. Keep that in mind, it may help you hold on to your fingers and limbs.
Now, some applications are just too mean and ugly for even highly hardened wear plate to handle. For those cases, CLAD-wear plate has been developed. There is not just one type of clad-wear plate. The overlay portion of the plate may be a heavy coating of hard weld, or a very fine diamond hard spray. For the most part, however, it will be brittle (not ductile). The bottom layer may be soft plate (A36), or it may be hardened wear plate. When these two layers are bonded together the top layer resists abrasive wear while the bottom layer holds it together and keeps it from crumbling. There are many fine grades and brands of this type of product available. Properly applied, it definitely solves big ugly maintenance problems.
When you believe you are ready to try something bigger and uglier than plain old hardened wear plate, share as much about your application as you can.
Is the medium being moved dry or wet, large or small, jagged or smooth, soft or hard?
Is it sliding dropping tumbling, or all of the above?
Is there heat involved (constant or intermittent)?
Does the medium drop onto the plate? If so, how far and how heavy is it?
Does the drop continue throughout the entire distance or does it dissipate (tumble and roll)?
(You may blend different types (grades) of clad plate along the length of your line).
The more specifics you are able to share with your vendor, the greater will be the success of matching the clad-plate to your needs. One man’s treasure in clad plate may be another’s garbage. There is that much variance.
-Howard Thomas, Dec 17th 2020
Recently, I thought I’d check the internet to see what was posted relative to bending steel. It is a very broad subject, like asking “What is the price of a car?”
Very difficult to answer without lots of clarification, clarification not only relative to the nature of the steel, the hardness, the bend, the bend radius, the equipment, the operator, and so on. Will you be cold bending, or applying heat? Quickly run through the above questions and then give some thought to the tools you might be using you to bend the steel: pliers, hammer, garden tools? You’ll want to add some simple protective gear (for hands, face, head, feet, etc.)
BENDING STEEL IS POTENTIALLY DANGEROUS. I’m not telling you not to attempt bending steel. But, if you’re a novice (beginner), your first consideration should be to have a professional, or experienced individual do it. If that is just not an option, then approach bending any steel with a high degree of caution. Bending even a small thin strip of steel may result in problems, including serious injury.
One foolproof caution a novice should employ before attempting to bend steel is this: Hold the bar of steel close enough to clearly see the surface finish and the sharp edges. Grasp it firmly in both hands and look closely to see if you can determine grain direction. Whack yourself in the forehead. It should hurt, causing you to reconsider what you are considering doing, or at least to insure you exercise extra caution and make use of safety gear such as gloves, safety goggles, helmet, whatever.
BENDING STEEL IS DANGEROUS! BENDING HARDENED STEEL IS NOT ONLY DANGEROUS; IT IS POTENTIALLY DEADLY. How do you determine if it is soft steel or if it has been hardened?
If you can grip it in both hands and bend it, it’s probably on the softer side. If you feel that it should be bending but it’s not budging, it’s time for some extra caution. It might be a piece of steel that is dead hard. If you hit that with a hammer, or even if you just apply too much force, it may shatter, discharging projectile pieces.
In general, avoid tight radius bends. Slow, minimal curves are safer for you, your neighbors, and the steel. If you do need to make a 90-degree bend, the curve at the point of the bend (bend radius) will have to be large, maybe ever 2” diameter or greater. If that is not going to work for your project, it’s time to consider that your attempted blacksmithing is perhaps ill conceived.
Bending steel at colder temperatures is riskier than bending it at higher temperatures.
Granted, that makes handling it more difficult, but the chances of successful results are increased.
When you anticipate bending steel, whether it is behind the garage at home or in your basement, respect it as a serious material and approach it with the caution it deserves; think danger like you would if you were working with large hungry predatory cats, people prone to projectile vomiting, or high voltage electrical current.
-Howard Thomas, November 6th 2020
In our earlier blogs we discussed magnetism and the Voodoo that surrounds it. This is just a little more on that mystery condition. Magnetism in steel is right up there with the loveliest things you would rather not encounter; Poison Ivy, Root Canal, Oil Canning on a steel plate, and filing your taxes. We are speaking of steel that picks up magnetism, i.e. will attract another piece of steel. This is different from whether or not the steel will attract a magnet.
How do steels pick up magnetism?
There are many situations that may induce magnetism during the performance of daily industrial procedures. Identifying the sources of magnetism is difficult; Exposure to an electrical or magnetic field, or to a device that utilizes a coil, or to, saws, grinders, power lines, etc. Exposure may mean direct contact or proximity. I have encountered steel service managers who have suspected “magnetism” they encountered was a result of changing the direction of how the steel bars were stored, North to South, or East to West. It is common to have bars leave for a destination, displaying little or no magnetism, only to arrive at their destination displaying noticeable magnetism. Burning and welding heavy plate often induces magnetism.
What type of steel may pickup magnetism?
All steels may pick up magnetism. The following is a general guideline: the lower the carbon range of the steel, the greater the degree of potential magnetism and the lesser degree of hold. (“Hold” is identified as the potential to retain the magnetism. Lesser hold would mean easier to remove.) So lower carbon steels may pick up magnetism rather easily, but it is generally fairly easy to remove. The opposite is true as carbon content increases.
How is magnetism removed, once a steel has become magnetized?
There are several means of removal; Note: these remedies are subject to the type of steel involved and the degree of hold. Striking the steel, or “Peening” (setting up a vibration). Peening with a hammer is more effective on the low carbon steels, such as 1018 and 1020. It becomes less effective as the carbon content range increases. Heating the steel to 800°F or to 900°F, and holding it at that temperature for approximately one hour per inch of greatest cross-section. The most effective method is to pass the material through a demag unit or a degaussing coil.
I have mentioned there is a past blog on the subject but is worth repeating for quick reference; Several years ago, an expert on removing magnetism advised me;
“Well son, you can heat it, you can beat it, but short of running it through a heavy capacity de-gauss unit, there’s not guarantee you’re going to fix it.”
-Howard Thomas, October 5th 2020
Endurance limit is another way of saying fatigue strength. It may be expressed in “Cycles to failure” as opposed to “PSI”. One of the most difficult questions to answer is a question relating to endurance limit. When someone asks about endurance limit, they are trying to find out how long a finished part will last in an application involving constant/repetitive motion or vibration. Failure may be anything from a small crack to an abrupt and catastrophic event.
While it is easy to see that this is a matter of great concern, there is unfortunately no formula for arriving at an answer based on a raw piece of steel. To accurately determine the response of a particular part in a particular application, the endurance test must be performed on the finished part in a simulation that duplicates as closely as possible the motion of the actual application.
The R.R. Moor Endurance Test, is an example of a test that utilizes bending and rolling contact to test torsional fatigue. [Variable introduced may be; vibration, compression, bending, twisting, rolling, etc.]. This test is extremely expensive and the evaluation period is lengthy. Individual companies, steel mills, and independent test labs, are unable to predict failure based solely on the chemical and physical properties of a type of steel. There are general guidelines published relative to standard SAE steel grades, but those are for general reference only. Steels that have been refined or otherwise modified to enhance toughness or to resist fatigue related failure (Steel produced to Clean Steel Production Standards) would not be adequately represented on a generic chart when it comes to endurance limit.
To repeat; in order to obtain any meaningful data, relative to endurance limits, the finished part must be tested under conditions that approximate actual service conditions. This is frequently done when production run parts are involved, because the quantity offsets the cost of testing. It is generally considered cost prohibitive to test steel for maintenance replacement parts for endurance limit.
- Generally there is no accurate published data to indicate a universal endurance limit for shaft material.
- Reference data published on steel by grade is at best general. It is not an accurate reflection of the expected service life of our material.
- Endurance limit relates to “Toughness.” Maintenance steel grades that have been manufactured to Clean Steel Production Refinement have enhanced toughness over their generic SAE or AISI counterparts strongly address concerns about endurance limit.
Steel that fails in service through fatigue related circumstances would have lasted longer if it was “tougher”. Toughness is achieved through an orchestrated combination of core integrity refinement during the production of the steel, combined with a specifically targeted thermal treatment and stress relief.
MAKE IT CLEANER, MAKE IT HARDER, REMOVE STRESS – INCREASE SERVICE LIFE, INCREASE ENDURANCE LIMIT.
Howard Thomas, September 8th 2020
Measurement science is its own language. These few notes barely scratch the surface. If you are new to this, or will just be peripherally involved, perhaps as a sales support person, it is suggested that you learn decimal equivalents down to the sixteenths, and key metric sizes, such as 5mm, 10mm, 20mm, 50mm, etc. It will make your life a lot easier.
15/16″ is fifteen sixteenths. Not fifteen sixteens.
.010″ is ten thousandths, .003″ is three thousandths, .0005″ is; half a tenth, or five ten thousandths.
In all methods of measurement tolerances nothing is an absolute single number. Tolerances are represented in a range. It is important to both parties involved in a transaction understand what that range involves. If you are not sure, ask. It may vary from company to company, product to prodcut, or even from material to material. In the case of machine tolerances, the spread may be just a few thousandths. Bar length ranges may involve many feet.
The above is not intended to be all-inclusive but a random exposure to the topic. We will try to broaden the scope in future posts.
August 5th, 2020 – Howard Thomas
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
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
In the steel industry and in the most general terms, anytime you see the word “stock” attached to another word; think, “stock used to make”. Barstock, Bushing Stock, Rifle Barrel Stock, Pump Shaft Stock, etc. would be stock that you can use to make those items. All details need to be clarified; is it pre-drilled, pre-hardened? What is the finish allowance? The term “stock” just means “may be used for”. Facetiously, a tree might be “Home Construction Stock”. i.e. not the finished product.
Keystock is generally a square or flat shaped lower to mid strength metal, either alloy or carbon steel, that is used to make keys. Those keys are inserted into shafts. A drive motor chuck will engage with the protruding key, and rotate the shaft. The idea is that this key is of less strength than the expensive shaft, so that if something interrupts the motion and causes failure, it will be the cheap little key that fails not the bin expensive shaft. Clear the obstruction, put a new key in, and you’re good to go, hopefully with an undamaged shaft.
The perfect piece of keystock would have less mechanical strength than the shaft, tuned to the actual application, but close enough that the shaft didn’t fail prematurely, contributing to expensive downtime. It would also be a cold drawn bar with good cross-sectional accuracy and a close oversize tolerance. The ideal oversize tolerance for many years was considered to be +.002″/-.000″. That tolerance would allow you to machine a standard keyway, in which the key would fit it in nice and snug. Undersized tolerance resulted in sloppy, loose keys. Too much oversize required un-welcomed machining.
My first experience with keystock was when I was about 10 years old. My uncle took me fishing in Canada. We were in a small aluminum boat with a little outboard motor. We were trolling at a very slow speed and he let me captain the “ship” for awhile. His only caution; stay away from the shallows and weeds; the only things I seemed to have a talent for. Every few minutes we snapped a key when the prop would strike something. We went through an entire little metal pill box of keys. That experience, and his humorous disapproval, stayed with me. The solutions were; chuck me out of the boat, or get somewhat stronger keys.
There is the conundrum. Too soft of a key and you have frequent expensive delays. Too hard of a key and you risk damaging an expensive shaft. (Goldilocks and the porridge issue).
Decades ago, Moltrup Steel, Pennsylvania, was considered the benchmark for keystock tolerance and cross-sectional accuracy. Having failed to secure the quality sufficient to satisfy their own needs, they embarked on producing the finest grade of keystock available. “Moltrup Quality” actually became a legitimate descriptor. I still see reference to Moltrup Keystock today, but am unfamiliar with the exact specifications, or how closely it follows the original “Moltrup Quality” of the past. Moltrup closed in 2002 and it has been my experience that the exacting tolerances disappeared with it. (Associated Steel always maintained a substantial inventory of Moltrup Quality material. It is a diminishing commodity but worth checking). When Moltrup closed, the potential market did not seem sufficient to justify the additional die work and drawing that would insure that high degree of accuracy. The tolerance on keystock gradually opened up to +/-.004″ to .007″ (that’s plus or minus). Even with sources that promote “Keystock”, or Moltrup Quality, pay close attention to the actual tolerance that you will most likely get.
The hardness (through multi-pass cold drawing/strain hardening), tolerance, and cross-sectional accuracy are all doable. Expensive, but doable. Requires a lot of fiddling in production for an item that does not represent any significant tonnage. Until something changes, keystock that is fine-tuned to allow maximum performance of the esoteric shaft application you are dealing with, will have to be made. Your choice, either make it, or chuck the kid out of the boat.
-Howard Thomas, April 3rd 2020
We have been actively pursuing adopting the metric system in the US roughly since the latter part of the 1700’s. Its been dubbed “Mandatory” in 1809. The success of those efforts has only been eclipsed by Y2K and the great reveal of the contents of Al Capone’s safe. In fact, for a quick chuckle, if you can still find a veteran businessman, mention you heard we are going to be exclusively adopting the Metric System in the USA next year.
At best we can say today that we have had success adopting the metric system in some of, but not all areas of measurement. Wikipedia does a nice job delineating areas where metric measurement has successfully been adopted in the US, (science, military, medicine). The only example of metric measurement that came to mind, however, was the 2 Liter bottles of soft drinks are now illegal in New York. At best we can say Americans are not keen on jumping quickly into metric measurement and saying goodbye to “foot-long” hot dogs and jokes about the inability of men to measure correctly.
A word of caution; while we are “actively” transitioning between metrics (written in decimal notation)
and “fractions”. Make sure both parties understand the exact point of accuracy that is being discussed. If you purchase a bar of 3-1/4″ Diameter, is your supplier visualizing the same 3-1/4″ Diameter bar (in fractional context?). Or are you really expecting a 3-1/4″ Diameter bar that is 3.250″ Diameter, accurate to the third decimal? What about 3-15/16″ Dia. (3.9375″ Dia. Are you expecting accuracy to the fourth decimal?). True, one topic is diameter size, while the subsequent text refers to accuracy or diameter tolerance. Normally, that would not be an issue. The two would be understood to be separate considerations. However, when you are ping-ponging two different measurement systems as interchangeable, there is a potential for surprise. Mishaps of this nature occur more often than should be the case.
For now, in the United States, think of any changeover of our measurement system sort of like METRXIT. It will likely still take a while. Over time, you will likely see dual notation on things like automobile speedometers, etc. But when it comes to steel bar sizes, fractional annotation may be here for a while. The “fractional” system, sometimes referred to as: The English System, or Imperial Units, has served us well. Change is inevitable. We know that. We’re workin’ on it.
-Howard Thomas, March 5th 2020
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