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.
Remember.
- 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
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Howard Thomas
Experience
Sr. Acct. Mgr. (US Southwest) / Metallurgical Consultant
Associated Steel Corporation
Jan 2017 – Present
Past Vice President / General Manager
Associated Steel Corporation
Apr 1998 – Jan 2017
Past Vice President / General Manager
Baldwin International
Apr 1974 – Mar 1997
Education
Cleveland State University
Kent State University
University of Denver
