There is a famous saying; “A man must know his limitations.” I am sure it is also appropriate for a woman. So it is with this topic. Some steel grades can be bent fairly easily. And, some steel grades in some conditions should never be bent. Before attempting to bend steel you must fully understand its limitations. If you are one of those who never reads instructions and just charges ahead, then there is another appropriate quote from the same person; “Do you feel lucky, kid? Well, do you…?”
The thing is, bending steel is dangerous, even steel listed as “formable”. Ideally, it should be left to experts. But, if you are going to do it anyway, you must know some things about the metal you are contemplating bending. The grade and internal cleanliness are important. But more important is the hardness and the depth and uniformity of that hardness. Soft malleable (ductile) steel in a very light gage may take a nice bend simply by “hand”. Harder (heat treated) heavier gage steel may require high capacity sophisticated equipment that has built-in protections for the machine operator. Very hard steel may not tolerate even the slightest bend, or even pressure for that matter. To put it in perspective, when you think of very hard steel, think of a pane of glass. You wouldn’t push the center of a large pane of glass to see if it bends. At least I hope not. When hard steel fails during a bending process, it literally explodes! As in, loud noise and a section of the roof leaving the building rather quickly.
Before you attempt to bend a piece of steel say this out loud three times; “This is an angry piece of steel that doesn’t want to be played with, and there is a reason why everyone behind me is stepping back.” Then step into your safety gear, study everything you can about the steel, then call a person who bends steel professionally. If that is just not possible and you are required to bend it yourself, do some serious research before you begin and remember, wear appropriate safety gear. Bending steel is not a job for amateurs. Use certified/qualified expert technicians.
Some key words that may help you discover a bit about bending steel are listed below:
Forming, Press Brake, Rolling, Open Air Die, Bottom Die, Bullnose Die, Arc, Degree of Arc, Knife Die (as in; don’t use this type of die), Degree of Bend, Radius of Bend, Hardness HB, Hardness RC, Decarb Removal, Surface Preparation Steel, Brinell, Rockwell, Plasticity, Plastic Deformation, Spring-Back, Work Hardening, Heat Treating, Surface Hardness, Through Hardness, Gushing Head Wound, Depressed Skull Fracture, Life Insurance
4T, 8T, 12T relate to how many times you multiply the thickness of the steel to determine a suggested minimum bend radius. 4T would require a radius of four times the thickness, 12T would be twelve times the thickness, etc.
And, one more famous quote; “Don’t try this at home!”
-Howard Thomas, June 4th 2019
So, what is Lean Duplex Stainless Steel? When and where would you use it? A big topic for a short article. This is merely a brief introduction. Perhaps it will encourage further investigation. Also, we are referring here only to solid round bar, sheet and plate.
For many decades, Austenitic Stainless Grades dominated the industrial and commercial marketplace. They provided excellent general corrosion resistant properties. Then, hardenable martensitic grades began to see usage where increased strength was required. The successful combination of the grain types (Austenite and Ferrite) into one steel introduced Duplex Stainless Steel. Duplex grain structures allowed the broadest utilization of the properties of each. The initial concept was not terribly new; having been introduced about 80 years ago. LEAN DUPLEX stainless steels were the offspring of that product. Early improvements to the Duplex grade involved the enrichment of chemistry of the initial Duplex grade creating upgrades called; Super Duplex and Hyper Duplex; elevated property products with elevated price tags. A significant nickel shortage in the late 1960’s sent engineers scrambling to reverse the “richer is better” trajectory. They embarked upon a project that would minimize the expensive elements in the steel to lower the cost. Minimizing the content of key elements was expected to likewise minimize effectiveness. That was acceptable provided any new grade was still effective in combatting corrosion (specifically Stress Corrosion Cracking, or SCC) and increasing strength over the levels provided by the Austenitic and Martensitic grades used prior to the inception of Duplex.
The resultant steel was Lean Duplex (LDX). It was leaner and cheaper by a long shot. The great surprise was that the resultant loss in corrosion resistance and strength was not as significant as was anticipated. In fact, it was minimal for most intended service applications.
Fairly quickly, the LDX grades enjoyed overwhelming acceptance in the global manufacturing of various tanks, vessels and tubing. So much so, that it is rare these days to find any of those items that do not contain some percentage of Lean Duplex Stainless Steel. What was not readily apparent was the huge potential for daily use as upgraded replacements for the myriad of mundane, and unheralded daily maintenance wear parts and widgets that represent the lowest rung on the maintenance metals food chain; the gremlin maintenance parts that bend and pit and wear. The parts that won’t disassemble because of galling.
My opinion: Lean Duplex shafting, sheet and plate is under-used as a maintenance material. It needs a publicist, promoter or talent agent. Some gnarly champion that might say; “You can use that sh..t on anything!”
It’s that good. Why, it’s the Ginsu knife, the Veg-O-Matic of stainless shafts.
the lean duplex grades are stronger than the austenitic grades of 304 and 316. In my opinion they are generally better grades than 410 and 416. But wait, there’s more, Lean Duplex resists Stress Corrosion Cracking in Sour Service Applications. Since it will most likely be non-similar to your current stainless grades and because it will most likely have a different hardness, it is not disposed to gall. Plus, it is stronger and easier to machine.
Conclusion & Sales Pitch: Associated Steel is one of the few service centers that carries Lean Duplex (ASC2250® LDX) in long shafts they will cut to size. They also carry IN STOCK two different shaft finishes; Fine Turned Oversize “the size will make the size” resulting in less machining and less wasted material, and a Precision polished finished guaranteed bearing fit. Try it! Inquire on hi-def plasma cut parts from plate. Make maintenance life a little easier. Note: Your particular maintenance application has unique characteristics. Always refer to published material information sheets for qualification.
-Howard Thomas, May 6th 2019
Let’s begin this post with two of my favorite words; Ubiquitous; (everywhere, like raindrops during a storm), and, Esoteric; (known by a select small group of people).
What do these mean? Brake Die, Gun Barrel or Rifle Stock, Pump Shaft Straightness, Boat Shaft, Food Service Grade Stainless, Cold Roll, “Ultrasonic Inspect to 388, (and even FDA approved). While they may have a specific meaning to someone (esoteric), they do not have a defined meaning to everyone (ubiquitous in certain industries). In reality these are generic descriptions without reference to defined requirements and properties, at best they are like answering someone’s question regarding the location of your pending vacation by responding; “Up North.”
From my experience, and from a supplier’s point of view, the only real commonality they have is the suggestion of liability. You cannot hope to avoid potential mishap if you really do not have more information on the chemical and physical requirements of the steel the person is discussing.
Brake Die Steel – Generally, a high quality carbon or alloy, appropriate for dies, that may be, or is, hardened. Often an alloy from the 4000 series. Is it pre-machined? Not necessarily. Is it pre-hardened? Not necessarily. Is it oversized square and shiny? Not necessarily.
Food Service Grade Stainless – Generally means it does not contaminate food with residue from the steel and it maintains a clean finish. Most often some grade of stainless. More information is needed.
Gun Barrel and Rifle Stock – Generally a 4000 series high integrity hardened alloy. But, not a specific grade.
Boat Shaft – You really have no information from that term. Could be anything, carbon, alloy, stainless, monel, bronze, etc. Most customers will require specific properties that conform to some sort of Marine Agency such as ABS, etc.
Cold Roll – Not a steel grade but a production method. Need more information.
FDA Approved – A misnomer. FDA does not grant approvals for metals.
Pump Shaft Straightness – The specifics are different for everyone. There are ASTM specifications but many large companies have their own “esoteric” specifications. You need to know more.
Ultrasonic Test 388 – An ASTM test method to determine the internal integrity of steel. Requires more detail such as acceptability and reject-ability levels.
-Howard Thomas, April 22nd 2019
Click here to add your own text
Associated Steel Corporation reserves the right to delete comments that contain vulgar language, personal attacks of any kind, or offensive comments that target or disparage any ethnic, racial, or religious group. Further Associated Steel Corporation also reserves the right to delete comments that are: spam, advocates illegal or unethical activity and infringes on copyrights or trademarks.
Click here to add your own text
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
