If memory serves, I did a post on Lean Duplex some time ago. It is an important grade of stainless and worth a revisit.

Basically, Lean Duplex is a leaner chemistry derivative of Duplex Stainless Steel. Duplex Stainless Steel is recognized as having a unique shared grain structure; Austenite and Ferrite. Each of those grain types contributes to the characteristics and performance of the steel grade. The grade was developed to provide resistance to Stress Corrosion Cracking (SCC), a type of corrosive failure prevalent in SOUR SERVICE applications in operations such as Refineries and Pulp & Paper plants. Sour Service applications involve acidic or base (alkaline) exposure. 2205 Duplex is probably the most common grade of Duplex that the industry is familiar with; although there are several others. I refer to 2205 as the “Original Grade”.

The short and sweet history of steel usage to combat SCC in sour service maintenance applications is this: 304 and 316 (Austenitic grain) worked tolerably well, but lacked strength. 410 and 416 (Martensitic Grain) provided the needed strength, but offered less general corrosion resistance. Turns out the catalyst was nickel content, but that’s another topic. The thought was, develop a grade that was half Austenite and half Martensite (Duplex), and enjoy the best of both worlds. The development of the original chemistry 2205 Duplex did just that. It fit the bill, but it was expensive and somewhat user unfriendly.

Years later, when the cost of elements used in the chemistry of the Duplex grades became prohibitive, those grades were pruned to the bone (reduced the expensive elements) to develop a new “More Economical” grade, Lean Duplex. Engineers were content to live with a much less effective product, in order to come up with a more affordable product. Nickel prices alone, had seen a ghastly increase at that time. The new LEAN DUPLEX, however, displayed an unexpected phenomenon; resistance to general corrosion and SCC was very near that of the original grade. Strength was also maintained; and, machinability was increased dramatically.

Today, LDX is most commonly used globally in tube and sheet form in construction of container vessels and conveyance items.

Lean Duplex (LDX)
Resists pitting and crevice corrosion similar to 316L
Resists Intergranular attack better than 304L or 316L
Resists Stress Corrosion Cracking better than 304L, 316L, 410, 416
Resists General Corrosion better than 304L, and 316L
Weldability – less restrictive than 2205

-Howard Thomas, July 6th 2021

This is the last of our three-part post on chromed shafts.

In order to extend service life, by resisting surface wear on the rod, the rod surface needs to be hard. It also needs to be relatively smooth, so as not to tear up the seals.
And the rod needs to be straight. In most cases, chrome is an ideal surface coat for Hydraulic Rods. Hard Chrome may be better. IHCP is better still.

The finish however, cannot be so bright that it will not attract and hold the lubricant. Inadequate lubrication is just one of many potential contributors to shaft failure, chromed or not. You might to consider the following information, for a broader scope on this topic:

Fatigue Failure and The Importance of Design;
I have always felt that approximately 80% of shaft failures in heavy industrial maintenance applications are related somehow to fatigue. The following article found in Machinery Lubrication magazine compliments that supposition.

In his article on cylinder rods, Brendan Casey states that it is recorded that approximately 25% of hydraulic rod failures are design related. In hydraulic cylinder applications, one in four shafts fails to provide adequate service life. Bent rods make up a considerable portion of failures. It is important to clarify the straightness tolerance your vendor is proposing to supply.

Rods that are of insufficient diameter and insufficient strength will often bend in service. Once the rod bends, excessive load is placed on the seal. That results in premature seal failure. If a rod is bent, and use of a larger diameter rod is not practical, then the tensile of the rod must be increased. Induction hardened material (IHCP) offers a significant boost in strength.

A NOTE ON BAR ENDS
When full bars are chromed, most mills hold the bars by the bar ends and vertically coat them. In those instances, the bars are not fully chromed the length of the mill random bar. Several inches on each end will be bare. This is generally not trimmed off when random bars are sold. It is recommended that you specify “trimmed ends” when you order random length chromed bars. Probably a good idea to specify this on even cut-to-length material, even though most vendors provide that service as a default.

This completes our post on chromed rods. If you want to pursue information gathering on this type of material, you may want to do some additional research on; Black Nitrided Rods. That process is showing improved service life in similar applications.

 

-Howard Thomas, June 11th 2021

Continuing from our last post, we are discussing chromed rods. When they are applied correctly, chromed Rods typically extend service life compared to standard carbon and alloy bars. Variables relative to those materials would be the steel type, actual hardness, and the type of hardness (surface or throughout). The benefits of chromed rods address sliding surface abrasion and corrosion.

In actual service, however, even sliding abrasion applications are not just limited to sliding abrasion. Small bits of debris (tramp elements) find their way onto the exposed rod and then get pulled through the seal (intended to keep tramp elements out), between the rod and the cylinder. The motion of the rod is often interrupted by impact causing shock and twisting or bending of the rod.

Deciding between IHCP and Hard Chrome HP & Too great of a surface finish has a downside.

Since chrome plating is most often applied to a rod surface very thin (thousandths), the importance of a surface hardened sub-straight should not escape consideration. Where severe impact and gouging may be experienced, a hardened sub-straight will resist damage. You would think that, to be on the safe side, everyone should always order the IHCP material. The problem is, surface hardened sub-straights may be furnished at a hardness of 60 to 62RC (approximately 600bhn). Not everyone has machinery sufficient to handle that hardness. Drilling, cutting, machining may be a problem.

The thin chrome “skin” covering the rod is easier to penetrate when the sub-straight is soft. Various fabrication processes are readily accomplished. Smaller shops will find fabrication processes easier.

It is also important to always remember that high hardness in steel (carbon or alloy surface or throughout) also affects ductility. Application consideration must be given to the propensity for fracture.

CHROME SURFACE FAILURE
Abrasive related chrome surface failures often damage seals. When chrome gets very thin due to wear, it cracks and peels, exhibiting a razorblade sharp projection that often curls up, like the bark on a Birch tree. This type of failure is often experienced where there the surface of the shaft is subjected to severe temperature change (furnace). That projection tears up seals. In applications were liquid may escape, such as sludge from a barge pump, the contamination could be catastrophic. Read as “expensive”. In those applications, some alternative (such as utilizing hardened stainless shafts) should be considered.

Our last post of this three-part series will cover, lubrication, bar cut-ends, and dent bars.

 

-Howard Thomas, May 6th 2021

You do not have to be a metallurgist or engineer to accurately order steel. But you don’t want to order steel plates and end up with dishes. Take some time to ensure your language will be understood by the vendor. I’m not speaking about dialects, but try to avoid esoteric terms that may just be what you use at your company. Avoid jargon. Take a moment to familiarize yourself with the terms the vendor uses. You will quickly learn there are common terms that will help to avoid misunderstandings.

In general steel suppliers and steel service centers are used to working with people that may need help drilling down to what they actually need. Mills on the other hand are a different animal all together. They don’t need calls from every person trying to fix air fryer. Still, they get calls that should never have been directed to them. As a result, and I’m just sayin’, they can get testy and come across a bit like a bear with a sore behind.

I remember a call I made early in my career. I was mumbling and stumbling around when the person kindly interrupted with; “Look kid, when you know what it is your looking for, give us a call.” It helps to get your ducks in a row before you make that call.

The first thing you are going to want to present is the “family” the steel belongs to; is it mild steel, carbon steel, alloy steel, stainless, tool steel, or a non-ferrous grade like brass or bronze. The general form the steel takes should be right here. Is it wire, coil, sheet, angle, bar, shapes, or some other form? They should ask what hardness, or what finish? Try to answer those questions with industry familiar language. “I don’t want it to be hard to machine.” Is not good, for all they know, you may be the worst machinist in the world. “I want to see a reflection but it shouldn’t stretch my head a lot.” No help there either.

Next advise the specific size shape length and quantity. Get this out of the way quickly. I have been in long conversations about applications and failures only to find out the customer was actually looking for wire or coil, or some other form that we didn’t handle.
If it is a repeat order, mention that upfront. It will save both of you a lot of time.

Caution on the length. Does it need to be an exact length (you will need a tolerance), or can you take a random bar length? See previous posts on random bar lengths. A common mistake is asking for a 36ft length because you’ve calculated your mults (finish lengths) to be optimal from that length. That results in a lot of no quotes. Advise your mults first. Then advise how many “finish length pieces” you will need.

When you are discussing quantities and descriptions, the following are universally accepted; Pieces, Bars, Sheets, Plates, Tons, Metric Tons, etc. If it is thin plate you can use the words sheet or plate; although sheet is understood to be thinner. Those items can be purchased in pieces, pounds, tons, hundred weight (cwt). Thick plate, maybe heavier than 3/16” thick, should always be plate.

Bars may be pieces, bars, or rods, even sticks will work. ”Bundles” should be avoided.

Food for thought; If every order you place is a “Rush-Breakdown”, you should know that after a while your urgent need won’t even be heard by your supplier.

A group of crows is a “Murder of Crows”. Just in case that ever comes up.

 

-Howard Thomas, April 5th 2021

Part one of three –

I thought we would sneak into 2021 by looking at a steel shaft that is often misunderstood; Chromed Steel Shafts (Rods).

Chromed steel shafts are referred to as “Rods”, or “Cylinder Rods”. Not all are used for Cylinder applications. The manufacturing and automation industry is a prolific user of this type of product. The default term Rod, is simply “jargon of the trade”. The base metal may be mild steel (soft), carbon steel, alloy steel, or stainless steel; it may be soft or hard, through-hard, or skin (surface) hard. Communicate with your vendor to understand what you are getting. The tolerance, type of chrome, and thickness of coating varies by supplier, so you will need to pay attention to that if you intend to compare brands, etc.

The base metal shafts are usually precision ground and precision straightened. Straightness is critical where telescoping is involved (such as with cylinder applications).
Diameter tolerance and surface finish are also critical. More about that later.

Persons working in industries other than heavy industry will still encounter Hydraulic Rods and Pneumatic Rods in their daily life. The door closer on a screen door, the shiny bars visible on a piece of landscaping equipment, are types of cylinder and shaft assemblies. Even a BB gun operates on the same principle.

Descriptive terms esoteric to chromed rods may be CP (Chrome Plated), IHCP (induction hardened chrome plated), HCP (Hard Chrome Plated), pneumatic rods, cylinder rods, hydraulic rods, etc. Typically, the differences identify the application.

Chrome plating generally begins as a powder. It may be considered “Hard Chrome”, or “Chrome). In some cases, it may be applied as a weld overlay. Chrome coating has its own hardness, intrinsic to the weld or powder. It then takes on the hardness of the sub-straight. If the shaft it is applied to is soft, it will be soft.

A bit of clarification is required here; The medium itself has its own hardness, important for initial sliding abrasion. The resistance to an impact or gouging event will come from the hardness of the sub-straight (the underlying shaft material), as will ductility. Think of a soft cream topping on a gingersnap cookie, or a hard chocolate coating on a marshmallow or strawberry. Each of those is subject to different adversities. A chocolate covered cherry may have a hard-coat, but most of us have put our thumb through it.

Next postings will look at; explanation of terms, cutting & drilling, how to order lengths (end-condition), failures, and how surface finish affects lubrication.

-Howard Thomas, March 3rd 2021

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.

Remember.

  1. Generally there is no accurate published data to indicate a universal endurance limit for shaft material.
  2. 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.
  3. 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