Cold Drawn – a Process Not a Material 

Cold Roll or Cold Drawn bar is often requested from a supplier as if the term indicated a grade of steel. Those terms refer to production methods not chemistry or grade. I point this out not to be stuffy, but to try to eliminate potential safety problems in the field.

Cold Roll, Cold Drawn, or Cold Finished bars may be made from 1018, 1020, 1045, 8620, 4140, etc. While most often they would be annealed (soft), there is the chance a cold drawn bar could be supplied in a hardened condition. The real problem is somewhat related to geography. In certain parts of the country, Cold Roll (Cole-roll), is most often produced as 1018 or 1020. Elsewhere, in other mills, the preponderance of production might lean toward 1045. The 1045 grade is hardenable; 1018 and 1020 are not. Expecting a material to be ductile in all circumstances could lead to significant problems should that steel turn out to be brittle.

Cold Drawn or Hot Rolled – When?
Cold Drawn steel materials may be used for various types of rails in heavy industrial applications. Hot Rolled Hardened wear bars may also be used for types of rails. If smooth and accurate travel along a rail is a concern, or if a finished cam/wheel is riding on it, you will probably want Cold Drawn, Cold Rolled, or Cold Finished (all the same) bars. If the application is “Big & Ugly”, let’s say a large heavy tank car is rolling over the rails and the rails eventually fail due to gouging, deforming, weight and wear, think Hot Rolled and Hardened. (Q&T).

Basically, a flat bar (cold drawn or hot rolled) is referred to as a rail when it has undergone some machining, and/or, hardening, or is used in an application where something is conveyed along it, or guided by it. A roller cam or trolley may ride along any surface of the flat bar, whether the bar is lying down flat, or is positioned up on end. Product may simply be slid along one surface of a flat, with no cam to assist movement. In the case of sliding, you will want to review “galling”.

If the application is “Big and Ugly”, such as moving bins of molten metal in a steel mill, the rail may be just hardened hot rolled bar stock. Pay close attention to the “out-of-square” allowable tolerance on hot rolled hardened mill bars. It is much more open than the tolerance of cold drawn bar.

WEAR BARS OR HOT ROLLED FLATS AS RAIL
Where the configuration is not sensitive to smooth uninterrupted movement (such as is required in an automation facility), hot rolled hardened bars may be used. These could be sizes like 3/8” x 2 ½”, or 5” x 8” depending on the weight of what is travelling the rail.

Generally, these types of rails will be welded or bolted to a substrate. Even Big and Ugly rails may require precise hole locations on the bars for alignment to pre-drilled holes in the substrate. When this is a requirement it is important to measure the holes centered on the length of the rail. So, you would not measure from the outside length dimension of the flat bar. You would find the center of the bar length and index the holes from that point radiating out in both directions. Otherwise, if the length was a bit oversize or undersize, the holes would not line up. The same goes for the width of the flat bar.

Our next post will focus on fabricating finished “Rails”; specifically impediments to fabrication and subsequent service-life. The third, and final post on CD bars will be an introduction to the trade-name rails produced and marketed by Associated Steel.

-Howard Thomas, May 9th, 2022

ASSOCIATED STEEL PRODUCTS: KROMITE® #3 (Hot Roll) & MIRRALOY® (TG&P)
The following tips assume you have an existing piece of shafting in 4140 or 4150 alloy steel, that is presently at a through hardness of approx. 30RC. And, that you require an increased hardness of approximately high 40’s to low 50’s RC.

PREFERRED METHOD: Long cycle anneal
Anneal at 1525F, one hour per inch of greatest cross section.
Cool in a furnace to 800F, at a rate of about 20F per/hour.
Re-heat to 1525F, one hour per inch of greatest cross section.
NOTE: In the event you have to move the material a significant distance between the heat temp and the oil quench, take precautions not to let the temperature drop below 1525F between the heat and quench. Cool in oil until smoking but no flame, approximately 250F to 300F.

NOTE: Alternate is a “sub-critical anneal”. Heat the bar to 1350F – 1400F, hold for one hour per inch of greatest cross section, atmosphere cool (in a protected atmosphere) to 350F. If the carbon is closer to .50, temper at approx. 700F to 800F for three hours per inch of greatest cross section (even for small diameters) should yield about 50 to 54RC. If carbon is closer to .40, lower the temp to approximately 400F to 600F.

NOTE: These are intended to be, and should be taken to be, suggestions for consideration, not instructions. This is not exact. If the material is too hard, repeat the cycle and try a higher tempering temperature. Repeated thermal cycling is not detrimental to the material, provided excessive temperatures are not encountered. If you do have to try several times, you may develop significant surface de-carb (powdery surface coat), which you will have to remove if you are not getting the results expected. CAUTION: Do not overlook removing all decarb in the area you will be checking hardness, no matter if using Rockwell “RC” or Brinell (bhn) equipment. Just grinding to “bright metal” does not mean you have removed all decarb. If your tests indicate you are only getting 18RC or lower, you are probably still into decarb. Even in an annealed condition those alloys would likely register a higher hardness than that.

Simply reaching for a higher hardness is not always the answer. If you try to go too high, brittleness may become a factor. In shaft applications where 28 to 32RC are deemed to be insufficient, you may want to try 32RC to 38Rc. Years ago, I was advised by an old friend; “With 4140 and 4150, “funny things begin to occur when you exceed 40RC (they tend to spit carbides). Don’t ask me what that means. I just got a strong negative visual and have been happy to follow that little gem for many years. (Real hard things can shatter like glass).

The above “tips” are just that; TIPS, as in “Hey, my brother in law’s uncle’s wife tried this once.” Plus, they are reduced to the simplest form. These basically relate to shaft stock and do not take into account a host of variables that may affect your safety and results. Part configuration, cross sectional differences, experience, etc. In all instances it is our recommendation that you utilize experienced thermal treatment personnel familiar with thermal conditioning alloys, who make use of all appropriate safety gear.

 

-Howard Thomas, April 8th, 2022

4140 and 4150 – KROMITE #3 AND MIRRALOY – modified grades of high strength alloy.

Last month, we talked about the word “modification” appearing on a Mill Test Report (MTR). This month I have been asked to clarify just how modifications have been incorporated into two key shaft materials provided by Associated Steel. Those items are Kromite #3 and Mirraloy. Both of those products incorporate changes (metallurgical and non-metallurgical), that address requirements of Heavy Industrial Maintenance.

Many times, in fact in most cases, modifications incorporated into the production of a grade of steel fall within the parameters of an established grade. They are usually adjustments to processing requirements and are specific to a particular customer. Modifications will appear on the MTRS. Some will change the allowable range of a chemical element but still carry the original numeric grade identifier, such as in the case of “H” Band Steel. H-Band steels have altered chemical ranges of certain elements to assist in thermal treatment. The change may allow slightly higher Carbon and Chromium content. The grade, however, remains basically the same. It retains the base metal grade numeric designation, plus a suffix addition. In this case “H”.

There are times when the modifications, intentional or not, may change the grade, i.e., prohibit the intended grade from being certified without an exception noted. Even a very small change in the content of an element may be sufficient to change the grade.

Many years ago, a manufacturer required a slight increase in resistance to service temperature for a part made of 4150. Over time, fatigue from repetitive motion, in elevated temperature, contributed to failure. One of the effects of vanadium is that it increases temperature resistance. The addition of approximately .15 vanadium content, to the 4150 chemistry resolved the customer’s problem and introduced a new grade of steel, 6150. In applications involving stainless steel, lowering the carbon content to .030, in type 304 stainless, created 304L, a modified grade. An “H” suffix in grades of stainless steel indicates elevated carbon content; again, a modification to the base grade.

The point is modifications are neither good nor bad. You just need to know how they will affect your application. The alloy steel grades Kromite #3 and Mirraloy, supplied by Associated Steel, are chemically modified to improve cleanliness of the melt. They incorporate bracket restrictions, (high-side for beneficial elements, low-side for detrimental or tramp elements). Improved cleanliness results in improved “toughness”, the key property that resists fatigue failure in shaft applications.

Associated Steel has been in continuous service to heavy industrial maintenance customers for nearly a century. Their products have been field proven in critical service.
The round bar shafts Kromite #3 and Mirraloy are both the same chemistry and follow the same thermal processing and grain refinement. Mirraloy is the precision finished product produced from Hot rolled Kromite #3.

 

-Howard Thomas, March 7th, 2022

Part One of Two

Steel grades in the U.S. are generally referred to by the materials standards and grading systems presented by various entities. The most common being: SAE (Society of Automotive Engineers), ASTM (American Society of Testing Materials), AISI (American Institute of Iron and Steel), and ASME (American Society of Mechanical Engineers). Those are certainly not all of them. Add to those an entire host of international agencies and it becomes a very large index. Grading systems are often common within a particular industry. Automotive may primarily use one numbering system, while pressure vessel operations would typically use another. As your time in a particular job builds up, it will serve you well to become familiar with the “esoteric” agencies and specifications typically used in that job. Be cautious, however, that your familiarity does not lead to assuming that grading systems used by your suppliers are the same because you recognize similar numbering. Be certain that the agency matches the specification referenced. Then pay special attention to any prefix, suffix, or reference to nomenclature, such as, “Modified”. The presence of that word does not have any specific connotation or purpose, other than to alert you to the fact that something relative to the specification is noteworthy. Nor does it mean that the original specification is no longer valid. While it may well mean an improved grade for one application, it may not affect your application at all.

The scope of potential modifications is broad. For instance, the content brackets for a certain element that the grade allows may have been tightened (restricted) for a particular heat-lot (melt) of steel, the bulk of which may have been destined for a particular industry. Let’s say the standard grade allows a carbon content of .38 to .42. If the melt content simply happens to fall within that grade, no modifier will be shown. However, if the ladle metallurgist has intentionally restricted the low-end content to be no less than .40, or a new restricted range of .40 to .42, the words “modified analysis” should be shown. For your needs, there may be no concern, since the content still falls within the range for the original grade. But, for the customer whose parts must hit a minimum hardness, it is very important that the carbon content is higher. For that privilege, that end-user will have paid an up-charge. Modifications may be made to element content to facilitate temperature resistance in service, strength, cleanliness, etc.

Prefix and suffix indications are more specific. An “E” prefix may mean Electric Furnace, which is a specific type of furnace treatment. An “H” suffix (H-band) relates to a chemistry adjusted to insure specific hardening results. An “H” modifier does not change the grade of the steel, it does change the hardenability potential. There may be “S” for sulfur additions, “L” for lead additions in steel, or low-carbon for stainless.

If you are not charged with the actual engineering and safety of the job, but are in an affiliated support position, you are not required to understand all of the specifics that relate to the metallurgy involved and the certification of the grade of steel. The thing to understand is that steel grades commonly bantered about in the industrial marketplace are a means of dialog. But, by the time the pen hits the paper on a requisition or purchase order, it is important that all parties are on the same page. Your general familiarity with numbering and grading systems will help you to effectively accomplish your tasks from a non-engineering position. The action you take will differ with each situation. It may be as simple as pointing out that a modifier appears. Expect a response like; “Thanks for the heads-up dimwit,” whether they were aware of it or not. Be forensically functional in whatever you do. Pay attention wherever you see the word “modified”, whether on your lunch order or marriage license.

 

-Howard Thomas, February 7th, 2022

MECHANICAL PROPERTIES: Generally, density, thermal and electrical conductivity are considered to be PHYSICAL PROPERTIES. The following represent MECHANICAL PROPERTIES.

If you expect a piece of steel to make a certain part, or provide certain benefits, you should know something about the nature of the steel you are purchasing. Understanding the mechanical properties of the steel will give you a better understanding as to how hard it will be to fabricate (cut, form, drill, tap), as well as an idea about how the steel might perform in your intended application (wear resistance, twist or bow, gouging, etc.).

HARDNESS How hard is it? This relates directly to strength, and/or brittleness.
Note: Hardness could well be an entire study i.e., variables affecting results, and interpretation.

YIELD At what point will it bend? (Plastic Deformation)

TENSILE At what point will it break? (Ultimate Tensile)

% REDUCTION IN AREA Pull it from both ends to the point of fracture. This measures the ratio of the reduced diameter at the break, to the original diameter. FUN WITH MECHANICAL PROPERTIES; roll a piece of Playdough to a pencil shape. Then pull it from each end until it breaks. The longer you can pull it and the smaller the diameter at the break, the more desirable.

% ELONGATION When pulled from both ends to the point of fracture, this measures the ratio of the length, at fracture, to the original length once it has been pulled apart from both ends. FOR MORE FUN SEE ABOVE. Once again, the longer you can pull it, the more desirable it is. There are always exceptions to your particular needs, but greater Reduction and Elongation are most often desired.

LCVN (Longitudinal Charpy “V” Notch) How much impact will it withstand?
Stick a short test specimen vertically protruding from a vice.
Notch it, then strike it above the notch with a weighted pendulum. Measure how far the pendulum travels after the specimen breaks
This is the closest indicator of “Toughness.” (Generally accepted as the standard for measuring impact strength.). “Toughness” is the main deterrent to Fatigue Failure, one of the greatest causes of shaft failure in heavy industrial applications.
.

RULES OF THUMB – NOT FOR ENGINEERING PURPOSES!
Two of the most common hardness testing methods are The Rockwell Test and The Brinell Test.
30 RC Hardness, in Rockwell “C” scale equals roughly 300BHN in The Brinell Test, 40RC = 400bhn, and so on…
Tensile (Breaking Point) equals about one half of The Brinell (BHN) reading.
EXAMPLE: Where BHN is 300, the Tensile will be approximately 150,000psi.
Yield (Bend Point, or point of plastic deformation) = is approximately 70% of Tensile
Generally, you want the yield strength to be somewhat lower (by 20 to 30%) than
the tensile. “Gives you a chance to get out of the room before the shaft breaks.”

THOUGHTS TO REFLECT ON: The test reports (TRs) for steel mill heat lots (batches of steel), are simply random checks. For 5000pcs of ½” Diameter steel bars, only a sampling will be tested. Even within those tests, results will vary. Recorded readings will usually show some variation which may be due to interpretation of results, test preparation, instrumentation, location in furnace, bar ends, etc. The surface of a wear plate may display several different hardness readings when tested in different places on the plate, by different facilities or by different people. This is not to suggest that readings recorded on Test Reports (TRs) are invalid. It is to encourage perspective within the realm of any mechanical testing. In fact, in situations where criteria are highly critical, the best method is to statistically check the actual finished part. Endurance limit testing is an excellent example of this. Many times, customers will request endurance limits on raw steel. Unless the actual finished part is tested, endurance limits posted on any raw steel product are useful only for the broadest suggestion of potential performance.

There is an excellent movie that illustrates this perspective; I believe it is “No Highway in the Sky”, starring Jimmy Stewart. It is an old movie (1950). Very popular among metallurgists and engineers. Enjoy.

 

-Howard Thomas, January 7th, 2022

From January 2020 post: NOTE: These are tips and guidelines/suggestions, acquired over the years. Not instructions.

There are steel grades (Mild Steel) that pretty much won’t harden by heat treatment. There are steel grades that are hardenable by thermal treatment. And there are steel grades that won’t harden during heat treatment but will harden if you whack em’ around; known as Work Hardening, Strain Hardening, or Cold Working steels. The most common of the work hardening grades (Austenitic) are the stainless grades 304L or 316L. They belong to a group of steel, categorized by grain type, as the austenitic stainless grades (typically 300 series, and the less common 200 series).

However, there is a non-stainless alloy steel that also work hardens; Hadfield Manganese Steel (or 11 to 14% Manganese, Austenitic Manganese Steel, or simply Manganese). It is a somewhat unique product that has found a home in heavy industrial applications where a combination of impact and abrasion tear up perfectly good steel. The railroad industry and the shot-blast industry are two of the prime venues for this product. As good as Manganese is in brutal service, it can also be somewhat “user adverse”; difficult to fabricate pretty much in every operation you might consider. It wants to work harden. During machining, it will harden ahead of your tooling, it will harden in the forming process, and it will be unforgiving of any misadventures in the welding process. Lack of attention to some simple details during welding, and you will be rewarded with embrittlement and fracture.

WELDING MANGANESE STEEL is not exotic or complex. The steel is just big and ugly, has a hard time making friends, and you need to respect some simple precautions. Think of everything you know about welding hard alloys, and pretty much reverse most of it. Don’t preheat Manganese Steel. Keep it cool, keep the interpass temp cool. Assist the welded unit to cool quickly; even if you have to spray some water to cool it. Employ techniques that tend to minimize welding temperature i.e short arc, minimize puddling, skip and backstep.

Don’t use carbon or low-alloy rods. Use Manganese Electrodes

If welding Manganese to Manganese:
Use Covered Electrodes (AWS A5.13, EFeMn-A) E-FeMnA
If welding Manganese to carbon or alloy
Use Covered Stainless Electrodes (AWS A5.4, E309) E-FeMn B
Use High Speed GMAW and FCAW not SMAW

If the Manganese has work-hardened in service (such as may likely be encountered in repair jobs),
cut away the hardened surface. Then apply a “butter-coat” of 307 stainless. The hardened surface, if not removed, will contribute to embrittlement and eventual fracture at the welded area.

Peen the welds while hot
Arc Welding is Good Don’t use OxyAcetylene (contributes to embrittlement)
Lean rod into direction of travel – flow the bead, don’t push it
Minimize energy input (65,000 joules max).

So, when welding hardened alloy steel, you are trying to get sound welds and maintain the hardness.
When welding Manganese, you’re trying to get sound welds period. Not protect any pre- hardened condition. Hardness will occur (or reoccur) when placed or placed back into service.

-Howard Thomas, December 7th 2021

Over the years we have looked at the nuisance of galling in several separate blogs.

That is because, every year galling makes it to the leader’s group of “Heavy Maintenance Royal Pains”, alongside, magnetism, barber pole-ing, and cupping or oil-canning.

So, let’s begin with this for anyone absent those days; Galling is the seizing of mating parts. A sort of Cold-Welding as it were.

When it is time to disassemble for inspection or repair, often the parts (hubs, casings, flanges), won’t come apart. That leads to hours of lost time and materials, often to find internal parts were savable, had you not destroyed the case. One industry I occasioned to visit finally gave up and inspections switched to mandatory replacements. Ouch!

Galling is a special thrill with the stainless assemblies often found in industries that prohibit the use of lubricants (food service and production).

Parts tend to gall as a response to friction and low-yield strength deformation. Eliminate the friction, eliminate the deformation, minimize galling. Not so fast. Can’t use most lubes in food service due to contamination.

If you’re using stainless shafts, you are most likely accustomed to a certain amount of gumminess in machining; a product of reduced strength that also contributes to deformation.

When mating parts encounter friction (resistance) they bind. Subsequently, they may deform and “cold-weld” together (gall). You can try minimizing binding during installation by slowing the installation speed; perhaps use a hand feed to detect potential galling areas; then back off pressure and speed. You can make sure the parts fit nicely (snug) to eliminate pulling the part together using the threads like a turnbuckle.

SMOOTHER & STRONGER THREADS would help as they would minimize friction and resist deformation. Using dissimilar steel parts with dissimilar hardness would also help deter galling. Try using “Rolled Threads”. Rolled Threads are smoother than cut threads so they have less surface defects which means less propensity for fatigue failure. But let’s keep the focus on galling. Rolled Threads are stronger because they are compressed or displaced into shape. That work-hardens (strain-hardens, cold-works) the thread; especially if it is a stainless steel.

“Roll-Threaded Rod Minimizes Galling”, may not be headline-making news. But it is a byproduct of that thread production method. Life is short. Be easy on yourself. Take advantage of available benefits before reengineering the whole job.

-Howard Thomas, November 8th 2021

Let me know if this reads a better, changed the order and made it (in my opinion ) a little easier of a flow without altering the message

Are there hardened (400bhn) wear plate angles and channels? November 2021 Blog

NO SUCH THING AS WEAR RESISTANT STRUCTURALS? (Other than low-hardness A588)

It is possible to make your own!

We stock a true 400bhn wear plate (sheet), 1/8” x 60” x 120”. It is clean, flat, and easy (relative to wear plates) to fabricate. We can Hi-def-plasma-cut pieces to order; simple rectangles and strips, or configurations per sketch. The cuts look almost like laser-quality with very little heat effected zone along the edge.

If you are involved with heavy plate maintenance and fabrication; more specifically, if you occasionally handle hardened wear plate, you will have a need for this unique product.

It forms well, is readily weldable (not too rich of a chemistry to cause problems), and it provides weight reduction where installation and handling might be a problem; not to mention you can make wear resistant containers, hoppers, tanks, that are lighter and therefore increase payload.

Where can it be used?

Strip it and tack weld it into the high wear areas of structural (A36) shapes. Tack it into the throat of a “U”, or, on the inside of one or both legs of an angle. You now have wear resistant structural steel.

Is a cart riding on top of a rail wearing down the top surface? Tack on a strip of this to add a 400bhn wear surface.

The material is perfect for emergency temporary patching of blow-outs on job sites until heavier fabricated pieces can be delivered. An installer can get the pieces into hard-to-reach places where a repairman could handle the plate by hand. This is an alternative to 3/8” and ½” thick A36 liners. That’s a big reduction in weight! You may even find you benefit from the competitiveness of your bids.

Cutting: oxy, plasma, band saw (use blades for hardened alloys), abrasive wheel, laser, and water-jet.

Welding: Standard Low Hydrogen Method (7018, 8018)

Form: using standard precautions for working with wear plate. Form against the grain. Leave a large radius at the bend (when wear-lining angles and channels utilize a cut-and-weld operation)

I know this reeks of a sales pitch, but, we have customers who keep this on hand around the plant for; “As Needed by Anyone Needing It” purposes. It is a life-saver for keeping things moving while you are otherwise attempting to resolve the issue.

CAUTIONARY NOTE; Working with hardened steel, anyone’s hardened steel, involves risks. Be sure to use appropriate safety gear (hot-mill gloves, hard hat, safety glasses, etc.), Utilize persons experienced in handling hardened steels, including certified welders, etc. Try to form against the grain, incorporate the largest bend radius the application will handle. And, COMMUNICATE, COMMUNICATE, COMMUNICATE.

If there is something you are not sure of; ask your vendor!

-Howard Thomas, October 27th, 2021

Or, “Keystock, we hardly knew ye. . .”

So, back in April of last year I was eulogizing Keystock; at least the longer length, higher strength, plus-tolerance kind, that for years had been a “go-to” product for a lot of people. It seemed Keystock would be going the way of the Dodo bird. But, I was apparently wrong. More correctly, it was going the way of Coke, or New Coke, or Original Coke, whatever. The point is . . . “It’s baaaack.” And, that’s a good thing.

As I mentioned then, in the steel business in most general terms, anytime you see the word “stock” attached to another word; think, “stock used to make”. Bar-stock, Bushing-stock, Brake-Die-Stock, Rifle-Barrel-Stock, Pump-Shaft-Stock, etc., would be stock that might typically be used to make those items. While it may seem to infer that there are other attributes specifically suited for the particular application specified, it may simply mean this is a material some people have chosen to make this type of part. Details should be clarified; is it closer tolerance, harder, squarer, whatever? Facetiously, a tree might be “Tooth-Pic Stock”. Works the same with the term Quality, as in; Rifle barrel quality, or Military Quality, or Drawing Quality. The explanation and caution remain the same; It may mean the steel possesses a special grade certification, but it may as likely mean that “Someone, at some time, used it for that.” So, “Trust but verify”.

Keystock is generally a low to mid-strength mild or carbon steel square or flat bar, 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 the key is of less cost and strength than the expensive shaft. If something interrupts the motion of the shaft and causes failure, it should be the cheap little key that fails not the big 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, but tuned to the actual application, close enough that the shaft doesn’t fail prematurely, contributing to expensive downtime. 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.

Ideally, commercial Keystock would be a precision cold drawn bar possessing slightly elevated strength properties, 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 cut a standard keyway that would fit nice and snug. Undersize tolerance resulted in sloppy, loose keys. Too much oversize required unwelcomed machining.

Unfortunately, over the past decade or so, tolerances on commercially available Keystock gradually opened up to +/- .004 to .007” (plus or minus); even with sources that promoted “Keystock”. For several years now, it has been common to only be able to source low property mild steel, undersize Keystock, in short lengths (12” and 36”).
Longer lengths, no matter how beneficial to the end user, require expensive additional processing to eliminate camber and bow.

Running multiple draughts (passing the bars repeatedly through drawing dies) is a good practice to increase strength (strain harden) and refine tolerance. However, that process adds cost, as does additional straightening. Those expensive practices were eliminated as the marketplace shrank.

Hardness (through multi-pass cold drawing/strain hardening), tolerance, cross-sectional accuracy and straightness, are all doable. Expensive, but doable. It requires a bit of fiddling in production for an item that does not represent significant tonnage. This current economic burst has allowed “The Return of Keystock”. Check with your vendor and take advantage of a simple perk that will make your life easier.

-Howard Thomas, September 15th 2021

The easier question to answer would be; who can’t use it?

A continuation of last month’s post:
Service temperatures should not exceed 750F. Any customer currently using stainless of the following types: 304L, 316L, 410, 416, 17-4ph should consider LDX, (ASSOCIATED STEEL’S ASC2250 LDX).

LDX is now made by several steel mills, to their own specific variances. In general, it is a great stainless grade for heavy maintenance applications where the grades listed immediately above are being used. It is more corrosion resistant, stronger, less apt to gall, better at resisting SCC, easier to machine and weld, than many of the commercial grades shown.

Lean Duplex work hardens. As shipped, it is generally about 28RC. The Austenitic portion of the grain structure contributes to strain hardening; it cold works as the size is drawn. As mentioned in part one; It is harder (hence stronger) than commercially available 304 and/or 316, but is still easier to machine. Duplex grades of stainless steel contain grain structures of equal parts Austenite and Ferrite. They are considered to be magnetic in their most common form.

It resists bending, (minimizes twisting), abrasive wear, resists failure due to SCC, resists galling, adds strength. It’s like the Ginsu knife of stainless steels. (Probably have to be my age to know what that means). Lean Duplex is not intended for use in applications currently requiring advanced alloy grades, such as; 2507, AL-6XN, Hastelloy C, 20cb, Ni625, etc.

ADVANTAGES OF ASC2250 LDX
The PRE (pitting resistance) is the accepted standard for determining a stainless grade’s comparable resistance to pitting and crevice corrosion. The lower the number, the less resistance.
304 is 18 316 is 24 Duplex grades are nearer to 40.
Associated Steel carries Lean Duplex (ASC2250 LDX) in two surface finishes; Fine-turned oversize (The size will make the nominal size), and Precision Polished Guaranteed Bearing Fit (Minus/minus tolerance). It is inventoried in long mill bars and may also be sold to specific required lengths.

ASC 2250 LDX offers advantage in:
Resistance to Stress Corrosion Cracking (SCC)
Resistance to Chloride pitting
Resistance to Crevice Corrosion Cracking
Elevated Strength Levels
Ease of machining
Ease of welding
Greater fatigue resistance
General corrosion resistance superior to 316L
Excellent resistance to “Thermal Shock” (low-cycle fatigue)
Excellent service to -30C

-Howard Thomas August 6th, 2021