Iron ore, found lying around near the surface of the earth, can be heated and primitively refined (a cave man could do it) to become iron. Iron is soft and pliable, great for lots of things and better than a poke in the eye, but begging for improvement. With minimal additional elements and a bit more refining “mild steel” made its debut. Mild steel is the leanest form of carbon steel. It is generally considered non-hardenable and is fairly pliable; stranger than iron and still fairly ductile. From that point you can add and subtract elements (manganese, chromium, nickel, moly, etc.) add heat and then cool and you can pretty much tweak it to be particularly well suited for an infinite variety of specific uses (carbon, alloy, stainless, and tool steel). You could make steel that holds a sharp edge; slices and dices, and could even cut someone’s shoe in half. You can make steel that gets very hard but is also very brittle, steel that gets very hard on the surface but stays softer at the core, and steel that gets very strong and will stand up to impact, shock and gouging. Fortunately for us in the present day, most any type of carbon or alloy steel you would want already has a recipe and a full set of instructions that have been worked out since people have been throwing rocks.
For most of us in the industry who will encounter grades of steel in our work-a-day-lives, we can generally categorize them into two separate camps: steel that is made into parts sold commercially to the general public and manufacturing companies, “production-steel”. And, steel that requires special properties to fix the machines that make those parts, “maintenance-steel”. When working with steel to make things, the steel used for the tooling takes quite a beating. It may have to stand up to bending, or breaking, or abrasive wear. It may be subject to twist, or corrosion.
4140 is pretty much the “Defacto-Standard” for a good all-around general-purpose maintenance steel for replacement parts. It has been designed to possess high strength (sometimes referred to as ultra-high strength), along with noticeable resistance to gouging, bending, fatigue, wear, and to an extent even corrosion. 4140 may be supplied in several hardness ranges to deliver several levels of strength. In most cases it is considered to be fairly machinable and weldable. You can forge it and bend it with caution.
It is considered to be a “through hardening steel”, but it will also accept surface hardening to maintain a ductile core. While it may on occasion be used in production manufacturing, as the steel that becomes the parts being made, it is generally not used where speed of machining is the requirement. With 4140, you will give up a little bit of machining time to gain strength and toughness.
4140 is a great basic chemistry that is easily modified at the steel mill by use of additional elements to achieve additional, and/or, specific properties for specific industries or jobs. For instance, if you need high hardness that is deeper and more uniform, you could add Nickel to the 4140. The subsequent grade would be an alloy called 4340. Want to increase resistance to softening in higher service temperatures, like a bracket for an exhaust pipe, add Vanadium and increase the carbon a bit; there was a grade for that, 6150. Want easier welding, forging, and maybe a hardened chisel edge but soft core, lower the carbon a bit, and add a bit of Tungsten, and you have 4135 non-tempering steel. And so on. Need to make a high strength shaft with a high surface hardness for wear resistance but a very tough core, increase the carbon a bit. Remember, a rough calculation for potential surface hardness is ten points over carbon content i.e. 4150, potential surface, flame or induction hardness 60RC.
So, when do you use 4140 alloy steel?
Pretty much anywhere. It is a great all around general maintenance alloy chrome, moly, manganese steel. A great platform chemistry for many other application specific steel grades. It is fairly resilient in thermal treatment and may be quenched in water, oil, or other mediums. It is readily machinable and weldable (standard low-hydrogen process), forgeable, and with limitations; formable. It is suitable for many various hardening methods including; furnace, flame, induction, carburization, and cryogenic treatment. There are improvements to the basic grade, but, keep in mind that as steel grades get pushed toward higher and higher levels of performance, they become more and more temperamental.
The producing steel industry that survived looks much different than our grandfather’s steel industry. “Standard Sizes” have taken on a whole new meaning. Bread and butter items that represented the largest tonnage sales require larger and larger purchase orders that are cost prohibitive to only the largest users or resellers. The plethora of smaller, more efficient mini-type-mills have made any return of the old steel business model doubtful. Into this new landscape, you will eventually be impacted by unavailability of grades, shapes, and sizes and lengths, that have forever been “Standards”.
Whatever is a person to do? Get to know your steel supplier. Understand their capabilities, their financial health, their industrial knowledge, their mill relationships. Think outside of the box. Buy smarter. Take another look at machining options that you thought were prohibitive. Using up a bar end-cut even though you have to remove a lot of stock, might not be as costly as you previously thought. The per pound price of a piece of steel is a relative number. Veal Scaloppini may be $18.00/lb, but if two can have a nice meal for $9.00, you can treat yourself now and again.
The specialty steel business is healthy; the heavy industrial maintenance facets of that business are even more healthy. It will remain so because it has always been more artform than mechanical. Because it is on a very low rung of the food chain of steel supply, don’t be disheartened by “Steel News”. Most doesn’t apply to you. Know your options. Get to know your suppliers AND competitors. Understand, that going forward, dead weight will become increasingly costly; whether that means inflated inventories, or an artistically challenged workforce.
On a clear night in the green valleys along the rivers that traverse the country, you can sometimes hear moaning. A frightfully eerie moaning that sounds a lot like… “Feed me Seymour.” That’s not you. You’re a small and lean and specialty maintenance mean! Different set of problems.
Shortly following the end of WWII, many special military grades of steel became available to feed the ravenous growth in industries like housing and manufacturing. During that boom, the commercial sector found uses for new steel grades developed by the military, and price was not an object. Existing steel mills previously occupied with feeding into the war effort, misjudged the massive needs of a burgeoning private sector.
Armor Plate became wear plate liners for steel mills and mine trucks. Hardened alloy round bar intended for gun barrels on battleships became mandrels and line shafts. The clamoring public would end up consuming all that was available and that which was not yet available. During the next 30 years or so, even newer grades were developed with special properties needed by big users and big buyers. Automotive, Appliance, Railroad, Mining, and an upgrading military drove invention and innovation. That amalgamation of industry was dubbed “The smoke stack industry”. Steel salesmen were “Smoke stack chasers”. If you were a part of that smoke stack industry, your request for a special modified grade of steel saw it quickly become a standard grade or stock size.
New alloy grades, new production methods, new shapes and sizes would soon become the bread and butter items for steel sellers. In the latter part of the twentieth century, it was hard to imagine a size that was not a stock size in whatever shape. But, the driving forces of heavy industrial activity are cyclical. In time, and on the buying-side of the equation, designs would change, requirements diminished, saturation achieved. On the supply-side, steel mills would react to the cyclical downturns by limiting production or “Hot idling” mills. (Putting them into a short hibernation).
Mills accepted the unavoidable downturns but nothing immediately coordinated industry’s permanent disuse of an item with the mills eagerness to accommodate the needs of those industries. All was viewed as the cyclical behavior; the natural order of things. Nothing specifically identified “gone-forever” items. Right about at this time, the concept of mega-mills was gaining traction. Capabilities of the mills, along with the efficiencies were being improved.
Mills reacted to this ebb and flow by limiting production of certain items to coincide with industrial cycles. Some items would disappear from the menu of available steel, but only until times got better. A signal of economic rebound brought a rebirth of increased production to include not just new demand, but to align production with virtually the same menu of sizes and shapes offered before the “correction”. Important buyers needed only to wait until the next upturn, at which time they could order their new unique items, comfortable in the knowledge that they would also have the ability to order standard, or, stock sizes when and if they needed. Like sugar and bread in a grocery store; there when needed.
For decades that symbiotic relationship seemed destined to go on forever. But, in time customers became more educated at recognizing and predicting boom and bust cycles. They began to hate the bust cycles and incorporated inventory management procedures and systems to assist them in limiting purchases to all but critical need items. Steel service centers, the now and again marketing arm of steel mills, subsequently began to make adjustments to their own inventories. Altruistic philosophy be damned. If you’re not going to sell it, don’t stock it! The attractive mill price of big tonnage orders became not so attractive, definitely not sufficient to offset the detrimental effects of maintaining a grossly obese inventory. Now, the monster sized “Feed me Seymour” steel mills had to react. Smaller appetizer orders from industry did not fill the bill. So, into a climate of tonnage resistance from astute service centers and with pragmatic acceptance of the realities of their existence; the mills launched programs requiring even greater tonnage orders. Eventually, they would be required to prune back their offerings (grades, sizes, and shapes), strategically re-align or network with more responsive and efficient mini-mills and processors; or go into a “Cold Shut-Down”. Generally, the state of being a little bit dead.
https://www.associatedsteel.com/wp-content/uploads/12_ASC_logo-1.gif00Michael Rosshttps://www.associatedsteel.com/wp-content/uploads/12_ASC_logo-1.gifMichael Ross2019-09-27 16:49:542019-09-27 16:49:54Steel Mills Are Changing - Take Two
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