THE 300 SERIES OF STAINLESS STEEL
If a steel has more than 10 ¾% Chromium content, it is classified as a type of Stainless Steel. There are many types (grades) of Stainless Steel, just as there are many types of corrosion. One grade of stainless steel may work well with one type of corrosion and then be terrible for service in another type of corrosion. The most common stainless grade is 304. Modify it a bit (improve) and you get 316. Enhance that a little, and you get 317. If you add Sulphur to type 304 stainless, you get 303 stainless, which is a “Free-machining grade”. Note: Generally, as you add elements to stainless steel to improve machinability, or strength, you may lessen strength and service-life.
Three hundred series grades are often referred to as; 18-8 stainless; where the 18 stands for percent of chromium content and 8 refers to the percent Nickel content. Those grades have some commonalities; grain structure of Austenite, non-magnetic, not generally responsive to thermal hardening, ability to work-harden.
Steel that has an Austenitic grain structure is not hardenable by heat treatment, but it is hardenable by cold working. Austenitic stainless grades are non-magnetic; i.e. they won’t, under general conditions, attract a magnet.
Strain-hardening, Cold-drawing, Cold-Finished, Cold-working, and Work-hardening, are all pretty much synonyms. Bang it around, Squash it, or keep bending it back and forth and it’s going to get harder; sometimes near 50RC hard.
18-8 Types of stainless steel are popular (common) for good reason. They are excellent for many applications exposed to corrosion, and they are readily available from suppliers. There are of course limitations imposed by various specific types of corrosion as well as limitations imposed by physical characteristics of the actual parts required (strength, straightness, etc). We will explore those in later posts.
-Howard Thomas, October 17th, 2022
Did you know you can buy precision finished high-strength shafting that already has a keyway machined in it? You can. You can purchase sizes from ½” Diameter through
2 15/16” Diameter. This product is available to ship from stock from Associated Steel.
The product name is Mirraloy FM (Free-Machining) Pre-Keyed. It is an elevated strength material that is also precision finished and polished, In most sizes accurate within a couple of thousandths. The keyway runs the entire length of the shaft.
For some, that configuration may work just as received; just cut it to the length you need. For others, it will be sufficient to get you back up and running quickly while you wait for an OEM part or custom machined part.
The main thing is, be aware that it is available, and the standard length (10/12ft rdm) can be cut-in-half as a courtesy, and rushed out via an expedited package service.
Cutting keyways can be a fun and surprising endeavor. Some materials, particularly stainless grades and hardened alloy, can move and bow, and not just a little. Re-straightening is often required; sometimes even an additional stress-relief is needed. When you purchase the shaft pre-keyed, Associated Steel has already insured you get a prime, accurate, usable shaft. Just install it and carry on.
-Howard Thomas, August 24th, 2022
IT IS A HUGE BENEFIT TO THOSE CUSTOMERS WHO PURCHASE ASSOCIATED STEEL KROMITE CD60 FINISHED RAIL TO BE ABLE TO JUST BOLT IT IN PLACE AND GET ON WITH THEIR LIFE. The manufacturer assumes the risk and accepts the liabilities associated with the production of the product.
ASSOCIATED STEEL;
“If we supply it, we stand by it”. We cannot guarantee the workmanship of our customer or their agents. Making finished hardened and machined custom wear rail is not for the faint of heart. Anyone who has done so knows there is truth in that statement.
Associated Steel has a Special Services Department (SSD) dedicated to custom fabrication. They have developed a specific fabricated rail from Kromite Cold Drawn Stock. Because of unique properties and characteristics, that product has been trade named; “Redi-Rail / Kromite CD60”.
Kromite CD60 is a semi-finished or finished rail that has been fabricated, to the customer’s specifications. Much like the unique processing technique used in the production of I.D. hardened wear pipe, the processing sequence and technique for Kromite CD60 is an inseparable component of the finished product. It is only CD60 when Associated Steel supplies it complete. Associated Steel has dedicated inventory, and devoted countless hours of engineering and refinement, toward making the highest quality product. CD60 is the product of an esoteric process. It has been field tested and proven to work exceptionally well. We do not share, nor do we release esoteric production technique or production sequencing information.
There is an “art” to making exceptional surface hardened rails, and that is why we trade-name finished and semi-finished rails. The actual process is an open-air process that is accomplished as much by sense and feel as by instructions and manuals. We have been supplying custom automation rails for over 50 years.
Occasionally, we will get a call from a customer who has made their own rails, advising they are getting low hardness readings. There are times where the actual hardness testing is the culprit. However, the majority of the calls could be avoided with a little bit of education. During the flame hardening process, De-carb is created on the surface of the bar. De-carb is that grey powdery coating that is visible on the surface that has been heat treated.
During the hardening process, carbon in the steel, at the surface, is burned off and disburses into the atmosphere. (No carbon, no hardness). Carbon near the surface can also burn off, although not completely. Testing into the De-carb will result in hardness readings that are not accurate, therefore a grind spot is recommended. A refined grain structure ensures the higher hardness range that we achieve after processing.
Surface hardening, when done correctly, allows the core of the bar to remain somewhat softer in order to maintain limited ductility. That is necessary for subsequent straightening and various other installation operations.
Heavier cross sections of flat bar retain more ductility. They are easier to work with during production and installation. Thinner flat bar will be more brittle and subsequently more difficult to manufacture and install. So, a 1” x 4” bar will generally be less troublesome than a piece of ¼” x 4”. On thinner sections, “crowning” across the flat becomes an issue and brittleness can come into play. At some point, if the ratio of thickness to width to length becomes unreasonable, Associated Steel will decline to quote. There are no charts to determine the exact point of concern. Experience and familiarity is required to make those determinations.
OUR COMMITMENT
To insure we provide the best possible hardened rails, we have developed unique jigs, fixtures, custom quenching mediums and procedures, at great expense to our company. There are times when we recognize that costlier additional processing procedures may be required. In rare instances, we may decline to quote certain configurations.
Associated Steel has the ability to provide custom surface hardened railroad type rails and custom hardened rail configurations specific to beef processing and other automation industries.
-Howard Thomas, August 6th, 2022
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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
