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
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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
