I’m looking for some advice on selecting grades & sizes of square tubing for a line of portable livestock containment & handling systems that I’m developing. In the past, we’ve used 14-gauge A513 mild steel in 1.5” squares with 14-gauge sheeting, which we’ve had excellent results with. Unfortunately, even our shortest panels (8’ x 60” - 72”, suspended between bows or gates) are extremely heavy, to the point that it can be difficult to market them as “portable.”
I have been trying to find a supplier who was willing to help price a different set of materials for me, with no luck. My goal is to reduce the weight, depth and feet of tubing per panel. Along with my suppliers, my business partners and I have no experience with medium-carbon, low-alloy or other higher-tensile-strength steels. Using 1-1/4” may be possible but would be less than ideal due to aesthetics (visual barrier to the animals, perceived quality to the customer). My thought was to make the panels out of 1-1/3” (or metric equivalent) square tube with about an .065 wall thickness and sheeting with a .065 wall thickness, using a grade that would put the strength on par with 1-1/2” at 14-gauge. Alternatively, we could continue to use 1-1/2”, only in a different grade and wall thickness.
At this point, I have not called any mills directly but we would probably be willing to purchase in truckload quantity for cost savings. Does anyone have any thoughts relating to the engineering, availability and cost aspects of what I’m talking about? Any thoughts would be appreciated.
A513 = ASTM A513, which is simply a specification of carbon steel commonly available as 1010, 1020, etc..
Carbon steel is very weldable, easily formed with the right tools. All you rally need to know is your sizes desired and whether you should buy normalized, seam or drawn tubing.
The weight for all carbon steels are going to be almost identical.
Chase cost and deliverability…
My goal isn't to lower the weight simply by switching grade, it is to lower the weight and overall dimensions by switching to a smaller tube with a thinner wall. 1.5" ERW square tubing at 14-gauge is about the minimum strength that I'd be willing to go, and it's possible that we might stay right there. Easy to find and inexpensive. However, using the same materials as the competition gives my product no advantages, perceived or otherwise.
What I'm trying to do is explore alternatives for product improvement and differentiation. To use an example, sticking with 1.5" tubing, the weight savings going from 14-gauge to 16-gauge is about 16%, which is significant. Using a deflection calculator (using random lengths and stresses just as an example) we could go from 1.36" of deflection to 1.62", an increase of 19%. If I can find a mill with the ability to send me a truckload of 1.5" 16-gauge square tubing with the properties necessary to get deflection under 1" in the aforementioned example, I could theoretically pay an additional 20% or more on a per pound basis (all other things equal, etc. etc.).
I am not a metallurgist or engineer (hence the less-than-scientific example above) but it seems that increasing the carbon content only slightly, or going from A513 Type 1 to A513 Type 5, may be ways to add sufficient yield strength to allow a reduction in wall thickness.
Nobody can tell you what end material you need to satisfy stress requirements or some generic weight vs cost vs strength requirements you may need based on a forum post.
You need a design layout first then explore materials adequate for function and strength.
ASTM A513 carbon steel is all roughly the same - don't overthink it.
My intention was to use the forum post to brainstorm and generate ideas for material selection and sourcing, I should have been more clear on that. Using mild steel in commonly available sizes for the prototype certainly worked, in fact it exceeded my expectations, I just thought I'd see if anyone with more experience and knowledge than I have had any obvious thoughts on how to make it better, with particular regard to perceived quality and perceived secondary benefits from the customer's viewpoint. It would be just like me to order a truckload of steel only to find out that there was a better option.Originally Posted by Kelly Bramble
I have actually stumbled on one idea that I'd like to explore; as far as I can tell, the difference in strength between A513 Type 1 and A513 Type 5 is not insignificant, which seems to be the opposite of what I've heard from distributors and others. Depending on which chart, manufacturer and ISO grade, the yield strength and tensile strength of HREW has a range of about 23-24 and 38-40 ksi, respectively, whereas the yield strength and tensile strength of DOM is 60-70 and 70-80.
I would be curious to hear from someone with more knowledge and experience how that actually translates to practical applications. As far as I can tell, I should be able to build a stronger product with a lower wall thickness, along with the other promised benefits of using DOM (warp resistance, uniformity and eliminating the process of removing mill scale are all very desirable traits).
FYI: No promotion or posting of "sourcing", companies, etc. allowed here.
You seem to be changing the question to fit? Your questions now appear to be more academic in nature with a need for sourcing. Depending on volume buy as local as you can and as common materials as you can use. Shipping can be more costly than the material.
“KIS”.
Remember – you started this discussion with “Portable Livestock Systems, Common Grades & Sizes”. Put wheels on it and a way to tow the thing if it’s too heavy to handle by person. Moreover think total costing, which includes manufacturing, handing, shipping and extra $$$ for non-standard materials. I'm beginning to think your NRE will be the most expensive line item.
Moving on… Let’s actually do real world.
First, engineering materials are normally considered and base lined by functional and environmental requirements. Corrosion, heat transfer, strength, paint-ability, shock and statics loading, … that's it, nothing more. If your designing a spacecraft non-standard materials maybe required by be prepared to pay for it and lead times will be long.,
Second material specifications, such of Yield and Modulus of Elasticity are minimums and depending of the quality of source (trace-ability) may or may not meet the specifications. Engineering materials without verifiable quality controls are often unknowns this is why we design in a Factor of Safety, and besides, quality of build and other variables can complicate the end item functional capabilities. Seriously, back in my university days we chased significant figures like it actually mattered – in most applications this is a waste of time. Round off the numbers figure out a suitable FOS.
Third – most materials are ultimately specified based on manufacturing requirements. Is the end item machined, welded, formed, etc.. Will we be doing field threading, or match drilling operations and so on. So, for example if we need the material capabilities of Aluminum, 6061-T51 which machines really well but does not form well - consider this. If we need a deep drawn shape maybe 5052 is the better selection for Manufacturing. Apply the appropriate FOS based on the material strength characteristics.
Lastly, going back to “Portable Livestock Systems, Common Grades & Sizes” – this will likely be utilized by farmer types – which means they probably only own hammers and pipe wrenches and tend to be rough with equipment. Consider the end users servicing, handling and using the end item and knowing a bunch of farmers – think durability.
As strange as it may have been, I appreciate you taking the time to help me through my mental processes; they may seem neurotic and/or unorganized, but I've been able to figure out solutions to some pretty tricky problems over the years. I have a bad habit of not keeping it simple - I overengineer plans in my head and develop the final product by working backwards from that point. In this case, I had two qualified welders and a shop full of metalworking tools to turn my thoughts into reality so yes, NRE is definitely the most expensive line item.
At the very least, it's now clear that redesigning the panels/product line to make use of some type of high-strength tubing or nonstandard size would have been a mistake (but it was still an option I had to consider and I don't regret the additional knowledge that I now have). For the material selection, al and 4130/4140 are almost certainly cost-prohibitive and would add unnecessary complications to the manufacturing process, as would any medium/high-carbon steels. DOM seems preferable to HREW for a variety of reasons and I can't say I dislike the idea of a HSLA with good machinability and welding. But the next step is to ensure local supply of anything and figure out how much of a premium could be justified. I'm in central Iowa, so I have a fairly decent set of options within a few hours' drive.
I’m sure you’re aware that you can mix carbon and nickel steels for functional requirements. For example, more than thirty years ago I worked at Bell Helicopter Textron and designed fatigue testing machines (weldments). We would use 1010 or 1020 carbon steel for the structural shapes and then weld in 4130 or 4140 pads at high stress locations for the threaded features. Just made sure there was proper gusseting and enough weld line between the two engineering materials.
Also, we would combine large section (area moment of inertia) channels into box beams by skip welding the seams to achieve the structural characteristics we needed since the large box beams were very expensive and unavailable.
Other strategies included structural section orientation to achieve the stiffness/strength needed.
We only analyzed selected sections and interfaces for deflections and strength based on experience and then monitored the machines performance in production and made adjustments and reinforcements as required.
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