How to Select a Material

ncsteinb · Jul 14, 2020

Hello,

Firstly, I know this is a big question. I'm not looking for a specific answer for a specific question, but rather a more general question on how one goes about selecting a material. To illustrate my question, I will pose a specific example just for sake of clarity.

OK, so I'm a mech engineer (I know..hahaha, an engineer asking machinists questions :willy_nilly:

), been in the field for 10+ years designing and making all sorts of things. I've worked as a machinist for a few years as well. I've never thought of materials and heat treating to be my strong suit, but I know enough to choose between a 1000 series carbon steel and a 2000 series aluminum.

The specific design problem: I have a machining fixture that I'm designing, and I need some sort of pad to locate my part in Z that also is wear resistant, as steel parts will be placed on this surface prior to machining and clamped up thousands of times. I know I want a low alloy steel that can be hardened and ground. I'm thinking of a 1050 steel...

I understand the differences between a 1010 and a 1095 carbon steel, but when would you chose a 1050 over a 1060? Where does one learn these nuances? When would a 6061-T4 fare better over a 6061-T6? These are things we are not taught in college (at least not in mine). I've always heard that these things come with experience, which is typically the way we all learn. However, as one of two engineers in an entire plant, I'm spread pretty thin, which doesn't allow me much time to spend on "gaining experience" in material selection and heat treating.

So, up to this point, I've discussed my applications and material selections with my go-to job shop, and they've always been very helpful, but I feel that it would be unfair to rely on them for material selection and design constantly. So please, what resources do you use to select materials? How have you learned how to select materials? Also, how do you factor heat treating and/or surface treatments into selecting a material? I have at least another 30+ years of engineering in my career, and I'd like to start making better choices of materials, rather than selecting materials based on Alro's descriptions of uses... :reading:

Thanks

Joe Gwinn · Jul 14, 2020

While it's a bit of an art, the best answer I can think of is that it's basically a process of elimination:

1. What strength level is required - this usually sorts steel from aluminum from plastic, never mind the alloy kind or alloy.

2. Is impact resistance needed?

3. Is wear/abrasion resistance required?

4. Is creep resistance needed? This kills most plastics and many metals.

5. Will the component be used as a spring? This drives one to spring steel, beryllium copper, et al.

6. Is corrosion resistance needed? How bad?

7. Will there be motion between pieces of such material? Is low friction needed? What about galling?

8. What is the field experience with such materials in the same or like applications?

And so on.

These checklists usually cut the list quite short, sometimes to zero candidates, and one picks the cheapest material in total cost (not just cost of raw material). Availability is often the main driver, so long as the choice is adequate.

rogertoolmaker · Jul 14, 2020

What material to meet a design requirement

ncsteinb said:
Hello,

Firstly, I know this is a big question. I'm not looking for a specific answer for a specific question, but rather a more general question on how one goes about selecting a material. To illustrate my question, I will pose a specific example just for sake of clarity.

OK, so I'm a mech engineer (I know..hahaha, an engineer asking machinists questions ), been in the field for 10+ years designing and making all sorts of things. I've worked as a machinist for a few years as well. I've never thought of materials and heat treating to be my strong suit, but I know enough to choose between a 1000 series carbon steel and a 2000 series aluminum.

The specific design problem: I have a machining fixture that I'm designing, and I need some sort of pad to locate my part in Z that also is wear resistant, as steel parts will be placed on this surface prior to machining and clamped up thousands of times. I know I want a low alloy steel that can be hardened and ground. I'm thinking of a 1050 steel...

I understand the differences between a 1010 and a 1095 carbon steel, but when would you chose a 1050 over a 1060? Where does one learn these nuances? When would a 6061-T4 fare better over a 6061-T6? These are things we are not taught in college (at least not in mine). I've always heard that these things come with experience, which is typically the way we all learn. However, as one of two engineers in an entire plant, I'm spread pretty thin, which doesn't allow me much time to spend on "gaining experience" in material selection and heat treating.

So, up to this point, I've discussed my applications and material selections with my go-to job shop, and they've always been very helpful, but I feel that it would be unfair to rely on them for material selection and design constantly. So please, what resources do you use to select materials? How have you learned how to select materials? Also, how do you factor heat treating and/or surface treatments into selecting a material? I have at least another 30+ years of engineering in my career, and I'd like to start making better choices of materials, rather than selecting materials based on Alro's descriptions of uses...

Thanks

Your presently designing a holding fixture that you question using SAE1050 or some material that may be a better choice. I question your wanting to use a lower carbon steel were wear is a requirement. A better choice for wear would be O1 tool steel hardened to 60-62 Rockwell and then ground. 6061T6 is a mealy material, good for extrusion and not so good for machining as an aluminum in the 2000 series.
The previous post does a good job replying to your general questions.

nihilistic · Jul 14, 2020

Thousands isn't that many to be honest. Also, process control can handle slight deviations over time. So would a .0001 deviation over 10k parts be too much? What are your tolerance needs?

Another suggestion would be to design your fixture to include replaceable components where wear is critical/significant. Sometimes it is better to plan for deviation than to try and imagine some impossible material that stays perfect in all conditions forever.

For example, I have run 100's of thousands of components using 7075 Al fixturing using replaceable clamping components like those at mitee bite and steel insert threading.

gbent · Jul 14, 2020

When evaluating different materials, one of the first considerations is the cost of failure.

michiganbuck · Jul 14, 2020

You can search 1018 verses ..all the other steels and make your own reference notes.

Never read this book so don;t have a clue.
Amazon.com: Science, Technology and Applications of Metals in Additive Manufacturing (Additive Manufacturing Materials and Technologies) (9780128166345): Dutta, Bhaskar, Babu, Sudarsanam, Jared, Bradley H.: Books

johnoder · Jul 14, 2020

Machinery's Handbook has a hefty section on what was used to make what

Carpenter Steel had MANY editions of Carpenter Matched Tool and Die Steels - and their idea of what tool should be made from which tool steel

snowman · Jul 14, 2020

johnoder said:
Machinery's Handbook has a hefty section on what was used to make what

Carpenter Steel had MANY editions of Carpenter Matched Tool and Die Steels - and their idea of what tool should be made from which tool steel

It is less great in modern editions and early editions. I want to say 24th edition was damn near perfect.

Sent from my iPhone using Tapatalk

Erich · Jul 14, 2020

Its all about finding the material that best fits ALL of your particular design requirements.

why 1060 vs 1050? a bit more carbon. Higher tensile strength bit less ductility? Maybe a bit higher price. If you are buying railroad cars full it matters.

As for your fixture, material cost is a tiny fraction of the total cost to acquire. Your design hours, machine shop hours all swamp the material costs of 1 part. I would be specifying an air hardening tool steel to get a hard wear resistant part that may not need post heat treat grinding to hit your tolerances. A2, A6 might fill the bill.

DDoug · Jul 15, 2020

ncsteinb said:
The specific design problem: I have a machining fixture that I'm designing, and I need some sort of pad to locate my part in Z that also is wear resistant, as steel parts will be placed on this surface prior to machining and clamped up thousands of times. I know I want a low alloy steel that can be hardened and ground. I'm thinking of a 1050 steel...

I like to BUY mine.
Try Carr Lane or Jergens.

Mike1974 · Jul 15, 2020

As someone else said, you need to evaluate what properties are important for your application - wear resistance, shock resistance, etc.

If I was designing a fixture (for in-house use) that needed some wear resistance for a clamping pad, D2 would be a good choice, but really almost any tool steel would work. Do you want to send out for heat treat, or do you have the means to do yourself? If neither, O1 is a good choice as you can torch and quench in oil using color as a guide for hardness/draw. But again, almost any, it sounds, without more info, for what you are doing - A2, D2, S7....

Mike1974 · Jul 15, 2020

digger doug said:
I like to BUY mine.
Try Carr Lane or Jergens.

I think Doug is referring to this -

Rest Buttons & Pads | Carr Lane

Search | Jergens Inc

jim rozen · Jul 15, 2020

nihilistic said:
Thousands isn't that many to be honest. Also, process control can handle slight deviations over time. So would a .0001 deviation over 10k parts be too much? What are your tolerance needs?

Another suggestion would be to design your fixture to include replaceable components where wear is critical/significant. Sometimes it is better to plan for deviation than to try and imagine some impossible material that stays perfect in all conditions forever.

For example, I have run 100's of thousands of components using 7075 Al fixturing using replaceable clamping components like those at mitee bite and steel insert threading.

+1 for replaceable locating pads. Also 7075 really is an amazing material.

BoxcarPete · Jul 15, 2020

To throw in my $.02 for the general case, I'd say that material selection is a venn diagram between availability and suitability. Any number of materials are likely to work in your case. Maybe there is a "best" one, but as an engineer it is your job to determine the cutoffs between "acceptable" and "unsuitable" for the application. Once that is done, take a look at the materials that you would have access to. That's your other circle. Pick anything inside the overlapped zone. Sometimes it'll be just about anything, others you'll struggle with design features just simply trying to get the circles to overlap at all.

Most will pick the lowest-cost material out of the center of their venn diagram, but with a little more work you might be able to determine lowest cost over time.

ncsteinb · Jul 15, 2020

Thanks for the replies. Up to this point, all of the wear pads and contact surfaces in my machining fixtures have been either 1050, then hardened and ground, or 4140 pre-hard. I haven't had any issues up to this point with my fixtures that are in service.

Really, my question pertains to what RESOURCES you use to help you select a material. Up to now, my main driving factor has been availability, as in what's listed as in stock at Alro, or whatever. Knowing what materials to choose seems like a chicken/egg scenario. For a newbie, the only materials you know to use are the materials you've seen up to then. And for a seasoned guy, they just know what material to use based on experience. But I feel like I'm stuck somewhere in the middle. So, if I wanted to avoid annoying my machine shop guys, and I don't have access to a seasoned guy to ask questions, where should I be looking?

Thank you for all of your responses.

DDoug · Jul 15, 2020

ncsteinb said:
Thanks for the replies. Up to this point, all of the wear pads and contact surfaces in my machining fixtures have been either 1050, then hardened and ground, or 4140 pre-hard. I haven't had any issues up to this point with my fixtures that are in service.

Really, my question pertains to what RESOURCES you use to help you select a material. Up to now, my main driving factor has been availability, as in what's listed as in stock at Alro, or whatever. Knowing what materials to choose seems like a chicken/egg scenario. For a newbie, the only materials you know to use are the materials you've seen up to then. And for a seasoned guy, they just know what material to use based on experience. But I feel like I'm stuck somewhere in the middle. So, if I wanted to avoid annoying my machine shop guys, and I don't have access to a seasoned guy to ask questions, where should I be looking?

Thank you for all of your responses.

Your Bio says your a "professor" ????

jim rozen · Jul 15, 2020

BoxcarPete said:
...
Most will pick the lowest-cost material out of the center of their venn diagram, but with a little more work you might be able to determine lowest cost over time.

Or "It's not an engineering equation unless one of the units involved, is dollars."

ncsteinb · Jul 15, 2020

digger doug said:
Your Bio says your a "professor" ????

Yep, I'm an adjunct professor for a section of Engineering Graphics and CAD. I teach a class on engineering drawing, standards, GD&T, and SolidWorks.

Mike1974 · Jul 15, 2020

ncsteinb said:
Thanks for the replies. Up to this point, all of the wear pads and contact surfaces in my machining fixtures have been either 1050, then hardened and ground, or 4140 pre-hard. I haven't had any issues up to this point with my fixtures that are in service.

Really, my question pertains to what RESOURCES you use to help you select a material. Up to now, my main driving factor has been availability, as in what's listed as in stock at Alro, or whatever. Knowing what materials to choose seems like a chicken/egg scenario. For a newbie, the only materials you know to use are the materials you've seen up to then. And for a seasoned guy, they just know what material to use based on experience. But I feel like I'm stuck somewhere in the middle. So, if I wanted to avoid annoying my machine shop guys, and I don't have access to a seasoned guy to ask questions, where should I be looking?

Thank you for all of your responses.

Machinery's Handbook, Toolbox Edition: Oberg, Erik: 9780831130916: Amazon.com: Books

aribert · Jul 18, 2020

Joe Gwinn said:
While it's a bit of an art, the best answer I can think of is that it's basically a process of elimination:.......

Availability is often the main driver, so long as the choice is adequate.

Commercial availability greatly affects the decision process. Early in my career (mid '80s) a vendor gave me a Ryerson Metals catalog - it was chock full of technical info such as heat treating curves, case hardening depths in addition to the various metals with their properties and in what form that metal was available. You don't want to design around an obscure material only to find out it takes a mill run to get it into stock. I'm retired, but I still refer to that Ryerson catalog from time to time. A few weeks ago I was trying to decide between 1144 stressproof vs fatigueproof vs ETD150 vs various steel alloys for a small project. The internet makes checking for material availability easier than it was a few decades ago.

I agree with the info you have been given by others. Most industry niches use the same 10 or 20 materials over and over - because these materials work, are available and cost effective.

How to Select a Material

Plastic

Stainless

Cast Iron

Aluminum

Diamond

Diamond

Diamond

Diamond

Hot Rolled

Diamond

Diamond

Diamond

Diamond

Stainless

Plastic

Diamond

Diamond

Plastic

Diamond

Cast Iron

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