DanO

This thread is designed to highlight the pro's and Con's of different materials and the components that they are used for

SAE 4130 steel vs. "mild steel" (usually 1018 or other similar metal).

Applications: SFC, STB, Control Arms, Roll Cage, Torque Arm, and various other parts

Modulus of Elasticity
This is a very important property that all metals have, basically its how much the metal "stretches" or compresses per unit of force (pressure). For example, a rubber band. You can have 2 rubber bands made from the same material but the thicker one will not strech as far with the same load on it. The thicker one has less force per area but the same "modulus of elasticity"

All Carbon and alloy steels, 4130, 1018, etc HAVE THE SAME MODULUS OF ELASTICITY!!!!!

This means that if you have a mild steel tube and a 4130 tube of the same dimensions, any force you place on it will result in equal deflection. Anyone who tells you 4130 is stiffer doesnt know much about metal.


Strength

The strength of the material is where the difference comes in. Again with the rubberband analogy. If you have two identically sized rubber bands with the same "Modulus of Elasticity" they will stretch equal distances with the same force, HOWEVER, the strength of one of the materials is greater allowing it to stretch further before it breaks.

This means that if you progressively increase the load on the equal sized Mild steel and 4130 tubes, the mild steel will fail before the 4130.

Example
There is a quote on BMR's website that i brought to their attension on more than one occasion. The Strut tower brace.

From BMR's site
If you would notice, the 4130 tube is a smaller wall thickness (i.e. smaller rubber band) and is less stiff than the larger wall Mild Steel version. Material properties show that the 4130 "more expensive" STB is actually not adding as much stiffness as the cheaper mild steel version.

Obviously, if i were to purchase one, i would choose the mild steel version. the increase in STRENGTH is not an issue due to the low loading in that location.

There are many designs for aftermarket components that have design flaws (materials, sizes, shapes, etc.) because the engineering knowledge to design these components is usually not had by the company. For one.. engineers are expensive, and two.. the parts are almost always better than "stock" but they are not Optimized which means, in most cases(disclaimer), you will not hurt anything by buying one of these, but you wont be getting exactly what you think you are and in some cases... will be spending more for a worse design.

Some great applications for this are:
Roll cages where strength is a concern for saftey. Also works great to reduce weight if more deflection is acceptable over the thicker mild steel design while maintaining the same overall strength.
Control Arms because the parts see high cyclic loading and fatigue is an issue. And once again, can be made lighter if more deflection is acceptable over the similar but thicker walled mild steel design

Many other applications benefit from using this material but make sure it is used for the right reason... if not, your wasting your money!

DanO

Titanium

This material is excellent in many applications and is an excellent replacement for steel in many cases. Titanium is the 4th most abundant element on earth however the reason the material costs so much is processing. Refining the Titanium is a costly procedure.

Like Steel, not all Titanium is the same; there are many “grades” of titanium with different strengths (even some alloys with different modulus of elasticity). For example, on my race team during college, one of the individuals purchased “titanium” for a driveline component. Then I asked… what grade did you buy? His response… “I bought titanium.” Once we looked, he had purchased Grade 3 titanium that was about as strong as 2024-T4 Aluminum!! Not good for driveline components!!! Grade 5 (Ti-6Al-4V) is the most commonly used grade for high strength applications.


To Be Continued... Titanium springs...

Nine Ball

iTrader: (38)

Good info Dan, I haven't read this sort of stuff since Material Science classes at college.

bowtieman81

iTrader: (35)

Good info Dan. You may want to point out what does distinguish the different grades of steel (ultimate strength, yield strength, etc), and maybe what the steel material codes mean (i.e. 4130 is so much nickel, chrome, etc).

Maybe I will chime in with some details, but not off the top of my head. Might need to consult the materials science book first.

DanO

Well.. i could go alot deeper, but im trying to keep this an informative "readable" post. I would put most to sleep if i went into detail about heat treating, grain structures, etc...

Besides, alot of books (5" thick books) are written for that very purpose. Quite a few are on my desk here at work.

Nine Ball

iTrader: (38)

What kind of work do you do?

Nine Ball

iTrader: (38)

Sounds like an interesting job, too bad there isn't any automotive manufacturers based in Houston. I'm in the deep sea oil/gas industry, working as a Project Manager, but I have a Mech Eng. degree also. Okay, back on topic

BlownChevy

iTrader: (20)

well, you will have an EATON supercharger on your vette soon.....

Old SStroker

The late (and sorely missed) Carroll Smith's "Engineer To Win" does a fairly good job in about .6 inches. I highly recommed it. He writes much like you do, DanO. Should that be "Book 'em, Dano"?

BJM

iTrader: (1)

Great post. Finally someone agrees with me. I have posted nearly the exact same points in suspension threads but I swear very few believe me. Very few will believe you either.

Few people understand the difference between stiffness and strength. The vendors do everyone a big dis-service charging a premium for a brace that does less. Perhaps they don't even realize the difference themselves.

Anther interesting topic is specific stiffness. Divide the elastic modulus of a material by its density. Steel, titanium, aluminum have nearly identical specific stiffnesses. All that to say that a SFC, STB, etc could be made of Steel, Ti, or Al and perform equally well for the mass. Aluminum would be the most bulky due to its lower stiffness. Magnesium has a few percent advantage over the others.

Duffster

iTrader: (103)

question about materials. . .
I've seen alot of kevlar boot covers lately available on ebay. . .isn't it useless for that material for that purpose?

Thanks!

Duff

Ric

DanO, remember your audience, here. This is for more hardcore enthusiasts, those who would more likely be very interested in your input... I'm interested like crazy.

So, how does 4340 compare to 4130, mild steel, yadda-yadda???

airflowdevelop

Dano...I have a question concerning this...Have you personally every bent .065 wall ChroMo? I would bend .095 wall mild steel anyday over .065 ChroMo?

Can you elaborate? Also, SAE spec chromo is about impossible to get, most of the chromo used today is mil-spec (6736 I think) Due to its primary use (aircraft).

Also, Historically in my industry, Every ounce of info supported by the SAE is about as usefull as a drunken sailor at a boy-george concert.

DanO

Yes Chromoloy will be much harder to bend, the reason being is that the strength is much greater. To bend metal you have to bring the stress levels above the yeild strength point for it to deform. mild steel will be easier to bend because it will "yeild" alot quicker than the chromoloy counterpart. That being said, it will still deflect the same (given same geometry) its just that it takes less deflection to bend the mild steel.

Also, when i build racecar chassis i only had 2 bent pieces in the whole thing. Straight tubing is much better for load carrying.

It wasnt too difficult to obtain 4130, there are quite a few places that have it. If you need a list, i'll be more than happy to let you know who.

By the way... what is your industry?

airflowdevelop

Pornography

What do you know about the memory of chromemoly tubing?

Brains

iTrader: (7)

I'd like to see more info on the different grades of 'stainless' steels, 304, 308, 316, 409, etc. I've found in a couple instances where I could buy 316 (higher nickel content, brighter, more corrosion resistant) cheaper than 304???

Robs98SS

iTrader: (1)

Ill second the request for more stainless information.

Would like to know the differences in the grades and specifically what makes 400 grade strainless magnetic (Ive heard that this is the only grade of stainless that is magnetic) and all the rest of them arent?

Jenson

iTrader: (32)

Great stuff. We only use 4130 certified material for our suspension components. Actually 17-4 stainless is also magnetic and much harder than other stainless. Our engineers mostly rely on Rockwell and tensile strength in determining what to use, and of course what they used before.

Old SStroker

Memory? Virtually all metals remember every stress that was ever applied to them. In that way they are much like women. If the stresses are below their yield point, they will return to their original state when the stress is removed. The cumulative amount of stress is also remembered, and if the total ever exceeds the fatigue limit, things go boom. Again, much like women.

What did you mean by memory, AFD?

DanO

Steels can be classified by a variety of different systems depending on:

The composition, such as carbon, low-alloy or stainless steel.
The manufacturing methods, such as open hearth, basic oxygen process, or electric furnace methods.
The finishing method, such as hot rolling or cold rolling
The product form, such as bar plate, sheet, strip, tubing or structural shape
The deoxidation practice, such as killed, semi-killed, capped or rimmed steel
The microstructure, such as ferritic, pearlitic and martensitic
The required strength level, as specified in ASTM standards
The heat treatment, such as annealing, quenching and tempering, and thermomechanical processing
Quality descriptors, such as forging quality and commercial quality.

Carbon Steels
The American Iron and Steel Institute (AISI) defines carbon steel as follows:
Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 per cent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60.

Carbon steel can be classified, according to various deoxidation practices, as rimmed, capped, semi-killed, or killed steel. Deoxidation practice and the steelmaking process will have an effect on the properties of the steel. However, variations in carbon have the greatest effect on mechanical properties, with increasing carbon content leading to increased hardness and strength. As such, carbon steels are generally categorized according to their carbon content. Generally speaking, carbon steels contain up to 2% total alloying elements and can be subdivided into low-carbon steels, medium-carbon steels, high-carbon steels, and ultrahigh-carbon steels; each of these designations is discussed below.

As a group, carbon steels are by far the most frequently used steels. More than 85% of the steel produced and shipped in the United States is carbon steel.

Low-carbon steels contain up to 0.30% C. The largest category of this class of steel is flat-rolled products (sheet or strip), usually in the cold-rolled and annealed condition. The carbon content for these high-formability steels is very low, less than 0.10% C, with up to 0.4% Mn. Typical uses are in automobile body panels, tin plate, and wire products.

For rolled steel structural plates and sections, the carbon content may be increased to approximately 0.30%, with higher manganese content up to 1.5%. These materials may be used for stampings, forgings, seamless tubes, and boiler plate.

Medium-carbon steels are similar to low-carbon steels except that the carbon ranges from 0.30 to 0.60% and the manganese from 0.60 to 1.65%. Increasing the carbon content to approximately 0.5% with an accompanying increase in manganese allows medium carbon steels to be used in the quenched and tempered condition. The uses of medium carbon-manganese steels include shafts, axles, gears, crankshafts, couplings and forgings. Steels in the 0.40 to 0.60% C range are also used for rails, railway wheels and rail axles.

High-carbon steels contain from 0.60 to 1.00% C with manganese contents ranging from 0.30 to 0.90%. High-carbon steels are used for spring materials and high-strength wires.

Ultrahigh-carbon steels are experimental alloys containing 1.25 to 2.0% C. These steels are thermomechanically processed to produce microstructures that consist of ultrafine, equiaxed grains of spherical, discontinuous proeutectoid carbide particles.

High-Strength Low-Alloy Steels
High-strength low-alloy (HSLA) steels, or microalloyed steels, are designed to provide better mechanical properties and/or greater resistance to atmospheric corrosion than conventional carbon steels in the normal sense because they are designed to meet specific mechanical properties rather than a chemical composition.
The HSLA steels have low carbon contents (0.05-0.25% C) in order to produce adequate formability and weldability, and they have manganese contents up to 2.0%. Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium and zirconium are used in various combinations.

HSLA Classification:

Weathering steels, designated to exhibit superior atmospheric corrosion resistance
Control-rolled steels, hot rolled according to a predetermined rolling schedule, designed to develop a highly deformed austenite structure that will transform to a very fine equiaxed ferrite structure on cooling
Pearlite-reduced steels, strengthened by very fine-grain ferrite and precipitation hardening but with low carbon content and therefore little or no pearlite in the microstructure
Microalloyed steels, with very small additions of such elements as niobium, vanadium, and/or titanium for refinement of grain size and/or precipitation hardening
Acicular ferrite steel, very low carbon steels with sufficient hardenability to transform on cooling to a very fine high-strength acicular ferrite structure rather than the usual polygonal ferrite structure
Dual-phase steels, processed to a micro-structure of ferrite containing small uniformly distributed regions of high-carbon martensite, resulting in a product with low yield strength and a high rate of work hardening, thus providing a high-strength steel of superior formability.
The various types of HSLA steels may also have small additions of calcium, rare earth elements, or zirconium for sulfide inclusion shape control.
Low-alloy Steels
Low-alloy steels constitute a category of ferrous materials that exhibit mechanical properties superior to plain carbon steels as the result of additions of alloying elements such as nickel, chromium, and molybdenum. Total alloy content can range from 2.07% up to levels just below that of stainless steels, which contain a minimum of 10% Cr.
For many low-alloy steels, the primary function of the alloying elements is to increase hardenability in order to optimize mechanical properties and toughness after heat treatment. In some cases, however, alloy additions are used to reduce environmental degradation under certain specified service conditions.

As with steels in general, low-alloy steels can be classified according to:

Chemical composition, such as nickel steels, nickel-chromium steels, molybdenum steels, chromium-molybdenum steels
Heat treatment, such as quenched and tempered, normalized and tempered, annealed.
Because of the wide variety of chemical compositions possible and the fact that some steels are used in more than one heat-treated, condition, some overlap exists among the alloy steel classifications. In this article, four major groups of alloy steels are addressed: (1) low-carbon quenched and tempered (QT) steels, (2) medium-carbon ultrahigh-strength steels, (3) bearing steels, and (4) heat-resistant chromium-molybdenum steels.

Low-carbon quenched and tempered steels combine high yield strength (from 350 to 1035 MPa) and high tensile strength with good notch toughness, ductility, corrosion resistance, or weldability. The various steels have different combinations of these characteristics based on their intended applications. However, a few steels, such as HY-80 and HY-100, are covered by military specifications. The steels listed are used primarily as plate. Some of these steels, as well as other, similar steels, are produced as forgings or castings.

Medium-carbon ultrahigh-strength steels are structural steels with yield strengths that can exceed 1380 MPa. Many of these steels are covered by SAE/AISI designations or are proprietary compositions. Product forms include billet, bar, rod, forgings, sheet, tubing, and welding wire.

Bearing steels used for ball and roller bearing applications are comprised of low carbon (0.10 to 0.20% C) case-hardened steels and high carbon (-1.0% C) through-hardened steels. Many of these steels are covered by SAE/AISI designations.

Chromium-molybdenum heat-resistant steels contain 0.5 to 9% Cr and 0.5 to 1.0% Mo. The carbon content is usually below 0.2%. The chromium provides improved oxidation and corrosion resistance, and the molybdenum increases strength at elevated temperatures. They are generally supplied in the normalized and tempered, quenched and tempered or annealed condition. Chromium-molybdenum steels are widely used in the oil and gas industries and in fossil fuel and nuclear power plants.

Thanks to http://www.key-to-steel.com/Articles/Art62.htm i did not have to type this all...