Some discussion came up on a thread at DP about billet steel being stronger than steel and forged billet being stronger than forged steel. I was always under the impression that billet was a term referring to a chunk of material to be used for manufacturing a part from not a term referring to the quality or grade of the material. I was hoping to have some input from you guys here.
Billet vs non-billet
- Thread starter JoshH
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Josh i think a billet block of steel can be made out of several different high quality metals, it all boils down to the carbon content.
that's the last 2 numbers in the layout
4340 billet is a billet high quality material. it means it has. .40% carbon content.
4330 billet would have .30% carbon content.
the higher the last two numbers the stronger it is of that series of metal.
When the term billet is used it generally refers to a cast piece machined out of a larger cast piece... not a sandcasted or form casted piece.
When you cast any metal there are alot of things that go on. When you have changes in geometry of your cast piece there will be weird temperature gradients and you'll end up with inclusions etc...
Long story short, you will have a product with superior properties (strength, ductility etc.) if you make one large cast piece where the bottom or center of it is guaranteed to be very homogenous metallurgical structure and then machine your part out of that area of the casting.
You don't really refer to steel parts like this as billet steel. Its more a term for materials like aluminum, stainless and other alloys. The advantages of this process aren't as noticed with plain low carbon steel. Like billet levers for motorbikes, billet clutch covers.. etc. A lot of aluminum is done this way.
Forged steel is a casting of steel that is heated up to high temperature and hot formed to whatever you want by stamping, rolling or other methods, no machining. You will get very good directional properties with a product like this, but there is very high residual stresses. So often, products will be forged and then heat treated to relieve stresses.
There is no such thing as a forged billet. You either make a billet part out of a casting by machining it. Or you forge the part out of the casting through hot working the casting.
Do to directly answer your question, a billet part is often of better quality and higher strength than an identical cast part. And a forged piece may be substantially better suited to an application, but that depends on the application.
In metallurgical terms, there often isn't one forming or finishing process thats the best. Each have advantages and disadvantages, and based on what the application is you'll know what properties you want the most and create the piece accordingly.
When you cast any metal there are alot of things that go on. When you have changes in geometry of your cast piece there will be weird temperature gradients and you'll end up with inclusions etc...
Long story short, you will have a product with superior properties (strength, ductility etc.) if you make one large cast piece where the bottom or center of it is guaranteed to be very homogenous metallurgical structure and then machine your part out of that area of the casting.
You don't really refer to steel parts like this as billet steel. Its more a term for materials like aluminum, stainless and other alloys. The advantages of this process aren't as noticed with plain low carbon steel. Like billet levers for motorbikes, billet clutch covers.. etc. A lot of aluminum is done this way.
Forged steel is a casting of steel that is heated up to high temperature and hot formed to whatever you want by stamping, rolling or other methods, no machining. You will get very good directional properties with a product like this, but there is very high residual stresses. So often, products will be forged and then heat treated to relieve stresses.
There is no such thing as a forged billet. You either make a billet part out of a casting by machining it. Or you forge the part out of the casting through hot working the casting.
Do to directly answer your question, a billet part is often of better quality and higher strength than an identical cast part. And a forged piece may be substantially better suited to an application, but that depends on the application.
In metallurgical terms, there often isn't one forming or finishing process thats the best. Each have advantages and disadvantages, and based on what the application is you'll know what properties you want the most and create the piece accordingly.
The word billet is over used in my opinion.
When you order something made out of "billet" that means it was not cast, forged, sintered, etc. It started out as "block" of material then machined. That's it.... period. Nothing more nothing less. That block that when speaking of aluminum, is typically plate (which is rolled), or bar (which is extruded). It implies nothing about the alloy or temper of the material. Billet = block.
A forging is a forging, cast is cast. Not "billet."
I make "billet" stuff for a living and I hate that word.
When you order something made out of "billet" that means it was not cast, forged, sintered, etc. It started out as "block" of material then machined. That's it.... period. Nothing more nothing less. That block that when speaking of aluminum, is typically plate (which is rolled), or bar (which is extruded). It implies nothing about the alloy or temper of the material. Billet = block.
A forging is a forging, cast is cast. Not "billet."
I make "billet" stuff for a living and I hate that word.
Accelerator - Your right, you can make a casting of whatever composition you like. But it doesn't boil down to the carbon content. You'll need to get all of your alloying elements in check to make a quality ingot. There is a lot that goes on besides carbon content.
The last two numbers of the material designation are not always the carbon content, it just so happens to be on those designations.
4340 is a material designation that tells you the composition of the material. Nothing is "billet" until there is a final product machined out of the casting.
While addition of carbon can sometimes make a material have a higher UTS (ultimate tensile strength) it does a ton of other things as well. One of the biggest to take into consideration is brittleness. More carbon usually means more brittle. So they might be able to have a higher load applied to them very gradually in a straight plane, but they will have terrible impact properties, no ductility and limited elastic deformation.
The last two numbers of the material designation are not always the carbon content, it just so happens to be on those designations.
4340 is a material designation that tells you the composition of the material. Nothing is "billet" until there is a final product machined out of the casting.
While addition of carbon can sometimes make a material have a higher UTS (ultimate tensile strength) it does a ton of other things as well. One of the biggest to take into consideration is brittleness. More carbon usually means more brittle. So they might be able to have a higher load applied to them very gradually in a straight plane, but they will have terrible impact properties, no ductility and limited elastic deformation.
OSUbeaver - Your right. But that "block" was cast once upon a time.
Not unless you go all the way back to the ingot state which then it is cast (poured into a mold in molten form). From there most materials like aluminum, copper, brass, steel are made into extruded, rolled shapes, drawn, etc.
At that point it is cut and machined (or insert your favorite process here).
ETA: Mic 6 Aluminum or similar tooling plate is cast, but the chances of buying a product for your truck made from it are slim to none (or at least you better hope....LOL)
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x2 what I wanted to say but worded much better
Basicaly we are dealing with alloys made from several different materials and every one of them serves a purpose, even a few tenths of a percent change in a alloying material can have HUGE effects on the end result.In the case of comparing rods made from the same material the greatest thing to concider is that billet can have a fatigue life do to the grain all going in one diection where with forged the grain generaly follows the shape of the part. But fatigue life can be extended with cryo treatment.
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i agree, but i was just trying to keep it simple, it seems when i expand more most tend to get confused and frustated, i dont want that to happen.
Also there IS a forged billet as i was taught. it is understood by some that a forged billet is a block/ or rod of high quality steel 4340(billet) that is used for forging varous things into a die and pressed into shape, then like you said it is heat treated(nitrided). While it may not be Labled as the accual term, that show it is expressed at least has been to me for years, but really it is a high quality forging out of what was once a block, or rod of billet steel......make any sence?
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Who here has expirence with cryo treatments? what exactly does it do?
Also there are millions of kinds of steel I worked in the Tool &Mold/Die trade for years and I have made many things for my cars in the past out of P-20 (Tool steel) and H-13 (Tool Steel) Both are high carbon steels with other things mixed in (.37-.40 carbon)
For the norm Steels have a look at this SAE_steel_grades
For the norm Steels have a look at this SAE_steel_grades
Cryogenics, or deep freezing is done to make sure there is no retained Austenite during quenching. When steel is at the hardening temperature, there is a solid solution of Carbon and Iron, known as Austenite. The amount of Martensite formed at quenching is a function of the lowest temperature encountered. At any given temperature of quenching there is a certain amount of Martensite and the balance is untransformed Austenite. This untransformed austenite is very brittle and can cause loss of strength or hardness, dimensional instability, or cracking.
Quenches are usually done to room temperature. Most medium carbon steels and low alloy steels undergo transformation to 100 % Martensite at room temperature. However, high carbon and high alloy steels have retained Austenite at room temperature. To eliminate retained Austenite, the temperature has to be lowered.
In Cryogenic treatment the material is subject to deep freeze temperatures of as low as -185°C (-301°F), but usually -75°C (-103°F) is sufficient. The Austenite is unstable at this temperature, and the whole structures becomes Martensite. This is the reason to use Cryogenic treatment.
I had to look it up it has been years but this is right on from what I remember.
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OK that helped thanks
i just did a quick search about cryo.......man that looks perdy cool!!
i wonder if you could cryo treat a nitrided crank??? For even better durability. i'll find out tomorrow
Billet is just an over used fancy word.
Billet is an finished rolled bar.
Nothing more than bar stock.
A forging is when a length of material(which can be billet) is heated and formed in a hammer forge.
The advantage of forging over billet is the the grain structure flow of the metal follows the form better. I use the example of a knot hole in a board of wood. The wood grain flows around the knot hole. If you where to drill a hole it would go thru the flow of grain. Same thing with rods.
Now with billet you have options material make up wise that you dont with forgings as not all materails respond well to be forged.
Both can be very strong when properly done.
Billet forged. To me that means a length is cut off a rolled bar that is heated and then forged. But some use the term billet to say the the entire part is machined.
Cyro is a heat treating process. Instead of using heat it uses extreme cold. When subjected to extreme cold the crystaline structure (grain) contracts. This contracting of the grain forces them tightly together. This creates a more uniform spacing of the grain. Also it does help to change over some of the material that has not completed the phase change from austenitic to martensitic.
This treatment doesn't preform miracles such as filling voids or adding utlimate strenght. What it does is to futher massage the metal. This is benifical in applications that see high cyclic stress. Such as aircraft landing gear.
We can cryo treat a work. Guess how much of my stuff has been through the tanks?
None. If you out right breaking parts from exceeding the yeild it will not help. But it parts are failing from repeated loading and unloading. It will help to last more cycles.
Billet is an finished rolled bar.
Nothing more than bar stock.
A forging is when a length of material(which can be billet) is heated and formed in a hammer forge.
The advantage of forging over billet is the the grain structure flow of the metal follows the form better. I use the example of a knot hole in a board of wood. The wood grain flows around the knot hole. If you where to drill a hole it would go thru the flow of grain. Same thing with rods.
Now with billet you have options material make up wise that you dont with forgings as not all materails respond well to be forged.
Both can be very strong when properly done.
Billet forged. To me that means a length is cut off a rolled bar that is heated and then forged. But some use the term billet to say the the entire part is machined.
Cyro is a heat treating process. Instead of using heat it uses extreme cold. When subjected to extreme cold the crystaline structure (grain) contracts. This contracting of the grain forces them tightly together. This creates a more uniform spacing of the grain. Also it does help to change over some of the material that has not completed the phase change from austenitic to martensitic.
This treatment doesn't preform miracles such as filling voids or adding utlimate strenght. What it does is to futher massage the metal. This is benifical in applications that see high cyclic stress. Such as aircraft landing gear.
We can cryo treat a work. Guess how much of my stuff has been through the tanks?
None. If you out right breaking parts from exceeding the yeild it will not help. But it parts are failing from repeated loading and unloading. It will help to last more cycles.
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Good post!, what kind of things would you cryo treat?
Parts the customer requests.
Parts subject to high cyclic loads that they want to insure will last the projected service life. Parts used in aircraft landing gear, braking systems, helicopter rotor parts are some examples.
Parts subject to high cyclic loads that they want to insure will last the projected service life. Parts used in aircraft landing gear, braking systems, helicopter rotor parts are some examples.
can items that have allready been heat treated be cryoed?
Cryo treating an item that is going to see higher temps would be useless. After a period of time in the higher temps it would likely undo all the initial effects of the cryo treat. Guess it depends on the temps though. I am thinking doing motor parts would be a waste.
If you want perfect engine parts metallurgically speaking, powder metallurgy is the way to go.
I never thought there would be this many people with a knowledge of metallurgy on here.
I still think that billet forged is a double term though. If its a forging, its a forging, doesn't really matter what it was made out of. If its a "billet" part, its been machined out of a larger piece.
The term billet and ingot can be used to describe the initial casting of material though. And I suppose if you really wanted to you could call something billet forged.
If you want perfect engine parts metallurgically speaking, powder metallurgy is the way to go.
I never thought there would be this many people with a knowledge of metallurgy on here.
I still think that billet forged is a double term though. If its a forging, its a forging, doesn't really matter what it was made out of. If its a "billet" part, its been machined out of a larger piece.
The term billet and ingot can be used to describe the initial casting of material though. And I suppose if you really wanted to you could call something billet forged.