13 replies to this topic

[jpf]

I just came across this PDF from a DOE Nat'l Lab about the development of a new manufacturing process for Ti, specifically considered for parts used in reciprocating motors. Apparently it's based on sintering Titanium Hydride powder, which allows more efficient use of material, and reduces the amount of machining required vs. starting with ingots. I'm not very familiar with standard manufacturing processes, but I know some people here are, so I thought I'd throw this out for comment.

It sounds like maybe it won't be suitable for peak performance applications, but it could allow for use of Ti in more middle market road cars. Looks like prototyping is underway.

PDF:
http://www1.eere.ene...22_lavender.pdf

Random blog post that was linked from Reddit:
http://nextbigfuture...ufacturing.html

[dosco]

I just came across this PDF from a DOE Nat'l Lab about the development of a new manufacturing process for Ti, specifically considered for parts used in reciprocating motors. Apparently it's based on sintering Titanium Hydride powder, which allows more efficient use of material, and reduces the amount of machining required vs. starting with ingots. I'm not very familiar with standard manufacturing processes, but I know some people here are, so I thought I'd throw this out for comment.

It sounds like maybe it won't be suitable for peak performance applications, but it could allow for use of Ti in more middle market road cars. Looks like prototyping is underway.

PDF:
http://www1.eere.ene...22_lavender.pdf

Random blog post that was linked from Reddit:
http://nextbigfuture...ufacturing.html

Interesting paper, thanks for posting.

Any ideas regarding effeciency improvements resulting from the use of Ti for rotating components?

Is Ti appropriate for use as a conrod?

[cheapracer]

Ti conrods have been around for a long time.

I will show this to my Mate who builds the Cold Isostatic Presses and see what he thinks.

The cold isostatic press (CIP) is also known as a rubber press.

Ceramic powder and metal powder fill a rubber mold, which is then dipped into the pressure vessel. The powder is compressed at a maximum pressure of 400 MPa/60,000lbs. Isostatic actions (hydrostatic pressure) can also form complicated shapes which cannot be compressed without a uniaxial press or machine press. The pin closure pressure vessel adopted by Nikkiso is installed in thousands of presses around the world due to the company’s over 40 year experience in manufacturin.

[dosco]

Ti conrods have been around for a long time.

I'm not surprised. How do they compare to "regular" (steel?) conrods?

Ceramic powder and metal powder fill a rubber mold, which is then dipped into the pressure vessel. The powder is compressed at a maximum pressure of 400 MPa/60,000lbs. Isostatic actions (hydrostatic pressure) can also form complicated shapes which cannot be compressed without a uniaxial press or machine press. The pin closure pressure vessel adopted by Nikkiso is installed in thousands of presses around the world due to the company’s over 40 year experience in manufacturin.[/i]

Did you note the other material forms they can make? Interesting stuff.

[cheapracer]

I'm not surprised. How do they compare to "regular" (steel?) conrods?




Did you note the other material forms they can make? Interesting stuff.

I haven't been that close in use with them although i have handled some bike parts and they are noticeably lighter. Google is your friend of course heres one from Google http://www.paeco.com...um Products.htm

This ones interesting in competition to Ti http://www.mxcomposites.com/index.php

CIP can use any metal that can be used in powdered form. Some of the more popular ones are byrillium or magnesium alloys but ceramics is the biggy to get diamond hard compounds. Pressed first in the CIP then shaped then sintered - non lubed ball bearings for those huge wind turbines for example.

Stuff like tomatoes are squeezed at these pressure and they can be stored for 100 years apparently and food stuffs like this are used for space travel because apparently no germ/bacteria etc can survive the pressures.

The CIP process for certain products is quite complicated and the pressure and time factors are kept close to the chest by the various companies - to get one example product you may go to 20,000 psi for 3 hours then 40,000 for 1 hour then release the pressures in varying similar stages.

Edited by cheapracer, 25 March 2010 - 17:38.

[gbaker]

CIP and HIP processes have been around for decades, and can be useful for producing near-net-shape product. Strength will be lower vis-a-vis ingot, and further below forged Ti. Not effective for high performance applications.

[Greg Locock]

Billet Ti alloy has about 2/3 the density of steel, and is roughly as strong as tool steel (or Unbrako bolts). Its stiffness is 2/3 that of steel. So if you need something strong and light it is a good choice.

Sintered components and the like tend not to have the same density or strength as billet or forged parts, due to porosity. I imagine you can do something clever like forging an oversized sintered part that might well cheer it up.

[jpf]

Yeah, it seems to me that even if the sintered material isn't suited for the highest performance applications where Ti or other relatively exotic materials are required, it could still be used in sports applications where steel would do, but sintered Ti parts would make engines lighter and more revvy.

[desmo]

Probably not so much upside for Ti vs. steel, given that most applications are stiffness rather than strength constrained and in those Ti doesn't look too good when cost is considered given its similar specific modulus to steel's.

If you are seeing potential big weight savings for substituting Ti for steel, it probably mostly means that the original use of steel was poorly optimized.

[gruntguru]

Probably not so much upside for Ti vs. steel, given that most applications are stiffness rather than strength constrained and in those Ti doesn't look to good when cost is considered given its similar specific modulus to steel's.

If you are seeing potential big weight savings for substituting Ti for steel, it probably mostly means that the original use of steel was poorly optimized.

Aluminium conrods show sufficient benefit over steel to be used in some forms of racing in spite of poor fatigue performance and low Youngs modulus. Titanium is far superior to Aluminium on both counts.

In some conrod applications Aluminium is actually preferred for its low Youngs modulus and the "give" that provides.

Edited by gruntguru, 27 March 2010 - 08:53.

[Engineguy]

If you are seeing potential big weight savings for substituting Ti for steel, it probably mostly means that the original use of steel was poorly optimized.

Really? Go out to your garage and disassemble the engines in your Z06 Corvette, Porsche GT3, Acura NSX, Lexus LF-A, Ferrari 458 Italia, F430, F360, and F355. All of these production cars have titanium connecting rods. F1 cars have titanium rods. I'm sure they're not just too lazy to design an optimized steel rod.

Be careful putting those engines back together.

Even when cost (or rules, or fabrication complexity) is no object, some parts are better made of magneseum, some, aluminum, some steel, some titanium, and some of carbon fiber. Depends on their function and shape, space available, fatigue considerations, attachment options or limitations, etc. ... not just a material strength property or two in isolation.
.

[gruntguru]

Really? Go out to your garage and disassemble the engines in your Z06 Corvette, Porsche GT3, Acura NSX, Lexus LF-A, Ferrari 458 Italia, F430, F360, and F355. All of these production cars have titanium connecting rods. F1 cars have titanium rods. I'm sure they're not just too lazy to design an optimized steel rod.

You lucky $*&%*& Desmo. Don't bother dis-assembling any of your expensive cars - just take his word for it.

Edited by gruntguru, 28 March 2010 - 03:19.

[J. Edlund]

Powder metals are used to produce parts with different intentions in mind, and using different processes and materials depending on the goal.

Hot isostatic pressing processes are usually rather expensive and used to produce high quality parts but at a very high cost. Typically a 'container' is made, filled with powder, and then put under isostatic pressure in a heated pressure vessel. The 'container' is then removed from the pressure vessel and cut a part. Then you have a billet piece of metal with better than cast properties due to the isotropic nature or the material. In a cast material you always end up with local variations of the alloying elements and inpurities which will degrade the material properties. This process is used for certain 'difficult' materials, such as AlBeMet and metal matrix composites, and for the production of some high quality materials such as expensive tool steels.

Then we have the common method with pressing followed by sintering. This is commonly used to produce near net shape components, but due to a slightly lower density these parts are not high strength. For iron based materials copper is usually added to improve density, but this also makes it difficult to recycle the material. The process also allows easy addition of lubricating materials such as graphite which can be useful in certain applications. Commonly used to produce simple high volume parts such as bearings, gears, various valvetrain components and other parts where strength isn't a critical issue.

Powder forging. This is a process commonly used to produce high performance OEM conrods. Although their fatigue strength is lower than for a forged conrod, they can be produced near net shape with only little maching required. The cost of the process is higher than forging, but the total cost including machining is lower. Commonly this process is combined with cracked big ends.

By the way, Toyota has used titanium metal matrix composites for valves in ordinary production engines. They are worth a few percent in terms of fuel consumption reduction due to lower valvetrain friction. The cost in relation to the fuel saving is still a bit too high for widespread use and hollow steel valves can probably be made cheaper for a similar benefit. But in the case of production engines, valves and conrods are the two most interresting applications for titanium. That and high pressure ratio compressor wheels for turbocharged commercial diesels.

It's also possible to use powder metals to make certain hollow, one piece components.

Stuff like tomatoes are squeezed at these pressure and they can be stored for 100 years apparently and food stuffs like this are used for space travel because apparently no germ/bacteria etc can survive the pressures.

Space food is usually subjected to radiation for the removal of bacteria. Some commerical food also use radiation for the same purpose, but the radation levels used for space food are often above what is allowed for commerial food.

Probably not so much upside for Ti vs. steel, given that most applications are stiffness rather than strength constrained and in those Ti doesn't look too good when cost is considered given its similar specific modulus to steel's.

If you are seeing potential big weight savings for substituting Ti for steel, it probably mostly means that the original use of steel was poorly optimized.

Usually you can't optimize a component purely for its properties, compromises have to be made so that the parts can be manufactured, or in order to fulfill another demand such as a specific shape, size etc. Lets for instance say that we have a simple flat piece of sheetmetal. If we design our piece of sheetmetal for a specific stiffness, an aluminium sheetmetal will offer a lower weight than a steel sheetmetal. That doesn't mean aluminum sheetmetal is always better than steel sheetmetal, but that under a certain set of limitations, an aluminium sheetmetal will outperform steel sheetmetal with regard to specific properties such as stiffness.

In the case of the conrod, practical applications seem to suggest that you can reduce conrod weight by approx. 30% when changing from a steel to a titanium rod. Stiffness is also only one property, fatigue is another important aspect, and so can the resonant frequency be (given that the conrod will behave like a spring in a mass-spring system).

[blkirk]

Here's another way to make near net shape parts with no porosity and no impurities.

http://www.sciaky.com/62.html
http://www.sciaky.com/64.html