Query regarding SS 316 Ti material

Please see this data sheet:

http://www.alleghenytechnologies.com/ludlum/Documents/316ti.pdf

It is hard to say if standard 316L is an appropriate substitute in this application because we do not know the reason why your client is specifying it. 316Ti is usually specified to avoid sensitization due to carbide precipitation above 800 deg F which leads to significantly degraded corrosion resistance. However, you state that this is for a hydraulic fitting and I have a hard time envisioning that you would see this high of a temperature.

I would specifically ask your client what is the reason they are asking for the titanium grade.

Sorry, I do not know the availability of this product.

Generally, in a hydraulic power unit, SS 316 would be fine. You should never see temps anywhere near the 800 degree range, or your power unit is not designed properly in the least. SS 316 is usually suitable for any hydraulic application, including aerospace. Your customer may have a "far from normal" operating condition, which may require the SS 316 Ti, But i'm not sure what it would be, (extremely high operating pressures 15,000+psi possibly). It really depends on the end users operating conditions.

Does your customer really want this special grade of 316 or did some young engineer click on the wrong material when he was putting the CAD drawing together (or some similar engineering mistake)? (Been there, seen that, all too often).

Worth a friendly inquiry to the customer's buyer.

Ed Weldon

SS 316 is a favorite of laser builders where the laser cavity (high voltage and all) must be flooded and cooled by de-ionized water (DI water). SS 316 does not contaminate (add ions to) the cooling water. Perhaps the Ti allows for higher than normal laser cavity cooling?

Hi all,

The main difference between this two SS grades is the small Ti content, which usually is required by the standards not as a specific mass percentage but relative to each heat carbon content.

The reason is that Ti is added to avoid chromium carbide precipitation at grain boundaries, the same happen when Niobium (Columbium for some US people): both elements form carbides easier than Chrome. Those "almost equal" SS grades with that small additions are called "stabilized grades".

Those materials are usually specified for the same service conditions as the non stabilized ones but just when welding operations are to be performed as the carbides formation takes place during cooling from molten pool to solid weld.

As some colleagues have pointed out, who knows why your customer specified that material?

If your fittings are of threaded type or some other "quick lock type" I can't see the reason.

One last comment, there are two known ways to avoid chromium depletion by carbide formation: adding some elements more avid for carbon or just to lower the carbon content in a way there is no carbon enough to produce significant chromium carbides.

These last grades are those known as "low carbon", in your case 316L grade which I think is easier to find in any product form than 316 Ti. Maybe you can propose your client use 316L if he really wants to avoid "sensitization" by carbide formation.

Kind regards

Very informative. Good answer. Thanks!

Probably it's an error and they are asking for SS 316L. As someone else said this materials is used in very specific applications at high temperature vwhere corrosion due to sensitization is an issue..

S

corrosion prevention

There may be a reason why 316Ti was specified instead of 316L. 316Ti is stronger due to the higher carbon content. I would suggest that since you are the vendor and he is the customer, you should never try to substitute materials without at least getting permission from the customer. You may find yourself liable for any failures that occur as a result.

The easiest way to solve your problem is to ask your client if he is willing to pay more for your cost to upgrade from your standard product, and if so, How Much! You will often find that these kinds of requests are not supported by need, only someone heard that a different grade product is superior.

TMF

I have heard that 316Ti is popular in Europe and that much of the 316 produced for use there has the Ti addition. I believe that the Ti addition is functional for preventing sensitization by bonding to all of the carbon so that the carbon doesn't migrate to the grain boundaries and cause corrosion problems. 316L does the same thing by having minimal carbon. I would guess that you could get your customer to agree to substitute 316L for 316Ti if you ask him.

Yes, you're right "stabilized grades" SS with Ti or Nb (Cb) are more common in Europe from many years ago, as well as "low carbon" equivalent grades (304L, 316L, etc) have been used more frequently in the US. I think I've heard more than 30 years ago that was a question of availability of materials and processes in those times between the US and Germany (at that time the European economics locomotive)

I've been involved in PWR Power plants with US technology and German technology, and for the same service conditions, US companies specified "L" grades while German ones specified just "stabilized grades". Both are different solutions for the same problem.

Kind regards

Dear Juzar Hk,

Both SS 316 & SS 316 Ti can be classified under the heading " AUSTENITIC

STAINLESS STEELS CONTAINING MOLYBDENUM "

However, in SS 316 Ti , Titanium content will be in the level of 0.35 %. This

Titanium stabilised grade is more suitable for welding applications and also

prefered by the Designers for Chemical & oil Industry applications.

Please refer to www.ugine-alz.com for further data & availability.

Regards. P. Rangasamy.