Please Characterize 9254, 9260, SRS 60, 9259 4

[twistedneck]

Spring folks, I'm looking at hot formed quenched and tempered sprigns for the automotive industry.

I know the chemical compositions of each.. but i don't know the engineer's characterization of 9254, 9259, 9260, or SRS60.

Have you guys worked with these steels? What is the good / bad / ugly of each?

Thanks much, twisetdneck.

 

[sbozy25]

I have worked with them all...

SRS60 is the top of the line out of this group. This is the equivalent to the material GM uses for their suspension springs on the Cadillac. It is a high strength Chrome Vanadium alloy material.

From highest to lowest that list should go

SRS60
9254
9259
9260
5160( you did not have this on the list, but it is next in line).

They are all good materials to use, what you need to decide is how strong do you need the part to be, and how much do you want to pay for material.

Currently SRS60 is running around $.89 per pound, (give or take)

 

[CoryPad]

There is much more to the quality of springs than just chemical composition (which is the only thing the numbers give you). Strength (static, fatigue), inclusions, surface roughness, etc. are equally important.

Having said this, these are good materials with which to make springs, including automobile suspension springs, which are among the most demanding products in terms of stresses and environment.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[twistedneck]

Thanks Sbozy and CoryPad.

I had no idea SRS60 was so expensive..

If we had to rank them in terms of grain size?

Sag resistance?

Decarburization potential?

Ultimate and shear strength?

Potential to be used in as rolled condition?

I believe Sbozy you ranked them in the composite 'engineer's best' ranking, and that is what i was seeking. thanks again.


PS I'm not asking for scientific answers, just directional feedback.. you guys rock and thanks for answering so quickly.

 

[sbozy25]

Yup, you are correct. That is how I ranked them. Also, FYI SRS60 is not an industrial standard name. That is a propriatary name given by... dang I can't remember their name... any way, it is their name. If you try to shop around for that material, I would make sure you include the chemistry with your request, incase they call it something different.

Also, I would say the way I ranked them holds true for all your other options. But, just an FYI if you go with a 5160 for example and say you centerless grind the bar before forming the part, it might come out slightly more cost effective. I was just working on a design for a heavy duty vehicle using 5160 (which was $.42 per lb) and I am grinding the bar prior to coiling. All in all, I will save about $1.25 per part by using 5160 instead of the others.

 

[twistedneck]

Sbozy25 wrote:

"FYI if you go with a 5160 for example and say you centerless grind the bar before forming the part, it might come out slightly more cost effective. "

We are being forced to go turn and polished (peeled and burnished, what ever it is..) as CG shops are going out of business. I believe its close to CG.

on 5160, you loose out on hardness and on strength / toughness ratio - so did you have more coils and larger wire?

5160 would be the way to go only if we were not trying to save weight AND cost.

 

[TVP]

The ranking by sbozy25 is the same as mine. 5160, 9259 and 9260 are conventional spring steels, and cannot achieve the weight reduction that SRS60 and newer grades can. 5160, 9259, and 9260 are all very prone to decarburization. SRS60 (Kobe originally developed this, but it is licensed to Republic and others) is a definite improvement in sag resistance. The ability to be used in the as-rolled condition really depends on how the bar is processed. It is extremely difficult to guarantee no defects that will affect the final performance of a spring when using bar that has no surface removal...

 

[sbozy25]

Actually in my situation, no I kept wire size and coils, however the wire size was not consatnt. I went with a variable rate, variable pitch, variable wire size design and have good numbers. As far as the strength issue is concerned, yes it is an inferior steel compared to the higher grades, however, if you process the heck out of it, you can get some justifiable numbers.

If this is truly an automotive situation, I say you pony up and go with the SRS60. hands down this will be the way to go. Just make sure you are clear with what your incoming bar surface requirements are.

 

[twistedneck]

Thanks for the excellent responses. Targeting even more, 9254 vs. srs60.. any thoughts?

sbozy25, variable rate and pitch.. now that is the way to go although processing is a headache!

TVP, the goal of the engineer is to save weight not cost so much.. but purchasing loves to make things hot rolled hence my question about what grade is least prone to decarb (least Si, most Cr?) and surface defects.

I forgot to discuss sulfer levels.. with low sulfer now available, a lot of these alloys can get better transverse (torsional) fatigue numbers..

 

[sbozy25]

Honestly, I don't think you will see a bunch of difference between the 9254 and SRS60. If you design and process the springs correctly, you could get away with 9254. Not to mention, you will make purchasing happy by saving them money up front.

Now you could be a little sneaky and launch with SRS60. Then some time down the time table, do a VAVE study, and change to 9254. It would make you look like a hero as you would have a great cost reduction... Just a thought...

As far as the variable rate and pitch go, it is less of a headache as you would think. As long as you are set up to run such products, it is only a matter of getting your calculations right. Lucky enough, there are many study's readily available and many people with the knowledge of how to quantify what you want, that it can be a piece of cake.

 

[twistedneck]

Fellow spring folks, any new materials on the horrizon to replace these alloy's?

What are the new cutting edge designs in coil spring materials? i'm curious about what's next from the OEM's..

Lighter, stronger, more corrosion resistant..

 

[sbozy25]

Well I did just see a titanium like alloy come across my desk just the other day.

Other than that, I have yet to see any real exciting materials or designs come through or out of here. The big push I have been seeing in the spring industry is a push to find new ways to process the springs. This might be something as simple as new machinery, or even run the manufacturing process in different processes.

Now there has been one trend I have been seing more lately, and that is companies inability to produce large wire diameter springs. There have been quite a few companies in the last few years drop all their hot wound springs. They have been doing this, because they never stayed with the times, and all their machinery is old, out-dated, and no one knows how to fix it. Fortunately for us, we have such a diverse work force that the guys in their 60's-80's are teaching the younger guys how to fix and work on our machinery. So for all you suspension guys, I would be very careful about picking your spring company, there is no telling if they will be capeable in 5yrs.

Just my thought.... kind of off topic, but oh well...

 

[TVP]

Kobe Steel is the leader in spring steel development. They have a number of grades other than SRS60 that have higher strength and toughness/corrosion resistance such as UHS1900. The following two links have some information (most of the text is Japanese, but some is English):

http://www.kobelco.co.jp/ICSFiles/afieldfile/2006/08/22/012baneyoko.pdf

http://www.kobelco.co.jp/technology-review/pdf/56_3/048-052.pdf

The following are some recent references on spring steel development for automotive suspensions:

SAE Technical Paper Series 2006-01-0897 Development of New Microalloy Steel Grades for Lightweight Suspension Systems

http://www.sae.org/

SAE Technical Paper Series 2000-01-0098 Development of New High Strength Spring Steel and its Application to Automotive Coil Spring

http://www.sae.org/

Materials Science Forum Vols. 500-501 (2005) pp. 753-760 Gears and Springs in Niobium Microalloyed Steels
for Automotive Applications

http://www.scientific.net/

NIOBIUM IN MICROALLOYED ENGINEERING STEELS, WIRE RODS
AND CASE CARBURIZED PRODUCTS

http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/sub_4/images/pdfs/042.pdf

Obviously some spring steels are suitable only for cold-wound springs instead of hot-wound, but this should give you an idea of the latest developments. Patents are also a good place to get detailed technical information on spring steels. Kobe, Daido, Aichi, and Mitsubishi are all active in spring steel development.

 

[twistedneck]

Thanks guys, FYI - UHS1900 is the top of the list.. we use it here rarely.. is it really 1900 Su? (i guess SU really doesn't matter to springs, why do they report it!).

Links are excellent. I'm going to SAE conf next year for sure.

I've got a few things up my sleeve (see my old posts )

My goal is to break out of the box and create a black swan!! LOL

Thanks a ton guys, and props once more to eng-tips.com!

 

[CoryPad]

Yes, it is 1900 MPa ultimate tensile strength. As ultimate tensile strength increases, so do fatigue strength and shear strength. Both of these are important to springs. Also, ultimate tensile strength is the highest strength reportable for a material, so it gives a company a chance to report the largest number possible (and helps with bragging rights, etc.).

Regards,

Cory

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