SKF EXPLORER HEAT TREATMENT 1

[ad12le]

I was told the other day that NTN sphericals use to have a major issue in terms of how they heat treated their bearings. So much so that bearing roller would split in heavy industries such as the Pulp and Paper Industry. After those stubborn Japanese finally realized the standards they used were not adequate the started making sphericals heated at higher tempters. Does anyone know what I am talking about? I find myself in a funny situation due to wanting to design my own bearings and do not want to fall into the same whole that companies like NTN did.... Does anyone know what heat processes and standards a company like SKF uses on their explorer sphericals?

 

[tbuelna]

ad12le,

What you describe just sounds like urban legend or old-wive's tales. NTN is a reputable and competent manufacturer of rolling element bearings.

As for the material/heat treatment used for the rollers of their spherical roller bearings, it is likely quite similar to that used for the rolling elements of any other type of bearing they manufacture. While NTN likely has their own in-house material specification for rollers, it is probably quite similar to AMS 6444, which is a premium quality double vacuum melt, high carbon, high chromium, alloy steel. It is probably through hardened to something like Rc 60-64.

Hope that helps.
Terry

 

[ad12le]

Hello Terry,

Thank you for your response. However, I have been more then just informed about this past issue regarding the poor quality of NTN Spherical roller bearings. We are a distributor of bearings and power transmission equipment in Canada and service the KRUGER paper in mills in three rivers. At the time Kruger had signed a contract with NTN to supply them with their roller bearing products.
Many bearings failed on different sized bearings in the Kruger mills. After a short period NTN started producing Spherical roller bearings specially for Kruger that included a unique suffix that designated a certain heat treatment level all major manufactures respected besides NTN. Nachi, another Japanese brand will tell you that they do not heat their bearings like NTN. In other words, of a lesser standard.

If anyone knows the proper temperatures to heat bearings please let me know.Or what would be the best way to heat them, something like the way SKF does it. I do not know much about steel and its heating processes but I am developing a super high quality bearing and must have this point secured.

 

[macmet]

I find your last sentence a little odd. I would hope/think that most companies who build "super high quality" products do not get their information from online forms and actually research and test the products themselves.

I also hope, that those designing or determinging the heat treatment processes for "super high quality" steel products are knowledgeable in steels and its heat treatment processes.

 

[arunmrao]

I have had the opportunity to produce stainless steel conveyor and other parts for SKF India. The plant is fully automated,atmosphere controlled and the whole process is well controlled,with just 1 shift Metallurgist. Their inspection process is rigorous.The bearings come out bright and shining with no spots.

I wonder how you could duplicate such a dedicated and critical process,by seeking some information over the net, ( probably inaccurate or incomplete).

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[ad12le]

In terms of my design, the bearings needs are such that they only need to be made in the right way, not skipping any basic steps!
If I had to bring an engineer or specialist in metals to china what sort would you suggest?
Does anyone know a metallurgist or engineer that either works or has worked in the bearing industry?

 

[dbooker630]

I first learned metallurgy at a bearing manufacturer and heat treater many years ago. The spherical roller bearings we made for turbine engines were made from SAE 8620 and were carburized. Bearings can be made from low carbon alloy steel like 8620, high carbon chromium steel like 52100 that is through hardened, specialty steels such as M50 that is vacuum heat treated.

We were in competition with NTN, SKF, and Timken among others. All of us were considered to have good heat treat practices. Bearings do have certain specific heat treat recipes based on operating temperatures and environment but the end hardness is typically in the range noted by tbuelna.

You mentioned that the bearings split - without analyzing the rollers you cannot automatically conclude that heat treat is at fault. Case-core separation and high retained austenite are some heat treat possibilities, but you must also consider non-metallic inclusions, contact pattern with the cup and cone, and the application itself. Make sure you are using the right type of bearing first.

Most reputable bearing makers have application engineers, that would be the first person I would contact. The paper mill will explain what loading and temperature extremes the bearing will be subject to. The bearing engineer will tell you whether a carburized or through hardened roller is best, ring designed to handle radial and/or thrust loads. The environment will also determine what accomodations the bearing assembly must have to avoid binding.

 

[mcguire]

Why assume the bearing is at fault? Surely Kruger has some idea whether their competitors have similar problems. Surely a distributor should know if the "NTN quality problem" exists elsewhere. It seems like very amateurish problem solving.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[mrfailure]

ad12le: Are you located in the US? If so and are looking for bearing engineering experience, I can suggest contacting a company called Tribology Systems in Warminster PA as one possible source.

 

[tbuelna]

ad12le,

Here's a link to NTN's spherical roller bearing data. There is some material and HT information. It seems the steel alloy NTN uses is 100Cr6 or similar.

http://www.ntnamerica.com/website/d...gs/premier_spherical_brochure_2007 lowres.pdf

Hope that helps.
Terry

 

[dbooker630]

NTN may have to deep freeze to support the claim of very little retained austenite, if you define very little as <3% RA.

 

[Maui]

DIN 100Cr6 is the equivalent of AISI 52100 bearing steel:

http://www.latrobesteel.com/assets/documents/datasheets/52100.pdf

And yes, for long term geometrical stability, a deep freeze cycle may be used to minimize the amount of retained austenite provided it is foillowed by at least one normal tempering cycle.

Maui

http://www.EngineeringMetallurgy.com

 

[dbooker630]

At the bearing manufacturer where I once worked there were several varieties of 'growth temper' with E52100 as the most common steel. Standard heat, quench & temper followed by a -100F deep freeze, then a 400F temper. Requirement was 3% or less RA and 58-62 HRC.