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Old 14-07-2015, 07:35   #1
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Chromium steel vs. stainless

I need to replace an open bearing with a sealed version, and I've two choices. One is chromium steel 52100 for 19.95 or stainless 440C for 129.95 all other specs being equal.
This is for an electric motor which is not designed for a marine application anyway. Thoughts as to which one are appreciated.
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Old 14-07-2015, 07:39   #2
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Re: Chromium steel vs. stainless

More detail?

- Motor HP
- high speed or low speed
- constant or intermittent duty
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Old 14-07-2015, 07:48   #3
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Re: Chromium steel vs. stainless

The most common material used to produce the load carrying components in precision ball bearings, roller bearings, and tapered roller bearings is 52100 chrome steel. These components are the bearings inner and outer rings, balls and rollers. The chemical composition of this steel has high carbon and about 1.5% chromium content. Using controlled processing and heat-treating methods the finished bearing components have high strength to resist cracking and a hard surface to resist subsurface rolling contact fatigue. The typical surface hardness for bearing components made from this material ranges from 60- 64 on the Rockwell hardness C scale (Rc).


The carbon content in 400 series stainless steels is high enough so it can be hardened using standard heat-treating methods up to Rc58. Due to the lower hardness, the load carrying capacity is 20% lower in bearings made from this material, than they are with 52100 chrome steel bearings. The level of carbon content means the components are magnetic. The corrosion resistance is “good”, when 440C material is exposed to fresh water and mild chemicals. This material is primarily used by US bearing manufacturers.


I would go with the chrome/steel bearing for $19.95
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Old 14-07-2015, 08:00   #4
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Re: Chromium steel vs. stainless

Quote:
Originally Posted by skipmac View Post
More detail?

- Motor HP
- high speed or low speed
- constant or intermittent duty
about 25 HP
low speed at 1800 rpm
very intermittent
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Old 14-07-2015, 08:57   #5
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Re: Chromium steel vs. stainless

Quote:
Originally Posted by jeanathon View Post
I need to replace an open bearing with a sealed version, and I've two choices. One is chromium steel 52100 for 19.95 or stainless 440C for 129.95 all other specs being equal.
This is for an electric motor which is not designed for a marine application anyway. Thoughts as to which one are appreciated.
Either. The 440C will be for an environment where the bearing will experience very high loads. Perhaps where the design warrants it or where material provenance is mandated.

I doubt whether your electric motor application would warrant the increased cost. 52100 is a generic bearing steel.

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Old 14-07-2015, 09:22   #6
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Re: Chromium steel vs. stainless

The stainless version is most likely designed for food grade applications. The question is what material the motor armature (shaft) is made of. If it is carbon steel no need to use stainless bearing. The reason is pulling bearing off a corroded shaft could be so difficult you could be buying a new motor.
Bear should be same as shaft for any gain.


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Old 14-07-2015, 14:16   #7
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Re: Chromium steel vs. stainless

Needless to say you could buy 6 chrome steel bearings for the price of one SS. What was the old bearing made of? You can usually check with a magnet. A fridge magnet will work. SS is usually not magnetic. How long did the old unsealed bearing last? And what caused it to need replacing? A sealed steel bearing should last much longer than the old unsealed one. Also is the proposed SS bearing completely SS. Perhaps the cage is not?? My Reef Rite headsail furler has auto grade sealed ball races sitting under the drum where the salt spray washes over. Absolutely no problem with them. The question is not load bearing capability rather it's corrosion resistance. Assuming the sealed bearing is packed with grease I doubt that corrosion will be a problem. I would definitely go with the cr steel bearing my self. If in doubt take steps to add protection to the installation from the environment. If you are dealing with a bearing speciality company I'm sure they can offer advise. In my experience if you purchase say an auto wheel bearing from the car franchise spares department you will pay a lot more than the identical bearing from a bearing speciality company. Going by cost I'm pretty sure that the sealed bearings in the bottom of a sail drive leg are not SS. (someone might know better)You can't get much wetter than that.
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Old 14-07-2015, 14:28   #8
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Re: Chromium steel vs. stainless

Quote:
Originally Posted by GrahamHO View Post
Needless to say you could buy 6 chrome steel bearings for the price of one SS.
That was one of my thoughts. Unless the bearing is really difficult to change out or is in a very critical application where failure would be a serious problem AND corrosion a concern, then go with the chrome/steel and buy a spare.



Quote:
Originally Posted by GrahamHO View Post
What was the old bearing made of? You can usually check with a magnet. A fridge magnet will work. SS is usually not magnetic.
Actually I believe 440C stainless is very magnetic.
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Old 14-07-2015, 18:39   #9
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Re: Chromium steel vs. stainless

Buy the least expensive and a spare. Unless the bearing will live in water/salt spray there should be no problem. It, like the interior of your iron engine, will be running in grease or oil and thus protected.
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Old 14-07-2015, 19:23   #10
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Re: Chromium steel vs. stainless

25HP electric motor? Have you replaced your diesel? If so, is this the output shaft to the propshaft?
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Old 15-07-2015, 07:23   #11
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Re: Chromium steel vs. stainless

Thanks all for the advice. The chromium steel bearing has been ordered. Just to satisfy some curiosity.
The motor used to be attached to a transmission that kept the bearing bathed in oil. It is in fine shape, but would not be for long without the oil.
Yes Guy this will be attached to the propshaft albeit the opposite end of the motor.
To change the bearing I had to completely disassemble the motor, and I plan on using an acceptable electrical protectant to coat all the parts as I reassemble it.
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Old 15-07-2015, 08:32   #12
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Re: Chromium steel vs. stainless

Quote:
Originally Posted by GrahamHO View Post
Needless to say you could buy 6 chrome steel bearings for the price of one SS. What was the old bearing made of? You can usually check with a magnet. A fridge magnet will work. SS is usually not magnetic. How long did the old unsealed bearing last? And what caused it to need replacing? A sealed steel bearing should last much longer than the old unsealed one. Also is the proposed SS bearing completely SS. Perhaps the cage is not?? My Reef Rite headsail furler has auto grade sealed ball races sitting under the drum where the salt spray washes over. Absolutely no problem with them. The question is not load bearing capability rather it's corrosion resistance. Assuming the sealed bearing is packed with grease I doubt that corrosion will be a problem. I would definitely go with the cr steel bearing my self. If in doubt take steps to add protection to the installation from the environment. If you are dealing with a bearing speciality company I'm sure they can offer advise. In my experience if you purchase say an auto wheel bearing from the car franchise spares department you will pay a lot more than the identical bearing from a bearing speciality company. Going by cost I'm pretty sure that the sealed bearings in the bottom of a sail drive leg are not SS. (someone might know better)You can't get much wetter than that.
4xx stainless are matensitic and therefore magnetic.

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Old 15-07-2015, 08:35   #13
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Re: Chromium steel vs. stainless

Quote:
Originally Posted by Sailor Doug View Post
The stainless version is most likely designed for food grade applications. The question is what material the motor armature (shaft) is made of. If it is carbon steel no need to use stainless bearing. The reason is pulling bearing off a corroded shaft could be so difficult you could be buying a new motor.
Bear should be same as shaft for any gain.


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440C is not food grade. It is a deep hardening martensitic stainless.

Typically specified in applications where its deep hardening properties are needed.

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Old 15-07-2015, 08:38   #14
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Re: Chromium steel vs. stainless

Are you taking the thrust through the motor? Electric motor beatings are rated for radial loads.


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Old 15-07-2015, 22:29   #15
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Re: Chromium steel vs. stainless

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Originally Posted by Sailor Doug View Post
Are you taking the thrust through the motor? Electric motor beatings are rated for radial loads.


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&^*^%&%! I didn't think about that!
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