HSLA RB-80 Used in Radial Ball Bearings
HSLA RB-80 Used in Radial Ball Bearings
(OP)
Has anyone ever heard over unground bearings using outer raceways manufactured from HSLA steel. Any input appreciated. I have put forth alot of effort into actual life/load dynamic testing and comparing to standard bearings using low carbon grade steel stamped outer races that have been case hardened with basically no success even at 1/2 load rating applied to HSLA outer races. Bearings are running at 60 surface feet a minute for comparative testing, both grease and oil have been run still no success on HSLA. Heavy ball paths are worn into the HSLA. Thoughts anyone?





RE: HSLA RB-80 Used in Radial Ball Bearings
HSLA steels were intended primarily to be used in the as-rolled condition. I don't recall having seen an instance of HSLA steel being carburized. From your description, it sounds like there is insufficient hardness in the raceway surface, or that the finished race surface geometry may lack adequate conformal contact (osculation curvature) with the balls, causing excessive contact stress.
While I have seen low-cost, low-performance ball bearings with outer races formed from sheet metal, I don't recall what material was used or the heat treatment. I think you would be better off sticking with a case hardened race made from a cold-rolled carbon steel. Cold-rolled material actually has pretty good grain structure and the surface is much smoother & clean than hot-rolled material. While it appears that cost is an issue for your application, if possible it would also be a good idea to give the race surface a low-cost finish process to improve smoothness (ie. honing, tumble & roller burnish, etc). If you are heat treating the race after forming, I would also recommend doing some tests to develop an "as-formed" part shape that compensates for any heat treat distortion.
Hope that helps.
Terry
RE: HSLA RB-80 Used in Radial Ball Bearings
RE: HSLA RB-80 Used in Radial Ball Bearings
RE: HSLA RB-80 Used in Radial Ball Bearings
Cost is a major issue, and driving cost out of commodity stamped bearings is one of my main jobs, yet having a product that meets required test revolutions. Bearing and raceways I am working with have a proven design for nearly 50 years, I am seeking alternative materials that may alleviate heat treatment particulary for gravity applications where either the Chinese have beat us up on pricing or plastic products suffice.
RE: HSLA RB-80 Used in Radial Ball Bearings
RE: HSLA RB-80 Used in Radial Ball Bearings
I am talking about metal stamped unground bearings using low carbon steels, well known to many roller conveyor manufacturers. These are not precisions bearings that are made of chrome steels. Driving out cost is the goal, please see some of my other posts with.
RE: HSLA RB-80 Used in Radial Ball Bearings
Thanks for the additional information. HSLA steels, with their predominantly ferritic microstructure, will not have sufficient resistance to contact stress to be used for ball bearing races. Low carbon steel + case carburizing is probably the lowest cost method to obtain adequate resistance to contact stress. Maybe substituting ferritic nitrocarburizing for case carburizing could provide enough case hardness & depth for very low load applications. Salt bath nitriding of low carbon steels can attain a case depth of ~ 0.2 mm in 90-120 minutes at a temperature of < 600 C, which means that the process costs can be less than traditional carburizing operations that take several hours at temperatures > 900 C. White layer formation provides wear resistance but may be too brittle for the contact conditions. I would contact Kolene/Nitromet to discuss this type of application. Ferritic nitrocarburizing also can be done in conventional gas furnaces or using plasma, which allow more tailoring of the surface conditions, but generally are not as productive as the other methods including case carburizing.
RE: HSLA RB-80 Used in Radial Ball Bearings
Thanks for the imformation.....Stay tuned