Nice to meet you.
Currently, we are using a friction ring for the locknut with SUS301 material (hardness Hv470-480) (value on the mill sheet). In addition, hot-dip galvanizing (about 500°C) is performed after the nut molding process. When the nut was used, the friction ring was cracked and the thread was torn, so the hardness of the friction ring was measured.
(1) Friction ring separately: Hv511 to 517
(2) New locknut: Hv494 to 498
(3) Cracked locknut: Hv485 to 496.
The tempered hardness of SUS301-CSP EH is Hv490 or higher, and the hardness does not seem to be a problem, but the cause of cracking is unknown. Can you think of any possible factors?
Spring Newbie, thank you for posting!
It seems that the friction ring broke during use, we recommend that you investigate the actual product to identify the cause. From the contents you have provided, did any of these things happen? ・Used in a high-temperature environment.
・ Embrittlement due to hot-dip galvanizing
・ Were there any scratches or cracks?
Thank you for your prompt reply.
It is not used at high temperatures, but is it possible that it became embrittled by hot-dip galvanizing (about 500°C) after tempering? (We have been conducting hot-dip galvanizing after molding for about 10 years.)
Could you please tell us in a little more detail about this phenomenon? I will also check for scratches and cracks.
Spring Newbie, for austenitic SUS, if you search for welding-related materials, you will find various information about zinc embrittlement.
Regarding the embrittlement related to hot-dip galvanizing, it seems difficult to answer without investigations… If you have a track record of the past 10 years and there have been no abnormalities so far, was there any process that was different from the normal process, including the plating process? How about looking at this time’s process?
