Technical Tutorial - Low cost automation
Strength Classifications Of Stainless-Steel Bolts And
Nuts
The strength classes of stainless steel bolts are
categorized according to the stainless-steel material types
used. MISUMI FA catalog '06, page 880 shows the strength
classification of socket head cap screws SCB in SUS304
stainless steel as A2-70
(1) Mechanical properties of stainless steel
bolts
1. Mechanical properties of stainless steel
bolts
- Properties of stainless steel bolts are also categorized
by strength classes, but with a different numbering system.
- [Table 1] shows a part of ISO 3506-1: 1997, the rules on
mechanical properties of stainless steel bolts.
2. How to read strength class in the
table
- The strength class number denotes 1/10th of the bolt's
minimumtensile strength. Example: Austenitic stainless steel
bolts with A2-70 strength class means: guaranteed tensile
strength of 500 (N/mm2), proof stress of 210 (N/mm2), and
elongation of 0.6d to the point of brakage.
- Classified according to the material the bolts are made
of (Austenitic SS, Martensitic SS, Ferrite SS).
Additionally, the Martensitic SS is further categorized into
different classifications according to heat treatments
applied or not.
(2) Mechanical properties of stainless steel nuts
- The mechanical properties of stainless steel nuts are
also categorized into strength classes like the standard
steel nuts, where represented by proof load stress numbers
used with matching bolts.
- The stainless steel bolts are classified according to
the type of material, and since the SS nuts are designed to
be used together with SS bolts, it can be assumed that the
strength classifications of SS nuts are the same with SS
bolts.
- For the reason above, there will be no thread damage at
the engagement region of SS bolts and SS nuts, but special
attention must given for thread damages when thin nuts with
fewer number of thread engagement is used.
[Table. 1] Mechanical properties of stainless
steel bolts (from ISO 3506-1: 1997)
Technical
articles written by Akihiro Inada, Ph.D. with an English
translation arranged by MISUMI Corporation