The materials of fasteners are in the most common order: carbon steel, stainless steel, stainless steel, copper, aluminum, etc.
Carbon steel is further divided into low carbon steel (such as C1008/C1010/C1015/C1018/C1022), medium carbon steel (such as C1035), high carbon steel (C1045/C1050), and alloy steel (SCM435/10B21/40Cr).
Generally, C1008 materials are all grades, such as 4.8 screws, common grade nuts; C1015 general lifting ring screws; C1018 general machine screws, of course, also used to do self-tapping screws; C1022 is generally used for self-tapping screws ; C1035 hits 8.8 screws; C1045/10B21/40Cr hits 10.9 screws; 40Cr/SCM435 hits 12.9 screws.
Stainless steel is the most common with SS302/SS304/SS316. Of course, a lot of SS201 products are also popular nowadays, even products with lower nickel content. We call them non-authentic stainless steel products; the appearance looks like stainless steel, but the corrosion resistance is quite different.
The strength grade of fasteners mainly refers to carbon steel fasteners.
The common strength grades of carbon steel screws are: 4.8, 5.8, 6.8, 8.8, 10.9, and 12.9. The nuts are correspondingly: 4, 6, 8, 8, and 12.
Generally, the screws below 8.8 are called ordinary screws, while those above 8.8 (including 8.8) are high-strength screws. The difference is that high-strength screws require heat treatment.