# classes and grades of steel and stainless steel

I'm trying to learn the standard nomenclature for the steel and stainless steel mainly used in the bolts, screws, nuts, and other fasteners in general. So far I have created this table:

|      Metric / Class     |   Imperial / Grade  |        Material        |
|:-----------------------:|:-------------------:|:----------------------:|
|      ISO 898-1 / 8.8    |     SAE J429 / 5    |          steel         |
|     ISO 898-1 / 10.9    |     SAE J429 / 8    |          Steel         |
|           12.9          |       ASTM A574     |          Steel         |
|            304          |          A2         |     Stainless steel    |
|            316          |          A4         |     Stainless steel    |


For example, metric system categories steels into classes according to the ISO 898-1 standard. While the Imperial system uses the SAE J429 standard to distinguish steels by grades. It seems like my table makes sense for steel, but for the stainless steels, I do not understand the grades/classes. For example, I'm not sure if 316 designates a metric class equivalent to the A4 imperial grade?

From time to time I also see notations such as A4-80 EPK. I understand that the 80 part determines the minimum tensile strength. But I have no clue what the EPK could stand for.

• You are mixing apples and oranges ; there is little or no correlation between steel alloys and fasteners. Such as 316 is a general designation of a stainless alloy ,no connection with form such as bar, plate, pipe , fastener, etc. Dec 8 '20 at 15:43
• @blacksmith37 thanks for the comment. True. I'm aware that those alloys are used in a variety of applications but I'm at the moment focused on the fasteners.
– Foad
Dec 8 '20 at 15:51
• And ASTM may have many alloys in a specification ,so you still need an alloy designation. Such as A 193 and 194, the standard fasteners in any industry with pipe flanges; Alloy can be anything from carbon steel to stainless. Dec 8 '20 at 20:42