ISO 3506-3 Specification specifies the mechanical properties of set screws and similar fasteners not under tensile stress made of austenitic stainless steel, when tested over an ambient temperature range of 10 °C to 35 °C. Properties vary at higher or lower temperatures.
It does not apply to screws with special properties, such as weldability.
NOTE: The designation system of this part of ISO 3506 can be used for sizes outside the limits given in this clause (e.g. d > 24 mm), provided that all applicable mechanical and physical requirements of the hardness classes are met.
This part of ISO 3506 does not define corrosion or oxidation resistance in particular environments.
The aim of this part of ISO 3506 is the classification of corrosion-resistant stainless steel fasteners into hardness classes.
Corrosion and oxidation performances and mechanical properties for use at elevated or sub-zero temperatures can be agreed on between the user and the manufacturer in each particular case. Annex D shows how the risk of intergranular corrosion at elevated temperatures depends on the carbon content.
All austenitic stainless steel fasteners are normally non-magnetic in the annealed condition; after cold working, some magnetic properties can be evident.
| Steel group | Steel grade | Chemical composition a mass fraction, % | Footnotes | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| C | Si | Mn | P | S | Cr | Mo | Ni | Cu | |||
| Austenitic | A1 | 0.12 | 1 | 6.5 | 0.2 | 0,15 to 0,35 | 16 to 19 | 0.7 | 5 to 10 | 1,75 to 2,25 | bcd |
| A2 | 0.1 | 1 | 2 | 0.05 | 0.03 | 15 to 20 | _e | 8 to 19 | 4 | fg | |
| A3 | 0.08 | 1 | 2 | 0.045 | 0.03 | 17 to 19 | _e | 9 to 12 | 1 | h | |
| A4 | 0.08 | 1 | 2 | 0.045 | 0.03 | 16 to 18,5 | 2 to 3 | 10 to 15 | 4 | gi | |
| A5 | 0.08 | 1 | 2 | 0.045 | 0.03 | 16 to 18,5 | 2 to 3 | 10,5 to 14 | 1 | hi | |
| Nominal thread diameter d | Minimum length a of set screws for test mm | Hardness class | ||||
|---|---|---|---|---|---|---|
| Flat point | Cone point | Dog point | Cup point | 12H | 21H | |
| Proof torque , min. Nm | ||||||
| 1.6 | 2.5 | 3 | 3 | 2.5 | 0.03 | 0.05 |
| 2 | 4 | 4 | 4 | 3 | 0.06 | 0.1 |
| 2.5 | 4 | 4 | 5 | 4 | 0.18 | 0.3 |
| 3 | 4 | 5 | 6 | 5 | 0.25 | 0.42 |
| 4 | 5 | 6 | 8 | 6 | 0.8 | 1.4 |
| 5 | 6 | 8 | 8 | 6 | 1.7 | 2.8 |
| 6 | 8 | 8 | 10 | 8 | 3 | 5 |
| 8 | 10 | 10 | 12 | 10 | 7 | 12 |
| 10 | 12 | 12 | 16 | 12 | 14 | 24 |
| 12 | 16 | 16 | 20 | 16 | 25 | 42 |
| 16 | 20 | 20 | 25 | 20 | 63 | 105 |
| 20 | 25 | 25 | 30 | 25 | 126 | 210 |
| 24 | 30 | 30 | 35 | 30 | 200 | 332 |
| Test method | Hardness class | |
|---|---|---|
| 12H | 21H | |
| Hardness | ||
| Vickers hardness HV | 125 to 209 | 210 min. |
| Brinell hardness HB | 123 to 213 | 214 min. |
| Rockwell hardness HRB | 70 to 95 | 96 min. |
Product Shall be Marked with our manufacturing trade mark "TorqBolt" or "TB" along with the designated Grade.
Grade and manufacturer’s identification symbols shall be applied to one end of studs and to the heads of bolts and screws of all sizes. (If the available area is inadequate, the grade symbol may be marked on one end and the manufacturer’s identification symbol marked on the other end.) For bolts and screws smaller than 1⁄4 in. [6 mm] in diameter and studs smaller than 3⁄8 in. [10 mm] in diameter and for 1⁄4 in. [6 mm] in diameter studs requiring more than a total of three symbols, the marking shall be a matter of agreement between the purchaser and the manufacturer.