Forgings, Fasteners, Boltings, Stud Bolts, Screws, Nuts
ASTM A522 specification covers 8 and 9 % nickel-alloy steel forged or rolled flanges, fittings, valves, and parts intended for use in welded pressure vessels for low-temperature service. The specification is applicable to forgings with maximum section thickness of 3 in. [75 mm] in the double normalized and tempered condition and 5 in. [125 mm] in the quenched and tempered condition. Forgings under this specification are intended for service at operating temperatures not lower than −320 °F [−196 °C] for Type I or −275 °F [−170 °C] for Type II or higher than 250 °F [121 °C].
Material under this specification is available in two types having different chemical compositions as follows:
| Type | Nominal Nickel Content, % |
|---|---|
| I | 9 |
| II | 8 |
ASTM A522 specification is expressed in both inch-pound units and SI units. However, unless the order specifies the applicable “M” specification designation (SI units), the material shall be furnished to inch-pound units.
| Composition, % | ||||||
|---|---|---|---|---|---|---|
| Type | Element | |||||
| C, max | Mn, max | P, max | S, max | SiA | Ni | |
| ASTM A522 Type I | 0.13 | 0.90 | 0.025 | 0.025 | 0.15-0.30 | 8.5-9.5 |
| ASTM A522 Type II | 0.13 | 0.90 | 0.025 | 0.025 | 0.15-0.30 | 7.5-8.5 |
|
||||||
| Tensile strength, min, ksi [MPa] | 100 [690] |
|---|---|
| Yield strength, min, (0.2 % off-set), ksi [MPa] | 75 [515] |
| Elongation in 2 in. [50 mm], min, % | 22 |
| Reduction of area, min, % | 45 |
The forgings shall be heat treated by the manufacturer by either of the following methods as mutually agreed upon between the purchaser and the manufacturer.
Quenched and Tempered—Heat to a uniform temperature of 1475 6 25 °F [800 6 15 °C]; hold at this temperature for a minimum time of 1 h/in. [2.5 min/mm] of thickness but in no case less than 30 min; quench by immersion in circulating water. Reheat until the forging attains a uniform temperature within the range from 1050 to 1125 °F [565 to 605 °C]; hold at this temperature for a minimum time of 1 h/in. [2.5 min/mm] of thickness but in no case less than 30 min; cool in air or water quench, at a rate not less than 300 °F [165 °C]/h.
Double Normalized and Tempered—Heat to a uniform temperature of 1650 °F [900 °C]; hold at this temperature for a minimum time of 1 h/in. [2.5 min/mm] of thickness but in no case less than 30 min; cool in air. Reheat until the forging attains a uniform temperature of 1450 °F [790 °C]; hold at this temperature for a minimum time of 1 h/in. [2.5 min/mm] of thickness but in no case less than 30 min; cool in air. Reheat to a uniform temperature within the range from 1050 to 1125 °F [565 to 605 °C]; hold at this temperature for a minimum time of 1 h/in. [2.5 min/mm] of thickness but in no case less than 30 min; cool in air or water quench, at a rate not less than 300 °F [165 °C]/h.
When stress relieving is to be performed after fabrication, the recommended stress-relieving treatment is as follows: gradually and uniformly heat the steel to a temperature between 1025 and 1085 °F [550 and 585 °C]; hold for a minimum of 2 h for thicknesses up to 1 in. [25 mm]. For thicknesses over 1 in. [25 mm], a minimum additional holding time in the ratio of 1 h/in. [2.5 min/mm] of thickness in excess of 1 in. [25 mm] shall be added. Cool at a minimum rate of 300 °F [165 °C]/h to a temperature not exceeding 600 °F [315 °C].
| S1 | Nondestructive Tests |
|---|---|
| S2 | Other Impact Test Temperatures |