Flat Countersunk Head Cap Screws in Inconel 718: FAQ
What are Inconel 718 Flat Countersunk Head Cap Screws per ASTM A1014?
Flat Countersunk Head Cap Screws made to the dimensions of ASME B18.3 in UNS N07718 (Inconel 718) bolting to ASTM A1014/A1014M, the specification for precipitation-hardening bolting for high temperature service. ASME B18.3 sets the dimensions; ASTM A1014 sets the melting practice, heat treatment, tests and marking, with ASTM A962/A962M as the common bolting requirements (4.1). After aging, the A1014 Table 2 room temperature minimums are 185 ksi [1275 MPa] tensile strength, 150 ksi [1035 MPa] 0.2 % offset yield strength, 12 % elongation, 15 % reduction of area and 331 to 444 HBW.
What heat treatment do Inconel 718 Flat Countersunk Head Cap Screws need per ASTM A1014?
Solution treatment at 1725 to 1850 °F [940 to 1010 °C], controlled within ±25 °F [±14 °C], held for a time commensurate with cross-sectional thickness and cooled at a rate equivalent to an air cool or faster (5.2.1). Precipitation treatment: 1325 °F [720 °C] for 8 hours minimum, furnace cool to 1150 °F [620 °C] at 100 °F [55 °C] per hour, hold 8 hours, cool to room temperature; or furnace cool at any rate with the time at 1150 °F adjusted so the total precipitation treatment is 18 hours minimum (5.2.2). Aging temperatures and cooling rates are controlled within ±15 °F [±8 °C]. Straightening is done only after solution treating and before aging (5.3).
How are Inconel 718 Flat Countersunk Head Cap Screws tested per ASTM A1014?
All tensile, hardness and stress rupture tests are made after aging (7.1). Headed bolting components with a body length of three times the diameter or longer are full-size tensile tested to the Table 2 tensile strength, using the ASME B1.1 stress area (7.3); one tensile test is made per lot (9.5). At 1200 °F [650 °C] the Table 2 minimums are 145 ksi [1000 MPa] tensile and 125 ksi [860 MPa] yield strength, and the stress rupture test at 100 ksi [690 MPa] must last 23 hours minimum with 5 % elongation (7.2, one test per lot per 9.2). Components are marked "718" with the manufacturer's identification symbol (11.1).
