What is a Metric Socket Head Cap Screws (DIN 912 equivalent) in Inconel 718 per ASTM A1014?

Metric Socket Head Cap Screws (DIN 912 equivalent) per ASME B18.3.1M dimensional standard, manufactured in UNS N07718 (Inconel 718 / Alloy 718) precipitation-hardening nickel-chromium superalloy per ASTM A1014 / A1014M for high-temperature bolting service to about 705 °C (1300 °F). Tensile strength ≥185 ksi (1275 MPa), 0.2% yield ≥150 ksi (1035 MPa), hardness 331–444 HBW after solution + double-age treatment.

What heat treatment is required for Metric Socket Head Cap Screws (DIN 912 equivalent) in ASTM A1014?

ASTM A1014 §5.2 mandates solution treatment at 1725–1850 °F (940–1010 °C) ±25 °F with air cool or faster, followed by precipitation aging at 1325 °F (720 °C) for 8 hours minimum, furnace cool to 1150 °F (620 °C) at 100 °F/hour, hold 8 hours, air cool. Total precipitation aging cycle minimum 18 hours. Straightening permitted only between solution and aging — never after aging.

Why use Inconel 718 for Metric Socket Head Cap Screws (DIN 912 equivalent) versus stainless or low-alloy steel?

Inconel 718 (Metric Socket Head Cap Screws (DIN 912 equivalent)) retains its 185 ksi tensile to 705 °C where 4140 (B7), 410SS (B6), and 304/316SS lose 60-80% of room-temperature strength. Stress-rupture rating: 23 h minimum at 1200 °F / 100 ksi per ASTM A1014. Used in gas-turbine engines, liquid-oxygen turbo-pumps, downhole H₂S service, and oxy-fuel petrochemical reactors where ASTM A193 grades cannot meet service temperature.

DIN 912 Socket Cap Screws Inconel 718

ASME B18.3.1M Metric Socket Head Cap Screws – Dimensions, Specifications & Standards

Metric Socket Head Cap Screws for Precision & Confined-Space Bolting.

ASME B18.3.1M Metric Socket Head Cap Screws are metric-series precision fasteners with a cylindrical head and internal hexagonal drive socket, designed for high clamping force in confined areas such as precision machine tools, hydraulic manifolds, medical devices, and aerospace assemblies. The standard specifies metric dimensions for head diameter, head height, socket size, key engagement depth, body diameter, thread pitch, and thread length. These are manufactured to ASTM A1014/A1014M for UNS N07718 (Inconel 718) bolting, providing superior tensile strength, corrosion resistance, and dimensional stability in high-temperature and chemically aggressive environments. The metric counterpart to ASME B18.3 Socket Head Cap Screws, they are also specified with ISO property class ratings or ASTM A574 for general high-strength applications. The internal socket drive reduces radial space needed for tightening, making these the preferred solution in space-constrained designs.

ASME B18.3.1M Metric Socket Head Cap Screws Dimensions

Nom. Sizeand Thread Pitch	Body Diameter, D	Head Diameter A	Head Height H	Chamferor Radius S	Hexagon Socket Size^a J	Spline Socket Size^a M	Key Engagement T	Transition Dia. B ^a
M1.6 × 0.35	1.6	1.46	3	2.87	1.6	1.52	0.16	1.5	1.829	0.8	2
M2 × 0.4	2	1.86	3.8	3.65	2	1.91	0.2	1.5	1.829	1	2.6
M2.5 × 0.45	2.5	2.36	4.5	4.33	2.5	2.4	0.25	2	2.438	1.25	3.1
M3 × 0.5	3	2.86	5.5	5.32	3	2.89	0.3	2.5	2.819	1.5	3.6
M4 × 0.7	4	3.82	7	6.8	4	3.88	0.4	3	3.378	2	4.7
M5 × 0.8	5	4.82	8.5	8.27	5	4.86	0.5	4	4.648	2.5	5.7
M6 × 1	6	5.82	10	9.74	6	5.85	0.6	5	5.486	3	6.8
M8 × 1.25	8	7.78	13	12.7	8	7.83	0.8	6	7.391	4	9.2
M10 × 1.5	10	9.78	16	15.67	10	9.81	1	8	...	5	11.2
M12 × 1.75	12	11.73	18	17.63	12	11.79	1.2	10	...	6	14.2
M14 × 2^b	14	13.73	21	20.6	14	13.77	1.4	12	...	7	16.2
M16 × 2	16	15.73	24	23.58	16	15.76	1.6	14	...	8	18.2
M20 × 2.5	20	19.67	30	29.53	20	19.73	2	17	...	10	22.4
M24 × 3	24	23.67	36	35.48	24	23.7	2.4	19	...	12	26.4
M30 × 3.5	30	29.67	45	44.42	30	29.67	3	22	...	15	33.4
M36 × 4	36	35.61	54	53.37	36	35.64	3.6	27	...	18	39.4
M42 × 4.5	42	41.61	63	62.31	42	41.61	4.2	32	...	21	45.6
M48 × 5	48	47.61	72	71.27	48	47.58	4.8	36	...	24	52.6
a See also Table 25. b The M14 ×2 size is not recommended for use in new designs. All dimensions are in millimeters LG is grip length and LB is body length. For length of complete thread. For additional manufacturing and acceptance specifications, see ASME B18.3.1M-1986.

Nom. Sizeand Thread Pitch

Body Diameter, D

Head Diameter A

Head Height H

Chamferor Radius S

Hexagon Socket Size^a J

Spline Socket Size^a M

Key Engagement T

Transition Dia. B ^a

Max

Min.

Max

Min.

Max

Min.

Max

Nom.

Min.

Max

M1.6 × 0.35

1.6

1.46

2.87

1.6

1.52

0.16

1.5

1.829

0.8

M2 × 0.4

1.86

3.8

3.65

1.91

0.2

1.5

1.829

2.6

M2.5 × 0.45

2.5

2.36

4.5

4.33

2.5

2.4

0.25

2.438

1.25

3.1

M3 × 0.5

2.86

5.5

5.32

2.89

0.3

2.5

2.819

1.5

3.6

M4 × 0.7

3.82

6.8

3.88

0.4

3.378

4.7

M5 × 0.8

4.82

8.5

8.27

4.86

0.5

4.648

2.5

5.7

M6 × 1

5.82

9.74

5.85

0.6

5.486

6.8

M8 × 1.25

7.78

12.7

7.83

0.8

7.391

9.2

M10 × 1.5

9.78

15.67

9.81

...

11.2

M12 × 1.75

11.73

17.63

11.79

1.2

...

14.2

M14 × 2^b

13.73

20.6

13.77

1.4

...

16.2

M16 × 2

15.73

23.58

15.76

1.6

...

18.2

M20 × 2.5

19.67

29.53

19.73

...

22.4

M24 × 3

23.67

35.48

23.7

2.4

...

26.4

M30 × 3.5

29.67

44.42

29.67

...

33.4

M36 × 4

35.61

53.37

35.64

3.6

...

39.4

M42 × 4.5

41.61

62.31

41.61

4.2

...

45.6

M48 × 5

47.61

71.27

47.58

4.8

...

52.6

a See also Table 25.
b The M14 ×2 size is not recommended for use in new designs.
All dimensions are in millimeters
LG is grip length and LB is body length. For length of complete thread.
For additional manufacturing and acceptance specifications, see ASME B18.3.1M-1986.

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ASME B18.3.1M Metric Socket Head Cap Screws – Dimensions, Specifications & Standards

ASME B18.3.1M Metric Socket Head Cap Screws Dimensions

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