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SMO 254 bolts are super austenitic stainless steel fasteners engineered for aggressive corrosive environments where standard stainless steels like 304 or 316 fail. Manufactured using high-alloy 6Mo (UNS S31254) material, these bolts deliver exceptional resistance to pitting, crevice corrosion, and chloride-induced stress corrosion cracking. They are widely used in seawater systems, offshore oil & gas platforms, desalination plants, and chemical processing equipment where long-term structural integrity is critical.
Designed for high mechanical strength combined with superior corrosion resistance, SMO 254 bolts comply with international standards such as ASTM A276 and DIN/ISO equivalents. Their high molybdenum and nitrogen content significantly improves PREN values, making them suitable for continuous exposure to harsh saline and acidic conditions.
KK Fasteners supplies SMO 254 bolts to global industrial clients with strict material traceability, ensuring consistent performance across critical engineering applications.
| Parameter | Specification |
|---|---|
| Material | SMO 254 (UNS S31254) – 6% Mo Super Austenitic Stainless Steel |
| Grade | ASTM A276 / ASTM A479 / EN 1.4547 |
| Size Range | M6 to M100 / 1/4" to 4" |
| Thread Type | Metric, UNC, UNF, BSW, ISO Metric |
| Standards | DIN, ISO, ASTM, BS, ASME |
| Finish | Bright, Polished, Passivated |
| Type Variants | Hex Bolt, Stud Bolt, Heavy Hex Bolt, Socket Head Cap Screw |
| Tensile Strength | ≥ 650 MPa (approx.) |
| Hardness | ~HB 250 max (solution annealed condition) |
| SMO 254 | Ni | C | Mo | Mn | Si | Fe | Cu | S | P | Cr |
| 17.5 – 18.5 |
0.02 max | 6 – 6.5 |
1 max | 0.8 max | – | 0.5 – 1 | 0.01 max | 0.03 max | 19.5 – 20.5 |
| Density | Melting Point | Yield Strength (0.2%Offset) | Tensile Strength | Elongation |
| 8.0 g/cm3 | 1320-1390 ℃ | 300 | 650 | 35 % |
| STANDARD | UNS | WERKSTOFF NR. | AFNOR | EN | JIS | SIS | GOST |
| SMO 254 | S31254 | 1.4547 | Z1 CNDU 20.18.06Az | X1CrNiMoCuN20-18-7 | – | 2378 | – |
All measurements in millimeters
NOMINAL SIZE (D) |
BODY DIAMETER |
BOLT HEAD THICKNESS |
ACROSS THE FLATS |
ACROSS CORNERS |
||||
|---|---|---|---|---|---|---|---|---|
D (MAX) |
D (MIN) |
H (MAX) |
H (MIN) |
F (MAX) |
F (MIN) |
C (MAX) |
C (MIN) |
|
m10 |
10.00 |
9.78 |
6.63 |
6.17 |
17.00 |
15.73 |
18.48 |
17.77 |
m12 |
12.00 |
11.73 |
7.76 |
4.24 |
19.00 |
17.73 |
20.78 |
20.03 |
m14 |
14.00 |
13.73 |
9.09 |
8.51 |
22.00 |
20.67 |
24.25 |
23.35 |
m16 |
16.00 |
15.73 |
10.32 |
9.68 |
24.00 |
23.67 |
27.71 |
26.75 |
m20 |
20.00 |
19.67 |
12.88 |
12.12 |
30.00 |
29.16 |
34.64 |
32.95 |
m24 |
24.00 |
23.67 |
15.44 |
14.56 |
36.00 |
35.00 |
41.57 |
39.55 |
m30 |
30.00 |
29.67 |
19.48 |
17.92 |
46.00 |
45.00 |
53.12 |
50.85 |
m36 |
36.00 |
35.61 |
23.38 |
21.63 |
55.00 |
53.80 |
63.51 |
60.79 |
m42 |
42.00 |
41.38 |
26.97 |
25.03 |
65.00 |
62.90 |
75.06 |
71.71 |
m48 |
48.00 |
47.38 |
31.07 |
28.93 |
75.00 |
72.60 |
86.60 |
82.76 |
m56 |
56.00 |
55.26 |
36.2 |
33.80 |
85.00 |
82.20 |
98.15 |
93.71 |
m64 |
64.00 |
63.26 |
41.32 |
38.68 |
95.00 |
91.80 |
109.70 |
104.65 |
m72 |
72.00 |
71.26 |
46.45 |
43.55 |
105.00 |
101.40 |
121.24 |
115.60 |
m80 |
80.00 |
79.26 |
51.58 |
48.42 |
115.00 |
111.00 |
132.72 |
126.54 |
m90 |
90.00 |
89.13 |
57.74 |
54.26 |
130.00 |
125.50 |
150.11 |
143.07 |
m100 |
90.00 |
99.13 |
63.9 |
60.10 |
145.00 |
140.00 |
167.43 |
159.60 |
| MM THREADS AS PER IS 1363/67 | ||||||||||
| APPROXIMATE WEIGHT IN KGS FOR 100 NOS | ||||||||||
| LENGTH | DIAMETER | |||||||||
| M 5 | M 6 | M 8 | M 10 | M 12 | M 14 | M 16 | M 18 | M 20 | M 22 | |
| 16 mm | 0.448 | 0.743 | 1.590 | 3.211 | ||||||
| 20 mm | 0.598 | 0.812 | 1.711 | 3.411 | 4.892 | |||||
| 25 mm | 0.660 | 0.897 | 1.871 | 3.660 | 5.252 | 8.170 | ||||
| 30 mm | 0.737 | 1.010 | 2.070 | 3.912 | 5.574 | 9.690 | 10.707 | 18.657 | ||
| 35 mm | 0.804 | 1.120 | 2.271 | 4.223 | 5.974 | 10.000 | 11.416 | 16.026 | 19.608 | |
| 40 mm | 0.881 | 1.230 | 2.470 | 4.533 | 6.410 | 10.288 | 12.107 | 16.667 | 20.747 | |
| 45 mm | 0.958 | 1.340 | 2.671 | 4.840 | 6.859 | 10.504 | 12.821 | 17.241 | 21.739 | |
| 50 mm | 1.030 | 1.450 | 2.870 | 5.155 | 7.299 | 11.261 | 13.624 | 17.857 | 22.727 | 28.409 |
| 55 mm | 1.560 | 3.071 | 5.464 | 7.740 | 11.628 | 14.409 | 18.868 | 23.810 | 30.120 | |
| 60 mm | 1.670 | 3.270 | 5.774 | 8.183 | 12.255 | 15.244 | 20.000 | 25.126 | 32.051 | |
| 65 mm | 1.781 | 3.472 | 6.083 | 8.621 | 12.626 | 16.026 | 21.008 | 26.455 | 34.014 | |
| 70 mm | 1.890 | 3.671 | 6.394 | 9.058 | 12.987 | 16.835 | 22.124 | 27.778 | 35.461 | |
| 75 mm | 2.000 | 3.873 | 6.702 | 9.506 | 13.228 | 17.606 | 23.256 | 29.070 | 39.063 | |
| 80 mm | 2.111 | 4.072 | 7.013 | 10.000 | 13.889 | 18.248 | 24.510 | 30.303 | 40.000 | |
| 90 mm | 4.472 | 7.634 | 10.917 | 14.925 | 19.841 | 26.042 | 33.113 | 41.667 | ||
| 100 mm | 4.873 | 8.251 | 11.820 | 16.340 | 21.459 | 27.778 | 35.714 | 46.296 | ||
| 110 mm | 8.881 | 12.723 | 17.730 | 23.041 | 31.250 | 38.168 | 47.170 | |||
| 120 mm | 9.506 | 13.624 | 18.797 | 24.631 | 32.895 | 40.984 | 50.000 | |||
| 130 mm | 10.101 | 14.535 | 20.000 | 26.316 | 34.722 | 43.478 | 52.632 | |||
| 140 mm | 10.707 | 15.432 | 20.833 | 27.933 | 35.461 | 46.296 | 55.556 | |||
| 150 mm | 11.312 | 16.340 | 22.222 | 29.412 | 37.594 | 48.544 | 58.824 | |||
| 160 mm | 11.905 | 17.241 | 24.272 | 31.056 | 40.984 | 50.505 | 61.728 | |||
| 170 mm | 12.500 | 18.116 | 32.680 | 53.191 | 64.935 | |||||
| 180 mm | 13.123 | 19.011 | 26.882 | 34.247 | 55.556 | 67.568 | ||||
| 190 mm | 13.736 | 19.920 | 35.971 | 58.140 | 70.423 | |||||
| 200 mm | 14.327 | 20.833 | 29.586 | 37.594 | 49.020 | 60.976 | 73.529 | |||
| 220 mm | 15.528 | 22.624 | 40.650 | 65.789 | 79.365 | |||||
| 240 mm | 16.722 | 24.510 | 43.860 | 71.429 | 84.746 | |||||
| 250 mm | 17.301 | 25.381 | 45.455 | 74.627 | 87.719 | |||||
| 260 mm | 17.921 | 26.316 | 47.170 | 76.923 | 90.909 | |||||
| 280 mm | 19.157 | 28.090 | 50.505 | 81.967 | 98.039 | |||||
| 300 mm | 20.325 | 29.940 | 53.763 | 87.719 | 104.167 | |||||
| 320 mm | 31.646 | 56.818 | 92.593 | |||||||
| 340 mm | 33.557 | 60.241 | 98.039 | |||||||
| 360 mm | 35.211 | 63.291 | 104.167 | |||||||
| 380 mm | 37.037 | 66.667 | 108.696 | |||||||
| 400 mm | 39.063 | 69.444 | 113.636 | |||||||
SMO 254 bolts are used in systems exposed to aggressive chloride, acidic, or high-moisture environments where conventional fasteners cannot maintain long-term performance.
SMO 254 bolts are produced through controlled hot forging followed by precision machining to achieve strict dimensional tolerances. The manufacturing process ensures uniform grain structure, which enhances both mechanical strength and corrosion resistance.
Each batch undergoes hardness testing, tensile verification, and chemical composition analysis to confirm compliance with ASTM A276 requirements. Surface passivation enhances the protective chromium oxide layer, improving corrosion resistance in chloride environments.
KK Fasteners implements full lot traceability and inspection protocols, ensuring every shipment meets international industrial standards such as ISO 9001 and RoHS compliance requirements.
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SMO 254 bolts are high-alloy super austenitic stainless steel fasteners made from UNS S31254. They are designed for extreme corrosion environments such as seawater, chemical processing plants, and offshore structures where standard stainless steels like SS 304 or SS 316 are not sufficient.
Yes. SMO 254 performs significantly better than SS 316 in seawater due to its higher molybdenum (≈6%) and nitrogen content. This improves resistance against pitting, crevice corrosion, and chloride stress corrosion cracking, making it suitable for long-term marine exposure.
SMO 254 typically complies with ASTM A276 and ASTM A479 standards. It is also classified under EN 1.4547. These standards define its chemical composition, mechanical strength, and corrosion resistance properties for industrial applications.
SMO 254 bolts are widely used in offshore oil and gas platforms, desalination plants, chemical processing units, marine engineering systems, and power plants. They are selected wherever high chloride resistance and long service life are required.
A reliable supplier should provide certified material test reports, ISO 9001 compliance, full traceability, and proven export capability. Consistent quality control and adherence to ASTM/EN standards are key indicators of a dependable manufacturer like KK Fasteners.
SMO 254 bolts are critical components for high-risk corrosion environments where failure is not an option. Their superior 6Mo chemistry ensures long-term reliability in offshore, chemical, and marine engineering systems.
KK Fasteners provides engineered fastening solutions with full material traceability and export-ready documentation for global industrial projects.
For technical specifications, pricing, or custom requirements, connect with the engineering team to request a detailed quotation and datasheet.
