ASTM A453 Grade 660 (A-286)
A-286 bolting for the hottest joints — 130 ksi at room temperature and rated by stress-rupture at 1200 °F, for gas and steam turbines, exhaust and high-temperature process equipment.
What A453 660 is.
ASTM A453 Grade 660 covers bolting in A-286, an iron-nickel-chromium superalloy strengthened by titanium and aluminum precipitates. Unlike the A193 grades it is qualified by room-temperature tensile properties and, for design temperatures above 800 °F, by a stress-rupture test at 1200 °F, because its purpose is to hold clamp load at temperatures where B16 and the austenitic stainless grades have already relaxed.
Four heat-treatment classes give different balances of strength and rupture ductility. Class A and B are the common bolting conditions; Class D is aged, with a second age if needed for properties, for a 105 ksi yield. We machine Grade 660 studs, bolts and nuts from certified A-286 bar with the aging cycle documented on the certificate.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.08 |
| Manganese | Mn | — | 2.00 |
| Phosphorus | P | — | 0.040 |
| Sulfur | S | — | 0.030 |
| Silicon | Si | — | 1.00 |
| Nickel | Ni | 24.0 | 27.0 |
| Chromium | Cr | 13.5 | 16.0 |
| Molybdenum | Mo | 1.00 | 1.50 |
| Titanium | Ti | 1.90 | 2.35 |
| Aluminum | Al | — | 0.35 |
| Vanadium | V | 0.10 | 0.50 |
| Boron | B | 0.001 | 0.010 |
Values per ASTM A453/A453M-17 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Class and size | Tensile strength, min (ksi) | Yield strength 0.2% offset, min (ksi) | Elongation in 4D, min (%) | Reduction of area, min (%) | Hardness |
|---|---|---|---|---|---|
| Class A — all sizes | 130 | 85 | 15 | 18 | 248–341 HBW / 24–37 HRC |
| Class B — all sizes | 130 | 85 | 15 | 18 | 248–341 HBW / 24–37 HRC |
| Class C — all sizes | 130 | 85 | 15 | 18 | 248–341 HBW / 24–37 HRC |
| Class D — 2½ and under | 130 | 105 | 15 | 18 | 248–321 HBW / 24–35 HRC |
| Class D — over 2½ | 120 | 95 | 15 | 18 | 248–321 HBW / 24–35 HRC |
Values per ASTM A453/A453M-17 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
| Test temperature | Stress (ksi) | Time to rupture, min (h) | Elongation, min (%) |
|---|---|---|---|
| 1200 °F (650 °C) | 56 | 100 | 5 |
Values per ASTM A453/A453M-17 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
| Class | Solution treatment | Precipitation (aging) treatment |
|---|---|---|
| A | 1650 ± 25 °F (900 °C), 2 h min, liquid quench | 1325 ± 25 °F (720 °C), 16 h, air cool |
| B | 1800 ± 25 °F (980 °C), 1 h min, liquid quench | 1325 ± 25 °F (720 °C), 16 h, air cool |
| C | 1800 ± 25 °F (980 °C), 1 h min, oil quench | 1425 ± 25 °F (775 °C), 16 h, air cool, then 1200 ± 25 °F (650 °C), 16 h, air cool |
| D | 1650 ± 25 °F (900 °C), 2 h min, or 1800 ± 25 °F (980 °C), 1 h min; liquid quench | 1325 ± 25 °F (720 °C), 16 h, air cool; second age 1200 ± 25 °F (650 °C), 16 h, if needed for properties |
Per ASTM A453/A453M-17 Table 4. The certified heat-treat record travels with every lot.
Specifications that apply.
How A453 660 ships from Houston.
- Full-thread studs and stud bolts
- Hex and 12-point bolts
- Socket head cap screws
- Heavy hex nuts in the same grade
- Machined components from certified bar
A453 660 fasteners we make.
Every item is manufactured to your drawing or standard in A453 660, imperial or metric, with an EN 10204 3.1 certificate.
What is ASTM A453 Grade 660?
A453 is the specification for high-temperature bolting materials whose thermal expansion matches austenitic stainless steel, and Grade 660 is its A-286 member. A-286 is about 25 percent nickel and 15 percent chromium in an iron base, with titanium, aluminum, vanadium and boron additions that let it be precipitation hardened. After solution treatment and a 16 hour age at 1325 °F it reaches 130 ksi tensile and holds useful strength to roughly 1300 °F, far beyond the alloy-steel grades. Because it expands like 300-series stainless it can bolt stainless and superalloy components without losing preload as the joint heats.
Classes A, B, C and D
- Class A: 1650 °F solution treatment, aged at 1325 °F.
- Class B: 1800 °F solution treatment, aged at 1325 °F.
- Class C: 1800 °F solution, aged at 1425 °F then 1200 °F.
- Class D: 1650 °F (or 1800 °F) solution, aged at 1325 °F with a second 1200 °F age if needed, with a 105 ksi minimum yield (95 ksi over 2½ in.) and a 35 HRC hardness cap; no stress-rupture test.
Nuts and washers
A453 660 nuts are made in the same alloy and class as the studs so the whole joint expands together; there is no separate A194 grade. Washers are usually A-286 or a stabilised stainless. Silver plating or a high-temperature anti-seize is recommended on the threads because A-286 galls readily.
Testing, certification and marking
- Tensile and hardness tested per heat-treat lot on the finished product
- Grade symbol 660 with class letter, the M1/M2/R1/R2 type designation and manufacturer's identification on every piece; Class D is also stamped NR
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
- Stress-rupture tested at 1200 °F where the design temperature is above 800 °F (not required for Class D; waivable on the order, with material marked NR)
- Heat-treat cycle (class) recorded on the certificate
Recent A453 660 jobs.
ASTM A193 Grade B16
Vanadium-strengthened Cr-Mo bolting that holds its strength where B7 starts to relax — steam turbines, HP steam flanges and hot valve bonnets.
ASTM A193 / ASME SA-193ASTM A193 Grade B8C Class 1 (347 Stainless)
347 stainless bolting stabilised with niobium against sensitisation — for hot hydrogen, refinery and welded stainless service between 800 and 1500 °F.
ASTM A193 / ASME SA-193ASTM A193 Grade B8 Class 1 (304 Stainless)
304 stainless bolting — Class 1 for corrosion resistance and cryogenic-to-1500 °F service, Class 2 strain hardened to 125 ksi for strength.