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Grade 660 Double End Stud
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Name: Grade 660 Double End Stud
Standard: ASTM
Material: A453 Gr.660
Size: 3/4 inch
Lenght: 130 mm
Temperature: 650-700℃
Surface: Natural color
Standard: ASTM
Material: A453 Gr.660
Size: 3/4 inch
Lenght: 130 mm
Temperature: 650-700℃
Surface: Natural color
Quantity
Grade 660 Double End Stud is manufactured from ASTM A453 Gr. 660 alloy, size 3/4"× 130 mm. It withstands 650–700 °C continuously and up to 800 °C for short periods while retaining high strength. Supplied in the as-rolled finish, it is the fastener of choice for nuclear heat-exchangers and petrochemical flanges.
What are the effects of the amount of Ni element content in ASTM A453 Gr.660 material on the material's performance?
ASTM A453 Gr. 31660 caps nickel at 24.0–27.0 %. The notes below split the influence of high vs. low Ni on critical properties so that design, purchasing and heat-treatment can make rapid trade-offs.
ASTM A453 Gr. 31660 caps nickel at 24.0–27.0 %. The notes below split the influence of high vs. low Ni on critical properties so that design, purchasing and heat-treatment can make rapid trade-offs.
1. Matrix stability and phase transformation
- Ni ↑ → austenite is stabilised, suppressing σ, α′ and other brittle phases during ageing or service; toughness is preserved at 650–700 °C and sudden brittle fracture at thread roots of Grade 660 Double End Stud is avoided.
- Ni ↑ → austenite is stabilised, suppressing σ, α′ and other brittle phases during ageing or service; toughness is preserved at 650–700 °C and sudden brittle fracture at thread roots of Grade 660 Double End Stud is avoided.
- Ni ↓ (<24 %) → matrix becomes meta-stable; stress–temperature coupling can trigger local martensite, a sudden hardness jump and a drop in impact toughness, leading to delayed cracking of Grade 660 Double End Stud during installation or thermal cycling.
2. High-temperature strength and creep life
- Ni is the “feed-stock” for γ′ (Ni₃Ti) precipitates. More Ni gives a larger, finer γ′ population, raising 650 °C rupture strength by 15–25 % and extending creep life exponentially so that flange preload of Grade 660 Double End Stud remains ≥80 % after 100 000 h.
- Ni is the “feed-stock” for γ′ (Ni₃Ti) precipitates. More Ni gives a larger, finer γ′ population, raising 650 °C rupture strength by 15–25 % and extending creep life exponentially so that flange preload of Grade 660 Double End Stud remains ≥80 % after 100 000 h.
- Ni ↓ → less γ′; creep voids cluster on grain boundaries, life shortens and the 10⁵ h target for ultra-super-critical cylinders cannot be met by Grade 660 Double End Stud.
3. Oxidation and corrosion
- Ni ↑ → a continuous NiO film forms in reducing, alkaline or chlorided environments, cooperating with Cr₂O₃ to improve general corrosion and stress-corrosion-cracking (SCC) resistance; for coastal plants it markedly lowers salt-fog pitting risk of Grade 660 Double End Stud.
- Ni ↑ → a continuous NiO film forms in reducing, alkaline or chlorided environments, cooperating with Cr₂O₃ to improve general corrosion and stress-corrosion-cracking (SCC) resistance; for coastal plants it markedly lowers salt-fog pitting risk of Grade 660 Double End Stud.
- Ni ↓ → the film is discontinuous, pitting potential drops and chloride–iron SCC appears, causing thread-galling of Grade 660 Double End Stud during start-ups/shut-downs.
4. Thermal expansion and flange matching
- Each extra 1 % Ni increases the mean expansion coefficient (20–700 °C) by ~0.2–0.3 × 10⁻⁶ °C⁻¹. Holding 24–27 % matches the alloy to austenitic piping/flanges, keeps preload loss <10 % across cycles and prevents “thermal-relaxation” leakage of Grade 660 Double End Stud.
- Each extra 1 % Ni increases the mean expansion coefficient (20–700 °C) by ~0.2–0.3 × 10⁻⁶ °C⁻¹. Holding 24–27 % matches the alloy to austenitic piping/flanges, keeps preload loss <10 % across cycles and prevents “thermal-relaxation” leakage of Grade 660 Double End Stud.
5. Weldability and hot-cracking sensitivity
- Ni ↑ → narrows the solid–liquid range, lowers hot-crack tendency and lets properties be restored by ageing alone; when Grade 660 Double End Stud is welded to 316H tube-sheet, rework is reduced.
- Ni ↑ → narrows the solid–liquid range, lowers hot-crack tendency and lets properties be restored by ageing alone; when Grade 660 Double End Stud is welded to 316H tube-sheet, rework is reduced.
- Ni ↓ → the range widens, low-melting Ni-S/Ni-P phases segregate to grain boundaries, raising micro-crack risk and causing early failure of Grade 660 Double End Stud weldments in 690 °C creep tests.
6. Practical engineering guidance
- For ≤600 °C and cost-sensitive duties, 24–25 % Ni is acceptable; Grade 660 Double End Stud still meets standard bolt properties.
- For 650–700 °C long-life parts (nuclear, ultra-super-critical turbines, gas-turbine rotor bolts) specify Ni ≥26 % plus 720 °C ×16 h ageing to fully develop γ′ and ensure Grade 660 Double End Stud stays tight for 100 000 h.
- For ≤600 °C and cost-sensitive duties, 24–25 % Ni is acceptable; Grade 660 Double End Stud still meets standard bolt properties.
- For 650–700 °C long-life parts (nuclear, ultra-super-critical turbines, gas-turbine rotor bolts) specify Ni ≥26 % plus 720 °C ×16 h ageing to fully develop γ′ and ensure Grade 660 Double End Stud stays tight for 100 000 h.
- On receipt, add a 650 °C creep or 100 h relaxation test to prove that the high-Ni advantage really reaches Grade 660 Double End Stud.
Summary: Raising Ni from 24 % to 27 % is the step that turns “stainless steel” into a “high-temperature alloy”; within design limits, the higher the better, giving Grade 660 Double End Stud its greatest insurance for long-term safe operation.
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