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7709 steel is a high-performance alloy steel, also known as 21CrMoV5-7, and is widely used in the manufacturing of high-strength, high-temperature-resistant fasteners such as bolts and nuts. The following is an in-depth introduction to the screws made of 1.7709 material:
It mainly consists of carbon (C: 0.17–0.25), silicon (Si: 0.15–0.35), manganese (Mn: 0.35–0.85), chromium (Cr: 1.20–1.50), molybdenum (Mo: 0.65–0.80), and vanadium (V: 0.25–0.35) and other elements. The reasonable proportion of these elements gives the steel excellent comprehensive properties.
In the heat-treated state, 1.7709 steel has high strength and good mechanical properties. Its yield strength (Rp0.2) can reach ≥550 MPa, tensile strength (PM) can reach ≥700 MPa, elongation (A) ≥16%, and reduction of area (A) ≥60%.
This material can still maintain good mechanical properties in high-temperature environments and is suitable for working conditions with temperatures exceeding 300°C.
Aerospace engine: The turbine blade fasteners are manufactured using nickel-based high-temperature alloys (such as GH4049), maintaining a tensile strength of ≥ 1000 MPa at 600–900℃, and achieving complex shape processing through die forging technology.
Spacecraft structure: Components used for connecting the combustion chamber of the rocket engine, must withstand instantaneous high temperatures (>1200℃) and vibration loads.
Nuclear power plant: The bolts of the reactor pressure vessel must meet a lasting strength of ≥ 95 MPa (at 700°C/100,000 hours), to prevent hydrogen embrittlement and stress corrosion cracking.
Gas turbine: High-temperature bolts (such as A286 alloy) are used to fix the turbine discs and must undergo creep limit tests (1% total deformation/1000 hours).
Refining and processing unit: The bolts of the hydrogenation reactor need to be used for a long time under high temperature and high pressure (400℃/20MPa), and the material must pass the hydrogen-induced delayed fracture test.
Mold manufacturing: The fastening components of composite material molds need to match a low thermal expansion coefficient (CTE ≤ 10⁻⁶/℃) to maintain dimensional stability.
New energy vehicles: The motor shaft bolts are made of titanium alloy (such as TC4), with a tensile strength of up to 900 MPa and no magnetic interference. The tapping process needs to be optimized to reduce work hardening.
| Digital Grade | Material | Executive Standard | Withstand Temperature |
|---|---|---|---|
| 2.4851 / UNS N06601 / Alloy601 | NiCr23Fe | DIN17742 / EN10095 / ASTM B166 | 1200℃ |
| 2.4633 / UNS N06025 / Alloy602 | NiCr25FeALY | DIN EN 10302 / ASTM B166 | 1200℃ |
| 2.4816 / UNS N06600 / Alloy600 | NiCr15Fe | DIN17742 / EN10095 / ASTM B166 | 1150℃ |
| 1.4841 / AISI310S / AISI314 | X15CrNiSi25-21 | EN10095 / SEW470 | 1150℃ |
| 2.4665 / UNS N06002 / Alloy X | NiCr19NbMo | ASTM B572 | 1100℃ |
| 2.4663 / UNS N06617 / Alloy617 | NiCr23Co12Mo | ASTM B166 | 1100℃ |
| 1.4845 / AISI310 / AISI3105 | X8CrNi25-21 | EN10095 / SEW470 / ASTM A276 | 1050℃ |
| 1.4828 / AISI3095 | X15CrNiSi20-12 | EN10095 / SEW470 / ASTM A276 | 1000℃ |
| 2.4969 / UNS N07090 / Alloy90 | NiCr20Co18Ti | DIN EN10302 / BS 2HR2 | 920℃ |
| 1.4878 / AISI 321H | X8CrNiTi18-10 | EN10095 / SEW470 | 850℃ |
| 2.4668 / UNS N07718 / Alloy 718 | NiCr19Fe19Nb5Mo3 | DIN EN 10269 / ASTM B637 | 700℃ |
| 1.4980 / Alloy268 / 660A/B/C/D | X6NiCrTiMoVB25-15-2 | DIN EN10269 / ASTM 453 | 650℃ |
| 1.7709 | 21CrMoV5-7 | DIN EN 10269 | 550℃ |
| 1.7218 | 25CrMo4 | DIN EN 10269 | 400℃ |
| 1.4404 / AISI 316L | X2CrNiMo17-12-2 | DIN EN 10269 / 10272 | 400℃ |
