21CrMoV5-7 Bolts (Werkstoff 1.7709 / EN 10269)

21CrMoV5-7 bolts are the parent fastener category covering every bolt form-factor machined from EN 10269 Werkstoff 1.7709 Cr-Mo-V Q+T bolting bar. The bolt range includes hex bolts (DIN 931 / ISO 4014), heavy hex bolts (ASME B18.2.1), stud bolts (double-end equal-thread), tap studs (DIN 938/939/940/949 for turbine half-joints), body-bound studs (H7/n6 ground-shank for cyclic-load joints), anchor bolts (L-bolts, J-bolts, headed anchors), and U-bolts. All forms ship with matched-grade nuts and washers from the same heat lot on call-out.

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21CrMoV5-7 Bolt Form-Factor Range

Universal Size Range

21CrMoV5-7 bolts ship in metric M-thread coarse and fine (ISO 261 / DIN 13) from M12 to M120, and in Unified UN, UNC, UNF (ASME B1.1) from 1/2 inch to 4 inch. Lengths from 40 mm cut-to-order for standard hex bolts up to 800 mm for tap studs and body-bound studs. Larger sizes on call-out from forged blank.

Standards Anchor

21CrMoV5-7 bolts are manufactured to EN 10269 for chemistry, mechanicals and inspection. Pressure-vessel parallel approval to VdTUV Wb 350. US cross-procurement uses ASTM A193 Grade B16 with dual-certification.

21CrMoV5-7 Chemistry (Werkstoff 1.7709 Element Ranges)

21CrMoV5-7 (Werkstoff 1.7709) chemistry is fixed within a tight Cr-Mo-V Q+T window to EN 10269. Carbon at 0.17 to 0.25 percent gives the Q+T hardenability backbone without over-hardening for the secondary temper. Chromium at 1.20 to 1.50 percent provides through-thickness hardenability and stabilises the carbide network for creep. Molybdenum at 0.55 to 0.80 percent suppresses temper embrittlement and contributes to the secondary hardening peak. Vanadium at 0.20 to 0.35 percent drives the V4C3 precipitation during the 680 to 740 deg C temper that locks in the creep envelope. The chemistry window is shared with the AFNOR 20CDV5.7 (French) and Polish 21HMF designations.

21CrMoV5-7 Mechanical Properties

21CrMoV5-7 in the quenched-and-tempered condition holds tensile 700 to 850 MPa, 0.2 percent proof stress at least 550 MPa, elongation A5 at least 16 percent, and Charpy V impact at least 63 J at 20 deg C to EN 10269 acceptance. Typical mill datasheet values run 10 to 20 percent above the standard floor. Elevated-temperature 0.2 percent proof stress holds 450 MPa at 500 deg C and 420 MPa at 550 deg C.

Creep Performance at 500-550 deg C (EN 10269 Annex A)

The defining value-prop of 21CrMoV5-7 is the secondary-hardening creep envelope driven by V4C3 carbide precipitation. The fine V4C3 dispersion formed during the 680 to 740 deg C temper pins dislocation motion during long-time elevated-temperature service. The result is a 100,000-hour stress-rupture envelope to EN 10269 Annex A of approximately 340 MPa at 500 deg C, 290 MPa at 525 deg C, 260 MPa at 540 deg C, and 180 MPa at 550 deg C. Above 550 deg C the V4C3 coarsens faster than the design can tolerate; this is the boundary where the design must step up to Durehete 1055 (Alloy T41 / 1.7729).

Heat Treatment (Q+T Cycle)

The standard cycle for 21CrMoV5-7 is austenitisation at 880 to 940 deg C with hold time of 1 hour per 25 mm section, followed by oil quench. The temper is at 680 to 740 deg C for minimum 2 hours then air cool. The temper temperature is chosen to land on the secondary-hardening peak; below 660 deg C the V4C3 carbide precipitation is under-developed and long-term creep performance suffers; above 750 deg C the carbides over-coarsen and the room-temperature yield drops below the EN 10269 floor of 550 MPa.

Welding Procedure (Matched Cr-Mo-V Filler + PWHT)

21CrMoV5-7 is welded with matched-composition Cr-Mo-V low-hydrogen filler (AWS A5.5 E9018-B3L for SMAW, AWS A5.28 ER90S-B3L for GTAW, AWS A5.23 EB3 for SAW) under preheat 200 to 300 deg C and diffusible-hydrogen cap of 5 ml per 100 g deposited. Post-weld heat treatment at 690 to 720 deg C for 1 hour per 25 mm joint thickness, minimum 2 hours, slow furnace cool to 300 deg C then air cool. The PWHT re-tempers the heat-affected zone and restores creep performance.

Material Selection: 21CrMoV5-7 vs ASTM A193 B16 vs B7 vs Durehete 1055

21CrMoV5-7 sits between ASTM A193 Grade B7 (carbon-Mo only, capped at 450 deg C) and Durehete 1055 (Alloy T41 with Ti+B microalloying, 568 deg C envelope). Direct US cousin: ASTM A193 Grade B16. Dual-certification on call-out.

21CrMoV5-7 Applications by Industry

21CrMoV5-7 covers the bolting envelope from 450 to 550 deg C continuous metal temperature across power generation, refinery and petrochem sectors.

• Steam Turbine Bolts
• Gas Turbine Bolts
• Power Plant Bolting
• Pressure Vessel Bolts
• Boiler Bolts
• Heat Exchanger Bolts
• Fired Heater Bolts
• Petrochem Reactor Bolts

Related 21CrMoV5-7 Forms and Fasteners

21CrMoV5-7 is supplied across the full bolting form-factor range, all to EN 10269 with EN 10204 type 3.1 mill test certificate by default and type 3.2 with third-party witness on call-out.

• Round Bar: raw stock OD 16 to 300 mm
• Bolts (Hub): all bolt form-factors
• Stud Bolts: M12 to M120, lengths 50 to 800 mm
• Hex Bolts + Heavy Hex Bolts
• Tap Studs + Body-Bound Studs
• Weld Studs: drawn-arc stud-welded fasteners
• Anchor Bolts + U-Bolts
• Threaded Rod + Welding Wire
• Nuts + Washers
• Forgings: closed-die and open-die blanks up to 800 kg

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TorqBolt supplies 21CrMoV5-7 (Werkstoff 1.7709) bolting stock and finished fasteners worldwide from Mumbai head office and Rajkot production plant. Type 3.1 EN 10204 mill test certificate by default; type 3.2 with Lloyd's Register, DNV, BV, SGS or TUV witness inspection on call-out. Send your enquiry →

Frequently Asked Questions