Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
21CrMoV5-7 Weld Studs (Drawn-Arc Stud Welding to ISO 13918)
21CrMoV5-7 weld studs are drawn-arc stud-welded fasteners machined from EN 10269 Werkstoff 1.7709 Cr-Mo-V Q+T bar for steam-turbine hardware that operates at elevated metal temperatures within the design envelope. The weld stud is welded directly to the parent casing or heat-shield plate using a drawn-arc stud-welding gun; no clearance hole is drilled in the parent metal. Once welded, the stud projects from the surface and accepts a nut to retain insulation blankets, thermocouple wells, or sheet-metal heat shielding. Welding qualified to ISO 14555 / AWS D1.6 stud-welding procedure.
Weld Stud Size Range
| Standard | Thread range | Length range |
|---|---|---|
| ISO 13918 (drawn-arc stud welding geometry) | M6 to M30 | 12 to 150 mm |
| Custom stud weld base ferrule | per drawing | per drawing |
Drawn-Arc Stud Welding Process (ISO 14555 / AWS D1.6)
The drawn-arc cycle: the stud is held in a stud-welding gun against the parent metal surface; a pilot arc is struck and the stud lifts a controlled distance; the main arc transfers and melts the stud base + parent surface; spring-loaded gun plunges the molten stud into the molten parent pool; the weld solidifies forming a full-strength fillet. ISO 14555 / AWS D1.6 governs the procedure qualification with witness coupon testing (bend test, hardness traverse, weld-base macroetch).
Standards Anchor
21CrMoV5-7 weld studs to EN 10269 for stud chemistry and mechanicals. Weld stud geometry to ISO 13918 with collar diameter 1.4 times the thread major and weld base ferrule profile suitable for the drawn-arc cycle. Welding procedure qualified to ISO 14555 (European) or AWS D1.6 (US stainless steel + nickel alloy welding code). PWHT for welded joints per the project welding engineer specification.
Inspection
EN 10204 type 3.1 mill test certificate by default with heat number, EN 10269 21CrMoV5-7 chemistry, Q+T heat-treatment cycle, mechanical results, hardness, and dimensional report. Type 3.2 with third-party witness on call-out (Lloyd's Register, DNV, BV, SGS, TUV). Drawn-arc weldability qualification to ISO 14555 / AWS D1.6 procedure-qualification record (PQR) on request; TorqBolt supplies witness coupons of the stud lot for the customer to run their own qualification weld trials.
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.
| Element | Min % | Max % | Role |
|---|---|---|---|
| Carbon (C) | 0.17 | 0.25 | Q+T hardenability |
| Silicon (Si) | — | 0.40 | Deoxidation |
| Manganese (Mn) | 0.40 | 0.80 | Hardenability + solid-solution |
| Phosphorus (P) | — | 0.030 | Tramp limit for toughness |
| Sulphur (S) | — | 0.030 | Tramp limit |
| Chromium (Cr) | 1.20 | 1.50 | Hardenability + creep |
| Molybdenum (Mo) | 0.55 | 0.80 | Secondary hardening |
| Vanadium (V) | 0.20 | 0.35 | V4C3 carbide strengthening |
| Nickel (Ni) | — | 0.60 | Residual |
| Aluminium (Al) | — | 0.030 | Grain refinement |
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.
| Property | Value | Condition |
|---|---|---|
| Tensile (Rm) | 700 to 850 MPa | RT, Q+T |
| 0.2 percent proof (Rp0.2) | ≥550 MPa | RT, Q+T |
| Elongation A5 | ≥16 percent | RT, longitudinal |
| Charpy V impact (KV) | ≥63 J | 20 deg C, longitudinal |
| 0.2 percent proof at 500 deg C | ≥450 MPa | EN 10269 elevated-temp |
| Hardness (HBW) | 210 to 250 | Q+T condition |
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
Request a Quote
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
Q. Why use weld studs instead of tap studs on turbine hardware?
Weld studs avoid drilling clearance holes in heat-shield plates or casing surfaces — quicker installation in restricted-access service areas, no thread-tap operation, no clearance-hole machining. Standard for retaining insulation blankets, thermocouple wells, and lagging sheets on turbine casings.
Q. What is the drawn-arc stud welding cycle?
The stud is held in a stud-welding gun against the parent surface; a pilot arc is struck and the stud lifts a controlled distance; the main arc transfers and melts the stud base plus parent surface; the gun plunges the stud into the molten pool; the weld solidifies forming a full-strength fillet in 0.1-0.5 seconds.
Q. Is PWHT required on 21CrMoV5-7 weld studs?
For drawn-arc welds on thin sheet (less than 3 mm parent) PWHT is not always required because the heat-affected zone is small enough that hydrogen content stays below the cracking threshold. For thicker parent material or critical-service welds, PWHT at 690 to 720 deg C to the standard 21CrMoV5-7 procedure is the conservative choice.
Q. What is the maximum stud size for drawn-arc stud welding?
M30 in standard production stud-welding equipment. Above M30 the energy + plunge depth requirements exceed typical portable gun capacity; gas-shielded short-cycle stud welding (M30 to M64) or capacitor-discharge stud welding (small studs only) are alternatives.
Q. Do you supply weld studs with the matched ferrule and flux pellet?
Yes. Drawn-arc weld studs ship with the standard ceramic weld base ferrule to ISO 13918 and (where applicable) the deoxidant flux pellet pre-fitted to the stud base. Customer-specific ferrule patterns on call-out.
Satisfaction Survey
