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 Tap Studs (EN 10269 / 1.7709) Cr-Mo-V Q+T Bolting
21CrMoV5-7 tap studs are double-end studs with a blind-tap end on one side (anchored into a tapped hole in the parent casing) and a nut-end on the other side. The dominant fastener for steam-turbine half-joint bolting and gas-turbine casing flange bolting, supplied from EN 10269 1.7709 bar in M16 to M120 thread sizes.
Tap Studs Designs and Variants
The tap-end thread length is conventionally 1.0 to 1.25 times the major diameter. The nut-end thread length is the overall stud length minus the tap-end length minus the central plain shank. Three configurations: standard tap stud (DIN 938 / DIN 939); extended tap stud for thick casing walls; reduced-shank tap stud for cyclic-fatigue service.
Size Range
| Standard | Thread range | Length range |
|---|---|---|
| DIN 938 (tap-end 1.0 x d) | M16 to M120 | 50 to 800 mm |
| DIN 939 (tap-end 1.25 x d) | M16 to M120 | 50 to 800 mm |
| DIN 940 / DIN 949 (tap-end 2.0 x d / 2.5 x d) | M16 to M120 | 50 to 800 mm |
| Unified inch tap studs (ASME) | 5/8 inch to 4 inch | 2 inch to 32 inch |
Mechanical Properties (Q+T, EN 10269)
| Property | Value | Condition |
|---|---|---|
| Tensile (Rm) | 700 to 850 MPa | RT, Q+T |
| 0.2 percent proof stress (Rp0.2) | ≥550 MPa | RT, Q+T |
| Elongation A5 | ≥16 percent | RT, longitudinal |
| Charpy V impact (KV) | ≥63 J | 20 deg C |
| 0.2 percent proof at 500 deg C | ≥450 MPa | elevated-temp |
| Hardness | 210 to 250 HBW | Q+T |
Standards Anchor
Manufactured to EN 10269 chemistry and mechanicals. Dimensional standards: DIN 938 / DIN 939 / DIN 940 / DIN 949 for tap-end length ratio. Thread to ISO 261 (metric coarse) or ASME B1.1 (Unified). Inspection to EN 10204 type 3.1 with type 3.2 witness on call-out, standard practice for turbine OEM procurement (Siemens, GE, BHEL, Mitsubishi Power).
Companion Hardware
Matched-grade Cr-Mo-V companions ship from the same heat lot on call-out: 21CrMoV5-7 nuts, washers, threaded rod, stud bolts and round bar.
Applications
Tap studs are specified primarily in steam turbine HP and IP casing bolting at metal temperatures to 550 deg C, and in gas turbine compressor casing flanges. Companion body-bound studs are used in the same joints when shear-load transfer through the bolt body is required.
Inspection Documentation
Default delivery is EN 10204 type 3.1 mill test certificate with heat number, melt-shop pour record, chemistry to EN 10269 21CrMoV5-7, room-temperature tensile and 0.2 percent proof stress, elevated-temperature 0.2 percent proof at the design temperature, Charpy V impact at 20 deg C, hardness, full Q+T cycle chart and dimensional report tied to the heat lot. Type 3.2 with Lloyd's Register, DNV, BV, SGS or TUV witness inspection on call-out and standard practice on turbine and pressure-vessel procurement.
Frequently Asked Questions
Q. What is the difference between DIN 938 and DIN 939 tap studs?
The tap-end thread length differs: DIN 938 is 1.0 x diameter; DIN 939 is 1.25 x diameter. DIN 939 gives slightly more thread engagement in the parent casing for heavier-loaded turbine joints. DIN 940 (2.0 x d) and DIN 949 (2.5 x d) are used for deeper engagement in cast-iron or aluminium parent material.
Q. Why use a tap stud instead of a through-bolt on a turbine casing?
On a turbine half-joint where the casing thickness can run 300 to 600 mm, a through-bolt would have to span the full casing thickness and the shank would be uneconomical. A tap stud anchors into a blind tapped hole one one side and accepts a nut on the other, halving the effective bolt length.
Q. What is the maximum thread size for 21CrMoV5-7 tap studs?
M120 in metric, 4 inch in Unified. Larger sizes on call-out from forged blank with custom thread cutting.
Q. Do you supply tap studs with EN 10204 type 3.2 certification?
Yes. Type 3.2 with Lloyd's, DNV, BV, SGS or TUV witness inspection is the standard practice on every Siemens, GE, BHEL, Mitsubishi Power turbine procurement.
Related 21CrMoV5-7 Form Factors
Browse the full 21CrMoV5-7 form-factor range: Round Bar · Stud Bolts · Hex Bolts · Heavy Hex Bolts · Body-Bound Studs · Anchor Bolts · U-Bolts · Threaded Rod · Nuts · Washers · Forgings. Back to the 21CrMoV5-7 Alloy Hub.
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