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Durehete 900 (EN 10269 / Alloy T22 / 42CrMoV5-6) Cr-Mo-V High-Temperature Bolting Steel
Durehete 900 is the lowest grade of the Durehete family of Cr-Mo-V creep-resistant bolting steels. Its EN designation is 42CrMoV5-6 and its trade alias is Alloy T22, as documented in EN 10269 Annex A. The primary controlling specification is EN 10269. Within the family, Durehete 900 sits one step below Durehete 950 / Alloy T31 / 40CrMoV4-6 and two steps below Durehete 1055 / Alloy T41 / 20CrMoVTiB4-10. The producer of the bar pedigree is Tata Steel UK (formerly Corus Products USA).
Durehete 900 is supplied by TorqBolt as custom-machined high-temperature bolts, stud bolts, hex bolts, heavy hex bolts, tap studs, weld studs, body-bound studs, couplings, U-bolts, fasteners, round bar and forging stock. Procurement is by EN 10269 specification call-out for European and UK power-generation, process-plant and turbine-fastener applications.
Durehete 900 Characteristics and Key Properties
Durehete 900 is engineered for creep-rupture-controlled low-pressure bolting in the elevated-temperature band defined in EN 10269 Annex C. The Cr-Mo-V (EN 10269 42CrMoV5-6) backbone gives the matrix solid-solution carbide stability. The absence of titanium and boron means no MC carbide pinning at grain boundaries; long-term creep performance is therefore governed by the M23C6 carbide population stability, which holds well to 480°C but coarsens above 500°C. Microstructure is tempered bainite with a fine prior-austenite grain size, delivering elevated-temperature creep-rupture design data in EN 10269 Annex C. The alloy is the default fitment for LP turbine casing flange bolts, fired-heater shell flange bolts, refinery flange bolting, and conventional power-plant low-pressure bolting where the simpler chemistry reduces mill cost versus 1055 or 950.
Durehete 900 Chemical Composition (Plain 1Cr-1Mo-V, No Ti, No B)
Durehete 900 chemistry is the simplest in the Durehete family: plain Cr-Mo-V without Ti or B microalloying. Vanadium sits in the 0.30 to 0.50 percent range, lower than Durehete 950 (0.40-0.60) and significantly lower than flagship Durehete 1055 (0.60-0.75). The chemistry is broadly compatible with the ASTM A193 B16 envelope, which is the dominant US standard for Cr-Mo-V stud bolting on refinery flanges. The side-by-side comparison lets the buyer confirm whether 900 is sufficient or whether stepping up to 950 or 1055 is required.
| Element | Durehete 900 | Durehete 950 | Durehete 1055 | ASTM A193 B16 | ASTM A193 B16 |
|---|---|---|---|---|---|
| Carbon (C) | 0.18 to 0.25 | 0.18 to 0.25 | 0.20 to 0.25 | 0.36 to 0.47 | 0.20 to 0.28 |
| Manganese (Mn) | 0.45 to 0.70 | 0.45 to 0.70 | 0.45 to 0.70 | 0.45 to 0.70 | 0.40 to 0.70 |
| Silicon (Si) | 0.10 to 0.35 | 0.10 to 0.35 | 0.10 to 0.35 | 0.15 to 0.35 | 0.15 to 0.35 |
| Chromium (Cr) | 1.00 to 1.50 | 1.00 to 1.50 | 1.00 to 1.50 | 0.80 to 1.15 | 1.00 to 1.50 |
| Molybdenum (Mo) | 0.85 to 1.25 | 0.85 to 1.25 | 0.85 to 1.25 | 0.50 to 0.65 | 0.40 to 0.70 |
| Vanadium (V) | 0.30 to 0.50 | 0.40 to 0.60 | 0.60 to 0.75 | 0.25 to 0.35 | 0.20 to 0.30 |
| Titanium (Ti) | not specified | 0.04 to 0.10 | 0.04 to 0.10 | not specified | not specified |
| Boron (B) | not specified | not specified | 0.005 to 0.010 | not specified | not specified |
| Sulfur, max (S) | 0.025 | 0.025 | 0.025 | 0.040 | 0.025 |
| Phosphorus, max (P) | 0.025 | 0.025 | 0.025 | 0.035 | 0.025 |
Durehete 900 Mechanical Properties (Room Temperature, 480°C and 100,000-Hour Stress-Rupture)
Mechanical envelope at room temperature is typical of the Cr-Mo-V Q&T family. The 480°C yield retention (380 MPa) and 100,000-hour stress-rupture line (180 MPa at 480°C) position Durehete 900 as the entry-grade choice for LP turbine and fired-heater bolting. Above 500°C metal temperature, step up to Durehete 950. Below 425°C, conventional ASTM A193 B7 (1Cr-0.5Mo, no V) is the lower-cost alternative.
| Property | RT | 480°C | 500°C | Test Standard |
|---|---|---|---|---|
| 0.2 percent proof stress (yield) | 650 to 750 MPa | 380 MPa | 340 MPa | BS EN ISO 6892-2 |
| Tensile strength | 800 to 950 MPa | 540 MPa | 500 MPa | BS EN ISO 6892-2 |
| Elongation on 5d | 14 percent min | 16 percent | 18 percent | BS EN ISO 6892-1 |
| Reduction of area | 45 percent min | 50 percent | 55 percent | BS EN ISO 6892-1 |
| Impact energy (Charpy V at 20°C) | 40 J min | not specified | not specified | BS EN ISO 148-1 |
| Hardness | 230 to 280 HB | same | same | ASTM E10 |
| 100,000 h stress-rupture (EN 10269 Annex C) | not specified | 180 MPa | 90 MPa | BS EN ISO 204 |
| Continuous service temperature | minus 30 to 480°C | manufacturer datasheet |
Durehete 900 Heat Treatment (Austenitize 930-960°C, Oil Quench, Temper 670-690°C)
The Durehete 900 cycle is austenitize at 930 to 960°C, oil quench, temper at 670 to 690°C, producing a tempered-bainite microstructure. The austenitizing temperature is the lowest in the Durehete family because the absence of Ti microalloying means no MC carbide undissolution concerns at the lower end of the range. The temper temperature is held at least 30°C above the maximum continuous service temperature (typically 690°C temper for 480°C service) to ensure microstructural stability over the 100,000-hour design life. The cycle is a quenched-and-tempered alloy-steel route. Forging is performed between 850 and 1150°C; stress-relief after final machining is at 640 to 670°C. Full detail on the heat treatment page.
Durehete 900 Welding (Low-Hydrogen, PWHT 650°C / 3 h)
Welding Durehete 900 follows the standard Cr-Mo-V hydrogen-controlled procedure. Pre-heat to 150 to 175°C minimum, GTAW or SMAW with matched 1Cr-0.5Mo-V low-hydrogen consumables (E8018-B2 or E9018-B3 family), interpass temperature held at 150 to 250°C, post-weld dehydrogenation hold at 250°C for 2 hours, then PWHT at 650°C for 3 hours minimum followed by controlled cool. PWHT temperature is held below the original temper temperature so the bulk hardness stays intact. Bolting is supplied in the Q&T condition and is not field-welded; welding procedure development is relevant for repair-weld qualifications and pipe-flange weld neck applications. Full detail on the welding page.
Durehete 900 Standards Cross-Reference (ASTM, EN, ASME)
International specifications relevant to Durehete 900 procurement. The grade has the broadest standards mapping in the Durehete family because plain Cr-Mo-V is a globally familiar chemistry; the closest US match is the universally specified ASTM A193 B16.
| Standard | Scope | Designation |
|---|---|---|
| ASTM A193 Grade B16 | Alloy-steel bolting for high-temperature service, Cr-Mo-V | Workhorse US Cr-Mo-V stud bolting standard |
| ASTM A193 B16 | Alloy-steel bolting for special applications, 1.25Cr-0.5Mo-V Q&T | Closest EN 10269 / A193 B16 match |
| EN 10269 21CrMoV5-7 | Steels and nickel alloys for fasteners with specified elevated-temperature properties | European harmonised match |
| EN 10269 (primary) | European steel forgings for pressure purposes — bolting at elevated temperature | EN 10269 Annex tables |
| EN 10269 + ASME Section II Part D | Allowable stress tables for code-stamped pressure vessels | Design-stress data for A193 B16 / EN 10269 families |
Durehete 900 Applications by Industry (LP Turbines, Fired Heaters, Petrochemical Bolting)
Durehete 900 is bought through specification call-out for low-pressure (LP) turbine bolting, fired-heater bolting, and conventional power-plant low-pressure flange bolting. The grade is preferred where the metal temperature at the bolt circle stays below 480°C, where ASTM A193 B16 is the procurement specification, and where the simpler chemistry (no Ti, no B) reduces mill cost. Application coverage:
- LP Steam Turbine Casing Bolts: low-pressure casing flange bolting at elevated temperature (EN 10269 Annex C) metal temperature, exhaust-end bolting.
- Fired-Heater Bolting: refinery fired-heater shell flange bolts, header-box bolting, return-bend studs.
- HP Turbine Casing Flange Bolting: 480°C maximum-design-condition flange and valve bolting on conventional power-plant casings.
- Petrochemical Heater Bolting: heat-exchanger channel-head studs, reactor flange bolting at intermediate temperatures.
- Subcritical Power-Plant Flange Bolting: secondary-steam piping at 425 to 480°C.
- Refinery Flange Bolting: alloy-steel stud bolts cross-referenced to ASTM A193 B16.
- In-kind replacement bolting on legacy CEGB-vintage UK power plant LP sections.
Durehete 900 vs Durehete 950 vs Durehete 1055 (Pick the Right Grade)
All three Durehete grades are Cr-Mo-V family bolting steels from EN 10269 specification holder. Pick by service temperature and creep-rupture demand. Durehete 900 is the right call for LP turbine, fired-heater and refinery service in the elevated-temperature band defined in EN 10269 Annex C. If service exceeds 500°C, step up to Durehete 950 (Ti microalloyed, 40CrMoV4-6). If service exceeds 540°C, step up to Durehete 1055 (Ti+B microalloyed, 20CrMoVTiB4-10).
| Grade | Microalloy | Continuous Service | YS at Service Temp | Stress-Rupture (100,000 h) | Typical Application |
|---|---|---|---|---|---|
| Durehete 1055 | Cr-Mo-V + Ti + B | 565°C | 480 MPa at 540°C | 280 MPa at 540°C | HP turbine casing, USC bolting |
| Durehete 950 | Cr-Mo-V + Ti (no B) | 525°C | 430 MPa at 525°C | 230 MPa at 525°C | IP turbine, subcritical bolting |
| Durehete 900 | Cr-Mo-V (no Ti, no B) | 480°C | 380 MPa at 480°C | 180 MPa at 480°C | LP turbine, fired-heater bolting |
Durehete 900 Forms and Fasteners (Bolts, Stud Bolts, Threaded Rod from Bar and Forging Stock)
Durehete 900 is a bolting steel, not a plate or pipe material. TorqBolt supplies it as custom-machined bolts and stud bolts produced from forged bar stock through the full Q&T heat-treatment cycle. Forging stock is held in inventory for short-lead-time turnaround orders. India domestic delivery is 3 to 7 working days for stock sizes; project-quantity orders ship through Mumbai port (JNPT) with full mill test certificate cross-referenced to ASTM ASTM A193 B16, third-party witness inspection on call-out, and project documentation pack.
| Form Category | Products |
|---|---|
| Bar and forging stock | Round bar (EN 10269 / ASTM A193 B16), forging stock for in-house bolt-making |
| LP turbine and refinery bolting | Bolts, hex bolts, heavy hex bolts, stud bolts, tap studs, weld studs, body-bound studs |
| Specialised power-gen fasteners | Couplings, U-bolts, threaded rod, nuts, washers, anchor bolts |
Durehete 900 Frequently Asked Questions
What is Durehete 900?
Durehete 900 is the entry-grade plain Cr-Mo-V bolting steel in the Tata Steel UK (formerly Corus); current EN 10269 specification holder Durehete family. Chemistry is 0.18-0.25 C, 1.0-1.5 Cr, 0.85-1.25 Mo, 0.30-0.50 V, with no titanium and no boron. It is qualified Annex C design curves and is used worldwide for LP steam-turbine casing flange bolts, fired-heater bolting, refinery flange bolting, and conventional power-plant low-pressure bolting. Closest US standards equivalents are ASTM A193 Grade B16 (workhorse Cr-Mo-V stud bolting) and ASTM A193 B16 (1.25Cr-0.5Mo-V Q&T).
What is the difference between Durehete 900 and Durehete 950?
The defining difference is titanium. Durehete 900 is plain Cr-Mo-V with vanadium at 0.30-0.50 percent; Durehete 950 adds 0.04-0.10 percent titanium and raises vanadium to 0.40-0.60 percent. The titanium addition refines the MC carbide dispersion and pins prior-austenite grain boundaries, extending the continuous-service envelope from 480°C (Durehete 900) to 525°C (Durehete 950). 900 is the call-out for LP turbine and fired-heater bolting; 950 is the call-out for IP turbine and subcritical plant.
What is the continuous service temperature of Durehete 900?
480°C continuous service. Short-term excursions to 500°C are tolerable. The 480°C upper bound is set by the 100,000-hour stress-rupture line (180 MPa at 480°C) and the M23C6 carbide coarsening kinetics. Above 500°C, the lack of MC carbide pinning (no Ti, no B) leads to faster carbide growth and creep cavitation; for those temperatures step up to Durehete 950 or 1055.
What is the heat treatment for Durehete 900?
Austenitize at 930 to 960°C, oil quench, temper at 670 to 690°C, air cool. The temper temperature is held at least 30°C above the maximum continuous service temperature so the bulk microstructure stays stable over the 100,000-hour design life. The cycle produces a tempered bainite. Stress-relief after final machining at 640 to 670°C is standard.
What MTC do you supply with Durehete 900 bolting?
EN 10204 type 3.1 by default and type 3.2 on request. Heat number, melt-shop pour record, full chemistry cross-referenced to ASTM ASTM A193 B16, mechanical test results at room temperature and at 480°C, Charpy V impact at 20°C, hardness reading to ASTM E10, full Q&T heat-treatment chart with austenitize, quench and temper temperatures and dwell times, dimensional report tied to the heat lot. PMI on request; third-party witness inspection (Lloyds Register, DNV, BV, SGS, TUV Rheinland) on call-out. Project documentation pack supplied for refinery, fired-heater and power-plant bolt-up packages.
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