Titanium Grade 2 Forged Flange, ASTM B381 — R50400 (UNS R50400) Flanges to ASME B16.5 from Baoji

Published by Engineering Team, Shaanxi Qianyi Tuoda Technology Co., Ltd on 2026-11-04

Titanium Grade 2 forged flange · ASTM B381 · ASME B16.5 · UNS R50400

Grade 2 (UNS R50400) forged flanges to ASTM B381 / ASME B16.5 give the corrosion resistance of titanium with the integrity only a forged body provides — no cut-from-plate weak points at bolt load. SXQYTD stocks and machines weld-neck, slip-on, blind, socket-weld, lap-joint and threaded flanges in NPS 1/2–24 in and Class 150–2500, with mill test certificate and PMI. Below is the procurement detail that decides type, class and drilling before you issue a PO.

Material	Grade 2 (UNS R50400)	Principle	Forged body, not cut from plate
Type & stock	WN / SO / BL / SW / LJ / TH, 1/2–24 in	Industry	Chemical, chlor-alkali, seawater, desalination
Standard	ASTM B381 / ASME SB-381 · dim. B16.5	Lead time	3–7 days stock; 2–4 weeks custom

1. What a Grade 2 forged flange is — by grade and by type

By grade, Grade 2 (UNS R50400) is unalloyed commercially-pure titanium — the corrosion-resisting workhorse of the family. ASTM B381 also covers Gr1, Gr3, Gr5, Gr7, Gr9 and Gr12 forgings, so the same forging route serves higher-strength or more corrosion-resistant bodies when the medium demands. By type, ASME B16.5 covers these flange forms: weld neck (WN) for high stress and cyclic load, slip-on (SO) for lower pressure and easy alignment, blind (BL) to close a line or vessel nozzle, socket weld (SW) for small-bore high-pressure, lap joint (LJ) with a stub end for frequent dismantling, threaded (TH) where welding is unwanted, and long weld neck (LWN) for vessel connections. The difference between a forged flange and a plate-cut disc matters: forging flows the grain along the contour and closes porosity, so the body holds bolt load without the laminations a sawn plate can hide.

2. Why Grade 2 — grade vs. medium vs. corrosion

Grade 2 is the default where the medium is oxidizing or neutral. Pick the grade by what flows through the line:

Medium	Recommended grade	Why
Seawater, brine	Gr2; Gr12 for hot crevice	Oxidizing chloride; Gr2 resists pitting.
Wet chlorine, hypochlorite	Gr2	Strong oxidizing duty.
Dilute HCl, H₂SO₄ (reducing)	Gr7 / Gr12	Gr2 dissolves; Pd or Mo/Ni needed.
High strength / high pressure	Gr5 (Ti-6Al-4V)	~2× strength of Gr2.
vs Grade 7 (R52400)	Gr7 only if spec mandates	Gr7 adds Pd for reducing acid, 30–40 % dearer.

Three things that sink a titanium flange if ignored: (1) a titanium flange must never share bolts directly with a carbon-steel flange — without insulating sleeves and washers, galvanic corrosion eats the titanium in any electrolyte; (2) the mating bolt-circle diameter and bolt-hole size must match the other flange exactly, and that is not visible on the material certificate — check it before shipping; and (3) titanium is soft and low in stiffness, so bolt torque must be even and to spec, or the flange rotates and the gasket leaks.

3. Technical standards we build to

• Forging spec: ASTM B381 / ASME SB-381, Grade 2, MTC EN 10204 3.1.
• Dimensions: ASME B16.5, NPS 1/2–24 in, Class 150 / 300 / 600 / 900 / 1500 / 2500.
• Chemistry (R50400): Fe ≤ 0.30 %, O ≤ 0.25 %, C ≤ 0.10 %, N ≤ 0.03 %, H ≤ 0.015 %, Ti balance.
• Mechanical (annealed): tensile ≥ 345 MPa, yield ≥ 275 MPa, elongation ≥ 20 %.
• Inspection: UT on forging, PT on machined faces, PMI on the heat, full dimensional.

4. Manufacturing flow — from billet to your flange

1) Gr2 billet release with MTC & PMI → 2) Induction / furnace heating to forging temperature → 3) Closed-die or open-die forging (grain follows contour) → 4) Trimming and punch → 5) Stress-relief anneal → 6) Pickling / passivation (remove α-case) → 7) CNC machining: facing, boring, bolt holes, RTJ groove → 8) Dimensional + UT/PT → 9) PMI and marking (grade, size, class, heat) → 10) Export packing. Stock flanges are forged and rough-machined ahead; final bore, drilling and facing are done to your class and drilling pattern on order.

5. Key performance

Item	Control value	Note
Tensile strength	≥ 345 MPa	CP-Ti Grade 2.
Yield strength	≥ 275 MPa	Good for pressure class.
Face finish	125–250 RMS (RF serrated)	Per B16.5 raised face.
Bolt-hole tolerance	± 0.8 mm on circle & size	Must match mating flange.
Density	4.51 g/cm³	~60 % lighter than steel.

6. Application industries

Industry	Medium	Typical flange
Seawater / desalination	Seawater, brine	WN / SO, Class 150–300.
Chlor-alkali	Wet Cl₂, bleach	WN, Class 300–600.
Chemical process	Oxidizing acids, salts	WN / BL, Class 150–600.
Marine / offshore	Seawater, splash	LJ / TH for service.

7. Selection guide

By medium: oxidizing / seawater → Gr2; reducing acid → Gr7 or Gr12; high pressure → Gr5. By type: WN for stress and thermal cycling, SO for low-pressure economy, BL to close, SW for small high-pressure bore, LJ for frequent opening, TH for no-weld joints. By class: pick the ASME B16.5 pressure class from design pressure and temperature — Class 150 / 300 cover most seawater and chemical lines, 600+ for high duty. Send medium, NPS, class, face (RF/FF/RTJ) and drilling pattern; we confirm grade and stock in one reply.

8. Customizable items & accessories

• Type and NPS (1/2–24 in), Class 150–2500, RF / FF / RTJ face.
• Drilling: standard ASME B16.5 pattern or custom bolt circle / hole count.
• Surface: pickled, bright-annealed; isolating gaskets and sleeves available.
• Bolting: titanium, Monel or insulated carbon-steel sets to avoid galvanic.
• PMI report, heat-number marking, third-party inspection (SGS / TUV).

9. Lead time, test reports & warranty

Item	Commitment
Lead time	3–7 days from stock; 2–4 weeks custom / exotic grade.
Test reports	MTC 3.1, UT, PT, PMI, full dimensional.
Warranty	12 months against material and workmanship defects from shipment.

10. FAQ

Grade 2 or Grade 7 flange — which should I specify?

For oxidizing media, seawater and wet chlorine, Grade 2 is correct and cheapest. Reach for Grade 7 (R52400, with palladium) only when the line carries a reducing acid with no oxidizer — that is where Gr2 is attacked. Grade 7 costs 30–40 % more, so don't pay for it unless the medium needs it. We stock both.

ASTM B381 or ASME B16.5 — which governs my flange?

Both, for different things. ASTM B381 is the material and forging-quality specification (grade, chemistry, mechanicals, tests). ASME B16.5 is the dimensional standard (NPS, class, facing, bolt circle, drilling). A flange is bought against B381 for the metal and B16.5 for the shape — check you have both on the certificate and drawing.

Can I bolt a titanium flange straight to a carbon-steel flange?

Not without isolation. Titanium and steel are far apart on the galvanic series; in any conductive fluid the titanium becomes the anode and corrodes fast. Use insulating sleeves and washers on the bolts (and an isolating gasket), or bolt up with titanium / Monel fasteners. We can supply the insulated bolting set with the flange.