640 Stainless Steel Pipe – 15-5PH Vacuum-Remelted Ultra-Tough Tubular Grade for 1310 MPa Strength with 304-Class Corrosion

640 Stainless Steel Pipe—marketed globally as 15-5PH or UNS S15500—is the vacuum-remelted precipitation-hardening (PH) tubular solution that delivers the cleanest, toughest PH stainless pipe on the market. With 14–15.5 % Cr, 3.5–5.5 % Ni, 2.5–4.5 % Cu and ≤0.07 % C, 640 Stainless Steel Pipe can be aged from 480 °C to 620 °C to reach 1310 MPa tensile while maintaining Charpy impact ≥ 25 J at –40 °C and corrosion resistance that equals or exceeds 630 pipe in most chloride media. The grade stays magnetic, machines like 304 in the solution-annealed state, and experiences < 0.05 % dimensional growth during aging—precision seamless or welded tubes hold tolerance without post-grind. From sour-service downhole tubing to aerospace hydraulic lines, 640 Stainless Steel Pipe gives piping designers the only PH stainless alloy that truly combines ultra-high strength, superior transverse toughness, excellent corrosion resistance and vacuum-grade cleanliness in one cost-effective tubular form.

Key Features & Benefits – Why 640 Stainless Steel Pipe Outperforms 630, 316 and Austenitic Tubular Grades

Precipitation Hardening = Customisable Ultra-High Strength

• H900 (480 °C) yields 1310 MPa tensile / 1170 MPa yield / 40 HRC—ideal for high-pressure downhole tubing and aerospace hydraulic lines.
• H1150 (620 °C) still provides 1000 MPa tensile with 20 % elongation and superior stress-corrosion resistance for subsea flowlines.

Vacuum-Remelted Cleanliness = Superior Transverse Toughness in Pipe

• VIM+VAR reduces inclusion count to < 5 ppm, raising Charpy impact to 25 J at –40 °C—double that of 630 pipe in the same orientation.
• Fatigue limit 550 MPa (H900) exceeds 630 pipe by 15 %, extending service life in rotating shafts and aircraft hydraulic circuits.

Excellent Corrosion Resistance in Marine & Chloride Piping Media

• PREN ≈ 18.5 meets ASTM G48 pitting test at 30 °C; outperforms 630 and equals 316L in neutral chlorides; passes 1000 h ASTM B117 with < 2 % red rust.
• NACE MR0175 approved for sour service up to H1150 condition—suitable for downhole tubing in H₂S partial pressure ≤ 10 bar at 120 °C.

Excellent Weldability & Machinability in Solution-Annealed Pipe

• Machines at 85 % of AISI B1112 baseline; solution-annealed hardness HB 270 allows high-speed trepanning before aging.
• Weldable with 15-5PH, 17-4PH or 309L fillers; no pre-heat on wall thickness < 25 mm, and aging restores full HAZ strength.

Low Distortion During Heat Treatment of Pipe

• Aging at 480–620 °C causes < 0.05 % dimensional change—precision seamless pipes hold ±0.05 mm wall tolerance without post-aging sizing.

Cost-Effective & Price-Stable Tubular Solution

• Nickel content 25 % lower than 316L; precipitation hardening eliminates costly quench/temper furnaces, cutting total pipe cost 15 % versus duplex 2205.

Technical Specifications

Tube dimensions: seamless OD 6–219 mm, wall 0.5–25 mm; welded OD 16–610 mm, wall 0.8–12 mm. Values comply with UNS S15500, AISI 640, EN 1.4545 and ASTM A693/AMS 5659.

Caption: Seamless 640 Stainless Steel Pipe showcasing smooth surface and precision manufacturing.

Applications and Use Cases – Proven 15-5PH Pipe Performance from Sour-Service Downhole Lines to Aerospace Hydraulic Circuits

Oil & Gas Downhole Tubing

H1150 640 Stainless Steel seamless pipe (OD 60 mm, wall 5 mm) resists 15 % H₂S at 120 °C while carrying 1 000 MPa tensile—allowing 30 % thinner wall than 17-4PH and eliminating costly clad layers.

Aerospace Hydraulic Lines

Cold-drawn OD 12 mm × 1.5 mm 640 pipe aged to H900 withstands 1 000 bar cyclic pressure; 40 HRC resists erosion while magnetic property enables non-destructive eddy-current inspection.

Marine Propeller Shaft Liners

H1025 640 pipe (OD 150 mm, wall 8 mm) resists seawater pitting while carrying 1 070 MPa yield—40 % higher than 316L, permitting smaller OD and lower inertia.

Chemical Processing Pipes

Welded 640 pipe in H1150 handles 200 °C hydrocarbon + brine; PREN 18.5 equals 316L while strength triples, eliminating thick-wall carbon steel with internal coating.

High-Pressure Pump Shaft Tubing

OD 25 mm × 3 mm seamless 640 tube drives centrifugal pumps at 500 MPa cyclic bending; vacuum remelt ensures zero transverse delamination after 10 million cycles.

Nuclear Reactor Piping

H950 640 seamless pipe (OD 40 mm, wall 2 mm) meets nuclear cleanliness (Co < 0.05 %); low magnetic permeability (< 1.05) avoids interference with control-rod sensors.

Plastic Injection Mould Cooling Lines

H900 640 pipe resists 40 % glass-filled nylon at 300 °C while thermal conductivity (19 W·m⁻¹·K⁻¹) speeds cycle times versus beryllium-copper lines.

Caption: Cross-sectional view of polished seamless 640 Stainless Steel Pipe, highlighting wall thickness and material integrity.

Comparison with Other Grades – 640 vs 630, 316, 304, 13-8PH Pipe

Pros: 640 Stainless Steel pipe offers the best combination of ultra-high strength, excellent transverse toughness and vacuum-grade cleanliness among standard PH pipe grades.
Cons: Higher alloy cost and magnetic properties; not suitable for non-magnetic or strong reducing-acid piping.

Caption: 640 Stainless Steel Pipe used in high-strength precipitation-hardening applications, demonstrating versatility in demanding environments.

Manufacturing Process & Quality Assurance

We produce 640 Stainless Steel Pipe via vacuum-induction melting (VIM) + vacuum-arc remelting (VAR) for aerospace cleanliness, then pierce or extrude to hollow shell. Cold-pilgering reduces OD and wall to final size, solution-annealing at 1040 °C produces soft, straight condition. Aging at 480 °C (H900) to 620 °C (H1150) precipitates nano-copper particles, raising hardness to 33–40 HRC. Finishes include pickled matte, ground OD Ra ≤ 0.4 µm and polished ID Ra ≤ 0.2 µm for hydraulic service. Every heat is certified to ASTM A693/AMS 5659, ISO 9001 and optional AS/EN 9100; tests include ICP chemistry, tensile at room and elevated temperature, Charpy impact, ASTM G48 pitting corrosion, ultrasonic wall thickness and grain size. Third-party inspection certificates accompany each shipment for direct aerospace PPAP submission.

Maintenance & Care Tips for 640 Stainless Steel Pipe

Clean pipe interiors with warm water and neutral detergent; rinse and dry to prevent chloride build-up. For marine service, periodic fresh-water flushing removes salt deposits. Passivate in 2 % citric acid after fabrication to dissolve free iron. Do not expose aged (H900) sections to >425 °C for prolonged periods to avoid over-aging. Store pipe horizontally on plastic-covered racks to prevent carbon-steel contact and subsequent rust staining.

Frequently Asked Questions on 640 Stainless Steel Pipe

Q: What are the advantages of 640 Stainless Steel Pipe over 630 (17-4PH) pipe?
A: Vacuum remelt gives 640 superior transverse toughness, fatigue life and cleanliness while matching 630 strength and corrosion resistance.

Q: What heat treatment conditions are available for 640 Stainless Steel Pipe?
A: H900 (480 °C) for max strength 1310 MPa; H1025 (550 °C) for balance; H1150 (620 °C) for max toughness and NACE sour-service compliance.

Q: Is 640 Stainless Steel Pipe suitable for sour service environments?
A: Yes—H1150 condition is NACE MR0175 approved for H₂S partial pressure ≤ 10 bar at 120 °C, outperforming 420 and 17-4PH pipe.

Ready to combine 1310 MPa strength with vacuum-clean toughness and 304-class corrosion in one seamless or welded pipe? Contact us today for custom quotes on 640 Stainless Steel Pipe—mill-direct pricing, global delivery and full metallurgical support included.