The ASTM B861 Specification
ASTM B861 defines the requirements for seamless titanium and titanium alloy pipe intended for general corrosive service. The standard covers dimensional tolerances, chemical composition, tensile properties and testing requirements, and it applies to pipe in nominal sizes from small bore through large diameter. Grade 2 is the most commonly ordered grade in this specification because it delivers the best overall balance of properties for industrial piping.
Composition and Identification
Grade 2 titanium is commercially pure material with maximum limits of 0.30 percent iron, 0.25 percent oxygen, 0.08 percent carbon, 0.03 percent nitrogen and 0.015 percent hydrogen. The UNS designation is R50400, and in European practice the material is cross-referenced to DIN W.Nr. 3.7035. These designations all describe the same Grade 2 chemistry, allowing buyers to specify the material under the naming convention they use locally.
Mechanical Properties and Service Limits
Grade 2 pipe provides a minimum tensile strength of 345 MPa and a minimum yield strength of 275 MPa, with good elongation that supports bending and flanging during installation. The material is normally supplied annealed for maximum ductility and stable properties. Its useful service temperature range is broad, and the alloy performs well from cryogenic temperatures up to about 300 degrees Celsius in most corrosive services.
Corrosion Resistance in Industrial Service
Grade 2 resists seawater, chloride brines, oxidizing acids, alkalis and most organic chemicals through its stable, self-healing oxide film. It is widely used in environments where stainless steels suffer pitting or stress corrosion, such as marine piping, heat exchanger tube bundles and chemical reactor piping. The material also resists erosion-corrosion in high-velocity seawater, which makes it a standard choice for sea water cooling circuits.
Manufacturing of Seamless Pipe
Seamless Grade 2 pipe is produced from forged or rolled hollow blooms using rotary piercing, elongation and final cold finishing or hot finishing, followed by annealing, straightening and testing. Each pipe receives hydrostatic testing and, when required, eddy current or ultrasonic examination. Dimensional control of outside diameter, wall thickness and straightness ensures the pipe fits flanges and fittings without rework.
Applications Across Industries
Grade 2 seamless pipe serves chemical plants, desalination facilities, power stations, offshore platforms, pulp and paper mills, and food processing plants. It is used for process lines, steam condensate lines, seawater supply and discharge piping, and instrument tubing. The long service life of titanium pipe, often exceeding the plant design life, reduces maintenance cost even though the initial material price is higher than carbon steel.
Frequently Asked Questions
Q: What is the difference between ASTM B861 and ASTM B862?
A: ASTM B861 covers seamless titanium pipe, while ASTM B862 covers welded titanium pipe produced from strip or plate with a longitudinal weld seam.
Q: What is UNS R50400?
A: UNS R50400 is the Unified Numbering System designation for Grade 2 commercially pure titanium, and DIN W.Nr. 3.7035 is the common European equivalent.
Q: What are the mechanical properties of Grade 2 titanium pipe?
A: Grade 2 pipe offers a minimum tensile strength of 345 MPa and a minimum yield strength of 275 MPa in the annealed condition.
Q: Can Grade 2 titanium pipe be welded in the field?
A: Yes. Field welding uses gas tungsten arc welding with inert gas shielding, and Grade 2 welds are ductile and corrosion resistant when the joint is kept clean.
Q: Is Grade 2 titanium pipe suitable for seawater service?
A: Grade 2 is one of the best materials for seawater piping, resisting pitting, crevice attack and erosion-corrosion in high-velocity chloride service.
