ASME SB338 UNS R50400 Seamless Titanium Tubes

Overview of ASME SB338 UNS R50400

ASME SB-338 is the standard specification for seamless and welded titanium and titanium alloy tubing for use in heat exchangers, surface condensers and evaporators. It defines chemical composition, mechanical properties, dimensions and testing requirements, including flattening, flaring and non-destructive testing. UNS R50400 is commercially pure (CP) Grade 2 titanium tubing that combines a low weight with high strength and the excellent corrosion resistance inherent in titanium. Because it has no longitudinal seam, seamless tubing offers higher strength and pressure resistance than welded tubing, and it is widely used in oil and gas, chemical processing, aerospace and power generation.

Chemical Composition

Requirements per ASME SB-338 for Grade 2/2H (UNS R50400).

Element (wt %)	Requirement
Carbon, max	0.08
Oxygen, max	0.25
Nitrogen, max	0.03
Hydrogen, max	0.015
Iron, max	0.30
Other elements, each	0.10
Other elements, total	0.40

Mechanical Properties

Requirements per ASME SB-338 for Grade 2 and Grade 2H tubing.

Property	Grade 2	Grade 2H
Tensile strength, min (ksi / MPa)	50 / 345	58 / 400
Yield strength (ksi / MPa)	40-65 / 275-450	40-65 / 275-450
Elongation in 2 in (50 mm), min (%)	20	20

Equivalent Designations

Standard system	Equivalent grade	Standard number
ASTM/ASME	Grade 2	ASTM B338 / ASME SB338
ISO	Grade 2	ISO 5832-2
DIN	3.7035	DIN 17860
JIS	Class 2	JIS H 4600
GB	TA2	GB/T 3625
AMS	4902	AMS 4902

Corrosion Resistance and Applications

Titanium Grade 2 performs excellently in chloride environments, including seawater and bleach, with corrosion resistance far exceeding that of stainless steel and effectively eliminating pitting and crevice corrosion. With a tensile strength of 345-400 MPa and a density of only 4.5 g/cm³, it enables lightweight heat exchanger designs and reduces structural support costs. It is also highly biocompatible and non-toxic, which supports use in pharmaceutical and medical applications. Typical applications include condensers, heat exchangers and evaporators in power plants and desalination facilities, marine piping systems, chemical processing equipment and aerospace components. Tubes are commonly supplied with mill test certificates per EN 10204 3.1 and optional third-party corrosion and metallurgical analysis reports.

Frequently Asked Questions

Q1. What is UNS R50400?
The UNS designation of commercially pure Grade 2 titanium, used for seamless and welded tubing in heat exchangers and condensers.

Q2. What is the difference between Grade 2 and Grade 2H?
Grade 2H requires a higher minimum tensile strength of 400 MPa versus 345 MPa for Grade 2; the yield strength range and elongation are the same.

Q3. Why is titanium used for condensers?
Its resistance to chloride pitting and crevice corrosion in seawater and brine makes it a long-life material for marine cooling service.

Q4. What are the GB and JIS equivalents?
GB/T 3625 TA2 and JIS H 4600 Class 2; the DIN equivalent is 3.7035 per DIN 17860 and the ISO equivalent is Grade 2 per ISO 5832-2.

Q5. Is seamless or welded titanium tubing stronger?
Seamless tubing has no longitudinal weld and offers higher strength and pressure resistance than welded tubing.

Q6. What testing applies?
Per ASME SB-338, tubing is tested by flattening, flaring and non-destructive methods, with mechanical testing of the delivered lots.