ASTM B338 Grade 7 Seamless Titanium Tube

 

GRADE 7 (UNS R52400) is not, strictly speaking, a "high-strength titanium alloy" in the traditional sense, but rather a corrosion-resistant modified material produced by adding 0.12% to 0.25% palladium (Pd) to industrial-grade pure titanium Grade 2. It retains the excellent formability, weldability, and biocompatibility of pure titanium, but achieves a qualitative leap in corrosion resistance through the addition of trace amounts of palladium.

ASTM B338 Grade 7 Seamless titanium tube is a precisely positioned, irreplaceable product within the titanium family. While it does not excel in strength, the electrochemical protection provided by trace amounts of palladium enables it to demonstrate a service life far superior to that of pure titanium in reducing acids, high-temperature chloride environments, and crevice corrosion conditions.

For corrosion-critical applications in the chemical, energy, and offshore engineering sectors, Grade 7 tubing is a proven solution that has been validated in industrial settings for over 50 years.

 

 

Grade 7 (Gr. 7) is essentially Grade 2 industrial-grade pure titanium with 0.12% to 0.25% palladium (Pd) added to the matrix. This trace amount of the precious metal brings about a qualitative change.

Element	Content (wt%)	Notes
Titanium (Ti)	Balance	α-phase matrix
Palladium (Pd)	0.12-0.25	A key alloying element that provides cathode depolarization protection
Iron (Fe)	≤0.30	Same upper limit as Grade 2
Oxygen (O)	≤0.25	Control interstitial elements to ensure toughness
Carbon (C)	≤0.08	Standard Control
Nitrogen (N)	≤0.03	Standard Control
Hydrogen (H)	≤0.015	Must be strictly controlled to prevent hydrogen embrittlement

 

 

Performance Metrics	Annealed State Values	Remarks
Tensile Strength(Rm)	≥345 MPa	Essentially the same as Grade 2
Yield Strength(Rp0.2)	275~475 MPa	The range is fairly broad and depends on the machining conditions.
Elongation(A)	≥20%	Excellent ductility
Modulus of Elasticity	~103 GPa	About half that of steel
Density	4.51 g/cm³	Same as pure titanium

 

 

1. Seamless Tubes: Piercing + rolling/drawing; suitable for high-pressure applications and those requiring high reliability
2. Welded Tubes: Rolled from sheet metal + TIG welding; lower cost; suitable for low- to medium-pressure heat exchangers
3. Size Range: Outer diameters typically range from 6 mm to 114 mm, with wall thicknesses ranging from 0.5 mm to several millimeters; customizable
4. Product Forms: We offer seamless pipes, welded pipes, coiled pipes, U-bends, finned tubes, and more.

5. Delivery Times and Costs: Palladium Sets the Tone. There is no standard spot inventory for Gr. 7 tubing; all production is made-to-order. Quotations are valid for only a very short period because pricing follows the standard "sponge titanium plus palladium surcharge" model. The international price of palladium directly affects costs, so prices must be locked in during negotiations.

 

 

1. Chemical Process Industry (CPI) - The Largest Application Market

Heat exchanger/condenser tube bundles: For processing media containing hydrochloric acid, sulfuric acid, and organic acids

Reactors/autoclaves: Chemical reaction vessels in acidic environments

Pipes and fittings: Pipeline systems for transporting corrosive fluids

Valves and pump components: Corrosion-resistant linings or monolithic components

Typical Case: At a chemical plant, shell-and-tube heat exchangers operating under conditions of 3–5% HCl and 80–120°C originally used Grade 2 tubes, which had to be replaced every 18–24 months due to corrosion perforation. After switching to Grade 7, the units have operated continuously for over 15 years without corrosion-related failures, reducing the total life-cycle cost by more than 50%.

2. Flue Gas Desulfurization (FGD) Systems

In desulfurization units at coal-fired power plants, the inlet area of the absorption tower is subject to combined corrosion from sulfuric acid/sulfurous acid, chlorides, and temperatures ranging from 50–150°C. Grade 7 is the standard material of choice for flue linings, baffles, and spray nozzles in this area.

3. Seawater Desalination and Offshore Engineering

Evaporator tubes, condenser tubes: High-temperature seawater (>70°C) or contaminated seawater environments

Brine heaters: High chloride concentration + high temperature

Subsea pipelines: Flange connections with high risk of crevice corrosion

4. Nuclear Power and Nuclear Waste Management

The U.S. Department of Energy previously evaluated Grade 7 as a material for storage tanks at the Yucca Mountain nuclear waste repository, concluding that it could provide resistance to localized corrosion (crevice/pitting) for over 10,000 years in the anticipated environment. Although the Yucca Mountain project was not implemented, this evaluation produced the most comprehensive corrosion database for Grade 7, which is cited throughout the industry.

5. Pulp and Paper Industry

Chlorine dioxide systems: Highly oxidative + chloride-containing environments

Bleaching plants: Equipment for handling chlorine-containing bleaching solutions

6. Electroplating and Electrochemical Systems

Titanium anode baskets: Anode components in electroplating production lines

Electrolytic cell components: Resistance to electrochemical corrosion

7. Pharmaceutical and Fine Chemicals

Reactors for the synthesis of pharmaceutical intermediates

Equipment for processing organic acids (formic acid, oxalic acid, citric acid)

 

 

 

 

E-mail: garychen3215@hotmail.com

Address: No.35, Baoti Rd, Baoji city, Shaanxi Province, China

Contact: Mr. Gary Chen

Phone: +86-917-8883215

Mobile/WhatsApp: +86 13092900605

 

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