What is the difference of Titanium alloy pipe

• Definition

Titanium alloy steel pipe is a kind of pipe made of titanium alloy material, with high mechanical properties, excellent stamping performance, and can be welded in various forms, welded joints strength up to 90% of the strength of the base metal, and good cutting and processing performance.

The industrial production of titanium started in 1948. The development of the aviation industry needs, so that the titanium industry to an average annual growth rate of about 8% of the development. At present, the world's annual output of titanium alloy processing materials has reached more than 40,000 tons, titanium alloy grade nearly 30 kinds. The most widely used titanium alloy is Ti-6Al-4V (TC4), Ti-5Al-2.5Sn (TA7) and industrial pure titanium (TA1, TA2 and TA3).

• Classification

1.Depending on the chemical composition, they can be divided into two categories: pure titanium and simple alloys, and multi-alloys.

• Pure titanium and simple alloys: Grade 1 is low-oxygen unalloyed titanium; Grade 2 is standard-oxygen unalloyed titanium; Grade 7 is standard-oxygen unalloyed titanium containing 0.12-0.25% palladium; 

• multi-alloys: Grade 5 is titanium alloy containing 6% aluminum and 4% vanadium; Grade 9 is titanium alloy containing 3% aluminum and 2.5% vanadium; Grade 19 is titanium alloy containing 3% aluminum and 8% vanadium, 6% chromium, 4% zirconium and 4% molybdenum. Grade 19 is a titanium alloy containing 3% aluminum, 8% vanadium, 6% chromium, 4% zirconium and 4% molybdenum.

Besides，Pure titanium and titanium alloys can be subdivided according to their properties as follows：

  1. industrially pure titanium (α type titanium alloy)

      Typical grades: Gr1, Gr2, Gr3, Gr5, Gr7 (ASTM standard).

      Characteristics: Excellent corrosion resistance (especially chloride ion environment)，Excellent weldability, good cold working performance

      Applications: chemical piping, desalination equipment, biological implants.

  2. Near-α type titanium alloys

     Typical grades: Gr8, Gr9, Gr12 (ASTM standard)

     Characteristics: excellent high temperature performance (long-term use temperature: 450-500 ℃)，High creep resistance, strong oxidation resistance

     Applications: aero-engine compressor blades, high-temperature structural components.

  3.α+β type titanium alloy

     Typical grades: Gr16, Gr17 (ASTM standard). High-temperature alloys (β-type titanium alloys): typical grades include Gr23, Gr24, Gr25 (ASTM standard)

     Characteristics: Optimal overall performance (balance of strength, toughness, processability)，Heat treatable strengthening (solid solution + aging)

     Applications: airplane fuselage/engine parts, artificial joints, racing car parts.

  4. β-type titanium alloys

     Typical grades: Ti-10V-2Fe-3Al, Ti-15V-3Cr-3Sn-3Al (β-21S)

     Characteristics: Ultra-high strength, excellent cold molding properties，Poor weldability, complex heat treatment required

     Applications: aerospace fasteners, springs, high performance sports equipment.

Performance Index	Industrially pure titanium	α+β type titanium	Near-α type titanium	β-type titanium
Tensile strength (MPa)	345-550	895-930	800-1000	1000-1350
Density (g/cm³)	4.51	4.43	4.54	4.84
Maximum service                   Temperature	350℃	400℃	500℃	300℃
Weldability	best	good	middle	bad
Typical Application	chemical equipment	Aerostructural part	engine components	Aerospace fastener

2. According to the mechanical properties of titanium alloys can be divided into strength and toughness of the different. 

• Strength: pure titanium Grade 1, Grade 2 strength is relatively low, Grade 2 tensile strength of 345MPa min. and Grade 5 titanium alloy strength up to 1000MPa or so, is 5 times that of stainless steel.

  
  

• Toughness: Generally speaking, those containing more alloying elements, such as Grade 5 and Grade 19, have better toughness while ensuring high strength; while pure titanium grades have certain differences in toughness performance with alloyed titanium alloys, and perform differently when subjected to impact and other loads.

  
  

3. Corrosion resistance: Titanium alloys containing palladium, such as Grade 7 and Grade 11, have better corrosion resistance than pure titanium grades without palladium (e.g., Grade 1 and Grade 2) in some specific corrosive environments, especially in reducing acids, etc. Grade 5 titanium alloys, due to alloying elements, have good corrosion resistance in seawater and other environments, but have differences in specific corrosion-resistant performance characteristics from alloys specially designed for corrosion resistance containing palladium and other elements; Grade 5 titanium alloys have good corrosion resistance in environments such as seawater due to the alloying elements, but differ from alloys containing palladium and other elements specifically designed for corrosion resistance in their specific corrosion resistance characteristics.

4.According to the different application scenarios can be divided into

• Aerospace: Grade 5 titanium alloy is commonly used in the manufacture of aircraft beams, wings, engine blades and other key components due to its high strength, good heat resistance and fatigue resistance.

• Chemical industry: Grade 2 titanium alloy is commonly used to make heat exchangers, reactors, pipelines and other chemical equipment due to its good corrosion resistance and moderate price.

• Biomedical field: Grade 23 titanium alloy has ultra-low clearance elements and good biocompatibility, and is often used to manufacture artificial joints, dental implants, fracture fixation devices and other biomedical implants.

5.Differ according to the processing difficulty and cost

• Generally speaking, the higher the content of alloying elements and the more complex the grade of titanium alloy, the more difficult it is to process. For example, Grade 5 titanium alloys are more difficult to process than pure titanium grades such as Grade 1 and Grade 2.

• From a cost perspective, titanium alloys containing rare or expensive alloying elements (such as palladium, etc.), as well as titanium alloys of grades that are more difficult to process, usually cost more. For example, Grade 7 contains palladium, so the cost is higher than ordinary pure titanium grades; Grade 19 and other titanium alloys with complex alloy compositions also have relatively high costs.

• Virtue

Compared with other metal materials, titanium alloy has the following advantages.

      ① than the strength (tensile strength / density) high (see chart), tensile strength of up to 100 ~ 140kgf / mm2, while the density of only 60% of steel.

      ② good strength at medium temperature, the use of temperature than the aluminum alloy a few hundred degrees higher, in the middle of the temperature can still maintain the required strength, can be in the temperature of 450 ~ 500 ℃ long-term work.

      ③ good corrosion resistance, in the atmosphere, titanium surface immediately form a uniform dense oxide film, the ability to resist a variety of media erosion. Usually titanium has good corrosion resistance in oxidizing and neutral media, and the corrosion resistance in seawater, wet chlorine and chloride solution is more excellent. But in reducing media, such as hydrochloric acid and other solutions, titanium's corrosion resistance is poor.

      ④ good low-temperature performance, the gap element is very low titanium alloy, such as TA7, in -253 ℃ can maintain a certain degree of plasticity.

      ⑤ Low modulus of elasticity, small thermal conductivity, no ferromagnetism.

      ⑥ High hardness.

      ⑦Poor stamping, good thermoplasticity.