Q1. What is a titanium-nickel composite panel?

A: It is a composite material consisting of a corrosion-resistant titanium layer bonded to a ductile nickel interlayer, or nickel matrix. It is usually combined with steel or aluminum for structural support. The nickel layer acts as a diffusion barrier, preventing the formation of brittle titanium-iron compounds and strengthening the interface.

Q2. Why use nickel as an interlayer?

A: Nickel is essential in:

1) Preventing brittle phases: Direct bonding of titanium to steel leads to the formation of TiFe/TiFe₂ intermetallic compounds, which reduce strength. Nickel prevents the diffusion of TiFe/TiFe₂ and enables a strong bond.

Improved weldability: Nickel's ductility enables it to withstand thermal stresses during welding or high-temperature processing.

Thermal conductivity gradient: In multilayer composites, such as Al/Ti/Ni/steel, nickel optimizes heat transfer in low-temperature applications, such as joints on liquefied natural gas carriers.

Q3. How are these composite plates manufactured?

A: The main methods include:

Explosive welding:

This method is used for complex, multi-layer stacks (e.g., aluminum, titanium, nickel, and steel). The explosive force causes the metal layers to form a metallurgical bond at high velocity. Precise control of explosive density (0.4–1.0 g/cm³) and spacing (3–15 mm) is required.

Hot roll welding:

Symmetrical "steel/titanium/nickel foil/steel" stacks are vacuum-sealed, heated to between 780 and 1000 degrees Celsius, and rolled with at least 70% deformation. The 0.5 mm nickel foil ensures that the formation of intermetallic compounds is minimized.

Q1: How can the quality of the composite layer be ensured?

A: Rigorous non-destructive testing (NDT) must be performed.

Ultrasonic testing (UT): This is the primary method used to detect adhesive defects, delaminations, and inclusions at the composite interface across the entire plate surface.

Visual inspection: Checks the surface quality of both the titanium and steel sides.

Additional tests (if specified): Shear strength test, sample bending test, or microstructure analysis of the composite area.

Q2: What standards govern titanium-steel composite panels?

A: Major international standards include:

ASTM B898 (Standard Specification for Reactive and Refractory Metal Composite Sheets) and B898/B898M (Standard Specification for Titanium-Steel Composite Sheets).

ASME: SA-263, SA-264, and SA-265 (specifications for corrosion-resistant chromium and chromium-nickel steel composite plates, stainless steel composite plates, and nickel and nickel alloy composite plates — titanium composite plates are often referenced through B898). The ASME Boiler and Pressure Vessel Code, Parts II and IX, are also critical for pressure vessel fabrication.

EN standards include EN ISO 23277 (non-destructive testing of welds), EN 10002 (tensile testing), and EN 10204 (inspection documents).

Q3: What thicknesses are usually available?

A: Titanium composite layer thicknesses typically range from 1.5 mm (0.06 in.) to 6 mm (0.24 in.) or greater depending on the severity of corrosion and the design life. Steel backing thicknesses range from 6 mm (0.24 in.) to over 100 mm (4 in.), depending on structural requirements. The total thickness of the composite plate is the sum of the two layer thicknesses.

Q4: How are titanium-steel composite panels handled and fabricated?

A:  Key considerations:

Protect titanium surfaces to prevent scratches, gouges, and contamination, especially from iron or steel particles, as these can lead to corrosion. Use protective film and specialized titanium tools, and clean the work area.

Material isolation: Keep titanium surfaces away from carbon steel grinding dust, welding spatter, and tools.

Cutting: Use methods suitable for both metals, such as plasma cutting (make sure the plasma gas used for titanium is clean), water jet cutting, or machining. Avoid methods that generate excessive heat or pollution.

Forming: Use caution when using standard methods such as rolling and pressing, and be aware of potential differences in rebound. Avoid damaging the bonding layer or the surface of the titanium alloy. Sharp bends require special attention.

Cleanliness: Maintain cleanliness throughout the manufacturing process to ensure corrosion resistance.

Q5: How are maintenance and inspections performed during use?

A: Perform regular visual inspections. Check the titanium surface for mechanical damage.

Avoid iron contamination. Avoid contact with carbon steel tools or debris during maintenance.

Repair: Damaged titanium alloy areas can usually be repaired using a qualified overlay welding process with titanium alloy.

Monitoring: For critical equipment, periodic ultrasonic testing (UT) of the bonding interface is recommended.

Q1: What is a titanium-steel composite panel?
A: It is a composite material consisting of a thin corrosion-resistant titanium layer (the "composite" layer) that is permanently bonded to a thicker, structurally sound base layer of carbon or low-alloy steel. The two metals retain their individual properties yet function as a single unit.

Q2: Why use titanium-steel composite panels instead of pure titanium or steel sheets?
A:  It combines the advantages of both.
○Cost Effectiveness: It is much cheaper than using pure titanium for the entire structure because titanium is only needed for surfaces exposed to corrosion.
○Structural strength: The steel base layer provides the necessary mechanical strength and stiffness for demanding applications, such as pressure vessels or structural components.
○Excellent corrosion resistance: Titanium layers are highly resistant to harsh environments (acids, chlorides, and seawater), whereas pure steel corrodes rapidly, even when coated.

Q3: What are the main applications of titanium steel composite panels?

A: Titanium steel composite panels are essential in industries where corrosion resistance and structural integrity are critical.

○Chemical and petrochemical processing: reactors, towers, heat exchangers, and storage tanks that handle corrosive acids (HCl, H₂SO₄, HNO₃, etc.) and chlorides.

○Power generation: Flue gas desulfurization (FGD) systems, condenser shells, and heat recovery equipment.

○Desalination and water treatment: Multi-stage flash (MSF) evaporators, reverse osmosis (RO) pressure vessels, and brine heaters.

○Marine and Offshore: Seawater piping systems, ballast tanks, and hull components for specialized vessels.

○Pulp and Paper Industry: Bleach Plants and Digesters

○Pollution control equipment includes scrubbers and chimneys.

Q4: How are titanium-steel composite panels manufactured?

A: The main industrial methods are:

Explosive welding (explosive composite): Uses a precisely controlled explosive force to form a metallurgical bond at the interface. This is the most commonly used method.

Rolling composite: Plates are heated and composited by rolling under high pressure. Multiple welds are usually required.

Cladding: Multiple layers of titanium weld metal are deposited on a steel substrate. Cladding is more commonly used for complex shapes or repairs than for producing initial plates.

Q5: What is the bond strength between the titanium and steel layers?

A: The bond strength achieved by explosion welding or roll lamination is extremely high, often exceeding the shear strength of the titanium layer itself. This process forms a true metallurgical bond, ensuring that the layers remain composite under load and preventing delamination under normal operating conditions.