Structural Requirements for All Titanium Containers: Key Specifications from Design to Manufacturing

2025-11-06

All titanium containers are widely used in fields such as chemical engineering, marine engineering, and aerospace due to their excellent corrosion resistance and lightweight characteristics. However, the special characteristics of Titanium Materials, such as high temperature strength attenuation, low elastic modulus, and easy reaction with impurity elements, pose strict requirements for container structure design. This article systematically outlines the technical requirements for the structural design of all titanium containers, covering four dimensions: welding process adaptability, material compatibility, stress control, and corrosion protection.

Welding process adaptability: dual constraints of protection and operability

Titanium Materials have extremely strong chemical activity in a molten state and are prone to react with elements such as oxygen, nitrogen, and hydrogen, leading to embrittlement of welds. Therefore, the structural design needs to prioritize meeting the welding process requirements:

1. Operational space guarantee

Sufficient space should be reserved at the welding site to ensure that the argon arc welding tool can move freely and avoid insufficient shielding gas coverage due to limited space.

The opening of the shell connecting pipe should be as perpendicular as possible to the axis, simplifying the design of the protective fixture and improving the protection effect of the welding area.

2. Protection in high-temperature areas

All welded joints in high temperature areas above 400 ℃ must be continuously protected by inert gas (such as high-purity argon) to prevent oxidation.

The structural design should avoid forming closed chambers and ensure that the protective gas can circulate sufficiently.

3. Blunt edge gap control

The blunt edge gap of butt welded joints should be smaller than that of steel containers (usually ≤ 1mm) to compensate for the difference in melt flow caused by the high melting point (1668 ℃) and low thermal conductivity (17W/m · K) of titanium materials.

Excessive gaps can cause collapse of the melt pool, while insufficient gaps can lead to incomplete fusion defects.

Material compatibility: Steel titanium fusion is prohibited, and impurity elements are strictly controlled

Titanium forms hard and brittle intermetallic compounds (such as TiFe, TiNi) with metals such as iron and nickel at high temperatures, significantly reducing the ductility of welds. The structural design should follow the following principles:

1. Isolate steel titanium contact

Except for explosive welding and brazing, direct welding of titanium and steel is strictly prohibited. If carbon steel is used for secondary components such as loose flanges and connecting bolts, electrical isolation must be achieved through insulation gaskets or coatings.

When connecting titanium containers to steel pipelines, titanium steel transition joints or non-metallic partitions should be used.

2. Avoid cross contamination

During the manufacturing process, it is necessary to strictly distinguish between titanium and steel processing stations to prevent the cross use of tools (such as grinding wheels and files) from contaminating the surface of titanium materials with iron elements.

Before welding titanium materials, it is necessary to remove the oxide scale through acid washing (HF+HNO ∝ mixed acid) or mechanical polishing to ensure the purity of the weld area.

Stress Control: Continuity Design and Geometric Parameter Optimization

The elastic modulus of titanium (105GPa) is only 55% of that of steel, and it is prone to deformation or cracking due to stress concentration. Structural design requires stress control through the following measures:

1. Structural continuity

To avoid sudden changes in cross-section, welding joints should adopt a smooth transition design (such as a fillet radius ≥ 3 times the plate thickness) to reduce stress concentration factors.

The connection between the shell and the connecting pipe needs to be reinforced with rings or locally thickened to enhance rigidity.

2. Forming process parameters

The minimum inner radius of bent parts should be ≥ 5 times the plate thickness (usually 2 times for steel parts) to prevent cracking caused by cold work hardening of titanium materials.

The expansion rate of the tube expansion process should be controlled at 1% -2% (3% -5% for steel parts) to avoid excessive deformation leading to grain boundary rupture.

3. Lower limit of shell thickness

The minimum thickness of the container shell is 2mm to meet the welding process requirements, geometric dimensional tolerances, and transportation and lifting stiffness requirements, while also considering material economy.

Corrosion protection: medium adaptability design and protective measures

Titanium Materials are prone to crevice corrosion or galvanic corrosion in reducing acids, chlorides, and other media. Structural design should take protective measures for different corrosion scenarios:

1. Avoiding crevice corrosion

Avoid designing narrow gaps or stagnant areas, and the weld seam height should be controlled within 0.5mm to reduce medium accumulation.

In environments with strong corrosive media such as wet chlorine gas, corrosion-resistant titanium alloys (such as Ti-0.2Pd) or polytetrafluoroethylene coatings should be used at the gaps.

2. Protection against galvanic corrosion

When titanium comes into contact with dissimilar metals such as copper and stainless steel, it is necessary to block the galvanic current by insulating gaskets, spraying ceramic coatings, or setting a third metal transition layer.

In conductive media such as seawater, the potential of titanium components should be lower than that of adjacent metals, or sacrificial anodes should be used for protection.

3. Erosion protection design

The medium flow rate exceeds the critical value (corrosive medium ρ v ²>740kg/(m · s ²); When the non corrosive medium ρ v ² is greater than 2355kg/(m · s ²), an anti-collision plate needs to be installed at the inlet.

When the tangential inlet or pipe mouth is facing the wall and the spacing is less than 2 times the pipe diameter, a protective plate needs to be installed to prevent high-speed media from directly impacting the wall.

Economic trade-off: applicable scenarios and material selection

The design of all titanium containers requires a balance between performance and cost:

1. Temperature and pressure limitations

The allowable temperature should not exceed 250 ℃ (the strength of titanium materials significantly decreases above 200 ℃), and the pressure is recommended to be controlled below 0.5MPa.

When the thickness is calculated to be greater than 13mm, the economy of pure titanium decreases, and it is necessary to evaluate the composite plate or local reinforcement scheme.

2. Priority given to small and medium-sized devices

Small and medium-sized containers (such as heat exchangers and storage tanks) with a temperature ≤ 150 ℃ and a pressure ≤ 0.5MPa are most cost-effective when using a fully titanium structure.

It is recommended to use titanium steel composite plates for large high-voltage equipment, taking into account both corrosion resistance and economy.

Conclusion

The structural design of all titanium containers should focus on "process adaptability", by optimizing the welding operation space, isolating dissimilar metals, controlling stress concentration, and providing targeted corrosion protection, to ensure the reliability and economy of the container under extreme working conditions. With the advancement of titanium processing technology, such as additive manufacturing and laser welding, the application boundaries of all titanium containers will continue to expand, providing key support for high-end equipment manufacturing.

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