As a key component of high-end pressure vessels, the manufacturing quality of titanium heads is directly related to the safety and reliability of equipment in harsh environments. Titanium alloy is widely used in chemical, energy, aerospace and other fields due to its high strength, low density, excellent corrosion resistance and good high temperature performance, but its processing difficulty is also significantly higher than that of ordinary metals. The following is a systematic explanation of the manufacturing process and quality control of titanium heads based on the characteristics of titanium alloy materials.
Titanium alloy material characteristics and processing challenges
Titanium alloys are prone to the following problems in machining:
High chemical activity: easy to react with oxygen, nitrogen, hydrogen and other elements at high temperatures, resulting in embrittlement;
Poor thermal conductivity: heat is easy to concentrate during processing, which aggravates tool wear and material deformation;
Low elastic modulus: large rebound after forming, difficult to control dimensional accuracy;
Poor wear resistance: easy to bond with molds, affecting surface quality.
Therefore, the manufacturing of titanium heads requires special process measures for the above characteristics.
Spinning molding process: precision shaping and process control
Process principle and adaptability
Spinning is gradually extended through local point deformation, which is suitable for titanium alloys, which are materials with narrow deformation intervals. Compared with overall stamping, spinning can reduce sudden stress and reduce the risk of cracking, especially suitable for the manufacture of small and medium-sized heads with complex shapes.
Key points of titanium alloy spinning
Temperature-controlled spinning: Heated spinning (300–500°C) is often used to improve the plasticity of the material and reduce cracks.
Mold and lubrication: The mold needs to have high hardness and wear resistance, and the surface is often chrome plating or special coating; Lubrication should be based on fluorine or graphite-based lubricants with good high temperature stability to prevent titanium from bonding with molds;
Intermediate heat treatment: annealing (700–800°C) should be carried out between multiple spinning sessions to eliminate work hardening and restore plasticity;
Speed and feed matching: Use lower rotational speeds and feed rates to avoid tissue deterioration due to heat buildup.
Welding process: weld integrity and tissue performance guarantee
Selection of welding method
Titanium head splicing often adopts:
Tungsten inert gas welding (GTAW): used for thin plates and critical welds;
Plasma arc welding (PAW): suitable for medium and heavy plates, with a small heat-affected zone;
Laser/electron beam welding: Used in high-precision requirements with minimal deformation.
Welding process control
Gas protection: high-purity argon gas (≥99.999%) must be used, and the mop cover and back protection device must be designed to prevent oxidation on the back of the weld;
Process parameters: Strictly control the heat input to avoid coarse grains or the formation of brittle phases;
Welding material matching: Choose welding wires that are homogeneous to the base metal or have low clearance elements, such as ERTi-5, ERTi-7, etc.
Post-weld heat treatment and testing
Stress relief annealing: usually performed at 500–600°C to reduce residual stress;
Solution aging treatment: suitable for β or α+β titanium alloys to improve strength and toughness;
Non-destructive testing: 100% radiographic testing (RT) or ultrasonic testing (UT), supplemented by penetrant testing (PT) to ensure that the weld is free of defects.
Stamping molding: dimensional accuracy and surface quality control
Panel weld treatment
Residual height control: the residual height of the weld needs to be smoothed to be flush with the base metal to avoid stress concentration and flow obstruction during stamping;
Smooth transition zone: The transition between the weld and the base metal should be smooth, and the slope should not be greater than 1:4.
Stamping process parameters
Cold stamping: suitable for thin-walled heads, but pay attention to rebound compensation;
Hot stamping: The usual temperature is 600–800°C to reduce the deformation resistance, but it is necessary to prevent the formation of oxide scale;
Mold design: Considering the rebound of titanium alloy, the mold cavity size needs to be corrected accordingly.
Surface and edge quality
Oxide layer treatment: After thermoforming, pickling or sandblasting needs to be carried out to remove the oxide layer;
Edge processing: The bevel is machined to avoid micro-cracks caused by thermal cutting.
The whole process quality control system
Material factory inspection: check the material certificate, conduct spectral analysis and mechanical property re-inspection;
Process evaluation and supervision: each process needs to pass the evaluation, and the inspector tracks the key processes throughout the process;
Dimension and position tolerance: 3D scanning or template detection of curvature and contour;
Final performance test: including water pressure test, air tightness test and stress corrosion test (if applicable).
Titanium heads are manufactured with a combination of cutting-edge practices in materials science, plastic machining, and welding technology. Through refined spinning, inert gas protection welding and controlled stamping process, combined with strict whole-process quality control, can the head be ensured to operate stably for a long time under extreme conditions such as high pressure, corrosion and radiation. In the future, with the application of numerical simulation, intelligent detection and other technologies, titanium head manufacturing will further develop in the direction of precision and digitalization.
