Research On Common Defects And Control Strategies In The Preparation Process Of Titanium Wire

Titanium wire is widely used in aerospace, medical and marine engineering fields due to its high specific strength and excellent corrosion resistance. However, its processing process is complex and prone to a variety of surface and internal defects, which directly affect the performance and service life of the finished product. This paper systematically combs the typical defects in the titanium wire preparation process, analyzes the causes and proposes targeted solutions to provide a reference for process optimization.

1. Surface Integrity Defects

1) Scratches and Abrasions

Causes: The surface treatment of the blank is incomplete, the lubricant fails or contains impurities, and there are burrs in the tool and mold.

Countermeasures: Strictly implement surface cleaning procedures, use evenly coated high-temperature lubricants, filter lubricants regularly and replace them; check the surface finish of wire drawing dies, guide wheels and other tools before each batch is produced.

2) Surface Oxidation

Causes: insufficient vacuum during annealing (residual oxygen reaction), excessive baking temperature (>200℃), and oil pollution in the rewinding link.

Countermeasures: The vacuum annealing furnace needs to be pre-pumped to 10-3Pa level and protected by argon filling; forced cooling to below 150℃ before baking; the operating area should be kept clean, and dust-free gloves should be used for contact parts.

2. Size and Shape Defects

Poor Size

Cause: The pore size of the drawing die is worn out or the design is biased, and the pickling time is too long, resulting in excessive local corrosion.

Countermeasures: Calibrate the mold aperture every 50 batches; use a rotating fixture to flip the wire at a uniform speed during pickling, and measure the diameter every3 minutes. The end point is based on micro-corrosion (removal ≤0.02mm).

3. Internal Organizational Defects

Internal Cracking And Longitudinal Cracking

Cause:

Internal cracking: The refractory metals such as Mo and V in the titanium alloy are isolated to form a hard and brittle phase, and the temperature drop rate of >50℃/min over a long period of time leads to the concentration of thermal stress.

Longitudinal cracking: The edges and corners of the square blank dissipate heat quickly (the temperature drop rate is 30% higher than the center), and the quenching stress occurs when the water is cooled in the high temperature section.

Countermeasures:

Three-time vacuum self-consumption smelting is used to ensure the uniformity of the composition; the final forging temperature is controlled at ≥850℃ during forging, and the cycle of “quick forging while hot, return to the furnace and keep warm” is adopted.

The chamfering temperature is increased to 30℃ above the β phase transition point, and the cooling method is changed to air cooling + asbestos slow cooling.

Hydrogen-induced cracks

Cause: The ambient humidity is >60%RH during welding or annealing, and the surface grease of the base material reacts with titanium to form a TIH brittle phase.

Countermeasures: Ultrasonic cleaning with acetone + pickling before welding (HF:HNO₃ = 1:3); the dew point of the protective gas is ≤-40℃, and the zirconium aluminum alloy hydrogen absorber is placed in the annealing furnace.

4. Macro-Metallurgical Defects

Dot-like defects (holes/segregation)

Cause: The current fluctuation during the smelting period leads to uneven composition, and the ingot shrinkage remains.

Countermeasures: The electron beam cold bed furnace is used for smelting to eliminate inclusions; the end face of the bar is 100% ultrasonic flaw detection, and the abnormal points are marked and removed.

5. Suggestions For Systematic Process Optimization

1) Parameter linkage control: Establish a coupling model of lubricant temperature (40±5℃), drawing speed (≤2m/s), and channel compression ratio (15%~20%).

2) Online monitoring: the introduction of a laser diameter gauge to feedback the size in real time, and an infrared thermal imaging camera to monitor the die temperature (automatic deceleration over 180℃).

3) Full process traceability: each roll of titanium wire is bound to the process ID, and the smelting batch number, annealing curve, and flaw detection results are recorded to facilitate the traceability of defects.

The prevention and control of titanium wire defects needs to take into account the multi-dimensional control of “surface-size-internal”. Through the refinement of process procedures, the strengthening of process testing and the introduction of intelligent monitoring methods, the pass rate of finished products can be significantly improved. In actual production, the equipment capabilities and grade characteristics (such as the difference between Gr5 and Gr2 process windows) should be combined to dynamically adjust the scheme to achieve high-quality and stable production.