Three Elements Of Titanium Wire Defect Control: Material, Process, And Equipment Collaborative Optimization Strategy

For its high strength, corrosion resistance and good bio-compatibility, titanium wire is widely used in aerospace, medical equipment, chemical equipment and other fields. However, in the preparation process of titanium wire, due to factors such as material properties, process parameter control and equipment status, it is prone to surface scratches, poor size, oxidation, cracking and other defects, which affect product quality and performance.

1. Surface Scratches And Abrasions

Cause:

Surface scratches are usually caused by improper surface treatment, insufficient lubrication, or tool defects. For example, the lubricant is applied unevenly or contains impurities, which can easily rub against the metal surface during the drawing process to produce scratches; burrs or wear on the surface of the tool can also directly damage the surface of the titanium wire. In addition, particulate matter such as sand and soil adhered to the metal surface may scratch the material during processing.

Solution:

1) Strictly follow the procedures for surface pre-treatment (such as pickling and sandblasting) to ensure the cleanliness of the substrate surface;

2) Apply lubricant by uniform spraying or dipping, and filter lubricant regularly to remove impurities;

3) Regularly check the surface condition of drawing molds, guide wheels and other tools, and repair or replace defective parts in time.

2. The Size Is Too Poor

Cause:

The poor size is mainly related to the accuracy of the mold and improper control of the pickling process. Mold aperture wear or design deviation will cause the diameter of the titanium wire to deviate from the standard value; during the pickling process, if the corrosion time is too long or the solution concentration is uneven, it may cause local excessive corrosion and reduce the diameter of the wire.

Solution:

1) Regularly calibrate the mold size to ensure that it meets the technical requirements;

2) During pickling, the dynamic material turnover method is used to make the wire evenly in contact with the acid solution, and the diameter change is monitored in real time, and the process parameters are adjusted in time.

3. Surface Oxidation

Cause:

The surface oxidation of titanium wire is usually caused by defects in the annealing process or improper subsequent treatment. Insufficient vacuum during annealing will cause titanium to react with residual oxygen to form an oxide film; the baking temperature is too high or the surface adhesion of pollutants (such as grease and dust) during the annealing process will accelerate the thickening of the oxide layer.

Solution:

1) Check the sealing of the vacuum furnace before annealing to ensure that the vacuum degree is up to standard;

2) Strictly control the baking temperature below 200℃, and use inert gas to protect and cool;

3) Clean the surface of the wire before rewinding to avoid pollution.

4. Internal Cracking

Cause:

Internal cracking is mostly due to metallurgical defects in materials or improper forging technology. The uneven distribution of refractory metal elements (such as aluminum and vanadium) in titanium alloys may form microscopic segregation, which reduces the toughness of the material; rapid cooling or excessive temperature gradient during the drawing process can lead to local stress concentration and cause cracks.

Solution:

1) Optimize the smelting process and adopt vacuum self-consuming arc smelting (VAR) or electron beam smelting (EB) technology to improve the uniformity of composition;

2) Control the forging temperature range to avoid low-temperature forging, and adopt a multi-stage small deformation process to reduce the temperature gradient.

5. Longitudinal Cracking

Cause:

Longitudinal cracking is usually related to stress concentration at the edges and corners of the blank. During the water cooling process of high-temperature titanium alloys, the edges and corners cool down much faster than the central area, causing the thermal stress to exceed the material strength limit; in addition, the surface defects of the blank (such as folding and scratches) may also become the origin point of cracks.

Solution:

1) Control the chamfering temperature to avoid rapid cooling at the edges and corners;

2) Adopt a slow cooling process (such as furnace cooling or air cooling) for high-temperature titanium alloys to reduce thermal stress;

3) Strengthen the surface inspection of the blank to remove defective areas.

6. Dot-Like Defects

Cause:

Dot-like defects (such as holes and inclusions) mostly originate from the smelting process. If there is component segregation or non-metallic inclusions on the end face of pure titanium bars, they may be exposed as surface defects in subsequent processing; in addition, impurities may be introduced if the suction or protective gas is impure during the smelting process.

Solution:

1. Multiple vacuum smelting processes are used to improve the purity of the melt;

2. Optimize the design of the pouring system to reduce the phenomenon of air convection;

3. Strengthen the control of component uniformity to avoid local segregation.

7. Hydrogen-Induced Cracks

Cause:

Hydrogen-induced cracks are typical defects in titanium wire welding or processing. Oil stains and moisture on the surface of the base material or welding wire decompose at high temperatures to produce hydrogen atoms. If the purity of the protective gas is insufficient or the ambient humidity is high, hydrogen can easily diffuse into the material and gather under stress to form cracks.

Solution:

1) Strictly clean the surface of the base material and welding wire (mechanical polishing + chemical cleaning) before welding to remove oil stains and oxide film;

2) Control the humidity of the welding environment to be less than 60%, and use high-purity argon gas (≥99.99%) to protect;

3) Optimize welding process parameters (such as heat input and cooling speed) to reduce hydrogen aggregation.

The control of defects in the preparation of titanium wire needs to be optimized from the three aspects of materials, technology and equipment. By strengthening the control of smelting composition, accurately regulating the thermal processing parameters, and improving the surface treatment process, the incidence of defects can be significantly reduced. In actual production, it is necessary to formulate targeted quality control plans based on specific product requirements and equipment conditions, and continuously improve process stability through process monitoring and data analysis, and ultimately achieve a balance between titanium wire performance and cost.