Aug. 18, 2023
The titanium rod filter, also known as a filter cartridge filter, employs stainless steel (304, 316L) as the outer casing material, and the internal filter element is composed of titanium tubes. These titanium tubes are created through high-temperature sintering of titanium powder, forming hollow filtering tubes using powder metallurgy techniques. This series of products feature a compact structure and appealing appearance. The titanium rod filter utilizes sintered micro-porous titanium rod filters. The filter element is a hollow tube-shaped filter made from titanium metal powder using powder metallurgy techniques, constituting a form of depth filtration.
The working process of the titanium rod filter is as follows:
When the filtering medium enters the filter cartridge through the inlet, impurities are initially intercepted by the surface of the titanium rods, forming a dense and porous filtering layer. This filtering cake layer can also perform filtration. Simultaneously, particles smaller than the diameter of the titanium rod's pores enter the micro-pores on the titanium rod walls. Because there are numerous bent channels on the tube wall, the channels become elongated and particles that enter are easily captured. Due to the compression and collisions caused by the flow of fluid, particles adhere closely to the pore walls. This type of filtration occurs within the titanium rods and is categorized as deep filtration. Impurities are retained on the outer surface and inner wall of the titanium rods. The filtered clean material flows out from the outlet. As impurities accumulate in the filter element, the pressure on the filter increases. When it reaches 0.3 MPa, the filter will be cleaned. The titanium rods need to undergo regeneration.
Titanium is highly stable in air at room temperature. When heated to 400-550°C, it forms a sturdy oxide film on the surface to prevent further oxidation. Titanium has a strong ability to absorb oxygen, nitrogen, and hydrogen. These gases are harmful impurities for metallic titanium. Even in small amounts (0.01% to 0.005%), they can significantly impact its mechanical properties. Among titanium compounds, titanium dioxide (TiO2) holds high practical value. TiO2 is inert to the human body, non-toxic, and possesses excellent optical properties. TiO2 is opaque, has high gloss and whiteness, high refractive index and scattering ability, strong covering power, and good dispersion. The resulting pigment is a white powder commonly known as titanium white, with a wide range of applications. The appearance of titanium rods is very similar to that of steel. Its density is 4.51 g/cm3, less than 60% of steel's density. It is the lowest density element among refractory metals. The mechanical properties of titanium, commonly referred to as its mechanical performance, are closely related to its purity. High-purity titanium has excellent machinability, good elongation and contraction rates, but low strength, making it unsuitable for structural materials. Industrial pure titanium contains a certain amount of impurities, giving it higher strength and plasticity, suitable for structural materials.
Titanium alloys are divided into low-strength high-ductility, medium-strength, and high-strength categories, ranging from 200 (low strength) to 1300 (high strength) MPa. Generally, titanium alloys are considered high-strength alloys. They are stronger than aluminum alloys, which are considered medium-strength, and can fully replace certain types of steel in terms of strength. Some titanium alloys can maintain good strength above 600°C, in contrast to the rapid strength decrease of aluminum alloys above 150°C. Dense metal titanium is highly valued in the aerospace industry due to its lightweight nature, high strength compared to aluminum alloys, and ability to maintain higher strength than aluminum at high temperatures. Given that titanium's density is 57% that of steel, its specific strength (strength-to-weight ratio or strength-to-density ratio) is high, and it boasts strong corrosion resistance, oxidation resistance, and fatigue resistance. Three-quarters of titanium alloys are used as structural materials, primarily representing aerospace structural alloys, and one-quarter is used as corrosion-resistant alloys. Titanium alloys possess high strength, low density, excellent mechanical properties, toughness, and corrosion resistance. Additionally, titanium alloy processing properties are poor, making machining difficult. During hot working, it easily absorbs impurities like hydrogen, oxygen, nitrogen, and carbon. It also exhibits poor wear resistance and involves complex production processes.
The industrial production of titanium began in 1948. The development of the aerospace industry requires the titanium industry to grow at an average annual rate of around 8%. Currently, the annual production of processed titanium alloy materials worldwide has exceeded 40,000 tons. The most widely used titanium alloy types are Ti-6Al-4V (TC4), Ti-5Al-2.5Sn (TA7), and industrial pure titanium (TA1, TA2, and TA3).
There are three heat treatment processes for titanium rods and titanium alloy rods:
1. Solution Treatment and Aging:
The goal is to increase their strength. Alpha titanium alloys and stable beta titanium alloys cannot be strengthened through heat treatment; annealing is the only treatment conducted during production. Alpha + beta titanium alloys and sub-stable beta titanium alloys containing a small amount of alpha phase can be further strengthened through solution treatment and aging.
2. Stress Relief Annealing:
The purpose is to eliminate or reduce residual stresses generated during processing. It prevents chemical attack in certain corrosive environments and reduces deformation.
3. Full Annealing:
The aim is to achieve good toughness, enhance processability, facilitate further processing, and improve dimensional and structural stability.