Titanium Tubes Research Articles

A comparative study on microstructure and mechanical properties between friction and laser beam welded titanium tubes

The microstructure and mechanical properties of friction and laser beam welded Grade 2 titanium tubes (wall thickness of 3.9 mm and outer diameter of 60 mm) are compared in the present investigation. Friction welding (FW) was conducted on a vertical friction processing system. Laser beam welding (LBW) was accomplished by utilizing a 4 KW Nd:YAGlaser. The microstructure evolution was observed by optical microscopy and advanced techniques such as TEM and EBSD. The friction welded joints showed fine grains due to dynamic recrystallization. A variation in grain size towards the outer circumference of the tube was observed due to flash formation. The laser beam welded joints displayed large grains with irregular boundaries. Both joints exhibited an elevated dislocation density due to severe plastic deformation and thermal stresses respectively. Strengthening of the joint area was recorded in both joints albeit due to different strengthening mechanisms. The failure location, during mechanical testing, occurred in the base metal for both processes. Overall when compared, LBW is probably the preferred process to join these tubes due to its higher welding speed and therefore reduced production cycle.

Section Flattening in Numerical Control Bending Process of TA18 High Strength Tube

Section flattening is an inevitable physical phenomenon in the forming process of tube bending, and severe section flattening will affect the reasonable assembly of the tube fittings, and therefore restricts its wide application. Finite element (FE) model for numerical control (NC) bending of titanium tube considering the variation law of contractile strain ratio (CSR) and the Young's modulus (E) was established in the present paper. The section flattening behaviors of TA18 tube under different geometric conditions and different process conditions were investigated. The results show that considering the variation law of CSR-E can change the cross-section, which has no remarkable influence on the change law. The reasonable range of geometric and process parameters are obtained, which provides a basis for studying the forming prediction and controlling the final precision for the NC bending of TA18 tube.

Condensation heat transfer of R134a, R1234ze(E) and R290 on horizontal plain and enhanced titanium tubes

An experimental investigation on the condensation of R134a, R1234ze(E) and R290 outside plain and enhanced titanium tubes was conducted. The saturation temperature in the experiments was 35 °C to 40 °C, and heat flux was in the range of 8–80 kW/m2. Effects of heat flux, refrigerant and saturation temperature on heat transfer were investigated. The heat transfer enhancement ratio of overall heat transfer coefficient decreased with increasing heat flux. It was found that the condensing heat transfer coefficient of R134a, compared with R1234ze(E) and R290, was the largest for plain and enhanced tubes. Saturation temperature had minor effect on condensing heat transfer coefficient for R134a, R1234ze(E) and R290 for plain tube. The effect of saturate temperature on the condensing heat transfer of R134a and R1234ze(E) was even negligible for enhanced tube. While, the condensing heat transfer coefficient of R290 for enhanced tube was increasing with increment of saturation temperature. Experimental condensing heat transfer coefficient were also compared with five predicting models for low-fin tube. It showed that the model of Briggs–Rose gave a better prediction result for R134a and R1234ze(E), while the model underestimated the experimental result for R290.

Characteristic Analysis of Superheater Tubes of Biomass Direct-fired Boilers

This paper studies the characteristics of superheater tubes in biomass direct-fired boilers through corrosive thinning and kinetic analysis, corrosion product analysis and the effect of HCI concentration. The experimental results show that the corrosion resistance of TC4 tube materials is good; the corrosion resistance of pure titanium tube is relatively poorer compared with the former; the tube with higher nickel content have better corrosion resistance. Therefore, in the selection of materials for superheater tubes of biomass direct-fired boilers, it is necessary to select tubes with higher nickel content to prolong the service life of superheaters.

Corrosion inhibition of heat exchanger tubing material (titanium) in MSF desalination plants in acid cleaning solution using aromatic nitro compounds

The inhibition impact of aromatic nitro compounds on the corrosion of heat exchanger tubing material (titanium tubes) in MSF desalination plants in acid cleaning solution (1.0 M sulfuric acid) was explored. Corroborative results between chemical and electrochemical (EIS) methods have been reported. FTIR and SEM analysis were further used to characterize the morphology and the nature of the film adsorbed on the titanium surface. The study informed that the maximum corrosion rate of titanium (0.260 mg cm−2 h−1) was obtained in 1.0 M sulfuric acid at 298 K. Aromatic nitro compounds act as effective corrosion inhibitors for titanium in acid cleaning solution. The efficiency of these compounds boosts with concentration and diminishes with temperature. The aromatic nitro compounds exhibit a maximum inhibition efficiency of 73.0% (NI), 82.6% (NII) and 94.6% (NIII) at 600 ppm. They form a good protective layer on titanium surface through their adsorption. The adsorption of aromatic nitro compounds on titanium surface obeys Langmuir model. The performance of these compounds decreases in sequence: (NI) < (NII) < (NIII).

Tribological behaviors in titanium sheet and tube forming at elevated temperatures: evaluation and modeling

Warm forming has been an efficient approach to exploiting the forming potential of titanium alloy sheet and tube materials. However, the tribological condition between Ti-alloy sheet/tube and tools at elevated temperatures is a non-trivial issue and has yet not been fully explored and articulated. Taking CP-3 tube and Ti-6Al-4V sheet as case study materials, the tribological behaviors between Ti-alloy sheet/tube and tools at elevated temperature are revealed and modeled. The main results show that (1) by using the high-temperature twist-compression test combined with the design of experiments, the suitable tool materials, surface modification approaches, and lubricants are determined for warm forming of Ti-alloy sheet/tube, and the significant influential factors and their affecting rules/mechanisms on the coefficient of friction are identified; (2) a pressure- and temperature-related dynamic friction model is developed and implemented in the 3D-FE simulation of warm forming via ABAQUS/VFRIC; taking warm rotary draw bending of CP-3 tube as an application, the proposed friction model is experimentally validated, and the comparisons between the experimental results and the simulated ones indicate that the proposed model is much better than the Coulomb friction model in prediction of forming defects, such as wall thinning/thickening and wrinkling instability.

Characterizing of Anisotropy and Asymmetry of Tubular Materials

Titanium tubular materials with high strength, long-lifetime and light weight has attracted wide attention in many industries such as aerospace, energy and chemistry. While, titanium tubular materials are subjected to complex multiple thermal-mechanical processing, and generally present pronounced anisotropy/asymmetry properties, which greatly affects the formability and the performance of the tubular materials. Meanwhile, thin-walled tubular materials are difficult-to-characterizing materials. Thus, how to accurately and comprehensively characterize the mechanical properties is the most vital issue and precondition for innovative design of the fabricating and forming of the tubular materials and components. However, the hollow structure of tubular materials, especially thin-walled geometry, makes the testing and characterizing of the mechanical properties a challenge. In this research, a general testing and characterizing framework is developed to determine anisotropic and asymmetrical mechanical properties for tubular materials. In the framework, Knoop microhardness is first employed to qualitatively identify anisotropy and asymmetry of titanium tubes. The basic tension and compression mechanical properties along axial direction are determined by mean of uniaxial tensile and compressive tests. Combined with tension and compression tests, the viscoplastic self-consistent crystal plasticity (VPSC) is calibrated to complement the deformation behaviors along other different loading directions. Taking Ti-3Al-2.5V titanium tube and commercial pure titanium (CP-Ti) tube as the case materials, the application of the above framework for the mandrel bending demonstrates the feasibility of the proposed methodology.

Formability of Thin-Walled Commercial Pure Titanium Tube upon Rotary Draw Bending

Under variations of bending radii and material properties, the multi-defect constrained formability of thin-walled commercial pure titanium (CP-Ti) tube was identified to explore the forming potential of this advanced lightweight material via explicit/implicit 3D-FE models and the experiments. The major results show that the variations of hardening exponents, thickness anisotropy exponent and Young's modulus, have great effects on bending formability; and compared with the wall thinning and cross-section deformation, the wrinkling instability is the dominant defect to restrain the bending formability of the large diameter thin-walled (LDTW) CP-Ti tube. The bending formability of CP-Ti tube, especially the anti-wrinkling capability, can be improved at elevated temperatures.

High power beta electron device - Beyond betavoltaics

Developing watt level power sources with beta emitting radioisotopes has been limited by the inability to utilize high energy (> 100KeV) beta emitters at high radioisotope loadings without damaging the energy conversion materials. A new type of beta electron power source is described that removes those restrictions. The approach contains the radioisotope in a beta transparent titanium tube and confines beta electrons emitted through the tube wall to spiral trajectories around the tube with an axial magnetic field. The confined beta electrons dissipate energy though multiple interactions with surrounding excimer precursor gas atoms to efficiently generate photons. Photovoltaic cells convert the photons to electrical power. Since the beta electrons dissipate energy in the excimer precursor gas, the device can be loaded with more than 1013Bq of radioisotope to generate 100 milliwatt to watt levels of electrical power without damaging the device materials or degrading its performance. The power source can use a variety of beta radioisotopes and scales by stacking the devices.

Microstructure evolution and mechanical characterization of Nd:YAG laser beam welded titanium tubes

Grade 2 titanium tubes of outer diameter 60mm and wall thickness 3.9mm were effectively joined by Nd:YAG laser. The welding speed was varied in five levels (2.50, 2.75, 3.00, 3.25 and 3.50m/min). The microstructure evolution was studied using optical microscopy and advanced characterization techniques. The bead geometry changed from parallel shape to wedge shape with increased welding speed due to changes in surface tension. The macrographs showed three zones namely fusion zone, heat affected zone (HAZ) and base metal. Coarse granular structure with irregular and serrated contours was observed in the fusion zone. Acicular α grains were observed at the extreme outer edge of the fusion zone due to rapid cooling. Spherical and irregular shaped pores were observed near the centerline of the fusion zone at lower welding speeds due to large amount of entrapped gases and downward sweeping solidification front. The grain size decreased with increased welding speed due to higher cooling rate. The misorientation angle distribution map showed three distinct regions. The increase in welding speed caused an increase in low angle boundaries and a reduction in very high angle boundaries. High density of dislocations was observed in the fusion zone due to thermal stresses caused by solidification. The microhardness of the fusion zone was recorded to be higher than base metal due to substructure boundaries, solute elements and dislocations. The increase in welding speed shifted the fracture location from fusion zone to base metal and fracture mode from brittle to ductile.

Activated soldering of dissimilar materials with amorphous solders

The features of soldering of dissimilar materials using amorphous solders (for example, steel–titanium pair) have been investigated. To reduce the soldering temperature below the phase transformation temperature and to retain the advantages of the solution-diffusion junction, compositions for amorphous alloy solders have been developed representing a powder mixture of amorphous solder based on titanium VPr-16 with low-melting solders based on gallium and indium. The efficiency of activated soldering has been tested from the standpoint of mechanical strength using cylindrical butt-soldered samples, the elements of a steel–titanium tube board, and some specific complex structures of heat exchange systems, etc. On the basis of the X-ray spectral analysis of soldered joints using a Camebax micro unit, it is established that the diffusion zone of a soldered joint is about 100 μm. The solder is completely consumed during the formation of the diffusion layer, the independent phase is not retained, which provides high strength properties of the soldered junction. The developed approach to the creation of hard-packed soldered structures from dissimilar materials is basic and has been successfully implemented for a number of other compositions, including the soldering of aluminum, steel, and NiCr; copper and a quasicrystalline Al–Cu–Fe alloy; and titanium and ruthenium. Examples of successful practical implementation of the results are presented.

Effect of flow-forming parameters on surface quality, geometrical precision and mechanical properties of titanium tube

In this study, the flow-forming process for fabricating seamless thin-wall tubes is experimentally investigated on a commercially pure titanium sample. For this purpose, the influence of three processing parameters including feed rate, mandrel revolution, and thickness reduction is studied on the surface quality and geometrical accuracy of flow-formed tube. It is found that the feed rate increment results in more longitudinal displacement of the roller on the tube sample. This intern results in, more area of the material to be in contact with the roller during the tube revolution; hence, higher tube surface roughness. Also, surface finish and dimensional precision of spun tube are lessened by increment of the mandrel revolution due to the intensification of machine vibration. Additionally, increased reduction of wall thickness leads to the enlargement of diametral growth and the loss of roundness. Also, it will increase the resistance of the material flow, which results in the wave creation at the tube surface, thereby decreasing the surface quality of the spun sample.

Outer heat transfer coefficient for condensation of pure components on single horizontal low-finned tubes

The outer heat transfer coefficient is determined for the condensation of pure components (iso-propanol, n-pentane, n-heptane, iso-octane and water) on low-finned carbon steel, stainless steel and titanium tubes. The outer heat transfer coefficient on these tubes is 3 to 8 times higher than on a smooth tube with the same reference surface area. The experimental data are compared with theoretical models from literature for the condensation of refrigerants and water. These models do not predict all experimental data for the condensation of iso-propanol and hydrocarbons on low-finned tubes with the accuracy given in the respective papers. Therefore, a new approach for calculation of the outer heat transfer coefficient based on dimensionless numbers is developed. With this new equation, it can be predicted with a maximum deviation of ±20%.

Flow Injection Photochemical Vapor Generation Coupled with Miniaturized Solution-Cathode Glow Discharge Atomic Emission Spectrometry for Determination and Speciation Analysis of Mercury.

A novel, compact, and green method was developed for the determination and speciation analysis of mercury, based on flow injection photochemical vapor generation (PVG) coupled with miniaturized solution cathode glow discharge-atomic emission spectroscopy (SCGD-AES). The SCGD was generated between a miniature hollow titanium tube and a solution emerging from a glass capillary. Cold mercury vapor (Hg(0)) was generated by PVG and subsequently delivered to the SCGD for excitation, and finally the emission signals were recorded by a miniaturized spectrograph. The detection limits (DLs) of Hg(II) and methylmercury (MeHg) were both determined to be 0.2 μg L-1. Moreover, mercury speciation analysis could also be performed by using different wavelengths and powers from the UV lamp and irradiation times. Both Hg(II) and MeHg can be converted to Hg(0) for the determination of total mercury (T-Hg) with 8 W/254 nm UV lamp and 60 s irradiation time; while only Hg(II) can be reduced to Hg(0) and determined selectively with 4 W/365 nm UV lamp and 20 s irradiation time. Then, the concentration of MeHg can be calculated by subtracting the Hg(II) from the T-Hg. Because of its similar sensitivity and DL at 8 W/254 nm, the simpler and less toxic Hg(II) was used successfully as a primary standard for the quantification of T-Hg. The novel PVG-SCGD-AES system provides not only a 365-fold improvement in the DL for Hg(II) but also a nonchromatographic method for the speciation analysis of mercury. After validating its accuracy, this method was successfully used for mercury speciation analysis of water and biological samples.

Experimental evaluation of the temporal effects of paint-based protective films on composite fouling inside admiralty brass and titanium steam surface condenser tubes

Paint-based protective films (PPFs) are inorganic thin coatings currently used in industry to mitigate corrosion and erosion. In this paper the fouling characteristics of one of these PPFs is experimentally investigated using a purpose-built test facility installed at a thermal power plant. Details are provided describing the apparatus which uses actual cooling water from the condenser outlet that passes through six parallel double-pipe heat exchangers. Admiralty brass and titanium tubes are tested simultaneously with and without the same PPF applied, enabling the fouling factor to be measured as a function of exposure time. The predominate fouling mechanisms occurring at this plant are found to be biological, precipitation, and particulate fouling. The results indicate that the PPF fouls identically to the titanium tube and the admiralty brass tube reaches the lowest fouling factor (five times less than all other tubes). The toxicity of the copper ions in the brass with respect to biofilm development is suggested to cause this. Therefore when a new tube alloy is used instead of a copper-based alloy, or when a non-biocidal PPF is employed in conditions liable to biofouling, the water treatment program must be effectively upgraded with respect to its biofouling countermeasures.

Large-Scale, Uniform, and Superhydrophobic Titania Nanotubes at the Inner Surface of 1000 mm Long Titanium Tubes

Large-scale and mass production of uniform nanostructured materials has been a growing challenge. Anodic titania nanotubes have been widely employed in various applications, which are usually demonstrated with limited size and planar geometry. In this study, a coaxial electrochemical anodization approach is explored and reported. With this method, uniform titania nanotube arrays are produced at the inner surface of titanium tubular electrodes of 1000 mm in length and 10 mm in diameter, in good contrast to the nonuniform nanotubes attained with a conventional anodizing scheme. Such an approach is cost-effective and energy-efficient. It is also capable of processing other valve metals possible for anodization and even longer tubular substrates. The wetting property of the resulting nanotube arrays is further tailored, with a maximum contact angle of 166° for water and 163° for glycerol, exhibiting a superhydrophobic feature. An equation is derived to compute the intrinsic contact angle of a spherical drople...

Gradient Structures in Thin‐Walled Metallic Tubes Produced by Continuous High Pressure Tube Shearing Process

A new severe plastic deformation process, the authors refer to as High Pressure Tube Shearing (HPTS), is proposed. This type of deformation processing enhances the strength of the walls of metallic tubes by producing gradient microstructures with ultrafine grained layers in near‐surface regions. The thickness of the layers associated with a gradient in microstructure can be controlled by tuning the rotational and translational speeds of the process. The paper describes several examples of steel and titanium tubes processed by different variants of HPTS. The possibility of producing gradient microstructures with ultrafine grained layers at inner or outer surface of a tube, or at both surfaces is demonstrated by in‐depth theoretical analysis, finite element simulations, and experimental investigation of the microstructure and texture of tube walls.

Microstructure and mechanical characterization of continuous drive friction welded grade 2 seamless titanium tubes at different rotational speeds

Friction welding is a near ideal process to join thin metallic tubes. Grade 2 titanium tubes of outer diameter 60 mm and wall thickness 3.9 mm were joined by friction welding. The effect of rotational speed on microstructure was evaluated for five different speeds. The process parameters were recorded during welding. The microstructure was observed using optical microscopy and electron back scattered diagram. The results revealed that the rotational speed had a significant effect on the process parameters, microstructure and joint integrity. An increase in rotational speed reduced the torque and rate of frictional power input and extended the welding duration. The rate of deformation increased with rotational speed and refined the grains in the weld zone. The grain size was observed to coarsen from the center of the weld zone towards the flash. The grain structure in the heat affected zone (HAZ) was identical to the parent metal. A maximum joint efficiency of 98.3% was achieved at rotational speed of 2200 rpm. The details of microhardness, failure location and fracture surface were reported.

Enhancement of R1234ze(Z) pool boiling heat transfer on horizontal titanium tubes for high-temperature heat pumps

R1234ze(Z), which has a global warming potential of less than 1, is a promising alternative refrigerant for high-temperature heat pumps designed for heat recovery in the industrial sector. The use of titanium as the material for heat exchangers exposed to acid exhaust is one solution to prevent oxidation. In this study, the pool boiling heat transfer characteristics outside of horizontal titanium tubes were experimentally investigated for R1234ze(Z). A plain tube and three enhanced titanium tubes were tested at saturation temperatures from 10°C to 60°C and heat fluxes from 0.55 to 79.8 kW m−2. Compared to the plain tube, the tested enhanced tube exhibited a 2.8 to 5.1 times higher heat transfer coefficient, on average, in the test range, which could compensate for the disadvantage in the thermal conductivity of titanium. The enhancement ratio predominantly depends on the saturation temperature and the wall heat flux. At conditions of higher saturation temperatures and lower heat flux, where smaller bubbles are observed, test tubes with smaller fin spaces exhibit higher heat transfer coefficients. The experimental results indicate the importance of fin geometry optimization to the operation conditions.

Interlayer Engineering on Friction Welded Titanium Tube to Stainless Steel Tube Plate by External Tool Process

Joining of titanium and stainless steel is challenging due to the formation of hard, brittle intermetallics. This study focuses on engineering ductile materials for joining transition metals. Friction welding of tube to tube-plate by an external tool, a novel solid state welding process was employed to join titanium tube and stainless steel tube plate. The interlayers engineered were copper, silver and Cu-Zn alloy. The micrographs revealed phase transformations in titanium tube and unaffected stainless steel base. Interface peak microhardness of 458 HV was observed for Ti/Cu-Zn/SS welded sample. The intermetallics formed were characterized by X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. A novel shear test procedure was developed to evaluate the maximum shear load. It was found that joints with silver as interlayer withstood the maximum shear load of 56 kN. The shear surfaces were further analyzed and investigated for fracture study.