Is 0.2 thick pure titanium plate the same as 0.2 thick titanium foil, what is the difference?
Depending on the specific material, first of all, the material is differentiated;
Secondly, generally 0.2 and titanium plates, mostly titanium foil sheet.
Titanium foil is relatively thin, and the width is not too wide, but the width of the sheet is wider, generally 0.1 or less is titanium foil.
The most important thing is the material, it can also be said that 0.2 is titanium foil.
Stress corrosion cracking (SCC) of titanium alloys was once one of the very active research topics at home and abroad, especially in the aerospace field. Industrial practice shows that most of the titanium welding wire used in the chemical industry are very resistant to stress corrosion. For cracking, stress corrosion cracking may occur only in some special media, such as pure methanol, fuming nitric acid, halide aqueous solution of nitrogen tetroxide, and liquid metal calcium and mercury. Industrial practice has proved that the actual occurrence of stress corrosion cracking accidents is much less than the stress corrosion sensitivity found in the laboratory.
The stress corrosion susceptibility is related to factors such as medium composition, pH value, potential, temperature, and even the viscosity of the medium. The addition of halogen ions improves the stress corrosion sensitivity and increases with the increase of ion concentration. Increased temperature and decreased viscosity can accelerate the rate of cracking.
The mechanism of stress corrosion cracking is still not completely unified. At present, there are two main types of viewpoints: stress-accelerated anodic dissolution and hydrogen enrichment at the crack tip. In fact, this may not necessarily be a tit-for-tat irreconcilable viewpoint. condition. However, a lot of practice shows that hydrogen-induced cracking is a very important cause of stress corrosion cracking, especially the SCC cracking phenomenon found in general industries (such as chemical industry).
Many process parameters of titanium alloys in forging, volume stamping and sheet stamping are close to those in steel processing. But there are some important features that must be paid attention to when pressing working titanium and titanium alloys. When the titanium alloy is cold plastically deformed, regardless of its chemical composition and mechanical properties, the strength will be greatly improved, and the plasticity will be correspondingly reduced. For this reason, annealing treatment between processes must be performed. The low thermal conductivity of titanium and the formation of non-coiled shavings are the reasons for the important characteristics of the machining of titanium and its alloys. When cutting titanium, the tool face will generate high temperature. In order to dissipate the heat, sharpened knives can be used, and a large amount of coolant and lubricant can be supplied. The tools made of carbide BK6M, BK8, BK4, BK2 have good cutting performance in grinding, milling and drilling.
The grinding and polishing of titanium alloys are divided into the following three methods:
(1) Fine grinding
That is to use conventional various emery rubber wheels to grind the surface of titanium and titanium alloy castings. The problem that needs to be paid attention to during grinding is still not to make the casting generate heat, not to cause grinding damage on the surface of the casting, and to make the entire surface smooth and smooth.
(2) Barrel grinding method
The so-called barrel grinding method is to put the processed castings, abrasives, water and additives into the barrel-type grinding tank, and the grinding barrels rotate and vibrate, so that friction is generated between the mixture of abrasives and the processed castings, and the surface of the castings is ground. Smooth and flat. It is characterized by no dust pollution, low labor intensity, and no heat generation in the conventional grinding process. At present, Japan has commercialized barrel grinders and abrasives for grinding Grade 1 Titanium Bar, other metal castings and plastics. It has been confirmed by experiments that the grinding efficiency of pk series abrasives is high, but the surface roughness is also very high. Although the grinding efficiency of SA and B series abrasives is not as good as that of PK, the surface smoothness of the ground titanium castings is higher. At present, the Fourth Military Medical University has successfully developed the first domestic dental barrel grinder.
(3) Mechanical polishing method
The method of polishing the surface of titanium and titanium-containing alloys using soft cloths or black brushes of different specifications, dipped in special polishing pastes for titanium and titanium-containing alloys. When polishing titanium castings, it is necessary to completely clear the contamination layer on the surface of the casting and no new grinding and hardening layer, which will not achieve the ideal polishing effect. When polishing, high speed and light pressure should be used for polishing. The author has also tested the use of green polishing paste to polish titanium and titanium-containing alloy castings, and achieved a relatively ideal polishing effect. Polished titanium and titanium-containing titanium alloy castings cannot be washed with water immediately. The surface oxide film must be completely formed before washing with water, otherwise the surface will be darkened.
With the continuous development of the seawater desalination industry, the evaporation heat transfer tube, which is one of the core components of thermal desalination devices, has also attracted the attention of scientific researchers and technicians. Traditional stainless steel, copper alloy, aluminum alloy, and other materials cannot fully meet the requirements of seawater application environment for material corrosion resistance, mechanical properties, and lightweight, while industrial pure titanium TA2 has excellent corrosion resistance, good plastic toughness and high It is an ideal material for making heat exchange elements of thermal seawater desalination devices. At present, in the large-scale thermal seawater desalination plants constructed in my country, rolled seamless titanium tubes have been applied to a certain extent, but the large-scale promotion of titanium heat transfer tubes is still greatly limited. The high price of seamed titanium pipes leads to high material investment costs.
Many scholars at home and abroad have been committed to the design and development of thin-walled Grade 2 Pure Titanium Tube and the research on corrosion resistance. The application history in the field of horizontal tube falling film seawater desalination technology is short, and the experimental data on the heat transfer coefficient and corrosion resistance of titanium tube falling film evaporators are insufficient, so it is difficult to guide the design of seawater desalination system. In addition, the wall thickness of titanium welded pipes used in seawater desalination projects is currently 0.5mm, which is difficult to meet the control requirements of seawater desalination projects on material costs. , reduce the amount of titanium used in equipment. Based on this, TA2 industrial pure titanium ϕ22mm×0.4mm thin-walled coiled titanium tube was prepared by tungsten argon arc welding (TIG) process, and the application experiment of low-temperature multi-effect distillation seawater desalination was carried out to test its corrosion resistance. performance and heat transfer performance, verify the quality of welded joints, obtain experimental data, and provide technical support for the large-scale production of 0.4mm thin-walled coiled titanium tubes and their popularization and application in seawater desalination projects.
The cutting force of titanium alloy processing is only slightly higher than that of steel with the same hardness, but the physical phenomenon of processing titanium alloy is much more complicated than that of processing steel, which makes titanium alloy processing face huge difficulties.
The thermal conductivity of most titanium alloys is very low, only 1/7 of steel and 1/16 of aluminum. Therefore, the heat generated in the process of cutting Grade 9 Ti3Al2.5V Titanium Tubes will not be quickly transferred to the workpiece or taken away by the chips, but will accumulate in the cutting area, and the temperature generated can be as high as 1 000 °C or more, which will cause the cutting edge of the tool to rapidly wear, chip and crack. A built-up edge is created, which quickly causes a worn edge, which in turn generates more heat in the cutting area, further reducing tool life.
The high temperatures generated during the cutting process also destroy the surface integrity of the titanium alloy parts, resulting in a decrease in the geometric accuracy of the parts and work hardening that severely reduces their fatigue strength.
The elasticity of titanium alloys may be beneficial for part performance, but during cutting, the elastic deformation of the workpiece is an important cause of vibration. The cutting pressure causes the "elastic" workpiece to move away from the tool and bounce so that the friction between the tool and the workpiece is greater than the cutting action. The friction process also generates heat, aggravating the problem of poor thermal conductivity of titanium alloys. This problem is even more serious when machining thin-walled or ring-shaped parts that are prone to deformation. It is not an easy task to machine thin-walled titanium alloy parts to the expected dimensional accuracy. Because when the workpiece material is pushed away by the tool, the local deformation of the thin wall has exceeded the elastic range and plastic deformation occurs, and the material strength and hardness of the cutting point increase significantly.
Titanium 6AL-4V ELI is the standard product for the fabrication of hip joints, bone screws, knee joints, plate bones or organs, dentures and surgical devices. However, cobalt-chromium alloys are being used more and more often because of their strength, tighter grain size, and cleanerness than titanium. Machining titanium alloys requires only slightly greater cutting forces than machining steels, however, the metallurgical properties of titanium alloys make them more difficult to machine than steels of moderate hardness. Titanium has a titanium work-hardenability that eliminates consolidated metal (hemming) in front of the cutting tool. This helps to increase the shear angle in machining, thus forming a thin chip that touches the cutting tool surface in a reasonably small area. Because of this work-hardening, the feed should not be suspended during the tool-workpiece motion contact. The large supporting force that occurs during machining, combined with the frictional force generated by the chips in the touch area, causes a large increase in heat in the tool part area. The heat generated by cutting titanium does not dissipate quickly because it is a poor conductor. Therefore, most of the heat is concentrated on the cutting edge and tool surface. The large bearing force and heat form a crater near the cutting edge, causing the tool to be damaged quickly. To make matters worse, Titanium Alloy Threaded Rod have a strong tendency to fuse with the products in the tool to form alloys or revive chemical changes at the working temperature of the tool. damage. These difficulties are multiplied when tools begin to break, so tools used to machine titanium and its alloys should be carefully monitored to ensure sharp edges and replacement before they become dull. The experience of machining titanium and titanium alloys is that if you see any changes during the machining process, you should change the tool immediately, because the change means that the tool will become dull. Another reason to insist on sharp knives is that titanium can catch fire when cutting with a damaged or damaged tool. When incinerated, the metal generates oxygen, so the fire will spontaneously ignite. Therefore, many workshops that process titanium do not report fires, and they are equipped with rescue systems on their machine tools.
Titanium has a moderately low modulus of elasticity and is more elastic than steel and therefore tends to defy the cutting tool when machined unless it is to be cut robustly or used as a proper support. Slender parts tend to deflect under tool pressure, causing problems with tool chatter, tool friction, and tolerance. Through the processing experience, it is believed that the rigidity of the entire system of the tool is very important, and the sharp and accurate shape of the tool should be used. As a result of these pressures, new technologies have been introduced to help shops that make medical parts cope with the competition, and the machining performance can produce these complex parts with very high precision; many innovations in EDM have enabled the production of high-quality parts faster, eliminating many old machining techniques inherent topics.
As a new type of product, titanium has only been developed and used in China's pharmaceutical industry, medical equipment, human implants and other fields for nearly two decades. However, it has achieved great success and achieved significant social and economic benefits, shortening the gap between China and the advanced countries in the world. The use of titanium equipment in the production of many commodities not only solves the equipment corrosion problem that has seriously plagued the company's production and development, but also greatly improves the quality of drugs.
Titanium and Grade 7 Titanium Plate are active metals, which can easily react with oxygen in the air to form a very thin transparent oxide film, which passivates the surface and forms a passivation film. On the one hand, this passivation film protects the base metal and improves the corrosion resistance of the metal surface; on the other hand, because the formation of the passivation film reduces the activity and electrical and thermal conductivity, it is difficult to coat the surface, which will obviously affect the bonding force between the coating layer and the substrate. Therefore, activation treatment must be performed before the surface of titanium and Grade 3 Pure Titanium Plate, which is a critical step to ensure the bonding force between the plated layer and the substrate.
As a new generation of future metal, titanium metal has strong corrosion resistance. The TC4 titanium rod produced, processed, and manufactured with titanium metal as raw material is quite stable in organic media and has a wide range of applications in the medical and chemical fields; machined titanium round rod High-temperature resistance, this feature allows it to be used in high temperature operating environments without deformation and aging; in addition, TC4 titanium rods have high strength, that is, they have super mechanical properties, so they can be used in high-pressure processes; TC4 The regeneration effect of titanium rods is good and the service life is long. There are two kinds of regeneration treatment methods: physical regeneration method and chemical regeneration method. The physical regeneration method includes pure water backflushing, steam backflushing and ultrasonic cleaning; chemical treatment methods include acid washing and alkali cleaning. Wash both.
The cutting force of titanium alloy processing is only slightly higher than that of steel with the same hardness, but the physical phenomenon of processing titanium alloy is much more complicated than that of processing steel, which makes titanium alloy processing face huge difficulties. The thermal conductivity of most titanium alloys is very low, only 1/7 of steel and 1/16 of aluminum.
Therefore, the heat generated in the process of cutting titanium alloys will not be quickly transferred to the workpiece or taken away by the chips, but will accumulate in the cutting area, and the temperature generated can be as high as 1 000 °C or more, which will cause the cutting edge of the tool to rapidly wear, chip and crack. A built-up edge is created, which quickly causes a worn edge, which in turn generates more heat in the cutting area, further reducing tool life.
The high temperatures generated during the cutting process also destroy the surface integrity of the titanium tubing for bike frame parts, resulting in a decrease in the geometric accuracy of the parts and work hardening that severely reduces their fatigue strength.
The elasticity of Grade 5 Ti-6Al-4V Titanium Plate may be beneficial for part performance, but during cutting, the elastic deformation of the workpiece is an important cause of vibration. The cutting pressure causes the "elastic" workpiece to move away from the tool and bounce so that the friction between the tool and the workpiece is greater than the cutting action. The friction process also generates heat, aggravating the problem of poor thermal conductivity of titanium alloys.
Titanium alloys are widely used in important load-bearing components of aircraft and aircraft engines because of their high specific strength, good medium temperature performance, corrosion resistance, and good welding performance, and are an important metal structural material. According to statistics, the weight ratio of titanium alloys used in foreign aircraft has reached about 30%, which shows that the application of titanium alloys in the aviation industry has a broad future.
However, titanium alloy flange also have some disadvantages, such as large deformation resistance, poor thermal conductivity, large notch sensitivity (about 1.5), and changes in microstructure have a significant impact on mechanical properties, which leads to smelting, forging and heat treatment. Complexity, prone to defects in titanium alloy forgings.
A few days ago, the technical project of "production process of titanium heat exchanger pipe" passed the evaluation of scientific and technological achievements. This technical process is mainly improved for the traditional hot rolling process of seamless steel pipes, and transplanted to the production of titanium alloy seamless pipes, which is similar to the traditional "extrusion forming, bar drilling and boring and cross-rolling and piercing followed by cold rolling and cold drawing" process. The finished product rate of pipes is significantly improved, reaching 97%.
Through the characteristics of titanium alloy tubes, the project has made targeted improvements in the production process. The addition of thermal insulation tunnels and rapid transfer devices to the power of the main motor is innovative to a certain extent. Large titanium alloy tubes up to 12m in length.
The cutting of titanium and titanium alloy pipes should be carried out mechanically, and the cutting speed should be low; when cutting or grinding Titanium Alloy Seamless Rectangular Pipe with grinding wheels, special grinding wheels should be used; flame cutting should not be used. The groove should be processed mechanically. Titanium alloy processing and welding should use inert gas shielded welding or vacuum welding, not oxygen-acetylene welding or carbon dioxide gas shielded welding, nor ordinary manual arc welding. When installing titanium and titanium alloy pipes, iron tools and materials should not be used to knock and squeeze; between carbon steel supports, hangers and titanium and titanium alloy pipes, rubber sheets or soft plastic sheets should be placed to prevent Titanium and titanium alloy pipes are in direct contact.
When the titanium and titanium alloy pipes pass through the wall and floor, the casing should be installed, the gap should not be less than 10mm, and the insulation should be filled, and the insulation should not contain iron impurities. Titanium alloy pipes should not be directly welded to other metal pipes. When a connection is required, a looper flange connection can be used. The non-metallic gaskets used are generally rubber gaskets or plastic gaskets, and the chloride ion content should not exceed 25ppm.
The lattice type, melting point, thermal conductivity, coefficient of linear expansion and chemical composition of Titanium Clad Copper Plates are very different, so it is very difficult to weld.
1) The weld is easy to form pores
(1) Copper and titanium have strong hydrogen absorption capacity at high temperature, and hydrogen has a large solubility in liquid copper and titanium.
(2) Gas is generated in the molten pool of pyrometallurgical reaction.
(3) Oxygen and nitrogen gases around the welding zone are immersed in the molten pool.
2) Welded joints tend to have large cracks
When copper and titanium are welded, eutectic and hydride can be formed on the metal side of the two base metals, and cracks are easily generated under the action of welding stress.
(1) Copper and bismuth form a (Cu+Bi) eutectic with a eutectic point of 270°C.
(2) Copper and aluminum form a (Cu+Pb) eutectic with a eutectic point of 326 °C.
(3) Copper and ferrous sulfide form a eutectic (Cu+Cu2O) with a eutectic point of 1067°C.
(4) Sheet-like hydride TiH2 is formed on the metal side of the titanium base material, resulting in hydrogen embrittlement.
(5) The coefficient of linear expansion of copper and titanium is more than 1 times different, and greater stress will be generated during welding.
3) Low mechanical properties of welded joints
(1) The oxide film can weaken the intergranular bond between copper and titanium. For example, when the oxygen content in the weld reaches 0.38%, the bending angle of the joint decreases from 180° to 120°.
(2) A large amount of eutectic and hydride significantly reduces the plasticity and toughness of welded joints.
(3) The mutual solubility of copper and titanium is very small, and it is easy to form intermetallic compounds at high temperatures. Such as Ti2Cu, TiCu, Ti3Cu4, Ti2Cu3, TiCu2, TiCu4, increase brittleness, reduce plasticity, and significantly reduce the corrosion resistance of weld metal.
Copper and titanium or titanium alloys can obtain excellent welded joints by vacuum diffusion welding, argon arc welding, plasma arc welding, brazing and electron beam welding.
After the titanium base metal (TA2) was cleaned with trichloroethylene, it was etched in an aqueous solution with a volume fraction of 2% HF and a volume fraction of 50% HNO3 by vibration for 4 minutes to remove the oxide film, and then cleaned with water and alcohol .
(4) Assemble the cleaned two base metals according to the process requirements, and then put them into a vacuum furnace for welding. The welding parameters are: the welding temperature is 810℃±10℃, the pressure is 5~10MPa, the time is 10min, and the vacuum degree is 1.3332×10-8~ 1.3332×10-9MPa. An intermediate diffusion layer can be added between the two base metals. Usually, the material of the diffusion layer is niobium metal, or no intermediate diffusion layer is required. After welding, carefully clean the joint surface.
If argon arc welding is used to weld copper and titanium, the selection of cerium tungsten electrodes can improve the welding quality and benefit human health. For example, when welding copper alloy (QCr0.5) and titanium alloy (TC2), niobium can be used as the transition layer material, and the purity of argon gas is 99.8% to obtain high-quality joints.
The processing difficulties of titanium alloy structural parts and the influencing factors of processing deformation of weakly rigid structures are presented. The control method of processing deformation of weakly rigid structural parts is proposed from the selection of machine tools, tool selection, and effective cooling. Titanium alloy materials have excellent properties such as lightweight, high strength, and high-temperature resistance. For example, using TC18 titanium alloy instead of high-strength structural steel for landing gear can reduce the weight of the aircraft structure by about 15%, so it is the main bearing of advanced foreign aircraft. A large number of new high-strength titanium alloys are used in the force parts. For example, Titanium Alloy Threaded Rod accounts for about 21% of the body structure materials of the American B-1 bomber; the titanium content of the Russian Il-76 aircraft reaches 12.5% of the body structure weight. , From the development trend, the use of titanium alloys in Europe and the United States is gradually increasing, and it also shows that a large number of titanium alloys are used, especially some new titanium alloys have become the development direction of aviation design. However, most aerospace products use thin-walled parts, which are relatively complex in structure and require high precision. Due to the thin wall, the rigidity of the parts is poor. Under the action of cutting force, it is easy to produce bending deformation during processing, and the wall thickness is inconsistent up and down, resulting in out of tolerance. . At present, the commonly used method in enterprises is repeated milling in finishing. Due to the small thermal conductivity of titanium alloy, low elastic modulus (about 1/2 of steel) and high chemical activity, the small allowance cannot be milled at all, often The phenomenon of "less cutting" occurs. In order to ensure the size of the parts, it can only be polished by hand, which greatly increases the processing cycle of the parts, and may cause the surface of the parts to burn.
