Sunday, October 11, 2020

Drawing process of titanium rod and titanium wire

Titanium alloy screws are not a high-strength material. It has high specific strength. The density of titanium alloy screws is about 50% to 60% of that of 45# steel, but the strength is equivalent. Titanium alloy screws not only have high strength but also have good heat resistance and low-temperature resistance. Titanium has good corrosion resistance to salt, seawater and nitric acid. It is a well-deserved space and ocean metal.
The development trend of my country's titanium industry is very fierce, and it has become a major country in the development of titanium production. The overall output of titanium screw products in my country has shown an increasing trend year by year, and titanium alloy screw materials are also widely used in machinery and equipment, electronic equipment, communication equipment, hardware lighting, construction bridges and other industries, and gradually entered the civilian field. Products usually made of materials are almost used to take advantage of the low density of titanium screws, usually in places where density requirements and weight requirements are combined.
Regarding the phenomenon of titanium screw sliding wire, we sometimes encounter the situation of titanium alloy screw overflow buckle, also called sliding wire. Commonly used on bicycles are the threaded holes of aluminum parts such as stems, cranks, and rod clamps. Titanium screws It's as good as a pedal axle. The perfect repair method is to ream and tap the titanium screw sleeve, but this process is troublesome and costly. In some places, the size is not rich and cannot be reamed. If you encounter a titanium screw thread overflow buckle, cut a short coil spring, fold the head, put it in the screw hole of the overflow buckle, and screw the titanium alloy screw directly into it. Basically, the original aluminum screw hole can be restored. Tight torque, and can be repeatedly disassembled and assembled, and the reed will not fall out. When screwing, you can choose different width coil springs according to the size of the titanium alloy screw hole, or put two coil springs into the titanium alloy screw hole. The possible ways to do it include wrapping a hemp knife, raw material tape, dispensing thread glue or 502, but the result is that the thread cannot be tightened and it is useless. Now introduce a simple repair method. Useless small measuring tapes, easy pull buckles and the like at home, as long as they are retractable, there must be a coil spring inside. Remove the coil spring for use before throwing it away.

Friday, October 9, 2020

Application of medical titanium alloy in the field of dental implants

When the hydrogen content in the titanium pipe is too much, the impact toughness and notched tensile strength will drop sharply due to the brittleness, so it is generally stipulated that the hydrogen content in the titanium pipe should not exceed 0.015%. In order to reduce the amount of hydrogen absorption, fingerprints, rolling mill marks, grease and other residues should be removed before heat treatment. There is no moisture in the heat treatment furnace. If the hydrogen content of the titanium pipe exceeds the allowable value, it must be removed by vacuum annealing.
When the temperature does not exceed 540 degrees, the oxide film of the titanium pipe fittings will not be significantly thickened, and at higher heat treatment temperatures, the oxidation rate will rapidly increase, and at the same time, the internal diffusion layer of the oxide material will become a pollution layer. The high brittleness ratio of the oxygen contamination layer causes cracks and damage on the surface of the part. There are mechanical processing methods for the deoxygenated pollution layer or chemical methods such as pickling and chemical milling. During the heat treatment, the heating time should be as short as possible under the premise of ensuring heat treatment. It can also be carried out in a vacuum furnace or an inert gas heating furnace. . The pollution caused by the titanium pipe fittings being heated in the air furnace should be appropriately avoided or reduced.

Sunday, September 27, 2020

Titanium alloy is an ideal armor material

The density of titanium alloy is small, the inertia of titanium liquid is small, and the fluidity of titanium liquid is poor, resulting in low casting flow. The temperature difference between the casting temperature and the mold is large, and the cooling rate is fast. The casting is carried out under a protective atmosphere. There are inevitably defects such as pores on the surface and inside of the casting, which have a great impact on the quality of the titanium casting. The following describes the surface treatment methods of titanium alloy parts processing.
1. Removal of the surface reaction layer
The surface reaction layer is the main factor affecting the physical and chemical properties of titanium castings. Before the titanium casting is ground and polished, the surface contamination layer must be thoroughly removed to achieve a satisfactory polishing effect. Pickling after sandblasting can completely remove the surface reaction layer of titanium.
Pickling: Pickling can quickly and completely remove the surface reaction layer, and the surface is not contaminated by other elements. The Hf-hcl system and Hf-hno3 system can be used for pickling titanic acid, but the Hf-hcl system has a large hydrogen absorption capacity, while the Hf-hno3 system has a small hydrogen absorption capacity. The hno3 concentration can be controlled to reduce the hydrogen absorption capacity and the surface can be brightened. . In general, the concentration of HF is about 3% to 5%, and the concentration of HNO3 is about 15% to 30%.
2. Treatment of casting defects
Internal pores and internal defects of the shrinkage cavity: Hot isostatic pressure can be eliminated, but it will affect the accuracy of the denture. X-ray flaw detection is used to remove exposed pores on the surface, and laser repair welding has a better effect. Surface pores can be repaired by laser welding.
Three, polishing
1. Mechanical grinding: Titanium has the characteristics of high chemical reactivity, low thermal conductivity, high viscosity, low mechanical grinding ratio, and easy reaction of abrasive tools. Ordinary abrasives are not suitable for grinding and polishing titanium. You can use super-hard abrasives with good thermal conductivity, such as diamond, cubic boron nitride, etc., and the polishing linear speed is generally 900-1800m/min, otherwise, the titanium surface is prone to grinding burns and micro-cracks.
2. Chemical polishing: Chemical polishing is the purpose of leveling and polishing through the oxidation-reduction reaction of metal in a chemical medium. The advantage is that chemical polishing has nothing to do with metal hardness, polishing area and structure shape. All parts in contact with the polishing liquid are polished without special complicated equipment.

Friday, September 25, 2020

Precautions for processing titanium alloy parts during processing

Titanium is stable in the air; because titanium has a low density and a high specific strength, the density is only 0.6 that of steel. The strength of pure titanium is almost the same as that of steel, and the alloy strength is nearly twice that of steel. It has excellent high-temperature resistance, low-temperature resistance, and corrosion resistance. characteristic. Titanium is called "space metal". It can maintain high strength and mechanical properties in a wide temperature range of -253℃~500℃. Since the 1950s, the proportion of titanium in aerospace has increased. The larger, titanium alloy is an important material for making rocket engine shells, artificial satellites, and spacecraft.
Titanium maintains its own color tone for life at room temperature, and its unique silver-gray tone is high polished and mercerized. Matte has a very good performance. It is the most suitable jewelry metal except platinum and gold. It is often used in modern foreign jewelry designs. However, due to the high technical requirements for titanium processing, it is difficult to cast it with ordinary equipment, and it is difficult to weld it with ordinary tools, so it is difficult to form a production scale. Titanium is light but extremely strong. It is an internationally popular jewelry material. In terms of design, its minimalist and clean cut, high design and low-key avant-garde style are highly respected by young white-collar workers.
TC4 titanium rod is a special metal. It has low density, light weight, high specific strength, and strong corrosion resistance. It will not turn black like silver, and will maintain its silvery white tone for life at room temperature. TC4 titanium rods and TC4 titanium forgings are often used in aerospace. Military precision parts. In terms of chemical reaction, the strong corrosive "Aqua regia" can swallow silver and gold, and even erode the so-called "stainless" stainless steel. However, the "Aqua regia" has nothing to do with titanium. ! Stainless steel is also added with titanium metal to achieve acid and alkali resistance.
Titanium plate has a unique purpose in medical doctors. When titanium metal comes into contact with substances, there will be no chemical reaction. In other words, because of the high corrosion resistance and stability of titanium, it will not affect its essence after long-term contact with people, so it will not cause human allergies. It is the only one that has no effect on human autonomic nerves and taste. metal. Titanium is also called "biophilic metal". In the bone damage, fix it with a titanium splint and a titanium bone nail. After a few months, the bone will grow on the titanium splint and the thread of the titanium bone nail, and the new muscle will be wrapped in the titanium splint. "Titanium bone" is like real bone, and even titanium artificial bone can be used instead of bone to treat fractures.

Tuesday, September 22, 2020

The plastics industry is the second largest user of titanium dioxide

When the hydrogen content in the titanium tube is too high, the brittleness of the titanium tube will reduce the impact of toughness and notched tensile strength of the titanium tube. Therefore, the hydrogen content in titanium pipe joints should not be higher than 0.015%. In order to reduce hydrogen absorption, fingerprints, abrasion marks, grease and other residues should be removed before heat treatment. There is no steam in the heat treatment furnace. When the hydrogen content of the titanium tube is higher than the allowable value, vacuum annealing cleaning is required.
When the temperature is not higher than 540°C, the oxide film will not thicken, but at a higher heat treatment temperature, the oxidation rate of the oxide film will increase, and the internal diffusion layer of the oxide film will become a pollution layer. The oxygen contamination layer has a high brittleness ratio, which causes cracks and damage on the surface of the part. Deoxidation pollution layer includes mechanical processing, pickling, chemical polishing and so on. During heat treatment, the heating time should be shortened as much as possible while protecting the heat treatment. It can also be carried out in a vacuum furnace or an inert gas furnace. The pollution caused by the heating of titanium pipe fittings in the air furnace should be avoided or appropriately reduced.
Features of titanium tube:
1 Corrosion resistance of titanium pipe joints. Titanium is a very active metal with a very low equilibrium potential and a strong tendency to thermodynamic corrosion in the medium. Titanium has good stability and corrosion resistance in oxidizing, neutral and weakly reducing media.
2 Titanium pipe joints have good heat resistance. It can be used for a long time at 600℃ or high temperature.
3Non-magnetic, non-toxic and titanium alloy pipe fittings are non-magnetic metals and will not be magnetized in a large magnetic field.

Sunday, September 20, 2020

Titanium alloy parts processing plays an important role in machinery manufacturing

Small-sized bars of titanium and titanium alloys are generally produced by rolling. However, during heating, rolling, and heat treatment, due to uneven distribution of temperature and plastic workability, as well as shearing, transportation and stacking, etc. Different degrees of bending is often produced. At this time, the titanium rod must pass through the straightening place to ensure that the bending degree of the rod can meet the requirements of use.
The commonly used straightening methods for titanium rod processing include pressure straightening and roller straightening, while small-sized bars generally use roller straightening, which has higher efficiency. However, for small-sized titanium and titanium alloy bars, the desired effect is often still not achieved after repeated straightening, and the problem of direct fracture during the straightening process often occurs.
The room temperature elastic modulus of commonly used titanium and titanium alloys is mostly lower than 120GPa. Therefore, titanium and titanium alloy bars will undergo greater elastic deformation under stress conditions under relatively small rolling production, and the rebound will be large. He plastic is easy to straighten, and the yield ratio of many titanium alloys is between 09-1. For reasons such as straightening, it is easy to break during straightening. Therefore, titanium and titanium alloy bars generally require hot straightening at the over-straightening point to ensure the straightening effect.

Friday, September 18, 2020

Slitting method for titanium plate and titanium strip

In the application of various titanium alloy products, forgings are mostly used in gas turbine compressor discs and medical artificial bones that require high strength, toughness and high reliability. Therefore, not only high dimensional accuracy is required for forgings, but also materials with excellent characteristics and high stability are required. For this reason, it is necessary to give full play to the characteristics of titanium alloy in the manufacturing process of titanium forgings to obtain high-quality forgings. Titanium alloys are difficult to forge and are prone to cracks. Therefore, the most important thing in the production of titanium alloy forgings is to properly control the forging temperature and plastic deformation.
Application fields of titanium alloy forgings:
1. The field of aerospace
50% of the world's titanium materials are used in the aerospace field. 30% of the body of military aircraft uses titanium alloys, and the amount of titanium used in civil aircraft is gradually increasing. In the aerospace field, titanium alloy forgings are used in the fuel tanks of rocket and satellite propulsion engines, the shell of attitude control engines, the blades of liquid fuel turbopumps and the inlet section of suction pumps.
2. Turbine blades for power generation
Increasing the length of the blades of the steam turbine for thermal power generation is an effective measure to improve the power generation efficiency, but lengthening the blades will increase the load on the rotor.

Monday, September 14, 2020

Pure titanium and titanium alloy are made into many daily necessities

At present, most of the domestic titanium alloy sheet production still adopts single-piece rolling. Due to the poor low-temperature plasticity of titanium alloys and large cold deformation work hardening, it is extremely difficult to produce thin plates by the monolithic method. In order to make the rolling process go smoothly and reduce the temperature drop of the metal during the forging process, especially to reduce the surface chilling of the blank, the die for forging the titanium alloy needs to be preheated. Otherwise, the temperature drop and surface chilling of the metal will make the metal not fill the mold groove well and may cause many cracks. The die preheating system for titanium alloy forging is usually detachable, but sometimes a heating device installed on a press is also used. The detachable mold heating system is usually a gas heater, which can slowly heat the mold to the required temperature range before the module is assembled into the forging equipment. The heating device fixed on the press usually adopts induction heating or resistance heating. With the expansion of the market, the new technology of superplastic forming and diffusion bonding of titanium alloy sheet has been widely used.

Friday, September 11, 2020

Titanium alloy is more suitable for spacecraft manufacturing than steel

In the 1980s, the research and application of titanium alloy pipes in the petroleum industry began in foreign countries. Chinese companies have also made certain progress in the development of titanium alloy tubing and casing. The current products have been initially tested in wells. It is believed that in the near future, titanium alloy pipes will have more applications in the petroleum equipment industry, and new breakthroughs will be made in the world industry as soon as possible.


1), lower density
Can significantly reduce the string load, especially ultra-deep oil well pipe.
2), higher strength
Including tensile strength, creep strength, fatigue strength, etc. The specific strength of different materials at different temperatures.
3), excellent corrosion resistance
Excellent seawater corrosion resistance
4) Wide operating temperature range
The operating temperature of conventional titanium alloy ranges from minus 269 ℃ to minus 600 ℃.
5), large elastic deformation capacity
Titanium alloy has high yield strength and low elastic modulus (E), so it is very suitable for springs and other parts, and more importantly, it is suitable for large-reach horizontal wells.
6), lower expansion coefficient
This feature makes petroleum equipment more adaptable to temperature changes and reduces the internal stress of structural parts.
7), non-magnetic
Meet the requirements of the normal use of some detection, communication and control methods in various equipment.
8), better processing performance
Titanium alloy pipes usually have good process properties such as casting, forging, welding, 3D printing, etc., which are often important factors in the selection process of various engineering materials.

Tuesday, September 8, 2020

What are the common machining processes for titanium alloys?

 Titanium alloy can obtain different phase composition and structure by adjusting the heat treatment process. It is generally believed that the small equiaxed structure has good plasticity, thermal stability and fatigue strength; the needle-shaped structure has higher endurance strength, creep strength and fracture toughness; the equiaxed and needle-shaped mixed structure has better comprehensive properties.
Commonly used heat treatment methods are annealing, solid solution and aging treatment. Annealing is to eliminate internal stress, improve plasticity and structural stability, and obtain better overall performance. Usually, the annealing temperature of α alloy and (α+β) alloy is selected at 120~200℃ below the (α+β)-→β phase transformation point; the solution and aging treatment are rapid cooling from the high-temperature zone to obtain martensite α′ Phase and meta-stable β-phase, and then keep these meta-stable phases in the middle-temperature zone to decompose, obtain α-phase or compound and other finely dispersed second-phase particles to achieve the purpose of strengthening the alloy. Usually (α+β) alloys are quenched at 40~100℃ below the (α+β)—→β phase transition point, and metastable β alloys are quenched at 40~80℃ above the (α+β)—→β phase transition point. get on. The aging treatment temperature is generally 450~550℃. In addition, in order to meet the special requirements of the workpiece, the industry also uses metal heat treatment processes such as double annealing, isothermal annealing, β heat treatment, and thermomechanical heat treatment.

Sunday, September 6, 2020

Titanium alloy tube installation related precautions

Industrial pure titanium is the most widely used titanium and titanium alloy material due to its low cost and easy production. The α-ti alloy in industrial pure titanium is commonly used in aviation, shipbuilding and chemical industries, and its impurity content has a great influence on its cold workability and the mechanical properties of finished materials. Increasing impurity content can increase the strength of titanium and reduce its plasticity. Once its quality is improperly controlled, the performance of the titanium material will not be guaranteed, and even the titanium ingot or billet cannot be processed into materials, resulting in waste products. This shows that the impurities The element content has a great influence on the mechanical properties of titanium materials.

Therefore, in the production of industrial pure titanium, the impurity content of titanium must be strictly controlled. After the pure titanium material is processed into titanium wires of different specifications, the problem of brittle fracture occurs in the subsequent drawing process. According to the site conditions, there is only a very small amount of titanium ingot forging remaining material and different specifications of the titanium material after processing. Titanium wire specifications range from 47.0, 465.5, 45.0, 44.5, and 03.0. In response to this situation, the failed samples were retrieved according to the method of random sampling and numbered from largest to smallest diameter: a, b, e, d, p. A small amount of titanium ingot forging numbered g was then inspected and analyzed.
 The nature of the brittle fracture problem of titanium wire has a lot to do with its impurity content. Therefore, it is necessary to understand its impurity source. The impurity elements in industrial pure titanium include Fe, S, 0, N, H, etc., and the content of these impurity elements is its finished product. The performance of the material has a greater impact, and once the impurity content is improperly controlled, the performance of the titanium material will not be guaranteed. It is not only difficult to process and even causes the risk of fracture. Due to the high chemical activity of titanium and titanium alloys, during the processing process , It will react violently with the oxygen and nitrogen in the atmosphere to form a dense oxide layer and getter layer, and prevent the re-infiltration and oxidation of gas. Therefore, oxygen is added as an added element during the production of titanium wire.
The nitrogen in the titanium wire mainly comes from several aspects in the preparation process of sponge titanium:
  (1) The residual air in the assembly of the reduction distillation equipment is absorbed by the titanium:
  (2) All nitrogen remaining in the argon gas is sucked into the titanium;
  (3) The gas leaked by the reduction distillation operation and the gas leaked when the negative pressure occurs in the discharge of MC2 and other reactors will increase the nitrogen content of titanium. After the gas leaks, yellow titanium nitride is formed on the surface of the sponge titanium, which is easier to identify.
 According to the above analysis, it can be known that the source of nitrogen in the titanium wire of this failure sample is sponge titanium, so the entry of nitrogen in the subsequent processing can be excluded. On the other hand, from the principle of plastic deformation of metal and related literature, it can be known that the formation of nitrogen atoms and titanium The interstitial solid solution hinders the slip of dislocations, which increases the strength of titanium and decreases its coherence, which affects its room temperature tensile properties. Among the interstitial impurities, the strengthening effect of N is the most obvious.

Thursday, September 3, 2020

Titanium crafts and titanium tableware have been widely used in life

The strength of titanium tube is relatively high, and the strength of ordinary steel is almost the same, even some high-strength titanium alloys are stronger than alloy structural steel. What is the performance of the titanium tube? Let's get to know.
The service temperature of the titanium tube is much higher than that of the aluminum alloy, and it can maintain a certain strength in a medium temperature environment. Titanium alloy works in a humid environment or in seawater, and its corrosion resistance is much better than stainless steel. And its corrosion resistance is also very strong, can resist alkali, chloride, chlorine organic substances, nitric acid, sulfuric acid and other corrosive substances.
But titanium also has disadvantages, that is, poor corrosion resistance to reducing oxygen and chromium salt media. The mechanical properties of titanium alloy can still be maintained at low and ultra-low temperature.
Generally speaking, aluminum alloy or stainless steel is easily confused with titanium, which is simply oxidation corrosion. Aluminum alloy is not corrosion-resistant, stainless steel is corrosion-resistant, stronger than aluminum alloy, and titanium alloy is completely corrosion-resistant. Secondly, high-temperature oxidation method and heating and dissolution method can be distinguished.

Tuesday, September 1, 2020

The forming process of titanium rod and titanium alloy rod under hot extrusion

Titanium rods and titanium alloy rod blanks have low thermal conductivity, which will cause a great temperature difference between the surface layer and the inner layer during hot extrusion. When the temperature of the extrusion cylinder is 400 degrees, the temperature difference can reach 200 to 250 degrees. Under the combined influence of suction strengthening and the large temperature difference of the blank section, the metal on the surface and the center of the blank produces very different strength and plastic properties, which will cause very uneven deformation during the extrusion process. Large additional tensile stress is generated in the extruded product, which becomes the source of cracks and cracks on the surface of the extruded product. The hot extrusion process of titanium rods and titanium alloy rod products is more complicated than the extrusion process of aluminum alloy, copper alloy, and even steel, which is determined by the special physical and chemical properties of titanium rods and titanium alloy rods.
Industrial titanium alloy metal flow kinetics research shows that in the temperature zone corresponding to the different phase states of each alloy, the metal flow behavior is greatly different. Therefore, one of the main factors affecting the extrusion flow characteristics of titanium rods and titanium alloy rods is the heating temperature of the blank that determines the state of the metal phase transformation. Extrusion at the temperature of a or a+P phase zone compares with extrusion at the temperature of p phase zone, the metal flow is more uniform. It is very difficult to obtain high surface quality for extruded products. So far, the extrusion process of titanium alloy rods must use lubricants. The main reason is that titanium will form a fusible eutectic with iron-based or nickel-based alloy mold materials at temperatures of 980 degrees and 1030 degrees, which will cause the mold to wear strongly.
 The main factors affecting metal flow during extrusion:
(1) Extrusion method. Reverse extrusion is more uniform than forward extrusion, cold extrusion is more uniform than hot extrusion, and lubricated extrusion is more uniform than non-lubricated extrusion. The influence of the extrusion method is realized by changing the friction conditions.
(2) Extrusion speed. As the extrusion speed increases, the unevenness of the metal flow increases.
(3) Extrusion temperature. When the extrusion temperature increases and the deformation resistance of the blank decreases, the uneven flow of the metal increases. During the extrusion process, if the heating temperature of the extrusion cylinder and the mold is too low, and the metal temperature difference between the outer layer and the center layer is large, the unevenness of the metal flow will increase. The better the thermal conductivity of the metal, the more uniform the temperature distribution on the end surface of the ingot.
(4) Metal strength. When other conditions are the same, the higher the metal strength, the more uniform the metal flow.
(5) Die angle. The larger the die angle "(that is, the angle between the end face of the die and the central axis), the more uneven the metal fluidity. When using porous die extrusion, the die hole arrangement is reasonable, and the metal flow tends to be uniform.
(6) Degree of deformation. If the degree of deformation is too large or too small, the metal will flow unevenly.

Monday, August 31, 2020

Operational characteristics of titanium alloy plate straightening process

Check whether the straightening machine is operating normally, and check and remove all dirt, oil and metal chips on the machine. Then, adjust the brief analysis between the upper and lower rolls of the straightening machine.
In the straightening operation, it is required that the titanium alloy plate cannot have corners or crimping, otherwise, it must be flattened with a mallet; dirt and titanium chips are not allowed on the titanium alloy plate, otherwise, it must be cleaned and cleaned in time; the titanium alloy plate is straightened It must be aligned to the center, no skew, if any skew is found, it must be adjusted; the titanium alloy plate is not allowed to pass through the straightening machine, nor is it allowed to straighten two overlapping plates at the same time.
When the titanium alloy plate is straightened, when local waves are found, the pressure of the machine must be adjusted in time to eliminate the waves. For example, when there is a wave in the middle of the iron plate, the support roller in the middle should be raised (that is, u value is lowered). The larger the wave, the larger the rise, and so on.
When the titanium alloy plate is straightened, if the effective plate is stuck in the machine and is not allowed to pass by force, stop immediately, raise the roller, and then return to the titanium alloy plate. If you need to retreat the titanium alloy plate, you should also lift the roller to work.
It is not allowed to pressurize the work roll during the shutdown. At the same time, the straightened titanium alloy plate should be re-examined, and if there is any unqualified straightening, repeat the straightening. If straightening is really impossible, you should send it to a tension leveler for straightening.

Friday, August 28, 2020

What are the titanium plate manufacturing processes?

Hot forging is a forging process performed above the metal recrystallization temperature. Hot rolling is a rolling process performed at a temperature higher than the recrystallization temperature. Cold rolling: A rolling process in which the plastic deformation temperature is lower than the recovery temperature. Annealing: A metal heat treatment process that slowly heats the metal to a certain temperature, keeps it for a sufficient time, and then cools it at an appropriate rate (usually slow cooling, sometimes controlled cooling). Pickling: The parts are immersed in an aqueous solution such as sulfuric acid to remove oxides and other films on the metal surface. It is the pre-treatment or intermediate treatment of electroplating, enamel, rolling and other processes.

Tuesday, August 25, 2020

Stress and deformation of metal titanium rod titanium tube during drawing

The cutting force of titanium alloy processing is only slightly higher than that of steel of the same hardness, but the physical phenomenon of processing titanium alloy is much more complicated than processing steel, which makes titanium alloy processing face huge difficulties. The thermal conductivity of most titanium alloys is very low, only 1/7 that of steel and 1/16 that of aluminum.
Therefore, the heat generated in the process of cutting titanium alloy will not be quickly transferred to the workpiece or taken away by the chips, but will be concentrated in the cutting area. The temperature generated can be as high as 1,000 ℃, causing the cutting edge of the tool to quickly wear, crack and Generate built-up edge, wear blades quickly appear, and generate more heat in the cutting area, further shortening the life of the tool.
The high temperature generated during the cutting process also destroys the surface integrity of the titanium alloy parts, resulting in a decrease in the geometric accuracy of the parts and a work hardening phenomenon that severely reduces its fatigue strength.
The elasticity of titanium alloy may be beneficial to the performance of parts, but in the cutting process, the elastic deformation of the workpiece is an important cause of vibration. The cutting pressure causes the "elastic" workpiece to leave the tool and rebound, so that the friction between the tool and the workpiece is greater than the cutting action. The friction process also generates heat, which aggravates the poor thermal conductivity of titanium alloys.
This problem is even more serious when processing thin-walled or ring-shaped parts that are easily deformed. It is not an easy task to process 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. At this time, machining according to the originally determined cutting speed becomes too high, which further leads to sharp tool wear.

Sunday, August 23, 2020

Process performance of industrial pure titanium

Titanium alloy is a very light material, it has small elasticity, high strength, and also has a good heat resistance and corrosion resistance. It is one of the important materials used to manufacture weapons and equipment, and it is also a relatively common material currently used by nuclear submarines. Whether it is Chinese nuclear submarines or US and Russian nuclear submarines, they use a large amount of titanium alloy materials in their own submarine construction. The proportion of titanium alloy materials used is also very different. For example, Russian nuclear submarines like to use a lot of titanium alloy materials, while the US military nuclear submarines use titanium alloy materials relatively low-key. China has abundant reserves of titanium alloy resources, and the reserves of ilmenite ore rank first in the world. The moderate use of titanium alloys on nuclear submarines will greatly improve the hardware performance of China's nuclear submarines.
 Titanium alloy has a huge advantage for China's nuclear submarines. In particular, China has made great achievements in the use of titanium alloy materials. The C919 large passenger plane and the CZ-5 high-thrust launch vehicle all use key rare metal materials such as titanium and titanium alloys. Titanium alloy, as one of the important materials for weapons manufacturing, is mainly used to manufacture rockets, missiles and other weapons components or engine and compressor parts. Not only that, but it can also be used to make delicate parts and even submarines.
Countries in the world are working hard to study the casting technology of titanium alloys, but the three countries with the highest achievements are the United States, Russia and China. The United States occupies a leading position in this regard, but because the domestic production of titanium is not high, it usually only uses titanium alloys in key and necessary places. Russia has continued to develop in the field of titanium alloy technology based on the former Soviet Union's experience in manufacturing many nuclear submarines from titanium alloys. And China, as a country that developed military science and technology late, is not lost to other military powers. According to records, my country has used nearly 20% of the titanium alloy material in the manufacture of the J-20 to increase the life of the airframe.
This is our great power weapon, and it will play an important role in the future. It also fully proves that our country has begun to grow stronger in industry and gradually rise in military power.

Friday, August 21, 2020

Industrial pure titanium is excellent in stress corrosion resistance, and damage to titanium equipment due to stress corrosion is rare.

The pickling conditions of titanium rods and titanium alloy rods are determined by the types (characteristics) of the oxide layer and the existing reaction layer, and the types of this layer are subject to high-temperature heating processes and increased processing temperatures (for example, forging, casting, welding, etc.) )Impact. At a lower processing temperature, it may be about 600 degrees: the following high-temperature heating temperature conditions only generate a thin oxide layer. Under high-temperature conditions, it forms an oxygen-rich dispersion zone near a certain oxide layer, and it is also necessary to go through pickling Remove this oxygen-rich dispersion layer. A variety of different methods for removing scale can be selected: the mechanical method of removing the thick oxide layer and hard outer layer, the method of removing oxide scale in a molten salt bath, and the method of removing oxide scale by acid elution in acid solution
In many cases, a combination of several methods can be used. For example, a combination of a mechanical method of removing oxide scale and then pickling, or a combination of salt bath and then pickling. In the case of an oxide layer and a dispersion layer formed at a higher temperature, a special method should be used^ but when heated to 600 degrees at a high temperature: most of the oxide layer formed can be dissolved after the usual pickling Drop.
The mechanical method of removing the oxide scale usually adopts the method of sandblasting, polishing, brushing and then pickling to remove the oxide layer formed under high-temperature conditions. In any case, it is necessary to adopt measures to prevent mechanically disposed of foreign impurities from passing through the metal surface, because the subsequent thermal processing or thermal treatment process may cause cracks due to the reduction of plasticity. Corundum, emery or steel grit is usually used when disposing of forgings. When disposing of plates, shot blasting is also used to remove the oxide scale. In order to achieve the surface quality of titanium, cold rolling or fine grinding is then performed. It can be unevenly removed by salt bath or pickling to remove more than 750 degrees: the thick adhesive oxide layer formed at the temperature, and the oxide scale can be removed beyond words only by grinding. In this case, it is difficult to choose a lower grinding speed (5*10m/s). This can prevent overheating of the grinding surface because a hardened layer develops due to oxygen absorption in the overheated area.
It is necessary to corrode or polish the deoxidized surface to improve the surface quality several times. Before the disposal, the external surface should be degreased. It can be dewaxed in organic solvents to prevent stress crack corrosion as much as possible. It should not be rich in chlorides or hydrocarbons with similar effects, or in alkaline solutions rich in water. During degreasing. Titanium is stable to this medium, as long as the dirt adhered to the surface can be dissolved, but the titanium surface itself does not corrode. In order to corrode the thinner oxide layer, an acid solution can be used for corrosion. Adjust the composition of the acid solution in the pickling tank according to the desired appearance or characteristics. In most cases, it is rich in hydrofluoric acid as the basic substance, and hydrochloric acid or sulfuric acid is also used in individual cases.

Tuesday, August 18, 2020

Types and production technology of titanium pipes for marine engineering

Titanium alloy pipes are divided into seamless pipes and welded pipes.
Titanium alloy seamless pipes are generally processed by extrusion + rolling or diagonal rolling piercing + rolling. Hot extrusion is a plastic processing technology that uses the principle of plastic material deformation to use a die to make a titanium alloy blank into a material with a certain shape, thickness and performance in a hot state. It is a complex process that combines plastic deformation and flow deformation. The material is in a state of three-way compressive stress during extrusion, which is beneficial to the plasticity of the material. The economic pressing process mainly uses rice to produce seamless pipes, bars and profiles for drinking gold. The main processing parameters of the extrusion process include extrusion ratio, extrusion temperature, extrusion speed and so on. When extruding the tube, a hollow tube made of titanium alloy loose material through deep hole processing or hot pressure perforation is also used as the original blank. The size of the hollow tube blank is determined by the inner diameter of the extrusion barrel of the extruder. Due to the high viscosity of drink alloys, copper, mild steel or other metals are usually covered during extrusion, or the surface of titanium alloy is covered with grease, glass lubricant, etc. for extrusion. Through extrusion, titanium alloy thick-walled pipes or titanium alloy pipes that do not require high dimensional accuracy can be directly prepared. High-precision alloy seamless pipes are generally produced by rolling technology. The billets are generally extruded pipe blanks. Commonly used pipe rolling methods include two-half pass cold rolling, two-roll ring pass cold rolling, and multi-roll cold rolling. Rolling, two-target warm rolling and multi-roll warm rolling, etc. For pure titanium with low strength and high plasticity, it is generally produced by cold rolling. The deformation of the pass is generally controlled at 20% to 60%. Annealing treatment is required between passes to eliminate work hardening and restore plasticity. For medium and high-strength titanium alloys, due to high tensile strength, large deformation resistance and poor processing plasticity: the warm-drying technology must be used when rolling seamless pipes, that is, induction heating devices or flame heaters are installed on the rolling mill. The heating temperature is controlled at about 100°C below the recrystallization temperature.
For large-diameter thick-walled titanium composite pipes: generally, the skew-rolling piercing method is also used for production. The cross-rolling piercing method uses tensile stress along the weave and transverse directions of the rolled blanks to cause micro-cracks in the core area of ​​the circular material, and then expand into a loose area. The use of high-temperature-resistant plugs enables the plastic deformation of the metal in the loose area: direct forming of the tube from the city. The heating temperature of the billet in this method is higher, which is beneficial to improve the new cracking properties of the pipe to achieve the purpose of high production efficiency, high material utilization rate and low production cost. Titanium alloy welded pipes are generally produced by welding, and welded pipes are produced with high precision A very efficient method for thin titanium alloy pipes: its production process is: titanium strip coil slitting → forming → welding → shaping and sizing ~ heat treatment straightening eddy current/ultrasonic inspection → airtight inspection of finished welded pipes. The production process is generally continuous production: The product quality has high stability, and the pipes produced are generally used for heat exchangers, condensers, etc.

Sunday, August 16, 2020

Preparation of titanium and titanium alloy seamless pipe blank

Industrial pure titanium contains a large amount of oxygen, nitrogen, carbon and many other impurity elements (such as iron, silicon, etc.). It is essentially a titanium alloy with a low alloy content. Compared with chemically pure titanium, its strength is greatly improved due to its more impurity elements, and its mechanical and chemical properties are similar to stainless steel (but the strength is still lower than that of titanium alloy).
The characteristics of industrial pure titanium are: the strength is not high, but the plasticity is good, it is easy to be formed, stamped, welded, and has good machinability; it has good properties in the atmosphere, seawater, wet chlorine and oxidizing, neutral, and weakly reducing media. The corrosion resistance and oxidation resistance are better than most austenitic stainless steels, but the heat resistance is poor, and the use temperature should not be too high.
Industrial pure titanium is divided into three grades: TA1, TA2, and TA3 according to its impurity content. The interstitial impurity elements of these three industrial pure titanium are gradually increasing, so its mechanical strength and hardness also gradually increase, but the plasticity and toughness decrease accordingly.
The industrial pure titanium commonly used in industry is TA2, because of its moderate corrosion resistance and comprehensive mechanical properties. TA3 can be used when the wear resistance and strength requirements are high. TA1 can be used when better-forming properties are required.
Industrial pure titanium is mainly used for working temperature below 350℃, with little force, but requires good plasticity stamping parts and corrosion-resistant structural parts, such as aircraft skeletons, skins, engine accessories; seawater corrosion-resistant pipelines for ships, Valves, pumps and hydrofoils, seawater desalination system components; chemical heat exchangers, pump bodies, distillation towers, coolers, agitators, tee links, impellers, fasteners, ion pumps, compressor valves and diesel Engine pistons, connecting rods, leaf springs, etc.