What are the types of corrosion of titanium tubes?

The corrosion form of Grade 2 Pure Titanium Tube includes two categories: general corrosion and local corrosion: general corrosion is a form of corrosion that is comprehensive and uniform; local corrosion is a form of local corrosion relative to general corrosion. It can also be divided into: crevice corrosion, point corrosion Corrosion, stress corrosion cracking, galvanic corrosion, abrasion, hydrogen absorption and hydrogen embrittlement.

1. Crevice corrosion: The corrosion phenomenon that occurs at the flange or fold and the gap near the accumulation, generally occurs in the narrow gap.

2. Pitting corrosion: Corrosion that occurs during opening, such as the corrosion phenomenon caused by the presence of halogen ions such as C1-, B-, I-, etc.

3. Stress corrosion cracking: In a specific environment, due to the action of tensile stress, a kind of brittle failure occurs.

4. Abrasion: The phenomenon that the fluid promotes electrochemical corrosion due to mechanical action.

5. Galvanic corrosion: also known as dissimilar metal contact corrosion, it is a phenomenon in which the metal with the lower potential is promoted to corrode under the condition of electrical short circuit.

6. Hydrogen absorption and hydrogen embrittlement: take hydrogen out of the material, and when the amount of hydrogen taken out exceeds the solid solution limit of the material, brittle hydrides will be formed, resulting in hydrogen embrittlement.

What must be guaranteed when welding titanium tubes?

Titanium tube welding is a TiG welding process that uses inert gas to effectively protect the welding area. Due to the special physical and chemical properties of titanium, its welding process is quite different from other metals. Titanium tubes have high strength, good plastic toughness, and corrosion resistance, and are more and more widely used in aerospace, shipbuilding, and chemical industries. In order to make better use of titanium tubes, it is necessary to master their weldability.

When welding Grade 9 Ti3Al2.5V Titanium Tube, it must be ensured that:

1. The metal in the welding zone will not be polluted by active gas N, 0, H and harmful impurity elements C, Fe, Mn, etc. above 250 °C.

2. Coarse-grained structure cannot be formed.

3. Can not produce large welding residual stress and residual deformation. Therefore, the welding process must follow the predetermined construction sequence, strictly follow the process quality management standards, and implement quality control of the whole process. Make the factors of man, machine, material, and method in a well-controlled state, so as to ensure the welding quality of titanium tubes within a reasonable construction period.

Matters needing attention in the cutting process of titanium tube

ASTM B861 25*1.2mm Titanium Tube For Chemicals are generally divided into two types, one is the extruded type called seamless titanium tube; the other is welded type called welded titanium tube.

1. If it is semi-automatic cutting, the guide rail should be placed on the titanium tube plane, and then the cutting machine should be placed on the guide rail, and the order should not be reversed.

2. The cutting parameters should be appropriate, and should be reasonably determined according to the thickness of the titanium heat exchanger tubing, so as to obtain a good cutting effect.

3. Check whether the cutting gas is unobstructed. If there is a blockage, it should be unblocked in time.

4. Before cutting, the surface should be cleaned and some space should be left, which can facilitate the blowing out of slag.

5. The distance between the cutting nozzle and the surface of the titanium tube should be appropriate, too close or too far is not good.

6. Preheating should be sufficient so as not to affect the cutting process.

7. If cutting workpieces of different sizes, the small ones should be cut first, and then the large ones.

Application of Titanium Petroleum Accessories

Under the conditions of petroleum machinery processing, titanium alloys can be used to manufacture the following titanium equipment: titanium heat exchangers, filters (settlers), storage tanks for storing petroleum and petroleum products, locking devices, sewage pipelines, and rough oil pipelines.

Certain petrochemical companies and petroleum processing industries have experience in manufacturing and using titanium alloy equipment. For example, the Moscow Petroleum Processing Plant manufactured the following equipment from BT1~0 titanium alloys: propylene polymerization reactors, pulsators for decomposers, condensers, and sieve washing towers.

Titanium Alloy Rectangular Tube-lined vessels are used for evaporation (concentration) or distillation or for reactions in weak acids or other chloride-containing solutions, followed by nitriding of organic materials with nitric acid and other chemical reactions with oxidizing media. As the container used for the reaction, a container with a titanium liner can also be used. Both the solution containing chromic acid and the chromic acid solution for sulfidation can be selected according to the reaction temperature needs of this titanium-lined container.

It has been proved in a certain application range in the field of the chemical raw materials industry that copper and other solutions containing vapors are used to catalyze the oxidation of carbon and chlorine compounds, and it can be used as a catalyst when it has a certain pH value. Then at about 150~200t: When catalyzing at a temperature of t, corresponding equipment must be installed, and acetaldehyde production equipment made of titanium is widely used. Grade 9 Ti-3Al-2.5V Titanium Plate-lined towers, piping, valves, and acid pumps consisting of rotors and stators are all made of engineered pure titanium. Distillation columns are often used for the purification of acetic acid, and most of the fractionation stages include assemblies made of titanium. Such as the middle layer and connecting parts of the tower used in the distillation device.

The coil heater, which prevents the formation of metal sulfates, is proven to increase heat transfer by 30% compared to an aluminized copper coil heater. For the urea reactor, in order to obtain (recover) carbon black and relieve stress, a reaction tower with a diameter of 43m and a length of 8.2m that withstands a temperature of 120T and a pressure of 130kPa should be used. The reaction tower should reduce the gas and other gases. pressure, this device is made of titanium.

The application field of titanium is further extended to the crude oil and petroleum processing industry, and the desalination equipment for producing freshwater or drinking water from seawater or the equipment for producing organic acid all use titanium. At the same time, the pumps, pipes, and heat exchangers made of welded titanium tubes have been tested to be reliable and durable. When copper is electrolyzed, a titanium plate is used to manufacture a titanium seed plate for the cathode.

Introduction of titanium alloy equipment manufacturing and its application

The one-time investment of my country's chemical titanium equipment is large, the main reason is that the price of titanium is high, and there are also design and manufacturing factors. At present, the economic benefits of chemical titanium equipment mainly come from the comprehensive advantages in the application process. Therefore, the development of chemical titanium equipment, in addition to continuing to open up new fields of "chemical titanium" and continuously expanding the use of titanium equipment, should also adopt appropriate technologies and methods to reduce the one-time investment of titanium equipment and improve the use of equipment. reliability.

Titanium equipment is a kind of corrosion-resistant metal, but in some oxidizing media, as the temperature and concentration of the media change, the surface of titanium can rapidly oxidize and produce violent spontaneous combustion reactions, resulting in combustion and explosion accidents. Therefore, before using Seamless Titanium Tube Grade 2equipment, it is necessary to understand the characteristics of the medium used in detail, and pay special attention to the corrosion and oxidation of the medium. In particular, it is strictly forbidden to expose titanium to a strong oxidizing environment without water, otherwise it is very prone to rapid oxidation and a violent spontaneous combustion reaction.

There are many types of titanium equipment, and their functions are also different. The more common one is the titanium reactor. At present, titanium reactors can be mainly divided into three categories: pure titanium reactors, titanium composite titanium reactors, and titanium-lined reactors, which are used in different process environments. Among them, the composite Grade 7 Titanium Plate reactor is widely used because of its superior performance and lower price than pure titanium reactor.

Titanium equipment has stable performance and can be used for corrosive experiments. In fact, the performance of titanium itself is relatively active, but it is easy to form passivation, and the passivation layer is relatively stable, and is usually used in the reaction of corrosive materials. Because titanium has the advantages of high specific strength, excellent heat resistance, corrosion resistance and fracture toughness, titanium reactors are greatly favored in the fields of aviation, aerospace, petrochemical, medical and geology.

With excellent performance, titanium alloy processing equipment is also being widely used in civilian fields, such as automobiles, electric power, leisure and other industries. With the widespread use of titanium and its alloys, its welding performance has attracted more and more attention from users. And there are many customized titanium reactors and stainless steel reactors widely used in petrochemical, pharmaceutical chemical, dye chemical, metallurgical chemistry and chemical research institutions and other major fields. Titanium equipment Titanium has its unique characteristics. Titanium equipment is widely used in aerospace, aviation, shipbuilding, chemical industry, building materials, medical treatment, sports, environmental protection, automobile manufacturing and other industries, and more and more people are familiar with and use it.

Mechanical behavior characteristics of metal materials at high temperature

Due to the increase of atomic diffusion ability at high temperature, the increase of the number of vacancies in the material and the change or increase of the grain boundary slip system, the high temperature strength of the material is very different from the room temperature strength. When considering the high-temperature strength of materials, in addition to the two most basic factors of temperature and mechanics, the influence of time and medium factors must also be considered. Under high temperature conditions, the deformation mechanism of the material increases, and plastic deformation is prone to occur, which is manifested by the decrease of strength, the weakening of deformation strengthening, and the increase of plastic deformation. The strength decreases with the increase of temperature, and the plasticity increases with the increase of temperature.

Under high temperature conditions, materials bear different loads, and the time required for their fracture is also different. Not only does the time to fracture decrease with increasing stress, but the form of fracture also changes. The trend of grain boundary strength and grain strength decrease with increasing temperature is different, and the intersection point corresponds to temperature T. (called isointense temperature), the material changes from transgranular fracture to intergranular fracture.

1. The strength decreases with the increase of temperature, while the plasticity increases with the increase of temperature.

2. The mechanical behavior and performance are closely related to the loading duration;

3. Even if the stress at high temperature is less than the yield strength at this temperature, the material will undergo slow and continuous plastic deformation as the load time increases, that is, the material will undergo creep.

4. At high temperature, the plasticity will decrease significantly with the increase of bearing time, the notch sensitivity of the material will increase, and the fracture will often be brittle.

5. Temperature affects the microscopic fracture mode of the material.

6. The corrosion effect of the environmental medium on the material is intensified as the temperature increases, thus affecting the mechanical properties of the material.

Therefore, the room temperature mechanical properties of the material cannot reflect its behavior under high temperature loading, and a special high temperature performance test must be carried out to determine the high temperature mechanical properties of the material;

Temperature and time are important factors affecting the high-temperature properties of Hollow Titanium Ball, so the relationship between temperature, stress and strain and time must be studied to study the high-temperature mechanical behavior of metals.

Advantages of hot die forging and conventional forging of titanium alloys

Like isothermal forging, hot die forging of titanium alloy processing technology is also a promising precision forging process. The difference is that the mold temperature of hot die forging is higher than that of ordinary forging, but lower than that of isothermal forging. Typical hot die forging die temperature is 110-225°C lower than the billet temperature. Compared with isothermal forging, the reduction of mold temperature can make a wider selection of mold materials, but the ability to form very thin and complex-shaped forgings is slightly worse.

Compared with conventional titanium alloy flange, hot die forging has the following advantages:

(1) Reduce the material consumption of forgings. During hot die forging, the chilling of the die contacting the blank and the work hardening of the material are reduced, and the forgeability of the material is improved, so the forgings are allowed to have a smaller fillet radius and a smaller draft The inclination and small forging allowance greatly reduce the quality of forgings. For example, a Ti-6Al-4V alloy structural part has a mass of 28kg. The mass of forging produced by conventional forging process is 154kg, while the mass of forging produced by hot die forging process is 109kg. The difference between the two methods is 45kg.

(2) Reduce the number of forging operations and improve the working capacity of the press. During hot die forging, the mold temperature is higher and the temperature drop of the billet is less. Conventional forging requires two fires, three fires or more fires to form forgings. Hot die forging Only one time, as many as two fires can be completed. And because of hot die forging, the deformation resistance of the metal is low, which relatively increases the working capacity of the equipment.

(3) Reduce the amount of machining of forgings Because the forgings produced are close to the weight and contour size of the parts, compared with the forgings produced by conventional forging, the amount of material removal in machining is reduced.

(4) The uniformity of the product is better. During the forging process, the temperature gradient is greatly reduced, and the uneven deformation caused by the temperature gradient is easy to reduce. Therefore, the uniformity and consistency of the structure and performance of the product are better than those produced by conventional forging. , but less than forgings produced by isothermal forging.

During hot die forging, although the billet has a temperature drop, it is still in the forging temperature range, and the deformation resistance does not rise as sharply as in conventional forging. The strain rate used in hot die forging varies within the range of 0.05-0.2s-1. If the strain rate is too low, the blank temperature may decrease.

In hot die forging of titanium alloys, forging heating temperature, strain rate, microstructure of preform and holding time are extremely important factors, which play a decisive role in the dimensional accuracy and microstructure of formed parts. Usually lower strain rates and longer dwell times increase the possibility of precision forming. However, the microstructure of the preform has a direct impact on the flow stress and superplasticity of the material, especially on the microstructure after forging. It cannot be attempted to completely eliminate the defects and uneven grains in the raw material through isothermal forging or hot die forging.

At present, whether titanium alloys and high-temperature alloys use hot die forging technology mainly depends on the total cost of forgings or the need for uniformity and consistency of products. The development trend of this process is to use conventional forging preforms, and finally carry out isothermal or hot die final forging.