What factors will affect the welding of titanium plates

When the world began to produce titanium tube parts, it also encountered a lot of troubles. They are mainly metalworkers and technicians who are familiar with aluminum tube parts, but they are very uncomfortable with titanium tube forming. First of all, the cutting and trimming process is too fast because the blades of the scissors wear too fast. When the shape is unbearable, the hammerhead is very easy to be arrogant and thick. Stick to the model. Because of this, everyone refers to titanium as a difficult-to-form material, and industry personnel calls it a hot forming material. This is a more general and perceptual evaluation of the forming performance of titanium tubes. But this can't affect people's specific analysis, after understanding its characteristics, in order to make appropriate treatment.

To be precise, titanium not only has the disadvantages of particularly large spring back, but it also has significant advantages. For example, in 1970, in the room temperature technical depth test of pure titanium pipes, it successfully processed cylindrical parts with a limit drawing coefficient of 2.75. , Which greatly exceeds the record of heavy materials such as steel, steel, and aluminum. Experiments conducted as early as 10 years ago achieved better results and also used conventional drawing models and other materials to process spherical parts with a height exceeding the radius in a single process. It laid the foundation for the development of our current titanium industry.

Ships will definitely be corroded in seawater, which will seriously affect their lifespan. Then improving the corrosion resistance of the hull has become the first goal of many shipbuilding companies. So what should I choose? If the flow velocity in the hull cooling water pipe is relatively high and needs to withstand strong impact and corrosion, titanium pipes should be selected for comparison.
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What are the methods of cleaning titanium rods?

Titanium alloys have a lot of knowledge here. Titanium alloys refer to alloys made up of other elements based on titanium. Titanium alloys include titanium aluminum alloys, titanium copper alloys, titanium manganese alloys, and other 70 metals containing titanium elements. . .

The density of titanium alloy is generally about 4.51g/cm3, which is only 60% of steel. Some high-strength titanium alloys exceed the strength of many alloy structural sheets of steel. Therefore, the specific strength (strength/density) of titanium alloy is much greater than that of other metal structural materials.

It can produce parts with high unit strength, good rigidity, and lightweight. The aircraft's engine components, skeletons, skins, fasteners, and landing gear all use titanium alloys. So when we customize titanium screws, how do we choose the material of the screws? In fact, titanium alloys are produced to meet the different needs of the industry.

Because all screws are used in different environments, the positions used on machine parts are also different, and the hardness, flexibility, thermal conductivity, and wear resistance of the screws required by the machine are also different. Therefore, when customizing the production of screw fasteners for customers, they will always ask the user where the screws are used and what kind of performance is required?

If hardness is required, then it is recommended to use titanium-cobalt alloy. Titanium-cobalt alloy is generally used to make cutting tools. When selecting the screw material, it is important to understand that when the hardness of the screw is high, the titanium screw is easy to break.

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Study on Corrosion and Wear Resistant Treatment of Titanium Rod Surface

In order to improve the overall flight performance of the aircraft and meet the requirements of relatively light weight, long life and good maneuverability, the working pressure of the pipeline system of large passenger aircraft and fighter jets will gradually increase, and various titanium alloy pipes with excellent comprehensive performance will gradually increase. It is widely used. In view of the importance of hydraulic piping systems in aircraft piping systems, it is feasible to first develop the application of titanium alloy pipes in new aircraft hydraulic piping systems. Considering the specific strength, specific rigidity, corrosion resistance, cold bending forming ability and material maturity, the use of TA18M (Ti-3Al-2.5V) titanium alloy conduit is currently an ideal choice.

TA18M titanium alloy is a low-aluminum equivalent nearly α-type titanium alloy evolved from TC4 (Ti-6Al-4V) alloy. It is developed as a cold-workable pipe application. It has good cold forming and welding properties and can be manufactured A variety of seamless pipes, welded pipes and honeycomb structures can achieve good strength and plasticity matching through heat treatment. The room temperature strength of this alloy is 20% to 50% higher than that of industrial pure titanium, it is not sensitive to notches, and has good corrosion resistance in many media. Therefore, it is suitable for manufacturing catheters on various aircrafts. TA18M titanium alloy pipes have been used as hydraulic and fuel piping systems on many high-tech military and civilian aircraft in the United States. For example, in the mid-1970s, it began to be used as aeronautical catheters on F-14A, F-15, Boeing 757, 767 and other aircraft types. TA18M catheter also has a certain application foundation in aviation and civil use in my country. It has been used as an air-conditioning pipeline on transport aircraft in my country and will be used in aero engine pipeline systems.

Due to the low density of TA18M titanium alloy, it can effectively reduce the weight compared to stainless steel pipes. What is more valuable is that its good welding performance makes subsequent pipe ends easy to connect, and it has excellent matching performance with the strength and stiffness of the composite structure. Can further obtain a good weight loss effect. Therefore, TA18M is currently the most suitable material for the production of high-pressure and lightweight conduits on advanced aircraft.
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Titanium materials can be used in the aerospace industry

As a new type of manufacturing method, additive manufacturing (also known as 3D printing) has the advantages of fast manufacturing, saving materials, and user-customizable. It has attracted more and more attention in the fields of aviation, aerospace, automobiles, and medical equipment. Due to the needs of industrial applications, the fatigue performance of additive manufacturing materials (especially the ultra-high cycle fatigue performance) and the corresponding fatigue mechanism have become one of the scientific problems that need to be solved urgently in the research field of additive manufacturing.

The Research Group of Metallic Materials Microstructure and Mechanical Properties of the Institute of Mechanics, Chinese Academy of Sciences has recently carried out a series of research work on the fatigue characteristics of additively manufactured titanium alloys (Ti-6Al-4V). The research team conducted fatigue performance tests on additively manufactured titanium alloys and obtained the high-cycle and ultra-high-cycle fatigue properties of the material. Through the observation of the fatigue fracture, it is reported that the high-cycle and ultra-high-cycle fatigue cracks of the additive-manufactured titanium alloy all originate in the internal holes and unfused defects of the material, and form a new phenomenon of "fish-eye" fracture morphology. This is quite different from the fatigue characteristics and cracks initiation mechanism of traditional forged metal materials. According to the distribution characteristics of crack source size, a statistical correlation between fatigue performance and crack size is constructed. Based on the fatigue life data of the material and the size of the fatigue crack defect, a probability statistical P-S-N analysis was carried out to obtain the relationship between the high-cycle and ultra-high-cycle fatigue failure probability of the material, the fatigue life, and the applied load. In addition, in order to further explore the characteristics of fatigue crack growth, the research team used an in-situ fatigue loading device to obtain Ti-6Al-4V crack growth rates at different temperatures and different preparation orientations, revealing the fatigue crack growth of titanium alloys with different orientations. Mechanisms.

This research not only provides effective fatigue performance data for engineering applications of additive manufacturing of titanium alloys. At the same time, it has laid a theoretical foundation for exploring the crack initiation and propagation mechanism of additive manufacturing of titanium alloys.
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What are the factors that affect the welding performance of titanium and titanium?

(1) High strength. The density of titanium alloy is generally about 4.5g/cm3, which is only 60% of steel. The strength of pure titanium is close to that of ordinary steel. Some high-strength titanium alloys exceed the strength of many alloy structural steels. Therefore, the specific strength (strength/density) of titanium alloy is much greater than that of other metal structural materials. See Table 7-1, which can produce parts and components with high unit strength, good rigidity, and light weight. At present, titanium alloys are used in aircraft engine components, skeletons, skins, fasteners, and landing gear.

(2) High thermal intensity. The service temperature is several hundred degrees higher than that of aluminum alloy. It can still maintain the required strength at medium temperature. It can work for a long time at a temperature of 450～500℃. These two types of titanium alloys are still very high in the range of 150℃～500℃. Specific strength, while the specific strength of aluminum alloy decreases significantly at 150°C. The working temperature of titanium alloy can reach 500℃, while that of aluminum alloy is below 200℃.

(3) Good corrosion resistance. Titanium alloy works in moist atmosphere and sea water medium, its corrosion resistance is far better than stainless steel; it is particularly resistant to pitting corrosion, acid corrosion, and stress corrosion; it is resistant to alkali, chloride, chlorine organic substances, nitric acid, sulfuric acid It has excellent corrosion resistance. However, titanium has poor corrosion resistance to reducing oxygen and chromium salt media.

(4) Good low temperature performance. Titanium alloys can still maintain their mechanical properties at low and ultra-low temperatures. Titanium alloys with good low temperature performance and extremely low interstitial elements, such as TA7, can maintain a certain degree of plasticity at -253°C. Therefore, titanium alloy is also an important low-temperature structural material.

(5) High chemical activity. Titanium has high chemical activity, and produces a strong chemical reaction with O, N, H, CO, CO2, water vapor, ammonia, etc. in the atmosphere. When the carbon content is more than 0.2%, it will form hard TiC in the titanium alloy; when the temperature is higher, it will also form a hard surface layer of TiN when it interacts with N; when the temperature is above 600℃, titanium absorbs oxygen to form a hardened layer with high hardness ; When the hydrogen content increases, an embrittlement layer will also be formed. The depth of the hard and brittle surface layer produced by absorbing gas can reach 0.1-0.15 mm, and the degree of hardening is 20%-30%. Titanium also has a high chemical affinity and is easy to adhere to the friction surface.

(6) The thermal conductivity is small, and the elastic modulus is small. The thermal conductivity of titanium λ=15.24W/(m.K) is about 1/4 of nickel, 1/5 of iron, and 1/14 of aluminum. The thermal conductivity of various titanium alloys is about 50% lower than that of titanium. The modulus of elasticity of titanium alloy is about 1/2 of that of steel, so its rigidity is poor and easy to deform. It is not suitable to make slender rods and thin-walled parts. The springback of the machined surface during cutting is very large, about 2～3 of stainless steel. Times, causing severe friction, adhesion, and adhesive wear on the flank of the tool. Alloying of Titanium Titanium alloy is an alloy composed of titanium as the base and adding other elements. Titanium has two isomorphs: close-packed hexagonal α titanium below 882°C, and body-centered cubic β titanium above 882°C.
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Advantages of titanium plate

Titanium tube is a highly active metal, and its activity increases with increasing temperature.

Titanium tubes and their alloys will interact with oxygen when heated in air or an oxygen-containing atmosphere. When heated below 428℃, a protective oxide film is formed. When the temperature rises, the thickness of the oxide film increases. When the temperature is above 538℃, the oxide film begins to lose its protective effect. Oxygen diffuses through the film into the metal, forming obvious gas infiltration. Floor. If it rises above 815°C, a loose oxide scale will form on the surface of the titanium alloy.

In order to prevent the titanium alloy from oxidizing, absorbing hydrogen, and other trace element pollution during superplastic forming, technical measures need to be taken to make the formed titanium alloy parts have excellent properties.

At present, the main measures are coating protection, vacuum heating, and inert gas (argon) protection.

1. Coating protection law

After cleaning, the surface of the formed blank is coated with a protective coating of a certain thickness. After the part is de-molded, the coating is removed by alkaline washing, acid washing, or sand blowing.

The coating should have the following main properties:

a. High temperature resistance, can be used under high temperature of 750-1050℃;

b. It should have a certain lubricating effect to prevent the blank from being scratched during forming;

c. The coating can be firmly attached to the surface of the blank under the working temperature;

d. Easy to remove after heating;

e. No harmful substances, no pollution to the environment and harm to human health.

The coatings that have been identified as suitable for superplastic forming of titanium tubes and titanium alloys are: Ti-2 alcohol-soluble preparations can be used in conjunction with Ti-3 graphite lubricants, suitable for hot forming at 750-1050°C; KBC-12 Water-soluble preparation, can be used in conjunction with graphite water agent.

2. Vacuum forming

For titanium pipes, vacuum forming is the most ideal for β-type titanium alloys with thinner parts, higher requirements for surface brightness, and stronger sensitivity to hydrogen embrittlement.

Vacuum forming does not necessarily require expensive vacuum heating equipment. As long as a sealed space is created between the blank and the upper and lower cavities of the mold, the air in the upper and lower cavities is gradually extracted by a vacuum unit during the heating process, especially when the temperature is above 400℃ to the forming temperature, the temperature of the upper and lower cavities of the mold When the vacuum degree is above 10^(-3) Torr, the valve of the pipeline is changed during forming, and the forming purpose is achieved by filling with argon gas. This method is used in the forming of the titanium foil corrugated board, and satisfactory results are obtained. When the vacuum degree is controlled at 10^(-3) Torr, the hydrogen content is lower than the standard requirement. When the vacuum degree reaches 10^(-5) Torr, a bright surface part can be obtained.

In addition, for parts with medium thickness and no higher requirements for surface and concave brightness, vacuum argon protection can also be used to test this aspect in the formation of spherical gas cylinders, and the effect is also good.
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Where is the application range of titanium standard parts?

With the further development of the aerospace industry and the continuous exploration of the deep space field, the performance requirements of cryogenic materials for spacecraft structural parts have further increased.

On the one hand, the spacecraft structural materials must have sufficient strength and toughness and excellent thermal properties at low temperatures; on the other hand, considering the complexity of the shape of the spacecraft structural parts, the materials must have good machinability.

Compared with traditional low temperature materials, titanium alloy has a higher yield strength at low temperatures, which is more than 3 times that of stainless steel, and its density is only 1/4 to 1/2 of that of stainless steel. In addition, titanium alloy also has a series of advantages such as low thermal conductivity, small expansion coefficient, and non-magnetic, so it is very suitable as a new low-temperature material in the aerospace field.

At present, low-temperature titanium alloys have been initially used in the field of liquid rocket engines, mainly as structural materials such as hydrogen-oxygen engine hydrogen storage tanks, hydrogen pump impellers, etc., greatly improving the thrust-to-weight ratio, working life and reliability of liquid rocket engines. The problem with the application of low-temperature titanium alloys is that the elongation and fracture toughness of titanium alloys are greatly reduced in low-temperature environments, and they show obvious low-temperature brittleness. Therefore, how to reduce the low-temperature brittleness of titanium alloys and improve the toughness and plasticity of titanium alloys under low-temperature conditions becomes low Titanium alloy research is the top priority.

Scholars at home and abroad have conducted a lot of research to solve this problem, and found that two methods of reducing the content of interstitial elements such as C, H, O and reducing the content of aluminum element can effectively improve the low-temperature performance of titanium alloys. Through these two methods, a series of new low-temperature titanium alloys with excellent properties have been developed at home and abroad.

The former Soviet Union was committed to the development and application of low-temperature titanium alloys. By reducing the content of aluminum, the former Soviet Union has developed a series of low-aluminum low-temperature titanium alloys, of which OT4 and BT5-1 are widely used. OT4 alloy has been used in spacecraft orbital docking parts, liquid rocket pipes and combustion chamber structural parts; BT5-1 alloy has been used in the manufacture of liquid hydrogen containers. In order to further improve the impulse driving ratio of liquid rocket engines, a Russian research institute conducted research and development of high-strength, high-plasticity, low-temperature titanium alloys suitable for extremely low temperature environments at -253 ℃.

The research on low-temperature titanium alloys in the United States has mainly focused on the α-type titanium alloy TA7 ELI (Extra low interstitial) and the α+β-type titanium alloy TC4 ELI. By reducing the content of interstitial elements, the strength and toughness of the two titanium alloys at extremely low temperatures have been significantly improved. TA7 ELI, as a near-α-type titanium alloy, still has good toughness, low thermal conductivity and notch sensitivity at low temperatures of 20 K. It has been successfully used in cryogenic vessels, cryogenic pipelines, and liquid rocket engine impellers. structure. In the Apollo project, TC4 ELI has been widely used as the main material of liquid hydrogen containers and liquid hydrogen pipes and has achieved good results. In addition, American scholars have also carried out basic research on a series of problems such as the fracture mechanism of low-temperature titanium alloys and hydrogen embrittlement, and obtained the mechanical properties and fracture mechanism data of various low-temperature titanium alloys such as TA7 ELI and TC4 ELI. The further development and application of titanium alloy laid the foundation.
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