Precision Problems in Machining of Titanium Alloy Fasteners

In the production and processing of grade 5 titanium round rod and candied fruit, the precision requirements for machinery will be higher. In mechanical production, because the tool is in a state of working wear during each production process, and it is calibrated according to the program, the density of titanium alloy fasteners is higher, and the tool is easily worn during the machining process. Under the state, the tool is still processed according to the program, and it is easy to cause the precision of the compact part to be affected during the processing. If the precision of the fasteners is not strictly controlled within the error range during the entire processing process, the titanium tubing for bike frame and other materials cannot be tightly connected during the use process, which will have a certain impact on the subsequent use and improve The precision of titanium alloy fasteners in the machining production process is a major problem that needs to be overcome in the production process. Fastener technology products are products made in high-precision production workshops, and the connection performance of such products is better.

The effect of laser welding on the surface treatment of titanium rods!

The process parameters of laser welding are difficult to grasp because the thermal efficiency fluctuates greatly during the welding process, and the surface condition of the welded titanium rod has a great influence on the thermal efficiency: the brighter the surface, the larger the emitted laser light, and most of the laser energy is reflected on other objects. , transferred to the surrounding material or medium in the form of "heat". But thermal efficiency changes suddenly. Before the grade 5 titanium round rod is melted, only about 10%-20% of the light energy is absorbed by the titanium rod and heats the titanium rod. When the temperature rises to the melting point of the weld metal and begins to melt, the light absorption rate of the titanium rod increases sharply. that at this time, about 60%-80% of the light capacity is absorbed by the metal, and the sudden change of thermal effect can easily cause the weld to burn through.

In order to avoid or reduce this adverse effect, you can take corresponding measures, such as welding titanium rods; roughening the surface, using a pulsed laser beam; adjusting the input energy; adjusting the spot size; Pulse width and steepness.

A ruby ​​natural crystal containing aluminum oxide and dissolved with a low concentration of chromium atoms is used as the working material of the laser generator, which is called a solid-state laser generator. If CO2 is used as the working substance of the laser generator, it is called a force gas laser generator.

At present, the power of the laser welding machine is only kilowatts, and it is expensive, the welding cost is high, and the application range is not wide. It is only used for the solder joints of some tiny parts in the manufacture of some instruments and meters, especially when some solder joints are hidden and cannot be welded by ordinary welding methods. Multi-station welding is possible using laser beams, optical fibers and deflection prisms.

What are the technical requirements for titanium tubes?

The titanium tube is light in weight, high in strength and superior in mechanical properties. It is widely used in heat exchange equipment, such as shell and tube heat exchangers, coil heat exchangers, serpentine heat exchangers, condensers, evaporators and conveying pipes, etc. Many nuclear power industries use titanium tubes as standard tubes for their units. titanium seamless tubing

skills requirement:

1. The chemical composition of titanium and titanium alloy pipes shall comply with the provisions of GB/T3620.1. When the buyer re-inspects, the allowable deviation of the chemical composition of Mingkun Titanium Industry shall comply with the provisions of GB/T3620.2.

2. The allowable deviation of the outer diameter of the pipe should meet the regulations.

3. The allowable deviation of the wall thickness of the pipe should not exceed ±12.5% ​​of its nominal wall thickness. The allowable deviation of the wall thickness of the pipe does not apply to the welding seam of the titanium welded pipe. Titanium Alloy Seamless Rectangular Tube

4. The length of the pipe should meet the regulations.

5. The fixed length or multiple length of the pipe should be within the range of its indefinite length, the allowable deviation of the fixed length is +10mm, and the multiple length should also be included in the incision amount when the pipe is cut, and each incision should be 5mm. .

What are the mechanical properties of high-quality titanium rods?

Titanium is a new type of metal, and the properties of titanium are related to the content of impurities such as carbon, nitrogen, hydrogen, and oxygen. Its characteristics are high strength, high thermal strength, good corrosion resistance, good low temperature performance, large chemical activity, small thermal conductivity, and small elastic modulus.

grade 5 titanium round rod are malleable. The elongation of high-purity titanium can reach 50% to 60%, and the section shrinkage rate can reach 70% to 80%, but the strength is low (the tensile strength of titanium iodide is 2.2-2.9MPa), and it is not suitable for structural materials. The impurities in titanium have a great influence on its mechanical properties, especially the interstitial impurities oxygen, nitrogen and carbon can greatly improve the strength of titanium, and significantly reduce its plasticity. Despite the low strength of high-purity titanium, the mechanical properties of titanium-based materials are significantly enhanced by the inclusion of small amounts of impurities and added alloying elements, making their strength comparable to high-strength steels. That is to say, the good mechanical properties of titanium as a structural material are achieved by many titanium rod manufacturers by strictly controlling the appropriate impurity content and adding alloying elements.

1. Corrosion resistance Titanium metal is an emotional metal with excellent corrosion resistance. The titanium rod filter element made of titanium metal can filter in strong alkali and strong acid media. It can be widely used in the chemical industry. In the filtration of the organic lysozyme production process in the pharmaceutical industry, due to the application of organic solvents such as acetone, ethanol, butanone, etc., if a polymer filter element such as PE, PP filter element is used to filter, It is easily dissolved by these organic solvents, and the titanium rod is quite stable in the medium of organic solvents and is widely used.

2. High temperature resistance The high temperature resistance of the titanium filter element can reach 300C, which is unmatched by other filter elements. This feature is widely used in high-temperature operating environments, and the filter element of polymer material has poor temperature resistance, generally not exceeding 50°C, and its support and filter membrane will change when it exceeds 50°C, resulting in a large deviation in filtration accuracy. Even if the PTFE filter element is above 120°C and the external pressure is 0.2MPa for a long time, the phenomenon of isolation and aging will occur. The titanium rod filter element can be used in this environment for a long time without any change in its micropores and appearance. Widely used in high temperature liquid filtration, steam filtration (steam filtration in fermentation process), air filtration at room temperature, etc.

3. Super mechanical properties (high strength) The Grade 1 Titanium Bar filter element has super mechanical properties, the external pressure is 20Kg, the internal pressure destructive force is 10Kg (no joint test), so the titanium rod can be used in the process of high pressure and fast filtration. When the external pressure of other polymer filter elements exceeds 0.5MPa, the micropore size will change or even be broken down. Application, chemical fiber manufacturing, pharmaceutical and chemical industry, compressed air filtration, deep underwater air distribution, coagulant air distribution and foaming, etc.

Titanium alloy fastener processing preservation corrosion problem

In the process of machining Titanium Flat Washers, because the tightness of the mechanical parts is not so high when the fasteners are installed, it is easy to generate a certain gap, so that there will be a surface between the metal gaps. Paint flows in, making fasteners susceptible to corrosion during production. In the subsequent use process, the connection tightness will be affected. The reason why titanium alloy materials have high corrosion resistance is because of the presence of oxygen in the air. A protective film is formed on the surface of the titanium alloy material after the oxidation reaction with oxygen. This layer of film can effectively protect the titanium alloy inside the material from being oxidized, thereby improving the corrosion resistance of the titanium alloy material. However, in the actual machining process of titanium alloy fasteners, due to the constant changes in the environment, including the influence of factors such as ambient temperature, humidity, and equipment oxidation during processing, it will lead to titanium alloy fasteners. Corrosion is easy to occur, which is one of the problems that are prone to occur in the production process of titanium alloy fasteners.

Defects that are prone to occur in ultrasonic flaw detection of alloy forgings

In the application of various titanium alloy products, titanium alloy forgings are mostly used in applications requiring high strength, high toughness and high reliability, such as gas turbine compressor disks and medical artificial bone. Therefore, not only high dimensional accuracy is required for titanium forgings, but also materials with excellent characteristics and high stability are required. The following mainly introduces the six problems existing in titanium alloy flaw detection.

Titanium alloy ring

1. Segregation defects

In addition to β segregation, β spot, Gr5 Ti-6Al-4V Titanium Wire-rich segregation and strip α segregation, the most dangerous is interstitial α stable segregation (type I α segregation), which is often accompanied by small holes and cracks around it, containing oxygen, nitrogen and other gases , is more brittle. There is also aluminum-rich α-stable segregation (type II α-segregation), which also constitutes a dangerous defect due to cracks and brittleness.

2. Inclusions

Most of them are metal inclusions with high melting point and high density. It is formed by the high melting point and high density elements in the titanium alloy composition that are not fully melted and left in the matrix (such as molybdenum inclusions), and there are also carbide tool chippings or inappropriate electrode welding processes mixed in smelting raw materials (especially recycled materials). The smelting of titanium alloys generally adopts vacuum consumable electrode remelting method), such as tungsten arc welding, leaving high-density inclusions, such as tungsten inclusions, and titanium compound inclusions.

The existence of inclusions can easily lead to the occurrence and expansion of cracks, so it is not allowed to exist defects (for example, the Soviet Union's 1977 data stipulated that high-density inclusions with a diameter of 0.3~0.5mm were found in the X-ray inspection of titanium alloys. record).

3. Residual shrinkage

In the central area of ​​the acid leaching test piece (in most cases), there are irregular folds, cracks or voids, and there are often serious looseness, inclusions (slag inclusions) and composition segregation on or near it.

4. Holes

The holes do not necessarily exist individually, but may also exist in a plurality of clusters, which will accelerate the growth of low-cycle fatigue cracks and cause premature fatigue failure.

5. Cracks

Mainly refers to forging cracks. grade 5 titanium round rod has high viscosity, poor fluidity, and poor thermal conductivity. Therefore, in the process of forging deformation, due to the large surface friction, obvious internal deformation unevenness and large temperature difference between inside and outside, it is easy to produce shear bands inside the forging ( Strain line), which will lead to cracking in severe cases, and its orientation is generally in the direction of maximum deformation stress.

6. Overheating

The thermal conductivity of titanium alloy is poor. In addition to overheating of forgings or raw materials caused by improper heating during the hot working process, it is also easy to cause overheating due to the thermal effect of deformation during the forging process, causing changes in the microstructure and producing an overheated Widmandarin structure.

Analysis of properties, classification and use of pure titanium

Among titanium materials, including titanium rods, titanium flanges,Titanium Hot Rolled Sheet, etc., are divided into pure titanium and titanium alloys. Compared with pure titanium, titanium alloys are added with Al, Mo, Cr, Sn, Mn, V and other alloying elements. Therefore, pure titanium has its unique excellent properties and different uses in terms of mechanical properties.

1. Performance

Ti: 4.507 g/cm3, Tm: 1688°C. It has allotrope transformation, α phase with hexagonal close-packed structure at ≤882.5°C, and β phase with body-centered cubic structure at ≥882.5°C.

Pure titanium has low strength, but high specific strength, good plasticity, good low temperature toughness and high corrosion resistance. Titanium has good pressure processing performance and poor cutting performance. Titanium can burn when heated in nitrogen, so titanium should be protected by argon during heating and welding.

2. Classification

According to the impurity content, titanium is divided into high-purity titanium (purity of 99.9%) and industrial pure titanium (purity of 99.5%). There are three grades of industrial pure titanium, which are respectively represented by Gr + serial number numbers 1, 2, and 3. The larger the number, the lower the purity.

3. Purpose

The content of impurities has a great influence on the performance of titanium. A small amount of impurities can significantly improve the strength of titanium. Therefore, the strength of industrial pure titanium is relatively high, close to the level of high-strength aluminum alloys. , reactors, ship parts, aircraft skins, etc.