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 titanium 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 Grade 23 Titanium Rod increases sharply. Titanium rod company tells you 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, the titanium rod company tells you that you can take corresponding measures, such as welding Grade 7 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.

Problems in CNC titanium machining!

Because the thermal conductivity of titanium exhaust flange processing is small, the heat generated during cutting cannot be dissipated and will be stored in the tool, so the wear on the tool will increase.

Because of the large chemical activity, when the cutting speed increases, cutting heat will occur, and the temperature of the cutting part will increase, so the activity will increase and the wear on the tool will increase.

Because the continuous deformation causes chips to be generated, the cutting resistance of the cutting edge increases, and the tip is prone to chipping and wear.

Because the elastic modulus is small, the machining material is prone to great deformation during cutting, especially when machining thin workpieces, the machining accuracy will be reduced and chattering will occur.

When cutting with a worn tool or when fine chips occur when cutting, the high temperature can sometimes cause the chips to ignite.

Titanium alloy processing parts occupy an important position in the machinery manufacturing industry!

Titanium alloy has the advantages of low density, high specific strength, good corrosion resistance and good process performance, and is an ideal aerospace engineering structural material. Titanium and its alloys are replacing traditional aluminum alloys in many aerospace applications. Today, the aerospace industry consumes about 42% of total global production, and demand for titanium is expected to continue growing at a double-digit rate between now and 2010. Advantages of titanium alloy materials Titanium alloys have high strength, high fracture toughness, and good corrosion resistance and weldability. With the increasing use of composite structures in aircraft fuselage, the proportion of titanium-based materials used in the fuselage will also increase, because the combination of titanium and composite materials is far better than aluminum alloys. For example: Compared to aluminum alloys, Titanium Threaded Rod can increase the life of airframe structures by 60%.

Because titanium alloys are more difficult to machine than ordinary alloy steels, titanium alloys are generally considered to be difficult-to-machine materials. The metal removal rate of a typical titanium alloy is only about 25% of that of most common steel or stainless steel, so machining a titanium alloy workpiece takes about 4 times as long as machining a steel workpiece. To meet the growing demand for titanium machining in the aerospace industry, manufacturers need to increase production capacity and therefore need a better understanding of the effectiveness of titanium machining strategies. The machining of a typical titanium alloy workpiece starts with forging until 80% of the material is removed to obtain the final workpiece shape.

The purity of high-quality titanium target blocks:

Purity is one of the main performance indicators of the Molybdenum Sputtering Target, because the purity of the target has a great influence on the performance of the thin film. However, in practical applications, the requirements for the purity of the target are not the same. For example, with the rapid development of the microelectronics industry, the size of silicon wafers has been developed from 6", 8" to 12", while the wiring width has been reduced from 0.5um to 0.25um, 0.18um, or even 0.13um, and the previous target purity was 99.995%. It can meet the process requirements of 0.35um IC, while the preparation of 0.18um lines requires 99.999% or even 99.9999% for the purity of the target.

Impurities in target solids and oxygen and moisture in pores are the main sources of contamination for deposited films. Targets of different uses have different requirements for different impurity contents. For example, pure aluminum and aluminum alloy targets used in the semiconductor industry have special requirements for alkali metal content and radioactive element content.

In order to reduce the pores in the target solid and improve the performance of the sputtered film, the target is usually required to have a higher density. The density of the target affects not only the sputtering rate, but also the electrical and optical properties of the film. The higher the target density, the better the performance of the film. In addition, increasing the density and strength of the target allows the target to better withstand the thermal stress during sputtering. Density is also one of the key performance indicators of the target.

 Usually the target material is of polycrystalline structure, and the grain size can be in the order of micrometers to millimeters. For the same target, the sputtering rate of the target with fine grains is faster than the sputtering rate of the target with coarse grains; and the thickness distribution of the thin film deposited by sputtering of the target with smaller grain size difference (uniform distribution) is more uniform.

 Is 0.2 thick pure titanium plate the same as 0.2 thick titanium foil, what is the difference?

Depending on the specific material, first of all, the material is differentiated;

Secondly, generally 0.2 and titanium plates, mostly titanium foil sheet.

Titanium foil is relatively thin, and the width is not too wide, but the width of the sheet is wider, generally 0.1 or less is titanium foil.

The most important thing is the material, it can also be said that 0.2 is titanium foil.

Titanium alloy stress corrosion cracking

Stress corrosion cracking (SCC) of titanium alloys was once one of the very active research topics at home and abroad, especially in the aerospace field. Industrial practice shows that most of the titanium welding wire used in the chemical industry are very resistant to stress corrosion. For cracking, stress corrosion cracking may occur only in some special media, such as pure methanol, fuming nitric acid, halide aqueous solution of nitrogen tetroxide, and liquid metal calcium and mercury. Industrial practice has proved that the actual occurrence of stress corrosion cracking accidents is much less than the stress corrosion sensitivity found in the laboratory.

The stress corrosion susceptibility is related to factors such as medium composition, pH value, potential, temperature, and even the viscosity of the medium. The addition of halogen ions improves the stress corrosion sensitivity and increases with the increase of ion concentration. Increased temperature and decreased viscosity can accelerate the rate of cracking.

The mechanism of stress corrosion cracking is still not completely unified. At present, there are two main types of viewpoints: stress-accelerated anodic dissolution and hydrogen enrichment at the crack tip. In fact, this may not necessarily be a tit-for-tat irreconcilable viewpoint. condition. However, a lot of practice shows that hydrogen-induced cracking is a very important cause of stress corrosion cracking, especially the SCC cracking phenomenon found in general industries (such as chemical industry).

Processability of Titanium Alloy and Technology of Grinding and Polishing

Many process parameters of titanium alloys in forging, volume stamping and sheet stamping are close to those in steel processing. But there are some important features that must be paid attention to when pressing working titanium and titanium alloys. When the titanium alloy is cold plastically deformed, regardless of its chemical composition and mechanical properties, the strength will be greatly improved, and the plasticity will be correspondingly reduced. For this reason, annealing treatment between processes must be performed. The low thermal conductivity of titanium and the formation of non-coiled shavings are the reasons for the important characteristics of the machining of titanium and its alloys. When cutting titanium, the tool face will generate high temperature. In order to dissipate the heat, sharpened knives can be used, and a large amount of coolant and lubricant can be supplied. The tools made of carbide BK6M, BK8, BK4, BK2 have good cutting performance in grinding, milling and drilling.

The grinding and polishing of titanium alloys are divided into the following three methods:

(1) Fine grinding

That is to use conventional various emery rubber wheels to grind the surface of titanium and titanium alloy castings. The problem that needs to be paid attention to during grinding is still not to make the casting generate heat, not to cause grinding damage on the surface of the casting, and to make the entire surface smooth and smooth.

(2) Barrel grinding method

The so-called barrel grinding method is to put the processed castings, abrasives, water and additives into the barrel-type grinding tank, and the grinding barrels rotate and vibrate, so that friction is generated between the mixture of abrasives and the processed castings, and the surface of the castings is ground. Smooth and flat. It is characterized by no dust pollution, low labor intensity, and no heat generation in the conventional grinding process. At present, Japan has commercialized barrel grinders and abrasives for grinding Grade 1 Titanium Bar, other metal castings and plastics. It has been confirmed by experiments that the grinding efficiency of pk series abrasives is high, but the surface roughness is also very high. Although the grinding efficiency of SA and B series abrasives is not as good as that of PK, the surface smoothness of the ground titanium castings is higher. At present, the Fourth Military Medical University has successfully developed the first domestic dental barrel grinder.

(3) Mechanical polishing method

The method of polishing the surface of titanium and titanium-containing alloys using soft cloths or black brushes of different specifications, dipped in special polishing pastes for titanium and titanium-containing alloys. When polishing titanium castings, it is necessary to completely clear the contamination layer on the surface of the casting and no new grinding and hardening layer, which will not achieve the ideal polishing effect. When polishing, high speed and light pressure should be used for polishing. The author has also tested the use of green polishing paste to polish titanium and titanium-containing alloy castings, and achieved a relatively ideal polishing effect. Polished titanium and titanium-containing titanium alloy castings cannot be washed with water immediately. The surface oxide film must be completely formed before washing with water, otherwise the surface will be darkened.