Standards and methods for quality inspection of titanium alloy forgings

The existence of defects in titanium forgings will affect the processing quality or processing quality of subsequent processes, and some will seriously affect the performance and use of the forgings, and even greatly reduce the service life of the finished products and endanger safety. Therefore, in order to ensure or improve the quality of forgings, in addition to strengthening quality control in the process and taking corresponding measures to prevent the occurrence of forging defects, necessary quality inspections should also be carried out to prevent subsequent processes (such as heat treatment, surface treatment, cold working) And forgings with defects that have adverse effects on performance flow into the follow-up process. After quality inspection, remedial measures can be taken for the forgings made according to the nature of the defect and the degree of influence to use, so that it meets the technical standards or requirements for use.
Therefore, in a sense, the quality inspection of forgings is to check the quality of the forgings that have been made on the one hand, and to point out the direction of improvement for the forging process on the other, so as to ensure that the quality of forgings meets the requirements of forging technical standards and meets the design Requirements on processing and use. The inspection of forging quality includes the inspection of appearance quality and internal quality. Appearance quality inspection mainly refers to the inspection of the geometric size, shape, surface condition and other items of the forging; the internal quality inspection mainly refers to the inspection of various items such as the chemical composition, macrostructure, microstructure and mechanical properties of the forging.
Specifically, the appearance quality inspection of forgings is to check whether the shape and geometric dimensions of the forgings meet the specifications of the drawings, whether the forgings have defects on the surface, what are the defects, and what are their morphological characteristics. The inspection content of the surface condition is generally to check whether the forging surface has surface cracks, folds, wrinkles, pits, orange peel, blisters, scars, corrosion pits, bruises, foreign objects, underfill, pits, lack of meat, scratches Defects such as marks. The internal quality inspection is to check the internal quality of the forging itself. It is a quality condition that cannot be found by the appearance quality inspection. It includes the inspection of the internal defects of the forgings and the inspection of the mechanical properties of the forgings. For important parts, key parts or large forgings Chemical composition analysis should also be performed. For internal defects, we will inspect the forgings through low-power inspection, fracture inspection, and high-power inspection to check whether there are internal cracks, shrinkage holes, porosity, coarse crystals, white spots, dendrites, streamlines that do not conform to the shape, and streamlines turbulence. , Flow through, coarse crystal ring, oxide film, delamination, overheating, overburning organization and other defects. For the mechanical properties, it is mainly to check the normal temperature tensile strength, plasticity, toughness, hardness, fatigue strength, high temperature instantaneous rupture strength, high temperature permanent strength, permanent plasticity and high temperature creep strength.
After forgings are made into parts, the force, importance, and working conditions are different during use, and the materials and metallurgical processes used are also different. Therefore, different parts are classified into categories according to the above conditions and the requirements of this department. , Different departments and different standards have different classifications of forgings. But no matter what, the overall quality inspection of forgings is inseparable from two major types of inspections, namely, the inspection of appearance quality and internal quality. It is just that the types of forgings are different, and the specific inspection items, inspection quantities and inspection requirements are different. . For example, some industrial departments classify structural steel, stainless steel, and heat-resistant steel forgings into Type IV for inspection, and some departments divide aluminum alloy forgings and die forgings into Type III for inspection according to their usage conditions, and some departments classify aluminum alloy, Copper alloy forgings are classified into Category IV for inspection.
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Introduction to the corrosion resistance of titanium tubes

Everyone knows that titanium tube is a new type of metal that we have formed in recent years. The performance of titanium is mainly related to its proportion of carbon, nitrogen, hydrogen, etc. It has been widely used. Now let us popularize the corrosion resistance of titanium tubes in neutral or weakly acidic oxide solutions.
The corrosion resistance of the titanium tube is highly stable in neutral or weakly acidic oxide solutions. For example, titanium and titanium alloys are in CuC12 at 100 ℃ FeCl at 100 ℃, HgC1 at 100 ℃: (all concentrations), 60 % AlCl2 and all concentrations of NaCl at 100°C are stable. Many other metal oxides of titanium are also stable in 100% monooxyacetic acid and 100% peroxyacetic acid. Therefore, titanium and titanium alloys are It has been widely used in the solution. Titanium and titanium alloys are also highly stable to ion-containing oxidant solutions, such as 100qC sodium hypochlorite solution, oxygen water, gas (up to 75°C), sodium oxide solution containing hydrogen peroxide, etc.
The corrosion resistance of titanium pipes in wet chlorine gas exceeds that of other commonly used metals. This is because chlorine has a strong oxidizing effect. Titanium and titanium alloys can be in a stable passive state in wet chlorine. In order to maintain the passivity of titanium in chlorine, A certain water content is required. The critical water content is related to oxygen pressure, flow rate, temperature and other factors, as well as the shape and size of titanium equipment or parts and the degree of mechanical damage to the titanium surface. Therefore, the critical water content of titanium passivation in oxygen in the titanium tube literature is Inconsistent, it is generally believed that the mass fraction of 0.01% to 0.05% can be used as the critical water content of titanium in oxygen, but actual experience has pointed out that in order to ensure the safe use of titanium equipment in oxygen, sometimes the water mass fraction is 0.6 % Is not enough, it needs to be as high as 1.5%. The critical water content also increases with the increase of chlorine temperature and the decrease of airflow velocity. Actual operating experience also shows that after the surface oxide film of titanium and titanium alloy is destroyed, higher water content is required to passivate titanium and titanium alloy again.
Titanium and titanium alloys will react violently in dry chlorine even below 0°C to form titanium tetrachloride. Titanium tubes pose a fire hazard. Once the destruction of titanium and titanium alloys in dry chlorine gas begins, the reaction is collapsible, and the addition of water cannot prevent the reaction from proceeding. The behaviour of titanium in the dry and wet zone of chlorine gas has not been fully understood. Based on the thermodynamic analysis, titanium and chlorine cannot exist in equilibrium at room temperature. According to the thermodynamic free energy, a stable compound titanium tetrachloride is formed in this reaction system. If it does not coexist with water, it will react further, namely TiC14+4H20.
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Do you know what are the corrosion forms of titanium rods?

1. Crevice corrosion: Titanium rod manufacturers pointed out that crevice corrosion is a local corrosion phenomenon that occurs in close gaps. The gaps can be caused by structures (such as flange connection surface or gasket surface, tube and tube sheet expansion joint, and The connecting surface of bolts or rivets, etc.) can also be caused by scaling or deposits under the covering surface. In the early days, it was believed that titanium did not undergo crevice corrosion at all in seawater and salt spray. Later, in high-temperature chloride medium (such as seawater heat exchanger), wet chlorine gas (such as wet chlorine gas tube condenser), oxidant corrosion inhibition hydrochloric acid solution In media such as formic acid and oxalic acid solution, crevice corrosion damage of equipment has occurred successively.
The crevice corrosion of titanium rods is related to many factors such as environmental temperature, chloride type and concentration, pH value, and the size and geometry of the crevice. In addition, the crevices composed of titanium and nonmetals such as polytetrafluoroethylene, titanium and asbestos are more sensitive to crevice corrosion than those composed of titanium and titanium.
2. Pitting corrosion: Pitting corrosion is a form of corrosion peculiar to passivated metals. Compared with stainless steel or aluminum alloy, the pitting corrosion resistance of titanium is very excellent. Due to the increasing application of titanium in high-temperature concentrated chloride solutions, the number of pitting corrosion cases of titanium equipment has gradually increased.
The titanium anode basket in electrolytic zinc, the titanium coil heated in zinc chloride solution, and the titanium ball valve of 72% calcium chloride solution at 175℃ have all experienced pitting corrosion damage. Generally speaking, pitting corrosion of titanium is more difficult than crevice corrosion, which usually appears in the form of pitting corrosion on the crevice surface.
3. Galvanic corrosion: Galvanic corrosion is a phenomenon in which dissimilar metals contact in the electrolyte solution (including electrical contact). Due to the difference in the steady-state potential of the metal, one metal accelerates the corrosion of another metal (ie, anode dissolution). The oxide film of titanium is very stable and is generally in the cathode state, and galvanic corrosion will not accelerate the anode dissolution of titanium.
However, attention must be paid to the hydrogen absorption of titanium in the cathode state, which will eventually lead to hydrogen embrittlement. At the same time, it is necessary to prevent the accelerated corrosion of the coupling metal (such as aluminum, copper, zinc, etc.). The size of the galvanic corrosion of the metal depends on the difference of the galvanic sequence of the coupled metal in the medium.
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Trimming process requirements and precautions for titanium alloy forgings and titanium forgings

The trimming of titanium alloy forgings and titanium forgings must meet the following requirements:
1. The cut is flat and the metal on the blank must not fall apart.
2. The part adjacent to the cut surface of the blank must not have cracks, and there must be no uneven grain size caused by uneven trimming deformation.
3. There should be no punch indentation on the trimmed blank, and the punch and parts should be completely consistent in appearance. forging titanium round bar
It can be trimmed with a milling machine or with a band saw and equipped with a specially designed friction plate. Regardless of the size or batch size of the large forgings and thick burrs, it is inconvenient to heat the edges, but flame cutting is an effective method. The use of oxygen-gas, plasma and other technologies can successfully and economically cut burrs of 50mm or thicker. After flame-cutting, heat treatment should be carried out to make the heat-affected zone available for mechanical processing. Titanium Planar Sputtering Target
For larger batches of medium and small titanium alloy forgings, the edges are usually hot trimmed with a die on a crank press, and the trimming is performed at 600-800°C. If correction must be done immediately after trimming, the trimming temperature should be close to the upper limit. Titanium alloys are rarely trimmed with a die in the cold state.  Ti 15V-3Cr-3Sn-3Al Titanium Strip
Because the burrs are hard and brittle, it is easy to cause uneven cuts, and even cause the danger of metal chipping and rapid splashing of chips; for some alloys with high alloying degrees, cold trimming It will cause cracks on the shear surface, and the cracks will expand into the metal from time to time. ASTM B265 Gr5 Titanium Strip

Application of Titanium Wire in Marine Fishing Nets

Fixed fishing nets used in marine aquaculture, after contact with organic matter and bacteria, diatoms will multiply, while shellfish, barnacles and other marine organisms that feed on diatoms will gather and adhere, which will not only increase the flow resistance and cause the fishing nets Decontamination of the fish, and will cause anoxic infections, causing problems such as stunted fish development. For this reason, antiseptics, fungicides, etc. are generally used, but in this case, the service life of the fixed net does not exceed 20 years, and in order to remove the attached microorganisms, the net must be regularly pulled ashore for the mechanical removal, resulting in increased labor costs and Problems such as deterioration of fishing nets. Researchers from the University of Tokyo have studied the weaving of Grade 12 Titanium Wire into existing polyethylene (PE) fishing nets and electrifying them to electrolyze the seawater near the Ti 6Al-2Sn-4Zr-6Mo Titanium Rod to produce chlorine and ClO, which can kill bacteria and inhibit bacterial growth. First, a mesh made of platinum-plated titanium wire with a diameter of 1 mm was used as the anode, and a stainless steel 312L plate was used as the cathode to conduct an electrolysis test. The results showed that the applied voltage was 3.0 V. After being placed in seawater for 14 days, the weight of the titanium mesh did not change, while the unpowered titanium mesh attached marine organisms.
The main purpose is to study the matching of the strength and elongation of the titanium wire and the PE wire. The existing fishing net is woven by twisting 10 PE monofilaments with a diameter of 0.10 mm into composite yarns and then twisting 2 composite yarns into twisted yarns. The researched titanium mesh is made by twisting 10 PE monofilaments and Grade 1 Titanium Straight Wire into twisted filaments, and then twisting the two twisted filaments into twisted filaments for weaving. Tensile tests of different diameter titanium wires (Φ0.10 mm, Φ0.25 mm, and Φ0.50 mm) and PE filaments of monofilament, combined filament and twisted filament were carried out. The results show that the elongation of titanium wire is lower than that of PE wire, especially the Medical Grade Titanium Wire of Φ0.10 mm. The titanium wire (Φ0.25 mm, Φ0.50 mm) in the titanium composite wire broke simultaneously with the surrounding PE, and the titanium wire (Φ0.25 mm) in the titanium twisted wire broke simultaneously with the surrounding PE. It shows that the fishing net twisted into the titanium wire has the same strength as the existing fishing net woven with polyethylene wire.

What are the types of heat exchangers?

1. Surface heat exchanger
Surface heat exchangers are two fluids with different temperatures flowing in a space-separated by a wall surface. The heat transfer between the two fluids is conducted by heat conduction on the wall surface and convection of the fluid on the wall surface. Surface heat exchangers include shell and tube, sleeve and other types of heat exchangers. Titanium Coil Tube
2. Regenerative heat exchanger
The regenerative heat exchanger transfers heat from a high-temperature fluid to a low-temperature fluid through a heat storage body composed of solid materials. The heat medium first reaches a certain temperature by heating the solid material, and then the cold medium is heated by the solid material to make it reach heat Purpose of delivery. The regenerative heat exchanger has a rotary type, valve switching type and so on. titanium exhaust pipe
3. Fluid connection indirect heat exchanger
The fluid connection indirect heat exchanger is a heat exchanger that connects two surface heat exchangers with a heat carrier circulating in it. The heat carrier circulates between the high-temperature fluid heat exchanger and the low-temperature fluid and accepts the high-temperature fluid The heat is released to the cryogenic fluid in the cryogenic fluid heat exchanger. titanium mig welding wire
4. Direct contact heat exchanger
A direct contact heat exchanger is a device that directly contacts two fluids for heat exchange, for example, a cold water tower, a gas condenser, etc. surgical medical titanium wire

Do you know which factors are related to the quality of titanium plates?

Titanium plates have high corrosion resistance and specific strength, and are widely used in electric power, chemical industry, aviation components, building materials, sports equipment, medical treatment and other fields and are still expanding. From the point of view of use and manufacturing technology, titanium plates are low in price, high in performance, multi-functional, and easy to produce. From the viewpoint of expanding usage, grade 5 titanium round bar represented by Ti-1Fe-0.35O, Ti-5Al-1Fe, Ti-5Al-2Fe-3Mo (mass%) make full use of cheap elements such as Fe, O, N, etc. It is a pure titanium plate for various surface finishing and to improve the resistance to discoloration. A remarkable feature of titanium plate is its strong corrosion resistance. This is due to its particularly high affinity for oxygen, which can form a dense oxide film on its surface, which can protect titanium from medium corrosion. , Neutral saline solution has good stability in oxidizing medium, and has better corrosion resistance than existing stainless steel and other commonly used non-ferrous metals.
The quality of the AMS 4900 CP Titanium Plate is largely determined by the smelting process of the titanium plate manufacturer, including the chemical composition of titanium, the cleanliness of titanium water (gas, harmful elements, inclusions) and the quality of the slab (component segregation, decarburization and Its surface condition), these aspects are the key control points of the smelting operation. In addition, industrial titanium plates also require sufficient hardenability to ensure uniform microstructure and mechanical properties throughout the spring section. The main cause of fatigue cracks is the inclusion of oxides in titanium, and Class D inclusions are more harmful to fatigue life than Class B inclusions. Therefore, foreign titanium factories and automobile factories have put forward higher requirements for oxide inclusions in industrial titanium plates. For example, the Swedish SKF standard requires that the oxygen content in titanium is less than 15×10-6, and class D inclusions are lower than class B inclusions. Thing. In particular, the inclusions of Al2O3 and TiN are extremely harmful to the fatigue life of titanium springs. In order to produce high-quality industrial Grade 23 Titanium Sheet, special smelting methods such as electric furnace-electroslag remelting or vacuum arc remelting are usually used in the past.
Because grade 7 titanium alloy plate and titanium rods have special physical and chemical properties, the welding process is very different from other metals. Titanium welding is a TiG welding process that effectively protects the welding area with inert argon gas. Before use, check the factory certificate on the bottle body to verify the purity index of the argon gas, and then check the bottle valve for leaks Or failure. The metal in the welding zone is not contaminated by the reactive gas N0H and the harmful impurity element CFeMn above 250℃. The purity should not be lower than 99.98%, the water content should be lower than 50Mg/m32 Argon: industrial grade pure argon. Coarse grain structure cannot be formed. The welding process must be in accordance with the predetermined construction sequence, and no large welding residual stress and residual deformation can be generated. and so. Strictly follow the process quality management standards and implement quality control of the entire process. All factors of man, machine, material and method are in a well-controlled state, so as to ensure the welding quality of titanium tubes within a reasonable construction period.

How to improve the quality and performance of titanium plate surface

The quality of the titanium plate is largely determined by the smelting process, including the chemical composition of titanium, the cleanliness of titanium water (gases, harmful elements, inclusions) and the quality of the slab (segregation of components, decarburization and surface conditions) These aspects are the key control points for smelting operations. In addition, industrial titanium plates also require sufficient hardenability to ensure uniform microstructure and mechanical properties throughout the spring section. The main cause of fatigue cracks is the inclusion of oxides in titanium, and Class D inclusions are more harmful to fatigue life than Class B inclusions. Therefore, foreign titanium factories and automobile factories have put forward higher requirements for oxide inclusions in industrial titanium plates. For example, the Swedish SKF standard requires that the oxygen content in titanium is less than 15×10-6, and class D inclusions are lower than class B inclusions. Thing. In particular, the inclusions of Al2O3 and TiN are the most harmful to the fatigue life of titanium springs. In order to produce high-quality industrial titanium plates, special smelting methods such as electric furnace-electroslag remelting or vacuum arc remelting are usually used in the past. Forging of titanium plate blanks is usually used to produce products with similar shapes and dimensions, followed by heat treatment and cutting. The final rough. The casting temperature and the degree of deformation are the fundamental factors that determine the arrangement and function of the titanium alloy. The heat treatment of the titanium plate blank products factory is different from the heat treatment of steel, and it has no resolution effect on the arrangement of titanium alloys. Therefore, the process standard of the final step of forging of titanium plate blank products factory has unique and important effects. In order to make the die forgings of the titanium plate blank products factory achieve higher strength and plasticity together, it is necessary to make the overall deformation of the blank not less than 30%, the deformation temperature does not exceed the phase transition temperature, and the temperature and deformation degree should be determined throughout The deformed blank can be evenly distributed as much as possible. Titanium plate rough products factory die forging arrangement and functional uniformity stainless steel forgings. In the violent metal activity area, after recrystallization heat treatment, the low magnification is ambiguous crystals, and the high magnification is equiaxed fine crystals; in the hard deformation area, due to the small amount of deformation or no deformation, the arrangement often saves the state before deformation. Therefore, in the forging of some important titanium plate blank products factory parts (such as compressor disks, blades, etc.), in addition to controlling the deformation temperature below TB and the appropriate degree of deformation, the arrangement of controlling the original blank is very important, otherwise, The coarse grain arrangement or some shortcomings will be inherited into the forging, and the subsequent heat treatment cannot be eliminated, which will cause the forging to be scrapped.

When the closed die forging method is adopted to process forged titanium plate blank products, the life of the die is reduced because of the high pressure. Therefore, closed die forging must strictly limit the volume of the original blank, which complicates the preparation process. Whether to choose closed die forging depends on both cost and process feasibility. In the open die forging, the burr loss accounts for 15% to 20% of the blank component, and some process scraps (if necessary according to the die forging conditions) must be held for 10% of the blank component. Relative loss of burr metal is usually added as the blank component is reduced. For some asymmetry layouts, large cross-sectional area differences, and some forgings that are difficult to fill, the burr cost can be as high as 50%. Although there is no burr loss in closed die forging, but the blank making process is messy, it is necessary to add more transitional grooves, which will undoubtedly add auxiliary costs.

The reaction layer on the surface of the titanium plate is the main factor that affects the physical properties of the titanium plate. After the titanium plate is rolled, it needs to be annealed. The oxide layer generated by the titanium plate needs to be removed by the method of explosive alkaline pickling to remove the surface reaction layer of the titanium plate.

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The difference between industrial pure titanium and titanium alloy

The density of titanium is 4.5g/cm3, which is 57% of steel; titanium is less than twice heavier than aluminum and three times stronger than aluminum. Specific strength is the ratio of strength to density. When compared with different materials, the specific strength of titanium alloys is almost the largest among commonly used industrial alloys. The specific strength of titanium alloy is 3.5 times that of stainless steel, 1.3 times that of aluminum alloy, and 1.7 times that of magnesium alloy, so it is an indispensable structural material for the aerospace industry. Comparison of the density and specific strength of titanium with other metals. Titanium has a high melting point, poor thermal conductivity and electrical conductivity, and is similar to or slightly lower than stainless steel. Titanium has superconductivity. The critical temperature of pure titanium is 0.38.4K. Metal titanium is a non-magnetic substance.

Titanium alloy is a single-phase alloy composed of phase solid solution and has a low density. Whether it is at a general temperature or at a higher practical application temperature, it is a phase, the structure is stable, the wear resistance is higher than that of pure titanium, and the oxidation resistance is strong. . At a temperature of 500-600 degrees, it still maintains its strength and creep resistance, can be strengthened by heat treatment, has good thermal strength and thermal stability, good welding performance, good room temperature, ultra-low temperature and high temperature performance.

Commercial pure titanium is a dense metal titanium with a titanium content of not less than 99% and containing a small amount of impurities such as iron, carbon, oxygen, nitrogen and hydrogen. The impurities with the strongest influence on the mechanical properties of pure titanium are oxygen, nitrogen and iron, especially oxygen. The reaction of hydrogen with titanium is reversible. The effect of hydrogen on the performance of titanium is mainly manifested as "hydrogen embrittlement". Usually, the hydrogen content should not exceed 0.015%, and generally contain 0.15%-0.3% oxygen and 0.03%-0.05% nitrogen. Although industrial pure titanium is a close-packed hexagonal lattice at room temperature, its axis is relatively small (c/a=1.587), and it has better workability. Pure titanium has good formability and welding performance, and is not sensitive to heat treatment.

Among titanium metals, including titanium plates, titanium rods, titanium tubes, etc., include pure titanium and titanium alloys. The obvious difference between pure titanium and titanium alloy is that titanium alloy is based on pure titanium with chemicals such as Al, Mo, Cr, Sn, etc. It is precisely because of these chemicals that these two titanium metals are The difference in performance. The following focuses on the analysis and introduction of the classification, performance and use of pure titanium.

1. Classification of pure titanium:

According to the content of impurities, 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 denoted by TA + sequence number 1, 2, 3, the larger the number, the lower the purity.

2. Performance of pure titanium:

Ti: 4.507 g/cm3, Tm: 1688°C. With allotropic transformation, ≤882.5℃ is the α phase of the close-packed hexagonal structure, ≥882.5℃ β phase of the body-centered cubic structure.

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

3. The use of pure titanium:

Impurity content has a great influence on the performance of titanium. A small amount of impurities can significantly increase the strength of titanium. Therefore, industrial pure titanium has high strength and is close to the level of high-strength aluminum alloy. It is mainly used to manufacture heat exchange for petrochemicals working below 350℃ Reactor, reactor, ship parts, etc.

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Titanium flange hot processing pay attention to details

Hot processing, mainly forging, rolling and extruding, is the basic production method of titanium flange semi-finished products and products. In view of the strong sensitivity of the titanium flange structure to the hot processing process, the correct selection and mastering of process parameters are not only important for ensuring the shape and size accuracy of the product, but also the key factor for the internal quality of the product.

Compared with general metal structural materials, the thermal processing feature of titanium flanges is that the deformation resistance is large and the deformation temperature range is narrow. Titanium with a hexagonal crystal structure is not easy to deform. In order to improve the plasticity, it is necessary to heat the metal to the b-phase region above the transformation point, so-called b-processing. However, due to the large tendency of titanium flanges to overheat, high-temperature heating will cause b grains to grow rapidly, but if the amount of deformation is insufficient, the formation of a coarse Weiss structure after cooling will significantly reduce the periodicity and fatigue strength of the alloy. The organization is difficult to eliminate in the subsequent heat treatment, so the current production of the finished product or the thermal processing starting temperature before the finished product is not required to pass the critical point Tb. Because the deformation resistance of the titanium flange is very sensitive to the reduction of the deformation temperature or the increase of the deformation rate, the temperature of the forging stop cannot be too low. The constraints of these two factors limit the processing temperature range of most titanium flanges to 800-950°C, which is not easy to grasp. However, for the opening of the ingot, the temperature range can be expanded to 850-1150 ℃, in the subsequent processing of the fire, the temperature is gradually reduced.

Titanium flange alloy has poor thermal conductivity. During rapid deformation, the temperature of the core of the workpiece rises quickly. It is easy to cause overheating due to slow heat transfer, and the surface temperature of the workpiece is low, and surface cracks are easy to form. Therefore, it is necessary to pay attention to the deformation during processing Rate and deformation.

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Corrosion resistance of titanium alloy materials

Corrosion-resistant titanium alloy refers to a corrosion-resistant titanium alloy produced by adding trace effective elements.
The corrosion resistance of titanium alloy materials is due to the formation of an inert thin film (stable oxide film) on the surface. In an oxidizing acid (nitric acid, etc.) that provides oxygen and chloride ion environments, it has the same Superior corrosion resistance. However, under the environment of reducing acids (hydrochloric acid, sulfuric acid, phosphoric acid, etc.), overall corrosion occurs, and in aqueous solutions containing chloride ions, crevice corrosion will occur between the crevices of the flange surface. In this environment, the effective elements that can improve the corrosion resistance are platinum group elements P, Pd and Ru, etc., and a small amount of Pd is added separately to the alloy. If it is used instead of expensive Pd, it is necessary to develop cheap Mo and Ni. , Ru, Co, Cr and other low-cost corrosion-resistant alloys added in small amounts. The addition of trace elements can form an oxide film and promote improved corrosion resistance.
The strength is the same as that of pure titanium, and it is controlled according to O and Fe. Its workability and welding are the same as Murata. Most corrosion-resistant titanium alloys are developed by domestic processing plants in Japan. Japan is based on pure titanium, reflecting the main body of demand as a corrosion-resistant material. Most of the corrosion-resistant titanium alloys developed are in the JS and ASTM standards and are recognized by the public as general materials.
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Development characteristics of titanium alloy materials and processing technology of titanium products

Due to the high manufacturing cost of titanium alloys, in order to reduce costs, the competitiveness of titanium alloys in the entire metal material market has increased at a lower price. It is generally believed that titanium has unparalleled superior performance compared to other materials, but the price of titanium often prohibits consumers (especially car manufacturers). The emergence of high-quality, low-cost titanium alloys will certainly contribute to the promotion and application of titanium and titanium alloys.

From the perspective of domestic and international application status and development of titanium processing technology, the plastic processing technology of titanium and titanium alloys will develop in the following directions in the future:

1) High performance, that is, to develop alloys with higher service temperature, higher specific strength, higher specific modulus, better corrosion resistance and wear resistance.

2) Multi-function, that is, the development of titanium alloys with various special functions and uses, such as high damping, low expansion, constant resistance, high resistance, electrolytic passivation and hydrogen storage, shape memory, superconductivity, low modulus biomedical And other titanium alloys to further expand the application of titanium and titanium alloys.

3) Deepen the research of traditional alloys, improve the practical performance of existing alloys, and expand the application range of traditional alloys through the improvement of equipment and processes.

4) Adopt advanced processing technology, large-scale continuous processing equipment, develop continuous processing technology, direct rolling technology, cold forming technology and near-net forming technology to improve titanium alloy production efficiency, yield and product performance.

5) Reduce costs, develop alloys that contain no or almost no precious metal elements, and add inexpensive elements such as iron, oxygen, and nitrogen to develop titanium alloys that are easy to process and shape, easy to cut, and alloy elements and master alloys are cheap. Develop titanium alloys and use prohibited materials to improve the recovery and utilization of prohibited titanium. This is particularly important for reducing the cost of civilian titanium alloys.

6) Use advanced computer technology to simulate the deformation and processing of the workpiece, predict the evolution of the metal microstructure, and even predict the mechanical properties of the product (yield strength, tensile strength, elongation, hardness, etc.). ), and design or improve moulds and tooling; analyze and process test results, reduce test volume, improve work efficiency, and reduce development costs.

TA6V Titanium Bar     Ti 10V-2Fe-3Al Titanium Thick Plate     ASTM B861 25*1.2mm Titanium Tube For Chemical  

How to use the mechanical and physical properties of titanium in the processing of titanium plates and tubes

(1) The elastic modulus of titanium is relatively low compared to its tensile properties. Therefore, in the operation of forming and rollers, a large rebound margin must be considered. Because of the low elastic modulus, in order to achieve the same stability, the cross-section of titanium parts is slightly larger than the same steel parts.
(2) Titanium is easy to machine, but to consider its sticking tendency (larger than stainless steel) and low thermal conductivity, it is necessary to appropriately improve the commonly used machining technology and the design of thread and bearing surface. At least a rigid machine tool, a sharp tool, slow speed, large cutting amount, and room for chip removal are also recommended. It is also recommended to use a large amount of cooling lubricant.
(3) The thermal expansion coefficient of titanium is 75% of carbon steel. Special attention should be paid to this point when it is necessary to combine these two materials in the design and manufacture of equipment.
(4) Because titanium is an active metal, when heated to above 600 ℃, it is easy to combine with oxygen in the air, so it is generally not recommended for long-term use of titanium above this temperature.
(5) When the temperature of industrial pure titanium exceeds 150~200℃, the mechanical strength decreases rapidly.
(6) The diffusion rate of hydrogen in titanium is faster than that of oxygen. Therefore, before hot working, the heating furnace used should have a slightly oxidizing atmosphere, so that although a relatively thin oxide film will be produced, it may avoid the possibility of hydrogen. Deep pollution.
(7) Softer industrial pure titanium plates are easy to cold-form after annealing; harder industrial pure titanium and Ti2.5Cu require medium temperature processing, and the processing temperature for Ti6Al4V is preferably 600~700℃.
(8) Composite plates can be obtained by explosive welding of thin titanium plates and thick steel plates, which can be used to manufacture high-pressure, high-temperature vessels and heat exchangers. But using it to replace the whole titanium or the titanium lining of the suit is not economically feasible.
Ti 6246 Titanium Rod     AMS 4900 CP Titanium Plate     Gr2 Polished Titanium Wire   

Causes of cracks in titanium rod extrusion

The thermal conductivity of the titanium rod and titanium alloy rod blanks is low, which will cause a great temperature difference between the surface layer and the inner layer during hot extrusion. When the temperature of the extrusion barrel is 400 degrees, the temperature difference can reach 200~250 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 produce very different strength properties and plastic properties, which will cause very uneven deformation during the extrusion process. Large additional tensile stress is generated in the medium and becomes the source of cracks and cracks on the surface of the extruded product.

Its main can be divided into:

1) Extrusion method. The reverse extrusion has a more uniform metal flow than the forward extrusion, the cold extrusion has a more uniform flow than the hot extrusion metal, and the lubricating extrusion has more uniform flow than the non-lubricating extrusion metal. The impact of the extrusion method is achieved by changing the friction conditions.

2) Squeeze speed. As the extrusion speed increases, the unevenness of metal flow increases.

3) Extrusion temperature. As the extrusion temperature increases and the deformation resistance of the billet decreases, the uneven metal flow increases. During the extrusion process, if the heating temperature of the extrusion cylinder and the mold is too low, and the temperature difference between the outer layer and the center layer is large, the unevenness of the metal flow increases. 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) Mold 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 fluidity of the metal. When the porous die is used for extrusion, the arrangement of die holes 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 flow is uneven.

Solution:

1: When the unit pressure is the same as forging hammer forging, when forging with a press. The heating temperature of the blank can be reduced by 50100℃. In this way, the interaction between the heated metal and the periodic gas and the temperature difference between the blank and the mold are correspondingly reduced, thereby improving the uniformity of the deformation, the uniformity of the structure of the die forging is greatly improved, and the consistency of the mechanical properties is also improved. .

2: Increase the forging slope and fillet radius and use lubricant: the height of the burr bridge on the forging die is larger than that of steel, and the deformation of the titanium rod is more difficult to flow into the deep and narrow die groove than steel.

3: Reduce the deformation speed, the most obvious increase in the surface shrinkage rate, the surface shrinkage rate is the most sensitive to tissue defects caused by overheating.

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The mechanical properties of titanium welded pipe and titanium seamless pipe are basically the same

Taking titanium and titanium alloy tubes for heat exchangers and condensers as an example, the national standard is GB/T 3625-2007, the American standard is ASTMB338, and the differences between titanium welded tubes and titanium seamless tubes in terms of chemical composition, mechanical properties, process performance and other indicators Not big, even the same. With the advancement of welding and heat treatment technology of titanium welded pipes, domestic thin-walled titanium welded pipes generally adopt single-gun or multi-gun TIG/PAW self-fusion welding. 

After welding, the online heat treatment process is adopted. By optimizing the welding and annealing processes, the microstructures of the base metal, welds, and heat-affected zone are basically close to each other, at the same time, the welding stress is eliminated and the weld structure is homogenized. Through comparison, it is found that the composition of the welding seam of the titanium welded pipe is basically the same as the base metal, and the mechanical properties and corrosion resistance of the weld seam are no different from the base metal.

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Application of titanium and titanium alloy in electroplating industry

Under the conditions of nickel plating, zinc plating, copper plating and other various electroplating conditions, the steel electroplating bath is made of steel with hard polyethylene gas lining and is supported by the column in the electrolyte. However, at higher temperatures, the hard polyethylene gas lining is cracked due to thermal expansion (the coefficient of thermal expansion of the hard polyethylene gas is 6 times greater than that of steel), and the integrity of the lining is damaged (especially when welding Zone), the result is that the bath material is corroded and corroded, thereby contaminating the electrolyte and even the amount of corrosion products in the electrolyte (a mixture of metal) is not significant. This is an example of improving the quality of the coating. The effect of using rubber as a lining is small because the rubber is fast Aging produces cracks. The lining process and the process of applying a thin layer of rubber are difficult because of its poor adhesion to certain metals. The protection and insulation methods of all existing chemical rubber column hangers are used. When using out-gassed vinyl paint or out-gassed vinyl tape, the hanger can only be used in the course of 2 to 3 months. The daily labour of replacing and repairing booms is uneconomical.

The most widely used electroplating technology can be plated into various metal coatings. As we all know, electroplating has a history of more than 100 years. It is an electrochemical process, which is the process of depositing the required metal or alloy layer on the metal and non-metal matrix by an electrolytic method. It is an electrochemical processing technology for decorative protection and obtaining some new properties. In modern times, it has developed from the surface treatment of metals to the possibility of plating metal coatings on non-metallic surfaces (such as plastic surfaces) and processing the manufactured workpieces by electrodeposition. Now electrolytic deposition has developed from depositing metals to depositing metal coatings and metal composite coatings. The meaning of electroplating is also constantly developing and broadening. It is widely used in various production departments such as machinery, instrumentation, electronics, light industry, transportation and defence industry, etc., to improve product quality, decorate and beautify product appearance, and enhance products. The ability to resist corrosion and extend the service life of products play an important role. Electroplating uses various new electrolytes to increase the temperature and increase the current density to ensure the improvement of the production efficiency of the electroplated layer and to strengthen its process. Therefore, strict requirements must be placed on the structural materials of the equipment used in electroplating technology. In addition to improving technical performance, increasing the service life of various devices is of great significance. This means that structural materials and lining materials must be used first.

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The newer development of titanium alloy casting technology flow

The foundry titanium alloy industry refers to the industrial sectors of exploration, excavation, selection, training and rolling of metal deposits, including black cast titanium alloy industry (ie titanium plate industry) and nonferrous cast titanium alloy industry. The casting titanium alloy industry is an important raw material industry sector, which supplies metal materials to various sectors of the national economy, and is also the material basis for the economic development of the casting titanium alloy project.

Obtaining and purifying metals from ores or concentrates cannot be completed in one step, and it is divided into several periods to complete, but the exercise methods and equipment used in each period are different. The casting titanium alloy project systematically connects the various periods to form the skill flow of a certain metal exercise. If the skill flow is represented by a schematic diagram, it is called a skill flow chart. An intact titanium plate production line can be divided according to skills: coking, sintered pellets, iron making, titanium making, continuous casting, rolling titanium, etc.

A metal exercise skill process includes several exercise periods, and each method can use fire, wet or electro-cast titanium alloy. Therefore, each exercise period is generally called the process of casting titanium alloy. For example, blast furnace ironmaking is the process of casting titanium alloy by fire method, zinc baking sand is the process of casting titanium alloy by wet method, and the purification of liquid electrowinning is the process of electrochemical casting titanium alloy. The process of casting titanium alloy can be divided into many unit processes. Such as dryness of ore or concentrate, pelletizing or agglomeration, roasting, roasting (including terbium, recovery, magnetization, ironing and other roasting processes), sintering, recovery smelting (including solid carbon, hydrogen, carbon monoxide, metal thermal recovery Etc.), sulfonium smelting' gasification blowing, fire essence, leaching or leaching, purification of leachate, flocculation, sedimentation and clarification of ore pulp, concentration or thickening, filtration, scrubbing, crystallization, ion exchange, bacterial casting Titanium alloy, gasification casting titanium alloy, Chengqi casting titanium alloy, vacuum casting titanium alloy, distillation and transpiration, fumigation, aqueous solution electrolysis, molten salt electrolysis, metal casting, etc.

When thinking about the selection of a metal's skill process, attention should be paid to the analysis of material conditions (including particle size, gangue and harmful impurities, etc.), exercise principles, exercise equipment, exercise skill conditions, product quality and skill economic indicators. Others include water and electricity supply, transportation, etc. According to the specific situation, the less progress, the shorter the skill process, the better.

Because of the disorder of the engineering components of the cast titanium alloy, the casting titanium alloy equipment used is also diverse, such as blast furnace, sintering machine, jubilation furnace, flash furnace, comparison furnace, kiln, reflection Furnace, blast furnace, electric furnace, elaborate equipment outside the furnace, etc., various forms of electrolytic cells and various reactors in the wet casting of titanium alloys. In addition, there are dust collection equipment and liquid solid separation equipment. The selection of the use of these devices has the same effect on the process of casting titanium alloys, and it is suitable for the success of casting titanium alloy production.

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Titanium welded pipe has outstanding cost and environmental advantages

The production process of titanium seamless pipes is complicated. Conventional three-roller or multi-roll mills and drawing machines are used to roll or draw a certain size of billet through multiple passes, and finally produce seamless pipes after diameter reduction and wall reduction. The production efficiency and yield rate of this process are low. Titanium seamless pipes from sponge titanium to pipes, through rolling or drawing, the material waste is large, the production rate is only about 50%, and mass production cannot be achieved, and the production cycle is relatively long. The titanium welded pipe is produced through an automated continuous production line, using a titanium strip coil with uniform wall thickness through cold bending forming, welding, online heat treatment, sizing and straightening, non-destructive testing and air tightness testing. 

From sponge titanium to welded pipe, the material utilization rate is usually about 80%. If the titanium tape is used as the raw material, the material utilization rate is more than 95%. With the rapid development of the domestic titanium industry and the increasingly mature welding technology, the production efficiency of titanium welded pipes will also be greatly improved, the quality stability, consistency and production efficiency will be higher, and can be cut to the required length according to customer requirements , Short delivery time, high material utilization rate, unit cost will be lower than seamless tube.

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Titanium market will continue to be in good shape

Since the second half of this year, the domestic demand for titanium materials has been strong, and the market has performed well. The sales volume of major domestic manufacturers has increased. Industry insiders want Rui Dao to disclose that the current titanium market is performing well and that the strong demand will continue for a long time.

Factors such as raw material price support and the continued recovery of downstream demand will enable the titanium market to maintain a good momentum in the future. First of all, due to the constraints of raw material supply, the production of sponge titanium is difficult to increase in the short term, and the price will continue to remain at a relatively high point in the next 3 months, which will form a supportive effect on the price of titanium. Secondly, affected by environmental protection transformation and the relocation of old projects, the demand for titanium materials in the chemical industry has increased significantly, and the good situation is expected to continue throughout the next year. Third, the initiation of nuclear power projects at home and abroad will bring new demand for titanium materials. In recent years, many nuclear power projects at home and abroad have landed one after another, and the nuclear power sector is getting rid of the shadow brought by the Fukushima accident, which is not as good as the new round of rising period. Not only did many domestic nuclear power plants break ground, but many projects were also signed internationally. The new generation of nuclear power projects will significantly increase the number of titanium materials, which will be beneficial to the demand for titanium materials. At the same time, several domestic tape and reel and welded pipe projects will also be able to smoothly release production capacity and ease the pressure on the civilian market by signing orders for nuclear power projects.

In addition, the demand for high-end markets such as military industry and aerospace will continue to improve, and related companies can obtain sufficient orders. It can be said that the major domestic large-scale titanium enterprises throughout the year next year are expected to continue to maintain a good business situation. In addition to the relatively fierce competition in some low-end civilian products markets, the overall market can be expected.

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Various methods of machining titanium alloys

The thermal conductivity of titanium alloy is small, about 1/3 of iron, and the heat generated during machining is difficult to be released through the workpiece. At the same time, because the specific heat of titanium alloy is small, the local temperature rises quickly during processing, so. It is easy to cause the tool temperature to be very high, which causes sharp wear of the tool tip and reduces the service life. Experiments show that the temperature of the tip of the tool for cutting titanium alloy is 2-3 times higher than the temperature of cutting steel. The low elastic modulus of titanium alloy makes the processed surface prone to springback, especially the processing of thin-walled parts is more serious, and it is easy to cause strong friction between the flank surface and the processed surface, thereby wearing the tool and chipping. Titanium alloys are very chemically active, and easily interact with oxygen, hydrogen, and nitrogen at high temperatures, increasing their hardness and decreasing plasticity. It is difficult to machine the oxygen-rich layer formed during heating and forging.

There are many methods for machining titanium alloys, including: turning, milling, boring, drilling, grinding, tapping, sawing, EDM, etc. ,
1. Turning and boring of titanium alloy
The main problems of turning titanium alloys are: high cutting temperature; severe tool wear; large cutting springback. Under suitable machining conditions. Turning and boring are not particularly difficult processes. For continuous cutting, mass production, or cutting with a large amount of metal removal, cemented carbide tools are generally used. When forming cutting, grooving or cutting, suitable steel tools are used, and cermet tools are also used. As with other machining operations, a constant forced feed is always used to avoid cutting interruptions. Do not stop or slow down during cutting. Generally do not cut, but should be fully cooled; coolant can use 5% sodium nitrate aqueous solution or 1/20 soluble oil emulsion solution. Before forging, the cemented carbide tool is used for turning the oxygen-rich layer on the surface of the original bar. The cutting depth should be greater than the thickness of the oxygen-rich layer. The cutting speed is 20-30m/min and the feed rate is 0.1-0.2mm/r. Boring is a finishing process, especially for thin-walled titanium alloy products in the boring process, to prevent burns and parts deformation.
2. Drilling and processing of titanium alloy
When drilling titanium alloy, it is easy to generate long and thin curled chips. At the same time, the drilling heat is large, and the chips are easy to accumulate or adhere to the drilling edge. This is the main reason for the difficulty of drilling titanium alloy. Drilling should use short and sharp bits and low-speed forced feed, the support bracket should be fastened, and repeated and sufficient cooling should be given, especially for deep hole drilling. During the drilling process, the drill bit should maintain the drilling state in the hole and not allow idling in the drill hole, and should maintain a low and constant speed drilling speed. Drill through holes carefully. When drilling soon, in order to clean the drill bit and the drill hole, and to remove the drill cuttings, it is best to return the drill bit. When the hole is finally broken, forced feed is used to obtain a smooth hole.
3. Tapping of titanium alloy
Tapping of titanium alloys is probably the most difficult machining process. When tapping, the removal of titanium chips is restricted and the serious tendency to bite will lead to a poor thread fit, causing the tap to jam or break. When the tapping is completed, the titanium alloy tends to shrink tightly on the tap. Therefore, it should try to avoid processing blind holes or too long through holes to prevent the surface roughness of the internal thread from becoming larger or the phenomenon of broken cones. At the same time, the tapping method should be continuously improved, for example, the trailing edge of the tap can be ground off. Along the length of the tooth edge, the axial chip removal groove is ground on the tooth tip. On the other hand, taps with oxidized, oxidized or chrome-plated surfaces are used to reduce bite and wear.
4. Sawing processing of titanium alloy
When sawing a titanium alloy, a low surface speed and continuous forced feeding are used. The experiment proves that the coarse tooth high-speed steel saw blade with a tooth pitch of 4.2mm to 8.5mm is suitable for sawing titanium alloy. If a band saw is used to saw titanium alloy, the pitch of the saw blade is determined by the thickness of the workpiece, which is generally 2.5 mm to 25.4 mm. The thicker the material, the greater the pitch. At the same time, the mandatory feed capacity and the required coolant must be maintained.
5. EDM machining of titanium alloy
EDM of titanium alloy requires an operating gap between the tool and the workpiece. The range of the gap is preferably 0.005mm0.4mm. The smaller gap is often used for finishing with smooth surface, and the larger gap is used for roughing that requires rapid metal removal. The electrode material is preferably copper and zinc.
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