Welding indiana Jones - brazing in aviation manufacturing industry
In the field of aviation, the linking of the new material, and the manufacture of fine structure, promote the fast development of brazing technology, its application in aviation manufacturing industry is becoming more and more widely.
The development of new materials, new technologies for aviation technology provides the larger development space, new materials and new technology is also widely used in aviation manufacturing industry.Brazing technology is a good way to complete the connection of some new materials and fine structure of manufacturing.All kinds of new brazing materials and brazing technology are related to it in the deep into the research.So brazing technology application in aviation manufacturing industry more and more, and can be used on important parts of the connection.
1. The titanium alloy brazing technology
Titanium alloy is a key technology in the field of aviation, the F - 22 stealth fighter adopted as much as 45% of titanium.Figure 1 is the F - 22 stealth fighter.In aviation manufacturing, aircraft components and aircraft engine, for example, there are a lot of need for brazing titanium alloy components.Early in the aviation industry with silver solder and aluminum brazing filler metals.Titanium because of its strength, mild and corrosion resistant performance to get people to pay attention to, starting in the 1970 s, the titanium alloy brazing technology got greater development, and began to used in the airline industry.
Ti3Al base brazing titanium alloy research test showed that Ti - Cu - Ni is braze welding head room temperature tensile strength and the parent metal close to, but at 649 ℃ and 760 ℃ is only 70% ~ 80% of parent metal.Of Ti3Al titanium alloy brazing technology at home and abroad in recent years has carried on the deep into the study, of the strength of the braze welding head close to the parent metal.Using 15 ni Ti - 15 cu - solder brazing TiAl alloy obtained the good experimental results, for example, use 1100 ~ 1100 ℃ / 30 ~ 60 s infrared induction heating process, the shear strength of sample can reach 319 ~ 322 mpa.
(1) the brazing of particle reinforced aluminum matrix composites
Graphite is added in the aluminum alloy, SiC and Al2O3 particles, can be effectively progress matrix of the elastic modulus, high and low temperature strength, fatigue performance and abrasion resistance.So this type of composite brazing in aviation manufacturing and other fields has a broad application prospect.
Soldering process simple and feasible, it is the most suitable Al alloy welding method.Soft soldering is usually lower than 450 ℃ environment using Cd - Ag or zinc - Al solder brazing B/Al.American-made brazing B/Al tube OVI satellite launcher, the joint shear strength can be up to 80 mpa.
Keep in mind, the temperature on the interface strength of the welding process has a certain influence, and can reduce the performance of the composite material itself.Therefore seek has lower brazing temperature of solder is the research objective of metal matrix composites vacuum brazing.Usually adopted abroad have Cu - 50 vacuum brazing filler metals Ni, Ti, Zr - Cu - Ni, welding way with laminate or amorphous foils.The Ti, Zr - Cu - Ni amorphous foils the tensile strength of the braze welding head with substrate.
(2) electronic encapsulation using composite brazing filler metals
Usually electronic packaging design using the composite solder will not affect the wettability of alloy system of process performance parameters, such as the province, so experienced from test to application the cycle short, put them into production becomes easy and convenient, direct application is available.Electronic packaging, microelectronics mechanical systems, automotive, aerospace, national defense and other fields will become the primary benefit of this technique.
In the field of aerospace and defense, because often contains quantity of heat of these service environment, braze welding head has excellent thermal fatigue performance, is vital for application of braze welding head.In order to simulate the braze welding head service environment in the field of aerospace and defense, the thermal fatigue test of temperature limit will be identified as to 40 ~ 125 ℃.Images 3, 4 respectively for the simulation of the thermal fatigue test curve and braze welding head structure.
(3) brazing ceramics and ceramic matrix composites
Ceramics and ceramic matrix composites is a high-performance turbine engine excellent structural material, high temperature section can be used for the flame stabilizer and turbine blades, etc., is an important material in the future advanced aircraft engine.
Soldering can efficiently complete the connection of ceramic and metal.But the strength of the ceramic connector and heat resistance compared with the requirements of practical application is still larger interval.Therefore the development of high temperature solder has been a research hot.
Foreign institutions adopt containing precious metal or try to contain precious metals Au - Pd, Pd, Pt or Ag as base of new type high temperature solder to complete the connection of Si3N4 ceramics and metal, but its heat resistance is generally not more than 700 ℃.In addition, the Ni - 50 ti solder complete SiC ceramic/metal brazing, at 700 ℃ when the shear strength of the joint can be up to 260 mpa, but its heat resistance is still not high enough, and the corresponding brazing temperature as high as 1550 ℃, apparently does not apply to ceramic and the connection of ordinary high temperature alloy.
Currently, Beijing institute of aviation materials designed for SiC ceramic brazing of Co - Ni - Fe - Cr - Ti series high temperature alloy solder, use quenched amorphous brazing alloy thin belt, the SiC/SiC braze welding head at room temperature to 800 ℃ temperature range of three-point bending strength value can be stable between 160 ~ 184 mpa.But the solder braze welding head of mechanical performance remains to be further improved.
The new structure of air brazing technology
Porous composite layer plate air-cooled structure is big in esteem than high performance engine adopts the advanced cooling structure, used in the combustion chamber and turbine blades.Usually with complex cooling loop porous layer board with brazing technology of composite pore structure, and USES the impact internal forced cooling and air cooling, film cooling of integrated cooling way, in order to achieve the best cooling effect.
Structural parts of modern aviation manufacturing industry more and more complex and delicate, for example, a new generation of phased array antenna often adopt aluminum alloy brazing structure array unit and installation.Foreign manufacturing planar slot array antenna, with precision CNC or edm out first antenna element, then use salt bath brazing or vacuum brazing methods welded into a whole.And salt bath brazing with environmental pollution, residual soluble salt is difficult to clean, do not apply to the closed structure of faults, thus gradually replaced by vacuum brazing.
In recent years, Beijing institute of aviation materials in cooperation with related to the vacuum brazing of antenna was studied, with the help of the vacuum brazing of multilayer structure of planar slot array antenna soldering, brazing antenna by welding the rate reached 100%, the overall flatness is less than 0.1 mm, brazing seam forming and beautiful.
Aluminum vacuum brazing process needs further research topic is the need to develop a low melting point of solder, suitable for heat treatment to strengthen aluminum vacuum brazing technology of low temperature.Beijing institute of aviation materials developed by Al - Si - Cu - Ni - RE solder, melting temperature range of 508 ~ 524 ℃, for a variety of aluminum alloy has good wettability, can be processed into amorphous foil is used.
On the plane of the hydraulic and pneumatic pipe welding, a large number of use induction brazing.Catheter induction brazing is divided into fixed brazing and soldering of installation.The design principle of induction brazing equipment is light weight, easy to brazing manipulation, the shape of the induction coil, should make uniform heating temperature of workpiece, can make the catheter positioning at the same time.
Brazing technology application in aviation engine parts to repair
In aircraft engine high pressure turbine blades and the hot end components in production, due to the complexity of structure of these parts, and more for casting, percent of pass is usually low, often because of parts such as trachoma, porosity, crack, and slag small defect and scrap;And qualified parts in work after period of time, there will always be a certain number of parts due to the defects such as cracks, wear, erosion, etc.) and failure, if will be generated in the process of the production and use of defect repair, make the parts to be put into use, its benefit is very considerable.
Brazing and soldering based some of the new repair technology, is an important part of aeroengine components repair technology.
Canada Liburdi company USES the powder brazing technology to repair aircraft engine blades to achieve equal to new leaf longevity, and can be served on active service engine.Beijing institute of aviation materials with large clearance brazing technique successfully repaired a engine casting crack of high pressure turbine guide vane 2, has been through the mouth to test and repair welding of blade air flight test, the effect is good.Beijing aviation manufacturing engineering research institute adopts vacuum arc brazing process of brazing alloy K417 joints in 900 ~ 950 ℃ high temperature has excellent mechanical performance, can also be used to repair the turbine blades.
Due to the brazing new structure in the future will be widely used in aircraft and engine, so the quality of braze welding head to detect this kind of structure of nondestructive testing technology also needs further research.To weld a plane or approximate plane structure, can be used in the ultrasonic C scan detecting welding seam is not welded, such as porosity defect.Eddy current testing technique is used to detect brazing solder of cellular distribution of seepage detection technology has been used in the detection of welding seam welded to the outer situation.Domestic in recent years also in nondestructive testing of braze welding head are studied, such as the ultrasonic C scan detecting brazing honeycomb seal YanHuan and brazing seam radar array antenna, porous layer board surface of weld and so on, to achieve a good detection effect, but for the multilayer structure of internal weld have yet to find a suitable test methods.
The development of new materials and new structure of high performance aircraft design requirements for the application of brazing technology has provided a broad space, put forward the great challenge at the same time.In fact, many new materials such as high temperature structural materials, such as aviation with composite solder connection basically is still in the vacancy, has yet to be further studied to solve many technical difficulties.