As solder advancedly technology (solder remotely for example and compound solder) gain ground increasingly, people need undertakes be discussinged carefully to how carrying the problem that protects gas. The requirement has the product of high quality to solder suitably process and condition, need proper solder pool temperature for instance. General, do not use protective gas and undertaking soldering in air merely is short of of this one condition. Be based on a tradition solder means, we know, in air, nitrogen, oxygen, mix to welding line with vapor weld zone is harmful. If the material of air and anneal is contacted, will form oxide, nitride and hole, this affected the exterior of welding line and its technology character, for instance but figuration sex and intensity. We notice, combustion process is in about 250 ℃ (525K) begins to appear. This kind of circumstance applies to sensitive data not only (like magnesium or zirconium) , also apply to rolled steel. To sensitivity material, weld zone region cannot any airy put be patient of in, otherwise they can become easy fragile. Graph 1: The automobile body data that laser beam welding receives but the comparative figure of figuration sex and reference material and this photograph is compared, say to the fetch of laser beam welding of rolled steel, more clients think air is a kind more effective, perhaps say, it is the protective gas that can accept at least. So, receive method and the test photograph that enclose material to compare with traditional solder, what differ? Welding line width is of course among them a kind of element: Laser beam welding receives gotten welding line to solder than the tradition get should many narrow. Sealed solder pool is small also much, because be the effective surface of bath,will be contacted with protective gas. In addition, do not use welding rod normally; The metallic droplet that it produces and air action, in can making exterior gas and reaction child be conveyed to take solder poll. The 2nd element is laser beam welding received rate is rapid, this limitted the reaction time of exterior gas and solder pool. Cooling rate is high also restricted heat to affect area (HAZ) with the reaction after solder. Laser beam welding receives the 3rd medium element is plasma to form. Gas needs energy and time to provide active in order to become more, that is to say, become by the condition of dissociation, or the condition of ionization. The origin of energy can be electric arc (MIG/MAG solders) the plasma that in perhaps stimulating beam of light and laser beam welding to receive, generates accordingly. The gas of weld zone is soldering area, the protective gas of whatever type is exceeded by park 10, the high temperature of 000K. All gas fall in the influence of high temperature by dissociation, ionization, be in activation condition. However, gas is depended on to what condition by activation after all aeriform type, and the time length that is issued by park high temperature. The influence of nitrogen is soldering below the circumstance of rolled steel, use argon - the CO2 laser beam welding that nitrogen mixes air is received can bring about azotic chroma to achieve its to balance solubility (the research according to Kokawa1) . On the other hand, in Nd:YAG laser beam welding is received in of nitrogen collect an amount relatively inferior. In TIG the amount collects in soldering bigger. Between the melting point of nitrogen that collects the temperature range that produce to be located in iron and boiling point, receive a process in laser beam welding so in, it is centered in the fluid photograph of iron, bath surface, the brim of spoon aperture, and on spoon hole wall. Solder in TIG in the process, spectrum becomes the nitrogen that there is state of high concentration dissociate in resembling showing the electric arc plasma in high temperature to gather. The nitrogen of such condition has in big solder pool distributing extensively. Contrary, content of the nitrogen in pool of laser beam welding is very small. The content of the free condition nitrogen that explores in the high temperature plasma that brings about in laser is gotten less much. In CO2 and Nd:YAG solders in different azotic content is thought to be concerned with the temperature of plasma, this temperature is in Nd:YAG laser beam welding receives a process in inferior. This means local intensity of pressure inferior, absorbed less nitrogen. In steam of metal of spoon aperture lower part local intensity of pressure reduced local intensity of pressure of nitrogen, people thinks this element brought about material in the fall of azotic content. Nitrogen is included to be in iron matrix. Although content is very small,also can bring about the addition of hardness and bulk, and but of figuration sex reduce. Be based on this reason, must avoid to use nitrogen, for example, when using wiring of laser beam welding to encircle material, juncture bulk is met to cause automatic quality testing system to sign up for a fault by enlarge general. This process is the feature that thin stencil steel appears when high speed solders. Anyhow, in the nitrogen in this application collecting an amount is so tall that let a person cannot be accepted from beginning to end. Graph 2: The phenomenon that use air regards those who protected gas to cause breach as to form nitrogen to gather is using laser beam welding to receive a car kind there also is a story in thin stencil steel, it brought about material but figuration sex and use helium gas, argon is enraged / CO2, and angry case photograph compares argon to drop apparently (if pursue 1) . In addition, be in when nitrogen dilute other gas, be enraged like argon or when helium gas is medium, physical character did not produce a change. We are in no less than the following treatise the lieutenant general gives out, use in the solder reinforce of solid state laser in, for photograph comparing of nitrogen gather to want it seems that a few lower. Use argon is enraged or nitrogen undertakes as protective gas laser beam welding receives gotten fatigue test is similar as a result, because here and use CO2 laser to undertake condition differs soldering to compare plasma. Use the plasma when solid state laser undertakes soldering, the plasma look that gets with CO2 laser is compared more rare, and temperature is apparent lower, this explicit active sex that made clear nitrogen is relatively inferior. Nextpage pursues 3: The airy of fatigue intensity graph of the sample that diode laser solders affects air (basic composition is nitrogen and oxygen) in high temperature weld zone region makes free appearance. The influence of nitrogen already above had discussed. Here, we will see aerobic effect, it is easier than nitrogen by activation. Notice oxygen is making an appointment with 250 ℃ oxide perhaps has been formed when 525K above. We know, oxygen is used at chastening iron matrix. However, if oxygen is too much, oxide is formed in the inside and outside of material, such soldering the exterior area of the pool and hot influence area (HAZ) be enclothed by oxide layer place. The melt temperature of oxide layer is high reduced wetability apparently, damaged the joint mechanism between metal and metal. So, caused soldering defect, and they may cause break. Contrary, in dynamic bear exam, the fatigue intensity of the sample that laser of use solid state solders in air is far under use nitrogen or the sample that argon gas regards protection as gas (if pursue 3) . The influence that gas carries right now, if you had decided to avoid to use air in weld zone, you may want to visit aeriform supply facility. Face solder pool transports protective gas and do not mean it to be able to be opposite the result that the gas of solder pool produces us to expect. What solder in laser is inchoate, basically be to use " plasma efflux " will break up the plasma cloud when CO2 laser beam welding is received. This has high-speed gas to flow with respect to the requirement, this air current is based on the principle in Wen Qiu the air all round the formal infuse with onflow. When using this system, solder pool and hot influence area (HAZ) be enclothed probably by air only. Develop a bigger spray head namely next, can blow air with inferior air current rate from flank. Storied gas flows in gas of one part helium is controlling plasma. Such layout has exact fixed position with respect to the requirement, and should adjust aeriform velocity of flow protect aeriform atmosphere in order to make sure one does not have airy. One oxidation nitrogen (NO) the test is used to the gas that the examination uses nozzle of this kind of flank to undertake protective and corresponding weld zone gas. If weld zone region exists,any air can have NO to arise. Graph 4 explanations why the velocity of flow that argon enrages needs to be 25 L/min (0 at least. 9ft3/min) , so that discharge clean gas and corresponding NO from weld zone region. The 3rd kind of usable method is conventional coaxal spray head, it gets be usinged effectively in solid state laser. On the other hand, solder in CO2 laser in, the hot plasma that because solder,rises inside the pool, it is very difficult to appear solder protective gas infuse area. If aeriform velocity of flow is too rapid, so it disturbed the athletic condition inside solder pool; If too low, so it removes less than allowing that why to protect action. Another hidden problem is " alternate efflux " . Nozzle is to should blow the slop content that comes loose to be brought about from optical equipment and smoke originally. However, to the gas of weld zone region, this unit becomes crisscross across state. If not be to adjust,get just in time " neither more nor less than " if, it blows air possibly toward weld zone region, perhaps absorb the gas of weld zone. Such, even if locates again well protective gas nozzle also cannot work effectively. Graph 4: The solder coherent system with the protective the most appropriate efficiency when argon gas regards protection as gas occupies a story, in CO2 laser solder reinforce is used in, include argon to enrage - what helium enrages is statified protective gas is the most effective. Gas mixture of this kind of foundation can try to adulterate, for example, CO2 can use at tailor-made plank solder. In Nd:YAG laser solders in, do not need helium breath; Argon is enraged or even nitrogen is appropriate protective gas it seems that. Fiber-optic laser power compares Nd:YAG wants big, so helium gas is optimal choice it seems that. However, notice these laser and include research still are in initial phase please. ReferencesHigh-quality Products Demand Suitable Welding Processes And Conditions Such As Adequate Weld Pool Atmosphere.
Avoiding Shielding Gases And Thus Welding In An Air Atmosphere Is Not Sufficient.
As Advanced Welding Techniques Such As Remote And Hybrid Welding Become More Popular, dr. The Issue Of How To Deliver The Shielding Gases Must Be Addressed Carefully Mark Faerber is the market department manager of laser application; Dr. Wolfgang Danzer is controller of laser Technical Division; Dr. Joachim Berkmanns is the project manager of laser application. They come from Linde AG company. Need knows more news, visit LASERMIX@Linde-Gas.
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