激光焊接原理及實(shí)踐應(yīng)用

1、激光焊接Lasers Welding,Girish P. Kelkar, Ph.D.,激光 LASER,受激輻射式光頻放大器的英文第一個字母的縮寫 Light Amplification by Stimulation of Emitted Radiation,參考資料 References,激光的工業(yè)應(yīng)用-J.F.Ready Industrial Applications of Lasers, J. F. Ready 激光焊接，W.W.Duley Laser Welding, W.W. Duley 激光加工，W.M.Steen Laser Materials Processing, W. M.

2、 Steen AWS 焊接手冊，1-4 AWS Welding Handbooks, 1-4 激光加工手冊-美國激光協(xié)會出版 Handbook of Laser Materials Processing Published by the Laser Institute of America 公開的相關(guān)文獻(xiàn) Published literature,請記住. Remember.,學(xué)習(xí)需要積極的參與 Learning requires active participation 不恥下問 Feel free to ask questions 無所顧及地提出個人不同見解 Do not hesitate

3、 to present different viewpoints,光 Light,光是一種電磁輻射 Light is electro-magnetic radiation 我們聽不到.Waves that you cannot hear 可見光的波長在0.4-0.7微米之間。Visible from 0.4-0.7 micron wavelength 波長小于0.4微米是紫外線和X光Below 0.4 ultraviolet to x-rays 波長大于700nm的光為紅外線和微波。 Above 0.7 infra-red to microwaves,1 m,光的吸收和顏色Absorption

4、 and Color,物體的顏色來源于它反射的光的波長 Color of an object (wavelength that it reflects),顏色和光的波長是相關(guān)聯(lián)的。 Color is associated with particular wavelength 黑色和白色代表著什么？ What is the meaning of black or white color? 黑色表面吸收了YAG光，而白色在反射了大部分光。 Black surface will absorb YAG light while white will reflect most of it,我們?yōu)槭裁葱枰?/p>

5、光？Why do we need Lasers?,材料加工需要吸收很強(qiáng)的光。 Absorption for materials processing requires very intense light 高強(qiáng)度的光可以通過激光聚焦成光束獲得。 Intensity can be generated by focusing a beam of laser light 普通光不能聚焦成很高的能量密度（或足夠小的點(diǎn)） Ordinary light does not focus down to a high enough power density (or small enough spot size

6、) 手持放大鏡可以把太陽光聚焦讓紙燃燒但是不能把金屬融化 Hand-held lens can focus sunlight to set fire to paper but not enough to melt metal,Light and Lasers,單頻的（單波長）Monochromatic (single wavelength) 校準(zhǔn)的（平行光）Collimated (parallel),激光Laser Light 普通光Ordinary Light,很多波長 Many wavelengths 不平行 Not parallel,Light and Lasers,激光 Laser L

7、ight 普通光Ordinary Light,激光的聚焦Focusing of Lasers,激光Laser Light 普通光 Ordinary Light,單頻（單波長）和校準(zhǔn)（平行）的光可以聚焦成很小的焦點(diǎn) Monochromatic (single wavelength) and Collimated (parallel) light can be focused to a very small spot,激光的種類Types of Lasers,激光能量傳輸 Laser Power Delivery 連續(xù)波 Continuous Wave (CW) 脈沖 Pulsed Q-開關(guān) Q-

8、switched 激光頻率 Laser Frequencies 基頻和倍頻 Fundamental and multiples,連續(xù)光纖激光Continuous Wave Fiber Lasers,激光在光纖中產(chǎn)生Laser light is created in the fiber 可在連續(xù)波和脈沖波中使用Can be used in pulsed mode as well as CW 可以被用于焊接和切割Can be used for welding and cutting,激光二極管光Laser Diode Light,激光二極管光 Laser Diode Light,光纖Fiber,脈

9、沖YAG激光（焊接）Pulsed YAG Lasers (Welding),閃光燈開關(guān)產(chǎn)生脈沖Flash lamp turns on and off to create pulses 光纖用于傳送激光Fiber is used to transmit laser light,閃光燈（光泵）Flash Lamp (Optical Pump),全反鏡100% mirror,90%反鏡 90% mirror,光纖Fiber,激光棒Laser Rod,脈沖打標(biāo)激光Pulsed Marking Lasers,Q-switching produces very short pulses, 10-100 n

10、ano-sec Cannot be used for welding Laser light delivered directly; no fiber Frequency can be doubled or tripled to get green or UV light,Rod,Mirrors,Q-switch,Galvo Mirrors,Focus Lens,Frequency Multiplier (not present in all markers),Galvo-光學(xué)器件Galvo-Optics,經(jīng)常用于打標(biāo)。Often used for marking applications 逐

11、漸受到焊接應(yīng)用的青睞。Is gaining popularity for welding applications,Nutfield, Inc.,激光頻率Laser Frequencies,上表只包括了大部分常用的和商業(yè)化的激光器。 Table includes only the most common and commercialized lasers。,脈沖YAG激光焊接典型示意圖Typical Layout for Pulsed YAG Welding Lasers,鍍膜反光鏡Coated Mirrors,激光Laser,光纖Optical Fiber,聚光頭 Focus Head,工件

12、Work piece,透鏡Lens,注：某些激光不通過光纖直接傳輸。 Note: Some lasers are delivered direct without fiber,聚焦高度和焦點(diǎn)尺寸Focus height and spot size,短焦距透鏡將光束聚焦成更小的點(diǎn)。Short focal length lens (of given diameter) will focus the beam to a smaller spot 高的能量密度。Higher energy density Focus height is critical due to shallow depth of

13、focus Lens protection from work piece spatter is important,短焦距Short Focal Length 長焦距Long Focal Length,Time Share,A single laser can be used for multiple applications on a time shared basis基于同一個理論,單雷射可以一次性用于多種應(yīng)用. Most convenient with transmission through optical fiber 通過可見纖維的轉(zhuǎn)換是最方便的. Processing stati

14、ons can be in different rooms 工作臺可以放在不同的房間.,Mirrors (100% Reflective)全反鏡,Energy Share,Laser energy split into multiple fragments 雷射能量分成多個部分 Typically three outputs for circumferential spot welding 典型的是圓周點(diǎn)焊接的3份輸出量,Mirrors (Partially Reflective)反光鏡(部分反光),33% 50% 100%,30 W,10 W 10 W 10 W,Total Internal

15、 Reflection完全內(nèi)反射,Light propagation through fibers depends on total internal reflection通過光纖的光線傳播完全取決于完全內(nèi)反射,Air空氣,Glass玻璃,Core核,Cladding覆層,Protective Sheath接地屏蔽,Optical Fibers光學(xué)纖維,Single mode has very small core diameter, 10 microns單模式只有很小的直徑10微米 Used for telecommunications and now for fiber lasers 用于

16、電訊,現(xiàn)用于光纖激光 SI and GI have cores from 0.1 mm to 1 mm單模式和分級模式的核從0.1mm到1mm Higher diameter for higher power level 能量級別越高直徑越大,Stepped Index (SI)步長指數(shù),Single Mode單模式,Graded Index (GI)分級模式,Index Profiles剖面指數(shù),SI vs. GI單模式 vs分級模式,SI and GI most frequently used in materials processing單模式和分級模式多用于材料加工過程. SI out

17、put is “top-hat” independent of input 單模式的輸出獨(dú)立于輸入呈大禮帽狀 more robust更有活力 GI output more faithful representation of input 分級模式的輸出與輸入呈保持靠近, Can create problems if input beam quality changes 如果輸入光束的質(zhì)量改變可能會產(chǎn)生問題. Can make deeper welds/cuts 可能焊接/切的更深. Weld profiles could change based on focus height 焦點(diǎn)高度可能產(chǎn)

18、生焊接側(cè)面的 變化,SI GI,0.6 Aspect Ratio縱橫比 1.5,“Top Hat大禮帽狀”,Weld Profiles焊接剖面,Fiber Input Alignment光纖輸入排列,Good Alignment 好的排列,Could burn fiber input end 可能燒焦光線輸入莫端,Could create plasma at focus 在焦點(diǎn)產(chǎn)生等離子體,Could burn cladding 可能燒傷覆層,Spot Size with Fiber光點(diǎn)直徑帶光纖,Spot size is an image of the output core diamete

19、r of the fiber 從光點(diǎn)的大小可以反應(yīng)出光纖核直徑的大小 Size depends on magnification of the two lenses in the focus head 其大小是由鏡頭前的兩個透鏡來決定的.,Optical Fiber光纖,Core Diameter核直徑,Spot Size光點(diǎn)直徑,Laser Safety,Common Sense常識 Do you not put your hand in direct path of a laser beam不要把手的頭放在雷射光束的路徑中. Do not look directly at a laser

20、beam不要直視雷射光束 even at those laser pointers beams!不要看雷射點(diǎn). Do not look at any laser process with a naked eye不要用不防護(hù)的肉眼看任何的激光過程. use plastic safety glasses for CO2 lasers 用塑料防護(hù)眼鏡來防護(hù)CO2雷射. use YAG safe glasses for YAG operations 在釔鋁石榴石操作中用釔鋁石榴石安全眼鏡,Eye Damage,Near UV from welding plasma and UV lasers If y

21、ou see bluish white during material processing, you need UV protection; ordinary plastic safety glasses are not sufficient!如果你在材料加工的過程中看見藍(lán)白的光,你需要UV 保護(hù),一般的塑料防護(hù)眼鏡是不起作用的 . Visible and Near IR from YAG and frequency doubled lasers,Cornea角膜,Lens透鏡子,Retina視網(wǎng)膜,Far UV and Far IR Near UV 接近UV Visible and Nea

22、r IR,Collateral Damage,Fumes煙 Solvents, grease, etc. from the work piece 溶劑,油脂等, Metal dust could be toxic 金屬顆粒可能有毒. Decomposition products of plastics processing (marking, welding, or drilling) could also be toxic 在朔料加工的規(guī)程中的分解產(chǎn)品,(打表,焊接,或者鉆孔)也是有毒的. Install vacuum pumps and appropriate filters 安裝真空泵和

23、合適的過濾器. Need special Ti dust collectors when welding Ti in a glove box for medical device applications 當(dāng)在用于醫(yī)療器械的手套盒子中焊接鈦的時候,需要特殊的吸鈦器.,Fire Hazard火災(zāi),Laser Beams can have been known to cause fires鐳射激光能夠引起火災(zāi). Breaks in optical fiber光纖削弱 Make sure optical fiber is not wound too tightly確保光學(xué)纖維不會太擊傷. Leaka

24、ge in CO2 direct optics Laser beam walking off work table onto plastic covers Laser beam interaction with gloves in a glove box,Laser-Material Interaction,For lens and windows, A and R have to be small對于透鏡和窗戶,A和R 應(yīng)該是小的. For mirrors, R has to high對于鏡子,R 應(yīng)該高一些 For Laser-based materials processing, A h

25、as to be high and R should be low對于以 雷射原理為基礎(chǔ)的材料加工,A 要高一些,R 應(yīng)該要低一些.,Incident Energy入射能,Reflection反射,Absorption吸收,Transmission轉(zhuǎn)播,I = A + R + T,Initial Reflectivity of Metals金屬的初始反射率,Grey metals (Ag and Al) are reflective to all colors in visible spectrum 灰色金屬(Ag and Al) 對所有的有色光譜中的顏色都有反射作用. Copper refl

26、ects near red wavelengths and absorbs others銅在紅色波長附近反射,在其他中吸收.,0.0,0.2,0.4,0.6,0.8,1.0,0.2,0.4,0.7,1.0,10,Wavelength (mm),Reflectivity,Ag,Carbon Steel碳鋼,Ni,Cu,Al,Nd:YAG,CO2,Source: Industrial Laser Applications - John Ready,Laser Angle雷射角落,For all welding applications, the laser should be angled off

27、 vertical to prevent laser energy from going back into the laser cavity and causing damage 對于所有的焊接應(yīng)用,雷射應(yīng)該與角落垂直以防雷射能量回到激光腔,引起損失.,5 degrees,Absorptivity of Materials材料的吸收率,Reflectivity is also affected by surface roughness, surface oxides, part geometry, and weld pool shape反射率也是由表面光滑度,表面氧化度,;零件幾何,以及焊接

28、池的形狀.,Laser Welding鐳射焊接,Configurations結(jié)構(gòu),Gap dimensions become more critical as parts get smaller由于零件尺寸變小,縫隙的尺寸變得更重要,Butt Weld對接焊接 Gap 0.1 t,t,Cap蓋子,Can罐子,t,Configurations,Gap dimensions become more critical as parts get smaller由于零件尺寸變小,縫隙的尺寸變得更重要 Can weld multiple layers罐子多層焊接,Lap Weld Gap 0.15 t,C

29、onfigurations,Prefer configurations where the molten material flows into the weld instead of pulling away from it 最好的形狀是融化的物質(zhì)是流入到焊接而不是脫離焊接.,Lap Weld,Lap Fillet,Lap Edge,Annular Welds,Fitup is important移動的臺 面很重要 . If gap is present, stresses will develop towards the end of the weld 如果有縫隙,應(yīng)力會隨著焊接而增大 P

30、ress-fit preferred最好有壓配合.,Small Volume Welds,Air/gas in the enclosed volume during final weld heats up and tries to escape 空氣在有限的空間里會隨著焊接的熱量膨脹,并試圖逸出. Can cause porosity towards the end of the weld可能會在焊接的最后引起多孔.,Air Pressure Increases During Welding在焊接餓過程中空氣的壓力增加,Pressure Relief卸壓,Allow pressure reli

31、ef on enclosed volumes 如下情況需要泄壓 Reduce crack-like features which may be caused by high pressure trapped inside 泄壓可以減少像這種由于內(nèi)部壓力過大而引起的類似裂紋的缺陷.,Shield Gas,Main function of shielding gas is to protect the molten metal from reacting with oxygen 保護(hù)氣體的保護(hù)作用主要是保護(hù)融化的金屬不與氧氣反應(yīng). Shielding gas also helps to:保護(hù)氣體也

32、有助于 Protect lens/lens cover from weld splatter 保護(hù)透鏡,透鏡蓋不受焊接潑濺 Control plasma cloud formation 控制等離子霧形成. Wash away metal vapors in the plume 吹散等離子體中的金屬蒸汽.,Shield Gas,What is plasma?什么是等離子體 Plasma is ionized gas等離子是離子化氣體 Electrons are separated from atoms (metal as well as shielding gas)電子與原子分離(金屬和屏蔽氣體

33、 ) Plasma is the fourth state of matter; other three are solid, liquid, and gas(等離子體是事物的第四種狀態(tài),其他的三種是固體,液體和氣體) What is plume?什么是等離子體? Plume is a mixture of plasma and metal vapors等離子體是等離子以及金屬氣體的混合體.,Plume,Shield Gases for YAG Lasers,Helium is ideal but very expensive氦很理想,但是很昂貴 Argon gas is most commo

34、nly used氬氣是最常用的 Nitrogen can be used for some alloys氮可以用于一些合金. Some welds are made in air (no shielding gas) but the weld surface is not very smooth有些焊接在空氣中做(沒有保護(hù)氣體)但是焊接表面不是太順滑 May still produce acceptable weld quality可能仍舊能夠產(chǎn)生有效的焊接質(zhì)量.,Soot,Soot is black colored dust, typically referred to as “soot”

35、though it is not composed of carbon煙是黑色的灰塵,雖然叫煤煙但它不是由碳組成的 . “Soot” is a fine dust of metal powder that is deposited from the plume煤煙是一種從等離子中沉淀下來的金屬粉末.,Chemical analysis of “soot” from Inconel 600,Shield Gas Configuration,Coaxial共軸 Too high destabilizes the weld pool, increased porosity太高-動搖焊接溶池,引起多孔

36、. Too low can cause negative pressure and pull up the weld metal太低-會引起負(fù)壓力,使融化的金屬突起. Better for shielding最好屏蔽 Side Flow側(cè)流 Useful for sweeping away the ionization products用于清理等離子體.,Pulsed YAG 脈沖釔鋁石榴石,Important Parameters 重要的參數(shù) Pulse 脈沖 Width寬度 Energy能量 Power能量 Shape形狀 Pulse Overlap脈沖交迭 Spot Size and F

37、ocus光點(diǎn)和焦點(diǎn),Pulsed YAG脈沖釔鋁石榴石,Energy (J) 能量= Power (kW) 力x Width 寬度(msec) Initial energy peak helps the laser energy to couple with the material 初始的高能量可以使激光能量與金屬耦合.,Programmed Pulse程序 脈沖,Peak Power,Pulse Energy脈沖能量,Pulse Width脈沖寬度,Actual Output實(shí)際輸出,Pulsed YAG脈沖釔鋁石榴石,Short pulse of high peak power can

38、cause expulsion高的峰值能量的短脈沖能引起坑. Long pulse of low peak power will produce a wider and shallower weld bead 低頂點(diǎn)能量的長脈沖會產(chǎn)生更寬和更淺的焊縫.,Power,Pulse Width,Deeper Penetration更深穿透 Greater Porosity更多多孔 More Expulsion/Spatter更多飛濺,Shallower Penetration更淺穿透 Less Porosity更少多孔 Cleaner welds with no porosity 更干凈焊接沒有飛濺

39、,Effect of pulse time on weld size脈沖時間對焊接尺寸的影響,Weld spot diameter increases rapidly in the first few milli-seconds; rate of growth reduces with time焊斑直徑在最初的千分之一秒期間迅速變大,增長的速度隨著時間的增長而降低.,Time,Weld Size,Effect of pulse time on penetration脈沖時間對焊接尺寸的影響,For a given peak power, weld penetration stabilizes

40、after a certain threshold weld time對于指定的能量高峰,焊接深度在一定的焊接時間后變得穩(wěn)定 . Maximum penetration is directly proportional to peak power 最大的深度是與能量高峰成直接正比的關(guān)系. Above a certain threshold of power, the laser will end up drilling/cutting/gouging instead of welding 在一定能量的之上,雷射將鉆孔,切斷,咆削而不是焊接.,Time,Penetration,Peak Powe

41、r 1,Peak Power 2,Pulse Shaping脈沖形狀,Single pulse or three sector pulse offered by capacitor based power supplies由電源電容器產(chǎn)生的單脈沖和三個脈沖 Newer machines offer inverter technology with continuous pulse shaping更新的提出的能夠提供 無間斷的脈沖形狀.,Time (msec),Peak Power,Energy (J) 能量= Power (kW) 力x Time時間 (msec),Single 單個 Thre

42、e-sector三部分 Multi-sector多部分,Weld Cracking焊接破裂,Can is anchored in the cap while can surface has leverage 罐子被錨在夾具中,而罐子的表面有杠桿作用. Weld cooling always introduces residual stresses 焊接冷卻往往引起殘余壓力. Combination of large weld volume and rapid cooling can introduce excessive residual stresses that cause crackin

43、g 大量焊接加之迅速冷卻能產(chǎn)生過量的殘余壓力從而引起破裂.,Laser Features: Pulse Shape雷射特征:脈沖形狀,Melting and Penetration Pulse溶解滲透脈沖 (Coupling Pulse偶合脈沖),Stabilization Pulse穩(wěn)定脈沖 (controlled cooling to reduce expulsion and residual stresses控制冷卻減少殘余應(yīng)力.),6.0 kW,0.5 0.5 1.0 2.0 m-sec,50%,30%,0.2,Pulse Shaping脈沖形狀,Modified pulse gave

44、 time for the weld to cool slowly and allow the pore to rise above the weld interface改良脈沖使焊接冷卻的時間變慢,而且使得氣孔有時間從熔融的金屬中上升到表面,Focus Height 焦點(diǎn)高度,At focus, spot size not sensitive to focus height在焦點(diǎn),點(diǎn)大小與焦點(diǎn)高度不相互影響. At focus, plume is tallest and sound is highest pitch在焦點(diǎn),等離子體是最高的,而且聲音也是最高調(diào)的. used to find f

45、ocus height用于找出焦點(diǎn)高度. Focus usually set at the surface for pulsed welding焦點(diǎn)通常設(shè)在表面為脈沖焊接. Focus set below surface for deeper penetration and keyhole mode welding焦點(diǎn)射在表面以下為更深的穿透和縮定焊接,Pulse Overlap脈沖交疊,Depends on thickness of component on top and shape of weld bead取決于零件上端的厚度和焊縫的形狀. Overlap should be great

46、er by a safe margin在一定安全范圍之內(nèi),交疊會大一些. Note: Excessive overlap is excess unwanted heat into the weld注意:過量的交疊是過度的熱量在焊接中出現(xiàn) .,Non-hermetic Overlap 不密封交疊,Hermetic Overlap 密封交疊,Pulse Overlap脈沖重疊,Lap welds require higher overlap重疊焊接要求更高的重疊 Butt welds can be hermetic even at 50% overlap對接焊接可以被密封,即便是50%的重疊,Bu

47、tt Weld 對接焊接,Lap Weld 重疊焊接,Butt Weld 對接焊接,Laser Weld Quality雷射焊接 質(zhì)量,Weld Surface Inspection焊接表面檢測 Weld surface should be clean and free of spatter焊接表面需干凈,沒有滴濺 No visible cracks or holes沒有可見的裂縫和孔.,Good,Not Good,Laser Weld Quality雷射焊接質(zhì)量,Mechanical Testing機(jī)械測試 Burst Strength爆發(fā)力量 Pull test or Shear Test

48、拉力測試和剪切測試 Leak Test測漏測試 Strength Analysis;力量分析 It is very important to keep track of where and when the failures occurred during testing在測試中,記錄在那里和什么時候失敗是十分重要的 Mark locations of failure for further analysis在失敗的地方做標(biāo)識是以便將來進(jìn)一步分析,Weld Section Analysis焊接部分分析,Cracked Weld 焊接破裂,Small Pressure Bubble ? 小壓力泡

49、沫,Good Weld 好焊接,X-ray AnalysisX-RAY 分析,Cracks grow at an angle and appear as straight lines in the x-ray (shallow weld on right)破裂在一個角中擴(kuò)大,在X-RAY 中顯示為一條直線 Small porosities may be difficult to see in such images在這樣的圖片中很難看到小孔. Check for alignment查看齊邊.,Weld Crack 焊接破裂,Shallow Weld 焊接陰影,Alignment,X-ray i

50、mages of good weldsX-RAY 中好的焊接,Laser Maintenance雷射維護(hù),Feedback monitor only checks laser cavity performance does not check power at weld反饋器只查看激光腔的性能-不會查看焊接時候的能量,Laser Cavity激光腔,Focus Head焦點(diǎn)頭,Energy Meter, Burn Marks, Plexiglas, etc.能量劑,火刺,樹脂玻璃,Lens透鏡,Feedback Monitor監(jiān)視器反饋,Energy Meters能量計(jì),Joule Meter

51、s焦耳 Set for single pulse or average over multiple pulses 定為單 脈沖或者平均大于多脈沖 Should be used periodically to confirm energy at the weld在焊接的時候周期性的確認(rèn)能量 Automation system can be set for measurement at warm up and after set number of pulse welds 在啟動的時候或者確定脈沖焊接的時候用自動化系統(tǒng).來確定量度.,Spot size and shape黑點(diǎn)的大小和形狀,Burn paper and burn plate