【焊接工藝】Laser Beam Welding (LBW) 雷射焊

Laser Beam Welding is a fusion welding process in which two metal pieces are joined together by the use of laser. The laser beams are focused to the cavity between the two metal pieces to be joined. The laser beams have enough energy and when it strikes the metal pieces produces heat that melts the material from the two metal pieces and fills the cavity. After cooling a strong weld is formed between the two pieces.

雷射焊接是利用雷射將兩個金屬件連接在一起的熔焊工藝。雷射束被聚焦到要連接的兩塊金屬之間的空腔上。雷射束有足夠的能量，當它擊中金屬碎片時，產生的熱量會融化兩塊金屬碎片中的材料並填滿空腔。冷卻後，在兩個部件之間形成牢固的縫。

It is a very efficient welding process and can be automated with robotics machinery easily. This welding technique is mostly used in automotive industry.

這是一個非常有效的焊接工藝，可以很容易與自動化與機器人機械結合。這種焊接技術主要應用於汽車工業。

1 Principle 

原理

Laser beam welding is a technique in manufacturing where by two or more pieces of material (usually metal) are joined by together through use of a laser beam. Laser stands for Light Amplification by Stimulated Emission of Radiation. It is a non-contact process that requires access to the weld zone from one side of the parts being welded.

雷射束焊接是一種製造技術，利用雷射束將兩塊或兩塊以上的材料(通常是金屬)連接在一起。雷射是通過受激發射光放大的輻射。這是一種非接觸過程，需要從焊接部件的一側進入焊接區。

2 Types 

類型

2.1 Gas lasers 氣體雷射

Gas Laser use a mixture of gases such as helium and nitrogen. There are also CO2 or carbon dioxide lasers. These lasers use a low-current, high-voltage power source to excite the gas mixture using a lasing medium. Operate in a pulsed or continuous mode.

氣體雷射使用氦氣和氮氣等氣體混合物。還有二氧化碳或二氧化碳雷射器。這些雷射器使用低電流高壓電源使用雷射介質激發氣體混合物。以脈衝或連續模式運行。

Carbon dioxide lasers use a mixture of high purity carbon dioxide with helium and nitrogen as the lasing medium. CO2 lasers are also used in dual beam laser welding where the beam is split into two equal power beams.

二氧化碳雷射器使用高純度二氧化碳與氦和氮的混合物作為雷射介質。CO2雷射器也用於雙光束雷射焊接，其中光束被分成兩個相等的功率光束。

2.2 Solid state lasers 固態雷射

2.2.1 Nd:YAG lasers

Nd:YAG lasers can operate in both pulsed and continuous mode, but the other types are limited to pulsed mode. The original and still popular solid-state design is a single crystal shaped as a rod approximately 20 mm in diameter and 200 mm long, and the ends are ground flat. This rod is surrounded by a flash tube containing xenon or krypton. When flashed, a pulse of light lasting about two milliseconds is emitted by the laser. 

Nd:YAG雷射器可以在脈衝模式和連續模式下工作，但其他類型的雷射器僅限於脈衝模式。先前與現在任然流行的固態設計是一個單晶形狀的棒狀，直徑約20毫米，長200毫米，兩端磨平。這根棒被一個含有氙或氪的閃光管所包圍。當閃光時，雷射會發出持續約兩毫秒的脈衝光。

Nd:YAG laser outputs between 0.04–6,000 W. To deliver the laser beam to the weld area, fiber optics are usually employed.

Nd:YAG雷射輸出在0.04-6,000W之間。為了將雷射束傳送到焊接區域，通常使用光纖

2.2.2 ruby lasers 紅寶石雷射

Ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. Ruby lasers produce pulses of coherent visible light at a wavelength of 694.3 nm, which is a deep red color. Typical ruby laser pulse lengths are on the order of a millisecond.

紅寶石雷射器是一種固態雷射器，使用合成紅寶石晶體作為增益介質。紅寶石雷射產生一種深紅色波長為694.3nm的相干可見光脈衝。典型的紅寶石雷射脈衝長度約為毫秒。

A ruby laser most often consists of a ruby rod that must be pumped with very high energy, usually from a flashtube, to achieve a population inversion. The rod is often placed between two mirrors, forming an optical cavity, which oscillate the light produced by the ruby's fluorescence, causing stimulated emission. 

紅寶石雷射器通常由紅寶石杆組成，必須用非常高的能量泵送，通常來自閃光管，以實現粒子數反轉。杆通常放置在兩個鏡子之間，形成光學腔，其振蕩由紅寶石的螢光產生的光，引起受激發射。

2.3 Fiber laser 光纖雷射

Fiber laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements. Fiber laser can be developed on the basis of fiber amplifier: under the action of pump light, the fiber is easy to form a high power density, causing the laser level of the laser working material "particle number inversion", when the appropriate addition of positive feedback loop (to form a resonator) can form laser oscillation output.

光纖雷射器是以摻雜稀土元素的光纖為有源增益介質的雷射器。光纖雷射器可在光纖放大器的基礎上開發:在泵浦光的作用下,纖維很容易形成高功率密度,造成雷射工作物質的雷射能級「粒子數反轉」,當適當加入正反饋迴路(構成諧振器)可以形成雷射振蕩輸出。

In fiber lasers, the main medium is the optical fiber itself. They are capable of power up to 50 kW and are increasingly being used for robotic industrial welding.

在光纖雷射器中，主要介質是光纖本身。它們的功率高達50 kW，並且越來越多地用於機器人工業焊接

3 Working 

工作

First the setup of welding machine at the desired location (in between the two metal pieces to be joined) is done.
首先，在所需位置（在待連接的兩個金屬件之間）完成焊接機的設置。

After setup, a high voltage power supply is applied on the laser machine. This starts the flash lamps of the machine and it emits light photons. The energy of the light photon is absorbed by the atoms of ruby crystal and electrons get excited to their higher energy level. When they return back to their ground state (lower Energy state) they emit a photon of light. This light photon again stimulates the excited electrons of the atom and produces two photons. This process keeps continue and we get a concentrated laser beam.
安裝完成後，在雷射器上加高壓電源。這啟動了機器的閃光燈，並發出光子。光子的能量被紅寶石晶體的原子吸收，電子被激發到更高的能級。當它們回到基態(低能態)時，就會發出光子。這個光光子再次刺激原子中被激發的電子並產生兩個光子。這個過程繼續下去，我們得到了一個集中的雷射束。 

This high concentrated laser beam is focused to the desired location for the welding of the multiple pieces together. Lens are used to focus the laser to the area where welding is needed. CAM is used to control the motion of the laser and workpiece table during the welding process.
這種高度集中的雷射束被聚焦到所需的位置，以便將多個部件焊接在一起。透鏡用來把雷射聚焦到需要焊接的地方。在焊接過程中，CAM用於控制雷射和工件工作檯的運動。

As the laser beam strikes the cavity between the two metal pieces to be joined, it melts the base metal from both the pieces and fuses them together. After solidification we get a strong weld.
當雷射束擊中要連接的兩塊金屬之間的空腔時，它會熔化兩塊金屬的基本金屬，並把它們熔合在一起。凝固後，我們得到一個牢固的焊縫。

4 Applications
應用

Automotive manufacturing 汽車製造

Fiber laser welding in shipbuilding and marine engineering 光纖雷射焊在造船及海洋工程方面的應用

Aircraft manufacturing 飛機製造

Medicine 醫學

5 Advantages and Disadvantages 

優點和缺點

5.1 Advantages 優點

It produces high weld quality.  焊接質量高

LBW can be easily automated with robotic machinery for large volume production.
雷射焊可通過機器人機械輕鬆實現自動化，實現大批量生產

No electrode is required.  無需電極

No tool wears because it is a non-contact process.  
沒有工具磨損，因為它是非接觸工藝。

The time taken for welding thick section is reduced. 
減少焊接厚截面所需的時間

It is capable of welding in those areas which is not easily accessible.  
能夠在不易接近的區域進行焊接。

It has the ability to weld metals with dissimilar physical properties. 
 能夠焊接具有不同物理特性的金屬

It can be weld through air and no vacuum is required.  
能夠在空氣中焊接，不需要真空。

X – Ray shielding is not required as it does not produce any X-Rays. 
不需要X射線屏蔽，因為它不會產生任何X射線

It can be focused on small areas for welding. This is because of its narrower beam of high energy.  
能夠專注於焊接的小區域，這是因為它的能量較窄。

Wide variety of materials can be welded by using laser beam welding.  
各種材料都可以通過使用雷射焊接。

It produces weld of aspect ratio (i.e. depth to width ratio) of 10:1.  
能產生縱橫比（即深寬比）為10：1的焊縫。

5.2 Disadvantages 缺點

Initial cost is high. The equipment used in LBW has high cost.
初始成本很高，雷射焊使用的設備成本高

High maintenance cost.  維護成本高

Due to rapid rate of cooling, cracks may be produced in some metals.
由於冷卻速度快，某些金屬可能會產生裂縫

High skilled labour is required to operate LBW.  操作雷射焊需要高技能工人

The welding thickness is limited to 19 mm.  焊接厚度限制在19毫米

The energy conversion efficiency in LBW is very low. It is usually below 10 %.
雷射焊的能量轉換效率非常低，通常低於10％