氣體金屬電弧焊接

焊接是製造或雕塑 過程的聯接材料，通常是金屬或熱塑性塑料 ，通過使聚結 。 這通常是由熔化的工件，並加入填充材料，以形成一個池熔化的材料（ 焊池 ）的冷卻，成為一個強有力的聯合，有壓力，有時與其一起使用熱 ，或本身，產生焊接。 這是在對比焊接和釬焊 ，熔化涉及低融點材料工件之間形成一個鍵之間，沒有融化的工件。

許多不同的能源來源，可用於焊接，包括天然氣火焰 ，一電弧 ，一個激光 ，一個電子束 ， 摩擦和超聲波 。 而往往是工業生產過程，焊接可以在許多不同的環境，包括開放式空氣， 水分和外層空間 。 無論位置，但是，焊接依然危險，採取預防措施，以避免燒傷， 電擊 ，眼睛損傷，有毒廢氣，過度暴露於紫外線 。

直到年底的19世紀，只有焊接過程焊接鍛造 ，其中鐵匠使用了幾百年加入鋼鐵加熱和錘擊他們。 弧焊和氧燃料焊接是最早開發進程，以在本世紀後期，和電阻焊接之後不久。 先進的焊接技術迅速在20世紀初的第一次世界大戰和第二次世界大戰的需求推動了可靠和廉價的連接方法。 繼戰爭，現代焊接技術進行了一些發達國家，包括手工方法，比如屏蔽金屬電弧焊接 ，現在一個最流行的焊接方法，以及半自動和自動過程，如氣體金屬電弧焊 ， 埋弧焊 ， 助焊劑芯電弧焊和電渣焊 。 繼續發展與發明的激光束焊接和電子束焊在後半世紀。 今天，科學將繼續推進。 焊接機器人正變得越來越普遍在工業環境中，研究人員繼續開發新的焊接方法，並取得更大的了解焊接質量和性能。

歷史

在德里鐵柱

加入金屬的歷史可以追溯到幾千年，最早的例子焊接從青銅時代和鐵器時代在歐洲和中東 。 焊接是用於建設的鐵柱在新德里 ， 印度 ，豎立廣告，體重約310 540 噸 。 ^[1]

在中世紀的進步帶來的鍛焊 ，其中鐵匠敲打反复加熱金屬粘接發生。 Welding, however, was transformed during the 19th century. 1540年， Vannoccio Biringuccio發表德拉pirotechnia ，其中包括描述的鍛造操作。 文藝復興時期的工匠們熟練的過程，並持續增長的行業在下一世紀。 ^[2]焊接，然而，在19世紀的轉變。 and subsequently proposed its possible practical applications, including welding. 1802年，俄羅斯科學家瓦西裡彼得羅夫發現了電弧 ^{[3] ，}隨後提出了可能的實際應用，包括焊接。 在1881年至1882年俄國發明家尼古拉別納爾多斯創造了第一個電弧焊接方法稱為碳弧焊 ，利用碳電極。 在電弧焊接的進展繼續與發明的金屬電極在1800年代末期由俄羅斯， 尼古拉斯拉維亞諾夫 （1888年），以及美國， 氯棺材 （1890年）。 大約1900年， 美聯社斯特羅門格發布了一個包裹的金屬電極在英國 ，這給了一個更加穩定的弧線。 1905年俄羅斯科學家弗拉基米爾米特克維奇提出使用三相電弧焊接。 1919年， 交流電焊接發明了終審法院首席法官Holslag但並沒有成為流行的另一個10年。 ^[4]

At first, oxyfuel welding was one of the more popular welding methods due to its portability and relatively low cost. 電阻焊還制定了在最後幾十年的19世紀，隨著第一個專利要伊萊休湯姆森在1885年，誰製作了進一步的進展在今後15年。 鋁熱welding是在1893年發明，並在那個時候另一個進程， 氧燃料焊接 ，成為確立。 乙炔被發現於1836年由埃德蒙戴維 ，但它的使用是不實際的焊接直到1900年，當一個合適的噴燈開發。 ^[5]首先，氧燃料焊接是一個比較流行的焊接方法由於其便攜性和成本相對較低。 隨著 20世紀的進展，但是，它失寵的工業應用。 這在很大程度上取代了電弧焊接，金屬材料（稱為流量 ）為電極的電弧穩定和盾牌的基礎物質雜質繼續得到發展。 ^[6]

第一次世界大戰造成了重大的激增，在使用的焊接工藝，與各軍事強國企圖以確定哪些幾個新的焊接工藝是最好的。 英國主要用於弧焊，甚至興建一船， Fulagar ，具有完全焊接船體。 Also noteworthy is the first welded road bridge in the world, designed by Stefan Bryła of the Warsaw University of Technology in 1927, and built across the river Słudwia Maurzyce near Łowicz, Poland in 1929. ^{[ 8 ]}電弧焊接是首先應用於飛機，以及在戰爭期間，一些德國飛機機身建造了使用該方法。 ^[7]另外值得注意的是第一個焊接道路橋樑在世界上，設計由斯特凡Bryła在華沙理工大學在1927年，建成過河Słudwia Maurzyce近沃維奇，波蘭在1929年。 ^[8]

在20世紀20年代，又取得一批重大的焊接技術，包括引進自動焊接於1920年，在這種電極絲是美聯儲不斷。 屏蔽氣體成為很值得關注的一個問題，因為科學家試圖從效果保護焊的氧氣和大氣中的氮。 During the following decade, further advances allowed for the welding of reactive metals like aluminum and magnesium .孔隙度和脆性是主要問題，以及解決方案，包括開發利用氫氣 ， 氬氣和氦氣作為焊接氣氛。 ^[9]在隨後的十年中，進一步發展允許焊接活性金屬如鋁和鎂 。 這種結合與發展，在自動焊接，交流，並通量美聯儲大規模擴展電弧焊接過程中，然後在20世紀30年代第二次世界大戰 。 ^[10]

在本世紀中葉，許多新的焊接方法發明。 1930年看到了釋放螺柱焊 ，很快走紅造船和建設。 埋弧焊發明的同一年，今天仍然是受歡迎的。 1932年俄羅斯， 康斯坦丁赫列諾夫成功地實施了第一次水下電弧焊接。 氣體鎢極氬弧焊焊接 ，經過幾十年的發展，完善，終於在1941年，和熔化極氣體保護焊在1948年之後，允許快速焊接非鐵材料但需要昂貴的屏蔽氣體。 屏蔽金屬電弧焊接在20世紀50年代被開發，使用助焊劑塗層電極消耗，並迅速成為最流行的金屬電弧焊接工藝。 In 1953 the Soviet scientist NF Kazakov proposed the diffusion bonding method. ^{[ 12 ]} 1957年，該通量芯電弧焊接過程中首次亮相，其中自屏蔽線電極可被用於自動化設備，導致大大提高焊接速度，並認為同一年， plasma弧焊發明。 電渣焊引入1958年，其次是其表弟， 氣電立焊 ，於1961年。 ^[11] 1953年，蘇聯科學家提出的核因子卡扎科夫擴散焊方法。 ^[12]

其他最近的事態發展，包括在1958年突破焊接的電子束焊接 ，使深而窄的焊接可能通過集中熱源。 繼發明的激光在1960年， 激光束焊接數十年後首次亮相，並已被證明是特別有用的高速，自動化焊接。 這兩種過程，但是，仍然是相當昂貴由於費用昂貴，必要的設備，這限制了他們的申請。 ^[13]

過程

弧

這些過程使用的焊接電源 ，以創造和維持一個電極之間的電弧和熔化金屬基材料在焊接點。 他們可以使用直接 （DC）或交流 （交流）電流和消耗或非消耗電極 。 焊接地區有時受某種類型的惰性或半惰性氣體 ，稱為保護氣體 ，並用填充材料，有時也。

電源供應器

提供必要的電能電弧焊接工藝，一個數字的不同電源均可使用。 最常見的焊接電源是恆定電流和恆定的電源電壓電源。 在弧焊，電弧的長度直接相關的電壓，以及熱輸入量是與當前的。 恆流電源是最常用的手工焊接工藝，如鎢極氣體保護焊和手工電弧焊，因為他們保持一個相對恆定的電流甚至電壓變化。 這一點很重要，因為在手工焊接，可能難以舉行電極完全穩定，因此，電弧長度，從而電壓往往波動。 恆壓電源電壓保持不變，改變電流，因此，是最常用的自動化焊接工藝，如氣體金屬電弧焊接，藥芯焊絲電弧焊和埋弧焊焊接。 在這些過程中，電弧長度保持不變，因為任何波動導線之間的距離和基礎材料是迅速糾正目前的一個大變化。 例如，如果the電線的基礎材料太接近，該電流將迅速增加，進而使得該heat to增加和尖端的電線to融化，返回到原來的separation distance。 ^[14]

目前使用的類型在弧焊也起著重要的作用，焊接。 電極消耗過程，如屏蔽金屬電弧焊及氣體金屬電弧焊接通常使用的是直流電，但電極可以充電，無論是正面還是負面的。 在焊接，帶正電的陽極將有一個更大的熱量集中，因此，改變極性的電極焊接性能的影響。 如果是帶正電電極，金屬基會更熱，增加熔深和焊接速度。 Nonconsumable electrode processes, such as gas tungsten arc welding, can use either type of direct current, as well as alternating current.另外，一個帶負電荷的電極焊接結果更淺。 ^[15]的惰性電極過程，如氣體鎢極氬弧焊，可以使用兩種類型的直流電，以及交流電。 Alternating current rapidly moves between these two, resulting in medium-penetration welds.然而，隨著直流，因為只有創造了電弧電極和填充材料不提供，一個正電荷的電極焊接淺層原因，而帶負電荷的電極，使深焊縫。 ^[16]交流電這兩者之間迅速移動，導致中等穿透焊縫。 交流的一個缺點，但事實上，電弧必須重新點燃後，每過零，已得到處理與發明的特殊權力單位，產生方波模式，而不是正常的正弦波 ，使快速通道盡可能減少為零這個問題的影響。 ^[17]

過程

其中最常見的類型是電弧焊接屏蔽金屬電弧焊 （SMAW的），它也被稱為手工電弧焊（MMA）的還是堅持焊接。 電流是用來取得一弧之間的基材及消耗品電極棒，which是鋼造的上覆蓋著通量的保護焊area從氧化和污染，製作CO ₂氣體在焊接過程。 該電極核心本身的行為作為填充材料，使一個單獨的填充物是不必要的。

屏蔽金屬電弧焊接

An operator can become reasonably proficient with a modest amount of training and can achieve mastery with experience.這個過程是靈活，可以執行相對便宜的設備，因而非常適合購物的工作和領域的工作。 ^[18]經營者可以成為一個合理精通少量的訓練，可以達到掌握的經驗。 Furthermore, the process is generally limited to welding ferrous materials, though special electrodes have made possible the welding of cast iron , nickel , aluminum , copper , and other metals.焊接時間是相當緩慢的，因為消耗電極必須經常更換，因為渣，助焊劑的殘留物，必須經過焊接一點點的蠶食。 ^[19]此外，這個過程是一般僅限於黑色金屬材料的焊接，雖然特殊電極成為可能的焊接鑄鐵 ， 鎳 ， 鋁 ， 銅和其他金屬。 沒有經驗的經營者可能難以彌補外的位置焊接這一過程。

氣體金屬電弧焊 （GMAW焊接），也稱為金屬惰性氣體或MIG焊接，是一個半自動或自動的過程，它使用一個連續送絲作為電極和一個惰性或半惰性氣體保護焊混合不受污染。 如同手工電弧焊，合理運營能力可達到溫和的培訓。 由於電極是連續的，焊接速度更大的GMAW焊接比手工電弧焊。 此外，規模較小的弧相比， 屏蔽金屬電弧焊接過程中可以更容易地使外的位置焊接（例如，架空接頭，作為下一個將是焊接結構）。

該設備需要執行的GMAW焊接過程更加複雜和昂貴，需要比手弧焊，需要一個更複雜的安裝過程。 因此，氣體保護焊是移植性較差，多才多藝，並且由於使用了一個單獨的保護氣體，是不是特別適合戶外工作。 不過，由於更高的平均速率可以完成焊接，氣體保護焊是適合生產焊接。 這個過程可以應用到各種各樣的金屬，有色金屬和兩個非鐵。 ^[20]

一個相關的過程中， 藥芯焊絲電弧焊 （藥芯焊絲），使用類似設備，但使用的鋼線組成的電極周圍一粉填充材料。 這是較昂貴的芯線比標準的實心線，可以產生煙霧和/或爐渣，但它允許更高的焊接速度和更大的金屬滲透。 ^[21]

氣體鎢電弧焊接 （氬弧焊），鎢惰性氣體（氬）弧焊（有時也錯誤地稱為heliarc焊接），是一個手工焊接工藝，使用的惰性鎢電極，惰性或半惰性氣體的混合物，1另填充材料。 尤其適用於焊接薄材料，這種方法的特點是電弧穩定和高質量的焊縫，但它需要大量的經營技巧，只能在相對較低的速度完成。

氬弧焊可用於幾乎所有的焊接金屬，雖然這是最經常採用不銹鋼和輕金屬。 A related process, plasma arc welding , also uses a tungsten electrode but uses plasma gas to make the arc.它往往是焊接時使用的質量是非常重要的，如自行車 ，飛機和海軍的應用。 ^[22]相關的流程， 等離子弧焊接 ，還採用了鎢電極，但使用等離子氣體，使電弧。 電弧更集中比GTAW電弧，使橫向控制更為關鍵，因此一般限制技術機械化進程。 由於其穩定的電流，該方法可用於更廣泛的材料厚度比可以氬弧焊過程，而且，它是要快得多。 它可以適用於所有相同的材料作為氬弧焊except 鎂 ，及自動焊接不銹鋼鋼是一個重要的應用程序。 一個變化的過程是等離子切割 ，高效率的鋼材切割過程。 ^[23]

埋弧焊 （鋸）是一種高生產率的方法，其中焊接電弧擊中覆蓋層下的通量。 這增加了弧形的質量，因為大氣中的污染物被阻止的流量。 表格上的鋼渣，焊縫通常還是自行關閉，並結合使用一個連續送絲，焊沉積速率高。 工作條件大大改善了其他電弧焊接工藝，因為隱藏的弧的流量，幾乎無煙霧產生。 Other arc welding processes include atomic hydrogen welding , carbon arc welding , electroslag welding , electrogas welding , and stud arc welding .這一過程通常用於工業，特別是大型產品及製造壓力容器的焊接。 ^[24]其他電弧焊接過程包括氫原子焊 ， 碳弧焊 ， 電渣焊 ， 氣電立焊和螺柱焊接 。

氣焊一鋼電樞使用氧炔進程。

氣

最常見的氣體焊接工藝焊接氧燃料 ，也被稱為氧乙炔焊。 這是一種最古老和最多才多藝的焊接工藝，但近年來它已成為冷門的工業應用。 它仍然被廣泛用於焊接管材，以及維修工作。 它也經常很適合，並贊成，為製造某些類型的金屬基藝術品。 氧燃料設備是通用，不僅因為它是首選的某些種類的鐵或鋼焊接，也因為它更傾向於使用釬焊，釬焊，金屬加熱（彎曲和成形），鏽蝕螺母鬆動和螺栓，並是無處不在的手段氧燃料切削有色金屬。

該設備是相對便宜和簡單，一般採用燃燒的乙炔在氧氣產生焊接火焰溫度約3100攝氏度 火焰，因為它是不超過 1電弧集中，焊縫冷卻速度較慢的原因，從而導致更大的殘餘應力和焊接變形，但它簡化了焊接高合金鋼。 Other gas welding methods, such as air acetylene welding , oxygen hydrogen welding , and pressure gas welding are quite similar, generally differing only in the type of gases used.一個類似的過程，一般名為氧切割，是用來切割金屬。 ^[6]其他氣體焊接方法，如空氣乙炔焊接 ， 氧氫焊接和焊接氣體的壓力是非常相似，一般只在不同類型的氣體的使用。 阿水火炬有時用於精密焊接的小物品，如珠寶。 氣焊也用於塑料焊接 ，雖然加熱物質是空氣，溫度低得多。

阻力

Resistance welding involves the generation of heat by passing current through the resistance caused by the contact between two or more metal surfaces. Small pools of molten metal are formed at the weld area as high current (1000–100,000 A ) is passed through the metal. In general, resistance welding methods are efficient and cause little pollution, but their applications are somewhat limited and the equipment cost can be high.

Spot welder

Spot welding is a popular resistance welding method used to join overlapping metal sheets of up to 3 mm thick. Two electrodes are simultaneously used to clamp the metal sheets together and to pass current through the sheets. The advantages of the method include efficient energy use , limited workpiece deformation, high production rates, easy automation, and no required filler materials. Weld strength is significantly lower than with other welding methods, making the process suitable for only certain applications. It is used extensively in the automotive industry—ordinary cars can have several thousand spot welds made by industrial robots . A specialized process, called shot welding , can be used to spot weld stainless steel .

Like spot welding, seam welding relies on two electrodes to apply pressure and current to join metal sheets. However, instead of pointed electrodes, wheel-shaped electrodes roll along and often feed the workpiece, making it possible to make long continuous welds. In the past, this process was used in the manufacture of beverage cans, but now its uses are more limited. Other resistance welding methods include flash welding , projection welding , and upset welding . ^{[ 25 ]}

Energy beam

Energy beam welding methods, namely laser beam welding and electron beam welding , are relatively new processes that have become quite popular in high production applications. The two processes are quite similar, differing most notably in their source of power. Laser beam welding employs a highly focused laser beam, while electron beam welding is done in a vacuum and uses an electron beam. Both have a very high energy density, making deep weld penetration possible and minimizing the size of the weld area. Both processes are extremely fast, and are easily automated, making them highly productive. The primary disadvantages are their very high equipment costs (though these are decreasing) and a susceptibility to thermal cracking. Developments in this area include laser-hybrid welding , which uses principles from both laser beam welding and arc welding for even better weld properties, and X-ray welding . ^{[ 26 ]}

Solid-state

如同第一焊接工藝， 焊接偽造 ，一些現代焊接方法不涉及被熔化的材料加入。 One of the most popular, ultrasonic welding , is used to connect thin sheets or wires made of metal or thermoplastic by vibrating them at high frequency and under high pressure. The equipment and methods involved are similar to that of resistance welding, but instead of electric current, vibration provides energy input. Welding metals with this process does not involve melting the materials; instead, the weld is formed by introducing mechanical vibrations horizontally under pressure. When welding plastics, the materials should have similar melting temperatures, and the vibrations are introduced vertically. Ultrasonic welding is commonly used for making electrical connections out of aluminum or copper, and it is also a very common polymer welding process.

Another common process, explosion welding , involves the joining of materials by pushing them together under extremely high pressure. The energy from the impact plasticizes the materials, forming a weld, even though only a limited amount of heat is generated. The process is commonly used for welding dissimilar materials, such as the welding of aluminum with steel in ship hulls or compound plates. Other solid-state welding processes include co-extrusion welding , cold welding , diffusion welding , exothermic welding , friction welding (including friction stir welding ), high frequency welding , hot pressure welding , induction welding , and roll welding . ^{[ 27 ]}

Geometry

Common welding joint types – (1) Square butt joint, (2) V butt joint, (3) Lap joint, (4) T-joint

Welds can be geometrically prepared in many different ways. The five basic types of weld joints are the butt joint, lap joint, corner joint, edge joint, and T-joint (a variant of this last is the cruciform joint ). Other variations exist as well—for example, double-V preparation joints are characterized by the two pieces of material each tapering to a single center point at one-half their height. Single-U and double-U preparation joints are also fairly common—instead of having straight edges like the single-V and double-V preparation joints, they are curved, forming the shape of a U. Lap joints are also commonly more than two pieces thick—depending on the process used and the thickness of the material, many pieces can be welded together in a lap joint geometry. ^{[ 28 ]}

Often, particular joint designs are used exclusively or almost exclusively by certain welding processes. For example, resistance spot welding, laser beam welding, and electron beam welding are most frequently performed on lap joints. However, some welding methods, like shielded metal arc welding, are extremely versatile and can weld virtually any type of joint. Additionally, some processes can be used to make multipass welds, in which one weld is allowed to cool, and then another weld is performed on top of it. This allows for the welding of thick sections arranged in a single-V preparation joint, for example. ^{[ 29 ]}

The cross-section of a welded butt joint, with the darkest gray representing the weld or fusion zone, the medium gray the heat-affected zone, and the lightest gray the base material.

After welding, a number of distinct regions can be identified in the weld area. The weld itself is called the fusion zone—more specifically, it is where the filler metal was laid during the welding process. The properties of the fusion zone depend primarily on the filler metal used, and its compatibility with the base materials. It is surrounded by the heat-affected zone , the area that had its microstructure and properties altered by the weld. These properties depend on the base material's behavior when subjected to heat. The metal in this area is often weaker than both the base material and the fusion zone, and is also where residual stresses are found. ^{[ 30 ]}

Quality

Most often, the major metric used for judging the quality of a weld is its strength and the strength of the material around it. Many distinct factors influence this, including the welding method, the amount and concentration of energy input, the base material, the filler material, the flux material, the design of the joint, and the interactions between all these factors. To test the quality of a weld, either destructive or nondestructive testing methods are commonly used to verify that welds are defect-free, have acceptable levels of residual stresses and distortion, and have acceptable heat-affected zone (HAZ) properties. Welding codes and specifications exist to guide welders in proper welding technique and in how to judge the quality of welds.

Heat-affected zone

The blue area results from oxidation at a corresponding temperature of 600 °F (316 °C). This is an accurate way to identify temperature, but does not represent the HAZ width. The HAZ is the narrow area that immediately surrounds the welded base metal.

The effects of welding on the material surrounding the weld can be detrimental—depending on the materials used and the heat input of the welding process used, the HAZ can be of varying size and strength. The thermal diffusivity of the base material plays a large role—if the diffusivity is high, the material cooling rate is high and the HAZ is relatively small. Conversely, a low diffusivity leads to slower cooling and a larger HAZ. The amount of heat injected by the welding process plays an important role as well, as processes like oxyacetylene welding have an unconcentrated heat input and increase the size of the HAZ. Processes like laser beam welding give a highly concentrated, limited amount of heat, resulting in a small HAZ. Arc welding falls between these two extremes, with the individual processes varying somewhat in heat input. ^{[ 31 ] [ 32 ]} To calculate the heat input for arc welding procedures, the following formula can be used:

where Q = heat input ( kJ / mm ), V = voltage ( V ), I = current ( A ), and S = welding speed (mm/min). The efficiency is dependent on the welding process used, with shielded metal arc welding having a value of 0.75, gas metal arc welding and submerged arc welding, 0.9, and gas tungsten arc welding, 0.8. ^{[ 33 ]}

Defects

There are many types of defects that can occur depending on the material and welding process. Types of defects include cracks, distortion, gas inclusions (porosity), non-metallic inclusions, lack of fusion, incomplete penetration, lamellar tearing, and undercutting.

Weldability

The quality of a weld is also dependent on the combination of materials used for the base material and the filler material. Not all metals are suitable for welding, and not all filler metals work well with acceptable base materials.

Unusual conditions

Underwater welding

While many welding applications are done in controlled environments such as factories and repair shops, some welding processes are commonly used in a wide variety of conditions, such as open air, underwater, and vacuums (such as space). In open-air applications, such as construction and outdoors repair, shielded metal arc welding is the most common process. Processes that employ inert gases to protect the weld cannot be readily used in such situations, because unpredictable atmospheric movements can result in a faulty weld. Shielded metal arc welding is also often used in underwater welding in the construction and repair of ships, offshore platforms, and pipelines, but others, such as flux cored arc welding and gas tungsten arc welding, are also common. Welding in space is also possible—it was first attempted in 1969 by Russian cosmonauts, when they performed experiments to test shielded metal arc welding, plasma arc welding, and electron beam welding in a depressurized environment. Further testing of these methods was done in the following decades, and today researchers continue to develop methods for using other welding processes in space, such as laser beam welding, resistance welding, and friction welding . Advances in these areas may be useful for future endeavours similar to the construction of the International Space Station , which could rely on welding for joining in space the parts that were manufactured on Earth. ^{[ 34 ]}

Safety issues

Arc welding with a welding helmet, gloves, and other protective clothing

Welding, without the proper precautions, can be a dangerous and unhealthy practice. However, with the use of new technology and proper protection, risks of injury and death associated with welding can be greatly reduced. Because many common welding procedures involve an open electric arc or flame, the risk of burns and fire is significant; this is why it is classified as a hot work process. To prevent them, welders wear personal protective equipment in the form of heavy leather gloves and protective long sleeve jackets to avoid exposure to extreme heat and flames. Additionally, the brightness of the weld area leads to a condition called arc eye in which ultraviolet light causes inflammation of the cornea and can burn the retinas of the eyes. Goggles and welding helmets with dark face plates are worn to prevent this exposure, and in recent years, new helmet models have been produced that feature a face plate that self-darkens upon exposure to high amounts of UV light. To protect bystanders, translucent welding curtains often surround the welding area. These curtains, made of a polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets. ^{[ 35 ]}

Oxyfuel welding with protective eyeware

Welders are also often exposed to dangerous gases and particulate matter. Processes like flux-cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides , which in some cases can lead to medical conditions like metal fume fever . The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Additionally, many processes produce fumes and various gases, most commonly carbon dioxide , ozone and heavy metals , that can prove dangerous without proper ventilation and training. Exposure to manganese welding fumes, for example, even at low levels (<0.2 mg/m ³ ), may lead to neurological problems or to damage to the lungs, liver, kidneys, or central nervous system. ^{[ 36 ]} Furthermore, because the use of compressed gases and flames in many welding processes poses an explosion and fire risk, some common precautions include limiting the amount of oxygen in the air, keeping combustible materials away from the workplace, ^{[ 37 ]} or making use of a positive pressure enclosure . Welding fume extractors are often used to remove the fume from the source and filter the fumes through a HEPA filter.

Costs and trends

As an industrial process, the cost of welding plays a crucial role in manufacturing decisions. Many different variables affect the total cost, including equipment cost, labor cost, material cost, and energy cost. Depending on the process, equipment cost can vary, from inexpensive for methods like shielded metal arc welding and oxyfuel welding, to extremely expensive for methods like laser beam welding and electron beam welding. Because of their high cost, they are only used in high production operations. Similarly, because automation and robots increase equipment costs, they are only implemented when high production is necessary. Labor cost depends on the deposition rate (the rate of welding), the hourly wage, and the total operation time, including both time welding and handling the part. The cost of materials includes the cost of the base and filler material, and the cost of shielding gases. Finally, energy cost depends on arc time and welding power demand.

For manual welding methods, labor costs generally make up the vast majority of the total cost. As a result, many cost-saving measures are focused on minimizing operation time. To do this, welding procedures with high deposition rates can be selected, and weld parameters can be fine-tuned to increase welding speed. Also, removal of welding spatters generated during welding process is highly labor intensive and time consuming. Implementation of Welding Anti Spatter & Flux which is safe and non-polluting is considered as a welcome change in cost cutting and weld joint quality improvement measures. Mechanization and automation are often implemented to reduce labor costs, but this frequently increases the cost of equipment and creates additional setup time. Material costs tend to increase when special properties are necessary, and energy costs normally do not amount to more than several percent of the total welding cost. ^{[ 38 ]}

In recent years, in order to minimize labor costs in high production manufacturing, industrial welding has become increasingly more automated, most notably with the use of robots in resistance spot welding (especially in the automotive industry) and in arc welding. In robot welding , mechanized devices both hold the material and perform the weld ^{[ 39 ]} and at first, spot welding was its most common application, but robotic arc welding increases in popularity as technology advances. Other key areas of research and development include the welding of dissimilar materials (such as steel and aluminum, for example) and new welding processes, such as friction stir , magnetic pulse , conductive heat seam , and laser-hybrid welding . Furthermore, progress is desired in making more specialized methods like laser beam welding practical for more applications, such as in the aerospace and automotive industries. Researchers also hope to better understand the often unpredictable properties of welds, especially microstructure, residual stresses , and a weld's tendency to crack or deform. ^{[ 40 ]}

See also

• Regulated Metal Deposition
• Welding Procedure Specification

Notes

參考資料

• ASM International (2003). Trends in Welding Research . Materials Park, Ohio : ASM International. ISBN 0-87170-780-2 .  
• Blunt, Jane; Nigel C. Balchin (2002). Health and Safety in Welding and Allied Processes . Cambridge : Woodhead. ISBN 1-85573-538-5 .  
• Cary, Howard B; Scott C. Helzer (2005). Modern Welding Technology . Upper Saddle River, New Jersey : Pearson Education. ISBN 0-13-113029-3 .  
• Henderson, JG (1953). Metallurgical Dictionary . New York, New York : Reinhold Publishing Corporation.  
• Hicks, John (1999). Welded Joint Design . New York : Industrial Press. ISBN 0-8311-3130-6 .  
• Kalpakjian, Serope; Steven R. Schmid (2001). Manufacturing Engineering and Technology . Prentice Hall. ISBN 0-201-36131-0 .  
• Lincoln Electric (1994). The Procedure Handbook of Arc Welding . Cleveland : Lincoln Electric. ISBN 99949-25-82-2 .  
• Smith, Dave (1984). Welding Skills and Technology . New York, New York : McGraw-Hill Book Company. ISBN 0-07-000757-8 .  
• The James F. Lincoln Arc Welding Foundation (1978). Principles of Industrial Welding . Cleveland, Ohio : The James F. Lincoln Arc Welding Foundation.  
• Weman, Klas (2003). Welding processes handbook . New York, NY: CRC Press LLC. ISBN 0-8493-1773-8 .  

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