Plasma ARC Welding 等离子弧焊

Plasma arc welding is a liquid state welding process in which, the metal to metal joint forms in molten state. The hot ionized gases are known as Plasma. These hot ionized gases used to heating the work plates, and the joint is created due to fusion. This welding process is same as TIG welding process except plasma is used to weld the work pieces instead of arc. Filler material may or may not be used in this type of welding. One big advantage of plasma arc welding is that, it uses less current input compare to TIG or MIG processes for produces same heat.
等离子弧焊是一种液态焊接工艺,其中金属与金属的接合形成熔融状态。热电离气体称为等离子体。这些热电离气体用于加热工作板,并且由于熔合而产生接头。这种焊接工艺与TIG焊接工艺相同,只是使用等离子焊接工件而不是电弧。填充材料可以用于或不用于这种类型的焊接。等离子弧焊的一个重要优点是,与TIG或MIG工艺相比,它使用更少的电流输入来产生相同的热量。

PLASMA ARC WELDING

1 Principle 原理

The hot ionized gases are known as plasma. When a sufficient amount of energy provided to any inert gas, some of its electrons breaks free from its nucleus but travel with it. After the electrons leave, the atoms are converted into hot ionized state. It is most common state of matter witch is known as fourth state of matter. These ionized atoms have high heat contain which is further used to join two plates. This is basic principle of plasma arc welding. This welding is extended form of TIG welding in which, a non-consumable tungsten electrode is used to produce arc. This arc heats up the inert gases which are provided from inner orifice around tungsten electrode. The heating temperature is about 30000 degree centigrade at which the gas converts into ionized form. This hot ionized gas further used to create a welding joint by fusion.
热电离气体称为等离子体。当向任何惰性气体提供足够量的能量时,其一些电子从其核中脱离但随之移动。电子离开后,原子转变为热电离状态。最常见的物质状态被称为第四物质状态。这些电离原子具有高热含量,其进一步用于连接两个板。这是等离子弧焊的基本原理。这种焊接是TIG焊接的延伸形式,其中使用非消耗性钨电极来产生电弧。该电弧加热从钨电极周围的内孔提供的惰性气体。加热温度约为30000摄氏度,在此温度下气体转变成电离形式。这种热电离气体进一步用于通过熔合形成焊接接头。

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2 Equipments 设备组成

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2.1 Power Source 电源

PAW process needed a high power DC supply to generate electric spark in between tungsten electrode and welding plates (For transferred PAW Process) or in between tungsten electrode and discharge nozzle (For Non-transferred PAW process). One of the main features of plasma arc welding which make it different from TIG, is its low ampere welding capability. This welding can weld at low ampere of about 2 amp and maximum current which it can handle is about 300 amp. It needs about 80 volts for proper working. The power source consist transformer, rectifier and control console.
PAW工艺需要高功率直流电源以在钨电极和焊接板之间(对于转移弧PAW工艺)或在钨电极和排放喷嘴之间(对于非转移弧PAW工艺)产生电火花。与TIG不同的是,等离子弧焊的主要特点之一是其低安培焊接能力。 这种焊接可以在约2安培的低安培下焊接,并且它可以处理的最大电流约为300安培。正常工作需要大约80V电压。电源包括变压器,整流器和控制台。

2.2 Plasma arc torch 等离子弧焊喷嘴

This is most important part of PAW process. This torch is quite similar as used in TIG welding but too complex. It consist four main parts which are tungsten electrode, collets, inner nozzle, and outer nozzle. The tungsten electrode is hold by the collet. The collet is available in varying diameters. The inner gas nozzle supply inert gases inside the torch to form plasma. The outside nozzle supply shielding gases which protect the weld area from oxidation. These nozzles wear out rapidly. PAW torches are water cooled because arc is contained inside the torch which produces high heat, so a water jacket is provided outside the torch.
这是PAW工艺中最重要的部分。这种喷嘴非常类似于TIG焊接,但过于复杂。它由四个主要部分组成,即钨电极,夹头,内喷嘴和外喷嘴。钨电极由夹头固定。夹头有不同的直径。内部的气体喷嘴提供惰性气体在喷嘴内形成等离子体。外部喷嘴供应保护焊接区域免受氧化的保护气体。这些喷嘴极易磨损。PAW喷嘴是水冷却的,因为电弧包含在喷嘴内部产生高热量,因此需要在喷嘴外部提供水套。

2.3 Shielding and Plasma Gas Supply 屏蔽与等离子气体供应

Generally, plasma gas is same as shielding gas which is supplied by a same source. Mainly inert gases like argon, Helium etc. are used as both inert and shielding gases. This gas is supplied at both inert and outer nozzles.
通常,等离子体气体一般与屏蔽气体相同,由同一气源提供。主要使用惰性气体如氩气,氦气等作为惰性气体和保护气体。这种气体由喷嘴内部和外部一起供应。

2.4 Filler Material 焊补材料

Mostly no filler material is used in this welding process. If filler material is used, it is directly feed into weld zone.
焊接过程中一般不使用焊补材料。如果使用焊补材料,则直接送入焊缝区。

3 Types 类型

Mainly plasma arc welding can be classified into two types.
等离子弧焊主要可分为两种类型。

3.1 Non-transferred plasma arc welding 非转移弧等离子弧焊

In this welding process, straight polarity DC current is used. In this process, the tungsten electrode is connected to the negative and the nozzle is connected to the positive pole. The arc produces between tungsten electrode and nozzle inside the torch. This will increase the ionization of gas inside the torch. The torch transfers this ionized gas for further process. It is used to weld thin sheets.
在这种焊接工艺中,采用直流电流。在此工艺中,钨电极连接到负极,喷嘴连接到正极。电弧在钨电极和喷嘴之间产生。这将增加喷嘴内气体的电离。喷嘴将这种电离气体做进一步处理。它用于焊接薄板。

3.2 Transferred plasma arc welding 转移弧等离子弧焊

This process also uses straight polarity DC current. In this process, the tungsten electrode is connected to the negative terminal and the work piece is connected to the positive terminal. The arc is produces between tungsten electrode and work piece. In this process both plasma and arc transferred to the work piece which increases the heating capacity of process. It is used to weld thick sheets.
该工艺还是使用直流电流。在此工艺中,钨电极连接到负端子,工件连接到正端子。电弧在钨电极和工件之间产生。在这个过程中,等离子体和电弧都转移到工件上,这增加了工艺的加热能力。它用于焊接厚板。

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4 Working 工作

This welding works on same as TIG instead, plasma is used to heat up the parent material. Its working can be summarized as follow.
这种焊接与TIG焊相同,等离子体用于加热母材。其工作总结如下。

  • First the work pieces are properly cleaned. The power source supply power which produces arc between tungsten electrode and nozzle, or tungsten electrode and workpiece.
    首先,正确清洁工件。电源提供钨电极与喷嘴或钨电极与工件之间产生电弧。

  • The tungsten electrode gives a high intense arc which is used to ionization of gas particles and converts orifice gases into plasma. This hot ionized gas is supplied to the welding plates from a small orifice.
    钨电极具有高强度电弧,用于气体粒子的电离,并将喷嘴气体转化为等离子体。这种热电离气体从一个小孔供应到焊接板上。

  • The shielding gases like argon etc. are supplied through pressure valve and regulating valve to the outer nozzle of welding torch. These gases create a shield around the welding area which protect it from atmospheric gases like oxygen, nitrogen etc.
    氩气等保护气体通过压力阀和调节阀供给到焊枪的外喷口。这些气体在焊接区域周围形成一个保护罩,保护焊接区域不受氧气、氮气等大气气体的侵害。

  • The plasma strikes the welding plates and fuses it into one piece. Next the welding torch is moved in the direction of welding.
    等离子体撞击焊接板并将其熔合成一体。接下来,喷嘴沿焊接方向移动。

  • If the welding required filler material, it is fed by the welder manually.
    如果焊接需要填充材料,则由焊工手动给料。

5 Application 应用

  • This welding is used in marine and aerospace industries.
    用于船舶和航空航天工业。
  • It is used to weld pipes and tubes of stainless steel or titanium.
    用于不锈钢或钛管的焊接。
  • It is mostly used in electronic industries.
    主要用于电子工业。
  • It is used to repair tools, die and mold.
    用于修理工装和模具。
  • It is used to welding or coating on turbine blade.
    用于涡轮叶片的焊接或涂层。

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6 Advantages and Disadvantages 优点与缺点

6.1 Advantages 优点

  • High welding speed.
    焊接速度快。
  • High energy available for welding. It can be easily used to weld hard and thick work pieces.
    更高能量用于焊接。它可以很容易地用于焊接坚硬和厚实的工件。
  • The distance between tool and work piece does not effects the arc formation.
    工具和工件之间的距离不会影响电弧形成。
  • Low power consumption for same size weld.
    相同尺寸焊缝功耗低。
  • More stable arc produced by PAW method.
    PAW方法产生的电弧更加稳定。
  • High intense arc or high penetration rate.
    高强度电弧或高穿透率。
  • It can work at low amperage.
    可以在低电流下工作。

6.2 Disadvantages 缺点

  • Higher equipment cost.
    设备成本较高。
  • Noisy operation.
    操作复杂
  • More radiation.
    更多的辐射
  • High skill labor required.
    需要高技能的工人
  • High maintenance cost.
    维护成本高。