Resistance Welding 电阻焊

Resistance welding is a liquid state welding process in which the metal to metal joint created in liquid or molten state. It is a thermo-electric process in which heat is generated at the interface surfaces of welding plates due to electric resistance and a controlled low pressure is applied to these plates to create a weld joint. It is named as resistance welding because it uses electric resistance to produce heat. It is a very efficient pollution free welding process but its applications are limited due to its high equipment cost and limited material thickness.
电阻焊是一种液态焊接工艺,在这种工艺中,金属与金属之间的连接是在液态或熔融状态下产生的。它是一种热电工艺,由于电阻的作用,焊接板的界面表面产生热,并对这些板施加受控的低压,形成焊接接头。它被称为电阻焊,因为它使用电阻产生热量。这是一种非常有效的无污染焊接工艺,但由于设备成本高、材料厚度有限,其应用受到限制。

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1 Principle 原理

All resistance welding like spot welding, seam welding, projection welding etc. are worked on same principle of heat generation due to electric resistance. When a current passes through electric resistance, it produces heat. This is same principle which is used in electric coil. The amount of heat produced is depends on resistance of material, surface conditions, current supplied, time duration of current supplied etc. This heat generation takes place due to conversion of electric energy into thermal energy. The heat generation formula is
所有电阻焊接,如点焊、缝焊、凸焊等,由于电阻而产生热量的原理是相同的。当电流通过电阻时,产生热量。这和电线圈的原理是一样的。产生的热量取决于材料的电阻、表面条件、供电电流、供电时间等。这种热能的产生是由于电能转化为热能而产生的。热能产生公式为

Q = I2RT

Where
Q = Heat generated in joule 产生的热量 焦耳
I = Electric current in ampere 电流 安培
R = Electric resistance in Ohm 电阻 欧姆
T = Time of current flow in second 电流时间 秒

This heat is used to melt the interface metal to form a strong weld joint by fusion. This process produces weld without application of any filler material, flux and shielding gases.
这种热量用于熔化界面金属,通过熔合形成牢固的焊缝。该工艺无需使用任何填充材料、焊剂和保护气体即可产生焊缝。

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2 Types 类型

2.1 Spot Welding 点焊

It is simplest type of resistance welding in which the work pieces are held together under pressure of anvil face. The copper electrodes are brought in contact with work piece and current start to flow through it. The work piece material applies some resistance in flow of current which cause local heat generation. At the interface surfaces the resistance is high due to air gap. The current start to flow though it which melt down the interface surface. The amount of current supply and time should be sufficient for proper melting of interface surfaces. Now the current stopped to flow but the pressure applied by electrode maintained for a fraction of second, while the weld rapidly cooled. After it, the electrodes remove and brought to contact at other spot. It will create a circular nugget. The nugget size depends on size of electrode. It is generally about diameter 4-7 mm.
这是一种最简单的电阻焊接,在这种焊接中,工件在砧面压力下被连接在一起。铜电极与工件接触,电流开始流过工件。工件材料在电流流动中施加一定的阻力,引起局部发热。由于气隙的存在,界面表面的电阻较高。电流开始流过它,熔化了界面表面。电流供应的数量和时间应足以使界面表面适当熔化。现在电流停止流动,但是电极施加的压力只维持了几分之一秒,同时焊缝迅速冷却。在此之后,电极被移除,并在其他位置接触。它会形成一个圆形的金块。熔核大小取决于电极的尺寸。一般直径约4-7毫米。

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2.2 Seam Welding 缝焊

Seam welding is also called continuous spot welding in which a roller type electrode is used to flow current through work pieces. First the rollers are brought in contact with work piece. A high ampere current is passed through these rollers. This will melt the interface surfaces and form a weld joint. Now the rollers start rolling at work plates. This will create a continuous weld joint. The timing of the weld and movement of electrode is controlled to assure that the weld overlap and work piece does not get too hot. The welding speed is about 60 in/min in seam welding. It is used to create air tight joints.
焊缝焊接又称连续点焊,用滚子式电极使电流通过工件。首先将滚轮与工件接触。高安培电流通过这些轧辊。这将熔化界面表面,形成一个焊接接头。现在滚轮开始在工作板上滚动。这将创建一个连续的焊接接头。控制焊缝的时间和电极的运动,以保证焊缝和工件不会产生过热。焊缝焊接速度约为60 in/min。这种焊接通常用来制造气密接头。

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2.3 Projection Welding 凸焊

Projection welding is same as spot welding except a dimple is produced on work pieces at the location where weld is desired. Now the work pieces held between electrode and a large amount of current pass through it. A small amount of pressure is applied through electrode on welding plates. The current pass through dimple which melt down it and the pressure causes the dimple flatten and form a weld.
凸焊和点焊是一样的,只是在需要焊接的地方,工件上会产生一个凹痕。现在工件之间的电极和大量的电流通过它。少量的压力通过电极施加在焊接板上。电流通过凹坑,凹坑熔化,压力使凹坑变平,形成焊缝。

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2.4 Flash butt Welding 闪光对焊

It is another type of resistance welding which is used to weld tubes and rods in steel industries. In this process, two work pieces which are to be welded will be clamped in the electrode holders and a high pulsed current in the range of 100000 ampere is supplied to the work piece material. In this two electrode holders are used in which one is fixed and other is movable. Initially the current is supplied and movable clamp is forced against the fixed clamp due to contact of these two work pieces at high current, flash will be produced. When the interface surface comes into plastic form, the current is stopped and axial pressure is increased to make joint. In this process weld is formed due to plastic deformation.
它是另一种类型的电阻焊接,用于在钢铁工业焊接钢管和钢棒。在此工艺中,电极夹紧两个将要焊接的工件,并向工件材料提供100000安培范围内的高脉冲电流。在这两种电极夹中,一种是固定的,另一种是可移动的。首先提供电流,在大电流下,由于这两个工件的接触,在固定夹上施加活动夹,产生闪光。当界面形成塑性时,电流停止,轴向压力增大,形成接头。在此过程中,焊缝由于塑性变形而形成。

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3 Application 应用

  • Resistance welding is widely used in automotive industries.
    电阻焊在汽车工业中得到了广泛的应用
  • Projection welding is widely used in production of nut and bolt.
    凸焊在螺母和螺栓的生产中被广泛使用
  • Seam welding is used to produce leak prove joint required in small tanks, boilers etc.
    在小型储罐、锅炉等设备中,采用缝焊工艺可产生密封接头
  • Flash welding is used to welding pipes and tubes.
    闪光焊主要用于焊接管道

4 Advantages and Disadvantages 优点与缺点

4.1 Advantages 优点

  • It can weld thin (0.1 mm) as well as thick (20mm) metals.
    它可以焊接薄(0.1毫米)和厚(20毫米)金属
  • High welding speed.
    焊接速度快
  • Easily automated.
    容易实现自动化
  • Both similar and dissimilar metals can be weld.
    相似和不同的金属都可以焊接
  • The process is simple and fully automated so does not required high skilled labor.
    该过程简单且完全自动化,因此不需要高技能人工
  • High production rate.
    生产率高
  • It is environment friendly process.
    对环境友好的工艺
  • It does not require any filler metal, flux and shielding gases.
    不需要任何填充金属,助焊剂和保护气体

4.2 Disadvantages 缺点

  • High equipment cost.
    设备成本高
  • The thickness of work piece is limited due to current requirement.
    由于电流要求,工件的厚度受到限制
  • It is less efficient for high conductive materials.
    对于高导电材料来说效率较低
  • High electric power required.
    需要高电力
  • Weld joints have low tensile and fatigue strength.
    焊接接头具有低拉伸强度和疲劳强度