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How to choose and use shielding gas correctly in laser welding


本身以外我们也要关注下焊接辅助的作用,焊接辅助是指保护气体或者焊接助剂的使用;在实际焊接 保护气体的使用比较频繁 使用 保护气体会影响焊缝成型、焊缝质量、焊缝熔深及熔宽,极大多数情况下,吹入保护气体会对焊缝产生积极的影响作用,但是也可能会带来不利的作用。 In the laser welding process, we must meet the high requirements of customers. In addition to the laser welding machine itself, we must also pay attention to the role of welding assistance. Welding assistance refers to the use of shielding gas or welding aid; in actual welding , the protection of gas It is used frequently , and the use of shielding gas will affect the welding seam formation, welding seam quality, welding depth and welding width. In most cases, blowing the shielding gas will have a positive effect on the welding seam, but it may also bring To adverse effects.

positive effects

1) The correct blowing of protective gas will effectively reduce the weld pool and even prevent oxidation;

2) The correct blowing of protective gas can effectively reduce the spatter generated during welding;

3) The correct blowing of protective gas can promote the uniform spreading of the weld pool when it solidifies, making the weld seam uniform and beautiful;

的屏蔽作用,增大激光的有效利用率; 4) The correct blowing of the protective gas can effectively reduce the shielding effect of the metal vapor plume or the plasma cloud on the laser and increase the effective utilization of the laser;

5) The correct blowing of protective gas can effectively reduce the weld air holes.

As long as the gas type, gas flow rate, and blowing method are selected correctly, the desired effect can be completely obtained. However, incorrect use of shielding gas can also adversely affect welding.

Negative Effects

1) Incorrect blowing of protective gas may cause the weld to deteriorate:

2) Choosing the wrong gas type may cause cracks in the weld, and may also reduce the mechanical properties of the weld;

3) Selecting the wrong gas blow-in flow may cause the weld to be more oxidized (whether the flow is too large or too small), or it may cause the weld pool metal to be severely disturbed by external forces and cause the weld to collapse or form unevenly;

4) Choosing the wrong gas injection method will cause the weld to fail to achieve protective effects, or even have no protective effect, or have a negative impact on the formation of the weld;

5) Blowing in protective gas will have a certain effect on the weld penetration, especially when welding thin plates, which will reduce the weld penetration.

Type of protective gas

N2、Ar、He,其物化性质各有差异,也因此对焊缝的作用效果也各不相同。 The commonly used shielding gases for laser welding are mainly N2, Ar, He, which have different physical and chemical properties, and therefore have different effects on the weld.

Nitrogen N2

N2 has a moderate ionization energy, which is higher than Ar and lower than He. The degree of ionization under the action of laser is moderate, which can better reduce the formation of plasma cloud and increase the effective utilization of laser. Nitrogen can chemically react with aluminum alloys and carbon steels at a certain temperature to produce nitrides, which will increase weld brittleness and reduce toughness, which will have a large adverse effect on the mechanical properties of weld joints, so nitrogen is not recommended Protected by aluminum and carbon steel welds.

The nitride produced by the chemical reaction between nitrogen and stainless steel can increase the strength of the weld joint, which will help improve the mechanical properties of the weld. Therefore, nitrogen can be used as a shielding gas when welding stainless steel.

Argon Ar

The ionization energy of Ar is relatively low, and the ionization degree is high under the action of laser, which is not conducive to the control of the formation of plasma clouds. It will have a certain impact on the effective utilization of laser, but the activity of Ar is very low and it is difficult to chemically interact with common metals. Reaction, and the cost of Ar is not high. In addition, the density of Ar is large, which is conducive to sinking above the weld pool, which can better protect the weld pool, so it can be used as a conventional shielding gas.

3. He

He has the highest ionization energy, and the degree of ionization is very low under the action of laser. It can well control the formation of plasma clouds. Laser can work well on metals, and He has very low activity, which basically does not chemically react with metals. Very good weld protection gas, but the cost of He is too high. Generally, this gas will not be used in mass production products. He is generally used for scientific research or products with very high added value.

Protective gas blowing method

1所示;另一种是同轴保护气体,如图2所示。 There are currently two main types of protective gas injection: one is to blow the protective gas on the side of the axis, as shown in Figure 1; the other is the coaxial protective gas, as shown in Figure 2.

激光焊接时如何正确用“气”

Figure 1 Sidebar blowing protective gas

激光焊接时如何正确用“气”

Figure 2 Coaxial shielding gas

How to choose the two blowing methods is comprehensively considered in many aspects. Generally, the side blowing protective gas method is recommended.

Selection principle of protective gas injection method

“氧化”仅是一种俗称,理论上是指焊缝与空气中有害成分发生化学反应导致焊缝质量变差,常见是焊缝金属在一定温度下与空气中的氧、氮、氢等发生化学反应。 The first thing to be clear is that the so-called "oxidation" of the weld seam is just a common name. In theory, it means that the weld seam reacts with harmful components in the air to cause the weld seam to deteriorate. It is common that the weld metal is at a certain temperature. Chemical reaction with oxygen, nitrogen and hydrogen in the air.

“氧化”就是减少或者避免这类有害成分与高温状态下的焊缝金属接触,这种高温状态不仅仅是熔化的熔池金属,而是从焊缝金属被熔化时一直到熔池金属凝固并且其温度降低至一定温度以下整个时间段过程。 Preventing welds from being "oxidized" is to reduce or prevent such harmful components from coming into contact with the weld metal at a high temperature. This high temperature is not only the molten pool metal, but from the time the weld metal is melted to the melt. The pool metal solidifies and its temperature decreases below a certain temperature during the entire time period.

300℃以上时能快速吸氢,450℃以上时能快速吸氧,600℃以上时能快速吸氮,所以钛合金焊缝在凝固后并且温度降低至300℃以下这个阶段内均需受到有效的保护效果,否则就会被“氧化”。 For example, titanium alloy welding can quickly absorb hydrogen when the temperature is above 300 ° C, quickly absorb oxygen when the temperature is above 450 ° C, and quickly absorb nitrogen when the temperature is above 600 ° C, so the titanium alloy weld is solidified and the temperature is reduced to 300 ° C. Effective protection is required in the following stages, otherwise it will be “oxidized”.

1所示的旁轴侧吹保护气体,因为这种方式的保护方式相对于图2中的同轴保护方式的保护范围更广泛,尤其是对焊缝刚刚凝固的区域有较好的保护。 It is not difficult to understand from the above description that the blowing protective gas not only needs to protect the weld pool in a timely manner, but also needs to protect the area that has just been solidified after welding, so generally the side axis shown in Figure 1 is used Blow protective gas, because the protection method of this method has a wider protection range than the coaxial protection method in FIG. 2, especially the area where the weld has just solidified has better protection.

For engineering applications, not all products can use the side shield blowing method. For some specific products, only coaxial shielding gas can be used, which needs to be carried out from the product structure and joint form. Targeted choice.

Selection of specific protective gas blowing method

Straight weld

3所示,产品的焊缝形状为直线状,接头形式为对接接头、搭接接头、阴角角缝接头或者叠焊接头均可,此类型的产品均是采用图1所示的旁轴侧吹保护气体方式为佳。 As shown in Figure 3, the shape of the weld seam of the product is straight, and the joint form can be a butt joint, a lap joint, a female corner joint or a stacked welding head. It is better to blow protective gas on the shaft side.

激光焊接时如何正确用“气”

3 直线状焊缝 Figure 3 Straight weld

2. Plane closed graphic weld

4所示,产品的焊缝形状为平面圆周状、平面多边形状、平面多段线状等封闭型图形,接头形式为对接接头、搭接接头、叠焊接头等均可,此类型产品均是采用图2所示的同轴保护气体方式为佳。 As shown in Figure 4, the shape of the weld seam of the product is a closed pattern such as a plane circumference, a plane polygon, and a plane multi-segment line. The joint form can be a butt joint, a lap joint, a stacked welding head, etc. The coaxial shielding gas method shown in FIG. 2 is preferred.

激光焊接时如何正确用“气”

激光焊接时如何正确用“气”

激光焊接时如何正确用“气”

4 平面封闭图形状焊缝 Figure 4 Plane closed shape weld

The selection of shielding gas directly affects the quality, efficiency and cost of welding production. However, due to the diversity of welding materials, the selection of welding gas is also more complicated in the actual welding process. It is necessary to comprehensively consider the welding material, welding method and welding position. As well as the required welding effect, only a more suitable welding gas can be selected through welding tests to achieve better welding results.

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