【Rayclass | 锐课堂】第11期：激光焊接，关于“气”的那些事，你都了解吗？

焊接过程中飞溅很大

焊缝成型不美观

焊接后出现大量气孔

这些焊接缺陷你是否也遇到过？当你还在考虑是不是因为激光焊接工艺参数设置问题时，你是否知道焊接保护气体的正确使用，也是影响焊缝成型及性能的重要因素，选择最佳焊接保护气体，其实是提高焊接质量和效率的方式。

A welding defect is any flaw that compromises the usefulness of a weldment. There is a great variety of welding defects such as cracks, distortion, inclusions, lack of fusion and incomplete penetration, lamellar tearing and undercut. It is well known that the correct use of welding shielding gas is also an important factor affecting weld formation and performance. Choosing the best welding shielding gas is a way to improve the quality and efficiency of welding.

既然焊接保护气体如此重要，那么：

Since the welding shielding gas is so important, then:

？

保护气体究竟有什么作用？

What is the role of shielding gas?

？

该如何选择保护气体的种类？

How to choose the type of shielding gas?

？

保护气体在焊接时应该如何吹入？

How should the shielding gas be blown during welding?

【Rayclass | 锐课堂】第11期

想跟你聊聊

关于“气”的那些事

Today,

we are going to talk about 

the shielding gas

保护气体的作用

the role of shielding gas

在激光焊接中，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 laser welding, the shielding gas will affect the weld formation, weld quality, depth of fusion and melt width. In most cases, the blowing of the shielding gas will have a positive effect on the weld and may also bring negative effects.

积极作用 Positive Effects

1）正确的吹入保护气体会有效保护焊缝熔池减少甚至避免被氧化；

Proper blowing of shielding gas can effectively protect weld molten pool from oxidation.

2）正确的吹入保护气体可以有效减小焊接过程中产生的飞溅；

Proper blowing of the shielding gas can effectively reduce the splash generated during the welding process;

3）正确的吹入保护气体可以促使焊缝熔池凝固时均匀铺展，使得焊缝成型均匀美观；

Proper blowing of the shielding gas can promote uniform spreading of the weld molten pool during solidification, so that the weld is uniformly formed and beautiful;

4）正确的吹入保护气体可以有效减小金属蒸汽羽或者等离子云对激光的屏蔽作用，增大激光的有效利用率；

Proper blowing of the shielding 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）正确的吹入保护气体可以有效减少焊缝气孔。

Proper blowing of shielding gas can effectively reduce weld porosity.

只要气体种类、气体流量、吹入方式选择正确，完全可以获得理想的效果。

As long as the gas type, gas flow rate, and blowing method are selected correctly, the desired effect can be obtained.

焊接样品 Welding Sample

但是

不正确的保护气体使用方式也会给焊接带来不利的影响

However,

Improper use of shielding gas can also adversely affect welding

1）不正确的吹入保护气体可能会导致焊缝变差：

Improper blowing of shielding gas may cause weld defects to deteriorate:

①选择错误的气体种类可能会导致焊缝产生裂纹，也可能会导致焊缝力学性能降低；

Choosing the wrong type of gas may cause cracks in the weld and may also result in reduced weld mechanical properties;

②选择错误的气体吹入流量可能会导致焊缝氧化更严重（无论是流量过大还是过小），也可能导致焊缝熔池金属被外力干扰严重造成焊缝塌陷或者成型不均匀；

Choosing 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 metal of weld molten pool to be disturbed by external force and cause the weld to collapse or form unevenly;

③选择错误的气体吹入方式会导致焊缝达不到保护效果甚至基本无保护效果或者对焊缝成型产生消极影响；

Choosing the wrong gas blowing method may cause the weld cannot achieving the protective effect or even the basic protective effect or negative impact on the weld formation;

2）吹入保护气体会对焊缝熔深产生一定影响，尤其的是薄板焊接时，会减小焊缝熔深。

Improper blowing of the shielding gas will have a certain effect on the weld penetration, especially when the thin plate is welded, the weld penetration will be reduced.

保护气体的种类

the type of shielding gas

常用的激光焊接保护气体主要有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 shielding gases commonly used in laser welding are N2, Ar and He, and their physicochemical properties are different, so their effects on welding seams are also different.

氮气N2

Nitrogen

N2的电离能适中，比Ar的高，比He的低，在激光作用下电离程度一般，可以较好的减小等离子体云的形成，从而增大激光的有效利用率。氮在一定温度下可以与铝合金、碳钢发生化学反应，产生氮化物，会提高焊缝脆性，韧性降低，对焊缝接头的力学性能会产生较大的不利影响，所以不建议使用氮气对铝合金和碳钢焊缝进行保护。

而氮与不锈钢发生化学反应产生的氮化物可以提高焊缝接头的强度，会有利于焊缝的力学性能提高，所以在焊接不锈钢时可以使用氮气作为保护气体。

The ionization energy of N2 is moderate, higher than Ar and lower than He. The ionization degree under the action of laser is general, which can better reduce the formation of plasma cloud and increase the effective utilization rate of laser. Nitrogen can react with aluminum alloy and carbon steel under a certain temperature to produce nitrides, which will improve the brittleness of the weld and reduce the toughness and have a great adverse effect on the mechanical properties of the welded joints. In consequence, nitrogen is not recommended to protect the welding seams of aluminum alloy and carbon steel. Nitrogen compounds produced by chemical reactions between nitrogen and stainless steel can improve the strength of welded joints, which is conducive to the improvement of mechanical properties of welded joints. Therefore, nitrogen can be used as a shielding gas when welding stainless steel.

氩气Ar

Argon

Ar的电离能相对最低，在激光作用下电离程度较高，不利于控制等离子体云的形成，会对激光的有效利用率产生一定的影响，但是Ar活性非常低，很难与常见金属发生化学反应，而且Ar成本不高，除此之外，Ar的密度较大，有利于下沉至焊缝熔池上方，可以更好的保护焊缝熔池，因此可以作为常规保护气体使用。

The ionization energy of Ar is relatively low, and the degree of ionization is high under the action of laser, which is not conducive to control the formation of plasma cloud, which will have certain influence on the effective utilization of laser. Nevertheless, the activity of Ar is too low to chemically react with common metals. The cost of Ar is also not high. Moreover, the density of Ar is large, which is favorable for sinking above the weld molten pool and can better protect the weld molten pool, so it can be used as a conventional shielding gas.

氦气He

Helium

He的电离能最高，在激光作用下电离程度很低，可以很好的控制等离子体云的形成，激光可以很好的作用于金属，而且He活性非常低，基本不与金属发生化学反应，是很好的焊缝保护气体，但是He的成本太高，一般大批量生产型产品不会使用该气体，He一般用于科学研究或者附加值非常高的产品。

The ionization energy of He is the highest, and the ionization degree is very low under the action of laser, which can well control the formation of plasma cloud, and the laser can well act on metal. Moreover, He is very low in activity and hardly reacts with metal, making it become a good weld shielding gas. But, the cost of He is too high to use in general mass-produced products. As a result, He is generally used in scientific research or products with high added value.

保护气体的吹入方式

the blowing method of shielding gas

保护气体的吹入方式目前主要有两种：一种是旁轴侧吹保护气体，如图1所示；另一种是同轴保护气体，如图2所示。

There are two main ways to blow the shielding gas: one is the side blowing shielding gas, as shown in Figure 1, and the other is the coaxial shielding gas, as shown in Figure 2.

图1 旁轴侧吹保护气体 Figure 1. side blowing shielding gas

图2 同轴保护气体 Figure 2. coaxial shielding gas

两种吹入方式具体该怎么选择是多方面综合考虑的，一般情况下建议采用侧吹保护气体的方式。

How to choose the two blowing methods is a comprehensive consideration in many aspects. In general, it is recommended to use side blowing shielding gas.

保护气体吹入方式选择原则

Principles for selection the blowing methods of shielding gas

首先需要明确的是，所谓的焊缝被“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。

Theoretically, the chemical reaction between the weld and the harmful components in the air causes the weld quality to deteriorate. It is common for the weld metal to react chemically with oxygen, nitrogen, hydrogen, etc. in the air at a certain temperature.

防止焊缝被“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。

To prevent the oxidation of the weld is to reduce or avoid the contact between these harmful components and the weld metal at high temperature. This high temperature state is not only the molten pool metal, but also the whole process from the period of weld metal is melted until the molten pool metal solidifies and its temperature drops below a certain temperature.

举例

比如说钛合金焊接，当温度在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”。

Taking titanium alloy welding as an example, when the temperature is above 300 °C, it can absorb hydrogen rapidly. When it is above 450 °C, it can absorb oxygen quickly. When it is above 600 °C, it can quickly absorb nitrogen. Consequently, the titanium alloy weld is subjected to effective protection after solidification and the temperature is lowered to below 300 ° C, otherwise it will be oxidized.

从上述描述不难明白，吹入的保护气体不仅仅需要适时对焊缝熔池进行保护，还需要对已经焊接过的刚刚凝固的区域进行保护，所以一般均采用图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 of the shielding gas not only requires timely protection of the weld molten pool, but also the protection of the newly solidified area that has been welded. In consequence, it is generally used side blowing shielding gas as shown in FIG.1 because the protection of this method is more extensive than the coaxial protection method in Figure 2 especially for the area where the weld has just solidified, it has better protection. 

旁轴侧吹对于工程应用来说，不是所有的产品都能够采用旁轴侧吹保护气体的方式，对于某些具体的产品，只能采用同轴保护气体，具体需要从产品结构以及接头形式进行有针对性的选择。

For engineering applications, not all products are capable of using side blowing shielding gas. For some specific products, only coaxial shielding gas can be used, which requires specific selection from product structure and joint form.

具体保护气体吹入方式的选择

The choice of specific shielding gas blowing method

1）直线焊缝 straight bead

如图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 welding seam of the product is in a straight line, and the form of the joint is either butt joint, lap joint, butt joint or lap joint. This type of product is preferred for using side blowing shielding gas as shown in FIG 1.

图3 直线状焊缝 Figure 3. straight bead

2）平面封闭图形焊缝 closed shape weld in 2D

如图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 welding seam of the product are closed graphs such as plane circumferential shape, plane multilateral shape, plane multi-segment linear shape. The form of joint is butt joint, lap joint and lap welding head. This type of product is preferably using coaxial shielding gas as shown in FIG. 2.

图4 平面封闭图形状焊缝 closed shape weld in 2D

保护气体的选用直接影响到焊接生产的质量、效率及成本，但由于焊接材质的多样性，在实际焊接过程中，焊接气体的选用也比较复杂，需要综合考虑焊接材质、焊接方法、焊接位置，以及要求的焊接效果，通过焊接测试才能选择更适合的焊接气体，达到更佳的焊接结果。

The choice of shielding gas directly affects the quality, efficiency, and cost of welding production. Nevertheless, due to the diversity of welding materials, the selection of welding gas is also complicated in the actual welding process, and it is necessary to comprehensively consider the welding material, welding method, welding position, and required welding effect. Through the welding test, the most suitable welding gas can be selected to achieve the best welding result.

作为2019年的

第一期【Rayclass | 锐课堂】

我们还是从市场前景广阔的焊接说起

不光是激光器本身的选择

我们还提供应用解决方案

想看哪些关于光纤激光器

使用、应用分享、测试方案

也可以直接写留言告诉我们

相关阅读：