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How Laser Power Affects Welding: Explained

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Are you interested in mastering the principles of selecting laser power and its impact on the quality of laser welding? Look no further!

In this article, we will explore the weld forming factor, how to calculate it, and the basis for selecting laser output power during laser welding.

We will also discuss the effects of decreasing laser output power on weld penetration and achievable welding speed.

Whether you’re a seasoned professional or just starting out, this article will provide valuable insights and knowledge to help you improve your laser welding skills.

So, let’s dive in and discover the world of laser welding!

Read this article with the following questions:

  • What is the weld forming factor? How to calculate?
  • What is the basis for selecting laser output power during laser welding?
  • What are the effect of decreasing laser output power on weld penetration and achievable welding speed?

1. Principle of double beam welding

Classification of laser welding

1) According to power density and weld formation characteristics:

  • Heat conduction welding: power density (laser output power / focal spot area) < 105W/cm2
  • Deep penetration welding: power density > 106W/cm2

2) According to the laser output mode:

Schematic diagram of pulsed laser welding and continuous laser welding

Fig. 1 Schematic diagram of pulsed laser welding and continuous laser welding

2. Selection of laser power P

The choice of P (laser power) is based on the thickness of the plate. P determines the power density of the spot and influences both the penetration depth and the welding speed.

Curve of power density and metal temperature with time

Fig.2 Curve of power density and metal temperature with time

3. Effect of laser power on penetration

As illustrated in the figure, the greater the power (P/kw), the deeper the penetration, and vice versa.

Relationship between laser penetration and power

Fig. 3 Relationship between laser penetration and power

4. Influence of laser power on welding speed

Supplementary knowledge points:

The form factor of a weld is defined in GB/T3375-1994 as the ratio of the weld width (B) to the calculated weld thickness (H) on the cross-section of a single weld (φ = B/H), as shown in Figure 4.

A small form factor results in a narrow and deep weld. However, the center of the weld tends to have higher concentrations of impurities and poor thermal crack resistance due to regional segregation. Therefore, the form factor should not be too small.

For example, the form factor of the weld should be greater than 1.3, meaning the width of the weld should be at least 1.3 times the calculated thickness of the weld.

Laser power and speed determine the forming of weld

Fig. 4 Laser power and speed determine the forming of weld

Relationship between welding speed and laser power

Fig. 5 Relationship between welding speed and laser power

5. Relationship between laser power, welding speed and penetration

Changes of penetration and welding speed of low carbon steel under different power

Fig. 6 Changes of penetration and welding speed of low carbon steel under different power

Summary:

The laser welding power determines the power density of the spot and controls the penetration depth and speed of welding. As the laser power increases, both the welding speed and penetration depth increase.

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