Electron Beam welding VS Laser Beam Welding

Introduction

As a welder, you’ll hardly escape the tricky issue about which welding method to use between Electron Beam Welding (EB) and Laser Beam (LB) Welding. Some welders vouch for the latter while others go for the former. Another group feels it’s all a matter of the welding particularities.

The last group contends that in the Electron Beam welding VS Laser beam welding debate, the choice you make depends on several factors, including what metals one is welding.

So the question of Electron Beam VS Laser Beam welding remains. This issue is the focus of this article. But for starters, it’s essential to get the primary differences between these two approaches to welding first. In doing so, we are not trying to turn you into a physics guru; that’s why we describe these processes in as simple a language as possible.

This understanding will help you appreciate the arguments for and against each of the two welding methods. The knowledge from this is vital; empowers you to know when and how to select the appropriate welding method for each of your welding projects

Electron Beam Welding

This is a process that uses electrons generated by an electron gun to achieve the welding feat. These electrons are then accelerated to super-high speeds using electrical fields. The stream of particles on high speed is then tightly focused and applied to the metals to be joined.

The beam of electrons creates a lot of kinetic energy as it hits the workpieces, causing the metals to melt and bond together.

An interesting fact about EB welding is that it can only be done in a vacuum.

The reason is that the presence of any gas during the welding process makes the beam scatter and diffuse the electrons. This, in turn, weakens the electrons and lowers the amount of kinetic energy necessary to melt the metals.

EB welding is therefore done in a vacuum chamber. This, requirement, of course, means the size of what you want to weld using this method is strictly restricted to the size of the vacuum chamber at hand.

Vacuum chambers can be large or small, but larger chambers require a longer time to establish the correct vacuum level. The need to use a vacuum, and the presence of X-radiation eliminates any human handling in the welding process. That’s why the entire EB welding process is externally controlled (there’s no human physical interference in the chamber).

Devoid of direct human interference, the process is generally controlled using CNC tables.

Over the years, EB welding has become fully automated. Since EB welding is a fusion welding process, it requires an exact fit between the parts that need to be welded. Material filler, standard in other less-technical methods of welding, is generally not needed or used in this process.

The parts to be welded must be securely fixture to a specialized table to precisely move the edges and surfaces to be welded so that they are in contact with the high-speed electron beam. Secure fixture serves another equally important purpose – it reduces warping and the effect of shrinkage during the welding process.

As if that is not enough already, the high-speed electron beam must be carefully calibrated, focused and times precisely using the CNC motion for it to deliver a consistent weld with minimal porosity and uniform penetration.

Even with all that, the process is not over yet. In each welding cycle, you have to load the welding chamber, pump down the vacuum, weld the part, and lastly, vent the vacuum chamber.

It’s clear the ingredients of this technology, namely: the vacuum environment, high voltage, and high-tech automation- mean the process requires well-trained and skilled operators. Besides, no one can refute the fact that the whole system requires very competent maintenance. All this means that getting up and running an EB welding system can be very costly.

The challenging bits of this process are the pumping down of the chamber and the loading and unloading of the parts you are welding. The technician and engineers should maximize the number of parts that can be welded in each cycle. When done correctly, this method of welding can deliver cost-effective and high-quality welds.

Interestingly this is probably one of the realities that make EB welding quite popular. EB welding systems can weld any weld-able metal as well as some of the metals that are generally not typically weld-able.

EB welding can be used to join dissimilar materials such as Iron and Copper which would be un-weld-able due to varying melting points. This variation typically causes intermetallic compounds which cause unwanted brittleness.

EB welding melts the lower melting point material onto the un-melted material with a higher melting point resulting in a vacuum-tight, compact weld.

Laser technology is a later development was developed sometime in the early 1960s, and by the middle of that decade, Carbon Dioxide lasers were already in use in the welding industry. By the mid-1970s, automated welding gained ground in the industry.

Laser welding uses a laser beam to form a weld that joins together metals or thermoplastics. Simply, this technology works by quickly raising and lowering the energy state of the target material. This process causes the emission of photons.

The photons are concentrated and lined up with each other and then projected. This action makes radiant heat, which melts the target material.

A cover gas is handy in this type of welding. This gas keeps oxygen out of the area you are welding and improves efficiency and weld purity. Not every gas is ideal for use as a cover gas; instead, the type of gas used will depend on the type of material being welded, the type of laser, and the specific type of application.

Hermetic sealing, for instance, requires an environment that is completely controlled. To create such an environment requires the use of the welder to use a sealed glove box.

Although in recent years, laser welding in a vacuum has taken ground, it is yet to be entirely accepted in the welding industry.

 Major Challenge of Laser Welding

Reflectivity is the most critical challenge with laser welding. The process works by focusing the laser’ beams light and energy on the target part and joint. Some materials tend to reflect some of this light and heat away from the point of focus.

This reflection minimizes the penetration of the beam and damages the material close to the weld joint.

However, there are some ways to overcome this challenge. The first method involves pulsing the laser; in other words, the laser’s energy is varied to break the surface. This method is useful because it minimizes the amount of heat applied on the weld surface, thus limiting part of the deformation.

Alternatively, they can use a continuous wave or CW; this means applying a constant laser beam on the target surface. CW lasers are useful when applying cutting applications or when the welding speed is crucial.

 Uses of Laser Beam Welding

You can easily use laser beam welding to join crack-prone materials, including aluminum and certain types of steel. And, just like EB welding, you can use laser beam welding to join dissimilar materials.

Since lasers are great at applying minimal heat to a surface, it can be the right choice if you are welding electronic packages, more so if they are hermetically sealed. Laser beam welding is also a popular choice for medical device applications. The reasons for this are that the welds can be quite tiny and cause minimal discoloration of the piece.

Also, you can apply the weld without having to use any secondary machining.

Well, as you might have sensed, there is no clear-cut answer to this question. As you can see, each of these two methods has its ups and downs. So, the best solution is that your choice of welding method will depend on the particular circumstances of the application.

Typically, many welders look to laser welding for a new application. This choice is informed by the fact that laser welding is far less expensive than Electron Welding. Moreover, with laser welding, it’s easier to tool and fixture the parts.

If deeper penetration is of paramount importance, like when you are welding metals that have a high thermal conductivity such as copper, then EB welding takes precedence. Laser welding can only penetrate up to about 0.020 inches in copper. An EB machine, on the other hand, can deliver a penetration of up to 0.500 inches of the same material.

When welding dissimilar materials, it’s good to note that different materials weld better with laser beam welding while others respond better to EB welding.

In reality, although there isn’t any significant difference between the two welding processes in terms of quality, requirements on quality standards and specifications can easily dictate which method to use.

EB welding showed up earlier than laser welding. As such, the quality standards and specifications for this method are quite elaborate and widely accepted. These requirements control all the aspects of this process, such as cleaning, joint design, machine qualification, vacuum requirements, inspection criteria, and operator training.

The quality standards and specifications for laser beam welding are not that elaborate. The engineer thus has to go the extra mile and personally seek to understand all the aspects of this process to make sure all the laser beam welding operations are correctly done.

In general, EB welding is an excellent choice if you want to join advanced materials such as semiconductors, medical devices, and items used in aerospace. On the same note, processes and applications of laser beam welding are quite common in the automotive industry and small medical and jewelry manufacturing. However, these are just generalizations, not prescriptive conclusions.

As earlier said, making value judgments as to which of the two welding methods is the best to use can be misleading. Remember, each welding case is unique, and so are the requirements. For instance, if you want to weld titanium, EB welding might be the best choice – but if the part you intend to weld can’t fit in a vacuum chamber, then the method becomes unsuitable.

Conversely, if you are welding small parts, laser beam welding might work very well, but part heat sensitivity might make EB welding a better choice.

To make it more comfortable for you to decide which between the two methods is the most appropriate, consider the following critical factors:

  • Cost-effectiveness

When it comes to cost-effectiveness, its obvious laser welding gets the crown; it’s far cheaper to weld using this method than to use EB welding.

  • Quality of weld joint

If you want best-quality weld joints, you simply go for EB welding.

  • Production Speed

With the right fixturing and the right parts, EB welding can deliver high production speeds that meet your speed requirements.

  • Aesthetic appeal

While laser beam welding can make beautiful, clean welds when done on the right materials and appropriate setup, it won’t give you the kind of weld joint that EB welding produces.

These two welding methods offer some similarities, as well as some marked differences. A close look at the features and operational requirements reveals that both are excellent approaches to welding. However, due to the unique needs of each of these methods, both are not equally suitable for every project.

On the Electron Beam Welding VS Laser Beam Welding debate, it is clear there is no clear-cut front-runner between these two welding methods. Each method has its pros and cons. However, both EB welding and Laser welding processes are versatile, flexible, and if applied correctly, each can make reliable and enduring welds.

What you need to do is to take note of the unique requirements of each welding project. Once these requirements are precise, factor in the particularities of these processes and use your informed knowledge to determine the best welding method to use.

In a nutshell, each of these welding methods has its pros and cons. The unique particularities of each welding project should guide you in choosing the most appropriate welding method.

 

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