Vacuum Weld Details And Why They Must Not Be Overlooked

Welding, a process that dates back to the Iron and Bronze ages, has evolved into a highly specialized procedure that provides innumerable benefits across a range of industries and applications. The process is being used to join or create small and large components, and its success has largely been attributed to vacuum solutions. From being able to give out superior quality to high precision, vacuum welding has many important benefits that explain why companies in the fields of electrical engineering, automotive, medical technology and many others are relying on it for their everyday operations.

For vacuum welding to be as successful as it should be, there are certain factors that you need to be meticulous and cautious about. They include the following:

Materials’ vapor pressure

Any material in a vacuum system contains an intrinsic vapor pressure. In other words, gas load emanates from the materials’ evaporation at varying levels depending on the material. If you want to achieve good welding results, you need to avoid materials that produce high vapor pressure as much as you can. Essentially, you want to reduce the evaporative gas load at any given time to the requisite minimum. Some of the materials that you should avoid include:

Lubricants, pump fluids and greases

When exposed to a vacuum environment, these substances tend to evaporate at a certain rate depending on the total surface area of the exposed material and temperature. Actually, they keep evaporating until they’re completely gone. That means that also assessing these materials’ total volume is critical.

Metallic materials

There are certain metallic materials that usually contain high vapor pressure, such as cadmium or zinc. It’s easy, for instance, to use zinc or cadmium-plated screws within a vacuum chamber. Doing so can lead to both gas load and material transfer, leading to cross contamination.

Why this is important

We know that gas load= pumping speed x pressure. That means that at any given pumping speed, the gas load will determine the pressure in the system. So, having a higher than usual gas load can create unnecessarily high pressure and mess up your project. One of the best ways of managing the gas load is understanding all the possible gas load sources in the system.

Integral leak tests

In vacuum welding, we’ve noted that having the correct operating pressure is critical. One of the most important factors you need to check, therefore, is the tightness of the system. It’s important to carry out an integral leak test with the pressure rise method. Just remember that a pressure rise can arise from other factors, such as surface desorption and internal leakages. To avoid any falsification of the results, ensure the chamber is clean, dry and empty while performing the test. This is very important if you want to achieve high performance and safety in the system. Moreover, remember that leaks can reduce the system’s and product’s reliability tremendously. What kinds of techniques are available for vacuum testing?

• Helium vacuum testing
• On stream leak testing
• Vacuum box testing

Why this is important

Incorporating a helium leak detector from High Vac Depot in your vacuum testing can, for instance, reduce production loss, speed up the process, verify the components’ integrity and maintain efficiency in the vacuum system. Under no circumstances should you overlook the relevance integral leak tests.

Oxide layers

Metals usually contain a layer of oxide, which is usually considered a barrier that prevents the diffusion of atoms between the pieces of metal during welding. Under normal circumstances, most metals always have a certain type of oxide layer on all their exposed surfaces.
In cold welding, you have to remove this oxide layer along with other contaminants, such as dust and grease, on the metals through wire brushing, degreasing, and other methods.

Why this is important

Aluminum and Magnesium are examples of metals that are highly sensitive to oxidation. When pure aluminum combines with air, it forms a layer of aluminum oxide or alumina. This layer is not only hard, but refractory and insulate as well. Its melting point is extremely high compared to pure aluminum (2071 degrees Celsius versus 660 degrees Celsius).

This thin layer of aluminum oxide easily restricts the free and steady flow of electrons to or from the base plate, preventing the stabilization of the arc in arc welding. Moreover, the alumina remains solid while the base aluminum melts down, preventing the molten filler metal from mixing with the melted base metal. This results in a poor coalesce.

This means that overlooking the aspect of the oxide layer in your metals can lead to negative consequences.

Gauges and valves

Vacuum gages are typically used to measure pressure in your vacuum. These gadgets are required to determine the chamber’s vacuum level at any given time. One of the secrets to success in vacuum welding is having the high quality, accurate gauges. Your ideal gauge should be able to withstand temperatures of up to 450 degrees Celsius and a pressure range of up to 10-11 torr. Also, you need to confirm that each of your gauges contains two independent filaments so that the pressure measurement is not affected when one filament fails.

For a vacuum to remain in a closed system, you need to have effective vacuum valves. A good valve can enable efficient control of gas flow into the chamber, facilitate venting, isolation, and control conductance. You need to pick valves that can withstand temperatures of up to 450 degrees Celsius. You should also make sure that their design allows operation in any form of orientation. Last but not least, your valves need to accommodate pressure levels of up to 10-8 torr. You can source such valves and gauges from High Vac Depot or another reputable vendor.

Why this is important

Having a substandard or faulty gauge can easily get the welding process out of control and make the calibration procedures extremely difficult. Moreover, using poorly selected valves can lead to unwarranted leaks, loss of energy and poor performance.

Regardless of the industry you’re in, as long as you’re relying on vacuum systems for your welding projects, you need to be extremely sensitive on the processes involved. That means that you should avoid overlooking certain details, including the oxide layers, the materials’ vapor pressure, the importance of leak tests and the quality of your gauges and valves.

High Vac Depot has the answers to all of your vacuum related questions

As always, if you need to chat with an expert about any vacuum solutions for your industrial or research process, feel free to contact us anytime!