Helium Conservation

It’s time to re-evaluate our dependency on helium and revise our strategy.

By Bryan C. George

Helium is currently, and for the foreseeable future, in rather short supply due to a number of issues that relate to plant shutdowns, dwindling reserves and weather-related problems. New sourcing opportunities are slow to bring on line, and global availability is in tight supply. The demand for helium is up over 80 percent over the past 20 years or so, with technologies such as arc welding, leak testing, laser welding, heat treating, party balloons, nuclear magnetic resonance and other high-demand users of helium in the research and medical fields consuming ever increasing volumes. We as an industry need to re-evaluate our dependency on this product, while at the same time, revise our strategy from an applications standpoint.

Helium is also a monatomic, inert gas, most commonly used for GTAW welding on non-ferrous materials. In contrast to argon, helium has a high conductivity and ionization potential, which gives the opposite effects. Helium will give a wide profile, good wetting on the edges of the bead and higher heat input than pure argon. The high ionization potential can create difficulty in arc starting unless high frequency or capacitive arc starting is used for GTAW. Somewhat higher flow rates are recommended due to the tendency of the gas to rise in air. Pure helium promotes globular transfer and is almost never used for GMAW (with the exception of pure copper).

Traditional Delivery and Procedures
With the advent of Lean Manufacturing and a more concentrated effort to trim the waste and excess costs out of fabrication processes, it becomes abundantly clear that revisions to decades-old delivery systems and procedures need to be addressed. Typically, more volume of gas is needed when utilizing helium, as the gas is considerably lighter than say argon. The welding industry has for many years relied on shielding gases that have been the industry norm for decades, without a significant motivational rationale for evaluating and embracing alternative compositions to any great extent.

Some of the more common helium mixes used for arc welding are shown in the table below.

Technology Reduces Dependence
Many of the major suppliers of welding gases in the United States have divested the cylinder side of their business with the consequence that much of the information that is available in the global market does not find its way to the U.S. distributor market. At the same time, keeping abreast of the changes in accessibility and cost of the raw materials necessary to blend and supply these products becomes an ongoing challenge.

Fortunately, there are advances in technology that reduce our dependence on some of the more scarce raw materials such as helium, while at the same time being more closely suited to the applications for which they were intended. There is an evolution toward compositions developed specifically for the welding of stainless steels and aluminum where the traditional mix compositions have required higher concentrations of helium.

An example of a composition that falls into this category is the traditional composition for the short arc welding of stainless steels, 90%He / 7.5%Ar / 2.5%CO2. This has been the shielding gas of choice for decades throughout our industry in the United States. When welding on the lighter materials, the increased heat input provided by the helium has a material effect on the distortion levels, burn-through, suck back and color match. It also can have detrimental effects on the mechanical properties of the base material.

The ionization potential of helium is 24.5 eV, meaning that it takes a considerable amount of voltage to properly transfer the metal across the arc, translating into additional heat input. With this additional amount of heat input into the base material, problems with distortion, color match, mechanical properties and cleaning become much more prevalent.

One of the main objectives in the joining of stainless sheet is to keep the heat input of the process to a minimum, thereby reducing the detrimental effects of distortion and burn through. At the same time, one needs to have enough fluidity of the puddle resulting in acceptable tie in at the toes of the weld.

Reducing the percentage of both the helium and the CO2 components in the mix by as much as 70 percent extends the usable parameter range of the mix.

Shielding Gas and Specialty Mixes
Traditionally, there have been two shielding gases for GMAW welding of the stainless: 90%He / 7.5%Ar / 2.5%CO2 for short circuit transfer, and 98%Ar / 2%O2 for spray transfer. The ability to weld in both the short circuit transfer as well as the spray transfer with a single-gas blend opens up a wealth of efficiencies in the process.

In addition, there are alternative compositions available that expand the range of applications to which these compositions can be applied. These would also curtail the need for the additional helium. Materials such as inconel, monel and hastalloy are materials that can be very effectively joined with resultant higher mechanical properties, reduced burn-through and distortion, as well as an excellent color match.

Specialty mixes have been developed for these higher nickel content materials, utilizing small components of H2 along with micro additions of CO2 for such alloys as 625 Inconel.

Shielding gases that are employed in the welding of aluminum, particularly on the heavier sections, traditionally have utilized increasing amounts of helium as the thickness of the base material increases. This increase in helium destabilizes the arc plasma to some extent, producing a larger, more volatile droplet transfer. This can, in some cases, increase the possibility of porosity if attention to voltage is not carefully monitored. By reducing the amount of helium, with minute additions of an alternative component to the mix, the arc can be stabilized, reducing dependency on the helium.

Reduce Reliance
These are but a few examples of technologies that are capable of increasing throughput and efficiencies in production, while maintaining high levels of quality. At the same time, one can reduce reliance on helium within certain aspects of the welding process and extend the capabilities of many of these applications.

In the spirit of Lean Manufacturing, the effects on productivity, efficiency and quality are all significant components of changes to industry norms, enhancing the profitability of the manufacturing process as it relates to welding, while at the same time dealing with the challenge of cost and availability of our natural resource, helium.