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Products made from specialised materials demand a lot from a machine shop. West Welding has the opportunity to use various specialised materials in production of which we have gained experience in various applications over the years. Specialised materials are an essential part of industrial sectors that require extreme temperature and corrosion resistance, as well as other specialised properties. These materials include, for example titanium, 310S stainless steel, and duplex steel.

The use of specialised materials in industry requires a precise understanding of their properties and handling. Our manufacturing experts, production manager Matti Tuomisto, along with welding coordinator and project manager Esa Ristiluoma, provide more information about their machining, welding, and best usage practices.

Titanium is an extremely lightweight and durable material, but not many machine shops can handle its welding

According to West Welding’s production manager, Matti Tuomisto, titanium is still a relatively unknown material in industry, but it is an excellent material for manufacturing due to its properties. Titanium is light, highly resistant to corrosion and erosion, and it has excellent tolerance to high temperatures. However, due to its hardness, it is one of the most challenging materials to work with, especially when it comes to cutting titanium. 

“Another challenge is that titanium should not be worked with sparking tools,” adds West Welding’s project engineer Esa Ristiluoma.

However, perhaps the biggest challenge in working with titanium is related to welding conditions. Conditions must be exceptionally clean when welding titanium.

“Titanium is certainly the most critical material in terms of cleanliness,” Ristiluoma explains. “There should be no oxide film, grease, or any other impurities on the surface of titanium during welding. The better the surface is cleaned before welding, the easier and higher quality the welding will be.”

In addition to ensuring the cleanliness of the titanium surface, all forms of contamination with other materials must be avoided.

“For example, when grinding carbon steel with an angle grinder, caution must be taken not to expose the titanium material to the spark spray, as it would cause titanium contamination. The work area must be well protected from external risk factors,” Ristiluoma says.

For this reason, the use of titanium limits the welding processes. The most sensible approach when working with titanium is to use either TIG welding, TIP-TIG welding, or plasma welding, all of which are available at West Welding.

Another critical aspect of working with titanium, in addition to taking care of the cleanliness, is the gas shielding of the finished weld. In this respect, titanium differs from other materials because it requires both the shielding gas from the welding torch and post-weld protection.

“The temperature of the finished weld must drop to a certain level to prevent it from reacting with oxygen,” Matti Tuomisto explains. “Otherwise, the weld will be ruined.”

Full Titanium or Titanium-Coated Device?

Titanium is typically chosen as the material when the process in use is highly corrosive or demanding, and no other material is durable enough. Titanium is particularly suitable for the mining and chemical industries due to its properties. It is used, for example, in storage tanks, process tanks, and heat exchangers. However, for high-pressure equipment, titanium alone is not very suitable because its tensile strength is low.

“However, the most effective way to use titanium in high-pressure equipment is to apply it as a coating in combination with a pressure-bearing carbon steel frame to combine the best qualities of both materials,” Ristiluoma clarifies.

“The most efficient method for coating welding is powder arc welding, which uses a strip-like welding additive to create a wide seam on the material,” says Ristiluoma.

Coating welding can also be successfully performed with other coating and base materials used by West Welding, such as Inconel 625 and stainless steel 316L.

 Titanium is also frequently used as a compound sheet, especially in large process tanks.

“The core of the compound sheet is made of black carbon steel, and titanium is attached to the inside by explosive bonding. This way, the inside is made durable,” explains Esa Ristiluoma.

On a case-by-case basis, we evaluate with the customer when it is worthwhile to use a fully titanium device or a device with a titanium coating.

Stainless Steel 310S Handles Heat Exceptionally Well

Stainless steel 310S is a heat-resistant austenitic stainless steel from which West Welding has manufactured, for example, sulphuric acid equipment for the mining industry.

 “Steel 310S can withstand both heat and corrosive materials well. At West Welding, we have designed equipment from this material for use at temperatures of up to 500 degrees Celsius,” says Matti Tuomisto.

 However, stainless steel 310S is a material that can be sensitized easily, which means that there are limits to which welding processes can be used.

“Similar to titanium, TIP and TIP-TIG welding methods are the best alternatives when working with stainless steel 310S. Powder arc welding can also be used, but it requires special measures. Additionally, stainless steel 310S requires a special additive for welding,” Matti Tuomisto explains.

Another crucial aspect to consider when working with stainless steel 310S is that the material must be rapidly cooled to a specific point.

 “For this reason, both heat input and the amount of molten weld must be kept to a minimum,” Matti Tuomisto emphasizes.

S301Duplex Steel Offers Excellent Corrosion Resistance

Duplex steel has higher strength than some other austenitic materials, and in certain applications, its corrosion resistance is particularly good. Duplex steel is used extensively in the paper and oil industries, especially in the evaporators of pulp mills.

However, welding duplex steel is more challenging than welding normal austenitic materials.

“The molten weld is quite stiff, making it less welder-friendly. Additionally, heat input must be kept within certain limits to ensure a high-quality weld seam,” says Esa Ristiluoma.

Both stainless steel 310S and duplex steel have in common that the temperature between weld blocks must be kept low. For stainless steel 310S, this means a maximum of 100 degrees Celsius, and for duplex steel, a maximum of 150 degrees Celsius.

Both materials also present challenges in terms of inspection techniques. Using both ultrasound and X-rays for inspections can be difficult.

“Ultrasound is challenging for austenitic materials because it requires the creation of custom calibration samples, which must be made the same way as the weld itself, so the manufacturer needs to create a calibration piece for each weld,” Ristiluoma explains.

For this reason, X-rays are usually preferred for inspections of stainless steel 310S and duplex steel, if possible. However, if the joint design is such that it cannot be inspected with X-rays, ultrasound must be used.

At West Welding’s machine shop, even very thick materials can be handled. 

When talking about specialised materials, an important aspect to consider is also the use of thick materials.

Matti Tuomisto mentions that West Welding has welded up to 140 mm thick materials. 

Esa Ristiluoma adds that as materials get thicker, preheating is necessary, and welding thick materials is best done using a powder arc with multiple wire feeds. Additionally, the optimal shape of the weld joint should be considered on a case-by-case basis.

Handling specialised materials in industry requires careful expertise and understanding. West Welding has a wealth of experience and expertise in demanding applications over many years. Our experts are ready to assist in choosing the right materials and processes for every need.