Skilled welders throughout the welding sector use a wide variety of metals for different projects, with metals being selected based on their unique characteristics. Nickel is part of the transition metal elements and is characterised as being hard and ductile and because of this it is often used to create metal alloys. The most common metal alloy created from nickel is stainless steel, with 68% of globally produced nickel used to produce the steel alloy. Nickel is also used to create a range of high nickel alloys including Inconel and AL6XN which are both used in specialised welding projects.
This article will explore the use of nickel to create metal alloys and the different factors to consider when welding nickel alloy metals.
Stainless steel is made through the combination of common earth elements; the initial iron ore is mixed with nickel, carbon, nitrogen, manganese, silicon and chromium. Chromium gives stainless steel its characteristic corrosion resistance quality, higher levels of chromium causes a higher resistance. Nickel is added to steel to help increase the hardenability of the alloy; it also increases the toughness and ductility. Austenitic stainless steel is the most commonly used type of stainless steel, equating to 70% of stainless steel production, it is commonly used in construction projects due to its increased strength and anti-corrosion properties. Stainless steel is also chosen for its aesthetic surface finish as well as stainless steel being completely recyclable.
Inconel is a commonly used high nickel alloy, originally developed in the 1940s to be used in the development of the Whittle jet engine. Like stainless steel, Inconel has high corrosion resistance and can be used in a variety of extreme environments. When heated, the alloy forms a thick passivating oxide layer of protection, Inconel also retains strength at high temperatures. Other famous projects that utilised Inconel’s ability to withstand high pressures and kinetic energy include the Space Shuttle which has Inconel studs to secure solid rocket boosters and the Jaguar F-Type through an Inconel titanium exhaust system. With a similar high-nickel, high-chromium composition to Inconel, AL-6XN is often used in a variety of industries including chemical processing and oil and gas sectors.
Fusion welding can be carried out on most nickel alloys using a gas shielded process such as TIG or MIG. If the ambient temperature is above 5°C preheating is generally unnecessary – preheating may only be needed if there is risk of porosity from moisture condensation. Before welding, it is important to clean the nickel alloy, especially stainless steel, which is incredibly sensitive to the presence of carbon steel. As quenching can not harden nickel alloys, cooling rates are less important than carbon-based steel. Post-weld heat treatment is not required to restore corrosion resistance however it may be used to relieve stress and avoid stress corrosion cracking. The most important two factors in stainless steel welding are that care must be taken in cooling and heating stainless steel and it is important to match the welded material with filler materials.
Orbital Fabrications has a team of specialised welding experts with years’ of experience in performing high nickel and stainless steel welding.
Orbital Fabrications is a leading provider of specialist welding services including orbital welding, stainless steel welding and manual welding. Based in Cambridge, the team at Orbital Fabrications are welding specialists with over 25 years’ of experience delivering fabrication engineering services. Orbital Fabrications has completed high-tech fabrication projects for customers in a range of industries including the pharmaceutical, oil and gas and automotive sectors.
In addition to specialised welding, Orbital Fabrications also offers machining services and helium leak testing to support your project requirements. Due to a recent expansion of its facilities, Orbital Fabrications now boasts Class 6 and Class 5 cleanroom workstations. Through continued investment into staff and its facilities, Orbital Fabrications remains one of the leading welding companies in the UK.
If you would like more information on Orbital Fabrications’ high nickel alloy and stainless steel welding services, speak to a member of the team on 01480 464 066 or contact us here