Welding is a vital process in fabricating stainless steel products and structures, from food processing equipment to architectural elements. However, the intense heat involved can significantly alter the microstructure of stainless steel, affecting its strength, corrosion resistance, and mechanical properties. When our customers come to us for stainless steel products for their projects, our team will determine the best grades and alloys for their plans and projects. If those projects involve welding, different factors will determine the best products.
When stainless steel is welded, it undergoes rapid heating and cooling cycles. This thermal stress can cause grain growth in the heat-affected zone (HAZ), leading to reduced toughness. For austenitic stainless steels (like 304 and 316), welding can cause chromium carbides to precipitate along grain boundaries, a phenomenon known as sensitization. This depletes chromium in the affected areas, compromising corrosion resistance and making the steel more susceptible to intergranular corrosion, especially in corrosive environments.
Ferritic stainless steels can become brittle after welding due to grain coarsening. Martensitic stainless steels are prone to cracking because they form hard, brittle structures upon cooling. This weakness in the metal makes post-weld heat treatment necessary in many cases to restore ductility and relieve stresses.
Despite these challenges, certain stainless steel alloys are more weld-friendly than others. Austenitic grades such as 304L and 316L (the “L” stands for low carbon) are among the most weldable. Their low carbon content minimizes carbide precipitation, reducing the risk of sensitization and retaining corrosion resistance.
To preserve strength and structure during welding, it’s essential to use appropriate filler metals, minimize heat input, and consider post-weld treatments like passivation or annealing. Understanding the properties of each alloy helps fabricators maintain both the mechanical integrity and corrosion resistance of stainless steel components after welding.
At Alliant Metals, ensuring that our customers have the information they need to select the right stainless steel products for their projects is an essential part of our business. If your plans include welding, the alloy you choose could determine the success of your project.
