Factors to Consider When Welding Dissimilar Metals

Blog | January 31st, 2020

Usually, the process of metal welding takes two similar metals. The welding of the said metals is easier since similar metals share the same chemical and mechanical properties. Dissimilar metals, on the other hand, have varying factors that make the welding process different from welding similar metals. The act of welding dissimilar metals is vital to construction and other industries since they normally use different types and kinds of metal.

As mentioned, numerous varying factors must be considered in welding dissimilar metals.

Solubility

One common problem in welding two different metals is their solubility. Solubility is a chemical property of a metal that pertains to the ability of a metal to solute or dissolve in a solvent. The solubility of the two dissimilar metals must be mutual so that the welding process can be successful. Otherwise, the welding process will fail if the two dissimilar metals cannot be dissolved together.

Corrosion

Corrosion can start on the area where the two dissimilar metals meet. The use of an electrochemical scale helps you determine a metal’s susceptibility to corrosion. If the two metals are on the different sections of the said scale, then their mixture will yield a high level of susceptibility to corrosion.

Inter-metallic Compounds

Successful welding of two different metals may produce a single metal that has inter-metallic compounds. Having inter-metallic compounds changes the overall structure and properties of a material. Some changes include the crack sensitivity, resistance to corrosion, and ductile ability. To make welding dissimilar metals work, a buttering layer is used to provide compatible weld metal between two dissimilar metals.

Weldability

Apart from being soluble, the involved dissimilar metals must have the ability to be successfully welded together. Poor weldability results in cracks and other types of damages and irregularities on the property of a newly welded metal. Since each type of metal has its own set of properties, one must know the weldability level of the involved dissimilar metals. Once the weldability of the metals is determined, a set of buttering layers or filling metals can help make the welding successful.

Calculating for the carbon equivalency (CE) can help you determine the temperature that is needed to use before, during, and after the welding process. CE also measures how susceptible your newly welded metals are to cracking. The chemical make-up of the dissimilar metals is also important before welding them since they possess different chemical and mechanical properties that can affect the overall welding process.

Thermal Expansion

As the welding process goes on, the shape of the involved metals changes according to the temperature changes. The coefficient of thermal expansion is crucial to determine the shape changes of your metal. If the coefficient of thermal expansion between two dissimilar metals is far too different from each other, then expect a greater internal residual stress once they are welded together. This residual stress can significantly reduce the operating life of your newly welded metal.

Melting Rate

Aside from different thermal expansion rates, each metal also has its own melting rate. A high heat input welding process can, however, help you melt and weld two dissimilar metals quickly.

Finding out the properties of two dissimilar metals is a must to know if a welding process is possible or not. If you have questions about welding dissimilar metals, then contact us now at McKean’s Sheetmetal Fabricators.

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