Wednesday, March 30, 2022

Is It Possible To Weld Two Different Metals Together?

A welding torch making sparks

Many different industries and applications join dissimilar materials together for a variety of reasons. Combining dissimilar metals can allow the best properties of each metal to be used. 

At Atlas Bronze, we know that before any welding operation can begin, the welder must be able to identify and understand the characteristics of each material. For these reasons, welding different metals together, requires expert skill and knowledge.

Equipped with that knowledge, whether for brass welding or copper welding, an experienced welder can join even materials that are difficult to weld, skillfully and successfully.

Dissimilar Metal Welding 

Dissimilar metal welding is the welding process that joins different metal alloys. 

To successfully weld these disparate types of material, the welder must understand:

  • Dilution and Alloying -  metals require a solid solution in which the mixture will produce stable metallurgical phases, whether that takes one or more phases. The amount of dilution necessary determines the phase.

  • Level of Weldability - joining dissimilar metals can lead to a high risk of hot or solidification cracking. Weldability measures how metals can be joined without cracking occurring.

  • Electrochemical characteristics -  Corrosion can develop at the part of the joint where the metals transition from one to the other, in what is called the intermetallic zone; or on the overlay surface. The risk of corrosion is highest if metals have significantly different electrochemical properties caused by dilution.

  • Melting point - metals may melt at different temperatures. A pre-heating process will rapidly bring all metals to their melting point, so melting is not required.

  • Thermal expansion coefficient - this expansion refers to the ways in which metals expand, changing size and shape, when heated. Should two metals being welded change shape at different rates or degrees, the weld can strain as it sets, causing thermal cracking.

  • Heat affected zone - if there are heat affected zones immediately adjoining the weld, that weld can display majorly different physical properties from the original base metal. Higher hardness occurs in this way with high carbon or cast iron, leading to reduced strength and brittle fracture.

How Dissimilar Metals are Joined

Traditionally, dissimilar metals are joined through fusion ARC welding to prevent degradation of strength, toughness, and corrosion.

Laser weld overlay can also be used to join these metals. Laser classing of dissimilar materials offers benefits such as: 

  • Less sensitive laser weld overlay to different melt temperatures.

  • Very low dilution

  • Thinner clads

  • Reduced sensitivity to thermal expansion 

  • Control of detrimental metallurgical phases

  • Reduction or elimination of solidification cracking 

  • Higher corrosion resistance in a single thin layer

  • Elimination of multiple layer requirements 

  • Lesser pre-machining

  • Smaller heat affected zone for less distortion

  • High hardenability of materials without preheat

  • Reduction or elimination of preheat requirements 

  • Ability of laser overlay of ductile cast iron without significant preheat

  • Post weld heat treatment eliminated or reduced

  • High quench rates for finer grain structure and higher corrosion potentials

In short, laser is the ultimate heat source tool for the welding/cladding of dissimilar materials.

Are There Any Materials That Can’t Be Welded?

The answer to this question depends on the type of welding method. Fusion welding can’t be used for the welding of:

  • Aluminum and carbon steel

  • Aluminum and copper

  • Aluminum and stainless steel

  • Titanium and steel

However, non-fusion welding, such as diffusion bonding, explosion welding, ultrasonic, and friction welding are very effective for joining these metal combinations as well as other insoluble metals.

Ready to Learn More about Welding Different Types of Metals?

At Atlas Bronze, our skilled experts are here to help. Reach out to us today!

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