As metal parts go through the various phases of production to achieve the desired results in the final product, the chemical makeup of those metals can experience changes. One of the most common places we see this happen is with castings. The surfaces of castings are exposed to air and oxidized during the formation of the cast product. As a result, the surface loses carbon, or becomes decarbonized, which makes it weak and soft.
Carbon restoration is a process that restores the carbon level on the surface of a part by heating the part in an atmosphere rich with carbon and allowing the carbon in the atmosphere to imprint into the oxidized surface.
This process can create several different levels of carbon restoration, depending on the level of carbon in the atmosphere and how long the part remains in the carbon-rich atmosphere. If the furnace atmosphere’s carbon level is the same as the base metal, it is called neutral hardening. If the surface of the part was previously decarburized, then this same carbon level can result in carbon restoration. If the atmosphere’s carbon level is greater than the base metal level, it’s called carbon enrichment. In this case, the part will have a carburized case on its surface.
Carbon restoration is an art and a science, wrapped up in precision and accuracy. The processing parameters must be adjusted for each part type, including the alloy, cross sectional thickness, load density, and desired end part properties. Heat treaters must understand the depth of decarburization to ensure full carbon restoration is achieved. Most industry quality standards require sample parts or test bars to be cut to verify surface properties.
The experts at Akron Steel Treating Company are well equipped to manage your carbon restoration needs. Talk to our team today to design the proper processing parameters for your part.« Back to General