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AMP Processes

American Metal Processing (AMP) performs three primary hardening services with our atmosphere-protected rotary retort furnaces:
Neutral Hardening icon
Neutral Hardening
Everything begins with neural hardening. Also known as "quench and temper," this process improves the strength and toughness of medium- to high-carbon steels evenly through the entire part. This result is achieved by heating parts above the phase-transformation temperature for a set period of time to change their crystalline structure from body-centered cubic to face-centered cubic. To preserve the steel in this new crystalline arrangement, the part is then plunged rapidly into a quenchant, thus giving it a remarkably high hardness. Oil and water are both common quenchants, with oil being the less aggressive of the two. The choice to use water or oil is determined by the material being used and the desired metallurgical properties of the finished part. After quenching, parts must be reheated (i.e., tempered or drawn down) to the desired hardness to create a tempered martensitic microstructure. Tempering of quenched steel is a critical final process to relieve microstructural stresses in the part and prevent distortion / cracking while simultaneously improving toughness and ductility. After the tempering process, the part is tested for hardness using the Rockwell scale, and several material properties can be extrapolated from that measurement.
Carburizing icon
Carburizing
Carburizing is a case-hardening process to improve surface hardness for low-carbon steels. This is achieved by adding free carbon to the processing atmosphere and allowing it to diffuse into the surface of the part. The carbon-infused surface layer has superior wear capabilities and high Rockwell hardness specifications.
Carbonitriding icon
Carbonitriding
Carbonitriding is a case-hardening process similar to carburizing. It is generally performed at lower temperatures with the addition of nitrogen via ammonia gas. This process increases wear resistance and surface hardness through the creation of a hardened surface layer, which is diffused at these lower temperatures. The diffusion of nitrogen at these temperatures provides a more resistant case and increases the hardenability of low-carbon steels. Carbonitriding is well suited for parts that require wear-resistant properties with reduced distortion. Case depths for carbonitriding are generally much lower than those of carburized parts, varying from a low of 0.003 to 0.030 inches (0.08mm to 0.76mm). Parts are commonly quenched in oil and tempered at low temperatures to increase toughness and reduce brittleness.
Rotary furnace cutaway

Rotary furnace hardening

Stage 1

AMP's computer-controlled rotary retort furnaces have a feeder system that performs two functions: (1) a two-stage electromagnetic vibratory feeder ensures gentle handling and (2) a scale weighs the parts to provide accurate feed rates.

Stage 2

Positive endothermic gas pressure and flame curtains protect parts in the furnace from oxidation and scale.

Stage 3

Radiant tubes both above and below the spiral rotary retort provide even, balanced heat to minimize hot spots and heat variation.

Stage 4

As the spiral rotary retort slowly revolves, gravity gently shuffles and conveys parts through the heat zones. The movement of parts through the furnace provides a more consistent and uniform heat treatment process than traditional batch- or belt-style furnaces.

Stage 5

The quench chute is where the majority of the quenchant agitation and martensitic transformation takes place. The quenchant curtain prevents fumes from contaminating the furnace.

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22720 Nagel St.
Warren, MI 48089
(586)757-7337