Screw barrels are integral components in material processing, and optimizing their wear resistance is essential for sustained performance.

Heat Treatments for Wear Resistance:

Flame Hardening:
One of the oldest methods, flame hardening, involves exposing AISI 4140 steel flights to an open gas/oxygen flame, followed by rapid quenching. The initial heat-treated condition is 28-32 Rc, and with flame hardening, the flights can achieve a hardness of 48-55 Rc. This process is suitable for materials with approximately 0.4% carbon content, offering excellent mechanical strength and machinability.This transformation not only fortified the mechanical strength to approximately 100,000 psi but also showcased exceptional machinability. Our pioneering approach enables us to cater to diverse applications, including those demanding high carbon content for optimal wear resistance.

Induction Hardening:
Similar to flame hardening, induction hardening provides comparable results but uses magnetic flux reversals for heat generation. This process ensures a hardened surface, contributing to enhanced wear resistance in screw barrels.

Nitriding (Ion or Gas):
Nitriding is a thermochemical diffusion process that increases the hardness and wear resistance of the surface of the screw barrel. It is a versatile treatment that can be used on a variety of materials, including stainless steel, tool steel, and cast iron.
Nitriding exposes screws or barrels to a high nitrogen atmosphere, typically ammonia gas, at around 950°F. This results in a very hard case with a hardness of 55-65 Rc and a depth of approximately .015-.020”. Nitriding is effective in minimizing distortion, but it's crucial to consider growth allowance during the design phase. Nitrided screws exhibit improved wear resistance, especially against abrasive materials like glass-filled substances. Proper nitriding steel selection, such as Crucible Nitriding 135 or Ryerson Nitralloy 135-M, is essential for optimal hardness.

However, nitriding can pose challenges during screw rebuilding, where hard surface welding may cause nitrides to bubble at the base material overlay intersection. Special precautions are necessary to mitigate these issues. While nitriding remains a preferred method for injection barrels, its application should be considered carefully, particularly in environments where chemical resistance is paramount.

Furthermore, our vertical oven configuration for nitriding minimizes distortion, ensuring optimal screw performance. In addressing challenges associated with the nitriding process during screw rebuilding, our proprietary hard surface welding techniques have successfully mitigated issues related to nitride bubbling at the base material overlay intersection.

Precipitation Hardening:
Utilizing low-temperature processes, precipitation hardening is effective for certain stainless steel grades. Examples include 17-4 PH stainless steel, which is supplied in Condition A before machining and hard surfacing. This method enhances wear resistance in screw barrels, particularly in applications where stainless steel is preferred.

Real-world data from production lines using precipitation-hardened screw barrels have consistently demonstrated extended service life and reduced downtime.

Barrelize is professional screw and barrel manufacturer, we offer complete solution for your project.