In stretch film and bubble film extrusion machines, the screw and barrel assembly operates under high temperature, pressure, and continuous mechanical stress. To maintain stable performance in these conditions, many extrusion systems use 38CrMoAl nitriding steel, which is equivalent to AISI 6470.
The screw is constantly exposed to friction from polyethylene materials such as LDPE and LLDPE, as well as various additives used in film production. 38CrMoAl steel undergoes a nitriding heat treatment process that forms a very hard surface layer. After nitriding, the surface hardness can exceed HV900, significantly improving resistance to wear and abrasion. This durable surface helps maintain the screw profile for a longer period and reduces wear during continuous extrusion.
Stable screw and barrel tolerances are important for maintaining consistent melt pressure and smooth material flow. The nitriding process used with 38CrMoAl steel produces minimal dimensional deformation during heat treatment. This allows the screw and barrel to maintain precise clearances, which supports stable melt flow and uniform extrusion conditions during film production.
The material also provides good core strength and fatigue resistance. During long production cycles, the screw is subjected to torsion and mechanical stress caused by high extrusion pressure and continuous rotation. The strong internal structure of 38CrMoAl steel helps maintain mechanical stability during extended operation.
Because of its combination of surface hardness, wear resistance, and structural strength, 38CrMoAl nitriding steel is widely used in extrusion screws and barrels for stretch film and bubble film machines. Its properties support stable extrusion performance and consistent film production over long operating periods.
