Hot extrusion is the earliest of several extrusion process used in extrusion technology, which is at forging temperature by means of a plastic material and good, for a variety of metal extrusion. Currently, the hot extrusion mainly used in the manufacture of ordinary prismatic elongated member, profiles, pipe, bar and various machine parts. Not only can the hot extrusion molding plastic, and the relatively low intensity of nonferrous metals and alloys, low, medium carbon steel, but also forming high strength carbon, high alloy steel, such as the structure of special steel, stainless steel, high-speed tool steel and heat-resistant steel. Since the billet must be heated to forging temperature extrusion, often accompanied by more severe oxidation and decarbonization and other heating defects, affecting the dimensional accuracy and surface roughness of extrusion. Under normal circumstances, after the hot extrusion machine parts, and then using cutting and other machining to improve the dimensional accuracy and surface quality of parts.

When hot extruded metal flow is divided into three basic stages: first, squeeze the beginning (filling phase), after the metal by squeezing pressure, the first full bore extruder barrel and die, extrusion pressure straight up to the maximum. The second stage is the basic extrusion stage, when the squeeze pressure reaches breakthrough pressure (maximum pressure), the metal began to flow from the die orifice that is instantly entrants stage. The third stage is the end stage of extrusion, in the second stage, with the narrow distance between the gasket and the extrusion mold, forcing the metal deformation zone toward the extrusion axis around violently by lateral flow toward the center. Easy to form and compressed tail at this stage.