First, the tool steel classification
Die steel according to their use can be divided into cold die steel, hot die steel and plastic mold steel these three categories.
Due to the different kinds of mold uses, working conditions are very complex, so the mold steel, mold manufacturing according to their working conditions, should have high hardness, strength, wear resistance, sufficient toughness, and high hardenability, quenching rigid and other process performance. Because of these different uses, working conditions are very complex, and therefore mold steel performance requirements are also different.
Second, cold work tool steel
Cold mold includes Die, drawing die, pressure die, thread rolling die, rolling plate, cold heading and cold extrusion die molds.
Cold die steel, according to the working conditions of their manufacturing equipment, should have a high hardness, strength, wear resistance, sufficient toughness, and high hardenability, hardened and other process performance. Alloy tool steel used for such purposes are generally high-carbon steel, carbon mass fraction of more than 0.80%, chromium is an important alloying elements such steel mass fraction is generally not more than 5%. But for some high wear resistance, mold steel after quenching deformation is small, the highest chromium content up to 13%, and for the formation of large carbides, the steel carbon content is also high, up 2.0% ~ twenty three%. Higher carbon content cold die steel, most of which belong to the organization eutectoid steel or ledeburite. Commonly used class of high-carbon low-alloy steel, high carbon high chromium steel, chromium molybdenum steel, carbon steel and other chromium tungsten Kushiro.
Third, the hot work die steel
Hot die forging into die, stamping die, hot extrusion die and die casting molds.
Thermal deformation of the mold at work in addition to withstand enormous mechanical stress, but also to withstand repeated heating and cooling to do with, and cause a lot of thermal stress. In addition to hot work die steel should have high hardness, strength, red hardness, wear resistance and toughness, but also has good high temperature strength, thermal fatigue stability, thermal conductivity and corrosion resistance, are also required to have a high hardenability, in order to ensure that the entire section has the same mechanical properties. For the die-casting mold steel, it should have properties of the surface layer after repeated heating and cooling without causing cracks and withstand shock and erosion liquid metal stream. Such steels are generally carbon steel, carbon mass fraction of 0.30% to 0.60%, below sub-eutectoid steel, also part of the steel due to the addition of more alloying elements (such as tungsten, molybdenum, vanadium, etc.) become eutectoid or hypereutectoid steel. Commonly used types of steel are chromium-manganese steel, chrome-nickel steel, chrome tungsten steel.
Fourth, the plastic mold steel
Plastic mold include thermoplastic and thermosetting plastic mold plastic mold.
Plastic mold steel requires a certain amount of strength, hardness, wear resistance, thermal stability and corrosion resistance and other properties. In addition, it requires a good process, such as heat treatment becomes small, good processing properties, corrosion resistance, good grinding and polishing properties, good welding performance, high roughness, thermal conductivity, good working conditions and the size and shape stability . In general, the injection molding or extrusion molding die can be used hot die steel; thermoset molding and require high wear resistance, high strength cold work die steel mold can be used.
