In accordance with the molding method, the plastic can be divided into thermoplastic and thermosetting plastics. Thermosetting plastics such as bakelite, are heated, pressurized under the pressure of permanent molding. Bakelite mold periodically under pressure and at 150-200 degrees Continuously heated, thermoplastics such as PVC, etc., are usually injection molded, the plastic is heated in a separate heating chamber, and then softened into the mold cavity to cold, exert pressure to make it cold forming.
Plastic mold manufacturing cost is high, the cost of materials only accounts for a small part of the mold cost, so the selection of steel, the process should be preferred performance, stable performance and long service life of steel, the specific requirements of the plastic mold made the following:
1. Good machining performance: the plastic mold cavity geometry is very complex, and requires processing deep holes, deep grooves and other difficult parts, steel must have cutting performance, the choice of steel, if other conditions can be met, is This condition is the basis for the final selection.
2. Excellent polishing performance: no matter what kind of plastic mold, the cavity surface roughness allowed to be minimal, almost all required to be able to do the mirror gloss, and to achieve the mirror gloss, the steel must have good hardness, first of all the debris in the steel to As little as possible, and can not have bubbles exist, and microstructure uniformity in the mass production of the mold, the surface roughness is also an important condition.
3. Good surface corrosion Machinability: Many molds require the molding of plastic parts for the surface of a variety of other material patterns, such as leather, silk pattern, cloth pattern, fine patterns, which requires thin and uniform steel texture, or corrosion not effectively.
4. Good wear resistance and toughness: plastic mold is long-term withstand thermal load, but also long-term withstand friction, such as considering only the friction side, regardless of the thermal alternating load side, the use of cold-die High-carbon high-alloy steel manufacturing, will inevitably lead to lack of toughness caused by cracking.
5. Quenching performance, deformation is small: Most of the plastic mold cavity must be heat treatment, which requires steel has good hardenability and small deformation, the general thermoplastic molding die, the use of quenching and tempering, pre-hardening Can be processed, and thermosetting plastic molds must be hardened.