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Application and Development of Plastic Mould Steel


With the increase of the variety of plastic parts and the improvement of quality requirements, as well as the trend of high-speed, large-scale, precise and multi-cavity molding process of plastic parts, higher processing technology requirements are also put forward for plastic mold materials.


Ⅰ. Performance requirements of plastic mold steel materials


In order to meet the development needs of the modern mold industry, the precision of the mold and the requirements for the mirror effect achieved after the polishing of high-precision plastic molds are getting higher and higher, and the surface roughness of the mold has a considerable impact on the quality and life of the product and the mold itself. Studies have shown that the performance level of mold steel, the quality of materials and the selection of heat treatment process are important factors that affect mold life.


Different components of plastic molds have different requirements for plastic mold steel materials. For structural parts, including gating systems, guides, fixed templates, ejector parts, etc., the materials selected are generally medium and low carbon carbon. Structural steel, alloy structural steel or carbon tool steel. For molded parts, including cavities, cores, inserts and so on, the selected materials determine the performance, life and cost of the mold.


The structure of the molded parts is complex. It requires precise dimensions, tight joints and smooth surface. The plastic mold steel materials used must have the following specific performance requirements: 

(1) It has certain comprehensive mechanical properties, less heat treatment deformation, and good dimensional stability. 

(2) The material is highly pure and the structure is uniform and dense. 

(3) It has good mirror polishing properties in the hardened state. Because the surface roughness requirements of some plastic products are very high, it is mainly ensured by the roughness of the mold cavity. The mirror processing performance of plastic mold steel is related to the composition, structure and hardness of the steel. 

(4) Because the geometry of the cavity of the plastic mold is more complex, usually with deep holes, deep grooves, narrow slits, etc., the steel must have good machinability. 

(5) When molding PVC or plastic products with additives such as flame retardants, due to the chemical corrosion effect on the surface of the plastic mold steel due to decomposition during the molding process, the selected mold steel should have good corrosion resistance.


Ⅱ. Types and applications of common plastic mold steel


At present, plastic mold materials are still dominated by mold steel. According to the different compositions and properties of steel, plastic mold steel can be divided into 7 categories. At present, free-cutting hardened steel, age-hardened steel and pre-hardened plastic molds are most used. steel.


Pre-hardened plastic mold steel: often used to make large, complex, and high-quality plastic molds. It has good cutting performance and can be directly processed for cavity processing. After processing, it can be used directly without heat treatment. Because heat treatment and finishing after heat treatment are omitted, the cost is reduced and the manufacturing cycle is greatly shortened.


Age-hardening plastic mold steel: It has good welding properties and can be surface nitrided. It is mainly used in the manufacture of complex, precise, and long-life plastic molds and transparent plastic product molds. It is widely used in various industries.


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