3Cr2Mo is more widely used plastic mold steel, its mechanical properties, hardenability, the larger cross-section of steel to teach a more uniform hardness, and has a good polishing performance mold surface finish. The steel mold, generally quenching and tempering treatment, hardness HRC28 ~ 35 (ie, pre-hardened), manufactured by the cold into the mold can be used directly. In this way, guarantee the performance of the use of molds, but also to avoid the heat treatment to cause deformation of the mold. Therefore, the steel appropriate for manufacturing large. Medium-sized and precision plastic mold and low melting point of tin, zinc, lead alloy die-casting mold and so on. 
 Introduction 
 Domestic mold steel: 3Cr2Mo (P20) Standard: GB / T 1299-1985 hot work die steel, carbon of Cr-Mo is the introduction of the P20 plastic mold steel. Applicable to the production of plastic mold and die casting mold material of low melting point metal. This steel has good cutting and mirror polishing performance. The P20 has a pre-hardened to 285-330HB (30-36HRC), Sweden 618 German GS-2311 status, can be directly used for molding processing, and has good dimensional stability characteristics of pre-hardened steel in order to meet the general purpose demand for die life of up to 50W mode. 
 Chemical composition 
 The chemical composition of the the 3C r2Mo steel (GB/T1299-2000) w /% [1] C Si Mn PS of Cr, Mo of Ni 
 0.28-0.4 0.2-0.8 0.6-1 ≤ 0.03 ≤ 0.03 1.4-2 0.3-0.55 0.85-1.15 

 Material properties 
 The vacuum degassing refining process pure steel for demanding polishing or etch processing plastic mold. 
 Pre-hardened state supplier, no need to heat treatment can be used directly in the mold processing, shorten the construction period. 
 By forging rolling processing, dense, 100% ultrasonic testing, nonporous, the eye of a needle defect. 
 The main purpose 
 Thermoplastic injection molds, extrusion the mold 3Cr2Mo sheet with. 
 Blow molds for thermoplastics. 
 Overloading the main mold parts. 
 Cold structure parts. 
 Commonly used in manufacturing television chassis, washing machine, refrigerator shells, buckets and so on.