First, the performance of mold materials
1. Mirror polish
2. Hardness and abrasion resistance
3. Strength and toughness
4. Corrosion resistance
Second: mold material selection principle
1. According to the function of the mold parts to make reasonable choice
A. Mold base, positioning parts, select carbon steel (45 #, S45C, S55, etc.)
B. Guide, reset, drive parts (T8, T8A, T10, T10A, SKD61, SKH51, SK3, SUJ2, etc.)
C. Forming parts for pre-hardened steel (P20, P5, NAK55, NAK80, 738, 718, 420, etc.)
D. Cooling parts select anti-rust steel (aluminum alloy, brass, copper, beryllium copper, etc.)
2. According to the production batch, mold precision requirements
A. Small quantity, the accuracy is not high (45 #, S45C, S55,718S, 738,2311,2312, etc.)
B. Large quantity, high precision then use hardened steel (NAK55, NAK80, 738H, 2711,420, etc.)
C. Quantity huge, complex row (H13,8402,8407, SKD11, etc.)
3. Select according to the characteristics of the plastic
General plastic such as PA, POM, PS, PE, PP, ABS etc(NAK55, NAK80,738,2711,718,420,638,2311)
High transparency such as PMMA, PS, AS, PC, etc (S136, S136H, NAK80, 2083, 818H, 2316)
Contains glass fiber reinforced, such as PC, PA, ABS, AS and other high wear resistance of hardened steel (8407, NAK55,236H)
Super-mirror polishing such as PMMA, PC and other selected corrosion-resistant steel (420,2316,2316H, 818H, HPM38, HPM38S)
For the use of PVC and add flame retardant ABS, PC, AS, PP, EP, PA, POM and other acidic plastic. Must use anti-corrosion corrosion of 420 stainless steel (236, 236H, S136, S136H)
Three: steel selection notes:
A. If for the injection of transparent and high-quality products, need mirror polishing, steel heat treatment reach to HRC50 ~ 56 degrees. Such as injection molding PVC and other corrosive and abrasive plastic, the steel heat treatment need reach HRC48 ~ 52 degrees.
B. Pre-hardened steel, generally can not be heat treatment again, for re-heat treatment, it must first annealed and then heat treatment, but this will lead to increased brittle steel.
C. Quenched and tempered by the pre-hardened 420 stainless steel, nitriding can not be carried out, because the chemical composition of stainless steel Cr (chromium) activity, nitriding is not anti-acid.
D. Pre-hardened steel (such as DAIDO-NAK80), in principle, can no longer be nitrided, because the nitriding treatment will affect the polishing performance of steel surface.