Differences between mold steels of P20, P20H, P20HH and P20-Ni

- Dec 11, 2018-

Differences between mold steels of P20, P20H, P20HH and P20-Ni


P20 mold steel is a model of mold welding consumables, the earliest is P20, followed by P20H, P20Ni have come out one after another. P20 steel is suitable for the production of plastic molds and die-casting low melting point metal mold materials. This steel has good machinability and mirror polishing properties.


Carbon C: 0.38

Manganese Mn: 1.30

Chromium Cr: 1.85

Molybdenum Mo : 0.40

Sulfur S : 0.008


  P20 mold steel has been pre-hardened to 285-330HB (30-36HRC), which is equivalent to 618 German GS-2311. It can be directly used for molding and has good dimensional stability. Pre-hardened steel can meet the requirements. General purpose requirements, mold life up to 50W mode.


     Uniform hardness, good polishing performance and photo-etching performance, good processing performance

The vacuum degassing refining process is pure and suitable for polishing or etching plastic molds.

Pre-hardened state supply, no need for heat treatment, can be directly used for mold processing, shortening the construction period.

After forging and rolling, the structure is compact, 100% ultrasonic inspection, no porosity, pinhole defects.


Applicable to plastic molds and mold bases such as TV front case, telephone, water dispenser, vacuum cleaner.

Thermoplastic injection molds, extrusion dies.

Thermoplastic blow molding dies.

Heavy load main parts of the mold.

Cold structural parts.

Commonly used in the manufacture of TV sets, washing machines, refrigerator inner casings, buckets, etc.


    In order to increase the die life to more than 800,000 mold times, the hardened steel can be hardened by adding hardening and low temperature tempering. Pre-heating at 500-600 ° C for 2-4 hours, then at 850-880 ° C for a certain period of time (at least 2 hours), cooling in oil to 50-100 ° C oil cooling, hardness after quenching up to 50 -52HRC, in order to prevent cracking, immediately carry out low temperature tempering at 200 °C, after tempering, the hardness can be maintained above 48HRC

Nitriding treatment

   Nitriding treatment can obtain high hardness surface layer structure, the surface hardness after nitriding reaches 650-700HV (57-60HRC), the mold life can reach more than 1 million times, the nitride layer has compact structure, smooth characteristics, mold release property and Improved resistance to moisture and lye corrosion.


Steel properties: pre-hardness hardness HRC25-29, with uniform hardness and texture, good machinability, polishing performance and weld repair performance


General purpose of steel: plastic mold steel, mold base, etc. Pre-hardness hardness HRC25-29, with uniform hardness and texture, good machinability, polishing performance and weld repair performance


  Most of the P20 die steels on the market are P20H die steels, because they are basically pre-hardened and have a hardness of 29-33HRC.

What does P20HH mold steel bring with H after the P20H mold steel? Is the pre-hardness hardness improved? Yes, the biggest difference between P20HH die steel and P20H die steel is the difference in hardness. The pre-hardness hardness of P20HH die steel can reach between 36-40HRC, which is the hardness that P20H die steel can't reach.

Can P20HH be replaced with NAK80 die steel? The main purpose of replacing with NAK80 die steel is that P20HH die steel on the market is not common, and the hardness of P20H die steel is not up to standard. However, NAK80 mold steel has no problem in hardness, and its normal pre-hardness hardness can reach 37-43HRC. The only disadvantage is that the unit price is high, which greatly increases the production cost.

The hardness of P20 is normally around 30HRC, mainly used to repair plastic injection molds and heat-resistant molds (cast copper molds).

    The hardness of P20H is normally around 30-33HRC. P20H is the argon welding wire which is suitable for the plastic injection mold in the advantage of P20. After machining, the machinability and etch resistance are good, and the material has uniform hardness and high hardness.

    The hardness of P20-Ni is normal at 28-30HRC, and the hardness is the same as that of P20, but in comparison, the polishing property is good, and the mechanical property after welding and the photoetching property are excellent.

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