Plastic mold

Plastic mold processing that requires high accuracy such as dimensional accuracy and surface roughness is processed at 480°C or less to suppress deformation.
(However, it may become deformed if the processing stress during mold processing is large.)
In addition, the surface hardness of the hardened layer matches the material properties, so it is rated highly for its wear resistance and durability.

High toughness (viscosity) value in nitriding treatment

The photo below is an indentation photograph that shows the surface of SKD-61 material that has been hardened and tempered to about 48HRC and then processed by EH treatment (left photo) and gas soft-nitriding (right photo), measured with a Rockwell hardness tester (HRC).
With gas soft-nitriding, there are cracks on the indentation edges, but with EH treatment this has not occurred.
This suggests that EH treatment has better toughness than gas soft-nitriding.

EH treatment
EH treatment indentation photograph (no cracks on surface)
A white layer (compound layer) is rare with EH treatment, meaning that textured and mirror surfaces can be treated. EH treatment + surface treatment is possible because it is rare for a white layer to occur.
Gas soft-nitriding
Gas soft-nitriding indentation photograph (with cracks on surface)
Gas soft-nitriding produces a white layer (compound layer). Hard, brittle, and unclean, and not suitable for textured and mirror surfaces.
Outstanding, unparalleled wrap-around properties
Since there are many fine slits and deep holes in complicated and precise plastic molds, we recommend EH treatment, which treats the entire surface evenly and has excellent wrap-around properties.
It prevents local wear and is effective in improving mold durability.
Comparison data of EH treatment and nitriding treatment of Company X

Material NAK55 Dimensions 30×30×25 Drill holes in ⌀0.6 and ⌀2.0 shown by the arrows to verify the hardened layer

Surface A

A hardened layer can be confirmed on Surface A (surface part) for both EH treatment and Company X nitriding treatment.

Hardened layers can be confirmed on surfaces B, C, D (inner diameter) with EH treatment, but cannot be confirmed for Company X nitriding treatment. From this, it can be seen that EH treatment has excellent wrap-around properties.

Since a hardened layer can be obtained even with complicated shapes such as product parts, it provides excellent wear resistance and leads to a longer lifetime.

Surface B/C/D  EH treatment
Surface B/C/D  Company X nitriding treatment
Also supports surface texturing
When nitriding is applied to a die to be textured, there may be concerns because there will be slight differences in surface roughness and gloss on the textured surface. However, with EH treatment, even molds can be used as they are after treatment.
In addition, since the surface hardness is uniformly hardened even with molds, a uniform texture can be obtained and the mold can be used without any problem in terms of durability.
Test data for textured surface (in-house comparison)
Surface roughness comparison data for EH-M treatment

Test material: STAVAX (pre-hardened)
Base material hardness 33.5HRc

Before EH treatment
After EH treatment
Polishing after nitriding #14000 finish is also possible

Development of PB nitriding (Piano Black) “PB 14000” for mirror molds
Piano Black nitriding that does not cause dents or dimples even if “mirror polishing” is performed in the polishing process after nitriding

Standard specifications that enable PB14000 #14000 finishing
* Special specifications with the addition of a process to prepare crystal grains over a longer period of time than the PB14000EX standard process.

The five reasons why polishing is possible are:

  1. ① Generates a uniform hardened layer…Affects dimples
  2. ② Generates a dense hardened layer…Affects #14000 finish
  3. ③ Establishes a nitriding layer polishing method after EH treatment…Pre-treatment polishing #8000 is recommended (aim for a post-treatment polishing allowance of 5 μm)
  4. ④ In order to achieve the highest densification, a special process (precipitation hardening crystal grain homogenization) may be required depending on the material (EX-HEAT).
    High cost & Long process (OPTION).
  5. ⑤ #14000 finishing is possible by carefully controlling the material used as the mold and the final process with the customer.
    Note. Our sales staff may ask you about the polishing method during our meeting with you.
Technical Data
SKD61 PB14000

(for Piano Black)

Nitride layer characteristic/Surface section and hardness curve
Hardness curve
EH treatment steel type hardness table