ASTM P20 718H Steel Plate

718H mold steel was developed to complement standard mold steel to eliminate problems such as hardness drop-off towards the middle of the mold, maching problem and inadequate etch-grainability with large sizes of more than 400mm in cross section. A significant step taken towards dealing with these problems is to increase hardenability by alloying approximately 1% nickel.

718 steel equivalent grades:

718 steel Chemical compositions (%):

718 Mold Steel Mechanical Properties:

Heat treatment

Annealing:

Heat to 710~740°C, with hold at minimum rate for 3 hours.

Slow furnace cooling to 600°C

Stress relieving:

To be carried out after machining and before the final heat treatment.

Heating to 530~580°C for 2 hours.

Hardening:

Preheating to 500~550°C;

- Austenitizing at 840~880°C

- Oil or thermal bath cooling at 200~300°C, then oil cooling according to the steel shape and size.

Quenched hardness: HRC 52~54

Tempering:

To be carried out after hardening and when the steel is at 60~80°C, at 500~600°C according to the required

hardness and with permanence for at least 2hours; cooling in air.

Application:

It features excellent hardening penetration, good workability, polishing and photoengraving properties. This steel is used for plastic moulds of medium and big size. It can be subject to a nitriding treatment to improve it's wear resistance. Injection and thermoplastic extrusion moulds, rubber moulds, mould carrier frames, containers.