Plastic Mold Steel is Classified According to Its Performance and Final Heat Treatment Method

Plastic mold steel can be divided into high wear-resistant plastic mold steel, free-cutting pre-hardened mold steel, non-magnetic plastic mold steel, corrosion-resistant plastic mold steel, mirror plastic mold steel, and high wear-resistant plastic mold steel.

Because glass fiber and inorganic mineral reinforced materials are added to some engineering plastics, the molds are severely scratched, so the mold steel is required to have high hardness and wear resistance after heat treatment. At the same time, the heat treatment deformation should be small.

Ⅰ. Plastic mold steel is classified according to its performance

1. Easy-cutting pre-hardened die steel

In order to improve the machinability of pre-hardened section steel, s, ca, pb, and other elements are added to the steel to form free-cutting pre-hardened plastic mold steel.

2. Non-magnetic plastic mold steel

Certain ferrite-added plastic products need to be injection molded in a magnetic field. The mold steel is required to be non-magnetic. Generally, non-magnetic austenitic steel 1cr18ni9ti is used. If the wear resistance is required, 7mn15cr2al3v2wmo, etc. are used.

3. Corrosion-resistant plastic mold steel

Flame retardants are added to engineering plastics to generate corrosive gases during the forming process. The molds are often made of corrosion-resistant alloy steel, such as 1cr18ni9ti and cr13 or cr17 series stainless steel products.

4. Mirror plastic mold steel

To make plastic product molds with smooth surface, high transparency, and visual comfort, the grinding and polishing properties of plastic mold steel and photoetching corrosion are better. In order to meet the polishing requirements, this type of steel must undergo vacuum smelting or electroslag remelting and other refining treatments, and metallurgical defects such as non-metallic inclusions, segregation, and porosity are strictly required.

Ⅱ. The plastic mold steel is divided according to the final heat treatment method

According to the final heat treatment method, plastic mold steel can be roughly divided into carburized hardened steel, quenched hardened steel, age-hardened steel and pretreated hardened steel.

1. Carburized hardened steel

Carburized hardened steel mainly includes low-carbon non-alloy steel, low-carbon low-alloy steel and low-carbon alloy steel. After cutting or cold extrusion, this type of steel is carburized or carbonitrided, and then quenched and tempered. Generally suitable for small molds with little load.

2. Quench hardened section steel

Plastic molds that can withstand larger loads have higher requirements for strength, hardness, wear resistance, plasticity, and toughness, and quench hardened steel should be used. This type of steel must have high hardenability and maintain a carbon content above medium carbon steel.

3. Age hardening section steel

Because the quenched hardened section steel cannot eliminate the influence of quenching deformation on the dimensional accuracy of the mold, some molds that require high dimensional accuracy use age-hardened section steel. This type of steel is treated with aging to ensure the strength and hardness of the matrix, and then through surface strengthening treatments, such as nitriding, the surface has high hardness, high wear resistance and high corrosion resistance.

4. Pretreatment hardened steel

In order to completely eliminate the influence of heat treatment on the dimensional accuracy of the mold, before making the mold, the plastic mold steel is pre-processed to the hardness and required strength and toughness when the mold is used. Under the condition of not reducing the performance, it can complete the mold processing.

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