Office Paper File Plastic Mold

Basic principles of selecting mold steel

1. Mold meets working conditions

* Wear resistance

When blank is plastically denatured in the mold cavity, it flows and slides along the surface of the cavity, causing severe friction between the surface of the cavity and the blank, which causes mold to fail due to wear. Therefore, the wear resistance of the material is one of the most basic and important properties of mold.

Hardness is a major factor affecting wear resistance. In general, the higher hardness of mold parts, the smaller the wear amount, and the better the wear resistance. In addition, wear resistance is also related to the type, quantity, shape, size, and distribution of carbides in the material.

* Toughness

Most of the working conditions of mold are very bad, and some often suffer from a large impact load, resulting in brittle fracture. In order to prevent mold parts from suddenly breaking during work, the mold must have high strength and toughness.

The toughness of mold depends mainly on carbon content, grain size, and the microstructure of the material.

* Fatigue fracture performance

During the working process of mold, under the long-term effect of cyclic stress, fatigue fracture is often caused. The form has small energy multiple impact fatigue fracture, tensile fatigue fracture, contact fatigue fracture, and bending fatigue fracture.

Fatigue fracture properties of a mold depend mainly on its strength, toughness, hardness, and amount of inclusions in the material.

* High-temperature performance

When the working temperature of the mold is higher, hardness and strength are lowered, resulting in early wear of mold or plastic deformation and failure. Because mold material should have high anti-tempering stability, to ensure that mold has high hardness and strength at working temperature.

* Resistance to cold and heat fatigue

Some molds are in a state of repeated heating and cooling during the working process, causing the surface of the cavity to be subjected to tensile and pressure-induced stresses, causing surface cracking, spalling, increasing friction, impeding plastic deformation, and reducing dimensional accuracy, thereby resulting in mold failed. Hot and cold fatigue is one of the main forms of hot work die failure. It should have high resistance to cold and heat fatigue.

* Corrosion resistance

Some molds such as plastic molding, when working, due to presence of chlorine, fluorine, and other elements in plastic, strong corrosive gases such as HCI, hf is resolved to analyze after heating, eroding the surface of the mold cavity, increasing its surface roughness, and aggravating wear and tear.

2. Mold meets process performance requirements

* Foreseeability

It has low hot forging deformation resistance, good plasticity, wide forging temperature range, a low tendency for forging cracking, and precipitation of reticulated carbides.

* Annealing processability

Spheroidizing annealing temperature range is wide, annealing hardness is low, fluctuation range is small, and spheroidization rate is high.

* Cutting processability

Large cutting amount, low tool loss, and low surface roughness.

* Oxidation, decarburization sensitivity

When heated at high temperatures, anti-oxidation energy is good, decarburization speed is slow, and it is not sensitive to the heating medium, and the tendency to produce pitting is small.

* Hardenability

Uniform and high surface hardness after quenching.

* Hardenability

After quenching, a deep hardened layer can be obtained, which can be hardened with a mild quenching medium.

* Quenching deformation cracking tendency

Conventional quenching volume change is small, the shape is warped, distortion is slight, and abnormal deformation tendency is low. Conventional quench cracking has low sensitivity and is not sensitive to quenching temperature and workpiece shape.

* Grindability

Relative loss of grinding wheel is small, the maximum amount of grinding without burn is large, and it is not sensitive to the quality of grinding wheel and cooling condition, and it is not easy to cause abrasion and grinding crack.

3. Mold meets economic requirements

In the selection of mold material, the principle of the economy must be considered to reduce mold manufacturing process cost as much as possible. Therefore, under the premise of satisfying performance of use. Firstly, the price is lower, carbon steel can be used without alloy steel, and domestic materials can be used without imported materials. In addition, the production and supply of the market should also be considered when selecting materials. Selected steel grades should be as small and concentrated as possible, and easy to purchase.