How to Choose the Right Steels for Making Dies and Molds?

How to choose the right steels for making dies and molds?

Firstly, we must understand some of the basic common knowledge of the die. According to the usage, it is generally divided into hot working dies, cold working dies and plastic molds. It can also be classified according to the of service lifetime: one level: more than 1 million shots; Level 2: 500,000 to 5 million shots; Level 3: 300,000-~ 500,000 shots; Level 4: 100,000 ~ -300,000 shots; Level 5: less than 100,000 shots; The first and second Dies require the tool steel with hardness of about 50HRC, otherwise it will be easier to wear out. Therefore, the tool steel should not only have good heat treatment performance, but also good machinability under high hardness. Certainly, there are other considerations. Because of the large number of domestic tool steel manufacturers and grades, the brands are confusing, so there is no reference steels for comparison and research. The tool steels mentioned below are all imported. A large number of industrial die & mold manufacturing in China was after the reform and opening up. At that time, the technology importing countries mainly included Japan, Europe, America, Hong Kong and Taiwan. Hong Kong generally used European and American technologies and materials, while Taiwan used Japanese materials and technologies.

The common used die steels are

Germany: Die Steel TQ1, HP1, USN (1.2343), USD (1.2344), 1.2379, 1.2083, 1.2316;

United States: Die Steel 420, H13, H11, P20, D2;

Japanese: Die Steel SKD61, DC53, NAK80, SKD11, High speed steel SKH-9;

Sweden: Die Steel S136, 8407, DF-2, 718;

To choose different steels has a great impact on the Injection molds. We also need to have a comprehensively consideration, such as adding reinforcement or other modifiers. For example, the glass fiber damage to the mold. Strong acidic plastic materials include PVC, POM, PBT. The weakly acidic plastic materials are PC, PP, PMMA, PA. Highly corrosive plastics are generally require the die steels as S136, 1.2316, 420, etc., and weakly corrosive can use the S136, 1.2316, 420, SKD61, NAK80, PAK90, 718, etc.. The appearance requirements of the product also have a great influence on the selection of tool steel. The transparent parts and surface products requiring mirror polishing require the steels of S136, 1.2316, 718, NAK80, PAK90, 420. Molds with high transparency requirements should use the steels of S136, second choice is 420. However, if you simply meet product requirements without considering production costs, you may not be a good designer. Mold manufacturing costs is also a top priority. Compared with imported 1.2316 and S136, they differs by dozens RMB/kg. If you make the wrong choice, it is difficult for the factory to make a reasonable profit.

Molds with 300,000 to 500,000 shots usually use the tool steels with pre-hardened condition, such as S136H, 1.2316H, 718H, 1.2083H, etc.. Mold below 300,000 shots use tool steel of P20, 1.2738, 1.2311, 1.2711 and so on. For ultra-low requirements of the mold, we can consider S50C, S45C, which directly makes a cavity in the mould.

Cold Work Tool Steel is mainly used to manufacture a die that presses and forms a work piece under cold conditions. Such as: Cold Blanking Die, Cold Stamping Die, Cold Drawing Die, Imprint Die, Cold Extrusion Die, Thread Pressing Die and Powder Pressing Tooling, etc.. Cold Work Tool Steel has a wide range, from various carbon tool steel, alloy tool steel, high speed steel to powder high speed steel and powder high alloy mold steel. Therefore, the recommendation and use classification of cold die steel are complex, that should be selected according to the actual situation.

Hot Work Tool Steel is mainly used to manufacture the dies for pressing the workpiece at high temperature. Such as: hot forging die, hot extrusion die, die casting die, hot upsetting forging die.

The commonly used hot die steel is: alloy die steels with high and medium carbon content, adding Cr, W, Mo, V and other alloy elements; High alloy austenitic heat-resistant die steel is sometimes used for special requirements.

Aluminum alloy die casting dies have relatively high requirements for steels, which should be selected according to specific die design requirements. Die casting dies have high requirements on heat treatment techniques.

Besides selecting reliable materials, heat treatment should also be fully considered.

The first choice of material origin is TQ1, HP1, USN, USD, H13, SKD61 etc..