The materials used for stamping molds include steel, hard alloys, steel bonded hard alloys, zinc based alloys, low melting point alloys, aluminum bronze, polymer materials, and so on.
At present, the majority of materials used for manufacturing stamping molds are steel. The commonly used types of mold working parts materials include: carbon tool steel, low alloy tool steel, high carbon high chromium or medium chromium tool steel, medium carbon alloy steel, high-speed steel, matrix steel, as well as hard alloys, steel bonded hard alloys, and so on.
1. Carbon tool steel
Carbon tool steels commonly used in molds are T8A, T10A, etc., which have the advantages of good processing performance and low cost. But the hardenability and red hardness are poor, the heat treatment deformation is large, and the bearing capacity is low.
2. Low alloy tool steel
Low alloy tool steel is made by adding an appropriate amount of alloying elements on the basis of carbon tool steel. Compared with carbon tool steel, it reduces quenching deformation and cracking tendency, improves the hardenability of the steel, and also has better wear resistance. Low alloy steels used for mold manufacturing include CrWMn, 9Mn2V, 7CrSiMnMoV (code CH-1), 6CrNiSiMnMoV (code GD), etc.
3. High carbon and high chromium tool steel
The commonly used high carbon and high chromium tool steels include Cr12, Cr12MoV, and Cr12Mo1V1 (code D2), which have good hardenability, hardenability, and wear resistance. They have minimal heat treatment deformation and are high wear-resistant micro deformation mold steels, with a load-bearing capacity second only to high-speed steel. However, severe segregation of carbides requires repeated upsetting and drawing (axial and radial) to reduce the unevenness of carbides and improve their performance.
4. High carbon medium chromium tool steel
High carbon medium chromium tool steels used for molds include Cr4W2MoV, Cr6WV, Cr5MoV, etc. They have low chromium content, fewer eutectic carbides, uniform distribution of carbides, small heat treatment deformation, good hardenability and dimensional stability. Compared with high carbon and high chromium steel with relatively severe carbide segregation, the performance has been improved.
5. High speed steel
High speed steel has the highest hardness, wear resistance, and compressive strength among mold steels, and has a high load-bearing capacity. Commonly used in molds are W18Cr4V (code 8-4-1) and W6Mo5 Cr4V2 (code 6-5-4-2, US grade M2) with low tungsten content, as well as the low-carbon and vanadium reducing high-speed steel 6W6Mo5 Cr4V (code 6W6 or low-carbon M2) developed to improve toughness. High speed steel also needs to be forged to improve its carbide distribution.
6. Matrix steel
Add a small amount of other elements to the basic composition of high-speed steel, and appropriately increase or decrease the carbon content to improve the performance of the steel. This type of steel is collectively referred to as base steel. They not only have the characteristics of high-speed steel, but also have certain wear resistance and hardness, and their fatigue strength and toughness are better than those of high-speed steel. They are high-strength and toughness cold work mold steel, but their material cost is lower than that of high-speed steel. The commonly used matrix steels in molds include 6Cr4W3Mo2VNb (code 65Nb), 7Cr7Mo2V2Si (code LD), 5Cr4Mo3SiMnVAL (code 012AL), etc.
7. Hard alloys and steel bonded hard alloys
Hard alloy has higher hardness and wear resistance than any other type of mold steel, but poor bending strength and toughness. The hard alloy used for molds is tungsten cobalt type. For molds with low impact resistance and high wear resistance requirements, hard alloys with lower cobalt content can be selected. For molds with high impact, hard alloys with higher cobalt content can be selected.
Steel bonded hard alloy is made by sintering iron powder with a small amount of alloy element powder (such as chromium, molybdenum, tungsten, vanadium, etc.) as the binder, titanium carbide or tungsten carbide as the hard phase, using powder metallurgy method. The matrix of steel bonded hard alloy is steel, which overcomes the disadvantages of poor toughness and processing difficulties of hard alloy. It can be cut, welded, forged, and heat treated. Steel bonded hard alloys contain a large amount of carbides. Although their hardness and wear resistance are lower than those of hard alloys, they are still higher than other types of steel. After quenching and tempering, their hardness can reach 68-73HRC.