An Introduction to Stamping Dies (Part Two)

Usually, a die is composed of two parts. One is the process part, which directly participates in the manufacturing process of the part and is directly in contact with raw materials, including punch parts, knife-edge parts, unloading parts, forming parts and adjusting parts. The other is the structural part. This type of part does not directly participate in the manufacturing process of the finished product, nor does it have direct contact with the raw materials. It only ensures that the mold completes the role of the manufacturing process and assembly of molds, or perfecting the mold function, including guide parts, fastening parts, positioning parts, springs and safety inspection parts and other parts. It should be noted that not all punching dies must have all the above-mentioned parts, especially single-process molds, but standard parts of molds are indispensable for any mold.
 
The mold material is also very important in the design.
The materials used to manufacture stamping dies include steel, cemented carbide, steel-bonded cemented carbide, zinc-based alloys, low melting point alloys, aluminum bronze, polymer materials, etc. At present, most of the materials used to make stamping dies are steel. Commonly used working parts of molds are carbon tool steel S45C, cold working die steel CALMAX, VIKING, XW-10, XW-42, SKD11, cemented carbide and steel-bonded cemented carbide VANADIS-4, VANADIS-23, VANADIS-60, H40S, etc.
 
Carbon tool steel: The carbon tool steel that is used more frequently in molds are S45C and S55C, which have the advantages of good processing performance and cheap prices. However, the hardenability and red hardness are poor; the heat treatment deformation is great, and the load-bearing capacity is low.

CALMAX: It has high strength, good toughness, good hardenability and weldability, which can be flame hardened to HRC56-60 with a hardening layer up to 5 mm. It is used for punching for thick plates, drawing dies, embossing dies, cold extrusion dies with complex shapes, and abrasive plastic forming dies.

VIKING: It has good wear resistance, toughness and small heat treatment deformation, which is used for high-load stamping dies, forming dies and abrasive plastic forming dies.

XW-10: It is Air-cooled hardenable chromium steel, which has excellent toughness, good wear resistance, small heat treatment deformation and is used for drawing dies, crimping dies, embossing dies and abrasive plastic molding dies.

XW-42: It is high chromium steel, which has good wear resistance and good impact resistance. It is used for precision punching dies, embossing dies, cold extrusion dies, cold forging dies,  stretching dies, crimping dies and abrasive plastic forming dies.

SKD11: It is a kind of high chromium, high carbon cold working die steel; it is specially heat-treated before leaving the factory, so that it has good processing performance, excellent hardenability, good toughness and wear resistance, and stable dimensions after heat treatment. It is used for precision punching dies, embossing dies, cold extrusion dies, cold forging dies, stretching dies, crimping dies and abrasive plastic forming dies.
 
Cemented carbide and steel-bonded cemented carbide: The hardness and wear resistance of cemented carbide are higher than any other type of die steel, but the bending strength and toughness are poor. The cemented carbide used for the mold is tungsten-cobalt. For molds with low impact resistance and good wear resistance, cemented carbide with lower cobalt content can be selected. For molds with great impact, cemented carbide with higher cobalt content can be selected. Steel-bonded cemented carbide is made by adding a small amount of alloying element powder such as chromium, molybdenum, tungsten and vanadium to iron powder as a binder, using titanium carbide or tungsten carbide as the hard phase, and sintering by powder metallurgy. The matrix of steel-bonded cemented carbide is steel, which overcomes the disadvantages of poor toughness and difficult processing of cemented carbide. It can be cut, welded, forged and heat treated. Steel-bonded cemented carbide contains a lot of carbides. Although its hardness and wear resistance are lower than that of cemented carbide, it is still higher than other steel grades. After quenching and tempering, its hardness can reach 68 to 73HRC.

VANADIS-4: It has good wear resistance and good toughness, and good dimensional stability after heat treatment. It is used for stamping high-viscosity materials, precision stamping dies with a long service life, cold extrusion dies, stretching dies, powder pressing dies.

VANADIS-23: It is crystal ultra-fine high-speed steel, and it has good wear resistance and good toughness, high compressive strength, uniform quality, no segregation, easy processing, good dimensional stability after heat treatment. It is used for punching hardened steel plates or cold-rolled steel strips for medium and high carbon steel blanking dies, powder pressing dies. 

VANADIS-60: It is crystal ultra-fine high-speed steel, which has good wear resistance and toughness, high compressive strength, uniform quality, no segregation, easy processing, good  dimensional stability after heat treatment. It is used for high-speed cutting tools, thin slices and high-grain wear materials punching forming dies, as an alternative to cemented carbide for easy chipping.
 
H40S: It is a hard straight alloy made from tungsten-cobalt alloys and has excellent performance of good wear resistance and high strength. It is used for punches and knife edges of punching, and sometimes for processing unloaded parts.
 
S55C steel can be a good choice for the upper and lower mold bases. S55C is high-grade medium carbon steel with excellent chipping performance, uniform metallographic structure, good wear resistance, low ductility, and low prices. It is most suitable for mold bases.
 
SKD11 steel can be selected for the mold plate. SKD11 is a kind of cold working die steel containing high chromium and high carbon. It is specially heat-treated before leaving the factory so that it can have good processing performance, excellent hardenability, good toughness and wear resistance, and dimensional stability after heat treatment.
 
H40S and CD337 cemented carbide are good for cutting punches, knife edges and forming parts. H40S is a hard straight alloy made from tungsten-cobalt alloy, which has excellent performance of good wear resistance and high strength. However, its impact resistance is not good, which makes it not suitable for stamping thick materials. CD337 steel is used for thick materials, which has good impact resistance and high crushing strength. SKD11 steel can be a good choice for guide plates, floating material parts, pressure blocks and other parts.