What kind of high temperature resistant material should be used for red stamping die?

The stamping die is made of steel, cemented carbide, steel-bonded cemented carbide, zinc-based alloy, low melting point alloy, aluminum bronze and polymer materials. At present, the materials for manufacturing stamping dies are mostly steel, and the commonly used materials for working parts of dies are: carbon tool steel, low alloy tool steel, high carbon and high chromium or medium chromium tool steel, medium carbon alloy steel, high speed steel, matrix steel, cemented carbide, steel bonded cemented carbide and so on.

1. carbon tool steels T8A, T 10A, etc. , widely used in molds, has the advantages of good processability and low price. However, 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 based on carbon tool steel, and appropriate alloying elements are added. Compared with carbon tool steel, it reduces the tendency of quenching deformation and cracking, improves the hardenability of steel and has better wear resistance. Low-alloy steels used to manufacture molds include CrWMn, 9Mn2V, 7CrSiMnMoV (code name CH- 1) and 6CrNiSiMnMoV (code name GD).

3. The commonly used high-carbon and high-chromium tool steels are Cr 12, Cr 12MoV, Cr1v1(code D2), which have good hardenability, hardening ability and wear resistance, and little deformation during heat treatment, and are high wear-resistant micro-deformation die steels. However, carbide segregation is serious, so repeated upsetting and drawing (axial upsetting and radial drawing) must be carried out to reduce the inhomogeneity of carbide and improve the service performance.

4. The high-carbon medium-chromium tool steels used in the high-carbon medium-chromium tool steel die include Cr4W2MoV, Cr6WV, Cr5MoV, etc. Low chromium content, less crystalline carbide, uniform carbide distribution, small heat treatment deformation, good hardenability and dimensional stability. Compared with high carbon and high chromium steel with relatively serious carbide segregation, its properties have been improved.

5. High-speed steel High-speed steel has the highest hardness, wear resistance and compressive strength among die steels, and has a high bearing capacity. W 18Cr4V (code 8-4- 1), W6Mo5 Cr4V2 (code 6-5-4-2, American brand M2) and 6W6 high speed steel 6Mo5 Cr4V (code 6W6 or low carbon M2) with less tungsten content are commonly used in dies. High speed steel also needs forging to improve its carbide distribution.

6. Matrix steel is to improve the properties of steel by adding a small amount of other elements to the basic components of high-speed steel and appropriately increasing or decreasing the carbon content. This kind of steel is collectively called matrix 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 high-speed steel. They are cold-working die steels with high strength and toughness, but the material cost is lower than that of high-speed steel. The matrix steels commonly used in dies are 6Cr4W3Mo2VNb (code 65Nb), 7Cr7Mo2V2Si (code LD), 5Cr4Mo3SiMnVAL (code 0 12AL) and so on.

7. The hardness and wear resistance of cemented carbide and steel bonded cemented carbide are higher than any other die steel, but the bending strength and toughness are poor. The cemented carbides used as molds are tungsten and cobalt. For dies with low impact and high wear resistance, cemented carbide with low cobalt content can be selected. For high impact dies, cemented carbide with high cobalt content can be selected.

Steel bonded cemented carbide is made by powder metallurgy with iron powder containing a small amount of alloying elements (such as chromium, molybdenum, tungsten and vanadium) as binder and titanium carbide or tungsten carbide as hard phase. The matrix of steel-bonded cemented carbide is steel, which overcomes the shortcomings of poor toughness and difficult processing of cemented carbide and 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 cemented carbide, it is still higher than other steel grades. After quenching and tempering, the hardness can reach 68 ~ 73HRC.

Material selection and heat treatment requirements of stamping die

When selecting blanking die materials, the batch production of workpieces should be considered. If the batch is not large, there is no need to choose long-life mold materials. The material of stamping workpiece should also be considered, and different materials are suitable for different mold materials. For blanking die, wear resistance is an important factor to determine the life of the die. The wear resistance of steel depends on the state of hard points, such as carbide and matrix hardness. The higher the hardness, the more carbides and the better the wear resistance.

The order of wear resistance of common stamping die steel is carbon tool steel-alloy tool steel-matrix steel-high carbon and high chromium steel-high speed steel-steel bonded cemented carbide.

In addition, the influence of the thickness, shape, size and accuracy requirements of the workpiece on the selection of die materials must be considered.

1. Traditional die steel For a long time, the domestic steel for sheet metal stamping die is T 10A, CrWMn, 9Mn2V, Cr 12 and Cr 12MoV, etc.

Among them, T 10A is carbon tool steel with certain strength and toughness. However, the wear resistance is not high, the quenching is easy to deform and crack, and the hardenability is poor. It is only suitable for blanking dies with simple workpiece shape, small size and small quantity.

The heat treatment process of T 10A carbon tool steel is: quenching in water or oil at 760~8 10℃, tempering at 160~ 180℃, and the hardness is 59~62HRC.

CrWMn and 9Mn2V are high carbon and low alloy steels, with simple quenching operation, better hardenability than carbon tool steels and easy deformation control. However, the wear resistance and toughness are still low, and it is suitable for blanking dies with medium batch and complex workpiece shape. The heat treatment process of CrWMn steel is: quenching temperature 820~840℃, oil cooling, tempering temperature 200℃, hardness 60~62HRC. The heat treatment process of 9Mn2V steel is as follows: quenching temperature 780~820℃, oil cooling, tempering temperature 150~200℃, air cooling and hardness 60~62HRC. Pay attention to temper brittleness and obvious volume expansion in the range of 200~300℃, which should be avoided.

Cr 12 and Cr 12MoV are high-carbon and high-chromium steels with high wear resistance, small deformation during quenching and good hardenability, which can be used for mass production dies, such as silicon steel sheet punching dies. However, this kind of steel has carbide inhomogeneity, which is prone to carbide segregation and edge collapse or fracture when blanking. Among them, Cr 12 has higher carbon content, and the uneven distribution of carbides is more serious and brittle than Cr 12MoV.

The choice of heat treatment process for Cr 12 steel depends on the use requirements of the die. When the die requires small deformation and certain toughness, it can be quenched and tempered at low temperature (quenching at 950~980℃ for Cr 12 and tempering at 150~200℃); Cr 12MoV is 1020~ 1050℃ quenching and 180~200℃ tempering). In order to improve the service temperature, hardenability and red hardness of the die, high temperature quenching and tempering (Cr1000 ~1100℃ quenching and tempering at 480 ~ 500℃) were adopted. Cr 12MoV is11140℃ quenching and 500~520℃ tempering). High chromium steel has temper brittleness at 275~375℃ and should be avoided.

2. New steel grades for common dies

In order to make up for the deficiency of traditional die steel, China has developed or introduced the following steels with better performance:

(1) Cr 12mo1v1(code D2) steel is an imported steel which imitates D2 steel in American ASTM standard and belongs to Cr12 section steel. Due to the increase of Mo and V content in D2 steel, the grains are refined and the distribution of carbides is improved. Therefore, the strength and toughness (impact toughness, bending strength and deflection) of D2 steel are higher than those of Cr 12MoV steel, and the wear resistance and tempering stability are also higher than those of Cr 12MoV steel. Low temperature treatment can be used to improve hardness and dimensional stability. The service life of D2 steel blanking die is longer than that of Cr 12MoV steel die. The forging properties and thermoplastic formability of D2 steel are slightly worse than those of Cr 12MoV steel, and the cutting properties and heat treatment process are similar to those of Cr 12 steel.