What mold material is easy to make a good mold

When the wear-resistant blank is plastically denatured in the mold cavity, it moves and slides along the surface of the cavity

(I) dies meet the requirements of operating conditions

1. When the wear-resistant blank is plastic denatured in the mold cavity, it moves and slides along the surface of the cavity, causing severe conflicts between the surface of the cavity and the blank, and then causing the mold to fail due to wear. Therefore, the wear resistance of the material is one of the most basic and important functions of the mold.

Hardness is the primary factor affecting wear resistance. In general, the higher the hardness of the mold parts, the smaller the wear and the better the wear resistance. In addition, wear resistance is also related to the variety, quantity, shape, size and distribution of carbides.

2, the working conditions of the strong resistance mold are mostly very bad, some often bear a large impact load, and then lead to brittle cracking. In order to prevent the mold parts from breaking suddenly during operation, the mold should have high strength and resistance.

The resistance of the mold depends primarily on the carbon content of the material, the grain size and the organization.

3, fatigue cracking function in the process of mold operation, under the long-term action of cyclic stress, often lead to fatigue cracking. The methods include low energy multiple impact fatigue cracking, tensile fatigue cracking, contact fatigue cracking and bending fatigue cracking.

The fatigue cracking function of the mold depends primarily on its strength, resistance, hardness, and the content of inclusions.

4. High temperature function When the operating temperature of the mold is higher, the hardness and strength will decrease, resulting in the early wear or plastic deformation of the mold and failure. Because the mold material should have a high resistance to tempering stability, in order to ensure that the mold in the operating temperature, with high hardness and strength.

5. The function of resistance to cold and thermal fatigue. Some molds are repeatedly heated and cooled during operation, which causes the surface of the cavity to be pulled and pressure to change stress, causing surface cracking and falling off, increasing conflict force, preventing plastic deformation, reducing standard accuracy, and then causing mold failure. Cold and hot fatigue is one of the primary ways of hot die failure, to help this type of mold should have a high resistance to cold and hot fatigue function.

6. Corrosion Resistance Some molds, such as plastic molds, are divided into strong corrosive gases such as hci and hf after heating due to the presence of chlorine, fluorine and other elements in the plastic mold during operation, which corrode the surface of the mold cavity, increase its surface roughness and aggravate wear failure.

(II) die meets process function requirements

Mold manufacturing generally have to go through casting, cutting, heat treatment and other processes. In order to ensure the quality of mold manufacturing, decreased production costs, the material should have excellent forgeability, machinability, hardenability, hardenability and grindability; should also have a small oxidation, decarburization sensitivity and quenching deformation cracking tendency.

1, forgeability has a low hot forging deformation resistance, good plasticity, casting temperature planning wide, forging crack cold crack and separation of the network carbide tendency is low.

2, annealing process spheroidization annealing temperature planning wide, low annealing hardness and not firm planning small, high spheroidization rate.

3. Machinability Large amount of cutting, low tool loss, low surface roughness.

4. Sensitivity of oxidation and decarburization. When heated at high temperature, the oxidation resistance is good, the decarburization speed is slow, the heating medium is insensitive, and the pitting tendency is small.

5. Hardenability After quenching, it has uniform and high surface hardness.

6, quenching after quenching can obtain a deeper hardening layer, the use of steep quenching medium can be hardened.

7, quenching deformation cracking tendency practice quenching volume change is small, shape warping, distortion is slight, abnormal deformation tendency is low. Practice quenching cracking sensitivity is low, the quenching temperature and the shape of the workpiece is not sensitive.

8, grinding wheel relative loss is small, no burn limit grinding amount is large, the quality of the grinding wheel and cooling conditions are not sensitive, not easy to wear and grinding cracks.

(III) mold to meet economic requirements

In the selection of mold material, it is necessary to consider the principle of economy, as far as possible to reduce manufacturing costs. Therefore, in order to meet the use of the function of the premise, the first choice of lower prices, can use carbon steel does not have to alloy steel, can use domestic materials do not have to import materials. Other, in the selection of materials should also consider the production and supply of shopping malls, the selected steel should be as few as possible and concentrated, easy to buy.

The selection of car stamping die materials is different due to the different functions of various parts in the die, so the requirements and selection principles of its materials are also different. Therefore, the rational selection of mold materials is also a very important job in die design, it is not only related to the cost of parts, but also seriously affect the production.

With the development of the car industry, people's demand for cars is growing, and the biggest factor affecting production is how to choose die materials.

Although, the materials used in the working parts of the mold should be better than the materials used in other parts. Generally speaking, depending on the application conditions and requirements of the mold, there are four main types:

1. About the mold operation parts with simple shape and small stamping parts standard. Commonly used carbon tool steel, such as T8A, T10A and so on. 2. On the shape of messy, stamping parts standard larger mold parts, often with alloy tool steel or high-speed tool steel, such as Cr12, CrWMn, Cr12MoV, W18Cr4V, W6MoSCr4V2 and so on.

2. About stamping parts precision or die life requirements are relatively high mold parts, commonly used carbide or steel bonded carbide, such as YG15, YG20, GW50 and so on.

3. For the working parts of large moulds (such as car masking dies), common cast iron may be cast carbon steel, and some of them are also strengthened by surfacing at the cutting edge, such as gray cast iron HT250, cast steel 2G270-500, etc.

In the selection of mold parts materials, in addition to the selection of operating parts is the most important, the more outstanding is the guide column, guide sleeve parts, the general selection of high-quality carbon steel in the low carbon steel carburizing quenching or selection of bearing steel.

It is necessary to point out that the material selection of mold parts is the most important and strict, and it also includes the necessary and reasonable requirements for its heat treatment industry.

In addition to the above-mentioned parts of other mold parts, the choice of carbon structural steel or high-quality carbon steel in the medium carbon steel can be.

The drawing die material for large drawing parts and car cover parts can be alloy cast iron or high-strength ductile iron. Ductile iron can be immersed in lubricating oil, the graphite in the organization has a self-lubricating effect, can effectively reduce the conflict in deep drawing, and the cost is low, simple processing.

High-strength ductile iron can be used for dual-medium delayed cooling martensite isothermal quenching to obtain high strength and resistance, with a hardness of 55 ~ 58HRC. First, slowly preheat the mold and then heat it to 880~900 ℃. After heat preservation, air pre-cooling is carried out first, then brine quenching is carried out to about 550 ℃ and then oil cooling is carried out. When the mold temperature drops to about 250 ℃, hot oil of 180~200 ℃ is put into the medium temperature for 2~3 hours, then the oil temperature drops to about 170 ℃ and isothermal for 5~7 hours, and finally air cooling is carried out.

After alloying, heat treatment and surface treatment, ductile iron can be used as a drawing die for car cover parts, and the actual application of ductile iron as a car cover mold is introduced.