Technical requirements for die forgings

Die forging manufacturers discuss the specified values of technical standards for cast steel parts, and high-precision forging manufacturers clarify that, unless otherwise specified, all relevant regulations of JB3835-85 and JB3834-85 shall be followed. The technical standards should normally be implemented in the order verified during the production of cast steel parts. The mold must meet the following working requirements:

 

1. Wear Resistance

 

During the plastic deformation of the blank in the mold cavity, it moves and rolls along the surface of the mold cavity, causing intense friction between the mold cavity surface and the workpiece, which may lead to mold failure due to wear. Therefore, the wear resistance of the material is one of the basic and key properties of the mold. Hardness is an important factor determining wear resistance. Generally, the higher the hardness of the mold part, the lower the wear rate and the better the wear resistance. In addition, wear resistance is also related to the type, quantity, shape, size, and distribution of carbides in the material.

 

2. Strength and Toughness

 

The working conditions of molds are often very extreme, and some often bear considerable loads, which may lead to brittle fracture. To prevent sudden brittle fracture of mold parts during operation, the mold must have high strength and toughness. Mold toughness depends entirely on the carbon content, grain size, and structure of the material.

 

3. Fatigue Fracture Characteristics

 

During mold operation, under the continuous influence of cyclic stress, fatigue fracture usually occurs. The modes include low-energy multiple impact fatigue fracture, tensile fatigue fracture, contact fatigue fracture, and bending fatigue fracture. The fatigue fracture characteristics of the mold depend entirely on its strength, toughness, hardness, and the content of inclusions in the material.

 

4. High-Temperature Performance

 

Universal joint manufacturers discuss that when the mold working temperature is high, it will reduce hardness and compressive strength, causing premature wear or deformation and failure of the mold. Therefore, mold steel should have high tempering stability to ensure that the mold maintains high hardness and compressive strength at the working temperature. 5. Resistance to Thermal Fatigue

 

Some molds are subjected to continuous heating and cooling during operation, causing bending and stress on the mold cavity surface due to working pressure. This leads to surface cracking and spalling, increasing friction, hindering shape changes, reducing processing accuracy, and potentially rendering the mold unusable. Thermal fatigue is one of the main forms of failure for hot-working molds; therefore, such molds should possess high resistance to thermal fatigue.

 

6. Corrosion Resistance

 

Some molds, such as plastic molds, are exposed to chlorine and fluorine in plastics during operation. When heated, these elements dissolve and release highly corrosive gases such as HCl and HF, corroding the mold cavity surface, increasing its surface roughness, and exacerbating wear failure.

 

Precision Forging of Cast Steel Parts

 

Precision forging refers to a forming technology where parts are forged into shape with minimal or no further processing required to meet part specifications. Precision forging is an indispensable part of modern manufacturing technology and is a widely used part processing technology in industries such as automotive, mining, energy, construction, aviation, aerospace, and weapons.

 

Precision forging not only saves materials and energy, reduces production processes and equipment, but also significantly improves production efficiency and product quality, reduces costs, and thus enhances the market competitiveness of products. The ability to form large and complex cast steel parts is an important indicator of a country's industrial and technological strength and international standing. The key structural cast steel materials used in critical manufacturing sectors such as aviation, aerospace, and energy are mainly heat-resistant alloys, titanium alloys, and high-strength alloy steels. These materials have been successfully used in aircraft and gas turbines, and are crucial for improving engine fuel efficiency, increasing aircraft speed, and improving gas turbine efficiency.

 

In recent years, with the rapid development of the economy and national defense, the demand for large and complex cast steel parts has surged, such as aircraft frames, engine integral blisks, large blades and discs for gas turbines and small turbines, with many forged parts having an expanded area exceeding 3 m². However, titanium alloys and heat-resistant alloys are not only expensive metal materials but also difficult to process and deform. On the one hand, this type of raw material has poor machinability; on the other hand, due to its high deformation resistance, high deformation temperature, and narrow deformation temperature range, it is generally necessary to forge it into rough castings before machining, resulting in excessively high raw material costs, which to a certain extent limits and severely impacts the application of the material.

 

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However, the emergence of hot precision forging technologies, represented by hot die forging and isothermal forging, has opened up a crucial path for near-net-shape forging of difficult-to-deform materials such as titanium and heat-resistant alloys, providing a new method for the production of large and complex castings.

 

Hot forging process: The casting process of high-precision castings at a forging temperature above the recrystallization temperature is called hot forging. Hot forging materials have low deformation resistance and good plasticity, making it easy to form complex workpieces. However, due to significant chemical reactions, the surface quality and processing accuracy of the material are relatively low. The common processing method for hot forging is closed-die forging.