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Molybdenum (Mo), a transition metal with unique properties, is widely used in various industries due to its high melting point, good corrosion resistance, and excellent mechanical properties. However, during the production process, especially during cold rolling, molybdenum plates may develop cracks. This article aims to provide a comprehensive analysis of the causes of molybdenum plate cracks and explore potential solutions.

Causes of Molybdenum Plate Cracks

1. Poor Plasticity:
   Molybdenum exhibits relatively poor plasticity. During cold rolling, excessive rolling force can lead to severe lamination within the molybdenum layer, generating numerous internal defects. These defects can quickly aggregate at grain boundaries during stretching, ultimately causing fracture.

2. Improper Heating Temperature:
   During the heated rolling process, if the local heating temperature is too high, recrystallization occurs, resulting in larger grains due to mutual annexation. This manifests as coarse and short fiber structures, which can adversely affect the material’s mechanical properties and increase the risk of cracks during cold rolling. Conversely, if the heating temperature is too low while the processing rate is high, the work hardening rate of the molybdenum plate may exceed the plastic deformation rate. This can lead to a situation where the sum of internal residual stress and external tensile stress exceeds the tensile strength of the molybdenum plate, causing it to crack.

3. Rolling Deformation Rate:
   The cold rolling deformation rate significantly impacts material properties. At lower deformation rates, metals are only mechanically engaged due to initial plastic deformation, and interfaces have not achieved firm bonding. This weak interface bonding can easily lead to cracking during stretching. As the deformation rate increases, although tensile strength may improve, excessive deformation rates combined with molybdenum’s poor plasticity can cause severe lamination and cracking.

4. Equipment Precision and Stability:
   The precision and stability of cold rolling equipment are crucial. Inadequate precision or poor stability can result in uneven stress distribution during rolling, leading to cracks.

5. Environmental Factors:
   Environmental factors such as temperature and humidity can also affect the cold rolling process. Extremely high or low temperatures can alter the material’s physical properties, increasing the risk of cracks.

6. Improper Operation:
   Factors such as excessive rolling speed and rolling force during the cold rolling process can contribute to crack formation.

7. Equipment Maintenance:
   Regular maintenance and upkeep of equipment are essential for maintaining good equipment condition. Poor maintenance can lead to decreased precision and stability, adversely affecting the cold rolling process.

   

Solutions to Molybdenum Plate Cracks

1. Optimizing Heating Temperature:
   Control the heating temperature to avoid excessive or insufficient heating. Proper heating can prevent recrystallization and excessive grain growth, ensuring optimal material properties.

2. Adjusting Rolling Deformation Rate:
   Find an appropriate rolling deformation rate to balance tensile strength and plasticity. Avoid excessive deformation rates to prevent lamination and cracking.

3. Enhancing Equipment Precision and Stability:
   Regularly inspect and maintain cold rolling equipment to ensure precision and stability. Address any issues promptly to prevent uneven stress distribution.

4. Managing Environmental Factors:
   Monitor and control environmental factors such as temperature and humidity to minimize their impact on the cold rolling process.

5. Improving Operational Practices:
   Train operators to follow proper rolling procedures, including controlling rolling speed and force to prevent cracks.

6. Enhancing Material Plasticity:
   Use annealing processes, such as high-temperature annealing followed by low-temperature annealing, to improve material plasticity. This reduces tensile stress and increases the material’s resistance to cracking.

7. Addressing Stress Concentrations:
   In deep drawing processes, remove stress concentrations by deburring the edges of molybdenum plates after each drawing step. This reduces the risk of longitudinal cracks.

Cracks in molybdenum plates during cold rolling can be attributed to various factors, including material properties, process conditions, equipment, environment, and operational practices. To minimize crack formation, comprehensive measures must be taken to address these factors. By optimizing heating temperature, adjusting rolling deformation rates, enhancing equipment precision and stability, managing environmental factors, improving operational practices, and enhancing material plasticity, the occurrence of cracks in molybdenum plates can be significantly reduced. This comprehensive approach ensures the production of high-quality molybdenum plates suitable for various industrial applications.