The Role of Rolling Parameters in the Formation of Porosity in Cold-Rolled Molybdenum Sheets

Molybdenum, known for its exceptional physical and chemical properties, finds numerous applications in high-temperature and corrosive environments. Its thin sheets are often produced through cold rolling, a process that shapes the material by passing it through a set of rollers at ambient or slightly elevated temperatures. However, a common challenge in cold rolling molybdenum sheets is the formation of porosity, which can significantly degrade the material’s performance.

Porosity refers to the presence of voids or pores within the material’s structure. In the context of cold-rolled molybdenum thin sheets, porosity formation can be attributed to several rolling parameters, including roll gap, roll speed, reduction ratio, and lubrication conditions.

The roll gap, which determines the thickness of the sheet, plays a crucial role in porosity formation. A narrow gap can lead to excessive thinning and tearing of the material, while a wide gap may not provide sufficient compression to achieve the desired material properties. Both scenarios can result in the formation of pores.

Roll speed also influences porosity. Higher speeds can lead to increased shear forces and frictional heating, which can cause localized melting and subsequent solidification with trapped gases, forming pores. Conversely, lower speeds may not provide enough energy for adequate material flow, leading to the development of voids.

The reduction ratio, which is the ratio of the initial to the final thickness of the sheet, is another critical parameter. Excessive reduction can cause excessive strain and tearing, while insufficient reduction may not eliminate pre-existing pores or may even introduce new ones.

Lubrication conditions during cold rolling also affect porosity formation. Adequate lubrication reduces friction and heat generation, minimizing the chances of material tearing or melting. However, insufficient lubrication can lead to increased friction and localized heating, promoting porosity formation.

To minimize porosity in cold-rolled molybdenum thin sheets, it is essential to carefully control these rolling parameters. Optimizing the roll gap, roll speed, reduction ratio, and lubrication conditions can significantly reduce porosity formation and enhance the overall quality and performance of the molybdenum sheets.

In conclusion, understanding the role of rolling parameters in porosity formation is crucial for producing high-quality cold-rolled molybdenum thin sheets. By carefully adjusting these parameters, manufacturers can achieve the desired material properties while minimizing porosity and ensuring the sheets’ reliability and durability in demanding applications.