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Hot pressing technology revealed: How to use high pressure and high temperature to change powder materials?
With the advancement of science and technology, powder metallurgy technology plays an increasingly important role in modern manufacturing, especially in the manufacture of hard and brittle materials. Among them, hot pressing technology changes the properties of powder materials with its unique high-pressure and high-temperature conditions, achieving the transformation from powder to solid material. This article will deeply explore the principles, processes and applications of hot pressing technology, and consider its future development direction.
Hot pressing technology is a process that combines high pressure and high temperature to change the properties of powder materials.
Basic principles of hot pressing
Hot pressing technology is a powder metallurgy process that utilizes high pressure and low strain rate to form powder or powder compact body by applying heat and pressure simultaneously to induce sintering and creep processes. One of the main applications of this technology is in the production of combined diamond-metal composite cutting tools and technical ceramics. The densification process of hot pressing occurs through particle reorganization and plastic flow at the particle contact points, ultimately achieving an increase in the density of the material.
In a typical hot pressing process, pressures can reach 50 MPa (7300 psi) and temperatures can rise to 2400 °C (4350 °F).
Heating technology in the hot pressing process
Hot pressing technology usually involves three different heating methods: induction heating, indirect resistance heating, and Field Assisted Sintering Technology (FAST)/direct hot pressing.
Induction heating
During the induction heating process, the mold generates heat in a high-frequency electromagnetic field. This process provides the flexibility to obtain independent pressure and induction power, suitable for a variety of powder materials. However, disadvantages of this method include the need for an expensive high-frequency generator and good alignment of the sample and mold to ensure uniform heating.
Indirect resistance heating
Different from induction heating, indirect resistance heating places the mold in a heating chamber composed of graphite heating elements, and the heat is transferred to the mold surface by convection. Although it can reach high temperatures, the heating time required is relatively long and has no dependence on the thermal conductivity of the mold.
Field-assisted sintering technology
Field-assisted sintering technology is an older sintering technology that mainly conducts heat through current in the mold. This method enables efficient material shaping even in short sintering cycles and suppresses particle growth.
Direct hot pressing technology allows the material to reach its final density at lower sintering temperatures and pressures.
Application of hot pressing technology
In recent years, hot pressing technology has been increasingly used in key projects such as manufacturing high-performance ceramic components and metal powders. For example, the manufacturing of materials such as boron nitride, titanium diboron, and silicon nitride takes full advantage of the conductivity of metal powders to quickly heat the workpiece. The technology is particularly suitable for applications requiring high heating rates and provides extremely high near-net shape accuracy, often eliminating the need for mechanically heavy work steps in difficult-to-machine materials.
In the friction material industry, the output of direct hot pressing is also gradually increasing, especially in the production of cast brake pads and clutches. As these technologies improve, more and more high-performance applications will be realized, such as braking systems for high-speed rail and motorcycles, and even the use of agricultural machinery and heavy-duty trucks.
Research facilities, such as universities and research institutes, use short sintering cycles to speed up the research process, resulting in many innovations.
However, with the advancement of material technology and changes in manufacturing needs, the future of hot pressing technology is still full of challenges and opportunities. In the exploration of how this technology is combined with new materials and their applications, what potential innovations and breakthroughs do you think will emerge?
