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Challenges of induction heating: Why is hot stamping die positioning so critical?
In today's manufacturing industry, hot pressing technology plays a vital role, and its application in powder metallurgy is particularly valued. Hot pressing is a high-pressure and low-strain-rate process that promotes sintering and creep reactions by applying high temperatures to powders or powder agglomerates. The core of this process is the simultaneous application of heat and pressure, which makes it widely applicable to the manufacture of hard and brittle materials, thereby meeting the market's growing demand for high-performance materials.
The range of materials that can be processed by hot pressing technology includes everything from steel to high-performance ceramics, especially key applications such as diamond metal composites.
The hot pressing process typically involves a graphite die that is inductively heated to temperatures up to 2400°C (4350°F) and applied pressures of up to 50 MPa (approximately 7300 psi). The three types of heating methods used in this technology include: induction heating, indirect resistance heating, and field-assisted sintering techniques such as rapid hot pressing. The following discusses in detail the principles, advantages, disadvantages and applications of each heating method.
Induction Heating
During the induction heating process, the mold is subjected to a high-frequency electromagnetic field, which is generated by an induction coil combined with an electronic generator. The biggest advantage of this technology is the complete independence between pressure and induction power. However, this process also has many challenges, especially in the accuracy of mold positioning, such as mold eccentricity will lead to uneven heating.
Once the air gap between the mold and the induction coil is uneven, the overall heating efficiency will decrease.
Indirect resistance heating
Unlike induction heating, indirect resistance heating technology places the mold in a heating cavity, where a graphite heating element heats the cavity through an electric current, and then transfers the heat to the mold through convection. Although higher heating temperatures can be achieved, the biggest disadvantage of this process is that the mold is heated slowly, depending on the efficiency of heat transfer from the furnace to the mold surface.
Field Assisted Sintering Technology (FAST)
Field-assisted sintering technology, also known as pulse equivalent sintering, is a relatively new method. The basic idea is to use electric current to pass through the mold for sintering. The advantage of this technology is that the sintering effect can be achieved in a shorter time and the temperature and pressure required for sintering can be significantly reduced.
Using field-assisted sintering technology, research has shown that the required finished product density can be achieved within minutes, which is difficult to achieve using traditional sintering processes.
Application Areas
Hot pressing technology has a wide range of applications, including the manufacture of high-performance ceramic components such as borides and titanium diborides. In recent years, this technology has had an increasing impact in industries such as motorcycles and high-speed rail, becoming one of the main technologies for producing brake pads and clutches.
In addition, research institutions and universities are also actively applying hot pressing technology to shorten the experimental cycle and promote technological innovation. Recent developments include the fabrication of metal-diamond composite heat sinks, an effective heat dissipation technology for LED and laser applications.
Proper positioning of the mold during the heat pressing process is critical to the quality and performance of the final product. Whether the improper position of the mold during the heating process can be effectively solved will directly affect the combustion uniformity of the material and the stability of the overall quality. This is why positioning of the mold and efficient heat transfer in induction heating technology, especially for delicate material processing, represent an important new challenge.
Faced with these higher requirements and challenges, will future hot pressing technology usher in greater development opportunities due to precise positioning and efficient heating solutions?
