Heating glass with tungsten wire requires careful operation to ensure safety and effectiveness. The following are specific steps and precautions:
1. Select a Suitable Tungsten Wire:
Tungsten wire is suitable for use as a heating element due to its high melting point (about 3422°C) and good conductivity.
According to the size and type of glass to be heated, select a tungsten wire of appropriate diameter and length. Thinner tungsten wire heats up faster, but has a lower current carrying capacity.
2. Design a Heating Device:
Fix the tungsten wire on a high-temperature resistant insulating bracket (such as a ceramic or quartz bracket) to avoid contact with other metals or conductive materials.
Tungsten wire can be wound into a spiral or straight shape, depending on the shape and size of the heating area.
Make sure that the tungsten wire is kept at an appropriate distance from the glass surface (usually a few millimeters) to achieve uniform heating and avoid direct contact that may cause local overheating of the glass.
3. Power and Control:
Use an adjustable DC or AC power source (such as a transformer or thyristor regulator) to power the tungsten wire. The tungsten wire has a low resistance and the current needs to be controlled to prevent overheating and burning.
Calculate the required temperature (usually 300-600°C is used to soften the glass, depending on the softening point of the glass, such as borosilicate glass or ordinary glass) according to the type of glass (such as borosilicate glass or ordinary glass).
Use a temperature sensor or infrared thermometer to monitor the surface temperature of the glass to avoid exceeding its softening point or breaking point.
4. Heating the Glass:
Place the glass on a heat-resistant platform (such as a quartz or ceramic substrate) to ensure that the glass is heated evenly.
Apply power to heat the tungsten wire and gradually increase the current to heat slowly to prevent the glass from breaking due to thermal shock.
If local heating is required (such as stretching or forming a glass tube), move the tungsten wire close to the target area and keep moving or rotating the glass evenly to ensure uniform heating.
5. Cooling and Post-Processing:
After heating is completed, slowly reduce the current to allow the glass to cool gradually to prevent stress concentration from causing cracking.
Some glasses may need to be annealed (kept at a lower temperature for a period) to eliminate internal stresses.
