Characteristics of PFA welding rods and their application in industrial furnace linings

1. What is a PFA welding rod?

PFA welding rod is a high-performance fluoroplastic welding material made from PFA resin extruded into rods or flat sheets. Its core advantages are:

1. Temperature resistance: It can operate stably in temperatures ranging from -80°C to 260°C for long periods of time, with short-term temperature resistance up to 300°C.

2. Corrosion resistance: It is resistant to strong acids (such as hydrofluoric acid and concentrated sulfuric acid), strong bases, and organic solvents, with a corrosion rate of less than 0.01 mm/year.

3. Low permeability: Its dense molecular structure allows for a gas permeability that is only 1/100th that of ordinary plastics.

2. Why do industrial furnace linings require PFA welding rods?

The linings of industrial furnaces (such as chemical reactors and steel heat treatment furnaces) have long faced three challenges:

High-temperature corrosion: Furnace media (such as molten salts and acidic gases) accelerate material aging at high temperatures.

Thermal stress cracking: Frequent furnace starts and stops cause the lining to expand and contract.

Weld failure: Traditional lining joints are susceptible to corrosion penetration.

PFA welding rods are used to repair cracks or join plates together, creating a seamless anti-corrosion layer and preventing corrosion of the furnace base material caused by media penetration.

III. Core Processes of PFA Welding Technology

1. Surface Preparation

The metal base material must be thoroughly cleaned and sandblasted to a Sa2.5 roughness (equivalent to a uniformly matte surface). A PFA-specific primer is then applied to enhance adhesion.

2. Hot Air Welding

Using a dedicated welding gun:

Temperature Control: PFA has a melting point of approximately 305°C to 310°C. The hot air gun must be precisely controlled during welding (usually 320°C to 340°C). Excessively high temperatures can cause carbonization, while excessively low temperatures prevent sufficient melting.

Speed ​​Control: The welding gun must be moved at a constant speed (approximately 10 cm/min) to ensure that the molten resin fully penetrates the base material pores.

IV. Application Scenarios of PFA Welding Rods in Industrial Furnace Linings

Dankai PFA welding rods are used for both "protection" and "sealing," primarily covering the following three scenarios:

1. Sealing Joints in Reactor/Tank Linings

Reactors in industrial furnaces (such as pickling reactors and chemical reactors) typically use fluororesin sheets as linings to isolate corrosive media from the furnace metal. The joints between fluororesin sheets are weak points in protection and require PFA welding rods. A hot air welding torch fuses the rods to the sheet seams, creating a seamless seal.

2. Lining Connections for High-Temperature Pipelines

Some industrial furnace pipelines (e.g., those transporting high-temperature corrosive gases or molten liquids) require fluororesin tubing as linings, with PFA welding rods used at the joints. Compared to traditional metal pipes, the PFA tubing + welding rod combination is not only corrosion-resistant but also prevents metal ion contamination (e.g., when transporting high-purity media in the semiconductor industry).

3. High-temperature-resistant production of furnace doors and seals

Industrial furnace door seals (such as gaskets and sealing strips) must be heat-resistant (furnace door temperatures can reach over 200°C), resist deformation, and resist sticking to molten metal. PFA welding rods can be welded into seals of various shapes. Their low coefficient of friction (0.01-0.03) prevents molten metal from sticking, and their thermal shock resistance (no deformation from -80°C to 260°C) allows them to withstand the temperature fluctuations associated with frequent opening and closing of furnace doors.