Ptfe molded products, in the production of box, flange, reinforced steel plate or complex structure of the parts, often use welding method. The welding of ptfe is different from that of other hot melt engineering plastics or other materials. The welding is difficult, and the processing is not good, and the welding strength cannot meet the requirements, resulting in weak welding. In order to ensure the welding quality of ptfe workpiece, make the welding seam smooth, no crack, the strength and mechanical properties of the welding place after processing are not lower than 80% of the original material. When welding, we must pay attention to the following three aspects.
First. Welding rod selection
Before the selection of welding rod is important, ptfe is a non-adhesive material, poor adhesion, can choose fusible and melt flow of good electrode. If butt welding or enhanced butt welding requires groove treatment on the workpiece welding surface, generally adopt "V" or "x" groove. The workpiece must be fixed firmly during welding. It is recommended to use Teflon PFA fusible polytetrafluoroethylene electrode, which is a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, to meet the requirements of this welding process. Teflon PFA not only has good weldability, but also has good weld strength and strong tear resistance after welding.
Second, clean up the work
Electric welding of the workpiece must be cleaned, not allowed to mix with other impurities, treatment is not clean, often welding effect will not be ideal, even take off welding. Therefore, the ptfe welding parts should be cleaned first, and then the welding surfaces should be cleaned and dried with organic solutions such as acetone or ethanol, as shown in the figure, which is a schematic diagram of welding operation. Welding gun 45 degree Angle near the welding parts, and the welding place to keep a distance of 5 ~ 10 mm, PFA electrode should be put in small pipe outside dew, a short while the pipe bottom should be a mule, operation is similar to solder, but when ptfe welding liquidity is poor, need to use iron pipe cant light according to the welding fusion electrode, the PFA accumulation within the v-shaped groove, welding rod best straight on the welding surface.
Third, preheating treatment
Workpiece bevel place needs preheating before welding, until the workpiece is transparent, can continue to welding, the temperature must be controlled well, continue to heat up to about 250 ~ 350 ℃ when ptfe softening, must begin immediately welding on the operation, general PFA electrode can melt, electrode after the molten liquid relatively well, and ptfe even under high temperature, it will not melt flow, will only decomposition, this is different and metal welding, ptfe welding is different from other thermoplastic materials. Generally, we choose 3mm PFA welding rod for welding, and the welding speed is 50 ~ 70mm per minute, while backing out at the same time, not too fast, during welding, the air pressure of the air gun is controlled at 0.098 ~ 0.294MPa. It is specially reminded that ptfe will release extremely toxic ions at extremely high temperature, so ventilation requirements must be done before operation.
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