When welding 65mn spring steel, in order to reduce the consumption of the electrode, the DC positive connection is selected for the butt welding test of the wire, that is, the DC power supply is selected, the wire is connected to the positive electrode of the power source, and the tungsten electrode is connected to the negative electrode of the power source.
The tungsten electrode containing 1% or 2% thorium oxide has high electron emission efficiency, good current carrying capacity, good anti-pollution performance, easy arc ignition and relatively stable arc. In order to facilitate the operation, a finer thorium tungsten electrode with a diameter of 2 mm was selected, and the tip of the electrode was sharpened.
In the test, it was found that when the welding current was 20 A, the arc burned violently, the metal spatter at the joint was serious, and the solder joint collapsed seriously. When the current is adjusted to 15 A, the arc burns more smoothly and the molten pool splashes less, but the weld still collapses. But when the current drops to 10 A, the arc is easy to start, the arc burns stably, and there is no collapse in the weld.
Since the lower arc voltage characteristics of argon are particularly beneficial for manual arc welding of thin plates and wires, argon is selected as the shielding gas.
A DC manual argon arc welding machine was used for the test. Before welding, both ends of the steel wire were carefully polished flat. In order to prevent pores in the solder joints, the end oil was cleaned with acetone. Place the flat wire on both ends on a flat and clean alignment plate, align the ends without leaving a gap at the joint, and press the two sides of the joint with a weight. Connect the wire to the positive electrode of the welding machine and the tungsten electrode to the negative electrode, and adjust the current to 20 A, 15 A, 10 A, and 8 A for welding. When welding, ignite the ignition arc next to the joint and make it stable. Move the arc to the joint to melt the joint metal and quickly extinguish the arc. At the same time, apply a slight upsetting force to complete the welding process after cooling. Use filler wire.