Principle:
Electric welding equipment is the use of electric energy, through heating and pressurization, that is, the high temperature arc generated by the positive and negative electrodes in the instantaneous short circuit, to melt the solder and the welded material on the electrode, with the help of the combination and diffusion of metal atoms, so that two or more weldments are firmly connected together. It is specifically composed of an electrode, an electric welding machine, an electric welding tong, a grounding clamp and a connecting wire. According to the type of output power supply, it can be divided into two types, one is AC welding machine and the other is DC welding machine.
Welding machine connection:
• The welding tongs are connected with the welding tongs connecting holes on the welding machine through the connecting wires;
• The grounding clamp is connected with the grounding clamp connecting hole on the welding machine through the connecting wire;
• Place the weldment on the flux pad and clamp the ground clamp to one end of the weldment;
• Then clamp the blessing end of the electrode to the welding jaws;
• Protective grounding or zero connection of the shell of the welding machine (the grounding device can use copper pipe or seamless steel pipe, the depth of its burial in the ground should be >1m, and the grounding resistance should be <4Ω), that is, use a wire to connect one end to the grounding device and the other end to the grounding end of the shell of the welding machine.
• Then connect the welding machine with the distribution box through the connecting line, and ensure that the length of the connecting line is 2 to 3 meters, and the distribution box should be equipped with an overload protection device and a knife switch switch, etc., which can control the power supply of the welding machine separately.
• Before welding, the operator should wear welding clothing, insulated rubber shoes, protective gloves, protective masks and other safety protection tools, so as to ensure the personal safety of the operator.
Connection of power input and output of welding machine:
There are usually 3 solutions for the power input line: 1)a live wire, a neutral wire, and a ground wire; 2)Two live wires and one ground wire; 3)3 live wires, one ground wire.
The output line of the electric welding machine is not distinguished except for the AC welding machine, but the DC welding machine is divided into positive and negative:
DC welding machine positive polarity connection: The polarity connection method of DC welding machine is based on the workpiece as a reference, that is, the welding workpiece is connected to the positive electrode output of the electric welding machine, and the welding handle (clamp) is connected to the negative electrode. The positive polarity connection arc has hard characteristics, the arc is narrow and steep, the heat is concentrated, the penetration is strong, the deep penetration can be obtained with a relatively small current, the weld bead (weld) formed is narrow, and the welding method is also easy to master, and it is also the most widely used connection.
DC welding machine negative polarity connection method (also called reverse polarity connection): the workpiece is connected to the negative electrode, and the welding handle is connected to the positive electrode. The negative polarity arc is soft, divergent, shallow penetration, relatively large current, large spatter, and is suitable for places with special welding process requirements, such as the back cover surface of the back cover, surfacing welding, where the welding bead requires wide and flat parts, welding thin plates and special metals, etc. Negative polarity welding is not easy to master, and it is rarely used in ordinary times. In addition, when using alkaline low-hydrogen electrodes, the reverse connection is more stable than the positive arc, and the amount of spatter is small.
As for whether to use positive polarity connection or negative polarity connection method during welding, it should be decided according to the welding process, welding condition requirements and electrode material.
How to judge the polarity of the output of the DC welding machine: The regular welding machine is marked with + and - on the output terminal or terminal board, + means the positive pole and - indicates the negative pole. If the positive and negative electrodes are not labeled, the following methods can be used to distinguish them.
1) Empirical method. When using low-hydrogen (or alkaline) electrodes for welding, if the arc combustion is unstable, the spatter is large, and the sound is violent, it means that the forward connection method is used; Otherwise, it is reversed.
2) Charcoal rod method. When the carbon rod method is used to determine the forward connection method or the reverse connection method, it can also be judged by observing the arc and other conditions:
a. If the arc combustion is stable and the carbon rod burns slowly, it is a positive connection method.
b. If the arc combustion is unstable and the carbon rod is burned severely, it is the reverse connection method.
3) Multimeter method. The method and steps of using a multimeter to judge the forward connection method or the reverse connection method are:
a. Place the multimeter in the highest range of DC voltage (above 100V), or use the DC voltmeter.
b. The multimeter pen and the DC welding machine are respectively touched, if it is found that the pointer of the multimeter is deflected clockwise, then the terminal of the welding machine connected with the red pen is the positive pole, and the other end is the negative pole. If you test with a digital multimeter, when a negative sign appears, it means that the red pen is connected to the negative pole, and no symbol appears, which means that the red pen is connected to the positive pole.
Of course, for the welding machine used, you still have to check the corresponding manual.
That's all for the basics shared today in this article. If there is any inappropriateness, please understand and correct
Post time: Mar-22-2025