CO2, MAG & MIG Welding: Optimal Current, Wire Diameter & Plate Thickness

1. The relationship between the commonly used steel manual arc welding current and the diameter of the welding rod, and the applicable range of plate thickness.

Instruction:

1. Low-alloy steels include heat-resistant steels and low-temperature steels (such as 15CrMo, 16MnDR).
2. For thicknesses greater than 4mm, a bevel should be opened, adopting a multi-layer, multi-pass welding process.
3. Low alloy steel plates thicker than 28mm should undergo a preheating process to prevent the formation of cold cracks.
4. The purple copper plate must be preheated to 400~600℃ before welding.
5. For direct current, the workpiece is connected to the positive terminal, and for reverse polarity, the workpiece is connected to the negative terminal.
6. For root welding, a cellulose welding rod is used with direct positive connection, while for hot welding, filler welding, and cover welding, a direct reverse connection is used.
7. The general welding speed range for manual arc welding is 2~15cm/min.

2. The relationship between the commonly used carbon arc gouging current and the carbon rod, as well as the applicable range for plate thickness.

Instruction

1. Carbon arc gouging is used for the gouging of carbon steel, common low-alloy steel (such as 16Mn, 15MnV, etc.), stainless steel, heat-resistant steel, and low-temperature steel. It is a process for beveling, cleaning the back of welds, and removing welding defects.
2. Carbon arc gouging should use a direct current reverse polarity power supply (the workpiece is connected to the negative).
3. The general planing speed ranges from 500 to 1200 cm/min.
4. Generally, for low-alloy steel plates with a thickness of ≥30mm, a preheating process must be adopted before planing to prevent the steel from forming hardened structures and developing cold cracks.

3. The relationship between the welding current and tungsten electrode diameter in commonly used material manual tungsten inert gas (TIG) arc welding, and the applicable range of plate thickness.

Instruction

1. The types of tungsten electrodes are thoriated and ceriated with a tip diameter of φ0.5, at an angle of 30 degrees. For AC welding, the tip diameter of the tungsten electrode is φ1.5, at an angle of 90 degrees.
2. For sheet metal thickness >4mm, a bevel should be opened, adopting multi-layer and multi-pass welding process. Preheating process should be applied for aluminum sheets with thickness >8mm and copper sheets with thickness >4mm. The welding speed for thin sheets is 15~55cm/min, and the automatic welding speed is 15-100cm/min.
3. TIG welding is suitable for flat, vertical, horizontal, and overhead all-position welding.

4. The relationship between CO2/MAG/MIG welding current and wire diameter, as well as the applicable range for sheet thickness.

Instruction:

1. Short circuit transition is applicable for flat, horizontal, vertical, and overhead welding positions; spray transition (droplet transition) is suitable for flat welding and fillet welding.
2. Low-alloy steel and austenitic stainless steel utilize flux-cored welding wire, resulting in good internal and external weld quality.
3. For plates thicker than 6mm, bevel edge welding is applied, utilizing multi-layer and multi-pass welding techniques. The maximum weldable thickness is 100mm.
4. Pre-heating techniques should be applied to low alloy steel plates with a thickness of 28mm or more, and for aluminum and aluminum alloy plates with a thickness of 34mm or more.
5. The general welding speed range for Gas Metal Arc Welding is 12-90cm/min.：12-90cm/min .

5. Recommended Method for Striking an Arc and Adjusting Thrust Current in a Direct Current Arc Welding Machine.

Instruction:

1. The SS300, SS400, SS630 welding machines, and the AT315 welding machine do not have an arc initiation current knob.
2. The TR315 tungsten electrode argon arc welding machine, when used for manual arc welding, allows for the adjustment of arc initiation and thrust current.
3. The numerical value of the arc thrust current (1/2, 1/3) indicates the clockwise rotation position of the knob.
4. The thrust current regulation is too high, causing the arc noise to be slightly louder and the spatter of molten droplets to increase. It can be adjusted to zero when the rod is not sticking.

6. The actual load sustainability of various arc welding processes under different operating modes.

Instruction:

1. The selection of a welding machine is based on the thickness of the welded part, the welding position, and the diameter of the welding material, to choose the maximum actual welding current value.
   Confirm the operation method and estimate the actual load duration. When the actual load duration exceeds the rated load duration, the actual welding current should be lower than the rated current of the welding machine for normal use, to avoid damage to the welding machine.
2. For a CO2 welding machine rated at 200KR, the rated current is 200A when the duty cycle is 60%. When used for small batch continuous semi-automatic welding, the actual duty cycle is 60%, with a maximum welding current of 200A. During automated large batch continuous operations, the maximum allowable current value is 155A, which still satisfies the welding production of workpieces with a thickness of 6mm.