DC welding machines have two connection methods: direct connection and reverse connection

DC welding machines do indeed have two connection methods: positive polarity (DC) and reverse polarity (DC). The core difference lies in the polarity of the power supply connected to the workpiece and the welding rod (or electrode), directly affecting the arc heat distribution, penetration depth, and applicable welding scenarios.

**I. Positive Polarity (DC Positive Polarity)**
Definition: The workpiece is connected to the positive (+) terminal of the power supply, and the welding rod is connected to the negative (−) terminal.

Characteristics: High anode (workpiece) temperature; heat is concentrated in the base material, resulting in deep penetration and a narrow weld.

The welding rod melts more slowly, making it suitable for welding thick plates requiring full penetration.

Applicable Scenarios: Welding thicker ferrous metals (such as carbon steel and alloy steel).

Positive polarity is commonly used when using acidic welding rods (such as J422).

Some special processes, such as plasma cutting, also use positive polarity.

**II. Reverse Polarity (DC Reverse Polarity)**
Definition: The workpiece is connected to the negative (−) terminal of the power supply, and the welding rod is connected to the positive (+) terminal.

Features: Heat is concentrated at the electrode tip, resulting in a stable arc, minimal spatter, shallow penetration, and wide weld.

It has a "cathode breakage" effect, effectively removing oxide films from metal surfaces, making it particularly suitable for welding aluminum, magnesium, and their alloys.

Applications: Welding thin plates to prevent burn-through.

When using basic electrodes (such as J507 and J506), reverse polarity must be used to reduce porosity and improve arc stability.

It excels at removing oxide films when welding non-ferrous metals (such as aluminum and magnesium alloys).