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1. The theoretical formula for current regulation: How is the current of a welding machine regulated? Generally, it can be determined using the empirical formula I=(35-55)d. In the formula, I represents the welding current in amperes, while d is the diameter of the welding rod in millimeters. An approximate welding current is calculated first, and then trial welding is carried out on the steel plate to make adjustments until the appropriate current is determined. 2. How to determine the magnitude of the welding current: a. Listen to the sound – when the welding current is high, a \"whooshing\" sound is produced, similar to that of water flowing in a river ； When the welding current is low, a \"rustling\" sound is produced, along with sharp crackling noises. b. Observe the splashing situation: When the welding current is too high, the arc exerts a strong force, causing larger droplets of molten material to splash out of the weld pool. There is also a loud cracking sound during welding, and the surface of the welded piece remains dirty ； When the welding current is too low, the electrode melts slowly, the arc force is weak, and it is difficult to separate the slag from the molten metal. c. Observe the melting condition of the electrode. When the welding current is too high, after most of the electrode has melted away continuously, it can be observed that the remaining part turns red ； When the welding current is too low, the arc burns unstably, and the electrode tends to stick to the workpiece. d. Observe the shape of the molten pool: when the welding current is high, the long axis of the oval-shaped molten pool is longer ； When the welding current is low, the molten pool is flat-shaped ； When the welding current is moderate, the shape of the molten pool is duck-egg shaped. e. Check the weld formation. When the welding current is too high, the amount of molten metal in the weld is low, the penetration depth is large, and edge chipping is likely to occur ； When the welding current is too low, the molten metal in the weld is narrow and tall, and its bond with the base material on both sides is poor ； When the welding current is appropriate, the height of the molten metal in the weld is suitable, and the areas on either side of the molten metal in the weld bond well with the base material.