Let me start with my personal summary. These three welding processes have different principles, different costs, and different applications. MIG/MAG welding is the mainstay, robust and durable; TIG welding is for precision work, producing beautiful welds; laser welding is high-end, generally unaffordable for small factories. Their relationship is like the three tools in your toolbox-IG/MAG is like a claw hammer, capable of handling almost anything; TIG welding is like a screwdriver set, specifically for precision parts; laser welding is like a power tool, fast and accurate, but incredibly expensive. Let's start with MIG/MAG welding. The "workhorse" of factories, MIG/MAG welding, also known as carbon dioxide gas shielded welding, involves spraying carbon dioxide gas from the welding torch, keeping out air and eliminating air bubbles and impurities from the weld. It's most commonly used in steel structures, bridges, ships, and excavators-these are the big machines you see on the road. The steel beams of buildings and highway guardrails you see are mostly welded with MIG/MAG. The biggest advantage of MIG/MAG welding is its speed. The same thick steel plate might take half an hour to weld by hand, but MIG welding can do it in ten minutes. It's also versatile, working even with rust or oil, making it ideal for outdoor applications and factory assembly lines. However, it has its drawbacks. It produces a lot of spatter, leaving a ring of small iron filings around the weld, requiring a lot of shoveling. The weld seam is also unsightly, resembling a winding earthworm. Furthermore, it can't weld aluminum or stainless steel, only ordinary carbon steel. In short, MIG welding is about speed and low cost; don't expect it to produce works of art. Now, let's talk about TIG welding, the "exclusive tailor" for stainless steel. TIG welding, also known as tungsten inert gas welding, differs from MIG welding mainly in that it uses a non-melting tungsten needle in its welding torch, with the arc burning between the needle and the workpiece. It uses argon as the shielding gas, which is significantly more expensive than carbon dioxide. TIG welding's greatest strength is its ability to weld stainless steel and aluminum beautifully. Look at the stainless steel operating tables in hospitals, the stainless steel sinks in kitchens, and those aluminum alloy doors and windows-they're all basically welded using argon arc welding. The weld seams are neat and even, like fish scales, and require almost no grinding. But it also has a major drawback: it's too slow. MIG welding can weld half a meter per minute, while argon arc welding can only weld ten centimeters per minute. Moreover, it requires extremely high skill from the welder; a skilled argon arc welder can't be trained in less than three to five years. Another point needs clarification: although argon arc welding is slow, it's indispensable for certain jobs. For example, the root pass welding of pipes and the welding of thin plates; other methods will penetrate immediately, only argon arc welding can slowly heat it up. Thirdly, let's talk about laser welding, the "secret weapon" of high-end manufacturing. Laser welding is completely different from the previous two. It uses a high-energy-density laser beam to directly irradiate the workpiece, instantly melting and welding the metal together. Laser welding is characterized by three words: fast, accurate, and ruthless. How fast? A steel plate on an automobile production line can be welded in a fraction of a second. How accurate? The welding precision can be as fine as a human hair. How precise is it? A steel plate several millimeters thick can be welded through in one pass. Laser welding is mainly used in three areas. First, automotive body-in-white. Go to a car factory and you'll see it's all robots and laser welding; a single production line can weld hundreds of cars a day. Second, power batteries. The tabs inside mobile phone batteries and electric vehicle batteries can only be welded using laser welding; other methods simply can't do it. Third, aerospace. For high-precision parts like engine blades, laser welding is standard. So why isn't laser welding used everywhere? It's too expensive. A laser welding machine starts at hundreds of thousands, and a good one costs millions. Moreover, it has extremely strict requirements for the fit of the workpieces; the gap between two plates cannot exceed 0.1 millimeters. Even a slight gap will prevent welding. Therefore, laser welding is currently only a toy for large factories and high-end manufacturing industries; small workshops simply can't afford it. Finally, let's talk about manual welding. You might confuse it with MIG welding. Many people think manual welding is a type of MIG welding because they both involve using a welding torch. These are completely different things; don't get them mixed up. Hand-held welding, also known as shielded metal arc welding, involves using a welding rod coated with flux. During welding, this flux burns, producing gas and slag that separate the welding from the air. The biggest advantage of hand-held welding is that it doesn't require gas cylinders; you can simply carry the welding machine to the field. Its advantages include inexpensive equipment, flexibility, and the ability to weld almost anywhere. Imagine repairing a pipeline in the field or welding an irregularly shaped component in a remote corner of a construction site. A MIG welding torch can't fit, and a laser welding torch can't be moved in the same way; in these situations, hand-held welding is the only option. Its problems are that it's slow, tiring, and produces a lot of smoke and dust. You have to change the welding rod frequently, resulting in only a few meters welded per day. Furthermore, it heavily relies on the welder's skill; a master welder's work is exquisite, while an apprentice's is poorly done. Now you understand: these four welding methods are parallel and none can replace the others. Large factories use MIG welding for mass production, precision stainless steel welding uses TIG welding, high-end automation uses laser welding, and field repairs and maintenance use hand-held welding.
