Argon-helium mixture ratio
The argon-helium mixing ratio determines the heat input and penetration depth during welding. A higher helium concentration increases thermal conductivity, while more argon leads to deeper penetration.
Physicochemical Mechanism of Action
The argon-helium mixing ratio affects thermal conductivity and behavior of the shielding gas. Helium is a light gas with high diffusion rate, allowing it to move quickly through metal gaps and conduct heat better. Argon, on the other hand, has higher density and prevents the shielding gas from dissipating too quickly, increasing penetration depth.
Metallurgical Relevance & Risks in Welding
An incorrect mixing ratio can cause various problems. Too much helium can lead to rapid cooling and formation of hard martensite, causing cracks. Too much argon can result in slow cooling of the weld, leading to grain coarsening and reduced toughness.
Workshop Practice & Instructions
The mixing ratio should be adjusted based on material and welding technique. For high-carbon steel, a higher helium ratio (e.g., 70/30) is recommended to ensure rapid cooling. For Delrin or other thermoplastics, a higher argon ratio (e.g., 95/5) is better to control penetration and heat input.