Centerway Steel Co., Ltd
Centerway Steel Co., Ltd
Centerway Steel Co., Ltd
carbon steel plate,steel coil,stainless steel plate,china export service provider.
carbon steel plate,steel coil,stainless steel plate,china export service provider.
The usage of stainless steel in China is increasing year by year, with the consumption rising from 300,000 tons in 1988 to 1.65 million tons in 2000, at an annual growth rate of 15.26%. Thin plates constitute the majority of stainless steel usage, with 910,000 tons consumed in 2000, accounting for half of the total usage. Thin wall stainless steel plates have been widely applied in various fields of national production and life, such as the food processing industry, pressure vessel industry, and electrical industry, as well as other sectors including kitchen equipment, architectural decoration, household appliances, and automotive industry. In these industries, welding of stainless steel is a crucial process determining the product quality. This article primarily elucidates how to optimize the welding processes and methods for thin wall stainless steel plates by controlling welding deformation and costs.
Welding of stainless steel thin plates often results in defects such as burn-through and welding deformation (mostly ripple deformation) due to their low inherent restraint, low thermal conductivity (about one-third of low alloy steel), and large linear expansion coefficient, leading to significant thermal stresses when the welding temperature changes rapidly.
The main forces acting on the weld pool include the arc force P, the gravity of molten metal Q, and the surface tension F of molten metal. When the volume, mass, and width of the molten pool are constant, the depth of the molten pool depends on the magnitude of the arc force P. The depth and arc force are related to the welding current, while the width is determined by the arc voltage. As the volume of the molten pool increases, so does the surface tension F. When the surface tension cannot balance the arc force and the gravity of the molten pool, the molten metal flows downward, causing burn-through. Arc force P and gravity Q are the forces causing burn-through, while surface tension F prevents sagging or burn-through of the molten pool. To prevent burn-through in thin plate welding, it is necessary to increase the surface tension F of the molten metal, which requires controlling the heat input of the molten pool, namely the line energy.
Stainless steel thin plates have low restraint and experience uneven heating and cooling during welding, leading to uneven stress and strain in the welded joints. When the longitudinal contraction of the weld seam exceeds a certain value, it results in severe ripple-like deformation, affecting the dimensional quality of the workpiece.
Main Measures to Address Overheating, Burn-through, Deformation, and Discoloration in Welding Stainless Steel Thin Plates:
(1) Strictly control the heat input on the welding joints, selecting appropriate welding methods and process parameters (mainly welding current, arc voltage, welding speed).
(2) Ensure precise assembly dimensions with minimal joint clearances. Larger clearances are prone to burn-through or the formation of larger weld beads.
(3) Precision fixtures must be used with even clamping forces. When welding thin stainless steel plates, strict control of the line energy on the welding joints is crucial. The aim is to minimize heat input while ensuring welding completion, thereby reducing the heat-affected zone and preventing the aforementioned defects.
Low output voltage (5-20 volts) belongs to resistance welding power sources. Thin wall stainless steel welding machines fall within the scope of resistance welding. They offer the ability to select suitable current and pulse duration according to the thickness of the plate during welding, enabling precise control of the heating temperature. Moreover, instantaneous arc initiation and melting of the workpiece are features of these machines. Consequently, the temperature remains low, preventing overheating or deformation of the welded workpiece.
