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Due to its excellent corrosion resistance, good formability, and moderate mechanical properties, 304 stainless steel plates are widely used in various fields such as architectural decoration, food processing, chemical equipment, medical devices, and kitchen equipment. However, in actual processing, cutting and welding are critical forming processes—improper operation can easily lead to a series of quality issues, which not only affect the appearance and performance of products but also may shorten their service life. Therefore, gaining an in-depth understanding of the common problems and their causes during the cutting and welding of 304 stainless steel plates, and adopting effective preventive measures, is crucial for ensuring processing quality. I. Common Problems in Cutting 304 Stainless Steel Plates 1. Oxidation and Discoloration in the Heat-Affected Zone (HAZ) When using thermal cutting methods such as plasma cutting, flame cutting, or laser cutting, high temperatures heat the metal near the cutting edge, forming a heat-affected zone (HAZ). At high temperatures, 304 stainless steel easily reacts with oxygen in the air, causing surface oxidation and the formation of a blue, purple, or black oxide layer. This not only affects aesthetics but also reduces the corrosion resistance of the area, as the oxide layer damages the original passive film. 2. Poor Cut Quality, with Burrs and Dross Improper setting of cutting parameters (e.g., cutting speed, power, gas pressure) often results in uneven cuts, severe edge burrs, or dross accumulation at the bottom. Burrs require subsequent grinding, increasing labor costs, and may pose safety hazards during subsequent welding or assembly. Dross, on the other hand, indicates incomplete cutting and affects dimensional accuracy. 3. Material Deformation and Stress Concentration Localized high temperatures during thermal cutting cause uneven expansion and cooling of the material, generating residual stress that further leads to warping or deformation of the plate. This deformation is more pronounced in thinner 304 stainless steel plates (e.g., 1-3mm thick). Additionally, stress concentration at the cutting edge can become a starting point for crack initiation, compromising structural strength. 4. Carbide Precipitation and Risk of Intergranular Corrosion Although cutting time is short, high temperatures can still cause chromium carbides to precipitate along grain boundaries in 304 stainless steel—especially under repeated heating or prolonged exposure to high temperatures. This reduces the chromium content near grain boundaries, weakening resistance to intergranular corrosion and creating hidden risks during long-term use. II. Common Problems in Welding 304 Stainless Steel Plates 1. Weld Joint Corrosion (Especially Intergranular Corrosion) This is one of the most prominent issues in 304 stainless steel welding. When the welding temperature falls within the “danger zone” of 450°C to 850°C, carbon combines with chromium to form chromium carbides, which precipitate along grain boundaries. This leads to chromium depletion near grain boundaries, resulting in the loss of corrosion resistance—a phenomenon known as “sensitization.” In corrosive environments, intergranular corrosion may first occur at the weld joint, causing structural failure. 2. Hot Cracks (Solidification Cracks and Liquation Cracks) 304 stainless steel is austenitic stainless steel with a relatively high coefficient of linear expansion, making it prone to significant thermal stress during welding. Meanwhile, the austenitic solidification mode makes it sensitive to impurity elements such as sulfur and phosphorus, which easily form low-melting eutectics during weld solidification, leading to solidification cracks. Additionally, in the heat-affected zone, low-melting substances at grain boundaries may re-melt at high temperatures, forming liquation cracks. 3. Weld Porosity Porosity is a common defect in welding, mainly caused by oil, moisture, oxides in the welding area, or impure shielding gas (e.g., oxygen or moisture in argon). 304 stainless steel is highly sensitive to gases; if pre-weld cleaning is incomplete or the shielding gas flow is insufficient, porosity can easily form in the weld, reducing weld density and strength. 4. Welding Deformation Since the coefficient of thermal expansion of 304 stainless steel is approximately 50% higher than that of ordinary carbon steel, thermal deformation during welding is more significant. When welding large structural parts or thin plates, angular deformation, bending deformation, or wave deformation are likely to occur, affecting assembly accuracy and appearance quality. 5. Weld Discoloration (Blackening) and Surface Oxidation Even with argon shielding, insufficient gas flow, blocked nozzles, or excessively slow welding speed can cause oxidation of the weld and heat-affected zone, resulting in black or gray-brown oxide scale. This not only affects aesthetics but also requires subsequent pickling or polishing, increasing costs. III. Solutions and Preventive Measures – **Optimize Cutting Processes**: Prioritize laser cutting or waterjet cutting to minimize the heat-affected zone; adjust cutting parameters to ensure cut quality; promptly remove oxide layers after cutting, and perform pickling and passivation if necessary. – **Standardize Welding Operations**: Adopt low heat input welding methods (e.g., TIG welding, MIG welding); use ultra-low carbon welding consumables (e.g., ER308L) to reduce carbide precipitation; ensure the purity and flow rate of shielding gas; thoroughly clean the weld groove and the oil/stains/oxides on both sides before welding. – **Control Interpass Temperature**: During welding, keep the interpass temperature below 150°C to avoid prolonged exposure to the sensitization temperature range. – **Post-Weld Treatment**: Conduct solution treatment (rapid cooling at 1050-1100°C) if necessary to restore corrosion resistance; perform pickling and passivation on the weld to regenerate the surface passive film. In summary, although 304 stainless steel plates are prone to various issues during cutting and welding, these problems can be effectively avoided through scientific material selection, standardized operations, and rational process control—ultimately ensuring the quality and performance of the final product. Key Terminology Notes 1. **304 stainless steel plate**: Retains the numerical grade “304” (an industry-standard designation per AISI/SAE) for global recognition; “plate” refers to flat metal sheets of moderate to thick gauge. 2. **Heat-Affected Zone (HAZ)**: Abbreviated as “HAZ” after first mention, consistent with welding/cutting industry conventions. 3. **Intergranular corrosion**: Literal translation of the core concept, with additional context (e.g., “sensitization”) to clarify the mechanism for technical readers. 4. **TIG/MIG welding**: Abbreviations for Tungsten Inert Gas welding and Metal Inert Gas welding, the standard English terms for these processes.