The impact of processing techniques on the strength of 201 stainless steel hot and cold vegetable basin swan pipes requires a comprehensive analysis of key processes, including cold working, hot working, welding, and surface treatment. The material's properties dictate that processing techniques must balance strength enhancement with corrosion resistance. Changes to the material's microstructure caused by different processes directly determine the pipe's ultimate performance.
Cold rolling and cold drawing, among the cold working processes, are key to improving the strength of 201 stainless steel swan pipes. Through plastic deformation at room temperature, the material's grains are elongated and form a fibrous structure, simultaneously producing a work-hardening effect. This process significantly increases the pipe's tensile strength and yield strength, making it more suitable for high-load-bearing applications. However, excessive cold working can lead to increased lattice distortion and residual stress concentration, potentially causing material embrittlement and cracking, particularly at curved areas. Therefore, in actual production, strict control of cold working deformation is required, and intermediate annealing is performed to eliminate residual stresses to achieve a balance between strength and toughness.
Hot rolling and hot extrusion, among the hot working processes, have a dual impact on the strength of 201 stainless steel vegetable basin pipes. Under high temperatures, the material enters an austenitic state, significantly enhancing its plasticity and enabling the formation of complex cross-sections through large deformations. Hot rolling refines the grains, eliminates casting defects, and improves the uniformity of the pipe. Hot extrusion, through triaxial compressive stress, inhibits crack propagation and enhances the pipe's density. However, improper heating temperature control or insufficient cooling rate can lead to grain coarsening or carbide precipitation, ultimately reducing strength. Therefore, precise control of the hot working temperature range and cooling path is crucial for ensuring pipe strength.
The impact of welding processes on the strength of 201 stainless steel swan pipes cannot be ignored. During fusion welding processes such as argon arc welding, grain growth and phase transformation occur in the heat-affected zone, resulting in a localized decrease in hardness. Improper welding parameters can lead to defects such as lack of fusion and porosity, creating stress concentration points and reducing the pipe's fatigue resistance. Furthermore, the manganese in 201 stainless steel easily evaporates during welding, potentially altering the weld composition and affecting corrosion resistance. Optimizing welding process parameters, employing low heat input techniques, and post-weld solution treatment can effectively mitigate the negative impact of welding on strength.
Surface treatment processes indirectly enhance pipe strength. Pickling removes scale and impurities, reducing stress corrosion sources and indirectly enhancing the pipe's long-term strength stability. Polishing eliminates surface microcracks and machining marks, reducing the likelihood of fatigue crack initiation. This is particularly suitable for hot and cold sink pipes subject to high-frequency vibration. Sandblasting increases surface roughness, improves coating adhesion, and provides additional mechanical protection for the pipe, indirectly extending its strength decay cycle.
The synergistic effects of the processing techniques determine the ultimate strength performance of 201 stainless steel pipe. For example, solution treatment after cold working eliminates residual stress and restores some plasticity, preventing brittle fracture caused by excessive strength. Cold rolling after hot extrusion further refines the grain size, achieving both enhanced strength and toughness. Furthermore, the pipe's cross-sectional design (such as the curved structure of a swan pipe) must be compatible with the processing technique. By optimizing the deformation path, stress concentration is reduced and uniform strength distribution is ensured.
From the application perspective, hot and cold sink pipes are subject to alternating hot and cold environments, placing higher demands on the pipe's resistance to stress corrosion cracking. Processing techniques must enhance the pipe's strength and stability in hot and humid environments by controlling residual stress, optimizing grain orientation, and improving surface quality. For example, low-temperature annealing can reduce residual tensile stress and reduce stress corrosion susceptibility. Surface passivation treatment forms a dense oxide film, blocking the intrusion of corrosive media and indirectly maintaining pipe strength.
The processing of 201 stainless steel hot and cold vegetable basin pipe swan tubes profoundly impacts pipe strength by altering the material's microstructure, controlling residual stress, and optimizing the surface condition. Choosing the right combination of cold working, hot working, and surface treatment processes, and strictly controlling parameters at each stage, is key to improving pipe strength and extending service life.
