How does the welding process of stainless steel pots affect their sealing performance?
Release Time : 2025-12-01
The welding process of stainless steel pots is a core factor determining their sealing performance, directly affecting the safety and durability of the cookware. Sealing performance depends on the continuity and structural stability of the weld seam. Parameter deviations, improper operation, or material incompatibility during welding can all lead to sealing failure.
Weld formation defects are one of the main hidden dangers to sealing performance. Excessive welding current, unstable arc, or excessive welding speed can easily lead to problems such as incomplete penetration, incomplete fusion, or undercut. Incomplete penetration manifests as incomplete fusion at the weld root, forming microscopic channels; incomplete fusion occurs when the base material and weld material are not fully bonded, leaving gaps; undercut weakens the weld edge strength, causing stress concentration in the pot body under pressure or temperature changes. These defects can all become entry points for media leakage, especially in high-pressure or high-temperature applications, where the risk of leakage increases significantly.
The impact of welding deformation on sealing performance is also significant. Improper control of the welding heat input in stainless steel pots, such as excessively high heat in a single weld or excessively slow cooling, can lead to localized thermal deformation of the pot body. For example, flange warping can disrupt the uniform stress distribution on the gasket, while localized tank dents can cause misalignment of the sealing structure. Even if the weld itself is defect-free, deformation-induced deviations in the flatness of the sealing surface can still lead to seal failure. Furthermore, if interpass temperature is not controlled during multi-layer welding, or if forced cooling is not implemented after welding, heat accumulation will exacerbate deformation, further threatening the seal.
Volume defects are hidden leakage risks. Insufficient shielding gas during welding, such as insufficient argon flow in TIG welding, or damp welding materials or incomplete beveling, can create pores or inclusions within the weld. Pores are voids formed when gas fails to escape in time, while inclusions are residual impurities. Although these defects do not directly penetrate the vessel body, they can expand into leakage channels under long-term use due to pressure fluctuations, temperature changes, or mechanical vibrations. For example, pores may be compressed and enlarged under high pressure, while inclusions may gradually peel off due to corrosion, ultimately leading to seal failure.
Material compatibility has a long-term impact on sealing performance. If the chromium and nickel content of the welding material is lower than that of the stainless steel in the pot body, such as using low-carbon steel welding material with a 304 stainless steel pot, the corrosion resistance of the weld will be significantly lower than that of the base material. When exposed to acidic or alkaline media, the weld will be preferentially corroded, forming "weld corrosion perforation."
Furthermore, the sensitization problem of the heat-affected zone (HAZ) cannot be ignored. Prolonged exposure of stainless steel to temperatures between 450-850℃ will cause Cr₂₃C₆ to precipitate at grain boundaries, forming a "chromium-depleted zone," losing its passivation protection ability, and thus initiating intergranular corrosion. This corrosion usually starts near the weld and gradually spreads to the entire pot body, eventually leading to the destruction of the sealing structure.
The stability of the welding process and the standardization of operations are fundamental to ensuring sealing. For example, manual welding relies on operator skill, and parameters such as arc length and welding speed are easily affected by human factors; while automatic welding can reduce human error, it requires high equipment precision. In addition, the rationality of the welding sequence is also crucial. Failure to follow principles such as "symmetrical welding and segmented back-welding" can lead to uneven stress on the pot body, increasing the risk of deformation. For example, when welding large stainless steel storage tanks, if the fixing points are not welded first before gradually expanding, localized stress concentration may cause overall deformation.
To improve the sealing performance of stainless steel pots, a comprehensive approach is needed, encompassing process control, material selection, and testing methods. In terms of process, welding methods with low heat input and minimal deformation, such as argon arc welding and laser welding, should be prioritized, and welding parameters should be strictly controlled. Regarding materials, it is essential to ensure that the welding material matches the base material composition and avoid prolonged exposure to the sensitization temperature range. For testing, a combination of non-destructive testing (such as ultrasonic testing and penetrant testing) and hydrostatic testing is necessary to comprehensively inspect for surface and internal defects. These measures can effectively improve the sealing performance of stainless steel pots and extend their service life.