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Why does the stainless steel tank leak?


Release time:

2019-06-04

In the use of stainless steel storage tank storage tank will inevitably leak, then stainless steel storage tank leakage of what are the reasons, the following take you to see the reasons. 1. appearance inspection After water leakage test, it is found that there is a leakage point at the connection between the nozzle and the shell. After careful observation, there are obvious tiny cracks at the weld. 2. macroscopic inspection of the fracture surface, it is found that the crack in the shell is located in the weld area near the weld with the nozzle, showing a serrated morphology. 3. chemical composition of the shell and nozzle is analyzed by chemical composition inspection. The chemical composition of the shell conforms to GB/T4237-2

In the use of stainless steel storage tank storage tank will inevitably leak, then stainless steel storage tank leakage of what are the reasons, the following take you to see the reasons.
1. appearance inspection
After water leakage test, it is found that there is a leakage point at the connection between the nozzle and the shell. After careful observation, there are obvious tiny cracks at the weld.
Macro-inspection of 2. fracture
Observing the cracking part of the shell, it is found that the crack in the shell is located near the weld area welded with the nozzle, showing a serrated morphology.
3. chemical composition examination
The chemical composition of the shell and nozzle is analyzed. The chemical composition of the shell is in accordance with GB/T4237-2007, the chemical composition of the nozzle is in accordance with GB/T14976-2012, and the data is in accordance with the standard requirements.
4. metallographic examination
Intercept the test block at the cracked part of the shell to prepare a metallographic sample, and observe the microscopic structure of the sample without corrosion. The level of non-metallic inclusions in the shell test block is rated as C1.5 and D1.5 according to GB/T10561-2005 standard, and the level of inclusions is relatively low. Further observation can be found that the crack extends from the shell surface to the inside in the form of along the crystal, the overall performance of the crack is reticular, and the combined crack appears at the position near the weld zone, which should belong to the welding heat affected zone, so the crack is the crystallization crack in the welding hot crack.
After erosion by aqua regia, it is found that the shell matrix is a small amount of austenite carbide. Continued observation can be found that the crack starts from the heat affected zone of the weld, and the black part is the place where the crystal falls off; and black carbide precipitation can be seen near the grain falling off and at the grain boundary.
5. hardness test
Cut out the hardness test block at the crack area of the shell, and inspect 4 points. Three points are greater than the standard value of 210HV.
Based on the above analysis, during the welding process of the shell and the nozzle, the heat affected zone adjacent to the shell is 500~850 ℃, forming a welding sensitization zone. At the same time, the hardness value of the shell steel plate exceeds the standard, the solid solution treatment effect is not good, and the carbon in incomplete solid solution and austenite also increases the tendency of welding sensitization. The joint action of the two causes intergranular corrosion cracking of the shell, thus causing cracking and leakage.
The above is the reason for the leakage of stainless steel storage tank, hoping to help you.