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Reasons of Heat Embrittlement of SS Heat Exchange Tubes
Jun 12, 2022
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Here are the reasons of heat embrittlement of stainless steel heat exchange tubes.
At present, the important heat transfer element is used in the chemical production of stainless steel heat exchange tubes. Because of its acid and alkali resistance, the corrosion resistance is better. It is made once. It belongs to the stainless steel seamless tube, which can be used as a transmission fluid pipe, such as oil, natural gas, water, gas, steam and other various industries. However, it has excellent acid and alkali resistance and corrosion resistance of stainless steel tubes. There may be cracks, and even serious cracking. What is the reason for this?
1. Because the heat exchange tube of stainless steel may be embrittlement. The stainless steel tubes are in juncture when heated. Due to the different expansion coefficient creates large thermal stress, especially in the rapid change in temperature. After many times of heating it will produce thermal fatigue crack, and the general high temperature fatigue is different. The former changes as the change of temperature due to the internal thermal stress caused by a thermal embrittlement. The latter is caused by the change of external load in high temperature. If we are in macroscopic inspection of stress corrosion engineering accidents of stainless steel welded pipes, we will find such a phenomenon: only local parts of the equipment and parts of welded pipes are damaged by stress corrosion.
2. The reason is maybe the increase of N content in duplex stainless steel. In duplex stainless steel, N is a strong outstanding element. With the increase of N content, the ferrite content decreases gradually, and the austenite with larger grain size increases gradually. Otherwise, the heat exchange tube of stainless steel pieces of local N concentration causes that there appeared abnormal tissue distribution, namely the coarse austenite grain size of single-phase area form here, bulky austenitic plasticity and strength than normal difference of dual phase steel. It makes it easier for the stainless steel in the process of heat exchange tube used in machining micro cracks, eventually extending, the phenomenon of the expansion pipe.
3. The reason also may be that the working condition of the use of the stainless steel heat exchange tube is hydrogen environment. It produces a large amount of hydrogen-induced martensite, leading to hydrogen-induced cracks on the heat exchange tube of stainless steel. In the process of heat exchange tube of stainless steel used, the local heating of the stainless steel heat exchange tube is serious due to the S, Cl – of tube medium and the existence of non-metallic inclusions, especially the existence of Cl -, Cl - oxidation potential energy is larger. Then, the passivation layer of stainless steel heat exchange tubes is damaged, and then it causes the cracking of the stainless steel heat exchange tubes. That is to say, the use of the stainless steel heat exchange tube has played a certain role in promoting cracking. It will make the stainless steel heat exchange tubes crack.
The above is about the content of stainless steel heat exchange tubes. We hope you use the correct stainless steel to produce stainless steel heat exchange tubes in the future processing process. However, we also pay attention to the use of stainless steel heat exchange tubes and the use of medium, in order to extend the service life of stainless steel heat exchange tubes.
At present, the important heat transfer element is used in the chemical production of stainless steel heat exchange tubes. Because of its acid and alkali resistance, the corrosion resistance is better. It is made once. It belongs to the stainless steel seamless tube, which can be used as a transmission fluid pipe, such as oil, natural gas, water, gas, steam and other various industries. However, it has excellent acid and alkali resistance and corrosion resistance of stainless steel tubes. There may be cracks, and even serious cracking. What is the reason for this?
1. Because the heat exchange tube of stainless steel may be embrittlement. The stainless steel tubes are in juncture when heated. Due to the different expansion coefficient creates large thermal stress, especially in the rapid change in temperature. After many times of heating it will produce thermal fatigue crack, and the general high temperature fatigue is different. The former changes as the change of temperature due to the internal thermal stress caused by a thermal embrittlement. The latter is caused by the change of external load in high temperature. If we are in macroscopic inspection of stress corrosion engineering accidents of stainless steel welded pipes, we will find such a phenomenon: only local parts of the equipment and parts of welded pipes are damaged by stress corrosion.
2. The reason is maybe the increase of N content in duplex stainless steel. In duplex stainless steel, N is a strong outstanding element. With the increase of N content, the ferrite content decreases gradually, and the austenite with larger grain size increases gradually. Otherwise, the heat exchange tube of stainless steel pieces of local N concentration causes that there appeared abnormal tissue distribution, namely the coarse austenite grain size of single-phase area form here, bulky austenitic plasticity and strength than normal difference of dual phase steel. It makes it easier for the stainless steel in the process of heat exchange tube used in machining micro cracks, eventually extending, the phenomenon of the expansion pipe.
3. The reason also may be that the working condition of the use of the stainless steel heat exchange tube is hydrogen environment. It produces a large amount of hydrogen-induced martensite, leading to hydrogen-induced cracks on the heat exchange tube of stainless steel. In the process of heat exchange tube of stainless steel used, the local heating of the stainless steel heat exchange tube is serious due to the S, Cl – of tube medium and the existence of non-metallic inclusions, especially the existence of Cl -, Cl - oxidation potential energy is larger. Then, the passivation layer of stainless steel heat exchange tubes is damaged, and then it causes the cracking of the stainless steel heat exchange tubes. That is to say, the use of the stainless steel heat exchange tube has played a certain role in promoting cracking. It will make the stainless steel heat exchange tubes crack.
The above is about the content of stainless steel heat exchange tubes. We hope you use the correct stainless steel to produce stainless steel heat exchange tubes in the future processing process. However, we also pay attention to the use of stainless steel heat exchange tubes and the use of medium, in order to extend the service life of stainless steel heat exchange tubes.
