Cause Analysis on the Lower Low-temperature Toughness of Container Steel

The low temperature pressure vessel steel for test is used in cryogenic environment,the requirements for low temperature toughness are extremely stringent.The fluctuations of low temperature toughness often occur in steel production,which affect the yield and delivery.To solve the above problem,using metallographic microscope,scanning electron microscope and energy spectrometer on the samples with different impact properties,the dendrite segregation,microstructure,grain size of austenite and so on was compared and analyzed from macro to micro.The results showed that the main factor led to the low temperature toughness fluctuations was found for mixed crystal,which caused by the improper finishing temperature and pass reduction,moreover the developed columnar crystals and dendrite segregation were inherited in steel,would have a negative impact on the rolled microstructure and low temperature toughness.