Effect Of Microstructure Of Enamel Steel On Hydrogen Diffusion

Enamel products have the advantages of smoothness,durability,corrosion resistance,etc.,and are widely used in industrial production and daily life.However,the enamel steel is prone to scale explosion after being coated,resulting in a decrease in the service life of the enamel product.Studies have shown that the scale explosion phenomenon is mainly related to the absorption,diffusion and escape of hydrogen in steel,and the crystal defects and the precipitated phase existing inside the material will form a reversible and irreversible trap of hydrogen,which affects the diffusion of hydrogen in steel.Different,in which the irreversible trap precipitation plays an effective role against the anti-scale explosion performance.Enamel thick plates are widely used in large-scale chemical reaction tanks in the chemical and pharmaceutical fields.Therefore,they are an enamel steel that has been developed in recent years.However,due to the increase in thickness,the requirements for the structural properties of thick plates are significantly improved.Due to the diffusion behavior of hydrogen in the steel plate,it is required that the hydrogen diffusion performance at each position of the thick plate is consistent,and the phenomenon that the surface position of the thick plate is good against scale explosion and the anti-scale explosion performance at the center position is poor.Therefore,the microstructure and hydrogen diffusion properties of different positions(surface,1/4 position,1/2 position)of enamel thick plates are studied.The microstructure includes the type and quantity of precipitated phase and grain size.It is mainly carried out by metallographic observation,transmission electron microscopy analysis,and European standard(EN10209:2013)hydrogen permeation experiment.At the same time,the micro-area potential difference is another auxiliary means to study hydrogen storage capacity.This paper also uses TEM analysis,atomic force microscopy and scanning electron microscopy analysis,and international standard(ISO17081:2008)hydrogen permeation experiment to study the precipitation of different enamel steel.The relationship between the potential difference of the phase and the hydrogen diffusion ability mainly leads to the following conclusions:1)Comparing the metallographic structure,the type of precipitated phase and the hydrogen permeation at different positions in different steel grades and different thickness samples,it is found that the grain sizes at different positions in different thickness enamel thick plates are different,and the surface is cooled by The speed is fast,the grain refinement is obvious,the grain size is small,and the cooling rate at the 1/2 position is slow,and the grain size is large.2)TEM analysis was carried out at three different positions of two samples in the thick plate.The precipitated phase was mainly Ti C and a small amount of Ti₄C₂S₂.The number of precipitated phases at different positions was different,and the number of precipitated phases at the surface position was larger.The number of precipitated phases at the 1/2 position below the surface is the least.3)There is a difference in the anti-scale explosion sensitivity value(TH value)at different positions in the enamel thick plate.The anti-scale explosion performance of the surface position is higher than 1/2 of the surface,and the anti-scale explosion performance at the 1/2 position is poor..Therefore,the research on thick plates can not be limited to a certain position,but the different positions of the thick plates should be comprehensively studied.4)From the results of hydrogen permeation experiments,the types of precipitated phases and the potential difference between the micro-regions,it is found that the potential difference is the largest when the Mn S is contained in the precipitated phase,and the trapping ability for hydrogen atoms is the largest,so the effective diffusion coefficient of the steel sheet is the smallest;When the composite precipitated phase consisting mainly of Ti(C,N)and some other elements,the potential difference decreases,the ability to capture hydrogen atoms is weakened,the effective diffusion coefficient of the steel plate increases,and the precipitated phase only exists.In Ti(C,N),the difference in potential of the micro-region is relatively small,the ability to capture hydrogen atoms is the weakest,and the effective diffusion coefficient of the steel plate is the largest.