| Enamel products are popular among users because of their safety,nontoxicity,beauty and duration.The enamel plate assembled tank structure has been introduced into China as an economic and environmental protection product in recent years.They are mainly used in sewage,landfill leachate treatment and other projects.As a leading product of an emerging industry,its market prospect is very broad.Through adjusting the chemical component and optimizing the rolling process,this paper is committed to develop the hot rolled double-sides enamel steel with high strength(480 MPa before enameling,340 MPa after enameling)and good fish-scale resistance.The main research contents and results are as follows:(1)The continuous cooling transition curve of austenite at 900? after undeformation and 40%deformation is investigated.The result shows that the Ac1 and Ac3 are 652? and 857?,the Ar1 and Ar3 are 613? and 808?;During continuous cooling at different cooling rates of 0.5?40?/s,there are ferrite,pearlite and bainite transformation,and no martensite transformation;The deformation increases the cooling rate ranges of ferrite,pearlite transformation and decreases the cooling rate range of bainite transformation.(2)The precipitation kinetics(PTT)curve is investigated.The result shows that the straininduced precipitation process at 930? is the fastest.A small amount of coarse Ti4C2S2 can be observed on the thermal simulated sample by direct quenching after 925? deformation,whose size is between 200 nm and 500 nm;A certain amount of fine Ti4C2S2 precipitated particles can be observed on a thermal simulation sample after quenching at 925? with a 50 s interval,whose size is about 30 nm;The grown and coarsened Ti4C2S2 can be observed on the thermal simulation sample after quenching at 925? with a 1000 s interval,whose size is between 80nm and 100 nm.(3)Through analysis of the microstructure and mechanical properties of the experimental steel,it is shown that the increasement of solid solution S and Mn elements before enameling increases the fine grain strengthening and precipitation strengthening,thus increasing the strength;Experimental steel has better mechanical properties at a finish rolling temperature of 830?;After twice enameling,the strength of the experimental steel is greatly reduced,and the influence of component and finish rolling temperature is weakened.And with different components have different decreases in yield strength.(4)Through analysis of the fish-scale resistance of the experimental steel,it is shown that the TH value of the hot rolled experimental steel under different components and processes are about 25.0 min,which meets the requirements;The increasement of S,Mn and other elements will promote the precipitation of the second phase,and has better fish-scale resistance;When the finish rolling temperature is 830?,the hydrogen storage capacity will be better than that of the finish rolling temperature of 880?;After twice enameling,the performance of resisting fish-scaling is greatly reduced,and the influence of component and finish rolling temperature is also weakened.However,the TH value of the enameled experimental steel is still greater than 6.7 min,which satisfies the requirements.(5)Through analysis of the microstructure,element distribution and adhesion of the experimental steel after actual enamel,it is shown that the thickness of the enamel layer is about 120 ?m,the matrix is still equiaxed ferrite grains and the grain size increases by comparing with the hot-rolled structure.However,there is no obvious difference between the edge and the core of the matrix.There are more fine pearlite structures at the three-phase intersection of the grain boundary.The diffusion depth of the element in the transition zone is between 0.5 ?m and 1.5 ?m;The ball drop test is carried out to prove that it has good adhesion properties. |
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