The Development Of Cold Rolled Steel Sheet For Enameling And Study On The Fish-Scaling Resistance

Under the premise of meeting the performance requirements and less addition of expensive alloying, the research purpose was to develop steel with high hydrogen storage properties and can be adapted to diversified enamel technology. The new low-carbon cold-rolled enameling steel was developed by the control of hot-rolling, cold rolling and annealing process. Based on the basic principles of electrochemical, with the self-design hydrogen permeation test device, the hydrogen permeation time tb and hydrogen diffusion coefficient D of the experiment steel was determined. Through the wet enameling experiment, the fish-scaling resistance of the steel was further studied and the credibility and practical value of the hydrogen permeation device is validated. The different state and properties of the enamel steel have been studied in this paper and the results of experiments and conclusions of theoretical analysis are as follows:[1] Process control methods suitable for DC01EK enamel steel are as follows:1) hot rolling: finish rolling temperature(880℃～930℃) and coiling temperature(650℃～730℃);2) cold rolling:a large cold rolling reduction rate(80%);3) batch annealing:DC01EK(690℃-730℃insulation for5h); DC01EK-Ti(700℃～730℃insulation for5h). The mechanical properties of the steel were:yield strength≤270MPa, tensile strength≤400MPa, elongation≥30.0%;[2] Organization of hot rolling at room temperature:ferrite+pearlite, ferrite grain size was8.0～9.5grade; annealed microstructure:ferrite, ferrite grain size of730℃was10.0-11.0grade; the microstructure after enameling remains ferrite, grain size was9.0-10.0grade;[3] The batch annealing process(350℃～730℃insulation for5h) was simulated and the recrystallization temperature range of DC01EK. was550℃～600℃and DCOIEK-Ti was500℃～650℃. For DC01EK-Ti:the smaller original grain size was the reason of the low beginning recrystallization temperature, while the hinder of grain boundary migration by second phase particles was the reason of high finishing recrystallization temperature; [4] The hydrogen storage property of steel sheet was valued by the hydrogen permeation test device, and the hydrogen trap of DC01EK was mainly MnS and Fe3C while DC01EK-Ti was mainly Ti4C2S2with a handful of MnS. The precipitates of steel were mainly round or oval, mainly size range was100-250nm;[5] The impact of different annealing temperature(650℃～730℃) on the hydrogen permeation time tb and hydrogen diffusion coefficient D was studied.With the annealing temperature rising, the decrease of Fe3C and the changes of the second-phase particle size caused the decrease of tb. Heat treatment at730℃for5h, the hydrogen permeation time tb of DC01EK and DC01EK-Ti were12min and20min, both to meet the requirement of enameled steel. With Ti steel has a greater amount of hydrogen permeation time of surplus;[6] Through the wet enameling experiment, the credibility and practical value of the hydrogen permeation device was validated. The enamel steel has good formability and fish-scaling properties and this research had provided necessary theoretical basis for the next theoretical research and industrial production.