Effect of Coiling Temperature on Ti(C,N) Precipitation and Properties of Batch Annealed DC06EK Enamel Steel

The effects of hot-strip coiling temperature on Ti（C,N） precipitation, texture and hydrogen permeation behavior in DC06 EK enamel steel were investigated by TEM, EBSD test and electrochemical hydrogen permeation experiment. It was found that the Ti（C,N） particles in hot-strip coarsened with increasing coiling temperature, whereas after cold-rolling and annealing, the size difference of Ti（C,N） particles was lessened. The hot-strip coiling temperature has a significant impact on the recrystallized texture in the subsequent cold-rolled and annealed sheet. Hot-strip using high temperature（700 ℃） coiling leads to strong {111} recrystallized texture in annealed sheet, with peak intensity 9.2. On the contrary, in annealed sheets using hot-strip coiling at 650 ℃, their {111} recrystallized textures were weaker, which was also reflected in their rmvalues. Even though the hydrogen diffusion coefficient is slightly lower（7.76×10^（-5） mm^2/s） in annealed sheet using low temperature coiling（600 ℃）, appropriately higher coiling temperature is more suitable for DC06 EK enamel steel combining both good drawability and fish-scale resistance.

Study on microstructure and properties of cold-rolled high strength steel for enameling

With its superior comprehensive properties, cold-rolled enameling steel is widely applied in many fields. However, its low yield stress greatly limits its application. This study aims to improve the yield stress of cold-rolled enameling steel under the premise of meeting formability and enameling properties by strengthening the ferrite matrix via solid strengthening of Mn. The grain size of ferrite before and after enameling,mechanical properties of annealed steel, and precipitation behavior of second-phase precipitates are obtained through studying the microstructure and properties of enameling steel at different stages. The microstructure of the steel investigated at room temperature is found to contain equiaxial ferrite and bunchy cementite particles;the ferrite grains have grown to some extent after enameling. The fine dispersed TiC particles and cementite particles contained in the annealed steel are the main factors improving the hydrogen storage capability. Finally, the result of a falling-ball impact test shows that the steel has achieved excellent adherence.

Microstructure and properties of Ti-bearing hot-rolled high-strength steel plates for two-sided enameling

The composition and production technology of the type of hot-rolled steel plate used in two-sided enameling were briefly described. The microstructure and mechanical properties before and after enameling were contrastively investigated,and the precipitates in the samples were analyzed using transmission electron microscope and energy dispersive spectrometer. The results show the ferrite grain size of the steel plate after high-temperature enamel firing to be fine,with a large number of TiC and Ti;C;S;precipitates dispersed throughout the ferrite matrix. After two rounds of enamel firing at a temperature range of 800-890 ℃,its yield strength can still reach342 MPa. The results of a hydrogen permeation test show that the hydrogen storage properties of the steel plate are much better than those of ordinary structural carbon steel. A better bubble structure in the enamel layer can be obtained by this steel plate,with no fish-scale defects on the enameled steel-plate surface.

Causes of the formation of pit defects on the surface of the enamel layer

During the production of the inner walls of ovens,pit defects were formed on the surface of the enamel layer that was enameled on the cold-rolled steel via electrostatic powder spraying and sintering.The paper elaborates on the microstructure and element distribution of the enamel-steel interface and the enamel layer.Optical microscopy,scanning electron microscopy,and energy-dispersive spectroscopy were adopted to investigate the microstructure of a longitudinal section of the defect,and the pit-forming causes were analyzed.The results show that rusty spots lead to pit defects.During high-temperature firing,there is an inadequate fusion and reaction between iron oxides of the rusty spots and the enamel glaze.The rusty spots are closely related to pretreatment process;thus,to avoid their occurrence,electrostatic powder spraying and sintering should be performed timely after forming,degreasing,and thorough drying of the metal sheets.

Effect of Ti(C,N)Precipitation on Texture Evolution and Fish-Scale Resistance of Ultra-Low Carbon Ti-Bearing Enamel Steel

The Ti（C,N）precipitation and texture evolution in ultra-low carbon Ti-bearing enamel steel were studied to discover their correlation.Two different cooling paths of simulative coiling were adopted to gain different morphologies of Ti（C,N）precipitate in hot strips.It is found that the Ti（C,N）precipitate in hot strip using Path 2（put into asbestos box and air cooled）are finer and much more in quantity than that in hot strip using Path 1（held at 730℃ for 30min and furnace cooled）.The morphology of Ti（C,N）precipitate in hot strip has great effect on recrystallization texture in the subsequent cold-rolled annealed sheet.γ-fiber texture of strong recrystallization is gained in coldrolled and annealed sheet came from Path 1.On the contrary,in the one came from Path 2,theγ-fiber texture is weak.This may be due to the pinning force of numerous fine Ti（C,N）precipitate which retard the growth of preferential nucleated{111}orientated grains.Annealed steel sheets in the test came from both paths have excellent fishscale resistance.

The Effect of Annealing Processes on Fish-Scaling Resistance in V-Ti-N Microalloyed Low Carbon Steel Sheets for Enameling

Annealing process will have greatly influence on microstructure of V,Ti and N microalloyed low carbon steel sheets.In this paper,the experimental steels with given amount of V,Ti and N elements were annealed at 4 routes to simulate batch annealing and continuous annealing processes,respectively.The enameling tests for the annealed steel sheets were undergone in same enameling and firing processes to study the relationship between microstructure and fishscale.The result shows that the cold-rolled steel sheets annealed at 750 ℃for 6 minutes even for 30 minutes exhibit excellent fishscale resistance.

Correlation between Microstructures and Yield Strength of a High Strength Enameling Steel

Numerical estimates of the components of yield strength of a high strength Fe-C-Mn-P-N-Si enameling steel were determined using empirical relationships between microstructure and yield strength. Results are reported for both the hot rolled （HR） and cold rolled （CR） forms before and after simulating an enamel-fire anneal （EFA）. To determine the solubilities of alloying elements, thermodynamic calculations were performed in combination with the considerations of process conditions and the element diffusivities. The results show that the main solid solution strengtheners were the elements Mn, Si, and P, while the elements C and N were nearly completely tied up as precipitates. The yield strength reduction, due to the EFA, resulted primarily from an increase in grain size and a decrease in dislocation density, and the EFA appeared to have a negligible effect on the element solubilities.