New device development for steel frame profile of steel plant

Continuous casting and chemical composition strictly control the degree of superheat of the molten steel, and it is blown with Ar to protect the cast and prevent secondary oxidation. Strictly control the speed of casting, the parameters of secondary cooling water and the straightening temperature of the slab, and the quality of the produced slab is good. Total production of 5 furnaces, physical chemical composition.

In the hot rolling process and controlled cooling, the dynamic transformation point of the steel was determined by dynamic compression deformation. Ar3 was 767%, and Ar1 was 713%. From the stress-strain curve and considering the actual strain rate, the dynamic recrystallization final stress-strain curve could be obtained. Around 950%. Based on this, the final hot rolling finishing temperature is (86020)% and the coiling temperature is (58020)%.

Depressing the formulation of the system, consider increasing the finish rolling compression ratio by increasing the thickness of the entrance blank of the F0 frame. The specification is 6.0mm (1250mm steel plate finishing rolling frame rate, temperature control situation, from which we can see, the first few use high temperature large deformation, F0, F1, F2 each frame deformation is more than 30%, can be refined After the austenite grains were rolled in the unrecrystallized zone, the cumulative deformation of the F3F6 frame reached 66%, which resulted in a large number of deformation bands and subareas in the austenite crystals by increasing the cumulative deformation in the unrecrystallized zone. The structure increases the number of nucleation sites of ferrite grains, and the laminar cooling after rolling is used to obtain finer ferrite grains and improve the strength and toughness of the steel.From the point of view, under the actual production hot rolling process system, each machine Frame rolling force is in the normal range.

Rack reduction ratio and temperature Rack reduction rate and rolling force 2.5 Roll size Control During rolling, use the R4, R5, R6 and F0 stand-up roll mills E4, E5, E6, and E0. Side, to ensure that the target width of the coil, width tolerance of 0 +15 mm. Finishing F4F6 hydraulic thickness automatic control (H-AGC) system.

The system uses a short-stroke hydraulic cylinder system with high responsiveness, high reduction speed, high setting accuracy, improved full-length thickness control accuracy of the coil, thickness tolerance of 50m. Work roll bending of the F1F6 frame of the finishing rolling mill The device (WRB) uses a closed loop control system; the F1F3 frame uses a work roll continuous crown control system (CVC). The WRB+CVC form control system realizes the dynamic control of the plate shape, effectively controls and maintains the roll crown, and achieves a good plate shape.

Trial Production Results and Analysis Metallographic Analysis Metallographic analysis was performed on samples taken from the QStE420TM plate. After grinding and polishing of the samples, inclusion grade and grain size ratings were performed under optical microscope objectives, using 3% 4% nitric acid alcohol. After the solution was etched, the microstructure was observed under an optical microscope objective. Due to the low sulfur content of the steel grades and the use of refining treatment, feeding calcium treatment and other means, the inclusions in the steel are spheroidized and the inclusions are Class D class 01, which is conducive to improving the cold forming properties of the steel sheet and reducing the brittle transition temperature of the steel. The microstructure is ferrite plus a small amount of pearlite; because hot rolling adopts technological measures such as increasing the cumulative deformation within the non-recrystallization temperature range, a strong deformation zone is formed in the austenite grains. The upper processing strain is concentrated in a large amount, and its strain energy directly or indirectly becomes the driving force of phase transformation, which promotes the increase of ferrite nucleation sites, and the grain refinement effect is obvious. The grain size level is 10.5 grades and the grain size is small. Inclusions and grain size levels.

Mechanical properties of the steel plate The performance test of the steel plate shows that the average yield strength is 453.3 MPa, the average tensile strength is 525.3 MPa, the average elongation is 31.3%, the yield ratio is 0.860.89, and the average value is 0.872. The strength and elongation control fluctuation is small. Better toughness and toughness matching, 180 wide cold bending performance, 100% pass rate of performance. Performance process control capability index is quite sufficient, including yield strength Cpk1.09, tensile strength Cpk1.54, elongation Cpk2.27.

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