Cold-rolled steel sheet having excellent bendability, method for producing same, and member employing same
A technology of bending workability and cold-rolled steel plate, which is applied in the field of cold-rolled steel plate, can solve the problems of ultra-fine particles hindering productivity, and achieve the effect of cost reduction
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Embodiment 1
[0074] Steel Nos. 1 to 11 having the composition shown in Table 1 with a final rolling ratio of 24% were used as the Ar of each steel plate. 3 Hot rolling was performed at a finishing temperature of 930° C. above the transformation point, and the coiling temperature was set at 590° C. to obtain a hot-rolled steel sheet with a thickness of 2.9 mm. The obtained hot-rolled steel sheet was cold-rolled at a rolling ratio of 72% to a thickness of 0.8 mm to obtain a cold-rolled steel sheet.
[0075] For the obtained hot-rolled steel sheet, the thick section of the sheet in the rolling direction was corroded with a nital solution, and the 1 / 4 position of the sheet thickness was observed at 200 times and a photograph was taken, and the average value was calculated according to the cutting method described in JIS G 0552 (1998). Crystal particle size. And, carry out picric alcohol corrosion and take 400 times the field of view of 0.21 × 0.16mm at the 1 / 4 position of the plate thickness ...
Embodiment 2
[0080] Using steel No. 7 in Table 1, a hot-rolled steel sheet was produced under the same conditions as in Example 1. Next, the front and back sides of the hot-rolled steel sheets were ground to form various thicknesses, and then cold-rolled while changing the rolling ratio in the range of 0 to 72%, to obtain cold-rolled steel sheets with a thickness of 0.8 mm. Then, for the hot-rolled steel sheet and the cold-rolled steel sheet with a rolling ratio of 0%, the average tensile strength TS, the yield ratio YR, the average ultimate deformation capacity in the thickness direction, the hole expansion ratio λ, and the thread breaking torque were measured in the same manner as in Example 1. , Bending workability was evaluated.
[0081] The results are shown in Table 2. The rolling ratio ≥ 9% achieves TS ≥ 390 MPa, and in this case, regardless of the rolling ratio, the bending workability and hole expandability are good. Furthermore, when the rolling ratio is 30% or more, the tensil...
Embodiment 3
[0085] Using the materials produced in Example 2 with a rolling ratio of 0% (TS=311MPa) and a plate thickness of 0.8mm (comparative example) and a material with a rolling ratio of 72% (TS=664MPa) and a plate thickness of 0.8mm (inventive example) , The case for an electronic device was produced by the following method.
[0086] As the case bottom, after cutting into a size of 150 mm×150 mm, pre-threaded holes were processed at three positions at positions 15 mm from the ends of three sides in the same manner as in Example 1. For the three sides subjected to thread pre-hole processing, a 90-degree bend (height 20mm) was performed with a curvature radius of 0mm (0R) at the tip of the punched hole. Furthermore, in order to increase the rigidity of the board, the remaining one side is subjected to close-contact bending (C-bending). Next, as a case cover, after cutting into a size of 152 mm×152 mm, three sides were bent at 90 degrees (height: 20 mm) with a curvature radius of 0 mm...
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Abstract
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