High-strength cold-rolled steel sheet with excellent aging resistance and sinter hardenability
A cold-rolled steel plate and sinter hardening technology, which is applied in the field of cold-rolled steel plate, can solve the problems of inability to combine aging resistance and sinter hardenability, and achieve the effect of low yield ratio and high elongation
Active Publication Date: 2017-04-26
JFE STEEL CORP
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Problems solved by technology
That is, in the production method that has been studied until now, there is a problem that both aging resistance and sinter hardenability cannot be achieved at the same time.
Method used
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[0107] The molten steel of the composition shown in Table 1 was melted in a converter, which is a common melting furnace, and a billet (steel material: 250 mm in wall thickness) was produced by a common continuous casting method. These slabs were heated to 1250° C., and subjected to rough rolling to obtain thin slabs. Next, these thin slabs were subjected to finish rolling under the conditions shown in Table 2 to obtain hot-rolled sheets, which were coiled into coils. Next, the coiled hot-rolled sheet was subjected to pickling treatment to remove surface scale, and then a cold-rolling step of cold-rolling with a cold reduction ratio of 70% was further performed to obtain a cold-rolled sheet.
[0108] The annealing process of performing the annealing process by a continuous annealing line on the conditions shown in Table 2 was further performed with respect to these cold-rolled sheets, and the annealing process of making a cold-rolled annealed sheet was performed. Then, on the...
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Abstract
Provided is a high-strength cold-rolled steel sheet that combines aging resistance with bake hardenability. By mass, said steel sheet contains 0.0010-0.0080% carbon, up to 1.0% silicon, 0.1-1.8% manganese, up to 0.100% phosphorus, 0.01-0.5% soluble aluminum, up to 0.0050% nitrogen, 0.005-0.050% niobium such that C* = C - (12 / 92.9)Nb > 0, and either 0.01-0.10% chromium such that Cr > 60C* - 0.03 or 0.010-0.050% copper such that Cu > 42.8C* + 0.018. This makes it possible to obtain a high-strength cold-rolled steel sheet that exhibits the following: high strength, with a tensile strength in the 340-440 MPa range; excellent bake hardenability, with at least 30 MPa of bake hardening after the application of a 2% prestrain followed by a 20 minute paint-bake hardening process at 170°C; and excellent aging resistance, with a yield elongation of no more than 0.5% in a tensile test after 60 days of natural aging at 70°C.
Description
technical field [0001] The present invention relates to a cold-rolled steel sheet suitable for automotive panel parts, in particular to a high-strength steel sheet with a tensile strength TS of 340-440 MPa and excellent anti-aging properties and excellent sinter hardenability ( Bake-hardening property) (hereinafter also referred to as BH property (BH property)) high-strength cold-rolled steel sheet. It should be noted that the "steel sheet" herein includes steel sheet and steel strip. [0002] In addition, the "cold-rolled steel sheet" also includes a cold-rolled steel sheet and a cold-rolled steel sheet subjected to surface treatment such as plating. The plating treatment includes pure zinc plating, zinc-based alloy plating with zinc as the main component and alloy elements added thereto, Al or Al-based alloy plating with Al as the main component and alloy elements added, and the like. Background technique [0003] In recent years, from the viewpoint of protecting the glo...
Claims
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IPC IPC(8): C22C38/38
CPCC21D8/0236C21D9/46C21D9/48C22C38/001C22C38/004C22C38/02C22C38/04C22C38/06C22C38/12C22C38/16C22C38/26
Inventor 奥田金晴木村英之
Owner JFE STEEL CORP