Cold-rolled steel sheet, manufacturing method thereof, and automobile component

A manufacturing method and technology for cold-rolled steel sheets, which are applied to manufacturing tools, furnaces, heat treatment equipment, etc., can solve the problems of unable to remove SiO, unable to expect corrosion resistance, unable to obtain corrosion-resistant high-strength cold-rolled steel sheets, etc. Excellent corrosion resistance, improved chemical conversion treatment properties, corrosion resistance after painting, and excellent chemical conversion treatment properties

Active Publication Date: 2019-10-18
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] However, for the high-strength cold-rolled steel sheet described in Patent Document 1, even if the Si concentration on the surface of the steel sheet is reduced before cold rolling, Si-containing oxides are formed on the surface of the steel sheet due to annealing after cold rolling. Anticipation of improvement in corrosion resistance after coating
[0008] For the high-strength cold-rolled steel sheet described in Patent Document 2, the corrosion resistance does not pose a problem in a corrosive environment such as the salt spray test specified in JIS Z2371, but it does not become a problem in the salt-warm water immersion test and the combined cycle corrosion test. In the harsh corrosion environment, sufficient corrosion resistance after painting cannot be obtained
[0009] That is, high-strength cold-rolled steel sheets excellent in corrosion resistance after coating cannot be obtained only by reducing the Si concentration on the surface of the hot-rolled steel sheet or by reducing the linear oxides containing Si.
[0010] In the technique described in Patent Document 3, SiO 2 Insoluble in hydrochloric acid, even if the iron ion concentration is set at 0.5 to 18%, SiO cannot be removed 2

Method used

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  • Cold-rolled steel sheet, manufacturing method thereof, and automobile component
  • Cold-rolled steel sheet, manufacturing method thereof, and automobile component
  • Cold-rolled steel sheet, manufacturing method thereof, and automobile component

Examples

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Embodiment 1

[0112] The present invention will be described in more detail by way of examples.

[0113] Steel containing C: 0.125%, Si: 1.5%, Mn: 2.6%, P: 0.019%, S: 0.008%, and Al: 0.040%, with the balance consisting of Fe and unavoidable impurities, is passed through a converter, degassed Melting and continuous casting are carried out in a normal refining process such as treatment to produce a steel raw material (steel billet). Next, the billet is reheated to a temperature of 1150-1170°C, then hot-rolled at a finish rolling temperature of 850-880°C, coiled into a coil at a temperature of 500-550°C, and made into a plate with a thickness of 3 ~4mm hot-rolled steel plate. Next, these hot-rolled steel sheets were pickled to remove scale, and then cold-rolled to obtain cold-rolled steel sheets with a thickness of 1.8 mm. Next, these cold-rolled steel sheets are heated to a soaking temperature of 750 to 780° C. and held for 40 to 50 seconds, then cooled from the soaking temperature to a coo...

Embodiment 2

[0137]The steels A to O having the composition shown in Table 5 were smelted and continuously cast by a common refining process such as a converter and a degassing treatment to form a slab. These slabs were hot-rolled under the hot-rolling conditions shown in Table 6 to make hot-rolled steel sheets with a thickness of 3 to 4 mm, pickled to remove scale on the surface of the steel sheets, and then cold-rolled to make hot-rolled steel sheets with a thickness of 3 to 4 mm. 1.8mm cold-rolled steel plate. Next, these cold-rolled steel sheets were continuously annealed and pickled under the conditions shown in Tables 6 and 7, washed with water, dried, and temper rolled with an elongation of 0.7% to obtain cold-rolled steel sheets No. 81 to 111. steel plate.

[0138] Test pieces were cut out from the above-mentioned cold-rolled steel sheets obtained in this way, and the surface coverage of the iron-based oxides on the surface of the steel sheet after pickling was measured in the sam...

Embodiment 3

[0150] Melting and continuous casting of steel containing C: 0.125%, Si: 1.5%, Mn: 2.6%, P: 0.019%, S: 0.008%, and Al: 0.040%, with the balance consisting of Fe and unavoidable impurities And made steel raw material (steel billet). After reheating the steel slab to a temperature of 1150-1170°C, it is hot-rolled at a finishing temperature of 850-880°C, coiled at a temperature of 500-550°C, and made into a hot-rolled plate with a thickness of 3-4 mm. steel plate. These hot-rolled steel sheets were pickled to remove scale, and then cold-rolled to obtain cold-rolled steel sheets with a thickness of 1.8 mm. Next, these cold-rolled steel sheets are heated to a soaking temperature of 750 to 780° C. and held for 40 to 50 seconds, and then cooled from the above soaking temperature to a cooling stop temperature of 350 to 400° C. at 20 to 30° C. / second. Continuous annealing was maintained for 100 to 120 seconds within the above-mentioned cooling stop temperature range, and then the sur...

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Abstract

The present invention provides a cold-rolled steel sheet excellent in chemical conversion treatability and excellent in corrosion resistance after painting, a method for producing the same, and an automobile component. For the steel sheet that has been continuously annealed after cold rolling, use any acid solution in the following i) or ii) for the first pickling, and then use an acid solution containing a non-oxidizing acid for the second pickling wash. i) an acid solution, which is an acid solution containing nitric acid and hydrochloric acid, wherein the concentration of the nitric acid is greater than 50g / L and less than 200g / L, and the ratio R1 of the concentration of the hydrochloric acid to the concentration of the nitric acid (hydrochloric acid / Nitric acid) is 0.01~0.25, and Fe ion concentration is 3~50g / L; ii) a kind of acid liquid, it is the acid liquid that contains nitric acid and hydrofluoric acid, wherein, described nitric acid concentration is greater than 50g / L and is 200g / L or less, the ratio R2 (hydrofluoric acid / nitric acid) of the hydrofluoric acid concentration to the nitric acid concentration is 0.01-0.25, and the Fe ion concentration is 3-50 g / L.

Description

technical field [0001] The present invention relates to cold-rolled steel plate and its manufacture as well as automobile components. In particular, it relates to a cold-rolled steel sheet excellent in chemical conversion treatability and also excellent in post-paint corrosion resistance as evaluated by a salt-warm water immersion test and a combined cyclic corrosion test, a method for producing the same, and an automotive component. Background technique [0002] In recent years, improvement in fuel efficiency of automobiles has been strongly demanded from the viewpoint of protecting the global environment. In addition, from the viewpoint of securing the safety of the crew during a collision, there is also a strong demand for higher strength of the automobile body. In response to these demands, efforts are being made to increase the strength and thickness of cold-rolled steel sheets, which are raw materials for automotive components, while reducing the weight and increasing...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23G1/08C21D9/46C22C38/00C22C38/06
CPCC21D9/46C22C38/06C22C38/02C22C38/04C23G1/00C23G1/081C23G1/085C23G1/086C21D8/0478C23G1/08
Inventor 增冈弘之平章一郎寺崎雄太近藤宏胤
Owner JFE STEEL CORP
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