Cold-rolled high-carbon steel plate and process for manufacturing method therefor

A technology of cold-rolled steel sheets and manufacturing methods, which is applied in the field of manufacturing high-carbon cold-rolled steel sheets, and can solve the problems of not being able to satisfy both uniformity and stretch flangeability at the same time

Inactive Publication Date: 2008-06-25
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

And can't meet this uniformity an

Method used

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  • Cold-rolled high-carbon steel plate and process for manufacturing method therefor

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Embodiment 1

[0103] Continuously cast slabs of steels A to D having the chemical compositions shown in Table 1 were heated to 1250°C, and hot-rolled, cold-rolled, and annealed under the conditions shown in Table 2 to manufacture steel sheets No. .1~16. In addition, the hot-rolled sheet annealing was performed under the conditions shown in Table 2 under several conditions. Each anneal was performed in a non-nitriding atmosphere (Ar atmosphere).

[0104] Here, steel plate Nos. 1 to 9 are examples of the present invention, and steel plate Nos. 10 to 16 are comparative examples. Then, the particle size and volume ratio of carbides, the hardness in the plate thickness direction, and the hole expansion ratio λ were measured by the following methods. Here, the hole expansion rate λ is used as an index for evaluating the stretch-flangeability. Then, the hardness in the sheet thickness direction of the hot-rolled sheet after coiling (after performing hot-rolled sheet annealing on the hot-rolled ...

Embodiment 2

[0130] E steel (C: 0.30 mass%, Si: 0.23 mass%, Mn: 0.77 mass%, P: 0.013 mass%, S: 0.0039 mass%, Sol.Al: 0.028 mass%, N: 0.0045 mass%, Ar 3 Phase transition point: 786°C, Ac 1 Phase transition point: 737°C),

[0131] F steel (C: 0.23 mass%, Si: 0.18 mass%, Mn: 0.76 mass%, P: 0.016 mass%, S: 0.0040 mass%, Sol.Al: 0.025 mass%, N: 0.0028 mass%, Cr: 1.2 Mass %; Ar 3 Phase transition point: 785°C, Ac 1 Phase transition point: 759°C),

[0132] G steel (C: 0.33 mass%, Si: 0.21 mass%, Mn: 0.71 mass%, P: 0.010 mass%, S: 0.0042 mass%, Sol.Al: 0.033 mass%, N: 0.0035 mass%, Cr: 1.02 % by mass, Mo: 0.16% by mass, Ar 3 Phase transition point: 775°C, Ac 1 Phase transition point: 755°C),

[0133] H steel (C: 0.36 mass%, Si: 0.20 mass%, Mn: 0.70 mass%, P: 0.013 mass%, S: 0.009 mass%, Sol.Al: 0.031 mass%, N: 0.0031 mass%, Ar 3 Phase transition point: 776°C, Ac 1 Phase transition point: 73 5°C),

[0134]And the D steel shown in 1 was continuously cast into a slab, heated to 1210° C., ho...

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Abstract

A process for manufacture of a cold-rolled high-carbon steel plate comprising the steps of: hot-rolling a steel containing 0.2 to 0.7% by mass of C at a finishing temperature lower by 20 DEG C than a Ar3 transformation point or higher to produce a heat-rolled plate; cooling the heat-rolled plate to a temperature of 650 DEG C or lower at a cooling rate of 60 DEG C/sec or higher and lower than 120 DEG C/sec; taking-up the cooled hot-rolled plate at a take-up temperature of 600 DEG C or lower; cold-rolling the resulting hot-rolled plate at a pressure reduction rate of 30% or more to produce a cold-rolled plate; and annealing the cold-rolled plate at an annealing temperature ranging from 600 DEG C and an Ac1 transformation point inclusive. The process can produce a cold-rolled high-carbon steel plate which is excellent in stretch-flange formalibity and evenness in hardness in the thickness-wise direction.

Description

technical field [0001] The present invention relates to a method for producing a high-carbon cold-rolled steel sheet that contains 0.2 to 0.7% by mass of C and is excellent in workability. Background technique [0002] High-carbon steel sheets used in tools and automotive parts (gears, transmissions), etc. are processed into various complicated shapes, so users require excellent machinability. On the other hand, in recent years, there has been a strong demand for reduction in component manufacturing costs, and the omission of processing steps and changes in processing methods have been made. For example, as a forming technology for automotive drivetrain components using high-carbon steel sheets, a double-acting forming techinique has been developed that enables thickness-addition forming and greatly shortens the process. And it has been partially implemented (for example, Journal of the JSTP, 44, 2003, p.409-413). [0003] Along with this, in high carbon steel sheets, work...

Claims

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Application Information

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IPC IPC(8): C21D9/46C22C38/00C22C38/58
CPCC22C38/04C21D8/02C22C38/02C21B11/00C21D8/0236
Inventor 仮屋房亮金本规生大久保英和楠本义治藤田毅
Owner JFE STEEL CORP
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