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Cold-rolled steel sheet with high yield ratio and excellent weather resistance

A cold-rolled steel sheet and high yield-strength ratio technology, applied in the field of high-strength cold-rolled steel sheet and its manufacturing, can solve the problems of cold-rolled steel product center segregation, damage workability, etc., achieve high yield-strength ratio, save energy, The effect of improving annealing efficiency

Inactive Publication Date: 2009-10-14
POSCO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, a large amount of P added will lead to central segregation of cold-rolled steel products, thereby rapidly destroying its machinability

Method used

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  • Cold-rolled steel sheet with high yield ratio and excellent weather resistance
  • Cold-rolled steel sheet with high yield ratio and excellent weather resistance

Examples

Experimental program
Comparison scheme
Effect test

Embodiment approach

[0045] The cold-rolled steel sheet of the invention has both high strength and high yield ratio. According to an exemplary embodiment of the present invention, the steel plate has a tensile strength of at least 80 kg / mm 2 , such as 80-110kg / mm 2 . The steel plate has a yield strength of at least 80%, such as 85% to 94%. In addition, the steel plate has a ductility of at least 10%.

[0046] These characteristics meet the requirements of the above-mentioned composition system and can be obtained by the low temperature annealing of the present invention. The low temperature annealing may partially retain the deformed grains in the microstructure, rather than fully recovering them. The microstructure of the present invention may be ferrite or a mixture of ferrite and pearlite, but is not limited thereto.

[0047] Hereinafter, a method of manufacturing a cold-rolled steel sheet will be described.

[0048] A method of manufacturing a steel material having the above composition...

Embodiment 1

[0060] The normalized corrosion index (CI) and weather resistance of steel materials having the compositions shown in Table 1 were measured. The results are shown in Table 2.

[0061] In the weather resistance test, the steel material was subjected to a salt spray test (SST) at 30° C. for 480 hours with 5% salt water (NaCl solution). Here, the corrosion resistance index (CI) is an index for estimating weather resistance according to ASTM G101. The higher the corrosion resistance index, the stronger the weather resistance.

[0062] The corrosion resistance index is mainly obtained based on alloying elements, and satisfies the following formula.

[0063] Corrosion resistance index (CI)≤26.01(%Cu)+3.88(%Ni)+1.2(%Cr)+1.49(%Si)+17.28(%P)-7.29(%Cu)(%Ni)-9.10(% Ni)(%P)-33.39(%Cu) 2

[0064] Table 1

[0065]

[0066] Table 2

[0067] steel type

Corrosion Index (CI)

Corrosion level (weight loss,

g / cm 2 )

Weather resistance evaluation

...

Embodiment 2

[0071] Each of the steel materials, that is, the inventive steel materials 1 and 2 and the comparative steel materials 1-4 in Table 1 of Example 1, was used to manufacture cold-rolled steel sheets under the conditions described in Table 3. The mechanical properties and workability properties of each steel sheet were measured, and the results are shown in Table 4.

[0072] table 3

[0073]

[0074] Table 4

[0075]

category

Yield Strength

(kgf / mm 2 )

tensile strength

(kgf / mm 2 )

Elongation

(%)

Yield ratio

(%)

Bending workability

Embodiment 1 of the present invention

84.9

90.4

11

93.9

excellent

Embodiment 2 of the present invention

82.1

92.4

13

88.9

excellent

Embodiment 3 of the present invention

86.3

101.0

10

85.4

exc...

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PUM

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Abstract

There is provided a cold-rolled steel sheet with a high yield ratio, and excellent weather resistance and workability. The cold-rolled steel sheet including, by weight: 0.08 to 0.20% C, 0.1 to 0.5% Si, 0.9 to 2.0% Mn, <0.02% P, <0.01% S, 0.02 to 0.07% Al, 0.03 to 0.06% Nb, 0.05 to 0.30% Ni, 0.2 to 0.5% Cu, 0.3 to 0.6% Cr, 0.001 to 0.004% B, 0.02 to 0.08% Co, the balance being Fe and unavoidable impurities. Also, there is provided a method of manufacturing the same.

Description

technical field [0001] The present invention relates to a high-strength cold-rolled steel plate with excellent weather resistance and a manufacturing method thereof for buildings, rail vehicles and containers, and more particularly, the present invention relates to a high-yield ratio and High-strength cold-rolled steel sheet with excellent weather resistance. Background technique [0002] In order to reduce the weight or prolong the service life of containers or rail vehicles, materials such as stainless steel or aluminum are generally used. These products are required to have properties such as bendability, weldability and durability. In addition, means of transportation are susceptible to impact force when transporting or loading goods, and thus it is necessary to suppress deformation caused by the impact force. For this purpose, a steel material having a high yield ratio may be desirably used. [0003] The yield ratio is defined as the ratio of the tensile strength to ...

Claims

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Application Information

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IPC IPC(8): C22C38/00
CPCC22C38/54C22C38/48C22C38/06C22C38/04C22C38/52C22C38/42C22C38/02
Inventor 金在翼郑琪朝金钟华李秀姬
Owner POSCO
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