High strength cold rolled steel sheet and hot dip galvanized steel sheet having excellent formability and coating property, and the method for manufacturing thereof

A cold-rolled steel sheet and formability technology, applied to high-strength cold-rolled steel sheets with excellent formability and coating properties, can solve problems such as difficulties and high production costs, and achieve improved coating properties, excellent formability, and high tensile strength intensity effect

Inactive Publication Date: 2008-12-17
POHANG IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, in order to obtain good workability, there are one or more heat treatment procedures before coating, resulting in high production cost of this patented process and many difficulties in practical application

Method used

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  • High strength cold rolled steel sheet and hot dip galvanized steel sheet having excellent formability and coating property, and the method for manufacturing thereof
  • High strength cold rolled steel sheet and hot dip galvanized steel sheet having excellent formability and coating property, and the method for manufacturing thereof
  • High strength cold rolled steel sheet and hot dip galvanized steel sheet having excellent formability and coating property, and the method for manufacturing thereof

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Experimental program
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Effect test

Embodiment approach

[0037] In addition, when formability needs to be further improved in addition to the above-mentioned coating characteristics, according to one embodiment of the present invention, it is preferable to control the content of nitrogen (N) to satisfy one or both of the following inequalities:

[0038] (Si / 28+Al / 27) / (N / 14)≥10(1)

[0039] N * =(N / 14) / (Al / 27+Ti / 48+Nb / 93+V / 51+B / 11)≥0.2(2)

[0040] Furthermore, in one embodiment of the present invention, the bake hardening characteristics are also improved due to the fixation of dissolved nitrogen after the steel sheet is coated.

[0041] The composition of the steel material according to the present invention will be described below.

[0042] Steel Composition

[0043] Carbon (C): 0.01-0.2%

[0044] Carbon (C) is a very important component for increasing the strength of the steel sheet and securing a composite structure consisting of ferrite and martensite. When the carbon content is less than 0.01%, it is impossible to obtain th...

Embodiment 1

[0106] Thick steel plates having the steel composition shown in Table 1 below were subjected to vacuum melting, heated in a heating furnace at a reheating temperature of 1150° C. to 1250° C. for 1 hour, and then hot rolled and bent. Finish hot rolling at 850°C-950°C. The bending temperature was set at 650°C. Then, the hot-rolled steel sheet is pickled and cold-rolled at a cold-rolling reduction ratio of 50-70%. Under the conditions shown in Table 2, the cold-rolled steel sheets were subjected to continuous annealing, primary cooling and secondary cooling. For tensile strength testing, JIS 5 test strips are taken from continuously annealed cold-rolled steel sheets to check their material quality.

[0107] In addition, in order to observe the coating characteristics, the continuously annealed steel sheet manufactured as described above was heated to 460°C, hot-dip galvanized for 5 seconds, alloyed at 500°C for 10 seconds, then cooled to room temperature, and then observed with...

Embodiment 2

[0121] Thick steel plates having the steel composition shown in Table 4 below were subjected to vacuum melting, heated in a heating furnace at a reheating temperature of 1150° C. to 1250° C. for 1 hour, and then hot rolled and bent. Hot rolling is terminated at 850°C-950°C. The bending temperature was set at 650°C. Then, the hot-rolled steel sheet is pickled and cold-rolled at a cold-rolling reduction ratio of 50-70%. The cold-rolled steel sheets were subjected to continuous annealing, primary cooling and secondary cooling under the conditions shown in Table 5.

[0122]For the tensile strength test, JIS 5 test bars were taken from the annealed cold-rolled steel sheets and examined for their material quality. In addition, in order to simulate the quality of the material after being coated on an automobile part, a 2% strain (strain) was added to the JIS 5 test strip prepared as described above, and then the test strip was boiled in oil at 170° C. for 20 minutes, Tensile stren...

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Abstract

The invention relates to high strength cold rolled steel sheet and high strength zinc-coated steel plate sheet mainly used as structural components and reinforcing members of a vehicle body, these steel sheets include remarkable formability and coating property and comprise: 0.01-0.2 weight percent of carbon (C), 0.01-2 weight percent of silicon (Si), 0.5-4.0 weight percent of manganese (Mn), less than 0.1 weight percent of phosphor (P), less than 0.03 weight percent of sulfur (S), less than 1.0 weight percent of soluble aluminum (Sol.Al), 0.001-0.1 weight percent of nitrogen (N), 0.005-1.0 weight percent of stibium (Sb), and remaining ferrum (FE) and inevitable impurities. The invention also relates to the zinc-coated steel plate sheet and a manufacturing method for these steel sheets. In accordance with the invention, remarkable coating property can be attained and tensile strength is more than 490 MPa. In the other hand, the formability thereof is ensured, TS*El balance thereof is more than 15,000. Furthermore, the outstanding bake hardenability of which BH value is more than 80 MPa can be attained.

Description

technical field [0001] The present invention relates to a steel sheet mainly used as a structural component and reinforcement of a vehicle body, a zinc-based metal-plated steel sheet (zinc-coated steel sheet) made therefrom, and a manufacturing method thereof. More specifically, the present invention relates to a high-strength cold-rolled steel sheet having a tensile strength greater than 490 MPa and excellent coating properties, a zinc-based metal-plated steel sheet (zinc-coated steel sheet) made therefrom, and a method of manufacturing the same. Background technique [0002] Recently, along with the strengthening and expansion of motor vehicle occupant safety regulations, a lot of research and studies have been actively conducted to achieve weight reduction and reinforcement of vehicle bodies to improve the impact resistance of vehicle bodies. In order to cater to this trend, high-tensile-strength steel plates with a tensile strength greater than 490MPa are actively used t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D8/02
CPCC22C38/001C22C38/02C22C38/04C22C38/06C22C38/14C22C38/22C22C38/60
Inventor 安衍相吴振根孙一领金成柱陈光根
Owner POHANG IRON & STEEL CO LTD
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