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High strength hot rolled steel sheet and cold rolled steel sheet having excellent continuous productivity, high strength hot dip galvanized steel sheet having excellent surface quality and plating adhesion, and manufacturing method therefor

A kind of technology of hot-dip galvanized steel sheet and hot-rolled steel sheet

Active Publication Date: 2019-08-06
浦项股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, similar to the internal oxides in the hot rolling process, the internal oxides formed on the grain boundaries of the surface of the steel sheet during the annealing process also adhere to various rolls in the annealing furnace, resulting in dent defects

Method used

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  • High strength hot rolled steel sheet and cold rolled steel sheet having excellent continuous productivity, high strength hot dip galvanized steel sheet having excellent surface quality and plating adhesion, and manufacturing method therefor
  • High strength hot rolled steel sheet and cold rolled steel sheet having excellent continuous productivity, high strength hot dip galvanized steel sheet having excellent surface quality and plating adhesion, and manufacturing method therefor
  • High strength hot rolled steel sheet and cold rolled steel sheet having excellent continuous productivity, high strength hot dip galvanized steel sheet having excellent surface quality and plating adhesion, and manufacturing method therefor

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0108] Billets having the compositions of Tables 1 and 2 below were reheated for 1 hour at a temperature of 1200° C. and finish rolled at a temperature of 900° C. higher than the Ar3 of all billets, and then cooled to Table 3 below. After the coiling temperature, it was forcibly cooled to a temperature of 550° C. at an average cooling rate of 3° C. / min, and then furnace cooled. With regard to the hot-rolled steel sheet that has been cooled, in order to observe the oxides inside the hot-rolled steel sheet, the cross-section of the steel sheet was observed with a scanning electron microscope. At this time, the maximum depth of the internal oxide of the hot-rolled steel sheet was measured at 5 places at a magnification of 5000, and the maximum depth among them was selected.

[0109] Then, the cooled hot-rolled steel sheet was pickled with a 17% by volume HCl solution at 60° C. for 40 seconds to dissolve iron oxide on the surface, and then cold-rolled at a rolling reduction of 45%...

Embodiment 2

[0150] In order to confirm the occurrence of dent defects while continuously producing products in the coil state, production and analysis are carried out in actual production facilities. The components having the compositions of the following Tables 6 and 7 were continuously cast, and steel slabs were produced. After keeping this billet at a temperature of 1200°C for 1 hour, finish rolling was performed at a temperature of 900°C higher than the Ar3 of all billets, cooled to the winding temperature shown in Table 8, and coiled as a coil, Then, it was forcibly cooled to a temperature of 550° C. at an average cooling rate of 3° C. / min, and then air-cooled.

[0151] With respect to the hot-rolled steel sheet cooled to normal temperature, the cross-section of the steel sheet was observed with a scanning electron microscope in order to observe oxides in the hot-rolled interior. At this time, the maximum depth of the internal oxide of the steel sheet was measured at 5 places at a m...

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Abstract

Disclosed are a high strength hot rolled steel sheet and the like, the hot rolled steel sheet comprising: by wt%, 0.14-0.3% of C, 1-2.0% of Si, 2.6-5% of Mn, 0.001-2% of sol.Al, (48 / 14)*[N]-0.1% of Ti, 0.04% or less (excluding 0%) of P, 0.015% or less (excluding 0%) of S, 0.02% or less (excluding 0%) of N, 0.08-0.2% of a sum of one or more types among Sb, Bi, Sn, and Zn, and the balance of Fe andinevitable impurities, wherein an internal oxide containing one or more types of elements among Si, Mn, Al, and Fe is present in the surface layer part of the hot rolled steel sheet, and a maximum depth of the internal oxide is 1 mum or less (including 0 mum).

Description

technical field [0001] The present invention relates to a high-strength hot-rolled steel sheet and a cold-rolled steel sheet excellent in continuous productivity, a high-strength hot-dip galvanized steel sheet excellent in surface quality and coating adhesion, and a method for producing them. Background technique [0002] Recently, there has been a need to increase the strength of steel sheets for automobiles in order to reduce the weight of automobiles in accordance with the regulation of carbon dioxide for protecting the global environment and to improve the collision stability of automobiles. [0003] In order to meet these needs, high-strength steel sheets of 950 MPa or more have recently been developed and applied to automobiles. [0004] In terms of methods for increasing the strength of steel sheets, high-strength steel sheets can be easily produced by increasing the amount of steel strengthening components including carbon, but steel sheets for automobile bodies cann...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/04C22C38/38C22C38/34C22C38/02C22C38/60C22C38/22C22C38/26C21D8/02C23C2/06
CPCC21D8/02C22C38/02C22C38/04C22C38/22C22C38/26C22C38/34C22C38/38C22C38/60C23C2/06C21D8/0226C21D8/0247C23C2/40
Inventor 金明守姜己哲朴一祯
Owner 浦项股份有限公司
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