Hot-rolled steel sheet and process for manufacturing same

A technology of hot-rolled steel plate and manufacturing method, which is applied in the direction of manufacturing tools, metal rolling, chemical instruments and methods, etc., and can solve the problems that the impact resistance cannot be expected

Active Publication Date: 2014-08-27
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Therefore, the steel sheet whose strength is increased to a tensile strength of 850 MPa or more has the following problems: the anisotropy of the mechanical properties becomes conspicuous, and due to the aniso

Method used

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  • Hot-rolled steel sheet and process for manufacturing same
  • Hot-rolled steel sheet and process for manufacturing same
  • Hot-rolled steel sheet and process for manufacturing same

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Embodiment

[0144] A steel raw material having a thickness of 250 mm having the composition shown in Table 1 was produced under the hot rolling conditions shown in Table 2 into a hot-rolled steel sheet having a thickness of 1.2 to 3.2 mm. In addition, the cooling rate described in Table 2 is the average cooling rate from the start of forced cooling to the stop of cooling. In addition, a part of the obtained hot-rolled steel sheet was passed through a hot-dip galvanizing line with an annealing temperature of 700 to 720°C, and then immersed in a 460°C plating bath (plating bath composition: Zn-0.13% by mass Al) Among them, it is made of hot-dip galvanized steel sheet (GI material). The other part of the steel sheets passed through the hot-dip galvanizing line in the same manner as above, then dipped in the coating bath, and then subjected to an alloying treatment at 520° C. to obtain an alloyed hot-dip galvanized material (GA material). Regarding the amount of coating, GI material and GA m...

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Abstract

The present invention pertains to a process for manufacturing a hot-rolled steel sheet which comprises: heating a steel raw material that contains, in mass%, 0.055 to 0.15% of C, at most 0.2% of Si, at most 1.3% of Mn, at most 0.03% of P, at most 0.007% of S, at most 0.1% of Al, at most 0.01% of N and 0.14 to 0.30% of Ti so as to satisfy the relationship 1.0 <= ([C]/12)/([Ti*]/48) (wherein [Ti*] = [Ti]-3.4[N]-1.5[S]) to a temperature (T) ( DEG C) which is equal to or higher than 1150 DEG C and which satisfies the relationship [Ti*] < 10{-7000/(T+273)+2.75/[C]; keeping the steel raw material in a temperature range down to 1150 DEG C for at least 15 minutes; subjecting the resulting steel raw material to hot rolling wherein the total rolling reduction in a temperature range up to 980 DEG C is 40% or less and the finish rolling temperature is 880 DEG C or higher; cooling the hot-rolled steel sheet at a cooling rate of 40 to 200 DEG C/s within three seconds after the completion of the finish rolling; and winding up the cooled steel sheet in a temperature range of 500 to 680 DEG C.

Description

technical field [0001] The present invention relates to a high-strength hot-rolled steel sheet useful for automotive components, having a tensile strength (TS) of 850 MPa or more and having low anisotropy in mechanical properties, and a method for producing the same. Here, the anisotropy of mechanical properties refers to the difference between the mechanical properties in the L direction (rolling direction) and the mechanical properties in the C direction (direction perpendicular to rolling) of the hot-rolled steel sheet. Background technique [0002] In recent years, from the viewpoint of protecting the global environment, in order to limit CO 2 In the entire automotive industry, the ambition is to improve the fuel efficiency of vehicles. In order to improve the fuel efficiency of automobiles, it is most effective to reduce the weight of automobiles by reducing the thickness of used components, so the usage of high-strength hot-rolled steel sheets as raw materials for aut...

Claims

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Application Information

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IPC IPC(8): C21D9/46B21B3/00C22C38/00C22C38/14C22C38/60C23C2/06C23C2/28
CPCC23C2/28C22C38/54C23C2/06C22C38/14C22C38/04C21D9/46C22C38/001C22C38/10C22C38/48C22C38/00C22C38/60C22C38/06B21B3/00C21D2211/005B32B15/01C22C38/008C22C38/002C21D8/0263C22C38/02C21D8/0226C22C38/12C22C38/005C22C38/007C22C38/42C22C38/50Y10T428/12799
Inventor 高坂典晃船川义正重见将人大久保英和金村笃谦
Owner JFE STEEL CORP
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