High-strength hot-rolled steel sheet having good ductility, stretch-flangeability, and material uniformity and manufacturing method thereof
A technology for extending flangeability and hot-rolled steel sheets, which is applied in manufacturing tools, chemical instruments and methods, heat treatment furnaces, etc. Excellent edge and high strength effect
Active Publication Date: 2016-10-12
JFE STEEL CORP
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Problems solved by technology
The high-strength hot-rolled steel sheet described in Patent Document 4 obtains a TS of 590 MPa or more by solid solution strengthening by Mn, but solid solution strengthening is relatively small in relation to the amount of added elements compared to precipitation strengthening by Ti, so poor cost
In addition, since the amount of C added relative to Ti is large, hard cementite is inevitably formed.
Therefore, there is also a problem of poor stretch flangeability
Method used
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[0086] Steels A to H having the chemical components (compositions) shown in Table 1 were melted in a converter and cast into slabs by continuous casting. These slabs were heated to 1250° C., and under the hot rolling conditions shown in Table 2, coiled hot-rolled steel sheets Nos. 1 to 18 with a plate thickness of 3.2 mm were produced.
[0087] In addition, underlines in Table 1 and Table 2 indicate that they are outside the conditions of the present invention.
[0088] [Table 1]
[0089]
[0090] [Table 2]
[0091]
[0092] Then, after pickling, the innermost and outermost turns of the roll and both ends in the width direction of the roll are trimmed by 10 mm, and then divided into 20 equal parts in the length direction of the roll and 8 equal parts in the width direction. , from 189 positions including the trimmed coil end, cut JIS No. 5 tensile test pieces parallel to the rolling direction, and perform a tensile test at a crosshead speed of 10mm / min in accordance wi...
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Abstract
The present invention provides a hot-rolled steel sheet having high strength, excellent ductility and stretch-flangeability, and good material uniformity with little variation in strength within a coil, and a method for producing the same. The steel slab is hot-rolled to form a steel structure in which 95% or more of the area ratio is a ferrite phase, the average ferrite particle size of the ferrite is 10 μm or less, and the average particle size of Ti carbide precipitated in the steel is 10nm or less and a hot-rolled steel sheet in which 80% or more of Ti* is precipitated as Ti carbides, the slab has a steel composition containing C: 0.020 to 0.065%, Si: 0.1% or less, Mn: 0.40 or more and Less than 0.80%, P: 0.030% or less, S: 0.005% or less, Ti: 0.08-0.16%, Al: 0.005-0.1%, N: 0.005% or less, the balance is composed of Fe and unavoidable impurities, and Ti *(=Ti-(48 / 14)×N) satisfies "Ti*≥0.08" and "0.300≤C / Ti*≤0.375".
Description
technical field [0001] The present invention relates to a high-strength hot-rolled steel sheet useful for frame members of large vehicles such as truck frames and a method for producing the same. Background technique [0002] In recent years, from the viewpoint of protecting the global environment, in order to limit CO 2 It is urgent to improve the fuel efficiency of automobiles, and it is required to achieve weight reduction by thinning the parts used, but thinning will lead to a decrease in crash characteristics. In order to ensure the safety of the occupants at the time of collision, it is also required to improve the safety, and therefore, for thinning the wall, it is necessary to increase the strength of the used members. [0003] Automobile components that use steel sheets as raw materials are mostly manufactured by press forming. In general, increasing the strength of a steel sheet lowers ductility, stretch-flangeability, etc., and increases springback, so formabili...
Claims
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IPC IPC(8): C22C38/14C21D8/02
CPCC21D8/0426C21D8/0463C21D2211/004C21D2211/005C22C38/001C22C38/02C22C38/04C22C38/06B32B15/013C22C18/00C21D8/04C21D8/0263C21D9/46C22C38/14
Inventor 高坂典晃濑户一洋川边英尚
Owner JFE STEEL CORP