Hot-rolled high-strength steel sheet and process for production thereof
A technology of hot-rolled steel plates and manufacturing methods, which is applied in the direction of manufacturing tools, metal rolling, heat treatment furnaces, etc., and can solve problems such as large mold load, wrinkles, and necking
Active Publication Date: 2014-12-17
JFE STEEL CORP
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- Abstract
- Description
- Claims
- Application Information
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Problems solved by technology
However, when forming a steel plate, the higher the strength, the more problems will arise such as poor shape freezing, excessive load on the die, and occurrence of cracks, necking, and wrinkles, etc.
Method used
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Embodiment 1
[0082] Steel Nos. A to L having the chemical compositions shown in Table 1 were smelted in a converter and cast into slabs by continuous casting. The above steel slabs were soaked and held, and coiled hot-rolled steel sheets No. 1 to 19 (thickness: 2.6 mm to 4.0 mm) were produced under the conditions shown in Table 2.
[0083] Cut from the front and end portions of the coil (both ends in the longitudinal direction of the hot-rolled steel sheet) and the central portion in the longitudinal direction of the coil for use in tensile tests, sinter hardening characteristics, and hole expansion tests. sample. It should be noted that before cutting these samples, pickling was carried out, and the innermost and outermost circles of the coils were cut off in advance without taking them as the object of evaluation.
[0084] The tensile test was carried out in accordance with JISZ 2241 by cutting the No. 5 tensile test piece described in JIS Z 2201 in the direction perpendicular to the roll...
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Abstract
The invention provides a high strength hot-rolled steel sheet with a tensile strength of not less than 590 MPa which exhibits excellent bake hardenability and stretch-flangeability, and a method for manufacturing the same. The chemical composition includes, in terms of mass%, C at 0.040 to 0.10%, Si at not more than 0.3%, Mn at 1.7 to 2.5%, P at not more than 0.030%, S at not more than 0.005%, Al at not more than 0.1% and N at 0.006 to 0.025%. The microstructure is such that a bainite phase represents not less than 60%, the total of a ferrite phase and a pearlite phase represents not more than 10%, and the bainite phase includes grains among which cementite grains have been precipitated at not less than 1.4 x 10 4 grains / mm 2 and the cementite grains have an average grain diameter of not more than 1.5 µm.
Description
technical field [0001] The present invention relates to a high-strength hot-rolled steel sheet having a tensile strength of 590 MPa or more, which is suitable for structural members and running parts of automobiles, and has excellent sinter hardenability and stretch flangeability, 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 The top priority is to improve the fuel efficiency of automobiles, and it is required to achieve weight reduction by thinning the used components. Furthermore, in order to ensure the safety of the crew during a collision, it is also required to improve the safety centering on the collision characteristics of the automobile body. Therefore, both weight reduction and reinforcement of automobile bodies are being actively promoted. [0003] In order to meet both the weight reduction and reinforcement of the automobile body, it is effective...
Claims
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IPC IPC(8): B21B3/00C22C38/06C22C38/58C21D9/46C22C38/00
CPCC21D9/46C22C38/14C22C38/12C22C38/04C22C38/22C21D2211/002C21D2211/003C22C38/06C21D8/0226C22C38/02C21D6/005C21D8/0263C22C38/08C22C38/001C22C38/24C22C38/38
Inventor 高坂典晃濑户一洋川边英尚田中靖
Owner JFE STEEL CORP