Hotforming martensitic steel

A martensitic steel, hot forming technology, applied in the field of alloy steel, to achieve the effect of reduced susceptibility to hydrogen-induced delayed fracture and good plasticity

Inactive Publication Date: 2008-10-01
CENT IRON & STEEL RES INST
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  • Application Information

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Problems solved by technology

For hot-formed martensitic steels, which are generally not tempered after the hot-forming process, the problem of hydrogen-induced delayed fracture may be more prominent due to the high dislocation density in the steel

Method used

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Embodiment Construction

[0027] Material preparation: According to the above-mentioned designed chemical composition range, 5 furnaces (furnace number 1-5) of the steel of the present invention and 2 furnaces of contrast steel (furnace number 8-9) were smelted on a 500kg induction furnace, and 2 furnaces (furnace number 8-9) were smelted in addition. Furnace No. 6-7) Steel of the present invention and 2 furnaces of comparison steel (furnace No. 10-11) produced by electric furnace (EAF)+refining (LF+VD) smelting+die casting+hot continuous rolling process, its specific chemical composition is as follows Table 1 shows. The test material is finally processed into a thin plate with a thickness specification of 1.8mm (for thermoforming) and a rod with a diameter of φ12mm (for the determination of mechanical properties and susceptibility to hydrogen-induced delayed fracture).

[0028] Tensile mechanical properties: Austenitize a bar with a diameter of φ12mm at 900-950°C for 30 minutes after rough machining. ...

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Abstract

The invention belongs to the field of alloy steel, more particularly relates to thermal forming martensitic steel, which is mainly suitable for the steel for thermal punching forming accessory with thin thickness whose tensile strength ranges from 1.3 to 1.7GPa. The mainly chemical ingredients (weight %) of the steel are: C 0.10-0.33%, Si, 0.50-2.30%, Mn 0.50-2.00%, P <= 0.020%, S <= 0.015%, Al 0.015-0.060%, [O] <= 0.002%, [N] 0.002-0.015%, the rests are Fe and unavoidable impurities. In addition, the steel is also added with any or more than one of the group consisting of B 0.0005-0.0050%, Ti 0.02-0.10%, Nb 0.02-0.10%, V 0.02-0.15% and RE 0.001-0.050%. Compared with the current thermal forming martensitic steel 22MnB5, the steel of the invention not only has the tensile strength enhanced from 1.0-1.5GPa to 1.3 to 1.7GPa, but also has good plasticity, the coefficient of extension is more than 15%, and hydrogen-induced delayed fracture sensitivity is obviously reduced, thus making the vehicle having lighter weight and higher secure performances become true.

Description

technical field [0001] The invention belongs to the field of alloy steel, and in particular relates to a hot-formed martensitic steel, which is mainly suitable for thin-thickness part steel with a tensile strength of 1.3-1.7 GPa and formed by hot stamping. Background technique [0002] With the improvement of automobile light weight and safety, the steel used for automobile structural parts is required to have higher and higher strength requirements under the premise of weight reduction. The strength levels of traditional ferritic steel, pearlitic steel and bainite steel are all lower than 1.2GPa, so only ultra-high strength martensitic steel can meet the requirements. Usually, martensitic steel is obtained by quenching and tempering heat treatment after processing and forming, and the quenching deformation of thin thickness parts is very serious; if heat treatment is used first and then cold stamping is used, it is difficult to deform and after deformation. There are probl...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/06C22C38/14
Inventor 董瀚时捷王毛球惠卫军
Owner CENT IRON & STEEL RES INST
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