Hot-rolled steel sheet having good cold workability and excellent hardness after working

A technology of cold workability and hot-rolled steel plates, which is applied in the field of hot-rolled steel plates, can solve problems such as the inability to achieve cost reduction, and achieve the effects of reduced deformation resistance and extended life

Inactive Publication Date: 2016-12-14
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0011] However, this technology has the problem that nitriding treatment is required after cold working, and that sufficient cost reduction cannot be achieved.

Method used

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  • Hot-rolled steel sheet having good cold workability and excellent hardness after working
  • Hot-rolled steel sheet having good cold workability and excellent hardness after working
  • Hot-rolled steel sheet having good cold workability and excellent hardness after working

Examples

Experimental program
Comparison scheme
Effect test

preparation example Construction

[0118] [Preparation of molten steel]

[0119] Regarding the content of N in molten steel, it can be determined by adding raw materials containing N compounds to molten steel when smelting with a converter, and / or controlling the atmosphere of the converter to N 2 atmosphere to adjust.

[0120] [heating]

[0121] Heating before hot rolling is performed at 1100 to 1300°C. In this heating, in order to solid-dissolve as much N as possible without generating N compounds, high-temperature heating conditions are required. A preferable lower limit of the heating temperature is 1100°C, and a more preferable lower limit is 1150°C. On the other hand, temperatures exceeding 1300°C present operational difficulties.

[0122] [hot rolled]

[0123] Hot rolling is performed so that the finishing temperature becomes 880° C. or higher. If the finish rolling temperature is too low, ferrite transformation will occur at high temperature, the precipitated carbides in ferrite (collectively refe...

Embodiment

[0140] The steel with the composition shown in the following Table 1 was smelted by the vacuum melting method, cast into a steel ingot with a thickness of 120 mm, hot rolled under the conditions shown in the following Tables 2 and 3, and then subjected to box annealing to produce a hot-rolled steel sheet . It should be noted that in any test, the cooling rate until the quenching stop after the finish rolling was 20°C / s or more, and the cooling condition after the quenching stop was slow cooling for 5 to 20s at a cooling rate of 10°C / s or less, After box annealing, cool to 600°C at a cooling rate below 10°C / h, cool to 600-400°C at a cooling rate below 15°C / h, and water-cool at a cooling rate below 400°C.

[0141] For the hot-rolled steel sheet obtained in this way, the amount of solid solution N, the area ratio of each phase of the structure in the steel sheet, and the average grain size of bainitic ferrite were obtained by each measurement method described in the above [Detail...

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Abstract

This hot-rolled steel sheet has a thickness of 3-20 mm and contains specific amounts of C, Si, Mn, P, S, Al and N with the balance made up of iron and unavoidable impurities. The contents of solid-solved N, C and N are within specific ranges, and bainitic ferrite having a specific average crystal grain size and pearlite have specific area occupancies in the structure, with the balance occupied by polygonal ferrite. This hot-rolled steel sheet has a specific hardness distribution in the thickness direction.

Description

technical field [0001] The present invention relates to a hot-rolled steel sheet that exhibits good cold workability (strong cold workability) during cold working such that extremely high deformation strain is generated locally and exhibits a predetermined hardness after working. Background technique [0002] In recent years, in order to improve the fuel consumption of automobiles from the viewpoint of environmental protection, there has been an increasing demand for reduction in weight or higher strength of steel materials used in various parts of automobiles, such as transmission parts such as gears and housings, etc. . In order to meet such demands for weight reduction and high strength, generally used steel materials are steel materials obtained by hot forging bar steel (hot forging materials). In addition, in order to reduce CO in the parts manufacturing process 2 The demand for cold forging of parts such as gears processed by hot forging is also increasing. [0003]...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00B21B1/26C21D8/02C21D9/46C22C38/60
CPCB21B2001/225B21B2261/22C21D8/0226C21D8/0263C21D8/0273C21D9/46C21D2211/002C21D2211/005C21D2211/009C22C38/00C22C38/001C22C38/002C22C38/02C22C38/04C22C38/06C22C38/08C22C38/16C22C38/26C22C38/60
Inventor 梶原桂
Owner KOBE STEEL LTD
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