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High-carbon steel tube having superior cold workability, machinability, and hardenability and method for manufacturing the same

a technology of high-carbon steel and cold workability, which is applied in the field of high-carbon steel tubes, can solve the problems of reducing productivity, increasing production costs, and deteriorating cold workability, and achieves superior machinability and high-frequency hardenability, and is easy to manufactur

Inactive Publication Date: 2015-10-01
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about a new way to make high-carbon steel tubes that can be easily manufactured at a low cost. These steel tubes have excellent cold workability, machinability, and can be hardened with high-frequency. These tubes are suitable for use in automotive parts like steering rack bars, steering shafts, and drive shafts. The invention also contributes to the reduction of weight of automotive bodies and helps conserve the global environment.

Problems solved by technology

A high carbon content, however, deteriorates the cold workability.
This causes the problem of decreased productivity and increased production costs.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

examples

[0068]Raw steel tubes were formed from hot-rolled steel strips (thickness: 7.0 mm) having the compositions shown in Table 1 by a tube-making process including continuously roll-forming the steel strips into substantially cylindrical open pipes and joining together the ends of the open pipes by electric resistance welding to form electric-resistance-welded steel tubes (outer diameter: 89.1 mm).

[0069]These raw steel tubes were subjected to stretch-reducing rolling under the conditions shown in Table 2 to form product steel tubes. As related-art examples, some of the steel tubes were subjected to annealing treatment at 700° C. for 10 hours or to normalizing treatment at 925° C. for 15 minutes. The raw steel tubes of the related-art examples were worked to a diameter of 40 mm before the above treatment.

[0070]The microstructure observation of the resulting steel tubes was performed, and they were also examined for their cold workability, hardenability, and machinability. These examinatio...

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Abstract

A raw steel tube has a composition containing, by mass, 0.25% to 0.60% carbon, 0.01% to 2.0% silicon, 0.2% to 3.0% manganese, 0.001% to 0.1% aluminum, 0.001% to 0.05% phosphorus, 0.02% or less sulfur, 0.0010% to 0.0100% nitrogen, 0.0003% to 0.0050% boron, and 0.0001% to 0.0050% calcium, the balance being iron and incidental impurities. The raw steel tube is heated to and soaked at an Ac3 transformation point or higher and is then subjected to stretch-reducing rolling at a finishing temperature of rolling of 900° C. to (Ac1 transformation point) with a cumulative reduction in diameter of 30% to 70% within the temperature range of 900° C. or lower.

Description

TECHNICAL FIELD[0001]The present invention relates to high-carbon steel tubes suitable for automotive parts such as steering rack bars mounted in automotive rack-and-pinion type steering devices or the like, steering shafts and drive shafts, and methods for manufacturing such high-carbon steel tubes, and particularly to improvements in cold workability, machinability, and hardenability.BACKGROUND ART[0002]There has recently been a strong need for improved automobile mileage for the conservation of the global environment. Accordingly, efforts have been made to reduce the weight of automotive bodies. The need for a reduction in the weight of automotive bodies has prompted the replacement of solid-core parts made of steel bars with hollow parts made of steel tubes in the field of steering-associated parts such as steering rack bars and steering shafts for mounting in steering devices, which transfer the motion of an automotive steering wheel to wheels, and drive-shaft-associated parts ...

Claims

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Application Information

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IPC IPC(8): C22C38/16C21D9/08C21D6/00C22C38/00C22C38/12C22C38/06C22C38/04C22C38/02C21D8/10C22C38/14
CPCC22C38/16C21D8/105C21D9/08C21D6/005C21D6/008C22C38/001C22C38/12C22C38/06C22C38/04C22C38/02C22C38/002C22C38/14B21B17/14B23K11/08B23K11/16B23K13/025B23K2101/06B23K2103/04C21D2211/003C21D2211/005
Inventor ARATANI, MASATOSHITOYODA, SHUNSUKEOKABE, TAKATOSHIKAWABATA, YOSHIKAZUIWAZAKI, KENICHI
Owner JFE STEEL CORP