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590 mpa high yield ratio round steel pipe for building structure with excellent shock resistance and production process

A steel pipe, round technology, applied in the field of round steel pipe and its manufacturing, can solve the problems of difficult to stabilize strength, unstable hardenability, uneven hardness distribution, etc., to achieve the effect of improving shock resistance and ensuring ductility

Inactive Publication Date: 2011-03-16
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In this technology, as the chemical composition, there is no regulation of B and N that form nitrides, BN and TiN cannot be controlled, and it is difficult to stably obtain the desired strength because of unstable hardenability
In addition, since B is not contained, the structure becomes ferrite, and the hardness distribution in the thickness direction is not uniform

Method used

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  • 590 mpa high yield ratio round steel pipe for building structure with excellent shock resistance and production process
  • 590 mpa high yield ratio round steel pipe for building structure with excellent shock resistance and production process
  • 590 mpa high yield ratio round steel pipe for building structure with excellent shock resistance and production process

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0087] Steels having the chemical composition shown in Tables 1 and 2 below were smelted by a normal smelting method to form slabs, which were then subjected to hot rolling, accelerated cooling (cooling after rolling), and tempering to manufacture steel sheets. Using the obtained steel sheet, it was formed into a circular steel pipe by a press bending method. In addition, Tables 1 and 2 also show the PCM values ​​defined by the aforementioned formula (1). The production conditions at this time are as follows.

[0088] (manufacturing conditions)

[0089] After the ingot is heated to 1150±10°C, hot rolling is carried out at the finishing temperature (surface temperature) in the range of 850±30°C to form a plate with a thickness of 70 mm, and then the cooling rate at the position of t / 4 (t: plate thickness) Control it at 5-15°C / sec, so that the surface temperature when the cooling stops is below 420±50°C. Moreover, it tempered in the range of 450-650 degreeC and turned into a ...

Embodiment 2

[0119] Steel sheets (Experiment Nos. 1 to 15) were manufactured under the various manufacturing conditions shown in Table 7 below using steel Nos. 1 to 8 shown in Table 1 above (the chemical composition satisfies the range specified in the present invention). Using the obtained steel sheet, it was formed into a circular steel pipe by a press bending method. Same as embodiment for the circular steel pipe obtained, to material (yield stress YS, tensile strength TS, yield ratio YR and toughness vE -20 ) and weldability were evaluated. In addition, the microstructure and hardness distribution (hardness at the center of the steel sheet, hardness ratio) of the steel sheets were measured in the same manner as in Examples, and the results are shown in Table 8.

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PUM

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Abstract

The round steel pipe not only satisfies the determined relational expression, but also regulates chemical composition, satisfies following conditions (A)-(C): (A) a microscopic constitution has bainitic steel with length-width ratio over 3 times, area percentage over 50% and dislocation density from 1.0*10[5](m[-2]) to 6.0*10[5](m[-2]); (B) the central portion for removing the surface portion 2mmfrom the front and the back face of the steel pipe has an average Vickers hardness of 180-280; (C) the surface portion 2mm from the front and the back face of the steel pipe has an average Vickers hardness below 1.4 times of the average Vickers hardness of the central portion. According to the construction, in utility of building steel reinforcement, hardness on external surface of steel pipe constituting a tensile stress field as an intrinsic subject of high hardness round steel pipe can be reduced, for a steel pipe of high hardness with tensile strength at 590MPa, which is helpful for shockresistance enhancement.

Description

technical field [0001] The present invention mainly relates to circular steel pipes for building steel bars that require shock resistance and a manufacturing method thereof, in particular to high strength and high yield ratios with a tensile strength of 590 MPa or more (590 MPa grade) and a yield ratio of 85% to 95%. Circular steel pipes, and useful methods for making such circular steel pipes. Background technique [0002] In order to ensure the earthquake resistance of building structures, steel for construction uses plastic deformation after elastic deformation to absorb earthquake energy. Based on this idea, it is stipulated that it is represented by the ratio of yield stress YS and tensile strength TS (YS / TS) There are many cases where the yield strength is higher than the upper limit of YR. In contrast, in recent years, although the plasticization of the column during a huge earthquake can save people without causing the overall collapse of the building structure, the...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/58C22C38/54C21D8/10
CPCC21D8/0226C21D8/105C22C38/001C22C38/002C22C38/02C22C38/06C22C38/48C22C38/50C22C38/54C22C38/58
Inventor 小林克壮盐饱丰明
Owner KOBE STEEL LTD