Steelpipe having high formability and method for production thereof

A manufacturing method and processability technology, applied in the direction of manufacturing tools, metal rolling, furnaces, etc., can solve the problems of r-value reduction and inapplicability

Inactive Publication Date: 2003-06-25
JFE STEEL CORP
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the method for increasing the r-value of the steel pipe is, for example, disclosed in JP-A-6-41689, and it is only known to increase the r-value of the steel strip, which is the raw material of the steel pipe.
When manufacturing electric-welded steel pipes, there is a problem that the r-value of the melted or phase-transformed portion decreases due to seam welding
In addition, there is also the problem that it cannot be applied to steel sheets that cannot obtain high r-values ​​such as hot-rolled steel sheets, high-strength steel sheets, low-carbon, medium-carbon, and high-carbon steel sheets.

Method used

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  • Steelpipe having high formability and method for production thereof
  • Steelpipe having high formability and method for production thereof
  • Steelpipe having high formability and method for production thereof

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Experimental program
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Embodiment Construction

[0033] The hot-rolled steel sheets with the chemical compositions shown in Table 1 were made into electric-welded steel pipes by the usual method, and were reduced-rolled under the conditions shown in Table 2. After the heating before reducing rolling reached the temperature shown in Table 2, the heat preservation was not carried out, or the heat preservation was carried out for 1 to 600 seconds. Take the JIS No. 12 A tensile test piece from the circumferential position of the obtained steel pipe at 0°, 90°, 180°, and 270°, attach a strain gauge with a punctuation distance of 2mm on it, and perform a nominal strain of 6 to 7 % tensile test, measure the value of the actual strain εW in the width direction relative to the actual strain εL in the length direction, and calculate the r value based on the slope ρ. which is,

[0034] ρ=ε L / ε W

[0035] r value = ρ / (-1-ρ)

[0036] In addition, the wall thickness ts of the weld portion and the average wall thickness tb of other p...

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Abstract

A steel pipe having high formability which has an r value in the longitudinal direction of 1.2 or more, preferably 1.6 or more over the whole region of perimeter direction containing a seamed portion; and a method of producing the steel pipe which comprises heating a steel pipe prepared by the electric welding of steel hoops to an Ac1 temperature or higher and subjecting the heated pipe to a stretch reducing of a diameter reduction percentage of 30% or more in a temperature region of 600 deg or higher and up to an Ac1 temperature, and optionally heating again the pipe during or after completion of cooling after said reduction to a temperature of 600 to 900 deg and holding it at the temperature for 1 second or longer.

Description

technical field [0001] The present invention relates to a steel pipe excellent in workability and a method for producing the same. technical background [0002] In order to reduce weight and reduce costs, the use of electric (resistance) welded steel pipes for automotive parts is being studied. However, the conventional electric resistance welded steel pipes cannot obtain sufficiently good workability. For example, the running part of a car needs to be bent. However, conventional electric-welded steel pipes have a problem that the amount of wall reduction on the outer side of the bend is large, and in severe cases, fracture occurs. In addition, even if fracture does not occur, if the amount of wall reduction is large, thick-walled materials must be used in order to meet the design stress, so weight reduction cannot be achieved. [0003] For such a problem, it is known that it is effective to increase the r value (Lankford value) in the tube axis direction as disclosed in ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B21B17/14B21C37/06B21C37/08C21D8/10C21D9/08C22C38/00C22C38/02C22C38/04C22C38/06
CPCC21D9/08C22C38/06C22C38/02C21D8/10C22C38/04B21B17/14B21C37/06B21C37/08
Inventor 丰冈高明河端良和依籐章西森正德板谷元晶冈部能知荒谷昌利
Owner JFE STEEL CORP
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