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Technical Briefs

Influence of Production Method on the Properties of Dual Phase Steel Tubes

[+] Author and Article Information
E. J. Pavlina

Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401epavlina@mines.edu

C. J. Van Tyne

Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401cvantyne@mines.edu

Y. H. Moon

Department of Mechanical Engineering, Pusan National University, Busan 609-735, Koreayhmoon@pusan.ac.kr

J. Eng. Mater. Technol 132(2), 024501 (Feb 17, 2010) (10 pages) doi:10.1115/1.4000221 History: Received January 03, 2009; Revised July 25, 2009; Published February 17, 2010; Online February 17, 2010

Dual phase steel tubes can be produced by a variety of methods. In the present study, comparisons between dual phase steel tubes produced directly from a dual phase steel sheet and tubes produced using a new method are made. The conventional method is to process dual phase sheet steel through a tube making operation with electrical resistance welding. In the new processing method, a ferrite/pearlite sheet steel is formed into a tube, which is then normalized, induction heated to an intercritical temperature, quenched, and tempered, producing a dual phase microstructure. Tubes produced directly from a dual phase steel sheet have variations in microstructure and mechanical properties between the weld region and nonweld region material; whereas, tubes that have been produced from ferrite/pearlite steel sheet and treated to create a dual phase microstructure following the tube forming operation show little or no variation between the weld and nonweld regions. Dual phase tubes produced by the new method appear to have three main advantages over tubes produced in the traditional manner: (1) microstructural uniformity between the weld and nonweld material, (2) mechanical property uniformity between the weld and nonweld material, and (3) compressive rather than tensile residual stress components on the outer surface of the tubes.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of the new processing steps used to produce dual phase steel tubes from conventionally processed steel tubes with a ferrite/pearlite starting microstructure

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Figure 2

(a) Schematic representation of the time-temperature process to create the dual phase microstructure in the DP600 tubes in relation to the tube making operation. The dual phase microstructure of the tubes is produced by conventional hot-rolling of the sheet feedstock material. (b) Schematic representation of the time-temperature process to create the dual phase microstructure in the tubes made from 1012M and 1019M sheet material in relation to the tube making operation. The dual phase microstructure of the tubes is produced by induction heating of the finished tubes into the intercritical region followed by a water quench and subsequent 180°C temper.

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Figure 3

Light optical micrograph of the (a) weld region and (b) nonweld region of DP600 tubes. Nital etch.

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Figure 4

(a) Representative Knoop microhardness traverse through the weld region of a DP600 tubes, (b) 12X tubes, and (c) 19X tubes. The step-size for all traverses was 0.13 mm.

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Figure 5

Light optical micrograph of the (a) weld region and (b) nonweld region of 12N tubes, (c) weld region and (d) nonweld region of 12L tubes, and (e) weld region and (f) nonweld region of 12H tubes. Nital etch.

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Figure 6

Light optical micrograph of the (a) weld region and (b) nonweld region of 19N tubes, (c) weld region and (d) nonweld region of 19L tubes, and (e) weld region and (f) nonweld region of 19H tubes. Nital etch.

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Figure 7

Representative stress-strain curves for the (a) DP600 tubes, (b) 12L tubes, (c) 12H tubes, (d) 19L tubes, and (e) 19H tubes

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Figure 8

Photographs of representative tubes used to measure the axial component of residual stress in the DP600 and 12R tubular material. Unit of scale is in millimeters.

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Figure 9

Knoop microhardness traverses through the wall thickness for DP600, 12L, 12H, 19L, and 19H tubular material

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Figure 10

Phase fraction of tempered martensite as a function of position in the tube wall for 12L, 12H, 19L, and 19H tubular material

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Figure 11

Instantaneous strain-hardening exponent (instantaneous n-value) curves for the (a) DP600 tubes, (b) 12L tubes, (c) 12H tubes, (d) 19L tubes, and (e) 19H tubes

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