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Method for producing line pipe

a production method and technology of steel line, applied in the direction of manufacturing tools, furnaces, heat treatment equipment, etc., can solve the problems of low low maximum hardness of pipe, and approaching yield to tensile ratios

Inactive Publication Date: 2005-04-28
NITED STATES STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Most current line pipe steels are produced with microalloyed high strength low alloy compositions and frequently result in yield to tensile ratios approaching, and in some cases exceeding, the 0.85 yield to tensile ratio requirement.
The pipe has low maximum hardness, good sour resistance and low yield ratio.

Method used

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Embodiment Construction

[0015] ) According to the present invention a method for the manufacture of steel line pipe includes providing a steel pipe having a composition consisting essentially of in weight percent: C 0.01 to 0.40, Mn 0.25 to 2.0, P residual to less than 0.5, S residual to less than 0.020, Si residual to 2.0, Cu residual to 1.0, Ni residual to 1.0, Cr residual to 2.0, Mo residual to 1.0, Al 0.010 minimum to less than 1.0, N residual to 0.030, V residual to less than 0.5, B residual to less than 0.02, Ti residual to less than 0.3, and Nb residual to less than 0.3, balance iron and incidental impurities. The pipe may be made by a seamless process or various other pipe manufacturing processes. The process for manufacturing the pipe is not in and of itself critical. Also, the pipe may have been subjected to various prior heat treatments.

[0016] The pipe is heated to a temperature within the intercritical Ac1 to Ac3 temperature range to obtain ferrite and austenite in the microstructure. Preferab...

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PUM

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Abstract

A method for producing steel line pipe having low yield strength to tensile strength ratio in order to improve the capability of steel line pipe to undergo reeling into coil form and unreeling therefrom. The method includes (a) providing a steel pipe having a composition consisting essentially of in weight percent: C 0.01 to 0.40, Mn 0.25 to 2.0, P residual to less than 0.5, S residual to less than 0.020, Si residual to 2.0, Cu residual to 1.0, Ni residual to 1.0, Cr residual to 2.0, Mo residual to 1.0, Al 0.010 minimum to less than 1.0, N residual to 0.030, V residual to less than 0.5, B residual to less than 0.02, Ti residual to less than 0.3, and Nb residual to less than 0.3, balance iron and incidental impurities. The pipe is heated to a temperature within the intercritical Ac1 to Ac3 temperature range, cooled to a temperature below the Ms (martensite start) temperature in order to obtain martensite, reheated to a temperature below the Ac1 temperature for a time sufficient to obtain the desired yield strength, tensile strength and yield strength to tensile strength ratio, and then air cooled.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for producing steel line pipe having low yield strength to tensile strength ratio, and particularly to a method for producing steel line pipe by intercritical annealing, quenching and tempering. The invention includes a method for improving the capability of steel line pipe to undergo reeling into coil form and unreeling therefrom which includes reeling steel line pipe into coil form which has been produced by intercritical annealing, quenching and tempering. BACKGROUND OF THE INVENTION [0002] Customers for steel line pipe are interested in acquiring pipe having relatively low yield strength to ultimate tensile strength ratios. The low yield to tensile strength ratio is thought to aid coiling of the pipe for transport. Typically it is desired that the pipe have a yield strength of less than 85 percent of the tensile strength. This requirement is specified so as to accommodate the pipe reeling and unreeling opera...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C21D1/18C21D9/08
CPCC21D1/185C21D2211/008C21D2211/005C21D9/08
Inventor MERWIN, MATTHEW J.
Owner NITED STATES STEEL CORP
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