A kind of steel plate for ni-mo low-temperature high-toughness X100 pipe fittings and its manufacturing method

Abstract

The invention discloses a Ni-Mo steel plate for low-temperature high-toughness X100 pipe fittings. The chemical composition of the steel plate is C: 0.09-0.12%, Mn: 1.5-1.9%, Si: 0.1-0.3%, and S: ≤0.003%, P: ≤0.015%, Nb: 0.04~0.065%, Ti: 0.008~0.03%, V: 0.02~0.10%, Alt: ≤0.06%, N:≤0.010%, O: ≤0.006%, Mo : 0.40~0.50%, Cu: ≤0.35%, Ni: 0.51~0.65%, Cr: ≤0.35%, Ca: ≤0.01%, and the rest is Fe. The manufacturing process includes molten steel smelting-external refining-slab reheating-TMCP process-quenching and tempering heat treatment. The finished product has high strength and high low-temperature toughness, which matches the welding of X100 main pipeline. The process window improves the yield and qualification rate of steel products.

Description

technical field [0001] The invention belongs to the field of steel plate manufacturing, and in particular relates to a steel plate for X100 pipe fittings with ultra-high strength, low temperature and high toughness and a manufacturing method thereof. It has excellent welding matching performance with the main steel pipe. Background technique [0002] At present, the energy structure is still dominated by fossil energy structures such as oil and natural gas. Oil and natural gas mainly rely on pipeline transportation. Considering the safety and economy of pipeline construction and operation, in recent years, the strength and toughness of pipeline steel have been raised. more stringent requirements. Under the same delivery conditions (such as delivery pressure), the use of higher-grade pipeline steel can reduce the wall thickness of the pipeline, thereby reducing the amount of steel used and saving pipeline construction costs; or in the case of the same pipe diameter and wall ...

AI Technical Summary

Problems solved by technology

[0003] Patent No. VN201010215728.8 discloses a steel for pipe fittings, involving two steel grades X80 and X100. The patent has the following characteristics: 1) The C content is between 0.13% and 0.23%, which is very high; 2) The Nb content Low, 0.01-0.04%, which will bring at least three deficiencies: First, the welding compatibility with the straight seam welded pipe is poor. In fact, the carbon content of the X100 steel grade straight pipe is ≤0.10%. In this way, The pipe fittings of this patent do not match the welding of the straight seam welded pipe section, and the trial performance is not high, especially in the high and low temperature regions, which exacerbates the inapplicability of this matching; the second is that the toughness is not high, especially the low temperature toughness. From this invention According to the performance data released later, the low-temperature impact toughness is not high and unstable; thirdly, from the strength data published by it, the C content in the patent is very high, so that in order to ensure the impact toughness value, subsequent tempering must be performed. The temperature is controlled very high, which leads to a large decrease in the strength value and a small margin. A little fluctuation in the process will cause unqualified strength or impact toughness, and the yield of the steel plate is low.

[0004] Patent No. CN201110043324.X discloses a method for preparing X100 steel grade elbows and pipe fittings. The invention has the following characteristics: First, the C content is 0.12-0.20%, and the Si content is 0.3-0.5%, both of which are relatively high , which brings instability to the impact toughness of pipe fittings; the second is that the Nb content in this invention example is all above 0.07%, and high Nb content will aggravate the formation of grains and other structures in the weld zone, eventually resulting in too low impact toughness and unstable

[0005] Patent No. CN200910196094 relates to a manufacturing method of steel for high-strength pipe fittings. The invention has the following characteristics: carbon content is 0.02-0.12%, Mo: 0.05-0.30%, Ni: 0.10-0.24%. Low carbon content can be better matched with longitudinal welded pipe welding, but at the same time, due to the low content of alloy elements such as Mo and Ni, the hardenability is not high, and finally the strength of the steel plate is not high. In order to ensure the strength and toughness of the steel Matching, the follow-up heat treatment process window is very narrow, which brings inconvenience to actual production, and the qualified rate of steel is low; from the performance data published in the examples, although it can meet the performance requirements of X100 steel grade, the margin is not high, and the impact toughness Low, high volatility, only applicable to steel grade X80 or below, and X100 steel grade is not practically applicable

[0006] Patent No. CN201110043719 relates to a manufacturing method of high-strength pipe fittings. The invention patent has the following characteristics: 1) The carbon content is very high, C is 0.11-0.25%, and Ceq is as high as 0.62%, and the welding matching between pipe fittings and straight pipe sections is poor ;2) Only applicable to steel grades X90 or below

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