Method for controlling nonmetal inclusions in X70 stage acidoresistant pipeline steel

A technology of non-metallic inclusions and control methods, applied in the manufacture of converters, etc., can solve the problems of inclusions that are harmful and fail to reach X70 steel grade, etc.

Inactive Publication Date: 2012-09-19
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Steel plates for pipelines transporting sour natural gas can currently be produced to grade X65, but not yet grade X70
Although there is a patent report that the HIC resistance of X80 steel grade is qualified, the HIC test of the B solution is carried out, and it is a steel coil instead of a steel plate
There are also patents reporting a method of controlling non-metallic inclusions in HIC pipeline steel plates, and controlling such inclusions as CaS-CaO-Al 2 o 3 Inclusions, but some of the large-sized CaO-Al 2 o 3 The inclusions are still harmful in the subsequent rolling process

Method used

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  • Method for controlling nonmetal inclusions in X70 stage acidoresistant pipeline steel
  • Method for controlling nonmetal inclusions in X70 stage acidoresistant pipeline steel
  • Method for controlling nonmetal inclusions in X70 stage acidoresistant pipeline steel

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Experimental program
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Effect test

Embodiment 1

[0024] A method for controlling non-metallic inclusions in X70 grade acid-resistant pipeline steel provided in this embodiment includes:

[0025] (1) Desulphurization pretreatment of molten iron requires strict slag removal operation. After slag removal, there should be no residue on the surface of the molten iron. It is required that the molten iron [S]≤0.002%, and spray Mg for strong desulfurization treatment;

[0026] (2) Guarantee that the number of times of carbon pulling at the end of the converter is ≤1 time; the end point of the converter [S]≤0.008%, [P]≤0.008%; converter tapping pre-refining: complete the slag fluorite, active lime, aluminum before tapping 2 / 5 Incorporation of lumps and alloys;

[0027] (3) Deep desulfurization during the refining process, refining with high alkalinity and strong reducing slag, the alkalinity of the slag is 7, the treatment time: 40min, the S content in the molten steel is controlled to be ≤15ppm; the LF treatment process meets the [A...

Embodiment 2

[0031] A method for controlling non-metallic inclusions in X70 grade acid-resistant pipeline steel provided in this embodiment includes:

[0032](1) Desulphurization pretreatment of molten iron requires strict slag removal operation. After slag removal, there should be no residue on the surface of the molten iron. It is required that the molten iron [S]≤0.002%, and spray Mg for strong desulfurization treatment;

[0033] (2) Guarantee that the number of times of carbon pulling at the end of the converter is ≤1 time; the end point of the converter [S]≤0.008%, [P]≤0.008%; converter tapping pre-refining: complete the slag fluorite, active lime, aluminum before tapping 2 / 5 Incorporation of lumps and alloys;

[0034] (3) Deep desulfurization in the refining process, refining with high alkalinity and strong reducing slag, the alkalinity of the slag is 10, the processing time: 50min, the S content in the molten steel is controlled to be ≤15ppm; the LF treatment process meets the [Als]...

Embodiment 3

[0038] A method for controlling non-metallic inclusions in X70 grade acid-resistant pipeline steel provided in this embodiment includes:

[0039] (1) Desulphurization pretreatment of molten iron requires strict slag removal operation. After slag removal, there should be no residue on the surface of the molten iron. It is required that the molten iron [S]≤0.002%, and spray Mg for strong desulfurization treatment;

[0040] (2) Guarantee that the number of times of carbon pulling at the end of the converter is ≤1 time; the end point of the converter [S]≤0.008%, [P]≤0.008%; converter tapping pre-refining: complete the slag fluorite, active lime, aluminum before tapping 2 / 5 Incorporation of lumps and alloys;

[0041] (3) Deep desulfurization during the refining process, refining with high alkalinity and strong reducing slag, the alkalinity of the slag is 15, the processing time: 60min, and the S content in the molten steel is controlled to be ≤15ppm; the LF treatment process meets ...

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Abstract

The invention relates to a method for controlling steel inclusions and particularly relates to a method for controlling nonmetal inclusions in X70 stage acidoresistant pipeline steel. The method controls types, quantity and sizes of nonmetal inclusions in rolling plates by controlling content of molten steel to guarantee suitable calcium (Ca)/sulfur (S) ratio of (1.2-5.0). The method controls inclusions in steel plates and guarantees that the content of calcium oxide and sulfur oxide ranges between 85% and 90% and the content of other substances is within a range of no more than 10%, and steel plates are not easy to deform in the process of rolling; the quantity and sizes of inclusions are reduced greatly through long-time refining processing; and X70 steel plates produced by the method can meet requirements of various indicators (the crack length rate is no more than 15%, the crack thickness rate is no more than 5% and the crack sensitive rate is no more than 2%.) of Hydrogen Induced Cracking (HIC) in the test of HIC of an A solution, and the hazard of large-size strip-shaped manganese sulfate and strip-cluster-shaped calcium oxide-aluminum oxide series B type inclusions to acidoresistant pipeline steel is avoided.

Description

technical field [0001] The invention relates to a method for controlling steel inclusions, in particular to a method for controlling non-metallic inclusions in X70 grade acid-resistant pipeline steel. Background technique [0002] Acid-resistant pipeline steel refers to steel for pipelines that not only has a high steel grade, but also has anti-corrosion safety. Some oil (gas) fields in my country, such as Sichuan Oilfield, foreign oil (gas) fields, such as Iran, Myanmar and other Middle East regions, and deep sea oil contain H 2 The amount of S is very high. In the future, oil and natural gas will no longer be dehydrated and dehydrogenated 2 S treated oil and gas, but untreated "rich gas" (H 2 S ≤300Pa), for this reason must improve pipeline steel resistance to hydrogen-induced cracking (HIC) and resistance to H 2 S stress corrosion performance. Steel plates for pipelines transporting sour natural gas can currently be produced to grade X65, but not grade X70. Although...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21C1/02C21C5/28C21C7/00
Inventor 唐春霞赵晋斌李强王军
Owner NANJING IRON & STEEL CO LTD
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