CN111187918B

CN111187918B - Control method for nonmetallic inclusions in 9Ni steel ingot with weight of more than 30 tons

Info

Publication number: CN111187918B
Application number: CN202010074519.XA
Authority: CN
Inventors: 李奇; 梁剑雄; 陈万华; 王太江; 王长军; 周恩民
Original assignee: Unit 63837 Of Pla; Shanghai Electric Shmp Casting & Forging Co ltd; Central Iron and Steel Research Institute
Current assignee: Unit 63837 Of Pla; Shanghai Electric Shmp Casting & Forging Co ltd; Central Iron and Steel Research Institute
Priority date: 2020-01-22
Filing date: 2020-01-22
Publication date: 2022-08-26
Anticipated expiration: 2040-01-22
Also published as: CN111187918A

Abstract

The invention discloses a method for controlling nonmetallic inclusions in 9Ni steel ingots with the weight of more than 30 tons, and aims to solve the problem that the nonmetallic inclusions in the existing 9Ni steel ingots with the weight of more than 30 tons do not meet the specification. The method comprises the following specific steps: firstly, producing a steel ingot by adopting an electroslag remelting mode, adopting a small-diameter consumable electrode and a high-alkalinity slag system as production raw materials, keeping the content and the oxygen content of impurities in the consumable electrode at a lower level, and paving a crystallizer and a water-cooled bottom plate in an electroslag furnace; and step two, reducing atmosphere is filled in an electroslag furnace in the electroslag remelting process, a deoxidizing agent is added in the electroslag remelting process, slag sample analysis is carried out once per hour, and the quantity of the deoxidizing agent is adjusted according to the result of the slag sample analysis. The invention has reasonable design, adopts the electroslag remelting mode to produce the 9Ni steel ingot, can control the diameter within the range of 1500-2000mm, can control the content of the non-metallic inclusion of the 9Ni steel ingot of more than 30 tons, and meets the technical specification.

Description

Control method for nonmetallic inclusions in 9Ni steel ingot with weight of more than 30 tons

Technical Field

The invention relates to the field of steel ingots, in particular to a method for controlling nonmetallic inclusions in 9Ni steel ingots with the weight of more than 30 tons.

Background

The molten steel is poured into a casting mould through a ladle and is solidified to form a steel ingot. After the molten steel is smelted in a steelmaking furnace, the molten steel must be cast into ingots or billets with certain shapes for processing. The process of casting a steel ingot by using a casting mold is simply called as ingot casting. Steel ingots are still the main raw material for steel rolling production. The quality of the steel ingot, the condition of the ingot shape and the weight of the ingot play an important role in the steel rolling production.

The 9Ni steel ingot is one of the steel ingots, and for the needs of some projects, the 9Ni steel ingot needs to be manufactured to be more than 40 tons, the maximum quantity of the existing 9Ni steel ingot is only 15 tons, and the obtained 9Ni steel ingot has the non-metal inclusion higher than the standard requirement, so that the use requirement of people cannot be met.

Disclosure of Invention

An object of an embodiment of the present invention is to provide a method for controlling nonmetallic inclusions in a 9Ni steel ingot of 30 tons or more to solve the problems suggested in the background art.

In order to achieve the above object, the embodiments of the present invention provide the following technical solutions:

a method for controlling nonmetallic inclusions in 9Ni steel ingots with the weight of more than 30 tons comprises the following specific steps:

firstly, producing a steel ingot by adopting an electroslag remelting mode, adopting a small-diameter consumable electrode and a high-alkalinity slag system as production raw materials, obviously removing non-metallic inclusions in steel, wherein the content and the oxygen content of the inclusions in the consumable electrode are at a lower level, and paving a crystallizer and a water-cooling bottom plate in an electroslag furnace to ensure that the whole remelting process is strongly cooled;

and step two, reducing atmosphere is filled in an electroslag furnace in the electroslag remelting process, a deoxidizing agent is added in the electroslag remelting process, slag sample analysis is carried out once per hour, and the quantity of the deoxidizing agent is adjusted according to the result of the slag sample analysis.

As a further scheme of the embodiment of the invention: and before electroslag remelting, impurities and garbage on the inner surface of the crystallizer are removed, so that the purity of a finished product is ensured.

As a further scheme of the embodiment of the invention: the consumable electrode is smelted in a vacuum induction mode, and the component requirements of the consumable electrode can be guaranteed.

As a further scheme of the embodiment of the invention: the surface of the consumable electrode is polished and coated with the anti-oxidation coating, and the consumable electrode is baked cleanly, so that the surface of the consumable electrode can be prevented from being oxidized, and the increment of the valence-change oxide in the remelting process is reduced.

As a further scheme of the embodiment of the invention: the high-alkalinity slag system comprises a mixture of fluorite, white corundum, lime, quartz sand and fused magnesia which are mixed according to the weight ratio of 62-67:18-23:10.2-12.6:4.5-5.7: 3.8-4.4.

As a further scheme of the embodiment of the invention: the deoxidizer comprises at least one of Si-Ca alloy, pure Ca and pure Al, and is selected by people according to the working requirements.

As a further scheme of the embodiment of the invention: the crystallizer adopts a copper wall water-cooling crystallizer with the diameter of 1500-.

Compared with the prior art, the embodiment of the invention has the beneficial effects that:

the invention has reasonable design, adopts the electroslag remelting mode to produce the 9Ni steel ingot, can control the diameter within the range of 1500-2000mm and the content of non-metallic inclusions in the 9Ni steel ingot of more than 30 tons, conforms to the technical specification and meets the use requirements of people.

Drawings

FIG. 1 is a schematic drawing of throwing impurities during electroslag remelting of a 9Ni steel ingot of more than 30 tons.

Detailed Description

The technical solution of the present patent will be described in further detail with reference to the following embodiments.

Example 1

firstly, producing a steel ingot by adopting an electroslag remelting mode, adopting a small-diameter consumable electrode and a high-alkalinity slag system as production raw materials, obviously removing non-metallic inclusions in steel, smelting the consumable electrode by adopting a vacuum induction mode, ensuring the component requirement of the consumable electrode, keeping the content and the oxygen content of the inclusions in the consumable electrode at a lower level, laying a crystallizer and a water-cooling bottom plate in an electroslag furnace, and ensuring that the whole remelting process is strongly cooled;

and step two, reducing atmosphere is adopted in an electroslag furnace in the electroslag remelting process, a deoxidizing agent is added in the electroslag remelting process, slag sample analysis is carried out once per hour, the quantity of the deoxidizing agent is adjusted according to the result of the slag sample analysis, the deoxidizing agent comprises a mixture of Si-Ca alloy, pure Ca and pure Al, and people select the deoxidizing agent according to own working requirements.

Example 2

firstly, producing a steel ingot in an electroslag remelting mode;

smelting the consumable electrode in a vacuum induction mode, wherein the content of nonmetallic inclusions and the content of O elements of the consumable electrode meet the requirements of table 1;

TABLE 1

A (Thick/thin)	B (Thick/thin)	C (Thick/thin)	D (Thick/thin)	Ds	Content of O
						≤1.0/1.0	≤1.5/1.5	≤1.0/1.0	≤2.0/2.0	≤1.5	≤0.0025％

Step three, coating a special protective coating after polishing the consumable electrode, and then baking;

removing garbage such as oxides and the like on the inner surface of the crystallizer;

step five, smelting by adopting a high-alkalinity slag system, wherein the adopted high-alkalinity slag system comprises the following raw materials in parts by weight: 65% of fluorite, 20% of white corundum, 11% of lime, 5% of quartz sand and 4% of fused magnesia, wherein the thickness of the high-alkalinity slag system is not more than 300 mm;

sixthly, adding a deoxidizing agent every five minutes for deoxidizing during electroslag remelting;

and seventhly, carrying out slag sample analysis once per hour, and adjusting the input amount of the deoxidizer according to the result of the slag sample analysis.

The steel ingot is produced by the method of example 2, the components of the finished product are tested, the test result of the 60-ton 9Ni steel ingot is shown in table 2, the test result of the 40-ton 9Ni steel ingot is shown in table 3, and the No. 1-5 steel ingot is the top-down sampling result of the steel ingot. No. 1 is the bottom of the steel ingot, and No. 5 is a riser.

TABLE 2

As can be seen from table 2, the requirements of the finished product are in compliance with the specifications.

TABLE 3

	A (Thick/thin)	B (Thick/thin)	C (Thick/thin)	D (Thick/thin)	Ds
						1	0/0	0/0	0/0	1.0/1.0	0.5
2	0/0	0/0	0/0	1.0/1.0	0.5
						3	0/0	0/0	0/0	1.0/0.5	0.5
4	0/0	0/0	0/0	1.0/1.0	0.5
						5	0/0	0/0	0/0	0.5/0.5	0.5

As can be seen from table 3, the requirements of the finished product are in compliance with the specifications.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. A method for controlling nonmetallic inclusions in 9Ni steel ingots with the weight of more than 30 tons is characterized by comprising the following steps:

firstly, producing a steel ingot by adopting an electroslag remelting mode, adopting a small-diameter consumable electrode and a high-alkalinity slag system as production raw materials, keeping the content and the oxygen content of impurities in the consumable electrode at a lower level, and paving a crystallizer and a water-cooled bottom plate in an electroslag furnace;

step two, reducing atmosphere is filled in an electroslag furnace in the electroslag remelting process, a deoxidizing agent is added in the electroslag remelting process, slag sample analysis is carried out once per hour, and the quantity of the deoxidizing agent is adjusted according to the result of the slag sample analysis;

wherein, in the step one:

the content of non-metallic inclusions and O elements of the consumable electrode meets the following requirements: coarse system A is less than or equal to 1.0, fine system A is less than or equal to 1.0, coarse system B is less than or equal to 1.5, fine system B is less than or equal to 1.5, coarse system C is less than or equal to 1.0, fine system C is less than or equal to 1.0, coarse system D is less than or equal to 2.0, fine system D is less than or equal to 2.0, Ds is less than or equal to 1.5, and O content is less than or equal to 0.0025 percent;

the high-alkalinity slag system is a mixture of fluorite, white corundum, lime, quartz sand and fused magnesia which are mixed according to the weight ratio of 62-67:18-23:10.2-12.6:4.5-5.7: 3.8-4.4.

2. The method for controlling nonmetallic inclusions in a steel ingot of 9Ni of 30 tons or more according to claim 1, wherein impurities and trash on the inner surface of the mold are removed before the electroslag remelting.

3. The method for controlling nonmetallic inclusions in a 9Ni steel ingot of 30 tons or more according to claim 1, wherein the consumable electrode is smelted by a vacuum induction method.

4. A method for controlling nonmetallic inclusions in a 30-ton or more 9Ni steel ingot according to claim 1 or 3, characterized in that the surface of the consumable electrode is polished and coated with an antioxidant coating.

5. The method for controlling nonmetallic inclusions in a 30-ton or more 9Ni steel ingot according to claim 1, wherein the deoxidizer includes at least one of Si — Ca alloy, pure Ca, and pure Al.

6. The method for controlling nonmetallic inclusions in a steel ingot of 9Ni of 30 tons or more as set forth in claim 1, wherein the mold employs a water-cooled mold with a copper wall of 1500-2400mm in diameter.