阅读说明：本技术 一种向钢水中加入稀土的方法 (Method for adding rare earth into molten steel ) 是由 刘成宝 刘茂文 许荣昌 陈良 杨密平 王毅 马光亭 于 2019-10-18 设计创作，主要内容包括：本发明属于钢铁冶金技术领域,具体涉及到一种向钢水中加入稀土的方法。从稀土的加入量、稀土加入的钢水条件、稀土的形状和稀土的加入方式,四个方面进行控制。通过氩气清洁、高效地将稀土送入钢液,成功克服了减少了冶炼环境下稀土的氧化现象,解决了稀土与精炼渣、保护渣反应等难题,原理和结构简单,便于维护,投资小,易于实现。(The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a method for adding rare earth into molten steel. The addition amount of the rare earth, the molten steel condition of the rare earth addition, the shape of the rare earth and the addition mode of the rare earth are controlled. The rare earth is cleanly and efficiently sent into the molten steel through argon, the oxidation phenomenon of the rare earth under the smelting environment is successfully overcome, the problems of reaction of the rare earth with refining slag and protective slag and the like are solved, and the method has the advantages of simple principle and structure, convenience in maintenance, small investment and easiness in implementation.)

1. A method for adding rare earth into molten steel is characterized in that the method is controlled in four aspects of the adding amount of the rare earth, the molten steel condition for adding the rare earth, the shape of the rare earth and the adding mode of the rare earth.

2. The method of claim 1, wherein the amount of rare earth added is controlled to be (10-200). times.10^-6。

3. The method of adding rare earth to molten steel of claim 2, wherein the rare earth is pure La, pure Ce, or a metallic material having La and Ce as main elements.

4. The method of adding rare earth to molten steel according to claim 1, wherein the molten steel conditions for rare earth addition are as follows: t [ O ]]≤10×10^-6，[S]≤30×10^-6。

5. The method of adding rare earth to molten steel according to claim 1, wherein the shape of the rare earth is: the method adopts blocky rare earth, the equivalent diameter of the blocky rare earth is 5-40mm, and the length-width ratio or the axial width ratio is 1-3.

6. The method of adding rare earth to molten steel according to claim 1, wherein the rare earth is added in a manner of: rare earth is sprayed into molten steel by a spray pipe by using inert gas as a carrier, the inert gas is argon, the service pressure of the argon is 0.2MPa-1.5MPa, the adding depth is continuously reduced, and the contact with a refractory material is reduced.

7. The method of claim 1, wherein the rare earth is supplied to the molten steel in a lance tube for delivering the rare earth, the lance tube having an outer layer made of a refractory material and an inner layer made of steel; further, the specific material may be a steel grade with less carbon element and alloy element types and lower alloy element content than the molten steel.

8. A method of adding rare earth to molten steel according to claim 6 or 7, wherein the diameter of the inner layer of the blowing tube is 1.1 to 1.5 times the equivalent diameter of the bulk rare earth, and the minimum diameter is not less than 10 mm.

9. The method of adding rare earth to molten steel according to claim 8, wherein the head of the injection tube is formed in a horn shape.

10. The method of adding rare earth to molten steel according to claim 1, wherein the specific steps for the manner of adding rare earth are as follows:

1) the injection pipe firstly conveys a small flow of argon above the steel ladle and blows off metallurgical slag on the surface of molten steel;

2) continuously injecting argon into the molten steel by using an injection pipe, and meanwhile, conveying the injection pipe into the molten steel to a depth of 2/3-1/3;

3) increasing the flow of argon, feeding the rare earth into a blowing pipe once or for a plurality of times, driving the rare earth into molten steel by the argon, and stirring the molten steel and homogenizing the rare earth components by the argon;

4) after the rare earth is added deeply into the first molten steel, the blowing pipe is lifted; rare earth is added through one or more different molten steel depths, so that the argon flow is reduced;

5) and (4) keeping the blowing pipe away from the slag air interface, and adding the rare earth steel to enter the next procedure.

Technical Field

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a method for adding rare earth into molten steel.

Background

Continuous casting, i.e., continuous casting of steel, is a molten steel forming technique in which refined molten steel is continuously fed into a mold, solidified and formed, and then drawn out from below the mold. Compared with the traditional die casting process, the continuous casting process is a great technical progress.

The addition of a proper amount of rare earth into steel has three main functions: purifying molten steel, modifying inclusion and microalloying, improving the toughness and plasticity, particularly the transverse impact toughness of the steel and improving the anisotropy of steel; for example, the rare earth can lead high-hardness alumina to be mixed and converted into spherical oxysulfide and rare earth aluminate, thereby obviously improving the fatigue resistance of the steel; the segregation of the rare earth in the grain boundary can inhibit the segregation of phosphorus and sulfur and low-melting-point impurities of lead, tin, arsenic, antimony and bismuth in the grain boundary or form compounds with higher melting points with the impurities, purify and strengthen the grain boundary, eliminate the harmful effect of the low-melting-point impurities, and be beneficial to improving plasticity, particularly high-temperature plasticity and the like. After the rare earth is applied to the steel, the effects of refining impurities, deeply purifying molten steel and strongly microalloying can be achieved, the toughness, plasticity and fatigue life of the steel are obviously improved, and the steel is more tough, heat-resistant, wear-resistant and corrosion-resistant.

When the rare earth is industrially applied to steel, two major bottleneck problems are not solved all the time: firstly, rare earth is added into molten steel to block a pouring system, and the continuous casting process is forced to be interrupted, so that the smooth process is seriously influenced; secondly, after the rare earth is added, large-size and high-density rare earth inclusions are easily formed, so that the performance of the steel is good, bad and unstable. The main reason is that no mature stable rare earth addition process has been formed. At present, a plurality of experimental researches on rare earth addition processes are carried out at home and abroad, and the mass production is realized under respective historical conditions, which mainly comprise the following steps: the method comprises eight methods, namely a large-ladle throwing method, a large-ladle pressing-in method, a method for blowing rare earth powder into a ladle, a method for feeding wires by using a casting injection center injection pipe, a method for hanging rare earth metal rods in a mould, a method for feeding wires by using a steel ladle, a method for feeding wires by using a tundish, a method for feeding wires by using a crystallizer and the like. The currently used methods mainly focus on: the method comprises a ladle wire feeding method and a crystallizer wire feeding method. Even under the condition of gas protection, the rare earth wire and the casting powder are contacted, when the low-temperature rare earth wire passes through a high-temperature casting powder layer, the casting powder in the contact area is possibly adhered to the surface of the metal wire and enters a molten pool along with the wire, and the defects of slag inclusion and the like are generated. Even when the sleeve is additionally arranged around the rare earth wire, the rare earth wire is continuously fed into the inner area of the sleeve, so that the temperature in the sleeve is too low, the casting powder is easy to solidify, and the rare earth wire is not beneficial to adding and casting protection; on the other hand, the wire feeding method of the crystallizer is easy to cause the performance deterioration of the continuous casting crystallizer casting powder, and the surface defect of the casting blank is caused.

Therefore, a low-cost, simple and effective rare earth adding method is urgently needed during the continuous casting production of steel.

Disclosure of Invention

Aiming at the problems that the addition of rare earth wires in the prior art is easy to clamp slag and oxidize, and the casting powder is easy to solidify and deteriorate, the invention provides a method for adding rare earth into molten steel, so as to solve the technical problems. The method has low cost, and is simple and effective.

The technical scheme of the invention is as follows:

a method for adding rare earth into molten steel is controlled by four aspects of the adding amount of the rare earth, the molten steel condition of the rare earth, the shape of the rare earth and the adding mode of the rare earth.

The invention relates to a method for adding rare earth into molten steel, which comprises the following steps:

(1) the addition amount of the rare earth is controlled to be (10-200) multiplied by 10^-6(ii) a The rare earth is pure La, pure Ce and a metal material taking La and Ce as main elements. The excessive addition of the rare earth can not improve the performance of steel, but also influence the normal production of steel and even cause the rejection of materials. The rare earth is not suitable for pre-deoxidization and desulfurization agent, in the invention, the rare earth element is only used as deep deoxidization and deep desulfurization agent, and the addition amount is (10-200) multiplied by 10^-6。

(2) Molten steel adding conditions of rare earth are as follows: t [ O ]]≤10×10^-6，[S]≤30×10^-6. When the deoxidation and desulfurization effects are good, the rare earth is added, so that the deep deoxidation and desulfurization effects are achieved, and the forms of oxygen and sulfur inclusions can be well controlled.

(3) Shape of rare earth: the method adopts blocky rare earth, the equivalent diameter of the blocky rare earth is 5-40mm, and the length-width ratio or the axial width ratio is 1-3.

Rare earth is close to the high-temperature environment of molten steel, oxidation can be accelerated, and the finer the particle size of the material, the larger the specific surface area, and the greater the probability and degree of oxidation. Therefore, the rare earth bulk material with larger specific surface area is more beneficial to adding molten steel. Since the density of the rare earth La and Ce is slightly less than that of steel, the larger the size of the block rare earth is at the same molten steel temperature, the longer the time required for melting is, and the higher the possibility of floating to a steel slag interface is.

(4) The rare earth addition mode is as follows: rare earth is sprayed into molten steel by a spray pipe by using inert gas as a carrier, the inert gas is argon, the service pressure of the argon is 0.2MPa-1.5MPa, the adding depth is continuously reduced, and the contact with a refractory material is reduced. The stirring effect caused by the carrier gas promotes the melting and the uniform distribution of the rare earth in the molten steel. The flow of argon is controlled by a gas flow pressure system, and the flow of argon can be increased on the premise of not causing liquid level rolling and air suction.

When the rare earth is added, the retention time of the rare earth above a slag-air interface is reduced as much as possible, the contact between the rare earth and metallurgical slag is reduced, the time required for the rare earth to be uniformly diffused in molten steel is reduced, and the rare earth can be added cleanly, safely and efficiently by the aid of inert gas.

Furthermore, the outer layer of the injection pipe for conveying the rare earth is made of refractory materials, and the inner layer of the injection pipe is made of steel; the specific material can be steel with less carbon element and alloy element types and lower alloy element content than the molten steel. In the rare earth conveying process, rare earth can corrode the inner layer material of the injection pipe, and steel is selected as the inner layer material, so that the pollution to molten steel can be reduced, and more rare earth block-shaped materials can be impacted.

Furthermore, the diameter of the inner layer of the blowing pipe is 1.1-1.5 times of the equivalent diameter of the blocky rare earth, and the minimum diameter is not less than 10 mm. The head of the injection pipe can be in a horn shape, a straight cylinder shape or other suitable shapes.

In the depth direction of molten steel, because the outer layer of the injection pipe is made of refractory materials, in order to reduce the reaction of refractory materials of the injection pipe and rare earth added into the molten steel and improve the service life of the injection pipe, particularly the head part of the injection pipe, the head part of the injection pipe is controlled above the position for injecting the rare earth as far as possible, which means that the rare earth is added at a deeper position of a steel ladle firstly and the position of the injection pipe is continuously and upwards lifted.

The specific steps of the rare earth adding mode in the step (4) are as follows:

1) the injection pipe firstly conveys a small flow of argon above the steel ladle and blows off metallurgical slag on the surface of molten steel;

2) continuously injecting argon into the molten steel by using an injection pipe, and meanwhile, conveying the injection pipe into the molten steel to a depth of 2/3-1/3;

3) increasing the flow of argon, feeding the rare earth into a blowing pipe once or for a plurality of times, driving the rare earth into molten steel by the argon, and stirring the molten steel and homogenizing the rare earth components by the argon;

4) after the rare earth is added deeply into the first molten steel, the blowing pipe is lifted; rare earth is added through one or more different molten steel depths, so that the argon flow is reduced;

5) and (4) keeping the blowing pipe away from the slag air interface, and adding the rare earth steel to enter the next procedure.

For the rare earth adding mode in the step (4), the rare earth adding device can be applied to operate, and the specific steps are as follows:

1) the lifting rotary system controls a blowing pipe to be arranged above the steel ladle, the gas flow pressure control system conveys small-flow argon, and the blowing pipe blows off metallurgical slag on the surface of molten steel;

2) continuously injecting argon into the molten steel by using an injection pipe, and meanwhile, conveying the injection pipe into the molten steel to a depth of 2/3-1/3;

3) the feeding device sends the rare earth into the blowing pipe once or for a plurality of times, the flow of argon is increased, the argon drives the rare earth metal to enter molten steel, and meanwhile, the argon also plays a role in stirring the molten steel and homogenizing the rare earth components;

4) after the rare earth is added into the first molten steel deeply, the lifting rotary system controls the ascending of the injection pipe; rare earth is added through one or more different molten steel depths, so that the argon flow is reduced;

5) the lifting rotary system controls the blowing pipe to be far away from the slag air interface, and the steel added with the rare earth enters the next procedure.

The relative position of the blowing pipe in the ladle and the relative depth of the blowing pipe in the molten steel are respectively controlled by the lifting rotary system.

The beneficial effect of the invention is that,

the rare earth is cleanly and efficiently sent into the molten steel through argon, the oxidation phenomenon of the rare earth under the smelting environment is successfully overcome, the problems of reaction of the rare earth with refining slag and protective slag and the like are solved, and the method has the advantages of simple principle and structure, convenience in maintenance, small investment and easiness in implementation.

In addition, the addition amount of the rare earth, the molten steel condition of the rare earth addition and the shape of the rare earth are further optimized and improved, and the performance of the steel is greatly improved by matching with the addition mode of the rare earth.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a schematic view showing a method of adding rare earth to molten steel.

Wherein: the method comprises the following steps of 1-steel ladle, 2-molten steel, 3-steel slag, 4-blowing pipe head, 5-blowing pipe, 6-rare earth, 7-rare earth bin, 8-feeding device, 9-gas storage tank, 10-gas flow pressure control system, 11-moving rotary system and 12-support rod.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The addition amount of rare earth, the molten steel condition to which the rare earth is added, the shape of the rare earth, and the manner of addition of the rare earth are more clearly defined in the examples, but not limited thereto.