阅读说明：本技术 含硫含铝钢及其冶炼方法和应用 (Sulfur-containing aluminum-containing steel, smelting method and application thereof ) 是由 余大华 张波 张志明 曾令宇 余衍丰 刘志明 万翔 龙鹄 刘成斌 胡现锋 刘志龙 于 2019-10-30 设计创作，主要内容包括：本申请涉及一种含硫含铝钢及其冶炼方法和应用,属于精炼技术领域。一种含硫含铝钢的冶炼方法,包括：对转炉冶炼过程的钢水进行脱氧合金化和一次造渣处理,其中,转炉冶炼前不进行铁水脱硫预处理。精炼过程中对经过一次造渣的钢水进行二次造渣处理和脱氧,出站前对钢水进行增硫处理,其中,转炉至精炼过程中不加入萤石。在真空处理过程中加入金属铝以调节铝含量。真空处理结束后加入金属钙以调节钙含量。该冶炼方法可以显著降低萤石对夹杂物的影响,可以显著减少在LF炉中调整铝含量导致的氧化铝等杂质的生成及结瘤的增加,可以显著减少钙在精炼及真空处理过程中生成钙铝酸盐等复合夹杂物,以降低夹杂物的生成,较大程度提高浇铸后钢的质量。(The application relates to sulfur-containing and aluminum-containing steel and a smelting method and application thereof, belonging to the technical field of refining. A smelting method of sulfur-containing aluminum-containing steel comprises the following steps: and carrying out deoxidation alloying and primary slagging treatment on the molten steel in the converter smelting process, wherein the molten iron is not subjected to molten iron desulphurization pretreatment before the converter smelting. And carrying out secondary slagging treatment and deoxidation on the molten steel subjected to primary slagging in the refining process, and carrying out sulfur-increasing treatment on the molten steel before the molten steel is taken out of the station, wherein no fluorite is added in the converter to the refining process. Metallic aluminum is added during the vacuum treatment to adjust the aluminum content. After the vacuum treatment is finished, metal calcium is added to adjust the calcium content. The smelting method can obviously reduce the influence of fluorite on the inclusion, can obviously reduce the generation of impurities such as alumina and the like and the increase of nodulation caused by adjusting the aluminum content in the LF furnace, can obviously reduce the generation of composite inclusions such as calcium aluminate and the like generated in the refining and vacuum treatment processes of calcium, so as to reduce the generation of the inclusions and greatly improve the quality of the cast steel.)

1. A smelting method of sulfur-containing aluminum-containing steel is characterized by comprising the following steps:

smelting in a converter and tapping: carrying out deoxidation alloying and primary slagging treatment on the molten steel in the converter smelting process, wherein molten iron desulphurization pretreatment is not carried out before converter smelting;

refining in an LF furnace: carrying out secondary slagging treatment and deoxidation on the molten steel subjected to primary slagging in the refining process, and carrying out sulfur-increasing treatment on the molten steel before the molten steel is taken out of the station, wherein no fluorite is added in the converter to the refining process;

and (3) RH furnace vacuum treatment: adding metal aluminum in the vacuum treatment process to adjust the aluminum content;

after the vacuum treatment is finished, adding metal calcium to adjust the calcium content, and then carrying out soft blowing treatment.

2. The method for smelting sulfur-containing aluminum-containing steel as recited in claim 1, wherein said aluminum metal is added to the molten steel after 3min of vacuum treatment until the aluminum content in the molten steel reaches the upper limit of the inner control range ± 0.005%.

3. The method for smelting sulfur-containing and aluminum-containing steel according to claim 1 or 2, wherein the degree of vacuum of the RH furnace vacuum treatment is less than 0.266KPa, and the vacuum treatment time is 28min to 33 min.

4. The method for smelting sulfur-containing and aluminum-containing steel as claimed in claim 1, wherein the amount of added metallic calcium is 0.01kg/t to 0.015kg/t after the completion of the vacuum treatment.

5. The method for smelting sulfur-containing aluminum-containing steel as recited in claim 1, wherein said deoxidizing alloying step comprises: adding aluminum iron into molten steel in the converter smelting process, and then adding alloy elements to adjust the components of the molten steel, so that the carbon content in the molten steel is between-0.02 percent of the internal control lower limit and the internal control lower limit;

optionally, the adding amount of the aluminum iron is 1.5kg/t-2.5 kg/t.

6. The method for smelting sulfur-containing aluminum-containing steel as recited in claim 1, wherein the step of deoxidation treatment in the refining process comprises: adding silicon carbide and metal aluminum into the molten steel subjected to primary slagging for slag surface deoxidation, adding metal aluminum for deep deoxidation, and then regulating the aluminum content in the molten steel to 0.010-0.030%;

optionally, the addition amount of the silicon carbide is 0.8kg/t-1.0kg/t, the addition amount of the metal aluminum in the slag surface deoxidation process is 0.4kg/t-0.8kg/t, and the addition amount of the metal aluminum in the deep deoxidation process is 0.1kg/t-0.25 kg/t.

7. The method for smelting the sulfur-containing and aluminum-containing steel as claimed in claim 6, wherein bottom-blown argon is used in the refining process, and wherein the flow rate of argon in the slagging and deoxidation process is 30Nm³/h-60Nm³H, the argon flow after the process of regulating and controlling the aluminum content is 10Nm³/h-20Nm³/h。

8. The method for smelting sulfur-containing aluminum-containing steel as recited in claim 1, wherein said step of sulfur-increasing treatment comprises: adding ferrosulfur into the molten steel before the molten steel is taken out of the station, so that the sulfur content in the molten steel reaches a target value +/-0.003%;

optionally, bottom-blown argon is adopted in the sulfur increasing treatment process, and the argon flow is 1Nm³/h-5Nm³/h。

9. A sulfur-containing aluminum-containing steel produced by the method for producing a sulfur-containing aluminum-containing steel according to any one of claims 1 to 8, comprising, in terms of mass percent: 0.010-0.030 percent of Als and 0.010-0.050 percent of S.

10. Use of the sulfur-containing aluminum-containing steel of claim 9 in the manufacture of key parts for automobile crankshafts, engines and transmissions.

Technical Field

The application relates to the technical field of refining, in particular to sulfur-containing and aluminum-containing steel, a smelting method and application thereof, and particularly relates to fluorite-free sulfur-containing and aluminum-containing steel, a smelting method and application thereof.

Background

In smelting sulfur-containing and aluminum-containing steel, the smelting process is the key to ensure the stable stopper curve of molten steel in the casting process. If the smelting process is unreasonable, the nozzle nodulation is serious in the casting process of the molten steel due to the poor purity of the molten steel in the casting process, the stopper rod curve obviously rises, and the nozzle nodulation falls off in the casting process to generate macroscopic inclusion defects. The fluorite is mainly composed of calcium fluoride, and the fluorite is adopted in the existing smelting process to improve the fluidity of the slag. However, the addition of fluorite causes serious erosion of the lining of the blast furnace, and the problem of hearth accumulation and the like is generated.

Disclosure of Invention

Aiming at the defects of the prior art, the purpose of the embodiment of the application comprises providing the sulfur-containing and aluminum-containing steel, the smelting method and the application thereof, so as to improve the technical problem of nozzle nodule generation.

In a first aspect, an embodiment of the present application provides a method for smelting sulfur-containing and aluminum-containing steel, including: smelting in a converter and tapping: and carrying out deoxidation alloying and primary slagging treatment on the molten steel in the converter smelting process, wherein the molten iron is not subjected to molten iron desulphurization pretreatment before the converter smelting. Refining in an LF furnace: and carrying out secondary slagging treatment and deoxidation on the molten steel subjected to primary slagging in the refining process, and carrying out sulfur-increasing treatment on the molten steel before the molten steel is taken out of the station, wherein no fluorite is added in the converter to the refining process. And (3) RH furnace vacuum treatment: metallic aluminum is added during the vacuum treatment to adjust the aluminum content. After the vacuum treatment is finished, metal calcium is added to adjust the calcium content.

This application adopts in the refining process not to add fluorite, adjust the calcium content after aluminium content and vacuum treatment in RH (vacuum cycle degasification) vacuum treatment process, can show the influence that reduces fluorite to the inclusion, can show the formation and the increase of nodulation that reduce the impurity such as aluminium oxide that adjustment aluminium content leads to in LF stove (ladle refining furnace), can show and reduce calcium and produce compound inclusion such as calcium aluminate in refining and vacuum treatment process, in order to reduce the formation of inclusion, the great degree improves the quality of steel after the casting.

In some examples of the present application, after 3min of vacuum treatment, metallic aluminum is added until the aluminum content in the molten steel reaches the upper limit of the internal control range plus or minus 0.005%.

The inventor of the application discovers that the adjustment of the aluminum content in the LF furnace refining process can cause the reduction of the aluminum content in the molten steel and waste of aluminum through experimental research. And the addition of aluminum during refining results in the production of more alumina impurities in subsequent processes, resulting in an increase in the amount of nodules. After the work of the inventors of the present application, it was proposed to adjust the aluminum content during the vacuum process. The molten steel and the slag do not react basically in the RH vacuum treatment process, so that the yield of the aluminum is stable.

In some examples of the present application, the amount of calcium metal added is 0.01kg/t to 0.015kg/t after the vacuum treatment is completed.

The inventor of the application finds that the calcium content is controlled in the LF refining or RH vacuum process by the current smelting process, and the calcium aluminate composite inclusion is produced due to large calcium treatment amount in the smelting process. The method adopts the vacuum treatment to adjust the calcium content, reduces the calcium consumption, and can obviously reduce the generation of a large amount of calcium aluminate composite inclusions caused by large calcium treatment amount, thereby improving the control effect of D, Ds-type inclusions. Wherein, the D-type inclusion is spherical oxide agglomeration, and the Ds-type inclusion is single-particle spherical.

In some embodiments of the application, the degree of vacuum of the RH furnace vacuum treatment is less than 0.266KPa, and the vacuum treatment time is 28min-33 min.

The method adopts a long-time vacuum system, on one hand, the possibility that air and the like participate in the molten steel reaction is isolated, and further enrichment of oxide inclusions is avoided; on the other hand, the high-temperature environment is kept still for a long time, the molten steel has good fluidity, and inclusions are convenient to float upwards, so that the effect of improving the content of B, D, Ds-type inclusions is achieved. Wherein the B-type inclusions are mainly alumina particles.

In some embodiments of the present application, the step of deoxygenation treatment during refining comprises: adding silicon carbide and metal aluminum into molten steel subjected to primary slagging for slag surface deoxidation, adding metal aluminum for deep deoxidation, and then regulating and controlling the aluminum content in the molten steel to be 0.010-0.030%. Optionally, the addition amount of the silicon carbide is 0.8kg/t-1.0kg/t, the addition amount of the metal aluminum in the slag surface deoxidation process is 0.4kg/t-0.8kg/t, and the addition amount of the metal aluminum in the deep deoxidation process is 0.1kg/t-0.25 kg/t.

According to the method, the slag surface deoxidation is carried out firstly, then the metal aluminum is fed from the furnace body for deep deoxidation, so that the oxygen on the surface of the molten steel is removed by the silicon carbide and the aluminum, the components in the molten steel can not react with the oxygen on the slag surface to generate impurities in the deep deoxidation and argon bottom blowing processes, and the generation of the impurities is reduced. Can avoid the generation of inclusions caused by the reaction of the components in the molten steel and the oxides in the slag in the process of bottom blowing argon after direct deep deoxidation.

In some examples of the present application, the refining process uses bottom-blown argon, wherein the argon flow in the slagging and deoxidation process is 30Nm³/h-60Nm³H, the argon flow after the process of regulating and controlling the aluminum content is 10Nm³/h-20Nm³/h。

According to the method, a large argon flow is adopted firstly, so that the components in the molten steel can be fully mixed to a large extent, the good deoxidation effect and the removal effect of deoxidation products are achieved, and the content of impurities in the molten steel is reduced. Reduce the argon gas flow in order to reduce the reaction between the slag at regulation and control aluminium content in-process, avoided a large amount of aluminium (Als) losses of middle and later stage refining process on the one hand to produce a large amount of inclusion, improved the control effect of B class inclusion, on the other hand has avoided because of blowing at the bottom that the argon gas flow is too big and lead to the slag entrapment phenomenon, and tiny slag liquid drop gets into the molten steel and produces D, Ds class inclusion, improves LF stove refining process inclusion and gets rid of the effect.

In some embodiments of the present applicationThe step of sulfur treatment comprises: before the molten steel is taken out of the station, ferro-sulphur is added into the molten steel, so that the sulphur content in the molten steel reaches a target value of +/-0.003%. In the process of sulfur-increasing treatment, low-flow bottom-blown argon is adopted, and optionally, the flow of the argon is 1Nm³/h-5Nm³/h。

The method has the advantages that the sulfur content is regulated and controlled in the LF refining process, the stability of the sulfur content is guaranteed to a large extent, the gradual adjustment of components is avoided, the yield of sulfur is reduced under the action of bottom blowing stirring of the steel ladle, and a large amount of impurities are generated.

In some embodiments of the present application, the step of deoxidation alloying comprises: adding aluminum iron into molten steel in the converter smelting process, and adding alloy elements to adjust the components of the molten steel, so that the carbon content in the molten steel is between-0.02 percent of the lower limit of internal control and the lower limit of internal control. Optionally, the adding amount of the aluminum iron is 1.5kg/t-2.5 kg/t.

This application strict control converter tapping carbon content is in order to can not carburetting at the LF stove refining process, avoids improving the bottom blowing argon gas flow because of adjusting carbon at LF stove refining process to a great extent, leads to a large amount of Als losses, guarantees to a great extent that LF stove refining process Als loses within 0.010%. The content of alumina inclusions in the LF furnace is obviously reduced, and a large amount of B-type inclusions in steel are avoided as much as possible.

In a second aspect, the embodiment of the present application provides a sulfur-containing and aluminum-containing steel, which is obtained by the above smelting method for sulfur-containing and aluminum-containing steel, and the sulfur-containing and aluminum-containing steel comprises the following components by mass percent: 0.010-0.030 percent of Als and 0.010-0.050 percent of S.

The steel prepared by optimizing the refining deoxidation method, the refining slag system control and the RH furnace vacuum treatment process has the advantages that the content of inclusions in the components is in a control range, and the steel has better mechanical properties.

In a third aspect, the embodiment of the application provides an application of the sulfur-containing aluminum-containing steel in manufacturing key parts of automobile crankshafts, engines and gearboxes.

The sulfur-containing and aluminum-containing steel provided by the application has low inclusion content and good mechanical property, and can be used for preparing parts with high requirements on the quality of steel, such as the fields of machinery, automobiles and aviation.

The beneficial effect of this application includes:

according to the method, the molten iron is not subjected to desulfurization pretreatment before smelting in the converter, so that sufficient sulfur is contained in the molten steel after smelting in the converter to a greater extent.

The carbon content is strictly controlled in the converter tapping process, so that Als loss caused by carbon adjustment in the refining process is avoided as much as possible, and inclusions caused by aluminum content adjustment are avoided.

Through not adding fluorite, slag surface deoxidation, deep deoxidation, control refining slag composition and sulfur increasing treatment, the yield of sulfur is improved when the refined molten steel has lower oxygen content to a greater extent, and the stable control of sulfur is ensured.

According to the method, the aluminum content is adjusted in the RH vacuum treatment process, the generation amount of aluminum oxide is reduced, and further the generation of nodules is reduced. The calcium content is adjusted after the vacuum treatment, so that the generation of calcium aluminate composite inclusions can be obviously reduced, and the control effect of D, Ds type inclusions is improved.

It should be noted that, although there are individual technical effects of the individual process steps, it is only possible to ensure the production of a sulfur-containing, aluminum-containing steel with excellent properties by a specific synergistic combination of the above-mentioned series of production processes according to the description of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

In the prior smelting process of sulfur-containing and aluminum-containing steel, the nozzle of molten steel has serious nodulation in the pouring process. The nozzle nodules fall into the production furnace during the casting process, resulting in the generation of inclusion defects in the steel. The inventor of the application finds that the content of the inclusions in the sulfur-containing and aluminum-containing steel has great influence on the generation of nodules through research, and therefore researches the process of the sulfur-containing and aluminum-containing steel.