CN113151636B - Method for reducing stainless steel pitting corrosion based on inclusion melting point control - Google Patents

Abstract

The invention belongs to the field of steel making in ferrous metallurgy, and particularly relates to a method for reducing stainless steel pitting corrosion based on inclusion melting point control. The method adopts a silicomanganese deoxidizer for deoxidation, adopts low-aluminum low-calcium alloy auxiliary materials, simultaneously adds low-alkalinity refining slag fine, modifies the refining slag to increase the content of manganese oxide in inclusions and reduce the melting point, finally carries out heat treatment temperature, and carries out hot rolling, improves the liquid fraction of the inclusions in the hot rolling process, avoids the generation of gaps between the inclusions and a steel matrix in the rolling process, thereby preventing the inclusions from causing stainless steel point corrosion behavior. The invention can obviously improve the stainless steel pitting corrosion behavior induced by the inclusion, reduce the pitting corrosion defect rate caused by the inclusion, prolong the service life of the stainless steel, improve the pitting corrosion resistance of the stainless steel and provide guarantee for the development of high-grade corrosion-resistant stainless steel.

Description

A method to reduce pitting corrosion of stainless steel based on inclusion melting point control

technical field

The invention belongs to the field of iron and steel metallurgy and steelmaking, and in particular relates to a method for reducing pitting corrosion of stainless steel based on inclusion melting point control.

Background technique

Stainless steel has good corrosion resistance, high temperature resistance, wear resistance, beautiful appearance and other characteristics, and is widely used in aerospace, atomic energy, ocean development, automobile manufacturing, medical equipment, architectural decoration, household appliances, kitchen utensils and other fields. For stainless steel, the first thing to pay attention to is its corrosion resistance. The chromium element in stainless steel can form an oxide film on the surface of stainless steel to prevent the stainless steel substrate from rusting. However, non-metallic inclusions in stainless steel can cause pitting corrosion of stainless steel and affect the corrosion resistance of stainless steel. Therefore, it is very important to study the effective control of non-metallic inclusions in stainless steel to prevent inclusions from causing pitting corrosion. Oxide inclusions are one of the important causes of pitting corrosion of stainless steel, and the initial location of pitting corrosion is the gap between Al ₂ O ₃ inclusions and surrounding stainless steel, and the steel matrix dissolves. At the same time, with the progress of corrosion, Al ₂ O ₃ inclusions inside the surface layer of shallow buried stainless steel began to appear, indicating that Al ₂ O ₃ inclusions deposited below the surface of the steel substrate will also promote the pitting corrosion of stainless steel. Mg-Al-Ca-O inclusions in stainless steel can also cause pitting corrosion, and the initial position of dissolution of the inclusions that cause pitting corrosion is located in the interface between the stainless steel matrix and the inclusions, and the dissolution of the inclusions or stainless steel matrix and the new The repulsion of the stainless steel matrix continues to cause pitting corrosion of the stainless steel. Therefore, the gap between non-metallic inclusions and steel matrix is one of the important reasons why stainless steel shows that inclusions cause pitting corrosion.

Contents of the invention

The invention discloses a method for reducing pitting corrosion of stainless steel based on inclusion melting point control, so as to solve any of the above-mentioned technical problems and other potential problems in the prior art.

In order to solve the above technical problems, the technical solution of the present invention is: a method for reducing pitting corrosion of stainless steel based on the melting point control of inclusions, which avoids excessive alumina and calcium oxide content in inclusions High temperature causes the melting point to rise; at the same time, low-alkalinity refining slag is used to refine and modify the inclusion composition to reduce the melting point of the inclusion; combined with the addition of manganese ore to the refining slag, the content of manganese oxide in the inclusion is increased and the melting point is lowered; finally, the heat treatment temperature is increased , Extend the heat treatment time, increase the rolling temperature, increase the liquid phase ratio of the inclusions during the rolling process, and avoid the gap between the inclusions and the steel matrix during the rolling process, thereby preventing the inclusions from causing stainless steel pitting corrosion.

Further, the method specifically includes the following steps:

S1) In the final stage of AOD refining, silicon-manganese deoxidation is used to avoid the formation of alumina inclusions; alloying with low-alumina and low-calcium alloy auxiliary materials is used to avoid the high content of alumina and calcium oxide in the inclusions, which will cause the melting point to rise ; AOD tapping strictly controls the amount of slag to reduce the thickness of refining slag in the subsequent process.

S2) In the LF refining process, the slag is modified at the initial stage of refining. By adding quartz sand, the alkalinity of the refining slag is reduced and the melting point of inclusions is lowered. By adding manganese ore to the refining slag, the content of manganese oxide in the inclusions is increased to reduce Melting point of inclusions; through soft blowing and stirring, promote the floating of inclusions; ensure the standing time of the ladle, and promote the full floating and removal of large-sized inclusions.

S3) During the continuous casting process, argon is blown through the tundish and the casting is protected to prevent secondary oxidation of the molten steel, and to avoid the generation of a large number of new inclusions leading to changes in the composition and quantity of inclusions.

S4) In the hot rolling process, by increasing the heating temperature, prolonging the soaking time, and increasing the rolling temperature, it is ensured that the inclusions are in a liquid state during the rolling process, and the fluidity of the inclusions in the steel matrix is improved to prevent the inclusions from interacting with the steel. Creation of gaps between substrates.

Further, at the end of AOD refining in S1), silicon-manganese deoxidation is performed, and high-purity ferrosilicon and electrolytic manganese are added to avoid the formation of alumina inclusions;

Further, alloying of low-aluminum and low-calcium alloy auxiliary materials is carried out at the end of AOD refining in S1). The content of aluminum and calcium in all alloy auxiliary materials should be controlled below 0.1%, so as to avoid the high content of alumina and calcium oxide in inclusions causing melting point raised;

Further, in S1), the amount of slag dropped during AOD tapping is strictly controlled, and the thickness of the refining slag in the subsequent process is stably reduced to 3 to 4 cm, so as to ensure the stability of the refining slag composition after subsequent slag reformation;

Further, in S2) in the LF refining process, the slag is modified at the initial stage of refining, and the alkalinity of the refining slag is reduced to 1.5 to 1.7 by adding high-purity quartz sand, and the modification reduces the alumina content in the inclusions and reduces the inclusions melting point;

Further, in S2), during the LF refining process, the slag is modified at the initial stage of refining, and the manganese ore is added to the refining slag to increase the manganese oxide content in the inclusions and reduce the melting point of the inclusions;

Further, the molten steel in the LF refining process in S2) is subjected to soft blowing and stirring, the soft blowing time is 12 to 15 minutes, and the flow rate of argon blowing is 100-200NL/min, so as to promote the floating removal of large-sized inclusions and reduce the number of inclusions;

Further, in the LF refining process in S2), the ladle is left to stand for 15 to 20 minutes, so as to promote the floating removal of inclusions and reduce the number of inclusions;

Further, in the continuous casting process in S3), the protective casting is carried out, and argon gas is blown from 10 minutes before the start of the tundish to the stable casting process to prevent the secondary oxidation of the molten steel and avoid the formation of a large number of new inclusions. and changes in quantity;

Further, during the hot rolling process in S4), the heating temperature is controlled at 1200-1280°C, the heat treatment time is 40-60 minutes, and the temperature of the hot rolling process is raised to 1150-1250°C, so that the melting point of the inclusions is lowered to be lower than that of the hot rolling process. The rolling temperature ensures that the inclusions are liquid during the rolling process, improves the fluidity of the inclusions in the steel matrix, and avoids the gap between the inclusions and the steel matrix.

The beneficial effect of this method is that due to the adoption of the above technical scheme, the method of the present invention optimizes the heat treatment and rolling process parameters of typical stainless steel through the control target of the low melting point of inclusions in stainless steel, and reduces the melting point of inclusions to be lower than the hot rolling temperature. Ensure that it is liquid during the rolling process, improve the fluidity of inclusions in the steel matrix, avoid the generation of gaps between inclusions and steel matrix, and reduce stainless steel pitting corrosion. The application of the invention can significantly improve the pitting corrosion behavior of stainless steel induced by inclusions, reduce the pitting corrosion defect rate caused by inclusions, increase the service life of stainless steel, improve the pitting corrosion resistance of stainless steel, and provide guarantee for the development of high-level corrosion-resistant stainless steel.

Description of drawings

Fig. 1 is a flowchart of a method for reducing pitting corrosion of stainless steel based on inclusion melting point control according to the present invention.

Fig. 2 is a schematic diagram of typical inclusions and surrounding matrix morphology after corrosion of the stainless steel product of Example 1 using the method of the present invention.

detailed description

The present invention will be described in further detail below in combination with specific embodiments.

As shown in Figure 1, the present invention is a method for reducing pitting corrosion of stainless steel based on inclusion melting point control. The method uses silicon-manganese deoxidizer for deoxidation, uses low-aluminum and low-calcium alloy auxiliary materials, and adds low-alkalinity refining slag at the same time. And modify the refining slag to increase the content of manganese oxide in the inclusions and lower the melting point, and finally perform heat treatment temperature and hot rolling to increase the liquid phase ratio of the inclusions during the hot rolling process and avoid inclusions during the rolling process The generation of gaps between the steel matrix and the steel matrix, thereby preventing inclusions from causing stainless steel pitting corrosion behavior.

The concrete steps of described method are:

S1) In the final stage of AOD refining, add silicon-manganese deoxidizer for deoxidation, and at the same time add low-aluminum and low-calcium alloy auxiliary materials for alloying to control the amount of slag during tapping;

S2) In the LF refining process, the refining slag is modified at the initial stage of refining, and soft blowing and stirring are performed at the same time, and the ladle is left to stand for a period of time;

S3) In the continuous casting process, the protective gas is introduced first, and then cast under the protective atmosphere to obtain ingots;

S4) During the hot rolling process, the ingot is firstly heat-treated, and then heated to a certain temperature for hot rolling to avoid gaps between the inclusions and the steel matrix.

The specific steps of said S1) are:

S1.1) At the end of AOD refining, carry out silicomanganese deoxidizer, and said silicomanganese deoxidizer is high-purity ferrosilicon and electrolytic manganese,

S1.2) At the end of AOD refining, low-aluminum and low-calcium alloy auxiliary materials are alloyed. The content of aluminum and calcium in all alloy auxiliary materials is below 0.1%, and the thickness of refining slag is stably reduced to 3-4 cm.

The specific steps of said S2) are:

S2.1) In the early stage of LF refining, the alkalinity of refining slag is reduced to 1.5-1.7 by adding high-purity quartz sand,

S2.2) In the LF refining process, add manganese ore to the refining slag to increase the MnO content in the refining slag to 4%-8%,

S2.3) Blow argon gas into the molten steel at a certain flow rate for a certain period of time, carry out soft blowing and stirring, and let it stand for a certain period of time after stirring.

The manganese ore described in S2.2) is manganese oxide.

The soft blowing time is 12-15 minutes, the argon blowing flow rate is 100-200 NL/min, and the standing time is 15-20 minutes.

The specific steps of S3) are as follows: the continuous casting process is for protective casting, and argon gas is blown from 10 minutes before the tundish starts to the stable casting process.

The specific steps of said S4) are:

S4.1) the heat treatment temperature is 1200-1280°C, and the heat treatment time is 40-60 minutes,

S4.2) Hot rolling the ingot after the soaking treatment in S4.1), the hot rolling temperature is 1150-1250°C.

Example 1:

In the final stage of AOD refining, high-purity ferrosilicon and electrolytic manganese are used for silicon-manganese deoxidation to avoid the formation of alumina inclusions; the aluminum and calcium content in alloying by using low-aluminum and low-calcium alloy auxiliary materials is up to 0.07% and 0.05%. , to avoid the high content of alumina and calcium oxide in the inclusions, which will cause the melting point to rise; AOD tapping strictly controls the amount of slag, and reduces the thickness of refining slag to 3.2 cm. In the LF refining process, the slag is modified at the initial stage of refining. By adding high-purity quartz sand, the alkalinity of the refining slag is reduced to 1.6, and the modification reduces the alumina content in the inclusions. By adding manganese ore to the refining slag, the inclusions are increased. The content of manganese oxide in the container is reduced to 5% to reduce the melting point of inclusions; carry out soft blowing and stirring, the soft blowing time is 15 minutes, and the flow rate of argon blowing is 150NL/min; The number of inclusions. Protective casting is carried out in the continuous casting process, and argon gas is blown from 10 minutes before the start of the tundish to the stable casting process to prevent secondary oxidation of the molten steel and avoid the formation of a large number of new inclusions leading to changes in the composition and quantity of inclusions; During the hot rolling process, the heating temperature is controlled at 1270°C, the soaking time is 45 minutes, and the hot rolling process temperature is increased to 1210°C to ensure that the inclusions are liquid during the rolling process and improve the flow of inclusions in the steel matrix There is no obvious gap between the inclusions and the steel matrix. After immersing the sample in an aqueous solution of 20ml HCl+350ml deionized water+69.9g ferric chloride pentahydrate for 30 minutes, the typical inclusion composition is Al ₂ O ₃ -SiO ₂ -MnO, and there is no pitting corrosion behavior around it, such as As shown in Figure 2, 110 μm.

Example 2:

In the final stage of AOD refining, high-purity ferrosilicon and electrolytic manganese are used for silicon-manganese deoxidation to avoid the formation of alumina inclusions; the aluminum and calcium content in alloying by using low-aluminum and low-calcium alloy auxiliary materials is up to 0.07% and 0.05%. , to avoid the high content of alumina and calcium oxide in the inclusions, which will cause the melting point to rise; AOD tapping strictly controls the amount of slag, and reduces the thickness of refining slag to 3.6 cm. In the LF refining process, the slag is modified at the initial stage of refining. By adding high-purity quartz sand, the alkalinity of the refining slag is reduced to 1.5, and the modification reduces the alumina content in the inclusions. By adding manganese ore to the refining slag, the inclusions are increased. The content of manganese oxide in the container is reduced to 4% to reduce the melting point of inclusions; perform soft blowing and stirring, the soft blowing time is 12 minutes, and the flow rate of argon blowing is 100NL/min; The number of inclusions. Protective casting is carried out in the continuous casting process, and argon gas is blown from 10 minutes before the start of the tundish to the stable casting process to prevent secondary oxidation of the molten steel and avoid the formation of a large number of new inclusions leading to changes in the composition and quantity of inclusions; During the hot rolling process, the heating temperature is controlled at 1280°C, the soaking time is 40 minutes, and the hot rolling process temperature is increased to 1250°C to ensure that the inclusions are liquid during the rolling process and improve the flow of inclusions in the steel matrix There is no obvious gap between the inclusions and the steel matrix. After immersing the sample in an aqueous solution of 20ml HCl + 350ml deionized water + 69.9g ferric chloride pentahydrate for 30 minutes, the typical inclusion composition is Al ₂ O ₃ -SiO ₂ -MnO, and no pitting corrosion occurs around it.

Example 3:

In the final stage of AOD refining, high-purity ferrosilicon and electrolytic manganese are used for silicon-manganese deoxidation to avoid the formation of alumina inclusions; the aluminum and calcium content in alloying by using low-aluminum and low-calcium alloy auxiliary materials is up to 0.07% and 0.05%. , to avoid the high content of alumina and calcium oxide in the inclusions, which will cause the melting point to rise; AOD tapping strictly controls the amount of slag, and reduces the thickness of refining slag to 4 cm. In the LF refining process, the slag is modified at the initial stage of refining. By adding high-purity quartz sand, the alkalinity of the refining slag is reduced to 1.7, and the modification reduces the alumina content in the inclusions. By adding manganese ore to the refining slag, the inclusions are increased. The content of manganese oxide in the steel is 8%, which reduces the melting point of inclusions; performs soft blowing and stirring, the soft blowing time is 13.5 minutes, and the flow rate of argon blowing is 200NL/min; The number of inclusions. Protective casting is carried out in the continuous casting process, and argon gas is blown from 10 minutes before the start of the tundish to the stable casting process to prevent secondary oxidation of the molten steel and avoid the formation of a large number of new inclusions leading to changes in the composition and quantity of inclusions; During the hot rolling process, the heating temperature is controlled at 1200°C, the soaking time is 60 minutes, and the hot rolling process temperature is increased to 1150°C to ensure that the inclusions are liquid during the rolling process and improve the flow of inclusions in the steel matrix There is no obvious gap between the inclusions and the steel matrix. After immersing the sample in an aqueous solution of 20ml HCl + 350ml deionized water + 69.9g ferric chloride pentahydrate for 30 minutes, the typical inclusion composition is Al ₂ O ₃ -SiO ₂ -MnO, and no pitting corrosion occurs around it.

A method for reducing pitting corrosion of stainless steel based on the melting point control of inclusions provided in the embodiment of the present application has been introduced in detail above. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation and application scope. To sum up, the contents of this specification should not be understood as limiting the application.

Certain terms are used, for example, in the description and claims to refer to particular components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use the difference in name as a way to distinguish components, but use the difference in function of components as a criterion for distinguishing. "Includes" and "comprising" mentioned throughout the description and claims are open-ended terms, so they should be interpreted as "including/including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred implementation mode for implementing the application, but the description is for the purpose of illustrating the general principles of the application, and is not intended to limit the scope of the application. The scope of protection of this application should be defined by the appended claims.

It should also be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a good or system comprising a set of elements includes not only those elements but also includes items not expressly listed. other elements of the product, or elements inherent in the commodity or system. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the article or system comprising said element.

It should be understood that the term "and/or" used herein is only an association relationship describing associated objects, which means that there may be three relationships, for example, A and/or B, which may mean that A exists alone, and A and B exist simultaneously. B, there are three situations of B alone. In addition, the character "/" in this article generally indicates that the contextual objects are an "or" relationship.

The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various Various other combinations, modifications and environments, and can be modified by the above teachings or the technology or knowledge in the related field within the scope of the application concept described herein. However, changes and changes made by those skilled in the art do not depart from the spirit and scope of the present application, and should all be within the protection scope of the appended claims of the present application.

Claims (2)

1. A method for reducing stainless steel pitting corrosion based on inclusion melting point control adopts a silicon-manganese deoxidizer for deoxidation, adopts low-aluminum and low-calcium alloy auxiliary materials, simultaneously adopts low-alkalinity refining slag for refining, modifies the refining slag to increase the content of manganese oxide in inclusions and reduce the melting point, finally carries out heat treatment and hot rolling, improves the liquid fraction of the inclusions in the hot rolling process, avoids the generation of gaps between the inclusions and a steel matrix in the rolling process, and prevents the inclusions from causing the stainless steel pitting corrosion behavior, and is characterized in that the method specifically comprises the following steps:

s1) in the last stage of AOD refining, adding a silicomanganese deoxidizer for deoxidation, and simultaneously adding a low-aluminum low-calcium alloy auxiliary material for alloying to control the slag amount during tapping;

the method specifically comprises the following steps: s1.1) carrying out a silicomanganese deoxidizer at the final stage of AOD refining, wherein the silicomanganese deoxidizer is high-purity silicon iron and electrolytic manganese,

s1.2) alloying low-aluminum low-calcium alloy auxiliary materials at the last stage of AOD refining, wherein the aluminum and calcium content in all the alloy auxiliary materials is below 0.1 percent, and the thickness of refining slag is stably reduced to 3-4 cm;

s2) in the LF refining process, modifying refining slag in the initial stage of refining, simultaneously carrying out soft blowing stirring, and standing a steel ladle for a period of time;

in particular to S2.1), in the initial stage of LF refining, the alkalinity of refining slag is reduced to 1.5-1.7 by adding high-purity quartz sand,

s2.2) adding manganese ore into the refining slag in the LF refining process to increase the MnO content in the refining slag to 4-8%,

s2.3) blowing argon into the molten steel at a certain flow rate for a certain time, carrying out soft blowing stirring, and standing for a certain time after stirring; the manganese ore is manganese oxide;

s3) in the continuous casting process, firstly introducing protective gas, and then casting under protective atmosphere to obtain a cast ingot;

protective casting is carried out in the continuous casting process, and argon is blown from 10 minutes before the pouring of the tundish to the stable casting process;

s4) in the hot rolling process, firstly carrying out heat treatment on the cast ingot, and then heating to a certain temperature for hot rolling to avoid generating gaps between inclusions and a steel matrix;

the method specifically comprises the following steps:

s4.1) the heat treatment temperature is 1200-1280 ℃, the heat treatment time is 40-60 minutes,

s4.2) carrying out hot rolling on the ingot subjected to the soaking treatment in the S4.1), wherein the hot rolling temperature is 1150-1250 ℃.

2. The method of claim 1, wherein the soft blowing time is 12-15 minutes, the argon blowing flow is 100-200NL/min, and the standing time is 15-20 minutes.

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