阅读说明：本技术 一种高耐蚀镀镁铝锌合金镀层钢板及其两步退火制备方法和应用 (High-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate and two-step annealing preparation method and application thereof ) 是由 杜昕 赵小龙 董世文 罗晓阳 田成辉 王瑾 刘晓华 于 2019-11-12 设计创作，主要内容包括：本发明涉及炼钢技术领域,公开了一种高耐蚀镀镁铝锌合金镀层钢板的两步退火制备方法,包括：将连铸连轧后的初步成型钢板依次进行罩式炉预退火、电解脱脂、立式退火炉退火及表面镀锌。还提供了通过此方法制得的高耐蚀镀镁铝锌合金镀层钢板,该钢板的表面稳定性好,耐蚀性好,冲压成型性好。还公开了上述钢板在生产钢铁产品或建筑领域中的应用。(The invention relates to the technical field of steelmaking, and discloses a two-step annealing preparation method of a high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate, which comprises the following steps: and sequentially carrying out bell-type furnace pre-annealing, electrolytic degreasing, vertical annealing furnace annealing and surface galvanizing on the preliminarily formed steel plate after continuous casting and rolling. The high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate prepared by the method is good in surface stability, corrosion resistance and stamping formability. Also discloses the application of the steel plate in the field of producing steel products or buildings.)

1. A two-step annealing preparation method of a high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate is characterized by comprising the following steps of:

and sequentially carrying out bell-type furnace pre-annealing, electrolytic degreasing, vertical annealing furnace annealing and surface galvanizing on the preliminarily formed steel plate after continuous casting and rolling.

2. The two-step annealing preparation method of the high corrosion-resistant magnesium-aluminum-zinc alloy plated steel plate according to claim 1, characterized in that, during the pre-annealing in the bell type furnace: setting the heating rate of the heating cover to be 35-45 ℃/h, heating to the temperature of 580-620 ℃, and keeping the temperature for at least 5 h; and carrying out primary cooling after the heat preservation is finished, controlling the cooling rate to be less than or equal to 30 ℃/h, changing the cooling cover of the heating cover after the temperature is reduced to 580 ℃, and discharging the furnace after the temperature is cooled to be less than or equal to 100 ℃.

3. The two-step annealing preparation method of the high corrosion-resistant magnesium-aluminum-zinc alloy plated steel sheet according to claim 1, wherein when the vertical annealing furnace is used for annealing: a vertical radiant tube is adopted to heat the continuous annealing furnace;

preferably, when the vertical annealing furnace is used for annealing, the speed of the strip steel in the annealing stage is set to be 80-90 m/min, the temperature of the plate in the soaking section is controlled to be 800-850 ℃, the heat preservation time is controlled to be 45-55 s, the temperature of the plate in the slow cooling section is 600-620 ℃, and the temperature of the plate in the zinc pot is 485-505 ℃;

preferably, the oxygen content in the furnace is less than 1000ppm, the mass percentage of the hydrogen is 6-8%, and the residual gas is nitrogen.

4. The two-step annealing preparation method of the high corrosion-resistant magnesium-aluminum-zinc alloy plated steel plate according to claim 1, wherein before annealing the continuous casting and rolling steel plate, the method further comprises the steps of sequentially performing LF molten steel refining treatment and RH molten steel refining treatment on the molten steel;

preferably, after LF molten steel refining treatment, the arrival temperature of RH molten steel refining treatment is guaranteed to be more than or equal to 1645 ℃;

preferably, after the RH molten steel refining treatment, a refined substrate with the following chemical components is obtained:

carbon is less than or equal to 0.0050 Wt%; silicon is less than or equal to 0.20 Wt%; manganese is less than or equal to 0.20 Wt%; phosphorus is less than or equal to 0.015 Wt%; sulfur is less than or equal to 0.010 Wt%; 0.030-0.050 Wt% of acid-melting aluminum; the sum of the contents of titanium and niobium is less than or equal to 0.10 Wt%, and the balance of iron and inevitable trace elements.

5. The two-step annealing preparation method of the high corrosion-resistant magnesium-aluminum-zinc alloy plated steel plate according to claim 4, wherein the preliminary formed steel plate is obtained by performing CSP thin slab continuous casting and rolling after RH molten steel refining treatment;

preferably, when the CSP thin slab is continuously cast and rolled: the tundish temperature is controlled to be 1550-1565 ℃, the casting blank drawing speed is controlled to be 4.5-4.8 m/min, the tapping temperature is controlled to be 1140-1180 ℃, the final rolling temperature is controlled to be 900-950 ℃, and the coiling temperature is controlled to be 600-650 ℃.

6. The two-step annealing preparation method of the high corrosion-resistant magnesium-aluminum-zinc alloy plated steel plate according to claim 1, wherein the annealing of the vertical annealing furnace is performed to obtain an annealed substrate, the surface of the annealed substrate is galvanized, and the plating material comprises: 8-12 Wt% of aluminum and 84.75-90.01 Wt% of zinc;

preferably, the coating material also comprises 2-3 Wt% of magnesium and 0.03-0.05 Wt% of nickel;

more preferably, the coating material further comprises 0.05-0.15 Wt% of silicon and 0.01-0.05 Wt% of germanium;

preferably, the coating amount of the material for forming the coating layer is 135-145 g/m²。

7. The two-step annealing preparation method of high corrosion-resistant magnesium-aluminum-zinc alloy coated steel plate according to claim 6, wherein the zinc coating is performed on the surface of the annealed substrate by a zinc pot coating method;

preferably, when the zinc pot is coated: ensuring that the temperature of a strip steel entering a zinc pot is 490-510 ℃, setting the speed of the strip steel to be the same as that of the annealing stage of a vertical annealing furnace, setting the temperature of the zinc pot to be 490-500 ℃, the dip plating time to be 3-7 s, the height of an air knife from a plating liquid surface to be 150-250 mm, the distance from a single-side air knife to a plate surface to be 10-20 mm, the pressure of the air knife to be 5-10Kpa, the temperature of a plating solution to be 485-495 ℃, and the cooling speed after plating;

preferably, nitrogen or inert gas is adopted for purging during cooling after plating, and more preferably, the gas flow rate during purging is 475-525 ml/min.

8. The two-step annealing preparation method of high corrosion-resistant magnesium-aluminum-zinc alloy coated steel plate according to claim 6, wherein the coating is coated and cooled and then the following steps are carried out in sequence: finishing and straightening, passivating, drying, electrostatic oiling and coiling.

9. A high corrosion-resistant magnesium-aluminum-zinc alloy plated steel sheet, characterized by being produced by the production method according to any one of claims 1 to 8.

10. Use of the high corrosion resistant magnesium aluminum zinc alloy coated steel sheet according to claim 9 in the production of steel products or in the construction field.

Technical Field

The invention relates to the technical field of steel making, in particular to a high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate and a two-step annealing preparation method and application thereof.

Background

The hot high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate has good corrosion resistance and processability, and is widely applied to the fields of buildings, household appliances and automobile manufacturing. The corrosion resistance of the high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate is in direct proportion to the thickness of the plated layer, and more zinc resources are consumed by improving the corrosion resistance of the high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate. In order to improve corrosion resistance, zinc plating on the surface of steel sheets has been developed in recent years to improve the surface properties of steel sheets.

The production method for producing the alloy coating steel plate at present generally comprises the following steps: blast furnace molten iron smelting → converter molten steel smelting → RH molten steel refining treatment → continuous casting and rolling → acid pickling and cold continuous rolling → electrolytic degreasing → annealing of vertical annealing furnace → zinc pot coating → cooling after coating → finishing, straightening and pulling → passivation → drying → electrostatic oil coating → coiling. The performance of the steel plate produced by the method still has room for further improvement.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention provides a high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate and a preparation method thereof, aiming at further improving the performance of the steel plate.

The invention is realized by the following steps:

in a first aspect, an embodiment of the present invention provides a two-step annealing preparation method for a high corrosion-resistant magnesium-aluminum-zinc alloy plated steel plate, including:

and sequentially carrying out bell-type furnace pre-annealing, electrolytic degreasing, vertical annealing furnace annealing and surface galvanizing on the preliminarily formed steel plate after continuous casting and rolling.

In an alternative embodiment, the bell-type furnace preanneals: setting the heating rate of the heating cover to be 35-45 ℃/h, heating to the temperature of 580-620 ℃, and keeping the temperature for at least 5 h; and carrying out primary cooling after the heat preservation is finished, controlling the cooling rate to be less than or equal to 30 ℃/h, changing the cooling cover of the heating cover after the temperature is reduced to 580 ℃, and discharging the furnace after the temperature is cooled to be less than or equal to 100 ℃.

In an alternative embodiment, the vertical annealing furnace, when annealing: a vertical radiant tube is adopted to heat the continuous annealing furnace;

in an optional embodiment, when the vertical annealing furnace is used for annealing, the speed of the strip steel in the annealing stage is set to be 80-90 m/min, the temperature of a plate in a soaking section is controlled to be 800-850 ℃, the heat preservation time is controlled to be 45-55 s, the temperature of a plate in a slow cooling section is 600-620 ℃, and the temperature of a plate in a zinc pot is 485-505 ℃;

in an optional embodiment, the oxygen content in the furnace is less than 1000ppm, the mass percentage of the hydrogen is 6-8%, and the residual gas is nitrogen.

In an optional embodiment, before annealing the continuously cast and rolled steel plate, the method further comprises the steps of sequentially performing LF molten steel refining treatment and RH molten steel refining treatment on the molten steel;

in an optional embodiment, after LF molten steel refining treatment, the arrival temperature of RH molten steel refining treatment is guaranteed to be more than or equal to 1645 ℃;

in an alternative embodiment, after the RH molten steel refining process, a refined substrate having the following chemical composition is obtained:

carbon is less than or equal to 0.0050 Wt%; silicon is less than or equal to 0.20 Wt%; manganese is less than or equal to 0.20 Wt%; phosphorus is less than or equal to 0.015 Wt%; sulfur is less than or equal to 0.010 Wt%; 0.030-0.050 Wt% of acid-melting aluminum; the sum of the contents of titanium and niobium is less than or equal to 0.10 Wt%, and the balance of iron and inevitable trace elements.

In an optional embodiment, after RH molten steel refining treatment, CSP thin slab continuous casting and rolling are carried out to obtain a primary forming steel plate;

in an alternative embodiment, in the case of continuous casting and rolling of a CSP sheet: the tundish temperature is controlled to be 1550-1565 ℃, the casting blank drawing speed is controlled to be 4.5-4.8 m/min, the tapping temperature is controlled to be 1140-1180 ℃, the final rolling temperature is controlled to be 900-950 ℃, and the coiling temperature is controlled to be 600-650 ℃.

In an alternative embodiment, the annealing substrate is obtained after annealing in the vertical annealing furnace, and the surface of the annealing substrate is galvanized, and the coating material comprises: 8-12 Wt% of aluminum and 84.75-90.01 Wt% of zinc;

preferably, the coating material also comprises 2-3 Wt% of magnesium and 0.03-0.05 Wt% of nickel;

more preferably, the coating material further comprises 0.05-0.15 Wt% of silicon and 0.01-0.05 Wt% of germanium;

in an alternative embodiment, the coating amount of the material for forming the plating layer is 135-145 g/m²。

In an optional embodiment, the galvanizing is carried out on the surface of the annealed substrate in a zinc pot coating mode;

preferably, when the zinc pot is coated: ensuring that the temperature of a strip steel entering a zinc pot is 490-510 ℃, setting the speed of the strip steel to be the same as that of the annealing stage of a vertical annealing furnace, setting the temperature of the zinc pot to be 490-500 ℃, the dip plating time to be 3-7 s, the height of an air knife from a plating liquid surface to be 150-250 mm, the distance from a single-side air knife to a plate surface to be 10-20 mm, the pressure of the air knife to be 5-10Kpa, the temperature of a plating solution to be 485-495 ℃, and the cooling speed after plating;

in an optional embodiment, nitrogen or inert gas is used for purging during cooling after plating, and more preferably, the gas flow rate during purging is 475-525 ml/min.

In an alternative embodiment, the coating is applied and cooled, followed in sequence by: finishing and straightening, passivating, drying, electrostatic oiling and coiling.

In a second aspect, the embodiment of the invention provides a high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate which is manufactured by adopting the manufacturing method of any one of the optional embodiments.

The third method, the embodiment of the invention, provides the application of the high corrosion resistant magnesium-aluminum-zinc alloy plated steel plate in the field of steel product production or construction.

The invention has the following beneficial effects:

according to the two-step annealing preparation method of the high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate, the cover annealing furnace and the vertical annealing furnace are sequentially annealed for annealing treatment after continuous casting and continuous rolling, the cover annealing furnace has the characteristics of slow heating rate and small superheat degree of a steel strip in the heating and cooling processes, the vertical annealing furnace has the characteristics of high heating rate and high heating temperature, and the two annealing modes are combined, so that the recrystallized structure of the annealed steel strip is more uniform, the equiaxial degree of crystal grains is higher, the size of the crystal grains is larger, the stamping forming performance of the steel plate is greatly improved, and the surface galvanization is performed after the annealing, so that the surface stability and the corrosion resistance of the steel plate can be obviously improved.

The high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate obtained by the design is prepared by the preparation method provided by the invention, so that the high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate has better surface stability, corrosion resistance and stamping formability. Is suitable for being applied to the fields of producing steel products or buildings.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention 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.

The following specifically describes a high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate provided by the present disclosure, and a two-step annealing preparation method and application thereof.

The embodiment of the invention provides a two-step annealing preparation method of a high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate, which comprises the following steps:

and sequentially carrying out bell-type furnace pre-annealing, electrolytic degreasing, vertical annealing furnace annealing and surface galvanizing on the preliminarily formed steel plate after continuous casting and rolling.

The two-step annealing preparation method of the high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate provided by the embodiment of the invention adopts a BAF cover type furnace for pre-annealing and a vertical annealing furnace for annealing after continuous casting and continuous rolling, the cover type annealing furnace has the characteristics of slow heating rate and small superheat degree of a steel strip in the heating and cooling processes, the vertical annealing furnace has the characteristics of high heating rate and high heating temperature, and the two annealing modes are combined, so that the recrystallized structure of the annealed steel strip is more uniform, the equiaxial degree of the crystal grains is higher, the size of the crystal grains is larger, and the surface quality and the stamping forming performance of the material are greatly. The two-step annealing process is obviously different from other methods of one-step annealing process, and the annealing method provided by the application can stabilize the surface of the material. The surface galvanizing can obviously improve the corrosion resistance of the steel plate.

Specifically, the preparation method sequentially comprises the following steps:

blast furnace molten iron smelting, converter molten steel smelting, LF molten steel refining treatment, RH molten steel refining treatment, CSP sheet billet continuous casting and rolling, acid pickling and cold continuous rolling, bell furnace pre-annealing, electrolytic degreasing, vertical annealing furnace annealing, zinc pot coating, cooling after coating, finishing and straightening, passivation, drying, electrostatic coating and coiling.

The refining treatment process is carried out according to the LF-RH process, so that the content of various impurity elements in the molten steel can be greatly reduced, particularly the carbon content can be reduced to be below 0.005 wt%, and the cold rolling raw material is produced by adopting a CSP sheet billet continuous casting and rolling production line.

In the LF molten steel refining treatment: carrying out aluminum deoxidation and calcium treatment on the molten steel in an LF furnace; according to the production rhythm of the RH process, the outbound temperature and time are well controlled, and the RH arrival temperature is ensured to be more than or equal to 1645 ℃.

In the RH molten steel refining treatment: vacuum degassing and component adjustment of molten steel in an RH furnace. CO and CO in the exhaust gas₂When the mass concentration is more than or equal to 8 percent, aluminum can be added for deoxidation alloying, and ferroniobium is added for niobium alloying after the aluminum addition cycle is more than or equal to 3 min; then, a calcium wire is added for calcium treatment, and a titanium wire is fed for alloying after the calcium treatment.

After the RH molten steel is refined, the following refining base plate with the chemical components in percentage by mass is obtained:

carbon is less than or equal to 0.0050 Wt%; silicon is less than or equal to 0.20 Wt%; manganese is less than or equal to 0.20 Wt%; phosphorus is less than or equal to 0.015 Wt%; sulfur is less than or equal to 0.010 Wt%; 0.030-0.050 Wt% of acid-melting aluminum; the sum of the contents of titanium and niobium is less than or equal to 0.10 Wt%, and the balance of iron and inevitable trace elements. The inevitable trace elements are impurities entering or being incapable of being removed in the preparation process, and the mass percentage of the inevitable trace elements is less than 0.01 percent and can be ignored.

Preferably, in order to further ensure the surface property of the prepared steel plate, when the bell-type furnace is pre-annealed: setting the heating rate of the heating cover to be 35-45 ℃/h, heating to the temperature of 580-620 ℃, and keeping the temperature for at least 5 h; and carrying out primary cooling after the heat preservation is finished, controlling the cooling rate to be less than or equal to 30 ℃/h, changing the cooling cover of the heating cover after the temperature is reduced to 580 ℃, and discharging the furnace after the temperature is cooled to be less than or equal to 100 ℃.

Preferably, in order to further ensure the surface performance of the prepared steel plate, when the vertical annealing furnace is used for annealing, the speed of the strip steel at the annealing section is 80-90 m/min, the annealing temperature is 800-850 ℃, the heat preservation time is 45-55 s, the temperature of the plate at the slow cooling section is 600-620 ℃, and the temperature of the plate in a zinc pot is 485-505 ℃; the temperature of each section is set mainly to ensure that the temperature of the zinc pot subsequently entering the zinc pot is within 490-510 ℃ during normal operation while the uniform annealing of the strip steel is ensured.

More preferably, the oxygen content in the furnace is less than 1000ppm, the mass percentage of the hydrogen is 6-8%, and the residual gas is nitrogen.

And performing annealing treatment twice to obtain an annealed substrate, and galvanizing the surface of the annealed substrate to enhance the performance of the steel plate.

Preferably, the plating material comprises: 8-12 Wt% of aluminum and 84.75-90.01 Wt% of zinc. The zinc-aluminum coating has the cathode protection capability of the zinc coating and the high corrosion resistance of the aluminum coating, the protection mechanism of aluminum element is mainly the passivation effect of corrosion product film, the zinc is more active than iron, when the zinc-aluminum coating is coated on the surface of iron and is subjected to electrochemical corrosion, the zinc is used as an anode, the iron is used as a cathode, and the purpose of sacrificing the anode and protecting the cathode can be achieved in the corrosion process.

Preferably, the coating material also comprises 2-3 Wt% of magnesium and 0.03-0.05 Wt% of nickel, the addition of the magnesium can reduce the corrosion potential of the coating and improve the protection effect of the coating on a cathode, and the addition of the nickel can improve the strength of the coating. Magnesium and nickel are added together, so that magnesium and nickel element enrichment can be formed on the surface of the coating, the oxidation resistance and corrosion resistance of the surface of the steel plate coating are effectively improved, and the blackening resistance of the steel plate coating is improved.

Preferably, the coating material further comprises 0.05-0.15 Wt% of silicon and 0.01-0.05 Wt% of germanium. Addition of appropriate amount of siliconForming Mg with Mg element in alloy coating₂Si can provide more durable cathodic protection, and germanium is added into the material as a rare earth element and is matched with aluminum and zinc to refine the coating structure and improve the coating adhesiveness, welding performance and processing performance.

It should be noted that, during the coating process, there are impurity elements entering the coating, but the content of the impurity elements in the coating is less than 0.02 Wt%, which can be ignored.

Preferably, in order to ensure better performance of the steel plate obtained after coating, the coating amount of the material for forming the coating is 135-145 g/m². Of course, in other embodiments of the present invention, the coating amount may be outside this range, which is mainly selected according to the practical application environment of the steel sheet.

Preferably, in order to ensure that the performance of the coating formed by coating is better and the adhesion performance of the coating and the annealed substrate is better, the coating is coated in a zinc pot coating mode. More preferably, when the zinc pot is coated: the temperature of a strip steel entering a zinc pot is kept at 490-510 ℃, the speed of the strip steel is kept the same as that of the annealing stage of a vertical annealing furnace, the temperature of the zinc pot is set at 490-500 ℃, the dip plating time is 3-7 s, the height of an air knife from a plating liquid surface is 150-250 mm, the distance from a single-side air knife to a plate surface is 10-20 mm, the pressure of the air knife is 5-10Kpa, the cooling speed after plating is greater than 10-15 ℃/s, and the temperature of a plating solution is 485. When the normal operation of the equipment is common, the temperature of the zinc-in pan of the vertical annealing furnace is set to be 485-505 ℃, the temperature of the strip steel in the zinc-in pan can be guaranteed to be 490-510 ℃, if the strip steel is cooled due to shutdown under special conditions, the strip steel needs to be heated to 490-510 ℃ before the cooled strip steel is put in the zinc-in pan. When the temperature of the strip steel in the zinc pot is set within the range, the temperature of the strip steel and the temperature of the plating solution are not greatly different, so that the crystal phase structure of the alloy plating layer formed after coating is poor.

Preferably, the coating is cooled after being coated, and in order to avoid the reaction between the high-temperature coating and substances in the air during cooling, nitrogen is adopted for purging, and more preferably, the nitrogen flow is 475-525 ml/min.

The high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate provided by the embodiment of the invention is prepared by adopting the two-step annealing preparation method of the high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate provided by the invention.

The high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate is prepared by the preparation method provided by the invention, so that the high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate has excellent stamping forming performance and surface stability.

Preferably, the steel plate comprises the following chemical components in percentage by weight:

the high-corrosion-resistance magnesium-aluminum-zinc alloy plated steel plate provided by the embodiment of the invention can be applied to the production of steel products or the field of buildings.

The features and properties of the present invention are described in further detail below with reference to examples.