Zinc-aluminum-magnesium alloy powder diffusion-coated steel plate and preparation method thereof

Abstract

The invention discloses a zinc-aluminum-magnesium alloy powder diffusion-coated steel plate and a preparation method thereof.The preparation method comprises the steps that the surface of a steel plate base material is pretreated, a pretreated steel plate is obtained, then the pretreated steel plate is transferred to a co-diffusion furnace and embedded in zinc-aluminum-magnesium alloy powder, heating diffusion coating is conducted, and a primary diffusion-coated steel plate is obtained; placing the primary diffusion-coated steel plate in a multi-arc ion plating machine, and forming a zirconium-titanium layer on the surface of the primary diffusion-coated steel plate by taking a zirconium target and a titanium target as target materials and high-purity nitrogen as reaction gas to obtain a secondary diffusion-coated steel plate; and finally, transferring the secondary diffusion-coated steel plate to a co-diffusion furnace, embedding the secondary diffusion-coated steel plate in cubic boron nitride micro powder, and carrying out heating diffusion coating and quenching. According to the preparation method, protection is formed on the steel plate through diffusion coating, the corrosion resistance of the steel plate is effectively improved, and the long-term use requirement in the marine environment is met.

Description

Technical Field

[0001] This invention relates to a zinc-aluminum-magnesium alloy powder-coated steel sheet and its preparation method. It belongs to the field of steel sheet preparation technology. Background Technology

[0002] With economic development and the construction of engineering facilities, the demand for steel plates is increasing. Marine engineering construction requires a large amount of steel plates as frame supports or pillars. As is well known, the marine environment is characterized by high salinity, high humidity, and sea breeze erosion, making it extremely corrosive to metal materials. Long-term immersion in seawater, corrosion, and oxidation from the air will cause steel plates to rust, deteriorate their mechanical properties, ultimately leading to workpiece failure, posing safety hazards, and causing huge losses. Therefore, improving corrosion resistance is paramount for steel plates used in marine engineering construction.

[0003] Galvanized steel sheets are inexpensive, have excellent performance, and are widely used. In marine environments, the zinc layer of galvanized steel sheets initially reacts with chloride ions and oxygen in seawater to form corrosion products, which to some extent inhibits subsequent corrosion. However, with prolonged exposure to the marine environment, the zinc layer is gradually consumed, eventually leading to corrosion and perforation. To improve the corrosion resistance of galvanized steel sheets, chromate passivation is commonly used for passivation protection. However, chromates severely pollute the environment and are highly toxic to humans, making them less than environmentally friendly.

[0004] Patent application CN106637184A discloses a process for preparing corrosion-resistant steel plates. The process involves impact grinding of the steel plate surface with alumina or corundum to roughen it and provide space for alumina powder to fill. Alumina powder with a particle size of 5-10 μm is then coated and used to fill the steel plate surface. The alumina-coated steel plate is then heated at 800-1200℃ for 10-20 minutes to ensure a tight bond between the alumina and the steel plate, and finally, fine grinding is performed to achieve a smooth surface. This patent application primarily achieves corrosion resistance through a surface alumina layer or by further coating the surface with a corrosion-resistant material PTEE. However, the corrosion resistance of this steel plate is generally limited and cannot meet the requirements for use in marine environments.

[0005] Patent CN116875938B discloses a corrosion-resistant composite steel plate and its preparation process. The process involves processing molten steel to obtain a steel plate; then, using silicon powder, ferrosilicon powder, and coal gangue powder as main infiltrating agents, the steel plate is heated and infiltrated with silicon to obtain a modified steel plate; the modified steel plate is pretreated, and then a coating is applied to its surface to obtain the finished product. This patented technology uses a coating prepared from modified water-based acrylic emulsion and curing agent amino resin to achieve corrosion protection for the steel plate. However, long-term use in a marine environment carries the risk of peeling off, resulting in the loss of its protective effect. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a zinc-aluminum-magnesium alloy powder-coated steel sheet and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing zinc-aluminum-magnesium alloy powder-coated steel sheet, the specific steps of which are as follows:

[0009] (1) First, the surface of the steel plate substrate is pretreated to obtain a pretreated steel plate. Then, the pretreated steel plate is transferred to a co-diffusion furnace and embedded in zinc-aluminum-magnesium alloy powder. It is heated and diffused to obtain a first-diffusion-coated steel plate.

[0010] (2) Then, the first-dip-coated steel plate is placed in a multi-arc ion plating machine, using zircon and titanium targets as target materials and high-purity nitrogen as reaction gas to form a zircon-titanium layer on the surface of the first-dip-coated steel plate, thus obtaining a second-dip-coated steel plate.

[0011] (3) Finally, the secondary diffusion-coated steel plate is transferred to the co-diffusion furnace and embedded in cubic boron nitride micro powder. It is heated for diffusion coating and then quenched to obtain the zinc-aluminum-magnesium alloy powder diffusion-coated steel plate.

[0012] Preferably, in step (1), the pretreatment method is as follows: grind the surface of the steel plate until the surface roughness is less than Ra0.05, completely immerse the steel plate in acetone, and treat it with ultrasonic vibration at 400-500W for 10-12 minutes, then completely immerse it in 1mol / L sodium hydroxide solution, and treat it with ultrasonic vibration at 400-500W for 5-6 minutes, take it out and wash it with water until neutral, rinse it with 1mol / L hydrochloric acid solution for 1-2 minutes, rinse it with 1mol / L sulfuric acid solution for 20-30 seconds, and wash it with water until neutral.

[0013] Preferably, in step (1), the mass ratio of zinc, aluminum and magnesium in the zinc-aluminum-magnesium alloy powder is 50-60:10-20:3-5.

[0014] Preferably, in step (1), the ratio of the mass of zinc-aluminum-magnesium alloy powder to the surface area of ​​one side of the pretreated steel plate is 700-900 kg: 1 m². 2 .

[0015] Preferably, in step (1), the heating and diffusion plating process conditions are as follows: the co-diffusion furnace rotation speed is 2-4 r / min, the pressure inside the co-diffusion furnace is 0.1-0.2 Pa, heating at 15-20℃ / min to 300-320℃, holding at that temperature for 1-2 hours, heating at 5-8℃ / min to 400-420℃, holding at that temperature for 3-4 hours, and then naturally cooling to room temperature before taking it out.

[0016] Preferably, the specific process of step (2) is as follows:

[0017] (2-1) Place the steel plate that has been dip-coated once in a multi-arc ion plating machine, evacuate the vacuum chamber until the pressure is less than 0.1 Pa, and heat it at a constant rate to 480-500℃ for 1-2 hours.

[0018] (2-2) Targets No. 1 and No. 3 are titanium targets, and targets No. 2 and No. 4 are zirconium targets. All doors of targets No. 2 and No. 4 are opened. The bias voltage is 150-200V. Nitrogen and acetylene are introduced into the vacuum chamber. The flow rate of nitrogen is 300-320sccm and the flow rate of acetylene is 20-30sccm.

[0019] (2-3) Open all doors of target material No. 2 and No. 4, open doors of target material No. 1 and No. 3 halfway, set the bias voltage to 80-100V, and introduce nitrogen into the vacuum chamber at a flow rate of 400-420sccm.

[0020] (2-4) Open all the doors of target material No. 1, No. 2, No. 3 and No. 4, set the bias voltage to 100-120V, and introduce nitrogen into the vacuum chamber at a flow rate of 350-370 sccm.

[0021] (2-5) Open all doors of target material No. 2 and No. 4, set the bias voltage to 80-100V, and introduce nitrogen into the vacuum chamber at a flow rate of 380-400 sccm.

[0022] Preferably, in step (3), the particle size of the cubic boron nitride micro powder is ≤1μm.

[0023] Preferably, in step (3), the ratio of the mass of cubic boron nitride micro powder to the single-sided surface area of ​​the secondary diffusion-coated steel plate is 750–850 kg: 1 m². 2 .

[0024] Preferably, in step (3), the heating and diffusion process conditions are as follows: the co-diffusion furnace rotation speed is 3-5 r / min, the pressure inside the co-diffusion furnace is 0.1-0.2 Pa, the temperature is heated to 800-850℃ at 15-20℃ / min, the temperature is held for 5-7 hours, and the temperature is naturally cooled to room temperature before it is taken out.

[0025] Preferably, in step (3), the quenching medium is mineral oil and the quenching temperature is 880-900℃.

[0026] A zinc-aluminum-magnesium alloy powder-coated steel sheet is obtained by the aforementioned preparation method.

[0027] The aforementioned application of zinc-aluminum-magnesium alloy powder-coated steel sheet in marine engineering.

[0028] The beneficial effects of this invention are:

[0029] This invention provides a zinc-aluminum-magnesium alloy powder-coated steel sheet and its preparation method. First, the surface of the steel substrate is pretreated to obtain a pretreated steel sheet. Then, the pretreated steel sheet is transferred to a co-diffusion furnace and embedded in zinc-aluminum-magnesium alloy powder, and heated for diffusing, resulting in a first-stage diffusing steel sheet. Next, the first-stage diffusing steel sheet is placed in a multi-arc ion plating machine, using zirconium and titanium targets as targets and high-purity nitrogen as the reactant gas, to form a zirconium-titanium layer on the surface of the first-stage diffusing steel sheet, resulting in a second-stage diffusing steel sheet. Finally, the second-stage diffusing steel sheet is transferred to a co-diffusion furnace and embedded in cubic boron nitride micropowder, heated for diffusing, and quenched to obtain the final product. The preparation method of this invention forms a protective layer on the steel sheet through diffusing, effectively improving the corrosion resistance of the steel sheet and meeting the requirements for long-term use in marine environments.

[0030] This invention combines two co-diffusion furnace plating processes with a single multi-arc ion plating process, creating a multi-layer composite that enhances the corrosion resistance of steel plates.

[0031] Zinc-aluminum-magnesium alloy powder infiltration provides basic corrosion resistance to steel plates, and multi-arc ion plating results in strong adhesion and high density. This invention uses zirconium and titanium targets as target materials, forming a zirconium-titanium layer through multi-arc ion plating to further improve corrosion resistance. Finally, this invention utilizes cubic boron nitride micropowder for heated infiltration plating, further enhancing the corrosion resistance of the steel plate. Detailed Implementation

[0032] The present invention will be further described below with reference to embodiments. It should be noted that the following description is only for explaining the present invention and does not limit its content.

[0033] Example 1:

[0034] A method for preparing zinc-aluminum-magnesium alloy powder-coated steel sheet, the specific steps of which are as follows:

[0035] (1) First, the surface of the steel plate substrate is pretreated to obtain a pretreated steel plate. Then, the pretreated steel plate is transferred to a co-diffusion furnace and embedded in zinc-aluminum-magnesium alloy powder. It is heated and diffused to obtain a first-diffusion-coated steel plate.

[0036] (2) Then, the first-dip-coated steel plate is placed in a multi-arc ion plating machine, using zircon and titanium targets as target materials and high-purity nitrogen as reaction gas to form a zircon-titanium layer on the surface of the first-dip-coated steel plate, thus obtaining a second-dip-coated steel plate.

[0037] (3) Finally, the secondary diffusion-coated steel plate is transferred to the co-diffusion furnace and embedded in cubic boron nitride micro powder. It is heated for diffusion coating and then quenched to obtain the zinc-aluminum-magnesium alloy powder diffusion-coated steel plate.

[0038] In step (1), the pretreatment method is as follows: grind the surface of the steel plate until the surface roughness is less than Ra0.05, immerse the steel plate completely in acetone, ultrasonically vibrate it for 10 minutes at 400W, then immerse it completely in 1mol / L sodium hydroxide solution, ultrasonically vibrate it for 5 minutes at 400W, take it out and wash it with water until neutral, rinse it with 1mol / L hydrochloric acid solution for 1 minute, rinse it with 1mol / L sulfuric acid solution for 20 seconds, and wash it with water until neutral.

[0039] The zinc-aluminum-magnesium alloy powder contains zinc, aluminum, and magnesium in a mass ratio of 50:10:3.

[0040] The ratio of the mass of zinc-aluminum-magnesium alloy powder to the single-sided surface area of ​​the pretreated steel plate is 700 kg: 1 m². 2 .

[0041] The process conditions for heating and diffusion plating are as follows: the co-diffusion furnace rotation speed is 2 r / min, the pressure inside the co-diffusion furnace is 0.1 Pa, heating to 300℃ at 15℃ / min and holding for 1 hour, heating to 400℃ at 5℃ / min and holding for 3 hours, and then naturally cooling to room temperature before removal.

[0042] The specific process of step (2) is as follows:

[0043] (2-1) Place the steel plate that has been dip-coated once in a multi-arc ion plating machine, evacuate the vacuum chamber until the pressure is less than 0.1 Pa, and heat it to 480℃ at a constant rate for 1 hour.

[0044] (2-2) Targets No. 1 and No. 3 are titanium targets, and targets No. 2 and No. 4 are zirconium targets. All doors of targets No. 2 and No. 4 are opened. The bias voltage is 150V. Nitrogen and acetylene are introduced into the vacuum chamber. The flow rate of nitrogen is 300sccm and the flow rate of acetylene is 20sccm.

[0045] (2-3) Open all doors of target material No. 2 and No. 4, open doors of target material No. 1 and No. 3 halfway, set the bias voltage to 80V, and introduce nitrogen into the vacuum chamber at a flow rate of 400sccm.

[0046] (2-4) Open all the doors of target material No. 1, No. 2, No. 3 and No. 4, set the bias voltage to 100V, and introduce nitrogen into the vacuum chamber at a flow rate of 350sccm.

[0047] (2-5) Open all doors of target material No. 2 and No. 4, set the bias voltage to 80V, and introduce nitrogen into the vacuum chamber at a flow rate of 380sccm.

[0048] In step (3), the particle size of cubic boron nitride micro powder is ≤1μm.

[0049] The mass ratio of cubic boron nitride micro powder to the single-sided surface area of ​​the secondary diffusion-coated steel plate is 750 kg: 1 m². 2 .

[0050] The process conditions for heating and diffusion plating are as follows: the co-diffusion furnace rotation speed is 3 r / min, the pressure inside the co-diffusion furnace is 0.1 Pa, the temperature is raised to 800℃ at 15℃ / min, the temperature is held for 5 hours, and the temperature is allowed to cool naturally to room temperature before removal.

[0051] The quenching medium is mineral oil, and the quenching temperature is 880℃.

[0052] Example 2:

[0053] A method for preparing zinc-aluminum-magnesium alloy powder-coated steel sheet, the specific steps of which are as follows:

[0054] (1) First, the surface of the steel plate substrate is pretreated to obtain a pretreated steel plate. Then, the pretreated steel plate is transferred to a co-diffusion furnace and embedded in zinc-aluminum-magnesium alloy powder. It is heated and diffused to obtain a first-diffusion-coated steel plate.

[0055] (2) Then, the first-dip-coated steel plate is placed in a multi-arc ion plating machine, using zircon and titanium targets as target materials and high-purity nitrogen as reaction gas to form a zircon-titanium layer on the surface of the first-dip-coated steel plate, thus obtaining a second-dip-coated steel plate.

[0056] (3) Finally, the secondary diffusion-coated steel plate is transferred to the co-diffusion furnace and embedded in cubic boron nitride micro powder. It is heated for diffusion coating and then quenched to obtain the zinc-aluminum-magnesium alloy powder diffusion-coated steel plate.

[0057] In step (1), the pretreatment method is as follows: grind the surface of the steel plate until the surface roughness is less than Ra0.05, immerse the steel plate completely in acetone, ultrasonically vibrate it for 12 minutes at 500W, then immerse it completely in 1mol / L sodium hydroxide solution, ultrasonically vibrate it for 6 minutes at 500W, take it out and wash it with water until neutral, rinse it with 1mol / L hydrochloric acid solution for 2 minutes, rinse it with 1mol / L sulfuric acid solution for 30 seconds, and wash it with water until neutral.

[0058] The zinc-aluminum-magnesium alloy powder contains zinc, aluminum, and magnesium in a mass ratio of 60:20:5.

[0059] The ratio of the mass of zinc-aluminum-magnesium alloy powder to the single-sided surface area of ​​the pretreated steel plate is 900 kg: 1 m². 2 .

[0060] The process conditions for heating and diffusion plating are as follows: the co-diffusion furnace rotation speed is 4 r / min, the pressure inside the co-diffusion furnace is 0.2 Pa, heating to 320℃ at 20℃ / min and holding for 2 hours, heating to 420℃ at 8℃ / min and holding for 4 hours, and then naturally cooling to room temperature before removal.

[0061] The specific process of step (2) is as follows:

[0062] (2-1) Place the steel plate that has been dip-coated once in a multi-arc ion plating machine, evacuate the vacuum chamber until the pressure is less than 0.1 Pa, and heat it to 500℃ at a constant speed for 2 hours.

[0063] (2-2) Targets No. 1 and No. 3 are titanium targets, and targets No. 2 and No. 4 are zirconium targets. All doors of targets No. 2 and No. 4 are opened. The bias voltage is 200V. Nitrogen and acetylene are introduced into the vacuum chamber. The flow rate of nitrogen is 320sccm and the flow rate of acetylene is 30sccm.

[0064] (2-3) Open all doors of target material No. 2 and No. 4, open doors of target material No. 1 and No. 3 halfway, set the bias voltage to 100V, and introduce nitrogen into the vacuum chamber at a flow rate of 420sccm.

[0065] (2-4) Open all the doors of target material No. 1, No. 2, No. 3 and No. 4, set the bias voltage to 120V, and introduce nitrogen into the vacuum chamber at a flow rate of 370sccm.

[0066] (2-5) Open all doors of target material No. 2 and No. 4, set the bias voltage to 100V, and introduce nitrogen into the vacuum chamber at a flow rate of 400sccm.

[0067] In step (3), the particle size of cubic boron nitride micro powder is ≤1μm.

[0068] The mass ratio of cubic boron nitride micro powder to the single-sided surface area of ​​the secondary diffusion-coated steel plate is 850 kg: 1 m². 2 .

[0069] The process conditions for heating and diffusion plating are as follows: the co-diffusion furnace rotation speed is 5 r / min, the pressure inside the co-diffusion furnace is 0.2 Pa, the temperature is raised to 850℃ at 20℃ / min, held for 7 hours, and then allowed to cool naturally to room temperature before being removed.

[0070] The quenching medium is mineral oil, and the quenching temperature is 900℃.

[0071] Example 3:

[0072] A method for preparing zinc-aluminum-magnesium alloy powder-coated steel sheet, the specific steps of which are as follows:

[0073] (1) First, the surface of the steel plate substrate is pretreated to obtain a pretreated steel plate. Then, the pretreated steel plate is transferred to a co-diffusion furnace and embedded in zinc-aluminum-magnesium alloy powder. It is heated and diffused to obtain a first-diffusion-coated steel plate.

[0074] (2) Then, the first-dip-coated steel plate is placed in a multi-arc ion plating machine, using zircon and titanium targets as target materials and high-purity nitrogen as reaction gas to form a zircon-titanium layer on the surface of the first-dip-coated steel plate, thus obtaining a second-dip-coated steel plate.

[0075] (3) Finally, the secondary diffusion-coated steel plate is transferred to the co-diffusion furnace and embedded in cubic boron nitride micro powder. It is heated for diffusion coating and then quenched to obtain the zinc-aluminum-magnesium alloy powder diffusion-coated steel plate.

[0076] In step (1), the pretreatment method is as follows: grind the surface of the steel plate until the surface roughness is less than Ra0.05, immerse the steel plate completely in acetone, ultrasonically vibrate it for 11 minutes at 500W, then immerse it completely in 1mol / L sodium hydroxide solution, ultrasonically vibrate it for 5 minutes at 500W, take it out and wash it with water until neutral, rinse it with 1mol / L hydrochloric acid solution for 1 minute, rinse it with 1mol / L sulfuric acid solution for 25 seconds, and wash it with water until neutral.

[0077] The zinc-aluminum-magnesium alloy powder contains zinc, aluminum, and magnesium in a mass ratio of 55:15:4.

[0078] The ratio of the mass of zinc-aluminum-magnesium alloy powder to the single-sided surface area of ​​the pretreated steel plate is 800 kg: 1 m². 2 .

[0079] The process conditions for heating and diffusion plating are as follows: the co-diffusion furnace rotation speed is 3 r / min, the pressure inside the co-diffusion furnace is 0.1 Pa, heating to 310℃ at 18℃ / min and holding for 1.5 hours, heating to 410℃ at 7℃ / min and holding for 3 hours, and then naturally cooling to room temperature before removal.

[0080] The specific process of step (2) is as follows:

[0081] (2-1) Place the steel plate that has been dip-coated once in a multi-arc ion plating machine, evacuate the vacuum chamber until the pressure is less than 0.1 Pa, and heat it to 490℃ at a constant rate for 2 hours.

[0082] (2-2) Targets No. 1 and No. 3 are titanium targets, and targets No. 2 and No. 4 are zirconium targets. All doors of targets No. 2 and No. 4 are opened. The bias voltage is 180V. Nitrogen and acetylene are introduced into the vacuum chamber. The flow rate of nitrogen is 310sccm and the flow rate of acetylene is 25sccm.

[0083] (2-3) Open all doors of target material No. 2 and No. 4, open doors of target material No. 1 and No. 3 halfway, set the bias voltage to 90V, and introduce nitrogen into the vacuum chamber at a flow rate of 410sccm.

[0084] (2-4) Open all the doors of target material No. 1, No. 2, No. 3 and No. 4, set the bias voltage to 110V, and introduce nitrogen into the vacuum chamber at a flow rate of 360sccm.

[0085] (2-5) Open all doors of target material No. 2 and No. 4, set the bias voltage to 90V, and introduce nitrogen into the vacuum chamber at a flow rate of 390sccm.

[0086] In step (3), the particle size of cubic boron nitride micro powder is ≤1μm.

[0087] The mass ratio of cubic boron nitride micro powder to the single-sided surface area of ​​the secondary diffusion-coated steel plate is 800 kg: 1 m². 2 .

[0088] The process conditions for heating and diffusion plating are as follows: the co-diffusion furnace rotation speed is 4 r / min, the pressure inside the co-diffusion furnace is 0.2 Pa, the temperature is raised to 820℃ at 17℃ / min, held for 6 hours, and then allowed to cool naturally to room temperature before being removed.

[0089] The quenching medium is mineral oil, and the quenching temperature is 890℃.

[0090] Comparative Example 1

[0091] A method for preparing zinc-aluminum-magnesium alloy powder-coated steel sheet, the specific steps of which are as follows:

[0092] (1) First, the surface of the steel plate substrate is pretreated to obtain a pretreated steel plate. Then, the pretreated steel plate is transferred to a co-diffusion furnace and embedded in zinc-aluminum-magnesium alloy powder. It is heated and diffused to obtain a first-diffusion-coated steel plate.

[0093] (2) Then the first-dimerized steel plate is transferred to another co-dimerization furnace and embedded in cubic boron nitride micro powder, heated for dimerization, and quenched to obtain the zinc-aluminum-magnesium alloy powder-dimerized steel plate.

[0094] In step (1), the pretreatment method is as follows: grind the surface of the steel plate until the surface roughness is less than Ra0.05, immerse the steel plate completely in acetone, ultrasonically vibrate it for 10 minutes at 400W, then immerse it completely in 1mol / L sodium hydroxide solution, ultrasonically vibrate it for 5 minutes at 400W, take it out and wash it with water until neutral, rinse it with 1mol / L hydrochloric acid solution for 1 minute, rinse it with 1mol / L sulfuric acid solution for 20 seconds, and wash it with water until neutral.

[0095] The zinc-aluminum-magnesium alloy powder contains zinc, aluminum, and magnesium in a mass ratio of 50:10:3.

[0096] The ratio of the mass of zinc-aluminum-magnesium alloy powder to the single-sided surface area of ​​the pretreated steel plate is 700 kg: 1 m². 2 .

[0097] The process conditions for heating and diffusion plating are as follows: the co-diffusion furnace rotation speed is 2 r / min, the pressure inside the co-diffusion furnace is 0.1 Pa, heating to 300℃ at 15℃ / min and holding for 1 hour, heating to 400℃ at 5℃ / min and holding for 3 hours, and then naturally cooling to room temperature before removal.

[0098] In step (2), the particle size of cubic boron nitride micro powder is ≤1μm.

[0099] The mass ratio of cubic boron nitride micro powder to the single-sided surface area of ​​a steel plate subjected to primary diffusion coating is 750 kg: 1 m². 2 .

[0100] The process conditions for heating and diffusion plating are as follows: the co-diffusion furnace rotation speed is 3 r / min, the pressure inside the co-diffusion furnace is 0.1 Pa, the temperature is raised to 800℃ at 15℃ / min, the temperature is held for 5 hours, and the temperature is allowed to cool naturally to room temperature before removal.

[0101] The quenching medium is mineral oil, and the quenching temperature is 880℃.

[0102] Comparative Example 2

[0103] A method for preparing zinc-aluminum-magnesium alloy powder-coated steel sheet, the specific steps of which are as follows:

[0104] (1) First, the surface of the steel plate substrate is pretreated to obtain a pretreated steel plate. Then, the pretreated steel plate is transferred to a co-diffusion furnace and embedded in zinc-aluminum-magnesium alloy powder. It is heated and diffused to obtain a first-diffusion-coated steel plate.

[0105] (2) Then, the first-dip-coated steel plate is placed in a multi-arc ion plating machine, using zirconium and titanium targets as targets and high-purity nitrogen as the reaction gas, to form a zirconium-titanium layer on the surface of the first-dip-coated steel plate, thus obtaining a zinc-aluminum-magnesium alloy powder-coated steel plate.

[0106] In step (1), the pretreatment method is as follows: grind the surface of the steel plate until the surface roughness is less than Ra0.05, immerse the steel plate completely in acetone, ultrasonically vibrate it for 10 minutes at 400W, then immerse it completely in 1mol / L sodium hydroxide solution, ultrasonically vibrate it for 5 minutes at 400W, take it out and wash it with water until neutral, rinse it with 1mol / L hydrochloric acid solution for 1 minute, rinse it with 1mol / L sulfuric acid solution for 20 seconds, and wash it with water until neutral.

[0107] The zinc-aluminum-magnesium alloy powder contains zinc, aluminum, and magnesium in a mass ratio of 50:10:3.

[0108] The ratio of the mass of zinc-aluminum-magnesium alloy powder to the single-sided surface area of ​​the pretreated steel plate is 700 kg: 1 m². 2 .

[0109] The process conditions for heating and diffusion plating are as follows: the co-diffusion furnace rotation speed is 2 r / min, the pressure inside the co-diffusion furnace is 0.1 Pa, heating to 300℃ at 15℃ / min and holding for 1 hour, heating to 400℃ at 5℃ / min and holding for 3 hours, and then naturally cooling to room temperature before removal.

[0110] The specific process of step (2) is as follows:

[0111] (2-1) Place the steel plate that has been dip-coated once in a multi-arc ion plating machine, evacuate the vacuum chamber until the pressure is less than 0.1 Pa, and heat it to 480℃ at a constant rate for 1 hour.

[0112] (2-2) Targets No. 1 and No. 3 are titanium targets, and targets No. 2 and No. 4 are zirconium targets. All doors of targets No. 2 and No. 4 are opened. The bias voltage is 150V. Nitrogen and acetylene are introduced into the vacuum chamber. The flow rate of nitrogen is 300sccm and the flow rate of acetylene is 20sccm.

[0113] (2-3) Open all doors of target material No. 2 and No. 4, open doors of target material No. 1 and No. 3 halfway, set the bias voltage to 80V, and introduce nitrogen into the vacuum chamber at a flow rate of 400sccm.

[0114] (2-4) Open all the doors of target material No. 1, No. 2, No. 3 and No. 4, set the bias voltage to 100V, and introduce nitrogen into the vacuum chamber at a flow rate of 350sccm.

[0115] (2-5) Open all doors of target material No. 2 and No. 4, set the bias voltage to 80V, and introduce nitrogen into the vacuum chamber at a flow rate of 380sccm.

[0116] The properties of the steel plates obtained in Examples 1-3 and Comparative Examples 1 and 2 were tested respectively. For ease of comparison, Q355B was selected as the base material for all steel plates. Specifically, the tests included:

[0117] 1. Test the impact energy (KV2) at 0℃ according to GB / T229-2020 "Metallic Materials Charpy Pendulum Impact Test Method".

[0118] 2. Under the conditions of 35℃ temperature, 70%RH humidity and sodium chloride salt spray corrosion, a weight loss corrosion test was conducted, with the steel plate substrate as a control, and the relative value of the weight loss corrosion rate was calculated.

[0119] The test results are shown in Table 1.

[0120] Table 1. Steel Plate Performance Testing

[0121] <![CDATA[Charpy impact energy KV2 / J at 0 °C]]> Relative value of weight loss corrosion rate / % Example 1 307 7 Example 2 309 7 Example 3 315 5 Comparative Example 1 296 21 Comparative Example 2 264 20

[0122] As shown in Table 1, the steel plates obtained in Examples 1 to 3 have excellent impact resistance and corrosion resistance, and can adapt to the impact of waves and seawater erosion in the marine environment.

[0123] Comparative Example 1 omitted the preparation of the zirconium-titanium layer, and Comparative Example 2 omitted the heating and diffusion plating of cubic boron nitride micropowder. Both the impact resistance and corrosion resistance were significantly worse, indicating that the multi-layer protection of the present invention works together to improve the performance of the steel plate.

[0124] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A method for preparing a zinc-aluminum-magnesium alloy powder-coated steel sheet, characterized in that, The specific steps are as follows: (1) First, the surface of the steel plate substrate is pretreated to obtain a pretreated steel plate. Then, the pretreated steel plate is transferred to a co-diffusion furnace and embedded in zinc-aluminum-magnesium alloy powder. It is heated and diffused to obtain a first-diffusion-coated steel plate. (2) Then, the first-dip-coated steel plate is placed in a multi-arc ion plating machine, using zircon and titanium targets as target materials and high-purity nitrogen as reaction gas to form a zircon-titanium layer on the surface of the first-dip-coated steel plate, thus obtaining a second-dip-coated steel plate. (3) Finally, the secondary diffusion-coated steel plate is transferred to the co-diffusion furnace and embedded in cubic boron nitride micro powder. It is heated for diffusion coating and then quenched to obtain the zinc-aluminum-magnesium alloy powder diffusion-coated steel plate.

2. The preparation method according to claim 1, characterized in that, In step (1), the pretreatment method is as follows: grind the surface of the steel plate until the surface roughness is less than Ra0.05, completely immerse the steel plate in acetone, and treat it with ultrasonic vibration at 400-500W for 10-12 minutes, then completely immerse it in 1mol / L sodium hydroxide solution and treat it with ultrasonic vibration at 400-500W for 5-6 minutes. After taking it out, wash it with water until neutral, rinse it with 1mol / L hydrochloric acid solution for 1-2 minutes, rinse it with 1mol / L sulfuric acid solution for 20-30 seconds, and wash it with water until neutral.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of zinc, aluminum and magnesium in the zinc-aluminum-magnesium alloy powder is 50-60:10-20:3-5.

4. The preparation method according to claim 1, characterized in that, In step (1), the ratio of the mass of zinc-aluminum-magnesium alloy powder to the surface area of ​​one side of the pretreated steel plate is 700-900 kg: 1 m². 2 .

5. The preparation method according to claim 1, characterized in that, In step (1), the process conditions for heating and diffusion plating are as follows: the rotation speed of the co-diffusion furnace is 2-4 r / min, the pressure inside the co-diffusion furnace is 0.1-0.2 Pa, the temperature is raised to 300-320℃ at 15-20℃ / min and held for 1-2 hours, the temperature is raised to 400-420℃ at 5-8℃ / min and held for 3-4 hours, and then the temperature is allowed to cool naturally to room temperature before being removed.

6. The preparation method according to claim 1, characterized in that, The specific process of step (2) is as follows: (2-1) Place the steel plate that has been dip-coated once in a multi-arc ion plating machine, evacuate the vacuum chamber until the pressure is less than 0.1 Pa, and heat it at a constant rate to 480-500℃ for 1-2 hours. (2-2) Targets No. 1 and No. 3 are titanium targets, and targets No. 2 and No. 4 are zirconium targets. All doors of targets No. 2 and No. 4 are opened. The bias voltage is 150-200V. Nitrogen and acetylene are introduced into the vacuum chamber. The flow rate of nitrogen is 300-320sccm and the flow rate of acetylene is 20-30sccm. (2-3) Open all doors of target material No. 2 and No. 4, open doors of target material No. 1 and No. 3 halfway, set the bias voltage to 80-100V, and introduce nitrogen into the vacuum chamber at a flow rate of 400-420sccm. (2-4) Open all the doors of target material No. 1, No. 2, No. 3 and No. 4, set the bias voltage to 100-120V, and introduce nitrogen into the vacuum chamber at a flow rate of 350-370 sccm. (2-5) Open all doors of target material No. 2 and No. 4, set the bias voltage to 80-100V, and introduce nitrogen into the vacuum chamber at a flow rate of 380-400 sccm.

7. The preparation method according to claim 1, characterized in that, In step (3), the particle size of cubic boron nitride micro powder is ≤1μm.

8. The preparation method according to claim 1, characterized in that, In step (3), the ratio of the mass of cubic boron nitride micro powder to the single-sided surface area of ​​the secondary diffusion-coated steel plate is 750–850 kg: 1 m². 2 ; The process conditions for heating and diffusion plating are as follows: the rotation speed of the co-diffusion furnace is 3-5 r / min, the pressure inside the co-diffusion furnace is 0.1-0.2 Pa, the temperature is raised to 800-850℃ at 15-20℃ / min, the temperature is held for 5-7 hours, and the temperature is allowed to cool naturally to room temperature before removal. The quenching medium is mineral oil, and the quenching temperature is 880-900℃.

9. A zinc-aluminum-magnesium alloy powder-coated steel sheet, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 8.

10. The application of the zinc-aluminum-magnesium alloy powder-coated steel plate according to claim 9 in marine engineering.