A method for preparing a wear-resistant and corrosion-resistant hot-dip galvanized steel sheet

Abstract

The application discloses a preparation method of wear-resistant and corrosion-resistant hot-dip galvanized steel plate and belongs to the technical field of surface strengthening. The preparation method comprises the following steps: S1, hot rolling; S2, cold rolling; S3, hot-dip galvanizing: the cold-rolled steel plate is heated to 700-718 DEG C and kept for 5-10 min, and then the hot-dip galvanizing is carried out by slowly cooling at 5-8 DEG C / s to 410-415 DEG C, the galvanizing temperature is 440-450 DEG C, the galvanizing time is 18-22 s; after the galvanizing, the galvanized steel plate is cooled and dried, the content of Sn in the melt for the hot-dip galvanizing is 0.8-1.0% by mass percentage, and the rest is Zn; the galvanized steel plate is obtained; S4, surface treatment: the galvanized steel plate is sprayed with a YSn3 coating by using plasma spraying to obtain the wear-resistant and corrosion-resistant hot-dip galvanized steel plate. The wear-resistant and corrosion-resistant hot-dip galvanized steel plate obtained by the application has a double-layer structure, the inner layer is a zinc layer, and the outer layer is covered with a YSn3 layer, so that the wear-resistant and corrosion-resistant hot-dip galvanized steel plate has the effects of wear resistance, corrosion resistance and surface repair.

Description

Technical Field

[0001] This invention relates to a method for preparing wear-resistant and corrosion-resistant hot-dip galvanized steel sheets and their applications, belonging to the field of surface strengthening technology. Background Technology

[0002] Home appliances are a major steel-consuming sector, with steel products including refrigerators, residential air conditioners, commercial air conditioners, washing machines, freezers, televisions, and kitchen appliances. Currently, refrigerators consume the largest amount of steel, followed by residential air conditioners. In terms of product type, steel used includes hot-dip galvanized, cold-rolled, electro-galvanized, and pickled steel sheets, with hot-dip galvanized accounting for the largest share at approximately 80%. With the rapid development of the home appliance industry, people have increasingly higher requirements for the corrosion resistance and appearance of home appliances. The proportion of galvanized products in home appliance steel is constantly increasing. Because home appliances experience varying degrees of wear during transportation and handling, galvanized steel sheets for home appliances require a certain degree of wear resistance. Furthermore, home appliances are used in diverse environments; some are humid and oxygen-rich, making them highly susceptible to surface corrosion, which can damage the aesthetics and practicality of the appliances. Therefore, new products with high wear resistance and corrosion resistance are likely to be the future development trend for steel used in home appliances. Yttrium coatings have excellent corrosion resistance; current technology commonly uses Y2O3 spraying, which can obtain highly dense and highly corrosion-resistant coatings. Although nano-yttrium oxide coatings possess properties such as high temperature resistance, wear resistance, and corrosion resistance, in practical applications, the high brittleness of the Y2O3 coating makes it prone to cracking and peeling during wear and corrosion processes, leading to a decrease in its wear and corrosion resistance. Therefore, those skilled in the art urgently need to develop a method for preparing wear-resistant and corrosion-resistant hot-dip galvanized steel sheets and its applications to solve the aforementioned problems. Summary of the Invention

[0003] The present invention aims to provide a method for preparing wear-resistant and corrosion-resistant hot-dip galvanized steel sheet. This method significantly improves the overall hardness of the galvanized layer, thereby significantly enhancing its wear resistance. It can also significantly improve the corrosion resistance of the galvanized steel sheet and has the function of repairing the surface of the galvanized steel sheet.

[0004] Meanwhile, this invention provides a method for preparing wear-resistant and corrosion-resistant hot-dip galvanized steel sheets, and the application of the resulting wear-resistant and corrosion-resistant hot-dip galvanized steel sheets in home appliances.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing wear-resistant and corrosion-resistant hot-dip galvanized steel sheet includes the following steps:

[0007] S1, Hot rolling: The cast billet is heated to 1255~1280℃, held for 2~2.8h and then hot rolling begins. The final rolling temperature is 955~970℃. After final rolling, it is cooled to 630~650℃ at a cooling rate of 160~180℃ / s to obtain hot-rolled steel plate.

[0008] S2, Cold rolling: After pretreatment of hot-rolled steel sheet, three cold rolling passes are started, with a reduction of 25-28% in each pass to obtain cold-rolled steel sheet;

[0009] S3, Hot-dip galvanizing: Cold-rolled steel sheet is heated to 700-718℃ and held for 5-10 minutes, then slowly cooled to 410-415℃ at a rate of 5-8℃ / s for hot-dip galvanizing. The galvanizing temperature is 440-450℃ and the galvanizing time is 18-22 seconds. After galvanizing, the sheet is cooled and dried. The Sn content in the hot-dip galvanized melt is 0.8-1.0% by mass, with the balance being Zn. Galvanized steel sheet is obtained.

[0010] S4, Surface treatment: Galvanized steel sheet is coated with YSn3 by plasma spraying to obtain wear-resistant and corrosion-resistant hot-dip galvanized steel sheet.

[0011] The preparation method of YSn3 powder is as follows:

[0012] Step 1: Mix pure Y and pure Sn in a 1:3 ratio by molar percentage and place them in a crucible in a vacuum arc furnace;

[0013] Step two: Begin melting after vacuuming; the vacuum level is 1×10⁻⁶. -2 ~1×10 -3 Under low vacuum conditions of MPa, the melting temperature is 1550~1650℃; the melting time is 0.3~0.5 hours.

[0014] Step 3: After melting, use a copper mold for water cooling at a rate of 50-80℃ / s until it reaches room temperature. Then, release the gas and remove the sample.

[0015] Step four: After the smelted metal ingot is crushed, it is placed in a ball mill for ball milling. The ball milling speed is 600-800 r / min, the ball milling time is 24-48 h, and the ball milling atmosphere is argon protective atmosphere. After the ball milling is completed, plasma spraying powder is obtained.

[0016] YSn3 powder spraying process: Operating current: DC250~750A; Power: 50~55kW; Spray gun moving speed: 200~1000mm / s; YSn3 powder particle size: 100~300nm; Spraying gas: pure Ar; Auxiliary gas: pure H2.

[0017] The pretreatment process is: acid washing to remove oxide scale and stains.

[0018] The surface of the wear-resistant and corrosion-resistant hot-dip galvanized steel sheet has a double-layer structure, with an inner zinc layer and an outer YSn3 layer. The outer surface of the YSn3 layer has an in-situ generated Y2O3 film.

[0019] The zinc layer is 40–60 micrometers thick, and the YSn3 layer is 8–15 micrometers thick.

[0020] The porosity of the Y2O3 membrane is 5.38–6.15%.

[0021] The surface hardness of the wear-resistant and corrosion-resistant hot-dip galvanized steel sheet is ≥350HB.

[0022] The application of wear-resistant and corrosion-resistant hot-dip galvanized steel sheets obtained by the preparation method of the present invention in home appliances.

[0023] Home appliances include refrigerators, residential air conditioners, commercial air conditioners, washing machines, freezers, televisions, and kitchen appliances.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] The wear-resistant and corrosion-resistant hot-dip galvanized steel sheet obtained by this invention has a double-layer structure, with an inner zinc layer and an outer YSn3 layer, which gives it the functions of wear resistance, corrosion resistance and surface repair. (Principle) Regarding the double-layer structure of this invention, namely, an inner zinc layer and an outer YSn3 layer, YSn3 is an intermetallic compound with high strength and hardness, which significantly improves the overall hardness of the galvanized layer and enhances its wear resistance. On the other hand, the YSn3 phase can react with O2 in the air to generate Y2O3 and Sn (chemical reaction formula: YSn3 + O2 → Sn + Y2O3). Y has a good affinity for oxygen and readily reacts with O2 during oxidation, thus protecting the zinc layer from oxidation corrosion. The generated Y2O3 has high density and chemical stability and can also cover the surface of the zinc layer of the galvanized steel plate to physically isolate the reaction between O2 and zinc, thereby significantly improving the corrosion resistance of the galvanized steel plate. Thirdly, the reaction of YSn3 with O2 can generate Sn, which fills the cracks and voids caused by corrosion in the zinc layer, thus repairing the surface of the galvanized steel plate.

[0026] In this invention, during hot-dip galvanizing, 0.8–1.0 wt.% Sn not only serves to fill and repair the surface of the galvanized steel sheet, but also increases the surface mechanical properties and provides good coating adhesion. If the Sn proportion is too high, it will affect the adhesion between the coating and the substrate, making the coating prone to peeling; if the Sn proportion is too low, the self-repairing and surface mechanical properties will not be optimal. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the microstructure of the wear-resistant and corrosion-resistant hot-dip galvanized steel sheet of the present invention;

[0028] Figure 2 This is a microstructure diagram of the Y2O3 film of the present invention. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0030] Example 1

[0031] A method for preparing wear-resistant and corrosion-resistant hot-dip galvanized steel sheet comprises four steps: hot rolling, cold rolling, hot-dip galvanizing, and surface treatment, as detailed below:

[0032] S1, Hot rolling: The cast steel billet is heated to 1265℃, held for 2.5h and then hot rolling begins. The final rolling temperature is 960℃. After final rolling, it is cooled to 640℃ at a cooling rate of 170℃ / s to obtain hot-rolled steel plate.

[0033] S2, cold rolling: After the S1 hot-rolled steel plate is pickled to remove oxide scale and stains, it is cold rolled in three passes, with a reduction of 26.5% in each pass;

[0034] S3, hot-dip galvanizing: The S2 cold-rolled steel sheet is heated to 710℃ and held for 8 minutes, then slowly cooled to 412℃ at a rate of 6℃ / s for galvanizing. The galvanizing temperature is 445℃ and the galvanizing time is 20 seconds. After galvanizing, the sheet is cooled and dried. The Sn content in the hot-dip galvanized melt is 0.9% by mass, and the balance is Zn. A galvanized steel sheet is obtained.

[0035] S4, Surface Treatment: The galvanized steel sheet obtained in S3 is coated with a YSn3 coating by plasma spraying. Spraying process: Operating current: DC500A; Power: 50kW; Spray gun moving speed: 500mm / s; Powder particle size: 200nm; Spraying gas: pure Ar; Auxiliary gas: pure H2. Wear-resistant and corrosion-resistant hot-dip galvanized steel sheet is obtained. The surface of the galvanized steel sheet has a double-layer structure, with an inner zinc layer and an outer YSn3 layer. The outer surface of the YSn3 layer has an in-situ generated Y2O3 film.

[0036] The preparation method of YSn3 powder is as follows:

[0037] Step 1: Mix pure Y and pure Sn in a 1:3 ratio by molar percentage and place them in a crucible in a vacuum arc furnace;

[0038] Step two: Begin melting after vacuuming; the vacuum level is 0.5 × 10⁻⁶. -3 The melting temperature was 1400℃ under a low vacuum of MPa; the melting time was 0.4 hours.

[0039] Step 3: After melting, the copper mold is water-cooled at a rate of 60°C / s until it reaches room temperature. Then, the gas is released and the sample is removed.

[0040] Step four: After the smelted metal ingot is crushed, it is placed in a ball mill for ball milling. The ball milling speed is 700 r / min and the ball milling time is 36 h. The ball milling atmosphere is argon protective atmosphere. After the ball milling is completed, plasma spraying powder is obtained.

[0041] like Figure 1 As shown, the wear-resistant and corrosion-resistant hot-dip galvanized steel sheet obtained in this embodiment has a double-layer structure on its surface. The inner layer is a zinc layer, and the outer layer is covered with a YSn3 layer. The zinc layer has a thickness of 51 micrometers, and the YSn3 layer has a thickness of 13 micrometers.

[0042] Figure 1 The diffusion layer in the coating is generated by atomic diffusion during hot-dip plating, and it can improve the bonding strength of the coating. For example... Figure 2 As shown, the outer surface of the YSn3 layer has an in-situ generated Y2O3 film. The Y2O3 film has high density and chemical stability. Covering the zinc layer surface of the galvanized steel sheet, it physically isolates the reaction between O2 and zinc, thereby significantly improving the corrosion resistance of the galvanized steel sheet.

[0043] Example 2

[0044] A method for preparing wear-resistant and corrosion-resistant hot-dip galvanized steel sheet comprises four steps: hot rolling, cold rolling, hot-dip galvanizing, and surface treatment, as detailed below:

[0045] S1, hot rolling: The cast billet is heated to 1255℃, held for 2 hours and then hot rolling begins. The final rolling temperature is 955℃. After final rolling, it is cooled to 630℃ at a cooling rate of 160℃ / s.

[0046] S2, cold rolling: After the S1 hot-rolled steel plate is pickled to remove oxide scale and stains, it is cold rolled in three passes, with a reduction of 25% in each pass.

[0047] S3, hot-dip galvanizing: The S2 cold-rolled steel sheet is heated to 700℃ and held for 5 minutes, then slowly cooled to 410℃ at a rate of 5℃ / s for galvanizing. The galvanizing temperature is 440℃ and the galvanizing time is 18 seconds. After galvanizing, the sheet is cooled and dried. The Sn content in the hot-dip galvanized melt is 0.8% by mass, and the balance is Zn. Galvanized steel sheet is obtained.

[0048] S4, Surface Treatment: The galvanized steel sheet obtained in S3 is plasma sprayed with YSn3 powder. Spraying process: Operating current: DC250A; Power: 50kW; Spray gun moving speed: 200mm / s; Powder particle size: 100nm; Spraying gas: pure Ar; Auxiliary gas: pure H2. Wear-resistant and corrosion-resistant hot-dip galvanized steel sheet is obtained. The surface of the galvanized steel sheet has a double-layer structure, with an inner zinc layer and an outer YSn3 layer. The outer surface of the YSn3 layer has an in-situ generated Y2O3 film. The zinc layer thickness is 40 micrometers and the YSn3 layer thickness is 8 micrometers.

[0049] The preparation method of YSn3 powder is as follows:

[0050] Step 1: Mix pure Y and pure Sn in a 1:3 ratio by molar percentage and place them in a crucible in a vacuum arc furnace;

[0051] Step two: Begin melting after vacuuming; the vacuum level is 1×10⁻⁶.-2 The melting temperature was 1350℃ under a low vacuum of MPa; the melting time was 0.3 hours.

[0052] Step 3: After melting, use a copper mold for water cooling at a rate of 50°C / s to cool to room temperature, then release the gas and remove the sample.

[0053] Step four: After the smelted metal ingot is crushed, it is placed in a ball mill for ball milling. The ball milling speed is 600 r / min and the ball milling time is 24 h. The ball milling atmosphere is argon protective atmosphere. After the ball milling is completed, plasma spraying powder is obtained.

[0054] Example 3

[0055] A method for preparing wear-resistant and corrosion-resistant hot-dip galvanized steel sheet includes four steps: hot rolling, cold rolling, hot-dip galvanizing, and surface treatment, as detailed below:

[0056] S1, hot rolling: The cast billet is heated to 1280℃ and held for 2.8h before hot rolling begins. The final rolling temperature is 970℃. After final rolling, it is cooled to 650℃ at a cooling rate of 180℃ / s.

[0057] S2, cold rolling: After the S1 hot-rolled steel plate is pickled to remove oxide scale and stains, it is cold rolled in three passes, with a reduction of 28% in each pass;

[0058] S3, hot-dip galvanizing: The S2 cold-rolled steel sheet is heated to 718℃ and held for 10 minutes, then slowly cooled to 415℃ at 8℃ / s for galvanizing. The galvanizing temperature is 450℃ and the galvanizing time is 22 seconds. After galvanizing, the sheet is cooled and dried. The Sn content in the hot-dip galvanized melt is 1.0% by mass, and the balance is Zn. Galvanized steel sheet is obtained.

[0059] S4, Surface Treatment: The galvanized steel sheet obtained in S3 is plasma sprayed with YSn3 powder. Spraying process: Operating current: DC750A; Power: 55kW; Spray gun moving speed: 1000mm / s; Powder particle size: 300nm; Spraying gas: pure Ar; Assist gas: pure H2. Wear-resistant and corrosion-resistant hot-dip galvanized steel sheet is obtained. The surface of the galvanized steel sheet has a double-layer structure, with an inner zinc layer and an outer YSn3 layer. The outer surface of the YSn3 layer has an in-situ generated Y2O3 film. The zinc layer thickness is 60 micrometers and the YSn3 layer thickness is 15 micrometers.

[0060] The preparation method of YSn3 powder is as follows:

[0061] Step 1: Mix pure Y and pure Sn in a 1:3 ratio by molar percentage and place them in a crucible in a vacuum arc furnace;

[0062] Step two: Begin melting after vacuuming; the vacuum level is 1×10⁻⁶. -3The melting temperature was 1450℃ under a low vacuum of MPa; the melting time was 0.5 hours.

[0063] Step 3: After melting, the copper mold is water-cooled at a rate of 80°C / s until it reaches room temperature. Then, the gas is released and the sample is removed.

[0064] Step four: After the smelted metal ingot is crushed, it is placed in a ball mill for ball milling. The ball milling speed is 800 r / min and the ball milling time is 48 h. The ball milling atmosphere is argon protective atmosphere. After the ball milling is completed, plasma spraying powder is obtained.

[0065] Comparative Example 1

[0066] The difference between Comparative Example 1 and Example 1 is that: commercially available hot-dip galvanized steel sheet, grade: Q195, was used. That is, the molten galvanized steel sheet does not contain Sn, and YSn3 powder is not subsequently sprayed on it.

[0067] Comparative Example 2

[0068] Compared with Example 1, Comparative Example 2 differs in that: in step S3, during the preparation of hot-dip galvanizing, the Sn content in the hot-dip galvanizing melt is 0.5% by mass, with the balance being Zn; galvanized steel sheet is obtained, and subsequent operations are the same as in Example 1.

[0069] Comparative Example 3

[0070] Compared with Example 1, Comparative Example 3 differs in that: in step S3, during the hot-dip galvanizing preparation, the Sn content in the hot-dip galvanizing melt is 1.9% by mass, with the balance being Zn. A galvanized steel sheet is obtained, and subsequent operations are the same as in Example 1.

[0071] Comparative Example 4

[0072] Compared with Example 1, Comparative Example 4 differs in that: Step S4 surface treatment: The galvanized steel sheet obtained in S3 is plasma sprayed with Y2O3, and the spraying process is controlled so that the hot-dip galvanized steel sheet has a zinc layer on the inner layer and a Y2O3 layer on the outer layer with a thickness of 15 micrometers.

[0073] Comparative Example 5

[0074] Compared with Example 1, Comparative Example 5 differs in the following: Step S4 Surface Treatment: The galvanized steel sheet obtained in S3 is plasma sprayed with a mixed powder of Y2O3 and nano tin oxide; wherein Y2O3 and tin oxide are mixed according to the atomic molar percentage Y:Sn = 1:3, and the spraying process is controlled to obtain a hot-dip galvanized steel sheet with an inner zinc layer and an outer Y2O3-SnO2 mixed powder layer, the thickness of which is 15 micrometers.

[0075] The performance results of the galvanized steel sheets obtained in the embodiments of the present invention and Comparative Examples 1 to 3 are shown in Table 1 below.

[0076] Corrosion resistance test: Sample piece (8×6cm) 2 The corrosion resistance of samples was determined by immersing them in a 15% NaCl aqueous solution at 25±2℃ for 8 days.

[0077] Surface hardness: GB / T 231.1-2019 "Metallic materials - Brinell hardness test - Part 1: Test method".

[0078] Wear resistance test: With the oil applied, a chrome-plated cold-working die steel ball is rotated on the sample under a load of 5 MPa and a speed of 200 mm / s. The number of friction rotations until the coefficient of friction exceeds 0.3 is measured and confirmed.

[0079] Bonding strength test: GB 5933-1986.

[0080] Porosity testing: QB / T 3823-1999.

[0081] Table 1 Performance test results

[0082]

[0083]

[0084] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0085] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0086] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a wear-resistant and corrosion-resistant hot-dip galvanized steel plate, characterized in that, S1, hot rolling: heating the cast billet to 1255-1280℃, holding for 2-2.8h, and then starting hot rolling, with a finishing temperature of 955-970℃, and cooling to 630-650℃ at a cooling rate of 160-180℃ / s to obtain a hot-rolled steel plate; S2, cold rolling: starting three-pass cold rolling after pretreatment of the hot-rolled steel plate, with a cold rolling reduction of 25-28% per pass, to obtain a cold-rolled steel plate; S3, hot-dip galvanizing: heating the cold-rolled steel plate to 700-718℃, holding for 5-10min, and then slowly cooling to 410-415℃ at a rate of 5-8℃ / s to perform hot-dip galvanizing, with a galvanizing temperature of 440-450℃ and a galvanizing time of 18-22s; after galvanizing, cooling and drying, the Sn content in the hot-dip galvanizing melt is 0.8-1.0% by mass, with the balance being Zn; to obtain a galvanized steel plate; S4, surface treatment: applying YSn3 powder to the galvanized steel plate obtained in S3 by plasma spraying to obtain a wear-resistant and corrosion-resistant hot-dip galvanized steel plate, with a zinc layer in the inner layer, a YSn3 layer covering the zinc layer, and a Y2O3 film generated in situ on the outer surface of the YSn3 layer.

2. The method of producing a wear and corrosion resistant hot-dip galvanized steel sheet according to claim 1, characterized by, The preparation method of the YSn3 powder is as follows: Step one: mixing pure Y and pure Sn at a molar ratio of 1:3 and placing them in a vacuum arc furnace crucible; Step two, start vacuum smelting, vacuum degree: 1 x 10 -2 ~1 x 10 -3 MPa low vacuum state, smelting temperature: 1350~1450℃; smelting time: 0.3~0.5 hours; Step three: after the smelting is completed, water cooling is performed using a copper mold at a cooling rate of 50-80℃ / s to room temperature, and then the sample is removed after gas release; Step four: placing the smelted metal ingot in a ball mill after crushing for ball milling at a speed of 600-800r / min for 24-48h in an argon protective atmosphere, and obtaining a plasma spraying powder after the ball milling is completed.

3. The method of producing a wear and corrosion resistant hot-dip galvanized steel sheet according to claim 1, characterized by, The spraying process of the YSn3 powder: operating current: DC 250-750A; power: 50-55kW; spray gun moving speed: 200-1000mm / s; YSn3 powder particle size: 100-300nm; spraying gas: pure Ar; auxiliary gas: pure H2.

4. The method of producing a wear and corrosion resistant hot-dip galvanized steel sheet according to claim 1, characterized by, The pretreatment process is: pickling to remove scale and stains.

5. The preparation method according to claim 1, characterized in that, The thickness of the zinc layer is 40-60 microns, and the thickness of the YSn3 layer is 8-15 microns.

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