Preparation method of zinc-based coating steel plate welded pipe

Abstract

The invention relates to a preparation method of a zinc-based coating steel plate welded pipe. The method comprises the steps that the edge of a formed zinc-based coating steel plate is heated; oxygen-containing gas with set oxygen content and set pressure intensity is adopted for blowing the outer side coating edge area of the formed zinc-based coating steel plate in the heating state, so that liquid zinc in the outer side coating edge area is oxidized, and the edges of the formed zinc-based coated steel plate are mutually closed in an extrusion welding mode to form a welding bead, and the zinc-based coated steel plate welded pipe is obtained. Wherein the outer side plating layer edge area comprises an area with the temperature higher than the melting point of the plating layer. According to the method, the cracking of the zinc-based plating steel plate welded pipe is reduced.

Description

Technical Field

[0001] The present application relates to the field of welding technology, and in particular to a method for preparing a zinc-based coated steel plate welded pipe. Background Art

[0002] Zinc-based coated steel plates have now become high-end products in the fields of photovoltaics, highway guardrails, etc.

[0003] The supporting structures such as the main shaft of the photovoltaic bracket, the transmission shaft and the high-speed guardrail column all use high-frequency induction welded pipes. When welding the zinc-based coated steel plate, the liquid zinc can easily penetrate into the welding heat-affected zone, forming liquid metal brittle cracks, causing the welded pipe to crack. At the same time, after the coated steel plate is scraped after high-frequency induction heating, the corrosion resistance of the weld and its surrounding areas is difficult to guarantee. Summary of the invention

[0004] The present application provides a method for preparing a zinc-based coated steel plate welded pipe to solve the following technical problem: how to reduce the cracking of the zinc-based coated steel plate welded pipe.

[0005] In a first aspect, the present application provides a method for preparing a zinc-based coated steel plate welded pipe, the method comprising:

[0006] Heating the edges of the formed zinc-coated steel sheets;

[0007] The outer coating edge area of ​​the heated formed zinc-based coated steel plate is purged with an oxygen-containing gas having a set oxygen content and a set pressure, so that the liquid zinc in the outer coating edge area is oxidized, and the edges of the formed zinc-based coated steel plate are closed to each other by extrusion welding to form a weld bead, thereby obtaining a zinc-based coated steel plate welded pipe; wherein the outer coating edge area includes an area where the temperature is greater than the melting point of the coating.

[0008] Optionally, the oxygen content is set to be ≥5 volume %.

[0009] Optionally, the set oxygen content is 15 volume % to 90 volume %.

[0010] Optionally, the set pressure is >2MPa.

[0011] Optionally, the set pressure is 5MPa to 100MPa.

[0012] Optionally, the outer coating edge region of the heated formed zinc-based coated steel plate is purged with oxygen-containing gas having a set oxygen content and a set pressure so that liquid zinc in the outer coating edge region is oxidized, and the edges of the formed zinc-based coated steel plate are mutually closed by extrusion welding to form a weld bead, thereby obtaining a zinc-based coated steel plate welded pipe, comprising:

[0013] The outer coating edge area of ​​the heated formed zinc-based coated steel plate is purged with oxygen-containing gas having a set oxygen content and a set pressure, so that the liquid zinc in the outer coating edge area is oxidized, and the edges of the formed zinc-based coated steel plate are closed to each other by extrusion welding to form a weld bead, so as to obtain a zinc-based coated steel plate welded pipe; wherein the welding speed of the extrusion welding is obtained by the set pressure, and the welding speed and the set pressure satisfy the following relationship: V≤P≤5V, V represents the welding speed, and P represents the set pressure.

[0014] Optionally, the molded zinc-based coated steel plate includes a steel substrate and a zinc-based coating, and the zinc-based coating includes one of the following: pure zinc coating, zinc-aluminum coating, zinc-aluminum-magnesium coating, and zinc-iron alloy coating.

[0015] Optionally, the method further includes:

[0016] The surface burrs of the weld are scraped off, and then the damaged area of ​​the coating is sprayed.

[0017] Optionally, the scraping temperature is >400°C.

[0018] Optionally, the spraying temperature is >200°C.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0020] The preparation method of the zinc-based coated steel plate welded pipe provided in the embodiment of the present application comprises heating and melting the edge of the formed zinc-based coated steel plate, and performing pressure welding under the action of extrusion to prepare the zinc-based coated steel plate welded pipe; using an oxygen-containing gas with a set oxygen content and a set pressure to purge the outer coating edge area of ​​the heated formed zinc-based coated steel plate (the area where the temperature is greater than the melting point of the coating is prone to zinc-induced LME cracks), and the oxygen-containing gas with a set oxygen content and a set pressure can improve the welded formed zinc-based coated steel plate The surface coating temperature is increased, the coating combustion is accelerated, and it is converted from liquid to solid; at the same time, the coating elements and the matrix are promoted to form AlFe3 and AlFe phases to isolate the liquid coating, and the surface modification of the area to be welded is realized, thereby continuously promoting the combustion or oxidation of liquid zinc in the area, and separating from the steel plate surface in the form of zinc oxide powder, and eliminating liquid zinc elements before extrusion welding, so as to achieve the absence of liquid zinc in the weld 3 times the plate thickness of the zinc-based coated steel plate welded pipe, thereby inhibiting the occurrence of zinc-induced LME cracks and greatly reducing the cracking rate of the welded pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 A schematic diagram of a process for preparing a zinc-based coated steel plate welded pipe according to some embodiments of the present application;

[0024] Figure 2 A picture of the surface of a zinc-coated steel plate welded pipe after welding with burrs removed according to some comparative examples of the present application;

[0025] Figure 3 A picture of a surface of a weld bead of a zinc-coated steel plate welded pipe after welding with burrs removed according to some embodiments of the present application;

[0026] Figure 4 A picture of cracking in a flaring experiment of a zinc-coated steel plate welded pipe provided according to some comparative examples of the present application;

[0027] Figure 5 A picture showing that a zinc-coated steel plate welded pipe does not crack during an expansion test according to some embodiments of the present application;

[0028] Figure 6 A picture showing that a zinc-based coated steel plate welded pipe does not crack in a flattening test according to some embodiments of the present application;

[0029] Figure 7 The following is a picture of the weld surface of a zinc-coated steel plate welded pipe after spraying according to some comparative examples of the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0032] In this application, the terms "include", "comprises", etc. mean "including but not limited to". In this article, "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0033] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0034] Figure 1 For a schematic diagram of a process for preparing a zinc-based coated steel plate welded pipe according to some embodiments of the present application, see Figure 1 The present application provides a method for preparing a zinc-based coated steel plate welded pipe, the method comprising:

[0035] S1. heating the edge of the formed zinc-based coated steel plate;

[0036] S2. Use oxygen-containing gas with a set oxygen content and a set pressure to blow the outer coating edge area of ​​the heated molded zinc-based coated steel plate to oxidize the liquid zinc in the outer coating edge area, and close the edges of the molded zinc-based coated steel plate to form a weld by extrusion welding to obtain a zinc-based coated steel plate welded pipe; wherein the outer coating edge area includes an area where the temperature is greater than the melting point of the coating.

[0037] In some embodiments, the set oxygen content is ≥5 volume %.

[0038] In some embodiments, the set oxygen content is 15 volume % to 90 volume %.

[0039] In some embodiments, the set pressure is >2 MPa.

[0040] In some embodiments, the set pressure is 5 MPa to 100 MPa.

[0041] In some embodiments, high-pressure gas can quickly drive water vapor away from the welding area, which can increase the welding temperature (a lubricant aqueous solution will be applied during the pressurization process), and oxygen-containing gas can increase the welding surface temperature, accelerate the combustion of the coating, and transform it from a liquid to a solid substance; at the same time, it promotes the formation of AlFe3 and AlFe phases between the coating elements and the matrix to isolate the liquid coating and achieve surface modification of the area to be welded; oxygen-containing gas can oxidize the edge of the steel strip, reduce the bonding force between the coating and the substrate, and facilitate the removal of the coating elements; the surface of the area to be welded is squeezed with AlFe3, Fe2O3 and residual zinc oxide to form an effective connection, and zinc oxide is burned to form zinc oxide, which is then driven away from the surface of the workpiece to be welded by the high-pressure gas. Limiting the oxygen content in the oxygen-containing gas can quickly support combustion, increase the surface temperature, and promote zinc combustion in the combustion-supporting gas to form a combustion product, zinc oxide; limiting the pressure of the oxygen-containing gas can achieve the evaporation of liquid water and the removal of surface zinc oxide. The high-pressure oxygen-containing gas can use compressed air, which has low investment costs. The high-pressure oxygen-containing gas purge area is greater than the melting point area of ​​the coating, which can continuously promote the combustion or oxidation of liquid zinc, separate from the surface of the steel plate in the form of zinc oxide powder, eliminate liquid zinc elements before welding, inhibit the generation of zinc-induced LME cracks, and greatly reduce the cracking rate of the welded pipe. Exemplarily, the above-mentioned set oxygen content can be 5 volume%, 6 volume%, 7 volume%, 8 volume%, 10 volume%, 15 volume%, 20 volume%, 30 volume%, 40 volume%, 50 volume%, 60 volume%, 70 volume%, 80 volume%, 90 volume%, etc., and further, the above-mentioned set oxygen content can be 15 volume%, 20 volume%, 30 volume%, 40 volume%, 50 volume%, 60 volume%, 70 volume%, 80 volume%, 90 volume%, etc. The above-mentioned set pressure can be 3MPa, 4MPa, 5MPa, 6MPa, 7, 8MPa, 10MPa, 20MPa, 30MPa, 40MPa, 50MPa, 60MPa, 70MPa, 80MPa, 90MPa, 100MPa, etc. Further, the above-mentioned set pressure can be 5MPa, 6MPa, 7MPa, 8MPa, 10MPa, 20MPa, 30MPa, 40MPa, 50MPa, 60MPa, 70MPa, 80MPa, 90MPa, 100MPa, etc.

[0042] In some embodiments, the outer coating edge region of the heated formed zinc-based coated steel plate is purged with an oxygen-containing gas having a set oxygen content and a set pressure so that the liquid zinc in the outer coating edge region is oxidized, and the edges of the formed zinc-based coated steel plate are closed to each other by extrusion welding to form a weld bead, thereby obtaining a zinc-based coated steel plate welded pipe, comprising:

[0043] The outer coating edge area of ​​the heated formed zinc-based coated steel plate is purged with oxygen-containing gas having a set oxygen content and a set pressure, so that the liquid zinc in the outer coating edge area is oxidized, and the edges of the formed zinc-based coated steel plate are closed to each other by extrusion welding to form a weld bead, so as to obtain a zinc-based coated steel plate welded pipe; wherein the welding speed of the extrusion welding is obtained by the set pressure, and the welding speed and the set pressure satisfy the following relationship: V≤P≤5V, V represents the welding speed, and P represents the set pressure.

[0044] In the embodiment of the present application, the welding speed and the set pressure satisfy V≤P≤5V, which can effectively promote the formation and removal of zinc oxide and inhibit brittle cracks of liquid metal.

[0045] In some embodiments, the molded zinc-based coated steel plate includes a steel substrate and a zinc-based coating, and the zinc-based coating includes one of the following: a pure zinc coating, a zinc-aluminum coating, a zinc-aluminum-magnesium coating, and a zinc-iron alloy coating.

[0046] In the embodiment of the present application, the zinc-based coating in the molded zinc-based coated steel plate may be one of pure zinc coating, zinc-aluminum coating, zinc-aluminum-magnesium coating, and zinc-iron alloy coating.

[0047] In some embodiments, the method further comprises:

[0048] S3, scraping off the surface burrs of the weld, and then spraying the damaged area of ​​the coating.

[0049] In some embodiments, the scraping temperature is >400°C.

[0050] In some embodiments, the spraying temperature is >200°C.

[0051] In the embodiment of the present application, the steel strip is squeezed by an extrusion roller to extrude the oxide and form a weld connection. After scraping off the burrs, the weld surface (at least including the outer surface of the weld) and the area where the coating is damaged are sprayed to ensure the quality and corrosion resistance of the weld. The scraping temperature is limited, and the welding burrs can be effectively scraped off, and the scraped area is flat. Exemplarily, the scraping temperature can be 401°C, 405°C, 410°C, 420°C, 425°C, 430°C, etc. The spraying temperature is limited, and the bonding force between the spray layer and the weld area and the heat-affected area is high and not easy to fall off, so as to improve the corrosion resistance of the weld. Exemplarily, the spraying temperature can be 201, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, etc. The spraying material contains one of zinc and aluminum elements, and the spraying material is a wire with a diameter of 0.6mm-6mm and a spraying thickness greater than 20μm.

[0052] In summary, the content of this application solves the problems of cracking in the heat-affected zone and insufficient corrosion resistance of the weld in high-frequency induction welding of zinc-based coated steel plate welded pipes. It has low cost and the yield rate can reach a level comparable to that of uncoated steel plates. At the same time, local corrosion protection is performed on the weld to ensure the overall corrosion resistance of the welded pipe.

[0053] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0054] The embodiment of the present application provides a method for preparing a zinc-based coated steel plate welded pipe. Please refer to the material parameters of the zinc-based coated steel plate welded pipe shown in Table 1 and the purging and welding process parameters of the zinc-based coated steel plate welded pipe shown in Table 2.

[0055] Table 1 Material parameters of zinc-based coated steel plate welded pipe

[0056]

[0057] Table 2 Process parameters for purging and welding of zinc-coated steel plate welded pipe

[0058]

[0059]

[0060] The welding results of the zinc-based coated steel plate welded pipes prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were evaluated. Please refer to Table 3 for the evaluation results.

[0061] Table 3 Welding evaluation results of zinc-based coated steel plate welded pipe

[0062] Serial number Welding conditions Example 1 good Example 2 good Example 3 good Example 4 good Example 5 good Example 6 good Comparative Example 1 Cracking Comparative Example 2 Cracking Comparative Example 3 Cracking Comparative Example 4 Cracking Comparative Example 5 Cracking Comparative Example 6 Cracking

[0063] Table 4 Evaluation results of burr scraping, spraying and corrosion resistance of zinc-based coated steel plate welded pipe

[0064]

[0065] Table 5 Phase composition of the surface of the heat affected zone of a zinc-based coated steel plate welded pipe provided in the comparative example

[0066] phase of matter Proportion <![CDATA[AlFe3]]> 30.27％ <![CDATA[Mg2Zn 11 ]]> 28.18％ Zn 14.38％ Al 13.83％ <h2 style=";text-align:left;direction:ltr"><![CDATA[(Mg <h2 style=";text-align:left;direction:ltr"> 0.4 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.6 <h2 style=";text-align:left;direction:ltr"> )Al<h2 style=";text-align:left;direction:ltr"> 1.8 <h2 style=";text-align:left;direction:ltr"> O4]]><h2 style=";text-align:left;direction:ltr"> 12.71％ <![CDATA[MgZn2]]> 0.63％

[0067] Table 6 Phase composition of the surface of the heat affected zone of a zinc-coated steel plate welded pipe provided in the embodiment

[0068]

[0069]

[0070] Figure 2 This is a picture of the surface of a zinc-based coated steel plate welded pipe after welding with burrs removed according to some comparative examples of this application; please refer to Figure 2 , indicating that cracking occurs in the heat affected zone of welding, reducing the welding strength. Figure 3 This is a picture of the surface of a zinc-coated steel plate welded pipe after welding with burrs removed according to some embodiments of the present application; please refer to Figure 3 , indicating that there is no cracking in the welding heat affected zone, and the welding strength requirements are met. Figure 4 This is a picture of cracking in the expansion experiment of a zinc-based coated steel plate welded pipe provided according to some comparative examples of this application; please refer to Figure 4 , indicating that cracking occurs in the heat affected zone of welding. The expansion test shows that cracking occurs in the heat affected zone. Figure 5 This is a picture of a zinc-coated steel plate welded pipe that does not crack during an expansion test according to some embodiments of the present application; see Figure 5 , indicating that there is no cracking in the heat affected zone of welding. The expansion test shows that there is no cracking in the weld and the base material, which meets the welding strength requirements. Figure 6 This is a picture of a zinc-based coated steel plate welded pipe that does not crack in a flattening test according to some embodiments of the present application; see Figure 6 , indicating that there is no cracking in the welding heat affected zone. The flattening test was used to check that there was no cracking in the weld and the parent material. Table 5 shows the phase composition of the welding heat affected zone surface of a zinc-coated steel plate welded pipe provided in the comparative example; it shows that there is still a large amount of liquid zinc on the welding surface, which will still cause liquid metal cracks; Table 6 shows the phase composition of the welding heat affected zone surface of a zinc-coated steel plate welded pipe provided in the embodiment, indicating that there is no liquid zinc on the welding surface, which will not cause liquid metal cracks, thereby ensuring the welding strength; Figure 7 The surface picture of the weld bead of a zinc-based coated steel plate welded pipe after spraying is provided according to some comparative examples of this application; please refer to Figure 7 , indicating that there is no coating element in the welding area, and the surface needs to be sprayed to ensure corrosion resistance. According to Table 4, the zinc-based coated steel plate welded pipe has good corrosion resistance after spraying.

[0071] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a zinc-based coated steel plate welded pipe, characterized in that: The method comprises: Heating the edges of the formed zinc-coated steel sheets; The outer coating edge area of ​​the heated formed zinc-based coated steel plate is purged with an oxygen-containing gas having a set oxygen content and a set pressure, so that the liquid zinc in the outer coating edge area is oxidized, and the edges of the formed zinc-based coated steel plate are closed to each other by extrusion welding to form a weld bead, thereby obtaining a zinc-based coated steel plate welded pipe; wherein the outer coating edge area includes an area where the temperature is greater than the melting point of the coating.

2. The method according to claim 1, characterized in that The set oxygen content is ≥5 volume %.

3. The method according to claim 2, characterized in that The set oxygen content is 15 volume % to 90 volume %.

4. The method according to claim 1, characterized in that: The set pressure is>2MPa.

5. The method according to claim 4, characterized in that The set pressure is 5MPa to 100MPa.

6. The method according to claim 1, characterized in that The outer coating edge area of ​​the formed zinc-based coated steel plate in a heated state is purged by using oxygen-containing gas with a set oxygen content and a set pressure, so that the liquid zinc in the outer coating edge area is oxidized, and the edges of the formed zinc-based coated steel plate are closed to each other by extrusion welding to form a weld bead, thereby obtaining a zinc-based coated steel plate welded pipe, comprising: The outer coating edge area of ​​the heated formed zinc-based coated steel plate is purged with oxygen-containing gas having a set oxygen content and a set pressure, so that the liquid zinc in the outer coating edge area is oxidized, and the edges of the formed zinc-based coated steel plate are closed to each other by extrusion welding to form a weld bead, so as to obtain a zinc-based coated steel plate welded pipe; wherein the welding speed of the extrusion welding is obtained by the set pressure, and the welding speed and the set pressure satisfy the following relationship: V≤P≤5V, V represents the welding speed, and P represents the set pressure.

7. The method according to claim 1, characterized in that The molded zinc-based coated steel plate comprises a steel substrate and a zinc-based coating, wherein the zinc-based coating comprises one of the following: a pure zinc coating, a zinc-aluminum coating, a zinc-aluminum-magnesium coating, and a zinc-iron alloy coating.

8. The method according to claim 1, characterized in that The method further comprises: The surface burrs of the weld are scraped off, and then the damaged area of ​​the coating is sprayed.

9. The method according to claim 8, characterized in that The scraping temperature is >400°C.

10. The method according to claim 8, characterized in that The spraying temperature is >200°C.

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