CN116200692A - Welding method of pure zinc coated steel - Google Patents

Abstract

The application relates to the technical field of steel rolling, in particular to a welding method of pure zinc coated steel. The method comprises the following steps: nickel pre-plating is carried out on the strip steel matrix so that a nickel layer is attached to at least part of the surface of the strip steel matrix, and nickel pre-plated steel is obtained; annealing the nickel preplating steel, and when the temperature of the nickel preplating steel reaches a set temperature, increasing the dew point to a target dew point temperature so as to form a decarburized layer on the surface of the nickel preplating steel; and (3) galvanizing the nickel-plated steel containing the decarburized layer so as to enable a zinc layer to be attached to at least part of the surface of the nickel-plated steel, and then cooling under the condition of setting cooling speed to obtain the pure zinc-plated steel. The method solves the problem that the pure zinc coated steel is brittle due to the fact that liquid metal appears in the spot welding process.

Description

A welding method for pure galvanized steel

technical field

The present application relates to the technical field of steel rolling, in particular to a welding method for pure zinc coated steel.

Background technique

With the improvement of corrosion resistance, safety, and lightweight requirements of automobile bodies, pure galvanized steel is widely used in the production of automobile bodies. Different parts of the car body need to be connected in different ways, resistance spot welding is one of the important ways of car body connection.

The coating temperature of pure zinc-coated steel is low, and liquid metal is prone to brittleness during the spot welding process, forming micro-cracks on the surface of the steel, resulting in reduced fatigue life during customer use and affecting the safety of the car body.

Contents of the invention

The present application provides a welding method for pure zinc-coated steel to solve the problem in the prior art that the pure zinc-coated steel appears brittle due to liquid metal during welding.

In a first aspect, the application provides a welding method for pure galvanized steel, the method comprising:

Carrying out pre-nickel-plating on the strip steel substrate, so that the nickel layer is attached to at least part of the surface of the strip steel substrate, to obtain pre-nickel-plated steel;

Annealing the pre-nickel-plated steel, when the temperature of the pre-nickel-plated steel reaches the set temperature, increasing the dew point to the target dew point temperature, so that the surface of the pre-nickel-plated steel forms a decarburization layer;

Galvanizing the pre-nickel-coated steel with decarburized layer, so that the zinc layer adheres to at least part of the surface of the pre-nickel-coated steel, and then cooling under the condition of a set cooling rate to obtain pure zinc-coated steel.

Optionally, the nickel layer has a thickness of 500mg/m ² -2500mg/m ² .

Optionally, the target dew point temperature is -10°C to 20°C.

Optionally, the thickness tolerance of the zinc layer is ≤2g/m ² .

Optionally, the set cooling rate is 5°C/s˜12°C/s.

Optionally, the set temperature of the pre-nickel-plated steel is 650°C-800°C.

Optionally, the strip steel substrate has a thickness of 0.4 mm to 6.0 mm.

Optionally, the strength of the pure zinc-coated steel is ≥780MPa.

Optionally, the strength of the pure zinc-coated steel is 780MPa˜1180MPa.

Optionally, if the strength of the pure zinc-coated steel is 780MPa˜1180MPa, the pure zinc-coated steel includes at least one of the following steel types: DH steel, Trip steel, and TBF steel.

Compared with the prior art, the above-mentioned technical solutions provided by the embodiments of the present application have the following advantages:

In the method provided by the embodiment of the present application, first, nickel is pre-plated on the surface of the steel strip substrate, and the thickness of the nickel layer and the alloying diffusion process after galvanizing are controlled, so that the nickel layer can prevent liquid pure zinc from being absorbed during spot welding of the steel plate. The coating penetrates into the austenite grain boundary on the surface of the steel plate, thereby reducing the liquid metal embrittlement of the pure zinc-coated steel during spot welding;

Secondly, the dew point control inside the annealing furnace makes the surface of the pre-nickel-plated steel form a decarburization layer, thereby reducing the yield strength of the outermost layer of the pre-nickel-plated steel, and reducing the crack sensitivity under the action of the electrode pressure head during the spot welding process. In addition, during the welding process of the decarburized layer, the austenitization temperature increases, and the austenite grain boundary is more sensitive to liquid metal embrittlement. By increasing the austenitization temperature, the phenomenon of liquid metal embrittlement is further suppressed.

Description of drawings

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

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, In other words, other drawings can also be obtained from these drawings without paying creative labor.

The schematic flow sheet of a kind of welding method of pure galvanized steel that Fig. 1 embodiment of the present application provides;

Fig. 2 is a metallographic structure diagram of a decarburized layer formed by dew point regulation provided in Example 1 of the present application;

Fig. 3 is the metallographic structure diagram of no dew point regulation and no decarburization layer provided by comparative example 1 of the present application;

The nickel layer electronic probe diagram between the 780MPa level pure zinc coating steel coating and the base body that Fig. 4 the application embodiment 1 provides;

Fig. 5 is an improvement effect diagram of liquid metal embrittlement in spot welding of 780MPa grade pure zinc-coated steel provided by Example 1 of the present application.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions 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 It is a part of the embodiments of this application, but not all of them. Based on the embodiments in the present application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present application.

Various embodiments of the present application may exist 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 construed as a rigid limitation on the scope of the application; therefore, the described range should be regarded as The description has specifically disclosed all possible subranges as well as individual values within that range. For example, a description of a range from 1 to 6 should be considered to have specifically disclosed subranges, 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., and Single numbers within the stated ranges, eg 1, 2, 3, 4, 5 and 6, apply regardless of the range. Additionally, whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range.

In the present application, unless otherwise stated, the used orientation words such as "upper" and "lower" specifically refer to the direction of the drawings in the drawings. In addition, in the description of the specification of the present application, the terms "including" and "comprising" mean "including but not limited to". In this document, relational terms such as "first" and "second", etc., are only used to distinguish one entity or operation from another, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or sequence. In this article, "and/or" describes the association relationship of associated objects, indicating that there may be three kinds of relationships, for example, A and/or B, which can mean: A exists alone, A and B exist simultaneously, and B exists alone . Among them, A and B can be singular or plural. Herein, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, "at least one item (unit) of a, b, or c", or "at least one item (unit) of a, b, and c" can mean: a, b, c, a-b( That is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

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.

With the improvement of corrosion resistance, safety, and lightweight requirements of automobile bodies, pure galvanized steel is widely used in the production of automobile bodies. Different parts of the car body need to be connected in different ways, resistance spot welding is one of the important ways of car body connection.

However, due to the low coating temperature of pure zinc-coated steel at present, the problem of liquid metal becoming brittle is prone to occur in the spot welding process.

The technical solutions provided by the embodiments of the present application are to solve the above technical problems, and the general idea is as follows:

In the first aspect, the application provides a welding method for pure zinc-coated steel, please refer to Fig. 1, the method includes:

S1. Pre-nickel-plating the strip steel substrate, so that the nickel layer is attached to at least part of the surface of the strip steel substrate to obtain pre-nickel-plated steel;

S2. Annealing the pre-nickel-plated steel, when the temperature of the pre-nickel-plated steel reaches a set temperature, increasing the dew point to the target dew point temperature, so that the surface of the pre-nickel-plated steel forms a decarburization layer;

S3. Galvanize the pre-nickel-coated steel containing the decarburized layer, so that the zinc layer adheres to at least part of the surface of the pre-nickel-coated steel, and then cool under the condition of a set cooling rate to obtain a pure zinc coating steel.

In the embodiment of this application, nickel is plated on the surface of the steel strip substrate, and the thickness of the nickel layer and the alloying diffusion process after galvanizing are controlled, so that the nickel layer can prevent the liquid pure zinc coating from penetrating into the surface of the steel plate during the spot welding process of the steel plate Austenite grain boundaries, thereby reducing the liquid metal embrittlement of pure zinc-coated steel during spot welding;

The dew point is controlled inside the annealing furnace to form a decarburized layer on the surface of the pre-nickel-plated steel, thereby reducing the yield strength of the outermost layer of the pre-nickel-plated steel, and reducing the crack sensitivity under the action of the electrode pressure head during the spot welding process. In addition, during the welding process of the decarburized layer, the austenitization temperature increases, and the austenite grain boundary is more sensitive to liquid metal embrittlement. By increasing the austenitization temperature, the phenomenon of liquid metal embrittlement is further suppressed.

In some embodiments, the nickel layer has a thickness of 500 mg/m ² to 2500 mg/m ² .

Nickel is electroplated on the ultra-high-strength surface by electroplating nickel equipment, and the thickness of the nickel layer is 500mg/m ² -2500mg/m ² . The role of the nickel layer is to prevent the liquid pure zinc coating from penetrating into the austenite grain boundaries on the strip surface. The effect of controlling the thickness of the nickel layer at 500mg/m ² -2500mg/m ² is that the thickness of the nickel layer is too low to improve the effect of making the liquid metal brittle; the thickness of the nickel layer is too high, resulting in high cost. Specifically, the nickel layer thickness can be 500mg/m ² , 600mg/m ² , 700mg/m ² , 800mg/m ² , 900mg/m ² , 1000mg/m ² , 1100mg/m ² ,

1200mg/m ² , 1300mg/m ² , 1400mg/m ² , 1500mg/m ² , 1600mg/m ² , 1700mg/m ² , 1800mg/m ² ,

1900mg/m ² , 2000mg/m ² , 2100mg/m ² , 2200mg/m ² , 2300mg/m ² , 2400mg/m ² , 2500mg/m ² , etc.

In some embodiments, the target dew point temperature is -10°C to 20°C.

"Dew point" refers to the air temperature at which the air is saturated with water vapor. The effect of regulating the dew point inside the annealing furnace is to form a decarburized layer on the surface of the strip, thereby reducing the yield strength of the outermost layer of the strip; and to reduce the crack sensitivity under the action of the electrode pressure head during the spot welding process. During the welding process of the decarburized layer, the austenitization temperature increases, and the austenitic grain boundary is more sensitive to liquid metal embrittlement. By increasing the austenitization temperature, the phenomenon of liquid metal embrittlement is further suppressed. If the dew point temperature is too high, it will cause excessive oxidation of the strip surface to a certain extent, which will affect the surface quality of the strip steel; if the dew point temperature is too low, it will not be able to form a sufficient decarburization layer to a certain extent. Specifically, the target dew point can be -10°C, -9°C, -8°C, -7°C, -6°C, -5°C, -4°C, -3°C, -2°C, -1°C, 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C , 18°C, 19°C, 20°C, etc.

In some embodiments, the thickness tolerance of the zinc layer is ≤2g/m ² .

In the process of hot-dip galvanizing, the thickness of the coating is strictly controlled, and the thickness tolerance of the zinc layer is set to be ≤2g/m ² . Specifically, the thickness tolerance of the zinc layer may be 2g/m ² , 1.5g/m ² , 1g/m ² and so on.

In some embodiments, the set cooling rate is 5°C/s˜12°C/s.

The role of controlling the cooling rate of pure zinc-coated steel is to reduce the alloying diffusion process between the nickel layer and the coating and maintain the surface quality of pure zinc-coated steel. In the embodiment of the present application, the pure zinc-coated steel is provided with a mobile cooling bellows at a position of 50cm-100cm above the air knife to adopt forced air cooling, and its function is to increase the overall cooling rate of the cooling process and reduce Alloying diffusion process between nickel layer and plating layer. If the cooling rate is too high, there will be no effect to a certain extent; if the cooling rate is too low, the coating will flow under the action of gravity to a certain extent, resulting in local inhomogeneity of the coating. Specifically, the cooling rate may be 5°C/s, 6°C/s, 7°C/s, 8°C/s, 9°C/s, 10°C/s, 11°C/s, 12°C/s, etc.

In some embodiments, the set temperature of the pre-nickel-plated steel is 650°C-800°C.

In the annealing process of the galvanizing production line, the dew point is increased to -10°C to 20°C at the set temperature of the strip steel substrate at 650°C to 800°C, and the surface oxidation reaction is carried out on the surface of the strip steel to decarburize, and the annealing temperature is too low. It is beneficial to decarburization; too high temperature is not conducive to oxidation. If the set temperature of the strip steel matrix is too high, it will cause excessive oxidation of the strip steel surface to a certain extent; if the set temperature of the strip steel matrix is too low, it will cause insufficient oxidation of the strip steel surface to a certain extent, and the decarburization layer cannot be formed. Specifically, the set temperature of the steel strip matrix can be 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C , 780°C, 790°C, 800°C, etc.

In some embodiments, the strip steel matrix has a thickness of 0.4 mm to 6.0 mm.

In the embodiment of the present application, specifically, the strip thickness of pure zinc-coated steel can be 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4 mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.0mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3.0mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, 3.6mm, 3.7mm, 3.8mm, 3.9mm, 4.0mm, 4.1mm, 4.2mm, 4.3mm, 4.4mm, 4.5mm, 4.6mm, 4.7mm , 4.8mm, 4.9mm, 5.0mm, 5.1mm, 5.2mm, 5.3mm, 5.4mm, 5.5mm, 5.6mm, 5.7mm, 5.8mm, 5.9mm, 6.0mm, etc.

In some embodiments, the strength of the pure zinc-coated steel is ≥780 MPa.

In the embodiment of the present application, the above-mentioned welding method for pure zinc-coated steel is applicable to pure zinc-coated steel with steel strength ≥ 780 MPa.

In some embodiments, the strength of the pure zinc-coated steel is 780MPa˜1180MPa.

In some embodiments, if the strength of the pure zinc-coated steel is 780MPa-1180MPa, the pure zinc-coated steel includes at least one of the following steel types: DH steel, Trip steel, and TBF steel.

For pure zinc-coated steel with a strength level above 780MPa, the steel types mainly involve DH steel, Trip steel, and TBF steel with a strength level of 780MPa-1180MPa. These steel types not only have high strength, but also have good plasticity and strong plasticity. The chemical composition of the aforementioned steel grades includes C, Al, and Si; C: 0.05% to 0.15% by weight, Al: between 0.05% and 1% by weight, and Si: 0.1% to 1.5% by weight. Among them, the retained austenite is one of the main structures to improve the plasticity of the steel plate. Specifically, the strength of pure zinc-coated steel can be 780MPa, 800MPa, 820MPa, 840MPa, 860MPa, 880MPa, etc.

The present application will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods not indicating specific conditions in the following examples are usually measured according to national standards. If there is no corresponding national standard, proceed according to general international standards, conventional conditions, or the conditions suggested by the manufacturer.

Example 1

The steel strip substrate is pre-plated with electroplating, so that the nickel layer is attached to at least part of the surface of the strip steel substrate to obtain pre-nickel-plated steel, wherein the thickness of the nickel layer is 1200 mg/m ² ; the thickness of the strip steel substrate is 1.5 mm;

Subsequently, the pre-nickel-plated steel enters an annealing furnace for annealing, and when the temperature of the steel strip substrate in the annealing process is 750°C, the dew point is increased to 0°C, so that the surface of the nickel-plated steel forms a decarburization layer;

subsequently galvanizing said nickel-plated steel containing the decarburized layer, such that the zinc layer adheres to at least part of the surface of said nickel-plated steel;

Finally, a mobile cooling bellows is used at a position 50cm above the air knife to force-cool the galvanized steel at a cooling rate of 10°C/s to obtain pure zinc-coated steel; among them, the thickness tolerance of the actual horizontal coating thickness of the strip is 1.5g/m ^2. The strength of pure zinc-coated steel is 780MPa, and the thickness of the zinc coating is 100g/m ² .

Example 2

The steel strip substrate is pre-plated with electroplating, so that the nickel layer is attached to at least part of the surface of the strip steel substrate to obtain pre-nickel-plated steel, wherein the thickness of the nickel layer is 500 mg/m ² ; the thickness of the strip steel substrate is 0.4 mm;

Subsequently, the pre-nickel-plated steel is entered into an annealing furnace for annealing, and when the temperature of the steel strip substrate in the annealing process is 650°C, the dew point is increased to -10°C, so that a decarburization layer is formed on the surface of the nickel-plated steel;

subsequently galvanizing said nickel-plated steel containing the decarburized layer, such that the zinc layer adheres to at least part of the surface of said nickel-plated steel;

Finally, a mobile cooling bellows is used at a position 50cm above the air knife to force-cool the galvanized steel at a cooling rate of 5°C/s to obtain pure zinc-coated steel; among them, the thickness tolerance of the actual horizontal coating thickness of the strip is 2g/ ^m2 , the strength of pure zinc-coated steel is 780MPa, and the thickness of the zinc coating is 100g/m ² .

Example 3

The steel strip substrate is pre-plated with electroplating, so that the nickel layer is attached to at least part of the surface of the strip steel substrate to obtain pre-nickel-plated steel, wherein the thickness of the nickel layer is 2500 mg/m ² ; the thickness of the strip steel substrate is 6.0 mm;

Subsequently, the pre-nickel-plated steel enters an annealing furnace for annealing, and when the temperature of the steel strip substrate in the annealing process is 800°C, the dew point is increased to 20°C, so that a decarburization layer is formed on the surface of the nickel-plated steel;

subsequently galvanizing said nickel-plated steel containing the decarburized layer, such that the zinc layer adheres to at least part of the surface of said nickel-plated steel;

Finally, a mobile cooling bellows is used at a position 50cm above the air knife to force-cool the galvanized steel at a cooling rate of 12°C/s to obtain pure zinc-coated steel; among them, the thickness tolerance of the actual horizontal coating thickness of the strip is 1.5g/m ^2. The strength of pure zinc-coated steel is 1180MPa, and the thickness of the zinc coating is 100g/m ² .

Example 4

The steel strip substrate is pre-plated with electroplating, so that the nickel layer is attached to at least part of the surface of the strip steel substrate to obtain pre-nickel-plated steel, wherein the thickness of the nickel layer is 1800 mg/m ² ; the thickness of the strip steel substrate is 3.0 mm;

Subsequently, the pre-nickel-plated steel enters an annealing furnace for annealing, and when the temperature of the steel strip substrate in the annealing process is 750°C, the dew point is increased to 0°C, so that the surface of the nickel-plated steel forms a decarburization layer;

subsequently galvanizing said nickel-plated steel containing the decarburized layer, such that the zinc layer adheres to at least part of the surface of said nickel-plated steel;

Finally, a mobile cooling bellows is used at a position 50cm above the air knife to force-cool the galvanized steel at a cooling rate of 8°C/s to obtain pure zinc-coated steel; among them, the thickness tolerance of the actual horizontal coating thickness of the strip is 1.5g/m ^2. The strength of pure zinc-coated steel is 900MPa, and the thickness of the zinc coating is 100g/m ² .

Example 5

Adopt electroplating method to carry out pre-nickel-plating to strip substrate, make nickel layer adhere to at least part surface of described strip substrate, obtain pre-nickel-plated steel, wherein, nickel layer thickness is 2000mg/m ² ; Strip substrate thickness is 2.0 mm;

Subsequently, the pre-nickel-plated steel enters an annealing furnace for annealing, and when the temperature of the steel strip substrate in the annealing process is 700°C, the dew point is increased to 10°C, so that a decarburization layer is formed on the surface of the nickel-plated steel;

subsequently galvanizing said nickel-plated steel containing the decarburized layer, such that the zinc layer adheres to at least part of the surface of said nickel-plated steel;

Finally, a mobile cooling bellows is used at a position 80cm above the air knife to force-cool the galvanized steel at a cooling rate of 10°C/s to obtain pure zinc-coated steel; among them, the thickness tolerance of the actual horizontal coating thickness of the strip is 1.5g/m ^2. The strength of pure zinc-coated steel is 780MPa, and the thickness of the zinc coating is 100g/m ² .

Comparative example 1

Put the strip into the annealing furnace for annealing, and raise the dew point to -50°C when the temperature of the strip substrate during the annealing process is 750°C;

Subsequent galvanizing of said steel strip so that the zinc layer adheres to at least part of the surface of the upper steel strip;

Finally, a mobile cooling bellows is used at a position 50cm above the air knife to force-cool the galvanized steel at a cooling rate of 10°C/s to obtain pure zinc-coated steel; among them, the thickness tolerance of the actual horizontal coating thickness of the strip is 1.5g/m ^2. The strength of pure zinc-coated steel is 780MPa, and the thickness of the zinc coating is 100g/m ² .

Comparative example 2

Adopt electroplating mode to carry out pre-nickel plating to strip substrate, make nickel layer adhere to at least part surface of described pre-nickel-plated steel, obtain pre-nickel-plated steel, wherein, nickel layer thickness is 300mg/m ; Strip substrate thickness ^is 1.5mm;

Subsequently, the pre-nickel-plated steel is entered into an annealing furnace for annealing, and when the temperature of the steel strip substrate in the annealing process is 750°C, the dew point is increased to -20°C;

Subsequent galvanizing of said steel strip so that the zinc layer adheres to at least part of the surface of the upper steel strip;

Finally, a mobile cooling bellows is used at a position 50cm above the air knife to force-cool the galvanized steel at a cooling rate of 10°C/s to obtain pure zinc-coated steel; among them, the thickness tolerance of the actual horizontal coating thickness of the strip is 1.5g/m ^2. The strength of pure zinc-coated steel is 780MPa, and the thickness of the zinc coating is 100g/m ² .

Fig. 2 is the metallographic structure diagram of adopting dew point regulation and control to form decarburization layer provided by Example 1 of the present application, and Fig. 3 is the metallographic structure diagram of no dew point regulation and non-formation of decarburization layer provided by Comparative Example 1 of the present application; it can be seen A uniform decarburization layer has been formed on the surface of the pre-nickeled steel surface in Example 1;

Fig. 4 is the electronic probe diagram of the nickel layer between the 780MPa level pure zinc-coated steel coating and the substrate provided in Example 1 of the present application. It can be seen that there is a nickel layer on the surface of the 780MPa level pure zinc-coated steel.

Table 1 Results of whether there are obvious LME cracks in spot welding liquid metal of pure zinc-coated steel in Examples 1-5 and Comparative Examples 1-2.

serial number Whether there are obvious LME cracks Example 1 No obvious LME cracks Example 2 No obvious LME cracks Example 3 No obvious LME cracks Example 4 No obvious LME cracks Example 5 No obvious LME cracks Comparative example 1 There are obvious LME cracks Comparative example 2 There are obvious LME cracks

Spot welding experiments were carried out on samples without artificial decarburization and nickel flash plating (comparative example 1-2) using the internal dew point regulation of the annealing furnace to carry out artificial decarburization + flash nickel plating (embodiment 1-5), and the welding current was not 6.5KA , The electrode pressure is not 4KN.

Figure 5 is an improvement effect diagram of spot welding liquid metal embrittlement of 780MPa grade pure zinc-coated steel provided by Example 1 of the present application, from which it can be seen that there is no obvious LME crack on the surface of 780MPa grade pure zinc-coated steel through welding experiments. From Table 1, it can be seen that there is no obvious LME crack in the spot welding of liquid metal on pure zinc-coated steel in Example 2-4, which shows that the method of artificial decarburization + flash nickel plating can significantly improve the spot welding of liquid metal on 780MPa-level pure zinc-coated steel. To brittle phenomenon.

The above descriptions are only specific implementation manners 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 readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the present application will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims (10)

1. A method of welding pure zinc coated steel, the method comprising:

nickel pre-plating is carried out on the strip steel matrix so that a nickel layer is attached to at least part of the surface of the strip steel matrix, and nickel pre-plated steel is obtained;

annealing the nickel preplating steel, and when the temperature of the nickel preplating steel reaches a set temperature, increasing the dew point to a target dew point temperature so as to form a decarburized layer on the surface of the nickel preplating steel;

and (3) galvanizing the nickel-plated steel containing the decarburized layer so as to enable a zinc layer to be attached to at least part of the surface of the nickel-plated steel, and then cooling under the condition of setting cooling speed to obtain the pure zinc-plated steel.

2. The method according to claim 1, wherein the nickel layer has a thickness of 500mg/m ² ～2500mg/m ² 。

3. The method of claim 1, wherein the target dew point temperature is between-10 ℃ and 20 ℃.

4. The method according to claim 1, wherein the zinc layer has a thickness overrun of 2g/m or less during galvanization ² 。

5. The method of claim 1, wherein the set cooling rate is from 5 ℃/s to 12 ℃/s.

6. The method according to claim 1, wherein the pre-nickel plated steel is set at a temperature of 650 ℃ to 800 ℃.

7. The method of claim 1, wherein the thickness of the strip substrate is 0.4mm to 6.0mm.

8. The method according to any one of claims 1 to 7, wherein the strength of the pure zinc coated steel is equal to or more than 780MPa.

9. The method of claim 8, wherein the strength of the pure zinc coated steel is 780MPa to 1180MPa.

10. The method according to claim 9, characterized in that if the strength of the pure zinc coated steel is 780MPa to 1180MPa, the pure zinc coated steel comprises at least one of the following steel grades: DH steel, trip steel and TBF steel.

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