CN115613030B - Production method of phosphorus-containing galvanized steel with excellent surface quality for automobiles - Google Patents

Abstract

The present application relates to the technical field of steel rolling, and in particular to a method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality. The method comprises the following steps: obtaining a phosphorus-containing steel sheet for automobiles; electroplating the phosphorus-containing steel sheet for automobiles with nickel to obtain a nickel-plated steel sheet; annealing the nickel-plated steel sheet under a protective atmosphere to obtain an annealed steel sheet, wherein when the temperature of the annealing treatment is 600-700°C, the dew point temperature is ‑30-‑20°C; hot-dip galvanizing the annealed steel sheet to obtain phosphorus-containing galvanized steel for automobiles. The nickel-plated layer in the nickel-plated steel sheet can inhibit the oxidative enrichment of phosphorus elements in the steel sheet to the steel surface during annealing, and at the same time reduce the dissolution of Fe elements into the zinc pot during hot-dip galvanizing treatment, thereby reducing the generation of zinc slag defects; controlling the dew point in the temperature range of 600-700°C during annealing, further inhibiting the oxidative enrichment of phosphorus elements to the surface of the strip, thereby avoiding the generation of bright spot defects, ensuring good adhesion of the coating, and ensuring the surface quality of the phosphorus-containing galvanized steel sheet.

Description

A method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality

Technical Field

The present application relates to the technical field of steel rolling, and in particular to a method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality.

Background Art

As the automotive industry's requirements for appearance quality gradually increase, the requirements for the surface quality of cold-rolled galvanized automobile outer panels are further improved. Due to the addition of phosphorus, phosphorus-containing steel is more likely to form nodules due to the reaction between phosphorus and the furnace rod coating, thereby forming bright spot defects, affecting the surface quality of phosphorus-containing galvanized automobile outer panels. In addition, in the traditional production process, the Fe element on the surface of the steel plate is easy to form zinc slag defects inside the zinc pot, and the zinc slag defects are easy to adhere to the surface of the strip, affecting the surface quality of phosphorus-containing steel galvanized automobile outer panels. Therefore, it is urgent to develop a phosphorus-containing galvanized steel for automobile outer panels with excellent surface quality, and clarify its supporting production process, so as to realize the application of phosphorus-containing galvanized steel on automobile bodies.

Summary of the invention

The present application provides a method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality, so as to solve the technical problem of poor surface quality of phosphorus-containing galvanized steel.

In a first aspect, the present application provides a method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality, characterized in that the method comprises the following steps:

Obtain phosphorus-containing steel sheets for automobiles;

Electroplating the phosphorus-containing steel sheet for automobiles with nickel to obtain a nickel-plated steel sheet;

Annealing the nickel-plated steel sheet under a protective atmosphere to obtain an annealed steel sheet, wherein when the annealing temperature is 600 to 700° C., the dew point temperature is -30 to -20° C.;

The annealed steel sheet is subjected to hot-dip galvanizing treatment to obtain phosphorus-containing galvanized steel for automobiles.

Optionally, the nickel plating amount of the nickel-plated steel plate is 200-800 mg/m ² .

Optionally, the protective atmosphere includes nitrogen and hydrogen.

Optionally, under a protective atmosphere, the nickel-plated steel plate is annealed at a speed of 60 to 120 m/min.

Optionally, the annealing treatment includes heating, soaking and cooling in sequence; the heating temperature is 25-780°C; the soaking temperature is 780-820°C; and the cooling temperature is 450-460°C.

Optionally, the temperature of the hot-dip galvanizing treatment is 445-455°C.

Optionally, the aluminum content in the zinc solution of the hot-dip galvanizing treatment is 0.15% to 0.25% by mass.

Optionally, before subjecting the automobile phosphorus-containing steel sheet to nickel electroplating to obtain the nickel-plated steel sheet, the method includes: cleaning the automobile phosphorus-containing steel sheet to remove surface impurities.

In a second aspect, the present application provides a phosphorus-containing galvanized steel for automobiles with excellent surface quality, wherein the phosphorus-containing galvanized steel is prepared by the method described in the first aspect.

In a third aspect, the present application provides an application of a method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality, wherein the application comprises applying the method of the first aspect to manufacture automobile outer panels.

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

According to the method provided in the embodiment of the present application, the nickel-plated layer in the nickel-plated steel plate can inhibit the oxidation enrichment of phosphorus in the steel plate to the steel surface during annealing, and at the same time reduce the dissolution of Fe into the zinc pot during hot-dip galvanizing, thereby reducing the generation of zinc slag defects; by controlling the dew point in the temperature range of 600-700°C during annealing, the oxidation enrichment of phosphorus on the surface of the strip is further inhibited, thereby avoiding the generation of bright spot defects, and the nickel plating and hot-dip galvanizing treatment processes work together to ensure good adhesion of the coating and the surface quality of the phosphorus-containing galvanized steel plate, which is convenient for use in automobile outer panels.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

FIG1 is a schematic flow chart of a method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality provided in an embodiment of the present application;

FIG2 is a detailed diagram of the surface quality of a steel plate provided in Comparative Example 1 of the present application;

FIG3 is a detailed diagram of the surface quality of the steel plate provided in Example 1 of the present application.

DETAILED DESCRIPTION

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.

The present application provides a method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality, as shown in FIG1 , the method comprising the following steps:

S1. Obtain phosphorus-containing steel sheets for automobiles;

As an optional implementation, before the nickel electroplating treatment, the phosphorus-containing steel sheet for automobiles is cleaned to remove impurities and oxide layers on the surface of the steel sheet.

S2. The phosphorus-containing steel sheet for automobile is subjected to nickel electroplating to obtain a nickel-plated steel sheet;

As an optional implementation, the nickel plating amount of the nickel-plated steel plate is 200-800 mg/m ² .

In the embodiment of the present application, the nickel plating amount may be 200-800 mg/m ² . If the nickel plating amount is too large, the Mn element may be enriched inside the nickel layer. If the nickel plating amount is too small, the oxidation of the P element may not be suppressed.

In the embodiment of the present application, the surface of the steel plate is electroplated with nickel using nano-plating technology.

S3. Annealing the nickel-plated steel sheet under a protective atmosphere to obtain an annealed steel sheet. When the annealing temperature is 600 to 700°C, the dew point temperature is -30 to -20°C.

In the embodiment of the present application, controlling the dew point temperature in the preset state of the annealing treatment to a preset value can inhibit the oxidation enrichment of phosphorus on the surface of the strip, thereby avoiding the generation of bright spot defects.

As an optional implementation, the annealing treatment includes heating, soaking and cooling in sequence; the heating temperature is 25-780°C; the soaking temperature is 780-820°C; the cooling temperature is 450-460°C.

As an optional implementation, the nickel-plated steel plate is annealed at a speed of 60 to 120 m/min under a protective atmosphere.

In the embodiments of the present application, if the annealing speed of the nickel-plated steel plate is too fast, it will cause the adverse effect of reducing the quality of the strip steel coating, and if the annealing speed of the nickel-plated steel plate is too slow, it will cause low production efficiency. If there is not enough interval time during the annealing process, the generation, expansion and growth of microcracks in the oxide film of the nickel-plated steel plate will be accelerated.

As an optional implementation, the protective atmosphere includes nitrogen and hydrogen.

S5. Performing hot-dip galvanizing on the annealed steel sheet to obtain phosphorus-containing galvanized steel for automobiles.

As an optional embodiment, the temperature of the hot-dip galvanizing treatment is 445-455°C.

As an optional implementation manner, the aluminum content in the zinc solution of the hot-dip galvanizing treatment is 0.15% to 0.25% by mass.

In the embodiment of the present application, controlling the appropriate zinc pot temperature, strip entering the pot temperature and zinc liquid composition can not only ensure good adhesion of the coating, but also further control the diffusion of Fe elements into the zinc pot and reduce the formation of zinc slag.

In a second aspect, the present application provides a phosphorus-containing galvanized steel for automobiles with excellent surface quality, wherein the phosphorus-containing galvanized steel is prepared by the method described in the first aspect.

In a third aspect, the present application provides an application of a method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality, wherein the application comprises applying the method of the first aspect to manufacture automobile outer panels.

The method of the present invention will be described in detail below with reference to embodiments, comparative examples and experimental data.

Embodiment 1:

The embodiment of the present invention provides a phosphorus-containing steel galvanized automobile outer panel with excellent surface quality and a production method thereof. The method provided by the embodiment of the present invention is particularly suitable for the production of phosphorus-containing steel automobile outer panels. In the embodiment of the present invention, a hot-dip galvanized 210 phosphorus + Z hot-dip galvanized automobile outer panel with a thickness of 0.7 mm and a width of 1500 mm is provided: (1) During the production process of the galvanizing production line, the surface of the strip is electroplated with nickel using nano-plating technology after the cleaning section. The nickel plating uses nickel sulfate and the thickness of the nickel plating layer is 400 mg/m ^2. (2) During the annealing process, the strip speed is 100 m/min. At 650°C, humidified nitrogen is used to control the dew point, and the dew point is controlled to -20°C. (3) The temperature of the zinc liquid inside the zinc pot is controlled to 450°C, the aluminum content of the zinc pot is controlled to 0.18%, and the temperature of the strip entering the pot is 455°C. The phosphorus-containing steel galvanized automobile outer panel is shown in Figure 3.

Embodiment 2:

In the embodiment of the present invention, a hot-dip galvanized 170 phosphorus + Z hot-dip galvanized automobile outer panel production with a thickness of 0.7 mm and a width of 1700 mm is provided: (1) During the production process of the galvanizing production line, the surface of the strip is electroplated with nickel using nano-plating technology after the cleaning section. The nickel plating uses nickel sulfate and the thickness of the nickel plating layer is 600 mg/m ^2. (2) During the annealing process, the strip speed is 100 m/min, and at 700°C, humidified nitrogen is used to control the dew point, and the dew point is controlled to -25°C. (3) The temperature of the zinc liquid inside the zinc pot is controlled to 452°C, the aluminum content of the zinc pot is controlled to 0.18%, and the temperature of the strip entering the pot is 456°C.

Embodiment 3:

In the embodiment of the present invention, a hot-dip galvanized 210 phosphorus + Z hot-dip galvanized automobile outer panel production with a thickness of 0.65 mm and a width of 1540 mm is provided: (1) During the production process of the galvanizing production line, the surface of the strip is electroplated with nickel using nano-plating technology after the cleaning section. The nickel plating uses nickel sulfate and the thickness of the nickel plating layer is 800 mg/ ^m2 . (2) During the annealing process, the strip speed is 100 m/min, and the dew point is controlled at 670°C using humidified nitrogen, and the dew point is controlled to -23°C. (3) The temperature of the zinc liquid inside the zinc pot is controlled to 450°C, the aluminum content of the zinc pot is controlled to 0.17%, and the temperature of the strip entering the pot is 458°C.

Comparative Example 1

In the embodiment of the present invention, the production of hot-dip galvanized 210 phosphorus + Z hot-dip galvanized automobile outer panels with a thickness of 0.7 mm and a width of 1650 mm is provided: before annealing, no surface flash nickel treatment is performed, the strip speed during annealing is 100 m/min, and the dew point is controlled inside the annealing furnace. The aluminum content inside the zinc pot is 0.18%, the strip temperature entering the pot is 460°C, and the phosphorus-containing steel galvanized automobile outer panel is shown in Figure 2.

The surface quality of the steel in the embodiment and the comparative example was tested, and the surface defect rates were as shown in Table 1.

Table 1 Steel surface quality test results of the embodiments and comparative examples.

From Table 1, it can be seen that after process optimization, the number of bright spots on the steel plate surface, the amount of zinc slag and the Fe content inside the zinc pot in the embodiment group are significantly reduced, while the surface quality in the comparative example is unqualified and the Fe content inside the zinc pot exceeds the standard.

As can be seen from FIG. 2 and FIG. 3 , the steel surface quality of the embodiment group is good without bright spots, while the steel surface of the comparative group has bright spots and the surface quality does not meet the standards.

It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims (6)

1. A method for producing phosphorus-containing galvanized steel for automobiles with excellent surface quality, characterized in that the method comprises the following steps: Obtain phosphorus-containing steel sheets for automobiles; Cleaning the phosphorus-containing steel plate for automobile to remove surface impurities; Electroplating the phosphorus-containing steel sheet for automobiles with nickel to obtain a nickel-plated steel sheet; Annealing the nickel-plated steel sheet under a protective atmosphere to obtain an annealed steel sheet, wherein when the annealing temperature is 600 to 700° C., the dew point temperature is -25 to -20° C.; Performing hot-dip galvanizing on the annealed steel sheet to obtain phosphorus-containing galvanized steel for automobiles; Nickel sulfate is used for nickel plating; The nickel-plated steel plate is annealed at a speed of 60 to 120 m/min; The annealing treatment includes heating, soaking and cooling in sequence; the heating temperature is 25-780°C; the soaking temperature is 780-820°C; the cooling temperature is 450-460°C, and the nickel plating amount of the nickel-plated steel plate is 200-800 mg/m ² . 2. The method according to claim 1, characterized in that the protective atmosphere comprises nitrogen and hydrogen. 3. The method according to claim 1, characterized in that the temperature of the hot-dip galvanizing treatment is 445-455°C. 4. The method according to claim 1, characterized in that, in terms of mass fraction, the aluminum content in the zinc solution of the hot-dip galvanizing treatment is 0.15% to 0.25%. 5. A phosphorus-containing galvanized steel for automobiles with excellent surface quality, characterized in that the phosphorus-containing galvanized steel is made by the method described in any one of claims 1 to 4. 6. Use of the method according to any one of claims 1 to 4, characterized in that the use comprises using the method in manufacturing automobile outer panels.