Production process for stably controlling adhesive force of DP steel zinc layer

Abstract

The invention provides a production process for stably controlling adhesive force of a DP steel zinc layer. The production process comprises the following steps: step 1, setting a heating section 1, a heating section 2 and a furnace nose section in a total radiation heating annealing furnace; 2, according to the model and thickness of DP steel, target dew points of a first heating section, a second heating section and a furnace nose section are set; 3, according to the target dew points set in the first heating section, the second heating section and the furnace nose section in the step 2, water vapor is put into the protective gas for humidification, and the water vapor reacts with Si, Mn and Cr elements enriched on the surface of the steel plate to generate volatile oxides; the dew point of the annealing furnace is precisely controlled in a segmented mode, different humidification modes are adopted, and the surface state is controlled, so that surface oxide residues are reduced, cleanliness of a steel substrate is guaranteed, and the binding force of a zinc layer is improved; the iron oxide layer formed on the surface of the steel plate enters a reducing atmosphere annealing furnace containing hydrogen, the hydrogen can reduce the iron oxide layer on the surface of the steel plate to form a reduced iron layer, and the adhesive force of a zinc layer is improved.

Description

Technical Field

[0001] This invention relates to the field of automotive parts technology, and more specifically, to a production process for stabilizing and controlling the adhesion of the zinc layer on DP steel. Background Technology

[0002] With the development of the automotive industry, galvanized DP steel not only meets the various requirements for automotive steel in terms of strength, but is also widely used in various automotive parts, such as various reinforcing plates, crossbeams, door sills and other components.

[0003] Because of the addition of a zinc coating, corrosion resistance is improved, but there are also requirements for the adhesion of the zinc coating. Compared with some conventional high-strength steels, LC steels, and IF steels, DP steel contains more alloying elements, such as Si, Mn, and Cr. After the conventional hot-dip galvanizing process, the adhesion of the zinc coating is relatively weak, and the coating is easy to peel off during cold stamping.

[0004] Because DP steel contains a large number of alloying elements, such as Si, Mn, and Cr, these alloying elements tend to accumulate and oxidize on the steel plate surface during heating, leading to reduced coating adhesion. To avoid this problem, the humidification process in the heating section is adjusted. Summary of the Invention

[0005] The purpose of this invention is to provide a production process for stabilizing and controlling the adhesion of the zinc layer on DP steel, so as to achieve stable control of the zinc layer adhesion on DP steel, thereby ensuring the stability of the coating during stamping and meeting the technical requirements of customers for stamping.

[0006] This invention is achieved through the following technical solution, including the following steps:

[0007] Step 1: Set up heating section 1, heating section 2, and furnace nose section in the total radiation heating annealing furnace;

[0008] Step 2: Based on the DP steel type and thickness, set the target dew points for heating section 1, heating section 2, and furnace nose section;

[0009] Step 3: Based on the target dew points set in step 2 for heating section 1, heating section 2, and furnace nose section, humidify the protective gas with water vapor, so that the water vapor reacts with the Si, Mn, and Cr elements enriched on the steel plate surface to generate volatile oxides.

[0010] To better realize the present invention, further, in step 2, the DP steel is HCT600X steel with a thickness > 1.5mm, the dew point temperature of heating section 1 is controlled at -15 (±2℃), and the dew point temperature of the furnace nose section is controlled at -30±2℃.

[0011] To better realize the present invention, in step 2, the DP steel is HCT600X steel with a thickness of ≤1.5mm, the dew point temperature of heating section 1 is controlled at -25 (±3℃), and the dew point temperature of the furnace nose section is controlled at -30±2℃.

[0012] To better realize the present invention, in step 2, the DP steel is HCT780X steel with a thickness of >2.1mm, the dew point temperature of heating section 1 is controlled at -10±3℃, and the dew point temperature of the furnace nose section is controlled at -40 (±2℃).

[0013] To better realize the present invention, in step 2, the DP steel is HCT780X steel with a thickness of ≤2.1mm, the dew point temperature of heating section 1 is controlled at -10±3℃, and the dew point temperature of the furnace nose section is controlled at -30 (±3℃).

[0014] To better realize the present invention, further, in step 2, the DP steel is HCT980X steel, the dew point temperature of heating stage 1 is controlled at -10±3℃, the dew point temperature of heating stage 2 is controlled at -32 (±3℃), and the dew point temperature of the furnace nose stage is controlled at <-40℃.

[0015] To better realize the present invention, further, in step 2, the DP steel is HCT1180X steel, the dew point temperature of heating stage 1 is controlled at -10±3℃, the dew point temperature of heating stage 2 is controlled at -30 (±3℃), and the dew point temperature of the furnace nose section is controlled at <-40℃.

[0016] To better realize the present invention, further, in step 3, the protective gas is an N2-H2 mixture with an H2 concentration of 4%.

[0017] The beneficial effects of this invention are: by precisely controlling the dew point of the annealing furnace in segments and using different humidification methods, the surface state is controlled, thereby reducing surface oxide residue, ensuring the cleanliness of the steel substrate, and improving the adhesion of the zinc layer; at the same time, dew point humidification also causes an iron oxide layer to form on the surface of the steel plate. The iron oxide layer formed on the surface of the steel plate enters the reducing atmosphere annealing furnace containing hydrogen, where hydrogen can reduce the iron oxide layer on the surface of the steel plate to form a reduced iron layer, thereby improving the adhesion of the zinc layer. Attached Figure Description

[0018] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the present invention will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0019] Figure 1This invention provides a production process diagram for stabilizing and controlling the adhesion of the zinc layer on DP steel.

[0020] Figure 2 This is a ball punch test image of the adhesion of the zinc coating on DP steel prior to the implementation of this invention;

[0021] Figure 3 This is a ball punch test diagram of the adhesion of the zinc coating on DP steel after the implementation of this invention. Detailed Implementation

[0022] The technical solutions of the present invention will now be described with reference to the accompanying drawings.

[0023] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] Example 1:

[0025] Please refer to Figure 1 The present invention provides a production process for stabilizing and controlling the adhesion of the zinc coating on DP steel, comprising the following steps:

[0026] Step 1: Set up heating section 1, heating section 2, and furnace nose section in the total radiation heating annealing furnace;

[0027] Step 2: Based on the DP steel type and thickness, set the target dew points for heating section 1, heating section 2, and furnace nose section;

[0028] Step 3: Based on the target dew points set in Step 2 for Heating Section 1, Heating Section 2, and Furnace Nose Section, humidify the protective gas with water vapor. This allows the water vapor to react with the Si, Mn, and Cr elements enriched on the steel plate surface to form oxides. The reaction formula is as follows:

[0029] ①Si removal:

[0030] Si(s)+2H2O(g)->SiO2(g)↑+2H2(g)

[0031] ②Mn removal:

[0032] Mn(s) + H₂O(g) -> MnO(g)↑ + H₂(g)

[0033] ③Cr removal:

[0034] 2Cr(s)+3H2O(g)->Cr2O3(s)+3H2(g)

[0035] In step 3, the protective gas is a N2-H2 mixture with an H2 concentration of 4%. During the humidification process in the annealing furnace, an iron oxide layer is also formed on the surface of the steel plate. The steel plate then enters the reducing atmosphere annealing furnace containing hydrogen. The hydrogen can reduce the iron oxide layer on the surface of the steel plate to form a reduced iron layer, thereby improving the adhesion of the zinc layer.

[0036] The reaction formula for the oxidation of Fe matrix is:

[0037] Fe + H₂O(g) → FeO + H₂

[0038] The reaction formula for the reduction of the iron oxide layer is:

[0039] FeO + H2 => Fe + H2O

[0040] The DP steel is HCT600X steel with a thickness greater than 1.5mm. The dew point temperature of the first heating stage is controlled at -15 (±2℃), and water vapor is introduced into the protective gas of the annealing furnace for humidification. No protective gas humidification is used in the second heating stage. The dew point temperature of the furnace nose section is controlled at -30±2℃, and water vapor is introduced into the protective gas of the annealing furnace for humidification.

[0041] Example 2:

[0042] Based on Example 1, the DP steel is HCT600X steel with a thickness of ≤1.5mm. The dew point temperature of the first heating stage is controlled at -25 (±3℃), and water vapor is introduced into the protective gas of the annealing furnace for humidification. No protective gas humidification is used in the second heating stage. The dew point temperature of the furnace nose section is controlled at -30±2℃, and water vapor is introduced into the protective gas of the annealing furnace for humidification.

[0043] Example 3:

[0044] Based on Example 1, the DP steel is HCT780X steel with a thickness of >2.1mm. The dew point temperature of the first heating stage is controlled at -10±3℃, and water vapor is introduced into the protective gas of the annealing furnace for humidification. No protective gas humidification is used in the second heating stage. The dew point temperature of the furnace nose section is controlled at -40 (±2℃), and water vapor is introduced into the protective gas of the annealing furnace for humidification.

[0045] Example 4:

[0046] Based on Example 1, the DP steel is HCT780X steel with a thickness of ≤2.1mm. The dew point temperature of the first heating stage is controlled at -10±3℃, and water vapor is introduced into the protective gas of the annealing furnace for humidification. No protective gas humidification is used in the second heating stage. The dew point temperature of the furnace nose section is controlled at -30 (±3℃), and water vapor is introduced into the protective gas of the annealing furnace for humidification.

[0047] Example 5;

[0048] Based on Example 1, the DP steel is HCT980X steel. The dew point temperature of the first heating stage is controlled at -10±3℃, and water vapor is introduced into the protective gas of the annealing furnace for humidification. The dew point temperature of the second heating stage is controlled at -32 (±3℃), and water vapor is introduced into the protective gas of the annealing furnace for humidification. The dew point temperature of the furnace nose stage is controlled at <-40℃, and water vapor is introduced into the protective gas of the annealing furnace for humidification.

[0049] Example 6:

[0050] Based on Example 1, in step 2, the DP steel is HCT1180X steel. The dew point temperature of heating stage 1 is controlled at -10±3℃, and water vapor is introduced into the protective gas of the annealing furnace for humidification. The dew point temperature of heating stage 2 is controlled at -30 (±3℃), and water vapor is introduced into the protective gas of the annealing furnace for humidification. The dew point temperature of the furnace nose stage is controlled at <-40℃, and water vapor is introduced into the protective gas of the annealing furnace for humidification.

[0051] In summary, the following is a table showing the humidification requirements for different process sections within the furnace:

[0052]

[0053] The adhesion of the zinc coating on the DP steel before the implementation of the current process was tested by ball punching. The results are shown in the appendix. Figure 2 The adhesion of the zinc coating on the DP steel after implementing the current process was tested by ball punching. The results are shown in the appendix. Figure 3 The test results showed that the zinc layer did not peel off, which met expectations.

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A production process for stably controlling the adhesion of zinc coating on DP steel, characterized in that, Includes the following steps: Step 1: Set up heating section 1, heating section 2, and furnace nose section in the total radiation heating annealing furnace; Step 2: Based on the DP steel type and thickness, set the target dew points for heating section 1, heating section 2, and furnace nose section; Step 3: Based on the target dew points set in step 2 for heating section 1, heating section 2, and furnace nose section, humidify the protective gas with water vapor, so that the water vapor reacts with the Si, Mn, and Cr elements enriched on the steel plate surface to generate volatile oxides.

2. The production process for stabilizing and controlling the adhesion of the zinc layer on DP steel according to claim 1, characterized in that, In step 2, the DP steel is HCT600X steel with a thickness greater than 1.5mm. The dew point temperature of the heating section 1 is controlled at -15 (±2℃), and the dew point temperature of the furnace nose section is controlled at -30 ±2℃.

3. The production process for stabilizing and controlling the adhesion of the zinc layer on DP steel according to claim 1, characterized in that, In step 2, the DP steel is HCT600X steel with a thickness of ≤1.5mm. The dew point temperature of the heating section 1 is controlled at -25 (±3℃), and the dew point temperature of the furnace nose section is controlled at -30±2℃.

4. The production process for stabilizing and controlling the adhesion of the zinc layer on DP steel according to claim 1, characterized in that, In step 2, the DP steel is HCT780X steel with a thickness greater than 2.1 mm. The dew point temperature of the heating section 1 is controlled at -10±3℃, and the dew point temperature of the furnace nose section is controlled at -40 (±2℃).

5. The production process for stabilizing and controlling the adhesion of the zinc layer on DP steel according to claim 1, characterized in that, In step 2, the DP steel is HCT780X steel with a thickness of ≤2.1mm. The dew point temperature of the heating section 1 is controlled at -10±3℃, and the dew point temperature of the furnace nose section is controlled at -30 (±3℃).

6. The production process for stabilizing and controlling the adhesion of the zinc layer on DP steel according to claim 1, characterized in that, In step 2, the DP steel is HCT980X steel. The dew point temperature of heating stage 1 is controlled at -10±3℃, the dew point temperature of heating stage 2 is controlled at -32 (±3℃), and the dew point temperature of the furnace nose stage is controlled at <-40℃.

7. The production process for stabilizing and controlling the adhesion of the zinc layer on DP steel according to claim 1, characterized in that, In step 2, the DP steel is HCT1180X steel. The dew point temperature of heating stage 1 is controlled at -10±3℃, the dew point temperature of heating stage 2 is controlled at -30 (±3℃), and the dew point temperature of the furnace nose section is controlled at <-40℃.

8. The production process for stabilizing and controlling the adhesion of the zinc layer on DP steel according to claim 1, characterized in that, In step 3, the protective gas is a N2-H2 mixture with an H2 concentration of 4%.

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