KR20010112747A - The method of manufacture Zn-Ni alloyed electro-galvanized steel with superior image clarity - Google Patents

Abstract

Disclosed is a passenger protection control system comprising two control mechanisms: one front airbag control device and one side airbag control device (8). Apart from a non volatile storage (4), the passenger protection control system comprises an additional storage (5), in which monitored data provided by the other passenger protection for detecting a possible accident are continuously stored. When an accident is detected, the data are transferred from the additional storage to the non volatile storage, in which accident-related data recorded by the passenger protection control system are stored on a long term basis.

Description

The method of manufacture Zn-Ni alloyed electro-galvanized steel with superior image clarity

This nickname relates to the manufacturing method of electro zinc-plated (EG) Zn-Ni steel sheet used as automotive exterior materials, and in particular, the roll is replaced by EDT (Electro Discharge Texturing) The present invention relates to a method of manufacturing a high-linearity Zn-Ni steel sheet by controlling the surface roughness of the CR steel sheet and the Zn-Ni steel sheet.

EG Zn-Ni steel sheet is applied to automobile exterior materials because of its beautiful surface, excellent corrosion resistance and paintability. Surface quality characteristics are the most important manufacturing conditions for use as automotive exterior materials. In particular, the outer panel of the car is finally coated, and there should be no scratches or scratches on the material (here, Zn-Ni steel sheet), and there should be no linear bending, because these defects appear on the surface of the product after painting. In order to manufacture Zn-Ni steel sheet, cold rolled hot coil and then re-roll the steel sheet and electroplating on EG Line. In this process, it is necessary to thoroughly remove the appearance defects of foreign substances, scratches and scratches. Of course, the roughness pattern of the final EG material is changed according to the roughness applied, and the shape of various linear bends must be controlled.

Therefore, many roll makers are struggling to supply Zn-Ni as an exterior plate material for automobiles while trying to secure such surface quality. The roll processing method is only a bright roll that is ground and a shot blasting method for imparting roughness, shot blast, electro discharge texturing (EDT), laser processing (LDT: Laser Dull Texturing), and electron beam Electron Beam Texturing (EBT). When illuminance is applied to the roll, the illuminance of the roll is transferred to the work material by pressing down on the work material.

Shot blasting is the most widely applied roll processing method and electric discharge machining has been widely applied recently and is being applied to production. However, this method of processing could not control the roughness precisely, there was a limit to the production of high-quality steel sheet. Therefore, high-precision manufacturing methods have been developed one after another through laser and electron beam processing methods that have recently been in the spotlight. However, such laser processing or electron beam processing has a lot of problems in application due to the extremely low productivity and expensive equipment. Until recently, the only method for obtaining high-linearity products was the manufacturing method using equipment such as laser processing or electron beam processing.However, due to the above-mentioned problems, many techniques for manufacturing high-linearity steel sheet using shot blasting and discharge processing have been studied. Research is ongoing.

In general, roughness (herein called Ra) has a very short wavelength (within 0.8mm) and most roughnesses are known to have no effect when applied, but wave roughness (herein called Wca) has a wavelength of 0.8 ~ 8mm. It is roughness that has a range of, and it affects even after painting, which has a great influence on product quality (bending and deflection). Wca should be within 0.5㎛ to show high sensibility. In case of laser processing or electron beam processing, Wca should be guaranteed within 0 ~ 1㎛ and the DOI (Distictness of Image) value is 93 ~ 97. It is reported that a value is obtained. As described above, such a facility is expensive, and it is difficult to introduce the facility due to low productivity and difficulty of maintenance. Shot blasting and electron beam processing are impossible due to the limitation of the facility.

This is because in the case of shot blasting, iron surface particles randomly applied to the surface of the roll can process the surface roughness of the roll, but it is difficult to control the surface roughness. This is because the applied powder randomly processes the rough acid and the bone. This is because control is difficult. In the case of electric discharge machining, it is possible to improve somewhat in terms of wave shape because it is sorted from high acid. Particularly, efforts to obtain good wave shape through optimum conditions have been studied because the processing characteristics are different for each processing mode. In this case, the application of the discharge processing roll to the cold rolling mill and the temper rolling roll, the selection of the appropriate mode, the appropriate roughness and the adjustment of the temper rolling elongation, etc.

In general, the background of adopting this method is to investigate that roughness and wavelength are generally proportional in the case of shot blast and to lower the Wca due to the limitation of quality requirement that the final roughness of the material should be 1.3 ~ 0.7㎛. In order to reduce the initial roughness of the roll, in this case, it is possible to satisfy some of the wave shapes due to the low roughness, but it is impossible to apply commercial production due to the disadvantage that the roll life is extremely short.

In the case of electric discharge machining, roughness and wave shape do not increase linearly regardless of the mode.However, when the roughness is 1.0㎛ or more, the wave life is partially overlaid with the high ray demand level. However, there is a limit in obtaining high sensibility of the whole product. However, some methods such as Cr coating as a method of extending the life of the roll have been implemented, but it is also difficult to apply due to pollution problems.

Therefore, in the case of electric discharge machining, it is known to select the proper mode, to reduce the initial roughness, and to provide the sensibility with the elongation less than 1.0% in temper rolling.

In order to overcome the above-mentioned problems, the present invention applies the electric discharge processing roll and selects the mode, after rolling and plating for the strict control of roughness and wave shape in the process of electro galvanizing after cold rolling and temper rolling. The purpose of this study is to manufacture high-strength Zn-Ni automotive steel sheets with a waviness of less than 0.4 ㎛ and a DOI of more than 90%.

In order to achieve the above object, the present invention applies the EDT roll to the cold rolled roll # 5 Stand. Also, after the EDT processing mode is set to the capacity (-), the roughness of the applied roll is 2.0 μm and 2.0 μm of the roller. It was lowered compared to 2.4㎛, so the cold wave rolling was controlled within 0.4㎛ and EDT was also applied to the temper roll, and the temper rolling elongation was applied to 0.7% and the EDT processing mode was set to the capacity (-). Roughness was adjusted to Ra 2.0 micrometers and Ra 2.0 micrometers, and the wave shape at this time was controlled to within 0.4 micrometers. It is also an object of the present invention to provide a high-linearity Zn-Ni manufacturing method having a Zn-Ni plating of the cold-rolled steel sheet thus prepared and having a wave shape of 0.4 µm or less and a DOI value of 90% or more.

1 is a schematic diagram of a plating process.

Therefore, the present invention applies the EDM roll processing method using a specific processing mode for cold rolling and temper rolling when manufacturing Zn-Ni steel sheet for automobiles, applying the optimum elongation in temp rolling and After the Zn-Ni plating of the cold rolled steel sheet, the cross-correlation control is performed to manufacture the high-strength Zn-Ni steel sheet with wave shape (Wca) ≤ 0.4 and DOI 90% or more. . In order to achieve the above object, the present invention applied the initial TCM # 5 roll (EDT) to discharge processing (EDT), and the processing mode was applied as the capacity (-). By applying the electric discharge machining (EDT) furnace, the processing mode was set to the capacity (-), and the upright roughness was 2.0 μm and the downright roughness was 2.0 μm, respectively. In addition, the material adopts IF (Interstitial Free) steel, and the temper rolling elongation was set to 0.7 after numerous tests on the material thickness of 0.8mm. Current density control through inter-pole distance control in the hot dip galvanizing process and conductor rolls are replaced with robber rolls and managed at 20 ~ 24g / ㎡ based on double-sided weight, ultimately the wave shape (Wca) in cold rolling ) To control 0.4μm or less, and to control the WC of temper rolling 0.4μm or less, control the EG Zn-Ni wave size to 0.4μm or less and manufacture the high-strength Zn-Ni sheet with 90% or more DOI index. It is to provide a method.

EDT discharge processing is the EDT (discharge machining) processing of the first grinding roll, and deep bone is not processed by discharge processing from the highest acid. Therefore, the roll has a characteristic of smoothing as a whole. This has the effect of lowering the long wavelength roughness index Wca. There are five machining modes for EDT machining, and the roughness conditions given to the rolls differ from mode to mode. The five modes are Capacity (+), Capacity (-), and Psedo Mode, and Impulse (+) and Impulse (-) modes. Operations are generally in the Capacity (-) and Impulse (+) modes. Use In general, TCM rolls do not apply EDT rolls to this day, but only bright rolls or shot blasts are generally applied.

The application of the EDT processing roll to the TEM # 5 Stand is to lower the WC as described above. Roughness is generally referred to as the centerline average roughness Ra, so that product roughness 0.7 ~ 1.2㎛ is applied to be used for automotive steel sheet. However, this roughness is not important because most of the roughness disappears during painting. This is because it is for automobile use.

However, the wavelength range of the wave is 0.8 ~ 8mm, and the roughness just before being visible, and even after coating, the wave remains and remains on the surface, which greatly affects the surface quality, ie sensibility. For this reason, EDT was applied to give roll roughness. In the case of bright trolley, roughness and wave shape are very small, but it is somewhat irregular, and it is hard to give total roughness in temper rolling. Although the shot blasting intensity can be arbitrarily controlled, the control of wave shape is theoretically difficult. Therefore, the EDT roll is applied to the cold rolled # 5 roll, which is not applicable. Typical roll roughness was 2.4 Ra μm, and in the case of the present invention, the upper roll was 2.0 μm and the lower roll was 2.0 μm. This prevents the wave shape from being somewhat high when the initial roller roughness is too high, and when the roughness is too low, the roll life is extremely low, making commercial use difficult. The overall rolling reduction in cold rolling is about 60 ~ 85%, but when rolling rolls are processed in five stages, most of them are rolled up to four stages and the rolling reduction is not large for the purpose of surface roughness and shape correction in # 5 roll processing. . Therefore, Wca (wavelength) was able to be managed to 0.4 µm or less after cold rolling by applying roughness in the final roll.

Cold rolled steel sheet is hard, so it performs heat treatment and performs skin pass for surface shape and roughness control. Process to μm. EDT processing and application modes also apply capacity. This is because the roll roughness of the temper rolling is transferred to the material in proportion to the elongation at the time of the temper rolling. When the roll roughness is high, the steel sheet roughness is prevented from increasing due to the large amount of transfer. This is because some of them may exceed 0.4 μm.

In general, when the impulse (+) mode is applied, the peak count increases, the illuminance is uniform, and the wave shape is known to be good, but in the present invention, both the cold rolling and the temper rolling have applied the capacity (-) mode. . It is shown that the number of peaks is small, but this is related to the plating process of the material. That is, when the number of peaks and the roughness width are short during Zn-Ni plating within 2 to 3㎛, the roughness of the plating layer may be unstable. Therefore, Impulse (+) is advantageous when looking at the cold rolled steel itself, but considering the plating side, it is advantageous to select a capacity (-) mode with a large roughness width and a small number of peaks.

Typically, the life of the Cr-treated roll is 250km, but this is the case when the roughness is processed to Ra 2.4㎛ and the roughness is processed to Ra 2.0 level, the roller life becomes extremely short, there is a problem in production. In fact, when the light is low, the roll life is not 100 km. Of course, this is to satisfy the minimum steel sheet roughness to be supplied for automotive use. Therefore, as a measure to solve this problem, as a result of examining the relationship by material and temper rolling elongation, the material used in the present invention (IF Steel) (C) 20 ~ 30ppm, N (16 ~ 20ppm), P (80 ~ 120ppm) ), The elongation applied to the material thickness of 0.8 mm was set to 0.7% for materials having component concentrations of S (40 to 60 ppm) and Ti (200 to 600 ppm). In addition, according to the proportionality of the elongation, the initial elongation is 0.7% 50km, 0.8% elongation at 100km, 0.9% elongation at 100-150km, and 1.0% elongation at 150-250km. Cold rolled steel sheet was manufactured without any gap. In the plating process, the distance between the pole was 32mm from the upper part to 16mm and the lower part was also reduced from 16mm to 8mm, so that the plating current density was increased even though a constant current was flowed, resulting in a smooth plating layer. The surface roughness quality could be secured by using rubber rolls instead of stainless steel rolls in the cell 13 which brings surface defects due to compression during plating. For this reason, there is no change in the roughness Ra and the wave shape Wca of the steel sheet even after plating.

Example

The present invention will be described through the following examples.

As shown in Table 1, it is found that Ra is generally very low, but somewhat irregular, and in the case of Wca, it is inappropriate to control low and high when applying bright rolls. In the case of shot blasting, roughness was generally in the range of 0.7 ~ 0.99㎛, and the waviness (Wca) was found to be generally high from 0.55 to 0.75㎛.

In the case of electric discharge machining (EDT), the existing 2.4㎛ and 2.0㎛ of the invention material were applied.

In the case of 2.4 Ra, roughness of the material was generally high (0.54 ~ 0.75), and Wca was also generally good, but high in some cases, from 0.32 to 0.57㎛. This is due to the early roughness, which may affect some of the wave index. As a result of lowering the initial roughness to 2.0㎛, the material Ra was very low, and Wca also satisfied 0.4㎛, the target wave level, from 0.29 to 0.4㎛, and there was no significant difference in the roll life in the cold rolling stage.

Table 2 shows the roughness and wave shape according to the rolling distance as a roughness analysis result after temper rolling. Even if EDT is used, when the initial illuminance is high, the initial illuminance of the material is high in relation to the transfer rate, and the wave form also exceeds the target 0.4 μm. As a result of lowering the initial roughness in cold rolling and temper rolling, it satisfies the target waviness value of 0.4㎛ from the beginning, but the distance to the raw material roughness of 0.7㎛ (Ra), which is the level of the waste disposal, is short, so the reduction of the roll life due to the replacement of the roll is problematic. do. Therefore, there is a need for a technique of maintaining the wave shape without shortening the roll life.

Table 3 shows the range of applied elongation according to the thickness.

As shown, the higher the elongation, the higher the elongation should be applied, and the lower the elongation, the lower the transfer rate of the steel sheet. Therefore, the elongation is directly related to the roll life. Depending on the material, high-strength steel can maintain the roughness of the steel sheet only when high elongation is applied compared to the general steel (IF) steel. Steel used in the present invention is usually 0.7mmt ~ 0.9mmt in thickness, in this embodiment based on 0.8mmt, the application elongation was selected as 0.7%, as shown in Table 2, the elongation is continuously applied to 0.7% Since the roller life is low due to low roller roughness, the elongation needs to be continuously increased. Therefore, as shown in Table 4, when the elongation was increased compared to the rolling distance, the desired wave shape and roughness value could be obtained without reducing the roll life.

As shown in FIG. 1, 32 mm and 16 mm were respectively applied to the upper and lower rolls of the anode gap in the plating process, but in the present invention, 16 mm and 8 mm were respectively applied to increase the current density under the same current. In order to obtain a plated layer with high surface smoothness, rubber rolls were applied to the 13th cell, which could generate pressed marks on the plated surface, to eliminate surface quality differences between the top and bottom of the plated layer and to prevent color difference.

As a result of the manufacturing method to obtain the roughness pattern for each process unit as shown in Table 5.

In other words, WC, which directly affects the sensibility as a result of temper rolling after cold rolling, was very good at 0.35㎛, and it was judged that the application of the capacity (-) mode was effective because the roughness after the tempered sheet and Zn-Ni plating was the same. Also, the sensibility of the final product, EG Zn-Ni sheet, could be maintained at 90 ~ 92% based on DOI.

According to the present invention, it is possible to manufacture Zn-Ni-coated steel sheet having good sensibility through controlling the surface state of the rolling roll in the cold rolling and temper rolling stages, controlling the temper rolling rate, controlling the discharge processing mode, and optimizing the plating process. It worked.

Table 1

TABLE 2

TABLE 3

Table 4

Table 5

Claims (1)

In the manufacture of electroplated Zn-Ni automotive outer plate material using IF steel as raw material, the application of EDM capacity (-) to cold rolling and temper rolling and the roughness of application roll are Ra 2.0, respectively. The rolling reduction rate was changed from 0.7% to 1.2% according to the rolling distance to make the wca (Wca) 0.4 탆 or less in the cold rolling and 0.4 m or less in the cold rolling and between the anodes during Zn-Ni plating. The distance between the upper roll and the rear roll is 16mm and 8mm, respectively, and the rubber roll is used in the 13th cell to improve the plating smoothness, so that the surface of the final Zn-Ni plated steel sheet has a wave shape (Wca) of 0.4㎛ or less. And a step of setting the degree of stiffness (DOI) to 90% or more.