CN117107181A - Precoated steel sheet for hot stamping and method for producing same, hot stamped part, method for producing same, and application - Google Patents

Precoated steel sheet for hot stamping and method for producing same, hot stamped part, method for producing same, and application Download PDF

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Publication number
CN117107181A
CN117107181A CN202311025831.XA CN202311025831A CN117107181A CN 117107181 A CN117107181 A CN 117107181A CN 202311025831 A CN202311025831 A CN 202311025831A CN 117107181 A CN117107181 A CN 117107181A
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China
Prior art keywords
rpc
surface roughness
weight
hot
coating
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CN202311025831.XA
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Chinese (zh)
Inventor
吴笑风
周世龙
吴德东
余林
杨红钢
徐海仁
陈直朋
刘春童
尹仁诘
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Magang Group Holding Co Ltd
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Magang Group Holding Co Ltd
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Priority to CN202311025831.XA priority Critical patent/CN117107181A/en
Publication of CN117107181A publication Critical patent/CN117107181A/en
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/12—Aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/50—Controlling or regulating the coating processes

Abstract

The invention provides a precoated steel sheet for hot stamping and a method for producing the same, a hot stamped part, a method for producing the same, and an application thereof, when the precoated weight is 20-60 g/m 2 In the time-course of which the first and second contact surfaces,ensuring that the coating has higher surface roughness Ra and Rpc after thermoforming by controlling the surface roughness Ra and Rpc of the pre-coating; the uniformity of the precoating weight is controlled stably by controlling the plate shape of the steel plate before aluminizing and the parameters of the air knife after aluminizing and the cutting; by controlling the uniformity of the weight of the precoat and the uniformity of the heating temperature in the heating process in the thermoforming, the uniformity of the liquefying flow of the heated coating is ensured, and the coating after the thermoforming is finally ensured to have uniform surface roughness Ra and Rpc. The coatings of the hot-stamped parts produced by the invention have higher and more uniform surface roughness Ra and Rpc, thereby ensuring good paint adhesion and corrosion resistance of the whole part.

Description

Precoated steel sheet for hot stamping and method for producing same, hot stamped part, method for producing same, and application
Technical Field
The invention belongs to a hot stamping forming member, in particular to a precoated steel plate for hot stamping forming and a manufacturing method thereof, a hot stamping forming part and a manufacturing method and application thereof, and is used for vehicles.
Background
In recent years, the requirements of various countries in the world on safety, energy conservation and emission of automobiles are increasingly strict, and high strength and thinning, energy conservation and emission reduction are always main development trends of the automobile industry. The method is mainly applied to the production of high-strength and formed complex parts, and can avoid the defects of difficult cold forming, large rebound, poor dimensional stability and the like.
In the hot stamping process, if bare plate hot forming steel is adopted, oxidation and decarburization are inevitably generated on the surface of the steel plate, so that the strength of the steel plate is affected, and the hot forming part is required to be subjected to shot blasting or pickling treatment, so that the dimensional accuracy of a product is affected. In view of the above problems, coated hot-formed steel is currently the dominant market product. The hot forming steel coating products developed at home and abroad mainly comprise aluminum-silicon (Al-Si), zinc (such as GI and GA) and the like, and the zinc coating is easy to generate liquid zinc brittleness during high-temperature stamping, so that stamping cracking is caused. The coating product which is used at present is mainly Al-Si, and the product is firstly proposed by Arcelor Mittal and successfully applied to industrial trial production, and the typical coating component (mass percent) is 87% Al-10Si-3% Fe.
When the Al-Si coating product is used for hot stamping forming, the coating and the matrix are mutually diffused in the heating process to form an Fe-Al and Fe-Al-Si alloying coating, so that the property of the coating is changed, and the coating cannot react with phosphating solution well at the moment, so that the subsequent painting adhesion such as electrophoresis is poor. In order to ensure good adhesion of the subsequent painting such as electrophoresis, the surface roughness of the coating after thermoforming needs to be in a higher value, and the high surface roughness is used for improving the mechanical binding force between the paint film such as electrophoresis and the coating layer. For example, it is stated in the general standard that the surface roughness after thermoforming of an Al-Si coating satisfies Ra. Gtoreq.1.8, rt. Gtoreq.12; the surface roughness after thermoforming of the Al-Si coating is specified in the Phideterkohler automobile company standard to satisfy Rz of between 10 and 25. The above Ra, rt, rz all represent the peak height or peak-valley size in the roughness profile (Ra means average roughness, it means absolute value of average value of surface profile height of a certain specific length, rt means sum of peak height and peak-valley height, rz means microscopic unevenness, and the distance difference between the highest peak and the lowest valley of the object surface).
The invention discloses a precoated steel sheet for hot forming, a preparation method thereof and a hot formed steel member and application thereof, wherein the precoated steel sheet is disclosed in patent CN113481451A published on 10/8 of 2021, and the invention discloses that when the thickness of the precoated layer is thinner than 5-19 mu m, the liquefied coating mainly fills pits due to the smaller liquefying amount of the coating after heating, and the larger surface roughness Ra cannot be ensured after heating. The invention improves the surface roughness Ra of the coating after thermoforming by improving the surface roughness Ra of the precoating, ensures that the surface roughness Ra of the coating after thermoforming is more than or equal to 1.80 mu m, and further ensures that the coating after thermoforming has good paint adhesion and paint corrosion resistance. However, in practical use, when the precoat weight is small, even if Ra is large, paint adhesion and corrosion resistance are poor, which is related to uneven surface roughness Ra of the thermoformed part, and high, uniform Rpc cannot be ensured.
Patent publication No. WO2021103805A1 by baoshan iron and steel co.ltd, 6/3 of 2021 discloses a thermoformed part having excellent paint film adhesion and a method of making the same. The patent provides a thermoformed part in which the weight average of the aluminized layer is 20 to 120g/m 2 The surface roughness Ra of the plate is 0.3-2.0 mu m, the surface roughness peak count Rpc of the plate is 30-150, the average roughness Ra of the surface of the hot formed part is 1.5-2.5 mu m, and the surface roughness peak count Rpc is 50-250. However, when the weight of the aluminized layer is small, the average roughness Ra of the surface of the thermoformed part hardly satisfies the above Ra requirement when the sheet surface roughness Ra is 0.3 to 2.0 μm. Further, the uniformity of the surface roughness Ra, rpc of the thermoformed part at this time is affected by the coating thickness uniformity of the raw material, the plate shape and the thermoforming process regime.
Therefore, for aluminum or aluminum alloy coatings, it is particularly important how to improve paint adhesion and corrosion resistance after the aluminum alloy coating is thermoformed when the precoat weight is small.
Disclosure of Invention
The invention aims to provide a precoated steel sheet for hot stamping and a manufacturing method thereof, which aims to control the surface roughness Ra and Rpc of a precoated layer to ensure that the coating layer has higher surface roughness Ra and Rpc after hot stamping when the precoated layer weight is lower. In addition, the uniformity of the pre-coating weight is controlled by controlling the plate shape of the steel plate before aluminizing and the parameters of the air knife after aluminizing and stabilizing, so that the liquefying and flowing uniformity of the coating after heating is ensured, and the coating after thermoforming is ensured to have higher and more uniform surface roughness.
It is still another object of the present invention to provide a hot-stamped and formed part and a method for manufacturing the same, which is manufactured by using the precoated steel sheet for hot stamping and formed as described above through a hot-forming process while controlling the stability of heating temperature in hot-forming, and which has a high and uniform surface roughness.
It is a further object of the present invention to provide a use of the hot stamped and formed part for land motor vehicles.
The specific technical scheme of the invention is as follows:
a precoated steel sheet for hot stamping forming, wherein a precoated layer is provided on at least one surface of a substrate; the precoating is aluminum or aluminum alloy.
The total thickness of the precoated steel plate for hot stamping forming is 0.7-3.0 mm;
the weight of the precoating is 20-60 g/m of the precoating weight of each single side 2 。
The surface roughness of the precoat is controlled as follows:
when 20g/m 2 The weight of each single-sided precoating layer is more than or equal to 40g/m 2 When the surface roughness Ra of the precoating is more than or equal to 2.0 mu m and the weight of each single-sided precoating of Rpc+ is more than or equal to 100;
when 40g/m 2 The precoating weight of each single side is less than or equal to 60g/m 2 When the surface roughness Ra of the precoat is more than or equal to 2.5 mu m and the weight of the Rpc+ precoat on each side is more than or equal to 100.
Rpc+ calculated as weight per single facecoat, values in Rpc per cm and weight per single facecoat in g/m 2 The values in units are added.
The substrate comprises low carbon steel, medium carbon steel or high carbon steel.
The invention provides a manufacturing method of a precoated steel plate for hot stamping forming, which comprises the following process flows: manufacturing a substrate, hot dip plating and finishing;
the base plate is manufactured by steelmaking, continuous casting, hot rolling and acid rolling, wherein the hot rolling and acid rolling processes control the plate shape of the steel plate by controlling the rolling parameters, so that the unevenness of the manufactured base plate is within 15mm, preferably within 10 mm.
The hot dip plating: immersing the substrate in an aluminum or aluminum alloy plating solution, and then spraying nitrogen or compressed air by an air knife to control the weight of the precoat, wherein each single side of the precoat is 20-60 g/m 2 The plating solution temperature is 640-680 ℃ and the dip plating time is 2-8 s; the parameters of the air knife after hot dip plating are mainly air knife pressure, distance and height, the parameters of the air knife are mainly adjusted along with the change of the weight of the precoat and the speed of the strip steel, when the production is stable, the speed of the strip steel is not changed greatly, the fluctuation of the parameters of the air knife is required to be controlled within 5%, and the weight of the precoat fluctuates along with the fluctuation of the pressure of the air knife. Wherein, the air knife parameter fluctuation= |air knife parameter maximum value or minimum value-air knife parameter average value|/air knife parameter average value multiplied by 100%, and the air knife parameter maximum value or minimum value is calculated to take a larger number.
The invention ensures that the uniformity of the precoating weight of the whole steel plate surface after aluminizing and siliceous is better through the plate type control of the steel plate before aluminizing and siliceous and the air knife parameter control, and particularly, the fluctuation of the precoating weight of the whole steel plate surface is within 30 percent.
The finishing: according to the roughness requirement of the precoat, the process parameters of a finishing roller are adjusted to produce, and the process has the effects of improving the mechanical property and the flatness of strip steel, wherein the average Ra value of the finishing roller is 3.5-6.0, the roller Rpc is more than or equal to the precoat Rpc, and the finishing elongation is 1.0-2.0%. The invention controls: when 20g/m 2 The weight of each single-sided precoating layer is more than or equal to 40g/m 2 When the average surface roughness of the precoat layer satisfies: ra is more than or equal to 2.0 and less than or equal to 4.8, and the weight of each single-sided precoat of rpc+ is more than or equal to 100; when 40g/m 2 The precoating weight of each single side is less than or equal to 60g/m 2 When the average surface roughness of the precoat layer satisfies: ra is more than or equal to 2.5 and less than or equal to 4.8, and the weight of each single-sided precoat of rpc+ is more than or equal to 100.
The hot stamping forming part provided by the invention is prepared by adopting the precoated steel plate for hot stamping forming through heating, hot stamping forming or other heat treatment operations.
The heating means may be resistance heating, radiation heating or induction heating, and is not limited to the above.
The invention provides a manufacturing method of a hot stamping formed part, which comprises blanking, heat treatment and hot stamping.
And (3) blanking: blanking or cutting a precoated steel sheet for hot stamping into a blank of a shape required for a hot-formed part;
the heat treatment: heating the blank in a heating furnace at 860-1000 deg.c for 2-10 min in air or nitrogen. The heating furnace can adopt a box-type furnace or a roller hearth heating furnace, but no matter which heating furnace is adopted, the temperature fluctuation of a heating area is controlled within 3%, and the uniformity of the surface roughness of the heated coating is ensured.
The hot stamping: and rapidly transferring the blank subjected to heat treatment into a die for stamping forming and cooling, wherein the transfer time is not more than 15s, the stamping forming dwell time is 5-15 s, and the cooling die stripping temperature is not more than 250 ℃.
The coating Ra of the hot stamping formed part is more than or equal to 1.5 mu m, and Rpc is more than or equal to 80/cm.
The fluctuation of the surface roughness Ra of the coating of the hot stamping forming part is less than or equal to 20 percent and the fluctuation of the Rpc is less than or equal to 20 percent. Wherein, the surface roughness Ra or Rpc fluctuation= |surface roughness maximum value or minimum value-surface roughness average value|/surface roughness average value multiplied by 100%, and the larger number is taken after the calculation with the surface roughness maximum value or minimum value.
The invention provides an application of a hot stamping formed part, which is used for a land motor vehicle.
Ra and Rpc in the hot stamped parts of this invention refer to the average value, where Ra is in μm and Rpc is in/cm.
Compared with the prior art, when the precoating weight of the precoated aluminum or aluminum alloy coated steel plate is 20 to 60g/m 2 When the coating is formed, the surface roughness Ra and the surface roughness Rpc of the pre-coating are controlled to ensure that the coating has higher surface roughness Ra and Rpc after thermoforming. In addition, the uniformity of the precoating weight is controlled stably by controlling the plate shape of the steel plate before aluminizing and the parameters of the air knife after aluminizing and the cutting; in thermoforming, the heating process is controlled for heating temperature uniformity. By controlling the pre-coat weightAnd the uniformity of the coating after heating and the uniformity of the heating temperature in the heating process, thereby ensuring the uniformity of the liquefying flow of the coating after heating and finally ensuring that the coating after thermoforming has more uniform surface roughness Ra and Rpc. The hot stamping formed part is manufactured by the hot stamping forming process, and the coating has higher and more uniform surface roughness Ra and Rpc, so that the whole part is ensured to have good paint adhesion and corrosion resistance.
Drawings
FIG. 1 is a graph of the average precoat weight per side of 35g/m 2 The surface roughness Ra and Rpc of the heated coating change with heating temperature and heating time.
Detailed Description
In order to ensure good adhesion of paint such as electrophoresis after hot forming of an al—si coating, the inventors found that, in the surface roughness of the coating after hot forming, not only the size (Ra) of the peak height or the peak valley is important, but also the peak count (Rpc) of the peak height or the peak valley is important, and even when Ra is large, if Rpc is small, good paint adhesion and corrosion resistance cannot be ensured. More importantly, when the thickness of the precoat is 5-19 μm, the coating thickness is uneven or the heating temperature is uneven, the flow difference is large after the coating at different positions is liquefied, the uniformity of the surface roughness Ra and Rpc of the coating at different positions is difficult to ensure, the condition that the surface roughness Ra or Rpc at the local position is abnormally low possibly exists, the coating adhesion and corrosion resistance at the position are poor, and the coating thickness uniformity and the thermoforming process system of raw materials need to be strictly controlled. In addition, if the surface roughness Ra and Rpc of the coating after thermoforming of different parts have large difference, obvious color difference defects exist at different parts after painting, and the appearance of the final product is affected.
For the patent publication No. WO2021103805A1, the inventors found that when the weight average value of the aluminized layer is 20 to 60g/m 2 When the surface roughness Ra of the raw material is 0.3 to 2.0 μm per one surface, it is difficult to ensure that the surface roughness Ra of the thermoformed part is not less than 1.5 μm and that the surface roughness Ra, rpc of the thermoformed part is uniform at this timeIs influenced by the coating thickness uniformity, plate shape and thermoforming process system of the raw materials.
In view of the fact that when the weight of the precoating is small, the surface roughness Ra and Rpc of the coating after thermoforming can not be ensured to be high and uniform, and in order to ensure good adhesion of the coating such as electrophoresis after thermoforming of the Al-Si coating, the size of peaks or peaks and valleys is important, and the peak count (Rpc) of the peaks or peaks and valleys is also important in the roughness profile; furthermore, the coating weights differ and the roughness effect on the coating after thermoforming also differs. The invention provides a hot-stamping formed part and a manufacturing method thereof, a precoated steel plate for hot-stamping forming and a manufacturing method thereof, wherein a coating after hot-stamping forming of the hot-stamping formed part has higher and more uniform surface roughness Ra and Rpc, thereby ensuring paint adhesion and corrosion resistance after hot-stamping of an aluminum alloy coating.
The inventors found that to ensure paint adhesion and corrosion resistance after hot forming of an aluminum alloy coating, the surface roughness Ra and Rpc of the hot stamped part need to be at a high value, satisfying Ra. Gtoreq.1.5 μm and Rpc. Gtoreq.80/cm. It should be noted that Ra and Rpc are equally important for ensuring paint adhesion and corrosion resistance, that is to say even if Ra is greater, for example when Ra. Gtoreq.1.5 μm, but if Rpc is smaller at this time, for example Rpc < 80/cm; or when rpc.gtoreq.80/cm, if Ra is smaller at this time, for example Ra < 1.5 μm, both of these cases are poor in paint adhesion and corrosion resistance.
More importantly, the inventor researches that the surface roughness Ra and Rpc of the coating after the aluminum or aluminum alloy coating is heated are mainly related to the weight of the precoat and the surface roughness Ra and Rpc of the precoat, and the specific heating process has relatively small influence on the surface roughness of the coating after heating under the condition that the coating is fully alloyed, and the average value of the weight of the single-sided precoat is 35g/m by using the common heating temperature and the common heating time 2 The effect of the surface roughness Ra and Rpc of the coating after heating is shown in FIG. 1, wherein the surface roughness Ra of the precoat is 2.01 μm and Rpc is 100/cm.
For precoated steel sheet for hot stamping, when the precoating weight is large, for example, more than 60g/m 2 The precoat weight at each side affects after heatingThe surface roughness Ra and Rpc of the coating are the main factors, and at the moment, the surface roughness Ra and Rpc of the coating of the hot stamping formed part after hot forming is higher no matter the surface roughness Ra and Rpc of the precoating, so that the Ra of the coating is more than or equal to 1.5 mu m and the Rpc is more than or equal to 80/cm; however, when the precoat weight is small, such as not more than 60g/m 2 At each side, the weight of the precoat and the surface roughness Ra and Rpc of the precoat both affect the surface roughness Ra and Rpc of the heated coating, the surface roughness Ra of the heated coating tends to be lower than that of the precoat Ra, and the surface roughness Rpc of the heated coating tends to be higher than that of the precoat Rpc. It should be noted that the magnitude of Ra decrease and Rpc increase before and after heating are positively correlated with the pre-coat weight, and the pre-coat surface roughness Ra and Rpc should be controlled if it is desired to ensure that the surface roughness Ra and Rpc of the coating after thermoforming is at a high value.
The weight of each single-sided precoat layer of the invention is not less than 20g/m 2 Because the weight of the precoat is too low, the surface of the steel plate is extremely easy to have the problems of plating leakage and the like, and the uneven weight of the plate surface plating layer is caused by the overlarge pressure of the air knife, so that the uneven roughness of the surface of the coating after thermoforming is caused.
As described above, the level of the surface roughness can be characterized by the magnitude of Ra and Rpc values, and the higher the surface roughness, the greater the Ra and Rpc values. It has been found that, in order to ensure good paint adhesion and corrosion resistance after thermoforming of the pre-coated aluminum or aluminum alloy coating, the surface roughness of the coating after thermoforming needs to be: ra is not less than 1.5 μm and Rpc is not less than 80/cm. When the pre-coat weight is small, the surface roughness Ra and Rpc of the pre-coat can be controlled to ensure that the surface roughness Ra and Rpc of the coating after thermoforming meets the requirements.
The invention is controlled as follows: when 20g/m 2 The weight of each single-sided precoating layer is more than or equal to 40g/m 2 When the reduction of the coating Ra after heating is smaller than 0.5 compared with that of the precoating Ra, the coating Rpc after thermoforming is increased by 5-100 compared with that of the precoating Rpc, and in order to ensure that the surface roughness Ra of the coating after heating is more than or equal to 1.5 mu m and the Rpc is more than or equal to 80/cm, the surface roughness Ra of the precoating is more than or equal to 2.0 mu m and the weight of each single-sided precoating of rpc+ is more than or equal to 100;
when 40g/m 2 < precoating per Single sideThe layer weight is less than or equal to 60g/m 2 When the reduction of the Ra of the coating after heating is smaller than 1.0 compared with that of the pre-coating, the Rpc of the coating after heating is increased by 30-150 compared with that of the pre-coating, so as to ensure that the Ra of the surface roughness of the coating after heating is more than or equal to 1.5 mu m and the Rpc is more than or equal to 80/cm, the Ra of the surface roughness of the pre-coating is more than or equal to 2.5 mu m and the weight of each single-sided pre-coating of Rpc+ is more than or equal to 100.
In order to realize the high surface roughness Ra and Rpc of the precoated layer, in the finishing process for preparing the precoated steel plate, the surface roughness Ra of a finishing roller is more than or equal to 3.5 mu m, but when the surface roughness Ra of the roller is more than 6.0 mu m, the uniform surface roughness of the roller is difficult to ensure, namely, the surface roughness of the roller is 3.5-6.0 mu m. In general, the surface roughness/roll roughness of the precoat is 0.8 or less, and the surface roughness Ra of the precoat is 4.8 μm or less. In addition, it should be noted that, to ensure the surface roughness Rpc value of the precoat, the roll Rpc is ≡precoat Rpc, and the roll surface roughness Ra and Rpc are also average values.
More specifically, when 20g/m 2 The weight of each single-sided precoating layer is more than or equal to 40g/m 2 In order to ensure that the surface roughness Ra of the coating after thermoforming is more than or equal to 1.5 mu m and Rpc is more than or equal to 80/cm, the average surface roughness of the precoat layer meets the following conditions: ra is more than or equal to 2.0 and less than or equal to 4.8, and the weight of each single-sided precoat of rpc+ is more than or equal to 100.
When 40g/m 2 The precoating weight of each single side is less than or equal to 60g/m 2 In order to ensure that the surface roughness Ra of the coating after heating is more than or equal to 1.5 mu m and the Rpc is more than or equal to 80/cm, the average surface roughness of the precoat meets the following conditions: ra is more than or equal to 2.5 and less than or equal to 4.8, and the weight of each single-sided precoat of rpc+ is more than or equal to 100.
In the finishing process, the average surface roughness Ra of the roller is 3.5-6.0, the roller Rpc is more than or equal to the precoat Rpc, and the finishing elongation is 1.0-2.0%.
In addition, the inventors have found that when the pre-coat weight is small, in order to ensure that the coating has relatively uniform surface roughness Ra and Rpc after thermoforming, the plate shape of the steel plate before aluminizing, the air knife parameter stability after aluminizing, and the uniformity of heating temperature during heating in thermoforming must be controlled.
When the plate shape of the steel plate before aluminizing and siliceous is poor, mainly when the unevenness of the steel plate is large, the uniformity of the coating weight of the whole surface is difficult to be ensured by blowing through an air knife after hot dip plating, and when the fluctuation of the coating weight is large, the roughness Ra of the region with large coating weight in the thermoforming process is wholly smaller, mainly because: the coating liquefies and flows more rapidly after the area is heated, and the overall roughness Ra of the area is smaller due to the larger coating weight and the larger filling pit amount of the liquefied coating. Moreover, when the air knife parameters fluctuate, mainly the air knife pressure, distance and height, the uniformity of the whole surface coating weight is poor, the uniformity of the surface roughness of the whole surface coating after heating is poor, the condition that the surface roughness Ra or Rpc of a local position is abnormally low can exist, and the paint adhesion and corrosion resistance of the position are poor. In addition, the heating temperature of the heating furnace is uneven in the heating process, the liquefying flow speed of the coating can be influenced, the liquefying flow of the coating is rapid in the region with higher temperature, and the roughness Ra of the region is small as a whole.
The plate type of the steel plate (substrate) before aluminizing and the parameter stability of the air knife after aluminizing mainly influence the weight uniformity of the precoating layer on the whole steel plate surface after dip plating, thereby influencing the uniformity of the surface roughness of the coating after heating. In order to ensure that the uniformity of the precoating weight of the whole steel plate surface after hot dip plating is better, the stable control of the parameters of the steel plate type before aluminizing and the air knife after aluminizing and the silicon is important. Wherein, the plate shape of the steel plate before aluminizing silicon, the whole steel plate unevenness is within 15mm, preferably within 10mm, the measurement of the unevenness is that the steel plate is freely placed on a platform (the smaller the unevenness is, the better), no pressure is applied except the weight of the steel plate, and the maximum distance between the lower surface of the steel plate and the platform is measured. The parameters of the air knife after aluminizing and siliceous are mainly air knife pressure, distance and height, the parameters of the air knife are mainly adjusted along with the change of the precoating weight and the strip steel speed, when the production is stable, the strip steel speed is not changed greatly, and the fluctuation of the parameters of the air knife is controlled within 5 percent.
Through plate type control and air knife parameter control before aluminizing and silicon, the uniformity of the precoating weight of the whole steel plate surface after hot dip plating is guaranteed to be good, and specifically, the fluctuation of the precoating weight of the whole steel plate surface is within 30%. Wherein the fluctuation of the precoat weight= |maximum precoat weight or minimum precoat weight-average precoat weight|/average precoat weight is multiplied by 100%, and the larger number is calculated by the maximum precoat weight or the minimum precoat weight. It should be noted that the fluctuation of the precoat weight of the steel sheet referred to herein includes fluctuation of the precoat weight in both directions along the rolling direction and perpendicular to the rolling direction, and for any one precoated steel sheet, five positions along the rolling direction or perpendicular to the rolling direction (equal distance between adjacent two positions) are selected, and the average value of the precoat weights at the five positions is taken as the average precoat weight, that is, average precoat weight= (edge 1+quarter+middle+three-quarters+edge 2)/5.
In addition, the uniformity of the heating temperature of the heating furnace in the heating process also affects the uniformity of the surface roughness of the coating after heating. The invention discovers that when the heating temperature fluctuation in the heating furnace is controlled within 3 percent, the uniformity of the surface roughness of the heated coating can be ensured. The heating temperature fluctuation refers to heating temperature fluctuation along the steel plate conveying direction or perpendicular to the steel plate conveying direction in the plane of the precoated steel plate in the heating furnace, wherein the heating temperature fluctuation is = |maximum temperature or minimum temperature-average temperature|/average temperature multiplied by 100%, and the maximum temperature or the minimum temperature is calculated to obtain a larger number.
By controlling the plate shape of the steel plate before aluminizing, the air knife parameter stability after aluminizing and the heating temperature uniformity in the heating process, the surface coating of the whole steel plate after thermoforming has more uniform surface roughness Ra and Rpc, specifically, the unevenness of the whole steel plate before aluminizing and the air knife parameter fluctuation is less than or equal to 15mm, preferably less than or equal to 10mm, less than or equal to 5%, the pre-coating weight fluctuation is less than or equal to 30%, the heating temperature fluctuation is less than or equal to 3%, and the surface roughness Ra fluctuation of the surface coating of the whole steel plate after final thermoforming is less than or equal to 20% and the Rpc fluctuation is less than or equal to 20%.
Surface roughness Ra or Rpc fluctuation= |surface roughness maximum value or minimum value-surface roughness average value|/surface roughness average value x 100%, and a larger number is taken after calculation with the surface roughness maximum value or minimum value.
For a precoated aluminum or aluminum alloy coated steel sheet, when the precoated weight is small, the coating after hot forming cannot ensure high and uniform surface roughness Ra and Rpc.
The present invention is further described below with reference to specific examples and comparative examples. The following examples or experimental data are intended to illustrate the present invention, and it should be apparent to those skilled in the art that the present invention is not limited to these examples or experimental data.
A precoated steel sheet for hot stamping forming is a precoated aluminum or aluminum alloy coated steel sheet with a thickness of 0.7-3.0 mm, wherein the precoated weight is 20-60 g/m per single side 2 The typical thickness of the steel plate of the following example is 1.4mm, and the average value of each single surface of the precoat weight is 20g/m 2 、35g/m 2 、60g/m 2 Wherein the precoating layer is coated on the upper and lower surfaces of the steel plate.
The base steel of the steel plate (substrate) adopts the 22MnB5 commonly used in the market, the precoating coating can be realized by hot dip plating, and typical hot dip plating bath comprises the following components in percentage by mass: 8-11% of Si, 2-4% of Fe, and the balance of aluminum or aluminum alloy and unavoidable impurities. Wherein, the Si element in the plating solution mainly plays a role of forming a Fe-Al-Si inhibition layer on the surface of the steel plate, which can effectively block brittle phase Fe 2 Al 5 The forming capability of the coating is improved, when the Si content exceeds 10%, the effect is obviously weakened, and experimental researches show that the Si content in the aluminum liquid is controlled to be 8-11% more proper. The solubility of Fe is different at different plating solution temperatures, the temperature of the conventional aluminum silicon plating solution is 640-680 ℃, and the solubility of Fe in the plating solution is 2-4%. The substrate composition and plating solution composition of specific parameters of the examples of the present invention are shown in table 1, and bal in table 1 represents the balance, among other elements.
TABLE 1 example 1 substrate and plating solution composition
The method for manufacturing the precoated steel sheet for hot stamping comprises the following steps:
1) Preparing a base plate before hot dip plating: the base steel is subjected to steelmaking, continuous casting, hot rolling and acid rolling to obtain a hot dip plating front substrate, wherein the hot rolling and acid rolling processes control the plate shape of the steel plate through the control of rolling parameters, so that the unevenness of the acid steel plate is within 15mm, preferably within 10 mm.
2) Hot dip plating: immersing the substrate in an aluminum plating solution, and then spraying nitrogen or compressed air by an air knife to control the weight of the precoat, wherein the weight of the precoat is 20-60 g/m per single side 2 The plating solution temperature is 640-680 ℃ and the dip plating time is 2-8 s. The parameters of the air knife after aluminizing and siliceous are mainly air knife pressure, distance and height, the parameters of the air knife are mainly adjusted along with the change of the coating weight and the strip steel speed, when the production is stable, the strip steel speed is not changed greatly, and the fluctuation of the parameters of the air knife is controlled within 5 percent; air knife parameter fluctuation = |air knife parameter maximum value or minimum value-air knife parameter average value|/air knife parameter average value multiplied by 100%, and taking larger number after calculating with the air knife parameter maximum value or minimum value. In general, the distance and the height of the air knife are not adjusted at the moment, and the weight of the coating fluctuates along with the pressure fluctuation of the air knife. The invention mainly controls the pressure fluctuation of the air knife to be within 5 percent.
The invention ensures that the uniformity of the coating weight of the whole steel plate surface after aluminizing and siliceous is better through the control of the plate shape of the steel plate before aluminizing and siliceous and the control of the parameters of the air knife, and particularly, the fluctuation of the coating weight of the whole steel plate surface is within 30 percent. Wherein the fluctuation of the precoat weight= |maximum precoat weight or minimum precoat weight-average precoat weight|/average precoat weight is multiplied by 100%, and the larger number is calculated by the maximum precoat weight or the minimum precoat weight. It should be noted that the fluctuation of the precoat weight of the steel sheet referred to herein includes fluctuation of the precoat weight in both directions along the rolling direction and perpendicular to the rolling direction, and for any one precoated steel sheet, five positions along the rolling direction or perpendicular to the rolling direction (equal distance between adjacent two positions) are selected, and the average value of the precoat weights at the five positions is taken as the average precoat weight, that is, average precoat weight= (edge 1+quarter+middle+three-quarters+edge 2)/5.
3) And (3) finishing: according to the roughness requirement of the precoat, the process parameters of a finishing roller are adjusted to produce, and the process has the effects of improving the mechanical property and the flatness of strip steel, wherein the average Ra value of the finishing roller is 3.5-6.0 mu m, the roller Rpc is more than or equal to the precoat Rpc, and the finishing elongation is 1.0-2.0%. According to the embodiment of the invention, according to the weight of the precoat, the following steps are realized: when 20g/m 2 The weight of each single-sided precoating layer is more than or equal to 40g/m 2 When the average surface roughness of the precoat layer satisfies: ra is more than or equal to 2.0 and less than or equal to 4.8, and Rpc+ has a precoating weight of more than or equal to 100 per single side, when 40g/m 2 The precoating weight of each single side is less than or equal to 60g/m 2 When the average surface roughness of the precoat layer satisfies: ra is more than or equal to 2.5 and less than or equal to 4.8, and the weight of each single-sided precoat of rpc+ is more than or equal to 100.
The precoated steel sheet for hot stamping manufactured by the above manufacturing method is hot-formed into a hot stamped part having a high and uniform surface roughness, and the manufacturing method comprises:
1) Blanking: blanking or cutting the high surface roughness precoated aluminum or aluminum alloy coated steel sheet manufactured as described above into a blank of a shape required for a thermoformed part;
2) And (3) heat treatment: heating the blank in a heating furnace at 860-1000 deg.c for 2-10 min in air or nitrogen. The heating furnace can adopt a box-type furnace or a roller hearth heating furnace, but no matter which heating furnace is adopted, the temperature fluctuation of a heating area is controlled within 3%, and the uniformity of the surface roughness of the heated coating is ensured. The heating temperature fluctuation refers to heating temperature fluctuation along the steel plate conveying direction or perpendicular to the steel plate conveying direction in the plane of the precoated steel plate in the heating furnace, wherein the heating temperature fluctuation is = |maximum temperature or minimum temperature-average temperature|/average temperature multiplied by 100%, and the maximum temperature or the minimum temperature is calculated to obtain a larger number. In the embodiment, the heating furnace adopts a box type heating furnace, the target heating temperature is 930 ℃, the target heating time is 5min, the complete alloying of the steel plate coating is ensured, the influence of incomplete alloying of the coating on the surface roughness is eliminated, and the surface roughness is higher as a whole after heating due to smaller liquefying and filling pit amount of the coating when the coating is not completely alloyed.
3) And (3) hot stamping: and rapidly transferring the blank subjected to heat treatment into a die for stamping forming and cooling, wherein the transfer time is not more than 15s, the stamping forming dwell time is 5-15 s, and the cooling die stripping temperature is not more than 250 ℃.
The examples and comparative examples of the present invention were described with the blanking direction of the precoated steel sheet perpendicular to the rolling direction, and the fluctuation of the precoated weight, the fluctuation of the temperature of the heating furnace, and the fluctuation of the surface roughness of the coating after the hot forming were also perpendicular to the rolling direction. And measuring the pre-coating weight, the temperature of a heating furnace and the surface roughness of the coating after thermoforming along the direction perpendicular to the rolling direction, and calculating corresponding fluctuation values, wherein the surface roughness measurement standard adopts a GB/T2523-2008 cold-rolled metal sheet (strip) surface roughness and peak value measurement method, the cutoff wavelength is 0.8mm, and the test distance is 4.8mm.
And then, coating (phosphating and electrophoresis) the hot formed part by adopting a proper process, and performing scratch corrosion test on coatings (corresponding to the positions corresponding to the fluctuation of the pre-coating weight) at different positions after coating, wherein the requirements are met when the maximum corrosion expansion width is not more than 4mm after the coating adhesion and corrosion resistance are evaluated.
The thermoformed sample was subjected to phosphating treatment with the phosphating agent and test parameters as in Table 2, and then subjected to electrophoresis (type of electrophoretic paint: guangxi HT-8000C) using the resulting phosphating plate, and the thickness of the electrophoretic dry film was about 18. Mu.m. Then, a cyclic etching method was used, and a single cycle was carried out including 8 hours of normal temperature maintenance (25.+ -. 3 ℃ C., 4 spraying saline solutions each for 3 minutes, the saline solution composition was 0.9% by weight of NaCl, 0.1% by weight of CaCl) 2 0.0750.9wt% NaHCO 3 Then, the mixture was subjected to damp heat (49.+ -. 2 ℃ C., 100% RH) for 8 hours, and finally, the mixture was dried (60.+ -. 2 ℃ C.,<30% rh) for a total of 26 cycles.
TABLE 2 parameters of the phosphating process
Table 3 is key process parameters for preparing the pre-coated aluminum or aluminum alloy coated steel sheet of each of the examples and comparative examples, and table 4 is the heating temperature, surface roughness after heating, and scratch corrosion test results.
Table 3 key process parameters for each of the examples and comparative examples of pre-coated aluminum or aluminum alloy coated steel sheet
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Table 4 heating temperature, surface roughness after heating, and scratch corrosion test results for each of examples and comparative examples
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The coating of the part formed by hot stamping of the precoated steel plate provided by the invention has higher surface roughness Ra and Rpc, namely Ra is more than or equal to 1.5 mu m and Rpc is more than or equal to 80/cm, and is mainly realized by controlling the surface roughness of the precoated layer, specifically, 20g/m 2 The weight of each single-sided precoating layer is more than or equal to 40g/m 2 When the average surface roughness of the precoat layer satisfies: ra is more than or equal to 2.0 and less than or equal to 4.8, and Rpc+ has a precoating weight of more than or equal to 100 per single side, when 40g/m 2 The precoating weight of each single side is less than or equal to 60g/m 2 When the average surface roughness of the precoat layer satisfies: ra is less than or equal to 2.54.8 and the weight of the Rpc+ precoating layer on each side is more than or equal to 100. The high surface roughness of the precoat is realized mainly by adopting a high-roughness finishing roller, specifically, the average Ra value of the finishing roller is 3.5-6.0 mu m, the roller Rpc is more than or equal to the precoat Rpc, and the finishing elongation is 1.0-2.0%.
As shown in examples 1-5: in examples 1-4, the target single-sided precoat weight was 20g/m 2 、35g/m 2 The average Ra value of the finishing roller is 3.5-6.0 mu m, the roller Rpc is more than or equal to the precoat Rpc, and the finishing elongation is 1.0-2.0%, so that the average surface roughness Ra of the precoat meets the following conditions: ra is more than or equal to 2.0 and less than or equal to 4.8, and average surface roughness Rpc of the precoat is more than or equal to 80/cm, and also meets the following requirements: the weight of each single-sided precoating layer of Rpc+ is more than or equal to 100, the average surface roughness Ra of the coating of the final thermoformed part is more than or equal to 1.5 mu m, and Rpc is more than or equal to 80/cm; in example 5, the target single-sided precoat weight was 60g/m 2 The average Ra of the finishing roller is 4.50 mu m, the average Rpc is 85/cm, the finishing elongation is 1.2%, the average surface roughness Ra of the precoat is 2.55 mu m, ra is more than or equal to 2.5 and less than or equal to 4.8, the average surface roughness Rpc of the precoat is 82/cm, and the following conditions are also satisfied: the weight of the Rpc+ precoating layer on each single surface is more than or equal to 100, the average surface roughness Ra of the coating layer of the final thermoformed part is 1.76 mu m, the Rpc is 181/cm, and the Ra is more than or equal to 1.5 mu m and the Rpc is more than or equal to 80/cm.
More importantly, the coating of the part formed by hot stamping of the precoated steel plate provided by the invention has higher surface roughness Ra and Rpc and has more uniform surface roughness Ra and Rpc. The invention controls the plate shape of the steel plate before aluminizing and the parameter stability of the air knife after aluminizing and the uniformity of the heating temperature in the heating process, and the surface coating of the whole steel plate after thermoforming has relatively uniform surface roughness Ra and Rpc, as shown in examples 1-5, the unevenness of the whole steel plate (acid rolled plate) before aluminizing and the silicon is ensured to be less than or equal to 15mm, preferably less than or equal to 10mm, the fluctuation of the parameter of the air knife is less than or equal to 5 percent, the fluctuation of the pre-coating weight is less than or equal to 30 percent, the fluctuation of the heating temperature is less than or equal to 3 percent, and the fluctuation of the surface roughness Ra of the surface coating of the whole steel plate after final thermoforming is less than or equal to 20 percent and the fluctuation of Rpc.
In comparison, in comparative example 1, the acid rolled plate had a large unevenness, 20mm > 15mm, resulting in a fluctuation of the precoat weight of > 30%,the coating weight of the individual parts is relatively high (such as 50g/m 2 ) The surface roughness Ra, rpc after thermoforming is low where ra=1.15 μm < 1.5 μm, resulting in unsatisfactory scratch corrosion at this point, and overall Ra fluctuation > 20% and Rpc fluctuation > 20%; in comparative example 2, the air knife parameters had a large variation of 6% > 5%, which also resulted in a variation of > 30% in precoat weight, with individual sites having a large coating weight (e.g., 51 g/m) 2 ) The surface roughness Ra, rpc after thermoforming is low where ra=1.12 μm < 1.5 μm, resulting in unsatisfactory scratch corrosion at this point, and overall Ra fluctuation > 20% and Rpc fluctuation > 20%; in comparative example 3, the fluctuation of the roughness of the acid rolled plate and the parameter fluctuation of the air knife are smaller, the fluctuation of the pre-coating weight is ensured to be smaller, but the fluctuation of the heating temperature is larger, 3.2 percent is more than 3 percent, the temperature of the middle part of the steel plate is 960 ℃ and is obviously higher than that of other parts, when the steel plate is heated, the coating is liquefied more rapidly, the surface roughness Ra and Rpc of the steel plate are lower, ra=1.10 mu m is less than 1.5 mu m, the scratch corrosion of the steel plate is not satisfied, and the fluctuation of the integral Ra is more than 20 percent and the fluctuation of Rpc is more than 20 percent; in comparative example 4, the single-sided weight target value of the precoat was 20g/m 2 The average surface roughness Ra=1.4 μm, rpc=62/cm of the precoat cannot meet 2.0.ltoreq.Ra.ltoreq.4.8 and rpc+ is equal to or more than 100 per single-sided precoat weight, the average surface roughness Ra=1.37 μm < 1.5 μm, rpc=65/cm < 80/cm after thermoforming, therefore the scratch corrosion spreading width > 4mm, and the requirements are not met.
When the precoat weight was small (20 g/m 2 The weight of each single-sided precoating layer is more than or equal to 60g/m 2 ) How to ensure the surface roughness Ra and Rpc of the coating after thermoforming, which is high and uniform, is particularly important for ensuring the paint adhesion and corrosion resistance of the aluminum alloy coating after thermoforming.
Through the embodiment, when the weight of the precoating layer is smaller, the precoating layer prepared by the method has higher and more uniform surface roughness Ra and Rpc after thermoforming, and can ensure good paint adhesion and corrosion resistance.
The foregoing embodiments have been described in some detail for purposes of illustration and description of the invention, and it is to be understood that the foregoing embodiments are merely illustrative of the presently preferred embodiments of the invention and are not intended to limit the spirit and scope of the invention.

Claims (10)

1. An aluminum or aluminum alloy precoated steel sheet for hot stamping, characterized in that the precoating of the precoated steel sheet for hot stamping is controlled to have a precoating weight of 20 to 60g/m per single surface 2 ；
Surface roughness control of the precoat: when 20g/m 2 The weight of each single-sided precoating layer is more than or equal to 40g/m 2 When the surface roughness Ra of the precoating is more than or equal to 2.0 mu m and the weight of each single-sided precoating of Rpc+ is more than or equal to 100; when 40g/m 2 The precoating weight of each single side is less than or equal to 60g/m 2 When the surface roughness Ra of the precoat is more than or equal to 2.5 mu m and the weight of the Rpc+ precoat on each side is more than or equal to 100.
2. The aluminum or aluminum alloy precoated steel sheet for hot stamping according to claim 1, wherein the fluctuation of the precoating weight is within 30%.
3. A method for manufacturing the precoated steel sheet for hot stamping as set forth in claim 1 or 2, comprising the following process steps: manufacturing a substrate, hot dip plating and finishing, wherein the manufacturing substrate has a substrate unevenness of 15mm or less.
4. The method according to claim 3, wherein the hot dip plating is performed at a plating solution temperature of 640 to 680 ℃ for a plating time of 2 to 8 seconds.
5. The manufacturing method according to claim 3 or 4, characterized in that the hot dip plating: controlling the fluctuation of the parameters of the air knife requires controlling within 5 percent.
6. A method of manufacturing according to claim 3, wherein the finishing: the average Ra value of the finishing roller is 3.5-6.0 mu m, the roller Rpc is more than or equal to the precoat Rpc, and the finishing elongation is 1.0-2.0%.
7. A hot-stamping formed part, which is produced by heat treatment of the precoated steel sheet for hot-stamping according to claim 1 or 2, wherein the coating surface roughness Ra of the hot-stamping formed part is not less than 1.5 μm and Rpc is not less than 80/cm, and the fluctuation of the coating surface roughness Ra of the hot-stamping formed part is not more than 20% and the fluctuation of Rpc is not more than 20%.
8. The hot stamped component of claim 7, wherein the heat treatment: the temperature fluctuation of the heating area is controlled within 3 percent.
9. A method of manufacturing a hot-stamped part according to claim 7 or 8, characterized in that the manufacturing method comprises a heat treatment at a furnace temperature of 860-1000 ℃ for a residence time of 2-10 min in the furnace.
10. Use of a hot stamped part according to claim 7 or 8 for a land motor vehicle.
CN202311025831.XA 2023-08-15 2023-08-15 Precoated steel sheet for hot stamping and method for producing same, hot stamped part, method for producing same, and application Pending CN117107181A (en)

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