阅读说明：本技术 表面具有含锰涂层的热冲压件的制造方法 (Method for producing hot stamped parts with a manganese-containing coating on the surface ) 是由 安健 陈汉杰 于 2019-07-30 设计创作，主要内容包括：本发明公开了一种表面具有含锰涂层的热冲压件的制造方法,其包括：获取设置有由第一金属材料形成的第一涂层的钢坯；在第一涂层的表面设置第二金属材料以形成第二涂层,第二金属材料为锰或含锰合金；将钢坯置于具有第一温度范围的无氧气氛环境下进行奥氏体化加热及热冲压成型加工以获得表面具有含锰涂层的热冲压件；其中,所述第一金属材料的熔点低于所述第一温度范围的最低值,所述第二金属材料的熔点高于所述第一温度范围的最高值。本发明可解决热采用铝硅涂层板及热镀锌板进行热冲压生产的奥氏体化加热过程中的涂层液化、升温速率低以及合金化后耐腐蚀性能下降的问题,加快生产节拍、延长加热炉陶瓷辊的使用寿命、提高所生产零件的耐腐性能。(The invention discloses a method for manufacturing a hot stamping part with a manganese-containing coating on the surface, which comprises the following steps: obtaining a steel blank provided with a first coating formed of a first metallic material; arranging a second metal material on the surface of the first coating to form a second coating, wherein the second metal material is manganese or a manganese-containing alloy; placing the steel billet in an oxygen-free atmosphere environment with a first temperature range to carry out austenitizing heating and hot stamping forming processing so as to obtain a hot stamping part with a manganese-containing coating on the surface; wherein the melting point of the first metal material is lower than the lowest value of the first temperature range, and the melting point of the second metal material is higher than the highest value of the first temperature range. The invention can solve the problems of coating liquefaction, low heating rate and reduced corrosion resistance after alloying in the austenitizing heating process of hot stamping production by adopting the aluminum-silicon coated plate and the hot galvanized plate, quickens the production takt, prolongs the service life of the ceramic roller of the heating furnace and improves the corrosion resistance of the produced parts.)

1. A method of manufacturing a hot stamped part having a manganese-containing coating on the surface thereof, comprising the steps of:

obtaining a steel blank provided with a first coating layer formed by a first metal material on part or all of the surface;

providing a second metal material at least part of the steel blank with the first coating layer to form a second coating layer, wherein the second metal material is manganese or a manganese-containing alloy;

placing the steel billet provided with the first coating and the second coating in an oxygen-free atmosphere environment with a first temperature range for austenitizing heating;

carrying out hot stamping forming processing on the austenitized steel billet to obtain a hot stamping part with a manganese-containing coating on the surface;

the melting point of the first metal material is lower than the lowest value of the first temperature range, and the melting point of the second metal material is higher than the highest value of the first temperature range, so that the first coating on the surface of the steel billet after austenitizing and heating is in a molten state, and the second coating on the surface of the first coating is in a solid state.

2. The method of manufacturing a hot stamped part having a manganese-containing coating on a surface thereof according to claim 1, wherein the step of obtaining a billet having a first coating layer of a first metallic material provided on a part or the entire surface thereof comprises directly selecting a billet having a first coating layer of the first metallic material provided on a part or the entire surface thereof, or forming the first coating layer by providing the first metallic material on a part or the entire surface of a bare billet having no coating layer.

3. Method for manufacturing a hot-stamped part with a manganese-containing coating on the surface according to claim 1, characterized in that the first metal material is zinc, a zinc-iron alloy, an aluminum-silicon alloy, an aluminum-zinc alloy, a zinc-magnesium alloy or an aluminum-zinc-magnesium alloy, preferably zinc, a zinc-iron alloy, an aluminum-zinc alloy or a zinc-magnesium alloy.

4. Method for manufacturing a hot-stamped part with a manganese-containing coating on the surface according to claim 1, characterized in that the first coating comprises a plurality of coating units formed from the first metal material, the first metal material used to form each of the coating units being one of zinc, a zinc-iron alloy, an aluminum-silicon alloy, an aluminum-zinc alloy, a zinc-magnesium alloy and an aluminum-zinc-magnesium alloy.

5. Method for manufacturing a hot-stamped part with a manganese-containing coating on the surface according to claim 1, characterized in that the thickness of the first coating is 1 to 30 μm, preferably 3 to 10 μm.

6. Method for producing a hot-stamped part with a manganese-containing coating on the surface according to claim 1, characterized in that the second metallic material is a ferromanganese, a manganese-zinc alloy, a manganese-aluminum alloy, a manganese-nickel alloy, a manganese-zinc-nickel alloy, a manganese-aluminum-nickel alloy, a manganese-chromium alloy, a manganese-zinc-chromium alloy or a manganese-aluminum-chromium alloy, preferably a ferromanganese alloy.

7. A method of manufacturing a hot stamped part having a manganese containing coating on the surface thereof according to claim 1, wherein: the second metal material is ferromanganese, manganese-nickel alloy, manganese-zinc alloy or manganese-aluminum alloy with the manganese content of more than 5%, preferably more than 90%.

8. Method for manufacturing a hot-stamped part with a manganese-containing coating on the surface according to claim 1, characterized in that the thickness of the second coating is 1 to 30 μm, preferably 1 to 5 μm.

9. The method for manufacturing a hot-stamped part with a manganese-containing coating on the surface according to claim 1, wherein the oxygen content in the oxygen-free atmosphere environment is 0.0001-5%.

10. The method according to claim 1, wherein the step of austenitizing and heating the steel blank provided with the first and second coatings in an oxygen-free atmosphere having a first temperature range of 870 to 950 ℃ for 0 to 10min comprises the step of austenitizing the steel blank.

11. The method of manufacturing a hot stamped part with a manganese-containing coating on the surface as claimed in claim 10, wherein the step of subjecting the steel blank provided with the first and second coatings to austenitizing heating in an oxygen-free atmosphere having a first temperature range includes alloying the steel blank between the substrate and the first coating, the substrate of the steel blank passing between the first and second coatings, and the first and second coatings.

12. The method of manufacturing a hot stamped part with a manganese-containing coating on the surface according to claim 1, wherein the composition of the steel blank comprises, in mass%:

c: 0.1-0.3%; si: 0.1 to 1.0 percent; mn: 0.1-1.5%; b: 0 to 0.02 percent; ti: 0 to 0.2 percent; nb: 0 to 0.2 percent; v: 0 to 1.0 percent; cr: 0 to 1.0 percent; the balance of iron and unavoidable impurities.

13. A method of manufacturing a hot-stamped part having a manganese-containing coating on its surface according to claim 1, wherein said steel blank is a strip, a sheet, a blanked sheet blank, a tailor-welded sheet blank or a thickened rolled sheet blank.

14. Method for manufacturing a hot stamped part with a manganese containing coating on the surface according to claim 2, characterized in that the method for providing the first coating on the steel blank is hot dip coating, electroplating, vacuum evaporation, powder spraying or powder impregnation, preferably hot dip coating or electroplating.

15. Method for manufacturing a hot-stamped part having a manganese-containing coating on its surface according to claim 1, characterized in that the method for providing the second coating on the first coating is electroplating, electroless plating, vacuum evaporation or powder spraying, preferably powder spraying or electroplating.

Technical Field

The invention relates to the field of hot forming, in particular to a method for manufacturing a hot stamping part with a manganese-containing coating on the surface.

Background

The hot forming and stamping process for ultrahigh strength steel is characterized by that the steel plate blank material made of a certain material is austenitized and heated, then quickly transferred into water-cooled mould to make press forming, and the pressure-holding quenching treatment is implemented in the mould to produce martensite.

In order to prevent the oxide skin from being generated when the blank of the bare steel plate is heated, the hot stamping process usually adopts the coated steel plate as the raw material, the coating of the coated steel plate is generally an aluminum-silicon alloy coating, a zinc alloy coating, an aluminum-zinc-magnesium alloy coating or a zinc-magnesium alloy coating, and the like, the aluminum-based or zinc-based metal materials belong to low-melting-point metals or alloys, and correspondingly, the melting point temperature of the coating prepared by the metal materials is generally lower than 700 ℃. And the austenitizing heating temperature in the hot stamping process is generally 860-950 ℃, and inevitably, the coatings are melted during the austenitizing heating, so that the coatings are adhered to a ceramic roller and a die in a heating furnace, the integrity of the coatings is damaged, and the ceramic roller is easy to break.

However, the alloying treatment is carried out at a slower temperature rise rate to prevent the low-melting-point metal material coating from generating a liquid phase in the austenitizing heating process, and the higher the thickness of the metal material coating, the longer the alloying treatment time is required.

In turn, a further improvement is to use a single layer of a refractory alloy, such as a zinc-nickel alloy, as the metallic material coating of the steel sheet, which avoids the above-mentioned problems. However, whether the zinc-nickel alloy coating, the zinc-chromium alloy coating or the nickel-chromium coating will raise the production cost of enterprises. Moreover, the electrode potential of commonly used high melting point alloy coatings such as zinc-nickel alloy is close to that of matrix iron, and sacrificial anode protection is weak. Although manganese is a good high-melting-point coating metal material, manganese is directly coated on an iron substrate to form a single-layer coating, and the coating is easy to peel off and has poor adhesion after being heated at high temperature. This is because the thermal expansion coefficients of the manganese coating and the iron matrix are different, and the diffusion of alloying between the high melting point coating and the steel sheet blank matrix is solid-to-solid diffusion, and the diffusion rate is slow. The austenitizing heating time of the steel sheet blank and the coating is not sufficient to provide the diffusion time required for the two to have sufficient metallurgical bonding. If the zinc-manganese alloy coating is adopted as the single-layer high-melting-point coating, the good corrosion resistance effect and high-melting-point performance cannot be provided when the manganese content in the zinc-manganese alloy is lower than 20%, and the corrosion resistance effect and the high-melting-point performance can be met by realizing the electro-deposition of more than 40% of manganese content in the electroplating process, which is difficult to realize industrially and economically in the level of the current electroplating process.

Furthermore, whether low melting point aluminum silicon alloy coatings, zinc alloy coatings or high melting point zinc nickel alloy coatings, a large number of cracks occur within the coating after austenitizing heating and rapid cooling. The greater the difference in the coefficient of thermal expansion between the coating alloy and the base iron, the more severe the cracks in the coating. The thermal expansion coefficient of zinc is 2 times different from that of matrix iron, the thermal expansion coefficient of aluminum is 1 time different from that of iron, and the crack degree of the zinc alloy coating is observed to be more serious than that of the aluminum alloy coating. These cracks will both lead to a reduction in the corrosion protection properties of the coating and may initiate cracking of the steel substrate. It is worth mentioning that the thickness, alloying temperature and time of the metal material coating are closely related to the generation of the cracks, and taking a common zinc alloy coating with the thickness of 14-18 μm as an example, if the coating does not fully alloy with the matrix iron during austenitizing heating, a low-melting-point zinc-rich alloy such as a phase or a phase zinc-iron alloy is left in the coating, although the sacrificial anode protection function of the coating can be obtained to enhance the corrosion resistance, the liquid zinc during stamping can cause the matrix cracks. The thinner the coating, the higher the alloying temperature, and the longer the evolution time, the more complete the diffusion of the matrix iron into the coating, the higher the iron content, and the more slight the cracking of the coating. However, the thinner the coating, or the longer the alloying time, the less severe the cracks in the coating, but the increased iron content in the coating results in a coating with poorer sacrificial anodic protection properties and poorer corrosion resistance properties.

In addition, the austenitizing heating process of hot stamping is usually performed in an oxygen atmosphere, and although a protective atmosphere is introduced into the heating furnace, the oxygen content in the heating furnace is still sufficient to generate an oxide layer (such as iron oxide, zinc oxide, manganese oxide, etc.) which is unfavorable for the coating or the substrate surface at a high temperature. These oxide layers will present obstacles to subsequent welding and electrophoresis of the thermoformed article. For this reason, these undesirable oxide layers usually need to be removed by shot blasting prior to the welding and electrophoresis process, but shot blasting will result in deformation of the product.

In summary, the billet with a single-layer coating on the surface has at least the following disadvantages in austenitizing heating and after heating, which affect the quality of the processing equipment or the formed part:

1. austenitizing and heating to eliminate the sacrificial anode protection effect of the metal material coating;

2. austenitizing heating will crack the interior of the metallic material coating.

3. In order to reduce coating cracks, the slow heating of the coating near the melting point of the coating slows down the production cycle;

4. austenitizing and heating to melt the aluminum-silicon coating and the zinc alloy coating to adhere the furnace roller;

5. the formed product is austenitized and heated in an aerobic heating environment, and oxide scale generated on the surface damages the hot stamping die.

6. After austenitizing heating, scale produced on the surface of the shot-blasting-treated formed part in an aerobic heating environment affects the dimensional performance of the formed part.

Therefore, the above problems need to be solved.

Disclosure of Invention

To overcome the disadvantages of the prior art, embodiments of the present invention provide a method for manufacturing a hot stamped part with a manganese-containing coating on the surface, which solves at least one of the above technical problems.

The embodiment of the application discloses: a method of manufacturing a hot stamped part having a manganese-containing coating on the surface thereof, comprising the steps of:

obtaining a steel blank provided with a first coating layer formed by a first metal material on part or all of the surface;

providing a second metal material at least part of the steel blank with the first coating layer to form a second coating layer, wherein the second metal material is manganese or a manganese-containing alloy;

placing the steel billet provided with the first coating and the second coating in an oxygen-free atmosphere environment with a first temperature range for austenitizing heating;

carrying out hot stamping forming processing on the austenitized steel billet to obtain a hot stamping part with a manganese-containing coating on the surface;

the melting point of the first metal material is lower than the lowest value of the first temperature range, and the melting point of the second metal material is higher than the highest value of the first temperature range, so that the first coating on the surface of the steel billet after austenitizing and heating is in a molten state, and the second coating on the surface of the first coating is in a solid state. The second coating with high melting point is set to improve the corrosion resistance of the formed hot stamping part, the first coating with low melting point is set to weld the first coating and the metal material with the billet base body and the second coating with high melting point by using the temperature of austenitizing heating, and if the first coating is not provided, the high melting point manganese or manganese-containing alloy of the second coating lacks the adhesion force with the billet base body.

Specifically, in the step of "obtaining a steel blank having a first coating layer formed of a first metal material on a part or all of the surface thereof", the step of directly selecting a steel blank having a first coating layer formed of the first metal material on a part or all of the surface thereof, or forming the first coating layer by providing the first metal material on a part or all of the surface of an uncoated bare steel blank may be included.

Specifically, the first metal material is zinc, a zinc-iron alloy, an aluminum-silicon alloy, an aluminum-zinc alloy, a zinc-magnesium alloy or an aluminum-zinc-magnesium alloy, and preferably zinc, a zinc-iron alloy, an aluminum-zinc alloy or a zinc-magnesium alloy.

Preferably, the first coating layer includes a plurality of coating units formed of the first metal material, and the first metal material used to form each of the coating units is one of zinc, a zinc-iron alloy, an aluminum-silicon alloy, an aluminum-zinc alloy, a zinc-magnesium alloy, and an aluminum-zinc-magnesium alloy.

Preferably, the thickness of the first coating is 1-30 μm, and preferably 3-10 μm.

Specifically, the second metal material is ferromanganese, manganese-zinc alloy, manganese-aluminum alloy, manganese-nickel alloy, manganese-zinc-nickel alloy, manganese-aluminum-nickel alloy, manganese-chromium alloy, manganese-zinc-chromium alloy or manganese-aluminum-chromium alloy.

Preferably, the second metal material is a ferromanganese alloy, a manganese-nickel alloy, a manganese-zinc alloy or a manganese-aluminum alloy with a manganese content of more than 5%, preferably more than 90%.

Preferably, the thickness of the second coating is 1-30 μm, preferably 1-5 μm.

Preferably, the oxygen content in the oxygen-free atmosphere environment is 0.0001-5%.

Preferably, in the step of placing the steel billet provided with the first coating and the second coating in an oxygen-free atmosphere environment with a first temperature range for austenitizing heating, the first temperature range is 870-950 ℃, and the heat preservation time for austenitizing is 0-10 min.

Preferably, the step of austenitizing and heating the steel blank provided with the first coating layer and the second coating layer in an oxygen-free atmosphere having a first temperature range includes alloying the steel blank between the base body and the first coating layer, the base body passing between the first coating layer and the second coating layer, and the first coating layer and the second coating layer.

Preferably, the steel billet comprises the following components in percentage by mass:

c: 0.1-0.3%; si: 0.1 to 1.0 percent; mn: 0.1-1.5%; b: 0 to 0.02 percent; ti: 0 to 0.2 percent; nb: 0 to 0.2 percent; v: 0 to 1.0 percent; cr: 0 to 1.0 percent; the balance of iron and unavoidable impurities.

Preferably, the steel billet is strip steel, a sheet material, a plate blank after blanking, a plate blank after tailor welding or a plate blank after thickening and rolling.

Preferably, the method for providing the first coating on the steel blank is hot dip plating, electroplating, vacuum evaporation, powder spraying or powder infiltration, and preferably hot dip plating or electroplating.

Preferably, the method for disposing the second coating layer on the first coating layer is electroplating, electroless plating, vacuum evaporation or powder spraying, preferably powder spraying or electroplating.

The method for manufacturing the hot stamping part with the manganese-containing coating on the surface, provided by the invention, is based on a preparation mode that a double coating (namely a first coating with a melting point lower than the austenitizing heating temperature and a second coating with a melting point higher than the austenitizing heating temperature) is arranged on the steel surface, and has the advantages that:

1. the hot stamping part obtained by the manufacturing method has better performance of sacrificial anode protection;

2. the cracks in the zinc alloy coating of the hot stamping part obtained by the manufacturing method are obviously reduced;

3. the manufacturing method adopts an oxygen-free heating process and equipment to perform austenitizing heating on the blank, thereby avoiding shot blasting treatment on a zinc oxide layer or an iron oxide layer in the prior art, namely avoiding product deformation possibly generated by shot blasting treatment;

4. in the heating process of the manufacturing method, the surface coating of the steel blank cannot be liquefied, the ceramic roller cannot be adhered, and the evaporation of zinc cannot occur, so that the surface coating of the prepared product is complete, and the service life of the ceramic roller is prolonged;

5. the manufacturing method can rapidly heat the steel billet and shorten the production time.

In order to make the aforementioned and other objects, features and advantages of the invention more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment provides a method for manufacturing a hot stamping part with a manganese-containing coating on the surface, which comprises the following steps:

first, a steel blank provided with a first coating layer formed of a first metal material on a part or the entire surface is obtained. It is to be understood that, in this step, a steel blank having a first coating layer formed of the first metal material provided on a part or all of the surface thereof may be directly selected, or the first coating layer may be formed by providing the first metal material on a part or all of the surface of an uncoated bare steel blank. Specifically, the first metal material may be zinc, a zinc-iron alloy, an aluminum-silicon alloy, an aluminum-zinc alloy, a zinc-magnesium alloy, or an aluminum-zinc-magnesium alloy, and is preferably zinc, a zinc-iron alloy, an aluminum-zinc alloy, or a zinc-magnesium alloy. The thickness of the first coating layer may be 1 to 30 μm, and preferably 3 to 10 μm.

Then, a second metal material is disposed at least a portion of the steel blank having the first coating layer to form a second coating layer, the second metal material being manganese or a manganese-containing alloy. Specifically, the second metal material is a ferromanganese alloy, a manganese-zinc alloy, a manganese-aluminum alloy, a manganese-nickel alloy, a manganese-zinc-nickel alloy, a manganese-aluminum-nickel alloy, a manganese-chromium alloy, a manganese-zinc-chromium alloy or a manganese-aluminum-chromium alloy, and is preferably a ferromanganese alloy. More preferably, the second metal material is a ferromanganese alloy, a manganese-nickel alloy, a manganese-zinc alloy or a manganese-aluminum alloy with a manganese content of 5% or more, preferably 90% or more. In addition, the thickness of the second coating layer can be 1-30 μm, and preferably 1-5 μm.

And secondly, the steel billet provided with the first coating and the second coating is placed in an oxygen-free atmosphere environment with a first temperature range for austenitizing heating. The melting point of the first metal material is lower than the lowest value of the first temperature range, and the melting point of the second metal material is higher than the highest value of the first temperature range. The first coating with the low melting point is used for welding the second coating with the high melting point with the steel blank substrate so as to increase the bonding force of the second coating and the steel blank substrate. The austenitizing heating process comprises 870-950 ℃ (namely the first temperature range) and heat preservation for 0-10 min. The melting points of the zinc-based or aluminum-based metals listed above as suitable first metallic materials are all below the lowest value of the first temperature range, while the melting points of the manganese-based metals listed above as suitable second metallic materials are all above the highest value of the first temperature range, so that the first coating layer on the surface of the steel blank after austenitizing heating is in a molten state and the second coating layer on the surface of the first coating layer is in a solid state.

And finally, carrying out hot stamping forming processing on the austenitized steel billet to obtain a hot stamping part with a manganese-containing coating on the surface.

Specifically, the billet may be a strip steel, a sheet material, a blanked plate material, a tailor welded plate material, or a thick-rolled plate material. The steel blank may be bare steel or coated steel with a first coating. In an optional real-time manner, the composition of the steel billet comprises, in mass percent: c: 0.1-0.3%; si: 0.1-1.0%; mn: 0.1-1.5%; b: 0 to 0.02 percent; ti: 0 to 0.2 percent; nb: 0 to 0.2 percent; v: 0 to 1.0 percent; cr: 0 to 1.0 percent; the balance of iron and unavoidable impurities. The first coating layer may be disposed on the surface of the steel billet by hot dip plating, electroplating, vacuum evaporation, powder spraying or powder impregnation, preferably hot dip plating or electroplating, in consideration of the properties of the first and second metallic materials. The second coating can be arranged on the surface of the first coating by electroplating, chemical plating, vacuum evaporation or powder spraying, and is preferably powder spraying or electroplating. The equipment for austenitizing heating may be a vacuum heating furnace, so that the steel slab provided with the first coating layer and the second coating layer can be heated in an atmosphere with an oxygen content of 0.002% (mass percentage) or less to avoid scale formation, and it should be noted that the oxygen-free environment may be an atmosphere with an oxygen content of 0.0001-5% in consideration of difficulty in achieving absolute oxygen-free conditions. In this embodiment, the austenitized steel billet may be hot stamped by a water-cooled die. Wherein, the temperature of the hot stamping forming processing can be 650-800 ℃. The billet takes less than 10 seconds to transfer from leaving the oxygen-free atmosphere environment to being placed in a die for hot stamping and closing the die to reduce scale formation on the surface of the billet during the process.

In a preferred embodiment, the first coating layer includes a plurality of coating units formed of the first metal material, and the first metal material used to form each of the coating units is different in one composition of zinc, a zinc-iron alloy, an aluminum-silicon alloy, an aluminum-zinc alloy, a zinc-magnesium alloy, and an aluminum-zinc-magnesium alloy. The metal material of each layer is selected from the listed alloys alternatively, and the material of each layer of the coating unit is different, or the material of any two adjacent coating units is different. It is understood that two adjacent coating units of the same material may be considered as one coating unit.

In a preferred embodiment, the step of austenitizing and heating the steel blank provided with the first coating layer and the second coating layer in an oxygen-free atmosphere having a first temperature range includes alloying the steel blank between the substrate and the first coating layer, the substrate of the steel blank passing between the first coating layer and the second coating layer, and the first coating layer and the second coating layer. The alloying treatment may include: and preserving the heat of the steel billet provided with the first coating and the second coating for 0-10 min.

The following five cases are used to illustrate the present example:

case 1

First, a hot-dip galvanized GA/GI 22MnB5 steel sheet having a 7 μm thick coating was blanked to obtain an automobile floor center tunnel blank.

Then, manganese with the thickness of 1-3 mu m is electroplated on the surface of the blank.

Secondly, the plated blank with the double-layer coating structure is placed into a 930 ℃ oxygen-free heating furnace for heating, and the blank is subjected to heat preservation for 1min at the temperature of 860-930 ℃ for austenitizing and alloying. Wherein, the oxygen content in the oxygen-free heating furnace is controlled below 0.0002 percent, and the manganese coating is prevented from being oxidized in the heating furnace.

And finally, carrying out hot stamping forming on the heated blank, and then carrying out laser edge cutting and hole cutting to obtain the ultrahigh-strength steel automobile central channel product.

Case 2

First, an uncoated 22MnB5 steel sheet was blanked to obtain an automobile rocker panel blank.

Then, zinc with the thickness of 3-5 mu m is electroplated on the surface of the blank, and manganese with the thickness of 1-3 mu m is electroplated on the surface of the electroplated zinc layer.

Secondly, the plated blank with the double-layer coating structure is placed into an oxygen-free heating furnace at 920 ℃ for heating, the blank is subjected to heat preservation at 860-930 ℃ for 1min, and austenitizing and alloying are carried out. Wherein, the oxygen content in the oxygen-free heating furnace is controlled below 0.0002 percent, and the manganese coating is prevented from being oxidized in the heating furnace.

And finally, carrying out hot stamping forming on the heated blank, and then carrying out laser edge cutting and hole cutting to obtain the ultra-high strength steel automobile threshold product.

Case 3

Firstly, a 22MnB5 uncoated steel plate is blanked and tailor welded into an automobile door ring blank.

Then, a zinc layer with the thickness of 3-5 μm is electroplated on the surface of the blank, and manganese with the thickness of 1-3 μm is electroplated on the local part (the automobile threshold area) of the surface of the electroplated zinc layer.

Secondly, the blank plated with the local double-layer coating structure is placed into a 930 ℃ oxygen-free heating furnace for heating, and the blank is subjected to heat preservation for 1min at 860-930 ℃. Wherein, the oxygen content in the oxygen-free heating furnace is controlled below 0.0002 percent, and the manganese coating and the zinc coating are prevented from being oxidized in the heating furnace.

And finally, carrying out hot stamping forming on the heated blank, and then carrying out laser edge cutting and hole cutting to obtain the ultrahigh-strength steel automobile door ring product.

Case 4

First, a hot-dip aluminum-silicon 22MnB5 steel sheet having a coating layer of 10 μm thickness was blanked to obtain an automobile floor beam blank.

Then, manganese was sprayed on the billet to a thickness of 5 μm.

Secondly, the plated blank with the double-layer coating structure is placed into a 930 ℃ oxygen-free heating furnace for heating, and the blank is subjected to heat preservation for 1min at 860-930 ℃. Wherein, the oxygen content in the oxygen-free heating furnace is controlled below 0.0002 percent, and the manganese coating and the aluminum coating are prevented from being oxidized in the heating furnace.

And finally, carrying out hot stamping forming on the heated blank, and then carrying out laser edge cutting line and hole cutting to obtain the ultrahigh-strength steel automobile floor beam product.

Case 5

First, a hot-dip galvanized GA/GI 22MnB5 steel sheet having a coating layer of 7 μm thickness was blanked to obtain an automobile floor beam blank.

Then, manganese powder with the thickness of 7 mu m is sprayed on the blank, and the granularity of the manganese powder is less than 2 mu m.

Secondly, the blank with the double-layer coating structure is placed into a 930 ℃ oxygen-free heating furnace for heating, and the blank is subjected to heat preservation for 1min at 860-930 ℃. Wherein, the oxygen content in the oxygen-free heating furnace is controlled below 0.0002 percent, and the manganese coating and the zinc coating are prevented from being oxidized in the heating furnace.

And finally, carrying out hot stamping forming on the heated blank, and then carrying out laser edge cutting line and hole cutting to obtain the ultrahigh-strength steel automobile floor beam product.

The method for manufacturing a hot-stamped part with a manganese-containing coating on the surface provided by this embodiment is based on a preparation manner that a double coating (i.e., a first coating with a melting point lower than the austenitizing heating temperature and a second coating with a melting point higher than the austenitizing heating temperature) is provided on the steel surface, and compared with the prior art that only a low-melting-point hot-dip aluminum-silicon coating or a hot-dip galvanized coating is adopted, the method has at least the following advantages:

1. the hot stamping part obtained by the manufacturing method has better performance of sacrificial anode protection:

aluminum-silicon coatings, as well as zinc alloy coatings, generally have more cracks after alloying with the matrix iron during austenitizing high temperature heating than the original uniform dense coating before heating, which cracks risk initiating matrix cracking. At the same time, the coating cracks themselves lead to a reduction in their corrosion protection. As noted above, to reduce cracking, longer alloying times are typically employed to obtain sufficient diffusion between the coating alloy and the base iron. But the increase in iron content within the coating results in a coating with a more positive electrode potential, i.e. a poorer sacrificial anodic protection function. These all reduce the corrosion resistance of the original coating to a great extent. To increase the corrosion resistance of the coating, only the thickness of the coating can be increased. However, an increase in the thickness of the coating leads to more severe cracking of the coating. It can be said that the coating mitigates cracks and the sacrificial anodic protection function of the coating, for low melting point alloy coatings, only one of them is available. In this embodiment, a manganese-based refractory alloy having a sacrificial anode protection function is used as the coating. In the austenitizing heating temperature range, the solid-solid diffusion rate between the manganese-based high-melting-point alloy and the matrix iron is very low, and the performance of sacrificial anode protection is hardly influenced. The high-melting-point alloy product is formed by liquid-solid diffusion between the low-melting-point alloy in the middle layer and the manganese-based high-melting-point alloy in the outer layer, so that the melting point of the low-melting-point alloy is improved, and the sacrificial anode protection function of the alloy product is also improved. The manganese-based metal of the second coating layer and the zinc-based metal of the first coating layer, the zinc-based metal of the first coating layer and the matrix iron, and the manganese-based metal of the second coating layer are respectively generated after alloying to form manganese-zinc alloy, manganese-aluminum-silicon alloy, zinc-iron-manganese alloy and aluminum-silicon-iron-manganese alloy, and the alloys have excellent corrosion resistance, for example, the sacrificial anode protection function of the zinc-manganese alloy is far higher than that of pure zinc or zinc-iron alloy.

2. The cracks in the zinc alloy coating of the hot stamped parts obtained by the manufacturing method are significantly reduced:

as mentioned above, the sacrificial anodic protection function of the zinc alloy coating comes at the expense of a large number of cracks in the coating. The first coating low melting point coating in this example is also a zinc alloy coating, but its thickness is 1/3 to 1/2 times the thickness of the existing zinc alloy coating. This is because the refractory alloy (i.e., manganese alloy) of the outer layer is responsible for the primary corrosion protection in this embodiment. Manganese, on the other hand, has the same coefficient of thermal expansion as aluminum and is closer to matrix iron than zinc. Thus, in this example, thinner zinc alloy coatings and manganese alloy coatings closer to the coefficient of thermal expansion of the substrate iron are used, resulting in reduced cracking in the coating than in the prior art coatings.

3. The manufacturing method adopts an oxygen-free heating process and equipment to perform austenitizing heating on the blank, thereby avoiding shot blasting treatment on a zinc oxide layer or an iron oxide layer in the prior art, namely avoiding possible product deformation caused by shot blasting treatment.

4. The second coating on the outermost layer of the billet in the heating process of the manufacturing method is a manganese-based high-melting-point coating, and the surface coating of the billet cannot be liquefied in the austenite heating process, so that the billet cannot be adhered to a ceramic roller, the evaporation of zinc cannot occur, the surface coating of the manufactured product is complete, and the service life of the ceramic roller is prolonged.

5. The second coating on the outermost layer of the billet in the heating process of the manufacturing method is a manganese-based high-melting-point coating, and the coating on the surface of the billet cannot be liquefied in the austenite heating process, so that the billet can be rapidly heated. The diffusion of the manganese-based high-melting-point coating to the low-melting-point coating enables the low-melting-point coating to simultaneously obtain the diffusion of high-melting-point materials on the upper surface and the lower surface (the matrix iron and the outer layer manganese), and meanwhile, the alloying time of the low-melting-point coating is greatly reduced due to the very thin low-melting-point alloy coating, so that the production time is shortened.

The principle and the implementation mode of the invention are explained by applying specific embodiments in the invention, and the description of the embodiments is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.