A composite coating for reducing hot forming cracking of high strength steel containing an inert coating layer

Abstract

The application discloses a composite coating with inert plating layer for reducing hot forming crack of high-strength steel, which is in a double-layer composite form and is obtained by pre-plating a layer of plating layer on the surface of high-strength steel, wherein the pre-plating layer contains at least one of B, Al, Cr, Cu, Mo and W elements, and the elements have positive mixing enthalpy with Zn element, that is, inert interaction with liquid Zn atoms. A conventional Zn plating layer is plated on the pre-plating layer. The thickness of each plating layer in the double-layer plating layer is 1-30 microns. The plating layer for reducing the hot forming crack tendency of high-strength steel combines chemical composition, element interaction and other factors, so that the liquid Zn atoms which are easy to penetrate along the grain boundary in the hot forming process are repelled by the plating component atoms in the pre-plating layer, the penetration of the liquid Zn atoms into the grain boundary of the steel base body is prevented, and the formation of the hot forming crack is reduced or even avoided. Through reasonable regulation and control of the element ratio of the plating layer, the purpose of effectively reducing the crack tendency of different types of high-strength steel in the hot forming and resistance spot welding processes can be achieved.

Description

Technical Field

[0001] This invention relates to a composite coating design containing an inert coating to reduce hot forming cracks in high-strength steel, and is applied in the field of high-strength steel technology for automobiles. Background Technology

[0002] With the development of my country's automobile manufacturing industry, the number of cars on the road is gradually increasing, having a profound impact on people's daily lives and work. However, the automobile manufacturing industry is also facing crises such as energy shortages and environmental pollution, making energy conservation and emission reduction a key issue that needs to be addressed by the automobile industry in my country and even the world. Lightweighting of automobiles has become a hot topic in the upgrading of the automotive industry. Lightweighting of automobiles can be achieved through the following approaches:

[0003] a. Increase the use of lightweight materials, such as aluminum, aluminum alloys, magnesium alloys, and carbon fiber composites, which are all lightweight materials with relatively low density;

[0004] b. Replace the ordinary steel used in the original automobiles with high-strength steel;

[0005] c. Strengthen the use of modern advanced manufacturing processes;

[0006] d. Conduct comprehensive optimization of the vehicle's structural design to reduce vehicle weight and achieve energy conservation and emission reduction.

[0007] From a cost and performance perspective, high-strength steel not only ensures sufficient crash safety in manufactured vehicles but also facilitates the achievement of lightweight vehicle body goals. Furthermore, the use of high-strength steel in automobile manufacturing can significantly improve the deformation resistance of automotive parts, further expanding the vehicle's elastic strain zone. Therefore, high-strength materials, represented by high-strength steel (HSS) and advanced high-strength steel (AHSS), have fully demonstrated their enormous potential for achieving energy conservation by reducing vehicle weight.

[0008] Hot forming technology represents an innovative manufacturing process for forming high-strength steel. This forming process can be used to manufacture automotive structural components with strengths up to 1500 MPa, thereby saving significant costs and offering clear advantages in addressing problems such as shape defects and high forming loads that easily occur during the cold working of high-strength steel sheets. To prevent oxidation of the steel sheet surface during heating and to obtain better corrosion resistance, Zn-based coatings and Al-Si coatings are widely used. However, coated high-strength steel is prone to cracking during subsequent hot working, becoming a significant obstacle to the application of high-strength steel in the automotive field. Typical high-strength steels such as DP (Dual-phase), TWIP (Twinning induced plasticity), QP (Quenching & partitioning), TRIP (Transformation induced plasticity), DH (Dual-phase high-ductility), and CP (Complex-phase) steels are all susceptible to cracking during hot forming and resistance spot welding. Therefore, researching the crack formation mechanism and countermeasures in the hot forming process of high-strength steel is urgently needed.

[0009] Traditional coatings are single-layered, composed of pure Zn or with a small amount of Al added to pure Zn to improve plating suitability. However, the tendency of high-strength steel to crack during hot forming has not been significantly improved. This invention designs the coating for high-strength steel by rationally controlling the element ratio of the coating and considering factors such as chemical composition and element interactions. It proposes a double-layer composite coating that reduces the tendency of high-strength steel to crack during hot forming, which can effectively reduce the cracking tendency of high-strength steel during hot forming.

[0010] Using "high strength steel + coating + crack" as keywords, searches in international scientific and technological databases such as Engineering Abstracts Index (EI), Sciencedirect, and ISI Web of Science, as well as online journal databases like CNKI and VIP, yielded no completely relevant literature. Further searches of the United States Patent and Trademark Office (USPTO), the European Patent Office (EPO), the World Intellectual Property Organization (WIPO), the China Patent Information Network, and the State Intellectual Property Office of the People's Republic of China also failed to find similar patent technologies. Summary of the Invention

[0011] To address the problems of existing technologies, the present invention aims to overcome the shortcomings of existing technologies and provide a composite coating containing an inert coating to reduce hot forming cracks in high-strength steel. The present invention aims to solve the technical problem that existing technologies and methods are insufficient to effectively address the tendency of high-strength steel to crack during hot forming and resistance spot welding. To solve the above problem, the present invention provides a coating design to reduce the tendency of high-strength steel to crack during hot forming. By combining factors such as chemical composition and elemental interactions, and rationally controlling the elemental ratio of the coating, the tendency of different types of high-strength steel to crack during hot forming and resistance spot welding can be effectively reduced.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A composite coating containing an inert coating to reduce hot forming cracks in high-strength steel is formed by pre-plating an inert coating on the surface of high-strength steel and then plating a Zn coating to form a composite coating with two layers.

[0014] The inert coating includes at least one of the elements B, Al, Cr, Cu, Mo, and W. In the inert coating, any one or more elements with a positive enthalpy of mixing with Zn are used as barrier components. The inert coating or Zn coating also contains other unavoidable impurities.

[0015] The inert coating forms a Zn atom diffusion barrier layer, which blocks the Zn atoms that penetrate from the Zn coating into the grain boundaries of the high-strength steel substrate during hot forming. The inert coating forms a Zn atom migration barrier system, making the high-strength steel less sensitive to the tendency to crack during hot forming.

[0016] Preferably, any one of the barrier components in the inert coating has a positive enthalpy of mixing with Zn. During the zinc plating process using the plating solution, the atoms of the barrier component have a repulsive effect on the liquid Zn atoms, preventing the liquid Zn atoms from penetrating into the steel matrix along the grain boundaries during hot forming or resistance spot welding.

[0017] Preferably, the enthalpy of mixing of any one of the barrier components with Zn is ≥1 kJ / mol.

[0018] Preferably, the thickness of each coating layer is 1-30 μm.

[0019] Preferably, the coating is formed by at least one of the following methods that can form a coating on the surface of high-strength steel: hot-dip galvanizing, electroplating, or zinc annealing.

[0020] Preferably, the high-strength steel with double coating is hot-formed at a temperature of 700-950℃ and the holding time is ≤30min.

[0021] Preferably, resistance spot welding is performed on high-strength steel with double coating. The resistance spot welding time is 10ms-10s, the welding current is 2kA-20kA, the welding pulses are 1-20, the interval time between welding pulses is 0ms-1s, and the hold time is 0s-5s.

[0022] Preferably, the interaction between different elements in the coating is controlled by adjusting the element ratio of the coating.

[0023] Preferably, the interaction between the elements is achieved by controlling the enthalpy of mixing, and by combining at least one physical quantity among free energy and electron concentration.

[0024] Preferably, the high-strength steel is at least one of DP (Dual phase), TWIP (Twinning induced plasticity), QP (Quenching & partitioning), TRIP (Transformation induced plasticity), DH (Dual-phase high-ductility), and CP (Complex phase) steel.

[0025] Preferably, the inert coating includes two elements, Al and Cr, forming an Al-Cr alloy coating.

[0026] Preferably, the coating of the present invention that reduces the tendency of high-strength steel to crack during hot forming achieves a smaller tendency of high-strength steel to generate cracks during hot forming and resistance spot welding processes.

[0027] Preferably, the coating for reducing the tendency of hot forming cracks in high-strength steel according to the present invention is based on existing process parameters for hot forming and resistance spot welding. The crack assessment parameters include crack location and crack length.

[0028] Compared with the prior art, the present invention has the following obvious and prominent substantive features and significant advantages:

[0029] 1. This invention proposes a coating design to reduce the tendency of hot forming cracks in high-strength steel by combining factors such as chemical composition and element interaction coefficients. By reasonably controlling the element ratio of the coating, the purpose of effectively reducing the tendency of different types of high-strength steel to generate cracks during the hot forming process can be achieved.

[0030] 2. The coating preparation process of this invention is simple and efficient;

[0031] 3. This invention relates to a coating design for reducing the tendency of high-strength steel to crack during hot forming. The design involves determining the type of high-strength steel and, based on its composition, determining the component ratio of the coating. High-strength steel with a double-layer coating is then subjected to hot forming or resistance spot welding, with parameters adjusted according to actual conditions. The crack formation during the hot forming process of existing coated high-strength steel is then compared to obtain a quantitative evaluation result. The double-layer coating, due to the strong repulsive effect of B, Al, Cr, Cu, Mo, and W atoms in the pre-coating layer on liquid Zn atoms, prevents liquid Zn atoms from penetrating into the steel matrix along grain boundaries during hot forming or resistance spot welding. Therefore, the double-layer coating of this invention effectively reduces the tendency of high-strength steel to crack during hot forming.

[0032] 4. The high-strength steel involved in this invention includes, but is not limited to, high-strength steels for automobiles such as QP, TWIP, DP, TRIP, DH, and CP steels, which are currently prone to cracking during the hot forming process. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the principle of a preferred embodiment of the present invention, showing how a double-layer coating design reduces the tendency of high-strength steel to crack during hot forming. Detailed Implementation

[0034] Traditional coatings are single-layered, composed of pure Zn or, to improve plating suitability, with a small amount of Al added to pure Zn, the Al content being 0-5 wt.%. The following pure Zn coatings, including Zn-Al coatings, with an Al content of 0-5 wt.%, are defined as traditional coatings.

[0035] The above solution will be further described below with reference to specific embodiments. The preferred embodiments of the present invention are described in detail below:

[0036] Example 1:

[0037] In this embodiment, a composite coating containing an inert coating to reduce hot forming cracks in high-strength steel is prepared by pre-plating an inert coating on the surface of the high-strength steel, followed by plating a Zn coating to form a composite coating with two layers, as detailed below:

[0038] (1) Select QP high-strength steel, whose chemical composition is shown in Table 1. The mixed enthalpy of Al and Zn elements is 1 kJ / mol. The larger the positive value of the mixed enthalpy, the stronger the repulsion between atoms.

[0039] Table 1. Chemical composition of QP high-strength steel (wt.%)

[0040]

[0041] (2) QP high-strength steel is pre-plated with Al, the thickness of the pre-plated Al layer is 5μm, and then hot-dip galvanizing is used to apply a traditional Zn coating on the pre-plated Al layer, the thickness of the Zn coating is also 5μm.

[0042] (3) Hot forming of QP high-strength steel with double-layer composite coating, hot forming temperature is 930℃, and holding time is 4min;

[0043] (4) Crack characterization of the hot-formed QP high-strength steel showed no obvious cracks.

[0044] like Figure 1 As shown, this embodiment, considering factors such as chemical composition and inter-element interactions, pre-coats a layer of Al on the surface of high-strength steel 3. This prevents direct contact between liquid Zn and high-strength steel 3 during hot forming. Furthermore, a positive enthalpy of mixing exists between Al and Zn (1 kJ / mol), repelling liquid Zn atoms 4 from the inert coating formed by the Al atoms 6, thus preventing Zn atoms 4 from penetrating along the high-strength steel 3 substrate. This effectively reduces the tendency of QP steel to crack during hot forming, significantly superior to the traditional single-layer Zn surface layer 1 on high-strength steel 3. The inert coating in this embodiment forms a Zn atom 4 diffusion barrier layer, blocking Zn atoms 4 from penetrating from the Zn coating to the high-strength steel grain boundaries 5 during hot forming. The inert coating forms a Zn atom 4 barrier migration system. This embodiment forms a composite coating with two layers 2, achieving insensitivity to the tendency of high-strength steel to crack during hot forming.

[0045] Example 2:

[0046] This embodiment is basically the same as Embodiment 1, except that:

[0047] In this embodiment, the coating on the surface of the high-strength steel is a double-layer composite coating:

[0048] (1) Select QP high-strength steel, whose chemical composition is shown in Table 1. The mixed enthalpy of Cr and Zn elements is 5kJ / mol. The larger the positive value of the mixed enthalpy, the stronger the repulsion between atoms.

[0049] (2) QP high-strength steel is pre-plated with Cr, the thickness of the pre-plated Cr layer is 5μm, and then Zn is plated on the pre-plated Cr layer by hot-dip galvanizing, the thickness of the Zn layer is also 5μm.

[0050] (3) Hot forming of QP high-strength steel with composite coating, hot forming temperature is 930℃, holding time is 4min;

[0051] (4) Crack characterization of the hot-formed QP high-strength steel showed no obvious cracks.

[0052] In this embodiment, considering factors such as chemical composition and inter-element interactions, a layer of Cr is pre-plated on the surface of high-strength steel. On the one hand, this prevents direct contact between liquid Zn and high-strength steel during hot forming. On the other hand, there is a positive mixing enthalpy (5kJ / mol) between Cr and Zn. Liquid Zn atoms are repelled by Cr atoms outside the pre-plating layer, preventing them from penetrating along the steel matrix. This effectively reduces the tendency of QP steel to crack during hot forming.

[0053] Example 3:

[0054] This embodiment is basically the same as the above embodiments, except that:

[0055] In this embodiment, the coating on the surface of the high-strength steel is a double-layer composite coating:

[0056] (1) Select QP high-strength steel. Its chemical composition is shown in Table 1. The mixed enthalpy of Al and Zn elements is 1 kJ / mol, and the mixed enthalpy of Cr and Zn elements is 5 kJ / mol. The larger the positive value of the mixed enthalpy, the stronger the repulsion between atoms.

[0057] (2) QP high-strength steel is pre-plated with Cr and Al, the thickness of the pre-plated Cr-Al layer is 5μm, and then Zn is plated on the pre-plated Cr-Al layer by hot-dip galvanizing, the thickness of the Zn layer is also 5μm; in the pre-plated Cr-Al layer, the mass percentage content of Cr does not exceed 20wt.%.

[0058] (3) Hot forming of QP high-strength steel with composite coating, hot forming temperature is 930℃, holding time is 4min;

[0059] (4) Crack characterization of the hot-formed QP high-strength steel showed no obvious cracks.

[0060] This embodiment combines factors such as chemical composition and inter-element interactions to pre-plate a Cr-Al layer on the surface of high-strength steel. On the one hand, it hinders the direct contact between liquid Zn and high-strength steel during hot forming. On the other hand, there are positive mixing enthalpies between Al and Zn, and between Cr and Zn. Liquid Zn atoms are jointly repelled by Cr and Al atoms outside the pre-plating layer, preventing them from penetrating along the steel matrix. This effectively reduces the tendency of QP steel to crack during hot forming.

[0061] Example 4:

[0062] This embodiment is basically the same as the above embodiments, except that:

[0063] In this embodiment, the coating on the surface of the high-strength steel is a double-layer composite coating:

[0064] (1) Select QP high-strength steel, whose chemical composition is shown in Table 1. The mixed enthalpy of B and Zn elements is 4kJ / mol. The larger the positive value of the mixed enthalpy, the stronger the repulsion between atoms.

[0065] (2) QP high-strength steel is pre-plated with B, the thickness of the pre-plated B layer is 5μm, and then Zn is plated on the pre-plated B layer by hot-dip galvanizing, the thickness of the Zn layer is also 5μm.

[0066] (3) Hot forming of QP high-strength steel with composite coating, hot forming temperature is 930℃, holding time is 4min;

[0067] (4) Crack characterization of the hot-formed QP high-strength steel showed no obvious cracks.

[0068] This embodiment combines factors such as chemical composition and inter-element interactions to pre-plate a layer of B on the surface of high-strength steel. On the one hand, this prevents direct contact between liquid Zn and high-strength steel during hot forming. On the other hand, there is a positive mixing enthalpy between B and Zn, and liquid Zn atoms are repelled by B atoms outside the pre-plating layer, preventing them from penetrating along the steel matrix. This effectively reduces the tendency of QP steel to crack during hot forming.

[0069] Example 5:

[0070] This embodiment is basically the same as the above embodiments, except that:

[0071] In this embodiment, the coating on the surface of the high-strength steel is a double-layer composite coating:

[0072] (1) Select QP high-strength steel, whose chemical composition is shown in Table 1. The mixed enthalpy of Cu and Zn elements is 1 kJ / mol. The larger the positive value of the mixed enthalpy, the stronger the repulsion between atoms.

[0073] (2) QP high-strength steel is pre-plated with Cu, the thickness of the pre-plated Cu layer is 5μm, and then Zn is plated on the pre-plated Cu layer by hot-dip galvanizing, the thickness of the Zn layer is also 5μm;

[0074] (3) Hot forming of QP high-strength steel with composite coating, hot forming temperature is 930℃, holding time is 4min;

[0075] (4) Crack characterization of the hot-formed QP high-strength steel showed no obvious cracks.

[0076] In this embodiment, considering factors such as chemical composition and inter-element interactions, a layer of Cu is pre-plated on the surface of high-strength steel. On the one hand, this prevents direct contact between liquid Zn and high-strength steel during hot forming. On the other hand, there is a positive mixing enthalpy between Cu and Zn, and liquid Zn atoms are repelled by Cu atoms outside the pre-plating layer, preventing them from penetrating along the steel matrix. This effectively reduces the tendency of QP steel to crack during hot forming.

[0077] Example 6:

[0078] This embodiment is basically the same as the above embodiments, except that:

[0079] In this embodiment, the coating on the surface of the high-strength steel is a double-layer composite coating:

[0080] (1) Select QP high-strength steel, whose chemical composition is shown in Table 1. The mixed enthalpy of Mo and Zn elements is 12kJ / mol. The larger the positive value of the mixed enthalpy, the stronger the repulsion between atoms.

[0081] (2) QP high-strength steel is pre-plated with Mo, the thickness of the pre-plated Mo layer is 5μm, and then Zn is plated on the pre-plated Mo layer by hot-dip galvanizing, the thickness of the Zn layer is also 5μm.

[0082] (3) Hot forming of QP high-strength steel with composite coating, hot forming temperature is 930℃, holding time is 4min;

[0083] (4) Crack characterization of the hot-formed QP high-strength steel showed no obvious cracks.

[0084] In this embodiment, considering factors such as chemical composition and inter-element interactions, a layer of Mo is pre-plated on the surface of high-strength steel. On the one hand, this prevents direct contact between liquid Zn and high-strength steel during hot forming. On the other hand, there is a positive mixing enthalpy between Mo and Zn, and liquid Zn atoms are repelled by Mo atoms outside the pre-plating layer, preventing them from penetrating along the steel matrix. This effectively reduces the tendency of QP steel to crack during hot forming.

[0085] Example 7:

[0086] This embodiment is basically the same as the above embodiments, except that:

[0087] In this embodiment, the coating on the surface of the high-strength steel is a double-layer composite coating:

[0088] (1) Select QP high-strength steel, whose chemical composition is shown in Table 1. The mixed enthalpy of W and Zn elements is 15kJ / mol. The larger the positive value of the mixed enthalpy, the stronger the repulsion between atoms.

[0089] (2) QP high-strength steel is pre-plated with W, the thickness of the pre-plated W layer is 5μm, and then Zn is plated on the pre-plated W layer by hot-dip galvanizing, the thickness of the Zn layer is also 5μm.

[0090] (3) Hot forming of QP high-strength steel with composite coating, hot forming temperature is 930℃, holding time is 4min;

[0091] (4) Crack characterization of the hot-formed QP high-strength steel showed no obvious cracks.

[0092] In this embodiment, considering factors such as chemical composition and inter-element interactions, a layer of W is pre-plated on the surface of high-strength steel. On the one hand, this prevents direct contact between liquid Zn and high-strength steel during hot forming. On the other hand, there is a positive mixing enthalpy between W and Zn, and liquid Zn atoms are repelled by W atoms outside the pre-plating layer, preventing them from penetrating along the steel matrix. This effectively reduces the tendency of QP steel to crack during hot forming.

[0093] Example 8:

[0094] This embodiment is basically the same as the above embodiments, except that:

[0095] In this embodiment, the high-strength steel employs a composite coating. By adjusting the elemental ratio of the coating, the interaction between any of the elements among B, Al, Cr, Cu, Mo, and W can be controlled. Furthermore, the inert coating can also be at least one of the following: B-Al, B-Cr, B-Cu, B-Mo, B-Mo, B-Al-Cr, B-Al-Cu, B-Al-Mo, B-Al-W, B-Al-Cr-Cu, B-Al-Cr-Mo, B-Al-Cr-W, Al-Cr, Al-Cr, Al-Cu, Al-Mo, Al-W, Al-Cr-Cu, Al-Cr-Mo, Al-Cr-W, Al-Cr-Cu-Mo, Al-Cr-Cu-W, Cr-Cu, Cr-Mo, Cr-W, Cr-Cu-Mo, Cr-Cu-W, Cr-Cu-Mo, Cr-Cu-W, Cr-Cu-Mo-W, Cu-Mo, Cu-W, Cu-Mo-W, and Mo-W. The Zn-based coating is prepared using electroplating, hot-dip galvanizing, chemical vapor deposition, or magnetron sputtering processes. This invention aims to achieve insensitivity to the tendency of high-strength steel to crack during hot forming, meeting the crack tendency detection standards for high-strength steel. The high-strength steels involved include, but are not limited to, QP, TWIP, DP, TRIP, DH, and CP steels, which are currently prone to cracking during hot forming in automotive applications. This embodiment can also effectively reduce the crack tendency of different types of high-strength steel during hot forming by rationally controlling the elemental ratio of the coating. The coating design of this invention, which reduces the crack tendency of high-strength steel during hot forming, combines chemical composition and elemental interactions to bind Zn atoms, which are normally prone to penetrating along grain boundaries during hot forming, within the coating by other additive components, preventing their penetration into the grain boundaries and reducing or even avoiding the formation of hot forming cracks. By rationally controlling the elemental ratio of the coating, the goal of effectively reducing the crack tendency of different types of high-strength steel during hot forming can be achieved.

[0096] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A composite coating containing an inert coating to reduce hot forming cracks in high-strength steel, characterized in that: An inert coating is pre-plated on the surface of high-strength steel, and then a Zn coating is plated to form a composite coating with two layers. The inert coating includes at least one of the elements B, Al, Cr, Cu, Mo, and W. In the inert coating, any one or more elements with a positive enthalpy of mixing with Zn are used as barrier components. The inert coating or Zn coating also contains other unavoidable impurities. The inert coating forms a Zn atom diffusion barrier layer, which blocks the Zn atoms that penetrate from the Zn coating to the grain boundaries of the high-strength steel substrate during hot forming. The inert coating forms a Zn atom barrier migration system, making the high-strength steel less sensitive to the tendency to crack during hot forming. During the zinc plating process using the plating solution, the barrier component atoms have a repulsive effect on the liquid Zn atoms, preventing the liquid Zn atoms from penetrating into the steel matrix along the grain boundaries during hot forming or resistance spot welding. The enthalpy of mixing any barrier component with Zn is ≥1kJ / mol; the thickness of each coating layer is 1-30μm; the high-strength steel with double coating layers is hot-formed at a temperature of 700-950℃ and a holding time of ≤30min.

2. The composite coating containing an inert coating for reducing hot forming cracks in high-strength steel according to claim 1, characterized in that: The coating is formed by at least one of the following methods: hot-dip galvanizing, electroplating, or zinc annealing, which can form a coating on the surface of high-strength steel.

3. The composite coating containing an inert coating for reducing hot forming cracks in high-strength steel according to claim 1, characterized in that: Resistance spot welding was performed on high-strength steel with double coating. The resistance spot welding time was 10ms-10s, the welding current was 2kA-20kA, the welding pulses were 1-20, the interval between welding pulses was 0ms-1s, and the hold time was 0s-5s.

4. The composite coating containing an inert coating for reducing hot forming cracks in high-strength steel according to claim 1, characterized in that: The interaction between different elements in the coating is controlled by adjusting the element ratio of the coating. The interaction between the elements is achieved by adjusting the mixing enthalpy and by combining at least one physical quantity among free energy and electron concentration.

5. The composite coating containing an inert coating for reducing hot forming cracks in high-strength steel according to claim 1, characterized in that: The high-strength steel is at least one of DP, TWIP, QP, TRIP, DH and CP steels.

6. The composite coating containing an inert coating for reducing hot forming cracks in high-strength steel according to claim 1, characterized in that: The inert coating consists of two elements, Al and Cr, forming an Al-Cr alloy coating.

Images