A method for heat treatment of aluminum-silicon coated hot-formed steel

Abstract

The present application relates to the technical field of hot stamping of hot-formed steel, and in particular to a heat treatment method for hot-formed steel with aluminum silicon coating. The thickness m of the alloying layer of the original part and the total coating thickness M of the aluminum silicon coating hot-formed steel are detected, and the ratio m / M of the two is obtained; the energy obtained in the first stage and the second stage is calculated based on the original holding temperature and the original holding time in the original heat treatment and the m / M; wherein, the heat treatment is divided into the first stage and the second stage based on the heating temperature in the heat treatment; the first stage and the second stage are respectively divided into several heating temperature gradients, and the holding time corresponding to each heating temperature is calculated based on the energy obtained in the first stage and the second stage; based on each of the above temperatures and times, the steel is heat treated in stages, and then stamped and held to obtain parts. The content of this application solves the technical problem of coating sticking to the roller of existing aluminum silicon coating hot-formed steel.

Description

Technical Field

[0001] The present application relates to the technical field of hot stamping of hot-formed steel, and in particular to a heat treatment method for hot-formed steel with an aluminum-silicon coating. Background Art

[0002] Using hot-stamped steel for hot stamping parts improves part strength and prevents springback during forming. When using bare hot-stamped steel, high temperatures can produce oxide scale. This scale affects part surface quality and requires shot peening to remove. To prevent this, an aluminum-silicon coating is applied to the bare steel surface. This coating eliminates the need for shot peening, improving production efficiency and part precision.

[0003] However, during the heating process, the coating is prone to roller sticking. When the coating sticks to the roller, it affects the quality of the coating and the service life of the heating roller. Therefore, it is necessary to study new heat treatment methods to avoid the occurrence of roller sticking or reduce the degree of roller sticking. Summary of the Invention

[0004] The present application provides a heat treatment method for aluminum-silicon coated hot-formed steel to solve the technical problem of aluminum-silicon coating sticking to the roller of existing aluminum-silicon coated hot-formed steel.

[0005] In a first aspect, the present application provides a heat treatment method for aluminum-silicon coated hot-formed steel, the method comprising:

[0006] The thickness m of the alloying layer of the original part and the total coating thickness M of the aluminum-silicon coated hot-formed steel are detected, and a ratio m / M between the two is obtained;

[0007] Calculating the energy obtained in the first stage and the second stage respectively based on the original holding temperature and the original holding time in the original heat treatment and the m / M; wherein the heat treatment is divided into the first stage and the second stage based on the heating temperature in the heat treatment;

[0008] Dividing the first stage and the second stage into a plurality of heating temperature gradients, and calculating the holding time corresponding to each heating temperature based on the energy obtained in the first stage and the second stage;

[0009] Based on each of the heating temperatures and each of the holding times, the aluminum-silicon coated hot-formed steel is heat treated in stages, and then stamped and held to obtain parts.

[0010] Optionally, the original insulation temperature is 880° C.-950° C., and the original insulation time is 3 min-8 min.

[0011] Optionally, the heat treatment is divided into two stages based on the heating temperature in the heat treatment, including:

[0012] If the heating temperature is less than the austenite transformation starting temperature, it is judged to be the first stage;

[0013] If the heating temperature is ≥ the complete austenite transformation temperature, it is judged to be the second stage.

[0014] Optionally, the energy obtained at each stage of the heat treatment process is calculated based on the original holding temperature and the original holding time in the original heat treatment and the m / M, including:

[0015] The energy obtained in the first and second stages of the heat treatment process is calculated based on the original holding temperature and the original holding time in the heat treatment and the m / M; wherein,

[0016] A ratio of the total energy obtained in the first stage and the second stage is determined based on the ratio m / M.

[0017] Optionally, determining the ratio of total energy obtained in the first stage and the second stage based on the ratio m / M includes:

[0018] If m / M ≥ 0.3, the proportion of total energy obtained in the first stage is 0, and the proportion of total energy obtained in the second stage is 100%;

[0019] If 0.3>m / M≥0.25, the proportion of total energy obtained in the first stage is 5%, and the proportion of total energy obtained in the second stage is 95%;

[0020] If 0.25>m / M≥0.2, the proportion of total energy obtained in the first stage is 15%, and the proportion of total energy obtained in the second stage is 85%;

[0021] If 0.2>m / M≥0.15, the proportion of total energy obtained in the first stage is 25%, and the proportion of total energy obtained in the second stage is 75%;

[0022] If 0.15>m / M≥0.1, the proportion of total energy obtained in the first stage is 35%, and the proportion of total energy obtained in the second stage is 65%;

[0023] If 0.1>m / M≥0.05, the proportion of total energy obtained in the first stage is 45%, and the proportion of total energy obtained in the second stage is 55%;

[0024] If 0.05>m / M, the proportion of total energy obtained in the first stage is 50%, and the proportion of total energy obtained in the second stage is 50%. Optionally, the energy expression is:

[0025] N = y*t*T;

[0026] Where N represents the energy in each stage; y represents the proportion of the total energy obtained in each stage; t represents the original holding time; and T represents the original holding temperature.

[0027] Optionally, the expression for calculating the heating temperature and holding time of each stage in the heat treatment process is:

[0028] N=T1*t1+T2*t2+T3*t3+......;

[0029] Where N represents the energy of each stage; T1 represents the first temperature; t1 represents the holding time corresponding to the first temperature; T2 represents the second temperature; t2 represents the holding time corresponding to the second temperature; T3 represents the third temperature; t3 represents the holding time corresponding to the third temperature.

[0030] Optionally, dividing the first stage and the second stage into a plurality of heating temperature gradients, and calculating the holding time corresponding to each heating temperature based on the energy obtained in the first stage and the second stage, respectively, includes:

[0031] Dividing the first stage into three heating temperature gradients, and calculating the holding time corresponding to each heating temperature in the first stage based on the energy obtained in the first stage;

[0032] The second stage is divided into three heating temperature gradients, and the holding time corresponding to each heating temperature in the second stage is calculated based on the energy obtained in the second stage.

[0033] Optionally, the three temperatures in the first stage are 500° C., 590° C. and 680° C. respectively.

[0034] Optionally, the three temperatures in the second stage are 880° C., 905° C. and 930° C. respectively.

[0035] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0036] The heat treatment method of the aluminum-silicon coated hot-formed steel provided in the embodiment of the present application is to form a hot-stamped part after hot stamping of the hot-formed steel, and the coating of the part is tested, mainly detecting the ratio m / M of the thickness of the alloyed layer in the coating to the total thickness of the coating, and optimizing the heat treatment process according to the ratio. By controlling the heating temperature and the holding time of the heat treatment in stages, it is beneficial to promote the reaction of the Fe-Al-Si three-phase structure, which has a higher melting point. Increasing the pre-alloying temperature or extending the pre-alloying time by the ratio m / M can promote the formation and growth of the Fe-Al-Si three-phase structure and form a thicker alloy layer. The more fully the material is pre-alloyed, the thicker the alloy layer, and the easier it is to overcome the roller sticking phenomenon, thereby solving the technical problem of aluminum-silicon coating roller sticking in the existing aluminum-silicon coated hot-formed steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0039] Figure 1 A schematic flow chart of a heat treatment method for aluminum-silicon coated hot-formed steel provided in an embodiment of the present application;

[0040] Figure 2 This is a scanning electron microscope image of an aluminum-silicon coated hot-formed steel provided in Example 1 of the present application;

[0041] Figure 3 This is a scanning electron microscope image of an aluminum-silicon coated hot-formed steel provided in Example 2 of the present application;

[0042] Figure 4 This is a scanning electron microscope image of an aluminum-silicon coated hot-formed steel provided in Example 3 of the present application;

[0043] Figure 5 This is a scanning electron microscope image of an aluminum-silicon coated hot-formed steel provided in Example 4 of the present application;

[0044] Figure 6 This is a scanning electron microscope image of an aluminum-silicon coated hot-formed steel provided in Example 5 of the present application;

[0045] Figure 7 This is a scanning electron microscope image of an aluminum-silicon coated hot-formed steel provided in Example 6 of the present application;

[0046] Figure 8 This is a scanning electron microscope image of an aluminum-silicon coated hot-formed steel provided in Example 7 of the present application;

[0047] Figure 9 This is a scanning electron microscope image of an aluminum-silicon coated hot-formed steel provided in Example 8 of the present application. DETAILED DESCRIPTION

[0048] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0049] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0050] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple.

[0051] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0052] In the first aspect, the present application provides a heat treatment method for aluminum-silicon coated hot-formed steel, see Figure 1 , the method comprising:

[0053] S1. Detecting the thickness m of the alloy layer of the original part and the total coating thickness M of the aluminum-silicon coated hot-formed steel, and obtaining a ratio m / M between the two;

[0054] S2. Calculating the energy obtained in the first stage and the second stage respectively based on the original holding temperature and the original holding time in the original heat treatment and the m / M; wherein the heat treatment is divided into the first stage and the second stage based on the heating temperature in the heat treatment;

[0055] S3, dividing the first stage and the second stage into a plurality of heating temperature gradients, and calculating the holding time corresponding to each heating temperature based on the energy obtained in the first stage and the second stage;

[0056] S4. Based on each of the heating temperatures and each of the holding times, the aluminum-silicon coated hot-formed steel is heat treated in stages, and then stamped and held to obtain parts.

[0057] In the embodiments of the present application, the heat treatment of the sheet material is primarily an austenitizing heat treatment. The thickness m of the alloyed layer and the total coating thickness M of the aluminum-silicon-coated hot-formed steel are measured for the parts obtained by the original heat treatment method, and the ratio m / M is obtained. The total energy of the heat treatment stage is then calculated based on the original holding temperature and holding time of the original heat treatment and the law of conservation of energy. In the new heat treatment method, the aluminum-silicon-coated hot-formed steel is heated in stages, divided into different stages according to the heating temperature. The energy obtained in each stage is determined by m / M, and the holding time is then calculated.

[0058] The heating furnace parameters are set based on the determined austenitizing heat treatment temperature and holding time. The sheet is then transferred to the heating furnace. Currently, roller-hearth furnaces are commonly used for hot stamping. The sheet moves from one end of the furnace to the other. Sheets can be placed in either a longitudinal or transverse direction. After the robot places the sheet into the furnace, it is moved forward by the rollers. When gradient heating is used, different zones of the furnace are set to different temperatures. By the time the sheet has moved from one end of the furnace to the other, the austenitizing heat treatment has been completed. Subsequent stamping processes can then be carried out.

[0059] After the sheet metal is removed from the heating furnace, it is transferred to the stamping die on the press by a robot or other means. The press then performs the stamping operation, forming the sheet metal into the part shape. The stamped part is placed between the male and female dies. The press applies pressure to the die, maintaining the pressure and achieving die hardening. The holding time is typically 10 seconds. The holding pressure is determined based on the specific part thickness and shape.

[0060] After the part is removed from the mold, the performance and coating thickness are tested. The tensile strength of the part is usually required to be above 1350MPa. The coating thickness can be measured by selecting the material on the part to make a sample for scanning electron microscopy (SEM) and then observing it under the SEM. Figure 2-Figure 9 .

[0061] The morphology and thickness of each layer of the coating can be observed using an electron microscope. The thickness of each layer in the coating can also be measured using an electron microscope. During the heat treatment of the material, the Fe element in the matrix diffuses into the coating, forming a Fe-Al-Si three-phase structure, which has a higher melting point.

[0062] Through electron microscopic observation and measurement, the thickness of the different layers in the coating can be determined. Due to the interdiffusion and reaction of elements between the substrate and the coating, the thickness of the alloyed layer between the substrate and the coating increases. The thickness of the alloyed layer and the total thickness of the coating are measured. The value of "alloyed layer thickness / total coating thickness" is calculated. Here, this ratio is defined as the "ratio of alloyed layer thickness to total coating thickness" and is represented by the letter "k", that is, k = m / M.

[0063] In the embodiments of the present application, the size of the k value is related to pre-alloying. Before the material is austenitized, a low-temperature heat treatment is performed and the heat is kept for a certain period of time, which is beneficial to promoting the reaction of the Fe-Al-Si three-phase structure, which has a higher melting point. By increasing the pre-alloying temperature or extending the pre-alloying time, the formation and growth of the Fe-Al-Si three-phase structure can be promoted to form a thicker alloy layer. The pre-alloying temperature usually needs to be controlled below the austenitizing temperature of the material. The more fully the material is pre-alloyed, the thicker the alloy layer, and the easier it is to overcome the roller sticking phenomenon. The heat treatment method optimized according to the k value can reduce the degree of roller sticking of the aluminum-silicon coating during the heating process and improve the stamping performance of the aluminum-silicon coating hot-formed steel. At the same time, it improves production efficiency and reduces energy loss.

[0064] In some embodiments, the original holding temperature is 880° C.-950° C., and the original holding time is 3 min-8 min.

[0065] During the hot stamping process of hot-formed steel, it is necessary to heat the steel above the austenitizing temperature and then maintain this temperature for a period of time. When bare hot-formed steel is heated, scale is easily formed. Therefore, an aluminum-silicon coating is applied to the bare steel surface to prevent scale formation. However, due to the low melting point of the aluminum in the coating, the aluminum-silicon coating can easily stick to the rollers during the heating process, reducing the service life of the heating rollers in the heating furnace and affecting the quality of the aluminum-silicon coating. Therefore, to prevent this, heating and holding are performed in stages.

[0066] The positive effect of controlling the original holding temperature to 880℃-950℃ and the original holding time to 3min-8min is: heating the sheet to 880℃-950℃ and holding it at this temperature, and setting a certain holding time, so that the steel plate is completely austenitized, and the temperature inside and outside the steel is uniform, reducing the internal force caused by the temperature difference, and facilitating processing. If the heating temperature is too low or the holding time is too short, the material cannot be uniformly and completely austenitized. If the heating temperature is too high or the holding time is too long, the austenite grains of the material will coarsen, resulting in unsatisfactory microstructure of the material, and ultimately affecting the mechanical properties of the material.

[0067] Before step S4, hot stamping process parameters, holding pressure quenching parameters and sheet metal shape profile are determined through simulation;

[0068] The blank is blanked according to the shape contour of the sheet material, and then coated with an aluminum-silicon coating to obtain aluminum-silicon coated hot-formed steel.

[0069] Simulation software can be used to simulate the hot stamping process of sheet metal, as well as the heat treatment process, hot stamping process, and press-hardening process. Hot stamping process parameters primarily include stamping speed, blank holder force (some parts have no blank holder force, in which case the blank holder force is assumed to be zero), and friction coefficient (this parameter is typically obtained through high-temperature friction testing of the material). Parameters related to the press-hardening process include holding pressure and holding time. Simulation can determine optimal hot stamping and press-hardening process parameters. Furthermore, it can determine the optimal sheet metal shape profile. Blanking is performed based on the sheet metal profile. The main elements of this material, by mass percentage, are: C: 0.1%-0.55%; Si: 0.2%-0.8%; Mn: 0.5%-3.1%; Cr: 0.1%-1.5%; Al: 0.02%-0.16%; and B: 0.0003%-0.09%. The substrate includes, but is not limited to, the above elements; niobium (Nb) and other elements are also added to improve performance. An aluminum-silicon coating is applied to both sides of the substrate, with the aluminum content of the coating being no less than 80% by weight and the silicon content being no less than 5%. The coating bath comprises approximately 90% aluminum and 10% silicon by weight. In addition to the above elements, the substrate and coating may also contain unavoidable impurities. The steel material is prepared through the sequential steps of steelmaking, rolling, and immersion plating.

[0070] In some embodiments, the heat treatment is divided into two stages based on the heating temperature during the heat treatment, including:

[0071] If the heating temperature is less than the austenite transformation starting temperature, it is judged to be the first stage;

[0072] If the heating temperature is ≥ the complete austenite transformation temperature, it is judged to be the second stage.

[0073] During heat treatment, materials must ensure sufficient energy is available. The heat treatment process can be divided into two main parts. The first is the pre-alloying stage (defined as the first stage), where the heating temperature is below the austenite transformation start temperature. The second is the austenitizing heat treatment stage (defined as the second stage), where the heating temperature is not less than the complete austenite transformation temperature.

[0074] In some embodiments, calculating the energy obtained at each stage during the heat treatment based on the original holding temperature and the original holding time in the original heat treatment and the m / M comprises:

[0075] The energy obtained in the first and second stages of the heat treatment process is calculated based on the original holding temperature and the original holding time in the heat treatment and the m / M; wherein,

[0076] A ratio of the total energy obtained in the first stage and the second stage is determined based on the ratio m / M.

[0077] In some embodiments, determining the ratio of the total energy obtained in the first stage and the second stage based on the ratio m / M includes:

[0078] If m / M ≥ 0.3, the proportion of total energy obtained in the first stage is 0, and the proportion of total energy obtained in the second stage is 100%;

[0079] If 0.3>m / M≥0.25, the proportion of total energy obtained in the first stage is 5%, and the proportion of total energy obtained in the second stage is 95%;

[0080] If 0.25>m / M≥0.2, the proportion of total energy obtained in the first stage is 15%, and the proportion of total energy obtained in the second stage is 85%;

[0081] If 0.2>m / M≥0.15, the proportion of total energy obtained in the first stage is 25%, and the proportion of total energy obtained in the second stage is 75%;

[0082] If 0.15>m / M≥0.1, the proportion of total energy obtained in the first stage is 35%, and the proportion of total energy obtained in the second stage is 65%;

[0083] If 0.1>m / M≥0.05, the proportion of total energy obtained in the first stage is 45%, and the proportion of total energy obtained in the second stage is 55%;

[0084] If 0.05>m / M, the proportion of the total energy obtained in the first stage is 50%, and the proportion of the total energy obtained in the second stage is 50%.

[0085] The proportion of the total energy obtained in the first stage and the proportion of the total energy obtained in the second stage are determined according to the value range of m / M, that is, the value range of k.

[0086] In some embodiments, the energy is expressed as:

[0087] N = y*t*T;

[0088] Where N represents the energy in each stage; y represents the proportion of the total energy obtained in each stage; t represents the original holding time; and T represents the original holding temperature.

[0089] In the embodiment of the present application, the energy obtained in the first stage is equal to the ratio multiplied by the total energy number; the energy obtained in the second stage is equal to the ratio multiplied by the total energy number.

[0090] Based on the known original holding time, the known original holding temperature, and the ratio y obtained based on the k value in the previous step, the energy N of each stage can be calculated.

[0091] In some embodiments, the expression for calculating the heating temperature and holding time of each stage in the heat treatment process is:

[0092] N=T1*t1+T2*t2+T3*t3+......;

[0093] Where N represents the energy of each stage; T1 represents the first temperature; t1 represents the holding time corresponding to the first temperature; T2 represents the second temperature; t2 represents the holding time corresponding to the second temperature; T3 represents the third temperature; t3 represents the holding time corresponding to the third temperature.

[0094] In some embodiments, dividing the first stage and the second stage into a plurality of heating temperature gradients, and calculating the holding time corresponding to each heating temperature based on the energy obtained in the first stage and the second stage, respectively, includes:

[0095] Dividing the first stage into three heating temperature gradients, and calculating the holding time corresponding to each heating temperature in the first stage based on the energy obtained in the first stage;

[0096] The second stage is divided into three heating temperature gradients, and the holding time corresponding to each heating temperature in the second stage is calculated based on the energy obtained in the second stage.

[0097] In the embodiment of the present application, the above two stages are divided into three gradients, so that the entire heat treatment stage is divided into six heating temperatures and six holding times.

[0098] In some embodiments, the three temperatures in the first stage are 500° C., 590° C., and 680° C., respectively.

[0099] According to N = T1*t1 + T2*t2 + T3*t3 + ..., we get N = 500*t1 + 590*t2 + 680*t3. The maximum temperature in the first stage is lower than the austenite transformation start temperature. In this embodiment, the maximum heating temperature is set to 680°C. Heating at three temperatures for different times ensures approximate energy conservation.

[0100] In the above formula, 500, 590, and 680 are in degrees Celsius; t1, t2, and t3 are in seconds. t1 is the holding time at 500°C; t2 is the holding time at 590°C; and t3 is the holding time at 680°C. The values ​​of t1 and t2 are greater than or equal to 0, and the value of t3 is greater than 0. The value of N is obtained from the first formula.

[0101] In the present embodiment, t2 and t3 are determined first, and then the value of t1 is determined by calculation. Because many heating furnaces are usually about 30 or 40 meters long, in actual production, the residence time and movement speed of the sheet metal in different sections of the heating furnace need to be adjusted accordingly.

[0102] In some embodiments, the three temperatures of the second stage are 880° C., 905° C., and 930° C., respectively.

[0103] According to N = T1*t1 + T2*t2 + T3*t3 + ..., we get N = 880*t1 + 905*t2 + 930*t3. The maximum temperature in the second stage is no higher than 930°C and no lower than the complete austenite transformation temperature. In this embodiment, the minimum heating temperature is 880°C. Heating at three temperatures for different times ensures approximate conservation of energy.

[0104] In the above formula, 930, 880, and 905 are in degrees Celsius; t1, t2, and t3 are in seconds. t1 is the holding time at 880°C; t2 is the holding time at 905°C; and t3 is the holding time at 930°C. The values ​​of t1, t2, and t3 must be greater than or equal to 0. The value of N is obtained from the first formula.

[0105] In the present embodiment, t2 and t3 are determined first, and then the value of t1 is determined by calculation. Because many heating furnaces are usually about 30 or 40 meters long, in actual production, the residence time and movement speed of the sheet metal in different sections of the heating furnace need to be adjusted accordingly.

[0106] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0107] Table 1. Heat treatment process parameters.

[0108]

[0109] Table 2 Temperature and time parameters for the first and second stages.

[0110]

[0111]

[0112] Using the heat treatment process parameters in Tables 1 and 2, as well as the time and temperature determinations for the first and second stages, new heat treatment parameter values ​​were obtained. The residence time and movement speed of the sheet metal in different sections of the heating furnace were then adjusted. The optimized parameter values ​​were then used in the new stamping process, including simulation, process parameter determination, sheet metal unloading, heating, stamping, and pressure-holding quenching. The k value was used to adjust the heat treatment process parameters to achieve more complete pre-alloying of the material and a thicker alloy layer, thereby making it easier to overcome roller sticking.

[0113] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for heat treatment of aluminum-silicon coated hot-formed steel, characterized in that: The method comprises: The thickness m of the alloying layer of the original part and the total thickness M of the coating of the aluminum-silicon coated hot-formed steel are detected, and a ratio m / M between the two is obtained; Calculating the energy obtained in the first stage and the second stage respectively based on the original holding temperature and the original holding time in the original heat treatment and the m / M; wherein the heat treatment is divided into the first stage and the second stage based on the heating temperature in the heat treatment; Dividing the first stage and the second stage into a plurality of heating temperature gradients, and calculating the holding time corresponding to each heating temperature based on the energy obtained in the first stage and the second stage; Based on each of the heating temperatures and each of the holding times, the aluminum-silicon coated hot-formed steel is heat treated in stages, and then stamped and held to obtain a part; The heat treatment is divided into two stages based on the heating temperature in the heat treatment, including: If the heating temperature is less than the austenite transformation starting temperature, it is judged to be the first stage; If the heating temperature is ≥ the complete austenite transformation temperature, it is judged to be the second stage; Determining the ratio of the total energy obtained in the first stage to that in the second stage based on the ratio m / M includes: If m / M ≥ 0.3, the proportion of total energy obtained in the first stage is 0, and the proportion of total energy obtained in the second stage is 100%; If 0.3>m / M≥0.25, the proportion of total energy obtained in the first stage is 5%, and the proportion of total energy obtained in the second stage is 95%; If 0.25>m / M≥0.2, the proportion of total energy obtained in the first stage is 15%, and the proportion of total energy obtained in the second stage is 85%; If 0.2>m / M≥0.15, the proportion of total energy obtained in the first stage is 25%, and the proportion of total energy obtained in the second stage is 75%; If 0.15>m / M≥0.1, the proportion of total energy obtained in the first stage is 35%, and the proportion of total energy obtained in the second stage is 65%; If 0.1>m / M≥0.05, the proportion of total energy obtained in the first stage is 45%, and the proportion of total energy obtained in the second stage is 55%; If 0.05>m / M, the proportion of total energy obtained in the first stage is 50%, and the proportion of total energy obtained in the second stage is 50%; The energy expression is: N=y*t*T; Where, N represents the energy of each stage; y represents the proportion of total energy obtained in each stage; t represents the original holding time; T represents the original holding temperature; The expressions for calculating the heating temperature and holding time for each stage in the heat treatment process are: N=T1*t1+T2*t2+T3*t3+......; Wherein, N represents the energy of each stage; T1 represents the first temperature; t1 represents the holding time corresponding to the first temperature; T2 represents the second temperature; t2 represents the holding time corresponding to the second temperature; T3 represents the third temperature; t3 represents the holding time corresponding to the third temperature.

2. The method according to claim 1, characterized in that The original insulation temperature is 880° C.-950° C., and the original insulation time is 3 min-8 min.

3. The method according to claim 1, characterized in that The step of dividing the first stage and the second stage into a plurality of heating temperature gradients, and calculating the holding time corresponding to each heating temperature based on the energy obtained in the first stage and the second stage, respectively, includes: Dividing the first stage into three heating temperature gradients, and calculating the holding time corresponding to each heating temperature in the first stage based on the energy obtained in the first stage; The second stage is divided into three heating temperature gradients, and the holding time corresponding to each heating temperature in the second stage is calculated based on the energy obtained in the second stage.

4. The method according to claim 3, characterized in that The three temperatures in the first stage are 500° C., 590° C. and 680° C. respectively.

5. The method according to claim 3, characterized in that The three temperatures in the second stage are 880° C., 905° C. and 930° C. respectively.

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