A stamping steel plate and its preparation method, a stamping part and its preparation method

Abstract

The present invention particularly relates to a stamping steel plate and a preparation method thereof, a stamping part and a preparation method thereof, and belongs to the technical field of metallurgical materials. A stamping steel plate, wherein the chemical composition of the steel comprises, by mass percentage, C, Mn, Si: ≤0.5%, Al: ≤0.06%, Cr: 0.1-0.7%, Mo: ≤0.7%, B: 0.001-0.005%, P: ≤0.01%, S: ≤0.005%, N: ≤0.01%, O: ≤0.003%; wherein: when 0.17≤C<0.23%, Mn is 2.0-3.0%; when 0.23≤C<0.29%, Mn is 1.8-2.5%; when 0.29≤C<0.33%, Mn is 1.6-2.0%; when 0.33≤C<0.40%, Mn is 1.2-1.8%. It is designed with specific chemical composition and increases the Mn content to expand the austenitizing temperature range, effectively reducing the hot stamping deformation temperature, thereby alleviating the problem of liquid metal embrittlement, improving strength and reducing the risk of cracking.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgical materials, and in particular relates to a stamping steel plate and a preparation method thereof, a stamping part and a preparation method thereof. Background Art

[0002] The use of high-strength and ultra-high-strength steel has a positive and effective effect on lightweighting automobile bodies. However, as the strength of automobile body steel continues to increase, its plasticity and formability have significantly decreased. This makes it prone to cracking and springback during the forming process, seriously affecting the shape and dimensional accuracy of parts. Hot stamping technology utilizes the properties of easy forming without springback at high temperatures and quenching and cooling the mold to produce ultra-high-strength parts exceeding 1300MPa, effectively solving the problems of cracking and severe springback caused by cold forming.

[0003] Traditional uncoated hot-stamped parts produce a large amount of surface scale during the heating process, reducing the life of the mold. The need for regular mold cleaning also reduces production efficiency. To prevent scale and decarburization on the surface of hot-stamped steel sheets and improve corrosion resistance, the main coatings currently suitable for hot-stamped steel include Al-Si, GI, GA, and Zn-Ni. Hot-stamped steel sheets with zinc-based coatings not only prevent surface oxidation and decarburization during heating, eliminating the need for subsequent shot peening, but also provide sacrificial anodic protection, improving corrosion resistance after painting. However, a problem with hot-stamped steel sheets with zinc-based coatings is that the liquefied zinc at high temperatures of 900°C causes embrittlement of the steel sheet, a phenomenon known as LME (Liquid Metal Embrittlement). Surface cracks are prone to forming during the stamping process above approximately 700°C and can propagate into the substrate, resulting in reduced strength. Summary of the Invention

[0004] The purpose of the present application is to provide a steel plate for stamping to solve the technical problem in the prior art that the strength of the steel plate for stamping is reduced due to embrittlement of liquid metal.

[0005] An embodiment of the present invention provides a steel plate for stamping, wherein the chemical composition of the steel comprises, in percentage by mass:

[0006] C, Mn, Si: ≤0.5%, Al: ≤0.06%, Cr: 0.1-0.7%, Mo: ≤0.7%, B: 0.001-0.005%, P: ≤0.01%, S: ≤0.005%, N: ≤0.01%, O: ≤0.003%;

[0007] in:

[0008] When 0.17≤C<0.23%, Mn is 2.0-3.0%;

[0009] When 0.23≤C<0.29%, Mn is 1.8-2.5%;

[0010] When 0.29≤C<0.33%, Mn is 1.6-2.0%;

[0011] When 0.33≤C<0.40%, Mn is 1.2-1.8%.

[0012] Optionally, the chemical composition of the steel further comprises, in mass percentage, any one or more combinations of: Ti: 0.02-0.15%, Nb: 0.02-0.15% and V: 0.02-0.15%, with the remainder being Fe and unavoidable impurities.

[0013] Optionally, the metallographic structure of the stamping steel plate includes ferrite, pearlite, bainite and martensite.

[0014] Based on the same inventive concept, an embodiment of the present invention further provides a method for preparing the stamping steel plate as described above, comprising the following steps:

[0015] After smelting and casting, a steel billet having the chemical composition is obtained;

[0016] The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip;

[0017] The steel strip is subjected to hot-dip galvanizing annealing, skin pass and tension leveling to obtain the stamping steel plate;

[0018] in:

[0019] The endpoint temperature of the first heating is 1100-1280°C;

[0020] The final rolling temperature of the hot rolling is 750-920°C;

[0021] The hot rolling coiling temperature is 500-700°C;

[0022] The total reduction rate of the cold rolling is 30-80%;

[0023] The temperature of the hot-dip galvanizing annealing is 400-600°C;

[0024] The thickness of the hot-dip galvanized coating is 20-300g / m 2 .

[0025] Based on the same inventive concept, an embodiment of the present invention further provides a stamping part, which is made of any of the above-mentioned stamping steel plates.

[0026] Optionally, the metallographic structure of the stamping part comprises, by volume percentage, 0-5% ferrite, 0-10% austenite, 0-10% bainite, and the remainder martensite.

[0027] Based on the same inventive concept, an embodiment of the present invention further provides a method for preparing any of the above-mentioned stamping parts, comprising the following steps:

[0028] Blanking the stamping steel plate to obtain a blank;

[0029] subjecting the sheet to a second heating and heat preservation step to obtain a preheated sheet;

[0030] The preheated sheet is precooled, hot stamped and quenched to obtain the stamped part.

[0031] Optionally, the second heating temperature is 800-1000° C., and the insulation time is 3-10 minutes.

[0032] Optionally, the precooling speed is greater than 10°C / s, and the end point temperature of the precooling is less than or equal to 700°C.

[0033] Optionally, the end point temperature of the pre-cooling is 560-680°C.

[0034] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0035] The stamping steel plate provided in the embodiment of the present invention is designed with a specific chemical composition and has an increased Mn content to expand the austenitizing temperature range, effectively reducing the hot stamping deformation temperature, thereby alleviating the problem of liquid metal embrittlement, improving strength, and reducing the risk of cracking.

[0036] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 is a flow chart of a method provided by an embodiment of the present invention;

[0039] Figure 2is a metallographic structure diagram of a stamping steel plate provided in an embodiment of the present invention;

[0040] Figure 3 This is an SEM image of the coating of the stamping part provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific embodiments and examples are for illustrating the present invention, rather than for limiting the present invention.

[0042] Throughout this specification, unless otherwise specified, the terms used herein should be understood as having the same meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. In the event of a conflict, this specification takes precedence. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. For example, room temperature may refer to a temperature within the range of 10 to 35°C.

[0043] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0044] The technical solution of the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows:

[0045] According to a typical embodiment of the present invention, a stamping steel plate is provided, wherein the chemical composition of the steel comprises, in percentage by mass:

[0046] C, Mn, Si: ≤0.5%, Al: ≤0.06%, Cr: 0.1-0.7%, Mo: ≤0.7%, B: 0.001-0.005%, P: ≤0.01%, S: ≤0.005%, N: ≤0.01%, O: ≤0.003%;

[0047] in:

[0048] When 0.17≤C<0.23%, Mn is 2.0-3.0%;

[0049] When 0.23≤C<0.29%, Mn is 1.8-2.5%;

[0050] When 0.29≤C<0.33%, Mn is 1.6-2.0%;

[0051] When 0.33≤C<0.40%, Mn is 1.2-1.8%.

[0052] The stamping steel plate provided in the embodiment of the present invention is designed with a specific chemical composition and has an increased Mn content to expand the austenitizing temperature range, effectively reducing the hot stamping deformation temperature, thereby alleviating the problem of liquid metal embrittlement, improving strength, and reducing the risk of cracking.

[0053] The functions and limited ranges of the above main alloying elements are detailed as follows:

[0054] C: In the present invention, C is the most effective and cheapest solid solution strengthening element, which can effectively ensure the strength level of the stamping steel plate; at the same time, C is an austenite stabilizing element and can most effectively stabilize austenite.

[0055] Mn: Mn is used to increase the austenite region, reduce the austenitizing temperature, improve hardenability, and reduce the stamping temperature.

[0056] Si: Si is a ferrite-forming element. When the stamping steel sheet is heated to the austenite (γ) zone and held at this temperature, Si atoms dissolve in the ferrite. The dissolution of Si in ferrite increases the activity of carbon atoms, promoting outward diffusion of carbon atoms from the ferrite, and increasing the carbon content in the surrounding austenite. As the carbon content in austenite increases, its stability also increases. During the cooling process, Si inhibits the precipitation of carbides, ensuring a certain amount of retained austenite in the structure. Therefore, the Si content is controlled to ≤0.5%.

[0057] Cr: Cr can significantly increase hardenability and reduce severe oxidation on the surface at high temperatures, but it promotes the formation of bainite and should not be too high. Therefore, the Cr content is controlled at 0.1-0.7%.

[0058] Mo: Mo can refine the grain size of steel and improve hardenability. Considering the cost of Mo, the Mo content is controlled to ≤0.7%.

[0059] B: A small amount of B ensures sufficiently good hardenability, so the B content is controlled at 0.001-0.005%.

[0060] P: P is easy to form micro segregation during the solidification of molten steel, and then segregates to the grain boundaries when heated to the post-austenite temperature, which significantly increases the brittleness of the steel and thus increases the sensitivity to hydrogen-induced delayed fracture. Therefore, the P content should be controlled below 0.01%.

[0061] S: S is an unavoidable impurity. The formation of MnS inclusions and segregation at grain boundaries will deteriorate the toughness of steel, thereby reducing the toughness and ductility of steel and increasing the sensitivity to hydrogen-induced delayed fracture. Therefore, the S content should be controlled below 0.005%.

[0062] N: N combines with Al, Ti, Nb, V, etc. to form compounds, thereby refining grains and reducing hydrogen-induced delayed fracture sensitivity. However, it also segregates at grain boundaries, reducing grain boundary strength. Therefore, the N content should be controlled at ≤0.01%.

[0063] O is a harmful gas that affects hydrogen-induced delayed fracture sensitivity and may form coarse alumina inclusions with aluminum, deteriorating the toughness of the steel. The O content should be controlled below 0.003% through various means.

[0064] It should be noted that the reason for controlling the relative ratio of the C content and the Mn content is to control the Ar3 phase transformation point to be lower than 700°C. When stamping at a temperature lower than 700°C, a full martensite structure can be obtained.

[0065] As an optional embodiment, the chemical composition of the steel further comprises, by mass percentage, any one or more combinations of: Ti: 0.02-0.15%, Nb: 0.02-0.15% and V: 0.02-0.15%, with the remainder being Fe and unavoidable impurities.

[0066] The functions and limited ranges of the above main alloying elements are detailed as follows:

[0067] Nb, Ti, V combine with C and N to form precipitates, which are mainly used to refine austenite grains.

[0068] As an optional embodiment, the metallographic structure of the stamping steel plate includes ferrite, pearlite, bainite and martensite.

[0069] The reason for controlling the metallographic structure of the steel sheet for stamping to be as described above is that the complex phase structure before stamping is conducive to uncoiling, leveling and blanking.

[0070] According to another typical embodiment of the present invention, a method for preparing the stamping steel plate provided above is provided, comprising the following steps:

[0071] S1. After smelting and casting, a steel billet having the chemical composition is obtained.

[0072] S2. The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip.

[0073] S3. The steel strip is subjected to hot-dip galvanizing annealing, skin pass and tension straightening to obtain the stamping steel plate.

[0074] in:

[0075] The endpoint temperature of the first heating is 1100-1280°C;

[0076] The final rolling temperature of the hot rolling is 750-920°C;

[0077] The hot rolling coiling temperature is 500-700°C;

[0078] The total reduction rate of the cold rolling is 30-80%;

[0079] The temperature of the hot-dip galvanizing annealing is 400-600°C;

[0080] The thickness of the hot-dip galvanized coating is 20-300g / m 2 .

[0081] According to another typical embodiment of the present invention, there is provided a stamping part, which is made of any one of the above-mentioned stamping steel plates.

[0082] The stamping part can simultaneously meet the requirements of high corrosion resistance and high resistance to metal (zinc) brittle cracking (LME) performance.

[0083] As an optional embodiment, the metallographic structure of the stamping part comprises, by volume percentage, ferrite 0-5%, austenite 0-10%, bainite 0-10%, and the remainder martensite.

[0084] According to another typical embodiment of the present invention, a method for preparing the above-mentioned stamping part is provided, comprising the following steps:

[0085] S4, blanking the stamping steel plate to obtain a blank;

[0086] S5, subjecting the sheet to a second heating and heat preservation step to obtain a preheated sheet;

[0087] S6. Precooling, hot stamping and quenching the preheated sheet to obtain the stamped part.

[0088] In order to ensure the high strength of the stamped parts, the matrix structure of the stamped parts is mainly a fine lath martensite structure containing high-thickness dislocations, supplemented by a bainite structure and a residual austenite structure. The original austenite grain size is controlled by hot rolling in the austenite region and adding Nb, Ti, V, etc., and the martensite size and lath spacing are further refined by refining the original austenite grain size. Secondly, the residual austenite between the martensite laths is obtained by controlling the mold opening temperature after hot forming, increasing the C partitioning time, and adding Si and Al elements. Finally, a multiphase composite structure of fine dislocation martensite, a small amount of bainite and ferrite is obtained. Its high strength is due to the fine grain strengthening and dislocation strengthening of martensite and multiphase structure, and its improved plasticity comes from the small amount of bainite and ferrite present in the structure. At the same time, grain refinement and coordinated deformation of multiple phases also help to improve plasticity.

[0089] As an optional embodiment, the second heating temperature is 800-1000° C., and the insulation time is 3-10 minutes.

[0090] The reason for controlling the second heating temperature is that if it is lower than 800°C, the heating speed is slow and complete austenitization cannot be achieved. If it is higher than 1000°C, the Zn layer evaporates quickly, the Fe content in the coating is high, and the corrosion resistance is reduced.

[0091] As an optional implementation manner, the precooling speed is greater than 10°C / s, and the end temperature of the precooling is ≤700°C.

[0092] The reason for controlling the pre-cooling speed is that ferrite transformation is likely to occur at a rate lower than 10°C / s, resulting in low strength.

[0093] Preferably, the terminal temperature of the pre-cooling is 560-680°C.

[0094] The present application will be described in detail below with reference to embodiments, comparative examples and experimental data.

[0095] Example 1

[0096] A stamping steel plate, the chemical composition of the steel including, by mass percentage:

[0097] C: 0.20%, Mn: 2.1%, Si: 0.3%, Al: 0.049%, Cr: 0.2%, Mo: 0.002%, B: 0.003%, P: 0.01%, S: 0.003%, N: 0.004%, Ti: 0.035%, Nb: 0.03%, V: 0%, and the balance is Fe and inevitable impurities.

[0098] The metallographic structure of stamping steel sheets includes ferrite, pearlite, bainite and martensite.

[0099] The method for preparing the stamping steel plate comprises the following steps:

[0100] S1. After smelting and casting, a steel billet with chemical composition is obtained.

[0101] S2. The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip.

[0102] in:

[0103] The endpoint temperature of the first heating was 1230°C;

[0104] The final rolling temperature of hot rolling is 900℃;

[0105] The coiling temperature of hot rolling is 570℃;

[0106] The total reduction ratio of cold rolling was 60%.

[0107] S3. The steel strip is subjected to hot-dip galvanizing annealing, skin-passing and straightening to obtain a steel plate for stamping.

[0108] in:

[0109] The temperature of hot-dip galvanizing annealing is 430℃;

[0110] The thickness of hot-dip galvanized coating is 140g / m 2 .

[0111] A stamping part is prepared by using the above-mentioned stamping steel plate.

[0112] The metallographic structure of the stamping parts includes, by volume percentage, 90% ferrite, 2% bainite, and the remainder martensite.

[0113] The method for preparing the stamping part comprises the following steps:

[0114] S4. Blanking the stamping steel plate to obtain a blank.

[0115] S5. The sheet is subjected to a second heating and heat preservation process to obtain a preheated sheet.

[0116] The second heating temperature is 900° C. and the holding time is 5 min.

[0117] S6. Precooling, hot stamping and quenching the preheated sheet to obtain a stamped part.

[0118] Among them: the forming temperature of hot stamping is 680℃, the precooling speed is 20℃ / s, and the end temperature of precooling is 700℃.

[0119] Example 2

[0120] A stamping steel plate, the chemical composition of the steel including, by mass percentage:

[0121] C: 0.22%, Mn: 2.2%, Si: 0.3%, Al: 0.049%, Cr: 0.18%, Mo: 0.002%, B: 0.003%, P: 0.01%, S: 0.003%, N: 0.004%, Ti: 0.03%, Nb: 0.04%, V: 0.02%, and the balance is Fe and inevitable impurities.

[0122] The metallographic structure of stamping steel sheets includes ferrite, pearlite, bainite and martensite.

[0123] The method for preparing the stamping steel plate comprises the following steps:

[0124] S1. After smelting and casting, a steel billet with chemical composition is obtained.

[0125] S2. The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip.

[0126] in:

[0127] The end temperature of the first heating was 1250°C;

[0128] The final rolling temperature of hot rolling is 900℃;

[0129] The coiling temperature of hot rolling is 560℃;

[0130] The total cold rolling reduction was 65%.

[0131] S3. The steel strip is subjected to hot-dip galvanizing annealing, skin-passing and straightening to obtain a steel plate for stamping.

[0132] in:

[0133] The temperature of hot-dip galvanizing annealing is 430℃;

[0134] The thickness of hot-dip galvanized coating is 120g / m 2 .

[0135] A stamping part is prepared by using the above-mentioned stamping steel plate.

[0136] The metallographic structure of the stamping parts includes, by volume percentage, ferrite 2%, bainite 1%, and the balance martensite.

[0137] The method for preparing the stamping part comprises the following steps:

[0138] S4. Blanking the stamping steel plate to obtain a blank.

[0139] S5. The sheet is subjected to a second heating and heat preservation process to obtain a preheated sheet.

[0140] The second heating temperature is 900° C. and the holding time is 5 min.

[0141] S6. Precooling, hot stamping and quenching the preheated sheet to obtain a stamped part.

[0142] Among them: the forming temperature of hot stamping is 660℃, the precooling speed is 20℃ / s, and the end temperature of precooling is 680℃.

[0143] Example 3

[0144] A stamping steel plate, the chemical composition of the steel including, by mass percentage:

[0145] C: 0.26%, Mn: 1.9%, Si: 0.2%, Al: 0.049%, Cr: 0.22%, Mo: 0.002%, B: 0.003%, P: 0.01%, S: 0.003%, N: 0.0041%, Ti: 0.03%, Nb: 0.03%, V: 0.03%, and the balance is Fe and inevitable impurities.

[0146] The metallographic structure of stamping steel sheets includes ferrite, pearlite, bainite and martensite.

[0147] The method for preparing the stamping steel plate comprises the following steps:

[0148] S1. After smelting and casting, a steel billet with chemical composition is obtained.

[0149] S2. The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip.

[0150] in:

[0151] The endpoint temperature of the first heating was 1220°C;

[0152] The final rolling temperature of hot rolling is 910℃;

[0153] The coiling temperature of hot rolling is 570℃;

[0154] The total reduction ratio of cold rolling was 60%.

[0155] S3. The steel strip is subjected to hot-dip galvanizing annealing, skin-passing and straightening to obtain a steel plate for stamping.

[0156] in:

[0157] The temperature of hot-dip galvanizing annealing is 430℃;

[0158] The thickness of hot-dip galvanized coating is 140g / m 2 .

[0159] A stamping part is prepared by using the above-mentioned stamping steel plate.

[0160] The metallographic structure of the stamping parts includes, by volume percentage, 90% ferrite, 2% bainite, and the remainder martensite.

[0161] The method for preparing the stamping part comprises the following steps:

[0162] S4. Blanking the stamping steel plate to obtain a blank.

[0163] S5. The sheet is subjected to a second heating and heat preservation process to obtain a preheated sheet.

[0164] The second heating temperature is 900° C. and the holding time is 5 min.

[0165] S6. Precooling, hot stamping and quenching the preheated sheet to obtain a stamped part.

[0166] Among them: the forming temperature of hot stamping is 680℃, the precooling speed is 20℃ / s, and the end temperature of precooling is 700℃.

[0167] Example 4

[0168] A stamping steel plate, the chemical composition of the steel including, by mass percentage:

[0169] C: 0.30%, Mn: 1.7%, Si: 0.2%, Al: 0.049%, Cr: 0.18%, Mo: 0.002%, B: 0.0027%, P: 0.01%, S: 0.003%, N: 0.0041%, Ti: 0.03%, Nb: 0.03%, V: 0.03%, and the balance is Fe and inevitable impurities.

[0170] The metallographic structure of stamping steel sheets includes ferrite, pearlite, bainite and martensite.

[0171] The method for preparing the stamping steel plate comprises the following steps:

[0172] S1. After smelting and casting, a steel billet with chemical composition is obtained.

[0173] S2. The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip.

[0174] in:

[0175] The endpoint temperature of the first heating was 1210°C;

[0176] The final rolling temperature of hot rolling is 910℃;

[0177] The coiling temperature of hot rolling is 550℃;

[0178] The total reduction ratio of cold rolling was 40%.

[0179] S3. The steel strip is subjected to hot-dip galvanizing annealing, skin-passing and straightening to obtain a steel plate for stamping.

[0180] in:

[0181] The temperature of hot-dip galvanizing annealing is 430℃;

[0182] The thickness of hot-dip galvanized coating is 100g / m 2 .

[0183] A stamping part is prepared by using the above-mentioned stamping steel plate.

[0184] The metallographic structure of the stamping parts includes, by volume percentage, 2% austenite, 3% bainite, and the remainder martensite.

[0185] The method for preparing the stamping part comprises the following steps:

[0186] S4. Blanking the stamping steel plate to obtain a blank.

[0187] S5. The sheet is subjected to a second heating and heat preservation process to obtain a preheated sheet.

[0188] The second heating temperature is 900° C. and the holding time is 5 min.

[0189] S6. Precooling, hot stamping and quenching the preheated sheet to obtain a stamped part.

[0190] Among them: the forming temperature of hot stamping is 650℃, the precooling speed is 20℃ / s, and the end temperature of precooling is 660℃.

[0191] Example 5

[0192] A stamping steel plate, the chemical composition of the steel including, by mass percentage:

[0193] C: 0.33%, Mn: 1.6%, Si: 0.2%, Al: 0.03%, Cr: 0.18%, Mo: 0.10%, B: 0.0022%, P: 0.01%, S: 0.003%, N: 0.0041%, Ti: 0.03%, Nb: 0.02%, V: 0.10%, and the balance is Fe and inevitable impurities.

[0194] The metallographic structure of stamping steel sheets includes ferrite, pearlite, bainite and martensite.

[0195] The method for preparing the stamping steel plate comprises the following steps:

[0196] S1. After smelting and casting, a steel billet with chemical composition is obtained.

[0197] S2. The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip.

[0198] in:

[0199] The end temperature of the first heating was 1250°C;

[0200] The final rolling temperature of hot rolling is 910℃;

[0201] The coiling temperature of hot rolling is 600℃;

[0202] The total reduction ratio of cold rolling was 50%.

[0203] S3. The steel strip is subjected to hot-dip galvanizing annealing, skin-passing and straightening to obtain a steel plate for stamping.

[0204] in:

[0205] The temperature of hot dip galvanizing annealing is 450℃;

[0206] The thickness of hot-dip galvanized coating is 160g / m 2 .

[0207] A stamping part is prepared by using the above-mentioned stamping steel plate.

[0208] The metallographic structure of the stamping parts includes, by volume percentage, 2% austenite, 2% bainite, and the remainder martensite.

[0209] The method for preparing the stamping part comprises the following steps:

[0210] S4. Blanking the stamping steel plate to obtain a blank.

[0211] S5. The sheet is subjected to a second heating and heat preservation process to obtain a preheated sheet.

[0212] The second heating temperature is 900° C. and the holding time is 5 min.

[0213] S6. Precooling, hot stamping and quenching the preheated sheet to obtain a stamped part.

[0214] Among them: the forming temperature of hot stamping is 680℃, the precooling speed is 20℃ / s, and the end temperature of precooling is 700℃.

[0215] Example 6

[0216] A stamping steel plate, the chemical composition of the steel including, by mass percentage:

[0217] C: 0.35%, Mn: 1.4%, Si: 0.22%, Al: 0.03%, Cr: 0.18%, Mo: 0.12%, B: 0.0023%, P: 0.009%, S: 0.002%, N: 0.004%, Ti: 0.03%, Nb: 0.04%, V: 0.11%, and the balance is Fe and inevitable impurities.

[0218] The metallographic structure of stamping steel sheets includes ferrite, pearlite, bainite and martensite.

[0219] The method for preparing the stamping steel plate comprises the following steps:

[0220] S1. After smelting and casting, a steel billet with chemical composition is obtained.

[0221] S2. The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip.

[0222] in:

[0223] The endpoint temperature of the first heating was 1220°C;

[0224] The final rolling temperature of hot rolling is 910℃;

[0225] The coiling temperature of hot rolling is 620℃;

[0226] The total reduction ratio of cold rolling was 50%.

[0227] S3. The steel strip is subjected to hot-dip galvanizing annealing, skin-passing and straightening to obtain a steel plate for stamping.

[0228] in:

[0229] The temperature of hot-dip galvanizing annealing is 445℃;

[0230] The thickness of hot-dip galvanized coating is 140g / m 2 .

[0231] A stamping part is prepared by using the above-mentioned stamping steel plate.

[0232] The metallographic structure of the stamping parts includes, by volume percentage, 2% austenite, 2% bainite, and the remainder martensite.

[0233] The method for preparing the stamping part comprises the following steps:

[0234] S4. Blanking the stamping steel plate to obtain a blank.

[0235] S5. The sheet is subjected to a second heating and heat preservation process to obtain a preheated sheet.

[0236] The second heating temperature is 900° C. and the holding time is 5 min.

[0237] S6. Precooling, hot stamping and quenching the preheated sheet to obtain a stamped part.

[0238] Among them: the forming temperature of hot stamping is 640℃, the precooling speed is 20℃ / s, and the end temperature of precooling is 650℃.

[0239] Comparative Example 1

[0240] A stamping steel plate, the chemical composition of the steel including, by mass percentage:

[0241] C: 0.23%, Mn: 1.23%, Si: 0.22%, Al: 0.043%, Cr: 0.18%, Mo: 0%, B: 0.003%, P: 0.009%, S: 0.002%, N: 0.004%, Ti: 0.03%, and the balance is Fe and inevitable impurities.

[0242] The metallographic structure of stamping steel sheets includes ferrite, pearlite, bainite and martensite.

[0243] The method for preparing the stamping steel plate comprises the following steps:

[0244] S1. After smelting and casting, a steel billet with chemical composition is obtained.

[0245] S2. The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip.

[0246] in:

[0247] The endpoint temperature of the first heating was 1220°C;

[0248] The final rolling temperature of hot rolling is 910℃;

[0249] The coiling temperature of hot rolling is 620℃;

[0250] The total reduction ratio of cold rolling was 60%.

[0251] S3. The steel strip is subjected to hot-dip galvanizing annealing, skin-passing and straightening to obtain a steel plate for stamping.

[0252] in:

[0253] The temperature of hot-dip galvanizing annealing is 435℃;

[0254] The thickness of hot-dip galvanized coating is 140g / m 2 .

[0255] A stamping part is prepared by using the above-mentioned stamping steel plate.

[0256] The metallographic structure of the stamping part includes, by volume percentage, 2% bainite and the remainder martensite.

[0257] The method for preparing the stamping part comprises the following steps:

[0258] S4. Blanking the stamping steel plate to obtain a blank.

[0259] S5. The sheet is subjected to a second heating and heat preservation process to obtain a preheated sheet.

[0260] The second heating temperature is 930° C. and the holding time is 5 min.

[0261] S6. Precooling, hot stamping and quenching the preheated sheet to obtain a stamped part.

[0262] Among them: the forming temperature of hot stamping is 720℃ without pre-cooling.

[0263] Comparative Example 2

[0264] A stamping steel plate, the chemical composition of the steel including, by mass percentage:

[0265] C: 0.32%, Mn: 1.33%, Si: 0.22%, Al: 0.043%, Cr: 0.18%, Mo: 0%, B: 0.0028%, P: 0.009%, S: 0.002%, N: 0.004%, Ti: 0.03%, Nb: 0.03%, and the balance is Fe and inevitable impurities.

[0266] The metallographic structure of stamping steel sheets includes ferrite, pearlite, bainite and martensite.

[0267] The method for preparing the stamping steel plate comprises the following steps:

[0268] S1. After smelting and casting, a steel billet with chemical composition is obtained.

[0269] S2. The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip.

[0270] in:

[0271] The endpoint temperature of the first heating was 1220°C;

[0272] The final rolling temperature of hot rolling is 910℃;

[0273] The coiling temperature of hot rolling is 620℃;

[0274] The total reduction ratio of cold rolling was 60%.

[0275] S3. The steel strip is subjected to hot-dip galvanizing annealing, skin-passing and straightening to obtain a steel plate for stamping.

[0276] in:

[0277] The temperature of hot-dip galvanizing annealing is 439°C;

[0278] The thickness of hot-dip galvanized coating is 140g / m 2 .

[0279] A stamping part is prepared by using the above-mentioned stamping steel plate.

[0280] The metallographic structure of the stamping part includes, by volume percentage, 2% bainite and the remainder martensite.

[0281] The method for preparing the stamping part comprises the following steps:

[0282] S4. Blanking the stamping steel plate to obtain a blank.

[0283] S5. The sheet is subjected to a second heating and heat preservation process to obtain a preheated sheet.

[0284] The second heating temperature is 930° C. and the holding time is 5 min.

[0285] S6. Precooling, hot stamping and quenching the preheated sheet to obtain a stamped part.

[0286] Among them: the forming temperature of hot stamping is 720℃ without pre-cooling.

[0287] Experimental example

[0288] The performance of the stamping steel plates provided in Examples 1-6 and Comparative Examples 1-2 was tested, and the specific results are shown in Table 1.

[0289] Table 1

[0290]

[0291] It can be seen from the above table:

[0292] The mechanical properties of the stamping steel provided in Examples 1-6 are significantly better than those in Comparative Examples 1-2, and the crack depth is significantly reduced. Therefore, the stamping steel provided in this application can effectively solve the technical problem in the prior art of reduced strength of stamping steel plates due to embrittlement of liquid metal.

[0293] Explanation of the accompanying drawings:

[0294] Figure 2 is a metallographic structure diagram of a stamping steel plate provided by an embodiment of the present invention, Figure 2 It can be seen that the matrix martensite content reaches more than 95%.

[0295] Figure 3 This is a SEM image of the coating of the stamping provided by the embodiment of the present invention. Figure 3 It can be seen that the crack depth is well controlled.

[0296] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0297] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0298] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A stamping part, characterized in that: The chemical composition of the stamping part includes, by mass percentage: Any one or more combinations of C, Mn, Si: ≤0.5%, Al: ≤0.06%, Cr: 0.1-0.7%, Mo: ≤0.7%, B: 0.001-0.005%, P: ≤0.01%, S: ≤0.005%, N: ≤0.01%, O: ≤0.003%, Ti: 0.02-0.15%, Nb: 0.02-0.15% and V: 0.02-0.15%, the balance being Fe and unavoidable impurities; in: When 0.17≤C<0.23%, Mn is 2.0-3.0%; When 0.23≤C<0.29%, Mn is 1.8-2.5%; When 0.29≤C<0.33%, Mn is 1.6-2.0%; When 0.33≤C<0.40%, Mn is 1.2-1.8%; The method for preparing the stamping part comprises the following steps: The stamping steel plate is blanked to obtain a blank; subjecting the sheet to a second heating and heat preservation step to obtain a preheated sheet; The preheated sheet is precooled, hot stamped and quenched to obtain the stamped part; The precooling speed is greater than 10°C / s, and the end point temperature of the precooling is 560-680°C.

2. The stamping part according to claim 1, characterized in that The method for preparing the stamping steel plate comprises the following steps: After smelting and casting, a steel billet having the chemical composition is obtained; The steel billet is subjected to a first heating, hot rolling, pickling and cold rolling to obtain a steel strip; The steel strip is subjected to hot-dip galvanizing annealing, skin pass and tension leveling to obtain the stamping steel plate; in: The endpoint temperature of the first heating is 1100-1280°C; The final rolling temperature of the hot rolling is 750-920°C; The hot rolling coiling temperature is 500-700°C; The total reduction rate of the cold rolling is 30-80%; The temperature of the hot-dip galvanizing annealing is 400-600°C; The thickness of the hot-dip galvanized coating is 20-300g / m 2 .

3. The stamping part according to claim 1, characterized in that The metallographic structure of the stamping part comprises, by volume percentage, 0-5% ferrite, 0-10% austenite, 0-10% bainite, and the remainder martensite.

4. A method for preparing a stamping part according to any one of claims 1 to 3, characterized in that: The steps include: Blanking the stamping steel plate to obtain a blank; subjecting the sheet to a second heating and heat preservation step to obtain a preheated sheet; The preheated sheet is precooled, hot stamped and quenched to obtain the stamped part.

5. The method for preparing a stamping part according to claim 4, characterized in that: The second heating temperature is 800-1000° C., and the insulation time is 3-10 minutes.

Images