TW201829806A - Press hardened steel with increased toughness and method for production - Google Patents

Abstract

A method for processing a press hardenable steel includes first heating a slab of the press hardenable steel. The slab is heated to a re-heat furnace temperature of approximately 2300 DEG F. The slab is subjected to rolling into a steel sheet having a predetermined thickness. The temperature of the slab during rolling corresponds to a rolling temperature that is greater than or equal to 1600 DEG F. The steel sheet is coiled. The temperature of the steel sheet during coiling corresponds to a coiling temperature of approximately 1050 DEG F.

Description

Pressurized hardened steel with increased toughness and manufacturing method

This application relates to press hardened steel, hot formed steel, hot stamped steel or any which is heated to austenitization temperature and shaped and quenched in a stamping die to achieve the desired mechanical properties in the final part. Improvement of other steels. These types of steel are sometimes referred to as "heatable treated boron-containing steels". In the present application, they are referred to as "pressurized hardened steel".

Pressurized hardened steel is mainly used as a structural component in automobiles, and high strength, low weight and improved intrusion resistance in automobiles are required by automobile manufacturers. A common structural component of pressurized hardened steel in automotive construction is the B-pillar. Current industrial processing of press hardened steel involves heating the billet (a steel sheet) to a temperature above the A ₃ temperature (austenification temperature) (usually in the range of 900-950 ° C), maintaining the material at that temperature for a sustained period of time. At a time, the austenitized blank is placed in a hot stamping die, the blank is formed into a desired shape, and the material is quenched in a mold to a low temperature to form a martensite. The result is a material with a high ultimate tensile strength and a complete Matian bulk microstructure. The quenched microstructure of the prior art pressurized hardened steel is a complete Ma Tian bulk. Conventional press hardened steels have an ultimate tensile strength of about 1500 MPa and a total elongation of about 6%.

The steel of the present application is improved over currently available press hardened steel alloys by the use of chemical methods and processing for achieving higher residual toughness under pressure hardening conditions. Residual toughness refers to the toughness of the material under pressure hardening conditions. The strength-ductility characteristics of the embodiment of the steel alloy of the present invention include an ultimate tensile strength of greater than or equal to 1100 MPa and an elongation of about 8%.

This application claims the US Provisional Application Serial No. 62/426,788, filed on November 28, 2016, entitled "Press Hardened Steel with Increased Toughness and Method for Production"Priority; the disclosure of which is incorporated herein by reference. Pressurized hardened steel is generally desirable due to its high strength characteristics. In practice, this allows the manufacturer to manufacture components that are stronger and less weight than components made from non-pressurized hardened steel. These high-intensity features are usually achieved by the formation of a microstructure dominated by the granules of the mai field. In particular, the billet is first subjected to an austenitizing heat treatment during the hot stamping process associated with the press hardened steel billet. During this heat treatment, the temperature of the blank rises to a temperature above the A ₃ specific component of the blank, so that the microstructure of the blank into austenite-based. Once the austenitizing heat treatment is completed, the billet is punched into a predetermined shape using an internal cooling mold. In addition to shaping the blank, the stamping process also has the effect of rapidly cooling the billet to below the starting temperature (M _s ) of the granules. Therefore, the austenite-based microstructure of the billet is transformed into a microstructure dominated by Ma Tian bulk. Because the Matian bulk is often characterized as a strong and hard microstructure, the stamping process typically results in a final part that is high in strength and high in hardness. While the high strength of the final hot stamped parts is often desirable for a variety of applications, in some cases additional toughness may be desirable. For example, as described above, hot stamping typically results in a final part of high strength and high hardness. The final part of high level hardness typically has a relatively low ductility and therefore relatively low toughness. Therefore, in some cases, it may be desirable to have the press-hardened steel have the characteristics of the high-strength characteristics of the conventional press-hardened steel but the residual toughness is improved. The press hardened steel is subjected to a plurality of pretreatment steps prior to the hot stamping process described above. Figure 1 shows a conventional pretreatment method (10). The pretreatment method involves subjecting the steel sheet to a plurality of pretreatment steps (20, 30, 40, 50). These steps (20, 30, 40, 50) are typically performed prior to hot stamping and prior to forming the final hard stamping treated press hardened steel billet. In general, these steps (20, 30, 40, 50) are carried out on a sheet in a continuous rolling mill. For example, press hardened steel initially begins with a cast slab containing a predetermined composition. The slab then enters the reheat boiler (20) and undergoes a reheat temperature of approximately 2300 °F (1260 °C). Once the slab is raised to the reheat temperature by the reheating boiler (20), the slab undergoes a rough roll (30) and then a fine roll (40). These rolling steps gradually reduce the thickness of the slab to the final sheet thickness. During the rolling process, the slab temperature is continuously reduced from the initial 2300 °F (1260 °C) reheating temperature to the coarse pressure temperature associated with the coarse roll pressure (30). In some examples, the roughing temperature is approximately 2000 °F (1093 °C). During the fine roll (40), the slab experiences a coining temperature of approximately 1600 °F (871 °C). As the temperature decreases, the slab undergoes a rolling operation which reduces the thickness of the slab by a relatively large amount during the rough rolling (30), gradually becoming a relatively small amount of thickness reduction during the sizing (40). . The chunk temperature is reduced from the initial reheat temperature associated with the reheat boiler (20) to the temperature associated with the fine roll pressure (40) at a relatively constant roll cooling rate (12). After the rolling is completed, the press-hardened steel material is in the form of a steel plate. In the form of a steel sheet, the steel sheet is subjected to a roll (50). The roll (50) can be carried out at a coil temperature of about 1200 °F (649 °C). In some examples, the roll (50) can begin immediately after coining (40). Thus, in some examples, the roll (50) can begin at about 1600 °F (871 °C) and reduce to a roll temperature of about 1200 °F (649 °C). Prior to forming the roll (50), as shown in Figure 1, the steel sheet can be cooled to a roll temperature at one or more different cooling rates (14, 16). For example, at a first cooling rate (14) or a second cooling rate (16), cooling of the steel sheet is relatively slow between about 18 °F/sec and about 20 °F/sec. At the end of the roll (50), the crimped steel sheet is allowed to cool to ambient or room temperature. The crimped steel sheet is subsequently successively formed as a blank of a press hardened steel material. The blank can then be subjected to the hot stamping process described above. As described above, in some cases it may be desirable to increase the toughness of press hardened steel parts. In some cases, the toughness can be improved by refining the particle size of the press hardened steel material by varying some of the parameters of the pretreatment steps described above. Figure 2 shows a modified pre-processing method (100). As with the pretreatment method (10) described above, the pretreatment method (100) of the present example includes a series of pretreatment steps (120, 130, 140, 150). Similar to that described above, these steps (120, 130, 140, 150) are typically performed prior to hot stamping and prior to forming the final hot stamped press hardened steel billet. In general, these steps (120, 130, 140, 150) are carried out on a sheet in a continuous rolling mill. For example, press hardened steel initially begins with a cast slab containing a predetermined composition. The slab then enters the reheat boiler (120) where the slab undergoes a reheat temperature. Similar to the reheating temperature described above with respect to the reheating boiler (20), the reheating temperature in this example is about 2300 °F (1260 °C). Once the slab is raised to the reheat temperature of the reheat boiler (120), the slab undergoes a rough roll (130) and then a fine roll (140). This gradually reduces the thickness of the slab to the final sheet thickness. As an example, during the rolling process, the slab temperature is continuously reduced from the initial 2300 °F (1260 °C) reheat temperature of the reheat boiler (120) to approximately 2000 °F (1093 °C) associated with the coarse roll pressure (130). The rough pressure temperature. Next, the slab is further reduced to a refining temperature of approximately 1600 °F (871 °C) associated with the fine roll pressure (140). Unlike the fine roll pressure (40) in the conventional pretreatment method (10) described above, the fine roll pressure (140) in this example is carried out at a relatively low temperature. As will be described in more detail below, this relatively lower temperature can result in increased grain refinement when performed in conjunction with the modified roll temperature. As the temperature decreases, the slab undergoes a rolling operation that reduces the thickness of the slab by a relatively large amount during the rough rolling (130), becoming a relatively small amount that reduces the thickness of the slab during the sizing (140). The chunk temperature is reduced from the initial reheat temperature associated with the reheat boiler (120) to the temperature associated with the fine roll pressure (140) at a relatively constant roll cooling rate (112). This cooling rate is similar to the previously processed roll cooling rate (12). After the rolling is completed, the press-hardened steel material is in the form of a steel plate. In the form of a steel sheet, the steel sheet is subjected to a roll (150). The roll (150) can be run at a roll temperature of about 1050 °F (566 °C). In some examples, the roll (150) can begin immediately after coining (140). Thus, in some examples, the roll (150) can begin at about 1600 °F (871 °C) and drop to a roll temperature of about 1050 °F (566 °C). Alternatively, in some examples, the roll (150) may be delayed until the steel sheet reaches a roll temperature of about 1050 °F (566 °C). Once the coiling temperature (150) is reached, the steel sheet can be isothermally stored for all rolls (150). Preferably, the coining (140) is carried out at a coining temperature of about 1600 °F (871 °C), the steel sheet is lowered to a coiling temperature of 1050 °F (566 °C), and is carried out when the steel sheet is stored at a coiling temperature. Volume (150). Regardless of how the coil temperature is reached, it is understood that the coiling temperature of about 1050 °F (566 °C) is generally lower relative to the coiling temperature described above with respect to the conventional pretreatment method (10). As will be appreciated, this reduced roll temperature can generally result in increased grain refinement of the steel sheet which can result in an increase in residual toughness of the final work product after hot stamping. Prior to winding (150), as shown in Figure 2, the steel sheet can be cooled to a coiling temperature at a cooling rate (114). In the present example, the cooling rate (114) is between about 35 °F/sec and about 50 °F/sec. Unlike the cooling rates (14, 16) described above, the cooling rate (114) in this example is typically relatively fast. This relatively fast cooling rate can be achieved using a run-out-table accelerated cooling method. As will be appreciated, this relatively fast cooling rate (114) can generally result in increased grain refinement in the final working product after hot stamping and associated increased residual toughness. At the end of the roll (150), the crimped steel sheet is allowed to cool to ambient or room temperature. The crimped steel sheet is subsequently successively formed as a blank of a press hardened steel material. The blank can then be subjected to the hot stamping process described above. As described above, the pretreatment method (10, 100) can be performed using a cast slab containing a predetermined composition. It will be appreciated that the specific composition of the chunks may vary such that the various components may be used by the methods (10, 100) described above. As will be described in more detail below, various elements can be added to the slab to affect the various metallurgical properties of the final work product. Carbon is added to reduce the initial temperature of the granules in the field, to provide solid solution strengthening and to increase the degree of hardening of the steel. Carbon is an austenite stabilizer. In certain embodiments, carbon may be present at a concentration of from 0.1 to 0.5% by mass; in other embodiments, the carbon may be present at a concentration of from 0.2 to 0.30% by mass. Manganese is added to reduce the initial temperature of the matrix in the field, to provide solid solution strengthening and to increase the degree of hardening of the steel. Manganese is an austenite stabilizer. In certain embodiments, manganese may be present at a concentration of from 1.0 to 10.0% by mass; in other embodiments, manganese may be present at a concentration of from 1.15 to 1.25 mass%. Add hydrazine to provide solid solution strengthening. It is a ferrite iron stabilizer. In certain embodiments, the ruthenium may be present at a concentration of from 0.02 to 2.0% by mass; in other embodiments, the ruthenium may be present at a concentration of from 0.24 to 0.30% by mass. Aluminum is added for deoxidation during steelmaking and provides solid solution strengthening. Aluminum is a ferrite iron stabilizer. In certain embodiments, aluminum may be present at a concentration of from 0.0 to 2.0% by mass; in other embodiments, aluminum may be present at a concentration of from 0.02 to 1.0% by mass. In other embodiments, aluminum is entirely present and may, in some embodiments, be omitted or limited to impurity elements. Titanium is added to the nitrogen collecting agent. In certain embodiments, titanium may be present at a concentration of from 0.0 to 0.045% by weight; in other embodiments, titanium may be present at a concentration that is a maximum of 0.035 mass%. In other embodiments, titanium is present entirely as appropriate, and in some embodiments may therefore be omitted or limited to impurity elements. Molybdenum is added to provide solid solution strengthening and increase the degree of hardening of the steel. In certain embodiments, molybdenum may be present at a concentration of from 0 to 4.0% by mass; in other embodiments, molybdenum may be present at a concentration of from 0 to 1.0% by mass. In other embodiments, molybdenum is present entirely as appropriate, and thus may be omitted or limited to impurity elements in some embodiments. The addition of chromium reduces the initial temperature of the granules in the field, provides solid solution strengthening and increases the degree of hardening of the steel. Chromium is a ferrite iron stabilizer. In certain embodiments, the chromium may be present at a concentration of from 0 to 6.0% by mass; in other embodiments, the chromium may be present at a concentration of from 0.18 to 0.22% by mass. Boron is added to increase the degree of hardening of the steel. In certain embodiments, boron may be present at a concentration of from 0 to 0.005% by mass; in other embodiments, boron may be present at a concentration of from 0.003 to 0.005% by mass. Nickel is added to provide solid solution strengthening and to reduce the initial temperature of the field. Nickel is an austenite stabilizer. In certain embodiments, nickel may be present at a concentration of from 0.0 to 1.0% by mass; in other embodiments, nickel may be present at a concentration of from 0.02 to 0.5% by mass. In other embodiments, nickel is completely present as appropriate, and thus may be omitted or limited to impurity elements in some embodiments. Niobium is added to provide improved grain refinement.铌 can also increase hardness and strength. In certain embodiments, the hydrazine may be present at a concentration of from 0 to 0.090% by mass. Example 1 A plurality of alloy compositions shown in Table 1 were prepared using standard steel preparation methods, except as described below. Table 1 : Range of ingredients. The ingredients are in mass %. The component 4310 of Table 1 in Example 2 of Example 2 was subjected to two pretreatment methods (10, 100) as described above. The steel is subjected to simulated hot stamping. The steel was heated to about 930 ° C for 5 minutes and then quenched in a water cooled copper mold. Samples subjected to various pretreatment methods (10, 100) plus simulated hot stamping were then subjected to a tensile test to generate a stress-strain curve. The resulting stress-strain curve is shown in Figure 3, where the pretreatment method (10) is shown in solid lines and the pretreatment method (100) is shown in dashed lines. As can be seen in Figure 3, the sample subjected to the pretreatment method (100) generally results in increased residual toughness relative to the sample subjected to the pretreatment method (10). Micrographs of each sample were prepared under hot rolling conditions prior to simulated hot stamping and are shown in Figures 10 and 11, wherein Figure 10 corresponds to pretreatment method (10) and Figure 11 corresponds to pretreatment Method (100). As can be seen, the pretreatment method (100) generally results in a finer grain structure relative to the grain structure prepared by the pretreatment method (10). As a result, an improved residual toughness was observed in FIG. Example 3 The ingredients 4311 of Table 1 in Example 1 were subjected to both the pretreatment methods (10, 100) described above. The steel is subjected to simulated hot stamping. The steel was heated to about 930 ° C for 5 minutes and then quenched in a water cooled copper mold. Samples subjected to various pretreatment methods (10, 100) plus simulated hot stamping were then subjected to a tensile test to generate a stress-strain curve. The resulting stress-strain curve is shown in Figure 4, where the pretreatment method (10) is shown in solid lines and the pretreatment method (100) is shown in dashed lines. As can be seen in Figure 4, the sample subjected to the pretreatment method (100) generally results in increased residual toughness relative to the sample subjected to the pretreatment method (10). Micrographs of each sample were prepared under hot rolling conditions prior to simulated hot stamping and are shown in Figures 12 and 13, wherein Figure 12 corresponds to pretreatment method (10) and Figure 13 corresponds to pretreatment Method (100). As can be seen, the pretreatment method (100) generally results in a finer grain structure relative to the grain structure prepared by the pretreatment method (10). As a result, an improved residual toughness was observed in FIG. Example 4 The ingredients 4312 of Table 1 in Example 1 were subjected to both the pretreatment methods (10, 100) described above. The steel is subjected to simulated hot stamping. The steel was heated to about 930 ° C for 5 minutes and then quenched in a water cooled copper mold. Samples subjected to various pretreatment methods (10, 100) plus simulated hot stamping were then subjected to a tensile test to generate a stress-strain curve. The resulting stress-strain curve is shown in Figure 5, where the pretreatment method (10) is shown in solid lines and the pretreatment method (100) is shown in dashed lines. As can be seen in Figure 5, the sample subjected to the pretreatment method (100) generally results in increased residual toughness relative to the sample subjected to the pretreatment method (10). Micrographs of each sample were prepared under hot rolling conditions prior to simulated hot stamping and are shown in Figures 14 and 15, wherein Figure 14 corresponds to pretreatment method (10) and Figure 15 corresponds to pretreatment Method (100). As can be seen, the pretreatment method (100) generally results in a finer grain structure relative to the grain structure prepared by the pretreatment method (10). As a result, an improved residual toughness was observed in FIG. Example 5 Component 4313 of Table 1 in Example 1 was subjected to both the pretreatment methods (10, 100) described above. The steel is subjected to simulated hot stamping. The steel was heated to about 930 ° C for 5 minutes and then quenched in a water cooled copper mold. Samples subjected to various pretreatment methods (10, 100) plus simulated hot stamping were then subjected to a tensile test to generate a stress-strain curve. The resulting stress-strain curve is shown in Figure 6, where the pretreatment method (10) is shown in solid lines and the pretreatment method (100) is shown in dashed lines. As can be seen in Figure 6, the sample subjected to the pretreatment method (100) generally results in increased residual toughness relative to the sample subjected to the pretreatment method (10). Micrographs of each sample were prepared under hot rolling conditions prior to simulated hot stamping and are shown in Figures 16 and 17, wherein Figure 16 corresponds to pretreatment method (10) and Figure 17 corresponds to pretreatment Method (100). As can be seen, the pretreatment method (100) generally results in a finer grain structure relative to the grain structure prepared by the pretreatment method (10). As a result thereof, an improved residual toughness or a maintainable ductility was observed in Fig. 6. Example 6 : The toughness of the samples having the ingredients identified in Table 1 of Example 1 above was further evaluated using a double edge-notch tensile test. Samples of the various components (e.g., 4310, 4311, 4112, 4313) were subjected to the various pretreatment methods (10, 100) described above. The steel was then subjected to a simulated press hardening procedure in which it was austenitized at about 930 ° C for 300 s and then quenched in a flat water-cooled mold. A tensile test of the double edge notch was then performed. A curve of the obtained data of each component was then prepared as shown in Figs. For example, Figure 7 shows the results of each sample subjected to the pretreatment method (100). Figure 8 shows the results of each sample subjected to the pretreatment method (10). For Figures 7 and 8, the data for each component can be identified by a symbol. For example, a circle corresponds to component 4310, a triangle corresponds to component 4311, a star corresponds to component 4312, and a cross corresponds to component 4313. As can be seen in Figures 7 and 8, the material undergoing the pretreatment method (100) exhibits a higher peak load/force prior to rupture than the material undergoing the pretreatment method (10). Thus, Figures 7 and 8 indicate that the pretreatment method (100) results in increased toughness or retained ductility. Example 7 further analyzes the information discussed above with respect to Example 6. In particular, the area integral under the force-displacement curve shown in Figures 7 and 8 can be used to obtain the value of the strain energy. The strain energy is considered to be a measure of the toughness of the material. Thus, measurements of the material toughness of each of the samples discussed above with respect to Example 6 were produced. The strain energy of each of the obtained samples was then plotted as a function of the concentration of ruthenium in the corresponding components of each sample. The resulting curve is shown in Figure 9. Unlike Figures 7 and 8 described above, Figure 9 utilizes different symbolic flows to identify the correspondence between specific data points and components. For example, in FIG. 9, the circle corresponds to component 4310, the cross corresponds to component 4311, the triangle corresponds to component 4312, and the square corresponds to component 4313. In addition, since the results of the samples subjected to the respective pretreatment methods (10, 100) are included in a single curve, FIG. 9 depicts a comparison of the sample subjected to the pretreatment method (10) with the sample subjected to the pretreatment method (100). In each case, the steel was subjected to simulated hot stamping prior to testing. In Fig. 9, the solid symbol represents the processing method (10), and the open symbol represents the processing method (100). As can be seen in Figure 9, the sample subjected to the pretreatment method (100) typically results in increased strain energy and thus increased toughness. In addition, it was observed that the toughness partially increased in response to the component having an increased enthalpy. For example, component 4313 includes the highest concentration of germanium and also includes the highest strain energy or toughness measurement. Example 8 A press hardenable steel comprising, based on the total mass % of steel: wherein the steel is subjected to the following processing: (a) heating the slab of press hardenable steel to a reheating boiler temperature of about 2300 °F; (b) pressing the slab into a steel sheet having a predetermined thickness, wherein the slab temperature during rolling corresponds to a rolling temperature higher than or equal to about 1600 °F (871 °C); and (c) rolling the steel sheet, The steel sheet temperature during the rolling period corresponds to a coiling temperature of about 1050 °F. Example 9 The press hardenable steel of any of Example 8 or any of the following examples, comprising: 0.10 to 0.50% carbon; 0.00 to 0.005% boron; 0.0 to 6.0% chromium; 1.00 to 10.0% manganese; 0.090% or less of bismuth; 0.02 to 2.00% 矽; 0.0 to 2.0% aluminum; 0.0 to 0.045% titanium; 0.0 to 4.0% molybdenum; 0.0 to 1.0% nickel; and the remainder including iron and impurities . Example 10 The press hardenable steel of any of Examples 8 or 9 or any of the following examples comprising 0.2-0.3 mass% carbon. Example 11 Example 8 to any one or any of the following examples of one of hardened steel pressurizable 10, comprising 1.15-1.25% by mass of manganese. Example 12 Examples 8 to 11 in any one or any of the following examples of one of the pressurizable hardened steel, which contains 0.24-0.30 mass% silicon. Example 13 Example 8 to any one or any of the following examples of one of the pressurizable 12 hardened steel, comprising 0.02 to 1.0 mass% aluminum. Example 14 Example 8 to any one or any of the following examples of one of hardened steel pressurizable 13, which comprises a maximum of 0.035% by mass of titanium. Example 15 Examples 8 to 14 in any one or any of the following examples of one of the pressurizable hardened steel, comprising 0 to 1.0% by mass molybdenum. Example 16 Example 8 to any one or any of the following examples of one of hardened steel pressurizable 15, containing 0.18-0.22 mass% of chromium. Example 17 Examples 8 to 16 in any one or any of the following examples of one of the pressurizable hardened steel, comprising by mass 0.003-0.005% boron. Example 18 Example 8 to 17 of any one or any of the following examples of one of the pressurizable hardened steel, comprising 0.02 to 0.5 mass% nickel. Example 19 Examples 8 to 18 in any of any one of the examples below or may be pressurized by a hardened steel, which contains 0 to 1.0% by mass molybdenum. Example 20 Examples 8 to 19 in any one or any of the following examples of one of the pressurizable hardened steel, wherein the rolling step includes a rough rolling operation and the finishing rolling operation. Example 21 Example 8 to any one or any of the following examples of one of hardened steel pressurizable 20, wherein the thickness of the block during the rough rolling operation temperature is higher than or equal to 2000 ℉. Example 22 Examples 8-21 of any one or any of the following examples of one of the pressurizable hardened steel wherein slabs during the rolling operation in the finishing temperature higher than or equal to about 1600 ℉ (871 ℃). Example 23 Examples 8 to 22 in any one or any of the following examples of one of hardened steel pressurizable, further comprising the step of: after the steel sheet into a roll at least part of a steel sheet for hot stamping. Example 24 Example 8 to any one of the following examples or according to any one of the hardened steel pressurizable 23, further comprising the steps of: at a first cooling rate may be pressurized from hardened steel reheat boiler is cooled to a temperature The temperature is rolled, and the press hardenable steel is cooled from the rolling temperature to the coiling temperature at a second cooling rate, wherein the second cooling rate is higher than the first cooling rate. Example 25 Example 8 to any one of the following examples or according to any one of the hardened steel pressurizable 24, wherein the pressurizable from hardened steel roll temperature was cooled to coiling temperature step to use the output of the accelerated cooling roller The method is carried out. Example 26. The press hardenable steel of any of Examples 8 to 25 or any of the following examples, wherein the chunk temperature during the rough rolling operation is about 2000 °F. Example 27 Examples 8-26 according to any one of the pressurizable hardened steel, wherein the thickness of the block during the operation of finishing rolling temperature of about 1600 deg.] F to 1700 ℉.

10‧‧‧Pretreatment method

12‧‧‧Rolling cooling rate

14‧‧‧First cooling rate

16‧‧‧second cooling rate

20‧‧‧Reheating boiler

30‧‧‧Rough roll pressure

40‧‧‧Fine roll pressure

50‧‧‧volume

100‧‧‧Pretreatment method

112‧‧‧Rolling cooling rate

114‧‧‧ cooling rate

120‧‧‧Reheating boiler

130‧‧‧Rough roll pressure

140‧‧‧Fine roll pressure

150‧‧‧volume

Figure 1 shows a schematic representation of the heat distribution and processing of an embodiment of the alloy of the present invention. Figure 2 shows another schematic diagram of heat distribution and processing of an embodiment of the alloy of the present invention. 3 shows a graph of stress-strain curves for component 4310, where the results from the first pretreatment method are shown in solid lines and the results from the second pretreatment method are shown in dashed lines. 4 shows a graph of stress-strain curves for component 4311, where the results from the first pretreatment method are shown in solid lines and the results from the second pretreatment method are shown in dashed lines. Figure 5 shows a graph of the stress-strain curve for component 4312, where the results from the first pretreatment method are shown in solid lines and the results from the second pretreatment method are shown in dashed lines. Figure 6 shows a graph of the stress-strain curve for component 4313, where the results from the first pretreatment method are shown in solid lines and the results from the second pretreatment method are shown in dashed lines. Figure 7 shows the results of a double edge-notch tensile test of an embodiment of the inventive alloy after undergoing a second pretreatment method. Figure 8 shows the results of a double edge-notch tensile test of an embodiment of the inventive alloy after undergoing the first pretreatment method. Figure 9 shows the results of strain energy calculations for an embodiment of the alloy of the present invention plotted as a function of erbium concentration. Figure 10 shows a photomicrograph of component 4310 after undergoing the first pretreatment method. Figure 11 shows a photomicrograph of component 4310 after undergoing a second pretreatment method. Figure 12 shows a photomicrograph of component 4311 after undergoing the first pretreatment method. Figure 13 shows a photomicrograph of component 4311 after undergoing a second pretreatment method. Figure 14 shows a photomicrograph of component 4312 after undergoing the first pretreatment method. Figure 15 shows a photomicrograph of component 4312 after undergoing a second pretreatment method. Figure 16 shows a photomicrograph of component 4313 after undergoing the first pretreatment method. Figure 17 shows a photomicrograph of ingredient 4313 after undergoing a second pretreatment method.

Claims (10)

A method of processing press hardenable steel, the method comprising: (a) heating the slab of the press hardenable steel to a reheating boiler temperature of about 2300 °F; (b) pressing the slab into a predetermined a steel plate having a thickness, wherein a temperature of the slab during rolling corresponds to a rolling temperature higher than or equal to about 1600 °F (871 ° C); and (c) winding the steel sheet, wherein a temperature of the steel sheet corresponds to a temperature during rolling The coiling temperature is about 1050 °F. The method of claim 1, wherein the rolling step comprises a rough rolling operation and a fine rolling operation. The method of claim 2, wherein the temperature of the chunk during the rough rolling operation is greater than or equal to 2000 °F. The method of claim 2, wherein the temperature of the chunk during the precision rolling operation is greater than or equal to about 1600 °F (871 °C). The method of claim 2, wherein the temperature of the chunk during the coarse rolling operation is about 2000 °F. The method of claim 2, wherein the temperature of the chunk during the precision rolling operation is between about 1600 °F and 1700 °F. The method of claim 1, further comprising hot stamping at least a portion of the steel sheet after the steel sheet is wound. The method of claim 1, further comprising cooling the press hardenable steel from the reheating boiler temperature to the rolling temperature at a first cooling rate, and applying the press hardenable steel to the second cooling rate The rolling temperature is cooled to the coiling temperature, wherein the second cooling rate is higher than the first cooling rate. The method of claim 1, wherein the step of cooling the press hardenable steel from the rolling temperature to the coiling temperature is carried out using an output roller accelerated cooling method. The method of claim 1, wherein the press hardenable steel has a composition comprising: 0.10 to 0.50% carbon; 0.00 to 0.005% boron; 0.0 to 6.0% chromium; 1.00 to 10.0% manganese; 0.090% or less铌; 0.02 to 2.00% 矽; 0.0 to 2.0% aluminum; 0.0 to 0.045% titanium; 0.0 to 4.0% molybdenum; 0.0 to 1.0% nickel; and the remainder including iron and impurities.