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  • 专利说明
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    • 专利摘要:
    COOLING METHOD FOR HOT CONFORMATION AND HOT CONFORMATION DEVICE. The present invention relates to the hot forming of a thin steel sheet K, when the thin steel sheet K is cooled by providing a refrigerant for an ejection hole (27) communicated from a supply path (28 ) inside a lower mold (12), pre-cooling in which an amount of ejection per unit time period of the refrigerant from the ejection hole (27) is suppressed is carried out and then the main cooling is performed by increasing the ejection amount per unit time period.
    公开号:BR112016003421B1
    申请号:R112016003421-0
    申请日:2014-09-11
    公开日:2021-02-09
    发明作者:Hiroshi Fukuchi；Naruhiko Nomura；Atsushi Seto
    申请人:Nippon Steel Corporation；
    IPC主号:
    专利说明:

    TECHNICAL FIELD
    [0001] The present invention relates to a cooling method for hot forming a thin steel sheet and to a hot forming apparatus. BACKGROUND OF THE TECHNIQUE
    [0002] Hot forming is recently adopted as a means of forming steel sheet for an automobile component or similar with the use of a high tension steel sheet. In hot forming, as a result of forming, a steel sheet at a high temperature, forming is carried out at a stage in which a resistance to deformation is low and tempering hardening by rapid cooling is carried out and, therefore, is it is possible to obtain a component or similar that has a high strength and a high precision of shape, without generating a formation defect such as deformation after forming.
    [0003] In hot forming, a steel sheet that has been heated to a predetermined temperature by a heating furnace in advance is supplied to a mold and in a state where the steel sheet is placed in a matrix or floated by a template like a lifter built into the mold, a perforator is lowered to a lower central position and then a coolant such as water, for example, is supplied between the steel sheet and the mold to cool the steel sheet quickly. Therefore, a mold surface is provided with a plurality of independent protruding portions with a constant height and the interior of the mold is provided with a water channel that communicates with refrigerant expulsion holes that are provided in a plurality of locations on the surface. of the mold and a channel for suction of the supplied water. In a conventional cooling method for hot forming a thin steel sheet, since the amount of flow is maintained while cooling is carried out by flowing the cooling water, the same amount of ejection is ejected from each ejection hole during a cooling time period.
    [0004] In a case where hot forming is performed using a mold of this configuration, it is considered to shorten a cooling time period by increasing the amount of cooling water flow in order to improve further productivity. However, it was found that a variation of qualities such as a formed shape (deformation) and a tempering characteristic occurs depending on a region. This is caused by non-uniform cooling due to a difference in cooling speed due to the flow of refrigerant in the vicinity of the expulsion hole and its periphery. In other words, the difference in cooling speed generates thermal stress, which causes the quality to vary. Additionally, as a result of the additional study done by the inventors, it was found that there is irregular cooling in a circular state centralized in the expulsion hole. It is considered that, if the cooling water is ejected in a predetermined amount of expulsion from the beginning of the cooling, the damping or the entry of air will occur in a concentric manner centralized in the expulsion hole, in order to generate irregular cooling. Therefore, a device of the same type is required with respect to a supplied quantity of the refrigerant.
    [0005] It is noted that the applicant has already suggested a hot forming method of Patent Literature 1 with regard to controlling the supply of a refrigerant in a hot forming method. In the hot forming method above, a heated thick steel sheet is placed in a quick cooling mold, the coolant is supplied to the thick steel sheet in order to perform quick cooling while the quick cooling mold is retained in a lower central position and then the refrigerant supply is controlled in a state in which the quick-cooling mold is retained in the dead center at the bottom. More specifically, interruption of refrigerant supply and conduction of refrigerant supply again after a predetermined period of time is repeated at least once or more or a predetermined amount of refrigerant flow supply is reduced once halfway through and the amount of refrigerant flow supply is increased again after a predetermined period of time.
    [0006] However, in the hot forming method of Patent Literature 1, a target steel sheet is what is called a thick sheet and its purpose is to produce a formed product in which a resistance is changed in one thickness direction of the steel sheet. Therefore, without a countermeasure, in the hot forming of a thin steel sheet, it is impossible to improve a distortion of a steel sheet shape or an irregular quality caused by non-uniform cooling due to the aforementioned difference in the cooling speed that occurs. in the vicinity of an expulsion hole and its periphery. LIST OF QUOTES Patent Literature
    [0007] Patent Literature 1: Publication of Patent ApplicationOpen to Public Inspection in JP 2011-143437. SUMMARY OF THE INVENTION TECHNICAL PROBLEM
    [0008] The present invention is made in view of the above circumstances and its objective is to suppress a distortion of a shape and a variation in quality caused by non-uniform cooling, in the hot forming of a thin steel sheet. SOLUTION TO THE PROBLEM
    [0009] As a result of a careful study and experiments by the inventors, it has been proven that a distortion of a shape or similar due to non-uniform cooling is caused by a variation in temperature as a result of cooling which is carried out quickly in the vicinity of a coolant expulsion hole while a cooling speed becomes slower in a position away from the expulsion hole. In addition, it has recently been found that this variation changes according to the change in the amount of coolant flow supplied.
    [00010] In view of the above findings, the present invention is a method of cooling for hot forming in which a thin steel sheet is cooled by providing a refrigerant for an expulsion hole from a mold surface whose expulsion hole it is communicated from a supply trajectory inside the mold in the hot forming of the heated thin steel sheet, in which the cooling method for hot forming includes: pre-cooling, in which an amount of expulsion per period unit time of the expulsion hole refrigerant is suppressed and then perform the main cooling by increasing the amount of expulsion per unit time period, when the thin steel plate is cooled by supplying the refrigerant to the exhaust hole. expulsion in a state in which the heated thin steel plate is placed in the mold and retained in a lower central position.
    [00011] Additionally, the present invention is a hot forming apparatus that cools a thin steel sheet by supplying a refrigerant to an expulsion hole from a mold surface whose expulsion hole is communicated from a trajectory of filling inside the mold in the hot forming of the heated thin steel plate, in which the hot forming device performs the pre-cooling in which a quantity of expulsion per unit period of time is suppressed and then performs the cooling main by increasing the expulsion amount per unit time period of the expulsion hole refrigerant, when the thin steel plate is cooled by supplying the refrigerant to the expulsion hole in a state in which the heated thin steel plate is placed in the mold and retained in a lower central position.
    [00012] By performing pre-cooling in which the amount of expulsion per unit time period is suppressed, as described above, it is possible to suppress excess cooling in the vicinity of the expulsion bore. Additionally, by performing pre-cooling in which the amount of expulsion per unit time period is suppressed, it is possible to suppress damping or air intake at the beginning of the cooling. Therefore, the main cooling, then uniform cooling, can be materialized across the thin steel sheet. ADVANTAGE EFFECTS OF THE INVENTION
    [00013] According to the present invention, it is possible to suppress a distortion of a shape or a variation in quality caused by non-uniform cooling in the hot forming of a thin steel sheet. BRIEF DESCRIPTION OF THE DRAWINGS
    [00014] Figure 1 is a diagram showing schematically a configuration of a hot forming apparatus; Figure 2 is a diagram showing an example of an arrangement of expulsion and suction ports; Figure 3 is a diagram showing schematically a configuration of a hot forming apparatus that has a flow rate adjustment valve; Figure 4 is a diagram showing a state in which an upper mold of the hot forming apparatus of Figure 1 is in a lower central position; Figure 5 is a graph showing an example of the amount of cooling water flow control; Figure 6 is a diagram showing a state in which a degree of opening of the flow rate regulating valve is completely closed; Figure 7 is a diagram showing a state in which the degree of opening of the flow rate regulating valve is average; Figure 8 is a diagram showing a state in which the degree of opening of the flow rate regulating valve is completely open; Figure 9 is a diagram showing schematically a configuration in which a plurality of supply tubes are provided; Figure 10 is a diagram showing a state in which the degree of opening of the flow rate regulating valve is 45 degrees; Figure 11 is a diagram showing a state in which the degree of opening of the flow rate regulating valve is 22.5 degrees; Figure 12 is a diagram that shows schematically a configuration of a hot forming apparatus that has a supply tube that can regulate the amount of flow and Figure 13 is a diagram that shows an example of a shape of a formed product. DESCRIPTION OF THE MODALITIES
    [00015] Hereinafter, an embodiment of the present invention will be described.
    [00016] Figure 1 is a diagram showing schematically a configuration of a hot forming apparatus 1 of the present embodiment. The hot forming apparatus 1 has an upper mold 11 (first mold) and a lower mold 12 (second mold) which constitute a forming mold 10 for forming a steel plate (thin steel plate) to the press K. Note it is assumed that the thin steel sheet means a steel sheet with a sheet thickness of less than 3 mm.
    [00017] In the present embodiment, a plurality of independent protruding portions (not shown) with a constant height is provided on a surface of the lower mold 12 and cracks are made between the steel plate K and the lower mold 12 in a lower central position . Cooling water as a coolant is provided in the crevices. The upper mold 11 can be lifted and lowered freely in a vertical direction at a predetermined pressure by a lifting and lowering mechanism (not shown). It is observed that the steel sheet K is heated to a predetermined temperature, for example, to a temperature of 700 ° C or more to 1,000 ° C or less by a heating device (not shown) in advance and is transmitted to the heating device. hot forming 1. The transported steel sheet is placed in a predetermined position of the lower mold 12 based on a positioning pin (not shown) adjusted to a predetermined position of the lower mold 12, for example.
    [00018] A cooling water supply pipe 21 to be the refrigerant and a suction pipe 31 to absorb excess cooling water are connected / installed in the lower mold 12. The feeding pipe 21 serves to supply cooling water in the mold lower 12 at a pressure predetermined by a feed pump 22. The suction tube 31 serves to discharge the cooling water that has been supplied between the lower mold 12 and the steel plate K out of the apparatus by a suction pump 32.
    [00019] Feed pump 22 captures cooling water from a cooling water supply source 23 through an inlet tube 24. Inlet tube 24 is connected to feed tube 21 on a side downstream of the pump feed tube 22. The feed tube 21 is branched into a first branch tube 21a and a second branch tube 21b on a side downstream of a portion connected to the inlet tube 24. The first branch tube 21a and the second tube branch 21b are a plurality of refrigerant supply systems to the feed tube 21. The first branch tube 21a and the second branch tube 21b are provided with opening / closing valves 25, 26 on one supply side that have a good functioning, in correspondence with them, respectively. The first branch pipe 21a and the second branch pipe 21b are joined again on one side downstream of the opening / closing valves 25, 26. The feed pipe 21 is communicated with a plurality of expulsion holes 27 provided on the surface of the lower mold 12, through a supply path 28 made inside the lower mold 12.
    [00020] Additionally, a plurality of suction holes 33 are provided on the surface of the lower mold 12. The suction hole 33 leads to a suction path 34 made inside the lower mold 12 and is communicated with the suction tube 31. The cooling water absorbed by the suction pump 32 is discharged in a discharge portion 36 from the suction pipe 31 through the discharge pipe 35. The suction pipe 31 is provided with an opening / closing valve 37 on one side suction.
    [00021] The opening / closing of the opening / closing valves 25, 26 on the supply side and the opening / closing of the opening / closing valve 37 on the suction side are controlled together with an action of the upper mold 11 by a control device C.
    [00022] Figure 2 is a diagram showing an example of the arrangement of the expulsion holes 27 and the suction holes 33 made in the lower mold 12. It is observed that the protruding portion is omitted in Figure 2. As shown in Figure 2 , the plurality of expulsion holes 27 with a diameter Ds is made in an interval I on the surface of the lower mold 12. Additionally, the suction hole 33 with a diameter Da is made in a center of four expulsion holes 27 positioned in a manner rectangular. Therefore, almost the same numbers as the expulsion orifices 27 and suction orifices 33 are made in the lower mold 12.
    [00023] In the present embodiment, the diameter Da of the suction hole 33 is made larger than the diameter Ds of the expulsion hole 27. As a result of making the diameter Da of the larger suction hole 33, it is possible to absorb the cooling water after cooling the suction hole 33 without accumulation even if the amount of expulsion from the expulsion hole 27 increases. Additionally, as a result of making the diameter Da of the larger suction hole 33, the cooling water ejected from the plurality of expulsion holes 27 is absorbed from the suction hole 33 without accumulation even if the cooling water accumulates in a borehole. suction 33.
    [00024] In the aforementioned hot forming apparatus 1 of the modality, the feed pipe 21 is branched into the first branch pipe 21a and the second branch pipe 21b halfway, the opening / closing valve 25 is provided in the first branch pipe 21a, the opening / closing valve 26 is provided in the second branch pipe 21b and the opening / closing valve 37 is also provided in the suction pipe 31, but it should be noted that the present invention is not limited to the above configuration.
    [00025] Figure 3 is a diagram showing schematically a configuration of a hot forming apparatus 41. In the hot forming apparatus 41, a feed tube 21 is not branched, in which the feed tube 21 is provided with a flow rate regulating valve 42 as a ball valve that can regulate a flow rate corresponding to a degree of valve opening and a suction tube 31 is similarly provided with a flow rate regulating valve 43. In this way, the flow rate adjustment valve can be used instead of the opening / closing valve.
    [00026] Next, an example of operation of the hot forming device 1 shown in Figure 1 will be described.
    [00027] First, a steel sheet K which has been heated to 900 ° C, for example, in advance, is placed in a predetermined position of the lower mold 12 by a delivery unit (not shown). Then, as shown in Figure 4, the upper mold 11 is lowered to the lower central position while the steel sheet K is pushed down vertically, so that the formation of the steel sheet K is carried out. In that time, the feed pump 22 and the suction pump 32 are already running.
    [00028] The upper mold 11 is retained at a time when the upper mold 11 is lowered to the lower central position while the steel plate K is pushed down vertically and first the opening / closing valve 25 is opened, so that cooling water of a predetermined flow quantity is supplied from the first branching tube 21a and the feeding tube 21 to the supply path 28 inside the lower mold 12. Therefore, the cooling water is ejected / supplied from the expulsion hole 27 in the gap between the steel plate K and the surface of the lower mold 12 (pre-cooling). Then, the opening / closing valve 37 on the suction side is also opened. Here, in a pre-cooling time, since the opening / closing valve 26 is kept closed, an amount of expulsion per unit time period of expulsion hole 27 is suppressed compared to a main cooling time that will be described later . The cooling water supplied in the gap between the steel sheet K and the lower mold 12 captures the heat of the steel sheet K and part of it is vaporized and dispersed from a gap between the upper mold 11 and the lower mold 12. The remaining cooling water is discharged to the outside of the appliance, from the suction hole 33 through the suction path 34 and through the suction tube 31.
    [00029] Then, after a predetermined period of time, the opening / closing valve 26 on the supply side is opened while the opening / closing valve 25 is maintained in an open state. Therefore, in addition to the cooling water of the first branching tube 21a, the cooling water of the second branching tube 21b is also provided, so that the flow rate of the cooling water supplied to the supply path 28 is increased. Therefore, the amount of expulsion per unit time period of the cooling water ejected from the expulsion hole 27 is increased by this amount (main cooling).
    [00030] Then, after a predetermined period of time and the steel sheet K has cooled to a predetermined temperature, the opening / closing valves 25, 26 are closed and the opening / closing valve 37 is also closed.
    [00031] It is observed that in a cooling process as above, it is preferable that the amount of pre-cooling expulsion is 1.0 ml / s for each expulsion hole at 3.0 ml / s for each drilling hole. expulsion. In addition, it is preferred that a ratio of a quantity of flow that flows only from the first branch pipe 21a when only the opening / closing valve 25 is in the open state at a pre-cooling time to a quantity of flow that flows from both the first branch tube 21a and the second branch tube 21b by opening both open / close valves 25, 26 in a main cooling time, then it is from 1: 5 to 2: 5. Therefore, it is preferred that a ratio of the amount of expulsion per unit time period of the cooling water ejected from the expulsion hole 27 in the pre-cooling time to the amount of expulsion per unit time period of the cooling water ejected from the borehole. expulsion 27 in the main cooling time is from 1: 5 to 2: 5.
    [00032] Additionally, it is preferred that a pre-cooling time ratio, i.e., a period of time during which the flow is carried out only from the first branch pipe 21a to the main cooling time, i.e., a period of time during which the flow is carried out from both the first branch tube 21a and the second branch tube 21b is from 1: 4 to 4: 1. Here, when a total period of time from the start of cooling to the interruption of cooling is indicated as T, it is preferable that the main period of cooling time is from T / 5 to 4T / 5 from the beginning. In addition, it is preferred that the main cooling time period is from 1 second to 4 seconds. In addition, it is preferred that the main cooling time period is from 1 second to 4 seconds.
    [00033] By controlling the amount of cooling water flow, as above, pre-cooling is possible in which the amount of cooling water supplied from the expulsion hole 27 is the amount of flow from the first pipe only branching 21a at the beginning of the cooling and, subsequently, the main cooling where cooling water is supplied from both the first branching tube 21a and the second branching tube 21b. Therefore, it is possible to carry out pre-cooling in which the amount of expulsion per unit time period is suppressed. By pre-cooling, rapid cooling is suppressed in the vicinity of the expulsion hole at the beginning of cooling and, as a result of gradual cooling, a difference in the vicinity of the expulsion hole and in a position distant from the expulsion hole can be decreased. Additionally, as a result of the gradual cooling, it is possible to suppress the damping or air intake at the beginning of the cooling.
    [00034] Therefore, it is possible to suppress a distortion of a steel plate shape or irregular quality caused by the irregular temperature.
    [00035] Next, an example of controlling the amount of cooling water expulsion from the hot forming devices 1, 41 of the present modality will be described with reference to Figure 5. Figure 5 shows the fluctuation of each amount of expulsion of a conventional method, a step method and a continuous method.
    [00036] In the conventional method, the same amount of expulsion is maintained from the beginning until the interruption of the cooling water supply. The step method is an operational example of the hot forming apparatus 1 of Figure 1. The continuous method is an operational example of the hot forming apparatus 41 of Figure 3.
    [00037] As shown in Figure 5, in the step method (hot forming apparatus 1 of Figure 1), starting from a cooling start time in the bottom dead center (position of 0.0 on a horizontal geometric axis in a graph of Figure 5) up to 1 second, only the opening / closing valve 25 is opened and filling is carried out in an expulsion quantity of 2 ml / s for each expulsion hole (pre-cooling). Then, until 2 seconds have passed, the opening / closing valve 26 is also opened and filling is carried out in an expulsion quantity of 7 ml / s for each expulsion hole in total (main cooling).
    [00038] Additionally, in the continuous method (hot forming apparatus 41 in Figure 3), the flow rate regulation valve 42 is controlled and from a cooling start time up to 0.8 seconds, the supply is carried out in an expulsion quantity of 1.5 ml / s for each expulsion hole (pre-cooling). Then, from a time in which 0.8 seconds elapsed, a degree of opening of the flow rate regulating valve 42 is made gradually large to increase the amount of flow, in which the degree of opening is made gradually large until 1.4 seconds elapse. Then, until 1.8 seconds elapse, the filling is carried out in an ejection amount of 8.0 ml / s for each ejection hole in a maximum opening degree (main cooling). Then, the flow rate regulating valve 42 is gradually closed and, in a time that has elapsed 2.0 seconds, the flow rate regulating valve 42 is closed.
    [00039] It can be seen that as the flow rate regulation valve 42, which can materialize the quantity flow control of the continuous method, it is possible to use a valve shown in Figure 6 to Figure 8 that can freely regulate a degree of opening of a valve element 44.
    [00040] Figure 6 shows a state in which the valve element 44 is completely closed. Figure 7 shows a state in which the valve element 44 is in the middle between the completely closed and completely open state. Figure 8 shows a state in which the valve element 44 is completely open. The flow rate regulating valve 42 is controlled by a control device C. The control device C detects the degree of openness of valve element 44 via an angle detection sensor (not shown) or similar. As shown in Figure 6 to Figure 8, the control device C can indicate the degree of opening detected by an arrow 45 or similar, for example. In addition, control device C opens / closes valve element 44 via a valve opening / closing drive mechanism (not shown) such as an electric motor. More specifically, the control device C can materialize the amount of expulsion control of the continuous method of Figure 5 by opening / closing the valve element 44 based on a program in which a cooling time period and a degree of opening of the valve element 44 are correlated and stored.
    [00041] As described above, with the use of the flow rate regulation valve 42 which can regulate the flow amount continuously, it is possible to moderate the expulsion of the cooling water in the pre-cooling start time and in the transition of the quantity expulsion from pre-cooling to main cooling. In addition, as a result that control device C performs the expulsion quantity control based on the program, an expulsion quantity pattern of the continuous method in Figure 5 can be adjusted to an arbitrary pattern just by changing the program. Therefore, a distortion of the shape of a steel sheet and an irregular quality can be precisely adjusted.
    [00042] Additionally, the number of flow rate regulating valve 42 to be supplied is not limited to one, but, as shown in Figure 9, it is possible that a plurality of feed tubes 21 for a mold are supplied in parallel. and these flow rate regulating valves 42a, 42b are provided in each of the feed tubes 21. In this case, it is possible to regulate a flow rate for each feed tube 21 and for a large mold, in particular, the pattern expulsion amount of the continuous method can be adjusted to an arbitrary pattern for each region of the mold. For example, it is possible to change an amount of cooling water expulsion for each supply pipe 21 making the degree of opening of a valve element 44 in the flow rate regulating valve 42a to be 45 degrees, as shown in Figure 10, and causing a degree of opening of a valve element 44 in the flow rate regulation valve 42b to be 22.5 degrees, as shown in Figure 11. Therefore, even in a case of conformation to the press by a large mold, it is possible to suppress a difference in the cooling characteristic (temperament) that is generated because a shape is different for each region of the mold. Additionally, it is possible to obtain a different cooling characteristic (temperament) for each region of the mold, intentionally generating a difference in the amount of cooling water expulsion.
    [00043] Additionally, an amount of cooling water expulsion from an entire mold can be done uniformly by intentionally synchronizing or differentiating the opening / closing speeds of a plurality of flow rate regulating valves supplied in a supply pipe cooling water, in which the feeding tube leads to a supply path inside the mold. In this case, a control device C controls the plurality of flow rate control valves.
    [00044] Additionally, in a case of a small mold, as shown in Figure 12, it is possible to use a flow rate regulation type feed pump 46 that can regulate a flow supply quantity and a flow suction pump type of flow rate regulation 47 that can regulate a flow suction amount. With the use of the flow rate regulation type 46 feed pump, flow rate regulation similar to that of the flow rate regulation valve is possible. As well as the flow rate regulation type 46 feed pump and a flow rate regulation type 47 suction pump, it is possible to use those in which the pump speed numbers are changeable by inverter control, for example. In this case, a control device C controls the number of pump speeds.
    [00045] As described above, both by the step method (hot forming apparatus 1 in Figure 1) and by the continuous method (hot forming apparatus 41 in Figure 3), it is possible to suppress a distortion of a shape of a steel plate or irregular quality caused by irregular temperature due to rapid cooling in the vicinity of an expulsion hole at the beginning of cooling.
    [00046] In the aforementioned modality, a case in which cooling water such as water is used as the refrigerant is described, but it should be noted that the refrigerant is not limited to that case. In other words, it is possible to use gas, steam or a mixture of gas and liquid in which water in the form of a mist is mixed with gas as the refrigerant.
    [00047] From now on, an example of an experiment with the use of the hot forming device 1 of Figure 1 will be described.
    [00048] Here, as an experiment condition, with respect to a sheet of steel, a steel plate laminated with aluminum of 1.4 mm thickness is used which consists of chemical components, in% by mass, C: 0, 22%, Mn: 1.2%, Cr: 0.2%, B: 0.002% and the rest is iron and an inevitable impurity. In addition, the steel sheet is heated to 900 ° C and cooled to 250 ° C, a target temperature.
    [00049] Cooling water (tap water or industrial water) from 5 ° C to 25 ° C in temperature is used as the refrigerant.
    [00050] A shape of a product formed by forming the press is aimed at a component whose rigidity to the section is low among parts of the structure of an automobile. More specifically, as shown in Figure 13, this component is a product formed 51 with a hat-shaped cross section that has outer flanges and a length L is 400 mm, a width WL of 140 mm, a height H of 30 mm and a width Wh of a 70 mm hat shape.
    [00051] Additionally, in the lower mold 12, an interval I between the discharge holes 27 is 30 mm, a diameter Ds of the discharge hole 27 is 1 mm and a diameter Da of the suction hole 33 is 4 mm. In addition, a height (distance from the mold surface to a top surface of the protruding portion) of the protruding portion is 0.5 mm.
    [00052] An amount of expulsion per unit time period of the cooling water is adjusted to be changed in two stages in the pre-cooling and in the main cooling. In other words, from the start of cooling to a predetermined period of time, pre-cooling is carried out, in which only the opening / closing valve 25 is opened and the amount of expulsion per unit time period is suppressed. Then, the main cooling is carried out, in which the opening / closing valve 26 is also opened and the amount of expulsion per unit time period is increased.
    [00053] In the experiment example, cooling is performed in seven patterns of ratios from the amount of expulsion from the pre-cooling to the amount of expulsion from the main cooling. More specifically, as shown in Table 1, the defaults are “pre-cooling: main cooling, 0.4: 2”, “pre-cooling: main cooling, 1: 5”, “pre-cooling: main cooling, 2: 5 "," pre-cooling: main cooling, 2:10 "," pre-cooling: main cooling, 3:10 "," pre-cooling: main cooling, 3:15 "," pre-cooling: main cooling, 4:10 ”. Here, “pre-cooling: main cooling, 0.4: 2”, for example, indicates that the pre-cooling expulsion amount is 0.4 ml / s for each expulsion hole and that the expulsion amount of the main cooling is 2 ml / s for each expulsion hole.
    [00054] Additionally, an expulsion time period, that is, a period of cooling time by the cooling water, is adjusted to 2 seconds to 5 seconds within a range of 5 seconds or less, in which an effect of a high productivity can be obtained.
    [00055] In the experiment example, the expulsion time period is set to 5 seconds and a ratio of a pre-cooling time period to a main cooling time period is changed by a unit of 1 second and the cooling is performed in six patterns. More specifically, as shown in Table 1, the defaults are “pre-cooling time period is 0 seconds, main cooling time period is 5 seconds”, “pre-cooling time period is 1 second, main cooling time period is 4 seconds ”,“ pre-cooling time period is 2 seconds, main cooling time period is 3 seconds ”,“ pre-cooling time period is 3 seconds, main cooling time period is 2 seconds ”,“ pre-cooling time period is 4 seconds, main cooling time period is 1 second ”and“ pre-cooling time period is 5 seconds, main cooling time period is 0 seconds ”. Here, "pre-cooling time period is 0 seconds, main cooling time period is 5 seconds" indicates that only the main cooling is performed from a cooling start time to a final cooling time, without pre-cooling. In other words, the cooling is carried out in the conventional method of Figure 5. Additionally, “pre-cooling time period is 1 second, main cooling time period is 4 seconds” indicates that the cooling in which the cooling time is pre-cooling is 1 second and the main cooling time is 4 seconds. In addition, “pre-cooling time is 5 seconds, main cooling time is 0 seconds” indicates that the cooling is carried out for 5 seconds in a pre-cooling state. In other words, the amount of expulsion is merely reduced in the conventional method of Figure 5.
    [00056] With respect to the seven patterns in which the ratio of the amount of pre-cooling expulsion to the amount of expulsion from the main cooling is changed and the six patterns in which the ratio of the pre-cooling time period to the period of main cooling time is changed, a precision in the shape of a formed product is measured for each standard and a result is shown in Table 1. TABLE 1

    [00057] Here, an “▲” mark shown in Table 1 indicates poor accuracy in format due to insufficient cooling. In addition, a “▼” mark indicates poor shape accuracy due to rapid cooling. A “△” mark indicates insufficient cooling, but that if a precision in conformation is good or bad, it is divided. A “▽” mark indicates rapid cooling, but that if an accuracy in the format is good or bad, it is divided. An “O” mark indicates good precision in shape due to good cooling. A “◎” mark indicates that the accuracy of the shape is stable and good due to good cooling. Here, precision in good shape means that an accuracy of a target dimension is ± 0.5 mm or less in all positions of a formed product. In addition, the precision in the format which is stable is good means that an accuracy of a target dimension is ± 0.4 mm or less in all positions of a formed product. On the other hand, poor accuracy in shape means that an accuracy of a target dimension exceeds ± 0.5 mm in at least part of a formed product. In addition, if the precision in the format is good or bad, which is divided, it means that an accuracy of a target dimension exceeds ± 0.5 mm in at least part of a formed product, but that an excess region is not clear and that it is possible to use the formed product depending on the intended use of the formed product.
    [00058] Based on the result shown in Table 1, in the component that has low section stiffness, a stable region cannot be obtained when the amount of pre-cooling expulsion is 0.4 ml / s for each bore hole. expulsion and 4 ml / s for each expulsion hole. In other words, in order to avoid poor precision in the format, it is preferable to adjust the amount of expulsion per unit time period of pre-cooling to 1 ml / s for each expulsion hole up to 3 ml / s for each expulsion hole . On that occasion, it is preferable to adjust a ratio of the expulsion amount per unit pre-cooling time period to an expulsion amount per main cooling unit time period to 1: 5 to 2: 5.
    [00059] Additionally, in a case where the ratio of the pre-cooling time period to the main cooling time period is changed, a stable region cannot be obtained when the pre-cooling time period is 0 second and the main cooling time period is 0 seconds. In other words, in order to avoid poor format accuracy, it is preferable to adjust the ratio of the pre-cooling time period to the main cooling time period to 1: 4 to 4: 1. In other words, when a total period of time from the start of cooling to cooling water supply is interrupted, it is indicated as T, it is preferable to pre-cool between T / 5 to 4T / 5 from the beginning.
    [00060] In addition to the aforementioned preferred cooling condition, if the ratio of the pre-cooling time period to the main cooling time period is set to 2: 3 to 3: 2, it will be possible to make the accuracy in the format good of all formed products obtained. In other words, in order for good format accuracy, it is preferable to adjust the ratio of the pre-cooling time period to the main cooling time period to 2: 3 to 3: 2.
    [00061] In order to apply the aforementioned preferential cooling condition, it is preferred that a condition below is satisfied as well. In other words, it is preferable that a steel sheet is a thin sheet steel laminated on the basis of aluminum or a thin sheet of galvanized steel to which metallization is applied, so that the scale is not generated when heated. With respect to a sheet thickness, it is preferable that it be a thin steel sheet from 1 mm to 2 mm that is used for an automobile component. Additionally, with respect to a steel sheet temperature, it is preferred that the steel sheet has been heated for tempering (generating a martensite structure by rapid cooling), at a temperature at which a ferrite structure does not precipitate (for example, 700 ° C) or more to 1,000 ° C or less. In addition, it is preferable that a soda is water, since water is comparatively easy to obtain and it is preferable that its temperature is from 5 ° C to 25 ° C, which is an ambient temperature. In addition, an expulsion time period, that is, a cooling time period which is a total of a pre-cooling time period and it is preferable that a main cooling time period is 2 seconds or more in order to cause the ejected cooling water to spread and it is preferable that it is 5 seconds or less in order to obtain a high productivity effect. It is observed that it is preferable that the diameter Ds of the expulsion hole 27 is from 1 mm to 4 mm in order to make the amount of expulsion per unit pre-cooling period of time be 1 ml / s to 3 ml / s.
    [00062] It is observed that in a component with a high stiffness to the section, it is expected that “▲”, “▼”, “△”, or “▽” changes to “O” or “◎”, the expansion of stable region. Additionally, it is confirmed in the experiment that in the component with the high stiffness to the section, the expulsion time period can be shortened to 2 seconds, although it is not shown in Table 1.
    [00063] Above, the preferred embodiment of the present invention is described, but the present invention is not limited to the aforementioned embodiment. It is evident that a person skilled in the art will be able to consider various modifications or corrections within the scope of the spirit described in the claims and it is evident that these modifications or corrections belong to the technical scope of the present invention.
    [00064] For example, in the aforementioned embodiment, a case in which the expulsion hole 27 and the suction hole 33 are provided in the lower mold 12 is described, but the present invention is not limited to that case and a configuration is possible wherein the expulsion hole 27 and the suction hole 33 are provided in at least one of the upper mold 11 and the lower mold 12.
    [00065] Additionally, in the aforementioned embodiment, a case in which the plurality of expulsion holes 27 are produced is described, but the present invention is not limited to that case, but the expulsion hole number 27 can be one depending on a size of a formed product. INDUSTRIAL APPLICABILITY
    [00066] The present invention is useful in the hot forming of a thin steel sheet.
    权利要求:
    Claims (10)
    [0001]
    1. Cooling method for hot forming of a thin steel sheet (K) in which the thin steel sheet (K) is cooled by providing a coolant for an ejection hole (27) of a mold surface ( 10) whose ejection hole (27) is communicated from a supply path (28) inside the mold (10) in the hot forming of the heated thin steel plate (K), being the cooling method for forming the hot characterized by the fact that it comprises: pre-cooling in which an amount of ejection per unit time period of the refrigerant from the ejection hole (27) is suppressed in a time of the beginning of cooling; and then perform the main cooling by increasing the amount of ejection per unit time period, when the thin steel plate (K) is cooled by supplying the refrigerant to the ejection hole (27) in a state in which the heated thin steel plate (K) is placed in the mold (10) and retained in a lower central position, in which the ejection amount per unit time in a pre-cooling time is 1 mL / sec to 3 mL / sec, in which the ratio of the amount of ejection per unit time period of the refrigerant from the ejection hole (27) of the pre-cooling time to a main cooling time is from 1: 5 to 2: 5, and where the ratio of a pre-cooling time period to a main cooling time period is 1: 4 to 4: 1.
    [0002]
    2. Cooling method for hot forming of thin steel sheet (K), according to claim 1, additionally, characterized by the fact that the ratio of the pre-cooling time period to the main cooling time period is 2: 3 to 3: 2.
    [0003]
    3. Cooling method for hot forming of thin steel sheet (K), according to claim 1 or 2, additionally, characterized by the fact that the thin steel sheet (K) is a thin steel sheet laminated to aluminum base or a thin galvanized steel sheet from 1 mm to 2 mm thick and is heated to 700 ° C to 1,000 ° C before pre-cooling, where the refrigerant is water from 5 ° C to 25 ° C, and in which a cooling time period obtained by combining the pre-cooling time period and the main cooling time period is from 2 seconds to 5 seconds.
    [0004]
    4. Hot forming apparatus (1) of a thin steel sheet (K) that cools the thin steel sheet (K) by providing a coolant for an ejection hole (27) of a mold surface (10 ) whose ejection hole (27) is communicated from a supply path (28) inside the mold (10) in the hot forming of the heated thin steel sheet (K), and the hot forming device ( 1), characterized by the fact that it performs the pre-cooling in which an amount of ejection per unit period of time is suppressed in a time from the beginning of the cooling and then performs the main cooling by increasing the amount of ejection by unit time period of the refrigerant from the ejection hole (27), when the steel plate (K) is cooled by supplying the refrigerant to the ejection hole (27) in a state in which the thin steel plate ( K) heated is placed in the mold (10) and retained in a lower central position, where the amount of ejection can be r unit time in a pre-cooling time is 1 ml / sec to 3 ml / sec, in which a ratio of the amount of ejection per unit time of the refrigerant from the ejection hole (27) of the time pre-cooling time for a main cooling time is 1: 5 to 2: 5, and in which a ratio of a pre-cooling time period to a main cooling time period is 1: 4 to 4: 1.
    [0005]
    5. Hot forming apparatus (1) of thin steel sheet (K), according to claim 4, additionally, characterized by the fact that the ratio of the pre-cooling time period to the cooling time period main is 2: 3 to 3: 2.
    [0006]
    6. Hot forming apparatus (1) of thin steel sheet (K), according to claim 4 or 5, additionally, characterized by the fact that the thin steel sheet (K) is a thin rolled steel sheet aluminum-based or a thin galvanized steel sheet from 1 mm to 2 mm thick and is heated to 700 ° C to 1,000 ° C before pre-cooling, where the refrigerant is water from 5 ° C to 25 ° C , and in which a cooling time period obtained by combining the pre-cooling time period and the main cooling time period is from 2 seconds to 5 seconds.
    [0007]
    7. Hot forming device (1) of thin steel sheet (K) according to any one of claims 4 to 6, characterized by the fact that a suction hole (33) is made in the center of the four holes ejection tubes (27) positioned rectangularly on the mold surface (10), and in which the diameter of the suction hole (33) is greater than the diameter of the ejection hole (27).
    [0008]
    8. Hot forming apparatus (1) of thin steel sheet (K) according to any one of claims 4 to 7, characterized in that a plurality of refrigerant supply systems (21a, 21b) are connected to a refrigerant supply tube (21), where the supply tube (21) leads to the supply path (28) inside the mold (10), and where an opening / closing valve (25, 26) is provided in each of the supply systems (21a, 21b).
    [0009]
    9. Hot forming apparatus (1) of thin steel sheet (K) according to any one of claims 4 to 7, characterized by the fact that a flow rate adjustment valve (42) is provided in the pipe supply (21) of the refrigerant, where the supply tube (21) leads to the supply path (28) inside the mold (10).
    [0010]
    10. Hot-forming apparatus (1) of thin steel sheet (K) according to any one of claims 4 to 7, characterized by the fact that a feed pump (46) which has the capacity to regulate the amount of flow is provided in the supply pipe (21) of the refrigerant, where the supply pipe (21) leads to the supply path (28) inside the mold (10).
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    MX2016001515A|2016-06-10|
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    US20160167101A1|2016-06-16|
    JPWO2015037657A1|2017-03-02|
    MX369615B|2019-11-14|
    EP3045236A1|2016-07-20|
    KR20160030265A|2016-03-16|
    WO2015037657A1|2015-03-19|
    CA2919823A1|2015-03-19|
    TW201524631A|2015-07-01|
    JP6056981B2|2017-01-11|
    EP3045236A4|2017-06-21|
    KR101837317B1|2018-03-09|
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    法律状态:
    2019-09-10| B25D| Requested change of name of applicant approved|Owner name: NIPPON STEEL CORPORATION (JP) |
    2019-12-17| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2020-08-11| B06A| Notification to applicant to reply to the report for non-patentability or inadequacy of the application [chapter 6.1 patent gazette]|
    2020-12-01| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2021-02-09| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 11/09/2014, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    JP2013-189218|2013-09-12|
    JP2013189218|2013-09-12|
    PCT/JP2014/074056|WO2015037657A1|2013-09-12|2014-09-11|Hot-press stamping cooling method and hot-press stamping device|
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