JP2013010129A - Method for drawing steel product and die device for drawing steel product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of drawing a steel product and a die device for drawing a steel product adapted to allow inhibiting variation in outer diameters of steel products from the initial stage of startup of the drawing process to achieve stabilization in sizes of outer diameters of the steel products.SOLUTION: The method of drawing a steel product employs a die device 1 for drawing a steel product adapted to hold a die 2 for a drawing process with a die hole 20 that permits the steel product to pass along its longitudinal direction. A drawing process is implemented to draw the steel product by making it pass through the die hole 20 of the die 2. In advance of starting up drawing of the steel product with the die 2, the die 2 is heated up by a heat source 7 to raise the temperature of the die 2 to a temperature region of the die 2 during the drawing process, or a temperature region as high as 70 to 100% with respect to the temperature region of the die 2 during the drawing process. After the temperature-raising operation, the drawing process of the steel product is started.

Description

  The present invention relates to a steel material drawing method and a steel material drawing die apparatus. Examples of the steel material include a steel bar, a wire, and a wire for cold forging.

  The steel material drawing method includes a step of preparing a steel material having a predetermined length and a steel material drawing die device for holding a drawing die having a die hole through which the steel material passes along the length direction thereof. Then, a drawing process is performed in which the steel material is drawn while passing through the die hole of the die. In recent years, there is a demand in the industry for dimensions with higher accuracy and reduced variation in the outer diameter of steel materials. For example, when the diameter of the steel material is 28 mm, extremely severe high accuracy is required so that the variation width of the diameter is within a range of about 0.02 mm. However, in drawing, because the die generates heat due to friction between the steel and the die, it is affected by the temperature rise after the beginning of drawing, and the variation in the outer diameter of the steel is reduced compared to the beginning of drawing. There was a limit to plan.

  In Patent Document 1, a heater is mounted on the outer periphery of a die, and the magnesium alloy bar wire is drawn while the die is heated to a temperature of 150 ° C. or higher and 500 ° C. or lower to prevent disconnection of the magnesium alloy bar wire. A manufacturing method is disclosed. However, according to Patent Document 1, it is intended for a magnesium alloy rod and wire, the heater is continuously turned on from the start to the end of the drawing process, and the die is heated to a temperature of 150 ° C. or more and 500 ° C. or less by the heater. Since the magnesium alloy bar wire is drawn in a heated state, there is a limit in suppressing variations in the outer diameter of the magnesium alloy bar wire.

JP 2004-17114 A

  However, according to Patent Document 1, since the magnesium alloy bar wire is drawn while the die is continuously heated to a temperature of 150 ° C. or more and 500 ° C. or less by the heater from the start to the end of the drawing process, the wire breakage occurs. The manufacturing method for preventing and suppressing the above is a target, and there is a limit in suppressing variation in the outer diameter of the magnesium alloy bar wire. Furthermore, as a conventional technique, there is a technique for heating the wire itself instead of heating the die, but in this case, since the wire itself is heated, in order to suppress variations in the outer diameter of the wire. There is a limit. The present invention has been made in view of the above-described circumstances, and a steel material drawing method and a steel material drawing method that can suppress variations in the outer diameter size of the steel material from the beginning of the drawing process and can stabilize the outer diameter size of the steel material. An object of the present invention is to provide a dice apparatus for use.

  (1) A steel material drawing method according to aspect 1 of the present invention is for drawing with a steel material group consisting of a plurality of steel materials having a predetermined length and a die hole through which the steel material passes along the length direction thereof. A steel material drawing method for carrying out a step of preparing a steel material drawing die device for holding a die of the steel material and a drawing step of sequentially drawing the steel material of the steel material group through the die holes of the die, the steel material group Prior to starting the drawing of the steel material with a die, the die is heated by a heating source, and the temperature of the die is set to 70 to the temperature range of the die during drawing or the temperature range of the die during drawing. Stabilize the outer diameter of the steel material from the beginning of the drawing process by performing a temperature raising operation to raise the temperature to a temperature range of 100% to 100% and starting the drawing process of the steel material after the temperature raising operation. It is characterized by.

  In this case, prior to starting drawing the steel members of the steel group with a die, the die is heated by a heating source, and the die temperature is set to the temperature range of the die during drawing or the temperature of the die during drawing. The temperature raising operation for raising the temperature to a temperature range of 70% to 100% with respect to the range is performed. In this case, 75%, 80%, 85%, and 90% are exemplified as the lower limit for the temperature range of the die at the time of drawing. Examples of the upper limit for the temperature range of the die during drawing are 100%, 98%, 95%, and 92%. After the temperature raising operation of the die, the drawing of the steel material is started. As a result, the temperature of the die can be set to an appropriate temperature range from the beginning of the drawing process. Therefore, it is possible to stabilize the outer diameter of the steel material from the beginning of the drawing process.

  After a while from the start time of the drawing process, the temperature rise of the die due to the frictional heat from the drawing process and the heat dissipation of the die are balanced, and the temperature of the die is stabilized. In the final stage, the outer diameter of the steel material can be stabilized. Any heating source may be used as long as it can heat the die, and examples thereof include electric heating and induction heating. Induction heating may be high-frequency induction heating, low-frequency induction heating, or energization heating with a heating resistor. The heating source may be separated from the steel material drawing die device, or may be integrated into the steel material drawing die device. The heating temperature differs depending on the die itself at the time of drawing. When the die temperature during the drawing process is 100 ° C., the heating source is turned on and the temperature of the die is raised to a temperature range of 70 ° C. to 100 ° C. prior to the drawing process. When the die temperature at the time of drawing is 120 ° C., the heating source is turned on prior to the drawing and the die temperature is in the range of 100 ° C. (about 83%) to 110 ° C. (about 92%). Alternatively, the temperature is raised to a temperature range within a range of 100 ° C to 120 ° C. In short, prior to the start of the drawing process, the temperature of the die is raised in advance to a temperature range of 70% to 100% with respect to the temperature range of the die during the drawing process. In addition, it is preferable to turn off the heating source during the drawing process. Examples of the steel material through which the die passes include a steel bar and a wire material, a wire material for cold forging.

  (2) According to the steel drawing method according to aspect 2 of the present invention, in the above aspect, the heating source is separated from the steel drawing die device, and the temperature raising operation is performed by removing the die from the steel drawing die device. In the detached state, it is carried out by an operation of heating the die by a heating source separated from the steel material drawing die device, and thereafter an operation of attaching the heated die to the steel material drawing processing device. . The heating source is separated from the steel material drawing die device. The temperature raising operation is performed by removing the die from the steel material drawing die device and, in that state, heating the die with a heating source separated from the steel material drawing die device. For this reason, heat transfer to other than the die is suppressed, and the temperature of the die is easily set accurately. Thereafter, the die heated to a predetermined temperature is attached to the steel material drawing apparatus. Thereafter, the drawing process is started. According to this aspect, since the temperature of the die can be raised to an appropriate temperature range from the beginning of the drawing process, it is advantageous for stabilizing the outer diameter of the steel material from the beginning of the drawing process.

  (3) A steel material drawing die apparatus according to aspect 3 of the present invention includes a drawing die having a die hole through which the steel material passes, a case having a recess for fitting the die, and a heating source for heating the die. The heating source is disposed at a position that does not overlap the die in a direction perpendicular to the axis perpendicular to the central axis of the die hole so as to suppress the drawing load from acting on the heating source. It is characterized by. In the drawing process, it is possible to suppress the drawing load from acting on the heating source, to suppress damage to the heating source due to the drawing load, and to improve the durability of the heating source and extend the life.

  (4) A steel material drawing die device according to aspect 4 of the present invention includes a drawing die having a die hole through which the steel material passes, a case having a recess for fitting and holding the die from the tip opening, and the die And a covering cover that is fixed to the case so as to cover the tip opening of the concave portion of the case and that prevents the die fitted in the concave portion of the case from coming off. It is arranged. In the drawing process, the drawing load is unlikely to act on the covering cover attached to the tip of the case. Since the heating source is arranged in the covering cover, it is suppressed that the drawing weight acts on the heating source. As a result, damage to the heating source due to drawing weight is suppressed, and the protection of the heating source is enhanced.

  According to the present invention, variation in the outer diameter of the steel material can be suppressed from the beginning of the drawing process. Stabilization of the outer diameter of the steel material can be achieved, and reliability can be improved.

It is the perspective view which decomposed | disassembled the principal part of the die apparatus for steel material drawing concerning Embodiment 1. FIG. 1 is a cross-sectional view of a steel material drawing die device according to Embodiment 1. FIG. It is sectional drawing which shows the state which concerns on Embodiment 1 and is mounted | worn with the die | dye removed from the steel material extraction die apparatus on a heating source. It is a graph which concerns on the test example which shows the change of the outer diameter dimension of steel materials. FIG. 5 is a cross-sectional view of a steel material drawing die device according to a second embodiment. It is sectional drawing of the dicing apparatus for steel materials drawing concerning Embodiment 3. FIG. It is a graph which concerns on Embodiment 4 and shows typically the relationship between time and the temperature of dice | dies.

(Embodiment 1)
1 to 3 show the concept of the first embodiment. A steel material drawing die apparatus 1 for holding a drawing die 2 having a die hole 20 through which a steel material passes along the length direction thereof is prepared. As shown in FIGS. 1 and 2, the steel material drawing die device 1 mainly holds a drawing die 2 having a die hole 20 having a central axis P and a die 2 from a tip opening 30. The case 3 having the recessed portion 31 to be held, the frame 4 having the holding hole 40 for fitting and holding the case 3, and the recessed portion 31 of the case 3 fixed to the case 3 so as to cover the tip opening 30 of the recessed portion 31 of the case 3. And a cover 5 that prevents the die 2 fitted to the cover from coming off. The covering cover 5 has a passage hole 5x through which the wire passes. As shown in FIG. 2, the case 3 has a bottom 33 having a passage hole 33x through which a wire passes and a cylindrical outer peripheral portion 35.

  The cover having the recess 31 includes a ring-shaped concave bottom wall surface 36 extending in a direction orthogonal to the central axis P of the die hole 20 and a ring-shaped concave inner peripheral wall surface 37 extending along the central axis P of the die hole 20. And a ring-shaped tip wall surface 38 extending in a direction orthogonal to the central axis P of the die hole 20. As shown in FIG. 2, the die 2 includes a cylindrical first die 21 made of alloy steel having a mounting hole 23, and a cemented carbide alloy fitted into the cylindrical mounting hole 23 of the first die 21. And a cylindrical second die 22 formed of Cemented carbides mainly contain a hard phase having high hardness such as tungsten carbide and a parent phase such as cobalt in which the hard phase is dispersed. As shown in FIG. 3, the heating source 7 is not mounted on the steel material drawing die device 1, and is separated from the steel material drawing die device 1. The heating source 7 includes a flat heating surface 70 on which the die 2 to be heated by induction heating is placed.

  First, prior to starting the drawing process of drawing the steel material of the steel material group with the die 2, the cover 5 is removed from the case 3 in advance and the die 2 is removed from the recess 31 of the case 3. In this way, the die 2 is separated from the steel material drawing die device 1. The die 2 thus separated is placed on the heating surface 70 of the heating source 7 (see FIG. 3), and in this state, the temperature of the die 2 is set to the temperature range of the die 2 at the time of drawing or at the time of drawing. A temperature raising operation for raising the temperature to a temperature range of 70% to 100% with respect to the temperature range of the die 2 is performed.

  In this case, as shown in FIG. 2, the tip opening 22e of the cylindrical second die 22 made of cemented carbide is made of alloy steel rather than contacting or approaching the heating surface 70 of the heating source 7. The die 2 is positioned so that the back surface portion 21x of the cylindrical first die 21 contacts or approaches the heating surface 70 of the heating source 7. It is considered that the first die 21 formed of alloy steel is easily induction-heated uniformly. For this reason, it is because it is desired to increase the degree to which the first die 21 indirectly heats the second die 22 formed of a cemented carbide that is in direct contact with the steel material during the drawing process. In particular, as can be understood from FIG. 3, the entire outer peripheral surface 22 p of the second die 22 made of cemented carbide is surrounded by the entire inner peripheral surface 23 i of the mounting hole 23 of the first die 21. It is advantageous for uniformly heating the second die 22 formed of a cemented carbide in which a hard phase is dispersed in a matrix phase. The heating source 7 is automatically controlled with respect to the set temperature so that the die 2 heated by the heating source 7 can be automatically maintained at the set temperature or a temperature in the vicinity thereof.

  Next, the die 2 heated in a state of being separated from the steel material drawing die device 1 based on the heating source 7 is fitted into the recess 31 of the case 3. Next, the cover 5 is attached to the case 3 via a fitting (not shown) (screw or the like) so that the cover 5 is applied to the tip wall surface 38 of the case 3. The die 2 whose temperature is thereby increased is assembled to the steel material drawing die device 1. Next, the steel material W is moved in the direction of the arrow WA to start the steel material drawing process, so that the steel material W is passed through the die hole 20 along the length direction of the steel material W and the drawing process is performed.

  Thus, according to the present embodiment, it is possible to use the die 2 that has been heated to an appropriate temperature range and thermally expanded in the radial direction from the beginning of the drawing process. For this reason, the amount of thermal expansion of the dimension of the dice 2 in the radial direction can be optimized from the beginning of the drawing process. As a result, the variation in the outer diameter of the steel material can be reduced from the beginning of the drawing process, and the outer diameter of the steel material can be stabilized. Examples of the steel material that allows the die 2 to pass through include a steel bar and a wire, and a wire for cold forging. Examples of the steel material include carbon steel, alloy steel, ordinary steel, and free-cutting steel.

  FIG. 4 shows the test results. In this test, the temperature Ttarget of the die 2 during the drawing process is set to 100 ° C. A steel material group consisting of a plurality of steel materials is prepared. Then, prior to starting the drawing of the steel material with the die 2, that is, prior to the start of the drawing process, the die 2 was detached from the steel material drawing die device 1. The die 2 thus separated is placed on the heating surface 70 of the heating source 7, and in this state, the temperature of the die 2 is set to a temperature range of 80% with respect to the temperature Ttarget of the die 2 at the time of drawing processing. The die 2 was heated to 80 ° C. by induction heating. The heating time was 2-5 minutes, especially 3 minutes.

  In FIG. 4, the horizontal axis indicates the number of steel materials that have been drawn, and the vertical axis indicates the outer diameter after drawing. A characteristic line W1 represented by a cross indicates a conventional example. A characteristic line W2 represented by a circle indicates an example. The steel material was STKM13B. The drawing process was performed while oiling the steel.

  As shown by the characteristic line W1, according to the conventional example, since the amount of thermal expansion in the radial direction of the die 3 is not always sufficient at the initial stage of the drawing process, the outer diameter of the steel material is determined in the middle and final stages of the drawing process. It can be made smaller than the outer diameter dimension of the steel material formed in this. According to such a conventional example, when observing from the initial stage to the final stage in the drawing process, the outer diameter dimension of the steel material is improved, but the outer diameter dimension tends to vary. On the other hand, according to this test example, as shown by the characteristic line W2, when observing from the initial stage to the final stage in the drawing process, the variation in the outer diameter dimension is suppressed to be small, and the outer diameter dimension of the steel material is highly accurate. It was converted. According to the present embodiment, when the steel material is in a pipe shape, a core metal (not shown) can be placed in a floating state in the die hole 20 of the die 2.

(Embodiment 2)
FIG. 5 shows a second embodiment. This embodiment has basically the same configuration and the same function and effect as the first embodiment. Hereinafter, the description will focus on the different parts. The steel material drawing die device 1B covers a drawing die 2 having a die hole 20 through which a steel material passes, a case 3 having a recess 31 into which the die 2 is fitted, and a tip opening 30 of the recess 31 of the case 3. As described above, the cover 3 for fixing the die 2 that is fixed to the case 3 and fitted in the recess 31 of the case 3 to prevent the die 2 from coming off, and the heating source 7 for heating the die 2 are provided. Thus, the heat source 7 is incorporated in the steel material drawing die apparatus 1B. The heating source 7 is formed of an induction coil built in the case 3 so as to be coaxial with the central axis P. The heating source 7 is automatically controlled with respect to the set temperature by the control unit, and the die 2 can be automatically maintained at the set temperature or a temperature in the vicinity thereof. A direction perpendicular to the axis perpendicular to the central axis P of the die hole 20 is indicated by an arrow PD. In the arrow PD, the heating source 7 is disposed at a position where it does not overlap the die 2. That is, when the die 2 is projected in parallel with the central axis P, the projection area of the die 2 is indicated as SD in the arrow PD. As shown in FIG. 5, in the arrow PD, the heating source 7 is disposed on the outer peripheral side of the projection area SD of the dice 2 so as not to overlap the projection area SD of the dice 2. For this reason, in a drawing process, it is suppressed that the drawing weight which acts on the die | dye 2 acts on the heating source 7 directly, and it is suppressed that the heating source 7 is damaged by a drawing load. During the drawing process, the drawing load is basically applied to the flat bottom wall surface 36 of the recess 31 of the case 3, but is not easily applied to the ring-shaped tip wall surface 38 of the die 2. As described above, since the heating source 7 is built in the steel material drawing die apparatus 1B, the die 2 can be rapidly heated without removing the die 2 from the case 3. Although the heating source 7 is turned on prior to the drawing process, it is preferable to turn off the heating source 7 during the drawing process. However, in some cases, even in the middle of the drawing process, if the temperature of the die 2 is low and the process is in the initial stage, the heating source 7 can be turned on to transfer heat from the heating source 7 to the die 2. In this case, the calorific value per unit time can be made smaller than the calorific value per unit time of the heating source 7 before the start of the drawing process.

(Embodiment 3)
FIG. 6 shows a third embodiment. This embodiment has basically the same configuration and the same operation and effect as the first and second embodiments. Hereinafter, the description will focus on the different parts. The steel material drawing die device 1 </ b> C includes a drawing die 2 having a die hole 20 through which a steel material passes, a case 3 having a recess 31 for fitting the die 2, and a die fitted in the recess 31 of the case 3. 2 is provided with a covering cover 5 that prevents detachment 2 and a heating source 7 that heats the die 2. The covering cover 5 is fixed to the tip wall surface 38 of the case 3 so as to cover the tip opening 30 of the recess 31 of the case 3, and faces the die 2 from the upstream side of the die 2. (See FIG. 6). Thus, the heat source 7 is incorporated in the steel material drawing die apparatus 1C. That is, the heating source 7 is formed of an induction heating coil disposed around the central axis P, and is disposed on the facing surface 50 side facing the die 2 in the covering cover 5. When the heating source 7 is energized, the die 2 is heated by the heating source 7. In this case, the first die 21 of the die 2 is heated by induction heating, and heat is transferred to the second die 22 surrounded by the first die 21 so that the second die 22 is heated. The heating source 7 is automatically controlled by the control unit with respect to the set temperature, and the die 2 can be automatically maintained at the set temperature or a temperature in the vicinity thereof. Since the heater heating source 7 is built in the steel material drawing die device 1 </ b> C, the die 2 can be heated quickly without removing the die 2 from the case 3. During the drawing process, basically, the drawing load is applied to the concave bottom wall surface 36 (see FIG. 6) of the concave portion 31 of the case 3 and is not applied to the covering cover 5. Therefore, as shown in FIG. 6, if the heating source 7 is attached to the covering cover 5, damage to the heating source 7 due to the drawing load can be suppressed, and the durability of the heating source 7 can be improved and the life can be extended. It can be planned. As shown in FIG. 6, the heating source 7 provided in the cover 5 directly faces the tip surface 200 of the die 2, and thus can effectively heat the die 2.

  Although the heating source 7 is turned on prior to the drawing process, it is preferable to turn off the heating source 7 during the drawing process. However, in some cases, even during the drawing process (after passing the steel material through the die 2), if the temperature of the die 2 is low, the heating source 7 is turned on and the die is turned from the heating source 7 to the die. 2 can also be used for heat transfer. In this case, the calorific value per unit time can be made smaller than the calorific value per unit time of the heating source 7 before the start of the drawing process.

(Embodiment 4)
FIG. 7 shows a fourth embodiment. The present embodiment has basically the same configuration as Embodiments 2 and 3 using the steel material drawing die devices 1B and 1C on which the heating source 7 is mounted, and has the same functions and effects. The horizontal axis in FIG. 7 indicates time, and the vertical axis indicates the temperature of the die 2. First, a steel material group composed of a plurality of steel materials having a predetermined length is prepared. Examples of the steel material include a steel bar, a wire, and a wire for cold forging. Examples of the steel material include carbon steel, alloy steel, ordinary steel, and free-cutting steel.

  Let Ttarget be the temperature of the die 2 during the drawing process. The temperature Ttarget can be appropriately set according to the material of the steel material, the area reduction rate, etc., and is set within a range of 70 to 120 ° C., for example, 100 ° C. However, it is not limited to this. N1 indicates the first drawing process in which the first steel material (1-2 tons) is passed through the die 2. N2 represents the second drawing process in which the second steel material (1 to 2 tons) of the same steel type and size is passed through the die 2. N3 indicates a third drawing process in which a third steel material (1 to 2 tons) of the same steel type and size is passed through the die 2. N4 indicates a fourth drawing process in which a fourth steel material (1 to 2 tons) of the same steel type and size is passed through the die 2. Thereafter, a plurality of drawing processes are performed in the same manner.

First, before the start of the first drawing N1 in which the first steel material is passed through the die 2, the die 2 before the drawing is in a normal temperature range. Prior to the start of the first drawing N1, the heating source 7 is turned on. Thus, based on the characteristic line _{T 1,} automatically raising the temperature of the die 2, the temperature Ta in the range of about 80 to 98% with respect to the temperature Ttarget of the die 2 during a drawing process (Ta <Ttarget) Let When the die 2 reaches the temperature Ta, the control unit automatically turns off the heating source 7. Thus, in order to heat the temperature of the die 2 to an appropriate temperature range prior to the start of the first drawing process N1, in the first drawing process N1, the outer diameter dimension of the steel material is changed from the start initial α1. Variations can be reduced.

If completed the first drawing processing N1, since the generation of frictional heat between the steel and the die 2 is eliminated, the temperature of the die 2 is lowered on the basis of the characteristic line T _2, the temperature is TR _1. However, prior to the start of the second drawing N2, the control unit turns on the heating source 7 mounted on the steel material drawing dies 1B and 1C again. When the heating source 7 is turned on, the heating source 7 automatically rises to a set temperature. Automatic Thereby, the die 2, based on the characteristic line _{T 3,} 80 to 100% approximately with respect to the temperature Ttarget of the die 2 during a drawing process, or, to a temperature Tb (Tb <Ttarget) of about 80 to 99% The temperature is increased. Temperature Tb is preferably located between the temperature TR ₁ and the temperature Ttarget. When the die 2 reaches the temperature Tb, the control unit automatically turns off the heating source 7. As described above, when the second drawing process N2 is performed, since the temperature of the die 2 is automatically heated to an appropriate temperature range from the initial start α2, the variation in the outer diameter of the steel material is reduced from the initial start. it can.

If the second round of drawing processing N2 is terminated, the temperature of the die 2 is lowered on the basis of the characteristic line T _4, the temperature becomes TR _2. However, prior to the start of the third drawing process N3, the control unit turns on the heating source 7 mounted on the steel material drawing dies 1B and 1C again. When the heating source 7 is turned on, the heating source 7 automatically rises to a set temperature. Thus the die 2 on the basis of the characteristic line _{T 5,} is automatically heated to a temperature Tc (Tc <Ttarget) of about 80 to 99% with respect to the temperature Ttarget of the die 2 during a drawing process. Temperature Tc is preferably located between the temperature TR ₂ and the temperature Ttarget. For this reason, in the third drawing process N3, the variation in the outer diameter of the steel material can be reduced from the initial start α3.

If the third drawing processing N3 is terminated, the temperature of the die 2 is lowered on the basis of the characteristic line T _6, the temperature becomes TR _3. However prior to the start of the fourth drawing process N4, steel drawing die apparatus 1B, the heat source 7 mounted on the 1C, die 2 is based on the characteristic line T _7, the temperature of the die 2 during a drawing process The temperature is raised to a temperature Td (Td <Ttarget) of about 80 to 99% with respect to Ttarget. Temperature Td is preferably located between the temperature TR ₂ and the temperature Ttarget. For this reason, in performing the fourth drawing process N4, it is possible to reduce the variation in the outer diameter of the steel material from the start initial α4. The same applies to the fifth drawing, the sixth drawing, and so on.

  Thus, according to the steel material drawing die apparatuses 1B and 1C in which the heating source 7 is integrally mounted, it is not necessary to perform the operation of detaching the heating source 7 from the steel material drawing dice apparatuses 1B and 1C each time. . For this reason, when continuously drawing a plurality of steel materials, the temperature of the die 2 can be maintained in an appropriate temperature range by the control unit from the initial stage α1, α2, α3, α4 of each drawing process. Variations can be reduced.

  The temperature rising form of the conventional example is shown as a broken line in FIG. According to the conventional example, since the temperature of the die 2 is not sufficiently increased at the initial start α1 of the first drawing N1, the variation in the outer diameter of the steel material is likely to occur. At the initial start α2 of the second drawing process N2, since the temperature of the die 2 is not sufficiently increased, the outer diameter of the steel material is likely to vary. In the initial start α3 of the third drawing process N3, since the temperature of the die 2 is not sufficiently increased, the outer diameter of the steel material is likely to vary. In the initial start α4 of the fourth drawing process N4, the temperature of the die 2 is not sufficiently increased, so that the outer diameter of the steel material is likely to vary. According to this embodiment, in order to suppress variations in the outer diameter of the steel material, a relationship of Ta = Tb = Tc = Td... Or a relationship of Ta≈Tb≈Tc≈Td. Ta, Tb, Tc, and Td can be as close as possible to the temperature Ttarget.

  In some cases, when the area reduction rate of the drawing process is large and the frictional heat of the drawing process is large, a relationship of Ta <Tb <Tc <Td. When the heat radiation per unit time of the die 2 is large, a relationship of Ta> Tb> Tc> Td. It should be noted that the degree of temperature increase and decrease indicated by the vertical axis in FIG. 7 is exaggerated for clarity. The present embodiment shown in FIG. 7 is merely an embodiment, and the present invention is not limited to this temperature raising mode. Although the weight of the steel material drawn by one time is set to 1 to 2 tons, it is not limited to this. Also in this embodiment, the apparatus shown in FIGS. 1, 2, 5, and 6 can be used.

(Embodiment 5)
This embodiment basically has the same configuration and the same operation and effect as the above-described fourth embodiment. However, according to the present embodiment, the temperatures Ta, Tb, Tc, and Td at the time of drawing are set in consideration of the outside air temperature, the heat dissipation to the outside air, and the like. In this case, while maintaining the relationship of Ta, Tb, Tc, and Td <Ttarget, when the outside air temperature is high, such as in a very hot region or summer, compared to when the outside air temperature is low, such as in a cold region or winter. The temperatures Ta, Tb, Tc, and Td during the drawing process can be made relatively low by Δα (for example, within a range of 0.3 to 3 ° C. and 1/100 to 1/10 with respect to the outside air temperature ° C.). . Further, while maintaining the relationship of Ta, Tb, Tc, Td <Ttarget, when the outside air temperature is low, such as in the winter, compared to when the outside air temperature is high, such as in the summer, the temperature Ta, Tb, Tc, and Td can be relatively increased by Δβ (for example, 0.3 to 3 ° C.). Also in this embodiment, the apparatus shown in FIGS. 1, 2, 5, and 6 can be used.

(Other)
In each embodiment, the heating source 7 may be a system in which the temperature of the die is raised by energization heating in which the die 2 is directly energized, instead of a method in which the die 2 is heated by induction heating. When the steel material is in a pipe shape, a core metal (not shown) can be placed in a floating state in the die hole 20 of the die 2. Prior to the start of drawing, the temperature of the die may be raised in advance to, for example, a temperature range of 80% to 100% and a temperature range of 90% to 95% with respect to the temperature range of the die at the time of drawing. it can. The present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within the scope not departing from the gist.

  1 is a steel material drawing die device, 2 is a die, 20 is a die hole, 21 is a first die, 22 is a second die, 23 is a mounting hole, 3 is a case, 30 is a tip opening, 31 is a recess, and 33 is a bottom portion , 35 is an outer peripheral portion, 4 is a frame, 5 is a covering cover, 7 is a heating source, and 70 is a heating surface.

Claims (4)

A step of preparing a steel material group composed of a plurality of steel materials having a predetermined length, and a steel material drawing die device for holding a drawing die having a die hole through which the steel material passes along the length direction; ,
A steel material drawing method for carrying out a drawing process of drawing a steel material of a steel group through a die hole of a die,
Prior to starting drawing of steel members of a steel group with a die, the die is heated by a heating source, and the temperature of the die is set to the temperature range of the die during drawing or the temperature range of the die during drawing. The temperature of the steel material is increased to a temperature range of 70% to 100%, and after the temperature increase operation, the steel material is started to be drawn, thereby stabilizing the outer diameter of the steel material from the beginning of the drawing process. A steel material drawing method characterized by comprising: In claim 1, the heating source is separated from the steel material drawing die device,
The temperature raising operation is an operation in which the die is heated by a heating source separated from the steel material drawing die device in a state where the die is separated from the steel material drawing die device, and then the heated die is a steel material drawing processing device. The steel material drawing method characterized by being implemented by operation attached to. It has a drawing die having a die hole through which a steel material passes, a case having a recess for fitting the die, and a heating source for heating the die,
The heating source is arranged at a position that does not overlap with the die in a direction perpendicular to the axis perpendicular to the central axis of the die hole so as to suppress the drawing load in the drawing process from acting on the heating source. Die device for drawing steel.   Covers the die for drawing with a die hole through which the steel material passes, a case with a recess for fitting and holding the die from the tip opening, a heating source for heating the die, and the tip opening of the case recess A steel material drawing die apparatus, comprising: a covering cover that is fixed to a case and that prevents a die fitted in a recess of the case from coming off; and a heating source is disposed on the covering cover.

Images