JP5402865B2 - Mouth drawing apparatus and mouth drawing method for steel pipe end - Google Patents

Description

  The present invention relates to a drawing apparatus and a drawing method for performing drawing on an end of a steel pipe. More specifically, the equipment cost can be reduced, and temperature variations occurring at the end of a heated steel pipe The present invention relates to a mouth-drawing apparatus and a mouth-drawing method for a steel pipe end that can reduce the above-mentioned and obtain good mouth-drawing performance.

  When a cold drawing process is performed on a steel pipe, a mouth drawing process is performed on the steel pipe to squeeze the end portion in the previous process. In the cold drawing process, the die is set in a state in which the mouth restricting portion of the steel pipe is passed through the die, and then the mouth restricting portion is pulled out and finished into a steel pipe having a predetermined size by a tool such as a die or a plug. The mouth restrictor used in this manner is generally formed by connecting a straight portion having a constant outer diameter to a tapered portion having a smaller outer diameter toward the tube end. In addition, the aperture stop portion may be formed by providing only a tapered portion whose outer diameter decreases toward the tube end.

  In the squeezing process to form such a squeezed part, depending on the dimensions of the steel pipe and the pressure applied by the squeezing machine, the end part of the steel pipe is heated after the end part is heated, and the end part of the steel pipe is heated. In some cases, the squeezing process is performed at room temperature without performing the process.

  FIG. 1 is a diagram showing the relationship between the dimensions of a steel pipe and the applied pressure (kN) applied to the end of the steel pipe at the time of mouth drawing at normal temperature. It is a value obtained by multiplying the thickness (mm) of the steel pipe before processing. Here, the outer diameter ratio is obtained by dividing the minimum outer diameter (mm) of the aperture portion of the steel pipe after the aperture drawing by the outer diameter (mm) of the steel tube before the aperture drawing. Further, the minimum outer diameter of the mouth restrictor is the outer diameter of the straight part when the mouth restrictor is formed by connecting the straight part to the taper part, and the mouth restrictor is formed by providing only the taper part. The case is the outer diameter of the narrowed tube end. The applied pressure applied to the steel pipe end shown in the figure was measured with a pressure gauge provided in the aperture drawing machine when the aperture drawing was performed. At this time, the material of the steel pipe was mainly austenitic stainless steel.

  Usually, the maximum pressing force that can be applied by a squeezer is about 1000 kN, and squeezing cannot be performed at room temperature when it is necessary to apply a pressing force that exceeds the maximum pressing force. In this case, heating the end portion of the steel pipe reduces the applied pressure required for the squeezing process. Therefore, the squeezing process is performed after the end part of the steel pipe is heated. When using a squeezing machine with a maximum pressure of 1000 kN, as shown in FIG. 1, under the dimensional condition of the steel pipe where the required pressure exceeds 1000 kN, the squeezing process is performed after heating the end of the steel pipe. Under the dimensional condition of the steel pipe that is squeezed at a pressure of 1000 kN or less, the squeezing process is performed at room temperature without heating the end of the steel pipe.

  When subjecting the end of the steel pipe to squeezing, an end portion of the heated steel pipe may have a higher or lower temperature portion than the target heating temperature. If such temperature variation occurs and the variation is large, the steel pipe may not be processed into a desired shape during the squeezing process, or cracks and internal voids may be generated in the squeezed part of the steel pipe. For this reason, when heating the end of a steel pipe, it is required to reduce the temperature variation that occurs.

  Various proposals have conventionally been made regarding methods for heating the ends of steel pipes, such as Patent Documents 1 to 3. Patent Documents 1 to 3 relate to a method of heating the end portion of the steel pipe before the abset processing in which the end portion of the steel pipe is thickened to secure a thread cutting allowance. Patent Document 1 is an apparatus that heats an end of a steel pipe while being conveyed, and is a burner type that can uniformly heat the end of a steel pipe on the exit side of an induction heating apparatus that enables rapid heating of the end of the steel pipe. A heating apparatus provided with a heating furnace has been proposed.

  In patent document 1, it is supposed that it can heat uniformly in a short time by using together the induction heating apparatus which can be heated rapidly, and the burner type heating furnace which can be heated uniformly. However, in the heating apparatus proposed in Patent Document 1, it is necessary to provide an induction heating apparatus and a burner type heating furnace, and the equipment cost becomes a problem.

  In Patent Document 2, when the end of a steel pipe is heated, the inner surface temperature of the end of the steel pipe is scanned in the longitudinal direction using a radiation thermometer, and the material to be heated is measured according to the measurement result. There has been proposed a method for controlling the heating of the end of a steel pipe that controls the amount of heat input from a plurality of heating sources arranged along the longitudinal direction.

  In the steel pipe end heating control method proposed in Patent Document 2, the inner surface temperature of the steel pipe end is scanned in the longitudinal direction and measured using a radiation thermometer. Thereby, the heating control method of the steel pipe end part proposed in Patent Document 2 reduces the influence of the scale and the surface cooling and increases the temperature of the steel pipe end part with high accuracy compared to the case of measuring the outer surface temperature of the steel pipe after heating. As a result, the temperature of the heated steel pipe end can be controlled with high accuracy. However, in the heating control method for the steel pipe end portion proposed in Patent Document 2, a plurality of heating sources are provided along the longitudinal direction of the material to be heated, and the amount of input heat is adjusted for each heating source, so the control is complicated. In addition, a plurality of control devices are required. For this reason, a heating apparatus becomes complicated and equipment cost tends to be a problem.

  In Patent Document 3, when the end of a steel pipe is induction-heated, the steel pipe end that makes the induction heating device move forward or backward to moderate the temperature gradient of the part that moves from the heated steel pipe end to the non-heated part. A heating method has been proposed. In the heating method of the steel pipe end portion proposed in Patent Document 3, it is possible to prevent the scale from being formed on the outer surface of the steel pipe and to reduce the set by the formed scale, as compared with the case where the burner type heating and the induction heating are used together. It is said that wrinkles can be prevented during processing.

  Moreover, in patent document 3, the curvature of the part which a taper part rises from a main body at the time of an abset process can be enlarged by loosening the temperature gradient of the part which transfers to the part which is not heated from the edge part of the heated steel pipe. It is said. However, in the heating method of the steel pipe end part proposed in Patent Document 3, temperature variations occurring at the end part of the heated steel pipe are not studied.

JP 58-107245 A JP 59-197324 A JP-A-6-31369

  As described above, when mouth drawing is performed after the end of the steel pipe is heated, it is required to reduce the temperature variation generated at the end of the heated steel pipe. If the end of the steel pipe is heated after the end of the steel pipe is heated by the conventional method of heating the end of the steel pipe, the end of the steel pipe can be heated uniformly, but the heating device becomes complicated and the equipment cost is a problem. Become.

  The present invention has been made in view of such a situation, and can reduce equipment costs, reduce temperature variations occurring at the end of a heated steel pipe, and obtain good squeezing performance. It is an object of the present invention to provide a mouth drawing device and a mouth drawing method for a steel pipe end.

  In order to solve the above problems, the present inventors have studied the temperature condition of the steel pipe end portion that can obtain good squeezing performance. As a result, satisfactory squeezing performance is obtained by satisfying the condition that the minimum temperature of the heated steel pipe end is 800 ° C. or higher and the temperature difference generated in the steel pipe end is 100 ° C. or lower. I found out. Moreover, when a part exceeding the melting temperature of 1300 ° C. occurs at the end of the steel pipe during heating, the steel pipe bends, resulting in a product defect. Therefore, the maximum temperature at the end of the steel pipe is set to 1300 ° C. or lower. There is a need.

  In order to satisfy the above temperature condition when the end portion of the steel pipe is heated using a heating apparatus by induction heating capable of rapid heating, the present inventors take out the induction heated steel pipe from the heating apparatus and allow to cool at room temperature. A basic test was conducted. In the basic test, one steel pipe was induction-heated to a position of 300 mm from the pipe end, the frequency was 17 Hz, the input power was 25 kW, and the heating time was 10 minutes. Further, a steel pipe made of SUS304TP stainless steel defined by JIS and having an outer diameter of 63 mm and a wall thickness of 8 mm was used.

  In the basic test, the temperature was measured at a position 5 mm from the tube end and a position 200 mm from the tube end. This is because when the end of the steel pipe is induction-heated, the range from the pipe end to about 10 mm tends to become high at the end of the steel pipe.

  FIG. 2 is a diagram showing the relationship between the heating time and the temperature at the end of the steel pipe in a basic test in which one steel pipe is heated by induction heating. As shown in the figure, at a position 5 mm from the end of the steel pipe, the temperature increased by induction heating and reached 1200 ° C. when the heating was completed, whereas at a position 200 mm from the end of the steel pipe, induction was performed. The temperature rose due to heating and reached 1000 ° C. when the heating was completed, and the temperature difference in the end of the steel pipe was 200 ° C. Thereafter, by cooling at room temperature, the temperature decreased at both the position 5 mm from the end of the steel pipe and the position 200 mm from the end of the steel pipe, and reached about 800 ° C. after about 45 seconds from the completion of heating, eliminating the temperature difference.

  As a result of examining the test results, the present inventors have found that if the temperature difference in the steel pipe end is set to 200 ° C. or less when the heating is completed, the temperature difference in the steel pipe end can be reduced to 100 ° C. or less in a short time. I found it. That is, in the squeezing device, if the temperature difference in the steel pipe end when heating is completed is 200 ° C. or less, the time required for transporting from the heating device to the squeezer is adjusted and allowed to cool. It has been found that squeezing can be performed by setting the temperature difference in the end portion of the steel pipe to 100 ° C. or less without using a special soaking equipment such as a burner type heating furnace.

Next, the present inventors have introduced the steel pipe dimensions such as the outer diameter and thickness of the steel pipe before the squeezing process, the minimum outer diameter of the squeezed part of the steel pipe after the squeezing process, and the power supplied to the heating device by induction heating. We examined the relationship. At the end of the steel pipe where induction heating for 10 minutes was completed, the electric power supplied to the heating device having a maximum temperature of 1300 ° C. or less and a temperature difference of 200 ° C. or less was investigated while changing the dimensions of the steel pipe.
The dimensions of the steel pipe used in this study were as follows.
Steel pipe 1: outer diameter 60.5mm before squeezing, wall thickness 8.7mm, minimum squeezed diameter 45mm
Steel pipe 2: 76 mm outer diameter before squeezing, 10.2 mm wall thickness, 50 mm minimum outer diameter of squeezed part
Steel pipe 3: outer diameter 70 mm before squeezing, wall thickness 14 mm, minimum squeezed diameter 50 mm
Steel pipe 4: Outer diameter 70 mm before squeezing, wall thickness 16.7 mm, minimum squeezed diameter 50 mm

FIG. 3 is a diagram showing the relationship between the dimensions of the steel pipe and the electric power supplied to the heating device. The dimension of the steel pipe on the horizontal axis is a value obtained by multiplying the outer diameter ratio by the thickness (mm) of the steel pipe before squeezing. It is. As shown in the figure, the present inventors have found that the value X obtained by multiplying the outer diameter ratio by the thickness (mm) and the electric power Y input to the heating device have a linear relationship of the following expression (3). did. That is, by adjusting the electric power supplied to the heating device according to the value obtained by multiplying the outer diameter ratio by the wall thickness, the maximum temperature is 1300 ° C. or less and the temperature difference is 200 ° C. at the end of the heated steel pipe. We found out that we can:
Y = 4.3 × X + 76 (3)

  Furthermore, the present inventors examined the relationship between the dimensions of the steel pipe and the cooling time required for the temperature difference to become 100 ° C. or less after the heating was completed. The steel pipe whose end is induction-heated for 10 minutes is allowed to cool, and a cooling time that satisfies the conditions that the maximum temperature is 1300 ° C. or lower, the minimum temperature is 800 ° C. or higher, and the temperature difference is 100 ° C. or lower is determined. The investigation was conducted while changing the dimensions. In this investigation, the steel pipes 1 to 4 were used, and the electric power supplied to the heating device was adjusted to the value calculated by the above equation (3).

FIG. 4 is a diagram showing the relationship between the dimension of the steel pipe and the time of cooling after the heating is completed. The dimension of the steel pipe on the horizontal axis is the thickness (mm) of the steel pipe before mouth drawing in the outer diameter ratio. It is the multiplied value. As shown in the figure, the present inventors have found that the value X obtained by multiplying the outer diameter ratio by the thickness (mm) and the cooling time T have a linear relationship of the following expression (4). That is, by adjusting the cooling time according to the value obtained by multiplying the outer diameter ratio by the wall thickness, the maximum temperature is 1300 ° C. or lower, the minimum temperature is 800 ° C. or higher, and the steel pipe end portion where the cooling time has elapsed. Any of the conditions where the temperature difference is 100 ° C. or less can be satisfied.
T = 6.6 × X−16 (4)

  The present invention has been completed on the basis of the above knowledge, and the following (1) and (2) steel pipe end drawing apparatus, and the following (3) and (4) steel pipe end drawing. The processing method is summarized as follows:

(1) A heating device capable of simultaneously inductively heating a plurality of materials to be heated, a conveyor that conveys an end of a steel pipe while heating the end of the steel pipe into the heating device, and an end of the conveyed steel pipe A squeezing machine for squeezing and squeezing, a squeezing and conveying device for conveying the steel pipe conveyed by the conveyor to the squeezing device, a basic input power calculated by the following equation (1), and the heating device A heating control means for adjusting the electric power supplied to the heating device in accordance with a value obtained by multiplying the number of steel pipes charged in the steel pipe, and when the mouth pipe is subjected to mouth drawing processing on the steel pipe whose end is heated And a cooling time control means for adjusting the cooling time required from the completion of heating by the heating device to the start of squeezing according to the time calculated by the following equation (2). Mouth drawing machine for steel pipe end.
W = 4.3 × (D2 / D1) × t + 76 (1)
T = 6.6 × (D2 / D1) × t−16 (2)
Here, W is the basic input power (kW), T is the time (s), D1 is the outer diameter (mm) of the steel pipe before squeezing, t is the wall thickness (mm) of the steel pipe before squeezing, D2 Is the minimum outer diameter (mm) of the aperture portion of the steel pipe after aperture drawing.

(2) If the conveyor is a steel pipe that needs to be heated before it is subjected to squeezing, the end of the steel pipe is loaded into the heating device and conveyed while being heated, and before the squeezing process is performed. In the case of a steel pipe that does not require heating, the end portion of the steel pipe is inserted into the heating device and conveyed without heating, and the mouth-drawing device for the steel pipe end portion according to (1) above.

(3) A steel pipe group in which the outer diameter and thickness of the steel pipe before the squeezing process and the minimum outer diameter of the squeezing part of the steel pipe after the squeezing process are the same is sequentially transported to the end of the transported steel pipe. A method of squeezing a steel pipe end that is squeezed by a squeezing machine, and when sequentially feeding the steel pipe group, a plurality of materials to be heated are charged into a heating device that can be induction heated at the same time. The power supplied to the heating device is multiplied by the basic input power calculated by the following formula (1) and the number of steel pipes charged in the heating device. The cooling time required from the completion of heating by the heating device to the start of the squeezing process when the squeezing process is performed on the end portion of the conveyed steel pipe is set as follows. (2) A steel pipe end that is adjusted according to the time calculated by the equation Mouth aperture processing method.
W = 4.3 × (D2 / D1) × t + 76 (1)
T = 6.6 × (D2 / D1) × t−16 (2)
Here, W is the basic input power (kW), T is the time (s), D1 is the outer diameter (mm) of the steel pipe before squeezing, t is the wall thickness (mm) of the steel pipe before squeezing, D2 Is the minimum outer diameter (mm) of the aperture portion of the steel pipe after aperture drawing.

(4) Steel pipe group in which the outer diameter and thickness of the steel pipe before squeezing are the same, and the minimum outer diameter of the squeezed part of the steel pipe after squeezing is the same, and heating is required before squeezing. The outer diameter and thickness of the steel pipe before the squeezing process, and the minimum outer diameter of the squeezed part of the steel pipe after the squeezing process, and a steel pipe group that does not require heating before the squeezing process, Is a method of squeezing the end of the steel pipe that is subjected to squeezing with a squeezing machine, and when squeezing the steel pipe group that requires heating, When the steel pipe group that does not need to be heated is subjected to a drawing process using the method for drawing a steel pipe end as described in (3) above, the steel pipes are sequentially conveyed without being inserted into the heating device. A method of squeezing the end of a steel pipe, characterized in that squeezing is performed on the end of the conveyed steel pipe.

The steel pipe end portion squeezing apparatus and the squeezing method of the present invention have the following remarkable effects.
(1) By adjusting the basic input power to be input to the heating device and the cooling time required for transporting from the heating device to the mouth drawing device according to the dimensions of the steel pipe, it is possible to reduce the temperature variation generated at the end of the steel pipe. .
(2) Since the end portion of the steel pipe with reduced temperature variation is squeezed, good mouth-drawing performance can be obtained.
(3) Since the temperature variation generated at the end of the steel pipe can be reduced without using a special soaking equipment such as a burner type heating furnace or a feedback control device using a radiation thermometer, the equipment cost can be suppressed.

It is a figure showing the relationship between the size of the steel pipe and the applied pressure (kN) applied to the end of the steel pipe when the drawing process is performed at normal temperature. The dimension of the steel pipe on the horizontal axis is the steel pipe before the drawing process in the outer diameter ratio. It is a value multiplied by the wall thickness (mm). It is a figure which shows the relationship between the heating time and the temperature of a steel pipe edge part in the basic test which heats one steel pipe by induction heating. It is a figure which shows the relationship between the dimension of a steel pipe, and the electric power input into a heating apparatus, and the dimension of the steel pipe of a horizontal axis is the value which multiplied the wall thickness (mm) of the steel pipe before a squeezing process to an outer diameter ratio. It is a figure which shows the relationship between the dimension of a steel pipe and the time to cool after completion of heating. The dimension of the steel pipe on the horizontal axis is a value obtained by multiplying the outer diameter ratio by the thickness (mm) of the steel pipe before squeezing. is there. It is a schematic diagram explaining the example of a squeezing process by the squeezing apparatus and the squeezing process method of the steel pipe end part of this invention. It is a figure explaining an example of the squeezing process flow by the squeezing apparatus and squeezing process method of the steel pipe end part of this invention, The figure (a) is the state which inserted the steel pipe which needs a heating in the heating apparatus. (B) is a state in which two steel pipes that need to be heated are inserted into a heating device, (c) is a state in which the steel pipe that needs to be heated is transported to a wringer, and (d) in FIG. The state in which the steel pipe that does not require heating is conveyed by the conveyor, and FIG. 9E shows the state in which the end of the steel pipe that does not require heating is conveyed to the aperture drawing machine.

  Below, the aperture drawing apparatus and aperture drawing method of a steel pipe edge part are demonstrated based on drawing.

  FIG. 5 is a schematic diagram for explaining an example of the squeezing process by the squeezing apparatus and the squeezing method for the end of the steel pipe according to the present invention. The figure shows an inspection table 2 used for dimensional measurement and surface quality inspection of a steel pipe that is subjected to squeezing at the end of the steel pipe, a squeezing device 1, and a rack 3 for storing the steel pipe whose end is squeezed. Show. The mouth drawing apparatus 1 shown in the figure includes a first aligning device 11 in which a steel pipe that has passed inspection is inserted and aligns the pipe end positions of the steel pipe, and a heating apparatus that can simultaneously inductively heat a plurality of materials to be heated. 12, a conveyor 13 that feeds and heats the end of the steel pipe into the heating device 12, a squeezing machine 14 that squeezes the end of the conveyed steel pipe to perform squeezing, and a conveyor. The steel pipe is transported to the mouth-drawing machine, and the mouth-squeezing transport device 15 for transporting the steel pipe whose end is squeezed by the mouth-squeezing machine, and the pipe end position of the steel pipe whose end is squeezed are aligned and transported to the rack 3. And a second aligning device 16.

  In the squeezing apparatus 1 shown in the figure, the squeezing machine 14 forms a squeezed portion 4a by connecting a straight portion 4c having a constant outer diameter to a tapered portion 4b whose outer diameter decreases toward the pipe end. To do.

  Furthermore, the squeezing apparatus 1 shown in the figure includes a heating control means 17 for adjusting the electric power supplied to the heating device 12, and a cooling time required for starting the squeezing process after the heating by the heating apparatus is completed. And a cooling time control means 18 for adjusting the temperature. In the squeezing apparatus 1 shown in the figure, the steel pipe is conveyed in the direction indicated by the black arrow.

The heating control means 17 adjusts the electric power supplied to the heating device 12 according to the basic input power calculated by the following equation (1) and the number of steel pipes charged in the heating device 12.
W = 4.3 × (D2 / D1) × t + 76 (1)
Here, W is the basic input power (kW), D1 is the outer diameter (mm) of the steel pipe before squeezing, t is the thickness (mm) of the steel pipe before squeezing, and D2 is the steel pipe after squeezing. This is the minimum outer diameter (mm) of the mouth restrictor.

  In the above formula (1), the value X obtained by multiplying the outer diameter ratio by the wall thickness in the above formula (3), the outer diameter D1 and the thickness t of the steel pipe before the squeezing process, and the steel pipe after the squeezing process. This is expressed using the minimum outer diameter D2 of the aperture stop.

  Using the above equation (1), the basic input power is calculated according to the dimensions of the steel pipe, such as the outer diameter and thickness before squeezing, and the minimum outer diameter of the squeezed part. Without causing a portion exceeding the temperature, induction heating can be performed with the temperature difference in the end portion of the steel pipe set to 200 ° C. or less. When the basic input power exceeds the value calculated by the above equation (1), a portion exceeding the melting temperature of 1300 ° C. occurs at the end of the heated steel pipe, and the steel pipe may be bent. On the other hand, if the basic input power is less than the value calculated by the above equation (1), the temperature difference generated in the end portion of the heated steel pipe exceeds 200 ° C., and the temperature difference is set to 100 or less by cooling. It takes time to reduce the productivity of the squeezing apparatus.

  Moreover, the heating control means 17 adjusts the electric power input into the heating device 12 according to the basic input electric power and the number of steel pipes charged in the heating device 12. As a result, when the number of steel pipes charged into the heating device increases when starting the squeezing process, or when the number of steel pipes charged into the heating device decreases when the squeezing process ends. However, induction heating can be performed by setting the temperature difference in the end of the steel pipe to 200 ° C. or less without causing a portion exceeding the melting temperature of 1300 ° C. at the end of the steel pipe.

  When adjusting the power input to the heating device 12 according to the basic input power and the number of steel pipes charged in the heating device 12, the heating device 12 is set to the basic input power calculated by the above equation (1). The electric power supplied to the heating device 12 can be adjusted to a value obtained by multiplying the number of steel pipes inserted into the heating device 12. The power input to the heating device is not limited to the value obtained by multiplying the basic input power by the number of steel pipes charged in the heating device 12, but the number of steel pipes charged in the heating device 12 to the basic input power. Even if it is adjusted to a range of ± 2% with respect to the multiplied value, the temperature difference in the end of the steel pipe is not more than 200 ° C. and induction heating is performed without causing the steel pipe end to exceed the melting temperature of 1300 ° C. Can do.

  In general, a heating apparatus capable of simultaneously heating a plurality of materials to be heated cannot set heating conditions such as input power for each steel pipe to be charged. For this reason, when processing steel pipes with different outer diameters and wall thicknesses before squeezing, and the minimum outer diameter of the squeezed part after squeezing, using a single squeezing machine, make the end of the steel pipe uniform. It becomes difficult to calculate the electric power supplied to the heating device 12 for heating. Although it is conceivable to simultaneously heat steel pipes having different dimensions by adopting a method in which a plurality of induction heating devices for heating the end portion of one steel pipe are provided and the electric power supplied to each heating device is adjusted. Since a plurality of heating devices are required, the equipment cost increases and becomes a problem. Therefore, in the squeezing apparatus and the squeezing method of the steel pipe end portion of the present invention, the steel pipe group having the same outer diameter and thickness before squeezing and the minimum outer diameter of the squeezing part is treated. .

The cooling time control means 18 is the cooling required for starting the squeezing after the heating by the heating device 12 is completed when the squeezing machine 14 performs the squeezing process on the steel pipe whose end is heated. The time is adjusted according to the time calculated by the following equation (2).
T = 6.6 × (D2 / D1) × t−16 (2)
Here, T is time (s), D1 is the outer diameter (mm) of the steel pipe before squeezing, t is the wall thickness (mm) of the steel pipe before squeezing, and D2 is the mouth of the steel pipe after squeezing. This is the minimum outer diameter (mm) of the throttle part.

  The above equation (2) is the value obtained by multiplying the outer diameter ratio by the wall thickness in the above equation (4), the outer diameter D1 and the wall thickness t of the steel pipe before squeezing, and the steel pipe after the squeezing process. This is expressed using the minimum outer diameter D2 of the aperture stop.

  When the cooling time is adjusted according to the time calculated by the above equation (2), the induction heated steel pipe has a temperature difference of 800 ° C. or more at the end of the steel pipe and a temperature difference in the end of the steel pipe due to cooling. It becomes 100 degrees C or less. If the cooling time exceeds the time calculated by the above equation (2), a portion that is less than 800 ° C. occurs at the end of the steel pipe, and the pressurizing force required for performing the drawing process increases. There is a risk of processing failure due to insufficient pressure. On the other hand, if the cooling time is less than the time calculated by the above equation (2), the temperature difference in the end of the cooled steel pipe exceeds 100 ° C., and the mouth drawing portion of the steel pipe subjected to mouth drawing processing. May cause cracks and internal voids.

  When adjusting the cooling time according to the time calculated by the equation (2), the cooling time can be adjusted to the time calculated by the equation (2). The cooling time is not limited to the time calculated by the equation (2), and the cooling time may be adjusted to a range of ± 4% with respect to the time calculated by the equation (2). The end of the steel pipe can be 800 ° C. or higher, and the temperature difference in the steel pipe end can be 100 ° C. or lower.

  In the squeezing apparatus shown in FIG. 5, the cooling time control means 18 increases / decreases the conveying speed of the squeezing / conveying device 15, and the time required for starting the squeezing after the heating by the heating device 12 is completed. Is adjusted according to the time calculated by the equation (2). In addition to this, as a method for adjusting the cooling time, the squeezing / conveying device 15 waits for a predetermined time from the time the steel pipe transferred by the conveyor is received until the transfer is started, and this waiting time is increased or decreased by the cooling time control means. The cooling time is adjusted, and a predetermined time is waited until the squeezing process is started after the steel pipe is transported to the squeezing machine 14, and the waiting time is increased or decreased by the cooling time control means. It is possible to adopt a method of adjusting

  As described above, the squeezing apparatus of the present invention adjusts the electric power supplied to the heating device 12 by the heating control means 17 in accordance with the basic input power calculated by the equation (1), and the cooling time control means 18. Adjusts the cooling time according to the time calculated by the equation (2). Thereby, the aperture drawing processing apparatus of this invention can carry out induction heating by making the edge part of a steel pipe into 800 degreeC or more and the temperature difference in a steel pipe end part to 100 degrees C or less.

  The squeezing apparatus of the present invention can reduce the temperature variation generated at the end of the steel pipe and heat it, so that good squeezing performance can be obtained. In addition, the squeezing apparatus of the present invention adjusts the time required for transporting the steel pipe from the heating device to the squeezing machine and cools it down, so a special soaking equipment such as a burner type heating furnace or a radiation thermometer is installed. It is not necessary to add the used feedback control device, and the equipment cost can be reduced.

  Here, in the squeezing apparatus, for example, after processing the steel pipe group that needs to be heated before the squeezing process, the steel pipe group that does not need to be heated may be processed before the squeezing process. In this case, when the squeezing apparatus shown in FIG. 5 is used, the steel pipe that does not need to be heated is conveyed to the squeezing machine 14 without being heated by the heating device 12, so that the steel pipe 4 is placed after the plurality of steel pipes that need to be heated. It is necessary to convey the steel pipe which does not require heating with a conveyor in a state where the interval for this is provided, and the productivity of the squeezing apparatus is reduced. The reason why the space is provided after the steel pipe that needs to be heated is that the ends of all the inserted steel pipes are heated in the heating device that simultaneously heats a plurality of materials to be heated. This is because it is not possible to charge steel pipes that are not required at the same time.

  For this reason, in the steel pipe end squeezing apparatus 1 according to the present invention, the conveyor 13 inserts the end of the steel pipe into the heating device 12 in the case of a steel pipe that requires heating before the squeezing process. In the case of a steel pipe that is transported while being heated and does not need to be heated before being subjected to the squeezing process, it is preferable to use a steel pipe that is loaded with the end of the steel pipe into the heating device 12 and transported without heating. Thereby, as will be described with reference to FIG. 6 described later, the steel pipe group that needs to be heated and the steel pipe group that does not need to be heated are alternately conveyed, and the end of the conveyed steel pipe is squeezed by a squeezer. When processing, it is not necessary to provide an interval at the conveyor 13, and the productivity of the mouth drawing device can be maintained.

  Next, an example of the squeezing process flow by the squeezing method for the end of the steel pipe of the present invention will be described. In this processing flow, a flow of processing a steel pipe group that does not require heating before the mouth drawing process after processing the steel pipe group that requires heating before the mouth drawing process will be described.

  FIG. 6 is a view for explaining an example of a drawing process flow by a drawing apparatus and a drawing method for an end of a steel pipe according to the present invention. FIG. 6 (a) shows a steel pipe that needs to be heated as a heating apparatus. Fig. 2 (b) shows a state where the steel pipes are charged. Fig. 2 (b) shows a state where two steel pipes that need to be heated are charged into the heating device. (D) shows the state which conveys the steel pipe which does not require heating with a conveyor, and the figure (e) shows the state which conveys the steel pipe end part which does not need heating to a wringer. In the figure, the inspection table 2 used for dimensional measurement and surface property inspection of the steel pipe that is subjected to squeezing at the end portion of the steel pipe, and the rack 3 for storing the steel pipe with the end portion being squeezed are omitted. Moreover, in the same figure, the steel pipe which does not require a heating is shown by giving hatching to the outer surface, and the flow of the steel pipe conveyed is shown by the black arrow.

  In the squeezing apparatus 1 shown in FIG. 6, the conveyor 13 conveys the steel pipe that needs to be heated before the squeezing process, while the end is inserted into the heating apparatus 12 and heated. In the case of a steel pipe that does not require heating before application, the end of the steel pipe is inserted into the heating device 12 and conveyed without heating. Moreover, the heating control means 17 adjusts the electric power input into the heating device 12 to a value obtained by multiplying the basic input electric power calculated by the equation (1) by the number of steel pipes inserted into the heating device 12. The cool-down time control means 18 adjusts the cool-down time to the time calculated by the equation (2) by increasing or decreasing the transport speed of the aperture stop transport device 15.

  Steel pipes whose dimensions such as inner diameter, outer diameter, and wall thickness are measured and whose surface properties are inspected are aligned by the first aligning device 11 and then conveyed by the conveyor 13. As shown to the figure (a), in the case of the steel pipe which needs a heating before a squeezing process, the conveyor 13 conveys, inserting the edge part of a steel pipe in the heating apparatus 12. FIG. At this time, the heating control means 17 adjusts the electric power supplied to the heating device 12 to a value obtained by multiplying the basic input electric power calculated by the equation (1) by the number of steel pipes charged. In the state shown in FIG. 5A, since the number of steel pipes charged in the heating device 12 is one, the power input to the heating device 12 is the value of the basic input power.

  Subsequently, when the steel pipe is supplied to the mouth drawing apparatus and a steel pipe of two steel pipes is inserted into the heating device 12 as shown in FIG. 5B, the heating control means 17 is put into the heating device 12. The electric power is adjusted to a value obtained by multiplying the basic input power calculated by the equation (1) by 2, which is the number of steel pipes charged in the heating device. Thus, the heating control means 17 adjusts the electric power input into the heating apparatus 12 according to the increase in the number inserted in the heating apparatus 12, and makes it increase in steps.

  As shown in FIG. 6C, when the heated steel pipe is transported and subjected to squeezing by the squeezing machine 14, the cooling time control means 18 increases or decreases the transport speed of the squeezing transport device, The cooling time required from the completion of heating to the start of squeezing is adjusted to the time calculated by the above equation (2). The steel pipe whose end has been squeezed is unloaded from the squeezing machine 14 by the squeezing / conveying device 15, and then the position of the pipe end is aligned by the second aligning device 16, and is unloaded to the rack and stored. Further, in the case shown in FIG. 5C, since the number of steel pipes charged in the heating device 12 does not increase or decrease, the power supplied to the heating device 12 is the basic input power. It is maintained at a value multiplied by 5 which is the number of.

  Sequentially, steel pipes that do not need to be heated (steel pipes that are hatched on the outer surface) are supplied to the mouth drawing machine, and as shown in FIG. The conveyor 13 loads a steel pipe that does not require heating into the heating device 12 and conveys it without heating. Thus, in the aperture drawing processing apparatus 1 shown in the figure, the conveyor 13 is heated by conveying a steel pipe that requires heating while conveying the steel pipe that does not require heating without being heated. When the steel pipe group that requires heating and the steel pipe group that does not require heating are alternately conveyed, and it is subjected to squeezing with the squeezing machine at the end of the transported steel pipe, there is no need to provide an interval at the conveyor 13, The productivity of the processing apparatus can be maintained.

  When a steel pipe that does not require heating is conveyed to the charging position of the heating device 12 by the conveyor, the heating control means 17 uses the basic input power calculated by the above equation (1) as the power input to the heating device 12. To 4 multiplied by the number of steel pipes charged in the heating device. Thus, the heating control means 17 adjusts the electric power input to the heating device 12 according to the decrease in the number inserted in the heating device 12, and decreases it stepwise.

  As shown in FIG. 5E, when a steel pipe that does not require heating is conveyed and subjected to squeezing by the squeezing machine 14, the squeezing is performed without controlling the cooling time.

  A test for evaluating the temperature at the end of the steel pipe when induction heating is completed, and a test for evaluating the temperature after the heated end of the steel pipe is allowed to cool. The mouth-drawing method was verified.

(1) Evaluation test upon completion of heating [Test method]
In this test, the end portion of the steel pipe was loaded into the heating device 12 using the conveyor 13 and conveyed while being heated by the aperture drawing apparatus shown in FIG. At that time, the outer surface temperature of the steel pipe end was measured at a position 5 mm from the pipe end and a position 200 mm from the pipe end.
The test conditions in this test were as follows.
Steel pipe: 70mm outer diameter before squeezing, 14mm wall thickness, 50mm minimum outer diameter of squeezed part
Material SUS304TP stainless steel heating conditions specified in JIS: Frequency 5.6 Hz, heating time 10 minutes

  The basic input power calculated by the equation (1) from the dimensions of the steel pipe used in this test is 119 kW. In Example 1 of the present invention, the basic input power calculated by the above equation (1) and the heating device are adjusted by adjusting the power supplied to the heating device to 117 kW multiplied by the number of steel pipes charged in the heating device. It adjusted according to the number of the steel pipes charged in. In addition, in Comparative Example 1, the power input to the heating device is adjusted to a value obtained by multiplying 125 kW, which exceeds the basic input power, by the number of steel pipes charged in the heating device, and in Comparative Example 2, less than the basic input power. Was adjusted to a value obtained by multiplying 102 kW by the number of steel pipes charged in the heating device.

  Table 1 shows the electric power (kW) per steel pipe put into the heating device, the temperature difference (° C.) and the maximum temperature at the position 5 mm from the pipe end and the position 200 mm from the pipe end when the heating is completed ( ° C) and the evaluation at the completion of heating.

[Evaluation criteria]
The meanings of the symbols in the “Evaluation at the completion of heating” column in Table 1 are as follows:
◯: When heating is completed, the temperature difference is 200 ° C. or less and the maximum temperature is 1300 ° C. or less at a position 5 mm from the tube end and a position 200 mm from the tube end.
X: When heating is completed, the temperature difference is 200 ° C. or less and the maximum temperature is 1300 ° C. or less at a position 5 mm from the tube end and a position 200 mm from the tube end. Indicates.

[Test results]
From the results shown in Table 1, in Comparative Example 1, the power input to the heating device was adjusted to a value obtained by multiplying the 125 kW exceeding the basic input power by the number of steel pipes charged in the heating device, and the temperature difference was 200 However, the maximum temperature exceeded 1300 ° C and the steel pipe was bent. Further, in Comparative Example 2, the power input to the heating device is adjusted to a value obtained by multiplying 102 kW, which is less than the basic input power, by the number of steel pipes charged in the heating device, and the maximum temperature is 1300 ° C. or lower. However, the temperature difference exceeded 200 ° C.

  On the other hand, in Example 1 of the present invention, the electric power supplied to the heating device is adjusted to a value obtained by multiplying 117 kW corresponding to the basic input electric power by the number of steel pipes charged in the heating device, and the temperature difference becomes 200 ° C. or less. In addition, the maximum temperature was 1300 ° C. or lower. Therefore, when the heating is completed by adjusting the power input to the heating device according to the basic input power calculated by the equation (1) and the number of steel pipes charged to the heating device, It has been clarified that the temperature difference at the end can be made 200 ° C. or lower and the maximum temperature can be made 1300 ° C. or lower.

(2) Evaluation test when the cooling time has elapsed [Test method]
In this test, the end portion of the steel pipe was loaded into the heating device 12 by the conveyor 13 by the mouth drawing device shown in FIG. At that time, the temperature of the steel pipe end was measured at a position 5 mm from the pipe end and a position 200 mm from the pipe end. Moreover, in this test, the electric power input to the heating apparatus was adjusted to a value obtained by multiplying 117 kW by the number of steel pipes charged in the heating apparatus. That is, since the basic input power calculated by the formula (1) is 119 kW, the basic input power calculated by the formula (1) and the number of steel pipes charged in the heating device were adjusted. .
The test conditions in this test were as follows.
Steel pipe: 70mm outer diameter before squeezing, 14mm wall thickness, 50mm minimum outer diameter of squeezed part
Material SUS304TP stainless steel heating conditions specified in JIS: Frequency 5.6 Hz, heating time 10 minutes

  The time calculated by the equation (2) from the dimensions of the steel pipe used in this test is 50 seconds. In Example 2 of the present invention, the cooling time required from the completion of heating by the heating device 12 to the start of squeezing was adjusted to 48 seconds according to the time calculated by the above equation (2). Further, the cooling time is adjusted to 72 seconds exceeding the time calculated by the equation (2) in the comparative example 3, and is less than the time calculated by the equation (2) in the comparative example 4 24. Adjusted to seconds.

  Table 2 shows the cooling time (kW), the temperature difference (° C.), the maximum temperature (° C.), and the minimum temperature (° C.) at a position 5 mm from the tube end and a position 200 mm from the tube end when the cooling time has elapsed. ) And evaluation when the cooling time has elapsed.

[Evaluation criteria]
The meanings of the symbols in the column “Evaluation when the cooling time has elapsed” in Table 2 are as follows:
○: When the cooling time has elapsed, the temperature difference is 100 ° C. or less, the maximum temperature is 1300 ° C. or less, and the minimum temperature is 800 ° C. or more at a position 5 mm from the tube end and a position 200 mm from the tube end. Also shows that
×: When the cooling time has elapsed, at a position 5 mm from the tube end and a position 200 mm from the tube end, the temperature difference is 100 ° C. or less, the maximum temperature is 1300 ° C. or less, and the minimum temperature is 800 ° C. or more. Indicates that either condition is not met.

[Test results]
From the results shown in Table 2, in Comparative Example 3, the cooling time was adjusted to 72 seconds exceeding the time calculated by the equation (2), the temperature difference was 100 ° C. or less, and the maximum temperature was 1300 ° C. or less. However, the minimum temperature was less than 800 ° C. In Comparative Example 4, the cooling time was adjusted to 24 seconds, which is less than the time calculated by the above equation (2), and the maximum temperature was 1300 ° C. or lower and the minimum temperature was 800 ° C. or higher. The temperature difference exceeded 100 ° C.

  On the other hand, in Inventive Example 2, the cooling time is adjusted to 48 seconds according to the time calculated by the equation (2), the temperature difference is 100 ° C. or less, the maximum temperature is 1300 ° C. or less, and the minimum temperature is 800 ° C. All of the above conditions were satisfied. Therefore, the electric power input to the heating device is adjusted according to the basic input electric power calculated by the equation (1) and the number of steel pipes charged to the heating device, and the cooling time is set to the equation (2). By adjusting according to the time calculated by the following conditions, when the cooling time has elapsed, at the end of the steel pipe, the temperature difference is 100 ° C. or less, the maximum temperature is 1300 ° C. or less, and the minimum temperature is 800 ° C. or more. , Both can be satisfied.

  From these, the mouth drawing apparatus and the mouth drawing method of the steel pipe end portion of the present invention are based on the basic input power calculated by the above equation (1) and the steel pipe charged in the heating apparatus. Since the cooling time is adjusted according to the time calculated by the above equation (2), the temperature is adjusted at the end of the steel pipe at the end of the steel pipe. The conditions that the difference is 100 ° C. or less, the maximum temperature is 1300 ° C. or less, and the minimum temperature is 800 ° C. or more can be satisfied. As described above, the squeezing apparatus and the squeezing method for the steel pipe end of the present invention can reduce temperature variations occurring at the end of the heated steel pipe, so that good squeezing performance can be obtained. It was revealed.

The steel pipe end portion squeezing apparatus and the squeezing method of the present invention have the following remarkable effects.
(1) By adjusting the basic input power to be input to the heating device and the cooling time required for transporting from the heating device to the mouth drawing device according to the dimensions of the steel pipe, it is possible to reduce the temperature variation generated at the end of the steel pipe. .
(2) Since the end portion of the steel pipe with reduced temperature variation is squeezed, good mouth-drawing performance can be obtained.
(3) Since the temperature variation generated at the end of the steel pipe can be reduced without using a special soaking equipment such as a burner type heating furnace or a feedback control device using a radiation thermometer, the equipment cost can be suppressed.

  Therefore, the steel pipe end portion squeezing apparatus and the squeezing method of the present invention can be used effectively in the manufacture of steel pipes using cold drawing.

1: mouth drawing device, 11: first aligning device, 12: high frequency induction heating device,
13: conveyor, 14: squeezing machine, 15: squeezing conveying device,
16: Second aligning device, 17: Heating control means, 18: Cooling time control means,
2: inspection table, 3: rack, 4: steel pipe, 4a: aperture part, 4b: taper part,
4c: Straight part

Claims (4)

A heating device capable of simultaneously inductively heating a plurality of materials to be heated;
A conveyor that conveys the steel pipe while charging and heating the end of the steel pipe,
A mouth drawing machine that squeezes the end of the conveyed steel pipe and performs mouth drawing processing;
A mouthpiece transporting device for transporting the steel pipe transported by the conveyor to the mouthdrawer,
A heating control means for adjusting power to be input to the heating device according to a value obtained by multiplying the basic input power calculated by the following equation (1) and the number of steel pipes charged in the heating device;
When performing the squeezing process on the steel pipe whose end is heated by the squeezing machine, the cooling time required from the completion of the heating by the heating device to the start of the squeezing process is expressed by the following equation (2). A steel pipe end drawing apparatus characterized by having a cooling time control means for adjusting according to the calculated time.
W = 4.3 × (D2 / D1) × t + 76 (1)
T = 6.6 × (D2 / D1) × t−16 (2)
Here, W is the basic input power (kW), T is the time (s), D1 is the outer diameter (mm) of the steel pipe before squeezing, t is the wall thickness (mm) of the steel pipe before squeezing, D2 Is the minimum outer diameter (mm) of the aperture portion of the steel pipe after aperture drawing.   When the conveyor is a steel pipe that needs to be heated before the squeezing process, the end of the steel pipe is inserted into the heating device and transported while heating, and heating is not required before the squeezing process is performed. In the case of a steel pipe, the end portion of the steel pipe is inserted into the heating device and transported without being heated. The steel pipe group with the same outer diameter and wall thickness before steel drawing and the minimum outer diameter of the steel pipe after drawing is transported sequentially, and the mouth drawing machine is attached to the end of the steel pipe. It is a method of squeezing the end of a steel pipe to be squeezed with
When sequentially transporting the steel pipe group, while heating the end of the steel pipe by charging into a heating device that can simultaneously induction heating a plurality of materials to be heated,
The power input to the heating device is adjusted according to a value obtained by multiplying the basic input power calculated by the following equation (1) and the number of steel pipes charged into the heating device,
When the end of the conveyed steel pipe is subjected to squeezing, the cooling time required from the completion of heating by the heating device to the start of squeezing is calculated by the following equation (2). A mouth-drawing method for a steel pipe end, characterized by adjusting according to time.
W = 4.3 × (D2 / D1) × t + 76 (1)
T = 6.6 × (D2 / D1) × t−16 (2)
Here, W is the basic input power (kW), T is the time (s), D1 is the outer diameter (mm) of the steel pipe before squeezing, t is the wall thickness (mm) of the steel pipe before squeezing, D2 Is the minimum outer diameter (mm) of the aperture portion of the steel pipe after aperture drawing. The outer diameter and thickness of the steel pipe before squeezing and the minimum outer diameter of the squeezed part of the steel pipe after squeezing are the same, and the steel pipe group that requires heating before squeezing, The outer diameter and thickness of the steel pipe before drawing, and the minimum outer diameter of the mouth drawing portion of the steel pipe after mouth drawing are the same, and the steel pipe group that does not need to be heated before mouth drawing is alternated. A steel pipe end squeezing method for carrying out squeezing with a squeezing machine on the end of the steel pipe that has been transported,
When performing the squeezing process on the steel pipe group that needs to be heated, the squeezing method of the steel pipe end part according to claim 3,
When carrying out a squeezing process on the steel pipe group that does not require heating, the steel pipes are sequentially transported without being inserted into the heating device, and the squeezing process is performed on the ends of the transported steel pipes. Mouth drawing method for steel pipe end.

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