KR101424207B1 - Apparatus and method for removing residual stress, and method for manufacturing pipe - Google Patents

Abstract

The present invention relates to a device to remove residual stress. An example of the device includes: at least one chamber which includes an inlet to which a pipe continuum is inserted and an outlet through which the pipe continuum is discharged; at least one heater which is installed inside the chamber and increases the temperature inside the chamber; at least one temperature sensor unit which senses the temperature status of the chamber and outputs a temperature sensing signal according to the temperature status; and a control unit which is connected to the temperature sensor unit, reads the temperature sensing signal outputted from the temperature sensor unit, determines the sensed temperature, compares the determined temperature with a predefined temperature range, and controls the operation of the heater. By doing so, as the residual stress is removed by thermally treating a manufactured pipe, problems due to the residual stress such as overlapping and toe-in can be largely reduced, and the quality of a product is improved since the natural properties of raw material are maintained. Furthermore, as the process of removing the residual process is performed during the process of manufacturing the pipe, the removal of the residual stress from the pipe is done easily.

Description

TECHNICAL FIELD [0001] The present invention relates to a residual stress relieving apparatus, a residual stress relieving apparatus, a residual stress relieving apparatus, a residual stress relieving apparatus,

The present invention relates to an apparatus and method for removing residual stress, and a pipe manufacturing method.

Generally, when a plastic product such as a plastic pipe is manufactured, the molecular orientation of the polymer is increased from the normal state during the extrusion process in which the polymer is melted at a high temperature of about 200 ° C. in the extruder and then flows through the channel, The molecular alignment state becomes unstable.

In this way, when the molecular orientation of the polymer is in an unstable pipe state, and when the pipe is rapidly solidified by cooling the pipe at a high temperature by using cooling water or the like, the degree of crystallization of the polymer depends on the position due to the temperature difference between the inside and the outside of the pipe. The molecular arrangement of the pipe, which is a product, differs depending on the position and generates stress, which is a residual stress.

When the residual stress is generated in the finished product pipe, cracks are generated due to the impact from the inside or outside of the pipe, so that the physical and chemical properties of the pipe deteriorate. As the outside temperature changes, The dimensions of the product are deformed and the linear expansion coefficient increases.

Further, when the finished product is further processed or an external influence such as cutting, cutting, welding or welding is applied to the finished product as in the case of construction, the finished product shrinks due to the current stress, Causing problems.

However, since a separate process for removing the residual stress existing in the manufactured plastic pipe is not performed, when the pipe is cut in the longitudinal direction or the radial direction, an overlap phenomenon in which the ends overlap each other, A toe-in phenomenon occurs, which causes a problem that a desired operation can not be easily performed.

Korean Patent Registration No. 10-0615539 (Publication Date: August 25, 2006, entitled: Tensile Residual Stress Reduction Device and Method of Reactor Nozzle) Korean Registered Patent Publication No. 10-0897986 (Date of Publication: May 18, 2009, entitled: Four-direction axial pressure pipe residual stress remover) Korean Registered Patent Publication No. 10-1288431 (Date of Notification: Jul. 22, 2013, entitled "Pipe Residual Stress Retrofitting Device")

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art.

The technical problem to be solved by the present invention is to easily remove the residual stress of the product.

According to an aspect of the present invention, there is provided a residual stress relieving apparatus comprising at least one chamber having an inlet through which a pipe continuum is introduced and an outlet through which the pipe continuum is discharged, at least one chamber provided in the chamber for increasing the internal temperature of the chamber, At least one temperature sensor for detecting a temperature state of the at least one chamber and outputting a temperature sensing signal in a corresponding state, and a temperature sensor connected to the temperature sensor, To determine the sensed temperature, and to compare the determined temperature with the set temperature range, and to control the operation of the at least one heater.

The at least one temperature sensing unit may sense a surface temperature of the pipe continuum discharged from the at least one chamber.

The temperature sensing unit may be an infrared temperature sensor.

The set temperature range may be 110 ° C to 130 ° C.

The at least one temperature sensing unit may sense a temperature inside the at least one chamber.

The residual stress relieving apparatus according to the above feature may further include at least one temperature sensing unit for sensing a surface temperature of the pipe continuum discharged from the at least one chamber, A warning signal can be output when the surface temperature of the pipe continuum detected by the temperature sensing unit is out of the set temperature range.

The residual stress relieving apparatus according to the above feature may further include at least one air circulator mounted in the at least one chamber and connected to the control unit to operate according to the control of the control unit to circulate the air in the chamber have.

The apparatus for removing residual stress according to the above feature may further include a shielding film mounted on the inlet and the outlet, respectively, wherein the diameter of the opening is changed according to the outer diameter of the pipe continuum flowing into and out of the chamber.

A residual stress relieving apparatus according to the present invention is characterized in that the residual stress relieving apparatus includes a position adjusting plate having a plurality of stages which are positioned facing each other at least in at least one of the interior of the chamber, the front of the inlet and the rear of the outlet, And a roller guide for supporting the pipe continuum.

The at least one heater may be a heating wire installed on the inner surface of the chamber.

According to another aspect of the present invention, there is provided a method for removing residual stress, comprising the steps of: operating a heater to heat a pipe continuum positioned in a chamber for a predetermined period of time; reading a signal output from a temperature sensing unit for sensing a temperature state of the chamber; And controlling the operation of the heater by comparing a temperature corresponding to the determined temperature state of the chamber with a set temperature range.

The temperature sensing unit may sense the internal temperature of the chamber or the surface temperature of the pipe continuity output from the chamber.

When the temperature sensing unit senses the surface temperature of the pipe continuum, the set temperature range may be 110 ° C to 130 ° C.

It is preferable that the predetermined time is increased as the diameter of the pipe continuum increases.

The residual stress removing method may further include circulating the air in the chamber by driving the air circulator mounted in the chamber.

According to another aspect of the present invention, there is provided a method of manufacturing a pipe, comprising melting a raw material and extruding the raw material, forming a pipe continuum of a desired shape for molding the raw material to be extruded, cooling the pipe continuum formed in the molding step, Treating the pipe continuum subjected to the cooling step for a predetermined time to remove the residual stress in the pipe continuum by making the temperature of the pipe continuum fall within a set temperature range.

The set temperature range may be 110 ° C to 130 ° C.

It is preferable that the predetermined time is elongated as the diameter of the pipe continuum increases.

According to this feature, since the residual stress remaining in the pipe is removed by heat treatment of the produced pipe, the problems caused by the residual stress such as the overlapping phenomenon and the toe shape are greatly reduced, and the inherent properties of the raw material are maintained, .

In addition, since the residual stress removing process is performed during the process of manufacturing the pipe, the residual stress removal operation of the pipe is easily performed.

FIG. 1 is a view sequentially illustrating a method of manufacturing a plastic pipe according to an embodiment of the present invention.
2 is a schematic structural view of a residual stress relieving apparatus according to an embodiment of the present invention.
Fig. 3 is a view showing a structure of a curtain film provided in the residual stress relieving apparatus of Fig. 2; Fig.
4 is a block diagram of a control unit for controlling a residual stress relieving apparatus according to an embodiment of the present invention.
5 is an operational flowchart of a residual stress removal method according to an embodiment of the present invention.
FIG. 6 is a flowchart illustrating operation steps of the internal temperature control steps of the first and second chambers of FIG. 5;

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Hereinafter, an apparatus and method for removing residual stress according to an embodiment of the present invention, and a method for manufacturing a pipe will be described with reference to the accompanying drawings.

First, a method of manufacturing a plastic pipe according to an embodiment of the present invention will be described with reference to FIG.

First, the process for manufacturing the plastic pipe P1 includes an extrusion process 10 in which a raw material 1 is inputted and then melted and extruded, a raw material 1 introduced by an extrusion process 10 is formed A molding step 20 for forming a pipe continuum PC1 which is a continuum of the uncut pipe P1 and a cooling step 30 for cooling the pipe continuum PC1 having a shape through the molding step 20, A residual stress removing process 40 for removing the stress inherent to the pipe continuum PC1 cooled through the process 30 and the pipe continuity PC1 after removing the stress are cut to a standard length And cutting the pipe P1 to finally complete the pipe P1.

In this example, the raw material 1 is a polymer such as polyethylene or polypropylene such as HDPE (high density polyethylene).

When such a raw material 1 flows into a process chamber (e.g., a heating cylinder) for the extrusion process 10, the granular or powder raw material 1 is heated in an extruder, which is a process chamber, Melted and melted and kneaded and extruded by the rotation of the screw 11 to be introduced into the molding process 20.

The molding process 20 proceeds in a vacuum state and the raw material 1 having been passed through the extrusion process 10 is passed through a molding die and molded into a desired shape to form a pipe continuum PC1 as a continuum having the shape of a pipe P1 . At this time, a primary cooling process using cooling water is also performed to prevent the shape of the formed pipe continuum PC1 from being deformed.

When the pipe continuity PC1 having the desired shape is produced by the molding process 20, the pipe continuity PC1 which is primarily cooled through the cooling process 30 is secondarily cooled.

At this time, the primary and secondary cooling are performed using cooling water, and the temperature of the cooling water may all be the same 10 ° C to 20 ° C.

The pipe continuum PC1 manufactured through the cooling process 30 is again subjected to the residual stress removal process 40 to remove the residual stress remaining in the pipe continuum PC1.

At this time, the residual stress removing step 40 optimizes the temperature of the pipe continuum PC1 by heat-treating the manufactured pipe continuum PC1 for a preset time to rearrange the molecular arrangement of the pipe continuum PC1 to a normal state, To be removed.

At this time, it is preferable to carry out the residual stress relief at a high temperature as much as possible. However, since the pipe continuity (PC1) made of thermoplastic is not melted or deformed, the heat treatment temperature is lower than the softening point of the pipe continuum (PC1) It can be lower or equal.

The heat treatment time of the pipe continuum PC1 for removing residual stress depends on the diameter of the pipe continuum PC1, that is, the diameter of the pipe P1 (e.g., the outer diameter of the pipe)?. Generally, as the outer diameter of the pipe continuum PC1 increases and the process time increases as the thickness increases, the magnitude (or amount) of the residual stress inherent in the pipe continuum PC1 during the heat treatment time also increases.

Therefore, as the magnitude of the residual stress increases, the heat treatment time for removing the residual stress also increases.

2 and 3, the stress relieving apparatus for the residual stress removing process 40 includes a first chamber (PC1) through which the pipe continuum PC1 having undergone the cooling process 30 flows through the opening 81 as an inlet A second chamber 42 through which the pipe continuum PC1 connected to the first chamber 41 and discharged through the discharge port 82 of the first chamber 41 flows through the inlet port 83, The first air circulator 43 mounted on the first chamber 41, the second air circulator 44 mounted on the second chamber 42, and the first chamber 41 mounted on the inner region of the first chamber 41, The first heating unit H1 having the first to fourth heaters H11 to H14 and the second heating unit H1 mounted to the second chamber 42 to increase the internal temperature of the second chamber 42, The second heating section H2 provided with the first to fourth heaters H21 to H24 and the outlet 82 of the first chamber 41 after the discharge port 82 of the first chamber 41 82) and the inlet (83) of the second chamber (42) The temperature of the surface of the pipe continuum PC1 discharged from the discharge port 82 of the first chamber 41 is sensed by being positioned in the connection pipe 91 for conducting the second chambers 41 and 42 to each other, A first temperature sensing unit T11 for outputting a signal and a surface temperature of a pipe continuum PC1 positioned after the discharge port 84 of the second chamber 42 and discharged through the discharge port 84, And a second temperature sensing unit T12 for outputting a temperature sensing signal of the temperature sensing unit T12.

Each of the first and second chambers 41 and 42 is shielded from the outside to maintain a constant internal temperature in order to uniformly apply a heat quantity to the pipe continuum PC1 flowing into the pipe.

3, the inlet port 81 of the first chamber 41 and the outlet port 84 of the second chamber 42 are connected to the inlet port 81 and the outlet port 84, respectively, according to the outer diameter of the pipe continuum PC1. And a diaphragm-shaped curtain film C1, C2 for changing the diameter of the discharge port 84, respectively. The curtains C1 and C2 are automatically or manually controlled to change the diameter of the inlet 81 and the outlet 84 and the degree of overlapping of a plurality of pieces arranged in a circular shape according to the principle of the iris operation The diameters of the inlet port 81 and the outlet port 84 can be increased or decreased by varying the degree of opening of the shielding films C1, C2.

Accordingly, only the open portion of the inlet 81 and the outlet 84 are open, and the remaining portion is blocked by the clogs C1 and C2.

A connection pipe 91 connecting the first chamber 41 and the second chamber 42 as well as the outer wall of the first and second chambers 41 and 42 is also connected to the heat insulating film (911).

In the first and second chambers 41 and 42, the same number of heaters H11-H14 and H21-H24 are located.

The plurality of heaters H11 to H14 located in the first chamber 41 are formed in the respective regions formed when the inner region of the first chamber 41 is uniformly and virtually divided into the lateral direction and the longitudinal direction, An upper region, a front lower region, and a rear lower region, which are located on the front side of the first chamber 41 (i.e., the side adjacent to the inlet 81), the rear side (i.e., the side opposite to the front side and adjacent to the discharge port 82) And a plurality of heating wires arranged at regular intervals on the inner surfaces of the heaters.

The plurality of heaters H21 to H24 located in the second chamber 42 are also located at the same positions as the first chamber 41, that is, the front upper region, the rear upper region, the front lower region, It consists of a heating wire installed at regular intervals.

At this time, the heaters H11-H14 and H21-H24 located in the respective regions are separated from each other and operate separately.

When the inner shapes of the chambers 41 and 42 have a circular sectional shape, the heating wires constituting the respective heaters H11 to H14 and H21 to H24 are divided into parallel chambers 41 and 42 Since the respective front faces of the front upper region, the rear upper region, the front lower region, and the rear lower region are spaced apart from each other substantially at regular intervals along the longitudinal direction of the chambers 41 and 42, ) The inner surface is substantially located with the heating wire.

This quickly and uniformly raises the temperature inside the chambers 41, 42, shortening the heating time of the chambers 41, 42 and greatly reducing the temperature difference according to the positions of the chambers 41, 42.

Since the heaters H11-H14 and H21-H24 in the first and second chambers 41 and 42 are located on the inner surfaces of the chambers 41 and 42 adjacent to the outside, So as not to interfere with the movement of the pipe continuum PC1.

 In this example, the number of divided regions of each of the chambers 41 and 42 is four, but is not limited to this and is variable.

The first and second air circulators 43 and 44 are all fans and forcefully circulate the air in the first and second chambers 41 and 42 so that the first and second chambers 41 and 42, 42 to reduce the temperature difference due to the difference. Accordingly, it is possible to uniformly and stably maintain the temperature deviation between the inner upper portion and the inner lower portion of each of the first chamber 41 and the second chamber 42, so that the first chamber 41 and the second chamber 42 are maintained at a constant internal temperature .

The first and second temperature sensing units T11 and T12 are each composed of an infrared temperature sensor.

In the stress relieving apparatus for the stress relieving step 40, as shown in FIG. 3, the inside of each of the chambers 41 and 42, the front of the inlets 81 and 83 and the rear of the outlets 82 and 84 A guide roller 310 for preventing the sagging phenomenon of the pipe continuum PC1 and preventing the sagging of the pipe continuum PC1 to be heated more uniformly to the pipe continuum PC1 and the two position control plates 320 are located.

At this time, the two position control plates 320 are positioned opposite to each other, and a plurality of stages having different heights are positioned on the respective position control plates 320.

The guide rollers 310 are placed on the guide rollers 310 at a predetermined height among the plurality of stages of the position adjustment plates 320 and the pipe continuity PC1 is positioned on the guide rollers 310, Thereby supporting the position of the pipe continuum PC1.

This guide roller 310 allows the pipe continuum PC1 to pass through the center portion of the chambers 41 and 42 so that a uniformly uniform amount of heat is transferred to the pipe continuum PC1.

 The number of the guide rollers 310 and the position adjusting plate 320 installed at each position can be added or subtracted as necessary.

Next, a structure of a control unit for controlling the operation of the residual stress relieving apparatus according to one embodiment of the present invention will be described with reference to FIG. The control unit also forms part of the residual stress control device.

4, the current stress relieving apparatus includes a temperature setting unit 100, an input terminal connected to the temperature setting unit 100, first and second temperature sensing units T11 and T12, And a control unit 200 having output terminals connected to the second heating units H1 and H2 and the first and second air circulators 43 and 44.

Accordingly, the first and second temperature sensing units T11 and T12, the first and second heating units H1 and H2 and the first and second chambers 41 and 42 located in the first and second chambers 41 and 42, 41 and 42 constitute a part of the residual stress relieving apparatus 1. The first and second air circulators 43 and 44,

The temperature setting unit 100 is for setting the surface temperature of the pipe continuum PC1 after heat treatment to the first and second chambers 41 and 42 through the user's operation. Therefore, the temperature setting unit 100 is an input device for inputting a desired temperature value such as a keyboard or the like.

At this time, the set surface temperature of the pipe continuum PC1, which is the surface temperature of the pipe continuum PC1 set by the temperature setting unit 100, is the temperature at which the residual stress of the pipe continuum PC1 can be removed , And may be low or the same adjacent to the softening point of the pipe continuum PC1.

Even though the set surface temperature of the pipe continuum PC1 is the same as the softening point, the pipe continuum PC1 does not immediately melt into the heat, so even if the set surface temperature is the same as the softening point, the pipe continuum PC1 is not deformed by controlling the heat treatment time It is acceptable. Therefore, the range of the set surface temperature of the pipe continuum PC1 according to this example is 110 占 폚 to 130 占 폚.

The first and second temperature sensing units T11 and T12 are for sensing a temperature state in each of the chambers 41 and 42. Based on the temperatures sensed by the temperature sensing units T11 and T12, And the heaters H11-H14 and H21-H24 in the second chambers 41 and 42 are controlled so that the surface temperature of the pipe continuum PC1 maintains the set temperature so that the residual stress can be removed.

The control unit 200 receives the set surface temperature of the pipe continuum PC1 input from the temperature setting unit 100 and receives the setting surface temperatures of the chambers 41 and 42 having the plurality of heaters H11 to H14 and H21 to H24 The operation of the heating units H1 and H2 is controlled so that the surface temperature of the pipe continuum PC1 heat-treated in the first and second chambers 41 and 42 maintains the set surface temperature.

The controller 200 also operates the air circulators 43 and 44 mounted in the first and second chambers 41 and 42 when operating the first and second heating units H1 and H2 Thereby quickly raising the internal temperature of the chambers 41, 42 to a desired temperature and also reducing the temperature difference according to the position in the chambers 41, 42.

Next, a method of eliminating the residual stress of the pipe continuum PC1 according to an embodiment of the present invention will be described with reference to FIG.

First, when an operation start switch (not shown) is turned on in a state where power required for operation of the residual stress relieving apparatus is supplied by using a power switch or the like (not shown), the operation of the control unit 200 is started (S10).

When the operation starts (S10), the control unit 200 reads the signal inputted from the temperature setting unit 100 (S11) and sets the range of the set surface temperature of the pipe continuum PC1 through the temperature setting unit 100 (S13).

When a signal for a minimum value and a maximum value of the set surface temperature is input from the temperature setting unit 100, the controller 200 controls the operation of the first and second chambers 41 and 42 And outputs a driving signal to each of the first and second heating sections H1 and H2 to operate the first and second heating sections H1 and H2.

As already described, the range of the set surface temperature of the pipe continuum (PC1) is 110 占 폚 to 130 占 폚.

Accordingly, the controller 200 outputs driving signals to the first to fourth heaters H11 to H14 located in the first chamber 41 and the first to fourth heaters H11 to H14 located in the first chamber 41, And outputs drive signals to the first to fourth heaters H21 to H24 located in the second chamber 42 (S15).

Then, the control unit 200 outputs the driving signals to the first and second air circulators 43 and 44 to operate the first and second air circulators 43 and 44 (S17).

As a result, the internal temperatures of the first and second chambers 41 and 42 are raised, and the internal air of the chambers 41 and 42 is circulated by the first and second air circulators 43 and 44 The rising speed of the internal temperature of each of the chambers 41 and 42 increases and the temperature difference depending on the position of the chambers 41 and 42 is lost or decreased.

At this time, the operation sequence of the first and second heating units H1 and H2 and the first and second air circulators 43 and 44 can be changed.

However, if no signal for the range of the set surface temperature of the pipe continuum PC1 (i.e., the minimum value and the maximum value of the set surface temperature range) is input through the temperature setting unit 100, (S11), it is judged whether or not a range value of the set surface temperature of the pipe continuum PC1 is input from the temperature setting section 100. [

Next, the control unit 200 reads the temperature sensing signals applied from the first and second temperature sensing units T11 and T12 to control the internal temperatures of the first and second chambers 41 and 42, The surface temperature of the pipe continuum PC1 heat-treated in the second chambers 41 and 42 is maintained at a temperature within the set surface temperature range (S19).

As shown in FIG. 6, the operation of the control unit 200 for controlling the internal temperature of the first chamber 41 will be described.

The control unit 200 reads the temperature sensing signal output from the first temperature sensing unit T11 and determines the surface temperature of the pipe continuum PC1 that has passed through the first chamber 41 (S191, S192).

Then, the control unit 200 determines whether the determined surface temperature of the pipe continuum PC1 is within the set surface temperature range (S193).

Therefore, the control unit 200 determines whether the surface temperature of the pipe continuum PC1 thus determined has a value between the minimum value and the maximum value of the set surface temperature.

If the determined surface temperature of the pipe continuum PC1 is within the range of the set surface temperature, the control unit 200 determines that the internal temperature of the first chamber 41 is presently appropriate. Accordingly, the control unit 200 maintains the current state of the first heating unit H1 mounted in the first chamber 41 (S194).

However, if the surface temperature of the pipe continuum PC1 thus determined is not within the range of the set surface temperature and is maintained higher than the maximum value of the set surface temperature range (e.g., 140 占 폚) It is determined that the internal temperature of the first chamber 41 is high (S195).

The control unit 200 stops the driving signals applied to the first to fourth heaters H11 to H14 of the first heating unit H1 that is currently operating, (S196). ≪ / RTI > At this time, the controller 200 may operate at least one of a warning light (not shown) and a warning sound generator (not shown) to inform the driver of the current operation state. Accordingly, the internal temperature of the first chamber 41 which has risen above the set value is reduced, so that the surface temperature of the pipe continuum PC1 passing through the first chamber 41 is reduced to within the set surface temperature range.

However, if the determined surface temperature of the pipe continuum PC1 is not higher than the maximum value of the set surface temperature range in a state where the temperature of the pipe continuum PC1 is out of the set surface temperature range, the control unit 200 determines that the surface temperature of the pipe continuum PC1 It is determined that the state is lower than the minimum value of the set surface temperature range.

Accordingly, the controller 200 determines whether the current state of the first heating unit H1 is in the operation stop state to improve the internal temperature of the first chamber 41 (S197).

The control unit 200 outputs driving signals to the first to fourth heaters H11 to H14 to output the driving signals of the first to fourth heaters H11 to H14, The operation is resumed (S198).

However, if it is determined that the first heating unit H1 is in the operating state, the controller 200 increases the magnitude of the driving signal applied to the first through fourth heaters H11 through H14 currently in operation by a predetermined amount, 1 to the fourth heater (H11-H14) (S199).

At this time, the controller 200 can improve the output of the first to fourth heaters H11 to H14 by increasing the magnitude of the current applied to the first to fourth heaters H11 to H14.

As a result, the internal temperature of the first chamber 41 increases and the surface temperature of the pipe continuum PC1 passing through the first chamber 41 also increases.

The operation of controlling the internal temperature of the second chamber 42 using the second temperature sensing unit T12 may be performed by using the second temperature sensing unit T12 instead of using the first temperature sensing unit T11, 6, except that the operating state of the second heating unit H2 is controlled instead of the heating unit H1, the detailed operation for controlling the internal temperature of the second chamber 42 is omitted do.

As described above, by using the surface temperature of the pipe continuum PC1 which has passed through the first and second chambers 41 and 42 determined through the first and second temperature sensing portions T11 and T12, When the internal temperature of the two chambers 41 and 42 is controlled, the controller 200 reads the signals output from the first and second temperature sensing units T11 and T12 at predetermined time intervals, 41, and 42 can be determined.

At this time, the set time may be determined in consideration of the residence time of the pipe continuum PC1 staying in each of the first and second chambers 41 and 42, the moving time of the pipe continuum PC1, and the like.

In this example, the operation of the controller 200 for controlling the internal temperatures of the first chamber 41 and the second chamber 42 can be performed separately from each other through a routine.

When the pipe continuity PC1 subjected to the cooling step 30 is subjected to the heat treatment under such a condition that deformation of the pipe continuity PC1 does not occur again by this heat treatment step, the pipe continuity PC1, which has not returned to the steady state due to the rapid temperature change PC1) is returned to the normal state and the residual stress existing in the pipe continuum PC1 is removed.

As shown in FIG. 1, the pipe continuum PC1, from which the residual stress has been removed through the residual stress removing process 40, is cut through the cutter 50 into a standardized length, The pipe P1 is completed.

At this time, the heat treatment time for removing the residual stress of the pipe continuum PC1 (eventually the pipe P1) depends on the diameter of the pipe continuum PC1 (eventually the pipe P1). Accordingly, as the diameter of the pipe P1 increases, the heat treatment time of the pipe continuum PC1 is increased, so that the residual stress can be stably removed.

Next, the heat treatment time (i.e., residence time) performed in the first and second chambers 41 and 42 according to the diameter of the pipe P1 is shown with reference to [Table 1]. At this time, the heat treatment time is the sum of the heat treatment time (i.e., residence time) performed in the first and second chambers 41 and 42.

Diameter of pipe (Ø) Setting surface temperature range [℃] Retention time of chamber [min] Below Ø160



110 ~ 130


5.4 to 6.8 Ø200 to Ø250 7.6 to 10.2 Ø315 ~ Ø400 11.6-12.6 Ø450 to Ø500 13.8 to 14.2 Ø560 ~ Ø630 18.6 to 14.2 Ø710 ~ Ø850 13.4 to 14.3 Ø900 ~ Ø1100 17 ~ 21 Ø1200 or more 28.5 to 31.3

When the molecular arrangement in the pipe continuum PC1 changes and the residual stress is more stably removed and the maximum value of the set surface temperature (130 DEG C) or lower is lower than the set surface temperature minimum value (110 DEG C) in Table 1, Since the pipe continuum PC1 is not melted or deformed, the shape of the pipe continuum PC1 is stably maintained and the residual stress is efficiently removed.

In the range of the residence time according to each diameter of the pipe P1, the residual stress remaining in the pipe continuum PC1 is more efficiently reduced in the case of staying in the chambers 41, 42 at least the minimum time of the residence time Residual stress is efficiently removed without changing the characteristics of the pipe continuum PC1 and the production efficiency of the pipe P1 due to the increase in the production time is reduced when the chamber 41, 42 remains below the maximum time of the residence time Do not decrease.

The control unit 200 controls the first and second heating units H1 and H2 and the first and second air circulators 43 and 44 so that the first and second heating units H1 and H2 and the first and second air circulators 43 and 44, And informs the driver of the current operation state by operating at least one of the warning lamp and the warning sound generator.

Further, the feeding operation of the pipe continuum PC1 for the cutting process from the extrusion process 10 can be performed by a houl-off device (not shown).

Thus, when the residual stress of the pipe P1 is removed through the residual stress removing process 40 according to the embodiment of the present invention, when the pipe P1 is cut one side in the longitudinal direction, The overlapping phenomenon is greatly reduced by the phenomenon that the two end portions facing each other are overlapped and dried.

With reference to the following Table 2, the measured degree of overlap is compared between when the residual stress of the pipe according to the present example is removed and when it is not.

The pipes used to compare the degree of overlap were two with a diameter of 630 mm, a thickness of 9.8 mm, a diameter of 1,100 mm and a thickness of 17.6 mm.

Pipe size (mm)
(Diameter × thickness)
After production
Elapsed time (hr)
Degree of overlap (mm
compare(%)
(Removed / unremoved)
When residual stress is not removed When residual stress is removed
630 mm x 9.8 mm One 360 85 24% 24 740 175 24% 72 820 210 26% 1,100 mm × 17.6 mm One 960 160 17% 24 1128 430 38% 72 1405 491 35%

As shown in [Table 2] above, when the residual stress removal process according to the present example is performed, the degree of overlap decreases significantly compared to the case where the residual stress removal process according to the present embodiment is performed.

As the residual stress is removed, the toe-in phenomenon occurring at the end of the pipe is also greatly reduced.

Generally, the toe phenomenon occurs when a pipe continuum is cut in a standardized length during the manufacturing process, or when an operation of cutting the pipe as an end product to a desired length by an operator during the work is performed, The end portion of the pipe, that is, the cut portion is contracted due to the residual stress and is curled toward the inside of the pipe, thereby reducing the outer diameter of the pipe P1.

The occurrence of such a toe phenomenon is further increased after the cutting process of cutting to the standardized length is performed because the deformation of the shape of the deformed molecules is stabilized in the pipe manufacturing process over time, .

The degree of occurrence of such a toe phenomenon greatly decreases as the residual stress relief process according to this example is performed, as shown in the following [Table 3].

In Table 3, the pipe used to measure the degree of occurrence of the toe phenomenon was a pipe having a diameter of 710 mm and a thickness of 11.5 mm.

Size of pipe
(Diameter × thickness) Degree of toe generation (mm)
compare(%)
(Removed / unclear) Residual stress unmeasured When residual stress is removed 710 mm x 11.5 mm 4.5 3 67%

In the case of [Table 3], it was found that the residual stress process according to the present example was performed, and the degree of the toe generation was reduced by 67% as compared with the case without the residual stress.

With reference to the following Table 4, a change in the material properties of the pipe after the residual stressing process according to this example is performed will be described.

(MD) of the pipe with the residual stress removed in the longitudinal direction of the pipe and the case (TD) of the pipe cut in the circumferential direction through the residual stress removal step (40) according to this example in Table 4 Yield strength enlongation, enlongation at break, enlongation, and longitudinal reversion were measured, respectively.

At this time, the pipe used was a pipe having a diameter of 450 mm and a thickness of 7.8 mm.

direction Residual stress
Whether to remove Yield elongation (%)  Elongation at break (%) Elongation (%) Bell of Blessing MD
When residual stress is not removed 12.89 735.04 738.41 0.82 When residual stress is removed 13.80 757.25 767.75 -0.10 TD
When residual stress is not removed 13.76 884.47 891.91 -0.26 When residual stress is removed 15.33 875.91 882.91 0.00

As shown in [Table 4] above, it was found that overall yield stress, elongation at break, elongation and return to longitudinal axis were significantly improved when the current stress was not removed.

The residual stress relief process according to the present example is performed at an extension of the process line for manufacturing the pipe P1. Therefore, since it is not necessary to move the position of the pipe P1 manufactured by using a vehicle or the like to remove the residual stress, the residual stress removing operation of the pipe P1 is easily and quickly performed.

2, the heat treatment chamber for removing the residual stress of the pipe P1 uses two chambers 41 and 42 in which the internal spaces are connected to each other, but the present invention is not limited thereto, and one or more chambers may be used have.

At this time, the chambers used may all have the same structure, and the number of chambers may be determined according to the production speed of the pipe.

That is, when the conveyance speed of the pipe continuum conveyed to the process (or the speed at which the pipe continuum taken by the drawing device passes to the process) (that is, the production speed) is constant, The number of chambers used to satisfy the required residence time is decreased according to the diameter of each pipe.

On the contrary, if the feed rate of the pipe continuum is increased, the residence time in the chamber decreases, so that the required residence time may not be satisfied depending on the diameter of each pipe. In this case, at least two chambers are arranged in series to increase the residence time of the pipe continuity in the chamber.

Accordingly, when three or more chambers are used, the number of temperature sensing units used to control the internal temperature of each chamber is also three, and each temperature sensing unit senses the surface temperature of the pipe continuum discharged through each chamber, 200, so that the pipe continuum is heat-treated at a temperature within the surface set temperature range.

For example, when manufacturing a pipe having various diameters shown in [Table 1], two chambers are required to remove the residual stress of the pipe having a diameter of 630 mm or less and the residual of the pipe having a diameter of 710 mm or more One chamber may be required to remove stress.

Further, when only one chamber is used, the number of temperature sensing portions that sense the surface temperature of the pipe continuum discharged from the chamber may be one.

Unlike the present embodiment, the heat treatment time of the pipe continuum can be controlled using only one chamber. That is, when the pipe continuum flows into the chamber, the feed rate of the pipe continuum is controlled so that the pipe continuum stays in the chamber for a desired time. In this case, the controller 200 controls the operation state of the conveying device (for example, a motor) that controls the conveying speed of the pipe continuum by using a sensing device that senses whether the pipe continuum has flowed into the chamber, It is possible to satisfy the heat treatment time required for heat treatment.

In the above example, the temperature of the chambers 41 and 42 is sensed using the surface temperature of the pipe continuum CP1, and the heaters H11-H14 and H21-H24 To control the temperature in the corresponding chambers 41 and 42. [

However, in an alternative example, the temperature in the first and second chambers 41, 42 may be sensed directly to sense the temperature condition of each chamber 41, 42 and the temperature detected in each chamber 41, The operation of the heaters H11-H14, H21-H24 in the respective chambers 41, 42 can be controlled individually to control the temperature of the chambers 41, 42.

To this end, the control unit controls each of the regions (for example, the front upper region, the front lower region, the rear upper region, and the rear lower region) where the respective heaters H11-H14, H21-H24 of the chambers 41, And a plurality of temperature sensing sensors for sensing the temperature of each region separately. The plurality of temperature sensing sensors are connected to the controller 200.

In this example, since the number of the chambers 41 and 42 is two and the number of divided regions of the chambers 41 and 42 is four, there can be four such temperature sensors in each of the chambers 41 and 42 have.

In this case, instead of the first and second temperature sensing units T11 and T12, the controller 200 controls the operation of the corresponding heaters H11-H14 and H21-H24 provided in the respective regions using the temperature sensing signals output from the respective temperature sensors Respectively.

To this end, the preset temperatures for the respective chambers 41 and 42 are stored in the memory of the control unit 200.

Accordingly, the controller 200 reads the temperature sensing signals output from the temperature sensors of the respective regions of the chambers 41 and 42, determines the current temperature of the corresponding region, And the operation of the heaters (H11-H14, H21-H23) located in the corresponding region is stopped or driven. At this time, since the temperature of the lower region of the chambers 41 and 42 is lower than the temperature of the upper region by convection of air, the set temperature of the temperature sensor installed in the lower region is set to the set temperature Can be set lower.

The control unit 200 reads the output signals of the first and second temperature sensing units T11 and T12 for sensing the surface temperature of the pipe continuity PC outputting the chambers 41 and 42, (Not shown) when the determined surface temperature set temperature (for example, 110 占 폚 to 130 占 폚) is not reached, an alarm is output from the manager by operating a warning device And informs the current state of each chamber 41, 42. Therefore, the manager checks the operation states of the plurality of temperature sensors, the heaters H11-H14 and H21-H24 provided in the chambers 41 and 42 and the controller 200 for controlling them, do.

When the temperature of each of the chambers 41 and 42 is controlled by the operation of the plurality of temperature sensing sensors provided in the regions of the chambers 41 and 42 as described above, The second temperature sensing units T11 and T12 function as a monitor for keeping the temperature of each of the chambers 41 and 42 constant by using the surface temperature of the pipe continuum PC1.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

41, 42: chamber 43, 44: air circulator
81, 83: Inlet port 82, 84: Outlet port
91: Connector 911: Insulating membrane
100: temperature setting unit 200:
C1, C2: Shielding film H1, H2:
H11-H14, H21-H24: Heater PC1: pipe continuity
P1: pipes T11 and T12: temperature sensing unit

Claims (18)

At least one chamber having an inlet through which the pipe continuum flows and an outlet through which the pipe continuum is discharged,
At least one heater installed in the chamber to increase the internal temperature of the chamber,
At least one temperature sensing unit for sensing a temperature state of the at least one chamber and outputting a temperature sensing signal of the corresponding state,
And a controller for controlling the operation of the at least one heater by comparing the determined temperature with a preset temperature range by comparing the sensed temperature by reading the temperature sensing signal outputted from the temperature sensing unit The control unit
And a residual stress relieving device. The method of claim 1,
Wherein the at least one temperature sensing unit senses a surface temperature of the pipe continuum discharged from the at least one chamber. 3. The method of claim 2,
Wherein the temperature sensing unit is an infrared temperature sensor. 3. The method of claim 2,
And the set temperature range is 110 ° C to 130 ° C. The method of claim 1,
Wherein the at least one temperature sensing unit senses a temperature inside the at least one chamber. The method of claim 5,
Further comprising at least one temperature sensing unit sensing a surface temperature of the pipe continuum discharged from the at least one chamber,
Wherein the control unit outputs a warning signal when the surface temperature of the pipe continuum detected by the at least one temperature sensing unit for sensing the surface temperature is out of the set temperature range. The method of claim 1,
Further comprising at least one air circulator mounted in the at least one chamber, the at least one air circulator being connected to the control unit and operating under the control of the control unit to circulate the air inside the chamber. The method of claim 1,
Further comprising a shielding film attached to the inlet and the outlet to change the diameter of the opening according to the outer diameter of the pipe continuum flowing into and out of the chamber. The method of claim 1,
A position regulating plate having a plurality of stages positioned opposite to each other at least at one of the inside of the chamber, the front of the inlet and the rear of the outlet, Further comprising a roller guide for supporting the residual stress. The method of claim 1,
Wherein the at least one heater is a heating wire provided on an inner surface of the chamber. Operating the heater to heat the pipe continuum located in the chamber for a predetermined period of time,
Reading a signal output from a temperature sensing unit for sensing a temperature state of the chamber to determine a temperature state of the chamber, and
Controlling the operation of the heater by comparing a temperature corresponding to the determined temperature state of the chamber with a set temperature range
And removing the residual stress. 12. The method of claim 11,
Wherein the temperature sensing unit senses the internal temperature of the chamber or the surface temperature of the pipe continuum output from the chamber. The method of claim 12,
Wherein when the temperature sensing unit senses a surface temperature of the pipe continuum, the set temperature range is 110 ° C to 130 ° C. 12. The method of claim 11,
Wherein the predetermined time is increased as the diameter of the pipe continuum increases. 12. The method of claim 11,
Further comprising circulating the air in the chamber by driving an air circulator mounted in the chamber. Melting and extruding the raw material,
A molding step of making a pipe continuum of a desired shape for molding a raw material to be extruded,
Cooling the pipe continuum formed in the forming step, and
Treating the pipe continuum through the cooling step for a predetermined period of time to remove the residual stress in the pipe continuum by making the temperature of the pipe continuum fall within a set temperature range
≪ / RTI > 17. The method of claim 16,
Wherein the set temperature range is 110 ° C to 130 ° C. 17. The method of claim 16,
Wherein the predetermined time is longer as the diameter of the pipe continuum increases.

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