JPH06330176A - Heat treatment apparatus for round corner part of large diameter square steel tube - Google Patents

Abstract

PURPOSE:To obtain a large diameter square steel tube having uniform and high quality without strain and torsion by executing heat treatment mainly to round corner parts while holding a material to be treated long in the axial direction in the vertical direction and uniformly heating and cooling the material symmetrically with the axis. CONSTITUTION:The large diameter square steel tube 1 formed by bending and welding a steel sheet, is positioned at a table 3 for standing a steel tube on its end at supplying side. To the table 3, a steel tube shifting truck 4 is faced and stopped. Successively, the steel tube 4 is stood up on the truck 4 from the table 3 and held on the truck 4 side. Further, this truck 4 is shifted to a pit providing the heat treatment apparatus 6 and a steel tube lifting device, etc., and after stopping at a prescribed position, the steel tube 1 is housed in a pit. At the same time, the heat treatment apparatus 6 is worked and the parts near the round corners R of the steel tube is heated at a temp. of 650-950 deg.C and the other part is heated at a temp. lower than the that of round corner parts by 100-150 deg.C. Successively, this steel tube is shifted to the truck 4 and delivered to a table 7 for standing a steel tube on its end and shifted to a carry-out table 8 side.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a heat treatment apparatus for an existing large-diameter square steel pipe formed by bending a hot-rolled steel sheet by cold plastic working and butt-welding the side edges in the longitudinal direction of the steel sheet. For details, post-heat treatment is applied to the corner R of the square steel pipe to remove the residual stress of the steel sheet at the relevant location caused by cold forming, improve the toughness reduction, and improve the uniform and high-quality thickness. The present invention relates to a heat treatment apparatus for a large-diameter square steel pipe corner R portion for producing a large-diameter square steel pipe.

[0002]

2. Description of the Related Art In the mass production method and apparatus for thick-walled large-diameter rectangular steel tubes, which have been in high demand for use as columns for steel frame structures, conventionally, either continuous molding method or individual molding method has been used. In order to form the corner portion of the rectangular steel pipe, a step of bending a thick steel plate having a flat or arcuate curved surface by approximately 90 ° by cold plastic working is included. When a thick steel plate is bent by approximately 90 ° in the cold, the steel plate is deformed while a tensile force or a compressive force acts on the inside and outside of the steel material with the neutral surface of the steel plate cross section at the corner R as a boundary. Plastic deformation significantly progresses, and the mechanical properties of the deformed portion, particularly the corner R member material, may deteriorate, causing brittle fracture.

[0003] For example, the steel material at the corner R of the steel pipe is subjected to cold bending, strain hardening of the material, deterioration of toughness, high residual stress, and the like, resulting in welding cracks during hot welding at low temperatures in winter and hot dip galvanization. Cracks may occur during construction. In addition, due to the presence of these cracks and minute defects in the base material, when a heavy load is applied to the thick-walled steel pipe at low temperature, the steel sheet may be brittlely fractured.

Steel structures, buildings and the like using this kind of large-diameter rectangular steel pipe as a pillar material are generally safe in response to a predetermined load applied to the structure over a long period of time, an untimely disaster, an external force caused by an earthquake, etc. In addition, it is often required to support without distortion, and these pillars are often constructed in a state in which they cannot be replaced or repaired or are extremely difficult. Especially in recent buildings, high-rise buildings occupy the mainstream. In addition to installing air-conditioning and heating equipment, living-related equipment, etc. in each room, OA equipment, computers, etc. are installed, and the weight of equipment attached to the building Since there is a tendency that the number of thick-walled large-diameter square steel pipes is adopted as a pillar material as a countermeasure, the above-mentioned problems inherent in the cold-formed thick-walled steel pipes are It is a situation that cannot be ignored for me.

Therefore, in recent years, there has been an increasing demand from a consumer group to provide a high-quality rectangular steel pipe having a corner R portion having sufficient toughness and less residual stress. In order to solve this type of material problem inherent in the conventional thick, large-diameter rectangular steel pipes that are available in the market, the manufacturer has decided to use ready-made round steel pipes made by cold plastic working to remove oil, gas, etc. It has been proposed to heat fossil fuel or electric energy as a heat source as a whole to heat the steel pipe through a plurality of stages of angle-forming rolls before the heating temperature is lowered to form a square cross section.

When the above method is used, the quality of the product is good, but at the time of cross-section forming, the cross-sections at both ends of the steel pipe are defective in shape and the yield of the material is poor. However, there are problems that the generation of deformation strain due to this cannot be ignored, that a large amount of oxide scale that is generated on the surface of the steel pipe must be removed, and that the productivity is low because the steel pipe is machined individually. Further, since the entire steel pipe is heated to a high temperature, the cost of annealing increases.

Separately, a large-diameter rectangular steel pipe is placed in an annealing furnace, and the whole is heated to such an extent that residual stress of the steel material is substantially removed, the toughness of the corner R member material is improved, and then gradually cooled. Is also known. Also in this case, there is a problem similar to the above. Alternatively, in the process of forming a thick steel plate into a round steel pipe by cold plastic working, the steel pipe is used for electric energy or gas,
A fossil fuel such as oil is heated into a strip shape, and while the temperature does not cool, the steel pipe cross section is hot-worked and formed into a square shape through multiple stages of square-shaped rolls, and then gradually cooled to form a large-diameter square steel pipe. (See Japanese Patent Application No. 2-180497) is also considered.

[0008] The above-mentioned method is problematic in that the molding cross section is defective due to thermal nonuniformity during heating and the deformation strain due to nonuniform temperature distribution of the steel material during cooling is maintained, and a uniform temperature distribution is maintained during the heat treatment process. Temperature control is difficult, and it is necessary to take a cooling zone long enough to gradually cool the steel pipe. Further, in the slow cooling step, unlike the round steel pipe, the flow of the refrigerant gas is disturbed near the corner R of the steel pipe, so that it is difficult to uniformly cool the steel pipe cross section. And, when the rectangular steel pipe is deformed, it is very difficult to correct it.

Further, when a heating furnace using fossil fuel is installed in a square steel pipe forming line (including a high-frequency welding process), 100 m to 150 m in the middle of the line for heating the steel material to a desired temperature. Since a heating furnace space of m is required, it may be difficult to select a factory location or the amount of capital investment may expand more than expected. In addition, heating with fossil fuels such as gas and oil cannot put a heat source inside the steel pipe, so it is difficult to uniformly heat a long steel pipe in the longitudinal axis direction, and there is a problem in terms of temperature control. High quality products cannot be obtained after all due to poor molding of the cross section of the steel pipe, occurrence of distortion, etc.

On the other hand, the heating device utilizing electric energy has a small space in the heating furnace and is capable of uniformly heating the cross section of the steel pipe and easily controlling the heating temperature, but on the other hand, it requires an extremely large amount of electric power and has a high heating cost. In addition, depending on the location, it may be difficult to obtain the necessary large-capacity electricity. It is known that there are technical problems.

[0011]

SUMMARY OF THE INVENTION The present invention was developed in view of the above-mentioned circumstances, and economically improves the mechanical properties of the existing steel pipe corner R member material, and also reduces residual stress. It is an object of the present invention to provide a heat treatment apparatus for forming a high-quality large-diameter square steel pipe that is uniform and stable and is kept below an allowable limit.

Another object of the apparatus of the present invention is to develop a heat treatment apparatus for sequentially heating a large-diameter rectangular steel pipe in a vertical direction while sequentially heating it along the longitudinal axis direction, and to distort or twist the heat-treated steel pipe. It is intended to form a uniform and high-quality large-diameter rectangular steel pipe without any problem, and to solve the above-mentioned problems inherent in the conventionally known heat treatment method as much as possible. Further, another object of the apparatus of the present invention is to improve the material of a large-diameter rectangular steel pipe including a corner R portion in spite of performing the heat treatment at a lower temperature than the common general knowledge in the conventional heat treatment method for steel materials. Especially.

[0013]

In order to achieve the above-mentioned object, the present invention has the respective constituent features as described below. (1) A strip steel plate, a single steel plate or a double steel plate is bent by cold pressing or / and cold roll forming to close its longitudinal opening and weld a butt surface to form a rectangular cross section. A large-diameter rectangular steel pipe of unit length is arranged in the longitudinal direction of the steel pipe supply table, and is arranged at the end of the table. A stopper is provided in the conveying direction of the supply steel pipe and the steel pipe is held, and the stopper side is provided. A steel pipe inverted table on the supply side, which repeats the operation of vertically raising the longitudinal axis direction around one end of the swing center and reopening the holding means to return to the old position,

The unit length steel pipe vertically moved by the swing of the table is transferred and held in that position while standing upright, and is conveyed to a position facing the carry-out side inverted table via the heat treatment device, and the steel pipe concerned. Steel pipe moving trolley designed to be released, a heat treatment device with a guide placed on the steel pipe moving path and provided at the entrance side of the pit and the pit bottom, and the steel pipe held vertically by the moving trolley is received and supported. And a vertical moving device in the direction of the longitudinal axis of the pit, and an elevating device provided with a steel pipe lower end face bearing having a stroke of at least the same length as the steel pipe longitudinal axis,

During the vertical movement of the steel pipe, the heat treatment apparatus and the steel pipe moving carriage, which face each pair of steel pipe corners R in a plane perpendicular to the longitudinal axis of the steel pipe, and are provided with means for uniformly heating the portions. Installed so as to face the stop position, having a stopper for supporting the lower end surface of the vertical steel pipe, and having means for receiving and holding the steel pipe on the moving carriage side,
The steel pipe inverted table on the unloading side and the steel pipe of the table in which the longitudinal axis of the vertical steel pipe is tilted horizontally around the lower end and the holding means is opened to carry out the steel pipe, and then the operation of returning to the old position is repeated. Installed on the carry-out end side,
A steel pipe unloading table that conveys the steel pipe in its longitudinal axis direction,

Residual stress of each corner R member material of the steel pipe is reduced by heating the steel pipe in the vicinity of the corner R portion in a strip shape and uniformly in the longitudinal direction of the steel pipe, and then performing natural cooling or gradual cooling. A heat treatment device for a large-diameter square steel pipe corner R portion, which is characterized by removing and recovering toughness.

(2) The post-heat treatment temperature of the steel material in the vicinity of the corner R portion is set to about 650 ° C to 950 ° C, and the post-heat treatment temperature of other portions is set to 100 to 150 ° C lower than the heat treatment temperature. A heat treatment apparatus for a large-diameter rectangular steel pipe corner R section according to the item (1).

[0018]

[Function] The material defects which are regarded as a problem with the large-diameter square steel pipes on the market are the decrease in the toughness of the thick-walled steel pipe corner R member due to the cold plastic deformation in the steel pipe forming process, and the increase in the residual stress. It is a weakening as a structural material due to deterioration of local material. (1) In the device of the present invention, a large-diameter square steel pipe having a unit length formed by cold plastic deformation according to the standard is received in the steel pipe supply side inverted table, positioned by the stopper and the holding means, and secured as it is. A steel pipe moving carriage equipped with a vertical support is opposed to and stopped at the rising position of the steel pipe supply side inverted table.

The steel pipe supply side inverted table is oscillated around the rotation shaft on the stopper installation end side, and the large-diameter rectangular steel pipe of unit length held on the inverted table is used as a vertical support on the steel pipe moving carriage. Along with this, the holding means provided on the support table is moved to the holding means side to activate the holding means, the holding means on the inverted table side is opened, and the large-diameter square steel pipe is secured on the moving carriage side. Move the moving carriage on which the large-diameter rectangular steel pipe is transferred to the position of the pit equipped with heating means and steel pipe lifting device,
Stop when the central axis of the steel pipe cross section and the center of the equipment in the pit coincide. Extend the elevating shaft of the steel pipe lifting device in the pit, contact the upper end surface of the steel pipe lower end surface of the moving carriage side to support it, transfer the weight of the steel pipe to the elevating shaft side, and open the holding means on the moving carriage side. Release the support of.

The elevating shaft of the steel pipe elevating device is lowered at a predetermined speed while supporting a large-diameter rectangular steel pipe, and the periphery of the steel pipe is guided by a guide device at the entrance of the pit,
Store steel pipes in the pit. At the same time, activate the heating device installed at the pit entrance,
While a specific portion of the peripheral surface of the steel pipe passes through the heating device, the temperature of the steel plate in the vicinity of the opposing steel pipe corner R portion should be at least 65.
About 0 ℃, the temperature of steel plate on other flat surface is 10
The steel pipe is heated at a low temperature of 0 to 150 ° C. for a certain period of time. However, the above heat treatment can be added when the rectangular steel pipe is lifted from the pit. In this case, the operation of accommodating the steel pipe in the pit may be relatively fast.

Thus, after the heat treatment is applied to the entire length of the steel pipe in the longitudinal axis direction and the stroke of the elevating shaft almost reaches the bottom dead center, the operation of the elevating shaft is reversed and the heat treated steel pipe is lifted. Delivered to the steel pipe holding means side of the old mobile truck. At that time, the projecting surface portion provided on the lower holding means on the moving carriage side supports the weight of the large-diameter rectangular steel pipe, and transfers the weight to the moving carriage side. After the trolley support holds the steel pipe, the steel pipe longitudinal axis is held in the vertical direction, and the moving trolley is moved while cooling, facing and stopping the rising position of the steel pipe unloading side inverted table. After the heat-treated steel pipe is delivered to the carry-out inverted table side by the process opposite to the description, the inverted table is horizontally swung to make the longitudinal axis of the rectangular steel pipe horizontal and transferred to the carry-out table side. .

(2) In the above post heat treatment, the heat treatment start position may be either above or below the steel pipe end face supported in the vertical direction. However, when a forced cooling device is installed side by side, the device must work behind the heat treatment direction. As a result of research, the range of deterioration of the steel sheet material due to cold plastic deformation for forming the corner R portion of the steel pipe is, as a result of research, at most, a width equal to the length of the steel sheet thickness in the flat surface direction from the corner R portion and both ends of the R portion. Since it is known to include the area, it is a condition that the target area of the corner R of the local heating includes at least the entire area.

In a cross section perpendicular to the longitudinal axis of the steel pipe, heating means, for example, a high (low) frequency heating coil, which is respectively arranged facing and close to each corner R portion thereof, is installed toward the central axis of the steel pipe. Then, the respective coil groups are simultaneously made to have a structure capable of advancing / retreating / adjusting in the radial direction with respect to the central axis, and the position / interval of the coils (heating means) is adjusted according to the size of the steel pipe to be heat treated. The above structure is the same in the guide device for the steel pipe peripheral surface provided in the pit. It is desirable to select a low / medium frequency or high frequency heating device for the local heating device at the corner R of the rectangular steel pipe.

According to the high-frequency heating device, it is easy to adjust the heating temperature distribution inside and outside the cross section of the steel pipe at right angles to the longitudinal axis and to control the heating temperature, the maintenance of the device is simple, and the space required for the heating device is small. It can be small. By adopting the induction heating method, the distribution of the heating temperature and the management of the heating temperature can be facilitated, and the effect of refining the steel material crystals can be obtained. For the high frequency current, a frequency is selected so that the entire thick steel plate can be heated uniformly.

The output of the high frequency heating coil is determined on the basis of conditions such as the size of the heat treated steel pipe, the thickness of the steel material plate, the desired heating temperature and the holding time of the heat treatment temperature. The output capacity of the coil is related to the above conditions. It is preferable to set it so that it can be changed significantly. However, as a heating means for the steel pipe, it is possible to use LP gas, fossil fuel such as petroleum, and coal gas, which are available in large quantities and are relatively low in cost.

In order to effectively utilize the generated thermal energy, the inner wall of the pit can be lined with a heat resistant material or a heat insulating material. The heated steel pipe may be gradually cooled by natural cooling or air cooling, or may be cooled to a certain extent and cooled to a certain temperature, and then uniformly cooled from the four circumferences of the steel pipe by spraying and / or showering. Good. The forced cooling start temperature does not necessarily have to be around room temperature. Even if the steel pipe cooled to near room temperature in the device is forcedly cooled thereafter, bending or twisting in the direction perpendicular to the longitudinal axis does not occur based on this.

(3) As a result, deterioration of the steel plate material such as residual stress and toughness due to cold plastic deformation applied to the steel plate in the step of forming a rectangular steel pipe from a strip steel plate or a single steel plate, particularly the steel pipe corner R part (EN) Provided is a high-quality and uniform large-diameter square steel pipe with improved mechanical properties of local member materials including. By locally heating the post-heat treatment of the cold-formed steel pipe corner R, energy can be saved compared to the amount of energy required to heat the entire steel pipe.

In the post heat treatment of the rectangular steel pipe, the steel pipe longitudinal axis is vertically supported, the heat treatment conditions are the same for each corner R and the peripheral surface, and the heat treatment is sequentially performed along the steel pipe longitudinal axis in a strip shape. , It reduces the processing strain caused by the posture of the rectangular steel pipe during the heat treatment, and simplifies the straightening device for the post-treatment. In the band-shaped heat treatment of the steel pipe material, since the temperature difference between the corner R portion and the flat surface is small, the thermal expansion strain between them is small. Since effective heat treatment is performed within a relatively low temperature range, energy saving can be realized, and the surface roughness of the steel pipe is small, increasing the commercial value of large-diameter square steel pipe. By performing the above-mentioned heat treatment, the axial and circumferential characteristics of the inner and outer materials of each corner R portion, flat portion, and welded portion of the rectangular steel pipe peripheral wall steel sheet are recovered to the point where they are almost the same as the characteristics of the steel sheet material before processing. I confirmed that it was improved. In any case, it is possible to relatively economically remove defects such as deterioration of the material of the corner portion R of the steel pipe due to cold plastic deformation of the corner portion of the large-diameter rectangular steel pipe, which is a problem in recent years, and the presence of large residual stress. You can

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the device of the present invention will be described below with reference to the drawings. However, the specific configuration of the right device can be partially modified within the range known to those skilled in the art at the time of this application. Therefore, it is not allowed to limit the configuration requirements of the device of the present invention based on only the specific description of the present embodiment without showing a special reason.

FIG. 1 is a schematic plan view of an embodiment of a heat treatment apparatus for a large diameter square steel pipe corner R of the present invention, and FIG.
3 is a detailed view of a steel pipe inversion table, FIG. 4 is a detailed view of a steel pipe moving carriage, and FIG. 5 is a detailed cross-sectional view of a heating device with a pit.

In FIGS. 1 and 2, reference numeral 1 indicates an existing unit long-thickness large-diameter square steel pipe (column), and the used steel material is SM490A.
The steel plate has a thickness of 22 mm and a 500 mm diameter rectangular steel pipe. Seen in the column transport order, 2 is a column carry-in table in which a plurality of transport rollers with a power unit are mounted on the upper side at the same pitch, and the columns are transferred to the carry-in side column inverted table 3 side by one side. Reference numeral 4 denotes a column moving carriage that is opposed to the end surface of the loading-side column inversion device 3 on the side of the swing shaft and is stationary. The carriage has the column 1 supported and placed by a holding means provided on the carriage. As it is, it moves intermittently on the endless rail 5.

Reference numeral 6 denotes a heating device provided along the rail 5, which is installed in the pit, stops the column moving carriage 4 at the same device 6, and heats the column 1 from the moving carriage at that position. Falling vertically into the device 6 in the longitudinal direction,
Then, the column 1 is post-heat-treated in the meantime. 7
Is an unloading-side column inverted table provided facing the stop position of the movable carriage 4 that moves while holding the heat-treated column 1. The configuration of the unloading-side column inverted table 3 is substantially the same.
, Which is the same as that. The heat-treated column 1 placed on the column moving carriage 4 is transferred from the moving carriage 4 to the unloading side column inversion table 7 at that position, and then rocked together with the inversion device to arrange the steel pipe longitudinal axis in the horizontal direction.

Reference numeral 8 denotes a column carry-out table continuously provided on the free end side of the carry-out side column inverted table 7, and its concrete structure is the same as that of the column carry-in table 2 described above. The column unloading table 8 has a function of receiving the heat-treated column 1 held on the unloading-side column inverted table 7 which is horizontally swung, and transporting the heat-treated column 1 to the cooling step.

3A and 3B show a detailed structure of a main part of the carry-out side column inverted table. FIG. 3A is a plan view and FIG. 3B is a side sectional view. In the figure, reference numeral 3 is a loading-side column upside-down table, which receives a column 1 from a column loading table 2 by driving a transport roller 9 with a power device provided on the upper surface of the table, and loads the column 1 to the left in the figure to remove the column end surface. The table 3 is brought into contact with and positioned by a stopper 11 provided near the swing shaft 10 side. Although not shown, left and right guides are required to be attached to the transport roller 9 and to fit the size of the column 1 to bring the center out of the table and transport the column. The stopper 11 is connected to the fluid pressure drive device and can move between the orientation value and the retracted position as required.

A fluid pressure drive unit 12 is rotatably supported by a support arm attached to the inner wall of the pit provided below the column upside-down table 3, while the tip of the plunger is inverted. The column inversion table 3 is moved to the horizontal position as shown by the arrow around the swing center axis 10 by locking the shaft at a position away from the swing center axis 10 on the back surface of the column and operating the fluid pressure drive device. To the vertical position. The fluid pressure drive operation can be replaced by operation by mechanical means. Column inverted table 3
At the horizontal position, the other end is connected to the column loading table 2, and at the vertical position, the other end is opposed to the holding means of the column moving carriage 4 stopped / positioned along the column inverted table 3.

Numeral 13 is a column holding means arranged on the column inverted table 3 along the conveying roller 9, and the means 13 secures / releases the transferred column 1 by a method of holding it from both sides thereof. . The structure of the same means is also useful as column holding means provided on the column moving carriage 4.

4A and 4B show the detailed structure of the column moving carriage 4, in which FIG. 4A is a plan view and FIG. 4B is a side view. In the figure, 14 is a stand having an L-shaped structure, on the lower side of the horizontal plate of which a wheel 15 with a driving device for the moving carriage to move on the rail 5 is provided, and at the other end of the upper side surface thereof. A balance weight 17 is attached to balance the weight of the column. Column holding means 16 each having a column holding means and a column lower end surface supporting surface are installed on the outer wall of the rising portion of the L-shaped base 14, and the column 1 held on the inverted table 3 with respect to the space surrounded by the means. When carried in, the column holding means 16 is activated to close the column lower end surface side, the stopper 11 on the column inverted table side is lowered, and the holding means 13 is opened to move the column 1 to the movable carriage 4
The column upside down table 3 is moved to a position where it does not hinder the movement of the movable carriage 4 while being moved to the side and rocking the table 3 toward the old position.

The holding means 16 is provided with a driving device for moving the pair of column restraining arms toward and away from each other in the horizontal direction as shown by the arrow, and holds the column 1 brought in between them from the lateral direction. Do or open. The lower end surface of the vertical column 1 is a holding means located at the lowermost side.
It is supported by a supporting surface which is provided so as to project inward of 16. When the column 1 is delivered, the column holding means 13, 16 and the stopper 11, the supporting surface portion of the holding means 16 must occupy positions that do not interfere with each other. Moreover, one of them needs to be always active.

Thus, the column 1 is placed on the movable carriage 4 while being held vertically in the longitudinal axis direction thereof and conveyed to the position of the heating device 6. Note that the process of transferring the column 1 whose longitudinal axis is held in the vertical direction from the column moving carriage 4 to the carry-out side column inverted table 7 includes the step of transferring the column from the carry-in side inverted table to the movable carriage 4 side. The description of this process is omitted as it is just the opposite procedure.

FIG. 5 is a sectional view of a heating device 6 having a pit. In the drawing, 1 is a column, 19 is a lifting shaft of a column lifting device 18 arranged at the bottom of the pit, and the upper end surface thereof. Supports the lower end surface of the column whose longitudinal axis is held in the vertical direction, and moves the column 1 in the heating device 6 in the pit upward and downward at a predetermined speed as indicated by an arrow. The heating means controls the lifting shaft so as not to be heated. However, it is desirable to attach a cooling means to the lifting shaft 19. The elevating shaft 19 is vertically supported, and a rack is cut along the longitudinal axis of the elevating shaft 19, and a pinion interlocked with the output shaft of the gad motor 20 is meshed with the elevating shaft 19 to control the motor 20 to move up and down. The shaft 19 can be reciprocally moved in the vertical direction and at a predetermined speed.

Further, the shape of the column end surface bearing surface at the upper end of the elevating shaft may be substantially the same as that of the stopper 11 described above, and a heat insulating / heat shielding means may be provided between the elevating shaft and the lower part of the elevating shaft. The vertical movement stroke of the elevating shaft 19 is at least slightly longer than the length in the longitudinal axis direction of the rectangular steel pipe 1 of unit length, and the lowest position of the upper end surface of the elevating shaft 19 is such that the upper end surface of the column 1 supported by the elevating shaft 19 is high (low ) It is set on the condition that it passes through the mounting position of the frequency coil 21, and the highest position is supported by the lower end surface of the column 1 which is carried on the moving carriage 4 and lifted slightly,
The lower end surface of the column is set at a position away from the support surface portion of the holding means 16 of the moving carriage 4. Thus, the weight of the column is
After moving to the side, the column holding means 16 of the moving carriage 4 is released.

Reference numeral 21 denotes a high (low) frequency heating coil installed near the opening of the pit, which is provided so as to face each corner R of the column 1, and the capacity of the heating coil is set within the column during the moving time of the column. It has enough power to heat up to a predetermined temperature. The coil 21 is attached so as to be movable in the radial direction according to the size of the column 1. In the case of the present embodiment, the rack is carved on the coil support rods that are supported so as to be slidable in the radial direction with respect to the pit wall side, and the pinions that engage with the rack are interlocked with each other, so that the high (low) frequency coil is 21 to the center axis of column 1,
It is provided so that they can be approached and isolated at once.

As a result, even if the size of the steel pipe (outer diameter and plate thickness) changes, it is possible to adapt to heat treatment of columns of all sizes without changing the attachment. The high (low) frequency heating coil 21 is supplied with a high frequency (selecting a frequency capable of uniformly heating the plate thickness) current, and the plate of each corner R part steel plate in the plane perpendicular to the column longitudinal axis. The entire thickness (22 mm in this embodiment) is locally heated evenly.

By the time the local portion of the column has finished passing through the high (low) frequency heating coil 21, the corner R steel material is heated at about 600 ° C. to 650 ° C. for about 30 minutes. At that time, since heat energy is also conducted to the flat portion side of the column steel plate, the flat portion side is indirectly heated and the amount of thermal expansion strain generated is reduced. Reference numeral 22 is a guide of the column 1, which is attached to the upper and lower pit walls of the high (low) frequency heating coil 21, respectively, and is used for the central axis of the column 1 that is lowered and raised by the lifting device and the center of the arrangement of the coil 21. However, it has a function of always guiding to match.

Therefore, the guides 21 must also be adjustable and movable in the radial direction in accordance with the size of the column 1. The material used for column 1 is SS400,
SM400A, SM490A, SM490B, SM490C, SM520B, C or non-refined high-strength steel 60 kg is selected, and the above-mentioned device can be applied to any of the steel materials and the desired effect is achieved. A heat-resistant / refractory material is lined on the inner wall of the pit of the heat treatment device 6 to form a heating chamber to prevent the dissipation of heating energy, and to block the radiant heat from the steel sheet surface of the corner R part of the column 1.
Also, it has a heat retaining effect.

Each high (low) frequency heating coil 21 surrounds each corner R of the column 1 and is divided into three parts (two to two).
The coil is divided into five parts, and all coils are installed at the same distance from the steel pipe peripheral surface. Of course, the coil 21 is provided with a cooling device. As described above, the range of the corner R portion in which material deterioration occurs due to cold bending of the thick steel plate depends on the cold working state, but the corner R portion is included in the column cross section. It is ascertained that the limit is a region extending from the terminal end of the corner R portion to the side of the steel plate flat plate portion by the plate thickness t of the steel plate in both directions.

Therefore, the heat treatment range has only to cover the above region in each corner R portion. The heating means may be a burner that utilizes fossil fuels such as gas or heavy oil. Further, a plurality of burners opposed to and arranged in the corner R portion of the column can be provided side by side in the longitudinal direction of the column.

When the apparatus of the present invention is operated, a post heat treatment temperature curve to be added to the steel material at the corner R of the column is tried, the heating gradient is 100 ° C./H, the cooling is natural cooling, and the set temperature is 500 ° C., respectively. 550 ℃, 600 ℃ and 650 ℃, ± 25 ℃
Then, when the heating time of 30 minutes was taken at the same temperature, the following results were obtained. The data described below was obtained from a test piece obtained by cutting out the longitudinal steel material at the front surface side and the inner surface side position of the steel material at the column cross-section corner R part, and the dimensions of the sample steel pipe are 22 mm in thickness and 500 mm in thickness. mm square,
The corner is R = 77 mm, and the material is the cold plastic working square steel pipe of SM490A which has been post-heat-treated under the above conditions.

According to the tensile test results for the test pieces obtained by taking the steel material of the inner surface of the corner R of the cold-formed large-diameter square steel tube subjected to the heat treatment along the above-mentioned post-heat treatment temperature curves, It was found that the values of tensile strength σu, yield point σy, and elongation% tended to be stable by heat treatment at a heat temperature of over 550 ℃ and around 600 ℃. The same applies to the yield ratio σy / σu. The tensile test results of the test piece similarly sampled from the inner surface portion of the column flat plate also show a tendency similar to the above.

Further, looking at the tensile test results of the test pieces obtained by sampling the steel material at the outer surface of the steel pipe corner R in the longitudinal axis direction,
After heat temperature exceeds 550 ℃ and around 600 ℃,
It can be seen that the values of tensile strength σ u, yield point σ y and elongation% are stable. The same applies to the yield ratio σy / σu.
The tensile test results of the test piece taken from the outer surface of the flat plate of the steel pipe also have a tendency similar to the above.

Examination of changes in the energy transition temperature vTre of the test pieces taken from the inner and outer surface portions of the steel pipe corner R and the inner and outer surface portions of the flat plate based on the post heat treatment revealed that the energy transition temperatures of all the test pieces were approximately the same. After heat temperature becomes 600
It was ~ 650 ° C. The change in hardness at the corner R of the steel pipe due to the post heat treatment reveals that the higher the post heat temperature, the smaller the variation in hardness (difference between the maximum and the minimum). It was also found that the change in residual stress due to post heat treatment was similar to that before processing if the post heat temperature was about 600 ° C.

From the analysis of the above test results, the post heat treatment for improving the deterioration of the material of the corner R portion of the cold plastic deformation column based on the known manufacturing method and for removing the residual stress of the flat plate portion is It can be seen that the object can be achieved by processing at least 600 to 650 ° C for 30 minutes, and there is no need for it or more. If the material is heated to a higher temperature, not only the energy consumption becomes expensive and uneconomical, but also the surface roughness of the steel pipe and the generation of scales increase, resulting in a decrease in commercial value.

If the heating is performed at a lower temperature or the processing time is shortened, a desired degree of processing cannot be performed. The post-heat treatment conditions described above may be slightly different depending on the size and material of the target column, but they do not change significantly. However, increasing the heat treatment temperature to about 850 to 950 ° C. is not hindered. The post heat treatment of the column may be performed at the same timing as the operation of lowering the column 1 by the lifting device 17, or the post heat treatment may be performed while raising the column.

In any case, the column is again moved by the carriage 4
By the time the column holding means 16 is secured, the heat treatment must be completed uniformly over the entire longitudinal direction of the column 1. When the heat-treated column 1 is lifted from the heat treatment device 6, the column-holding means 16 of the movable carriage 4 stopped at the same position ascends while the tip is guided, and then the longitudinal axis is vertically supported. While it is being conveyed to the position of the unloading side column inverted table 7 as it is, it is naturally radiated and cooled to significantly lower the temperature.

According to the present embodiment, the post-heat treatment is performed in the state where the column 1 is held in the vertical position so that the peripheral wall of the column can be uniformly heat-treated, and each non-uniform thermal stress or gravity generated in the steel pipe at the time of heating. It is possible to significantly prevent the occurrence of distortion due to. Further, since the column material after heat treatment can be cooled and allowed to cool under the condition that the entire circumference is even, it is possible to prevent the occurrence of uneven thermal strain such as twisting and bending. In this example, the minimum heating temperature necessary for clearing the conditions desired by the user was found for the column that was cold plastically formed from a predetermined material, and as a result, it was possible to obtain extremely economical and high quality. Heat treated columns can be produced. By using the apparatus described in the present embodiment, it is possible to perform post heat treatment on all of the cold plastically formed columns (including the flat plate portion) and, if necessary, seam welded joints.

[0056]

EFFECT OF THE INVENTION The heat treatment apparatus for the corner R portion of the rectangular steel pipe of the present invention is as described above. (1) Since the post-heat treatment is carried out while holding the material to be treated long in the axial direction in the vertical direction, The material can be heated and cooled axially symmetrically under uniform conditions, and distortion due to heat treatment is less likely to occur. (2) The material to be treated that is long in the axial direction is divided into apparently short parts in the longitudinal direction, and the four corners R are uniformly locally heated, so that the steel material does not soften in the entire steel tube due to heating, and the square steel tube Thermal expansion strain and heat treatment strain in the longitudinal axis direction hardly occur.

(3) Since the post heat treatment is carried out at the minimum necessary temperature as a whole, the energy saving effect is great and the economical heat treatment becomes possible. (4) Only the heat treatment temperature of the steel pipe corner R part is set relatively high, the temperature of the flat part is set relatively low, and the heating time is maintained for a while, so that the corner R due to the cold plastic deformation of the steel plate. High-quality large-diameter rectangular steel pipe that meets the user's request, which is made of a homogeneous steel material and has a large resistance to twisting, which effectively eliminates deterioration of the material quality, brittleness, and residual stress of flat material. Can be manufactured.

(5) Since the purpose is to heat-treat the ready-made steel pipe corner R portion, there is an energy saving effect, and the heat treatment is possible with a relatively simple equipment cost, and good results are obtained. Therefore, the heat treatment cost of the large-diameter square steel pipe can be significantly reduced, and a high-quality large-diameter square steel pipe can be provided at low cost.

(6) According to the apparatus of the present invention, it becomes easy to design the structure of one post-heat treatment apparatus for steel pipes so as to be adjustable so as to suit the processing of rectangular steel pipes of various sizes. Heat treatment can be performed regardless of the plate thickness of the steel material, the size of the steel pipe, etc. (7) The treated thick-walled rectangular steel pipe is also subject to welding at the low temperature when welding is performed near the R corner of the steel pipe. There is no risk of weld cracking.

(8) Even when the rectangular steel pipe is hot dip galvanized, there is no inconvenience of cracking from a part of the steel pipe material. (9) Even if a large twisting force is applied to the longitudinal axis of the steel pipe,
The area near the corner R of the steel pipe will not be destroyed first. And so on, the operation of the apparatus of the present invention brings about special actions and effects that cannot be expected from the conventionally known steel pipe heat treatment means.

[Brief description of drawings]

FIG. 1 is a schematic plan view of an embodiment of a heat treatment apparatus for a large diameter square steel pipe corner R portion of the present invention.

FIG. 2 is a sectional view of the main part of the device,

FIG. 3 is a detailed view of a steel pipe inverted table of the device,

FIG. 4 is a detailed view of a column moving carriage of the device,

FIG. 5 is a cross-sectional view of a heat treatment apparatus having pits attached to the apparatus.

[Explanation of symbols]

 1 column (large-diameter rectangular steel pipe) 2 column carry-in table 3 carry-in side column inverted table (apparatus) 4 column moving carriage 5 rail 6 heating device 7 carry-out side column inverted table (apparatus) 8 column carry-out table 9 powered roller 10 Swing central shaft 11 Stopper 12 Fluid pressure drive 13, 16 Column holding means 14 L-shaped stand 15 Wheel with drive 17 Balance weight 18 Column lifting device 19 Lifting shaft 20 Gear motor 21 High (low) frequency heating coil 22 Guide.

Claims (2)

[Claims] 1. A strip steel plate, a single steel plate or a double steel plate is bent by cold pressing or / and cold roll forming, the longitudinal opening thereof is closed, and the butt faces are welded into a rectangular cross section. Formed large-diameter rectangular steel pipe with unit length,
A steel pipe supply table for conveying in the longitudinal axis direction, arranged at the end of the table, provided with a stopper in the conveying direction of the supply steel pipe and holding the same steel pipe, with one end near the stopper being the swing center, The supply side steel pipe inverted table which repeats the operation of vertically raising the longitudinal axis direction and opening the holding means again to return to the old position, and the unit length steel pipe vertically made by swinging the table In the pit entrance, the steel pipe is moved and held in an upright position, transported to a position facing the unloading-side inverted table via the heat treatment device, and the steel pipe moving carriage that releases the steel pipe holding is placed in the steel pipe moving path. Side heat treatment apparatus with a guide and the bottom of the pit, which receives and supports the steel pipe vertically held by a moving carriage, and vertically moves in the pit in the longitudinal axis direction. And a lifting device provided with a steel pipe lower end surface bearing having at least a stroke of the same length as the steel pipe longitudinal axis, at each pair of steel pipe corners R in a plane orthogonal to the steel pipe longitudinal axis during vertical movement of the steel pipe. Opposing, the heat treatment apparatus having means for uniformly heating the location, installed opposite to the steel pipe moving carriage stop position, with a stopper for supporting the lower end surface of the vertical steel pipe,
A means for receiving and holding the steel pipe on the side of the movable carriage, an operation of tilting the vertical steel pipe longitudinal axis horizontally around the lower end near the swing center, opening the holding means to carry out the steel pipe, and then returning to the old position And a steel pipe unloading table that is installed on the steel pipe unloading end side of the table and that conveys the steel pipe in the longitudinal axis direction thereof. The large diameter square shape is characterized in that the residual stress of each corner R member material of the steel pipe is removed and the toughness is restored by performing natural cooling or gradual cooling after sequentially heating in the longitudinal direction of the steel pipe. Heat treatment equipment for steel pipe corner R part. 2. A steel material post heat treatment temperature in the vicinity of a corner R is set to a level of about 650 ° C. to 950 ° C., and a post heat treatment temperature at other portions is set to be 100 to 150 ° C. lower than the heat treatment temperature. Heat treatment equipment for the large radius square steel pipe corner R part.