JP2011127187A - Heat-treatment method and rapid cooling device for bar steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-treatment method and a rapid cooling device for bar steel with which a plurality of bar steels heated into a prescribed temperature zone and lined up in each shaft direction along the horizontal direction can rapidly be cooled and the bending can be reduced. <P>SOLUTION: The heat-treatment method for bar steel includes a heating process for heating the bar steel M having round shape in the cross section to a prescribed temperature zone, and a rapid cooling process for rapidly cooling such heated bar steel M; and such rapid cooling process is the one, with which the plurality of bar steels M lined up in the each shaft direction along the horizontal direction, are ascended/descended over the plurality of times in a water vessel 10 for circulating the water (cooling liquid) W in the water vessel (liquid vessel) 10 while flowing along the diameter direction of the above bar steel M together with a loading table 2 for loading these bar steels. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for heat-treating a plurality of steel bars whose axial directions are long and in which individual axial directions are arranged in parallel along the horizontal direction while suppressing bending in the radial direction, and a steel bar quenching apparatus used for the heat treatment About.

  A steel bar made of stainless steel and having a diameter of about 30 to 50 mm and a total length of about 5 to 6 m (meters) is subjected to heat treatment such as solution treatment or quenching in order to give the required characteristics after hot rolling. Is done. For example, the solution treatment of austenitic stainless steel is performed by heating and holding a plurality of parallel steel bars at about 1080 ° C. in a heat treatment furnace, and then immersing them in water and rapidly cooling them. In this water cooling, if the long steel bar is not cooled uniformly, a bending occurs in which the axial intermediate portion is biased in the radial direction. In order to correct such bending, there is a problem that a correction process is required and productivity is lowered.

In order to cool a long steel bar uniformly, a long table is made by swinging a mounting table having a bowl shape in the vertical and horizontal directions and placing one or more long materials inside the mounting table and allowing it to cool. A material cooling method has been proposed (see, for example, Patent Document 1). However, this cooling method has a problem that it cannot be applied to heat treatment involving rapid cooling such as water cooling.
Further, one long steel bar / wire supplied along the axial direction is fed into the adjacent water-cooled pipe from the guide hole of the male fitting element, and along the outer peripheral side of the male fitting element. There has also been proposed a water-cooling method for steel bars and wire rods in which cooling water discharged spirally is injected in an annular shape on the outer peripheral surface of the steel bars (see, for example, Patent Document 2). However, this cooling method has a problem that a plurality of steel bars arranged in parallel cannot be subjected to rapid cooling such as water cooling at the same time.

JP 2000-345235 A (pages 1-8, FIGS. 1-7) JP-A-5-115914 (pages 1-8, FIGS. 1-8)

  The present invention solves the problems described in the background art, and is capable of uniformly quenching and bending a plurality of steel bars heated to a predetermined temperature range and having individual axial directions aligned along the horizontal direction by water cooling or the like. It is an object of the present invention to provide a steel bar heat treatment method and a rapid cooling apparatus capable of reducing the above.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-mentioned problems, the present invention has been conceived by repeatedly elevating and lowering a plurality of steel bars in a flowing cooling liquid in a liquid tank to be rapidly cooled.
That is, the steel bar heat treatment method according to the present invention (Claim 1) includes a heating step of heating a steel bar having a circular or square cross section to a predetermined temperature zone, and a quenching step of rapidly cooling the heated steel bar, Such a rapid cooling process is to raise and lower a plurality of steel bars in which individual axial directions are aligned along the horizontal direction a plurality of times in a liquid tank in which the cooling liquid in the tank is circulating while flowing. Features.

  According to this, the plurality of steel bars heated to a predetermined temperature zone are moved up and down several times in the liquid tank in which the coolant is circulating while flowing, and thus contact with the flowing coolant. Thus, the whole is cooled substantially uniformly with high heat exchange efficiency. As a result, it is possible to suppress as much as possible the bending that is biased in the radial direction due to variations in temperature distribution. Therefore, since the correction process after heat treatment can be eliminated or reduced slightly, it is possible to contribute to improvement of productivity and reduction of production cost.

The steel bar is made of stainless steel, various alloy steels, etc., and has an axial length of about 5 to 7 m (meter) and a diameter of about 30 to 60 mm, or a side of about 30 to 50 mm. It has a square cross section.
Further, the square in the cross section of the steel bar includes a square and a cross section with rounded corners (R) at each corner.
Further, the plurality of bar steels include a plurality of bar steels in which the respective axial directions are arranged in parallel as one set of bar steel groups, and two or more sets of steel bar groups in which the axial directions thereof are parallel to each other and are in series. The form arrange | positioned in is also included.
Moreover, although the said predetermined temperature range is selected according to steel types, it is the range of 850-1100 degreeC.
Furthermore, the liquid tank includes, for example, a water tank or an oil tank, and the cooling liquid includes, for example, water or oil.
In addition, the flow of the cooling liquid in the liquid tank is not limited to the horizontal circular shape, the oval shape, or the elliptical shape that flows and circulates as described below, and from the opposite side wall toward the other side wall. A type in which the cooling liquid in the liquid tank flows almost in parallel is also included.
In addition, the heat treatment includes hardening, in addition to solution treatment.

Further, in the present invention, the cooling liquid in the liquid tank is circulated in the liquid tank while flowing in a circular shape or an elliptical shape with the axial direction of the plurality of steel bars as a rotation center. A heat treatment method (Claim 2) is also included.
According to this, the coolant in the liquid tank first flows under the plurality of steel bars along the radial direction thereof, and then flows upward on one side of the plurality of steel bars, It flows in a laterally circular shape, an elliptical shape, or an elliptical shape that flows and circulates along the radial direction of the steel bar. As a result, the multiple steel bars come into contact with the coolant on almost the entire surface, so that the entire surface can be cooled more uniformly with a high heat exchange rate. Therefore, the steel bars can be bent in the radial direction due to variations in temperature distribution. It can be suppressed as much as possible.
In the liquid tank, a part of the cooling liquid that has flowed along the radial direction on the upper side of the plurality of steel bars overflows the overflow portion formed at the upper end of the side wall of the liquid tank. Therefore, by controlling the temperature of the coolant when it overflows, it becomes possible to easily and reliably manage the temperature of the steel bar.
Further, the direction in which the coolant circulates is not fixed, and it may be possible to back flow by alternately rotating clockwise and counterclockwise in the horizontal direction.

  On the other hand, a steel bar quenching device according to the present invention (Claim 3) is a device for quenching a plurality of steel bars used in the quenching step of the heat treatment method, and supports the plurality of steel bars and rotates substantially orthogonal thereto. A gantry to which a plurality of rollers having shafts are attached, elevating means for raising and lowering the gantry between the upper part of the liquid tank and these liquid tanks, and a pump or a fan arranged near one side wall in the liquid tank It is characterized by including these.

According to this, a plurality of the steel bars heated to a predetermined temperature zone are moved up and down multiple times in the liquid tank in which the coolant flows and circulates, so that high heat exchange is achieved by contacting with the flowing coolant. Depending on the rate, the entire surface can be made substantially uniform and cooled. Therefore, it is possible to suppress as much as possible the bending of the steel bar that is biased in the radial direction due to variations in temperature distribution.
The gantry and the liquid tank (water tank, oil tank, etc.) may be a steel bar rapid cooling device located adjacent to or close to the carry-out port of the heat treatment furnace.
The elevating means includes a chain and a sprocket (chain gear) that winds and rewinds the chain, a wire rope and a drum that winds and rewinds the wire rope, a fluid pressure cylinder such as air or oil, a rack and a pinion that meshes with the rack. .
Furthermore, the pump may be arranged outside the side wall of the liquid tank, and the discharge pipe may pass through the side wall, or a submersible pump arranged near the side wall in the coolant.

Further, according to the present invention, the elevating means is a steel bar rapid cooling that is attached to a carriage that traverses between the upper side of the liquid tank and the sides thereof together with the gantry raised above the liquid tank. A device (claim 4) is also included.
According to this, a plurality of steel bars that have undergone a rapid cooling step are raised together with the gantry above the liquid tank by the elevating means, and then conveyed in the lateral (horizontal) direction of the liquid tank by the conveying vehicle, and the elevating and lowering are performed. It can be lowered to the required level by means. Accordingly, since the plurality of steel bars can be quickly and reliably fed onto the rollers of the conveyance line to the inspection process after the rapid cooling process, productivity including heat treatment can be improved.

1 is a vertical sectional view schematically showing a steel bar quenching apparatus according to the present invention. The vertical sectional view which shows the outline of the said rapid cooling apparatus of the state in which the steel bar was conveyed on the mount frame. The vertical sectional view which shows the outline of the said rapid cooling apparatus of the state which lowered | hung the said mount frame in the water tank. FIG. 4 is a vertically enlarged vertical sectional view along the line XX in FIG. 3; Schematic which shows the steel bar and water flow in the water tank of a state different from FIG. 4 and 5 are schematic views showing a steel bar and a water flow in water tanks in different states. Schematic which shows the cross-sectional square steel bar and water flow in the said water tank. Schematic which shows the said rapid cooling apparatus which shows the effect | action after a rapid cooling process. The vertical sectional view which shows the outline of the quenching apparatus of a different form. Furthermore, the vertical sectional view which shows the outline of the quenching apparatus of a different form.

Hereinafter, modes for carrying out the present invention will be described.
FIG. 1 is a vertical sectional view schematically showing a steel bar quenching apparatus 1 according to an embodiment of the present invention.
As shown in FIG. 1, the steel bar quenching apparatus 1 includes a horizontal frame 2 that supports a plurality of steel bars (M) heated to a predetermined temperature zone in a heat treatment furnace F, and a door on the outlet side of the heat treatment furnace F. a water tank (liquid tank) 10 adjacent to d and in which the gantry 2 is immersed, and elevating means comprising chains c3 and c4 and a sprocket 7 that elevate and lower the gantry 2.
The heating furnace F has a plurality of rollers r which are substantially tunnel-shaped as a whole and which transport a plurality of steel bars (M) whose axial directions are arranged in parallel along the horizontal direction, near the bottom of the furnace. Is attached with a door d that can be opened and closed by raising and lowering.
The plurality of steel bars are bound by a plurality of wires (not shown) in a direction perpendicular to the conveying direction so as to be adjacent to each other and not separated.

Further, as shown in FIG. 1, the gantry 2 is a frame body having a substantially rectangular shape in plan view, and a plurality of parallel rollers r supporting a plurality of steel bars (M) are arranged on the upper surface thereof in the front-rear direction of FIG. (A direction perpendicular to the axial direction of the steel bar). A chain c1 spanning a sprocket s fixed to the shaft end of each roller r is stretched along one long side of the gantry 2, and the sprocket s at one end (right end in FIG. 1) and the gantry 2 A driving chain c <b> 2 is suspended between the sprocket s fixed to the rotating shaft of the motor m <b> 1 attached on the support stand 3 erected from above. That is, when the motor m1 is driven, the respective rollers r are similarly rotated through the chains c2 and c1.
The upper end of the support 3 is set to a height that does not sink into the water (cooling water) W in the water tank 10 when the mount 2 is lowered.
Furthermore, the aquarium 10 has a rectangular shape in plan view and an area in which the gantry 2 can be immersed. The water (cooling water) W has a depth of about 1.5 to 1.8 m (meters) inside. 1, two side walls 11 are erected at right angles on the right side and the near side in FIG. 1, and a side wall 12 having an overflow portion 13 to be described later is erected on the back side in FIG. is doing.
In addition, the said mount frame 2 and the water tank 10 are the substantially rectangles where the left-right direction of FIG. 1 becomes a long side.

Around the water tank 10, a plurality of support columns 18 are erected along the front-rear direction of FIG. 1, and a steel structure comprising the support columns 18 and a beam 19 installed horizontally on the upper ends thereof. 17 is configured. On the rails 20, 20 laid along the upper surface of each of the left and right beams 19 in FIG. 1, the transport vehicle 5 is supported so as to be able to travel.
At the four corners of the transport vehicle 5, four carriages 6 are attached, in which wheels (not shown) that roll on the rails 20 by the motor m 2 are installed. The transport vehicle 5 also has a substantially rectangular shape in plan view, and a motor m3 is rotated on the upper surface of the transport vehicle 5 through the gear train by the motor m3. The sprocket 7 and a plurality (four) of relay sprockets 8 and 9 are provided.
As shown in FIG. 1, on the pair of long sides of the gantry 2, a total of four support pillars 4 are erected on each of the two long sides, and chains c3 and c4 each having one end fixed at each upper end thereof are The other end is fixed to a dedicated sprocket 7 for individual rewinding and winding via relay sprockets 8 and 9. That is, by driving the motor m3 and rotating the plurality of sprockets 7, the frame 2 is wound around the teeth rows on these peripheral surfaces individually or through the chains c3 and c4 that are wound up and down. Can be moved up and down.

Here, the steel bar heat treatment method according to the present invention using the quenching apparatus 1 will be described.
In advance, a plurality of steel bars M made of austenitic stainless steel are heated and held in a heat treatment furnace F for about 1080 ° C. for 1 hour (heating process). As shown by the horizontal arrow in FIG. 2, the heated steel bars M raise the rear end side door d, open the carry-out port of the heat treatment furnace F, and bind to a plurality of wires. The plurality of steel bars M that are arranged in parallel in the horizontal direction on the plurality of rollers r rotating on the gantry 2 side waiting at a predetermined height from the rollers r on the furnace F side. Move to.
In addition, the axial direction of the some steel bar M is along the left-right direction of FIG. 2, and it is paralleling along the front-back direction of FIG. Further, the door d descends immediately after this, closes the carry-out port of the heat treatment furnace F, and is used for the next heating step.
Next, the motor m3 on the transport vehicle 5 is driven, the plurality of sprockets 7 are rotated, and the chains c3 and c4 wound around these are rewound, whereby a plurality of steel bars M are passed through the chains c3 and c4. At the same time, the gantry 2 is lowered. As a result, as shown in FIG. 3, the plurality of steel bars M descends into the water W of the water tank 10 together with the gantry 2.

FIG. 4 is an enlarged vertical sectional view taken along line XX in FIG.
As shown in FIG. 4, the height of the right side wall 12 in the water tank 10 is lower than that of the left side wall 11, and an overflow portion 13 that is inclined obliquely outward is attached to the upper end of the side wall 12. . Below the overflow portion 13, a ridge 16 is disposed substantially horizontally along the front-rear direction of FIG. 4. A pump P connected between a discharge pipe 14 penetrating the side wall 12 and a water supply pipe 15 communicating with a water supply source (not shown) is disposed outside the side wall 12. The temperature of the water W discharged from the discharge pipe 14 into the water tank 10 through the water supply pipe 15 and the pump P is previously cooled to 20 ° C. or less (for example, about 16 ° C.).
As indicated by the gray arrows in FIG. 4, the water W discharged from the discharge pipe 14 into the water tank 10 flows along the radial direction below the plurality of steel bars M supported on the gantry 2. After flowing (fw) the side of the plurality of steel bars M immediately before the side wall 11 facing the side wall 12, the upper side of the plurality of steel bars M flows along their radial direction. It becomes the flowing water fw which does. That is, the water W circulates in the water tank 10 in a laterally long oval shape or an elliptical shape so as to surround the plurality of steel bars M and flows (fw).

As shown in FIG. 4, a part of the flowing water fw that has flowed above the plurality of steel bars M becomes overflowing water ofw that overflows from the overflowing part 13 and flows into the ridge 16 and then includes cooling means. After being supplied to the water supply source and cooled to 20 ° C. or lower, the water is returned to the water tank 10 from the water supply pipe 15 through the pump 15. That is, the water W in the water tank 10 circulates inside and outside the water tank 10 while rapidly cooling the plurality of steel bars M, and during this time, the temperature rise and the temperature fall are repeated.
Next, the motor m3 is driven, and the plurality of steel bars M are further lowered together with the gantry 2 in the water W of the water tank 10 through the chains c3 and c4 as shown in FIG. At this time, the motor m1 for rotating the roller r on the gantry 2 and the upper end portion of the support base 3 on which the motor m1 is placed are kept higher than the water surface of the water W.

Subsequently, the motor m3 is driven in the reverse direction, and the plurality of bars M together with the gantry 2 are raised to a position just below the water surface in the water W of the water tank 10 through the chains c3 and c4 as shown in FIG. . The vertical stroke (height) when rising and lowering is approximately 600 to 900 mm (for example, 800 mm), and the cycle time required for one ascending and descending is approximately 8 to 12 seconds (for example, , About 10 seconds).
Further, the forward rotation and the reverse rotation of the motor m3 are alternately performed a plurality of times, and the lowering shown in FIG. 5 and the rising shown in FIG. 6 are alternately performed a plurality of times. In the meantime, the plurality of steel bars M positioned on the gantry 2 roller r move along the vertical (vertical direction) with respect to the flowing water fw of the water W flowing along the radial direction on the lower side and the upper side thereof. By contacting, high heat exchange with the water W is uniformly received on the entire surface.

As a result, the plurality of steel bars M are rapidly and uniformly cooled from a high temperature state of about 1080 ° C. heated in the heating furnace F to a normal temperature range of several tens of degrees C. (for example, 10 to 40 ° C.) (rapid cooling step). ).
Incidentally, when a plurality of steel bars M made of SUS316L and having a length of 6 m × a diameter of 46 mm are rapidly cooled while moving up and down by the rapid cooling step, the bending amount biased in the radial direction is the case where the plurality of steel bars M are not moved up and down. 10% or more (15 to 20%) could be reduced from the bending amount. Thereby, the correction process performed conventionally can be omitted.
As described above, in order to cool the steel bar M quickly and uniformly and reduce the amount of bending, the temperature of the water W supplied from the pump P into the water tank 10 is kept at 20 ° C. or lower, and the water tank 10 It is important to control the temperature of the water W in the rapid cooling process so that the temperature of the overflow water ofw overflowing from the temperature is kept below 30 ° C.

FIG. 7 is a schematic view showing a rapid cooling process of a plurality of steel bars M ′ having a square cross section.
The steel bar M ′ has a side of about 40 mm and a substantially square cross section, and each corner has a round (R). For this reason, on the heat treatment furnace F and the roller r of the gantry 2, the individual axial directions are arranged in parallel along the horizontal direction. However, since the individual steel bars M ′ are difficult to roll, use wires as described above. Without being tied up, they are parallel with a gap between them. For the plurality of steel bars M ′, the heating process and the quenching process using the quenching apparatus 1 can be performed in the same manner as the steel bar M having a circular cross section.

As shown by the arrows in FIG. 8, the plurality of steel bars M (M ′) that have finished the rapid cooling process drive the motor m3 and move it from the water tank 10 together with the gantry 2 via the chains c3 and c4. Further, the motor m2 of the transport vehicle 5 is driven, and the transport vehicle 5 is caused to travel along the rails 20 so that the transport vehicle 5 traverses to the side of the water tank 10 together with the gantry 2. Then, when it reaches the side of the water tank 10 and directly above the conveyance line 30 along the front-rear direction in FIG. 8, the motor m3 is driven to transfer a plurality of steel bars M (M ′) to the conveyance line 30. It is transferred onto rollers r and r. The plurality of transferred steel bars M (M ′) are sent to the next inspection process or the like by the transfer line 30.
On the other hand, the gantry 2 that has been emptied is returned again to the carry-out port side of the heating furnace F, and is placed in a standby state in order to support a plurality of steel bars M (M ′) to be rapidly cooled.

According to the heat treatment method for the steel bar M (M ′) using the quenching apparatus 1 as described above, the plurality of steel bars M (M ′) heated to a predetermined temperature zone in the heating furnace F are aligned along the horizontal direction. The individual axial directions move onto the gantry 2 in a parallel posture, and the ascending and descending are repeated a plurality of times in the water W of the water tank 10 together with the gantry 2. In the meantime, the plurality of steel bars M (M ′) are in contact with the flowing water fw of the water W that circulates along the lower side and the upper side along these radial directions, and thus are cooled by a high heat exchange rate. , The whole surface is quenched rapidly. Therefore, since the amount of bending that deviates in the radial direction can be reliably reduced, the correction process for correcting bending that has been conventionally performed can be eliminated, or the amount of correction can be reduced to a very small amount, thereby improving productivity. Is also possible.
Instead of the pump P, a submersible pump may be disposed in the water W near the side wall 12 in the water tank 10, or an axial fan or a sirocco fan may be disposed at a similar position.

FIG. 9 is a vertical sectional view schematically showing a quenching apparatus 1a having a different form.
As shown in FIG. 9, the rapid cooling apparatus 1a includes the same gantry 2 and a transport vehicle 5 as described above. A portion of the quenching device 1a that is different from the quenching device 1 is that a rack 22 is vertically attached to the upper ends of four support pillars 4 erected from the gantry 2 and these penetrate the carriage 5 vertically. In other words, the four pinions (gears) 24 mounted on the conveyance vehicle 5 are individually meshed with each other. Each pinion 24 is rotated by a motor (none shown) via a reduction gear train. Accordingly, by repeatedly raising and lowering each rack 22, it is possible to uniformly cool the plurality of steel bars M (M ′) located on the gantry 2 to be raised and lowered in the same manner as described above.

FIG. 10 is a vertical cross-sectional view schematically showing a quenching device 1b having a different form.
As shown in FIG. 10, the quenching device 1 b also includes the same stand 2 and a transport vehicle 5 as described above. The portions different from the quenching device 1 are four support pillars 4 erected from the stand 2. And the piston rods 28 of the four hydraulic cylinders 26 that vertically pass through and are attached to the transport vehicle 5 are individually connected. The hydraulic cylinder 26 is positioned on the gantry 2 by supplying and discharging high-pressure oil to and from an oil tank (not shown) disposed on the transport vehicle 5 and repeatedly raising and lowering the piston rod 28. A plurality of steel bars M (M ′) can be uniformly cooled as described above.
Instead of the hydraulic cylinder 26, an air cylinder or a hydraulic cylinder may be used.

The present invention is not limited to the embodiments described above.
For example, the heat treatment that is an object of the present invention includes various heat treatments that are quenched and quenched rapidly after heating.
The liquid tank used in the rapid cooling process may be an oil tank, and the cooling liquid may be oil.
Furthermore, the raising / lowering means for raising and lowering the gantry between the upper part of the liquid tank and the inside of the liquid tank includes a plurality of wire ropes having one end fixed to the gantry side and a plurality of these other ends wound up and wound on the transport vehicle. It is good also as a form which consists of a combination with this drum, or which consists of a plurality of sets of pantograph mechanisms.
In addition, the direction in which the coolant flowing in the liquid tank flows may be a direction substantially along the axial direction of the plurality of steel bars located on the gantry when the plurality of steel bars are relatively short.

  In the present invention, a plurality of long steel bars that are rapidly cooled immediately after being heated can be uniformly quenched in a parallel posture, and can be subjected to the required heat treatment, and the occurrence of bending can be reduced. This contributes to efficient heat treatment applied to steel bars.

1, 1a, 1b ... Rapid cooling device 2 ............... Stage 5 ... ……………… Carrier 7 ………………… Sprocket (lifting means)
10 ……………… Water tank (Liquid tank)
12 ……………… Side Wall r …………………… Roller M, M ′ …………… Steel W …………………… Water (Coolant)
c3, c4 ... Chain (lifting means)

Claims (4)

A heating step of heating a steel bar having a circular or square cross section to a predetermined temperature range;
A quenching step of quenching the heated steel bar, and
The rapid cooling step is to raise and lower a plurality of steel bars in parallel with each other along the horizontal direction in a liquid tank in which the cooling liquid in the tank is circulating while flowing.
A method for heat treating a steel bar. The coolant in the liquid tank circulates in the liquid tank while flowing in a circular shape or an elliptical shape with the axial direction of the plurality of steel bars as the rotation center.
The steel bar heat treatment method according to claim 1. A steel bar quenching device used in the quenching process in the heat treatment method according to claim 1 or 2,
A gantry to which a plurality of rollers supporting the plurality of steel bars and having a rotation axis substantially orthogonal thereto is attached;
Elevating means for raising and lowering the gantry between the upper part of the liquid tank and the inside of these liquid tanks;
A pump or a fan disposed near one side wall in the liquid tank,
A steel bar quenching device characterized by that. The elevating means is attached to a carriage that traverses between the upper side of the liquid tank and the sides thereof together with the gantry raised above the liquid tank.
The steel bar rapid cooling apparatus according to claim 3.

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