JP3670817B2 - Steel joining method for hot continuous rolling - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel joining method applied when, for example, in the steel industry, a preceding steel material and a subsequent steel material are subjected to running joining for hot continuous rolling.
[0002]
[Prior art]
For example, in the iron and steel industry, there is a process of joining steel materials that are continuously conveyed in the hot continuous rolling line. There is a growing demand for so-called inter-running joints. Conventionally, as a running joint facility for performing this running joining, for example, as shown in FIG. 7, a traveling body b equipped with a welding device a and a clamping device ka, kb is driven by a driving device (not shown). A preceding steel material sa and a rear side which are disposed so as to be able to travel by a driving device e on a track r laid on a gantry d across a transport roller c to be transported continuously by the transport roller. While traveling synchronously with the row steel material sb, the clamping device ka, kb clamps the rear end portion of the preceding steel material sa and the tip end portion of the following steel material sb, and the rear end surface of the preceding steel material sa being conveyed by the conveyance roller d 2. Description of the Related Art A running welding facility configured to weld a butted portion of a leading end surface of a subsequent steel material between runnings is known. (Reference technology: Japanese Patent Laid-Open Nos. 7-1007 and 7-16611)
[0003]
When the joint obtained by running with this running welding equipment breaks during the finish rolling process, continuous rolling operation becomes impossible, and semi-finished product processing is required, resulting in an increase in cost. Therefore, the joint is required to have sufficient strength to withstand the load (tension) in the finish rolling process. It has also been attempted to secure a joint having such joint strength and shorten the joint time.
[0004]
As a method for shortening the joining time, as shown in FIG. 8, two traveling carriages Rd, Rw each having an arc or laser welding torch rt are arranged in the direction of the plate width a of the steel material s. A traveling carriage is disposed at a predetermined interval in the plate width direction of the steel material s, and is moved along the abutting portion (joining line) in a synchronized manner to join the abutting portion, and the joining area is shared in the plate width direction of the steel material. There is a way.
[0005]
In this case, the two traveling trolleys are connected to the side end on one side from the center line CL in the width direction of the steel material s to be joined, as shown in FIG. The joining torch rt of the traveling carriage Rw is structured to be moved from the other side of the steel material s to the center line CL in the width direction, and the moving distances dd and dw of the two joining torches rt are the same.
[0006]
On the other hand, when the abutting portion of the preceding steel material and the subsequent steel material is melted and joined, and after a predetermined time, finish-rolling is performed as it is, an ear crack is generated at the steel material side end portion, and this joint portion is started from this. May lead to breakage. This is due to the fact that sulfur embrittlement occurs in the process where the molten metal at the joint is heated and cooled, and the side end cannot withstand the tension generated during finish rolling. Often occurs at the edges.
[0007]
For this reason, at the stage where the temperature at the end of the steel material that has been finally joined is lowered to 1200 ° C. or less, it is avoided that the mechanical strength is weakened due to the occurrence of sulfur embrittlement by applying compressive strain to the joint. Thereafter, rolling is performed with the finish rolling mill. However, in this case, as shown in FIG. 9, after the joining of the steel material side end (Ds side) by the joining torch rt of the traveling carriage Rd is completed, the temperature of this portion is decreased to 1200 ° C. or less ( For about 4 seconds), compression strain could not be applied, and this was an obstacle to shortening the time from the start of joining until it could be bitten into the finishing mill. Therefore, from the viewpoint of shortening the time, it cannot be said that the request is sufficiently satisfied.
[0008]
[Problems to be solved by the invention]
In the present invention, when the preceding steel material and the subsequent steel material for continuous hot rolling are welded in the running direction in the sheet width direction using two joining torches, there is no sulfur embrittlement and breakage occurs in the finish rolling process. Provided a steel joining method that can shorten the time from the start of joining until it can be bitten into a finishing mill, on the premise of ensuring stable joints that do not occur and ensuring the quality of the steel sheet after finish rolling. is there.
[0009]
[Means for Solving the Problems]
The first invention of the present invention is a method of joining a preceding steel material and a succeeding steel material with a running joint facility for hot continuous rolling, in the side end portion side on one side from the width direction center portion side of the steel material to be joined. The first joining torch to be moved and the second joining torch to be moved from the other side end portion side to the width direction central portion side share the joining in the width direction of the steel material, and after the joining is completed, the joining portion When compressive or tensile strain is applied to the steel plate to avoid sulfur embrittlement at the joint, and then the finish rolling is performed, the joining end time of the first joining torch is determined as the joining end of the second joining torch. For hot continuous rolling, characterized in that compression or tensile strain is applied at a stage earlier than the time and the steel material side end temperature joined by the first joining torch is in the range of 1200 ° C to 1100 ° C. Steel joining method. A second invention is characterized in that, in the first invention, the joining end time in the first joining torch is made earlier than the joining end time in the second joining torch by a time ΔT obtained by the following equation. Steel joining method for continuous hot rolling.
△ T = Ta
However,
Ta: Time until the temperature reaches 1200 ° C. by applying compression or tensile strain to the steel material side end after the joining with the first joining torch.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the first joining torch that moves from the width direction central portion side of the steel material to the one side end portion side, and the second joining torch that moves from the other side end portion side to the width direction central portion side. When joining in the width direction of the steel material, for example, the joining time in the first joining torch is shortened earlier by shortening the joining time in the first joining torch than the joining time in the second joining torch. Until the temperature of 1200 ° C. or less at which the steel material side end can avoid sulfur embrittlement is accelerated by the time difference (several seconds), and compression or tensile strain is applied quickly until it is bitten into the finishing mill. Can be shortened. Therefore, it is possible to stably secure a joint portion free from sulfur embrittlement, to ensure stable quality of the steel sheet after finish rolling, and to support high-speed rolling.
[0011]
In order to finish the joining with the first joining torch earlier than the joining time with the second joining torch, as described above, the method of making the joining distance of the first joining torch shorter than the joining distance with the second joining torch, There is a method in which the intensity of the laser beam (or arc) of the first joining torch is made stronger than the intensity of the laser beam (or arc) of the second joining torch to increase the joining speed of the first joining torch. Simple, economical and advantageous.
[0012]
If the joining with the first joining torch is finished as soon as possible than the second joining, there will be such an effect, but the case of time ΔT determined by the following equation is most preferable.
ΔT = Ta (seconds)
However,
Ta: Time from the completion of joining with the first joining torch until the temperature reaches 1200 ° C. at which sulfur embrittlement can be avoided by applying compression or tensile strain to the steel material side end.
FIG. 1 shows the arrangement and moving distance of the first joining torch 8d and the second joining torch 8w in the present invention. (Here, the joining torch is a joining torch of a laser welding apparatus.)
As shown in FIG. 1, the first joining torch 8d and the second joining torch 8w are arranged so as to be movable in the plate width a direction, and the two joining torches are simultaneously started to move in the same direction (arrow direction). However, here, the moving distances of the two joining torches are not the same. That is, the first joining torch 8d moves the distance da from the position 0x shifted by the distance x from the center 0 of the plate width to the one side end Pd, and the second joining torch 8w moves the distance wa from the other end Pw to 0x. To do.
Therefore, when the moving speed (joining speed) is the same, the joining by the first joining torch 8d having a short moving distance ends earlier by the moving time of the distance x, and the joining by the second joining torch 8w is moved by the moving time of the distance x. It will be completed a few minutes later.
[0014]
FIG. 2 shows an example of joining in the case of sharing the joining in the plate width direction by the first joining torch 8d and the second joining torch 8w in the present invention when the plate width a of the steel material 1a (1b) is 1100 mm. FIG. 3 shows the relationship between the distance (position) in the plate width direction and the temperature of the weld when the joining with the 2-joint torch 8w is completed, and FIG. 3 shows the temperature of the weld ( (° C.) and the temperature drop over time.
[0015]
In the case of FIG. 3, Ta in the above formula is 4 seconds until the temperature of the steel-side end part finally joined by the first joining torch reaches 1200 ° C., so this is equivalent time (4 seconds) It turns out that. In this case, the compression or tensile strain imparting to prevent the occurrence of sulfur embrittlement at the joint is 2 seconds from the case where the first joint torch 8d and the second joint torch 8w are jointed by halving the plate width. This can be done quickly, and accordingly, the time from the start of joining to the time when it can be bitten into the finish rolling mill can be shortened.
[0016]
In the case of FIG. 2, the joining distance wa at the first joining torch 8d is shorter than 1/2 of the plate width a by 2 seconds, and the joining distance wa of the second joining torch 8w is 2 seconds from 1/2 of the plate width. The total joining time is 2 seconds longer than the case of joining by halving the plate width, but the joining with the second joining torch 8w is the joining with the first joining torch 8d. At this completion point, the temperature at the end of the steel material end joined with the first joining torch is compressed or tensile strained to prevent sulfur embrittlement. It is 1200 degrees C or less which is the temperature which provides this, and it is in the state which can provide compression or tensile distortion. From this, the time from the start of joining to the application of strain can be shortened by 2 seconds as compared with the case of 1/2 joining.
[0017]
Even if the temperature of the steel material side end joined by the first joining torch 8d is 1200 ° C., the central part in the plate width direction is just after completion of joining by the second joining torch w, and the temperature is as high as 1500 ° C. or higher, In the experiment, it has been confirmed that in the case of the central part in the plate width direction, the sulfa embrittlement phenomenon does not cause breakage. Therefore, there is no problem even if distortion is applied immediately after the joining with the second joining torch 8w is completed.
[0018]
In addition, when the said distortion is provided in the temperature range where the temperature of a welding part exceeds 1200 degreeC, a sulfur embrittlement phenomenon cannot be prevented and a possibility that a joint part fracture | rupture will occur in a finish rolling process increases. In addition, when strain is applied in a temperature range of less than 1100 ° C., the effect of imparting compression or tensile strain is small, the effect of preventing the occurrence of sulfur embrittlement is insufficient, and it is not possible to ensure stable joint strength. Therefore, it is preferable to apply the strain in a temperature range of 1200 ° C. or lower and 1100 ° C. or higher where the influence of welding heat is small, and in order to shorten the time, it is performed in a temperature range of 1200 ° C. or lower and close to 1200 ° C. More preferred.
[0019]
The present invention can be applied not only to single-sided bonding but also to double-sided bonding. In the case of double-sided bonding, the upper surface side and the lower surface side are bonded at the same time, and the temperature affects each other. Therefore, it is necessary to set conditions in consideration of this.
[0020]
The present invention can be implemented in a hot continuous rolling facility (example) shown in FIGS.
As shown in FIG. 4, this hot continuous rolling facility (example) hot-rolls a heated steel piece 1 with a roughing mill 2 and temporarily stores the obtained steel material 1o in a coil box 3, and then transport rollers. 4, when the steel sheet 1p is produced by continuous hot rolling with this finishing mill, the steel sheet 1p is continuously conveyed back and forth by the conveying roller 4 between the coil box 3 and the finishing mill 5. It is provided with a running welding facility 6 that enables welding of the steel materials 1a and 1b between runnings.
[0021]
The running joint facility 6 includes a traveling body 9 that can travel in synchronization with the steel materials 1a and 1b that are continuously transported forward and backward by the transport roller 4 on the track 11 by the driving device 10, and this traveling body. Includes a clamping device 7a, 7b for clamping the preceding steel material 1a and the following steel material 1b, and a first joining torch 8d of the laser welding device 8 for joining the DS side of the steel material 1a (1b) as shown in FIG. And the 2nd joining torch 8w which joins WS side is mounted.
[0022]
The transport roller 4 has a structure (not shown) that can be retracted and returned to a position where it does not interfere with the clamping devices 7a and 7b and the joining torches 8d and 8w, and is advanced by the clamping devices 7a and 7b while the traveling body 9 is traveling. The steel material 1a and the following steel material 1b are clamped, the first joining torch 8d is driven by the driving device Md, the second joining torch 8w is made the same by the driving device Mw in the plate width a direction of the preceding steel material 1a and the following steel material 1b. It is made to move synchronously in the direction, and the butted portions of the preceding steel material 1a and the succeeding steel material 1b are simultaneously shared and run-to-run joined.
[0023]
In the figure, reference numeral 12 denotes a hydraulic cylinder connected to the clamping device 7b, which imparts distortion to the preceding steel material 1a and the following steel material 1b (in the case of compressive strain, it operates in the direction of pressing the preceding steel material 1a and the following steel material, In some cases, it is used as a device that operates in the direction of pulling both). Reference numeral 13 denotes a track for moving the first joining torch 8d and the second joining torch 8w.
[0024]
The laser welding apparatus 8 having the first joining torch 8d and the second joining torch 8w used here conceptually includes, for example, a laser beam oscillator 14, reflecting mirrors 15 and 16, and a shutter 17 as shown in FIG. The laser beam 18 from the laser beam oscillator 13 is irradiated from one side of the abutting portion between the rear end of the preceding steel material 1a and the front end of the following steel material 1b through the reflecting mirrors 15 and 16 and the shutter 17. Then, by moving both joining torches 8d, 8w in the direction of the steel plate width a along the joining line WL by the drive devices 8p, Md, Mw, and melting and solidifying the butted portion, It is comprised so that the front-end | tip of the following steel material 1b may be joined.
[0025]
In this example, the first joining torch 8d that joins the DS side and the second joining torch 8w that joins the Ws side are configured so that the first invention and the second invention of the present invention can be implemented. Joining conditions according to the line speed, sheet thickness, sheet width, rolling conditions set in the arithmetic unit 19, joining rate that does not cause breakage, and joining range (joining depth, joining start point, joining) for obtaining this joining rate The distance, the joining end point), and the movement pattern are controlled via the drive control device 20d20w.
[0026]
In addition, a compression strain applying condition is set in the arithmetic unit 19, and the output of the hydraulic pump 22 is controlled via the output control unit 21 after a predetermined time has elapsed since the WS side joining completion time by the second joining torch 8 w. Thus, compression strain application control is performed.
[0027]
Then, with the rear end of the preceding steel material 1a clamped by the clamping devices 7a and 7b and the front end of the subsequent steel material 1b running against each other, the plate width of the first joining torch 8d and the second joining torch 8w is driven by the drive devices Mw and Md. In the abutting portion, a predetermined range on the WS side with respect to the DS side is simultaneously started to be joined at a predetermined joining rate, and after a predetermined time has elapsed, the hydraulic cylinder 12 Compression bonding can be applied to complete the joining. In this case, without using the arithmetic unit 18, a table may be created to set and control the welding conditions. The timing of applying the strain may be managed by actually measuring the temperature, but it is easier to manage the strain by the elapsed time from the completion of the joining than the timer. The elapsed time in this case is a few seconds.
[0028]
The running joint equipment for carrying out the present invention is not limited to the above running joint equipment example. For example, the structure of the distortion imparting device such as the laser welding device, the clamp structure, the transport roller, and the retracting / returning structure constituting the running joint equipment is changed depending on the joining object, rolling conditions, and the like.
The present invention can be implemented using the running joint equipment configured as described above.
[0029]
【Example】
Using the running joint equipment as shown in FIGS. 4 to 6, the general structural steel material that is continuously conveyed and supplied from the coil box is used as a joining object in the stage before the hot finish rolling mill. Adopting the invention, the two laser welding apparatuses share the joint, run butt joint (single-sided joint), impart compressive strain, and then hot finish roll to produce a steel sheet. The state of the joint by laser welding, the presence or absence of breakage of the steel material (steel material) in the finish rolling process, the quality of the steel material after finish rolling, and the shortening rate of the joining time were investigated. The results will be described below.
[0030]
Implementation conditions
Bonded steel grade: Chemical composition of ordinary steel (weight%)
C: 0.058, Si: 0.016, Mn: 0.230, P: 0.019
S: 0.014, Al: 0.033, Ti: 0.001, Fe and others: 99.629
Size: 40mm thickness, 1100mm width
Temperature: 1050 ° C
Transfer speed: 60m / min
Joining condition Laser beam output: 45kw (constant)
Joining speed: 5m / min
Joining depth: 20mm
Bonding distance (setting value)
First joining torch: 383mm
Second joining torch: 717mm
Compressive strain application condition Compressive stress: 2kg / mm ²
Temperature steel material side end when applying load (WS side): 1100 ° C
Steel center: 1300 ° C
Steel side end (DS side): 1200 ° C
Ta: 4 seconds ΔT: 4-second finish rolling conditions Steel plate size: 2 mm thick, 1000 mm wide
Rolling temperature: 1000 ° C
Reduction ratio: 50% (7 stands)
Rolling speed: 1510 m / min
[0031]
(1) to the first invention and examples that satisfy the second inventions of the present invention that the bonding length of the first joining torch 334mm shorter than the junction length of the second joining torch, applying a compressive strain after bonding Was 8.6 seconds, and the time from the start of joining to the finish rolling was 38 seconds. (In comparison with the comparative example in which the joining distance of the first joining torch is the same as the joining distance of the second joining torch, the total joining time of both is the same, and the time from the start of joining to the finish rolling machine is 2 Seconds can be shortened)
The obtained joint had no sulfur embrittlement phenomenon, the joint was not broken during the finish rolling process, and no defects due to the joint were observed in the steel after the finish rolling.
[0032]
(2) In the comparative example in which the joining distance of the second joining torch is increased so that ΔT is 5.5 seconds, which is a value larger than Ta, the joining time is 12.1 seconds, and the finish rolling is started from the start of joining. The time required to bite into the machine was 41.5 seconds. However, in comparison with the comparative example in which the joining distance of the first joining torch is the same as that of the second joining torch, the joining time is the same. The time from start to biting into the finishing mill could not be shortened.
[0033]
(3) In the comparative example in which compressive strain was applied when the temperature of the steel material side end was 1250 ° C., the joining time was 7 seconds, which was shorter than in the case of the above-described embodiment of the present invention. Although the time until the time was shortened by 3 seconds, the occurrence of sulfur embrittlement could not be sufficiently avoided, and the joint fracture sometimes occurred in the finish rolling process.
[0034]
(4) In the comparative example in which compressive strain was applied when the temperature of the steel material side end was 1090 ° C., the joining time was 12 seconds longer than in the case of the example of the present invention, and the biting into the finish rolling mill from the start of joining. The time until is 12 seconds longer. In addition, the effect of imparting compressive strain is small, the effect of preventing the occurrence of sulfur embrittlement is insufficient, and joint breakage may occur in the finish rolling process.
[0035]
【The invention's effect】
In the present invention, the first joining torch that moves from the width direction central portion side of the steel material to the one side end portion side, and the second joining torch that moves from the other side end portion side to the width direction central portion side. In the case where the joining in the width direction of the steel material is performed in a shared manner, the joining time in the first joining torch is terminated earlier by making the joining time in the first joining torch shorter than the joining time in the second joining torch. , The time difference (several seconds) until the temperature of the steel material side end can be reduced to 1200 ° C. or less at which sulfur embrittlement can be avoided, the compression or tensile strain is applied quickly, and the finish rolling machine is bitten. Time can be shortened. Therefore, it is possible to stably secure a joint portion free from sulfur embrittlement, to ensure stable product quality after finish rolling, and to cope with high-speed rolling.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory side view illustrating an example of a joining torch arrangement and an example of joint sharing in the present invention.
FIG. 2 is an explanatory diagram showing an example of a temperature change in the plate width direction of a joint when joining is performed by two joining torches in the present invention.
FIG. 3 is an explanatory diagram showing the relationship between the temperature of the joint and the elapsed time from the completion of joining in the case of joining by laser welding.
FIG. 4 is a partial cross-sectional side view showing an example of arrangement of a hot continuous rolling facility equipped with a running joint facility to which the present invention is applied.
FIG. 5 is an explanatory plan view showing an enlarged part of the example of the running joint facility in FIG. 4 to which the present invention is applied.
FIG. 6 is a three-dimensional conceptual explanatory diagram showing a structural example of a laser welding apparatus used in the present invention.
FIG. 7 is an explanatory side view showing an example of the structure of a conventional running joint facility.
FIG. 8 is a side conceptual view showing an arrangement example and a joint assignment example of a laser welding apparatus in a conventional example.
FIG. 9 is an explanatory view showing an example of a temperature change in a plate width direction of a joint portion when joint is shared by two laser welding apparatuses in a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel piece 1a, 1b Steel material 1p Steel plate 2 Rough rolling mill 3 Coil box 4 Conveying roller 5 Finishing rolling mill 6 Running welding equipment 7a, 7b Clamping device 7c Hydraulic cylinder 7o Upper clamp plate 7u Lower clamp plate 8d First joining torch ( Drive side)
8w 2nd joining torch (workside)
Mw drive unit (work side)
Md drive (drive side)
9 Traveling body 10 Driving device 11 Track 12 Hydraulic cylinder (distortion imparting device)
13 Orbit 14 Laser oscillators 15 and 16 Reflector 17 Shutter 18 Laser beam 19 Arithmetic units 20d and 20w Drive control unit 21 Output control unit 22 Hydraulic pump

Claims (2)

In the joining method of the preceding steel material and the succeeding steel material by the running joining equipment for hot continuous rolling, a first joining torch moved from the width direction center portion side of the steel material to be joined to one side end portion side; The second joining torch that moves from the other side end portion side to the width direction center portion side shares the joining of the steel material in the width direction, and after the joining is completed, compresses or tensile strain is applied to the joined portion. , Avoiding sulfur embrittlement in the joint, and then performing the finish rolling, the joining end time in the first joining torch is made earlier than the joining end time in the second joining torch, and the first joining A method for joining steel materials for hot continuous rolling, characterized in that compression or tensile strain is imparted at a stage where the temperature of the steel-side end portion joined by a torch is within a range of 1200 ° C to 1100 ° C. The joining end time in the first joining torch is made earlier than the joining finish time in the second joining torch by a time ΔT obtained by the following formula. Steel joining method.
△ T = Ta
However,
Ta: Time until the temperature reaches 1200 ° C. by applying compression or tensile strain to the steel material side end after the joining with the first joining torch is completed

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