JPS58122189A - Automatic controlling method of forge welding temperature of forge-welded steel pipe - Google Patents

Abstract

PURPOSE:To manufacture a product which is satisfactory in a quality of a butt welding part, by measuring a temperature of a pipe-like skelp edge part before forge welding, and adjusting an output of a heating coil so that a temperature of both edge parts becomes within a target range. CONSTITUTION:A control device 11 inputs and operates a signal from a forge welding thermometer 7 and a signal from a skelp thermometer 9, and sends a control signal to a thyristor voltage regulator 14. A voltage level is controlled by the thyristor voltage regulator 14, a high frequency current is generated by a high frequency oscillator 13, thereby a current flowing to a high frequency induction heating coil 6 is controlled. Also, a control signal is sent to a left and right adjusting device 15 for adjusting the left and right position of the high frequency induction heating coil 6, and the left and right position of the high frequency induction heating coil 6 forming one body structure with a transformer 12 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic forge welding temperature control method for controlling the temperature of a tubular skelp before forge welding to a temperature suitable for forge welding in a manufacturing process of forge welded steel pipes.

Conventionally, forge welded steel pipes are produced by forming a band-shaped skelp heated in a heating furnace into a tubular shape using forming rolls, and heating the edges of the tubular skelp by blowing oxygen from a welding horn. After heating using a high-frequency induction heating coil, the edge portions were forge-welded using a forge-welding roll. However, the band-shaped skelp described above has a plate thickness variation of about 5%, and the band-shaped skelp leaving the heating furnace also has temperature fluctuations in the heating furnace, so its temperature is ±40°C.
The temperature difference between the left and right edges is 20℃.
It has occurred to some extent.

Furthermore, when heating the edge part of the tubular skelp by induction heating, the temperature of the edge part is increased by 200 to 400 degrees Celsius, but in this case, due to changes in the plate thickness of the edge part and fluctuations in the skelp running speed, etc. The temperature will further vary.

In order to eliminate these drawbacks, methods for keeping the heating furnace extraction temperature constant include measuring the temperature at the time of heating furnace extraction and adjusting the running speed of the skelp, or adjusting the heating temperature using the fuel in the heating furnace. Methods such as doing this were used.

However, with the above method, the response speed of the heating furnace is slow, so it is not possible to sufficiently follow the sudden temperature change caused by the sudden change in wall thickness before and after the connection between the bottom and top of the strip-shaped skelp.
There is a problem that temperature variations cannot be resolved. or,
Methods for keeping the temperature increase due to induction and heating constant include adjusting the output of the high-frequency induction heating coil in response to changes in squelp speed and wall thickness, and measuring the temperature of the forge weld abutment after forge welding. Examples include adjusting the output of a high-frequency induction heating coil. However, even with this method, when measuring the temperature after forge welding, it is difficult to measure the temperature after forge welding because some time has elapsed since the temperature of the tubular skelp edge was completed. It is unclear whether the temperature is the problem or the temperature of the left and right edges, and there is no way to control the temperature of the left and right edges, so changes in the wall thickness of the left and right edges or squirting in the heating furnace will directly affect the temperature of the left and right edges. There is a problem in that it is impossible to keep the temperature of the left and right edges constant.

In order to manufacture forge-welded steel pipes with good quality forge-welded joints, the temperature of the edge portion to be forged-welded must be set to a temperature suitable for forge-welding (1, 3
It is most important to forge weld at a constant temperature (approximately 50° C.), but with these methods, it has been impossible to maintain the temperature of the edge portion to be forged welded constant at the forge welding temperature.

The present invention eliminates the drawbacks of the above-mentioned methods, and is capable of forge welding in the manufacturing process of forge-welded pipes, in which the temperature of the edge portion of the tubular skelp to be forged welded can always be maintained at the forge welding temperature, and the temperature of the left and right edge portions can be maintained at an even temperature. The purpose of this invention is to provide an automatic temperature control method.

That is, the present invention forms a band-shaped skelp heated in a heating furnace into a tubular shape with a forming roll, heats the edge portion of the tubular skelp formed into the tubular shape with a heating device, and then forge-welds the edge portion with a forge-welding roll. In the initial manufacturing process of a forge-welded steel pipe to be made into a pipe, high-frequency induction heating coils are placed on both edge parts of the tubular skelp as a heating device to heat the edge parts of the tubular skelp, and the edge parts are heated. The edge temperature before forge welding is measured using a thermometer installed upstream of the tubular skelp, and the temperature difference between both edges of the tubular skelp is
Adjust the position of the high frequency induction heating coil in a direction perpendicular to the tube axis so that the temperature is within the target range, and adjust the output of the high frequency heating coil so that the temperature of both edges before forge welding is within the target range. This is an automatic forge welding temperature control method in the manufacturing process of forge welded steel pipes.

Next, the method of the present invention will be explained in detail with reference to examples shown in the figures.

In FIGS. 1 and 2, a strip-shaped skelp 2 heated to a hot working temperature in a heating furnace 1 is formed into a tubular shape by forming rolls 3 and 4. Both edge portions 2a of the tubular skeleton 2' shown in Figure 2
, 2a are arranged to uniformly heat the end face of the edge portion 2a of the band-shaped squelp 2'.

A squelp thermometer 9 consisting of a scanning radiation thermometer and a forge welding thermometer 7 are provided at the outlet of the heating furnace 1 and on the upstream side of the forge welding roll 5. , and the temperature of the edge portion of the tubular skelp 2' before forge welding.From the measured temperature value, both edge portions 2a of the tubular skelp 2' before forge welding are measured.

As shown in FIG. 2, the high-frequency induction heating coil 6 is adjusted in position from side to side so that the temperature difference between 2a and 2a is within a range of 10°C.

The left-right adjustment device 15 performs two-position adjustment in the direction perpendicular to the tube axis, and both edge portions 2a before forge welding.

The output of the high-frequency induction heating coil 6 is adjusted so that the temperature of the skelp 2a becomes 1350±10°C, and the edge part 2a of the tubular skelp 2' during forge welding is always forged (automatically kept at two consecutive temperatures). to control.

Next, the control system of the method of the present invention will be explained in detail with reference to the embodiment shown in the drawings. Extract the belt-shaped skelp 2 from the heating furnace 1 with an instantaneous field of view about 5 meters wide.

A Skelp thermometer 9 that measures radiant energy by optical scanning measures the side temperature continuously in the width direction, and separates the left and right circuits 22.
The peak keep circuit 23 separates the temperature pattern from the center of the band-shaped Skelp 2 to the left (in the direction of pipe making) and the temperature pattern to the right from the center of the band-shaped Skelp 2. Outputs signals of the highest temperature TLI among the temperature patterns to the left of , and the highest temperature TR of the temperature patterns to the right from the center of the band-shaped Skelp 2 .

Usually, the band-shaped skelp 2 heated in the heating furnace 1 is heated with a burner from almost the same plane as the plane of the band-shaped skelp 2, but the edge part of the band-shaped skelp 2 is Since the area receiving heat radiation per volume is large, the temperature of the edge part is higher than the temperature of the center part. Therefore, among the temperature patterns to the left from the center of the band-shaped Skelp 2, the highest temperature TL is as follows. This is the temperature of the left edge, and the highest temperature TR in the temperature pattern from the center to the right of the band-shaped squelp 2 is the temperature of the right edge.

Next, the tubular skelp 2' heated by the high-frequency induction heating coil 6 is optically scanned by a rotating mirror with an instantaneous field of view of about 1M width x 5 dragon lengths, and the radiant energy is measured by a forge welding thermometer 7. The thermometer position pulse generator 20 outputs a pulse signal at a fixed position of the one-rotation mirror by continuously measuring the temperature in the width direction in the width including the two edge parts 2a and 2a and outputting a signal. .

The temperature signal detected by the forge welding thermometer 7 is sent to the Skelp thermometer 9.
By the left/right separation circuit 16 and the peak keep circuit 17 in the same way as the temperature signal processing.

The left edge temperature TL2 of the tubular kelp 2' and the right edge temperature TR2 of the tubular kelp 2' are output. Also, the temperature at the edge is higher than the temperature at the center, and the temperature change at the edge is the least likely, so the temperature signal detected by the forge welding thermometer 7 is output as a differential signal by the differential circuit 18, and the peak position is A pulse 2 generator 19 outputs left and right edge position signals. This edge position signal and the output signal from the thermometer position pulse generator 20 are input to the peak position calculation circuit 21 to calculate the time from the thermometer constant position to the edge position. By multiplying the distance from the forge welding thermometer 7 to the tubular skelp 2', the horizontal distance LL from the thermometer position to the left edge of the tubular skelp 2' and from the thermometer position to the tubular skelp 2' are calculated. The horizontal distance LR to the right edge portion of 2' is calculated and input to the control device 11.

The control device 11 inputs and calculates the signal from the forge welding thermometer 7 and the signal from the Skelp thermometer 9, sends a control signal to the thyristor voltage regulator 14, and adjusts the voltage level at the thyristor voltage regulator 14. The high-frequency oscillator 13 generates a high-frequency current to control the current flowing to the high-frequency induction heating coil 6 through the transformer 12, and sends a control signal to the left-right adjustment device 15 that adjusts the left-right position of the high-frequency induction heating coil 6. is sent to control the left and right positions of the high frequency induction heating coil 6, which is integrated with the transformer 12.

In order to stabilize the quality of the forge welded joint, it is desirable to keep the temperature constant during forge welding, but the temperature during forge welding cannot be measured because of the presence of forge welding rolls and other equipment.

Therefore, in the method of the present invention, the temperature during forge welding is estimated and calculated based on the signals from the Skelp thermometer 9 and the forge welding thermometer 7, and machine control is performed to reduce the difference from the target temperature during forge welding. From the measurement position of forge welding thermometer 7.

Up to the forge welding position, the temperature of the edge of the tubular skelp 2' decreases due to heat radiation, convection and heat conduction to the central part of the tubular skelp 2'.

In particular, when the edge of a tubular skelp is rapidly heated by high-frequency induction heating, the depth of heat penetration is shallow and the temperature change due to heat conduction is rapid. The amount of temperature drop from the measurement position to the forge welding position changes. The amount of temperature decrease ΔT from the measurement position of the forge welding thermometer 7 to the forge welding position is approximately expressed by the following formula.

T2L', T2R: Temperature of the edge part 2a of the tubular skelp 2' at the measurement position of the forge welding thermometer 7 ('C) T machining + T-
, u: Band-shaped Skelp 2 at the measurement position of Skelp thermometer 9
Edge part 2a Temperature (℃) C: Constant ('C) o ~ 30
C. α: Coefficient α is a coefficient determined by the thickness of the skelp, the speed of the skelp, the distance from the measurement position of the forge welding thermometer 7 to the forge welding position, the depth of heat penetration, etc., and is used in the range of 0 to 1.

The squelp edge temperature (T3) at the forge welding position is expressed as T3, which is the lower temperature between T3L and T3H, and is compared with the target temperature 'I''30, and the deviation output is input to the thyristor voltage regulator 14. .or.

Temperature of both edges of tubular skelp 2' at forge welding position, T3
The deviation ΔT3 of L + T3R is ΔT3-T3L T3R・・・・・・・・・・・・
(3), so that ΔT3 becomes O, Δ
The output of T3 is input to the left and right adjusting device 15 of the high frequency induction heating coil 6. The amount of heat input Q by the high frequency induction heating coil 6 and the amount of rise TUP in the temperature of the edge portion of the tubular skelp 2' at the forge welding position are approximately proportional to each other.

Therefore, the thyristor voltage regulator 14 is controlled so as to adjust the amount of heat input to the high frequency induction heating coil 6 in proportion to the output difference between T3 and T3o.

Next, when the high frequency induction heating coil 6 is shifted to the left,
Since the left edge begins to be heated by the right coils 6 to 2, the amount of temperature increase at the left edge becomes larger than that at the right edge. - Also, when the high-frequency induction heating coil 6 is shifted to the right, the right edge begins to be heated by the left coils 6 to 1, so the amount of temperature increase at the right edge is greater than that at the left edge. Get bigger □.

Therefore, when ΔT3>O, the high-frequency induction heating coil 6 is moved to the right, and when ΔT3<○, the high-frequency induction heating coil 6 is moved to the left.
The position adjustment is performed by inputting the signal ΔT3 to the left and right adjusting device 15.

Next, the control device 11 will be explained in detail.

FIG. 3 is a block diagram showing the configuration of the control device 11 shown in FIG. 1. From the forge welding thermometer 7 to the input terminal of the left edge temperature TL2 of the tubular squelp 2', the tubular squelp 2
The signal from the forge welding thermometer 7 is input to the input terminal 43' of the right edge temperature TR2 of ', and the input terminal 24 of the horizontal path force LR from the fixed position of the forge welding thermometer to the right edge of the tubular squelp 2'. The left edge temperature of the band-shaped Skelp 2 is input.
The signal from the Skelp thermometer 9 is input to the input terminal 44' of the right edge temperature TRI of the right edge portion of the Skelp 2 in the Lx input terminal 44'. 25 is a comparator, and input terminal 43
The input current signal from the input terminal 44 is compared with the input current signal from the input terminal 44, and the difference signal is outputted to the comparator 27. The comparator 27 compares the output signal of the comparator 25 with the output signal of the constant generator 26, and outputs the difference signal to the coefficient unit 28, which multiplies the multiplication by a coefficient and outputs it. Find ΔTL in the equation.

29 is a comparator that connects the output signal from the input terminal 43 and the coefficient unit 2.
The output signals from the sun are compared, the difference signal is outputted, and the above equation (2) is calculated. This output signal is an estimated value of the forge welding temperature of the left edge portion, and is input to the comparator 31. A comparator 31 compares the output signal from the comparator 29 and the signal from the forge welding temperature target setting device 30, and outputs the difference signal to the calculator 32. The estimated value of the forge welding temperature of the right edge part,
The same control as described above is performed also when outputting a difference signal of the forge welding temperature target value.

32 is an arithmetic unit which outputs the output signal of the comparator 31 and the comparator 31'.
The output signals of the two are compared, and the smaller signal is output to the converter 33, and the difference signal is output to the converter 37.

The converter 33 is a converter that converts a current signal into a voltage signal and outputs it to the gate 45.

The gate 45 is closed when the output of the high-frequency induction heating coil 6 is manually adjusted, and is opened when the output is automatically adjusted. A heater 35 adds the output signal from the gate 45 and the output signal 34 from the thyristor voltage regulator 14 and inputs the result to the thyristor voltage regulator 14 . The converter 37 is ΔT
Gate 40 is a converter that converts the current signal of 3 into a voltage signal.
Enter.

38 is a position movement range setting device for the high-frequency induction heating coil 6, which ranges from the horizontal pressure distance LIO from the forge welding thermometer fixed position to the left edge of the tubular skelp 2', and from the thermometer fixed position to the right side of the tubular skelp 2'. This is to set the horizontal distance LRO to the edge. If the fixed position of the forge welding thermometer is chosen so that the left edge of the tubular skelp 2' is always to the right of the fixed position of the forge welding thermometer, then Lt, > LLO+ LH<
If the high-frequency induction heating coil 6 is out of this range, there is a risk that the high-frequency induction heating coil 6 will come into contact with the edge of the tubular skelp 2' and be damaged. Make the control stop.

39 is a comparator, which compares the input signal from the input terminal 24 and the input signal from the position movement range setting device 38.
LO and "LOL R" are output to the gate 40. The gate 4o is open only when LL LLO > O and LROLR > 0, and is closed when the above conditions are not met, and the signal from the converter 37 is input to the gate 46. The gate 46 is closed when the left-right adjustment of the high-frequency induction heating coil 6 is manually adjusted, and is opened when automatic adjustment is performed. 42
is an adder that adds the output signal from the gate 46 and the output signal 41 from the left-right adjustment device 15 of the high-frequency induction heating coil 6, and inputs the result to the left-right adjustment device 15 of the high-frequency induction heating coil 6 for position adjustment. .

Since the present invention is an automatic forge welding temperature control method in the manufacturing process of forge welded steel pipes as described above, the peak temperature at the left edge portion and the peak temperature at the right edge portion immediately before forge welding are measured, and the peak temperature at the right edge portion is measured. It is possible to reduce the deviation temperature and control the edge temperature to a constant value, so the edge temperature immediately before forge welding can be kept constant, and the forge welding temperature can be controlled to an appropriate value, resulting in good quality forge welded joints. It is possible to manufacture products with high quality, and the effect in terms of quality control is extremely large.

In addition, in the method of the present invention, the forge welding temperature is estimated and calculated from the edge temperature of the strip-like skelp measured with a skelp thermometer and the edge temperature of the tubular skelp measured with a forge welding thermometer. Assuming that the temperature obtained by adding a certain constant to the edge temperature of the tubular skelp measured at is the forge welding temperature,
Although the difference from the true forge welding temperature is somewhat large, it is also possible to easily substitute this method.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the method of the present invention, FIG. 2 is a sectional view taken along the line AA in FIG. 1, and FIG. 3 is a block diagram of a control device according to the method of the present invention. l...Heating furnace 2...Band-shaped skelf. 2a... Edge portion 3, 4... Forming roll 5
...Forge welding roll 6...High frequency induction heating core...Forge welding thermometer Ile

Claims (1)

[Claims] A band-shaped skelp heated in a heating furnace is formed into a tubular shape with a forming roll, an edge portion of the tubular skelp formed into the tubular shape is heated with a heating device, and the edge portion is forge-welded with a forge-welding roll. In the process of manufacturing a forge-welded steel pipe to be used as a pipe, high-frequency induction heating coils are arranged on both edge parts of the tubular skelp as a heating device for heating the edge parts of the tubular skelp. The edge portion is heated, and the temperature of the tubular skelp edge portion before forge welding is measured with a thermometer provided upstream of the forge welding roll, and the temperature difference between the two edge portions of the tubular skelp is within the target range. Forge welding, characterized in that the position of the high frequency induction heating coil is adjusted in a direction perpendicular to the tube axis, and the output of the high frequency heating coil is adjusted so that the temperature of both edge portions before forge welding is within a target range. Automatic forge welding temperature control method for steel pipes.