JPH01197010A - Electric resistance welding method and its equipment line - Google Patents

Abstract

PURPOSE:To improve welding quality by arranging thermometers and a heating device for correction respectively in front of a forming machine and a welding machine and further providing with a thermometer behind the welding machine, too, to correct the deviations of temperature of steel strip and pipe edge. CONSTITUTION:The thermometer 12 for the steel strip 1 and the heating device 15 for correcting the deviated heating of the steel strip are provided on a suitable position in front of the forming machine 4. Then, the thermometers 13, 14 for the pipe body are arranged in front of an behind the high frequency electric resistance welding machine 5 and the heating device 16 for correcting deviated heating of a pipe body edge is arranged in front of the welding machine 5. As a result, the deviated heating of the steel strip 1 coming out of a heating furnace 2 and the deviated heating of the pipe body edge after forming are corrected and heated respectively by the heating devices 15, 16 for correction through the feedback or feed-forward information of the thermometers 12, 13, 14. Since temperatures of the edge parts of the steel strip 1 and the pipe body 7 are distributed adequately, the welding quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a warm electric resistance welding method and equipment arrangement for stabilizing the quality of a welded part in warm electric resistance welding of steel pipes.

(Conventional technology) Warm electric resistance welding method of forming and electric resistance welding a heated steel strip;
The steel pipe manufacturing method, which is also called high-temperature electric resistance welding, generally consists of a steel strip preheating furnace, a steel strip reversing machine, a steel strip heating furnace, a forming machine, a welding machine, a tube heating furnace, and a drawing machine. Showa 58-97
No. 14, JP-A-59-27788, JP-A-Sho. 5
8-122121) and an equipment arrangement of a steel strip heating furnace, a steel strip rolling mill, a forming machine, a welding machine, a tube heating furnace, and a drawing machine (Japanese Unexamined Patent Publication No. 1982-137120), or a steel strip heating furnace - steel An equipment arrangement of a band reversing machine, a forming machine, a welding machine, a tube heating furnace, and a drawing machine (Japanese Patent Application Laid-Open No. 62-238018) and a manufacturing method using them have been disclosed.

(Problems to be Solved by the Invention) In these conventional techniques, the heating of the steel strip depends on the steel strip preheating furnace and the steel strip heating furnace, or only on the steel strip heating furnace, and the heating of the steel strip occurs after passing through the heating furnace. Alternatively, there is no corrective means for the discovered temperature deviation of the steel strip. However, in the warm electric resistance welding method, temperature deviations tend to occur in the material after passing through the heating furnace. The cause of this temperature deviation is that the steel strip loses heat to the forming rolls, that roll cooling water is splashed on the steel strip, or that some conditions in the manufacturing process have been changed. Examples include cases where it is lowered. In these cases, the strip edge temperature is particularly sensitive. Of course, various efforts have been made to prevent these causes, but it is impossible to completely prevent the occurrence of steel strip temperature deviations, resulting in variations in forming shape and welding temperature. This is linked to a decline in the quality of welded parts.

In order to eliminate this unavoidable temperature deviation in the steel strip, it is effective to apply local heating to the steel strip in accordance with the temperature deviation. To do this, it is necessary to detect the temperature distribution of the steel strip at any point in front of the forming process or the welding process, and to apply local heating to the steel strip so that this temperature distribution can be maintained within a predetermined range. However, in the steel strip heating furnace based on the conventional technology, it is difficult to control the local heating of the steel strip, and when heating is required in a short time, the response speed is not sufficient.

On the contrary, it depends on the type of furnace and the operating conditions of the furnace.
There are problems such as uneven heating that may even occur in the steel strip heating furnace. Furthermore, as mentioned above, the conventional technology has a steel strip inversion machine (Japanese Unexamined Patent Publication No. 62-238018) or a squelp rolling machine (Japanese Unexamined Patent Publication No. 62-137120) on the front side of the forming machine, which promotes steel strip temperature deviation. It has the disadvantage of

The present invention prevents and eliminates temperature deviations that occur in the heated steel and tube edges during the warm electric resistance welding process by applying local heating to these areas, thereby stabilizing the quality of the welded part. There are things.

The present inventor conducted research to solve the above problems and came to the following conclusion. That is, among the temperature deviations observed in the steel strip after passing through the heating furnace, the one that has the greatest effect on forming and welding is the temperature non-uniformity at the left and right edges of the steel strip as shown in FIG. If this degree is severe, it becomes difficult to keep the heating temperature of both the left and right edges within a predetermined temperature range suitable for welding when heating the edge of the steel strip by an electric resistance welding machine (hereinafter referred to as Case 1).

Next, when the temperature pattern of the steel strip is unbalanced from side to side with respect to the center line in the axial direction (forming/welding direction) of the steel strip not only at the edge of the steel strip but also over a wide area, the deformation resistance of the steel strip will be affected. This creates a left-right imbalance, which induces forming torsion, and subsequently causes uneven heating of the tube edge by the electric resistance welding machine, leading to poor welding quality and defective weld bead cutting (hereinafter referred to as Case 2).

Furthermore, when starting forming or welding work, or if the forming or welding area is unavoidably lowered temporarily due to changes in operating conditions,
Cases 1 and 2 occur together and become more severe, and it is inevitable that weld quality defects will continue to occur until the forming/welding speed returns to a steady value (hereinafter referred to as case 3).

(Means for Solving the Problems) The present invention provides a method and a series of equipment to which the following uneven heating correction method for steel strips and tube edges is applied as an improvement measure for the above-mentioned cases 1, 2, and 3. The gist is as follows: 1. In the warm electric resistance welding method, in which a steel strip is fed longitudinally in a heated state and formed into a tubular shape, the edges on both sides are abutted, and the abutting portions are electric resistance welded, a forming machine is used. A thermometer to detect the temperature of the steel strip at any position in front of the steel strip and a heating device to compensate for the temperature deviation of the steel strip.
A thermometer is installed at any position on the front of the welding machine to detect the temperature at the edge of the tube, and a heating device is installed to correct temperature deviations at the edge of the tube, and a thermometer is also installed at the rear of the welding machine. , the temperature measured by these thermometers is fed back or fed forward, and the temperature deviation of the steel strip and the tube edge is corrected by the steel strip heating device and the tube edge heating device, and electric resistance welding is performed. Warm electric resistance welding method.

2. In an electric resistance welding equipment arrangement consisting of a steel strip heating furnace, a forming machine, a welding machine, a tube heating furnace, and a drawing machine, there is a thermometer that detects the temperature of the steel strip at an arbitrary position in front of the forming machine, and a thermometer that detects the temperature of the steel strip. A heating device is installed to compensate for deviations, and a thermometer and tube edge are installed at any position on the front of the welding machine to detect the temperature of the tube edge.

This is a line of warm electric resistance welding equipment characterized by being equipped with a heating device for correcting temperature deviation in the welding machine, and also equipped with a thermometer on the rear surface of the welding machine.

The present invention will be explained in detail below.

Case 1: Since the temperature at both edges of the tube is non-uniform, this can be resolved by heating at least one edge. It is desirable that the heating device for correcting uneven heating of the tube edge be similar to a welding machine in terms of heating efficiency and heating response. This pipe body edge uneven heating correction heating device is fed forward or fed back with both class heating temperatures measured between the front side of the welding machine, the back side of the welding machine, and upstream of the welding point, and the heating temperature pattern on both edges. Based on this, corrective heating of the tube edges is performed so that the heating temperature of both edges of the tube and the temperature pattern fall within a predetermined range.

Case 2: When eight forming screws are fired, temperature deviation occurs over a considerably wider portion of the steel strip than in Case 1. However, this temperature deviation must be corrected before the molding process is completed. In this case, the heating device for correcting uneven heating of the steel strip is preferably located between the heating furnace outlet and the forming machine, except for the steel strip reversing machine, because the device can be simplified, and in particular, it is preferable to use the heating device directly in front of the forming machine from the viewpoint of thermal efficiency.

Further, it is preferable that the heating device for correcting uneven heating of the steel strip is of a type that is divided into at least four parts in the width direction of the steel strip, and each part can be independently heated. The temperature of the steel strip and tube body measured at the inlet of the forming machine or in front of the high-frequency electric resistance welding device is fed forward or fed back to this steel strip uneven heating correction heating device, and the steel strip heating temperature is adjusted based on this information. , and the heating control so that the temperature pattern falls within a predetermined range.

Case 3: In this case, the temperature of the entire steel strip is decreasing and at the same time there is partial heating, so Case 1,
This can be handled by using both the edge of the steel strip in case 2 and the heating device for correcting uneven heating of the steel strip, or by using only the heating device for correcting uneven heating of the steel strip.

The steel strip thermometer and tube thermometer used in the present invention are preferably of a type using a photoelectric element. According to this type of thermometer, since steel strip temperature information is sent from each photoelectric element arranged in the width direction of the steel strip, the temperature distribution in the width direction of the steel strip can be obtained from this information. In the case of a tube thermometer, the photoelectric elements sufficient to cover the width of the tube edge are lined up almost perpendicularly to the tube edge and circumferentially on the outside of the tube. Body limb temperature and tubular body temperature distribution are measured.

Further, the heating device for correcting uneven heating of the steel strip and the correcting heating device for uneven heating of the pipe body edge used in the present invention preferably use a medium frequency induction heating method, and the frequency thereof is determined by the thickness of the steel strip and the welding speed. , normally 1-10k for steel strip uneven heating correction heating equipment.
Hz, and in the tube edge uneven heating correction heating device, 5-10
0kHz is valid.

(Example) The present invention will be described below with reference to an example apparatus shown in the drawings. FIG. 1 shows an example of an apparatus configuration for implementing the present invention. The steel strip 1 is heated to 600° C. in a heating furnace 2, passes through a steel strip reversing machine 3, and is continuously formed into a tubular shape in a forming machine 4. Next, the tube body 7 is electrically welded using the high frequency electrical resistance welding device 5 and the squeeze and tandro. After passing through the weld bead cutting device 8, the tube 9 is heated to 950° C. in a reheating furnace 10, and then finished to a predetermined size in a reducing mill 11. 12.1.3.14 is a thermometer for the steel strip 1 and the tube body 7, and has a function of continuously measuring the temperature distribution in the width direction of the steel strip and the temperature distribution in the outer circumferential direction of the tube body, They are installed at the inlet of the molding machine (thermometer 12), the outlet of the molding machine (thermometer 13), and immediately behind the welding device (thermometer 14), respectively. 15 is a heating device for correcting uneven heating of the steel strip, which is installed between the thermometer 12 and the forming machine 4; 16 is a steel strip that has been formed, that is, a tube edge whose purpose is to heat only the edge of the tube body 7; The uneven heating correction heating device is installed between the forming machine 4 and the high-frequency electric resistance welding device 5, and heating is controlled based on information fed forward or fed back from the thermometers 12, 13, and 14. FIG. 3 is a conceptual diagram showing an example of the heating device 15 for correcting uneven heating of the steel strip, and FIG. 4 is a conceptual diagram showing an example of the heating device 16 for correcting uneven heating of the tube edge.

As a result of applying the present invention described above to the warm electric resistance welding process, the inappropriate heating temperature of both edges of the tube body and the forming twist of the tube body are reduced, and the poor weld quality and defective weld bead cutting shape caused by these are reduced. , as shown in Table 1, decreased significantly.

Table 1 Effects of the present invention (Unit: %) (Effects of the invention) According to the present invention, the uneven heat up to welding that occurred after the conventional steel strip heating furnace as described above can be effectively eliminated, and the Since the temperature distribution of the steel strip and the temperature distribution of the tube edge during welding are maintained appropriately, remarkable effects such as the ability to dramatically improve welding quality can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an arrangement of warm electric resistance welding equipment according to an embodiment of the present invention, FIG. (a) is a partially enlarged explanatory diagram of the Tl-75 heating isotherm (T 1 > T 2 >・
->T5), FIG. 3 is a conceptual diagram showing an example of a heating device for correcting uneven heating of a steel strip, and FIG. 4 is a conceptual diagram showing an example of a heating device for correcting uneven heating of a tube edge. 1... Steel strip 2... Steel strip heating furnace 3...
・Steel strip reversing machine 4...Forming machine 5...High frequency electric resistance welding machine 6...Squeeze stand 7...Pipe body 8...Weld bead cutting device 9...Pipe 10...Pipe Heating furnace 11・
... Squeezing machine 12 ... Thermometer 13 ... Thermometer 14 ... Thermometer 15 ... Steel strip uneven heating correction heating device 16 ... Pipe body edge uneven heating correction heating device

Claims (1)

[Scope of Claims] 1. In a warm electric resistance welding method in which a steel strip is fed longitudinally in a heated state and formed into a tubular shape, both side edges are abutted, and the abutting portions are electric resistance welded, a forming machine is used. A thermometer that detects the temperature of the steel strip and a heating device that corrects the temperature deviation of the steel strip are installed at any position on the front of the welding machine, and a thermometer that detects the temperature of the tube edge is installed at any position on the front of the welding machine. A heating device is provided to correct the temperature deviation at the edge of the tube body, and a thermometer is also provided at the rear of the welding machine, and the temperature measured by these thermometers is fed back or fed forward, and the temperature of the steel strip heating device and the tube body is A warm electric resistance welding method characterized in that electric resistance welding is performed by correcting temperature deviations of the steel strip and the tube edge using an edge heating device. 2. In an electric resistance welding equipment arrangement consisting of a steel strip heating furnace, a forming machine, a welding machine, a tube heating furnace, and a drawing machine, a thermometer for detecting the temperature of the steel strip and a temperature gauge of the steel strip are installed at any position in front of the forming machine. A heating device is installed to correct the deviation, and a thermometer to detect the temperature of the tube edge and a heating device to compensate for the temperature deviation of the tube edge are installed at any position on the front of the welding machine. Similarly, a row of warm electric resistance welding equipment is characterized by being equipped with a thermometer.