JPH0341269B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a welding heat input control method for an electric resistance welded pipe such as an electric resistance welded steel pipe.

[Prior Art] FIG. 5 is a control system diagram showing a conventional welding heat input control method described in Japanese Patent Publication No. 60-8144. In this welding heat input control method, a strip material 1 is formed into a tubular shape by a plurality of forming roll stands 2A, 2B, etc., and both abutting surfaces of the strip material 1 formed into a tubular shape are welded by a welding machine 3. When heating and pressure welding with the squeeze roll 4, the pipe forming speed of the strip material 1,
The plate thickness, the welding temperature, and the pressure applied by the squeeze roll 4 are each measured using a speed meter 5, a plate thickness gauge 6, a thermometer 7, and a load cell 8, and the output of the plate thickness gauge 6 is used to determine the plate thickness. The tracking device 9 memorizes and delays the welding point according to the speed, inputs these factors to the calculation device 10, adjusts the welding input according to the deviation of these factors from the reference value, and brings the welding input to the optimal state. It is to be maintained.

[Problems to be Solved by the Invention] By the way, in the manufacturing process of the above-mentioned electric resistance welded pipe, the V-shape angle formed by both abutting surfaces of the strip material immediately before the welding point has a large influence on the welding efficiency. That is, as the V-shape angle increases, the proximity effect of high-frequency current decreases, and welding efficiency decreases (welding cannot be performed unless a larger current is supplied than usual). The factors that determine this V-shape angle include roll caliber,
These include the thickness and mechanical properties of the strip material, as well as the tension acting on the strip material. Therefore, in an electric resistance welded pipe manufacturing facility that does not have band splicing equipment, the tension acting on the strip material decreases each time the rear end portion of the strip material passes through each stand. In particular, when the rear end of the strip material passes through the fin pass roll stand, a large drop in tension occurs, resulting in a V
Shape angle increases. As a result, as mentioned above, the welding efficiency fluctuates, and if the heat input remains the same,
The welding conditions change, resulting in an open pipe with a weld defect.

However, in the conventional welding heat input control method, no consideration is given to the large effect that forming fluctuations such as the V-shape angle fluctuations have on the welding state when the rear end of the strip passes through each stand. I haven't. As a result, open pipes with defective welds are discarded, leading to a decrease in yield. Note that even if fluctuations in the welding condition are feedback-controlled by measuring the welding temperature, the feedback control itself corrects the fluctuation after detecting it, so it is impossible to completely prevent fluctuations in the welding condition due to forming fluctuations. I can't.

An object of the present invention is to reliably prevent fluctuations in welding conditions due to molding fluctuations caused by tension fluctuations in a strip material, and to improve welding quality and yield.

[Means for Solving the Problems] The present invention involves forming a strip material into a tubular shape using a plurality of forming roll stands, heating both abutting surfaces of the tubular shaped strip material, and then applying the heat to the material using squeeze rolls. In the welding heat input control method for electric resistance welded pipes, the welding input is controlled based on various factors such as the pipe forming speed, the thickness of the strip material, the temperature of the weld zone, and the pressure welding load of the squeeze roll. A heat input correction amount is predetermined to prevent fluctuations in the welding state due to forming fluctuations that occur when the rear end passes through each stand, and the heat input is A correction amount is applied.

[Function] In implementing the present invention, forming variations (V-shape angle variations, etc.) when the rear end of the strip material passes through each stand are investigated by classifying them according to the thickness of the strip material, mechanical properties, etc. However, as shown in FIG. 3, the relationship between the amount of molding variation (such as the amount of V-shape angle variation) and the appropriate heat input correction amount is determined in advance. As a result, each time the rear end of the strip material passes through each stand, a heat input correction amount corresponding to the forming fluctuations (V-shape angle fluctuations, etc.) is applied, and the forming fluctuations (V-shape angle fluctuations, etc.) It is possible to prevent fluctuations in the welding condition due to

[Embodiment] FIG. 4 is a control system diagram showing an embodiment of the present invention. In this welding heat input control method, a strip material 11 is formed into a tubular shape by a plurality of forming roll stands 12A, 12B, etc., and both abutting surfaces of the tubular shaped material strip 11 are heated by a welding machine 13. However, when pressure welding is performed using the squeeze roll 14, the strip material 1
The pipe forming speed, plate thickness, welding temperature, and pressure welding load caused by the squeeze roll 14 in step 1 are measured using a speed meter 15 consisting of a measuring roll or the like, a plate thickness gauge 16, a thermometer 17, and a load cell 18, and Regarding the thickness, the output of the plate thickness gauge 16 is memorized and delayed by the tracking device 19 until the welding position according to the pipe manufacturing speed, and these various factors are input to the calculation device 20, and the calculation is performed according to the deviation of these factors from the reference value. Adjust the welding input to maintain the welding input at the optimum condition.

Furthermore, in this welding heat input control method, a strip material rear end detector 21 made of a phototube or the like and a welding input correction indicator 22 are provided. That is, the welding input correction indicator 22 determines the position immediately before the welding point when the rear end of the strip 11 passes through each stand 12A, 12B, etc., with respect to the various plate thicknesses, mechanical properties, etc. of the strip 11. The heat input correction amount for preventing fluctuations in the welding state due to fluctuations in the V-shape angle of the strip material 11 in the above is determined in advance as shown in FIG. moreover,
The welding input correction indicator 22 is installed on the most advanced stand 1.
The time at which the rear end of the strip 11 enters each stand 12A, 12B, . This results in
The welding input correction indicator 22 applies a heat input correction amount corresponding to the V-shape angle variation to the arithmetic unit 20 every time the rear end of the strip material 11 passes through each stand 12A, 12B... Prevents fluctuations in welding conditions due to V-shape angle fluctuations.

Note that the computing device 20 may also perform feedback control based on measurements of welding temperature and the like.

Hereinafter, specific implementation results of the present invention will be explained. API5LX, X-52, outer diameter 20 inches, wall thickness 12.7
An electric resistance welded steel pipe (mm) was produced at a speed of 20 m/min. As a result, in the conventional method shown in Figure 2, the welding temperature
The temperature is set at 1420°C, and the temperature reduction time and temperature when the rear end of the strip passes through the first fine pass roll, second fine pass roll, and third fine pass roll are 10 °C for 2 seconds and 14 °C for 2.3 seconds, respectively. It was kept at 20°C for 3 seconds. In contrast, by carrying out the method of the present invention, the welding input is corrected to 3kw, 4kw, and 5kw when the trailing end of the strip passes through the first, second, and third finpass rolls, respectively. As a result, no decrease in welding temperature was observed as shown in FIG. That is, according to the present invention, fluctuations in welding conditions can be more completely corrected.

[Effects of the Invention] As described above, according to the welding heat input control method for electric resistance welded pipes according to the present invention, fluctuations in the welding state due to forming fluctuations caused by tension fluctuations in the strip material can be reliably prevented, and the welding Quality and yield can be improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the welding heat input control state according to the method of the present invention, Fig. 2 is a schematic diagram showing the welding heat input control state according to the conventional method, and Fig. 3 shows the relationship between the V-shape angle and the appropriate amount of heat input. FIG. 4 is a control system diagram showing an embodiment of the present invention, and FIG. 5 is a control system diagram showing a conventional example. 11... Strip material, 12A, 12B... Forming roll stand, 13... Welding machine, 14... Squeeze roll, 15... Speed meter, 16... Plate thickness gauge, 17
... Thermometer, 18 ... Load cell, 20 ... Arithmetic device, 21 ... Strip material rear end detector, 22 ... Welding input correction supporter.

Claims (1)

[Scope of Claims] 1. When forming a strip material into a tubular shape using a plurality of forming roll stands, heating both abutting surfaces of the tubular shaped strip material, and pressure welding it with a squeeze roll, the pipe forming method is speed, strip thickness, welding temperature,
In the welding heat input control method for electric resistance welded pipes, which controls the welding input based on various factors of the pressure welding load of the squeeze roll, welding conditions due to forming fluctuations that occur when the rear end of the strip passes through each stand. A heat input control method for welding electric resistance welded pipes, characterized in that a heat input correction amount is predetermined to prevent fluctuations in the temperature, and the heat input correction amount is applied each time the rear end of a strip material passes through each stand. . 2. In claim 1, the heat input correction amount is determined in response to the variation in the V-shape angle of the strip immediately before the welding point when the rear end of the strip passes through each stand. Method for controlling welding heat input of ERW pipes.