JPH0686020B2 - Heat input control method for ERW pipe welding - Google Patents

Description

The present invention relates to a heat input control method for improving the welding quality, stabilizing the quality and greatly improving the production yield in high frequency electric resistance welded pipe welding.

1 (a) shows induction type high frequency electric resistance welded pipe welding, and FIG. 1 (b) shows contact type high frequency electric resistance welded pipe welding. In the figure, 1 is a work coil for electromagnetic induction, 2 is a chip (contact) for contact energization, 3 is a squeeze roll, 4 is a material to be welded, 5 is a V seam, 6 is an electric resistance welded pipe, 7 Is a high frequency oscillator.

The work coil 1 or the chip 2 is arranged at the front stage of the squeeze roll 3, and when these are applied with a high-frequency current to the V seam 5 formed on the material 4 by the multi-stage forming rolls (not shown), they project from each other. The edges to be joined are heated by a high-frequency current and then pressure-welded by a squeeze roll 3.

In the above-mentioned electric resistance welded pipe welding, as a conventional heat input control method for controlling the high frequency current flowing through the edge (V seam) 5, (1) the operator visually checked the temperature (flame color) of the welded portion and cut it. Observe the shape of the welding bead and manually adjust the heat input amount according to these conditions. (2) Detect the feed rate of the material to be welded, and output the heat input value corresponding to the feed rate from the function generator. The speed-linked control that adjusts the temperature by (3), (3) the temperature control that detects the temperature of the welded part and controls it so that this temperature becomes constant are adopted.

However, the heat input control methods such as (1) to (3) above are still insufficient in terms of the following (a) to (c).

(A) It is not possible to follow a factor that causes a sudden change such as a change in the feed rate of the material and a change in the plate thickness.

(B) Welding is not possible in the vicinity of the feed rate of zero when starting and stopping, and an open pipe occurs.

(C) Due to these factors, excess or deficiency of heat input occurs, and therefore, penetrator (a state in which oxides such as scale are caught in the weld portion to cause poor welding), cold welding (incomplete welding at low temperature) As a result, defects in the weld zone occur and good welding quality cannot be obtained. In addition, there is a disadvantage that the production yield is greatly reduced because a portion (open pipe) that cannot be welded is generated each time the engine is stopped.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to provide a method capable of continuously and stably performing heat input control even when the feed speed changes from zero to a constant speed.

The structure of the method of the present invention for achieving such an object is, in a heat input control method for electric resistance welded pipe using a high frequency oscillator, (a) the following relational expression between the feed rate of the pipe material and the welding heat input is calculated. In the arithmetic processing unit, the coefficients a, b, c, d, e and f of the relational expression are different in the welding method between the induction type and the contact type, the pipe diameter,
A table should be prepared in advance according to the plate thickness and the distance between the squeeze roll center and the work roll or chip. Where υ _r is the feed rate, E _p I _p is the welding heat input, E _p is the plate voltage of the high frequency oscillator, I _p is the plate current of the high frequency oscillator, a is the moving heating region velocity coefficient, and b is the static heating reference. Value, c is static heating region velocity coefficient, d is static heating region velocity correction value, e is static heating region correction value, f is static heating region acceleration / deceleration correction value, t is plate thickness, (b) Input of each condition According to the above, the arithmetic processing unit automatically retrieves the coefficient corresponding to the condition from the table and sets it in the relational expression. (C) The coefficient is detected by detecting the feed rate of the pipe material and inputting it by the arithmetic processing unit. Calculating the welding heat input corresponding to the feed rate from the above relational expression, (d) detecting the plate voltage and the plate current of the high-frequency oscillator, and performing a constant power control based on the calculated welding heat input by a feedforward method. And Controlling the welding heat input online, it characterized.

The details will be described below.

First, when arranging the operation data for ERW pipe welding, the required heat input power E _p I _p for each feed rate υ _r is the difference in the welding method between the induction type and the contact type, the pipe diameter, the plate thickness t, and the squeeze roll. Center of 3 and work coil 1 or chip 2
When the distance l _υ between them is determined, it is considered that it is expressed by a linear expression as shown in FIG. In FIG. 2, a is a gradient (velocity coefficient) and b is an intercept (static heating amount). Therefore, the heat input power for each feed speed υ _r is calculated by this linear expression, and if this heat input power is given, the heat input should be automatically adjusted according to the change in the feed speed. Note that E _p ,
I _p is the plate voltage and plate current of the high-frequency oscillator 7, and the device shown in FIG. 5 is generally used as this device 7. In FIG. 5, 8 is a vacuum tube, 9 is a DC power supply, 10 is a tank capacitor, and 11 is an output transformer.

However, as a result of repeated experiments using the above-described linear equation, it was found that heat input becomes insufficient when the linear equation is applied in the vicinity of the feed rate at the time of welding start or stop. Therefore, since it is necessary to heat the part of the distance l _υ between the squeeze roll 3 and the work coil 1 or the chip 2 to the welding temperature even when the feed rate is near zero, the ν _r -E _p I _p / t characteristic shown in FIG. It is possible to apply thermal power. However, υ _{l in} Fig. 3
Is the feed rate at the time when the portion of the material located at the work coil 1 or the chip 2 at the feed rate of zero at the start of welding comes to the center of the squeeze roll 3.

However, adjusting the heat input power with the υ _r −E _p I _p / t characteristic as shown in FIG. 3 was still insufficient.

That is, in the electric resistance welded pipe welding, when the pipe making line is activated, it is accelerated with a substantially constant acceleration from zero feed speed to a predetermined constant feed speed. Therefore, as shown in FIG.
If the amount of heat input is constant in the static heating region of υ _l , there is insufficient welding input near the feed rate due to the input level of heat input in the static heating region, and there is no stable welding continuity. I found out.

Therefore, as shown in FIG. 4, the stationary heating region (0-υ _l )
Then, decrease the heat input power with increasing feed rate υ _r
Experiments were repeated with −E _p I _p / t characteristics. Of course, if it is υ _l or more, the heat input increases. As a result, it was found that welding was continuously and stably performed from zero feed speed to a predetermined speed. In other words, there is no occurrence of open pipes when starting and stopping, and the production yield is greatly improved.

Further studying the ν _r −E _p I _p / t characteristic in FIG. 4 preferably has the following relational expression.

Where E ₀ is the control output, υ _r is the feed speed, E _p is the plate voltage (KV) of the high frequency oscillator, I _p is the plate current of the high frequency oscillator (A), a is the velocity coefficient of the moving heating region, and b is the static heating. Reference value, c is static heating region velocity coefficient, d is static heating region velocity correction value, e is static heating region correction value, f is static heating region acceleration / deceleration correction value, and t is plate thickness.

The curve according to equation (1) depends on each coefficient or correction value.
_In the vicinity of zero of _r , there is a convex change as shown in FIG.

The coefficients a, b, c, d, e, f in the above formula (1) are the welding method (difference between induction type and contact type), pipe diameter, plate thickness t, center of squeeze roll 3 and work coil. It is determined by the distance l _υ between 1 or the chip 2, and both are obtained by experiments. For example, under the conditions of induction type, pipe outer diameter 25.4 ^mmφ , plate thickness t = 1.2 mm, distance l _υ = 65 mm, a = 1.4 b = 33 c = 10 d = 3 e = 62 f = 0 Is.

As a specific heat input control by the relational expression (1), first, the arithmetic operation of the relational expression (1) is programmed in an arithmetic processing unit such as a microcomputer, and the coefficients a to f in the equation are The internal constants of the arithmetic processing unit are used, and a table is prepared according to the welding method, pipe diameter, plate thickness t, and distance l _υ . Next, in the control, by inputting each of the above conditions into the arithmetic processing unit, the corresponding coefficient is retrieved from the table and automatically set in the relational expression (1). The feed speed υ _r of the sewing tube 6 is detected by a sensor, and the detection signal is input to the arithmetic processing unit to calculate the welding heat input with respect to the feed rate at every moment from the relational expression (1). Based on this calculated value, the welding heat input is online controlled by the feedforward method. To adjust the welding heat input, it is preferable to detect the plate voltage E _p and the plate current I _p of the high-frequency oscillator 7 and use one or both of E _p and I _p (constant power). The plate thickness t may be the nominal plate thickness of the material.

As described above, according to the present invention, stable welding can be continuously performed from zero feed speed to a constant speed. This improves the welding quality, stabilizes the quality, and there is no open pipe at the time of starting and stopping, which greatly improves the production yield.

[Brief description of drawings]

1 (a) and 1 (b) are explanatory views of induction type and contact type of electric resistance welded pipe welding, and FIGS. 2 and 3 are characteristic diagrams of feed rate-heat input power used for consideration of the present invention. , Fig. 4 shows the feed rate of the present invention-
FIG. 5 is a circuit diagram showing an example of a high-frequency oscillator, which is a characteristic diagram of heat input power. In the drawings, 1 is a work coil, 2 is a chip, 3 is a squeeze roll, 4 is a material, 5 is a V seam, 6 is an electric resistance welded pipe, and 7 is a high frequency oscillator.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-57-195587 (JP, A) JP-A-57-106483 (JP, A) JP-A-49-90649 (JP, A)

Claims (1)

[Claims] 1. A heat input control method for electric resistance welded pipes using a high frequency oscillator, comprising: (a) a relational expression in a calculation processing device for calculating the following relational expression between a pipe feed rate and welding heat input: Of the coefficients a, b, c, d, e and f of
A table should be prepared in advance according to the plate thickness and the distance between the squeeze roll center and the work roll or chip. Where υ _r is the feed rate, E _p I _p is the welding heat input, E _p is the plate voltage of the high frequency oscillator, I _p is the plate current of the high frequency oscillator, a is the moving heating region velocity coefficient, and b is the static heating reference. Value, c is static heating region velocity coefficient, d is static heating region velocity correction value, e is static heating region correction value, f is static heating region acceleration / deceleration correction value, t is plate thickness, (b) Input of each condition According to the above, the arithmetic processing unit automatically retrieves the coefficient corresponding to the condition from the table and sets it in the relational expression. (C) The coefficient is detected by detecting the feed rate of the pipe material and inputting it by the arithmetic processing unit. Calculating the welding heat input corresponding to the feed rate from the above relational expression, (d) detecting the plate voltage and the plate current of the high-frequency oscillator, and performing a constant power control based on the calculated welding heat input by a feedforward method. And Controlling the welding heat input online, heat input control method for electric-resistance-welded pipe welding according to claim.