JPS59220289A - Method for controlling heat input of welding electric welded pipe - Google Patents

Abstract

PURPOSE:To improve welding quality and the yield of production in welding an electric welded pipe by detecting the feed speed of a pipe material, calculating the weld heat input corresponding thereto by specific expression and controlling the weld heat input. CONSTITUTION:The feed speed of a pipe material is detected and is inputted to an arithmetic processing unit which determines the optimum heat input value corresponding to the detected feed speed from the equation expressing the relation between the feed speed and the required welding heat input and controls online the welding heat input by a feed-forward method. In the equation, vr is the feed speed, Ep the plate voltage of a high frequency oscillator, Ip the plate current of the high frequency oscillator, (a) the coefft of speed in the moving and heating region, (b) the reference value of static heating, (c) the coefft. of speed in the static heating region, (d) the correction value for the speed in the static heating region, (e) the correction value for the static region, (f) the correction value for the acceleration and deceleration of the static heating region and (t) the thicknes of the plate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat input control method for improving welding quality, stabilizing quality, and significantly increasing production yield in high-frequency electric resistance welding pipe welding. Figure 1 (b) shows induction type high frequency electric resistance welding pipe welding.
) indicates contact type 1% frequency ERW pipe welding.

In the figure, ■ is a work coil for electromagnetic induction, 2 is a tip (contact) for (χ), 3r is a squeeze roll, 4 is the material to be welded, 5 is ■ seam, and 6 is an electric resistance welding tube. ,7
is a high frequency oscillator.

The work coil 1 or the tip 2v is placed in front of the squeeze roll 3, and when a kine frequency current is applied to the V seam 5 made in the material 4 by a multi-stage forming roll (not shown), they mutually The edges to be butted are heated by a high frequency current and then pressure welded by a squeeze roll 3.

In the above-mentioned ERW pipe welding, the conventional heat input control force method for controlling the high frequency current flowing to the edge (■ seam) 5 is as follows: (1) The operator visually observes the temperature (flame color) of the welded part and Manual control that observes the shape of the weld bead and manually adjusts the amount of heat input according to these conditions. (2) Detects the feeding speed of the material to be welded and adjusts the amount of heat input commensurate with the feeding speed (3) Temperature control that detects the temperature of the welding part and controls it so that this temperature is constant.

However, the heat input control methods described in (1) to (3) above are still insufficient in the following points (a) to (C).

(a) It is not possible to follow rapidly changing factors such as material feed speed fluctuations and sheet thickness fluctuations.

(b) Welding cannot be performed when the feed speed is near zero when starting or stopping, and open vibration occurs.

(C) These factors cause excess or deficiency in heat input,
As a result, weld defects such as penetrators (a condition in which oxides such as scale are involved in the weld, resulting in poor welding) and cold welding (incomplete welding at low temperatures) occur, making it difficult to obtain good welding quality. do not have. In addition, each time the device is started or stopped, there is a portion (oven pipe) that is not welded, resulting in a drawback such as a significant drop in production yield.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a method that can continuously perform stable heat input control even when the feed rate changes from zero to one-speed.

The structure of the method of the present invention to achieve such an object is that, in a heat input control method for electric resistance welding pipe welding, the feed speed of the material to be welded is detected and inputted to a processing unit 7, and the feed speed and optimal welding are determined. The welding heat input corresponding to the detected feed rate is calculated based on the relational expression with the heat input, and the welding heat input is controlled online using a feed-forward method.

This will be explained in detail below.

First, if we organize the operational data for ERW pipe welding, we will find the required heat input power "pIpiz" for each feed speed Ut'l, the difference in welding method (induction type or contact type), pipe diameter, plate thickness, and squeeze roll 3. If the distance t? between the center of is the intercept (stationary heating amount). Therefore, by calculating the heat input power for each feed speed 7r using the following equation, and giving this heat input power, the power input will automatically occur according to changes in the feed speed. The heat should be adjusted. Note that E, IP are the plate voltage and plate current of the high frequency oscillator 7, and the circuit shown in FIG. 5 is generally used as this device 7. .In Figure 5, 8 is a vacuum tube, 9 is a DC power supply, 10 is a tank condenser, 11
is the output transformer.

However, as a result of repeated experiments using the above-mentioned linear equation, it was found that applying the linear equation results in insufficient heat input when the feed rate at the time of starting or stopping welding is near zero. Therefore, the distance between the squeeze roll 3 and the work coil 1 or the tip 2 is 1. It is necessary to heat the part to the welding temperature even when the feed rate is near zero, as shown in Figure 3. It is conceivable to give the heat input power using the characteristic rEplp/. However, in Figure 3? 4i'j is the feeding speed at the time when the part of the material that was located at the work coil 1 or the tip 2 at the feeding speed of zero at the start of welding comes to the center of the squeeze roll 3.

However, even if the heat input power was adjusted using the characteristic of 1Pr-Eplp/ as shown in FIG. 3, it was still insufficient.

That is, in electric resistance welding pipe welding, when the pipe making line is started, it is accelerated from a feed speed of zero to a predetermined constant feed speed of 1 with a constant acceleration of about t.

Therefore, if the amount of heat input is constant in the stationary heating region of (0~)·t as shown in Fig. 3, in the vicinity of the feeding speed of zero,
It was found that there was no stable welding continuity because the heat input in the stationary heating area was partially over or under depending on the level of heat input.

Therefore, as shown in Fig. 4, the stationary heating region (0-)・t
), the heat input power is decreased as the feeding speed increases.
We conducted repeated experiments using the characteristics of r -EpIp/.

Of course, when the value is 1 or more, the amount of heat input increases.As a result, it has been found that welding can be performed continuously and stably from the feed speed of zero to a predetermined speed. That is, open pipes do not occur when starting or stopping (and the production yield is greatly improved).

Further examining the yr BpIp/t% property shown in FIG. 4, it is preferable that the following relational expression is satisfied.

However, E6 is the control output, IPr is the feed rate, EP is the plate voltage of the high frequency oscillator (KV) IP is the plate current of the high frequency oscillator (A) a is the moving heating area velocity coefficient, b is the static heating reference value, C is the stationary heating area rate coefficient; d is the stationary heating area speed correction value, e is the stationary heating area correction value, f is the stationary heating area acceleration/deceleration correction value, t is the plate thickness.

Each coefficient a+b+c+d, e, f in the above formula (1) is
Welding method (induction type or contact type), pipe diameter, plate thickness t,
It is also determined by the distance t- between the center of the squeeze roll 3 and the work coil l or tip 2, both of which can be determined by experiment.

To give an example, in the case of an induction type, tube outer diameter 25.4 mφ, plate thickness l = 1.2 tran, distance t = 65, a = 1. 4 1) = 3 3 C-10 d = 3 e -62 -0.

As a concrete heat input control using the above relational expression (1), first, the calculation of the relational expression (1) is programmed into an arithmetic processing device such as a microcontroller, and each coefficient a - f in the equation is is an internal constant of the processing unit, and the welding method, pipe diameter, plate thickness, and distance are tabulated according to each condition. Next, for control, when each of the above conditions is input to the arithmetic processing device, the corresponding coefficients are retrieved from the table and automatically set in relational expression (1). Or the feed speed V of the ERW tube 6,
is detected by a sensor, and the detected signal is input to an arithmetic processing unit to calculate the welding heat input with respect to the momentary feed rate from relational expression (1). Based on this calculated value, welding heat input is controlled online using a feedforward method. To adjust the welding heat input, the plate voltage E of the high frequency oscillator 7
It is preferable to detect P and plate current Ipffi and use control of one or both of bp and ip (with constant power).

Alternatively, each coefficient af may be input into the arithmetic processing device each time each condition changes, without forming one table. The nominal thickness of the plate thickness tH is sufficient.

As explained above, according to the present invention, stable welding can be performed continuously from a feed speed of zero to a constant speed. This improves welding quality.1-1 Quality is stabilized, and there are no open pipes at startup or shutdown, greatly improving production yield.

[Brief explanation of drawings]

Figures 1 (a) and (b) are explanatory diagrams of the contact type and contact type of ERW pipe welding, and Figures 2 and 3 are diagrams showing the relationship between feeding speed and heat input power used in the discussion of the present invention. FIG. 4 is a characteristic diagram of the transmission speed versus heat power of the present invention, and FIG. 5 is a circuit diagram showing one example of a high frequency oscillation device. . In the drawing, ■ is a work coil, 2 is a chip, 3 squeeze rolls, 4 is a material, 5 is a V seam, 6Vi electric resistance welding tube, and 7 is a high frequency oscillator. Patent applicant Meidensha Co., Ltd.

Claims (4)

[Claims] (1) In the heat input control method for electric resistance welding pipe welding, the feed speed of the pipe material is detected and input to the arithmetic processing unit, and the detected feed speed is adjusted based on the relational expression between the feed speed and the required welding heat input. A heat input control method for electric resistance welding pipe welding, which is characterized by calculating the corresponding welder's heat and performing online control using a feedforward method. (2) The relational expression in l is, however, 'LFr is the feed rate, EP is the plate voltage of the high frequency oscillation device, IP is the plate current of the high frequency oscillation device, a is the moving heating area speed coefficient, b is the stationary heating reference value, C is the stationary heating area velocity coefficient, d is the stationary heating area velocity coefficient value, e is the stationary heating area correction value, f is the stationary heating area acceleration/deceleration correction value, t is the plate thickness, 2. A heat input control method for electric resistance welding pipe welding according to claim 1, characterized in that an optimum human heat value is determined and the welding heat input is controlled to reach this value. (3) The coefficients a, b, c, d, e, and f of the above relational expression are calculated based on the difference in welding method (induction type or contact type), pipe diameter, plate thickness, and the distance between the squeeze roll center and work roll or tip. A table is prepared in advance in an arithmetic processing unit according to each distance condition, and by inputting each condition, coefficients corresponding to the conditions are automatically searched from the table and set in the relational expression. The heat input control method for electric resistance welded pipe welding according to item 2. (4) Heat input for electric resistance welding pipe welding according to claim 2, characterized in that the plate voltage and plate current of the high-frequency oscillator are detected, and the welding human heat is controlled by electric car foot control. Control method.