JPH07204869A - Beginning method of electroslag welding - Google Patents

Abstract

PURPOSE:To introduce the excellent welding state by automatically adding a flux suitable for the thickness of an object to be welded in a welding beginning time of an electroslag welding and forming a slag bath while keeping the steady state. CONSTITUTION:An arc generating material is preliminarily scattered onto a groove's bottom part, a consumable electrode is fed through a consuming nozzle or an un-consuming nozzle, arc is generated between the consumable electrode and the arc generating material, an arc generating signal is detected, after a prescribed arc generating time, a flux adding amount suitable for the groove's cross-sectional area of the welding place is preliminarily controlled with the adding frequency, the adding time and the waiting time, and a slag bath is formed by intermittently adding the flux.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic flux addition method for electroslag welding.

[0002]

2. Description of the Related Art When performing electroslag welding using a consumable nozzle or a non-consumable nozzle, it is necessary to add a flux that can form a slag bath suitable for the plate thickness of a welded portion at the start of welding. However, since there is no slag bath at the start of welding, an arc is generated, and then flux is added to the groove, but since the four faces of the groove are surrounded by steel plates or copper plates, the longer the welding length, the longer the bottom It is impossible to visually detect the welding state of, and it is a so-called black box state. In order to form a slag bath while maintaining an appropriate state, recognize the slight brightness and welding sound in the groove, and add intuition and empirical rules to obtain an appropriate amount of addition and a post-addition interval. As to whether or not the added flux has melted to form a slag bath, the work of connecting to the next addition must be repeated to form a slag bath while always maintaining a stable state.

In the prior art, a worker adds flux at the start of welding, and when some abnormality appears in the slag bath during welding, the flux is added by an automatic addition method. -42229 and Japanese Patent Publication No. 50-22498, there is a means, but since this addition means is an automatic flux addition method during welding, the problem at the start of welding cannot be solved. Further, in recent years, chronic shortage of skilled workers and aging of skilled workers have become problems, and the advent of a welding skill unnecessary device capable of solving these problems is desired.

[0004]

The problem to be solved by the present invention is to solve the conventional problems as described above,
It is designed to be skillless so that anyone can easily operate it.At the start of welding, a flux suitable for the plate thickness of the welded part is automatically added to form a slag bath while maintaining a stable state. To lead to a good welding condition.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in an automatic flux adding method in a method of starting electroslag welding, an arc generating material is previously sprayed on the bottom of the groove and is consumed. A consumable electrode is sent through a nozzle or a non-consumable nozzle, an arc is generated between the consumable electrode and the arc-generating material, the arc generation signal is detected, and after a predetermined arc generation time, the groove cross-sectional area of the welding location is determined in advance. It is intended to provide a method for starting electroslag welding, which is characterized in that a suitable flux addition amount is controlled by the number of times of addition, an addition time, and a waiting time, and flux is intermittently added to form a slag bath.

[0006]

In the automatic flux addition method for electroslag welding, an arc is generated when welding is started. After this arc is generated for several seconds, a flux amount suitable for the cross-sectional area of the weld groove is intermittently added. What is intermittent addition?
It means that the flux is added in an appropriate amount, the next addition is not performed until the flux is sufficiently melted, and the next addition is performed after the flux is melted. This operation is automatically repeated to form an appropriate slag bath at the start of welding.

The automatic flux adding method of the present invention will be described in detail with reference to FIGS. FIG. 2 is a longitudinal sectional view of the welded portion showing the state before the start of welding, and FIG.
Add a flux amount suitable for the groove cross section of the welded part,
It is a longitudinal cross-sectional view of a welded portion in a state where a proper slag bath 14 is formed and good welding is performed. In the figure, 12 is weld metal, 1
3 is a molten metal.

In FIG. 2, a non-consumable nozzle 4 which is automatically raised by a roller 8 is inserted into a groove 10 formed by being surrounded by a member to be welded 1, a wire 6 is fed out from a tip of a welding power supply tip 5, and a wire is ejected. A water-cooled copper plate 7 having a length L of, for example, 35 mm and attached to the welding start point of the member 1 to be welded
The cut wire 9 is sprinkled on the bottom of the. Further, the non-consumable nozzle 4 is pulled up so that the tip of the wire does not contact the bottom. Further, a flux adding device 3 and a tube 2 for guiding the flux into the groove are installed above the groove 10.

When the welding start switch is turned on, a no-load voltage is generated. The no-load voltage is instantly switched to the arc voltage and an arc is generated. For example, the start of welding is not always performed well, and there are cases in which poor wire feeding occurs immediately after the start of welding due to deterioration of welding conditions, welding tips for welding, welding materials, and other factors. Therefore, in order to determine an appropriate flux addition time, it is necessary to accurately grasp the time when the no-load voltage is generated and the arc voltage is switched. In addition, it must be taken into consideration that wire feeding failure occurs after switching to the arc voltage.

Further, the time for generating an arc also belongs to the region of intuition and experience. As a result of thoroughly pursuing the procedure of welding work by a skilled person in order to clarify this, it was found that the arc generation duration time is preferably about 1 second to 3 seconds, and of these, about 2 seconds is the best. The length of this arc generation duration leads to the following problems. If the arc generation time is extremely short, for example, an instantaneous arc is generated immediately after the start of welding, but if you add flux to catch this arc generation, the arc generation time is short, so the preheating effect of the arc is small and the wire is Repeating feeding and short-circuiting so as to repel the base metal, the slag is violently scattered and eventually adheres to the chip, causing wire feeding failure. Further, the penetration at the welding start portion becomes shallow due to the effect of insufficient heat quantity.

Next, when the arc generation duration time is extended, a water-cooled copper plate is usually used at the welding start portion for the purpose of avoiding defective penetration at the welding start portion. It melts the bottom of the water-cooled copper plate too much and shortens the life of the water-cooled copper plate. After the welding is finished, the water-cooled copper plate is hit with a hammer or the like to remove it. However, the bottom part is too melted, and it may be impossible to remove and must be broken. In order to avoid such a situation, the arc generation duration must be an appropriate time.

Next, the circuit and detection method shown in FIG. 4 will be described. 30 is a welding power source, and 4, 5, 6, 8 etc. are shown in FIG.
1 schematically shows a non-consumable nozzle or the like similar to that shown in 1.
Reference numeral 5 schematically shows a material to be welded and the like. First, when welding starts, a no-load voltage is generated, and then the voltage is switched to the arc voltage. A meter relay (MR) 31 capable of comparative detection is used to reliably detect the timing of this switching. Set the upper limit detection contact (MR _H ) and lower limit detection contact (MR _L ) as the reference. The upper limit detection contact (M
_RH ) and lower limit detection contact (MR _L ) a contact (normally open contact,
The same applies hereinafter) When both 33 and 36 are closed, it is determined that a no-load voltage has occurred.

Normally, if the welding operation works normally, the arc voltage is switched to. However, in some cases, wire feeding failure may occur, and the arc voltage may not be switched. In this case, since the no-load voltage continues to be generated, an abnormality detection timer 37 that detects the duration of the no-load voltage is provided in association with the start of welding in order to detect an abnormality in wire feeding failure at an early stage. There is. The circuit configuration is such that it is determined to be normal and the abnormality detection is reset if the arc voltage is switched to before the abnormality detection timer completes the time limit. But,
When the abnormality detection timer does not switch to the arc voltage even after the time is completed, the time contact 38 is closed and an alarm is issued by the lamp 39 or the buzzer 40 to inform the operator of the abnormality. The abnormality detection time is set to about 3 seconds at the shortest to prevent erroneous detection, and about 6 seconds at the longest is most suitable for detection control in order to quickly detect the occurrence of the abnormality.

Next, when an arc occurs, the voltage drops to the arc voltage value, the a-contact 36 for the upper limit detection is opened, the b-contact (normally closed contact, the same applies hereinafter) 32 is closed, and the a-contact 33 for the lower limit detection continues. It's closed. In this state, it means that the no-load voltage is switched to the arc voltage, the relay 35 for arc generation detection is energized, and the contact 41 holds the contact,
The arc generation timer 42 is activated. An arc is generated for 2 seconds until the time limit of the arc generation timer is completed, and the contact 45 and the contact 43 for operating the addition timer 44 are closed with the completion of the time period. With this, the addition timer 44
Is started and the addition is started.

The method of controlling the flux addition amount used in the present invention is performed by variably controlling the addition amount and the rotation speed of the motor 47 of the addition device. Specifically, the flux addition time control is set to a common time regardless of the groove cross-sectional area of each welding location. For example, the groove cross section is 62
When a flux amount suitable for each of the 5 mm ² and 1250 mm ² welded spots is added under the common addition time control, 6
When the rotation speed of 25 mm ² is 1, the rotation speed of 1250 mm ² is doubled to 2 so that a stable slag bath can be formed even with a common addition time. In addition, the motor controller (M
CR) 48.

Next, it is most preferable to control the number of additions by a common number for the groove cross-sectional area of each welded part. The result of investigation of the number of additions by a skilled person for each groove cross-sectional area of each plate thickness It is most suitable for automatic addition control that the slag bath is added in batches of about 10 times, and the slag bath can be formed in a stable state.

Further, after the flux is added, a waiting time is provided for sufficiently melting the flux, and control is performed so that the next flux is not added within the waiting time. With respect to this addition time, when the addition timer 44 is timed, the a contact 49 is closed, the b contact 46 is opened, the motor 47 is stopped, and the standby timer 50 starts timing. This waiting time is set in comparison with the amount of flux added, and is basically determined in consideration of the time for the flux to sufficiently melt and the time for further stabilizing the slag bath. However, from the start of welding up to about 3 times, arc is still generated even if flux is added to form a slag bath. Therefore, it is necessary to shorten the waiting time in order to quickly shift to electroslag welding. is there. Therefore, 1-3
The time is controlled by setting the minimum required time for melting. The waiting time after the transition to electroslag welding is about 5 to 8 seconds, which is suitable for control, and of these, about 6 seconds is most preferable. In this way, the addition and the standby are combined into one, and the flux is added in 1 to 10 times.

Further, in order to form the slag bath in a good state using this control method, it is desirable to perform along the line 61 in the graph showing the slag bath depth for each number of additions in FIG. However, in the control method in which the amount of addition is increased once, as in 62, the next flux is added before the added flux is melted, the tip of the chip is buried in the semi-molten slag, and the wire is fed. It may cause a defect. In addition, in the control method in which the addition amount for each time is reduced as in 63, the transition from arc welding to slag welding is delayed, that is, the arc generation time is lengthened, so that welding defects are easily induced.

In the circuit example shown in FIG. 4, the above-described operation is sequentially stepped 1 to 10 times, and the operation is stopped when the 10th addition and the standby are completed. Fig. Time limit contact 51,
Reference numeral 53 is a contact of the 9th timer, 52 is a 10th addition timer, 54 and 55 are its time-delay contacts, and 56 is a 10th standby timer. It should be noted that the abnormality detection is controlled to operate until the welding is completed. Further, a good slag bath can be formed even if the number of additions, the addition time, and the waiting time are changed for each plate thickness and controlled under optimum conditions for each plate thickness.

Although the present invention has been described with reference to the embodiment in which the voltage is used as the detecting means, as shown in the graph of the welding current in FIG. it can.

Although FIG. 4 shows a contact circuit, the TTL
It goes without saying that the same operation can be performed by any of the logic elements such as, a sequencer, and a one-chip microcomputer. Although the electroslag welding using the non-consumable nozzle has been described with reference to FIGS. 2 to 4, the present invention can be naturally applied to the case where a consumable nozzle that sequentially consumes the flux-coated nozzle is used.

[0022]

EXAMPLES An example of performing non-consumable nozzle type electroslag welding method using a DC constant voltage power source by using an automatic flux addition method for flux addition at the start of welding according to the present invention will be described below. To do.

The welding test plate used was a model of a box column, 21 was a column plate, 22 was a diaphragm plate, and 2 was a plate.
Reference numeral 3 corresponds to a side plate, and the groove shape (T ₁ = 25 mm, T ₂ = 50 mm, T shown in (a) plan view and (b) perspective view of FIG.
₃ = 25 mm, G = 25 mm, L = 500). The welding conditions are welding current 380A, welding voltage 46V, and the welding wire used is welding wire Si-Mn with an outer diameter of 1.6 mm.
Welding was carried out under the additive conditions shown in Table 1 using a medium-oxidized Mn-based molten type flux as the system solid wire and flux. The amount of flux added was 53 (g), and the slag bath depth was set to about 35 mm. The condition for determining the time and amount (g / sec) of the addition motor is 3
The conditions were g / sec and 4 g / sec, and the number of additions was 10 times.

[0024]

[Table 1]

As a result, the no-load voltage is detected at A, the arc starting time is activated at B, the flux is added at C, and the waiting time is good at D, as shown in the graph of welding voltage in FIG. Controlled to. As shown in the graph of the slag bath depth over time in FIG. 1, the addition amount of 1 to 3 times and the waiting time were optimal, and the slag bath could be formed early in a good state. Further, for the fourth and subsequent additions, a sufficient waiting time was maintained with respect to the addition amount, and a slag bath could be formed while always maintaining a stable state, and stable welding could be performed from beginning to end.

In Comparative Example 1, the addition motor speed (3 g / sec) and the addition amount were the same as those of the present invention, and the total standby time was shortened. As a result, throughout the total number of additions, the next addition was performed before the flux was completely melted with respect to the addition amount, and the shortage of waiting time was noticeable.

In Comparative Example 2, the addition motor speed (4 g / sec)
Was set earlier than in the example of the present invention, and the amount of addition within the time was increased, and the waiting time was the same as in the example of the present invention. As a result, since the addition amount from the 1st to 3rd times was large and the addition rate was high, the wire feeding failure occurred before the completion of the 3rd addition. After that, welding was performed several times under the same conditions to examine the state after the fourth time. As a result, it was found that the standby time and the addition amount after the fourth time were almost good in terms of time, but the flux was difficult to melt and the formation of the slag bath was made unstable due to the high addition rate.

[0028]

The automatic flux adding method in electroslag welding according to the present invention automatically adds the flux at the start of welding, which must rely on the intuition and experience of an expert, for each plate thickness. It was made possible to add to.
Therefore, unsupervised welding can be performed, and chronic problems of shortage of skilled workers and aging of skilled workers can be solved, slag can be easily operated by anyone and always maintains a good condition. The industrial value of the present invention capable of forming a bath is very high.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the slag bath depth, the number of additions, the addition time, and the waiting time.

FIG. 2 is a vertical cross-sectional view of a welded portion before the start of electroslag welding using the present invention.

FIG. 3 is a longitudinal sectional view of a welded portion showing a stable state of the slag bath after the start of welding in the welding shown in FIG.

FIG. 4 is a circuit diagram of an embodiment of the present invention.

FIG. 5 is a graph showing the state of formation of a slag bath depending on the addition amount and the number of times.

FIG. 6 is a graph showing an example of elapsed time of welding current.

FIG. 7 is a graph showing an example of elapsed time of welding voltage.

FIG. 8 shows the shape of the test plate used in the examples, (a) is a plan view showing the groove shape, and (b) is a perspective view.

[Explanation of symbols]

 1 Welded member 2 Tube 3 Flux addition device 4 Non-consumable nozzle 5 Welding power supply tip 6 Welding wire 7 Water-cooled copper plate 8 Roller 9 Cut wire 10 Bevel 12 Weld metal 13 Molten metal 14 Slag bath 15 Welded material 21 Column plate 22 diaphragm plate 23 side plate 30 welding power source 31 meter relay 47 motor 48 motor controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Hoshino 3-5-4 Tsukiji, Chuo-ku, Tokyo Inside Nittetsu Welding Industry Co., Ltd.

Claims (1)

[Claims] 1. In the automatic flux addition method in the electroslag welding start method, an arc generating material is previously sprayed on the groove bottom, and a consumable electrode is sent through a consumable nozzle or a non-consumable nozzle so that the consumable electrode and the arc generating material are connected to each other. An arc is generated, the arc generation signal is detected, and after a predetermined arc generation time, a flux addition amount suitable for the groove cross-sectional area of the welding location is controlled in advance by the number of times of addition, the addition time, and the standby time, and then intermittently. A method for starting electroslag welding, which comprises adding a flux to form a slag bath.