JP3103475B2 - How to start electroslag welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically adding flux to 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 sufficient to form a slag bath suitable for the thickness of a portion to be welded at the start of welding. However, at the start of welding, an arc is generated because there is no slag bath, and then flux is added to the groove. It is impossible to visually grasp the welding state of the steel sheet, which 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, take into account intuition and empirical rules, take the appropriate amount In order to determine whether or not the added flux has melted to form a slag bath, the operation of connecting to the next addition must be repeated to form a slag bath while always maintaining a stable state.

In the prior art, an operator adds flux at the start of welding and adds flux using an automatic addition method when an abnormality appears in the slag bath during welding. No.-42229, Japanese Patent Publication No. 50-22498, but the addition means is a method of automatically adding flux during welding, and therefore cannot solve the problem at the start of welding. In recent years, chronic shortage of skilled workers and aging of skilled workers have become problems, and the emergence of welding skill-free equipment capable of solving these problems is desired.

[0004]

SUMMARY OF THE INVENTION The present invention seeks to solve the above-mentioned conventional problems.
De-skilling is designed to make it easy for anyone to operate.At the start of welding, a flux suitable for the thickness of the welded part is automatically added, and a slag bath is formed while maintaining a stable state, It is 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 sprayed on a groove bottom in advance to reduce consumption. 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 generating signal is detected, and after a predetermined arc generating time, the groove cross-sectional area of the welding location is previously determined. An object of the present invention is to provide a method for starting electroslag welding, characterized in that a suitable amount of added flux is controlled by the number of additions, the addition time, and the standby time, and the flux is added intermittently to form a slag bath.

[0006]

In the automatic flux addition method of electroslag welding, an arc is generated when welding is started. After this arc is generated for several seconds, a flux amount suitable for the sectional area of the welding groove is intermittently added. What is intermittent addition?
This 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 a state before the start of welding, and FIG.
Add the flux amount suitable for the groove cross-sectional area of the welding point,
It is a longitudinal cross-sectional view of the welding part in the state which forms the appropriate slag bath 14 and performs favorable welding. In the figure, reference numeral 12 denotes a 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 1 to be welded. The length L is set to, for example, 35 mm, and the water-cooled copper plate 7
A cut wire 9 is sprayed on the bottom of the. In addition, the non-consumable nozzle 4 is raised 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 provided above the groove 10.

When a welding start switch is turned on, a no-load voltage is generated. The no-load voltage is instantaneously switched to the arc voltage, and an arc is generated. For example, welding cannot always be started satisfactorily every time, and a wire feed failure may occur immediately after the start of welding due to welding conditions, aging of the welding power supply tip, welding material, and other factors. Therefore, in order to determine the appropriate flux addition timing, it is necessary to accurately capture the point in time when the no-load voltage is switched to the arc voltage. It is also necessary to consider that a wire feeding failure occurs after switching to the arc voltage.

[0010] The time for generating an arc also belongs to the area of intuition and experience. As a result of thoroughly pursuing the procedure of welding work by a skilled person in order to elucidate this, it was found that the arc generation continuation time is preferably from 1 second to about 3 seconds, and among them, about 2 seconds is the best. The length of the arc generation duration leads to the following problem. If the arc generation time is too short, for example, an instantaneous arc is generated immediately after the start of welding, but if this is caught as arc generation and flux is added, the arc generation time is short, so the arc preheating effect is small, and the wire The slag is scattered violently while repeating feeding and short-circuiting so as to repel the base material, and eventually adheres to the chip and causes wire feeding failure. Further, the penetration at the welding start portion becomes shallow due to the influence of the insufficient heat.

[0011] Next, when the arc generation duration is extended, a water-cooled copper plate is usually used at the welding start part for the purpose of avoiding poor penetration at the welding start part. The bottom of the water-cooled copper plate is melted too much, shortening the life of the water-cooled copper plate. Further, after the welding is completed, the water-cooled copper plate is beaten off with a hammer or the like. However, since the bottom portion is melted too much, the bottom cannot be removed and may have to be broken. In order to avoid this, the arc generation duration must be set to an appropriate time.

Next, the circuit and detection method shown in FIG. 4 will be described. Reference numeral 30 denotes a welding power source, and 4, 5, 6, 8, etc.
Non-consumable nozzles similar to those shown in FIG.
Reference numeral 5 schematically shows a material to be welded and the like. First, a no-load voltage is generated at the start of welding, and then the voltage is switched to the arc voltage. In order to reliably detect the timing of the switching, a meter relay (MR) 31 capable of performing comparative detection is used. Set the upper limit detection contact (MR _H ) and the lower limit detection contact (MR _L ) as the reference. The upper limit detection contact (M
R _H ) and lower limit detection contact ( _{M 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, when the welding operation is performed normally, the voltage is switched to the arc voltage. However, in some cases, a wire feeding failure occurs and the voltage is not switched to the arc voltage. In this case, since the no-load voltage is continuously generated, an abnormality detection timer 37 for detecting the duration of the no-load voltage is provided in conjunction with the start of welding in order to detect an abnormal wire feeding failure at an early stage. I have. If the arc voltage is switched before the abnormality detection timer expires, it is determined that the operation is normal, and the abnormality detection is reset. But,
If the voltage is not switched to the arc voltage even when the abnormality detection timer has expired, the time limit contact 38 is closed and it is determined that there is an abnormality, and a warning is issued by the lamp 39 or the buzzer 40, and the abnormality is transmitted to the operator. The setting of the abnormality detection time is at least about 3 seconds in order to prevent erroneous detection, and the setting of about 6 seconds at most is most suitable for detection control in order to quickly detect the occurrence of an abnormality.

Next, when an arc is generated, the voltage drops to the arc voltage value, the a contact 36 for upper limit detection is opened, the b contact (normally closed contact, the same applies hereinafter) 32 is closed, and the a contact 33 for lower limit detection continues. It is closed. In this state, the voltage is switched from the no-load voltage to the arc voltage, and the electric current is supplied to the arc detection relay 35 to hold the contact 41.
The arc generation timer 42 is operated. An arc is generated for 2 seconds until the completion of the time limit of the arc generation timer, and the contact 45 and the contact 43 for operating the addition timer 44 are closed with the completion of the time limit. This allows the addition timer 44
Starts counting and addition starts.

The method of controlling the amount of added flux used in the present invention is performed by variably controlling the amount of added flux and the rotation speed of the motor 47 of the adding device. Specifically, the flux addition time control is set to a common time regardless of the groove cross-sectional area of each welding point. For example, if the groove cross section is 62
When a flux amount suitable for each of 5 mm ² and 1250 mm ² welding spots is added by common addition time control, 6
Assuming that the rotation speed of 25 mm ² is 1, the rotation speed of 1250 mm ² is doubled to 2 so that control is performed 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 with a common number for the groove cross-sectional area of each welded portion. It is most suitable for the automatic addition control to add in about 10 times, and the slag bath can be formed in a stable state.

Further, a standby time for sufficiently melting the flux after the addition of the flux is provided, and control is performed such that the next flux is not added within the standby time. When the addition timer 44 completes the time limit, the a contact 49 is closed, the b contact 46 is opened, the motor 47 is stopped, and the standby timer 50 starts counting time. This standby time is set in comparison with the amount of added flux, and is basically determined in consideration of the time required for the flux to sufficiently melt and the time required for further stabilizing the slag bath. However, up to about three times from the start of welding, an arc is still generated even if a flux is added to form a slag bath. Therefore, it is necessary to shorten the standby time in order to quickly shift to electroslag welding. is there. Therefore, 1-3
The time is controlled by setting a minimum necessary time for melting. Also, as a standby time after shifting to the electroslag welding, about 5 to 8 seconds is suitable for control, and among them, about 6 seconds is most preferable. As described above, the addition and the standby are combined, and the flux is added in 1 to 10 times.

Further, in order to form the slag bath in a good condition by using the present control method, it is desirable to perform the slag bath 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 addition amount is increased each time as in 62, the next flux is added before the added flux is melted, and the tip of the chip is buried in the semi-molten slag to feed the wire. Failure may occur. In addition, in the control method in which the addition amount is reduced each time as in 63, the transition from arc welding to slag welding is delayed, that is, the arc generation time is prolonged, so that welding defects are easily induced.

In the circuit example shown in FIG. 4, the above-described operation is sequentially advanced one to ten times, and the operation is stopped when the tenth addition and the standby are completed. FIG.
53 is a ninth timer contact, 52 is a 10th addition timer, 54 and 55 are timed contacts, 56 is a 10th standby timer, and a control operation end signal is obtained by a timed contact (not shown). In addition, abnormality detection is controlled so as to operate until welding is completed. Further, a good slag bath can be formed even if the number of additions, the addition time, and the standby time are changed for each sheet thickness and controlled under the optimum conditions for each sheet thickness.

Although the present invention has been described in the embodiment using the voltage as the detecting means, as shown in the graph of the welding current in FIG. it can.

Although FIG. 4 shows a contact circuit, TTL
Naturally, the same operation can be performed by any of the logic elements, the sequencer, the one-chip microcomputer, and the like. Although the electroslag welding using the non-consumable nozzle has been described with reference to FIGS. 2 to 4, the present invention can naturally be applied to a case where a consumable nozzle that sequentially consumes the nozzle to which the flux is applied is used.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in which a non-consumable nozzle type electroslag welding method using a DC constant voltage power supply is performed by using a flux automatic addition method at the start of welding. I do.

The welding test plate used is a model of a box column, 21 is a column plate, 22 is a diaphragm plate, 2
3 corresponds to a side plate, and includes a groove shape (T ₁ = 25 mm, T ₂ = 50 mm, T ₂ ) shown in the plan view (a) and the perspective view (b) of FIG.
₃ = 25 mm, G = 25 mm, L = 500). The welding conditions were 380 A welding current, 46 V welding voltage, and the welding wire used was a 1.6 mm outer diameter Si-Mn for mild steel.
Welding was performed under the addition conditions shown in Table 1 using a medium oxide Mn-based molten flux as a solid wire and flux. The addition amount of the flux was targeted at 53 (g), and the slag bath was formed to have a depth of about 35 mm. The conditions for determining the time and amount (g / sec) of the addition motor are 3
The conditions were g / sec and 4 g / sec, and the number of additions was uniformly 10 times.

[0024]

[Table 1]

As a result, the no-load voltage is detected at A, the arcing time is activated at B, the addition of flux is performed at C, and the standby time is improved at D, as shown in the graph in FIG. Was controlled. As shown in the graph of FIG. 1 showing the lapse of time of the slag bath depth, the amount of addition and the waiting time were optimal once to three times, and the slag bath could be formed early in a good condition. In addition, for the fourth and subsequent additions, a sufficient waiting time was maintained for the addition amount, and a slag bath was formed while always maintaining a stable state, and stable welding was performed throughout.

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

In Comparative Example 2, the addition motor speed (4 g / sec)
Was made faster than in the examples of the present invention, and the amount of addition in time was increased, and the standby time was performed under the same conditions as in the examples of the present invention. As a result, the amount of addition from one to three times was large, and the addition rate was high, so that wire feeding failure occurred before the end of the third addition. Thereafter, welding was performed several times under the same conditions to check the state after the fourth time. As a result, it was found that the waiting time and the amount of addition after the fourth time were almost good in terms of time, but the flux was not easily melted due to the high rate of addition, making the slag bath formation unstable.

[0028]

According to the method for automatically adding flux in electroslag welding of the present invention, the addition of flux at the start of welding, which had to rely on the intuition and experience of a skilled person, is automatically performed for each sheet thickness. To be added.
Therefore, welding can be performed without monitoring, and the problem of chronic shortage of skilled workers and aging of skilled workers can be resolved.Slag can be easily operated and maintained in good condition by anyone. The industrial value of the invention for forming a bath is very high.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view of a welded portion before starting electroslag welding using the present invention.

FIG. 3 is a longitudinal sectional view of a weld showing a state in which a slag bath is stabilized after the start of welding in the welding of FIG. 2;

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

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

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

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

8A and 8B show a test plate shape used in the examples, where FIG. 8A is a plan view showing a groove shape, and FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 welded member 2 tube 3 flux adding device 4 non-consumable nozzle 5 welding power supply tip 6 welding wire 7 water-cooled copper plate 8 roller 9 cut wire 10 groove 12 weld metal 13 molten metal 14 slag bath 15 welding material etc. 21 column plate 22 Diaphragm plate 23 Side plate 30 Welding power supply 31 Meter relay 47 Motor 48 Motor controller

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tadashi Hoshino 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding Industry Co., Ltd. (56) References JP-A-52-138036 (JP, A) 37-11509 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 25/00

Claims (1)

(57) [Claims] In an automatic flux adding method in a method of starting electroslag welding, an arc generating material is sprayed on a groove bottom in advance, and a consumable electrode is sent through a consumable nozzle or a non-consumable nozzle, and a consumable electrode and an arc generating material are supplied between the consumable electrode and the arc generating material. An arc is generated, the arc generation signal is detected, and after a predetermined arc generation time, the flux addition amount suitable for the groove cross-sectional area of the welding location is controlled in advance by the number of additions, the addition time, and the standby time, and intermittently. A method for starting electroslag welding, wherein a slag bath is formed by adding a flux.