JPH0871761A - Method for monitoring abnormal welding of butt resistance welding machine - Google Patents

Abstract

PURPOSE: To preliminarily prevent the breakage of a welded part by finding the distribution of the unit heat input in the width direction from the space in the width direction between the rear end of a preceding member and the forward end of a succeeding member, and judging the presence and absence of an abnormal welding. CONSTITUTION: A welding machine consists of a fixing table 3 to clamp the rear end la of a preceding member 1 and a forward end 2a of a succeeding member 2, a moving table 4, and welding electrodes 5, 6. The prescribed welding voltage V and the welding current are supplied through the welding electrodes 5, 6, and the moving table 4 is moved toward the fixing table 3 to press the forward end 2a of the succeeding member 2 against the rear end 1a of the preceding member 1. The spaces XOP, XDR on the operator side and the drive side between the rear end la and the forward end 2a are detected by a position sensor 7, and inputted to a monitoring device 8. The welding voltage V and the welding current are simultaneously inputted, the heat input is compared with the reference value Ps by an arithmetic unit, and in the case of an abnormal welding, an alarming device 11 is activated to display the abnormal welding on the CRT 12. This can monitor the quality and prevent the breakage of the welded part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding abnormality monitoring method for a butt resistance welding machine.

[0002]

2. Description of the Related Art In various continuous processing lines such as a continuous pickling line for steel strips and a continuous tandem rolling line, a butt resistance welding machine (hereinafter simply referred to as a welding machine) provided on the inlet side of the line is usually used. The steel strips are continuously processed by welding and connecting the steel strips together to improve the operating rate.

By the way, in such a welding machine, in evaluating the welding quality for each welding, it is often based on whether or not a proper heat input amount is given, for example, in Japanese Patent Laid-Open No. 3-32473. As shown, from the instantaneous value of the welding current and welding voltage to the flash previous period,
A method is known for determining the presence / absence of welding abnormality by obtaining the heat input amount in the welding period in each of the latter period of flash and the upset period and comparing the heat input amount with a predetermined reference value of the heat input amount. There is.

Further, as a method of evaluating the welding quality other than the heat input amount in the welding machine, the amount of movement of both ends in the width direction at the time of abutting metal strips as disclosed in JP-A-2-84278 is measured. A method has also been proposed in which the amount of movement is compared with a reference value given in advance to make a determination.

[0005]

However, when the trailing edge 1a of the leading material 1 and the leading edge 2a of the trailing material 2 are butted as shown in FIG. 2, the butting is performed on the operator side and the drive side. Even if the amounts L _OP and L _DR are the same value and the total heat input is also within the reference value, if the control abnormality occurs in the cutting machine or the welding machine, the heat input becomes uneven in the width direction, For example, heat input is insufficient on the operator side in the figure, and heat input is excessive on the opposite drive side. The solid line in the figure indicates
The dotted line schematically shows the state after completion of welding.

In such a case, the above-mentioned Japanese Patent Laid-Open No. 3-
Since the abnormalities cannot be detected by the methods described in Japanese Patent No. 32473 and Japanese Patent Laid-Open No. 84278/1990, there is a possibility that welding breakage may occur. SUMMARY OF THE INVENTION It is an object of the present invention to provide a welding abnormality monitoring method for a butt resistance welding machine, which solves the problems of the prior art as described above.

[0007]

DISCLOSURE OF THE INVENTION The present invention is a method for monitoring a welding abnormality of a butt resistance welding machine used for welding connection of a preceding material and a trailing material, and a welding current supplied to the butt resistance welding machine. And the heat input calculated from the welding voltage, and the widthwise interval between the trailing edge of the preceding material and the leading edge of the trailing material on the operator side and the drive side, the distribution of the unit heat input in the width direction is calculated. A welding abnormality monitoring method for a butt resistance welding machine, characterized in that the presence or absence of welding abnormality is determined by comparing this unit heat input amount with a reference value given in advance.

[0008]

[Operation] According to the present invention, since the heat input amount per unit time and unit width of each part in the width direction is monitored,
It is possible to monitor to maintain good welding quality at each part in the width direction. That is, the principle of the present invention will be described below with reference to FIG. In the figure, the trailing edge 1a of the leading material 1 and the leading edge 2a of the trailing material 2 on the operator side in the width direction
The spacing and X _OP, representing it at time t as X _OPt. Also, the front and rear ends 1a, 2 on the drive side
Also in a, the intervals are similarly set as X _DR and X _DRt . Further, the matching start time is t = 0, and the matching completion time is t = T. Further, it is divided into n sections in the width direction, and an arbitrary section is set to i (where i = 0 to n).

Therefore, if the total heat input P _t within the unit time dt is expressed using the welding current I and the welding voltage V, the following equation (1) is obtained. P _t = V · Idt (1) Now, assuming that the interval between the trailing edge 1a of the preceding material 1 and the leading edge 2a of the following material 2 at time t in section i is X _it , this total heat input P _{It is considered that t} is uniformly added to the section where X _it ≤0. Here, the section where X _it ≦ 0 means the section where the preceding material 1 and the following material 2 are in contact with each other. That is, X
_The current flows only in the section where _it ≤ 0, and the total heat input P
It is assumed that _t is added evenly over the interval X _it ≤0. It should be noted that the front end 1a of the preceding material 1 on the fixed side is used as a reference, and the trailing material 2 can be moved to the right in the drawing from this reference, if it is X
_it becomes negative.

Then, X _it is calculated using the equation (2) using the relationship between the positions X _OP0 and X _{DR0 on} the operator side and the drive side at the start of matching (when t = 0). X _it = X _OPt + (i / n) · (X _OP0 −X _DR0 ) ... (2) Here, let k _t be the number of sections i where X _it ≦ 0 in calculation at time t. Then, the heat input amount P _ti per unit time / unit width in the width direction section i at the time t is given by the following expression (3).

P _ti = (k _t / n) · V · Idt (3) When X _it > 0, P _ti = 0, so it is not a target. Therefore, the heat input amount P _i per unit width of the section i between the time t from 0 to T is given by the following equation (4),

[0012]

[Equation 1]

With this, it is possible to obtain for each section of i = 0 to n. As described above, the heat input amount P _i in each section of i = 0 to n is calculated, and all P _i are the reference values P _S.
It is possible to monitor the welding quality at each portion in the width direction by assuming that the normal welding is performed only when the welding is performed inside.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a welding abnormality monitoring device for a welding machine used in the present invention. As shown in this figure, the welding machine is equipped with the trailing edge 1a of the leading material 1 and the trailing material 2
The fixed base 3 and the moving base 4 for clamping the tip 2a of the above, and the welding electrodes 5 and 6 attached to the fixed base 3 and the moving base 4. Then, by supplying a predetermined welding current I at a predetermined welding voltage V via the welding electrodes 5 and 6,
While moving the arc between the trailing edge 1a of the preceding material 1 and the leading edge 2a of the trailing material 2, the moving table 4 is moved toward the fixed table 3 to move the leading edge 2a of the trailing material 2 to the trailing edge of the preceding material 1. The upset is formed by pressing on 1a.

On the other hand, the welding abnormality monitoring device includes a position sensor 7
And monitor device 8, totaling device 9, arithmetic device 10, alarm device 1
1 and CRT12. And the position sensor 7
The operator-side and drive-side distances X _OP and X _DR between the trailing edge 1a of the leading material 1 and the leading edge 2a of the trailing material 2 which are being butt-welded by butt welding are detected at a predetermined cycle and input to the monitor device 8. It The welding voltage V and the welding current I are also input at the same timing.

These analog signals are A / D converted and sent to the totalizing device 9 for storage, and at the same time, the totalizing value P of the welding voltage V and the welding current I is calculated in the totalizing device 9 according to the equation (3). _ti is calculated. At this time, the number n of divided sections in the width direction and the unit time dt are set in the monitor device 8 in advance. Immediately after the welding is completed by the welding machine, all the data are sent from the totalizing device 9 to the computing device 10, and the heat input amount P _i is calculated based on the above equation (4), and then the reference value P _S is calculated. When the comparison is made and the reference value P _S is exceeded, an alarm is output by the alarm device 11, and at the same time, the content of the abnormality is displayed on the CRT 12.

When the present invention is applied, the number n of divided sections in the width direction is set to 20, for example, and the unit time dt is 1 ms.
ec is preferable. However, the present invention is not necessarily limited to this, and a more effective result can be obtained by further shortening the unit time and further reducing the number of sections within the range of the calculation capacity or the A / D conversion capacity of the totaling device 9 and the calculation device 10. Needless to say.

[0018]

As described above, according to the present invention,
Since the amount of heat input per unit time / unit width at each position in the width direction of the trailing edge of the preceding material to be welded and the leading edge of the following material is monitored, more accurate welding quality monitoring and evaluation can be performed. It becomes possible to prevent the fracture of the welded part in the line.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a welding abnormality monitoring device for a welding machine used in the present invention.

FIG. 2 is a schematic diagram showing a conventional example.

FIG. 3 is an explanatory diagram of the principle of the present invention.

[Explanation of symbols]

 1 Leading material 2 Trailing material 3 Fixed base 4 Moving base 5,6 Welding electrode 7 Position sensor 8 Monitor device 9 Aggregation device 10 Computing device 11 Alarm device 12 CRT

Claims (1)

[Claims] 1. A method for monitoring a welding abnormality of a butt resistance welding machine used for welding connection between a preceding material and a following material, the heat input amount calculated from a welding current and a welding voltage supplied to the butt resistance welding machine. And the distribution of the unit heat input in the width direction from the operator-side and drive-side widthwise intervals between the trailing edge of the preceding material and the leading edge of the trailing material, and the unit heat input is given in advance. A welding abnormality monitoring method for a butt resistance welding machine, characterized by determining whether or not there is a welding abnormality by comparing the obtained reference value.