JPH10263834A - Method for flash welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent defective welding due to shortage of heat input in the case of low temperature of billet and the generation of defective yield at the time of high temperature and to stabilize joining work by detecting the temperature of abutting billet to be welded and adjusting the flashing time according to the detected temperature. SOLUTION: The temperature of billets 1, 2 transferred from a continuous casting equipment I to a flash welding device III is measured by a temperature sensor 14 just prior to welding. Generally, there is a temperature difference between the billets 1 and 2, so it is preferable to take up the lower temperature side as the temperature of the members. In the flash welding device III, a member transfer control unit 11 is used which controls the welding current at a constant value depending on the welding power or a constant voltage. In an arithmetic unit 13 for flashing time, required flashing time tf1 is calculated from the heat quantity, heat input efficiency, and welding power charged during welding the billet 1 and 2. From the time tf1 and the output of the member transfer control unit 11, the valve 5C of cylinder unit 5 is operated by a welding controller 12, and thus after a time duration of flashing tf1 from the beginning of welding, pressure welding is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a flash welding method.

[0002]

2. Description of the Related Art Two members to be welded are gripped and brought into contact by clamp members respectively connected to both output terminals on the secondary side of a power supply transformer, and the two members to be welded are flash-welded at the contact surfaces. Methods are known.

[0003] In flash welding, a low-voltage large current flows between two members to be welded through an abutting surface to generate an arc at the abutting surface, thereby heating and melting the contact surface between the members, and This is a welding method that presses (upsets) after the contact surface is sufficiently heated. At that time, the amount of heat Q required to melt the contact surface
Is Q = k (T _m −T _w ) cal (k: physical property value and determined by the shape of the member, T _m : melting point of the member, T _w : initial member temperature). In a relationship.

In flash welding control for making the power or current required for flash constant, the amount of heat input to a member per unit time is constant because it is proportional to the power value. For this reason, if the initial temperature increases, the flash time can be shortened in proportion to it. Conversely, if the member temperature decreases, it is necessary to extend the flash time to compensate for the heat input to the member.

In a usual flash welding apparatus, the temperature of a member is room temperature, and the melting temperature of the member (about 1,500 for steel).
(° C), the variation in the member temperature is small. For this reason, it is often not necessary to correct the welding conditions (flash time) based on the member temperature. In the case of flash welding using a high-temperature member, for example, in a process in which steel such as a chain is heated by another heating means and then welding is performed, the heating temperature of the member and the time until welding after heating are controlled (typically, the variation is almost the same). By doing so, the member temperature immediately before welding can be made substantially constant.

For this reason, in the conventional welding control method, the welding conditions are not changed based on the member temperature information, and some variation in the member temperature is dealt with by increasing the flash time.

However, for example, in a flash welding machine for continuous rolling of a mini-mill which is directly fed from a continuous casting machine, the casting speed is not constant but changes with time, and the flash temperature immediately before welding changes accordingly. For this reason, variations in the member temperature increase. When the welding conditions (flash time) are adjusted to the lowest member temperature, the flash time is too long when the member temperature is high, and the flash amount increases when the flash time is long, so that the member consumption increases and the yield decreases. . Further, if the welding conditions (flash time) are determined in accordance with the average member temperature, there is a problem that when the member temperature is low, welding failure is caused by insufficient heat input, and when the member temperature is high, the yield deteriorates.

An object of the present invention is to provide a flash welding method capable of performing optimum welding even when the temperature of a member to be welded is not constant.

[0009]

According to the present invention, an object of the present invention is to grasp and contact two workpieces by clamping members respectively connected to both output ends on the secondary side of a power supply transformer. In a method of flash-welding two members to be welded on a contact surface, the method is achieved by detecting a temperature of the member to be welded and changing a flash time according to the detected temperature.

In the present invention, when there is a temperature difference between the two members to be welded, the temperature of the two members to be welded is detected, and if the lower temperature is determined as the detected temperature, a reliable flash can be obtained. Gain time.

[0011] Then, in the present invention, when the reference flash time t _ref, a coefficient determined outside temperature of the detected temperature T _w and welded member is a, flush time t
_fl can be determined by the relationship of t _fl = t _ref −a · T _w .

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral I denotes a continuous casting machine, and a billet B sent out from a discharge port thereof is sent as a member to be welded to a flash welding apparatus III by a conveying means II such as a roller conveyor and welded. The welding device III is controlled by a control device IV.

In the flash welding apparatus I, rod-shaped steel materials 1 and 2 are clamped as the members to be welded, respectively.
At 4, it is releasably gripped. The clamp member 3 is attached to the cylinder body 5A of the cylinder device 5, and the other clamp member 4 is attached to the tip of the rod 5B of the cylinder device 5 and is movable in the axial direction.

A secondary side 7B of a welding transformer (feeding transformer) 7 is connected to the clamp members 3 and 4. Detection means 9 for detecting the voltage V and the current I is connected to the primary side 7A connected to the AC power supply 8, and the output is sent to the control device IV. The control device IV has a power calculation device 10, a member feed control device 11, a welding control device 12, a flash time calculation device 13, and a temperature sensor 14 as a temperature measuring means.

The power calculation device 10 of the control device IV determines the power P from the voltage V and the current I detected by the detection means 9. Such power P is sent to the member feed control unit 11, it is compared with the reference power P _ref, member feed control to be equal to the reference power P _ref is made.

A non-contact temperature sensor 14 is provided near the member 2 to be welded. The temperature sensor 14 is input to the flash operation device 13 together with the reference flash time t _ref , and the output t _fl from the flash operation device 13 is used for welding. It is sent to the control device 12. The welding control device 12 controls the valve 5C of the cylinder device 5 based on the output from the member control device 11 and the output from the flash time calculation device 13.

In this embodiment, the billet B generated by the continuous casting machine I is conveyed to the flash welding apparatus III by the conveying means II. The casting speed of the continuous casting machine I changes every moment depending on the temperature of the molten steel, the temperature of the billet B generated changes every moment, and the time taken to transfer from the continuous casting machine I to the flash welding device III (waiting time, etc.) (Due to other factors). As a result, the temperature of the billet B conveyed also varies.

The temperature of the steel material 2 transported as a billet B to the flash welding device III is measured by a temperature sensor 14 such as a radiation thermometer immediately before welding. Even if this temperature sensor 14 is installed inside the flash welding device III,
It may be installed at the entrance of the flash welding device III. Since there is usually a temperature difference between the steel material 2 and the steel material 1, it is preferable to measure two steel materials and use the lower value as the member temperature. However, any temperature may be employed as long as the temperature difference is within the allowable range. In the present example, the temperature of the steel material 2 on the low temperature side is measured, since the member temperature often varies from 700 to 950 ° C.

The steel material whose member temperature has been measured is welded by a flash welding device III.
In III, the control is performed using the member feed control device 11 that can control the welding current to be constant with the welding power or the constant voltage.

The heat quantity Q _f which is introduced into the two members at the time of flash welding, the heat input efficiency eta, the welding power P _w, a time t
In this case, Q _f = η · ∫P _w · dt ············································································································ If the P _w is constant, the flash time is replaced by t _fl For example, Q _f = η · P _w · t _fl ………………………………….

The amount of heat Q required to melt the member
_m is physical value determined by the member shape (constant) k, melting point T _m of a member, when the initial members temperature is _{T w, Q m = k (} T m -T w) ..................... ………………… Since the amount of heat Q _w necessary welding is proportional to the amount of heat Q _m required to melt _{the, Q w = g · k (} T m -T w) = η · P w · t fl ............ , and this From the equation, t _fl = [g · k (T _m −T _w )] / (η · P _w ) is derived. The other T _w of the formula is a fixed value or set value, if these values is constant, it is clear that the t _fl and T _w is a linear relationship.

In the present invention, t _fl is calculated by the flash time calculating device 13 using the relationship of the above expression, and the flash control device 13 _{combines the} flash time t _fl with the output from the member feed control device 11 to calculate t _fl. 12, the valve 5C of the cylinder device 5
Control.

Next, as a specific example of this embodiment, a billet (member to be welded) having a member section of about 30,000 mm ² is extracted from a continuous casting furnace, and is conveyed to a flash welding apparatus by conveying means. Immediately before the welding device, the two billet temperatures to be welded are measured by a radiation thermometer.

Flash welding is performed by clamping a billet as a member to be welded by a flash welding device. This flash welding device detects power by welding power means (even if welding current is detected by welding current detection means). Good), the feed speed is controlled by the member feed control device so that the electric power (or current) is kept constant.

From the measured member temperature, the flash time t
_fl is calculated by t _fl = t _ref −a · T _w ………………………………….

Here, t _ref is a reference flash time, _Tw is a member temperature, and a is a constant.

In the above member having a section of 30,000 mm ² , t _ref = 75 (sec) and a = 0.05, and t _fl = 75−0.05 × T _w. ………………… Therefore, for example, a billet temperature of 700 to
At 1,000 ° C, flash time t _fl is 40
~ 25 sec.

Thus, the flash welding control means performs the pressure welding step after the elapse of the flash time _tfl from the start of welding to complete the flash welding.

[0030]

As described above, according to the present invention, even if the temperature of the member to be welded is not constant, this temperature is detected and the flash time is corrected. Irrespective of the temperature of the member, it is possible to provide high-quality and high-yield welding.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1, 2 Welded member (billet) 3, 4 Clamp member 7B Secondary side of transformer

Claims (3)

[Claims] A clamp member connected to both output ends on the secondary side of a power supply transformer grips and abuts two members to be welded, and flash-welds the two members to be abutted on a contact surface. A flash welding method comprising: detecting a temperature of a member to be welded; and changing a flash time according to the detected temperature. 2. The flash welding method according to claim 1, wherein the temperatures of the two members to be welded are detected, and a lower one is set as a detected temperature. 3. When the reference flash time is t _ref , the detected temperature is T _w , and the coefficient determined by a factor other than the temperature of the member to be welded is a, the flash time t _fl is given by t _fl = t _ref.
Flash welding method according to claim 1, be determined in relation -a · T _w.