JPS61154797A - Backing device for welding machine - Google Patents

Abstract

PURPOSE:To prevent the martensitic transformation of a weld zone and to prevent the cracking and embrittlement of the part to be welded by providing an induction heating coil to a back bar and heating the butt part. CONSTITUTION:The part to be welded of strips 1, 2 is backed by the back bar 7 from below. An insulating plate 8 is attached to a top end face 7b enclosing a hollow groove 7a provided to the bar 7 and the induction heating coil 9 is fixed atop the same. A shielding plate 10 is provided atop the coil 9. The AC current generated by a high-frequency transformer enters the coil 9 from one end thereof and escapes from the other end to apply about 5-100kW high- frequency current between the two terminals. Eddy current is then passed to the end faces of the parts 1, 2 to be welded, by which said parts are locally welded. The martensitic transformation of the part to be welded of a high- carbon steel, etc. is thus prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a backing device for a welding machine, particularly for a laser beam welding machine or a TIG welding machine for high carbon steel and high alloy steel. This invention relates to a backing device.

[Conventional technology]

Laser beam welding to weld strips together,
When it comes to TIG welding, it's best to strictly control the accuracy of the butt, so the gap is small.

A clamp is provided on the exit side, and a grooved back bar is pressed against the back side of the strip to be welded (see Figure 4). In addition, the temperature of the heated part during welding drops to room temperature in a few seconds immediately after welding, and a part of this welded part and heat-affected zone undergoes martensitic transformation, so a separate heating device (gas burner) is used.

After welding, the strip is moved to this heating device and heated and tempered to transform the welded part into ferrite-pearlite.

[Problem that the invention seeks to solve]

However, the above conventional example has the following problems.

That is, since there are clamps on the entry and exit sides of the strip weld and a grooved back bar that presses against the weld on the back of the strip, it is not possible to provide a separate heating device within this welding machine. In addition, especially in the case of laser beam welding,
Due to its characteristics, the area heated by the beam is narrow, so the melting area is also narrow and the cooling rate of heat is fast (temperature drops to room temperature within a few seconds immediately after welding), making it easy to rapidly cool and become martensitic. For this reason, the welded part undergoes a volume change (expansion) due to martensitic formation, and becomes structurally brittle.If the welded part is allowed to stand for a long time before heating after welding, microscopic racks will form starting from brittle grain boundaries. There was a problem that the crank progressed during heating and the welded area (boundary between the molten zone and the heat affected zone) cracked.

Further, even if the time between heating after welding is short, when an impact is applied to the welded part, cracks similar to those described above occur, and there is a problem in that cracks similar to those caused during heating occur.

Furthermore, in the case of a process line, when the strip is transported to a heating device after welding, the strip is subjected to impact during this transport, making it impossible to obtain good welding strength.

This invention aims to solve such problems.

[Means for Solving the Problems] The backing device for a welding machine of the present invention abuts each cut end surface of a pair of workpieces to be welded and supports this abutted portion from the back side. An induction heating coil for inductively heating the abutting portion is installed on a bank bar that abuts the abutting portion from the back side.

[Effect]

An induction heating coil installed in the back par heats the welded parts by butting each cut end surface of the welding material to prevent martensitization of the welded part, and also applies tempering heat treatment to the welded part after welding. give

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in the drawings will be described in detail below.

First, a process line to which a backing device for a welding machine according to the present invention is applied will be explained.

In the figure, 1 is a leading strip, 2 is a trailing strip, and these strips 1 and 2 are made of high carbon steel (Ca2
．． 5%), high alloy steel (Ca2.3% and Cr≧0.3%,
or Mo≧0.2%, or Ni≧0°2%, etc.), and is made of a steel type that is prone to weld cracking.

Further, these strips 1.2 are unwound from an uncoiler (not shown), sent along a line by a feed roll (not shown), etc., and end each other at the position where the laser beam welding machine 3 is arranged. The parts are set so that they touch each other. The strip 1.2 set in this way is attached to an upper clamp 4.4' and a lower clamp 5, which are provided at the front and rear positions of the welding area in the strip movement direction, as in the conventional example shown in FIG. 5 supports the strip 1.2 from above and below.

The laser beam welding machine 3 is arranged above the part to be welded, and the welding machine backing device 6 according to the present invention is arranged below it.

Next, this welding machine backing device 6 will be explained in detail.

In the figure, reference numeral 7 denotes a backper that rises from below and backs the welding portions of the strips 1 and 2 during welding. A groove 7a is provided on the upper end surface of the second back bar 7 along the welding area. Insulating plates 8, 8' are laid on the upper end surfaces 7b, 7b of the back par 7, which sandwich the groove 7a, and an induction heating coil 9 is placed on the upper surface of the insulating plates 8, 8.
．． 9' is fixed. Furthermore, induction heating coil 9.9
A shield plate 10.10 is placed on the upper surface of the shield plate 10.10.

The induction heating coils 9.9' are arranged in parallel on the upper end surfaces 7b and 7b' of the back par 7 with the groove 7a in between, with the width direction of the strips 1 and 2 being the longitudinal direction. These induction heating coils 9 and 9' are connected and short-circuited at one end, and a flexible cord 13, which is connected to a terminal of a high frequency transformer, is connected to the other end.
13' is connected. Moreover, this high frequency transformer 11
A high frequency generator 12 is connected to.

Therefore, the alternating current generated in this high frequency transformer 11 is
The induction heating coil 9 enters from one end and exits from the other end, applying a high frequency current of 5 to 1100K between both terminals. As a result, an eddy current flows through the end face of the welded part (the butt part of the strips 1 and 2), and local heating is achieved.

The temperature of this local heating is 700°C to 80°C.
The temperature is expected to be around 0°C, and electricity is applied for a few seconds to several tens of seconds before and after welding to prevent martensitization of the welded part after welding and to perform tempering heat treatment at the welding process location.

Furthermore, a cooling device 14 for passing cooling water is provided inside the induction heating coil 9 to prevent damage to the coil 9 due to heating.

After the above-mentioned process is performed, this welding machine backing device 6 is lowered. At the same time, the upper and lower clamps 4.5 also move to release the strip 1.2.

In the above embodiments, the case of laser beam welding has been described, but it goes without saying that the present invention can also be applied to TIG welding.

Furthermore, although the above embodiments have been described as being applied to a process line, it is of course possible to use them in various welding processes.

Although the embodiments have been described above, the present invention is not limited to these embodiments, and considerable design changes are planned in accordance with the gist of the configuration of the present invention.

〔Effect of the invention〕

As is clear from the above explanation, in this invention,
It is possible to prevent the occurrence of martensitic transformation in the welded parts of high carbon steel and high alloy steel, or to shift the structure from martensitic transformation to ferrite-pearlite transformation, and it is possible to prevent the occurrence of martensitic transformation in the welded parts of high carbon steel and high alloy steel. Occurrence of cracks in welds.

It has the effect of preventing vulnerability.

Therefore, it becomes possible to increase the number of turns and tandem rolling of strips in laser beam welding and T'IG welding of high carbon steel and high alloy steel, which greatly improves product yield between cold pressing sections and line efficiency. effective.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a backing device for a welding machine according to the present invention;
FIG. 2 is a bottom view of the backing device for the welding machine, FIG. 3 is a perspective view of the same, and FIG. 4 is an explanatory diagram showing a conventional example. 1.2... Strip, 3... Laser beam welding machine, 6... Backing device for welding machine, 7
・・・・・・Ba・7 Bar、9・・・Induction heating coil.

Claims (1)

[Claims] In a backing device for a welding machine that abuts each cut end surface of a pair of welded materials and supports this abutted portion from the back side, the abutted portion is heated by induction on a back bar that abuts the abutted portion from the back side. A backing device for a welding machine characterized by being equipped with an induction heating coil.