JPS59125287A - Gas pressure welding method for steel pipes - Google Patents

Abstract

PURPOSE:To form a joint part having good quality in the stage of heating and joining the joining end part of steel pipes by forming a gaseous flame for heating into a flame richer in oxygen than a neutral flame and melting the joining part thereby joining said part with upsetting. CONSTITUTION:Steel pipes 1, 2 to be joined are respectively clamped by a movable clamp 5 which is movable by a hydraulic cylinder 6 and a stationary clamp 4. A ring burner 7 is disposed around the joining part 8 of both pipes 1, 2 and gaseous C2H2 and O2 for heating are supplied to the burner 7 through a hose 13 to generate a flame in a nozzle 14 and to heat the part 8. The feed rate of C2H2 and O2 is regulated in this stage to make the flame richer in oxygen than a neutral flame to melt the part 8 and thereafter said part is upset quickly by the clamp 5 and is thus joined. The joint having good quality is formed in a shorter stage and required time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the method of gas pressure welding of individual and separate motions.

In conventional gas pressure welding of steel, welding = 1+ outside rjc' t
Power with a burner [1 heat, pt! 'This is a method of joining by performing an absent when the temperature of the inner surface joint part, which is difficult to rise due to Y conduction, reaches the pressure welding critical temperature or higher.

The conventional gas pressure welding method for FJ pipes will be explained using Fig. 1 as an example. As shown in Fig.
In the axial direction of the fixed side clamp 4 and the main body 3 fixed to the
They are each clamped by a movable clamp 5 which is made slidable by a hydraulic cylinder 6,
The joint portion 8 is heated with a ring burner 7, and pressurized with a hydraulic cylinder 6 at an appropriate time for pressure welding.

At this time, heating gas is passed from a gas source (not shown) through hoses 9 and 10, mixed at a constant ratio in a mixer in control box 12, and then passed through hose 13 to ring burner 7.
leading to. Thereafter, combustion is ejected from the crater 14 provided in regular pinches on the inner circumferential surface of the ring burner, and the joint portion 8 is heated at that temperature. 11 is a cooling water hose surface.

Further, the ring burner 7 (d) is swung in the axial direction and circumferential direction of the steel pipe 2 by the oscillating device 15.

The gas properties used at that time are neutral flame or weak reducing flame, which heats the joint surface without acetylating or melting it much, and the flow rate of the gas used is set before the inner joint reaches the appropriate pressure welding temperature. Select a flow rate that will prevent the external joints from melting. Therefore, the heating time is

It depends on the heat conduction speed of the joint, and the thicker the wall, the more time it takes. Furthermore, as the wall thickness increases, heat conduction in the axial direction increases, and not only will the inner surface joint not be able to reach the appropriate temperature for pressure welding, but even if you forcibly apply an upset, the heating width will expand, causing a flare shape. , it is not possible to form a good bond in terms of quality and shape.

The present invention has come to the conclusion that the cause of the above problem is that the conventional gas pressure welding method for steel pipes raises the temperature of the joint due to heat conduction, and has developed a new gas pressure welding method as follows. This is what led to its development.

That is, the present invention is characterized in that, in gas pressure welding of steel pipes, heated coal from a ring burner is made into an oxygen-rich flame that is more than a neutral flame, and after a molten layer is formed over the entire joint, an absent is rapidly added to join. This is a gas pressure welding method for steel pipes.

The present invention will be explained in detail below.

First, regarding the apparatus for carrying out the method of the present invention, the conventional apparatus shown in FIG. 1 may be used.
There is no need to add any new means.

Next, when carrying out the pressure welding method of the present invention, first, the joint is strongly heated and melted from the outer surface, regardless of the temperature rise characteristics due to heat conduction of the inner surface joint, until it reaches the inner surface joint. Either by penetrating it or by providing a gigang at the joint before heating and heating that surface with a two-gas flame to create a molten layer. When a molten layer is thus formed over the entire joint surface, an abrupt pressure is applied suddenly to push scale, foreign matter, etc. on the joint surface out of the joint surface and press the joint. In this case, "abrupt" means that the abrupt speed is approximately 0.5 m/sec or more.

That is, in the present invention, unlike the heating means in the one-pass gas pressure welding method, which performs width baking in the vicinity of the joint and raises the temperature of the inner surface joint to the appropriate temperature for pressure welding by heat conduction, the present invention does not By selectively forcibly heating the
A molten layer is formed on the joint surface, and the entire joint reaches the appropriate pressure welding temperature before the heating width expands.

In order to carry out such heating, the heating gas used is of a composition that produces an oxygen-rich flame that is higher than the so-called neutral flame, which is more oxygen-rich than conventional flames, and the flow rate used is the same as that used in conventional gas pressure welding. The amount should be equal to or greater than that.

In this way, in the method of the present invention, the joint is rapidly melted by igniting the joint using an oxygen-rich flame, so if absent is not applied immediately after the molten layer is formed, the joint will become excessively oxidized and the quality of the joint will deteriorate. will deteriorate. For this reason, in the method of the present invention, it is necessary to rapidly apply an absent as soon as a bath melt layer is formed at the joint.

As described above, the method of the present invention not only allows a joint of good quality to be obtained without flaring in the hollow wall and pipe, but also allows the joint to be heated rapidly. Absent pressure is also applied rapidly, which has the additional effect of significantly shortening the time required for the press-welding process. Furthermore, the fact that pressure welding can be carried out in such a short time allows us to expect the possibility of carrying out pressure welding on a production line.

In the method of the present invention, it is necessary to melt the entire joint surface at the same time and to form and maintain a molten layer uniformly, so it is effective to swing the ring burner in the circumferential direction. Of course, some axial rocking is possible depending on the situation.

Next, the effects of the present invention will be illustrated more specifically by Examples.

S T P G 38, 100 A as an example test steel pipe
, 5CH40 (: L 14..3φ x 6 thickness) was used, the burner was a nozzle mix type, and the burner was 0.7. He used a ring burner that created 60 diameter craters.

Table 1 shows the gas pressure welding conditions for the conventional method and the method of the present invention, respectively.

Table 1 Table 21 shows the shapes of joints joined by gas pressure welding under these conditions.

In the same figure, (A+ shows the joint shape by the conventional method, and (B) shows the joint shape by the present invention method. In (A), the joint part becomes flared with upsetting, and the pressure welding is not performed properly
The adhesion on the introvert side was insufficient. Therefore, when performing a tensile test, when the same joint is stretched straight, the inner joint -
No. 16 easily broke and was rejected.

On the other hand, in case (13), only the bonded portion is forcibly heated and pressure welded, so the deformation is local and does not result in a flared shape.

Moreover, the joint quality is good because the inner surface joint is melted and reaches a temperature above the appropriate pressure welding temperature. Furthermore, the strength of the joint in a tensile test was also sufficient.

Furthermore, in the method of the present invention, the total time required for the gas pressure welding step is less than half of that of the conventional method, and it is clear that the method of the present invention is an extremely efficient method.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a gas pressure welding device for steel pipes, and FIG. 2 is a sectional view of a pressure welding joint. l, 2: Steel pipe 3: Main body 4: Fixed side lamp 5: Moving side clamp 6: Hydraulic cylinder 7. Ring burner 8: Joint part 9.1
0: Hose 11: Cooling hose 12: Control box 13' hose E4: Crater 15: Rocking device

Claims (1)

[Claims] In gas pressure welding of steel pipes, heating coal from a ring burner is made into an oxygen-rich flame that is more than a neutral flame, and after forming a molten layer over the entire joint, ``absent is rapidly added to join the steel pipes.'' Scrap pressure welding method.