JPS643598B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas pressure welding method for steel materials such as reinforcing bars, and more particularly to a gas pressure welding method in which relative motion and sliding motion are applied between abutting contact surfaces while transitioning to pressure welding.

Two-stage or three-stage upsetting methods are currently used for gas pressure welding of steel materials, mainly reinforcing bars.

As shown in Figs. 1 and 2, the above two-stage upset method involves clamping one of the reinforcing bars 1 and 2 to be welded with a fixed chuck 3 and the other with a movable chuck 4 (bolts 5
While applying a constant pressing force a according to the cross-sectional area with the cylinder 6 (the pressure in practical use is a constant pressing force selected in the range of 3 to 6 kgf/ ^mm2 ), Heating was started from point P1 with a ring gas burner (not shown), and as the heating progressed under the constant pressure, the butt gap closed and a slight compression bulge occurred, and then the pressurizing pump was stopped at point P2. (initial pressure welding process), while heating continues, pressure welding proceeds with residual pressure a′,
When the pressure has decreased to a predetermined value at point P3, pressure is applied again until a constant pressure is reached to encourage the growth of the bulge, and the work is completed when the bulge reaches a predetermined size.

The latter three-stage upsetting method is a method that was developed relatively recently, and as detailed in Japanese Patent Publication No. 23192/1983, after going through the same initial pressure welding process as the two-stage upsetting, the same method is used. This is a pressure welding method in which pressure welding is completed through primary repressurization and secondary repressurization under predetermined pressure control as described in the publication.

Both of the above pressure welding methods have in common that the initial pressure welding process is carried out while maintaining the initial pressure a at a constant high level.

By the way, welding defects in gas pressure welded joints are mainly determined based on the presence or absence of flat fracture surfaces and the area where they occur. A flat fracture surface is a flat, grayish-white, non-crystalline surface that is observed at the fracture when a pressure-welded joint is broken, and its elimination is a major factor in determining the health or failure of pressure-welded joints. .

In the first place, the joining principle or joining mechanism of the welding method called gas pressure welding is thought to be similar to diffusion welding or, in the old days, forge welding. Therefore, as in the gas pressure welding of reinforcing bars using the above-mentioned two-stage and three-stage upset methods, applying a constant pressure a or at least a high pressure of at least half that pressure between the butt end faces before heating is not a good idea. This is based on the idea that closing the gap as quickly as possible is more advantageous in preventing oxidation of the end face.

However, the inventor has already
No. 1) provides a new gas pressure welding method that is different from both the above-mentioned two-stage and three-stage upsets.

The present invention addresses the requirements of heating the butt portions until the appropriate temperature for pressure welding is reached while maintaining the butt pressure at zero at the beginning of butting the steel materials to be welded, and the requirement that the pressure applied to the butt portions be maintained at the appropriate temperature for pressure welding. a requirement to start and increase the pressurizing force stepwise;
The gas pressure welding method of steel materials is characterized by the requirement to provide sliding movement between the butt contact surfaces from the beginning of butting the steel materials, and then performing initial pressure welding.

In other words, to explain the same gas pressure welding method using FIG. Pressure a2 where the pressure increases
During the very early stages of the region (this interval is
For example, relative movement (fine sliding contact movement) between the joint surfaces (depending on the power of the vibrator and the rising speed of the pressurizing force, which will be described later)
By giving a It is characterized by a gas pressure welding method that attempts to eliminate the generation of fractured surfaces.

During gas pressure welding, it was common knowledge to keep the mating surfaces of steel materials as static as possible. However, when proceeding with butt welding of steel materials,
As mentioned above, it is extremely advantageous to move the end surfaces of the steel materials into pressure contact while making slight sliding contact while still being in contact with each other. If the vibrator includes the section where slight sliding contact is required, even if it is operated during the entire pressure welding process, it can generate sliding contact on the butt surfaces only in the initial stage of butt contact depending on its power setting. .

In other words, when a stronger pressure is applied to the abutment part during a certain process leading to fusion, the vibrator will be in the same state as if it were not functioning at all, and it would not produce vibrations that would have any negative effect on the abutment part. do not have. Of course, the power to the vibrator may be turned off at the initial stage of the pressurizing area a2.

Examples of the present invention will be specifically described according to experimental examples. The reinforcing bars used were SD35 and D25, and the pressurization method shown in Figure 5 was used. In addition, in this experiment, as shown in Figs. 3 and 4, as a means for imparting the above-mentioned relative motion between the end faces of the steel materials 1 and 2, the movable side chuck portion 4 (this portion is the Since it is an upset, it is of course movable in the axial direction, but because it is necessary to align the central axis of the reinforcing steel, it is also movable within a certain range perpendicular to the axis). vibrator V
4B (trade name) 7 (input 25W, impact force 10Kg) was attached with bolt 8. This vibrator is an electromagnetic vibrator in which a piece of iron is placed opposite to the end face of a coil, and the vibration of the piece of iron is obtained by applying electricity to the coil.

As a result, the end face of the reinforcing bar gripped by the movable side chuck will make a slight relative movement in the direction perpendicular to the axis between the end face of the fixed side reinforcing bar, and in this experiment, from before the start of heating to the end of pressure welding. The vibrator 7 was kept in operation for the entire period.

The gaps between the end faces of the reinforcing bars were 0 mm and 3 mm, and the end faces were pretreated by grinding using a hand grinder called a sander, as in the field work. In this way, the reinforcing bars 1 and 2 are butted together as shown in Fig. 3, and the pressing force a1 is initially set to 0 Kgf/mm ² as shown in Fig. 5.
Under the operation of the vibrator 7, heating is started using a ring burner for pressure welding of reinforcing bars (heating start point Pa1),
A state equivalent to zero pressurization (zero pressurization force a1) is maintained from the heating start point Pa1 until the temperature of the contact portion of the reinforcing bars reaches the appropriate pressure welding temperature (around 900°C to 1000°C).

The time required from the initial heating start point Pa1 to the pressure welding appropriate temperature point Pa2 under zero pressure was 24 seconds.

At the optimum temperature point Pa2, the pressure is increased stepwise as shown in the figure, and finally at point Pa3, a predetermined pressure a (5 kgf/mm ² per nominal cross-sectional area of reinforcing steel in this experiment) is applied.
).

In the figure, a2 indicates the state of the pressurizing force that is increased stepwise, and the stepwise pressurizing force a2 is obtained by operating the electric pump with pulsed energization according to a predetermined program. At the very early stage of the stepwise application of pressure a2, the power of the vibrator is completely suppressed.

The time required from the pressure welding appropriate temperature attainment point Pa2 (which is also the initial pressurization start point) to the predetermined pressurization pressure attainment point Pa3 was about 17 seconds.

Then, the pressurized state with the predetermined pressure a was maintained until the butt gap closed (in the experiment, the butt gap + 1 mm was compressed just to be sure), and a slight compression bulge occurred in the butt part, so that the butt gap was completely no longer recognized. By the way, the operation of the electric pump is stopped in accordance with the pressurization procedure of the two-stage upset described above. The process up to the initial pressurization end point P2 corresponds to the initial press-welding process described in the two-stage and three-stage upset methods.

Although the pressure gradually decreases with the passage of time due to the stop of the pressurizing force, the compressed bulge continues to be encouraged to grow due to the residual pressure.

Next, when the pressurizing force a is halved, the pump is operated again to re-pressurize (re-pressurize starting point P3)
The joining was completed when the compression bulge reached a predetermined amount.

The total time required for welding per piece based on the above is approximately 90
seconds, the total compression amount was approximately 25 mm.

Fracture surface inspection and mechanical tests were performed on the test pieces according to the above procedure. For fracture surface inspection, a notch was mechanically made in the joint, the fracture was caused from the notch using a tensile tester (a bending tester may also be used), and the fracture surface was visually observed. There were no defects. Also, the mechanical test is 1.0D (the standard specification is 0.8D, but
In this test, we did not want to machine cut out the flat fracture surface, which tends to occur along the circumference near the periphery, which is often observed in the past. Bending tests were conducted, and in the tensile test, the base material could be cut, and in the bending test, it could be bent up to 170° without any defects.

As another experiment, we stopped the work at point P2 in Fig. 5 and determined whether a vibrator was added or not.
Comparing the fracture surfaces of the joint surfaces at that point, it was found that in the vibrator addition test, approximately two-thirds of the fracture surface was broken at this point.
The remaining one-third of the area showed a crystal fracture surface, and crystal fracture surfaces were observed in spots in the remaining one-third of the area, and a clear difference was observed compared to the fracture surface of the test piece without the addition of a vibrator (in gas pressure welding, A research report has been published stating that the upset process that follows has an extremely large effect on bonding.)

An example of the experimental results for D25 reinforcing bars has been shown above, but the effect of removing the oxide film using a vibrator can be seen in the initial stage of the gas pressure welding work described above, that is, although both end faces of steel material 1 are in contact (of course, the entire surface is It is more effective when relative motion is still possible even with a small power vibrator under no or very slight pressurization (although this is not the case).

The present invention is applicable regardless of the reinforcing bar diameter, and in fact, it has been confirmed in other experiments with SD35 and D32 that extremely satisfactory gas pressure welding joints similar to those of D25 described above can be obtained.

In addition, in this experiment, a vibration frequency of 6000 times/min was used, but since it is only necessary to give relative motion (sliding motion of rubbing together) between the end faces, it is necessary to apply a vibration frequency of 6000 times/min in a direction perpendicular to the reinforcing bar axis at an extremely low speed. Alternatively, an arcuate reciprocating motion should be sufficiently effective, and in this sense, the use of a vibrator is not necessarily limited to inducing relative motion.

As described above, the present invention provides an element to proceed with heating under zero pressure at the initial stage of pressure welding, which has not been considered at all in the conventional gas pressure welding method for steel materials, to reach the appropriate pressure welding temperature, and to start pressurization at the appropriate pressure welding temperature and to apply the This method incorporates into the pressure welding process an element that increases the pressure in stages and an element that provides sliding movement between the abutting contact surfaces from the beginning of the butt under zero pressure, and thereby, JP-A-60-1999 No. 72689 (Special request 1982)
By applying this method to the conventional gas pressure welding method for steel materials related to two- or three-stage upsets, including the method (No. The effect of making the joints of reinforcing bars, which are important components, even more sound is extremely significant. Furthermore, this method can be applied not only to the field of reinforcing bars, but also to a wide range of general steel materials, such as gas pressure welding of rails, and can be expected to be sufficiently effective.

The sliding motion on the abutting contact surfaces may be applied indirectly through the chuck, or may be applied directly to the steel material.

[Brief explanation of drawings]

Fig. 1 is a graph illustrating the earliest method of gas pressure welding of steel materials in terms of the relationship between pressure and time, Fig. 2 is a plan view showing a typical example of a gas pressure welding device, and Fig. 3 is a diagram illustrating the implementation of the present invention. FIG. 4 is a plan view illustrating the gas pressure welding apparatus used in the example, FIG. 4 is a front view of the same, and FIG. be. 1, 2...Reinforcement bar, 3...Fixed side chuck, 4...
...Movable chuck, 7...Vibrator.

Claims (1)

[Claims] 1. At the beginning of butting steel materials, the butt part is heated until it reaches the appropriate pressure welding temperature while maintaining the butt pressure at zero pressure, and at the appropriate welding temperature, the pressurization of the butt part is started, and the pressurizing force is increased. A gas pressure welding method for steel materials, characterized in that initial pressure welding is carried out while increasing the pressure in stages as heating progresses, and applying sliding motion between the butt contact surfaces from the beginning of the butt of the steel materials.