JPS594234B2 - density - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electron beam welding method.

Electron beam welding is performed at high speed using high-density energy, has deep penetration, produces a narrow weld bead, has little welding distortion, is easy to control welding conditions, and can be performed in a vacuum. It has many advantages5, such as less material change in the weld bead, and has been used for welding nuclear power industry equipment, aerospace development equipment, precision structures, precision parts, etc. Recently, it has been considered to introduce this method to weld general large heavy structures such as general shells and pressure vessels.

However, when welding large heavy structures by electron beam welding, for example, there are the following problems, making it difficult to put it into practical use.

That is, when welding general large heavy structures, one-sided welding that does not require reversal is desired, and since this type of structure is difficult to machine, the beveling process is usually performed by gas cutting. Therefore, the machining accuracy of the groove is poor, and it is difficult to align the grooves, resulting in groove gaps and meandering of the groove thread, resulting in poor groove accuracy μ<.
In electron beam welding, the narrow width of the 20 weld bead is a real problem. In other words, if there is a groove gap g as shown in Fig. 1a, the weld metal will melt downward, creating creves 2 as shown in Fig. 1b and c on the lower surface of the base metals 1 and 1. A board 4 is formed within the weld bead 3. In addition, if the groove line 5 is meandering as shown in Fig. 2a, poor penetration portions 6 as shown in Fig. It turns out. Therefore, in order to cope with the above welding conditions, the welding speed is made extremely low, and the electron beam is moved in a sine wave shape or in a spiral shape with an amplitude corresponding to the desired weld bead width. , it is considered to obtain a wide weld bead.

However, according to such a method, base materials 1', 1
' can be melted over a wide range to form a wide bead 3', but at this time, a large melt pool is formed, resulting in a disordered solidification pattern and low melting point impurities in the base material 1', 1'. A large amount of impurities are mixed in, and the segregation of the impurities is promoted, and together with an increase in shrinkage stress, a third impurity is mixed into the weld bead 35.
Cracks 7 as shown in Figures A and b may occur, and as the molten metal increases and the solidification rate decreases, the surface tension of the molten metal decreases and melts downward, forming the weld bead 3'.
An underpool 8 is formed on the upper surface of the creve 25 on the lower surface side of the clave 25, so that it has not been put to practical use.

This invention was made in view of such problems, and it is made to vibrate an electron beam in a direction perpendicular to the weld line with an amplitude corresponding to the desired weld bead width while moving in the weld line direction. vibrating the electron beam also in the welding line direction while shifting the phase of its movement trajectory, setting the vibration frequency in the direction perpendicular to the welding line to be higher than the vibration frequency in the welding line direction, and setting the amplitude appropriately. The feature is that the welding conditions such as the molten state and solidification rate of the welded part are adjusted by adjusting the welding condition, and while taking advantage of the original characteristics of electronic bead welding, such as deep penetration and high-speed welding, it does not affect the bevel accuracy. The purpose of the present invention is to provide an electron beam welding method that enables one-sided welding without being welded, and can also efficiently weld general large important structures.

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 shows a state in which an I-shaped groove 12 made by butting base materials 11 and 11 is welded by an electron beam 13. The electron beam 13 is directed in the Y direction directly parallel to the welding line , it is made to vibrate (oscillate) at an amplitude WY corresponding to the desired weld bead width W, and also to vibrate (oscillate) in the welding line X direction with an appropriate amplitude and frequency using a deflection coil 15. be.

In this case, the period ratio is set larger in the Y direction than in the X direction.
FIG. 5a shows the electron beam 13 that is printed on the base materials 11, 11.
This is a photograph showing the trajectory of. With such a configuration, the electron beam 13 is moved sinusoidally in the direction of the welding line X while vibrating in a direction directly parallel to the welding line X with an amplitude of WY, and the electron beam 13 is moved in the phase of its movement trajectory. Oscillation can also be performed in the welding line X direction while shifting the welding line. Therefore, by appropriately setting the amplitude Wx and frequency f of the oscillation of the electron beam 13 in the welding line As shown in FIGS. 5B and 5C, it is possible to obtain a good weld bead 16 free of internal defects such as boards, poor penetration, cracks, and surface defects such as creves and underpools.

In other words, when the electron beam 13 is oscillated only in the Y direction directly parallel to the welding line X, a weld bead with many defects as shown in FIG. By combining the oscillations L1 and oscillation in the welding line Therefore, the solidification rate of the molten metal is accelerated, the surface tension of the molten metal is increased, and the falling of the molten metal can be prevented, thereby preventing internal defects and surface defects from occurring in the weld bead 16.

Furthermore, as a result of the electron beam 13 oscillating in the welding line X direction, the welded portion is melted and solidified many times. As a result, the low melting point impurities in the base materials 11, 11 are diffused and their segregation is prevented, and the generation of cracks is prevented. In addition, any cracks that occur will be melted and removed. According to the above embodiment, high-quality one-sided welding can be performed at high speed even on thick plates with poor groove precision.

The reason why the vibration frequency Yf in the direction perpendicular to the welding line is set higher than the welding line direction Xf (Xf<Yf) is as follows.

When the vibration frequency Yf is made lower than the vibration frequency Xf, the locus of the weld line becomes as shown in Figure R, A. In this case, the low melting point impurities in the molten metal are diffused in the direction of the weld line, but the cross section of the weld becomes linear as shown in Figure 8A, and the shrinkage stress (perpendicular to the weld line) during solidification is Causes cracks. Further, when the vibration frequency Yf is made equal to the vibration frequency Xf, the locus of the weld line becomes as shown in FIG. 7. In this case, as shown in FIG. 8Q, the diffusion effect is small, and impurities gather in the center where solidification is slow and cracks are more likely to occur than in the case where Xf>Yf. It also tends to melt off. On the other hand, if the conditions of the present invention, that is, the vibration frequency Yf is set higher than the vibration frequency Xf, the trajectory in the weld line direction will be
The result is as shown in FIG. 7C.

In this case, as shown in FIG. 8C, the impurities are effectively diffused and are not segregated at least in the center of the final solidification zone, thereby preventing the occurrence of cracks. In addition, the beam heat is diffused and a wide bead that does not melt through can be obtained. Therefore, in order to obtain the effects of the present invention, a wide pead without burn-through can be obtained. The condition must be Xf<Yf. However, in addition to the above embodiment, the amplitude Wx of the oscillation of the electron beam 13 in the welding line Of course.

The following table shows a comparison of the results of welding carbon steel plates with a thickness of 25 m using the conventional method and the method of the present invention. Also, the 6th
The figure shows a conventional method that does not oscillate (dotted line), oscillates only in the Y direction directly parallel to the welding line X, and increases the amplitude to 3? Bead width (1q constant on the lower surface side) and welding speed when welded by the conventional method with m1 frequency of 750 Hz (dotted chain line) and the method of the above embodiment with oscillation in the X and Y directions (solid line), respectively. This is a comparison of the relationship between

In the method of the above embodiment, the oscillation in the X direction has an amplitude of 5 to 107!1f11. , the frequency was 100 Hz, the oscillation in the Y direction had an amplitude of 1.5 to 3 rwt, and a frequency of 750 Hz, and the welding voltage was 5 for each method.
The welding current of 0 to 52 KV1 was 450 to 500 mA, and a mild steel plate with a thickness of 25 mm was used as the base material. As is clear from this figure, welding could be performed faster using the method of the present invention. As described in detail above, the present invention moves the electron beam in the direction of the welding line while vibrating the electron beam in a direction perpendicular to the welding line with an amplitude corresponding to the desired weld bead width, By vibrating in the direction of the welding line while shifting the phase of the movement trajectory, and setting the vibration frequency in the direction perpendicular to the welding line to be higher than the vibration frequency in the welding line direction, and setting the amplitude appropriately, the welded area can be melted. It is characterized by adjusting the welding conditions such as welding speed and solidification rate, and this makes use of the original characteristics of electronic bead welding, such as deep penetration and high-speed welding, while affecting the bevel accuracy. To provide an electron beam welding method capable of performing one-sided welding without being damaged and effectively performing machining of weld grooves and welding general large heavy structures that are difficult to reverse. It is something that can be done.

[Brief explanation of drawings]

Figures 1 to 3 show separate conventional examples, where Figure 1a is a cross-sectional view of the base metal before welding, Figure b is a photograph showing a cross-section of the welded part, Figure c is an explanatory diagram of Figure 2, Figure a is a perspective view, b is a photograph showing the cross section of the welded part, c is an explanatory view of b, Figure 3 a is a photograph showing the cross section of the welded part, b is an explanatory view of a, Figures 4 and 5. 4 shows an embodiment of the present invention, FIG. 4 is a perspective view, FIG. 5a is a photograph showing the movement trajectory of the electron beam,
b is a photograph showing a cross section of the welded part, c is an explanatory diagram of b, Fig. 6 is a graph comparing the relationship between bead width and welding speed by the conventional method and the method of the above embodiment, and Fig. 7 8A and 8B are explanatory diagrams showing the beam trajectory when the conditions of the present invention are not met, C is an explanatory diagram showing the beam trajectory according to the method of the present invention, and A and the mouth of the same figure are explanatory diagrams showing the beam trajectory when the conditions of the present invention are not met. An explanatory diagram showing a welded part when it comes off, and Figure C is an explanatory diagram showing a welded part according to the method of the present invention. 11... Base material, 13... Electron beam,
16...Welding bead.

Claims (1)

[Claims] 1 The electron beam is moved in the welding line direction while being vibrated in a direction perpendicular to the welding line with an amplitude corresponding to the desired weld bead width, and the electron beam is moved in the welding line direction while shifting the phase of its movement trajectory. In an electron beam welding method that vibrates to both sides, the vibration frequency in the direction perpendicular to the weld line is set higher than the vibration frequency in the weld line direction, and by setting the amplitude appropriately, the molten state and solidification of the weld zone can be controlled. An electron beam welding method characterized by adjusting welding conditions such as speed.