JPS61255773A - Electron beam welding method by electron beam shape control - Google Patents

Abstract

PURPOSE:To control the defect of a spike, etc. by forcibly deforming to the ellipse that its major axial direction intersects at right angles each other at the vicinity of the surface of the body to be welded and the vicinity of the penetration root part the shape of the electron beam on the electron beam axis and vertical plane. CONSTITUTION:The electron beam shape control device 3 composed of the plural magnetic poles or electrodes having >=two poles under the convergent lens 2 is set up to control the shape on the electron beam axis and vertical cross section. The welding is performed by adjusting the major axis in the elliptical shape of the electron beam so as to become in the weld line direction as the 5b close to the surface of the body to be welded and in the right angles direction with the weld line as 8b close to the penetration root part. In this case, the molten metal is smoothly flowed out of the inside of the electron beam hole 11, the local hollow of a solidified wall 10 is dissolved and the porosity and solidification crack are prevented due to the electron beam hole 11 being enlarged in the weld line direction by the electron beam 5b close to the surface of the body to be welded. In the vicinity of the root part the control in the spike and cold shut can be performed in partial penetration welding by the electron beam 8b.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved method of electron beam welding. Electron beam welding has a smaller diameter heat source than other welding methods.
Since the power density is extremely high, a weld bead with a narrow weld width and a large penetration depth can be obtained. On the other hand, as the mechanism for obtaining deep penetration, welding is always performed while forming a long and narrow electron beam hole, which complicates the flow of the molten metal. Defects are likely to occur. Typical examples of these defects include porosity and various solidification cracks (vertical cracks, horizontal cracks) that occur near the center of penetration, as well as spikes and cold shut that occur near the root.

Conventional technology Defects such as porosity-1 and solidification cracking occur when the weld metal accumulated in the electron beam hole remelts the already solidified metal, resulting in local depressions in the solidification machine plate. These defects occur due to a complicated solidification mechanism. Therefore, suppressing the formation of local depressions can be said to be an effective means of preventing the above-mentioned defects.

Conventionally, as a preventive measure against this, a method has been adopted in which welding is performed while the electron beam is vibrated along the welding line or in a direction perpendicular to the welding line. However, in the former case, the electron beam reheats the high-temperature molten metal, resulting in severe spatter.
It has the disadvantage of forming a sharp spike at the root. Moreover, in the latter case, there is a drawback that the melting width widens and the penetration depth is reduced.

Purpose of the Invention The present invention aims to eliminate the above-mentioned drawbacks of the conventional method, and its purpose is to control the shape of the electron beam to form a stable solidified wall and prevent defects such as porosity and solidification cracking. It is therefore desirable to provide an electron beam welding method that does not reduce the penetration depth or generate sharp spikes or spatter in conventional methods.

Structure of the Invention As a result of intensive research to achieve the above object, the present inventor has found that by forcibly deforming the shape of an electron beam using a magnetic field or an electric field and controlling the flow of molten metal, the plurality of defects can be simultaneously prevented, Moreover, it was found that it is possible to obtain a good welded joint without impairing the penetration depth. The present invention was completed based on this knowledge.

The gist of the present invention is that, in welding with a high power density electron beam, the electron beam that passes through a converging lens and is in the process of being converged is
The electron beam is passed through a magnetic field or electric field generated by an even number of magnetic poles or electrodes, and the shape of the electron beam in a plane perpendicular to the electron beam axis is determined so that the long axis direction is near the surface of the workpiece and near the penetration root. This is an electron beam welding method that is characterized by welding by forcibly deforming the weld into mutually orthogonal ellipses or a similar shape.

To explain this based on the drawings, Fig. 1 is a schematic diagram showing an electron beam shape control method in the method of the present invention, Fig. 2 is a schematic diagram showing an embodiment of an electron beam shape control device, and Fig. 3 is an electron beam shape control method. The shape of the electron beam in the horizontal section obtained by the control, and FIGS. 4 and 5 are diagrams schematically explaining the welding method.

As shown in FIG. 1, an electron beam shape control device 3 consisting of an even number of magnetic poles or electrodes with two or more poles is installed under the converging lens 2, and is used to control the electron beam axis of the electron beam 1. Controls the shape in the vertical cross section. The controlled shape of the electron beam is used to weld. 4 in the figure indicates the focal position when the electron beam shape control device is not used.

Next, one embodiment of the electron beam shape control device 3 is shown in FIG. The magnetic field that changes the shape of the electron beam is excited by four excitation coils 3a', 3b', 3c', 3d', and four magnetic poles 3 are arranged symmetrically at an angle of 90' to each other.
Generated by a, 3b, 3c, and 3d. The magnetic poles 3a and 3c, 3b and 3d facing each other are the same and have the same magnetic potential.

If the magnetic poles 3& and 3c are N poles and the magnetic poles 3b and 3d are S poles, then in the electron beam shape control device 3, the electron beam 1 has an
A force acts that diverges in the axial direction and converges in the Y-axis direction. Now, the current flowing through the converging lens 2 is set to an appropriate value, and each excitation coil 3a', 3b of the electron beam shape control device 3 is set to an appropriate value.
If the currents flowing in ', 3c', and 3d' are set to appropriate values, as shown in FIG. 3, the electron beam 5a at each position along the electron beam axis,
6a, 7a, and 8a have their long axes in the X-axis direction like 5a and 6a on the electron beam shape control device 3 side from the focal position 4 when the electron beam shape control device 3 is not used, and 8a on the opposite side. The shape is an ellipse or a shape similar to the ellipse with the long axis in the Y-axis direction.

That is, when the electron beam shape control device 3 is not used, the electron beams 5a, 6a, and 8a in a cross section perpendicular to the electron beam axis on both sides of the focal position 4 are formed into an ellipse or an ellipse whose long axis directions are orthogonal to each other. It can be molded into a similar shape.

Electron beams 5a, 5a, 7a, 8a having such shapes
can also be obtained by using an electric field instead of a magnetic field.

That is, if electrodes are used instead of the magnetic poles 3a, 3b, 3c, and 3d, and a positive pole is placed at the north pole position and a negative pole is placed at the south pole position, electron beams 5a, 6a, and 7 having similar shapes can be obtained.
a, 8a are obtained.

Welding is performed using the electron beam shaped in this way, and by adjusting the focal position 4 so that it is located near the center of the electron beam hole when the electron beam shape control device 3 is not used. Next, two typical examples of welding methods will be shown.

(1) As shown in Figure 4, the long axis of the elliptical shape of the electron beam is in the direction of the welding line near the surface of the workpiece as shown in 5, and in the vicinity of the penetration root in the direction perpendicular to the welding line as shown in 8b. Adjust as shown and perform welding. In this case, near the surface of the workpiece, the electron beam hole 11 is expanded in the welding line direction by the electron beam 5b, so that the molten metal flows out smoothly from within the electron beam hole hole 1, and local depressions in the solidified wall 10 are formed. porosity and solidification cracking can be prevented. Furthermore, near the root, the electron beam 8b expands perpendicularly to the welding line, reducing the effective power density and slowing down the melting process of the metal by the electron beam. Also, in penetration welding, the beautiful Uranami bead shape can be achieved.

(2) As shown in Figure 5, the long axis of the elliptical shape of the electron beam is in the direction perpendicular to the welding line near the surface of the workpiece, as shown in 5C, and in the direction of the welding line, as shown in 8C, near the penetration route. Adjust as shown and perform welding. In this case, the electron beam 5C spreads the electron beam hole 11 in the direction perpendicular to the welding line near the surface of the workpiece, so the molten metal flows out smoothly as in (1) above, causing porosity, solidification cracking, etc. Defects can be prevented. Also, unlike the conventional method of vibrating the electron beam in a direction perpendicular to the welding line, the electron beam 8c becomes elliptical with its long axis in the direction of the welding line near the root, so the penetration depth is almost reduced. I won't let you. moreover,
Since the electron beam 5C near the surface of the object to be welded spreads in a direction perpendicular to the welding line, a beautiful surface bead can be formed.

The above is a typical example of an electron beam welding method that controls the shape of the electron beam. It will be done.

EXAMPLE Electron beam welding of the present invention was carried out using an electron beam shape control device using four magnetic poles as shown in FIG. In addition,
A conventional method was also used for comparison.

Using 8M50A steel as the sample material, acceleration voltage 50 kV, electron beam current 200 mA, 1 welding speed 25 cm/min
The results were as shown in Table 1 below.

Note that bead 1 was welded by the conventional method, bead 2 by the welding method shown in FIG. 4, and bead 3 by the welding method shown in FIG.

Table 1 As shown in the results, in the conventional method, local depressions occurred in the solidified wall and defects such as porosity-1 vertical cracks and horizontal cracks occurred, whereas according to the method of the present invention, both In this case, there is almost no decrease in the penetration depth, and a stable solidified wall is formed, thereby avoiding the defects of the conventional method.

Further, the first welding method has a large effect of suppressing spikes, and the second welding method has the effect of forming a beautiful surface bead.

Effects of the Invention According to the electron beam welding method of the present invention, defects such as spikes and cold shuts, which are disadvantageous to conventional methods, are suppressed, and the penetration depth is not impaired, and porosity and solidification cracking are suppressed. Defects can be prevented. Further, excellent effects such as a beautiful bead with less spatter emission, improved reliability of the joint, and expansion of the range of application to thick plate welding can be achieved.

[Brief explanation of drawings]

The drawings show one embodiment of the method of the present invention, and FIG. 1 is a schematic diagram of the electron beam shape control method, FIG. 2 is a schematic diagram of the electron beam shape control device, and FIG. 3 is a schematic diagram of the electron beam shape control method. FIGS. 4 and 5 show schematic diagrams of the welding method. 1: Electron beam 2: Converging lens 3: Electron beam shape control device 3a, 3b, 3c13d: Magnetic poles 3a', 3b', 3c', 3d': : Iil 4: Focus when electron beam shape control device is not used Positions 5a, 6a17a, 8a, 5b16b, 7b,
8b, 5c16c, 7c. 8C: Electron beam 9: Welding direction 1o: Solidified wall 11: Electron beam hole 12: Welded object patent applicant
Science and Technology Agency, Research Institute for Metals and Materials Research

Claims (1)

[Claims] In welding with a high-power-density electron beam, the electron beam that is in the process of converging after passing through a converging lens is passed through a magnetic or electric field generated by an even number of two or more magnetic poles or electrodes. An electron beam welding method characterized by welding by forcibly deforming the shape of the electron beam into an ellipse or a similar shape in which the long axis direction of the electron beam is orthogonal to each other near the surface of the workpiece and near the penetration root. .