JPS6054287A - Electron beam welding method - Google Patents

Abstract

PURPOSE:To form a weld metal exhibiting high toughness as welded by disposing filler metals consisting principally of Ni in the butt parts of thick-walled steel plates in such a way that the density distribution of Ni become higher as nearing to the surface side of the plate thickness and subjecting said parts to electron beam welding. CONSTITUTION:Grooves 6 for inserting filler metals are formed in the different positions in the thickness direction of the butt surfaces of base metals 1, 1 which are thick-walled steel plates in the stage of subjecting the butt parts of said materials to partial penetration electron beam welding with deep penetration. Plural pieces of filler metals 5 consisting principally of Ni are inserted approximately parallel with the surface of the thickness and are disposed in such a way that the weighted mean density distribution of Ni in the metals 5 viewed in the thickness direction becomes higher as nearing to the surface side of the thickness. The butt parts are subjected to electron beam welding in this state, by which the decrease in the toughness on the front side where the cooling rate of the weld metal is low is prevented and the weld metal having high toughness is obtd. in the as- welded state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electron beam welding of thick steel plates, and more particularly, to a method of electron beam welding of thick steel plates, and more particularly, to partial penetration electron beam welding (hereinafter referred to as EBW) of thick steel plates.
This relates to a method for obtaining weld metal that exhibits high toughness even after welding.

The EBW method has the characteristic that it can achieve deeper penetration than other welding methods, and it can remove filler metal by simply butting together ordinary thick steel plates without special beveling. Can be welded without use. By the way, E B W weld metal, which is made by melting and solidifying only the base metal, cannot be said to have good toughness in the as-welded state, but relatively good toughness is achieved by heat treatment after welding. This is the actual situation, and especially when welding thick EBW plates, a considerable amount of welding heat input is applied even if the plate is EBW, so a high degree of toughness cannot be expected from welding as is.

Incidentally, in EBW, welding is normally performed without using a filler metal, but in rare cases, a filler metal may be used. For example, the following method is known. That is, one of them is the filler wire method as shown in FIG. 1, in which EBW is performed without continuously supplying the filler wire 4 into the electron beam 2 or into the molten pool 8 near the surface of the base material 1. It is.

However, this method has the disadvantage that the various elements in the filler wire 4 are difficult to sufficiently diffuse to the penetration tip (i.e., deep in the thickness direction), so usually a filler wire with almost the same composition as the base material is used. ■It is only used for the purpose of compensating for the lack of excess material due to groove gap fluctuations, and it cannot be expected to improve the toughness of EBW weld metal. Another EBW method using filler metal is the in-reet metal method as shown in Fig. 2, as disclosed in Japanese Patent Publication No. 51-11052, Japanese Patent Application Laid-open No. 49-24858, etc. A filler material 5 in the form of metal foil (or thin metal plate) is placed on the butt surface of the base material 1.
EBW is performed by inserting the filler metal 5, and alloying elements are added from the filler metal 5 to adjust the chemical composition of the weld metal and improve physical properties such as toughness. Although this insert metal method is slightly more complicated than the filler wire method in terms of workability, it can be said to be an excellent method in that it allows a predetermined alloying element to be uniformly added to the weld metal. However, this insert metal method is effective in terms of improving toughness when it is applied to penetrating EBW as shown in Figure 8 or partial immersion EBW with shallow penetration depth as shown in Figure 4. In this case, partially immersed EBW with a deep penetration depth as intended in the present invention (see FIG. 5) shows almost no effect as shown in the example described later.

Therefore, the present inventors aimed to solve the above-mentioned problems observed in deep penetration partially immersed EBW and to establish a technology that can obtain weld metal that exhibits high toughness even as welded. We investigated the reason why high toughness could not be obtained. As a result, deep penetration part EB
With W, for example, as shown in Table 1, the cooling rate at each position in the weld metal penetration depth direction is significantly different, and the toughness of the surface side, where the cooling rate is slow, deteriorates, so the toughness of the entire weld metal deteriorates. I found out that it becomes scarce.

Table 1 Cooling time for each position of the weld and from the viewpoint of increasing the toughness of the entire weld metal, it is not necessarily appropriate to make the amount of alloying elements uniform throughout the weld metal, and the cooling rate of the weld metal The conclusion was reached that the content of toughness-improving elements should be adjusted depending on the position in the penetration depth direction.

The present invention was completed as a result of further research based on these findings, and its configuration is such that when applying a deep penetration partial immersion electron beam welding method to the butt part of thick steel plates, the plate of the butt surface is Ni at different positions in the thickness direction
A plurality of filler metals whose main component is The main idea is to weld the parts so that they are placed higher on the thicker surface side of the plate.

In the present invention, as shown in Table 1 [7], the cooling rate in the direction of the penetration depth of the weld metal due to deep penetration partial immersion EBW is significantly different. Based on the confirmation result that the toughness of the side becomes poor, the filler metal was used to obtain a concentration gradient in which the content of Ni, which is an element that improves toughness, gradually increases from the deep penetration toward the surface. The weld metal J'
1 has improved overall toughness.

That is, Fig. 6 shows the conventional partially soaked EBW (no filler metal).
Table 2 shows the Nj content and Charpy impact strength (measured at -55°C) of the weld metal obtained in the penetration depth direction.The chemical composition of the test base metal is shown in Table 2, and the welding conditions are Table 8 shows the sampling positions of the test pieces as indicated by the chain lines in FIG.

As is clear from Figure 6, when no filler metal is used, the amount of Nl in the weld metal is constant, but the impact value rapidly decreases toward the surface because the cooling rate slows down. .

・-The thickness of the cylinder in Figure 8 is 0.1 mry as shown in Figure 9.
Or, the Ni foil 5 with a thickness of 0.2πm was inserted into the groove surface, and the N1 plate and Charpy impact v value in the penetration depth direction were investigated in the same manner as above. child.

As is clear from the figure, it does not necessarily mean that the higher the Ni content, the higher the impact value, but it is thought that there is an optimum Niff1 depending on the cooling rate of the weld metal.

In addition, Fig. 1θ shows that Ni wire is inserted into the groove surface as a filler metal instead of Ni foil, and the N in the weld metal is removed in the same manner as above.
This figure shows the results of a Charpy impact test when the amount of 1 was kept approximately constant (the dimensions and insertion position of the Ni wire are as shown in FIG. 10). This figure also confirms that simply increasing N1fi in the weld metal does not uniformly improve toughness. There is a tendency that the lower the Niff1 is on the deep side where the cooling rate is faster, the higher the toughness is, and the higher the Niff1 is on the surface side where the cooling rate is slower, the higher the toughness is. However, if Niff1 is too large even on the surface side, high toughness cannot be obtained, and the optimum Niff1 is determined depending on the cooling rate of the weld metal.
It is also clear that there are

Incidentally, Fig. 11 shows a welding process using the same welding conditions and sample base material as above, and inserting a 1.4mmφ Ni wire into the surface side of the joint and a 1.2mmφ Ni wire into the deep side. , which shows the Charpy impact test results when the weighted average density of Ni was gradually decreased from the surface side to the deeper part, and the Ni
Since the concentration is an appropriate value according to the cooling rate, a high level of impact value is obtained overall. The overall conclusion, including these experimental results, is that the appropriate Niff1 for each part of the penetration depth is approximately 2.5% at the surface, approximately 2% at the center, and approximately 1.5% at the bottom. This was confirmed. - In this way, in the present invention, the Ni-containing n1 insertion pinch and thickness of the groove filler are adjusted so that the weighted average density of Ni on the surface side becomes higher in consideration of the cooling rate of the weld metal. E
BVi is carried out, and specifically, for example, it is carried out in the following manner. That is, FIG. 12 is a partially broken diagram showing an example of inserting filler metal into the abutting surfaces, in which a groove 6 for inserting the filler metal is formed in the abutting surface of the base material 1.1, and a groove 6 with a circular cross section is formed in this groove. (
Alternatively, a plurality of filler metals 5 having a square cross section, a rectangular cross section, a band shape, etc. (of course it does not matter) are inserted along the welding line approximately parallel to the base metal surface, and the filler metal 5 is By using a material with a larger cross section for the surface side, it is possible to
1 Adjust so that the amount added is large. Alternatively, use a plurality of filler metals 5 with the same cross section 17, each filler metal 5 closer to the surface side.
The weighted average density of Ni can be made gradient by narrowing the insertion interval, or by using a filler metal with high Ni content on the surface side and inserting a filler metal with low Ni content and R on the deep side. It is also possible to have

The present invention is roughly constructed as described above, but the point is that in deep immersion partial immersion EBW, by providing a concentration gradient such that the Ni'a concentration is higher on the weld metal surface side where the cooling rate is slow, it is possible to reduce the concentration from the deep part to the surface. It has become possible to improve the toughness of the entire weld metal over the sides, and to secure an EBW weld metal that exhibits sufficient physical properties even as welded.

[Brief explanation of the drawing]

Figure 1.2 shows conventional EBW examples, Figure 1 is a filler wire method, Figure 2 is a schematic cross-sectional view showing the insert metal method, Figure 8 is a through-hole EBW joint, and Figure 4 is a shallow welding method. Fig. 5 is a schematic cross-sectional view of a deep-immersion EBW joint, and Fig. 6 shows the relationship between the distance from the plate surface of the EBW joint obtained by heating the filler metal, Charpy impact strength, and Ni content. Figure 7 is an explanatory diagram showing the location of sample collection of the test material, Figures 8 and 10 are graphs showing the results of a control experiment, and Figure 9 is a cross section showing the insertion method of filler metal in the control experiment. FIG. 11 is a graph showing the test results of the weld metal obtained by the present invention, and FIG. 12 is a broken sketch of the main part showing an example of insertion of filler metal. DESCRIPTION OF SYMBOLS 1... Base material, 2... Electron beam, 3... Melting Poonope 4... Filler wire, 5... Melting metal,
6...Groove. Fig. 1 Fig. 314 No. 41 So1 Ko:: Fig. 5 -' Fig. 2'1 1 ■ st I ・″Pe9′-3-・:5.; 99-;, 1 (/L,)
,+,1\

Claims (1)

[Claims] When applying the deep-penetration partial penetration electron beam welding method to the butt joints of thick steel plates, filler metal mainly composed of Ni is applied to the butt surfaces at different positions in the thickness direction of the plates. In addition to inserting multiple pieces in parallel, the filler metal is placed so that the weighted average density distribution of Ni in the filler metal as seen in the plate thickness direction is higher on the plate thickness surface side. A partial penetration electron beam welding method for thick copper plates.