JPS59183990A - Electron beam welding method - Google Patents

Abstract

PURPOSE:To decrease accumulation of low melting impurities in a bead and to prevent welding crack in the stage of applying electron beam welding to a steel material of carbon steel, etc. by adding Ti into the weld metal. CONSTITUTION:Powder or granules 5 of Ti or Ti alloy are put into a groove 4 provided on the weld line 3 in the upper part of joint faces 1 of a steel material contg. >=0.2wt% carbon, and the Ti is melted by slight beam current. Prescribed penetration is thereafter performed by a normal current beam. If the regular current beam is irradiated without melting the Ti in this state, the Ti powder or granules 5 are scattered by the flow of the metallic vapor and the penetration of the Ti in the weld metal is not possible. There are a method of adding the Ti by using powder and granules, a method of welding perliminarily the Ti on the joint surfaces and a method of adding the same in the form of a filler wire as the method of adding the Ti.

Description

DETAILED DESCRIPTION OF THE INVENTION Specifically, the present invention relates to an electron beam welding method that prevents weld cracks that occur when steel materials such as low alloy steel and carbon steel are electron beam welded.

When low alloy steel, carbon steel, etc. are electron beam welded, weld cracks as shown in FIG. 1 are likely to occur.

These types of weld cracks can be roughly divided into solidification cracks a (see Figure 1 (a)) and cold cracks b (see Figure 1 (see side)).
The main cause common to both is the low melting point impurity C that accumulates in the center of the pead during the melting and solidification process. That is,
When the base metal contains a large amount of S, iron sulfide (I'tS) is produced, which forms a eutectic with a low melting point (988°C), gathers at the grain boundaries of steel, and prevents grains from adhering to each other. Therefore, if shrinkage tensile stress acts there, grain boundary cracks will occur (see Figure 1 (see #7l).Also, even if such solidification cracks occur, the central part of the bead where impurities have accumulated and the adhesion strength has decreased During cooling, hydrogen d (residual diffusible hydrogen) in the steel collects and reduces the adhesion force, causing cold cracking (first
(See figure (B)).

By the way, in electron beam welding, the penetration depth is generally larger than the surface bead width, and cooling is rapid.
Impurities tend to accumulate in the center of the bead. Furthermore, in order to prevent misalignment, it is desirable that the melting width inside the bead be large to some extent. Therefore, it is difficult to reduce the amount of low melting point impurities by reducing the amount of molten metal.

For these reasons, it has been difficult to apply electron beam welding to parts made of low-alloy steel or carbon steel, especially thick plates.

The present invention was made in view of the above circumstances, and its purpose is to prevent weld cracks that occur when electron beam welding steel materials such as low alloy steel and carbon steel, especially thick plate parts. That is, an object of the present invention is to provide an electron beam welding method that can perform satisfactory welding without the above-mentioned weld cracks.

By the way, as mentioned above, the cause of weld cracking is low melting point impurities that gather at the grain boundaries in the center of the bead. Therefore,
The problem can be solved by fixing S, which is a source of low melting point impurities, at a high temperature.

The inventors of the present invention have conducted intensive research from this viewpoint and have found that if Ti is added to the weld metal, T1 can be reduced to S.
It forms T15 because of its strong affinity with
The melting point of S is 2000°C, which is higher than the solidification temperature of steel, so it was discovered that S can be fixed at a high temperature and weld cracking could be prevented, leading to the completion of the present invention.

That is, the electron beam welding method according to the present invention has a carbon content of 0.
In addition to electron beam welding of steel materials such as low-alloy steels and carbon steels with a modulus of 2 or higher, it is special to carry out electron beam welding in the presence of 1゛i or T1 alloy in the welding area, and to add T1 to the weld metal. It's what you do with him.

Here, methods for adding T1 into the weld metal (solid solution) include a method in which 1"1 or T1 alloy powder is used to create a zero loading, a method in which it is thermally sprayed on the joint surface in advance, and a method in which T1 is added as a filler wire. There are various methods of adding Tif& to the weld metal.In addition, when using T1 alloy, there is a relationship between Tif& in the weld metal and bath weld cracking, as will be explained later. Enough amount of 7 inside
It is preferable to use a T1 alloy having a weight coefficient of 7'i of 50 or more so that 'i can be added.

Hereinafter, the effects of the present invention will be explained in detail by showing specific examples to which the electron beam welding method of the present invention is applied. In addition,
The method of adding T1 is basically the same whether it is added using a powder, sprayed on the joint surface in advance, or added as a filler, but the following examples are used to add T1. In this case, we used a method of adding powder.

Example Applying the electron beam welding method of the present invention (7 parts)
The cross-sectional shape of □ (HD+200 gear) is shown in Figure 2. H
D + 200 key 'rha SIVCM 7120 H
K material-T' was used, and in order to perform electron beam welding after carburizing, the joint surface 1 and upper surface 2 were treated with anti-carburization treatment and roughly cut into three corners.

On the other hand, a groove 4 as shown in FIG.
Put it in. The shape of the groove 4 is F x H = 2x 4
In addition, as addition T1, ferrotitanium TFT-1, which was a component shown in Table 1 below, was used.

Table 1 Chemical composition of addition T1 (weight 41) In such a condition, 15
After preheating to 0° C. (below the tempering temperature), electron beam welding was performed.

For comparison, electron beam welding was also carried out without providing any grooves and therefore without adding 11 grains, as shown in FIG.

Figure 5 shows a process diagram of the first suitable method of electron beam welding. However, the construction time is the value when a 25 V type electron beam welding device is used, and when using other types of equipment, the appropriate construction time may be set accordingly.

In addition, when performing electron beam welding by the T1 addition method according to the method of the present invention, 7゛1 grain 5 is placed in the groove 4 provided on the welding line 3 on the upper part of the joint surface 1, and the minute beam current is applied. After the Q Ti was melted (alloyed), the current beam was used to perform the specified penetration. If the main current beam is directly irradiated to increase the T1 melting force, the Ti powder will be scattered by the metal vapor flow coming out of the beam hole, making it impossible to melt 1゛1 into the weld metal. Therefore, T1
The beam conditions for pre-melting are superimposed.

The appropriate conditions for electron beam welding are shown below.

Electron beam welding conditions: However, the appropriate conditions for the above electron beam welding are 25nl'g.
This is the value for the 7-coupled beam using an electron beam welding device, and if other types of devices are used, appropriate conditions may be set accordingly.

The cycle time is 30 minutes/piece, but by performing steps 1 and B shown in Figure 5 in parallel, it can be reduced to 18 minutes/piece.
It is possible to shorten the number to .

FIG. 6 shows a photograph of a cross section of the welded part when electron beam welding was performed under the above conditions. Figure 6 shows the case of electron beam welding using the 11 additive method of the present invention; Figure 6 shows the case of electron beam welding without the T1 additive; Although a noticeable solidification crack occurs in the center (see Fig. 6), no crack occurs in the specimens that were electron beam welded using the T1 addition method.

In this way, during electron beam bath welding, T
By adding i, it becomes possible to form a sound cupid without weld cracks.

In addition, when we took and observed microscopic photographs of the weld metal parts with Ti addition and without T1 addition, we found that Tj,
In the case of no addition, it was observed that the developed granular crystals extended toward the center of the bead and collided with each other at the center of the bead. On the other hand, the material to which T1 was added had a fine structure, and no significant collision of granular crystals at the center of the bead was observed. From this, it can be concluded that in the Ti addition method, the solidification form of the weld metal part changes, and as a result, the accumulation of low melting point impurities in the bead center is reduced.

Additionally, FIG. 7 shows the results of an EPMA investigation of the distribution of Ti in the welded metal parts that were electron beam welded using the Ti addition method of the present invention. From FIG. 7, it can be seen that T1 is almost uniformly distributed.

As a result of the above, it can be said that the T1 addition method according to the present invention is very effective in preventing cracking, especially when electron beam welding is applied to thick carbon steel plates.

Next, we investigated the relationship between the T1 addition groove shape, 7"il, and the Ti @ content in the weld metal at that time. The results are shown in Table 2 below. Note that the groove shape 2C is The groove shape is chamfered as shown in FIG. 3. The groove shape of /162 to 7I is the shape shown in FIG. 3, and is shown in WxHQ size.

(Leaving space below) Table 2 - Relationship between groove shape and Ti content in weld metal) Welding material: SNCM 7I20H, material, disk fitting test %2 pieces, each 4 cross-sectional adjustment strain, component measurement; cant back by.

As is clear from the results shown in Table 2, in the case of groove shape 2c (chamfered t)), sufficient Ti melting is not performed, and T1ff1. is also small, O,l 5 'J.

At this time, some cracks were observed in the welded area. However, T
The effect of item 1 is recognized.

No cracks were observed in any case where the groove shape was 1X212X2.2X71. However, in the case of a 2×2 groove shape, the amount of Ti in the bath weld metal is somewhat small. Therefore, when welding with a bathing depth of 11 oyre, the T1 addition groove is 1×2
I like the shape of 2X/I.

[Brief explanation of the drawing]

(4 and () in Figure 1 are schematic explanatory diagrams of weld cracks,
Figure 1 (4 shows the case of solidification cracking, Figure 1 (Kalpa) shows the case of cold cracking, Figure 2 is a cross-sectional view of a part to which electron beam bath welding was applied in an example, and Figure 3 shows the case of the method of the present invention. Ti when applied
Figure 4 is an enlarged cross-sectional view of the electron beam irradiation part (X section in Figure 2) showing the additive groove shape. The figure is a process diagram of the appropriate construction method of the electron beam welding method of the present invention, No. 6
In the figure, (A and () are cross-sectional photographs of the metal structure of the welded part when electron beam welding is performed. Fig. 7 is a graph showing the distribution of Ti in the weld metal part welded by the simulator beam welding by the method of the present invention. This is an enlarged cross-sectional view. 1 is a joint, 3 is a weld line, 4 is a groove, and 5 is 11 grains. A) ×XpeX-Toki (11)

Claims (1)

[Scope of Claims] 1. Electron beam welding of steel materials with a carbon content of 02 or more is carried out with T1 or a Ti alloy present in the welding area, and T1 is added to the weld metal. Welding method. 2. Claims characterized in that a groove is provided on the weld line at the upper part of the joint surface, 7'i grains are placed in the groove and T1 melted, and then Ti- is added to the weld metal by electron beam welding. The electron beam welding method according to item 1. 3 Ti is applied to the joint surface by thermal spraying of Ti-$ or T1 alloy.
After adhering, electron beam welding is performed to form a 1”1
The electron beam welding method according to claim 1, characterized in that: is added. 4. The electron beam welding method according to claim 1, wherein Ti is added to the weld metal during electron beam welding using a filler wire made of Ti or T1 alloy.