JPH0334434B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for welding and manufacturing cylindrical continuous casting molds, melting crucible furnaces, etc. made of copper or copper alloy materials, and in particular, a method for producing high quality products with few defects in welded parts. The present invention relates to a butt welding method using copper or copper alloy as a base material, which can provide high quality and work efficiency. [Conventional technology] Continuous casting has been used for a long time in steel ingot making for the purpose of saving energy and improving yield, and the molds used for continuous casting are generally made of copper or copper alloys. However, in consideration of heat resistance and strength, copper alloys are often used. Molds for continuous casting are formed into a cylindrical shape, and molds with an inner dimension of about 150 mm or less are integrally molded by extrusion, but those larger than the above dimensions are made of copper or copper alloy plates using fasteners. The assembled mold is used. An example of a typical assembly mold is shown in FIG. 2 (cross-sectional view). On the other hand, in recent continuous casting equipment, electromagnetic stirring casting has been put into practical use with the aim of improving the quality of cast products, and molds are required to be smaller and lighter in order to improve stirring efficiency, resulting in large-scale structures. Increasingly, welded integral molds are being used instead of assembled molds. For example, a continuous casting mold is produced by integrating two or four divided copper or copper alloy molding materials by TIG welding or MIG welding. However, copper or copper alloy materials have extremely high thermal conductivity and high heat dissipation rate compared to steel materials, so it is very difficult to melt only the groove part of the base metal when welding. It's difficult. Moreover, since the solidification rate of the molten metal is fast, wetting of the molten metal is poor, and welding defects such as poor fusion and blowholes at the weld are likely to occur. Therefore, when TIG welding or MIG welding thick copper or copper alloy plates, it is generally necessary to preheat the entire weld base material to 300° C. or higher before welding. [Problems to be Solved by the Invention] When welding a copper or copper alloy plate material, which is a welding base material, while preheating it at a high temperature, the following problems occur. (1) Not only does it require a great deal of energy and labor, but it also reduces work efficiency. (2) Because the base metal is heated to a high temperature, the base metal, which had achieved high strength through cold working and heat treatment before welding, becomes annealed due to preheating, reducing the strength of the base metal. Put it away. (3) Furthermore, since the base metal is significantly deformed during cooling from the preheating temperature to room temperature, the amount of work such as cutting to correct deformation after welding is completed is significantly increased. In particular, when arc welding is performed on age-hardening copper alloys while preheating, both the base metal and the welded part are annealed, and in order to ensure strength, high-temperature heating and Solution treatment must be performed by rapid cooling in water. Therefore, rapid cooling causes large deformations in the product, and in order to ensure product quality, a lot of correction work such as cutting is required. Therefore, the present inventors have developed a method for welding an integral structure made of copper or copper alloy material, such as a continuous casting mold, without causing a decrease in strength or deformation of the weld base material, and without causing any defects. As a result of various research efforts aimed at establishing a welding method that can form a welded joint, the present invention has been completed. [Means for Solving the Problems] In order to solve the above problems, the gist of the present invention lies in specifying the material of the copper or copper alloy material and the welding method as described below. That is, electron beam welding is performed by using copper or copper alloy material whose hydrogen component content is limited to 5 ppm or less and oxygen component content to 100 ppm or less, and a backing material made of copper or copper alloy is brought into contact with the back side of the butt weld. There is a gist in the points. [Function] Electron beam welding is characterized by a much higher energy density than normal arc welding, and has high thermal conductivity like copper or copper alloys.
Deep penetration welding is possible in one pass without preheating even materials with a high heat dissipation rate. Furthermore, there is little heat influence from the welded part to the base metal, and softening and deformation of the base metal can be minimized. In addition, since copper and copper alloy base materials inherently have a fast heat dissipation rate, the weld and surrounding heat-affected zone are rapidly cooled, so that they do not undergo annealing softening, but instead undergo solution treatment. It has the same effect as that, and becomes a forced solid solution state. Furthermore, since the weld width during electron beam welding is very narrow and parallel, almost no angular deformation occurs during welding, and the amount of lateral shrinkage is extremely small at around 0.15 to 0.4 mm. Become. However, in electron beam welding, as mentioned above, the solidification rate of the molten metal is fast, so the bubbles generated in the molten metal cannot escape and remain in the welded area as blowholes. . A method for reducing the blowhole is to apply oscillation to the electron beam. Alternatively, methods such as slowing down the progress speed of electron beam welding and allowing the generated air bubbles to come out of the fusion zone can be considered, but there are limits to slowing down the progress speed of welding, and this is not sufficient as a measure to reduce blowholes. . Therefore, we focused on oxygen and hydrogen, which are gas components in the copper or copper alloy material that is the welding base material, and investigated the relationship between the amount of blowholes generated and the oxygen content and hydrogen content in the base material. As a result, we found the following. I discovered that.
In other words, as shown in Figure 1 (graph), in order to obtain a weld zone of grade 2 or higher (white circle) based on JIS Z3104, the oxygen content in the base metal must be 100 ppm or less and the hydrogen content must be 5 ppm or less. It turned out that it was necessary. However, when electron beam welding is performed by butting copper or copper alloy materials, there is a problem in that the welded part's back wave shape is prone to defects such as underfill and pits, making it difficult to obtain a good back wave shape. However, it has been found that defects such as underfill and pits can be avoided by placing a metal-based backing material on the groove and welding. That is, by using a backing material that is thick enough to prevent the electron beam from penetrating it, underfill and pits can be avoided. As the material for the backing material, it is preferable to use a matching material, considering that a part of the backing material may melt and mix into the welded part of the base metal. However, when attempting to improve the physical properties of the weld metal through mutual diffusion between the base metal alloy and the backing material alloy during welding, a copper alloy different from the base metal or blunt copper may be used as the backing material. . [Example] The mechanism of the electron beam welding machine is as shown in FIG.
The emitted electrons are accelerated by the anode 8 and focused by the focusing lens 10. These electrons collide with the object to be welded 12, and the object to be welded is heated to a high temperature by the collision energy and welded. Electron beam welding is performed using copper and copper alloy materials with different hydrogen and oxygen component contents, and JIS Z3104
Based on this, a radiographic test was conducted to determine the occurrence of blowholes in welds. The results are shown in Table 1, and Examples satisfying the hydrogen and oxygen component content conditions according to the present invention are Nos. 1, 2, 4, 7, 9, 11, 13, 14, 15 and 16, and these had welding performance equivalent to class 1 or 2 based on JIS Z3104. Note that Nos. 3, 5, 6, 8, 10, and 12 in Table 1 are comparative examples, which do not meet the hydrogen and oxygen component contents of the present invention, and the blowhole generation determination results are all grade 3. Or it was equivalent to grade 4.

[Table] Next, as shown in Figure 5a, the base materials 2 are butted together,
A backing material 3 made of copper or copper alloy was placed on the back side of the groove and electron beam welding was performed to obtain a welded part 13 as shown in FIG. 5b. In this case, since the electron beam does not penetrate to the front side, there is no need to provide a beam absorption plate on the back side of the groove, which is normally required in electron beam welding, and the work is simplified. However, the present invention is not limited to partial penetration welding in which the beam stops inside the backing material, and even when penetration welding in which the beam penetrates the backing material is adopted, a sound welded part without defects can be achieved. Obtainable. However, in any of the above cases, the welding base material and the backing material 3 are welded together, so the work of cutting and removing the backing material 3 is required after welding is completed. Next, Table 2 shows the results obtained to clarify how the material of the backing material affects the tensile strength of electron beam welded joints.

[Table] As a result, it is not necessarily the best material for the backing material to match the base metal, but it is better to use a Cu-Cr-Zr alloy as the backing material. The tensile strength of the welded part shows a slightly high value. In addition, when using a Cu-Cr-Zr alloy as the base material,
It is known that Zr has a negative effect on weld cracking, but it was also confirmed that by using pure copper as the backing material, the amount of Zr in the weld was reduced and weld cracking was reduced. Therefore, by using a backing material made of a material different from that of the base material, better results may be obtained than when using a matching material. One of the major characteristics of electron beam welding is that the bead width is narrower than that of arc welding, which requires strict groove precision, and if the groove has poor straightness, misalignment may occur. Also, if the gap in the groove is large, it may cause defects such as underfill and blowholes. When integrating a cylindrical continuous casting mold with a circular, square, or polygonal cross-sectional shape by electron beam welding, the best groove welding line can be obtained by dividing the mold into two vertically. However, if a mold is manufactured that requires only one seam welding, the material will spring back when the weld groove lines are aligned, making it difficult to keep the gap amount of the groove small. Further, if the parts are divided into three or more parts, the assembly work before welding becomes complicated, so in terms of both quality and work efficiency, it is most preferable to perform two-seam welding by dividing the parts into two parts as shown in FIG. 4, for example. The order of integrating by welding and producing a continuous casting mold etc. is to perform solution treatment in the state of the A plate, then form the plate into divided pieces, perform aging treatment, and integrate the divided pieces by welding. There is a method in which the B divided pieces are integrated and a post-aging treatment is performed. However, when welding is performed by arc welding for integration, the base metal is completely annealed due to the preheating of the base metal and the welding heat input, and the Vickers hardness of both the weld base metal and the welded part is As shown in Fig. 6b, it shows about 60 to 70 (load: 5 kg). This value does not change much even if the order of arc welding and aging treatment is reversed. On the other hand, Figure 6a
As shown in Figure 2, for products that have been welded with electron beams, if welding is performed after aging treatment, there is a small part at the center of the bead that has softened and the Vickers hardness has decreased, but the overall product The hardness shows a much better value than that of the arc welded one [Fig. 6b]. In this case, if a method of performing aging treatment after electron beam welding is adopted, the hardness of the bead center can also be improved. Table 3 shows copper alloy (Cu-0.6%Cr-0.15%Zr)
This figure shows the results of a joint tensile test of a welded part.

[Table] As is clear from this result, a higher level of welded joint strength can be obtained in both cases of aging treatment and electron beam welding and electron beam welding and aging treatment, compared to arc welding. be able to. [Effects of the invention] By using electron beam welding to integrate continuous casting molds made of copper or copper alloy, thermal deformation of the product can be minimized, and the base material can be easily removed by preheating etc. strength deterioration can be minimized. In addition, blowhole defects that tend to occur in welded parts can be reduced by limiting the gas component content in the base metal, and by using a copper or copper alloy backing material, good welding can be achieved. It was possible to secure the bead shape.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the occurrence of blowholes in welds and the content of oxygen and hydrogen components in the base metal, Figure 2 is a cross-sectional view showing an assembled mold for continuous casting, and Figure 3 is an electron beam An explanatory diagram showing the principle of the welding machine, Fig. 4 is an explanatory diagram showing an example of seam welding of a continuous casting mold, and Figs. 5 a and b show the shape of the welded part before and after electron beam welding using a backing material. A cross-sectional view, Figure 6a is a graph showing the hardness distribution when electron beam welding is performed, and Figure 6b is a graph showing the hardness distribution when electron beam welding is performed.
It is a graph showing hardness distribution when MIG welding is performed. 1... Welding base material, 1a... Assembly mold for continuous casting, 2... Welding base material, 3... Backing material, 4... Electron beam, 5... Copper plate, 6... Cooling jacket,
7... Cathode filament, 8... Anode, 9... Electron gun, 10... Focusing lens, 11... Vacuum chamber, 1
2... Work to be welded, 13... Welding part.

Claims (1)

[Claims] 1. In the method of welding and manufacturing cylindrical continuous casting molds or melting crucibles made of copper or copper alloy, the hydrogen component content is 5 ppm or less and the oxygen component content is
Cylindrical continuous casting made of copper or copper alloy, characterized by using a base metal with a concentration of less than 100 ppm, and electron beam welding with a backing material made of copper or copper alloy in contact with the back side of the butt weld. A welding manufacturing method for a mold or melting crucible furnace.