JPS61222691A - Manufacture of zirconium clad material - Google Patents

Abstract

PURPOSE:To make a joining strength sufficient with preventing the formation of embrittled layer at a joining part by making a base metal and zirconium group clad material in a laminated body with overlapping by providing a gap between them so as not to come into contact directly and by subjecting to hot rolling after reducing the pressure of the gap to be vacuum eta1torr. CONSTITUTION:The clad material 2 having smaller size than that of base metal 1 is placed on it by pinching supporting rod 3, then side face frame material 4 is placed along the edge part of the four sides of the base metal 1 and the clad material 2 is surrounded by placing upper face frame piece 5 thereon further. The base metal 1, side face frame material 4 and upper face frame material 5 are then tack-welded and hermetically sealed by electron beam welding inside the vacuum chamber reduced to <=1torr. This tack-welded assembly material is taken out of the vacuum chamber to subject the tack-welded part to main welding and this assembly material is inputted into heating furnace as it is and after heating to the prescribed temp. the whole assembly material with frame materials is subjected to hot rolling by the specified rolling schedule and after removing the frame material after rolling the part to pinch the supporting rod 3 of both ends is cut.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a method in which steel such as ordinary steel, low alloy steel, stainless steel, or a nickel-based alloy is used as a base material, and pure zirconium or a zirconium alloy is used as a bonding material. The present invention relates to a method for manufacturing a zirconium-based cladding material.

(Prior Art) Pure zirconium and zirconium alloys such as zircaloy (hereinafter collectively referred to as zirconium-based materials) have excellent corrosion resistance and an extremely small thermal neutron absorption cross section, so they are used as nuclear reactor materials, especially light water reactors. It has been mainly used for fuel cladding. Recently, attention has been paid to the excellent corrosion resistance of zirconium, and although zirconium-based materials are relatively expensive, their use in other applications such as the electronic industry and medical equipment materials has begun to be considered.

However, because it is difficult to weld with general-purpose materials such as ordinary steel, highly corrosion-resistant stainless steel, or nickel-based alloys such as Inconel, the field of application of zirconium-based materials is extremely limited.

The reason why this welding is difficult is that direct fusion welding of dissimilar metals generally produces a very brittle alloy layer on the joint surface, and Zr and Fe or Zr and Ni are no exception. One example is the lack of contact materials.

Diffusion welding is one of the welding techniques developed to join dissimilar metals that are difficult to weld directly, such as iron and zirconium. This is done by bringing the materials to be welded into close contact, either directly or with an insert between them, and then heating the materials to a temperature below the solidus line under light pressure that does not cause deformation, usually in a vacuum or inert atmosphere. It is a joining method that causes metal to diffuse into the mating material at the joint surface by heating, and even high-melting point metals are welded at a very low temperature (usually about half the melting point of the metal). Therefore, there is extremely little deterioration such as embrittlement at the joint surface.
In addition, due to diffusion, the joint becomes homogenized with the base metal and the joint itself disappears, so the joint strength is extremely high. Diffusion welding is not limited to welding between dissimilar metals, but direct fusion welding Attempts have also been made to use it for welding similar metals that are difficult to weld, such as tungsten and molybdenum, which have extremely high melting points (and which are susceptible to embrittlement due to recrystallization).

Examples of diffusion welding for zirconium-based materials include joining Zircaloys of the same type with steel as an insert material, as well as joining Zircaloys and austenitic stainless steel II (SUS302) materials without intervening inserts. In this method, Zircaloy and stainless steel are directly brought into close contact with each other and heated to a temperature of approximately 1020'C, so that 2"
The formation of a brittle alloy layer of Fe and Fe is unavoidable, and even by diffusion welding, it has not been possible to weld zirconium-based materials to dissimilar metals such as steel with sufficient bonding strength.

(Problems to be Solved by the Invention) In welding between different materials such as iron-based materials such as steel and zirconium-based materials, as shown in Fig. (In other words, if there is a crund steel plate made of the same type of steel and zirconium material), this can be used as a joint in the figure, and the same type of materials can be welded without causing embrittlement of the joint surface.

Clad steel plates made of high-melting-point metals such as zirconium are made by hot-rolling the base steel and the laminate, placing explosives on a rolling clamp, and using the explosive force to join them together. It is most commonly manufactured using the cladding method.

However, when hot-rolling zirconium or zirconium alloy and steel such as ordinary steel, low-alloy steel, or stainless steel, the dissimilar metals are heated and the joint contains brittle intermetallic compounds, as described above. It is difficult to obtain a joint with sufficient strength due to the formation of an alloy layer.

Furthermore, since both zirconium and zirconium alloys have a strong affinity for oxygen, nitrogen, etc., when heated to high temperatures, they absorb atmospheric air and become brittle. Because of these problems, a method for manufacturing clad steel plates using zirconium-based materials as a laminated material by rolling has not yet been established. On the other hand, in the explosive bonding cladding method, we have described the case where the base material is steel, but the situation is exactly the same when the base material is nickel-based alloy, and for the same reason, nickel-based alloy There is no satisfactory method for manufacturing crund material from a base material and a composite material of zirconium-based material.

However, since zirconium has extremely good corrosion resistance,
If a method for manufacturing cladding materials of steel or nickel-based alloys and zirconium-based materials is established, it will be possible to weld zirconium-based materials to steel or nickel-based alloys, promoting the use of zirconium-based materials in various fields. It is expected that this will be done.

(Means for Solving the Problems) The present inventors have studied to develop a rolling cladding method that minimizes the formation of brittle phases caused by using zirconium-based materials as laminated materials. By keeping the base material and composite material from coming into contact with each other during heating, substantially blocking the atmosphere, and controlling the rolling schedule, the formation of brittle phases at the joint is prevented and sufficient joint strength is achieved. The present invention was achieved based on the knowledge that a zirconium-based cladding material having the following properties can be manufactured.

Here, the present invention provides a laminate by laminating a base material made of steel or a nickel-based alloy and a laminated material made of pure zirconium or a zirconium alloy with a gap therebetween,
After heating the laminate to a temperature higher than the eutectic temperature of the base matrix metal and zirconium while maintaining the void in a vacuum with a pressure of 1 torr or less, 5 to 60% of the laminate is rolled to the eutectic temperature. The above is a method for producing a zirconium-based crund material, characterized in that the remaining rolling is performed at a temperature lower than the eutectic temperature to join the base material and the laminated material by hot rolling.

(Operation) Hereinafter, the present invention will be disclosed in detail with reference to the accompanying drawings.

The cladding material manufactured by the method of the present invention has a nickel-based alloy as the steel base material, and a bonding material of pure zirconium or a zirconium alloy. In this specification, "steel" includes not only ordinary steel but also alloy steel. Furthermore, the base material of the cladding material generally refers to the cheaper material, and therefore the laminated material is not necessarily thinner.

According to the knowledge obtained by the present inventors, the total amount of one or both of Fe and Ni is 5J1! When a metal material containing % or more is brought into close contact with a zirconium-based material and heated to a high temperature,
An alloy layer of Fe and Zr or Ni and Zr is formed, and the joint surface becomes brittle. Therefore, the method of the present invention can be applied not only to cases where the base material is steel or nickel-based alloy, but also to the production of zirconium-based cladding materials using a total of five materials of one or more of Fe and Ni. I can do it.

Particularly suitable steels for the base material are ordinary steel, low alloy steel, and austenitic stainless steel from the viewpoint of hot workability and usefulness as clad steel, and heat-resistant steels containing Cr and Mo can also be used as the base material. .

Examples of nickel-based alloys suitable as the base material include Inconel (8ONi-14Cr-6Fe), Incoloy, and Hastelloy.

The bonding material is pure zirconium or a zirconium alloy, and currently available zirconium alloys include Zircaloy-2 (1,55n-0,12Fe-0, lCr-0).
,05Ni) and Zircaloy-4 (1,55n-0°18Fe-0,ICr), Zircaloy has improved corrosion resistance in high temperature water and nitrogen-containing atmospheres compared to pure zirconium. Note that the zirconium alloy is not limited to zircaloy, and other zirconium alloys can also be used in the present invention.

The zirconium alloy preferably contains 50% or more of Zr.

The types of base material and bonding material are appropriately selected depending on the application. For example, when the cladding material is used as a joint, it is advantageous to select a base material and a mating material of the same type as the material to be welded.

According to the method of the present invention, the base material and the zirconium-based laminated material are stacked with a gap between them so as not to come into direct contact to form a laminate, and the pressure in the gap is reduced to a vacuum of 1 Torr or less. The reason why the base material and the composite material are separated is that if they come into direct contact, even if they are kept in a vacuum to eliminate the influence of the atmosphere, the fragile Zr and Fe will be scraped by a eutectic reaction during heating before rolling. Furthermore, since an alloy layer of Zr and N1 is formed, this is to prevent the formation of such an alloy layer.

For this purpose, it is preferable that the gap between the voids is 0.5n or more.If the gap is too large, it may cause problems during subsequent rolling, so the gap between the voids is usually less than lotm. shall be.

Maintaining the voids at a high degree of vacuum with a pressure of 1 Torr or less prevents Zr in the laminated material from absorbing the atmosphere at the interface and reacting with the atmosphere, especially nitrogen, and becoming brittle when the laminate is heated to high temperatures. This is to do so. In a high temperature environment, Zr is, for example, 40 p
Since it is filled with extremely small amounts of nitrogen such as p-, it is necessary to remove the atmosphere from the high vacuum. When the pressure exceeds 1 Torr, the above-mentioned weakening becomes significant and the bonding strength of the resulting cladding material decreases. For this purpose, the higher the degree of vacuum (that is, the lower the pressure), the more desirable it is, and in fact, even in a high vacuum of 1 torr or less, there is a tendency for the bonding strength to increase somewhat as the degree of vacuum increases. However, the increase is small, and on the other hand, the higher the degree of vacuum, the higher the cost.
The pressure in the cavity may be selected within a range of 1 Torr or less in consideration of economic efficiency.

Next, the laminate is heated for hot rolling while maintaining the high degree of vacuum in the gap. In order to produce a gland material with sufficient bonding strength, it is necessary to create a metallic bond between the base material and the composite material at the interface during rolling. It is heated to a temperature above the crystallization temperature to ensure the formation of metallic bonds at the interface during rolling. Note that the eutectic temperature is Zr
-Fe is 960°C and Zr-Ni is 946°C, so
In general, the heating temperature before rolling will be in the range of 1000 to 1300°C, preferably 1050 to 1250°C.The appropriate heating time to above the eutectic temperature is about 1 hour per 25III11 of the total plate thickness. The laminate is then hot-rolled to a desired thickness to bond the base material and the laminated material to obtain a clad material. Total rolling (=
The remaining rolling is carried out at a temperature lower than the eutectic temperature.Rolling above the eutectic temperature is limited to a certain extent in order to form the metallic bond necessary for joining at the joint interface. is necessary, but when rolling is performed at a temperature higher than the eutectic temperature, the alloy layer formed at the interface becomes thicker, which weakens the interface and causes a decrease in bonding strength. As a result, rolling performed above the eutectic temperature resulted in a total reduction of 5.
It has been found that sufficient bonding strength can be obtained at the interface when the ratio is within the range of ~60%. If rolling at a temperature above the eutectic temperature is less than 5% of the total reduction rate, the metal bond necessary for bonding will not be sufficiently formed, and if it exceeds 60%, the thickness of the brittle alloy layer will increase, resulting in failure of bonding. This causes a decrease in strength. The rolling at a temperature higher than the eutectic temperature is preferably performed at a total reduction rate of 10 to 50.
%.

In order to provide sufficient joint strength to the clad material manufactured by hot rolling, the total reduction rate during rolling must be at least 70
% is preferable.

According to the present invention, it is possible to manufacture a zirconium-based cladding material in which a base material containing one or more of Fe and Ni and a Zr-based composite material are bonded with sufficient strength by the method described above. As mentioned above, the obtained clad material is useful as a joint for welding steel or nickel-based alloys with zirconium-based materials (see Figure 1), and this joint allows zirconium-based materials to be used as general-purpose structural materials. It is now possible to weld ordinary steel, stainless steel, or nickel-based alloys, contributing to the expansion of applications for zirconium-based materials. Note that welding of the same type of zirconium-based materials can be performed by TIG welding, electron beam welding, or the like.

The clad steel obtained by the method of the present invention can be used not only for joints but also for
Clad steel can be used for its original purpose, for example, as a highly corrosion-resistant structural material with zirconium on the side facing severe corrosive environments and steel on the other side to ensure strength. As an example, if a tank for a highly corrosive liquid such as nitric acid is manufactured from clad steel so that the inner surface is made of Zr, a tank with high corrosion resistance can be manufactured at a relatively low cost.

One example of a specific implementation means of the method of the present invention described above is shown in the second example.
This will be explained using figures.

A base material 1 of an appropriate thickness and a mating material 2 of an appropriate thickness, which is one size smaller than the base material, are prepared, and placed in a vacuum chamber for electron beam welding that is depressurized to a predetermined degree of vacuum of 1 torr or less. , As shown in the figure, the laminate is placed in the center of the base material with support rods 3 sandwiched between both ends of the laminate. The support rod 3 is
The material is used to separate the base material and the laminate material, and a material with a thickness that creates a gap of the desired size is selected.

The material of the support rod may be a material that does not react eutectically with the materials of the base material and the mating material, such as tungsten. Next, as shown in the figure, side frame members 4 are attached along the edges of the four sides of the base material. Then, the top frame material 5 is placed on the side frame material 4 to surround the laminated material. For example, the frame material is 5S4
It can be manufactured from 1 steel or 5 US 304 stainless steel, and preferably has a fairly strong structure considering scale loss.

Instead of performing assembly in a vacuum chamber with reduced pressure from the beginning, it may be assembled externally and transferred to a vacuum chamber after assembly to reduce pressure, or it may be assembled in a vacuum chamber before reducing pressure and then reduced in pressure.

Next, in a depressurized vacuum chamber, as shown in the figure, the contact areas between the base material and the side frame material and the contact areas between the side frame material and the top frame material are temporarily attached from the outside by electron beam welding, and the frame is assembled. The container consisting of wood and base material is sealed. As a result, the gap between the base material and the laminated material and the space surrounding the laminated material are isolated from the outside, and a high degree of vacuum inside the material can be maintained regardless of the ambient pressure.

The tacked assembly is removed from the vacuum chamber, and the tacked electron beam welded parts are welded using, for example, shielded arc welding, MIG, T
Main welding is performed by IG welding, etc., and the welded part is strengthened so that the internal vacuum can be maintained during heating.

Next, this assembled material is put into a normal heating furnace as it is,
After heating to a predetermined temperature, the entire assembled material including the frame material is hot rolled according to the rolling schedule according to the present invention.

The frame material is removed after rolling, but if there is scale etc. attached to the surface of the frame material plate, it is difficult for the clean surface to come into direct contact with the frame material, which prevents the frame material from joining with the base material and laminated material during rolling. can be removed. Thereafter, by cutting and removing the portions that sandwich the support rods at both ends, the desired cladding material can be obtained.

Those skilled in the art will understand that the specific method described above is merely an example, and that the present invention can be practiced in other ways.

Next, the production of the cladding material according to the present invention will be specifically explained using examples.

(Example) As shown in Table 1 below, mild steel (SS41), austenitic stainless steel (StlS310), and nickel-based alloy (Inconel 625) were used as the base materials, and pure zirconium (AsTM clay) was used as the bonding material. 12607
02) and a zirconium alloy (Zircaloy-2), cladding materials were produced by a rolling method under various conditions as described below. Note that the crund material using Zircaloy as the laminating material was manufactured only when the base material was austenitic stainless steel.

The dimensions of the materials used in Table 1 are as follows: The base material is 50 mm thick x 200 mm wide.
i x length 300 m, thickness of mating material 35 x width 140 m
It was mx length 240 cranes. Using this base material and mating material, the assembly material with the configuration shown in Figure 2 was manufactured.
The process was carried out in a vacuum chamber for electron beam welding, which was initially reduced to various predetermined pressures within the range of 0.01 to 200 Torr, and a tungsten rod with a diameter of 3.2 m * 8- was used as a support rod. The gap between the base material and the laminated material was maintained at 2 mm. The same material as the base material with a thickness of 28-1 was used for the frame material. For comparison, we also produced an assembled material in which the base material and the laminate were in direct contact without sandwiching the tungsten rod.

The assembled materials that have been temporarily attached by electron beam welding are taken out of the vacuum chamber, and after main welding is performed by shielded arc welding,
The material was placed in a heating furnace and heated in the furnace to a maximum temperature of 1200°C for 180 minutes, and the rolling schedule was changed as described later and hot rolled at a reduction rate of 75% to remove the frame material and the support rods at both ends. The material was cut to obtain a 20-inch thick kraft material.

For comparison, the heating temperature was 1000℃ and 900℃.
Experiments were also conducted at 800°C.

Hot rolling is rolling from a starting temperature of 1050°C (960°C
The process was divided into two stages: 1st stage rolling) and rolling from a starting temperature of 900°C (2nd stage rolling).

As mentioned above, the eutectic temperature is 960°C for Zr-Fe, and
-Ni is 946°C, so even if the base material is steel or a nickel-based alloy, the first stage rolling will be at a temperature above the eutectic temperature, and the second stage rolling will be at a temperature below the eutectic temperature. This results in rolling. Hot rolling was carried out by changing the ratio of rolling performed in the first stage rolling and the second stage rolling. For comparison, 100% rolling was performed within the range of 1050°C to 960°C (
Figure 3 shows a typical hot rolling schedule in which the cladding material was produced by carrying out the hot rolling at a temperature (above the eutectic temperature) or below 900°C (below the eutectic temperature). In Fig. 3, A is within the scope of the present invention. B is outside the scope of the present invention. Further, 960°C is the eutectic temperature of Zr-Fe.

The shear strength of the obtained cladding material at the bonding interface when the base material and the composite material are peeled in the equilibrium direction is measured in accordance with the shear strength test method specified in JIS G 0601,
The bonding strength was evaluated. The results are summarized and shown in graphs in FIGS. 4 to 6.

FIG. 4 is a graph showing the influence of the degree of vacuum in the gap between the base material and the bonding material on the bonding strength.

The maximum heating temperature before hot rolling is 1200°C, and the rolling schedule is A in Figure 3 (i.e., 3 times above the eutectic temperature).
0%, and the remaining 70% rolled below the eutectic temperature).As is clear from this graph, when a gap is provided between the base material and the composite material, a high degree of vacuum with a pressure of 1 Torr or less is achieved. So,
Although an excellent interfacial shear strength of around 20 kgf/m can be obtained with any material, the shear strength rapidly decreases when the pressure exceeds 1 Torr, and the bonding strength is almost It becomes zero. On the other hand, when the base material and the plying material were brought into close contact with each other without creating any voids, the bonding strength improved significantly even if the degree of vacuum was increased to 1 Torr or more (not observed).
It remains as zero. Therefore, it can be seen that both the conditions of spacing the base material and the bonding material and maintaining a high degree of vacuum are essential to ensure sufficient bonding strength.

FIG. 5 is a graph showing the relationship between the maximum heating temperature in the furnace before rolling and the interfacial shear strength when heated and hot rolled at a pressure of 0.1 torr. The rolling schedule is line A in Figure 3 when the heating temperature is 1200°C, and when the heating temperature is 1000°C, 20% of the total rolling is at 960°C or higher and the rest is rolling at 900°C or lower. When the heating temperature was 900° C. or lower, 100% rolling was performed from that temperature. When a gap is provided between the base material and the mating material, the bonding strength is almost zero if the heating temperature is lower than the eutectic temperature, but the bonding strength is approximately 20 k if the heating temperature exceeds the eutectic temperature.
It can be seen that the temperature rises rapidly to gf/m& or higher, and that heating to the eutectic temperature or higher is necessary for bonding. On the other hand,
If they are brought into close contact, the bonding strength will remain almost zero even if heated above the eutectic temperature, and if they are brought into close contact, a fragile alloy layer will form thickly and no bond will be obtained in practice.However, here Values marked as zero include those where the bonding interface was peeled off due to machining during the fabrication of the shear test piece of the cladding material.

Figure 6 is a graph showing the influence of the ratio of rolling at temperatures above and below the eutectic temperature on the interfacial shear strength when the degree of vacuum during heating and rolling is 0.1. The lower horizontal axis is the rolling temperature above the eutectic temperature (1050 to 9 in the first stage).
As this graph shows, the upper horizontal axis shows the ratio of rolling below the eutectic temperature (rolling from 900°C in the second stage). If the rolling rate is within the range of 5 to 60%, the bonding strength will be significantly improved when the base material and the composite material are spaced apart, and if it is outside this range, sufficient bonding strength will not be obtained. In particular, if the ratio of rolling above the eutectic temperature is 0% or exceeds 80%, the bonding strength will be 0 or will vary greatly, and if this ratio is 10 to 50%, the joint strength will be 15kgf/
+a! This is in contrast to the above-mentioned interfacial shear strength obtained. On the other hand, in the case of a close arrangement, even if the ratio of rolling above the eutectic temperature is limited to 5 to 60%, the bonding strength remains almost zero, and it is difficult to achieve bonding depending on the close arrangement. Can not.

(Effects of the Invention) As can be understood from the above description, the present invention enables a base material made of a metal material containing 5% or more of Fe or Ni, such as steel or a nickel-based alloy, and pure zirconium or a zirconium alloy. A method for manufacturing a zirconium-based cladding material with sufficient bonding strength at the interface has been established from a laminated material of

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram showing the weldability of a cladding material made of iron-based material and zirconium-based material as a joint, and Fig. 2 shows the structure of the assembled material used for manufacturing the cladding material by the method of the present invention. 3 is a diagram showing an example of a rolling schedule, FIG. 4 is a graph showing the influence of the degree of vacuum in the gap between base material and mating material on joint strength, and FIG. 5 is a diagram showing an example of a rolling schedule. FIG. 6 is a graph showing the influence of the maximum heating temperature in the previous furnace on the bonding strength, and FIG. 6 is a graph showing changes in the bonding strength due to variations in the rolling ratio above the eutectic temperature. 1: Base material 2: Laminating material 3: Support rod 4.5: Frame material Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Akira Hirose - Figure 1 Clad material Figure 2 1 tha drunken procedure Amendment dated October 30, 1985 Michibe Uga, Commissioner of the Patent Office, 1985 Patent Application No. 064161 2, Title of invention: Process for manufacturing zirconium-based cladding material 3, Person making the amendment Relationship with the case Patent applicant Address 5-15 Kitahama, Higashi-ku, Osaka Name (211) Sumitomo Metal Industries Co., Ltd. 4, Agent (attached sheet) (1) R after "Inconel" on page 2 of the specification, line 155 (Inco's product name) (2) Add "(Inco's product name) 1" after "Incoloy" on the 9th line of the same page, and after "Hastelloy" on the 9th to 10th lines of the same page. “(Cabot product name)
join. (3) rsUs 310 J in Table 1 on page 15, line 9 and page 16 of the same page is rSUS.
Corrected to 310SJ. (4) Figures 4, 5, and 6 are corrected as indicated in red on the attached drawing copy.

Claims (2)

[Claims] (1) A base material made of steel or nickel-based alloy and a mating material made of pure zirconium or zirconium alloy,
A laminate is formed by stacking the laminate with a gap between them, and the laminate is heated to a temperature equal to or higher than the eutectic temperature of the base matrix metal and zirconium while maintaining the gap in a vacuum with a pressure of 1 torr or less. The body is hot-rolled so that 5 to 60% of the rolling occurs at a temperature above the eutectic temperature and the remaining rolling occurs at a temperature below the eutectic temperature, thereby bonding the base material and the laminate. , a method for producing zirconium-based cladding material. (2) The method according to claim 1, wherein the base material is ordinary steel, low alloy steel, austenitic stainless steel, or nickel-based alloy.