JPH0471635B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a titanium-based metal clad steel and a method for producing the same. In particular, the present invention relates to a rolled titanium-based metal clad steel using a low carbon steel plate and a nickel plate as insert materials, and a method for manufacturing the same. (Prior art) Clad materials made by joining dissimilar materials, especially clad steel that uses steel plates as the base material, have been gaining popularity in recent years because they can take advantage of the characteristics of the materials of the composite material and the base material. Clad steel, which is made from titanium as a laminated material, is expanding, and in particular, the drawbacks of titanium materials are compensated for by steel plates, and its practical use is progressing.
It has important significance in promoting generalization. Today, clad steel made of titanium material is
Manufactured by explosion bonding method and rolling method using low carbon steel plate (containing pure iron material) as insert material. However, in the explosion bonding method, there is a limit to the size of the assembled slab, and the product size is small. Furthermore, due to poor dimensional accuracy, there are drawbacks such as lack of uniformity in the cladding layer. Furthermore, the bonding strength decreased significantly due to SR (post heat treatment), and the bonding strength was not yet fully satisfactory. On the other hand, in the rolling method using a low carbon steel plate as the insert material, the diffusion rate of C in Fe is high, so C in the base steel plate reaches the Ti interface through the insert material and TiC is generated. Even if the thickness of the insert material is increased, C in the base steel plate will easily diffuse through the grain boundaries. In particular, when the SR treatment is applied after the thickness of the clad steel is reduced by hot rolling, the diffusion becomes easy. Since TiC produced in this way is extremely hard and brittle, it is inevitable that the strength of the clad steel obtained in this way will deteriorate. (Problems to be Solved by the Invention) As described above, the precipitation of TiC leads to a decrease in bonding strength, so its formation must be prevented as much as possible. For example, assembling large slabs and heating them at high temperatures.
When manufacturing clad steel sheets by rolling, it is known that if medium- and high-carbon Ti steels are directly rolled together without an insert material, TiC will precipitate at the Ti/base steel interface and the joint strength will be significantly inferior. Therefore, as mentioned above, in order to suppress the formation of TiC, low carbon steel or pure iron is inserted at the Ti/base steel interface. However, when manufacturing clad steel sheets by heating and rolling to high temperatures, even if insert materials are used, the carbon contained in the base steel sheet will diffuse through these insert materials to the Ti interface, resulting in a decrease in joint strength. This will cause TiC to precipitate. This tendency is greater as the thickness of the insert material is thinner and the heating temperature is higher.
In particular, recently, clad steel has become thinner and processed in large quantities, and rolling at high temperatures has become necessary to increase the amount of reduction in order to increase productivity. In recent years, the generation of TiC as mentioned above has become an important issue. Thus, an object of the present invention is to provide a method for manufacturing clad steel that does not cause the problem of TiC formation despite thinning of the insert material and high rolling temperature. (Means for Solving the Problems) The present inventors have conducted various studies to achieve this objective, and have found that the insert material is a combination of a low carbon steel plate, including a pure iron plate, and a nickel plate. was found to be effective. In other words, brittle intermetallic compounds and TiC are present on the laminate side.
By using a low-carbon steel sheet that generates less carbon and creates an appropriate interdiffusion layer, and using a Ni plate as an insert material between the low-carbon steel sheet and the base steel to retard carbon diffusion, it is possible to improve the rolling process. The present invention was completed based on the knowledge that it is possible to produce a clad steel sheet with excellent bonding strength and which can effectively prevent TiC precipitation even when post-heat treatment is applied. Therefore, the gist of the present invention is to provide a bonded material made of titanium metal, a low carbon steel plate with a carbon content of 0.01% by weight or less bonded to the bonded material, and a nickel bonded to the low carbon steel plate. This is a titanium-based metal clad steel made of a plate and a base steel plate joined to the nickel plate. In addition, from another aspect, the present invention provides a method for manufacturing clad steel by laminating a titanium-based metal laminate and a base steel plate and hot rolling, in which carbon content is added to the laminate side between the two members. A low carbon steel plate with a carbon content of 0.01% by weight or less is further used as a cladding material by interposing a nickel plate on the base steel plate side, and the cladding material is sealed to prevent oxygen from being supplied to the joint surface between these parts. After welding, at least the joint surface between the titanium-based metal laminate and the low carbon steel plate is
This is a method for manufacturing clad steel with titanium-based metals, which is characterized by performing deaeration treatment to a vacuum of 10 ^-1 Torr or less, and then rolling it with rolls at a rolling start temperature of 500°C or higher and 1050°C or lower. “Titanium-based metals” include pure titanium and titanium-based alloys, and include “carbon content of 0.01
% by weight or less of low carbon steel sheet" also includes pure iron. That is, according to the present invention, in order to bond the laminate and the base steel plate with high bonding strength, it is important to cause mutual diffusion of Ti and Fe without precipitating TiC at the interface, and furthermore, it is important to cause mutual diffusion of Ti and Fe without precipitating TiC at the interface. This is based on the knowledge that SR treatment of materials further promotes the precipitation of TiC and reduces joint strength.To solve this problem, it is important not to supply C to the interface with Ti, so A low carbon steel plate is used as the insert material, and a Ni plate with a small diffusion coefficient of C is used as the insert material on the base steel plate side, and an oxidized layer is formed on the surfaces of the laminate, the base steel plate, and the insert material during heating before rolling. Since mutual diffusion of Ti and Fe does not occur, vacuum degassing is performed prior to heating to prevent the formation of such an oxide layer. Here, the required thickness of the Ni insert plate may be changed as appropriate depending on the heating temperature and time, and the thickness of the low carbon steel (and pure iron) insert material. Prior to rolling, the clad material is heated to a predetermined temperature, and as mentioned above, during this heating, when oxygen is supplied to these bonding interfaces, a surface oxidation layer is generated, which is the basis of solid phase bonding. Interdiffusion of elements will not occur. In order to prevent this, in the present invention, it is preferable to perform seal welding on the clad material prior to heating and perform deaeration treatment to a temperature of 10 ^-1 Torr or less. Since the melting temperature of the intermetallic compound formed at the Ti/Fe interface is 1085°C, the upper limit of the heating temperature at this time was set to 1050°C. In order to suppress the diffusion of C from the base steel SS41 steel plate, it is more effective to increase the thickness of the low carbon steel insert material, but if the thickness exceeds 2 mm, the strength of the insert in the shear test will decrease. This is not preferable because it indicates the shear strength of the material itself. (Operation) Next, the present invention will be described in further detail with reference to the accompanying drawings. FIG. 1 is a perspective view of a cladding material seen in the manufacturing process of a titanium-based metal clad steel plate according to the present invention. Even in the final clad steel, the clad structure itself is the same, so to explain with reference to FIG. 1, a nickel plate 2, which is an insert material, is provided on a base steel plate 1. Furthermore, a low carbon steel plate 3, which is another insert material, is provided. A titanium plate, which is a cladding material, is clad with this low carbon steel plate 3 interposed therebetween. There is no particular limit to the thickness of each plate material, but preferably,
The total thickness of the insert material as the final material is preferably about 0.1 to 10%, usually about 0.5 to 3.0%, of the total thickness of the combined steel plates. Next, the method for producing clad steel according to the present invention will be described. First, a base steel plate, a titanium material as a cladding material, a nickel plate and a low carbon steel plate as insert materials are prepared. It is preferable that each surface to be joined be made as clean as possible through a process such as degreasing. (1) Assembly: As shown in Fig. 1, each material, steel plate 1, nickel plate 2, low carbon steel plate 3, and titanium plate 4, are laminated, and the sizes of each insert material and titanium plate are adjusted to the base steel plate. By making the material slightly smaller, each material on the base material is covered with a cover 5 made of another low carbon steel plate, and each seam 6 is welded and sealed to form a clad material 7.
The insert material shall be low carbon steel on the mating material (titanium or titanium alloy) side and Ni plate on the base steel plate side. In FIG. 1, a suction port 8 for degassing is provided in a part of the steel plate 1. (2) Deaeration: After obtaining the clad material 7, the inside is deaerated through the suction port 8 using a rotary pump, etc., and the temperature is reduced to 10 ^-1 Torr.
The degree of vacuum shall be as follows. At this time, the vacuum degassing treatment is performed at least on the joint surfaces of the insert materials. In the degassing process, high vacuum can be achieved more easily by degassing while heating. When a predetermined amount of degassing is completed, the suction port 8 is shut off by appropriate means such as cutting it by melting. (3) Rolling: The heating temperature is below 1050℃ and above 500℃.
Preferably, a temperature of 700 to 900°C is sufficient. If rolling is finished at too low a temperature, deformation resistance will increase due to work hardening and martensitic transformation.
A finishing temperature of 0.degree. C. or higher is preferred. Thus, in the clad steel produced according to the present invention, virtually no TiC formation was observed, and no decrease in strength was observed even after post-heat treatment. After rolling, the desired titanium-based metal clad steel is obtained by peeling off the steel plate serving as the cover. Next, examples of the present invention will be shown. Example Titanium plate (thickness 10mm) equivalent to JIS H46001 class
Various tests were conducted using carbon steel plates (90 mm thick) equivalent to SS41. A low carbon steel plate and/or Ni plate having the chemical composition shown in Table 1 is used as the insert material,
The relationship between heating temperature and required thickness of these insert materials was investigated in relation to their shear strength according to JIS 601 and JIS 3603.

[Table] These materials were assembled as shown in Figure 1, and evacuated using a rotary pump through a deaeration hole provided at the end.
After reducing the pressure to below 10 ^-1 Torr, the deaeration hole was plugged by welding and heated to 850°C for 5 hours. Then, the shear strength of the rolled material and the plate subjected to post-heat treatment was measured. The investigation was conducted under conditions where the rolling reduction ratio was 5 and the post heat treatment conditions were constant at 600°C for 5 hours. Figures 2a and 2b show the results of calculating the diffusion length of C in Fe and Ni as a function of temperature and time. Here, the values of the frequency term Do and activation energy Q used in these calculations are as follows. () Diffusion of C in α-Fe (500-700°C) Do=0.20cm ² /s Q=24.6kcal/mol It is shown by the dotted line in Figure 2a. () Diffusion of C in γ-Fe (800-1400°C) Do=0.15cm ² /s Q=32kcal/mol This is shown in the solid line graph in Figure 2b. () Diffusion of C in Ni (600-900°C) Do=0.13cm ² /s Q=34.5kcal/mol Shown in Figure 2b. From this, it is clear that Ni is effective in slowing down the diffusion of C. Figure 3 shows the titanium clad steel plate made of titanium/low carbon steel/SS41 clad steel plate, which was heated at 850°C for 5 hours with various thicknesses of the low carbon steel insert material and hot rolled at a reduction ratio of 5. /This is the result of actually measuring the amount of TiC precipitated at the low carbon steel interface. Here, the horizontal axis indicates the thickness of the low carbon steel insert material before rolling, and the vertical axis indicates the area ratio (%) occupied by TiC at the Ti/low carbon steel interfacial exfoliation fracture surface. As is clear from this, if there is no insert material, TiC is likely to precipitate almost entirely at the Ti/SS41 interface. And TiC precipitation decreases as the insert material thickness increases.
However, even if only a low carbon steel plate with a thickness greater than the C diffusion distance shown in FIG. 2a is inserted, about 10% of TiC will precipitate. This development is due to the diffusion of C through the grain boundaries of the insert material mentioned above. Note that the deaeration conditions before heating in carrying out these tests were in the range of 1.1×10 ⁻¹ Torr to 8×10 ⁻² Torr. Figure 4 shows the above-mentioned Ti/low carbon steel interface.
The relationship between TiC precipitation amount and shear strength is shown. As is clear from this, the shear strength tends to increase as the amount of TiC precipitated at the Ti/low carbon steel insert interface decreases; Even at a TiC occupancy rate of about 10%, which corresponds to the above, most of the TiC is inferior to the shear strength (14 Kg/mm ² ) of explosive bonded clad steel sheets. Figure 5 shows the interface when the sample clad steel plate of this example was further heated in the atmosphere at 600℃ for 1 hour.
The relationship between TiC precipitation amount and shear strength is shown. Hot rolling also reduces the thickness of the low carbon steel insert material to about 1/5, making it easier for C to diffuse into TiC.
There should also be an increasing trend in the precipitation of . As is clear from the figure, even if the original insert material thickness is 1 mm, it becomes 200 μm after rolling.
Furthermore, as can be seen from Figure 2a, the diffusion distance of C during heating at 600°C for 1 hour can reach 220 μm, and if the insert material thickness is less than this, the amount of TiC precipitated will be extremely large. . Original thickness of insert material is 1/2mm (thickness after rolling: 200 to 400μm)
However, the amount of TiC formed at the interface was greater than that of the rolled material. Furthermore, it can be seen that even if the material has relatively good shear strength when hot rolled, the strength significantly decreases when subjected to post-heat treatment. Figure 6 shows that a 300 μm thick Ni plate is inserted between the low carbon steel insert material and the base steel plate (SS41), and the thickness of the low carbon steel insert material between the laminate and the Ni plate is the same as in Figure 3. Heat-rolled material at 850℃ for 5 hours (rolling ratio 5) with a change in the range of 0 to 2 mm.
The results of investigating the amount of interfacial TiC precipitation are shown. Also,
Changes in shear strength are also shown in the figure. As is clear from this, if a 300 μm thick Ni plate is inserted to suppress the diffusion of C from SS41, TiC precipitation can be prevented when the thickness of the low carbon steel insert material is 400 μm or more, and the shear strength is also excellent. Summer. Of course,
When low carbon steel was not used, Ti-Ni intermetallic compounds grew significantly, resulting in poor shear strength. Figure 7 shows the same test material as the one in Figure 6.
The relationship between the amount of TiC precipitated and shear strength after heat treatment in the air for 1 hour at ℃ is shown. As is clear from Figure 2b, at 600℃
Because the diffusion of C in Ni is extremely small, even if heat treatment is performed when the Ni plate thickness is reduced after rolling, such as from 300 μm to 60 μm, TiC will not precipitate and increase the shear strength. It was also good. As is clear from FIG. 2, the thickness of the low carbon steel and Ni plate necessary to suppress the precipitation of TiC at the titanium/low carbon steel interface changes depending on the heating temperature and time. Therefore, the relationship between these required thicknesses and the heating temperature was investigated under conditions where the heating time was 5 hours, the rolling reduction ratio was 5, and the post heat treatment was constant at 600° C. for 1 hour. The results are shown in Figure 8. In order to obtain a shear strength ≧20Kg/ ^mm2 , low carbon steel with a thickness of 1/2 and 1/4 of the diffusion distance of C into Fe shown in Figure 2a is required. It was found that a thick Ni plate was required. Moreover, the thickness of the low carbon steel and the Ni plate may be changed according to the relationship of √(t: time) with respect to the heating time.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a cladding material; FIGS. 2 through 8 are graphs collectively showing various data in the embodiments of the present invention. 1: Base steel plate, 2: Ni plate, 3: Low carbon steel plate,
4: Titanium plate, 5: Cover, 6: Seam, 7: Clad material, 8: Suction port.

[Claims]

1. In a dissimilar pipe joint of stainless steel and zirconium or zirconium alloy, in which the ends of a first tubular member made of stainless steel and a second tubular member made of zirconium or zirconium alloy are joined to each other, The length of the joint surface at the cut plane including the tube axis is greater than the wall thickness of the first and second tubular members, and the first tubular member and the second tubular member are explosively crimped using tantalum as a welding material. A highly corrosion-resistant stainless steel-zirconium joint pipe joint. 2. A method for manufacturing an abnormal pipe joint of stainless steel and zirconium or zirconium alloy, in which the ends of a first tubular member made of stainless steel and a second tubular member made of zirconium or zirconium alloy are joined to each other, wherein the first tubular member and a second tubular member are explosively crimped using a tantalum pipe as a welding material,
forming a laminated composite tube of a stainless steel tube and a zirconium tube or a zirconium alloy tube;