JPH0471636B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] Highly corrosion-resistant stainless steel-zirconium joint pipe joint used to join a tubular device part made by welding zirconium or zirconium alloy to a tubular device part made by welding stainless steel, and its manufacture. In particular, the present invention relates to a dissimilar pipe joint with good mechanical properties and corrosion resistance, and a method for manufacturing the same. [Prior Art] Clad plates and pipes made using the explosive crimping method have been used in many fields as joint materials for dissimilar metals, and their superiority has been recognized. Examples include (1) the combination of a steel hull and an aluminum deck structure;
Al/Steel joint (2) Al/Steel joint between spherical aluminum liquid tank and steel support structure (3) Al/Steel joint between steel electrode rod of mercury electrolyzer and aluminum bus bar (4) Diaphragm The connection between the piezo electrode of the electrolytic cell and the copper busbar
Ti/Cu joint (5) Connects aluminum wire and copper terminal
Al/Cu joint (6) For various low temperature liquid circuits such as refrigerators and air conditioners.
Cu/Al tubular joint (7) Al/for various low temperature liquid circuits such as refrigerated fish boats and freezers
Steel tubular joints (8) For low-temperature cryogenic industrial fields such as LNG and LPG.
Al/SUS pipe fittings (9) There are Zr/SUS Ti/SUS pipe fittings for strong acid liquid circuits, etc., and these have met the requirements depending on the usage conditions, but in recent years, they have become increasingly difficult to use. There are also joints that require further improvement to meet the requirements of the conditions. For example, zirconium or zirconium alloys, which have excellent corrosion resistance, are widely used as materials for various chemical equipment, and the joints between these zirconium or zirconium alloy liquid tanks and pipes and stainless steel liquid pipes are flange joints or screw joints. Mechanical joining methods such as joints have been used, but by adopting joints using the explosive crimping method,
The inventors have discovered that the joint performance can be greatly improved. Even in the Zr/SUS annular joint manufactured by the inventors by hollowing out the exploded SUS clad plate in the thickness direction, the Zr/SUS
Since alloy layers and intermetallic compounds with low corrosion resistance that are formed at the joint interface may be selectively corroded and cause deterioration of joint strength, further improvements have been desired. The inventors of the present invention have further researched these shortcomings, and have investigated explosive crimping conditions that do not produce a defective alloy layer, as well as explosive crimping methods.
It was determined that Zr/Ta/SUS joints have the best corrosion resistance. Conventional explosive bonding between stainless steel and zirconium plates is performed by interposing a titanium layer between the stainless steel and zirconium plates, as described in Japanese Patent Application Laid-open No. 46163/1983. Further, JP-A-59-47078 describes a zirconium clad steel in which an alloy such as niobium or an alloy such as tantalum is bonded between steel and a zirconium plate, and these metals are integrally joined via titanium. This multi-layer clad steel is made by blast welding multiple layers of medium welding materials to improve bonding properties, and is not made by blast welding stainless steel and zirconium through Ta, and there is no disclosure whatsoever regarding joints that require high bond strength. do not have. [Problems to be solved by the invention] Clad steel made by the conventional explosive joining technology of dissimilar materials is manufactured taking into consideration that the surface of the zirconium plate that is the clad plate is exposed to a corrosive environment. It does not take into account that the bonding interface is exposed to a corrosive environment. Membrane stress is assumed to be the stress that will be applied when used as a structure, and the zirconium plate and stainless steel were not joined with consideration to the tensile stress that would cause them to tear. In other words, joints formed by conventional explosive joining techniques are not designed to be used as joints. For example, when the explosion joint of a joint such as a piping joint is directly exposed to corrosive liquid, no consideration is given to corrosion at the joint interface and the strength effects caused by the plate thickness of the welding material. There were problems with localized corrosion and joint strength due to intermetallic compounds or alloy layers with low corrosion resistance. An object of the present invention is to provide a highly corrosion-resistant stainless steel-zirconium joint pipe joint that is resistant to corrosion in highly corrosive environments such as nitric acid and has high joint strength, and a method for manufacturing the same. [Means for Solving the Problems] The present invention provides a first tubular member made of stainless steel and a second tubular member made of zirconium or zirconium alloy whose ends are joined to each other. In the dissimilar pipe joint with the first and second
The first tubular member and the second tubular member are larger than the wall thickness of the tubular member.
The tubular member is a highly corrosion-resistant stainless steel that is explosively crimped using tantalum as a mediating material.
Found in zirconium joint pipe fittings. Furthermore, the present invention provides a method for manufacturing 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, A step of explosively crimping the first tubular member and the second tubular member using a tantalum pipe as a mediating material to form a laminated composite pipe of a stainless steel pipe and a zirconium pipe or a zirconium alloy pipe, and one end of the composite pipe. Remove the stainless steel pipe and tantalum pipe at one end, remove the zirconium pipe or zirconium alloy pipe and tantalum pipe at the other end, and remove the stainless steel pipe and the zirconium alloy pipe at the other end in the pipe axial direction of the dissimilar joint between the stainless steel pipe and the zirconium pipe or zirconium alloy pipe. A highly corrosion-resistant stainless steel-zirconium joint characterized by comprising a removal step in which the length of the joint surface on a parallel cut plane including the tube axis is greater than the wall thickness of the first and second tubular members. It is in the manufacturing method of pipe fittings. The pipe joint of the present invention can be manufactured by first manufacturing a double pipe using the explosive crimping method, and then explosively crimping other metal pipes to this clad pipe to obtain a triple clad pipe. The tubes are fitted in three layers with a gap between them, and the Zr/
There is a way to obtain Ta/SUS triple pipe cladding. Here, to explain the pipe joint of the present invention, the straight Zr/Ta/
A SUS triple clad pipe is cut to any size. All metal pipes other than the stainless steel pipe are cut off at one end, leaving only stainless steel. At the other end, all metal pipes other than the zirconium pipe are cut off, leaving only zirconium. Each tube of zirconium/tantalum/stainless steel is characterized by a metallurgical joint by explosive crimp. The thickness of this pipe joint is basically determined by the thickness of the pipe to be connected, but within the length of the joint,
Triple pipe section (a section where the joining surfaces of each tube are completely metallurgically connected around the entire circumference by explosive crimping)
The arbitrary dimensions are determined by considering airtightness, mechanical strength, and corrosion resistance. In addition, the length of each cut portion at both ends must be such that the welding heat of the weld joint with the pipe to be connected does not adversely affect the crimp interface of the three-layer cladding. Furthermore, the shape of the pipe joint is not limited to the explosion bonding of straight pipes; for example, the pipe ends may be expanded or contracted to any diameter and connected to zirconium or stainless steel pipes. The cutting shape of the inner and outer surfaces of the tube may be any shape depending on the liquid feeding conditions. Furthermore, the outer metal is zirconium, the inner metal is stainless steel, or the outer metal is stainless steel,
Zirconium may be used as the inner metal. [Function] From the viewpoint of corrosion resistance, the stainless steel pipe base material should be low carbon, especially austenitic, austenite-ferritic duplex stainless steel, or ferritic stainless steel with a content of 0.03% by weight or less, which has a tensile strength greater than tantalum pipe. is good. The wall thickness needs to be about 2.5 times that of the zirconium tube. If the thickness of the base material is less than 2.5 times, there is a risk of deformation or cracking due to explosive force. Therefore, if the explosive force is weakened, the joint will be incomplete, so it is preferable to use stainless steel with an appropriate thickness. Tantalum tubes should have a purity of 99.80% or more, and other impurities such as carbon, oxygen, and tungsten should each be below 0.03% by weight, iron, silicon, and nickel should be below 0.02%, nitrogen, hydrogen, and titanium should be below 0.01%, and niobium should be below 0.1% each. % by weight or less. The tensile strength of this material is 25-35Kg
f/mm ² , elongation should be at least 20%, and hardness should be 130 or less on the Vickers hardness. Also, the wall thickness is 0.1
~5.0mm is used. When the wall thickness becomes thinner than about 0.1 mm, joining becomes technically difficult. As the tantalum tube becomes thinner, the strength of the joint increases due to the binding force between the stronger stainless steel and zirconium. 5.0mm
In the above case, it is necessary to increase the explosive force, so that intermetallic compounds are generated, leading to a decrease in corrosion resistance and strength of the joint interface. Furthermore, the thicker the tantalum wall, the smaller the binding force between the base material and composite material, resulting in a decrease in strength as a joint. Preferably
It is 0.7 to 1.5 mm, and in this case, a tensile strength comparable to that of the base material can be obtained. The purity of the zirconium tube is 99.2% or more of zirconium + hafnium, 4.5% or less of hafnium, 0.2% or less of iron + chromium, 0.05% or less of carbon, 0.16% or less of oxygen, 0.005% or less of hydrogen, and 0.025% of nitrogen.
% or less, and the tensile strength should be higher than that of tantalum tubes. In particular, the elongation should be at least 25% or more, preferably 30% or more. The higher the elongation rate, the thicker the zirconium tube can be made for joining. The thinner the wall thickness, the better the bonding performance. An explosion welding material made by combining and joining such materials does not generate intermetallic compounds, has sufficient strength, and can be used as a joint with high reliability in a corrosive environment. As described above, the method for manufacturing a composite pipe constituting the pipe joint of the present invention may involve joining a zirconium or zirconium alloy plate to stainless steel, or the reverse configuration, and in either case, it is possible to weld the joint as a joint. It is necessary to consider welding in advance and set the length so that the weld heat affected zone does not enter the joint. As mentioned above, the dissimilar pipe joint of the present invention is explosively welded using tantalum as a welding material, and has a high bonding rate at both interfaces of the tubular members and a high bonding rate between the welding material at the welding interface and each other's tubular members. In order to prevent excessive alloying or the formation of intermetallic compounds and to obtain the high corrosion resistance against high concentrations of nitric acid mentioned above, the thickness of the tubular member, the thickness of the welding material, the impact force during explosion welding, the tubular shape, etc. This cannot be achieved unless various conditions such as the hardness of the member are taken into consideration. Example 1 Stainless steel pipe (SUS304L): 50φ _i × 10t × 200 Tantalum: 72φ _i × 1t × 200 Zirconium tube: 76φ _i × 5t × 200 Table 1 shows the chemical composition (wt%) of the tubes used. be. A tantalum tube is fitted to the outside of a stainless steel tube whose inside is densely filled with asphalt compound and solidified, and a zirconium tube is fitted to the outside of the stainless steel tube, and then these three tubes are arranged coaxially so that the clearance between them is even. After obtaining a triple clad pipe using the tube explosive crimping method, in which explosives are uniformly loaded and arranged all over the outer circumference of the zirconium tube and detonated coaxially from one end, the inside of the stainless steel tube of this triple clad pipe is The asphalt compound was removed by heating and melting, and washed with kerosene and acetone. As a result of conducting an ultrasonic flaw detection test to investigate the crimping condition of this triple clad pipe, it was found that both ends of the triple clad pipe were not crimped for a length of about 20 mm, but Zr/Ta/SUS was completely bonded for a length of about 160 mm. It was crimped. Next, connect both ends of this triple clad pipe.
After cutting 30mm, cut the stainless steel and tantalum intermediate layer to a length of 50mm on one side, and cut the outer zirconium and tantalum intermediate layer to a length of 50mm on the other side. The triple cladding part is larger than the thickness.
The pipe joint shown in Fig. 1 with a length of 60 mm was obtained. A nitric acid test was conducted to investigate the corrosion resistance of this Zr/Ta/SUS pipe joint. 14 Normal concentrated nitric acid
The fittings were immersed for 48 hours in a boiling solution supplemented with 100 ppm ruthenium nitrate. As a result, the stainless steel surface was completely corroded to a thickness of 25 μm,
The joint interfaces between stainless steel and tantalum and between tantalum and zirconium were found to be sound with no defects such as local corrosion observed.

〔Effect of the invention〕

As described above, the pipe joint of the present invention can improve all at once the various problems that are difficult to achieve with the annular pipe joint made by hollowing out a multilayer clad plate. Due to explosive crimping, even if stress is applied in a direction perpendicular to the axis of the pipe, no shear stress is applied to the crimped interface, resulting in a highly reliable pipe joint structure in terms of strength. This pipe joint is used not only as a joint for welding a zirconium pipe and a stainless steel pipe, but also as a joint for taking out liquid from a zirconium liquid tank chamber, and as a joint for attaching various parts. The pipe fitting of the present invention provides a joint between stainless steel and zirconium that does not generate intermetallic compounds, so it is effective as a highly corrosion-resistant joint in environments where corrosion is severe in concentrated nitric acid. . By using this pipe joint to join spent nuclear fuel reprocessing plant pipes that are exposed to a concentrated nitric acid atmosphere, it is possible to perform multilayer arc welding of stainless steel pipes and zirconium pipes of the same type, resulting in highly reliable Plants can be manufactured.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views of the pipe joint of the present invention.

[Claims]

1 The average length a in the rolling direction and the average length b in the plate thickness direction of the crystal grains of the core material immediately before solder melting of a brazing sheet with a core material thickness t are such that a/b≧3, and t/ A brazing sheet characterized by being configured to satisfy the relationship b≧2.

Claims (1)

Remove the tantalum tube, remove the zirconium tube or zirconium alloy tube and the tantalum tube at the other end, and align the tube axis parallel to the tube axis direction of the dissimilar pipe joint between the stainless steel tube and the zirconium tube or zirconium alloy tube. Production of a highly corrosion-resistant stainless steel-zirconium joint pipe joint characterized by comprising a removing step of making the length of the joint surface at the cut surface including the joint surface larger than the wall thickness of the first and second tubular members. Law.