JPH02104482A - Pipe joint for joining high corrosion resistant stainless steel-titanium and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a pipe joint for joining high corrosion resistant stainless steel to Ti by forming Ta as a joint medium for first and second tubular members and forming alloys of the tubular members and the joint medium at prescribed intervals in the joint medium of the interface between the first tubular member and the joint medium. CONSTITUTION:A Ta plate of the joint medium 2 is subjected to explosive joining to a low C stainless steel plate of base metal 1 and alloy Ti plates 3 are subjected to explosive joining thereon. Further, the two Ti plates thicker than the first layer Ti plate are subjected to explosive joining in order. At the time of explosive joining of the Ti plates 3 of the second and subsequent layers, heat treatment to soften the joining interface between the Ti plates and the stainless steel plate which are subjected to explosive joining is carried out. The above-mentioned heat treatment is carried out at the temperature in which Ta and stainless steel are not diffused mutually substantially and in addition, in Ar where Ti and Ta are not oxidized. The heat treatment is carried out when every explosive joining is finished.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is for highly corrosion-resistant stainless steel-titanium joints used to join equipment parts welded with titanium or titanium alloy and equipment parts welded with stainless steel. The present invention relates to pipe joints, and particularly to a pipe joint for joining dissimilar materials with good mechanical properties and corrosion resistance, and a method for manufacturing the same.

[Conventional technology]

Conventional explosion bonding between stainless steel and titanium plates.

As described in Japanese Unexamined Patent Publication No. 53-10347, explosion bonding is performed between stainless steel and a zirconium plate with a nickel layer interposed between them.

Clad steel is blast welded through a nickel layer so that it has sufficient bonding strength and bending workability even if it is rolled after blast welding.

[Problem to be solved by the invention]

The above-mentioned clad steel made by the conventional explosive joining technology of dissimilar materials is made with consideration to the fact that the surface of the titanium plate that is the clad plate will be exposed to a corrosive environment. When used as a structure, no consideration is given to

It is assumed that the applied stress is membrane stress, and the titanium plate and stainless steel were not joined with consideration to the tensile stress that would cause them to tear apart. That is, joints formed by conventional explosive joining techniques are not considered for use as joints. For example, in cases where the explosion joint of a joint is directly exposed to corrosive liquid, such as in a piping joint, corrosion at the joint interface and the strength effects due to the plate thickness of the welding material are not taken into consideration. There were problems with local corrosion and joint tension due to intermetallic compounds with low corrosion resistance or alloy layers that occur at the interface.

An object of the present invention is to provide a highly corrosion-resistant stainless steel and titanium joint pipe joint that is resistant to corrosion in highly corrosive environments such as nitric acid, and a method for manufacturing the same.

[Means to solve the problem]

The present invention provides a dissimilar pipe joint in which the ends of a first tubular member made of stainless steel, titanium, or a titanium alloy and a second tubular member made of stainless steel, titanium, or a titanium alloy are joined to each other. The first tubular member and the second tubular member are metallurgically bonded using tantalum as a junction material, and the first tubular member and the second tubular member are a junction material.

The joint interface between the second tubular member and the junction material both has a wave pattern, and the first tubular member and the junction material are in the junction material at the interface between the first tubular member and the junction material. A highly corrosion-resistant stainless steel characterized by an alloy formed at predetermined intervals.
Found in titanium joint pipe fittings.

In the present invention, a first member made of a stainless steel plate, a titanium plate, or a titanium alloy plate is explosively welded using tantalum as a welding material, and then a stainless steel plate, a titanium plate, or a titanium alloy plate is placed on the welding material. A composite plate of stainless steel and titanium or a titanium alloy is formed by explosive welding the second member in one layer or in multiple layers, and the composite plate is cut into a tubular shape in the thickness direction. The end portions of the second tubular member consisting of the tubular member and the second member are a dissimilar pipe joint of a stainless steel pipe and a titanium pipe or a titanium alloy pipe, which are joined to each other, and the first tubular member and a junction material, and explosive pressure welding between the second tubular member and the welding material.

The explosion pressure welding between the first tubular member and the welding material is performed so that a wave pattern is formed, and the explosion pressure welding between the first tubular member and the welding material is performed so that an alloy of the first tubular member and the welding material is formed at predetermined intervals within the welding material. The present invention provides a method for manufacturing a highly corrosion-resistant stainless steel-titanium joint pipe joint.

That is, the abnormal type joint of the present invention can be applied to a thick stainless steel plate,
First, a tantalum plate, which is much thinner than stainless steel, is explosively bonded, and then a titanium plate, which is thinner than stainless steel but thicker than tantalum plate, is explosively bonded to the tantalum plate, and if necessary, titanium is bonded to the titanium plate. A clad plate made of titanium/tantalum/stainless steel obtained by sequentially explosively bonding the plates is hollowed out in the thickness direction.
You can get pipe fittings. In addition, tantalum is explosively welded to a titanium plate or a titanium alloy plate as a medium bonding material, and then a stainless steel plate is explosively welded to the tantalum plate, and these composite plates are hollowed out in the thickness direction by cutting, etc. A pipe fitting can be formed with ends of a steel section and a titanium section.

Such a pipe joint has high corrosion resistance as the joint boundary between stainless steel and titanium is exposed to a corrosive environment containing a high concentration of nitric acid.

[Effect]

Stainless steel base material is low carbon, especially 0, from the viewpoint of corrosion resistance.
．． 03% by weight or less austenitic.

Austenite-ferritic duplex stainless steel or ferritic stainless steel is preferable, and it is preferable that the tensile strength is greater than that of tantalum plate. The plate thickness needs to be about 2.5 times the thickness of the titanium plate composite material. 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 joining will be incomplete, so it is also preferable to use a multilayer plate of stainless steel with an appropriate thickness. Tantalum plates should have a purity of 99.80% or higher, and other impurities should be 0 for each of carbon, oxygen, and tungsten.
．． Below the 03 heavy picture, iron, silicon, and nickel are 0.02% or less, nitrogen, hydrogen, and titanium are 0.01% or less, and niobium is each 0.1% by weight or less.

The tensile strength of this material is 25-35kgf/ns2. The elongation should be 20% or more, and the hardness should be 130 or less on Vickers hardness. Further, a plate having a thickness of 0.1 to 5.0 m is used. When the plate thickness becomes thinner than about 0.1 mm, joining becomes technically difficult. As the tantalum plate becomes thinner, the strength of the joint increases due to the binding force between the stronger stainless steel and the titanium plate. If the thickness exceeds 5.0 mm, it is necessary to increase the explosive force, so intermetallic compounds will be generated, leading to a decrease in corrosion resistance and strength at the joint interface.Also, the thicker the tantalum plate, the more difficult the bond between the base material and composite material will be. Since the restraining force becomes smaller, the strength of the joint decreases. Desirably, it is 0.7 to 1.5 Peng,
In this case, the tensile strength of the joint is comparable to that of the base material.

Titanium plates are suitable for piping applications, especially.

Although it is not necessary to specify, it is preferable that the tensile strength is higher than that of tantalum plate. In particular, the elongation is 25% or more, preferably 30%.
% or more is better. The higher the elongation rate, the thicker the titanium plate can be used for joining. The thinner the plate thickness, the better the bonding performance, but in order to ensure that the thickness of the titanium plate after bonding is the same as that of stainless steel, thicker titanium plates require fewer bondings, so titanium plates The plate thickness is 6III
11 or above is good. If the stainless steel plate is sufficiently thick, the titanium plate may be approximately 12 m thick. Explosive bonding of titanium plates of the same type is possible even with a plate thickness of about 15 ounces. 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 corrosive environments. As described above, the method for manufacturing the clad plate constituting the pipe joint of the present invention involves laminating titanium or titanium alloy plates onto stainless steel, or conversely joining stainless steel onto titanium or titanium alloy. In either case, it is necessary to consider welding in advance and laminate the layers to a thickness that prevents the weld heat affected zone from entering the joint.

As mentioned above, the dissimilar pipe joint of the present invention is explosively welded using tantalum as a welding material, and exhibits a wave pattern at any interface in the tubular member, and sometimes there is a wave pattern between the tantalum and the welding material at a predetermined interval. After melting, an alloy is formed that appears to be solidified. Such a bonding interface is formed by suitable explosive bonding. In order to obtain a high bonding rate as such a bonding interface, prevent excessive alloying between the welding material and each other's tubular members at the bonding interface, or prevent the formation of intermetallic compounds, and obtain high corrosion resistance against high concentration nitric acid. This cannot be achieved unless various conditions such as the thickness of the tubular member, the thickness of the welding material, the impact force during explosion welding, and the hardness of the tubular member are taken into account.

In the present invention, the joining condition is that the hardness of the joint part of the tubular members is 20% or more higher than the hardness of each material before joining, and the width of the part is 5 mm or less. As a result, better corrosion resistance can be obtained. This change in hardness is caused by work hardening due to explosion welding, and is highest at the interface and gradually decreases.

The above-mentioned width of the portion whose hardness has changed due to explosive welding is preferably 3 m or less for better corrosion resistance, and particularly preferably 1 to 3 I.

Furthermore, the alloys formed at predetermined intervals in tantalum affect the bonding properties by explosive welding, and when the wave pattern wavelength is 50 to 300 μm and the wave height is 10 to 100 μm, it is necessary to form the alloy with good spacing and size. be done. The wave pattern is formed on the tantalum side, and the alloy is formed within the tantalum in a manner that is wrapped between the waves. The ratio of wave height to wavelength is 0 on average at the bonding interface.
．． 05 to 0.3 is preferable. The length of the alloy to be formed in the joining direction is preferably 100 μm or less, and the joining is performed so that this alloy is formed.

〔Example〕

<Example 1> FIG. 1 is a schematic diagram showing the joining mode of the present invention. Base material 1: 5US304L low carbon stainless steel plate 30x2
50x300 (++n+), a titanium plate 1x300x350 (mm) of the intermediate junction material 2 is explosively welded, and a titanium plate 10x300x350 (rrn) of the plywood 3 is explosively welded thereon. Further, two titanium plates 15 x 300 x 350 (m) thicker than the -th layer titanium plates are explosively bonded one after another. During explosion contact of titanium 3 from the second layer onwards, 520℃
Heat treatment was performed in an argon atmosphere for 30 minutes to soften the bonding interface between the explosively welded titanium plate and stainless steel. This heat treatment was carried out at a temperature at which tantalum and stainless steel do not substantially interdiffuse, and in argon at which titanium and tantalum do not oxidize. This heat treatment may be performed in vacuum. An appropriate heat treatment time was selected to soften the hardened layer at the joint. The longer the time, the better, but the quality of the material may deteriorate depending on the purity of argon, degree of vacuum, and control of heat treatment temperature, so it should be selected appropriately taking these conditions into consideration. Heat treatment was performed when all explosive bonding was completed. In Figure 1, explosive bonding was performed four times. Table 1 shows the chemical composition and main properties of the materials used.

When performing explosive bonding, it is necessary to reduce the wave height at the bonding interface, and preferably, it is desirable to bond with substantially no wave height.

Figure 2 shows the microwitzker hardness of the bonding interface (load 1
．． 0g). Hardness of 5O530 female (Hv
) is approximately 210, which is 2% higher than the hardness before joining.
The width of the part whose hardness is 0% or more higher is about 3 m, and the hardness (Hv) of titanium before bonding is about 160, and the width of the part whose hardness is 20% or more higher than this hardness. was approximately 3 m.

In the micrograph of the bonded surface of 5US304L and tantalum, a regular wave pattern is formed and 5US304L is formed in the tantalum.
An alloy of 4L and tantalum is formed between the waves in a rolled-up form. The wavelength of this bonded surface is 50 to 10
The wave height was approximately 6 to 18 μm. The alloy formed in tantalum has a size of about 40 to 7 in the joining direction.
It was 0 μm.

In other examples, the wavelength is 200 to 260 μm, and the wavelength is 40 to 260 μm.
70 μm, wavelength 80-150 μm, wave height 12-30
It was μm.

In a micrograph of a cross-section of the tantalum and titanium joint surface, a wave pattern is formed, with titanium wrapped around the tantalum. The wavelength of the bonded surface is 70 to 130 μm, and the wave height is 2
It was 0 to 40 μm.

For comparison, a stainless steel plate and a titanium plate were directly explosively bonded without using the tantalum plate as the welding material 3.
I built the cladding to get the pipe fittings. In this case, since a large explosive force is required for joining, the interface between the stainless steel plate and the titanium plate becomes a large corrugated joint interface, and an intermetallic compound is generated. Table 2 compares the results of a tensile test of a joint between a stainless steel plate and a titanium plate with and without tantalum as a junction material.

Table 2 Tensile test specimens have a diameter of 4.0 mm and a gage distance of 5.0.
m, and its center was set to be the bonding interface between the stainless steel and the titanium plate, or the center of the plate thickness of the tantalum welding material. By using a tantalum plate as a mediating material, the ductility of the joint becomes good. A series of experiments revealed that as the tantalum plate used as the welding material becomes thicker, the joint properties approach those of the tantalum plate and the joint strength decreases. The thickness of the tantalum plate as a mediating material is 0, 5 + m + ~ 3
．． Onm is good.

The maximum is 5.0 mm, preferably 0.5 to 1.5
m is good. The strength of the joint between titanium plates of the same type of material is better than that of the raw material, and the titanium plate elongates and the aperture decreases, but this tendency is extremely slight and can be practically eliminated by selecting the material.

A nitric acid test was conducted on the joint. 10 to 14 normal nitric acid
48 in a boiling solution with the addition of ruthenium nitrate at 0 ppH.
A specimen with a bonded interface between stainless steel and a titanium plate was immersed for an hour. As a result, the stainless steel surface of the test piece that did not use the tantalum plate as a junction material was completely corroded to a thickness of 30 μm, and the joint interface between the stainless steel and titanium plate was selectively eroded to a depth of <100 μm. . This erosion is associated with the formation of intermetallic compounds. Note that the titanium plate will not corrode. On the other hand, in the case where a tantalum plate is used as the intermediate material of the present invention, the stainless steel surface is fully corroded to a thickness of 25 μm, but there is localized corrosion at the bonding interface between the stainless steel and the tantalum plate, and between the tantalum plate and the titanium plate. , no selective corrosion occurred on any part.

FIG. 3 shows a piping component for a welded joint obtained by cutting from a clad steel plate that has been explosively welded according to the above-mentioned invention.

The stainless steel and titanium are joined via the tantalum plate approximately at the center of the part, and the axial end of the part is a welding groove 4.

(a) has a constant wall thickness of the joint, and is suitable for use in corrosive environments and locations where strength is moderate. (b)
is also suitable for use in harsh environments. The thickness of the joint interface between stainless steel and tantalum is made thicker than other parts to compensate for the decrease in strength of the tantalum part. This thick portion has the effect of reducing the influence of welding heat when welding the groove 4.

Part (c) is suitable for use in the most severe environments. Compared to (b), the inner diameter is slightly larger at the joint with the stainless steel. In (C), corrosive fluid is flowing from the titanium plate side of 3, and corrosion is prevented by locally reducing the pressure of the fluid at the stainless steel joint. Conversely, if the flow changes from the stainless steel side to the titanium plate side, it is better to slightly increase the inner diameter of the tantalum plate and titanium plate side.

In the above embodiments, the tantalum plate used as the intermediate material must have a hardness lower than that of titanium or titanium alloy material, and it was found that a Vickers hardness of 130 or less is sufficient.

<Example 2> In Fig. 1, the base material 1 is a titanium plate, the tantalum plate of the intermediate material 3 is explosively crimped onto it, and the stainless steel of the composite material 2 is sequentially placed on the tantalum plate. , explosive bonding,
Different types of pipe joints were similarly cut from the obtained clad plate. In this example, the base material and composite material of Example 1 are reversed.

The joint of Example 2 exhibited the same characteristics as Example 1, such as corrosion resistance at the joint interface and joint strength.

〔Effect of the invention〕

According to the present invention, a joint can be obtained in which no intermetallic compounds are formed between stainless steel and titanium plates, and a joint with high corrosion resistance can be obtained in an environment where corrosion is severe in concentrated nitric acid.

[Brief Description of the Drawings] Fig. 1 is a sectional view of a clad plate according to an embodiment of the present invention;
The figure is a diagram showing the microvitsker's hardness of a cross section of the clad plate of the present invention, and FIG. 3 is a cross-sectional view of a welded joint for joining a stainless steel pipe and a titanium pipe. 1... Stainless steel plate or titanium plate, 2... Tantalum plate, 3... Titanium plate or stainless steel plate, 4...
Welding groove. Figure 1 Figure 2 Kagone Keytone (4n Figure 3)

Claims (1)

[Claims] 1. A stainless steel product in which the ends of a first tubular member made of stainless steel, titanium, or a titanium alloy and a second tubular member made of stainless steel, titanium, or a titanium alloy are joined to each other. In a dissimilar pipe joint made of steel, titanium, or titanium alloy, the first tubular member and the second tubular member are metallically bonded using tantalum as a junction material, and the first tubular member and the junction material are The joint interface between the second tubular member and the junction material both has a wave pattern, and the first tubular member and the junction material are formed in the junction material at the interface between the first tubular member and the junction material. A highly corrosion-resistant stainless steel-titanium joint pipe joint, characterized in that an alloy with a welding material is formed at predetermined intervals. 2. Explosive pressure welding to a first member made of a stainless steel plate, a titanium plate, or a titanium alloy plate using tantalum as a welding material,
A second member made of a stainless steel plate, a titanium plate, or a titanium alloy plate is explosively welded in one layer or in multiple layers onto the intermediate material to form a composite plate of stainless steel and titanium or a titanium alloy, and the composite plate A stainless steel pipe and a titanium pipe, or a titanium pipe, in which the first tubular member made of the first member and the second tubular member made of the second member are joined to each other by cutting into a tubular shape in the plate thickness direction. A pipe joint of a different type with an alloy pipe is formed, and the explosive pressure welding is performed so that a wave pattern is formed at the interface between the first tubular member and the welding material, and the interface between the second tubular member and the welding material, The interface between the first tubular member and the junction material is explosively welded so that an alloy of the first tubular member and the junction material is formed at a predetermined interval within the junction material. A manufacturing method for highly corrosion-resistant stainless steel-titanium joint pipe fittings.