JPH0679771B2 - Joining method for high chromium-nickel alloy steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to a high chromium-nickel alloy steel (hereinafter referred to as high Cr
-Ni-based alloy steel) for joining members made of steel.

"Prior art" In recent years, as a metal material that has better heat resistance and corrosion resistance than stainless steel, the composition ratio of Cr (chromium) is about 19 to 32%,
The composition ratio of Ni (nickel) is about 18 to 37%, which is higher than stainless steel, and is high Cr-Ni alloy steel, that is, HK material and HP material defined in ASTM standard A351, or Incoloy 800 (International Nickel).・ Company company's product name) etc. are attracting attention. For example, naphtha
In a heating furnace for producing ethylene by heating and decomposing at a high temperature of about 1,000 to 1,100 ° C, a radiant tube for heating naphtha at a high speed and a header part which is a collective part thereof are High Cr-N
It is formed of i-based alloy steel.

When the members made of the high Cr-Ni alloy steel as described above are joined together, the TIG welding method, which is a kind of fusion welding method, is generally used in the past.

"Problems to be solved by the invention" However, when pipe materials such as radiant tubes made of high Cr-Ni alloy steel are joined by TIG welding, so-called back wave portions are formed at the joints to form the inner surface of the pipe. It is unavoidable that discontinuity occurs. Therefore, when a tubing material having such a shape discontinuity is used as a radiant tube, erosion is likely to occur in the joint portion, and carburization easily occurs, and as a result, cracks or the like occur in the joint portion. There was a problem that defects would occur early.

In addition, it is difficult to automate TIG welding on the inner surface of the pipe, and it is necessary to rely on manual work, so that work efficiency is not good and it is affected by the skill of the worker. There is a risk that welding defects will occur, and when joining the radiant tube and the header part, the work is extremely poor because it is a welding operation at a narrow place where many radiant tubes approach. There was also a problem.

The present invention has been made in view of the above circumstances, and it is possible to join members made of high chromium-nickel alloy steel with sufficient strength and in a good state, and to join with sufficient strength in terms of creep characteristics. It is intended to provide a way.

"Means for Solving the Problem" The present invention, when joining members made of high chromium-nickel alloy steel, which is an alloy steel having a higher composition ratio of chromium and nickel than stainless steel, the joining is performed. The members to be pressed are pressed against each other through an insert metal made of a nickel-chromium-based amorphous material such as Ni-Cr-Si system or Ni-Cr-B system under an inert gas atmosphere, and the butted part is pressed at 1275. At a temperature of ℃ or higher, the temperature is lower than the melting point of the high chromium-nickel alloy steel.
It is characterized in that the members are liquid phase diffusion-bonded by melting the insert metal by high-frequency heating for more than a second.

"Operation" In the method of the present invention, the insert metal made of an amorphous material of nickel-chromium type by high-frequency heating the joint part at a temperature of 1275 ° C or more to a temperature lower than the melting point of the high chromium-nickel alloy steel for 300 seconds or more. Melts into a liquid phase, and the insert metal that has become a liquid phase fills up many microscopic irregularities between the end faces of both pipe materials, and the tip surfaces of both pipe materials are in close contact with each other. The metal element diffuses into the base material to join the two pipe materials.

[Examples] Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a view showing a state in which one ends of pipe materials 1A and 1B made of high Cr-Ni alloy steel are joined, and reference numeral 2
Is a chamber in which the inside can be replaced with an inert gas such as Ar or N ₂ , 3 is a high frequency heating generator, 4 is a heating coil, 5 is a heating temperature control device, and 6 is a detection end of a thermocouple thermometer.
Reference numeral 7 is an insert metal sandwiched between the tips of the two pipe materials 1A and 1B to be joined.

The above pipe materials 1A and 1B are high Cr-Ni alloys in which the composition ratio of Cr is 19 to 32%, the composition ratio of Ni is 18 to 37%, and the composition ratio of C is 0.05 to 0.75%. Steel is formed into a tubular shape by bending, stretching, casting or centrifugal casting, and is used as a radiant tube of a heating furnace for producing ethylene by thermally decomposing naphtha, for example. It should be noted that it is possible to add an appropriate additive element as necessary.

In joining the above-mentioned pipe materials 1A and 1B, the tips of both pipe materials 1A and 1B are processed beforehand to be smooth, and the tip portions of these pipe materials 1A and 1B are inserted into the chamber 2 respectively, and the insert metal 7 are sandwiched between them and abutted against each other, and the heating coil 4 is arranged outside the abutted portion.

As the insert metal 7, a Ni-Cr-Si-B-based or Ni-Cr-B-based amorphous material (commercially available products, for example, MBF-50, MBF-80 equivalent products of Allied Chemical Co., Ltd.) is used. It is good to process it into a ring shape having a thickness of several tens of μm and a width dimension equal to the wall thickness of the pipe materials 1A and 1B.

Then, one pipe material 1A is clamped and fixed by a clamp jig 10, while the other pipe material 1B is supported movably in the longitudinal direction by a support jig 12 provided with a roller 11, and the other pipe material 1B is 0.01-1Kg / mm for 1A of pipe material
² Press with a pressing force of about 0.1 to about 10 MPa.

Subsequently, after replacing the inside of the chamber 2 with an inert gas such as Ar or N ₂ , the heating coil 4 is heated by the high frequency heating generator 3.
Is energized to heat the joint at high frequency, the temperature of the joint is detected by a thermocouple thermometer, and the output of the high-frequency heating generator 3 is controlled based on the detected value to maintain the heating temperature at the set value. , That state is maintained for a predetermined time. In this case, the heating temperature is 1,200 ° C. or higher and the heating time is 300 seconds or longer. This is because if the heating temperature is 1,200 or less and the heating time is 300 seconds or less, sufficient bonding strength cannot be obtained as shown in the experimental examples described later.

As a result of the above, the insert metal 7 melts into a liquid phase,
Both pipe materials 1A and 1B are liquid phase diffusion bonded. That is, the insert metal 7 that has become a liquid phase fills the microscopic unevenness between the end faces of the two pipe materials 1A and 1B, thereby pressing the two pipe materials 1A and 1B with such a large pressing force. Even without doing so, the tip surfaces of both pipe materials 1A and 1B are completely adhered to each other, and the element of insert metal 7 is the base metal (tube materials 1A and 1B).
B) and the two pipes 1A and 1B are firmly joined and integrated.

According to the above bonding method, as described above,
Sufficiently by setting the bonding time to 1,200 ° C or more and the bonding time to 300 seconds or more, and combining these bonding conditions appropriately, for example, to lengthen the bonding time when the bonding temperature is low and to shorten the bonding time when the bonding temperature is high. In addition to ensuring a sufficient joint strength, there is no occurrence of a back wave portion which was inevitable in the case of conventional TIG welding. Therefore, when the pipe materials 1A and 1B joined by the above method are used as a radiant tube, erosion and carburization do not occur unlike in the conventional case, and therefore the life can be made sufficiently long.

Further, since the joining portion is heated at high frequency, it is possible to easily automate the joining work. Therefore, the work efficiency can be significantly improved as compared with the conventional TIG welding, and the skill of the worker can be improved. Is not affected and the work in a narrow space is facilitated, so that the joining is always performed under the optimum conditions.

Furthermore, since the inside of the chamber 2 is replaced with an inert gas and the bonding is performed in that atmosphere, an oxidation reaction due to oxygen in the atmosphere does not occur at the time of bonding, and there is no adverse effect.

Although the embodiment in which the pipe materials 1A and 1B are joined to each other has been described above, when joining the pipe materials to the header portion, it is advisable to perform as shown in FIG. In this case, the header part 15
Clamp and fix, and attach each pipe 1 to the header part 15 ...
It suffices to successively join the ... By the same procedure as above.
By doing so, the pipe material 1 and the header portion 15 can be surely joined to each other exactly as in the case of the above-described embodiment, and since the pipe material 1 is close to each other, it is difficult to perform the work in the related art. It is possible to easily perform the joining work at the place.

In the above embodiment, the pipe members are joined together, and the pipe member and the header portion are joined together. However, the form of the members to be joined together is not limited to a tubular form; for example, even rod-like members are completely joined together. It can be joined in the same way.

Next, with reference to FIG. 3 to FIG. 9, the test conducted for demonstrating the effectiveness of the method of the present invention will be described.

In each of the tests described below, incoloy 800 having the composition shown in FIG. 3 was used as the test pieces 20 and 20 in the form of a prism having a cross-sectional dimension of 10 mm × 10 mm as shown in FIG. Of the two kinds shown in FIG. 3, MBF-50 was used as the insert metal 21. The test device shown in FIG. 5 was used. In FIG. 5, reference numeral 22 is a vacuum container, 23 is a high-frequency heating generator, 24 is a heating coil, 25 is a detection end of a thermocouple thermometer, 26 is a rod for pressing the test pieces 20, 20, and 27 is vacuum exhaust. A pump, 28 is a load cell, and 29 is a recorder. Then, the inside of the vacuum container 22 of the above test equipment was evacuated to 4 × 10 ^-1 Torr (about 50 Pa) or less, and then replaced with Ar gas, and the rod 26 was used to test the test piece 20, 20 to 0.05 K.
Welding was performed while applying a load of g / mm ² (about 0.5 MPa).

(Test Example 1) As shown in FIG. 4, the insert metal 7 is placed between the test pieces 20 and 20.
And the tungsten wire rod 30 as a spacer is sandwiched and pressed, the joining time is set to 600 seconds, the joining temperature is changed and the joining is performed a plurality of times, and the joined test piece is cut to obtain a microstructure with a microscope. I observed. Junction temperature is 1,448K
It was set every 25K within the range of ~ 1,598K (1,175 ℃ ~ 1,325 ℃).

As a result, as shown in the micrographs of FIGS. 6 (a) to 6 (g), when the bonding temperature is 1,523 K (1,250 ° C.) or less, the formation of silicon compound or the like that deteriorates the mechanical properties at the bonding part. However, the bonding temperature was 1,548K (1,27K).
No such product was observed for those above 5 ° C), indicating that the joint was almost completely integrated.

(Test Example 2) The bonding temperature was set to 1,548K (1,275 ° C), the bonding time was changed, and the bonding was performed a plurality of times. The bonding test piece was cut in the same manner as in Testing Example 1 and the microstructure was microscopically observed. . The joining time was appropriately set within the range of 60 seconds to 180 seconds.

As a result, as shown in the micrographs of FIGS. 7 (a) to 7 (d), it was confirmed that the joints were almost completely integrated with the joint time of 300 seconds or more. (Test Example 3) A tensile strength test was performed on each bonded test piece bonded under the conditions of Test Example 2, and the results shown in FIG. 8 were obtained.

As shown in Fig. 8, when the joining time was 60 seconds, it broke at the joining surface, but when the joining time was 300 seconds or more, it broke at the base metal, and it was found that the joining strength was sufficient. did. In all cases, the minimum tensile strength of Incoloy 800 specified in JIS (JIS G 3467
It was found that the tensile strength of NCF 800 HCF is 450 N / mm ² ).

(Test Example 4) Creep characteristics of a test piece and a base material joined under the conditions of a joining temperature of 1,273K (1,000 ° C) and a joining time of 600 seconds were investigated, and the results shown in Fig. 9 were obtained.

As shown in FIG. 9, it was found that the creep characteristics of the bonded test piece had a fracture life equivalent to or higher than that of the base material test piece.

"Effects of the Invention" As described in detail above, the present invention is a high chromium-nickel alloy steel to be joined between Ni-Cr-Si system or Ni-Cr-B system under an inert gas atmosphere. Butt and press through the thin-layer insert metal made of nickel-chromium amorphous material of
Melting the insert metal by high-frequency heating for 300 seconds or more at a temperature lower than the melting point of the high chromium-nickel alloy steel at a temperature of 1275 ° C. or higher, and performing liquid phase diffusion bonding between the members. By joining at a temperature and for a time, it is possible to join without producing a product such as a silicon compound that deteriorates the mechanical properties in the joined portion, so that sufficient joining strength equal to or higher than the strength of the base material itself can be secured. Further, when joined by the method of the present invention, the creep characteristics are also excellent, and the creep characteristics equivalent to or higher than those of the base material can be obtained.

Further, when the present invention is carried out, a back wave portion is not generated unlike in the case of TIG welding, and therefore, the present invention is particularly suitable for joining pipe materials used as radiant tubes.

[Brief description of drawings]

1 and 2 each show an embodiment of the method of the present invention. FIG. 1 is a view showing a state in which pipe materials made of high Cr-Ni alloy steel are joined together, and FIG. 2 is a pipe material. It is a figure which shows the state which has joined the header part. FIG. 3 to FIG. 9 are views for explaining a test conducted for demonstrating the effectiveness of the method of the present invention, and FIG. 3 is a view showing a composition of a test piece and an insert metal, and FIG. Is an enlarged view of the test piece and the insert metal, FIG. 5 is a schematic configuration diagram of the test apparatus, and FIGS. 6 (a) to (g) are metal of the joint portion when the joint time is constant and only the joint temperature is changed. Micrographs showing the structure, Figs. 7 (a) to 7 (d) are micrographs showing the metal structure of the joint when the joining temperature is kept constant and the joining time is changed, and Fig. 8 is the tensile strength of the joining test piece. FIG. 9 is a diagram showing the creep characteristics of the bonded test piece. 1,1A, 1B …… Pipe material (member), 2 ... Chamber, 3 ...
High-frequency heating generator, 4 ... Heating coil, 5 ... Heating temperature control device, 6 ... Thermocouple thermometer detection end, 7 ... Insert metal, 10 ... Clamp jig, 12 ... Roller, 13 ...
… Support jig, 15… Header part (member).

Claims (1)

[Claims] 1. When joining members made of high chromium-nickel alloy steel, which is an alloy steel in which both the composition ratio of chromium and nickel is higher than that of stainless steel,
The members to be joined should be Ni-Cr-Si in an inert gas atmosphere.
Of the high chromium-nickel alloy steel at a temperature of 1275 ° C or higher, as well as by pressing through a thin-layer insert metal made of a nickel-chromium amorphous material such as Ni-Cr-B or Ni-Cr-B A method for joining high chromium-nickel alloy steel, characterized in that the members are liquid phase diffusion joined by melting the insert metal by high-frequency heating at a temperature lower than the melting point for 300 seconds or more.