JPH0952194A - Welding method for high Cr Ni alloy members - Google Patents

Abstract

(57) Abstract: When welding members made of a high-Cr Ni alloy that does not contain Nb, the occurrence of weld cracks is minimized. SOLUTION: C: 0.1 to 0.5% (weight%, the same applies hereinafter), Si: 4% or less, Mn: 3% or less, Cr: 40 to
50%, Fe: 10% or less, Ti: 0.05 to 0.6%,
Zr: 0.05-0.6%, Ti + Zr: 0.2-0.8
%, W: 0.5 to 5%, the balance being substantially Ni and high Cr
Welding of members made of Ni-based alloys with C: 0.1-
0.5%, Si: 4% or less, Mn: 3% or less, Cr: 4
0 to 50%, Fe: 10% or less, Ti: 0.05 to 0.6
%, Zr: 0.05 to 0.6%, Ti + Zr: 0.2 to 0.2.
8%, W: 0.5 to 5%, Nb: 0.5 to 3%, and the balance is a Ni-containing high Cr-based Ni alloy welding rod which is substantially Ni.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding a member made of a high Cr Ni alloy such as a cracking tube for ethylene production in the petrochemical industry.

[0002]

2. Description of the Related Art Ethylene production is carried out at a high temperature (about 800 to 10) while circulating naphtha in a cracking tube.
It is pyrolyzed under the conditions of (00 ° C) and low pressure (less than about 5 kg / cm ² ). During its operation, solid carbon is precipitated from the reaction system and adheres to the inner surface of the pipe wall and diffuses into the inside of the pipe wall Carburizing phenomenon occurs. In order to improve this carburization resistance, the applicant has previously proposed a high Cr-based Ni alloy.

By the way, the cracking tube (1) for ethylene production has an inner diameter of about 50 to 150 m as shown in FIG.
The bent portion (3) is welded to the end of the straight pipe portion (2) having a length of m, a wall thickness of about 6 to 10 mm, and a length of about 8 to 10 m to be assembled into a coil shape. The straight pipe portion (2) is formed by welding the ends of the cylindrical body (20) having a length of about 3 m to each other as indicated by reference numeral (4). A common gold welding rod is generally used for welding such members. A common metal welding rod is a material that is cut from a cast tubular body that constitutes a straight pipe and is used as a welding rod.The material component of the welded portion and the material component of the base metal are the same, and the entire cracking tube is used. The material is homogenized.

[0004]

[Problems to be Solved by the Invention] However, C: 0.1 to
0.5% (wt%, same below), Si: 4% or less, Mn:
3% or less, Cr: 40 to 50%, Fe: 10% or less, T
i: 0.05 to 0.6%, Zr: 0.05 to 0.6%, Ti
+ Zr: 0.2 to 0.8%, W: 0.5 to 5%, the balance depends on the welding conditions when a common gold welding rod is used for welding members made of a high Cr Ni alloy that is substantially Ni. In some cases, weld cracking occurred. This weld crack occurs at the grain boundary, and it is necessary to improve the grain boundary strength at high temperature. An object of the present invention is to improve the grain boundary strength at high temperature and provide a welding method in which welding cracks are less likely to occur in the welding of members made of the high Cr-based Ni alloy having the above-described composition.

[0005]

Means for Solving the Problems C: 0.1 to 0.5% (weight%, the same applies hereinafter), Si: 4% or less, Mn: 3% or less,
Cr: 40-50%, Fe: 10% or less, Ti: 0.0
5 to 0.6%, Zr: 0.05 to 0.6%, Ti + Zr:
0.2-0.8%, W: 0.5-5%, balance Ni substantially
In welding of members made of a high Cr-based Ni alloy, C: 0.1 to 0.5%, Si: 4% or less, Mn: 3
% Or less, Cr: 40 to 50%, Fe: 10% or less, T
i: 0.05 to 0.6%, Zr: 0.05 to 0.6%, Ti
+ Zr: 0.2 to 0.8%, W: 0.5 to 5%, Nb: 0.0.
5 to 3%, the balance being substantially Ni, Nb-containing high Cr-based N
Welding is performed using a welding rod of i alloy. In addition, Al:
In the case of containing 0.02 to 0.5%, N constituting the welding rod
The b-containing high Cr Ni alloy is also Al: 0.02 to 0.5.
% Is included. The balance substantially Ni means that Ni is an impurity element such as P and S that is inevitably contained during normal melting and Ni.

[0006]

When members made of a high Cr-based Ni alloy containing no Nb are welded using a common gold welding rod, Cr carbide is precipitated at the grain boundaries during melting and solidification. Since this Cr carbide is lumpy, if a fine crack is generated at the grain boundary due to heat shrinkage or the like, the crack propagates to the inside through the Cr carbide and propagates into a large crack, which is a so-called weld crack. . However, when welding is performed using a welding rod containing a predetermined amount of Nb as in the present invention, Nb is melted and solidified.
C preferentially deposits at the grain boundaries over the Cr carbide. Since this NbC is layered, even if a fine crack is generated at the grain boundary, the crack remains in the layer portion, is prevented from propagating inward, and does not propagate to a large crack. Also,
Due to the inclusion of Nb, the crystal grains are made finer, the grain boundary strength is enhanced, and cracks themselves are less likely to occur.

[0007]

Example 1 A cast pipe (outer diameter 130 mm, inner diameter 110 mm, length 570 mm) having the composition shown in Table 1 was produced by centrifugal casting, and after the cast pipe was cut in several radial directions. As shown in FIG. 2, a test tube machined into a groove shape was produced. Next, butt welding was performed using the welding rod 1 and the welding rod 2 having the composition shown in Table 1. The welding rod 1 is an example of the present invention and is a welding rod of a high Cr-based Ni alloy containing Nb, and the welding rod 2 is a comparative example and is a common metal welding rod cut out from the casting pipe. The size of the welding rod is 2.4 × 2.4 mm in cross section. The welding was performed by manual TIG welding in an Ar gas atmosphere while rotating the test tube on a rotating roller. Welding was carried out by stacking layers from the first layer to the fifth layer, and a liquid penetration inspection of the welded portion was performed for each layer to check for weld cracks. The laminated form of welding is shown in FIG. Table 2 shows the welding conditions and the results of the liquid permeation inspection for each layer. In the welding test using the welding rod 2, welding cracks were found in the stage of the first layer, so the tests of the second and subsequent layers were stopped.

[0008]

[Table 1]

[0009]

[Table 2]

As is clear from Tables 1 and 2, no welding cracks were observed in the welding test using the welding rod 1 according to the embodiment of the present invention. On the other hand, in the welding test using the welding rod 2 as the comparative example, welding cracks were observed at the stage of the first layer.

Example 2 A test tube having an Al-containing component composition as defined in claim 2 was prepared, and a welding test and a liquid penetration test were conducted in the same manner as in Example 1. Table 3 shows the composition of the test tube, the welding rod 3 and the welding rod 4. Table 4 shows the welding conditions and the results of the liquid permeation inspection for each layer. The welding rod 3 is an example of the present invention and is a welding rod of a high Cr-based Ni alloy containing Nb, and the welding rod 4 is a comparative example and is a common metal welding cut from the test casting pipe. It's a stick.

[0012]

[Table 3]

[0013]

[Table 4]

As is clear from Tables 3 and 4, no welding cracks were found in the welding test using the welding rod 3 of the present invention. On the other hand, in the welding test using the welding rod 4 as the comparative example, welding cracks were observed at the stage of the first layer.

[0015]

EFFECTS OF THE INVENTION It is possible to cause welding cracks by welding members made of the above-mentioned alloy component of high Cr-based Ni alloy with a welding rod made of the above-described component of Nb-containing high Cr-based Ni alloy. It is possible to reduce the sex as much as possible. The welding is not limited to the TIG welding described above, and MIG welding or other welding methods can be used. By using the welding method of the present invention, the efficiency of the cracking tube assembling process can be significantly increased.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an assembled state of a cracking tube.

FIG. 2 is a cross-sectional view showing a groove shape of end welding of a test tube.

FIG. 3 is a cross-sectional view illustrating a laminated form of a welding test.

Claims (2)

[Claims] 1. C: 0.1-0.5% (weight%, the same applies hereinafter), Si: 4% or less, Mn: 3% or less, Cr: 40-
50%, Fe: 10% or less, Ti: 0.05 to 0.6%,
Zr: 0.05-0.6%, Ti + Zr: 0.2-0.8
%, W: 0.5 to 5%, the balance being substantially Ni and high Cr
Welding of members made of Ni-based alloys with C: 0.1-
0.5%, Si: 4% or less, Mn: 3% or less, Cr: 4
0 to 50%, Fe: 10% or less, Ti: 0.05 to 0.6
%, Zr: 0.05 to 0.6%, Ti + Zr: 0.2 to 0.2.
8%, W: 0.5 to 5%, Nb: 0.5 to 3%, the balance being a Ni-containing high Cr-based Ni alloy welding rod, which is characterized in that A welding method for a Cr-based Ni alloy member. 2. The welding method according to claim 1, wherein the high-Cr Ni alloy and the Nb-containing high-Cr Ni alloy each contain Al: 0.02 to 0.5%.