JPH01299791A - Wire for welding ni-base alloy having excellent high-temperature cracking resistance - Google Patents

Abstract

PURPOSE:To suppress the high-temp. cracking of a multi-layered weld zone by incorporating respectively specific weight % of C, Si, Mn, P, S, Cr, and Fe into the compsn. of the wire for welding Ni-base alloys and forming the balance of Ni and unavoidable impurities. CONSTITUTION:The wire is formed by incorporating, by weight %, <=0.1% C, 0.01-0.75% Si, 0.01-1.0% Mn, <=0.04% P, <=0.02% S, 6-14% Cr, and 16-52% Fe, into the wire compsn. and consisting the balance of the Ni and unavoidable impurities. Since the contents of the C and Fe are regulated respectively to the optimum ranges, the sensitivity to ductility degrading cracking is lowered and the thermal impact resistance is improved. Since the component contents of the P and S are confined to the min. limits, the intergranular embrittlement and the formation of low melting eutectic are prevented. The Si and Mn are effective as a deoxidizing agent and the C improves the heat resistance and strength. The high temp. cracking of the multilayered weld zone of the Ni alloys is suppressed by the combined effects thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a Ni-based alloy gas-shielded arc welding wire that has excellent resistance to hot cracking during multilayer welding, particularly resistance to ductility drop cracking.

[Prior Art] N1-based alloys have excellent corrosion resistance and heat resistance, and are used under severe conditions in petrochemical plants, nuclear reactor plants, and the like. Furthermore, due to strength issues, thick plates are often used, and multi-layer welding is inevitably adopted for welding in such cases.

However, when performing multilayer welding of N1-based alloys, microcracks (under-bead microcracks) often occur in the weld metal, which can pose a problem.

This cracking occurs in the heat-affected zone where the front layer bead is reheated by the rear layer bead, and is a high-temperature cracking (ductility reduction cracking) caused by Sl and P and S components contained as unavoidable impurities.

Conventionally, in order to prevent this cracking, a method has been adopted in which preheating is performed during welding, the restraint is reduced, and welding is performed using dwarf heat. However, when welding with dwarf heat,
When the bead is small and multi-layer welding requires a large number of passes, the problem arises that the welding efficiency is extremely poor.

As a solution to these problems, Japanese Patent Application Laid-open No. 62-
There is No. 13025. This is an Inco company (Intern
N1 base alloy 1nconel (registered trademark) 718, which is a product of ational N1ckel Co, Inc.
Based on the composition of , Nb and Ta are reduced to prevent weld microcracks.

However, even if the welding material shown in this technical content is manufactured, there is a problem in improving the hot cracking resistance. That is, Incon
Even if the basic composition is 71g of cl and Nb and Ta are reduced, it still contains several percent of Nb and Ta, so a Rough S phase is generated at the grain boundaries, causing embrittlement and local melting during welding reheating. , which causes hot cracking.

Furthermore, even when using other welding materials that are conventionally said to have low hot cracking susceptibility, impurities such as P and S may be mixed into the grain boundaries due to dilution of the base metal or the influence of flux. . These P and S also cause grain boundary embrittlement and produce low melting point eutectics at the grain boundaries, causing hot cracking.

[Problems to be Solved by the Invention] The present invention prevents ductility reduction cracking that occurs when Nl-based alloys are welded in multiple layers, and provides N1 alloys with excellent hot cracking resistance.
The purpose is to provide a base alloy welding material.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors conducted extensive and detailed research on the influence of chemical composition on hot cracking of Nl-based alloy multilayer weld metal.

That is, the test material consisting of the chemical composition shown in Table 1 was plated with a thickness of 3
III! No. 11 was processed to a length of 100 mm and a width of 50 mm, and a Rossbede parestrain test was conducted as shown in FIG.

After performing bead-on-plate welding of the first layer by TIG welding in the width direction of the plate and removing oxide scale on the bead surface, a second layer is welded by TIG welding in the diametrical direction from point A to point B on the first layer bead 5. Bead-on-plate welding was performed.

The TIG welding conditions for the first layer and the second layer are as shown in Table 2. At the moment when the weld pool of the second layer bead 6 reaches the first layer bead at point B, the yoke 2 is dropped at a falling speed of 300 m + w/s to add strain, and the amount of strain on the test piece surface is 4.1%) , a hot crack was generated in the first layer bead, and the total crack length was measured.

As a result, it has been found that by performing welding using a welding material having the composition of the present invention, the hot cracking resistance (ductility reduction cracking resistance) during multilayer welding is improved.

That is, in the present invention, in weight %, c: o, i% or less, S
i: 0.01~0.75%, Mn: 0.01~
1.0%, P: 0.04% or less, S: 0.02% or less, Cr: 6 to 14%, Fe: 16 to 52%,
This is an N1-based alloy gas-shielded arc welding wire with excellent hot cracking resistance, characterized in that the remainder consists of N1 and unavoidable impurities.

Table 2 [Function] The reasons for limiting the content of each element according to the present invention will be described below.

C: Addition of 0.1% or less C improves heat resistance and tensile strength, but if it is added in excess, it combines with C to form carbides at grain boundaries.
Degrades corrosion resistance. Furthermore, since it also deteriorates ductility and toughness, it is set at 0.1% or less.

Si: 0.01 to 0.75% St is essential as a deoxidizing element, but if it is contained in excess, it will precipitate as inclusions and deteriorate ductility and toughness. Moreover, since the desired hot cracking resistance cannot be ensured with 0.75% oil, it is set at 0.01 to 0.75%.

Mn: 0.01-1.0% Mn is added as a deoxidizing and desulfurizing element, but excessive addition deteriorates corrosion resistance, oxidation resistance, and tensile strength, so 0.0%
It was set at 1 to 1.0%.

P: 0.04% or less P is an unavoidable impurity that causes grain boundary embrittlement and the formation of low melting point eutectics at grain boundaries, causing hot cracking.
It has been set at 4% or less.

S: 0.02% or less S is an unavoidable impurity that causes grain boundary embrittlement and the formation of low melting point eutectics at grain boundaries, causing hot cracking.
It has been set at 2% or less.

Cr: 6-14% Figure 2 shows the results of an investigation into the influence of Cr on the ductility reduction cracking susceptibility of Ni-based alloys having the basic components of the present invention.

From Figure 2, the effect of preventing ductility deterioration cracking decreases when the content of C is less than 6% and more than 14%.
As CrHk increases, the grain boundary segregation of S decreases, resulting in the effect of decreasing ductility-degrading cracking susceptibility.

On the other hand, an increase in the amount of Cr has the effect of increasing susceptibility to ductility-degrading cracking due to an increase in C carbides at grain boundaries and an increase in hardness.
~14% reduces ductility cracking susceptibility. Therefore, in order to ensure the desired hot cracking resistance, the content was determined to be 6 to 14%.

Fe: 18-52% Fe has the effect of improving thermal shock resistance, and must be contained in an amount of 16% or more. On the other hand, if it exceeds 52%, the intergranular stress corrosion cracking resistance in a chloride environment will decrease, so
It was set at 2%.

[Example] Based on the above findings, welding wires having the chemical compositions shown in Table 3 were manufactured, and hot cracking resistance tests of weld metals were conducted by TIG welding and MIG welding.

The hot cracking resistance test was conducted using the same ingredients as IOc F-B shown in Table 1, thickness 15m+s, width 120m+s, length 200m.
Three-layer welding as shown in Figure 3 (A) is performed on a plate of 1.5 mm in diameter, and after welding is completed, the distance from the base metal surface is h 1 (1.5 mm) as shown in Figure 3 (B). , h 2 (3
The upper layer of the bead was polished stepwise up to h 3 (4.5 m+*) and evaluated by the number of cracks per unit area.

Table 3 also shows the welding conditions for each welding method.

Table 4 shows the results of the hot cracking resistance test of weld metal.

For both TIG welding and MIG welding, the welding material of the present invention (7
3-T9. The weld metal of M3 to M9) is the comparative material (TI
, T2. TIO, Tll, Ml, M2゜MIO, Mll
) is clearly superior in hot cracking resistance.

From the above, it can be seen that the welding material according to the present invention suppresses hot cracking and has excellent hot cracking resistance.

Table 4 (Na marks indicate comparative materials) [Effects of the invention] As is clear from the above examples, the welding wire of the present invention has excellent hot cracking resistance during multi-layer welding, and its industrial effects are extremely high. Remarkable.

[Brief explanation of the drawing]

Figure 1 is a plan view (A) and side view (B) showing an overview of the crossbead pallet train test method, and Figure 2 is the influence of Cr on the ductility-degrading cracking susceptibility of the N1-based alloy having the basic components of the present invention. FIG. 3 is a perspective view showing a method for testing hot cracking resistance of weld metal, in which (A) shows the multilayer welding method and (B) shows the crack measurement position. 1...TIG torch 2...Yoke 3...
Test piece 4...Bending jig 5...1st layer bead 6...2nd layer bead 7...Welding direction agent Patent attorney Tate Chanogi 1 Figure 1 (A)! Figure 2 Figure 3 (A) (8)

Claims (1)

[Claims] In weight percent, C: 0.1% or less Si: 0.01 to 0.75% Mn: 0.01 to 1.0% P: 0.04% or less S: 0.02% A Ni-based alloy gas-shielded arc welding wire with excellent hot cracking resistance, characterized by comprising the following: Cr: 6-14% Fe: 16-52%; remaining Ni and unavoidable impurities.