JPH01299792A - Ni alloy coated electrode having excellent high-temperature cracking resistance - Google Patents

Abstract

PURPOSE:To suppress the high-temp. cracking of a multilayered weld zone by incorporating C, Si, Mn, P, S, Cr, Fe, and Ni at specific ratios into a core wire and coating the wire with a coating material contg. prescribed ratios of metal carbonate and metal fluoride. CONSTITUTION:The core wire is formed by consisting the compsn. thereof, by weight %, of <=0.1% C, 0.01-0.75% Si, 0.01-1.0% Mn, <=0.04% P, <=0.02% Si, 6-14% Cr, and 16-52% Fe, and consisting the balance of Ni and impurities. Further, the metal carbonate is incorporated at 20-60% into the coating material and the metal fluoride at 10-40% therein and the balance thereof is constituted of a deoxidizing agent, coating agent, alloy agent, and slag forming agent. The Cr and Fe components in the core wire lower the sensitivity to high-temp. cracking of the weld zone and improves the thermal impact resistance. The carbonate and fluoride of the metal in the coating agent improve the sealing effect of molten metal and the flowability of slag. The high-temp. crack of the weld zone is suppressed by the combined effects thereof.

Description

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

[Prior Art] Ni-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 multi-layer welding of Ni-based alloys, microscopic cracks (under-bead microcracking) 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,
In multi-layer welding where the bead is small, the number of buses increases, resulting in a problem of extremely poor welding efficiency.

As a solution to these problems, Japanese Patent Application Laid-open No. 62-
There is No. 13025. This is an Inco company (Intern
atonal Nie, KEL Co, Inc.)
Product Ni-based alloy 1neonet (registered trademark) 7
Based on the composition of No. 18, 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 el 718 and Nb and Ta are reduced, it still contains a few 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.

In addition, even when using other welding materials that are conventionally said to have low hot cracking susceptibility, 1. Due to dilution of the base material or the influence of flux, P, S, etc. may be mixed into the grain boundaries as impurities. These P and S also cause grain boundary embrittlement and produce low melting point eutectics at the grain boundaries, causing hot cracking.

[Issue to be solved by the inventionffi] The present invention prevents ductility-degrading cracking that occurs when Ni-based alloys are welded in multiple layers, and produces Ni that has 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, a sample material having the chemical composition shown in Table 1 was processed into a plate having a thickness of 3 vams, a length of 10011%, and a width of 501 m1.
A Rossbyde parestrain test was conducted as shown in FIG.

The first layer is welded by TIG welding in the plate width direction, and after removing the oxide scale on the bead surface, the second layer is welded by TIG welding from point A to point B in the direction perpendicular to the first layer bead 5. Bead-on-plate welding was performed for each layer.

The TIG welding conditions for the first layer and the second layer are as shown in Table 2. At the moment when the molten pool of the second layer bead 6 reaches the first layer bead at point B, the yoke 2 is moved at a falling speed of 300 mm/s.
(The amount of strain on the surface of the test piece was 4.1%), and high temperature cracks were generated in the first layer bead.
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.

Although the above findings are based on TIG welding, they can also be applied to shielded arc welding.

That is, in the present invention, C: 0.1% or less, Si
: 0.01~0.75%, Mn: 0.0L~1
．． 0%, P: 0.04% or less, S: 0.02% or less, C: 6 to 14%, Fe: 16 to 52%, and the remainder is Nl and unavoidable impurities. One or more metal carbonates based on the total weight of the coating material = 2
0-60%, one or more metal fluorides: 10-60%
40%, and is further coated around the core with a coating consisting of a slag forming agent, a deoxidizing agent, an alloying agent, and a coating agent other than those mentioned above, and has excellent hot cracking resistance.
This is a base alloy coated arc welding rod.

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, but if excessively contained, C
It combines with r to form carbides at grain boundaries and deteriorates corrosion resistance. Furthermore, since it also deteriorates ductility and toughness, it is set at 0.1% or less.

Si: 0.01 to 0.75% Sl is essential as a deoxidizing element, but if it is contained in excess, it will precipitate as inclusions and deteriorate ductility and toughness. In addition, if it exceeds 0.75%, the desired high-8 cracking resistance cannot be ensured, so 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 and causes grain boundary embrittlement and the formation of low melting point eutectics at grain boundaries, causing hot cracking, so 0.0
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.

As can be seen from FIG. 2, when the Cr content is less than 6% and more than 14%, the effect of preventing ductility deterioration cracking is reduced.

This is because as the amount of Cr increases, grain boundary segregation of S decreases, resulting in a decrease in ductility-degrading cracking susceptibility. On the other hand, Cr
An increase in the amount has the effect of increasing ductility-degrading cracking susceptibility due to an increase in Cr carbides at grain boundaries and an increase in hardness.

These contradictory effects work together, and Crff1 becomes 6
~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: 1B to 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%.

Metal carbonate = 20 to 60% The metal carbonate referred to in the present invention refers to, for example, lime carbonate, barium carbonate, magnesium carbonate, manganese carbonate, etc.
These give high basicity to the slag, lower P and S in the weld metal, and the CO2 gas generated by decomposition shields the molten metal from the atmosphere and lowers the gas partial pressure of hydrogen and nitrogen in the arc atmosphere. It is effective and needs to be added in an amount of 20% or more based on the total weight of the coating material.

On the other hand, if it exceeds 60%, the amount of gas generated will be excessive, resulting in frequent occurrence of pits, and the melting point of the slag will rise, resulting in poor fluidity of the slag, making it impossible to obtain a good bead shape. Therefore, it was set at 20 to 60%.

Metal fluoride: 10-40% The metal fluoride used in the present invention refers to, for example, fluorite, barium fluoride, magnesium fluoride, etc. These reduce the melting point of slag, so they improve the fluidity of slag. do. In addition, fluoride decomposed in the arc reacts with hydrogen in the molten metal and molten slag, reducing the amount of hydrogen in the weld metal and creating a weld metal with good hydrogen cracking resistance. It is necessary to add 10% or more.

On the other hand, if it exceeds 40%, the viscosity of the slag becomes insufficient, resulting in poor bead shape and poor welding workability. Therefore, it was set at 10-40%.

As a deoxidizing agent, either a single metal such as Al, Ti, St, or Mn or an iron alloy such as Fe-Mn is contained in the coating, but the range of the added deoxidizing agent is not particularly specified. isn't it.

[Example] Based on the above knowledge, welding rods made of a core wire with the chemical composition shown in Table 3 and a coating material shown in Table 4 were manufactured, and a hot cracking resistance test of the weld metal was carried out by coated arc welding. I did it. The hot cracking resistance test was conducted using IOc F-B shown in Table 1.
Same ingredients as 15m thick plate.

Three-layer welding as shown in Fig. 3 (A) is performed on a plate with a width of 120 m + s and a length of 200 m + s.
As shown in B), the distance from the base material surface is h 1 (1,
5mm), h2 (3,0mm), h3 (4,
The upper layer of the bead was polished in a stepwise manner until the surface reached 50 mm, and the number of cracks per unit area was evaluated.

The welding conditions are 120A-24 with a rod diameter of 4mm.
V -L5cm/a+In, and the temperature between the baths is 150
The temperature was below ℃.

Table 5 shows the results of the hot cracking resistance test of weld metal.

When coating materials A and B of the present invention are used, the weld metal of the weld cores (S3 to S9) of the present invention is
S2. It is clear that the hot cracking resistance is significantly superior to that of SI0.5ll), and the bead shape and welding workability are excellent.

Moreover, when comparative coating material C was used, the weld core wire of the present invention (8
3 to S9) is relatively thinner than the core wires (Sl, S
2. 810. 5ll), but the bead shape and welding workability are inferior.

Table 3 (weight%) (*marked is comparative material) Table 5 (Chestnut marks are comparative materials) Table 5 (continued) (*marked is comparative material) From the above, welding material according to the present invention (No.

3-9. It can be seen that N (L14-20) suppresses hot cracking and has excellent hot cracking resistance, as well as excellent bead shape and welding workability.

[Effects of the Invention] The welding rod of the present invention has excellent hot cracking resistance during multilayer welding, and its industrial effects are extremely significant.

[Brief explanation of the drawing]

Figure 1 is a plan view (A) and side view (B) showing an outline of the crossbead pallet train test method, and Figure 2 is a diagram showing the effect of C on the ductility-degrading cracking susceptibility of Nl-based alloys having the basic components of the present invention. Figure 3 is a perspective view showing the hot cracking resistance test method for weld metal, where (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 Tatsuo Chanoki Figure 1 (A) Figure 2 Figure 3

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% The following is an alloy consisting of Cr: 6 to 14%, Fe: 16 to 52%, and the remainder consisting of Ni and unavoidable impurities, as a core wire,
Contains one or more metal carbonates: 20-60%, one or more metal fluorides: 10-40%, and further contains slag forming agents and deoxidizing agents other than the above, based on the total weight of the coating material. A Ni-based alloy coated arc welding rod with excellent hot cracking resistance, characterized in that the core wire is coated with a coating agent consisting of an agent, an alloying agent, and a coating agent.