JP3352857B2 - Ni-base alloy TIG welding wire for cryogenic steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to LNG (Liquid Natural Gas)
And cryogenic temperature for LEG (liquid ethylene gas) tank 9
% Ni steel, 5.5% Ni steel or 3.5% Ni steel is used for welding. The weld metal has high strength and suppresses the generation of slag on the bead surface or enhances the slag removability. The present invention relates to a Ni-based alloy TIG welding wire for cryogenic steel that can improve weldability.

[0002]

2. Description of the Related Art Recently, with the increase in size of tanks, there has been an increasing demand for obtaining high-strength welds in order to ensure the safety of tanks. Therefore, in TIG welding, in which a weld metal superior in quality to other welding methods can be obtained, in particular, there is an increasing expectation for automatic TIG welding capable of performing high welding work.

However, when high welding is performed by automatic TIG welding, the amount of slag generated on the surface of the bead increases, and defects such as slag entrainment may occur. Therefore, since the slag needs to be polished with a grinder or the like, it may not be possible to perform highly efficient construction even with high welding welding.

[0004] In such automatic TIG welding, 9% Ni for cryogenic temperature used in a liquefied gas tank or the like is used.
Ni-based alloys are widely used for TIG welding wires such as steel. Although the Ni-based alloy has excellent impact resistance at extremely low temperatures, the strength of the welded portion is lower than that of the base metal, and therefore, a Ni-based alloy to which Cr is added is used to ensure the strength. However, when Cr is added to the Ni-based alloy, the Cr is combined with O during welding to generate slag, so that the amount of slag generated further increases.

Accordingly, high-efficiency construction can be performed,
In order to obtain an automatic TIG welding wire having excellent impact resistance, it is necessary to develop a wire that generates a small amount of slag. Therefore, Ti, Ca, M
It is known that the amount of slag generated can be suppressed by regulating the contents of g, Al, Si, and the like to appropriate amounts (Japanese Patent Application Laid-Open No. 6-277875).

[0006]

However, by regulating the content of the chemical component to an appropriate amount, the amount of slag generated can be suppressed, but the Cr content, which has the effect of ensuring strength, is not considered. Since it is not limited, there is a problem that the strength of the weld is low. As described above, in the conventional technique, in the automatic TIG welding, a Ni-based alloy TIG welding wire for cryogenic steel capable of simultaneously realizing a high-strength weld and improving the amount of slag has not been developed.

[0007] The present invention has been made in view of the above problems, and has a high weld metal strength and suppresses the generation of slag on the bead surface or enhances the slag peelability to improve the weldability. It is an object of the present invention to provide a Ni-based alloy TIG welding wire for cryogenic steel capable of improving the temperature.

[0008]

The Ni-based alloy TIG welding wire for cryogenic steel according to the present invention comprises 65 to 80% by weight of Ni, 0.1 to 5.0% by weight of Cr, and 16.0% of Mo.
To 23.0% by weight, W: 1.0 to 4.5% by weight, T
i: 0.02 to 0.10% by weight and Al: 0.003
To 0.030% by weight, with the balance being Fe and unavoidable impurities, the unavoidable impurities being Cu: 0.
10% by weight or less, Mg: 0.0020% by weight or less, C
a: 0.0020% by weight or less, C: 0.10% by weight or less, Si: 0.10% by weight or less, Mn: 0.10% by weight
Hereinafter, Zr: 0.010% by weight or less, total amount of Y and rare earth elements: 0.005% by weight or less, P: 0.003% by weight
And S is regulated to 0.003% by weight or less ,
Further, the depth of the scratch on the wire surface is 0.05 mm or less.
Characterized in that that.

[0009]

[0010]

The inventors of the present invention have conducted intensive experimental studies to solve the above-mentioned problems. As a result, not only the amount of slag generated was reduced by reducing Ca, Mg and Si, but also T
It has been found that by positively adding i and Al, the generated slag can be spheroidized and easily separated. That is, when the slag has good releasability, defects such as slag entrapment do not occur, and thus the generated slag can be rendered harmless.

If Cu is present in the Ni-based alloy wire, the Cu forms a low melting point compound, and cracks occur on the surface of the wire during wire fabrication such as hot forging and cold rolling of the wire. . The cracks become places where the coating agent and the lubricant mainly composed of Ca and the like remain at the time of wire drawing, and cause slag. Furthermore, since Zr, Y and rare earth elements also cause slag generation, the amount of slag generation can be suppressed by defining these components in appropriate amounts.

On the other hand, Ni-
Mo alloys have extremely poor drawability compared to carbon steel or stainless steel. Therefore, in order to reduce the drawing cost and obtain an inexpensive wire, it is necessary to use a coating agent for improving the drawability and a lubricant made of Ca or the like. Since this Ca remains on flaws on the wire surface and generates slag at the time of welding, it is possible to further reduce the amount of generated slag by reducing the remaining Ca by limiting the depth of the flaw on the wire surface. it can.

The reasons for limiting the composition of the components contained in the TIG welding wire of the present invention will be described below.

Ni (nickel): 65 to 80% by weight Ni is an element for stabilizing the austenite structure, and has an effect of securing impact resistance at cryogenic temperatures. If the Ni content is less than 65% by weight, sufficient impact resistance cannot be secured. On the other hand, if the Ni content exceeds 80% by weight, it is impossible to sufficiently add a component for increasing the strength of the welded portion. Therefore, the Ni content in the wire is set to 65 to 80% by weight.

Cr (chromium): 0.1 to 5.0% by weight Cr has an effect of improving the strength of the weld metal. Cr
When the content is less than 0.1% by weight, the effect is reduced. On the other hand, if the Cr content exceeds 5.0% by weight, the amount of slag generated increases, and the weldability becomes poor. Therefore, the Cr content in the wire is set to 0.1 to 5.0% by weight.

Mo (molybdenum): 16.0 to 23.
0% by weight of Mo has an effect of securing impact resistance at cryogenic temperatures. If the Mo content is less than 16.0% by weight, the effect is reduced. On the other hand, if the Mo content exceeds 23.0% by weight, it becomes difficult to produce a wire. Therefore, the Mo content in the wire is set to 16.0 to 23.0% by weight.

W (tungsten): 1.0 to 4.5 layers
The amount% W has the effect of improving the strength of the weld metal. When the W content is less than 1.0% by weight, the effect is reduced.
On the other hand, if the W content exceeds 4.5% by weight, the impact resistance at cryogenic temperatures decreases. Therefore, the W content in the wire is set to 1.0 to 4.5% by weight.

Ti (titanium): 0.02 to 0.10 weight
The amount% Ti has the effect of refining the crystal grains and increasing the strength of the weld metal. Further, it has an effect of improving the blow hole resistance and detoxifying the generated slag. T
When the i content is less than 0.02% by weight, the effect is reduced. On the other hand, if the Ti content exceeds 0.10% by weight, the amount of slag generated increases, resulting in poor weldability. Therefore, the Ti content in the wire is 0.02 to 0.5.
10% by weight.

Cu (copper): 0.10% by weight or less As described above, Cu forms a low melting point compound in a Ni-based alloy wire. This low melting point compound causes cracks in the weld metal during wire fabrication, especially during forging, which becomes a high temperature, and these cracks become residual places of coating agent and lubricant during wire drawing, causing slag generation. Become. Cu
If the content exceeds 0.10% by weight, slag tends to be generated. Therefore, the Cu content in the wire is set to 0.10% by weight or less.

Mg (magnesium): 0.0020 weight
% Or less Mg has the effect of promoting the generation of slag in the weld metal, so it is preferable to reduce the content in the wire as much as possible. If Mg exceeds 0.0020% by weight, the weldability becomes poor due to an increase in the amount of slag generated. Therefore, the Mg content in the wire is set to 0.0020% by weight or less.
Preferably, the Mg content is not more than 0.0010% by weight.

Ca (calcium): 0.0020% by weight
Since Ca has the effect of promoting slag generation of the weld metal, it is preferable to reduce the content of the wire as much as possible. If Ca exceeds 0.0020% by weight, the weldability becomes poor due to an increase in the amount of slag generated. Therefore, the Ca content in the wire is set to 0.0020% by weight or less.
Preferably, the Ca content is less than or equal to 0.0010% by weight.

[0022]Al (aluminum): 0.003 or more
0.030% by weight Al has the effect of detoxifying the slag generated on the bead surface
Have. When the Al content is less than 0.003% by weight,
Its effect decreases. On the other hand, the Al content is 0.030 weight
If the amount exceeds%, the amount of slag generated increases,
Becomes defective. Therefore, the Al content in the wire is 0.0
03 to 0.030% by weight.

C (carbon): 0.10% by weight or less C has the effect of increasing the strength of the weld metal. However, when the C content exceeds 0.10% by weight, the impact resistance decreases. Therefore, the C content in the wire is set to 0.10% by weight or less.

Si (silicon): 0.10% by weight or less Si is an element effectively acting as a deoxidizing agent. However, if the Si content exceeds 0.10% by weight, it becomes impossible to secure crack resistance. Further, the amount of slag generated increases, resulting in poor weldability. Therefore, the Si content in the wire is set to 0.10% by weight or less.

Mn (manganese): 0.10% by weight or less Mn is an element that effectively acts as a deoxidizing agent. However, if the Mn content exceeds 0.10% by weight, the conformity of the weld pool to the base metal decreases. Further, the amount of slag generated increases, resulting in poor weldability. Therefore, the Mn content in the wire is set to 0.10% by weight or less.

Zr (zirconium): 0.010% by weight
Since Zr has the effect of promoting the generation of slag in the weld metal, it is preferable to reduce the content in the wire as much as possible. If the Zr content exceeds 0.010% by weight, the weldability becomes poor due to an increase in the amount of slag generated. Therefore, the Zr content in the wire is set to 0.010% by weight or less.

[0027]Total of Y (yttrium) and rare earth elements
Amount: 0.005% by weight or less Y and rare earth elements promote slag generation
Therefore, the content in the wire can be reduced as much as possible
preferable. The total amount of Y and rare earth elements is 0.005% by weight
Exceeds, the weldability is poor due to an increase in the amount of slag generated
Becomes Therefore, the content of Y and rare earth elements in the wire
Is 0.005% by weight or less.

[0028]P (phosphorus): 0.003% by weight or less, S
(Sulfur): 0.003% by weight or less When the content of P and S in the wire increases,
Cracks are likely to occur. Therefore, the P content in the wire
Is 0.003% by weight or less, S content is 0.003% by weight
The following is assumed.

As elements inevitably mixed into the wire,
In addition to the above elements, there are Nb, V, Co, B, O, N, H, and the like. Cu, Mg, Ca, C, Si, Mn, Z
The total amount of unavoidable impurities excluding r, P, S, Y and rare earth elements is preferably 0.1% by weight or less.

Defect depth on the wire surface: 0.05 mm or less As described above, if there is a deep flaw on the surface of the wire, Ca, which is a raw material of a coating agent and a lubricant, remains in the flaw and the amount of slag generated is reduced. To increase. Therefore, the depth of the flaw on the wire surface is set to 0.05 mm or less.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a Ni-based alloy T for cryogenic steel according to the present invention will be described.
An example of the IG welding wire will be specifically described in comparison with a comparative example.

First, in a 30 kg vacuum melting furnace, all the components contained in the wire were within the scope of the present invention as examples, and at least one of the components was excluded from the scope of the present invention as a comparative example. After adjusting the ingredients,
A 30 kg ingot was produced by casting. Thereafter, a wire having a diameter of 5.0 mm was formed by hot forging and cold rolling. Next, the wire was heated to 1100 ° C.
After bright annealing in a heated strand furnace, the wire was pickled with nitric acid and visually inspected for flaws on the surface of the wire. Then, the diameter of the wire was reduced to 4.0 mm by passing the wire through a peeling die, and rolling scratches on the surface of the wire were removed.

Further, by using a resin coating agent and a lubricant containing Ca, intermediate drawing and bright annealing are repeated for a 4.0 mm wire to have a diameter of 1.28 m.
m. Thereafter, finish wire drawing was performed using oil, the wire diameter was reduced to 1.20 mm, and the surface was washed and dried with high-temperature steam to produce a TIG welding wire. The components contained in each TIG welding wire and the scratch depth on the wire surface are shown in Tables 1 to 6 below. However, the depth of the surface flaw was measured by polishing the cross section of the wire and then magnifying the depth by 50 times.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

[0039]

[Table 6] Ni steel was welded in accordance with JISZ3332 using TIG welding wires having the chemical components shown in Tables 1 to 6 above. Table 7 below shows the welding conditions.

[0040]

[Table 7]

FIG. 1 is a schematic sectional view for explaining a welding test method. As shown in FIG. 1, an oblique groove is provided in a welding base material 1 made of 9% Ni steel, and the two are butted to form a V-shaped groove, and on the back surface of the V-shaped groove, The backing material 2 was arranged. This groove portion is referred to as Example No. Nos. 1 to 11 and Comparative Example Nos. TIG welding was performed using 12 to 30 wires to form a weld metal as shown in FIGS. 2 and 3 and welding workability such as generation of slag was evaluated.

Further, a test piece was sampled from the weld metal thus formed and subjected to a mechanical test by a tensile test, an impact test and a longitudinal bending test.

FIG. 2 is a schematic cross-sectional view showing the positions where test pieces for impact test and tensile test are taken from the weld metal. In the present embodiment and the comparative example, as shown in FIG. 2, the V-shaped groove angle of the weld metal is set to 45 °, and the groove width of the lower part where the backing material 2 is arranged is 12 mm. did. The plate thickness of the welding base material 1 is 20 mm.

The test piece 4 for the tensile test is a rod-shaped test piece having a circular section with a parallel portion having a diameter of 12.5 mm, and the center of the weld metal 3 is the center of the circle of the test piece section.
Test piece 4 was collected. Using this test piece 4, at room temperature, the proof stress and tensile strength at an elongation of 0.2% were measured, and the tensile strength was evaluated by calculating the elongation at break. The test piece 5 for the impact test is a rod-shaped test piece having a square parallel section of 10 mm × 10 mm. The test piece 5 extends over the welding base metal 1 and the welding metal 3 welded thereto. Was collected. A V-notch having a depth of 2 mm was formed on the test piece 5, an impact test was performed at -196 ° C, and the impact resistance was evaluated by measuring the absorbed energy.

FIG. 3 is a schematic sectional view showing a sampling position from a weld metal for a vertical bending test. The plate thickness and groove angle of the welding base material were the same as those shown in FIG. The test piece 6 for the longitudinal bending test is a plate-like test piece having a thickness of 10 mm and a width of 40 mm. Like the test piece for the impact test, the welding base material 1 and the weld metal 3 welded thereto are formed. It was collected so as to straddle. The test piece 6 was sampled from the surface of the V-groove slightly from the center of the weld metal and the base metal. Using this test piece 6, a bending radius of 32 mm and a bending angle of 180 °
A longitudinal bending test was carried out, and crack resistance was evaluated by observing defects such as cracks. The results of each evaluation are shown in Tables 8 to 11 below.
Shown in However, in the evaluation column for welding workability in the table,
Indicates excellent, ○ indicates good, and × indicates bad.

[0046]

[Table 8]

[0047]

[Table 9]

[0048]

[Table 10]

[0049]

[Table 11]

As shown in Tables 1 to 6 and 8 to 11,
Example No. 1 in which all the components contained in the wire are within the scope of the present invention. Regarding 1 to 11, the amount of slag generated was suppressed, the welding workability was good, and the mechanical performance was also excellent. In Example N, the depth of the scratch on the wire surface is small.
o. In Nos. 1 to 8, the amount of slag generated was further reduced, and welding workability was further improved.

On the other hand, in Comparative Example No. Sample No. 12 had a low impact resistance because the C content exceeded the upper limit of the range of the present invention. Comparative Example No. In No. 13, since the Si content exceeded the upper limit of the range of the present invention, the amount of slag generated increased, and a large number of cracking defects occurred in the longitudinal bending test. Comparative Example No. In Nos. 14 and 15, both of the Mn or Cr contents exceeded the upper limit of the range of the present invention, so that the amount of slag generated increased. Also, in Comparative Example No. In No. 16, the strength of the weld metal was insufficient because the Cr content was less than the lower limit of the range of the present invention.

Comparative Example No. In No. 17, since the Mo content was less than the lower limit of the range of the present invention, the impact resistance was low. Comparative Example No. In No. 18, since the Mo content exceeded the upper limit of the range of the present invention, cracks occurred during forging, and a wire could not be produced. Comparative Example No. In Comparative Example No. 19, since the W content was less than the lower limit of the range of the present invention, the strength of the weld metal was low. In No. 20, the impact resistance was reduced because the W content exceeded the upper limit of the range of the present invention. Comparative Example No. In No. 21, since the Cu content exceeded the upper limit of the range of the present invention, scratches occurred frequently during forging and rolling of the wire, and the amount of slag generated increased.

In Comparative Example No. In Nos. 22 and 24, since the content of Ti or Al was less than the lower limit of the range of the present invention, the generated slag was not spherical, and it was difficult to remove the slag. Comparative Example No. For 23 and 25-30, T
Since the total content of i, Al, Mg, Ca, Zr or Y and the rare earth element exceeded the upper limit of the range of the present invention, the amount of slag generated increased and the removal of slag became difficult.

[0054]

As described in detail above, according to the present invention,
Reduces slag forming elements in the wire, and further reduces Ti and A
By adding l positively, the weld metal has a high strength, and can suppress the occurrence of slag on the bead surface or enhance the slag peelability to improve weldability. A Ni-based alloy TIG welding wire can be obtained. Further, the amount of slag generated can be further reduced by regulating the depth of the scratch on the wire surface.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a welding test method.

FIG. 2 is a schematic cross-sectional view showing a position where a test piece for an impact test and a tensile test is sampled from a weld metal.

FIG. 3 is a schematic cross-sectional view showing a sampling position from a weld metal for a vertical bending test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1: Base material 2: Backing material 3: Weld metal 4, 5, 6; Test piece

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-63789 (JP, A) JP-A-7-136796 (JP, A) JP-A-7-290280 (JP, A) JP-A-60-1985 37290 (JP, A) JP-A-9-277085 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 35/02, 35/30

Claims (1)

(57) [Claims] 1. Ni: 65 to 80% by weight, Cr: 0.
1 to 5.0% by weight; Mo: 16.0 to 23.0% by weight; W: 1.0 to 4.5% by weight; Ti: 0.02 to 0.10% by weight; 0.030% by weight, with the balance being Fe and unavoidable impurities, the inevitable impurities being: Cu: 0.10% by weight or less, Mg: 0.0020% by weight or less, Ca: 0.002%
0 wt% or less, C: 0.10 wt% or less, Si: 0.1
0% by weight or less, Mn: 0.10% by weight or less, Zr: 0.
010% by weight or less, total amount of Y and rare earth elements: 0.00
5% by weight or less, P: 0.003% by weight or less and S: 0.
It is regulated to 003 wt% or less, further, the wire surface
The Ni-based alloy TIG welding wire for cryogenic steel , wherein the depth of the scratches is 0.05 mm or less .