JP2660708B2 - Stainless steel gas shielded arc welding wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to austenitic and austenitic
The present invention relates to a stainless steel gas shielded arc welding wire which is used for welding ferritic duplex stainless steel and has particularly high efficiency.

(Prior Art) Conventionally, as gas shielded arc welding of stainless steel, TIG welding using an inert gas and MIG welding using a mixed gas obtained by adding a small amount of an active gas to an inert gas have been applied.

TIG welding is shielded with an inert gas, so there is almost no intrusion of O and N in the atmosphere, and the performance of the weld metal is very good, but the wire generated in the arc generated between the tungsten electrode and the base metal Is inserted and the wire is melted by the heat of the arc. Therefore, there is a problem that the melting speed of the wire is limited and efficiency is poor.

MIG welding is highly efficient because the wire itself becomes an electrode and emits and melts the arc, but if the shielding gas is only inert gas, the arc is unstable and penetration is small, and welding defects such as poor fusion are likely to occur .

A method of adding a small amount of an active gas to a shielding gas in order to improve these welding defects is disclosed in Japanese Patent Publication No. 54-32745. However, the addition of the active gas inevitably increases the amount of O in the weld metal, impairs low-temperature toughness and corrosion resistance, and oxidizes the weld metal to form slag with a high melting point on the bead surface, which results in poor fusion. Easy to cause.

As means for solving such problems in MIG welding, Japanese Patent Application Laid-Open No. 61-71185 discloses a method of stabilizing an arc with an inert gas shield by using a wire to which a rare earth element is added, and this method. Is disclosed in JP-A-62-197294.

(Problems to be Solved by the Invention) The use of a wire to which a rare earth element is added makes it possible to perform MIG welding with an inert gas shield, but there is a problem in that blowholes are generated in the weld metal.

In view of these circumstances, an object of the present invention is to provide a stainless steel gas shielded arc welding wire which can provide a high-efficiency, low-temperature toughness, and high-corrosion-resistant weld metal and does not generate blowholes in the weld metal.

(Means for Solving the Problems) The present invention relates to a stainless steel gas shielded arc welding wire used for MIG welding performed under a shielding gas made of an inert gas, wherein C: 0.001 to 0.08% by weight, Si: 0.01 to 1.0%, Mn: 0.01 to 5.5%, Cr: 18 to 27.5%, Ni: more than 9% and 22% or less, N: 0.01 to 0.50%, Rare earth element: 0.020 to 0.40%, and Al: It is limited to 0.020% or less, P: 0.030% or less, S: 0.020% or less, O: 0.015% or less, characterized by the balance of low-temperature toughness, high corrosion resistance, and gas blowhole, with the balance being Fe and unavoidable impurities. For stainless steel gas shielded arc welding wire that does not generate, and for stainless steel gas shielded arc welding wire used for MIG welding performed under a shielding gas consisting of an inert gas, C: 0.001 to 0.08% by weight, Si: 0.01 to 1.0%, Mn: 0.01-5.5%, Cr: 18-27.5 , Ni: more than 9% and 22% or less, Mo: 0.01 to 7.0%, N: 0.01 to 0.50%, rare earth element: 0.020 to 0.40%, and Al: 0.020% or less, P: 0.030% or less, S : O: 0.020% or less, O: 0.015% or less, characterized by low-temperature toughness, high corrosion resistance and no gas blow hole, characterized by the balance being Fe and unavoidable impurities. is there.

(Operation) First, MIG welding is used to achieve high efficiency, and rare earth elements are added to the wire to secure low-temperature toughness and high corrosion resistance, and welding with an inert gas is realized, thereby reducing O. I was able to hold down.

However, in MIG welding using a rare earth element and using only an inert gas, blowholes are often generated in the weld metal as described above, and this tendency is particularly remarkable when the N content in the wire is large. It is. The present inventors have studied various measures for preventing blowholes, and as a result, have found that the amount of Al in the wire has a great effect. That is, since the occurrence of blow holes increases when the amount of Al is large,
, A blowhole is not generated regardless of the amount of N, and a sound weld metal can be obtained.

 Next, the reasons for limiting the components of the wire of the present invention will be described.

C is required to be 0.001% or more to maintain strength. However, it combines with Cr and precipitates as carbides at grain boundaries and the like, impairing toughness and corrosion resistance. Therefore, the upper limit is made 0.08%.

Si needs to be 0.01% or more to maintain the deoxidizing effect and strength. However, if contained in a large amount, the crack resistance is reduced, so the upper limit is made 1%.

Mu is a deoxidizing element and also an austenite stabilizing element. It promotes the solid solution of N and must be 0.01% or more. However, if contained in a large amount, precipitation of intermetallic compounds harmful to corrosion resistance and the like is observed. The upper limit is set to 5.5%.

Since both P and S significantly impair the welding hot cracking susceptibility, the upper limits are limited to P0.030% or less and S0.020% or less.

Cr is a main element that imparts corrosion resistance, and 18% or more is necessary to make its effect sufficient. On the other hand, if contained in a large amount, the productivity of the wire is significantly reduced, and precipitation of intermetallic compounds harmful to corrosion resistance is promoted.
%.

Ni is a main element for stabilizing austenite, and at least 9% is necessary for securing austenite-ferrite phase balance and securing toughness. On the other hand, if the content exceeds 22%, not only the effect is not remarkably exhibited but also the crack resistance is lowered, so the upper limit is made 22%.

N forms a solid solution in the matrix to improve the corrosion resistance and strength, but 0.01% or more is necessary to make the effect sufficient. On the other hand, even if it is added more than 0.50%, the effect does not appear remarkably, so the upper limit is made 0.50%.

O lowers the toughness of the austenitic weld metal.
If it exceeds 0.015%, the decrease in toughness becomes remarkable, so 0.015%
Limited to the following.

When Mo is contained in order to improve corrosion resistance and increase strength, 0.01% or more is necessary. However, if more than 7% is contained, intermetallic compounds harmful to corrosion resistance are found, so the upper limit is made 7.0%. .

Rare earth elements are very effective in enabling MIG welding using an inert gas, but at least 0.020% is necessary to obtain the effect. However, if it exceeds 0.40%, the toughness decreases, so the upper limit is made 0.40%.

Regarding Al, Japanese Patent Publication No. 61-9112 discloses a method for preventing blowholes in stainless steel MIG welding.
It is disclosed that Al and B are restricted. Tokiko Sho 61-91
No. 12 is a MIG welding method using a shielding gas to which an active gas is added, inevitably increasing the amount of O in the weld metal, and it is an essential requirement that not only Al but also B be simultaneously restricted. Has become. Al is used as a deoxidizer in the melting of stainless steel solvent materials, and the aforementioned Japanese Patent Publication No. 61-9112 discloses that about 0.015 to 0.05% is contained in a commercially available Y308-based melting wire. I have.

The present invention adds a rare earth element to the wire, in MIG welding performed only with an inert gas shielding gas, as a measure to prevent blowholes found in the weld metal, the transfer of droplets is performed smoothly when Al is held low, Based on the new finding that the occurrence of blowholes in the weld metal is reduced, the effect becomes significant at Al 0.020% or less.
Limit to 0.020% or less.

These can be applied to welding of austenitic and austenitic / ferritic duplex stainless steels, as well as repair welding of those structures or overlay welding.

In addition, the wire of the present invention is manufactured by melting and casting an ingot in a vacuum or air atmosphere into a coil by hot forging, and then drawing the wire to a predetermined wire diameter by cold working. Can be.

(Examples) Hereinafter, the effects of the present invention will be described more specifically with reference to examples.

Table 1 shows the chemical composition of the wire. Each wire diameter is 1.2 mmφ.

Table 2 shows the test steel materials. All steel materials have a thickness of 12 mm.

 Table 3 shows the welding conditions.

Table 4 shows combinations of test wires and test steel materials and performance test results.

The performance test plate is a steel material shown in Table 2 (plate thickness 12 mm, width 150 m
m, length 500mm), assemble by attaching two restraining plates with Y-groove (80mm, root face; 1mm, root gap; 2mm), also serve as welding crack test, laminating the front side, back Hanging was performed and welding was performed under the same welding conditions.

The X-ray performance test was carried out on the bead body excluding the start portion and the crater portion in accordance with JIS Z 3106 (radiation transmission test method for stainless steel welded portion and classification method for transmission photograph).

In the crack test of the welded portion, after the completion of the first layer welding, it was observed whether or not cracks were observed in the bead body excluding the start portion and the crater portion.

In the tensile test of the weld metal, a JIS Z 3111 A2 test piece (parallel portion 6 mmφ) was sampled from the welded portion and subjected to a tensile test at room temperature.

For the impact test of the weld metal, a JIS Z 3112 No. 4 test piece (2 mm V notch Charvi test piece) was sampled from the welded part, and the temperature was -196 ° C.
Was tested.

In the corrosion test, JIS G 0575 (a method of testing sulfuric acid and copper sulfate corrosion of stainless steel) as a grain boundary corrosion test and JIS G 0578 (a method of testing ferric chloride corrosion of stainless steel) as a pitting corrosion test.

In the intergranular corrosion test, a test piece of 3 t × 10 w × 70 lmm was sampled from the welded part, immersed in a corrosive liquid for 16 hours continuously, and then bent to a bending radius of 2 t and a bending angle of 180 °. The presence or absence was observed.

In the pitting corrosion test, a 3t × 10w × 30lmm test piece was sampled from the welded portion, and the critical pitting occurrence temperature (CPT) in a chloride environment was determined and evaluated. The corrosion liquid used was a 6% ferric chloride + 0.05N hydrochloric acid aqueous solution, and the CPT was immersed in a corrosion liquid controlled at 5 ° C. intervals for 24 hours, and the maximum temperature at which pitting did not occur was defined as CPT. A CPT of 55 ° C or higher was judged to be acceptable.

In addition, the weld metal tensile test, impact test, and corrosion test piece, for the wire symbol A13 and B19, after the end of welding,
After heat treatment (water cooling after holding at 1150 ° C. for 60 minutes), test pieces were collected. In all other tests except A13 and B19, specimens were taken as welded.

From the above results, Examples A1 to A15 are all excellent in the X-ray transmission test performance of the welded portion and the crack resistance of the weld metal,
It is clear that a sound weld is obtained and the performance of the weld metal is excellent.

On the other hand, in Comparative Example B1, C exceeded 0.08%, and the corrosion resistance was poor. B2 contains more than 1.0% of Si and B5 contains 22% of Ni
%, B10 has P exceeding 0.030%, B11
In S, the S exceeded 0.020%, and cracks were observed in the bead body in the crack test.

B3 has less than 5.5% Mn, B4 has less than 5.5% Ni, B6 has less than 18% Cr, B7 has more than 27.5% Cr, B9 has more than 0.50% N In the case of B18, Mo exceeds 7%, and all have poor corrosion resistance.

B12 contains more than 0.015% O and B14 contains rare earth elements
Exceeding 0.40%, all have poor toughness.

B8 had an N of 0.010% or less, and the tensile strength of the weld metal was low.

B13 contains less than 0.020% of rare earth elements, and blowholes are found in the welds. B15, B16 and B17 contain more than 0.020% of Al, and all have blowholes. Met.

B1 and B14 have poor corrosion resistance and low weld metal impact value.

(Effects of the Invention) As is clear from the above embodiments, the wire of the present invention can perform good MIG welding using an inert gas, thereby preventing an increase in O of the weld metal and having excellent X-ray performance. ,
A sound weld is obtained, and there is no crack in the weld metal.
It has excellent tensile performance, impact performance and corrosion resistance, and its industrial effects are extremely remarkable.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tadao Ogawa 5-10-1 Fuchinobe, Sagamihara City, Kanagawa Prefecture New Nippon Steel Corporation Second Technical Research Institute (56) References JP-A-62-28097 (JP, A JP-A-62-197294 (JP, A) JP-A-49-13054 (JP, A) JP-A-54-76452 (JP, A) JP-B-61-9112 (JP, B2)

Claims (2)

(57) [Claims] (1) In a stainless steel gas shielded arc welding wire used for MIG welding performed under a shielding gas comprising an inert gas, C: 0.001 to 0.8% Si: 0.01 to 1.0% Mn: 0.01 to 5.5% by weight % Cr: 18 to 27.5% Ni: Over 9% to 22% or less N: 0.01 to 0.50%, Rare earth element: 0.020 to 0.40%, Al: 0.020% or less P: 0.030% or less S: 0.020% or less O: A stainless steel gas shielded arc welding wire characterized by being limited to 0.015% or less, the balance being Fe and unavoidable impurities. 2. In a stainless steel gas shielded arc welding wire used for MIG welding performed under a shielding gas comprising an inert gas, C: 0.001 to 0.8% Si: 0.01 to 1.0% Mn: 0.01 to 5.5% by weight % Cr: 18 to 27.5% Ni: Over 9% to 22% or less Mo: 0.01 to 7.0% N: 0.01 to 0.50% Rare earth element: 0.020 to 0.40%, and Al: 0.020% or less P: 0.030% or less S: 0.020% or less O: 0.015% or less, a stainless steel gas shielded arc welding wire characterized by the balance of Fe and unavoidable impurities.