JPH0555239B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an austenitic stainless steel wire for gas-shielded arc welding, in particular, the wire contains Al and has excellent weldability and cracking resistance in gas-shielded arc welding, and is resistant to acid at high temperatures. The present invention relates to an austenitic gas-shielded arc welding wire that provides a weld metal with excellent corrosion resistance, corrosion resistance, and high-temperature strength. [Prior Art] In recent years, heat-resistant stainless steel is often used for components exposed to high temperatures such as heating furnaces and incinerators from the viewpoint of high-temperature combustion countermeasures to further extend the life of the furnace. Conventionally, such heat-resistant stainless steel is made of Cr.
By selectively oxidizing Cr in a high-temperature oxidizing atmosphere, a Cr ₂ O ₃ film is formed on the surface to protect the inside and ensure heat resistance. However, even with such steel, abnormal oxidation may occur due to combustion atmosphere conditions or other factors, resulting in rapid wear. On the other hand, in the technology of Japanese Patent Publication No. 55-43498, Al4.5 is added to austenitic stainless steel as a material that is resistant to abnormal oxidation.
By containing more than 6% Al ₂ O ₃ on the surface
It has been proposed to form a film to increase oxidation and corrosion resistance at high temperatures. However, when trying to use common metal wire, for example, in gas-shielded arc welding of stainless steel that contains a large amount of Al, cracks tend to occur in the weld metal, making it difficult to use for this purpose. At present, wires that can be used are still unknown. [Problems to be Solved by the Invention] An object of the present invention is to efficiently produce a weld metal with excellent high-temperature properties and good cracking resistance in gas-shielded arc welding of stainless steel containing a large amount of Al. The object of the present invention is to provide a welding wire obtained. [Means for Solving the Problems] In view of the above circumstances, the present inventors have developed a welding method that has excellent high-temperature properties and excellent cracking resistance by applying it to gas-shielded arc welding of stainless steel containing a large amount of Al. As a result of studying welding wires that can obtain metals, we found that P, S, and N are significantly involved in the cracking resistance of weld metals in such welding wires, and we decided to limit each of these elements. It has been found that the above-mentioned cracking resistance is improved. That is, in the present invention, C0.7% or less in weight%,
Si1% or less, Mn2% or less, Cr9~25%, Ni12~40
%, Al4.5-9%, or further contains (A)Ti, Nb
1% or less of each element,
In addition, Mo5% or less, W5% or less, V5% or less,
A total of 15 types of 1% or 2 or more types with Co10% or less
% or less, or (B) one or more rare earth elements with atomic numbers 57 to 71, Ca, in a total amount of 0.1
Contains one or both of (A) and (B), P0.015% or less, S0.01% or less,
An austenitic stainless steel gas-shielded arc welding wire characterized in that N is limited to 0.05% or less, and the remainder is mainly Fe. The present invention will be explained in detail below. [Function] First of all, in the present invention, gas shielded arc welding refers to arc welding performed in an atmosphere containing an inert gas such as Ar or He, or a small amount of active gas to which a small amount of active gas is added. Refers to welding and plasma welding. Next, the reasons for limiting the composition of the wire of the present invention will be described. First, C is an austenite-forming element that stabilizes the austenite phase and increases high-temperature strength, but if it exceeds 0.7%, the ductility of the weld metal decreases, so it should be kept at 0.7% or less. Next, Si improves oxidation resistance, and in the present invention, oxidation resistance is improved by forming an Al ₂ O ₃ film, so there is no need to particularly strengthen oxidation resistance with Si. Improves the flow of weld metal. However, if it exceeds 1%, the cracking resistance of the weld metal deteriorates, so the upper limit is set at 1%. Although Mn is an austenite-forming element, too much Mn deteriorates oxidation resistance, so the upper limit is set to 2%. In addition, Cr is a basic element necessary to obtain a high degree of oxidation resistance, and is essential for stable formation and adhesion of the Al ₂ O ₃ film, so 9%
or more is required. However, if added in excess of 25%, the ductility of the weld metal will deteriorate, so the upper limit is set at 25%. Furthermore, Ni is a basic element for austenite formation, and a minimum of 12% is required to maintain high-temperature strength and creep properties, so 12% is set as the lower limit. However, if it exceeds 40%, hot workability deteriorates, so it is set at 12 to 40%. Next, by adding 4.5% or more of Al,
A film based on Al ₂ O ₃ is formed at high temperatures and remains stable, dramatically improving oxidation resistance. However, if it exceeds 9%, the ductility of the weld metal will deteriorate, so the range should be limited.
4.5% to 9%. On the other hand, P deteriorates cracking resistance. In particular, this tendency becomes stronger as the amount of C increases, so it is essential to limit it to 0.015% or less. Further, like P, S also deteriorates cracking resistance. This tendency is particularly strong as the amount of C increases, so 0.01%
The following restrictions are essential. Furthermore, like P and S, N also deteriorates cracking resistance. This tendency becomes more pronounced as the C content increases, so it is necessary to limit it to 0.05% or less. The above is the basic component system of the wire of the present invention, but in the present invention, in addition to these, one or both of Ti and Nb, Mo, W,
In order to stabilize the Al ₂ O ₃ film and improve hot workability, one or more of V and Co may be added to
One or both of REM 57-71 and Ca can be further added. First, Ti and Nb form and stabilize Al ₂ O ₃ , strengthen oxidation resistance, and precipitate fine carbides to increase high-temperature strength. However, if the total content of one or two elements exceeds 1%, the ductility of the weld metal will decrease, so the upper limit should be set at 1%.
The following shall apply. Furthermore, Mo, W, V, and Co are all effective for increasing high-temperature strength. However, if added in large amounts, the ductility of the weld metal decreases, so Mo, W
and V are each 5% or less, Co is 10% or less, and the total of one or more types is 15% or less. Furthermore, rare earth elements (REM) with an atomic number of 57 to 71% and Ca contribute to the stability of the Al ₂ O ₃ film and have the effect of improving hot workability, but one or more of them Adding more than 0.1% in total will actually impair hot workability, so the upper limit is set to 0.1% or less. Therefore, referring to the method for manufacturing the wire of the present invention, the method involves melting in a vacuum or atmospheric atmosphere,
The ingot obtained by casting is hot-forged, then hot-rolled into a coil, which is then cold-drawn to a predetermined wire diameter. In addition, hot forging and hot rolling are approximately 1000 ~
The hardness of the wire can be adjusted by heating to about 1200°C, and in the cold wire drawing process, annealing can be performed at about 1000 to 1200°C as needed. Hereinafter, the effects of the present invention will be described in more detail with reference to Examples. [Example] Table 1 shows the chemical composition of the test welding wire. Table 2 shows the cracking resistance test results for weld metal. For the cracking resistance test, a steel plate with the same composition as Al shown in Table 1 and dimensions of 12 mm thick, 120 mm wide, and 250 mm long was used, and the test plate was restraint welded with a groove angle of 70°, a root face of 2 mm, and a root gap of 2 mm. and welded a bead length of 200mm under the welding conditions shown in Table 3.
The crack length on the surface of the bead was measured. The cracking rate was calculated by measuring the total crack length B in the bead body A excluding the start part and the crater part, and expressing it as B/A x 100 = cracking rate. Table 4 shows the oxidation resistance test results. The oxidation resistance test was conducted on a difficult steel plate under the welding conditions shown in Table 3.
Overlay welding was performed with a thickness of 50 mm, a width of 50 mm, and a length of 200 mm, and a test piece of 2 mm thick, 20 mm long, and 30 mm wide was taken from the upper layer of the weld metal by machining, and a continuous heating test was performed in a combustion atmosphere. The combustion atmosphere was a mixture of gasoline engine exhaust gas and air (mixed volume ratio 2:1), and the mixture was placed in an electric furnace maintained at 1200℃.
It was heated for 30 minutes, after which the sample was removed and air cooled for 30 minutes. This was regarded as one cycle and 150 cycles were repeated, and the change in weight of the sample was measured. Table 5 shows the room temperature and high temperature tensile properties of the deposited metal. Room temperature and high temperature tensile tests of weld metal were conducted using a 12 mm thick steel plate with the same composition as Al shown in Table 1.
The inside of the groove assembled with a groove angle of 45° and a root gap of 6 mm was laminated for 10 passes under the welding conditions shown in Table 3, and a test piece was taken from the center of the weld metal. The room temperature tensile test was conducted according to JIS Z3111, and the high temperature tensile test was conducted according to JIS G0567. The test temperatures were room temperature (20°C), 600°C, 750°C, and 900°C. From the above, it is clear that the weld metals A1 to A24 of the present invention have good cracking resistance, and have excellent oxidation resistance and high-temperature tensile properties. On the other hand, comparison wire B1 has a C content of over 0.7%, and the elongation of the weld metal is low, and B2 has a Si content of 1%.
In the cracking resistance test, cracks were observed in the bead body, B3 had a Mn content of more than 2% and had poor oxidation resistance, and B4 had a Cr content of more than 25%.
The elongation of the weld metal was low, B5 had more than 40% Ni, and hot workability was poor, making it impossible to obtain a test wire. B6 and B7 have less than 4.5% Al and have poor oxidation resistance and high temperature tensile properties. The oxidation resistance of the wire of the present invention is due to the formation of an Al ₂ O ₃ film.
Comparative wires B3, B6, and B7 showed significant oxidation loss, whereas they showed only a slight weight gain or a negligible weight loss due to partial oxidation progression. B8 has Al exceeding 9% and the elongation of the weld metal is poor, B9, B10, B11 and B12 have P,
S and N are 0.015%, 0.010%, and
It exceeded 0.050%, and cracks were observed in the bead body in both cases in the cracking resistance test. In B13 and B14, Ti and Nb each exceeded 1%, and the ductility of the weld metal deteriorated. B15, B16, and B17 have 5 Mo, W, and V, respectively.
%, and in B18, Co exceeded 10%, and the ductility of the weld metal deteriorated in both cases. B19, B20 have 0.1% REM and Ca each
was exceeded, the hot workability deteriorated, and a test wire could not be obtained.

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〔Effect of the invention〕

As is clear from the above examples, the wire of the present invention contains a suitable amount of Al, and also contains Ti, Nb, Mo,
By adding appropriate amounts of W, V, Co, REM, and Ca, and controlling P, S, and N, high-Al-containing heat-resistant stainless steel has good cracking resistance and oxidation resistance at high temperatures. In addition, gas-shielded arc welding, which produces weld metal with excellent high-temperature tensile properties, can be carried out with good workability, and the industrial effect is extremely significant.

Claims (1)

[Claims] 1% by weight, contains C 0.7% or less, Si 1% or less, Mn 2% or less, Cr 9-25%, Ni 12-40%, Al 4.5-9%, P 0.015% Hereinafter, an austenitic stainless steel gas-shielded arc welding wire characterized in that S is limited to 0.01% or less and N is limited to 0.05% or less, with the remainder mainly consisting of Fe. 2% by weight, C 0.7% or less, Si 1% or less, Mn 2% or less, Cr 9-25%, Ni 12-40%, Al 4.5-9%, and one or two of Ti and Nb, respectively. 1% or less for elements, Mo5% or less, W5% or less, V5% or less,
A total of 15 types of 1% or 2 or more types with Co10% or less
% or less, P is limited to 0.015% or less, S is 0.01% or less, N is limited to 0.05% or less, and the remainder is mainly Fe. 3% by weight, C 0.7% or less, Si 1% or less, Mn 2% or less, Cr 9-25%, Ni 12-40%, Al 4.5-9%, and rare earth elements with atomic numbers 57-71, Ca. 1
An austenitic stainless steel gas containing one or more species in a total amount of 0.1% or less, limited to P 0.015% or less, S 0.01% or less, N 0.05% or less, and the balance mainly consisting of Fe. Wire for shielded arc welding. 4% by weight, C 0.7% or less, Si 1% or less, Mn 2% or less, Cr 9-25%, Ni 12-40%, Al 4.5-9%, and one or two of Ti and Nb, respectively. 1% or less for elements, Mo5% or less, W5% or less, V5% or less,
A total of 15% of one or more types of Co10% or less
Below, and rare earth elements with atomic numbers 57 to 71, 1 of Ca
An austenitic stainless steel gas shield containing one or more species in a total amount of 0.1% or less, limited to P 0.015% or less, S 0.01% or less, and N 0.05% or less, with the balance mainly consisting of Fe. Wire for arc welding.