JP3483657B2 - Austenitic stainless steel coated arc welding rod for high temperature - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for welding an austenitic stainless steel containing Mo having excellent high-temperature characteristics and used for a long time at a high temperature in the field of nuclear power. It relates to a covered arc welding rod. More specifically, the present invention relates to an austenitic stainless steel-coated arc welding rod containing Mo, in which a weld metal has excellent creep rupture strength and creep rupture ductility at a high temperature of 500 ° C. or higher. [0002] Mo-containing austenitic stainless steels have excellent properties at high temperatures, and are used in chemical plants,
It is used as various heat-resistant members for nuclear facilities. Recently, steel materials with improved high-temperature creep properties, especially breaking strength and fracture ductility, have been developed for long-life applications for such high-temperature applications. Also, those having excellent high-temperature creep rupture strength and rupture ductility like the base material are required. However, among the various welding materials, the coated arc welding rod has a gas generating agent, a slag agent, etc. in the coating agent for securing so-called welding workability. Higher than welding materials and welding methods,
Particularly, it has been extremely difficult to simultaneously secure both excellent properties of high temperature creep rupture strength and rupture ductility. SUMMARY OF THE INVENTION The present invention relates to a weld metal having excellent creep rupture strength and creep rupture ductility at a high temperature of 500 ° C. or more when welding Mo-containing austenitic stainless steel having excellent high temperature properties. It is an object of the present invention to provide a Mo-containing austenitic stainless steel-coated arc welding rod capable of ensuring the following. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to solve the above-mentioned problem. ), C is 0.025% or less, Cr is 1
5.0 to 21.0%, Ni is 7.0 to 14.0%, Mo
Austenitic stainless steel consisting of 1.2 to 3.2% and the remainder Fe and unavoidable impurities as a core wire, and around the core wire, 25 to 55% of titanium oxide based on the total weight of the coating agent. %, 5 to 25% of metal carbonate, 4 to 20% of metal fluoride, 1 to 15% of silicate compound and 1 to 35% of metal powder are coated at a coverage of 20 to 40%. In one or both of the core wire and the coating agent, P is 0.015 to 0.044% and N is 0.03% by weight of the core wire.
~ 0.25 &, contains V 0.03-0.80%, Nb
Is limited to less than 0.10%, and the value of Nb / V is 0.1%.
An austenitic stainless steel coated arc welding rod for high temperature, characterized in that the value of N / (5Nb + V) is controlled to be 0.30 or more at 25 or less. The term "core weight ratio" as used herein refers to a ratio represented by the following formula, and the coating compounding ratio in the same formula means the ratio of the additive material to the total weight ratio of the coating agent. Means the ratio, and the coverage means the weight% of the coating agent with respect to the total weight of the welding rod. You. Core weight ratio = content in core wire (% by weight) + mixing ratio of coating agent (% by weight) × coverage ratio (% by weight) / (100−coverage ratio) In order to improve both the high temperature creep rupture strength and creep rupture ductility of the weld metal of austenitic stainless steel coated arc welding rod,
The amount of P, the amount of N, and the amount of V are specified from the core wire and the composition of the coating agent, the amount of Nb is further restricted, and Nb / V, N / (5N
b + V) to control the amount of P in the weld metal,
The amount of N, the amount of V, and the amount of Nb are controlled in optimal ranges. An object of the present invention is to provide a Mo-containing austenitic stainless steel-coated arc welding rod which can secure a weld metal having excellent creep rupture strength and rupture ductility comparable to a base material without impairing welding workability. Various studies were carried out on the composition of the core wire and the composition of a so-called lime titania-based coating agent containing titanium oxide, metal carbonate, and metal fluoride as main components. As a result, the following findings were obtained. [0009] In the case of welding metal with a coated arc welding rod of austenitic stainless steel containing Mo,
In order to improve the creep rupture strength at a high temperature of 0 ° C. or higher, the addition of P, N, V, C and Nb is effective. On the other hand, the addition of P has a slight effect in improving the creep rupture ductility, N and V do not significantly affect the creep rupture ductility, and Nb and C significantly reduce the creep rupture ductility even in trace amounts. In addition, the tendency of creep rupture ductility to decrease is greatly affected by the value of Nb / V. Further, in order to simultaneously secure both the characteristics of creep rupture strength and rupture ductility, the value of N / (5Nb + V) must be controlled. It turned out not to be. Hereinafter, the present invention will be described in more detail. First, the core wire according to the present invention is basically made of M having excellent high temperature characteristics.
Any austenitic stainless steel containing o may be used. Regarding the C content in the core wire, taking into account the amount mixed in from the coating agent, welding is performed to prevent a decrease in creep rupture ductility of the weld metal. It is desirable to suppress C in the metal to 0.06% or less. For this purpose, the lower the C content in the core wire, the better. However, if the amount of C in the core wire is limited to 0.025% or less, later As described above, the C in the weld metal can be kept at 0.06% or less in combination with the coating with a so-called lime titania-based coating agent containing titanium oxide as a main component. Therefore, C in the core wire is limited to 0.025% or less. The components other than C in the core wire are basically Mo-containing austenitic weld metal having high temperature characteristics such as excellent tensile strength characteristics, creep rupture characteristics, and aging toughness at high temperatures. Cr for all weight
Is 15.0 to 21.0%, Ni is 7.0 to 14.0%,
Mo is 1.2 to 3.2%, and the remainder is composed of Fe and inevitable impurities. In addition, besides these components, Si: 0.75% or less, Mn: 2.5 for the purpose of improving core wire productivity, welding workability, resistance to hot cracking of the weld metal, and the like.
%, The characteristics of the present invention are not impaired. Next, in one or both of the core and the coating agent, P is 0.015 to 0.044% and N is 0.0
3 to 0.25%, 0.03 to 0.80% of V,
The main configuration of the present invention is to limit b to less than 0.10% and to control the value of Nb / V to be 0.25 or less and the value of N / (5Nb + V) to be 0.30 or more. Requirements. [0013] Of the elements contained in one or both of the core wire and the coating agent, P is present in the weld metal in the form of interstitial solid solution or phosphide, and its presence improves the creep rupture strength at high temperatures. Further, the creep rupture ductility is improved from the effects of facilitating the movement of the crystal grain boundaries of the weld metal. However, if the weight ratio of the core wire and / or the coating agent is less than 0.015%, the effect is small, and if it exceeds 0.044%, the hot metal crack resistance deteriorates. Therefore, the core wire weight ratio is 0.015 to 0.0
Control to 44%. N exists in the form of interstitial solid solution or nitride in the weld metal, and its presence improves the creep rupture strength at high temperatures. However, less than 0.03% by weight of one or both of the core wire and the coating agent has little effect, and if it exceeds 0.25%, the creep rupture ductility is reduced and the slag removability is reduced. The welding workability deteriorates. Therefore, the core weight ratio is 0.03
Control to ０．２0.25%. V is present in the weld metal in the form of substitutional solid solution or in the form of a nitride, carbide, oxide or the like, and its presence improves the creep rupture strength at high temperatures. However, less than 0.03% by weight of the core wire and / or the coating agent is less effective at a core weight ratio of less than 0.80%.
If it exceeds 300, the creep rupture ductility will decrease. Therefore, the core wire weight ratio is controlled to 0.03 to 0.80%. Nb is present in the weld metal as a substitutional solid solution or in the form of a nitride, carbide, oxide or the like. Even if the Nb is present in a very small amount, it significantly deteriorates the creep rupture ductility at high temperatures. In order to prevent remarkable deterioration of creep rupture ductility, the lower the amount of Nb, the better. However, deterioration of creep rupture ductility becomes particularly remarkable at 0.10% or more in one or both of the core wire and the coating agent. Therefore, the amount of Nb in one or both of the core wire and the coating agent is limited to less than 0.10% by weight of the core wire. Further, since Nb and V tend to exist in a similar form such as nitride, carbide, oxide and the like in the weld metal, the addition of V has an effect of suppressing remarkable deterioration of creep rupture ductility due to Nb. When the ratio between the Nb content and the V content exceeds 0.25, the effect of preventing the deterioration of creep rupture ductility of Nb due to V is hardly recognized. Therefore, the value of Nb / V is set to 0.25 or less. As described above, N improves the creep rupture strength of the weld metal in either solid solution or nitride form. In this case, the effect of improving the creep rupture strength is greater when the compound is present in the form of a nitride, but the tendency to decrease the creep rupture ductility is greater. On the other hand, the solid solution has a small degree of impairing the creep rupture ductility, but the effect of improving the creep rupture strength is somewhat small. For this reason, if the ratio of Nb and V, at which nitrides are easily formed, is less than 0.30, most of N becomes nitrides and the creep rupture ductility is significantly deteriorated. Therefore, the value of N / (5Nb + V) is controlled to 0.30 or more. As for the coating agent, a so-called lime titania-based coating agent which basically has good welding workability in all positions and relatively little C is mixed into the weld metal from the coating agent, that is, the entire coating agent is used. 25 to 55% of titanium oxide, 5 to 25% of metal carbonate, 4 to 20% of metal fluoride, 1 to 15% of silicate compound, and 1 to 35% of metal % Of the coating agent, and the coating rate is 20 to
It is desirable to set it to 40%. Of these coating components, especially titanium oxide, as an impurity, N
Since there are many raw materials containing b, it is desirable to carefully select and use raw materials having a low Nb content. In addition, in order to ensure good welding workability or improve productivity in the welding rod of the present invention,
l ₂ O ₃ , ZrO ₂ , K ₂ O, Na ₂ O, CaO, Mg
A metal oxide such as O can be contained in the coating agent. As described above, the high-temperature austenitic stainless steel-coated arc welding rod according to the present invention has a low carbon M
The o-containing austenitic stainless steel core wire is coated with a so-called lime titania-based coating agent, and the contents of trace components P, N, and V added to one or both of the core wire and the coating agent are controlled within an appropriate range. By limiting the Nb content to a very low level and controlling the values of Nb / V and N / (Nb + V), 5
Excellent creep rupture strength even at high temperatures of 00 ° C or higher,
A weld metal having properties such as creep rupture ductility can be easily obtained. Here, the method of manufacturing the welding rod will be described. A carefully selected titanium oxide material (preferably having an Nb content of 0.2% by weight or less as an impurity) having a small core wire and Nb content is mixed with a dry process. A mixed coating powder is prepared, and the coating powder is wet-mixed with a binder of water glass (aqueous solution of potassium silicate and sodium silicate), and then applied to the outer periphery of the core wire. Is dried and fired. Examples of the present invention will be described below. Table 1
Shows the chemical composition of the test core wire. Of these, the core symbol T1
T4 is the present invention, and T5 and T6 are comparative examples.
Tables 2 to 4 show the compositions of the coated arc welding rods by the combination of the test core wire and the coating agent. Table 5 shows the chemical components of the base material used. Tables 6 to 8 also show Tables 2 to 4
5 shows the results of component analysis of a weld metal performed using the coated arc welding rod of No. 1 and the base metal shown in Table 5, and the results of a tensile test at 600 ° C. and a creep rupture test at 600 and 650 ° C. Underlined data in these tables indicate that they are outside the scope of the present invention. [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] The welding test was performed using a welding rod having a rod diameter of 4.0 mm, a welding current of 140 A (AC), and an arc voltage of 22 to 26.
V, the welding speed was 150 to 220 mm / min, and the welding was performed on the grooved test plate shown in FIG. In FIG. 1, 1 is a base material, 2 is a backing metal, the plate thickness t = 20 mm, the groove angle θ = 45 °, and the root gap G = 12 mm. As a high-temperature tensile test piece of the weld metal 3, a test piece 4 having a parallel portion diameter of 6.0 mm and a parallel portion length of 25 mm was taken as shown in FIG. Also, the creep rupture test piece is shown in FIG.
A test piece 4 having a parallel part diameter of 6.0 mm and a parallel part length of 30 mm was collected in the same manner as described above. As is clear from Tables 6 to 8, the symbols No. No. 1-14, No. 1
It is clear that samples 6, 18 and 20 have a long breaking time in a creep rupture test at 600 ° C. and 650 ° C., a large breaking elongation, and excellent creep rupture strength and ductility at high temperatures. The 0.2% proof stress, tensile strength and elongation in the tensile test at 600 ° C. were also good. On the other hand, the symbol N
o. 15, 19 and 26 have low values of the high temperature creep rupture elongation because the value of N / (5Nb + V) is less than 0.30. No. Sample No. 17 has a low high-temperature creep rupture elongation because the P content is less than 0.015% by weight of the core wire. No. Reference numeral 21 indicates that the amount of Nb is 0.1
At 0% or more, the value of Nb / V exceeds 0.25 and N / (5
Since the value of (Nb + V) is less than 0.30, the high temperature creep rupture elongation is low. No. Sample No. 22 used the core wire of the comparative example in which the C content exceeded 0.025%, so that the C content of the weld metal was 0.25%.
More than 06%, the high temperature creep rupture elongation is low. Note that N
o. Micro-cracks were observed in the weld metal No. 22. No. 23 has a P content of 0.04 in terms of a core weight.
Since the Nb content exceeds 4% and the Nb content is 0.10% or more in terms of the core wire weight, the high temperature creep rupture elongation is low. No. 24 is N / (5Nb + V) where the V amount exceeds 0.80% in terms of the core weight.
Is less than 0.30, the high temperature creep rupture elongation is low. No. In No. 25, the value of Nb / V exceeds 0.25 and the high temperature creep rupture elongation is low. No. In No. 27, the high-temperature creep rupture time is short because the P content is less than 0.015% by weight of the core wire and the N content is less than 0.03% by weight of the core wire. No. No. 28 has a short high-temperature creep rupture time because the V content is less than 0.03%. No. No. 29 is a so-called lime type in which the coating agent is a metal carbonate and a metal fluoride outside the present invention as main components, so that the C content of the weld metal exceeds 0.06%,
Low high temperature creep rupture elongation. No. Sample No. 29 was inferior in welding workability such as slag peelability and bead shape. As described above, the high-temperature austenitic stainless steel-coated arc welding rod of the present invention can provide a weld metal having excellent creep rupture strength and creep rupture ductility at a high temperature of 500 ° C. or more. Moreover, welding workability is also good. Therefore, by applying the present invention to welding of a structure used in a high-temperature environment such as a nuclear-related field, it is possible to secure a long-lasting welded part that has never been provided before.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a groove shape of a test plate in an embodiment. FIG. 2 is a cross-sectional view showing a sampling position of a high-temperature tensile test piece and a high-temperature creep rupture test piece of a weld metal.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-50287 (JP, A) JP-A-63-13692 (JP, A) JP-A-61-88999 (JP, A) JP-A 52-287 52140 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 35/30 B23K 35/365

Claims (1)

(57) [Claims 1] In an arc welding rod coated with austenitic stainless steel for high temperature, weight% with respect to the total weight of the core wire.
And C is 0.025% or less and Cr is 15.0 to 21.
0%, Ni is 7.0 to 14.0%, and Mo is 1.2 to 3.0%.
Austenitic stainless steel consisting of 2%, the balance being Fe and unavoidable impurities was used as a core wire, and around the core wire, titanium oxide was added in an amount of 25 to 55% based on the total weight of the coating agent.
%, 5 to 25% of metal carbonate and 4 to 20 of metal fluoride.
%, Silicate compound 1-15%, metal powder 1-35%
The coating agent contained is coated at a coverage of 20 to 40%, and one or both of the core wire and the coating agent is provided with a core wire weight ratio of:
P is 0.015 to 0.044%, and N is 0.03 to 0.2.
5%, V 0.03-0.80%, Nb 0.1
Austenitic stainless steel coating for high temperature, characterized in that the Nb / V value is controlled to be 0.25 or less, and the N / (5Nb + V) value is controlled to be 0.30 or more. Arc welding rod.