JPH0342195A - Flux-cored wire for cr-base stainless steel welding - Google Patents

Abstract

PURPOSE:To manufacture weld metal having excellent workability, specially detachability of slag and further, excellent cracking resistance, etc., by using flux having specified chemical composition in a wire formed by filling flux in a metallic sheath. CONSTITUTION:In the wire formed by filling the flux in the metallic sheath, the flux containing 10 - 35% Cr and 0.3 - 1.2% Nb with respect total weight of the wire and containing 1 - 8% TiO3 and 0.2 - 4% SiO2 and a metallic fluoride so as to satisfy F/Nb >= 0.2, F <= 1.5% expressed in terms of the quantity of F with respect to total weight of the wire as flux is used. Since Nb is specially added and the metallic fluoride is added in proper quantity to adjust the composition, the weld metal excellent is welding workability and specially, having satisfactory detachability of slag is obtained. Accordingly, it is suitable for welding various Cr-base stainless steels and specially ideal for gas shielded arc welding.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a flux-cored welder for welding Cr-based stainless steel, and more specifically, it has excellent welding workability (particularly good slag removability) and excellent welding cracking properties. The present invention relates to a flux-cored wire for welding Cr-based stainless steel, which yields a deposited metal with good strength and toughness and is suitable for gas-shielded arc welding. (Conventional technology and section M to be solved) Due to the demand for highly efficient construction, automatic and semi-automated welding has progressed, and flux-cored wire is characterized by excellent welding workability.
In recent years, the demand has particularly increased. Among them, austenitic stainless steel 9% CCr-
The use of flux-cored wire as welding materials for Ni stainless steel and Cr stainless steel is also progressing. However, the conversion of welding materials for Cr-based stainless steel into flux-cored wires is currently delayed due to the difficulty of construction. That is, since Cr stainless steel has a high sensitivity to cold cracking due to diffusible hydrogen, it is generally more difficult to weld than austenitic stainless steel. Among these, welding materials in which the ferrite phase of the structure is stabilized by adding Nb have low hardness of the weld metal and are less likely to cause cold cracking. This Nb addition promotes slag seizure and deteriorates slag removability, which is a problem especially in flux-cored wires that require good welding workability. Furthermore, compared to a coated arc welding rod, the current used by a flux-cored wire is higher and the welding heat input is larger, so that slag seizure is more likely to occur. On the other hand, in a weld metal in which Nb is added to stabilize the ferrite phase of the structure, when the crystal grains become coarse, the toughness is significantly deteriorated. Weld metal obtained by flux-cored wire has a higher welding heat input, which tends to cause coarse grains, and a higher oxygen content, which makes it less tough. This has become a problem. The present invention has been made to solve the problems of the prior art described above, and is a welding material for Cr-based stainless steel that has excellent welding workability, particularly slag removability, and also has excellent resistance to slag. The object of the present invention is to provide a flux-cored wire from which a weld metal with excellent crackability and even better toughness can be obtained. (Means for Solving the Problems) In order to achieve the above object, the present inventor has conducted intensive research on flux-cored wires with a composition similar to that of tubs, and has found that, in particular, Nb is added to the metal sheath or flux. We have discovered that this can be achieved by containing a predetermined amount of metal fluoride and further regulating the flux components, and have hereby accomplished the present invention. That is, the flux-cored wire for welding Cr-based stainless steel according to the present invention contains Cr: 10-35% and Nb: 0, 3-1.2%, as necessary, based on the total weight of the wire. Furthermore, C: 0.01-0.12%, A flood:
0.05-2%, Ti: 0.05-2% and N: 0.0
Contains 2 to 0.06%, and as a flux, TiO2: 1 to 8% and SiO2: 0 based on the total weight of the wire.
．． 2 to 4%, F/Nb≧0 when metal fluoride is converted to F amount
．． It is characterized by using a flux that satisfies 2.12185%. The present invention will be explained in more detail below. (Function) As mentioned above, the flux-cored wire for welding Cr-based stainless steel according to the present invention requires that a predetermined amount of Cr and Nb be added to the metal sheath or flux, based on the total weight of the wire. Further predetermined amounts of C and AQ as necessary
, Ti and X, and predetermined amounts of TiO2, Sio, and metal fluoride (F conversion) as flux.
This includes the following: Cr: Cr is an element that has an effect on corrosion resistance, and when added in an amount of 10% or more, it becomes particularly good. However, if it exceeds 35', the toughness deteriorates significantly, so the Cr content is set to 10 to 35%. Note that Cr can be added to both the metal sheath and the flux, and when added to the flux, Cr powder, Fe-Cr
It can be added in the form of powder. Nb: Adding Nb to flux-cored rewire for Cr-based stainless steel 11I welding stabilizes the ferrite phase of the weld metal structure, suppresses the precipitation of the martensitic phase, and centralizes the hardness of the weld metal, as described above. , the cracking property is improved. This effect is achieved by adding 0.3% or more of Nb. However, when added in excess of 1.2%,
Ferrite crystal grains become coarse and toughness deteriorates significantly. Furthermore, the addition of Nb, even in a small amount as described above, promotes slab seizure and deteriorates the slag removability, but this can be countered by the addition of metal fluoride, which will be described later. Therefore, Nbi is set to 0.3 to 1.2%. Note that Nb is mostly added from flux in the form of Fe-Nb or the like. Metal fluoride: While carrying out various experiments, the present inventor found that the addition of metal fluoride to the flux is very effective in preventing slag seizure caused by the above-mentioned Nb addition. That is, the amount of metal fluoride added is F/Nb≧0.2 in terms of F.
The effect will appear by satisfying the following. However, if more than 1.5% is added in terms of F, spatter will increase. Significantly deteriorates welding workability. Note that the effect of adding metal fluorides is the same regardless of the type thereof, and examples thereof include aluminum fluoride, barium fluoride, lithium fluoride, sodium silicate, and potassium silicate. Among these, sodium silicofluoride particularly improves arc stability and improves welding workability. T, LO,: TiO2 primarily acts as a slag former, protecting the weld metal from atmospheric oxidation and improving bead shape. The appropriate amount is 1 to 8%. However, if it is less than 1%, it has no effect, and if it is added in excess of 8%, the viscosity of the slag increases significantly, making welding defects such as poor fusion more likely to occur. 5in2: Sio2 also mainly acts as a slag forming agent and also improves the bead shape. The appropriate amount is 0.2 to 4%. However, less than 0.2% has no effect, and 4%
If added in excess of 10%, the viscosity of the slag will increase, making welding defects such as poor fusion more likely to occur. With the above configuration, it is possible to obtain a weld metal with good welding workability, a stable ferrite phase in the structure, and excellent crack resistance. Furthermore, by adding appropriate amounts of the following components (optional additions) to the metal shell or flux, a weld metal with significantly superior toughness can be obtained. C: C is a martensite-forming element, but if it is less than 0.01%, the crystal grain size becomes large and the toughness deteriorates.
If it is added in excess of 12%, the martensite phase tends to precipitate and the cracking resistance deteriorates, so the amount of C should be 0.01%.
~0.12%. Note that C can be added to both the metal shell and the flux, but when added to the flux, it can be added in the form of high-C Mn, chromium carbide, or the like. A4: Adding Afl refines the crystal grains and improves toughness. However, if it is less than 0.05%, it has no effect, and if it exceeds 2%, spatter will increase and welding workability will be significantly deteriorated, so AQIJ is 0.0.
It is set at 5-2%. Note that AQ can be added to both the metal shell and the flux, but when added to the flux, it can be added in the form of Afl powder, Fe-AQ powder, etc. T1: Ti refines crystal grains and improves toughness. However, 0
．． If it is less than 0.5%, there is no effect, and if it is added in excess of 2%, the crystal grains will become coarser and the toughness will deteriorate.
The amount of Ti is 0.05 to 2%. Note that Ti can be added to both the metal shell and the flux, but when it is added to the flux, it can be added mainly in the form of Fe-Ti powder. N: N refines crystal grains and improves toughness. However, 0.
If it is less than 0.02%, it has no effect, and if it is added in excess of 0.06%, blowholes will occur and the pore resistance will deteriorate. Note that N can be added to both the metal shell and the flux, but when added to the flux, it can be added mainly in the form of chromium nitride or the like. In addition, as the metal outer shell, mild steel and 409.410.4
30 series Cr stainless steel or the like can be used. The cross-sectional shape of the wire to be inserted into the franks can be any suitable cross-sectional shape, with the shape shown in FIG. 1 as an example, and the wire diameter, flux filling rate, etc. are not particularly limited. Of course, the applicable Cr stainless steels include various compositions,
Needless to say, various compositions are possible. Next, examples of the present invention will be shown. (Example) Flux-cored test wires with the compositions shown in Tables 1 and 2 were prepared, and their welding workability, crack resistance, X-ray performance, and toughness were evaluated using the procedures and evaluation criteria described below. went. The results are also listed in Tables 1 and 2. ■Welding workability Bead-on-plate welding was performed on a 5US410 steel plate (20 mm thick) under the conditions shown in Table 3, and the welding workability was evaluated. Although there are two types of shielding gas as shown in Table 3, the evaluation results of welding workability tended to be the same. ■Crack resistance, Xi performance, toughness In accordance with J4S Z 3323 (stainless steel arc welding flux-cored wire), the inside of the groove of the 5M41B test plate was battered in three layers with the sample wire (ill contact conditions: Table 2, but Weld metal was prepared using only 100% CO3 shielding gas, and tests were conducted. Crack resistance was evaluated by microstructure observation, X-ray performance was tested according to JIS Z 3106, and toughness was evaluated by Charpy impact test. The evaluation criteria for each are shown in Table 4. In Tables 1 and 2, Na 1 to Na 9 are comparative examples, and Na 10 to Na 3 are examples of the present invention, which will be discussed as follows. Comparative Example 41 has a martensitic phase precipitated in the structure due to the lack of Nb, resulting in poor cracking resistance. Furthermore, in Comparative Example Nα2, due to excessive Nb, the ferrite grains become coarse and the toughness is poor. Comparative Example Nα3 lacks Tie, resulting in poor slag coverage, poor welding workability, and poor bead shape. Furthermore, in Comparative Example &4, the amount of Tie is excessive, resulting in poor fusion and poor X-ray performance. Comparative Example Nα5 has an excessive amount of metal fluoride, so spatter occurs frequently and welding workability is poor. Moreover, Comparative Example Nα6 lacks metal fluoride, so slag removability is poor and welding workability is poor. Comparative example Na 7 is. Since the metal fluoride is even more deficient than in 〉7α6, the slag removability is extremely poor and the welding workability is poor. In Comparative Example Nα8, since Sio is insufficient, slag coverage is poor and welding workability is poor. Also, comparative example Nα9
Because of excess Sio2, poor fusion occurs and the X-ray performance is poor. On the other hand, inventive examples &10 to Nn31 are all excellent in welding workability such as slag removability, slag coverage, and spatter generation, and also excellent in crack resistance and X-ray performance. However, since the present invention example Na L O has a small amount of C, and the present invention example Xα11 has a large amount of C, the toughness is slightly inferior. Inventive examples ' and +112 have a small amount of AQfi, and inventive example Na 13 has a large amount of AIl, so they are both slightly inferior in toughness. Inventive example Na 4 has a small amount of Ti, and inventive example Na 15 has a large Ti amount, so they are both slightly inferior in toughness. Since the present invention example & 16 has a small amount of N, the present invention example N
Since α17 has a large amount of N, its toughness is slightly inferior.

[Left below]

(9! Bright effect) As detailed above, according to the present invention, in a flux-filled ear for welding Cr-based stainless steel, the composition is adjusted by adding an appropriate amount of metal fluoride in addition to Nb. , has excellent welding workability and particularly good slab removability,
In addition, it is possible to obtain a deposited metal with excellent crack resistance and toughness, making it suitable for welding various Cr-based stainless steels.
It is particularly suitable for gas shielded arc welding.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1(a) to 1(d) are diagrams showing examples of cross-sectional shapes of flux-cored wires.

Claims (2)

[Claims] (1) In a wire whose metal sheath is filled with flux, Cr: 10 to 35% and N based on the total weight of the wire.
b: 0.3 to 1.2%, and as a flux, TiO_2: 1 to 8% and Si based on the total weight of the wire.
O_2: 0.2 to 4%, metal fluoride converted to F amount
A flux-cored wire for welding Cr-based stainless steel, characterized in that it uses a flux that satisfies /Nb≧0.2 and F≦1.5%. (2) In a wire whose metal sheath is filled with flux, Cr: 10-35%, Nb based on the total weight of the wire
:0.3~1.2%, C:0.01~0.12%, Al
:0.05-2%, Ti:0.05-2% and N:0.
02 to 0.06%, and as a flux, TiO_2: 1 to 8% and SiO_
2: 0.2 to 4%, F/N of metal fluoride in terms of F amount
A flux-cored wire for welding Cr-based stainless steel, characterized in that a flux containing b≧0.2 and F≦1.5% is used.