JPH01178375A - One-side welding method for stainless clad steel plate - Google Patents

Abstract

PURPOSE:To efficiently perform one-side welding by filling metal powder with specific composition in a groove and welding carbon steel plates to each other by using submerged arc welding material for stainless steel and welding the groove surface side constituted of stainless steel plates with the same kind of metal material. CONSTITUTION:Stainless clad 1 steel plates formed by cladding the stainless steel plates S on the surfaces of the carbon steel plates C are subjected to one-side welding from the stainless steel plate S clad side. In this case, the metal powder consisting of, by weight, 50-70% Cr, 20-30% Ni and the balance Fe with impurities is filled in the groove. The submerged arc welding material for the stainless steel is then used to weld the carbon steel plates to each other and an austenitic metallic structure containing 3-15% ferrite is obtained. The groove surface side constituted of the clad stainless steel plates is then welded by using the same kind of welding metal material. By this method, weld metal excellent in the corrosion resistance and the impact resistant performance is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention enables efficient single-sided welding of a stainless steel plate, in which the surface of a carbon steel plate is clad with a stainless steel plate, from the stainless steel plate side. The present invention relates to a single-sided welding method that makes it possible to obtain weld metal with excellent impact resistance.

[Prior art] When constructing various types of chemical industrial equipment, seawater desalination equipment, crude oil tankers, etc., it is necessary to satisfy both corrosion resistance and economical requirements at the same time, so stainless steel is applied to the surface of carbon steel sheets. Stainless steel clad steel plates are often used. That is, the necessary strength is to be ensured by inexpensive and high-strength carbon steel plates, and corrosion resistance is to be achieved by cladding the surface layer with relatively thin stainless steel plates.

By the way, when trying to weld such stainless clad steel plates, the chemical composition of the base metal is significantly different between the carbon steel plate part and the stainless steel plate part, so the dilution effect of the base metal is completely different, and it is necessary to weld them all at once using the same welding material. I can't afford to do that. Therefore, the welding materials must be changed in a complicated manner, taking into consideration the chemical composition of each base material and mutual dilution during welding. For example, Fig. 1 (A) is a known example of laminated layers when double-sided welding of stainless clad steel plates, and Fig. 1 (B)
1 shows a known example of layers in the case of single-sided welding from the cladding side of a stainless steel plate, and the number shown for each layer indicates the layer type. In other words, the formation ■ in Figure 1 (^)
, ■ and the formations ■ and ■ in Fig. 1 (B), welding is performed using a welding material similar to that of the carbon steel sheet C, since alloying elements from the stainless steel sheet S will not be mixed in. . And carbon steel plate C and stainless steel plate S
The cumulative N near the boundary [■ in Figure 1 (A), Figure 1 (B)
Regarding [■], considering that the stainless steel plate is diluted by the carbon steel plate, welding materials with a high Ni-high Cr composition (for example, 309 series or 309 Mo series) are used to prevent cracking due to the formation of martensitic structure. We are trying to prevent this from happening. Next, the formation layer on the stainless steel plate S side [first
Regarding [■ in Figure (A)] and ■ in Figure 1 (B)], there is no need to consider dilution by the carbon steel plate, so a metal-based welding material for the stainless steel plate S is used.

In this way, when welding stainless clad steel sheets, at least three types of welding materials must be used, and the welding method to be applied should be a covered arc welding method, taking into account dilution by the base material. , gas-shielded arc welding using solid wire or flux-cored wire is used in combination, but the work is complicated and inefficient because there are many types of welding materials and the number of welding steps is large. There was a problem that happened.

In addition, regarding the carbon steel plate part of the clad steel plate,
A method of increasing the efficiency of welding using submerged arc welding materials for carbon steel is also being considered, but the height of the deposited metal is unstable due to variations in groove precision and fluctuations in welding conditions, etc. When a part of the stainless steel plate is melted, alloy components such as Cr and Ni are mixed into the weld metal layer, and martensite is generated in the weld metal, making it more likely to cause hardening cracks, which is a serious safety issue. It becomes a defect.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned circumstances, and its purpose is to fabricate a stainless clad steel plate with a relatively simple operation and with a sufficient welding area. The purpose of the present invention is to provide a single-sided welding method that can provide good mechanical properties and corrosion resistance, and also achieve high welding efficiency.

[Means for Solving the Problem] The configuration of the single-sided welding method according to the present invention is such that a stainless steel clad steel plate, in which the surface of a carbon steel plate is clad with a stainless steel plate, is welded on one side from the stainless steel plate cladding side. Cr: 50-70 plate amount%, Ni: 20-
30! Metal powder consisting of 1% by weight, balance Fe and inevitable impurities or Cr: 45-55! ! Amount%, Ni: 20~
By filling the groove with metal powder consisting of 30% by weight, Motto ~ 20% by weight, the balance being Fe and unavoidable impurities, and welding the carbon steel plates together using a submerged arc welding material for stainless steel, 3~ The gist of this method is to obtain an austenitic metal structure containing 15% ferrite, and then weld the groove front side portion made up of the clad stainless steel plate portion using a matching welding material.

[Operations and Examples] The structure and operation effects of the present invention will be clarified by following the experimental history.

First, the present inventors investigated whether carbon steel plates in stainless clad steel plates could be welded together without any problems using a normal submerged arc welding material for stainless steel. That is, carbon steel plates with a thickness of 1611III+ are butted together with the groove shape shown in Fig. 2 (A), a refractory-based bracing material is placed on the back side of the groove, and a 309 series welding wire is used to assemble the plates as shown in Fig. 2 (B). ) A tandem submerged single-sided welding experiment was conducted under the conditions shown below. The carbon steel used was 30
The chemical components of the 9-series welding wire and the weld metal obtained by the welding wire without diluting the base metal are shown in Table 1, and the welding conditions were as follows 6 (welding conditions) Welding speed: 65 cm/akin Welding current: Leading electrode...1050A Trailing electrode...-700A Welding voltage: Leading electrode...37V Trailing electrode...-40V In the above welding experiment, the penetration rate of weld metal into the base metal and When the weld metal structure was examined, it was confirmed that the penetration rate of the weld metal into the base metal was about SO%, and the weld metal had a martensitic structure, making it extremely brittle and impractical. By the way, Figure 3 is a diagram when the weld metal structure obtained under the above welding conditions is estimated by applying it to Schaeffler's structure chart, and from this figure, the weld metal structure when the dilution rate exceeds 50% is also estimated. It can be seen that the structure becomes a martensitic structure.

The present invention is based on the above preliminary experimental results, and in order to provide excellent physical properties (especially cracking resistance) to the weld between carbon steel sheets in stainless clad steel sheets, weld metal must be adjusted to obtain an appropriate metal structure. We believed that it was necessary to adjust the chemical components, and proceeded with our research along that line. In order to improve the cracking resistance of the weld metal, we considered that it is necessary to appropriately adjust the chemical composition of the weld metal so that the weld metal structure becomes an austenite structure containing some ferrite with excellent toughness. For this purpose, it is necessary to
We thought that the decrease in the concentration of i could be compensated for by adding alloying elements from the outside, and as a result of further research, we found that Cr, Nt, or Mo together with these elements were added to the groove part of the stainless clad steel sheet made of carbon steel. If metal powder containing a large amount of
It has been found that by increasing the Mo1 degree, the weld metal can be made to have a metal structure with excellent toughness even when dilution by the base metal occurs.

By the way, the chemical components that have the greatest effect on the structure of weld metal are influenced by the following:

■Welding conditions: Composition of welding wire, melting amount, and base metal dilution rate ■Composition and filling amount of metal powder filled into the groove Therefore, the above items are adjusted appropriately, and the weld metal has a high toughness metal structure. A chemical component suitable for this may be used. As a standard for this purpose, we believed that it was necessary to clarify the metal structure of weld metal that exhibits excellent toughness, and conducted the following experiments. As a result, it was found that an austenite structure containing 3 to 15% ferrite is the condition under which high toughness can be stably exhibited. Therefore, further experiments were carried out to clarify the welding conditions for obtaining such a weld metal structure.

(1) Welding conditions First, a 317L stainless clad steel plate (plate and chemical composition shown in Table 2), which is widely used as a structural material for chemical tankers, etc., was selected as the material to be welded, and welding materials shown in Table 3 were selected. We conducted submerged arc welding experiments on carbon steel plate parts using the In addition, as a welding wire, JIS 23321<
7) Y309 &: Use the corresponding 4 mmφ submerged arc welding wire, and as the filling metal powder, select the optimal metal composition (this metal composition is 10-12% Ni, 16-12% Ni, 16-12% Ni, 19% Cr.

50% Cr-27% Ni-14 was determined through preliminary experiments to be 2-3% Mo stainless steel (previously determined from Schaeffler's organizational chart).
%Mo-9%Fe metal powder" was used. In addition, the groove shape is shown in Figure 4 (S stainless steel plate, C: carbon steel plate,
Me: Filled metal powder, De: Weld metal, B: Backing material, H
; filling height, G: root gap, θ: groove angle), and welding was performed with the distance between poles *CIL> as shown in FIG. 5 (L: leading electrode, T: trailing electrode) at 30. 60 or 90
The tandem submerged arc welding method was set to mm.

The welding conditions and results are summarized in Table 4. The structure of the weld metal was determined using the Schiefler structure chart based on the chemical analysis values of each weld metal, and the presence or absence of weld cracks was confirmed by an X-ray transmission test, and the presence or absence of segregation was confirmed by an X-ray microanalyzer. (These confirmation methods are common to all experimental examples below).

(Left below) As is clear from Table 4, when using the tandem submerged arc welding method, the distance between the welding electrodes and the leading electrode (
It can be seen that the performance and structure of the weld metal are greatly affected by the balance of current and voltage between the electrode (L) and the trailing electrode (T).And for symbols B, C, G, and H, the interelectrode distance is 60
mn+ or 90), so the molten pool formed by the leading electrode and the molten pool formed by the trailing electrode do not combine as a pool, and the components after solidification do not have the same composition, resulting in segregation in the weld metal. occurred. In addition, since the current value of the preceding electrode is too low, the filling metal powder is not sufficiently melted in the welding process using the preceding electrode, which not only causes fusion failure at the root but also causes segregation in the weld metal. It is occurring. On the other hand, with codes E and J, go behind! Since the current value of the pole is too low, the arc of the trailing electrode does not spread enough and the bead shape deteriorates.

As is clear from these experiments, when the tandem submerged arc welding method is adopted in the present invention, the molten pool formed by the leading electrode and the molten pool formed by the trailing electrode merge, and the welding of the leading electrode Carefully adjust each current value and balance so that the filling metal powder can be completely melted, and the welding current of the trailing electrode to give sufficient spread to the arc and ensure an appropriate bead shape. It is desirable to do so.

In addition, when tandem submerged arc welding is adopted, the amount of heat that concentrates at one point in the weld can be kept low compared to single electrode submerged arc welding, and as a result, the dilution rate by the base metal can be kept low. Therefore, the amount of filler metal powder used can be reduced. Therefore, in the present invention, it is most advantageous to employ the tandem welding method, but the application of the single electrode submerged arc welding method is of course not excluded.

By the way, in normal single-sided welding, 1 boule welding, 2 boule welding
It is known that the cracking resistance of the weld metal improves in the order of boule welding and semi-one boule welding, and in the present invention, from the viewpoint of preventing segregation in the weld metal, as described above, welding One pool welding method shall be adopted. Nevertheless, in order to ensure good cracking resistance, the composition and filling amount of the metal powder filled into the groove are important, as detailed below.

(2) Composition of filler metal powder As mentioned above, filler metal powder is used to compensate for the decrease in Cr9Ni concentration in the weld metal caused by dilution of the base metal and to ensure a metal composition that provides an appropriate metal structure. It is necessary to use a metal powder containing Ni, Or, etc. in a well-balanced manner so that the weld metal structure becomes an austenite structure containing 3 to 15% ferrite. From this point of view, an experiment was conducted to clarify the composition of the filling metal powder required to ensure an appropriate metal structure. However, the welding conditions are the same as the code F in Table 4 above, and various Cr powders with different compositions are used as the filling metal powder.
-Ni-Mo-Fe powder was used. In addition, when the height of the filling metal powder of 11 mm is converted to the area ratio of the cross-sectional area of the groove made of the carbon steel plate of the material to be welded, it is 51%, which is 51% when welding is performed under the welding conditions shown in the table. The base material dilution rate is in the range of 40 to 60%.

The structure, performance, etc. of the weld metal obtained in this experiment are summarized in Table 5.

(Hereinafter referred to as "Brown") ・-11 Nizo Table 5 In Table 5, symbols a, d, e, g, t, and m indicate that the component composition of the filler metal powder is appropriate and the weld metal composition is correct. , 3~
Since it has an appropriate structure consisting of austenite containing 15% ferrite, a sound weld metal without weld cracking is obtained.

On the other hand, the symbols f, j, and o lack Ni, Cr, etc. in the filling metal and cannot sufficiently compensate for the decrease in concentration of Ni and Cr caused by dilution of the base metal, so the weld metal becomes a martensitic structure. There are minute weld cracks. In addition, although a weld metal having an austenitic structure containing several percent of ferrite can be obtained in the case of No. 2, weld cracking still occurs because the amount of ferrite is too low. Further, in cases c and n, on the contrary, the amount of ferrite in the weld metal structure is too high, so that the weld metal undergoes an embrittlement phenomenon and weld cracking occurs.

From these experimental results, the preferred component composition of the filling metal powder is determined as follows: Cr: 45-55% Ni: 20-30% Mo: 10-20% Balance: Fe and unavoidable impurities.

The preferred composition of the filling metal powder is the dilution rate of the base metal or Cr, Ni, M in the welding wire used.

If the base material dilution rate is high, the amounts of Cr, Ni, and Mo in the filling metal powder will be relatively increased, and if the dilution rate is low, the amounts of each of the above elements will be relatively increased. Cr, Ni, Mo in the welding wire should be reduced.
Similar adjustments should be made depending on the content, but in the present invention, the base metal dilution rate under welding conditions that can ensure good welding conditions is in the range of 40 to 60% in most cases. Considering this and the fact that a submerged arc welding wire for stainless steel welding is used as the welding wire, the composition of the filling metal powder was determined to be within the above range.

In the above description, the case where Cr-Ni-Mo-Fe-based filling metal powder was used was explained, but Cr-N
A similar experiment was conducted using an L-Fe-based filling metal powder, and it was found that a filling metal powder with a composition of Cr: 50 to 70%, Ni: 20 to 30%, and the balance Fe and unavoidable impurities was used. 3-1 depending on
It was found that a weld metal with an appropriate structure consisting of austenite containing 5% ferrite and excellent crack resistance could be obtained.

(3) Filling amount of metal powder The chemical composition of the weld metal not only changes depending on the composition of the filling metal powder as described above, but also naturally changes depending on the filling amount of the metal powder. Therefore, an experiment was conducted to clarify the most preferable filling amount for actual welding work.

That is, a single electrode submerged arc welding method using a 317L clad steel plate with a thickness of 91II11 as the base material, and a plate thickness of 1
A 317L clad steel plate of 2a+■ or 16+am was used as the base material, the distance between the poles was set to 30m+a, and the tandem submerged arc welding method was adopted. Submerged arc welding was carried out by varying the filling height (H in Figure 4) and the structure of the weld metal and the presence or absence of weld cracks were examined in the same manner as above. In each case, the filling metal powder was Cr:50. Ni:27. Mo:
.

No. 14, the remainder consisting of Fe and unavoidable impurities was used. The filling amount of the metal powder was expressed as the area ratio occupied by the filling metal powder to the cross-sectional area of the groove.

Results in table 6.7.8.9.10.11.12 1□1
',・ From Tables 6 to 12, it can be considered as follows.

(1) Nos. 1 to 22 are examples in which the single electrode submerged arc welding method was adopted, and Nos. 23 to 67 are examples in which the tandem submerged arc welding method was adopted, and regardless of which method is adopted, the specified requirements of the present invention are met. As long as they match, a good weld metal with no cracks can be obtained.

(2) Those marked with an O in the appropriate conditions column in Tables 6 to 12 satisfy the specified requirements of the present invention, and the weld metal has a suitable structure containing 3 to 15% ferrite in austenite. Good cracking resistance was obtained in all cases.

(3) No. of Table 6, 7, 1.14, No. of Table 8.9
, 23.35 is a comparative example in which the amount of metal powder packed into the groove is insufficient, and due to the lack of supplementary elements such as Cr, Ni, Mo, etc., the weld metal structure becomes a martensitic structure with high crack susceptibility, and the bead Vertical or horizontal cracks have occurred.

(4) No. 6.7, 3.11, 15, 9.10 of Table 6.7
In No. 38.42 in the table, the amount of metal powder filled into the groove was insufficient, so the weld metal structure became an austenite single phase, and fine cracks were generated.

(5) No. in Table 6.7, No. 7.19, No. in Table 8.9
, 24.27, 31, 38, No. 4 in Table 10.11
13.49 and 57.60 are comparative examples in which the filling amount of metal powder is slightly insufficient, and weld metal giI1m contains a small amount of ferrite in austenite, but since the amount of ferrite is less than 3%, it is difficult to scratch. Cracks have occurred.

(6) No. in Table 6.7.8, 6. 10. I
B.

22, No. 9.10 of Table 34.45, No. 11.12
Nos. 52.56 and 63.67 in the table are comparative examples where the amount of metal powder filling is too large, and since the amount of ferrite contained in the austenite structure of the weld metal exceeds 15%, embrittlement occurs. Transverse cracking occurs due to the interaction between the welding temperature and the welding thermal strain.

(7) The appropriate amount of metal powder to be filled into the groove is:
Strictly speaking, in addition to the chemical composition of the metal powder, the influence of the chemical composition of the welding wire and the dilution rate of the base metal, which varies slightly depending on the welding conditions (groove shape, welding heat input, etc.), must be fully considered. It is necessary to decide after consideration. However, in actual welding work, the welding conditions that can ensure proper welding conditions are within a relatively narrow range, and as mentioned above, the normal dilution rate of the base material is usually in the range of 40 to 60%. be. Therefore, based on this base metal dilution rate, the preferred composition of the metal powder as described above, the standard composition of the stainless steel submerged arc welding wire selected as the welding wire, the specific gravity of the metal powder, etc. Considering this, the metal structure of the weld metal is changed to austenite +
)% When determining the preferred filling rate that can obtain the chemical components necessary to make ferrite, a range of 35 to 100% can be derived, and this preferred filling rate range is the result obtained in Tables 6 to 12 above. is consistent with

The composition and filling rate of the filling metal powder are adjusted so that the weld metal at the bottom of the groove, which is made of carbon steel plates, has a chemical composition that is likely to form austenite + (3 to 15)% ferrite as described above. When properly adjusted and welded using a submerged arc welding material for stainless steel such as 309 series, the weld between carbon steel plates exhibits excellent cracking resistance and does not require reheating (post-weld heat treatment). The result is a sound weld that does not become brittle even in cases where it is added.

The reason why the submerged arc welding method is adopted in the present invention is to increase the welding heat input and increase the welding efficiency. Therefore, during the welding stage of the carbon steel plate part, a part of the stainless steel plate that is the clad material is used. It is inevitable that the two will melt and mix. However, in the present invention, as described above, welding conditions are determined so that the weld metal of the carbon steel plate portion has a high Ni and high Cr composition, so even if a part of the stainless steel plate is melted and mixed, no actual damage will occur.

After welding the carbon steel plate portions in this manner, the remaining groove formed by the stainless steel plate may be welded using a matching welding material. At this time, both surfaces of the groove are made of stainless steel, and the bottom surface is made of high Cr/high Ni alloy steel, so
There is no fear that the welded portions between the stainless steel plates constituting the surface layer will lose their corrosion resistance due to the contamination of the base metal.

Therefore, any method may be used to weld the welded portion between the stainless steel plates, including covered arc welding, TIG welding,
MIG welding, welding using flux-cored wire, etc. can be arbitrarily selected and employed, and when the groove width is wide, it is also effective to employ overlay welding using a band-shaped electrode.

Next, the most typical embodiment of the present invention will be shown.

Example 1 317L clad steel plate with a thickness of 16+nm (carbon steel plate 13
mm, stainless steel plate: 3 mm), and the carbon steel plate portion was welded under the following conditions.

(Conditions) Groove shape: Compliant with Figure 4, however, root width (L): 2mm
.

Groove angle: 55 degrees, metal powder filling height (H): 10.5 mm (filling rate: 47%) Electrode arrangement: according to Fig. 5, however, distance between electrodes = 30 mm, forward inclination angle of front and rear electrodes: 5 degrees Metal powder: 50%Cr-27%Ni-14%MO-9
%Fe Welding wire: Leading electrode...Y2O2 (4mmφ) Trailing electrode... Same as above Welding current: Leading electrode...750A Trailing electrode...650A Welding voltage: Leading electrode...37V Trailing electrode ...42V Welding speed: 60 cpm Through this welding, a welded part of the carbon steel plate as shown in FIG. 6 was obtained.

Next, the grooves between the remaining stainless steel plates S were
317L-C flux wire (1,2m+nφ)
MAG welding (
Current: 200A, voltage: 30V, speed: 12cpm, weaving width: 22mm, shielding gas: 100% CO
2.25 Jl/min) to complete welding of the stainless clad steel plates.

The chemical composition of the obtained weld metal and the amount of ferrite in the austenite structure (Daylong structure diagram) are shown in Table 13, and the mechanical properties of the welded part are shown in Table 14.

'7''・1, (Left below) As is clear from the results in Table 13, the metallographic structure of the weld metal is a resistant structure containing an appropriate amount of ferrite in austenite for both carbon steel sheets and stainless steel sheets. It has a structure with good crackability, a chemical composition with high corrosion resistance, and as shown in Table 14, it has very excellent mechanical strength.

[Effects of the Invention] The present invention is configured as described above, and a stainless clad steel plate can be welded on one side extremely efficiently. Moreover, it is possible to form a weld metal consisting of a metal structure with excellent mechanical properties, and it is possible to obtain a welded part with extremely excellent performance both in terms of strength and corrosion resistance. As a result, strength defects in welded structures can be eliminated while maximizing the advantages of stainless clad steel sheets.

[Brief explanation of the drawing]

Figures 1 (8) and (B) are explanatory diagrams showing the known layered layer method adopted for welding stainless clad steel plates, and Figure 2 (
A) and (B) are explanatory diagrams showing the groove shape and electrode arrangement adopted in the experimental example, Figure 3 is a diagram showing Schaeffler's organizational chart, and Figure 4.5 is the groove shape also adopted in the experimental example. FIG. 6 is a cross-sectional view showing a welded portion of a carbon steel plate portion obtained in an example. S stainless steel plate C: carbon steel plate

Claims (2)

[Claims] (1) A method of welding a stainless clad steel plate in which a stainless steel plate is clad on the surface of a carbon steel plate from one side from the cladding side of the stainless steel plate, in which Cr: 50 to 70% by weight, Ni: 20 to 30% by weight, the balance being Fe. By filling the groove with metal powder consisting of unavoidable impurities and welding the carbon steel plates together using a submerged arc welding material for stainless steel, an austenitic weld metal structure containing 3 to 15% ferrite is formed. Then, the groove front side portion consisting of the clad stainless steel plate portion,
A single-sided welding method for stainless clad steel plates, which is characterized by welding using a co-metallic welding material. (2) A method of welding a stainless clad steel plate in which a stainless steel plate is clad on the surface of a carbon steel plate from one side from the stainless steel plate cladding side, in which Cr: 45 to 55% by weight, Ni: 20 to 30% by weight, Mo: By filling the groove with metal powder consisting of 10 to 20% by weight, the balance being Fe and unavoidable impurities, and welding the carbon steel plates together using a submerged arc welding material for stainless steel,
A stainless clad steel plate characterized by having an austenitic weld metal structure containing 15% ferrite, and then welding the groove surface side portion consisting of the clad stainless steel plate portion using a matching welding material. Single side welding method.