JPH07102465B2 - One-sided welding method of stainless clad steel plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is capable of efficiently welding one side of a stainless steel clad steel plate in which a stainless steel plate is clad to the surface of a carbon steel plate from the side of the stainless steel plate, and has corrosion resistance and The present invention relates to a single-sided welding method capable of obtaining a weld metal having excellent impact resistance performance.

[Prior Art] In constructing various chemical industrial equipment, seawater desalination equipment, crude oil tankers, etc., it is necessary to satisfy both requirements of corrosion resistance and economy at the same time. Stainless steel clad steel plates are often used. That is, the necessary strength is secured by a carbon steel plate which is inexpensive and excellent in strength, and the corrosion resistance is dealt with by clad a relatively thin stainless steel plate on the surface layer.

By the way, when attempting to weld such a stainless clad steel plate, the chemical composition of the base metal is remarkably 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 the same welding material is used to perform welding at once. I can't do it. Therefore, the welding material must be changed intricately in consideration of the chemical composition of each base material and mutual dilution during welding. For example, FIG. 1 (A) shows a known example of formation when stainless-clad steel plates are welded on both sides, and FIG. 1 (B).
Shows a known example of formation in the case of single-sided welding from the stainless steel plate clad side, and the numbers shown in each formation show the formation order. That is, regarding the formation shown in FIG. 1 (A) and the formation shown in FIG. 1 (B), alloy elements are not mixed in from the stainless steel plate S, and therefore eutectic welding to the carbon steel plate C is performed. Weld using the material. Regarding the formation near the boundary between the carbon steel plate C and the stainless steel plate S [in FIG. 1 (A), FIG. 1 (B)], considering that the stainless steel plate is diluted by the carbon steel plate, Ni-high Cr composition welding material (such as 309 series or 309Mo series) is used,
We are trying to prevent the occurrence of cracks due to the formation of martensite structure. Next, regarding the formation on the side of the stainless steel plate S [of FIG. 1 (A), FIG. 1 (B)], it is not necessary to consider dilution by the carbon steel plate. Is used.

In this way, at least three types of welding materials must be used when welding stainless clad steel plates, and whether the applicable welding method should be covered by the covered arc welding method, taking into consideration the dilution by the base metal. , A solid wire or flux-cored wire is used in combination with a gas shielded arc welding method. Since there are many types of welding materials and many man-hours for welding work, the work is complicated and inefficient. There was a problem.

Regarding the carbon steel plate portion of the clad steel plate,
A method for improving welding efficiency by using a submerged arc welding material for carbon steel has also been studied, but the height of the deposited metal is not stable due to variations in groove precision and changes in welding conditions, Part of the stainless steel plate is melted into the weld metal layer.
When alloy components such as Cr and Ni are mixed in, martensite is generated in the weld metal and hardening cracks easily occur, which is a serious defect in terms of safety.

[Problems to be Solved by the Invention] The present invention has been made by paying attention to the above circumstances, and an object thereof is to provide a stainless clad steel plate with a relatively simple operation and sufficiently for a welded portion. The present invention aims to provide a single-sided welding method that can provide excellent mechanical properties and corrosion resistance, and can obtain high welding efficiency.

[Means for Solving the Problem] A configuration of a single-sided welding method according to the present invention is a method of single-sided welding a stainless steel clad steel plate in which a stainless steel plate is clad on a surface of a carbon steel plate from the stainless steel plate clad side. : 50-70 wt%, Ni: 20-30 wt%, balance Fe
And metal powder consisting of inevitable impurities or Cr: 45-55
Wt%, Ni: 20 to 30 wt%, Mo: 10 to 20 wt%, the metal powder consisting of the balance Fe and unavoidable impurities is filled in the groove, and the carbon steel sheet is prepared by using a latent arc welding material for stainless steel. An austenitic metallographic structure containing 3% to 15% of ferrite is obtained by welding the two together, and then the groove front side portion composed of the clad stainless steel plate portion is welded using a common metal welding material. However, it has a gist.

[Operations and Examples] The configuration and operation effects of the present invention will be clarified below with reference to the history of experiments.

First, the present inventors examined whether or not welding of carbon steel plates in a stainless clad steel plate can be carried out without problems using a normal submerged arc welding material for stainless steel. That is, a carbon steel plate having a thickness of 16 mm is butted in a groove shape shown in Fig. 2 (A), a refractory-based backing material is arranged on the rear surface of the groove, and a second welding wire of 309 series is used.
A tandem submerged single-sided welding experiment was conducted under the conditions shown in FIG. The chemical components of the carbon steel used, the 309 series welding wire, and the connecting metal that is not diluted with the base metal obtained by the welding wire are as shown in Table 1, and the welding conditions were as follows.

(Welding conditions) Welding speed: 65cm / min Welding current: Leading electrode ... 1050A Trailing electrode ... 700A Welding voltage: Leading electrode ... 37V Trailing electrode ... 40V When the penetration rate of the weld metal into the base metal and the weld metal structure were examined in the above welding experiment, the penetration rate of the weld metal into the base material was about 50%, and the weld metal became a martensite structure and was very fragile. It has been confirmed that it becomes unpractical. By the way, Fig. 3 is a diagram when the weld metal structure obtained under the above-mentioned welding conditions is estimated by applying it to the Schaeffler structure diagram. From this diagram as well, the weld metal structure when the dilution rate exceeds 50% It turns out that is a martensite structure.

The present invention is based on the above preliminary experiment results, in order to give excellent physical properties (particularly crack resistance) to the welded portions of the carbon steel sheets in the stainless clad steel sheet, in order to obtain an appropriate metal structure, We thought it necessary to adjust the chemical composition, and proceeded with the research along that line. Then, in order to improve the crack resistance of the weld metal, it was considered necessary to appropriately adjust the chemical composition of the weld metal so that the weld metal structure becomes an austenite structure containing some ferrite having excellent toughness. For that purpose, Cr and Ni generated by dilution with the base material
As a result of further research, we thought that it would be better to compensate for the decrease in the concentration of Al by adding an alloying element from the outside, and as a result of further research, Cr, Ni or Mo together with these was added in the groove portion composed of the carbon steel plate in the stainless clad steel plate. If filled with a large amount of metal powder, these are mixed in the weld metal in the welding process to increase the Cr, Ni, Mo concentration in the weld metal,
It was found that the weld metal can have a metal structure with excellent toughness even when the base metal dilutes.

By the way, the chemical composition that most affects the structure of the weld metal depends on the following.

Welding conditions: Composition of welding wire, melting amount and base metal dilution rate Composition and filling amount of metal powder filled in the groove Therefore, the above items should be adjusted appropriately and the weld metal should have a metal structure with high toughness. It may be a suitable chemical component. As a criterion for this, it was considered necessary to clarify the metallographic structure of the weld metal exhibiting excellent toughness, and the following experiments were conducted. As a result, it has been found that an austenite structure containing 3 to 15% of ferrite is a condition capable of stably exhibiting high toughness. Therefore, further experiments were conducted to clarify the welding conditions for obtaining such a weld metal structure.

(1) Welding conditions First, as the material to be welded, the 317L stainless clad steel plate (plates and chemical components shown in Table 2), which are widely used as structural materials such as chemical tankers, are selected, and the welding materials shown in Table 3 are selected. Was used to conduct a latent arc welding experiment on a carbon steel plate. The welding wire corresponds to JIS Z3321 Y309.
Using a wire for submerged arc welding of 4 mmφ, as the filling metal powder, the optimum metal composition (the metal composition is 10-12% Ni, 16-19
% Cr, 2 to 3% Mo stainless steel was determined in advance by Schaeffler's organizational chart.) "50% Cr-27% Ni-14% Mo -9%
Fe metal powder ”was used. The groove shape is shown in Fig. 4 (S:
Stainless steel sheet, C: Carbon steel sheet, Me: Filled metal powder, De: Weld metal, B: Backing material, H: Filling height, G: Root gap,
θ: groove angle) and welding was performed with a gap between electrodes (l) of 30,60 as shown in Fig. 5 (L: leading electrode, T: trailing electrode).
Alternatively, the tandem submerged arc welding method was set to 90 mm.

Welding conditions and results are collectively shown in Table 4. The structure of the weld metal was obtained by using a Schaeffler structure chart based on the chemical analysis value 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 the experimental examples below).

As is clear from Table 4, when the tandem submerged arc welding method is adopted, the performance of the weld metal depends on the distance between the welding electrodes and the balance of the current and voltage between the leading electrode (L) and the trailing electrode (T). It turns out that organizations and organizations are greatly affected. And in the symbols B, C, G, H, since the distance between the electrodes is as wide as 60 mm or 90 mm, the molten pool formed by the leading electrode and the molten pool formed by the trailing electrode do not combine as a pool, and Segregation occurred in the weld metal because the components did not have the same composition. Further, since the current values of the leading electrodes are too low for the symbols D and I, the filling metal powder is not sufficiently melted in the welding process by the leading electrode, and not only fusion failure occurs in the root part but also segregation in the weld metal. Has occurred. On the other hand, with reference signs E and J, since the current value of the trailing electrode is too low, the arc spread of the trailing electrode is insufficient and the bead shape is deteriorated.

As apparent 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 are united, and the welding of the leading electrode is performed. Regarding the electric current, it is possible to completely melt the filled metal powder, and for the welding current of the trailing electrode, the current value and its balance are adjusted well so that the arc is sufficiently spread and the proper bead shape is secured. It is desired to do.

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

By the way, in normal one-sided welding, 1 pool welding, 2
It is known that the weld metal has good crack resistance in the order of pool welding and semi-1 pool welding, and the present invention is most disadvantageous for the crack resistance from the viewpoint of preventing segregation in the weld metal as described above. 1 Pool welding method must be adopted. Nevertheless, in order to secure good crack resistance, the composition and filling amount of the metal powder filled in the groove are important as will be described in detail below.

(2) Composition of filled metal powder As described above, the filled metal powder is used to secure a metal composition that compensates for the decrease in the Cr and Ni concentrations in the weld metal caused by the dilution of the base metal and provides an appropriate metal structure. And
It is necessary to use a metal powder containing Ni, Cr, etc. in a well-balanced manner so that the weld metal structure becomes an austenite structure containing 3 to 15% of ferrite. From this point of view, an experiment was conducted for the purpose of clarifying the component composition of the filled metal powder required to secure an appropriate metal structure. However, the welding conditions were the same as those indicated by symbol F in Table 4 above, and various Cr-Ni-Mo-Fe powders having different component compositions were used as the filling metal powder. Also, when converting the height of the filled metal powder of 11 mm into the area ratio of the groove cross-sectional area composed of the carbon steel plate of the material to be welded,
It becomes 51%, and the base metal dilution rate when welding is performed under the welding conditions shown in the table is in the range of 40 to 60%.

Table 5 collectively shows the structure and performance of the weld metal obtained in this experiment.

In Table 5, the symbols a, d, e, g, i, m indicate that the composition of the filler metal powder is proper and that the composition of the weld metal is austenite containing 3 to 15% ferrite. As a result, a sound weld metal without weld cracks is obtained.

On the other hand, the symbols f, j, and o are insufficient in Ni, Cr, etc. in the filler metal and cannot sufficiently compensate for the decrease in Ni and Cr concentration caused by the dilution of the base metal, so the weld metal has a martensitic structure, Fine weld cracks have occurred. Also, the codes b and k
For example, although a weld metal having an austenite structure containing a few percent of ferrite can be obtained, weld cracks still occur because the ferrite content is too low. Further, with the symbols c and n, conversely, since the amount of ferrite in the weld metal structure is too high, the weld metal causes an embrittlement phenomenon and weld cracking occurs.

From these experimental results, when the preferable component composition of the filled metal powder is determined, Cr: 45 to 55% Ni: 20 to 30% Mo: 10 to 20% balance: Fe and inevitable impurities are derived.

Incidentally, the preferred composition of the filling metal powder, depending on the base metal dilution rate, or the amount of Cr, Ni, Mo in the welding wire to be used, etc., so if the base metal dilution rate is high, Cr, Ni in the filling metal powder, Mo
The amount of each element should be relatively decreased when the dilution ratio is small, and the same adjustment should be made depending on the contents of Cr, Ni and Mo in the welding wire. However, in the present invention, the dilution ratio of the base metal under welding conditions that can secure a good welding condition is in the range of 40 to 60% in most cases, and stainless steel welding as a welding wire. Using submerged arc welding wire for
In consideration of the above, the component composition of the filled metal powder was set in the above range.

In the above, the case where the Cr-Ni-Mo-Fe-based filling metal powder was used was described, but the same experiment was performed for the case where the Cr-Ni-Fe-based filling metal powder was used. 50 ~ 70% Ni: 20 ~ 30% balance: Fe and inevitable impurities 3 ~ 15
It was found that a weld metal having an appropriate structure composed of austenite containing 10% of ferrite and having excellent crack resistance can be secured.

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

That is, a single electrode submerged arc welding method using a 9 mm thick 317L clad steel plate as a base material, and a plate thickness of 12 mm or 16 mm
317L clad steel plate is used as the base material, and the distance between contacts is 30mm
The tandem submerged arc welding method is adopted, and the root gap (L in FIG. 4) and the filling height (H in FIG. 4) which are parameters of the filling amount of the filling metal powder are variously changed to submerge. Arc welding was performed, and the structure of the weld metal and the presence or absence of weld cracks were examined in the same manner as above.
In any case, the filling metal powder is Cr: 50, Ni: 27, Mo: 1.
4, a balance of Fe and inevitable impurities was used. Further, the filling amount of the metal powder is described as the area ratio of the filling metal powder to the groove cross-sectional area.

The results are shown in Tables 6, 7, 8, 9, 10, 11, and 12.

From Tables 6 to 12, the following can be considered.

(1) No. 1 to 22 are single electrode submerged arc welding methods, No. 2
Nos. 3 to 67 are examples in which the tandem submerged arc welding method is adopted, and regardless of which method is adopted, a good weld metal without cracks is obtained as long as it meets the requirements of the present invention.

(2) In Tables 6 to 12, those marked with "○" in the column of appropriate conditions satisfy the requirements of the present invention, and the weld metal has a suitable structure containing 3 to 15% ferrite in austenite. In all cases, good crack resistance is obtained.

(3) Nos. 1 and 14 of Tables 6 and 7 and Nos. 23 and 35 of Tables 8 and 9 are comparative examples in which the metal powder filling amount in the groove is insufficient, and C
Since the supplemental amounts of r, Ni, Mo, etc. are insufficient, the weld metal structure becomes a martensite structure with high cracking susceptibility, and longitudinal cracks or lateral cracks occur in the beads.

(4) No.3,11,15 of Tables 6 and 7, No.38,42 of Tables 9 and 10
In the case of, the weld metal structure becomes an austenite single phase and fine cracks occur because the metal powder filling amount in the groove is insufficient.

(5) No.7,19 of Tables 6 and 7, No.24,27,3 of Tables 8 and 9
1, 36, No. 46, 49, 57, 60 of Tables 10 and 11 are comparative examples in which the filling amount of the metal powder is slightly insufficient, the weld metal structure contains a small amount of ferrite in austenite,
Since the ferrite content is less than 3%, extremely fine cracks occur.

(6) No. 6, 10, 18, 22 in Tables 6, 7, and 8 and N in Tables 9 and 10
o.34,45, No.52,56,63,67 of Tables 11 and 12 are comparative examples when the filling amount of the metal powder is too much, and the amount of ferrite contained in the austenite structure of the weld metal is 15 %, The lateral cracking occurs due to the interaction between the embrittlement phenomenon and the welding thermal strain.

(7) The proper filling amount of the metal powder filled in the groove is
Strictly speaking, in addition to the composition of the metal powder, the effects of the base metal dilution rate, which slightly changes depending on the chemical composition of the welding wire or the welding conditions (groove shape, welding heat input, etc.), should be taken into consideration. Need to be specified in. However, in the actual welding process, the welding conditions that can ensure a proper welding condition are within a relatively narrow range, and as described above, the normal base metal normal dilution ratio is usually in the range of 40 to 60%. is there. Therefore, based on such a base metal dilution rate, the preferred composition of the metal powder as described above and the standard composition of the stainless steel submerged arc welding wire selected and used as the welding wire and the specific gravity of the metal powder, etc. in view of,
When a preferable filling rate that can obtain the chemical component necessary for making the metal structure of the weld metal austenite + (3 to 15)% ferrite is obtained, a range of 35 to 100% can be derived, and this preferable filling rate is obtained. The range is consistent with the results obtained in Tables 6-12 above.

The composition and filling rate of the filling metal powder are appropriately adjusted so that the weld metal at the bottom of the groove formed by the carbon steel sheet as described above has a chemical composition that easily forms austenite + (3 to 15)% ferrite. However, for example, when welding is performed using a submerged arc welding material for stainless steel such as 309 series, the welded portion between carbon steel sheets exhibits excellent crack resistance and it seems that reheating (post-welding heat treatment) has been applied. Even in any case, the welded part is sound and does not become brittle.

Incidentally, the reason why the submerged arc welding method is adopted in the present invention is that the welding heat input is increased to improve the welding efficiency. Therefore, a part of the stainless steel plate that is the clad material at the welding stage of the carbon steel plate part. It is inevitable that they will be melt mixed. However, in the present invention, as described above, the welding conditions are determined so that the weld metal of the carbon steel plate portion has a high Ni and high Cr composition, and therefore, even if a part of the stainless steel sheet is melt-mixed, no actual damage occurs.

After welding the carbon steel plate portion in this manner, the groove portion formed of the remaining stainless steel plate may be welded using a common metal welding material. At this time, the groove both sides are made of stainless steel and the lower surface is made of high Cr / high Ni alloy steel, so that the welded part of the stainless steel plates forming the surface layer loses its corrosion resistance due to the mixing of the base metal. There is no fear.

Therefore, any method may be used to weld the welded portions of the stainless steel plates, such as covered arc welding, TIG welding, and MIG welding.
Welding, welding using a flux-cored wire, etc. can be arbitrarily selected and adopted. When the groove width is wide, it is also effective to adopt a build-up welding method using a strip electrode.

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

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

(Conditions) Groove shape: Based on Fig. 4, except root width (L): 2mm, groove angle: 55 degrees, metal powder filling height (H): 10.5mm (filling rate: 47%) Electrode arrangement: According to Fig. 5, but distance between electrodes: 30 mm, forward tilt angle of front and rear electrodes: 5 degrees Metal powder: 50% Cr-27% Ni-14% Mo-9% Fe Welding wire: Leading electrode ... Y309 (4 mmφ) Row electrode: Same as above Welding current: Leading electrode ... 750A Trailing electrode ... 650A Welding voltage: Leading electrode ... 37V Trailing electrode ... 42V Welding speed: 60cpm Welding part of carbon steel sheet as shown in Fig. 6 is obtained by this welding. It was

Then, the groove portion between the remaining stainless steel plates S is
MAG welding (current: 200A, voltage: 3) while weaving in the groove width direction using 7L-C flaked wire (1.2mmφ)
0V, speed: 12cpm, weaving width: 22mm, shield gas:
100% CO ₂ , 25 / min) was performed and welding of the stainless clad steel plate was completed.

Table 13 shows the chemical composition of the obtained weld metal and the amount of ferrite in the austenite structure (Dellong structure diagram), and Table 14 shows the mechanical properties of the weld.

As is clear from the results in Table 13, the metal structure of the weld metal has a structure with good crack resistance including a proper amount of ferrite in austenite for both parts of the carbon steel plate and the stainless steel plate, and also has high corrosion resistance. It has a chemical composition of and has extremely excellent mechanical strength as shown in Table 14.

[Advantages of the Invention] The present invention is configured as described above, and it is possible to extremely efficiently single-side weld a stainless clad steel plate. In addition, it is possible to form a weld metal having a metal structure having excellent mechanical properties, and it is possible to obtain a weld having excellent performance in terms of strength and corrosion resistance. As a result, it is possible to eliminate the strength defect of the welded structure while maximizing the superiority of the stainless clad steel plate.

[Brief description of drawings]

FIGS. 1 (A) and 1 (B) are explanatory views showing a known formation method used for welding stainless clad steel plates, and FIGS. 2 (A) and 2 (B) are groove shapes used in experimental examples and FIG. 3 is an explanatory view showing the electrode arrangement, FIG. 3 is a view showing the organization chart of Schaeffler, FIGS. 4 and 5 are explanatory views showing the groove shape and electrode arrangement adopted in the same experimental example, and FIG. 6 is obtained in the embodiment. It is a cross-sectional view showing the welded portion of the carbon steel plate portion. S: Stainless steel plate, C: Carbon steel plate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takeshi Kurokawa 7-66 Midorigahama, Chigasaki City, Kanagawa Prefecture (56) References JP-A 61-162274 (JP, A) JP-A 61-154776 (JP, A) Special Kai 61-140378 (JP, A) JP 52-114455 (JP, A)

Claims (2)

[Claims] 1. A method of single-sided welding of a stainless clad steel plate in which a stainless steel plate is clad on the surface of a carbon steel plate from the stainless steel plate clad side, wherein Cr: 50 to 70% by weight, Ni: 20 to 30% by weight, An austenitic weld metal containing 3 to 15% ferrite by filling the groove with a metal powder consisting of the balance Fe and unavoidable impurities and by welding the carbon steel plates to each other using a latent arc welding material for stainless steel. A single-sided welding method for a stainless clad steel plate, which comprises forming a structure, and then welding a groove front surface part constituted by the clad stainless steel plate part using a metallurgical welding material. 2. A method for single-sided welding of a stainless clad steel plate in which a stainless steel plate is clad on the surface of a carbon steel plate from the stainless steel plate clad side, wherein Cr: 45 to 55% by weight, Ni: 20 to 30% by weight, Mo: 10 to 20% by weight, the metal powder consisting of the balance Fe and unavoidable impurities is filled into the groove, and the carbon steel plates are welded to each other by welding the carbon steel plates to each other by using a latent arc welding material for stainless steel to form 3 to 15 % Of an austenitic weld metal structure containing ferrite, and then the groove front side part composed of the clad stainless steel plate portion is welded using a common metal welding material. Welding method.