JPS594994A - Submerged arc welding method of heat resistant low alloy steel - Google Patents

Abstract

PURPOSE:To improve the low temp. toughness and embrittling characteristic during use of the weld metal of a heat resistant low alloy steel, by limiting the compsn. of a wire for submerged arc welding and the characteristics of a flux and obtaining the weld metal having a specific compsn. contg. V, etc. CONSTITUTION:A narrow groove of <=20mm. distance between the groove faces is subjected to submerged arc welding in multi-layered build-up welding of single layer and single pass by using a wire consisting of specific compsns. of C, Si, Mn, Cr, Mo, V, and if necessary, Ti and substantially Fe, and a flux having the baking type compsn. compounded with 2.3-4.5 basicity BL expressed by the equation, 2-15wt% metallic carbonate in terms of CO2, and required amts. of V and Ti sources, whereby the weld metal of the compsn. contg. 0.030- 0.080% V and further 0.005-0.014% Ti according to need, and contg. 0.08- 0.15% C, 0.10-0.50% Si, 0.30-0.90% Mn, 0.90-3.50% Cr, 0.40-1.20% Mo in addition to the above is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for submerged arc welding of heat-resistant low-alloy steel, and in particular to a method for submerged arc welding of heat-resistant low-alloy steel. A submerged arc welding method that can be significantly improved is proposed.

When pressure vessels used at high temperatures and pressures are operated continuously for long periods of time, there is an increased risk of brittle failure during shutdown, start-up and sometimes during pressure tests, which is therefore particularly problematic when operating in cold regions. Natteguru.

Therefore, there has recently been a strong demand for welding materials and welding methods that have excellent low-temperature toughness and resistance to embrittlement during use.

As shown in FIG. 1, the conventional submerged arc welding method for heat-resistant low-alloy steel has been to stack the steel in a multi-pass method with a relatively wide groove i1. According to this method, in the n-th pass weld metal, Dn, which is a part of the columnar structure of the weld metal of the n-th bus, is regrained by the weld heat-affected zones Hn+1 and Hn+2 of the successive n+1 and n+2 buses. , most of the particles come to exhibit a fine structure. This phenomenon is repeated as welding baths are stacked, and compared to C, which corresponds to the four-quarter position of the groove width W, the refined structure area increases at the bisecting position O□, and generally the C0 position has a higher toughness. Excellent, but 0
Layer position shows low toughness.

On the other hand, as a submerged arc welding method for heat-resistant low-alloy steel, Ti is added to the weld metal by 0.020 to 0.0% by weight (hereinafter referred to as 0.020 to 0.0% by weight) using a single-layer multi-pass lamination method as shown in Figure 1. Although a method of adding a certain amount (expressed simply in %) has been proposed in the past, it still tends to cause variations in toughness and low toughness at the C2 position, and has not been sufficiently improved. In other words, even if high toughness is obtained at the C□ position, the C
This is because unless the toughness is improved at the 2nd position, there will be no substantial improvement in toughness.

On the other hand, most of the steel materials used in pressure vessels are extremely thick-walled materials, and narrow gap welding is preferred for the purpose of reducing welding costs.
Although it is considered to be a pass lamination method, the weld metal of the nth pass □ is regrained by the weld heat affected zone (heat affected zone) in+1 of the next n+1 bus, and Dn, which is the - □ part of the columnar structure of weld metal n, is regrained and becomes fine. Compared to the case shown in Figure 1, the number of times and area affected by bath welding heat, which contributes to regraining, is much smaller, and therefore the dust is lower than that of the single-layer multi-pass lamination welding method. It shows your gender.

In other words, it is impossible to expect to improve low-temperature toughness with a welding method that involves lamination of one layer and one pass, and thus materials and welding methods for submerged arc welding that are highly resistant to embrittlement during use have not yet been developed. It can be said that

Based on the above, this invention aims to propose a submerged arc bath welding method that has excellent low-temperature toughness and resistance to embrittlement during use, not only for single-layer multi-pass welding, but also for single-layer, single-pass welding. be.

However, multi-layer welded joint weld metals are affected by complex welding heat, making it impossible to accurately compare their toughness. Therefore, the inventors quantitatively compared and investigated one-pass bath welding metals with different weld metal compositions by adding simulated thermal cycles with various reheating temperatures. It has been found that metals are effective in terms of toughness and resistance to embrittlement during use.

In accordance with the results of the above-mentioned development research, this invention has been developed by applying ■: o, oa to the weld metal based on the combination of the requirements of QIF notes (1) to (8) for the wire and flux for submerged arc welding.
o~o, oso%, or even Ti: 0.005
Contains ~0.014%, and other c: o, os ~0.
15%.

Si: 0. ]O~0.50%, In: 0.8
~0.9%, Or: 0.9-8.5%, MO: 0.
It has been found that obtaining a welding metal with a composition containing 4 to 1.20% can contribute to an effective solution to the existing problems regarding submerged arc welding of heat-resistant low alloy steel. The requirements are: (1) 0: 0.04 to 0.18 per wire
%, Si: 0.60% or less, In: 0.30-0
．． 90%, Qr: +1.90~3.5%, MO
: Contains 0.40 to 1.20%, and has the remaining required amount vl or further has a composition of Ti and substantially Fe; (2) For the flux, the basicity calculated by the following formula is 2.8 ~4.5 and accounting for 2 to 15% in terms of CO2, is a sintered composition in which a metal carbonate having a content of 2 to 15% in terms of CO2 is blended with a necessary amount of V or further a Ti source, and (8) ■ Source - ! Furthermore, regarding the Ti source, when these are included as wire components, O, OS
% or less, 0.06% or less for Ti, 0% or less when blended as a flux component], or 0% or less.

It is. As described above, it is particularly desirable to apply the method in a single-pass laminated multilayer structure in a narrow groove with a distance between the groove surfaces of 20 mm or less.

That is, according to the submerged arc welding method of the present invention, not only the toughness of the weld metal in the single layer multi-pass method as shown in FIG. Extremely excellent low-temperature toughness and resistance to embrittlement during use can be obtained;
Even when layer 1 bus welding is performed, a sound welded part can be obtained without losing the toughness and resistance to embrittlement during use.

Now, the sintered flux used in the present invention requires a metal carbonate content in the range of 2.0 to 15% by weight calculated as CO8.

If this value decreases by more than 2%, the amount of diffusible hydrogen in the weld metal will increase, making it unsuitable for this hydrogen to accumulate and cause hydrogen cracking when performing multi-layer welding of extremely thick steel materials. It is. Moreover, if it exceeds 15%, the arc becomes unstable and welding defects such as slag entrainment, undercut, and poor fusion are likely to occur.

Here, the metal carbonates are 0aOO8, Ba008. Mg
OO8°Mn0O,, Li2Co3. All of these include Na2GO8.

When adding a V source to the flux, the V content should be 1.0% or less, and if it is more than 1.0%, the V in the weld metal will be 0.08%.
%, and the toughness decreases by 1 degree. As the V source, metal vanadium or vanadium alloy powder such as ferrovanadium can be used;
It is sufficient if the weight % calculated as ] is 0% or less.

The same is true for the Ti source (Ti source should be 1.0% or less; if it is higher than 1.0%, welding slag tends to adhere to the weld bead surface and impairs slag removability. Ferrotitanium is used as a Ti source. Tetanium alloy powders such as tetanium alloys can be used.

Next, if the basicity expressed as the ratio of basic components to acidic components is less than 2.8p, glassy slag tends to form, and even though the slag removability is relatively good, oxygen in the weld metal If the amount increases, the toughness of the weld metal deteriorates, and if it exceeds -4.5, the melting point of the slag will rise, worsening the bead appearance, and the slag peelability will deteriorate, causing welding defects. It is less likely to occur.

Therefore, BL must be in the range of 2.8 to 4.5.

Next, the chemical composition range of the welding wire is closely related to the chemical composition range of the weld metal, so both will be explained in detail.

When the C content in the weld metal is less than 0.08%, it is difficult to ensure not only room temperature strength but also high temperature strength of about 4 ry o "O, and the toughness is also poor.
When the percentage is too high, hot cracking and cold cracking are likely to occur in the weld metal, and more precipitated carbides are likely to be generated, and coarse carbides aggregate at the old R grain boundaries, resulting in poor toughness and resistance to embrittlement during use. It makes both of them worse.

If C in the wire exceeds 11.18%, O>0.15% in the weld metal, which is not preferable.

On the other hand, if it is less than 0.04%, it is not appropriate because it would improve the quality of the wire.

Si is necessary to reduce oxygen in the weld metal and improve the dust density. When the Si content in the weld metal is less than 0.10%, the amount of oxygen increases and the toughness deteriorates. Furthermore, if the amount exceeds 0.5%, the toughness and ductility will decrease, and furthermore, during actual operation, embrittlement will occur more easily, cracks will occur at the old R grain boundaries, and brittle fracture will occur. There is a risk.

For this reason, unless the Si content in the wire is kept below 61J%, the content of 5iil in the weld metal will exceed 0.5%, causing the above-mentioned problems. Note that the reason why the upper limit of Si is 0.1% less in the weld metal than in the wire is that it is consumed in the deoxidation reaction.

Mn is necessary to ensure room temperature strength and high temperature strength. If the Mn content in the weld metal is less than 0.80%, it is not suitable because the strength will be insufficient. On the other hand, 0.90%
If the amount is more than 1, the embrittlement during use will be significant and there is a risk of brittle fracture, which is not preferable.

In order to obtain good characteristics within these ranges of In content in the weld metal, Mn in the wire should be 0.30% to 0.90%.
Must be in the range of %.

0rFi is necessary to improve corrosion resistance.

If Qr in the weld metal is less than 0.9%, corrosion resistance will not be sufficiently exhibited. Moreover, if the amount exceeds 8.5%, embrittlement during use becomes significant. In order to obtain good properties by keeping the Cr1b in these weld metals in the range, the Or
¥ir 0.9 (must be in the range of 1-3.50%.

No is limited in terms of high temperature strength, toughness, and resistance to embrittlement during use. If the MO content in the bath-welded metal is less than 0.40%, the high temperature strength will decrease, which is not preferable.

If it exceeds 1.20%, the toughness deteriorates and embrittlement during use becomes significant, so it is not suitable.

It goes without saying that the amounts of Qr and No mentioned above need to be limited depending on the type of steel for pressure vessels.

V is necessary to improve toughness and resistance to embrittlement during use. If the V content in the weld metal is less than u, oao%, the toughness will decrease, and furthermore, it will not be good for embrittlement resistance during use.

If the amount is more than 0.0%, the toughness will decrease, embrittlement will be promoted during use, and the ductility will be insufficient. In order to obtain good characteristics with the amount of V in the weld metal within these ranges, the amount of V in the wire must be within a range of 0.08% or less. Note that (2) may be blended with 7lux as described above, or may be added as a wire component, or may be used in combination with both.

Ti is useful especially when necessary because it reduces variations in toughness and provides high toughness, but if the Ti content in the bath weld metal is less than 0.005%, it will not work as expected. If the amount exceeds 0.014%, the variation in toughness will become larger and stable toughness will not be obtained.

Thus, in order to stably obtain high toughness, T1 in the wire must be 0.06% or less.

Note that Ti can also be added to at least one or both of the flux and the wire in the same way as in (2).

Ni cannot be added in large amounts because it promotes embrittlement during use. In other words, if the amount of Ni in the weld metal increases by more than 0.80%, embrittlement during use becomes significant and the risk of brittle fracture increases. It is also necessary to limit the content to 0.30% or less.

Other than the metal elements mentioned above, both weld metal and wire are basically composed of FB and impurity elements, but At as a general component in steel, a small amount of At is added to flux or wire. However, neither the welding workability nor the toughness is affected. However, when At exceeds 15% of lJ in the weld metal, the toughness deteriorates. Similarly, for B, 0.0080 in the weld metal
%, it is difficult to warm up, and it is also unfavorable for toughness and embrittlement during use.
l) is 0. (12) If it exceeds 1%, the toughness and resistance to embrittlement during use deteriorate, so it should be limited.

Next, in the eighth aspect of the invention, in addition to the above, by containing Ti together with V in the weld metal, the low temperature toughness and the effect of preventing embrittlement during use are further improved. In this case, Ti can also be transferred into the weld metal as a wire component, as in (2), and by adding a Ti source to the fluff. In this case, the [Ti] content as a wire component is 0.06%, and the flux component exceeds 1.0%.
If it exceeds 0.014%, the slag releasability will be impaired, and there will be disadvantages such as arc stability and bath contact defects due to undercut.
We cannot expect any special effects to be enhanced by this.

Incidentally, since impurities such as P, Sn, A, s, and Sb act as grain boundary embrittling elements, it is preferable to reduce them as much as possible to prevent embrittlement during use.

When submerged arc welding is performed using a combination of the above-mentioned fluxes and wires, sufficient low-temperature toughness and resistance to embrittlement during use can be obtained not only for single-layer multi-pass welding metals but also for single-pass welding metals. Note that the groove width W is 20t.
I-no-1 bath bath contact is possible up to rar, but 1. In this case, welding defects such as sludder entrainment and poor fusion are likely to occur, and to prevent this, it is necessary to increase the amount of welding heat input, resulting in low toughness. Therefore, when the groove width W becomes larger than 20 mm, it is more advantageous to use multi-pass weld metal in terms of toughness and the occurrence of welding defects.

Example 1 2'/4 ar-i MO steel plate (AS
TMA887 Gr, 22, O4, 2: U, 1
5% O, U, 20% Si.

0.59%Mn, (1,1JU5%P, 0.U
(34%S, 2.28%Or,], old %No) was made into a groove shape as shown in Fig. 3, and wire W-4 with a diameter of 4 among those shown in Table 1 and wire W-4 with a diameter of 4 among those shown in Table 2 were used. Flux It"1
, 2.8, 10 and 11 were combined to perform the following experiment.

The welding conditions were welding current A, 050 U A, same voltage 28 V, welding speed y 25 cm/mj-n, and multi-layer welding was performed with one layer and one bus lamination.

As shown in Table 8, the workability during welding and the results of ultrasonic non-destructive testing after completion of welding, the flux Fl, 2.8 according to the present invention has good welding workability, slag entrainment,
There were no welding defects such as poor fusion. However, C.O.
Flu with too much 3 amount and Fll with too much Ti amount are
In both cases, many welding defects occurred due to slag flaking, arc stability, undercutting, etc.

Table 8 Example 2 21/4Or-IMONo steel plate AST with plate thickness of 100mm
MA887 Gr, 22. Ot, 2: 0.14
%0, 0.24%Si.

0.58%Mn, (1,UO4%P, 0.UO
4%S, 2.26%Or, 1.02%No,
Multi-layer welding was performed on a restrained crack test specimen made of 0.14% Ni) as shown in FIG. 4 by laminating each layer in one pass. In the figure, 1.1 is the base material, 2 is the restraint material, 3.8' is the restraint welding bead, and the groove has a root radius of 6M and a diameter of 4°.

The wire used in this case was W4 with a diameter of 4.0/l,
Four types of flux were used: Fl, F2, F8, and F9, and each was used after being allowed to absorb moisture for 12 hours in an atmosphere at a room temperature of 30° C. and a humidity of 80%.

The welding conditions are 50 U A, 27 V, 2
2(In/, i.

The temperature between the baths was 150°C.

Forty-eight hours after completion of welding, the presence or absence of cracks was examined by non-destructive testing using ultrasonic flaw detection and longitudinal section macro testing. As a result, as shown in Table 4, the flux Fl of this invention,
F2. In F8, no cracks were observed and the welded part was sound, but with F8, a comparative example with an insufficient amount of CO1.
9, many horizontal cracks had occurred.

Table 4 Example 8 Plate thickness 75 mm 1'/4. cr-F2 No steel plate (AS
TMA1387 Gr, ] 1, Ot, 2
: U, 15%0, 0.52%si, 0.
57%) 4n, U, UO4%P, U, OU5%
S.

1.80%Qr, 0.52%No)k Again, multi-layer welding was carried out using the 1-layer 1-pass 1@ method with the groove shape as shown in FIG. 8 while varying the wire and flux. In this case, the preheating and interpass temperatures were in the range of 120°C to 175°C.

The chemical composition of the weld metal is shown in Table 5, and the impact test results are shown in Table 6.
Shown below. The welding material combinations WIXF6 and W2XF5 according to the present invention yielded extremely excellent low-temperature toughness, but the comparative example W 2 X F 7°W8XF9 yielded only poor results.

Example 4 A V-groove with a groove angle of 20° as shown in FIG.
In this, 55 CI A, 25 V, 17 cI
Test bead 4 was made by performing one pass welding under the conditions of rL/min.

After this, a reproduced thermal cycle test piece 5 of 11/0 was taken, and a thermal cycle shown in the chart of FIG. 6 was added to process the impact test piece 6.

Table 7 shows the chemical composition of the one-bath weld metal obtained by welding using one type of flux (Fl) and changing only the wire, and Table 8 shows the toughness at each reheating temperature.

The combination of W4XF1 and W5XF1 according to the present invention shows high toughness at all temperatures, of which U, 008%
W5XF1, which is Ti, has less Ti than W4X
F]' shows higher tenacity.

On the other hand, the combination of W8XF1 with low V and W9XF with high amount of Ti and reheating temperature of 750℃,
It shows low toughness at 1350°0, and there is a significant variation especially in W9XF1.

Example 5 Using the steel plate and welding material used in Example 4, the groove shape shown in Fig. 8 was prepared at 550A 28V 28~ soil.

Multi-layer welding was carried out in one pass on 11 cars with preheating and an interpass temperature of 150" CN30110. The tenacity of the weld metal in that case is shown in Table 9, and as with the results in Example 4, W4XF1 and W4XF1 according to the present invention With the combination of W5XF1 welding materials, extremely excellent results were obtained in both low-temperature toughness and resistance to embrittlement during use.

Table 9 East temperature rise 50″0/hr, cooling 27°C/hr.

The results are shown in Table 11. The combination of W8XF7 according to this invention shows good values for toughness, tensile strength, and elongation.
(2) If too much oxygen is present, not only the toughness but also the elongation decreases.

Table 18 Example 7 3Qr-IMO steel plate with a plate thickness of 150 mm (ASTM A38
7Gr, sl OL, g: o, ua%0, 0.
24%si, 0.50%1(n, 0.0118
%p, u, uoa%S, 3.10%gr.

1.06% MO) was beveled as shown in Figure 8, welding conditions were 550A, 28V, 28cm/min, and preheated.

Multilayer welding was carried out with one layer and one pass lamination at an inter-bus temperature of 200°C to 250°C. The chemical composition of the weld metal is shown in Table 12, and the impact test results are shown in Table 18. Welding material combination W6xF4 according to the present invention. W7xF8 has excellent toughness and resistance to embrittlement during use, but WIUXF has too much V content.
No. 5 has poor toughness and resistance to embrittlement during use.

As mentioned above, the present invention is applicable to heat-resistant low-alloy steel, especially 0.
90-8.50% Or, 0.40-1. ! o% MO
As explained with the study results for Or -Mo@ as a representative example, it is not limited to this composition range, and can be applied not only to single electrode but also to multi-electrode welding, to produce heat-resistant low-alloy steel. The low-temperature toughness and in-use embrittlement resistance of the weld metal obtained by submerged arc welding can be significantly improved.

[Brief explanation of drawings]

Figure 1 shows multi-pass lamination using the conventional method, and Figure 2 shows
Each cross-sectional view shows the one-layer, one-pass lamination method, FIG. 8 is a cross-sectional view of the groove shape used in the example, FIG. 4 is an external view showing the shape of the restrained crack test specimen, and FIG. 5 is Example 4. FIG. 6 is a diagram showing the heat cycle added in Example 4. Patent applicant: Kawasaki Steel Corporation Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. Wire and flux for submerged arc welding include the following (
]) to (3), v in the weld metal.
; Other c including o, oao~U, 08U heavy leaf%
: u, os~0.15% by weight, si: o, 1o~
0, 513% by weight, In: 0. ao ~0.9
o heavy eggplant °%. Or: o, 90-8.50% by weight, No: 0
．． A method for submerged arc welding of heat-resistant low alloy steel, comprising obtaining a weld metal gold having a composition containing 40 to 1.20% by weight. (1) Wire 0: 0.04 to 0.18% by weight, st: o,
6o weight% or less, In: (1,10 to 0.90 weight%, Or: 0.90 to 3.5 weight%, No: U
, 40 to 1.20%, with the remaining required amount of ■ and a substantially Fe composition. (2) The basicity of the flux is 2.8 to 4.5 and 002
The metal carbonate, which accounts for 2 to 15% by weight in terms of weight, is blended with the necessary amount of V source to form a repellent firing type composition. (3) When incorporated as a V source wire component, 0.08% or less; when incorporated as a flux component, 1. Select 1 with at least 1 force below lJ vehicle volume %. The method according to the claims, wherein the application of submerged arc welding is multilayer stacking of single-layer baths in narrow grooves with a distance between groove surfaces of 20 mm or less. & Wire and flux for submerged arc welding (
Based on the combination of requirements 1) to (8), v: o, uaυ~o, oso weight% and Ti:
Contains 0.005 to 0.014% by weight, and other o:
o, os ~ 0.15% by weight, Si: o, 10-0
．． 1i. Weight %, In: 0.8U ~ 0.90 weight 19%,
cr: 0.90-8.507 layer amount%, MO:
A process for latent arc welding of heat-resistant low-alloy steel, comprising obtaining a weld metal having a composition containing 0.40 to 1.20% by weight. Mouth (1) Wire 0: 0.04~0, 18% by weight, Si: 0.
60% by weight or less, Mn: 0.8+) ~0.90
Weight%, ar: U, 90-8.5 weight%, No
: 0.40 to 1.20 %, including residual, required amounts of V and Tj, and substantially Fe composition. (2) The basicity of flux hail is 2.8 to 4.5, 002
A firing mold composition containing a metal carbonate, which accounts for 2 to 15% by weight, together with the necessary amounts of V source and Tl source. (8) V source, Ti source When included as a wire component, ① is O, OS weight % or less, Ti is 0.06% by weight, and when incorporated as a flux component, both are 1.0
% by weight or less on at least one side. 4. The method according to the claims and description, wherein the application of submerged arc welding is single-pass multilayer stacking in a narrow groove with a distance between groove surfaces of 20 mm or less.